Note: Descriptions are shown in the official language in which they were submitted.
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PCT PATENT APPLICATION
METHODS FOR REMOVING POTASSIUM, RUBIDIUM, AND CESIUM,
SELECTIVELY OR IN COMBINATION, FROM BRINES AND RESULTING
COMPOSITIONS THEREOF
Related Applications
[0001] This application claims the benefit of and priority to U.S.
Provisional Patent
Application Serial No. 61/780,308, filed on March 13, 2013, and U.S.
Provisional Patent
Application Serial No. 61/873,212, filed on September 3, 2013; also claims the
benefit of and
priority to U.S. Patent Application Serial No. 14/062,781, filed on October
24, 2013, U.S. Patent
Application Serial No. 14/188,293, filed on February 24, 2014, and U.S. Patent
Application
Serial No. 14/187,961, filed on February 24, 2014, all of which are
incorporated herein by
reference in their entireties.
Technical Field of the Invention
[0002] The invention generally relates to methods of removing silica and
iron from
brines, as well as removing potassium, rubidium, and/or cesium, selectively or
in combination,
from brines using tetrafluoroborates, as well as the treated brine
compositions that result
therefrom. Additionally, the invention relates to methods of producing
potassium chloride,
rubidium chloride, and/or cesium chlorides using ionic liquids and ion
exchange media, and
treated brine compositions that result therefrom.
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Background
[0003] A number of brine sources exist naturally. For instance, brine
sources include
brine deposits like the Salar de Atacama in Chile, Silver Peak Nevada, Salar
de Uyuni in Bolivia,
or the Salar de Hombre Muerte in Argentina. Other common brine sources are
geothermal,
oilfield, Smackover, and relict hydrothermal brines. These brines, however,
have not previously
been commercially exploited very well.
[0004] Geothermal brines are of particular interest for a variety of
reasons. First,
geothermal brines provide a source of power due to the fact that hot
geothermal pools are stored
at high pressure underground, which when released to atmospheric pressure, can
provide a flash-
steam. The flash-steam can be used, for example, to run a power plant.
Additionally,
geothermal brines contain useful elements, which can be recovered and utilized
for secondary
processes. In some geothermal waters and brines, binary processes can be used
to heat a second
fluid to provide steam for the generation of electricity without the flashing
of the geothermal
brine.
[0005] One problem associated with geothermal brines when utilized for the
production
of electricity results from scaling and deposition of solids. Silica and other
solids that are
dissolved within the geothermal brine precipitate out during all stages of
brine processing,
particularly during the cooling of a geothermal brine, and may eventually
result in fouling of the
injection wells or processing equipment.
[0006] It is known that geothermal brines can include various metal ions,
particularly
alkali and alkaline earth metals, as well as silica, iron, lead, silver, and
zinc, in varying
concentrations, depending upon the source of the brine. Recovery of these
metals is potentially
important to the chemical, pharmaceutical, and electronic industries.
Typically, the economical
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recovery of metals from natural brines, which may vary widely in composition,
depends not only
on the specific concentration of the desired metal, but also upon the
concentrations of interfering
ions, particularly silica, calcium, and magnesium, because the presence of the
interfering ions
will increase recovery costs, as additional steps must be taken to remove the
interfering ions.
Economical recovery also depends upon the commercial cost and availability of
the desired
metal already present in the relevant market.
[0007] Some of the desired metals that can be present in brines are
potassium, rubidium,
and cesium. Economically recoverable deposits of potassium are rare. The
potassium
concentration in the Salton Sea geothermal brine, however, is around 24,000
parts per million.
Potassium that has been extracted from brines can easily be converted into
potassium chloride,
which is useful in a variety of applications including agriculture, medicine,
food processing, and
as a standard measure of conductivity of ionic solutions in the chemical arts,
[0008] Currently, there are no existing potassium, rubidium, and cesium
removal
technologies that remove potassium, rubidium, and/or cesium, selectively or in
combination,
from geothermal brines generally. Therefore, it would be advantageous to
develop a method to
remove potassium, rubidium, and/or cesium, selectively or in combination, from
brines and
convert them into chlorides. Additionally, this technology presents an
economic advantage. For
example, the price of potassium chloride in the chemical market is relatively
low, so it would be
advantageous to develop a method of production of potassium chloride using
extracted
potassium from geothermal and other brines that is cost competitive.
[0009] Silica is known to deposit in piping as scale deposits, typically
as a result of the
cooling of a geothermal brine. Frequently, geothermal brines are near
saturation with respect to
the silica concentration and upon cooling; deposition occurs because of the
lower solubilities at
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lower temperatures. This is combined with the polymerization of silica and co-
precipitation with
other species, particularly metals. This is seen in geothermal power stations,
and is particularly
true for amorphous silica/silicates. Additionally, silica is a known problem
in reverse osmosis
desalination plants. Thus, removal of silica from low concentration brines may
help to eliminate
these scale deposits, and thus reduce costs and improve efficiency of
facilities that use and
process brines.
[0010]
Known methods for the removal of silica from geothermal brines include the use
of a geothermal brine clarifier for the removal and recovery of silica solids
that may be
precipitated with the use of various seed materials, or the use of compounds
that absorb silica,
such as magnesium oxide, magnesium hydroxide, or magnesium carbonate. In
addition to a less
than complete recovery of silicon from brines, prior methods also suffer in
that they typically
remove ions and compounds other than just silica and silicon containing
compounds.
[0011]
Geothermal brines can be flashed via several processes. There is the
conventional
method to produce steam for power. There have also been modifications to the
conventional
dual direct flash evaporation method to include multiple flash evaporation
stages.
[0012] One
modification to the conventional dual direct flash method is the crystallizer
reactor clarifier process. In
the crystallizer reactor clarifier process, a reactor clarifier
precipitates components that can cause scaling, such as iron rich amorphous
silica, and removes
suspended particles from the brines before injection into the flash process.
The process also
seeds the brine in the flash vessels to reduce scale formation. Thus, when
precipitation occurs it
is more likely that it will occur on the seed slurry than on the metal
surfaces of the flash
apparatus.
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[0013] There is also the pH modification process that differs from the
crystallizer reactor
clarifier process. In the pH modification process, compounds that cause
scaling are maintained
in solution. By lowering the pH of the brine solution, for example, as low as
3.0, compounds
that typically cause scaling on the flash apparatus are maintained in
solution. By lowering pH
and modifying pressures, the compounds are maintained in solution and scaling
is prevented or
reduced.
[0014] Thus, although conventional methods employed in the processing of
ores and
brines can remove some of the silica present in silica containing solutions
and brines, there exists
a need to develop methods that are selective for the removal of silica from
brines and other silica
containing solutions at high yields to produce treated compositions with
reduced silica
concentrations. Additionally, once certain components are removed, the
geothermal brine
compositions may be injected into a geothermal reservoir, such as into the
original reservoir.
Compositions for improving injectivity of such brines will improve the
efficiency of the process,
as improved injectivity will reduce the costs and time associated with
cleaning the equipment
used for injecting such brines and will also increase long-term permeable
flow. While current
practices at geothermal plants have focused on reduction of scaling on the
apparatus associated
with the flash process, there is still a need to reduce scaling after the
processing of the brine for
energy. The current practice at Salton Sea geothermal plants is to clean
injection wells on an
annual basis. This is a significant expense as there are typically multiple
wells (i.e., three wells)
to clean out. This is typically done by hydroblasting or acid treatment. After
a certain time,
typically three years, this is no longer effective and portions of wells must
be routed out to
remove blockages, which is expensive and time consuming. The routing process
can usually be
repeated twice before the wells have to be completely replaced. Thus,
compositions and
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processes that would reduce fouling and prolong the time between required
cleanings would be
of substantial benefit.
SUMMARY OF THE INVENTION
[0015] In some aspects, the invention provides methods for the extraction
of potassium,
rubidium and/or cesium from brines, selectively or in combination, as well as
compositions that
result therefrom. An exemplary method includes providing a brine solution that
includes
potassium, rubidium and/or cesium dissolved therein and then contacting the
brine solution with
a tetrafluoroborate compound to produce a tetrafluoroborate precipitate and an
aqueous layer.
The tetrafluoroborate precipitate containing potassium, rubidium and/or cesium
is then separated
from the aqueous layer.
[0016] In other aspects, the invention provides methods for preparing
potassium chloride,
rubidium chloride and/or cesium chloride from a tetrafluoroborate. An
exemplary method
includes contacting potassium tetrafluoroborate, rubidium tetrafluoroborate,
and/or cesium
tetrafluoroborate with an ionic liquid containing chloride anions to produce a
tetrafluoroborate/ionic liquid solution. The tetrafluoroborate/ionic liquid
solution is then heated
to produce a tetrafluoroborate layer and an aqueous layer. The
tetrafluoroborate layer is then
separated from the aqueous layer and the aqueous layer is evaporated to
produce potassium
chloride, rubidium chloride, and/or cesium chloride.
[0017] In another aspect, the invention provides methods for preparing a
chloride from a
solution containing potassium tetrafluoroborate, rubidium tetrafluoroborate,
and/or cesium
tetrafluoroborate. An exemplary method includes contacting potassium
tetrafluoroborate,
rubidium tetrafluoroborate, and/or cesium tetrafluoroborate with an aqueous
solution containing
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an ion-exchange media to produce a tetrafluoroborate/ion-exchange media
mixture. The
tetrafluoroborate/ion-exchange media mixture is then heated to produce an ion-
exchange media
layer and an aqueous layer. The aqueous layer is then separated from the ion-
exchange media
layer. The aqueous layer is then evaporated to produce a potassium, rubidium
and/or cesium
chloride.
[0018] In other aspects, the invention provides compositions that result
from the various
methods described herein. For instance, disclosed is a treated geothermal
brine composition
having a concentration of silica ranging from about 0 mg/kg to 15 mg/kg, a
concentration of iron
ranging from about 0 to about 10 mg/kg, and a concentration of potassium
ranging from about
300 mg/kg to about 8500 mg/kg. The compositions can be used for further
mineral extraction or
for injection into a geothermal reservoir.
[0019] In other aspects, the invention provides a treated geothermal brine
composition
having a concentration of silica less than about 10 mg/kg, the concentration
of iron less than
about 10 mg/kg, and the concentration of potassium less than about 4000 mg/kg.
[0020] In other aspects, the invention provides a treated geothermal brine
composition
having a concentration of silica less than about 5 mg/kg, the concentration of
iron less than about
mg/kg, and the concentration of potassium less than about 4000 mg/kg.
[0021] In other aspects, the invention provides a treated geothermal brine
composition
having a concentration of silica less than about 10 mg/kg, the concentration
of iron less than
about 10 mg/kg, and the concentration of potassium less than about 2000 mg/kg.
[0022] In other aspects, the invention provides a treated geothermal brine
composition
having a concentration of silica less than about 10 mg/kg, the concentration
of iron less than
about 10 mg/kg, and the concentration of potassium less than about 1000 mg/kg.
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[0023] In other aspects, the invention provides a treated geothermal brine
composition
having a concentration of silica less than about 5 mg/kg, the concentration of
iron less than about
mg/kg, and the concentration of potassium less than about 1000 mg/kg,
[0024] In other aspects, the invention provides a treated geothermal brine
composition
having a concentration of silica less than about 10 mg/kg, the concentration
of iron less than
about 10 mg/kg, and the concentration of potassium less than about 500 mg/kg.
[0025] In other aspects, the invention provides a treated geothermal brine
composition
having a concentration of silica less than about 5 mg/kg, the concentration of
iron less than about
10 mg/kg, and the concentration of potassium less than about 500 mg/kg.
[0026] In other aspects, the treated geothermal brine compositions
described herein have
a concentration of rubidium ranging from about 30 mg/kg to about 200 mg/kg.
[0027] In other aspects, the treated geothermal brine compositions
described herein are
Salton Sea geothermal brines. In other aspects, the treated geothermal brine
compositions
described herein are concentrated geothermal brines. In other aspects, the
treated geothermal
brine compositions described herein are used in a mineral extraction process.
In other aspects,
the treated geothermal brine compositions described herein are injected into
geothermal
reservoirs.
[0028] In other aspects, the invention provides a treated geothermal brine
composition
having a concentration of silica ranging from about 0 mg/kg to about 15 mg/kg,
a concentration
of iron ranging from about 0 mg/kg to about 10 mg/kg, and a concentration of
rubidium ranging
from about 30 mg/kg to about 200 mg/kg, In other aspects, this treated
geothermal brine
composition having a concentration of potassium of less than about 4000 mg/kg.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0029] So that the manner in which the features and benefits of the
invention, as well as
others which will become apparent, may be understood in more detail, a more
particular
description of the embodiments of the invention may be had by reference to the
embodiments
thereof which are illustrated in the appended drawings, which form a part of
this specification. It
is also to be noted, however, that the drawings illustrate only various
embodiments of the
invention and are therefore not to be considered limiting of the invention's
scope as it may
include other effective embodiments as well.
[0030] Figure 1 is an illustration of an apparatus for the removal of
silica from a silica
containing brine according to an embodiment of the present invention.
[0031] Figure 2 is an illustration of an apparatus for the removal of
silica from a silica
containing brine according to an embodiment of the present invention.
[0032] Figure 3 is an illustration of an apparatus for the removal of
silica from a silica
containing brine according to an embodiment of the present invention.
[0033] Figure 4 is an illustration of an apparatus for the removal of
silica from a silica
containing brine according to an embodiment of the present invention.
[0034] Figure 5 is an illustration of a process for the removal of silica
and iron from a
geothermal brine, followed by the subsequent removal of lithium according to
an embodiment of
the present invention.
[0035] Figure 6 is an illustration of a continuous process for the
management of silica
according to an embodiment of the present invention.
[0036] Figure 7 shows a process according to an embodiment using a pH
modification
process.
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[0037] Figure 8 shows a process according to an embodiment using a
crystallizer reactor
clarifier process.
[0038] Figure 9 shows a process according to an embodiment using a
crystallizer reactor
clarifier process.
[0039] Figure 10 is a flow diagram of selectively extracting potassium and
recovering
potassium chloride from brines using ionic liquids.
[0040] Figure 11 is a flow diagram of selectively extracting potassium and
recovering
potassium chloride from brines using ion exchange media.
[0041] Figure 12 is a graph showing the packed bed differential pressure
versus time for
an untreated brine.
[0042] Figure 13 is a graph showing the packed bed differential pressure
versus time for
an untreated brine.
[0043] Figure 14 is a graph showing the packed bed differential pressure
versus time for
an untreated brine.
[0044] Figure 15 is a graph showing the packed bed differential pressure
versus time for
a 50:50 blend brine.
[0045] Figure 16 is a graph showing the packed bed differential pressure
versus time for
a 50:50 blend brine,
[0046] Figure 17 is a graph showing the packed bed differential pressure
versus time for
a 50:50 blend brine.
[0047] Figure 18 is a graph showing the packed bed differential pressure
versus time for
a treated brine.
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[0048] Figure 19 is a graph showing the packed bed differential pressure
versus time for
a treated brine.
[0049] Figure 20 is a graph showing the packed bed differential pressure
versus time for
a treated brine.
[0050] Figure 21 shows the chemistry of an untreated brine before and
after packed bed
testing.
[0051] Figure 22 shows the chemistry of a treated brine before and after
packed bed
testing.
[0052] Figure 23 shows the chemistry of a treated brine before and after
packed bed
testing.
[0053] Figure 24 shows the chemistry of a 50:50 blend brine before and
after packed bed
testing.
[0054] Figure 25 shows the chemistry of a 50:50 blend brine before and
after packed bed
testing.
[0055] Figure 26 shows a SEM image from a packed bed test of untreated
brine.
[0056] Figure 27 shows a SEM image from a packed bed test of untreated
brine.
[0057] Figure 28 shows a SEM image from a packed bed test of treated
brine.
[0058] Figure 29 shows a SEM image from a packed bed test of treated
brine.
[0059] Figure 30 shows a SEM image from a packed bed test of a 50:50 blend
brine.
[0060] Figure 31 shows a SEM image from a packed bed test of a 50:50 blend
brine.
[0061] Figure 32 shows TSS by in-line pressure filter of untreated,
treated, and 50:50
blend brines.
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[0062] Figure 33 shows TSS by vacuum filtration of untreated, treated, and
50:50 blend
brines.
[0063] Figure 34 shows the weight gain of packed bed tubes after the
processing of
untreated, treated, and 50:50 blend brines.
[0064] Figure 35 shows the porosity change of packed bed tubes after the
processing of
untreated, treated, and 50:50 blend brines.
[0065] Figure 36 shows the concentration of iron and silica in an
exemplary treated brine
composition as a function of time during the silica management process.
[0066] Figure 37 shows the concentration of iron and silica in an
exemplary treated brine
composition as a function of time during the silica management process.
[0067] Figure 38 shows the concentration of iron and silica in an
exemplary treated brine
composition as a function of time during the silica management process.
[0068] Figures 39A and 39B show histograms of silica concentrations in an
exemplary
treated brine composition during the silica management process.
[0069] Figures 40A and 40B show histograms of iron concentrations in an
exemplary
treated brine composition during the silica management process.
[0070] Figures 41A and 41B show histograms of silica concentrations in an
exemplary
treated brine composition during the silica management process.
[0071] Figures 42A and 42B show histograms of iron concentrations in an
exemplary
treated brine composition during the silica management process.
DETAILED DESCRIPTION OF THE INVENTION
[0072] As used herein the following terms shall have the following
meanings.
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[0073] As used herein, "brine" or "brine solution" refers to any aqueous
solution that
contains a substantial amount of dissolved metals, such as alkali and/or
alkaline earth metal
salt(s) in water, wherein the concentration of salts can vary from trace
amounts up to the point of
saturation. Generally, brines suitable for the methods described herein are
aqueous solutions that
may include alkali or alkaline earth metal chlorides, bromides, sulfates,
hydroxides, nitrates, and
the like, as well as natural brines. In certain brines, other metals like
lead, manganese, and zinc
may be present. Exemplary elements present in the brines can include sodium,
potassium,
calcium, magnesium, lithium, strontium, barium, iron, boron, silica,
manganese, chlorine, zinc,
aluminum, antimony, chromium, cobalt, copper, lead, arsenic, mercury,
molybdenum, nickel,
silver, thallium, vanadium, and fluorine, although it is understood that other
elements and
compounds may also be present. Brines can be obtained from natural sources,
such as Chilean
brines or Salton Sea brines, geothermal brines, Smackover brines, sea water,
mineral brines (e.g.,
lithium chloride or potassium chloride brines), alkali metal salt brines, and
industrial brines, for
example, industrial brines recovered from ore leaching, mineral dressing, and
the like. The
present invention is also equally applicable to artificially prepared brine or
salt solutions. Brines
include continental brine deposits, geothermal brines, and waste or byproduct
streams from
industrial processes, Smackover brines, synthetic brines, and other brines
resulting from oil and
gas production. In some embodiments, the brines are brines from which energy
has already been
extracted. For instance, brines used herein include brines from which a power
plant has already
extracted energy through methods such as flashing.
[0074] The term "geothermal brine" refers to a saline solution that has
circulated through
the crustal rocks in areas of high heat flow and has become enriched in
substances leached from
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those rocks. Geothermal brines, such as those found in the Salton Sea
geothermal fields, can
include many dissolved metal salts, including alkali, alkaline earth, and
transition metal salts.
[0075] The term "Salton Sea brine" refers to geothermal brines obtained
from the
geothermal fields in San Diego County, Imperial County, and Riverside County,
in California,
USA.
[0076] The term "treated" in reference to a brine (e.g., "treated brine"
or "treated
geothermal brine") refers to brines that have been processed such that the
concentration of at
least one metal or elemental component has been reduced in the brine. For
instance, a brine in
which the concentration of silica and iron has been reduced is a treated
brine, also referred to as
reduced silica and iron brine.
[0077] The term "concentrated" in reference to a brine (e.g.,
"concentrated brine" or
"concentrated geothermal brine") refers to brines that have reduced water
content compared to
the original brine. The reduce water content brine may be subsequently diluted
post-
concentration to prevent salt precipitation. In some embodiments, concentrated
brines can result
from evaporative processes.
[0078] The term "synthetic brine" refers to a brine that has been prepared
such that it
simulates a naturally occurring brine. For instance, a synthetic brine can be
prepared in an
attempt to simulate the brine composition of various geothermal brine
reservoirs found in the
Salton Sea region (Calif., U.S.). Generally, the synthetic brine simulating a
Salton Sea
geothermal brine has a composition of about 280 ppm lithium, 63,000 ppm
sodium, 20,000 ppm
potassium, 33,000 ppm calcium, 130 ppm strontium, 700 ppm zinc, 1700 ppm iron,
450 ppm
boron, 50 ppm sulfate, 3 ppm fluoride, 450 ppm ammonium ion, 180 ppm barium,
160 ppm
silica (reported as Si02), and 180,000 ppm chloride. Additional elements, such
as manganese,
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aluminum, antimony, bromine, chromium, cobalt, copper, fluorine, lead,
arsenic, mercury,
molybdenum, nickel, silver, thallium, and vanadium, may also be present in the
brine.
[0079] The term "lithium salts" can include lithium nitrates, lithium
sulfates, lithium
bicarbonate, lithium halides (particularly chlorides and bromides), and acid
salts. For example,
the Salton Sea brines have lithium chlorides.
[0080] As used herein, precipitates of iron oxides include iron oxides,
iron hydroxides,
iron oxide-hydroxides and iron oxyhydroxides.
[0081] Exemplary embodiments of the present invention include treated
geothermal brine
compositions. In certain embodiments, the composition contains a treated
geothermal brine
having a concentration of silica ranging from 0 to 80 mg/kg and a
concentration of iron ranging
from 0 to 800 mg/kg. In certain embodiments, the composition contains a
treated geothermal
brine having a concentration of silica ranging from 0 to 30 mg/kg and a
concentration of iron
ranging from 0 to 300 mg/kg. In another embodiment, the concentration of
silica is less than
about 5 mg/kg, and the concentration of iron is less than about 5 mg/kg in the
treated geothermal
brine composition. In another embodiment, the concentration of silica is less
than about 5
mg/kg, and the iron concentration is less than about 10 mg/kg in the treated
geothermal brine
composition. In another embodiment, the concentration of silica is less than
about 5 mg/kg, and
the iron concentration is less than about 100 mg/kg. In another embodiment,
the concentration
of silica is less than about 10 mg/kg, and the iron concentration is less than
about 100 mg/kg. In
another embodiment, the concentration of silica is less than about 20 mg/kg,
and the iron
concentration is less than about 100 mg/kg, In another embodiment, the
concentration of silica is
less than about 10 mg/kg, and the iron concentration is less than about 200
mg/kg, In another
embodiment, the concentration of silica is less than about 20 mg/kg, and the
iron concentration is
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less than about 200 mg/kg. In another embodiment, the concentration of silica
is less than about
30 mg/kg, and the iron concentration is less than about 300 mg/kg. In another
embodiment, the
concentration of silica is less than about 40 mg/kg, and the iron
concentration is less than about
300 mg/kg. In another embodiment, the concentration of silica is less than
about 40 mg/kg, and
the iron concentration is less than about 200 mg/kg. In another embodiment,
the concentration
of silica is less than about 60 mg/kg, and the iron concentration is less than
about 300 mg/kg. In
another embodiment, the concentration of silica is less than about 70 mg/kg,
and the iron
concentration is less than about 300 mg/kg.
[0082] In another embodiment, the treated geothermal brine compositions
described
herein have a concentration of arsenic ranging from 0 to 7 mg/kg. In another
embodiment, the
treated geothermal brine compositions described herein have a concentration of
barium ranging
from 0 to 200 mg/kg. In another embodiment, the treated geothermal brine
compositions
described herein have a concentration of lead ranging from 0 to 100 mg/kg. In
another
embodiment, the treated geothermal brine compositions described herein are
Salton Sea brines.
In certain embodiments, the treated geothermal brine is a concentrated
geothermal brine.
[0083] Also disclosed are exemplary embodiments of methods of using the
treated
geothermal brine compositions described herein. For example without
limitations, a treated
geothermal brine can be supplied to a process for mineral extraction. For
example without
limitations, the minerals that can be extracted from the treated geothermal
brine include lithium,
manganese, potassium, rubidium, cesium, phosphates, zinc, and lead. Also
disclosed are
exemplary embodiments of methods of using the treated geothermal brine
compositions
described herein that include injecting the treated geothermal brine
compositions into a
geothermal reservoir.
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[0084] Also disclosed are exemplary embodiments of treated Salton Sea
geothermal
brine compositions containing a concentration of silica ranging from 0 to 80
mg/kg and a
concentration of iron ranging from 0 to 800 mg/kg. Also disclosed are
exemplary embodiments
of treated Salton Sea geothermal brine compositions containing a concentration
of silica ranging
from 0 to 30 mg/kg and a concentration of iron ranging from 0 to 300 mg/kg. In
another
embodiment, the treated geothermal brine compositions described herein have a
concentration of
arsenic ranging from 0 to 7 mg/kg. In another embodiment, the treated
geothermal brine
compositions described herein have a concentration of barium ranging from 0 to
200 mg/kg. In
another embodiment, the treated geothermal brine compositions described herein
have a
concentration of lead ranging from 0 to 100 mg/kg. In another embodiment, the
treated
geothermal brine compositions described herein have a concentration of arsenic
less than about 7
mg/kg, barium less than about 200 mg/kg, and lead less than about 100 mg/kg.
In another
embodiment, the invention provides a geothermal brine composition having a pH
of about 4.0 to
about 6.0 that has less than 20 ppm by weight of silica, less than 20 ppm by
weight of iron, and
further wherein the geothermal brine composition has total suspended solids
("TSS") of less than
ppm.
[0085] In some embodiments, the treated geothermal brine has a
concentration of silica
that ranges from 0 mg/kg to 30 mg/kg. In some embodiments, the treated
geothermal brine has a
concentration of silica that is less than about 25 mg/kg. In some embodiments,
the treated
geothermal brine has a concentration of silica that is less than about 20
mg/kg. In some
embodiments, the treated geothermal brine has a concentration of silica that
is less than about 15
mg/kg. In some embodiments, the treated geothermal brine has a concentration
of silica that is
less than about 12 mg/kg. In some embodiments, the treated geothermal brine
has a
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concentration of silica that is less than about 10 mg/kg. In some embodiments,
the treated
geothermal brine has a concentration of silica that is less than about 8
mg/kg. In some
embodiments, the treated geothermal brine has a concentration of silica that
is less than about 5
mg/kg. In some embodiments, the treated geothermal brine has a concentration
of silica that is
less than about 1 mg/kg. Exemplary embodiments of the present invention
include treated
geothermal brine compositions with reduced concentrations of silica. In an
embodiment, the
concentration of silica ranges from 0 to 5 mg/kg. In another embodiment, the
concentration of
silica ranges from 0 to 10 mg/kg. In another embodiment, the concentration of
silica ranges from
0 to 15 mg/kg. In another embodiment, the concentration of silica ranges from
0 to 20 mg/kg. In
another embodiment, the concentration of silica ranges from 0 to 25 mg/kg. In
another
embodiment, the concentration of silica ranges from 0 to 30 mg/kg. In another
embodiment, the
concentration of silica ranges from 0 to 35 mg/kg, In another embodiment, the
concentration of
silica ranges from 0 to 40 mg/kg. In another embodiment, the concentration of
silica ranges from
0 to 45 mg/kg. In another embodiment, the concentration of silica ranges from
0 to 50 mg/kg. In
another embodiment, the concentration of silica ranges from 0 to 55 mg/kg. In
another
embodiment, the concentration of silica ranges from 0 to 60 mg/kg. In another
embodiment, the
concentration of silica ranges from 0 to 65 mg/kg, In another embodiment, the
concentration of
silica ranges from 0 to 70 mg/kg. In another embodiment, the concentration of
silica ranges from
0 to 75 mg/kg. In another embodiment, the concentration of silica ranges from
0 to 80 mg/kg. In
another embodiment, the concentration of silica ranges from 0 to 85 mg/kg. In
another
embodiment, the concentration of silica ranges from 0 to 90 mg/kg, In another
embodiment, the
concentration of silica ranges from 0 to 95 mg/kg, In another embodiment, the
concentration of
silica ranges from 0 to 100 mg/kg.
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[0086] In some embodiments, the treated geothermal brine has a
concentration of iron
that ranges from 0 mg/kg to 300 mg/kg. In some embodiments, the treated
geothermal brine has
a concentration of iron that ranges from 0 mg/kg to 250 mg/kg. In some
embodiments, the
treated geothermal brine has a concentration of iron that ranges from 0 mg/kg
to 200 mg/kg. In
some embodiments, the treated geothermal brine has a concentration of iron
that ranges from 0
mg/kg to 150 mg/kg. In some embodiments, the treated geothermal brine has a
concentration of
iron that ranges from 0 mg/kg to 100 mg/kg. In some embodiments, the treated
geothermal brine
has a concentration of iron that ranges from 0 mg/kg to 50 mg/kg. In some
embodiments, the
treated geothermal brine has a concentration of iron that ranges from 0 mg/kg
to 25 mg/kg. In
some embodiments, the treated geothermal brine has a concentration of iron
that ranges from 0
mg/kg to 20 mg/kg. In some embodiments, the treated geothermal brine has a
concentration of
iron that ranges from 0 mg/kg to 10 mg/kg. In some embodiments, the treated
geothermal brine
has a concentration of iron that is less than about 300 mg/kg. In some
embodiments, the treated
geothermal brine has a concentration of iron that is less than about 250
mg/kg. In some
embodiments, the treated geothermal brine has a concentration of iron that is
less than about 200
mg/kg. In some embodiments, the treated geothermal brine has a concentration
of iron that is
less than about 100 mg/kg. In some embodiments, the treated geothermal brine
has a
concentration of iron that is less than about 75 mg/kg. In some embodiments,
the treated
geothermal brine has a concentration of iron that is less than about 50 mg/kg.
In some
embodiments, the treated geothermal brine has a concentration of iron that is
less than about 40
mg/kg, In some embodiments, the treated geothermal brine has a concentration
of iron that is
less than about 30 mg/kg. In some embodiments, the treated geothermal brine
has a
concentration of iron that is less than about 20 mg/kg. In some embodiments,
the treated
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geothermal brine has a concentration of iron that is less than about 10 mg/kg.
In some
embodiments, the treated geothermal brine has a concentration of iron that is
less than about 9
mg/kg. In some embodiments, the treated geothermal brine has a concentration
of iron that is less
than about 8 mg/kg. In some embodiments, the treated geothermal brine has a
concentration of
iron that is less than about 7 mg/kg. In some embodiments, the treated
geothermal brine has a
concentration of iron that is less than about 6 mg/kg. In some embodiments,
the treated
geothermal brine has a concentration of iron that is less than about 5 mg/kg.
In some
embodiments, the treated geothermal brine has a concentration of iron that is
less than about 4
mg/kg. In some embodiments, the treated geothermal brine has a concentration
of iron that is
less than about 3 mg/kg. In some embodiments, the treated geothermal brine has
a concentration
of iron that is less than about 2 mg/kg. In some embodiments, the treated
geothermal brine has a
concentration of iron that is less than about 1 mg/kg,
[0087] In some aspects, the invention provides a method for producing
geothermal power
using geothermal brines and producing a reduced silica and iron brine having
improved
injectivity. The method includes flashing a geothermal brine containing silica
and iron to
generate electrical power. This flashing produces precipitated silica and a
reduced silica brine.
The precipitated silica is then separated from the reduced silica brine and
returned to the flashing
the geothermal brine step. The reduced silica brine is then exposed to air to
facilitate oxidation
and to produce precipitated silica and iron solids, and a reduced silica and
iron brine. The silica
and iron solids are then separated from the reduced silica and iron brine and
optionally, at least a
portion of the silica and iron solids are returned to the exposing the reduced
silica brine to air
step. The reduced silica and iron treated brine is then injected into a
separate injection well, but
the same reservoir, such as a geothermal reservoir, wherein the reduced silica
and iron brine has
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improved injectivity as compared to the reduced silica brine. In further
embodiments, the treated
brine having reduced silica, and optionally iron, concentration is further
treated to remove
additional components, such as lithium, potassium, rubidium, and/or cesium,
selectively or in
combination.
[0088] In geothermal power plants, heat may be recovered from a geothermal
brine
through the use of one or more flash tanks in a process known as flashing. Any
method of
flashing may be used in the present invention. In some embodiments, the
crystallizer reactor
clarifier process is used. In other embodiments, the pH modification process
is used. In some
embodiments, the brine will be treated after it has left the first clarifier
of a two clarifier
processing system. In some embodiments, the brine will be treated after it has
been completely
processed by the clarifier system.
[0089] In some embodiments, the reduced silica and iron brine has a
concentration of
silica that ranges from 0 mg/kg to 30 mg/kg. In some embodiments, the reduced
silica and iron
brine has a concentration of silica that is less than 5 mg/kg. In some
embodiments, the reduced
silica and iron brine has a concentration of silica that is less than 10
mg/kg. In some
embodiments, the reduced silica and iron brine has a concentration of silica
that is less than 20
mg/kg. In some embodiments, the reduced silica and iron brine has a
concentration of silica that
is less than 30 mg/kg.
[0090] In some embodiments, the reduced silica and iron brine has less
than 20 ppm of
silica. In some embodiments, the reduced silica and iron brine has less than
20 ppm of iron. In
further embodiments, the reduced silica and iron brine has less than 20 ppm of
silica and less
than 20 ppm of iron. In some embodiments, the reduced silica and iron brine
has less than 15
ppm of silica. In some embodiments, the reduced silica and iron brine has less
than 15 ppm of
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iron. In further embodiments, the reduced silica and iron brine has less than
15 ppm of silica and
less than 15 ppm of iron. In some embodiments, the reduced silica and iron
brine has less than
ppm of silica. In some embodiments, the reduced silica and iron brine has less
than 10 ppm
of iron. In further embodiments, the reduced silica and iron brine has less
than 10 ppm of silica
and less than 10 ppm of iron. In some embodiments, the reduced silica and iron
brine has less
than 5 ppm of silica. In further embodiments, the reduced silica and iron
brine has less than 5
ppm of silica and less than 10 ppm of iron.
[0091] In further embodiments of the process, other components may be
removed from
the brine before the brine is injected into an underground region, such as a
reservoir. In one
embodiment, lithium is removed from the geothermal brine before the reduced
silica and iron
brine is injected into the underground region. In another embodiment,
manganese is removed
from the reduced silica and iron brine before it is injected into the
underground region. In
another embodiment, zinc is removed from the reduced silica and iron brine
before it is injected
into the underground region. In another embodiment, potassium is removed from
the reduced
silica and iron brine before it is injected into the underground region. In
another embodiment,
rubidium is removed from the reduced silica and iron brine before it is
injected into the
underground region. In another embodiment, cesium is removed from the reduced
silica and iron
brine before it is injected into the underground region. In further
embodiments, any combination
of these components is removed from the reduced silica and iron brine before
it is injected into
the underground region.
[0092] In some embodiments, the reduced silica and iron brine has a
concentration of
silica ranging from about 0 mg/kg to about 15 mg/kg, a concentration of iron
ranging from about
0 mg/kg to about 10 mg/kg, and a concentration of potassium ranging from about
300 mg/kg to
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about 8500 mg/kg. In other embodiments, the concentration of silica is less
than about 10
mg/kg, the concentration of iron of less than about 10 mg/kg, and the
concentration of potassium
is less than about 4000 mg/kg.
[0093] In other embodiments, the concentration of silica is less than
about 10 mg/kg, the
concentration of iron is less than about 10 mg/kg, and the concentration of
potassium is less than
about 4000 mg/kg. In other embodiments, the concentration of silica is less
than about 5 mg/kg,
the concentration of iron is less than about 10 mg/kg, and the concentration
of potassium is less
than about 4000 mg/kg. In other embodiments, the concentration of silica is
less than about 10
mg/kg, the concentration of iron is less than about 10 mg/kg, and the
concentration of potassium
is less than about 1000 mg/kg. In other embodiments, the a concentration of
silica is less than
about 10 mg/kg, the concentration of iron is less than about 5 mg/kg, and the
concentration of
potassium is less than about 1000 mg/kg. In other embodiments, the a
concentration of silica is
less than about 5 mg/kg, the concentration of iron is less than about 10
mg/kg, and the
concentration of potassium is less than about 1000 mg/kg. In other
embodiments, the a
concentration of silica is less than about 20 mg/kg, the concentration of iron
is less than about 10
mg/kg, and the concentration of potassium is less than about 1000 mg/kg. In
other embodiments,
the concentration of silica is less than about 10 mg/kg, the concentration of
iron is less than about
mg/kg, and the concentration of potassium is less than about 500 mg/kg. In
other
embodiments, the concentration of silica is less than about 5 mg/kg, the
concentration of iron is
less than about 10 mg/kg, and the concentration of potassium is less than
about 500 mg/kg.
[0094] In further embodiments, the treated geothermal brine composition
has a
concentration of silica ranging from about 0 mg/kg to about 15 mg/kg. In other
embodiments,
the treated geothermal brine composition has a silica concentration of less
than about 0 mg/kg.
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In other embodiments, the treated geothermal brine composition has a silica
concentration of less
than about 5 mg/kg. In other embodiments, the treated geothermal brine
composition has a silica
concentration of less than about 10 mg/kg. In other embodiments, the treated
geothermal brine
composition has a silica concentration of less than about 15 mg/kg,
[0095] In further embodiments, the geothermal brine has a concentration of
iron ranging
from about 0 mg/kg to about 10 mg/kg. In other embodiments, the treated
geothermal brine
composition has an iron concentration of about 0 mg/kg. In other embodiments,
the treated
geothermal brine composition has an iron concentration of less than about 5
mg/kg. In other
embodiments, the treated geothermal brine composition has an iron
concentration of about 10
mg/kg.
[0096] In further embodiments, the geothermal brine has a concentration of
potassium
ranging from about 300 mg/kg to about 8500 mg/kg. In other embodiments, the
treated
geothermal brine composition has a potassium concentration of less than about
300 mg/kg. In
other embodiments, the treated geothermal brine composition has a potassium
concentration of
less than about 500 mg/kg. In other embodiments, the treated geothermal brine
composition has
a potassium concentration of less than about 1000 mg/kg. In other embodiments,
the treated
geothermal brine composition has a potassium concentration of less than about
4000 mg/kg. In
other embodiments, the treated geothermal brine composition has a potassium
concentration of
less than about 8500 mg/kg.
[0097] In other embodiments, the treated geothermal brine has a
concentration of
rubidium ranging from about 30 mg/kg to about 200 mg/kg, In other embodiments,
the treated
geothermal brine composition has a rubidium concentration of less than about
200 mg/kg. In
other embodiments, the treated geothermal brine composition has a rubidium
concentration of
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less than about 150 mg/kg. In other embodiments, the treated geothermal brine
composition has
a rubidium concentration of less than about 100 mg/kg. In other embodiments,
the treated
geothermal brine composition has a rubidium concentration of less than about
50 mg/kg.
[0098] In further embodiments, the treated geothermal brine has a
concentration of silica
ranging from about 0 mg/kg to about 15 mg/kg, a concentration of iron ranging
from about 0
mg/kg to about 10 mg/kg, and a concentration of rubidium ranging from about 30
mg/kg to about
200 mg/kg.
[0099] Embodiments of the present invention yield treated brines with
improved
injectivity over untreated brines solutions. Injectivity is defined in terms
of change in pressure
over a given flow rate over time. Improvements in injectivity indicate that a
brine is able to flow
more freely over time, and thus will lead to less required cleanings of a
well. One way to assess
improved injectivity is through packed bed testing.
[00100] In another aspect, the invention provides a method for preventing
silica scale in
geothermal brine injection wells and improving injectivity of a treated
aqueous brine solution by
selectively removing silica and iron from a geothermal brine solution. The
method includes
obtaining a geothermal brine solution comprising silica and iron from a
geothermal reservoir.
The geothermal brine solution is then supplied to a silica management process
to produce a
reduced silica geothermal brine solution relative to the geothermal brine
solution. The reduced
silica geothermal brine solution is then supplied to an iron removal process
to produce a treated
aqueous brine solution relative to the reduced silica geothermal brine
solution. The treated
aqueous brine product solution is then injected into the geothermal reservoir.
The treated brine
also has a packed bed test result that yields an operation time at least 50%
greater than an
operation time of the geothermal brine solution.
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[00101] In some embodiments, the step of supplying the geothermal brine
solution to a
silica management process and the step of supplying the reduced silica
geothermal brine solution
to an iron removal process are the same step. In other embodiments, the step
of supplying the
geothermal brine solution to a silica management process and the step of
supplying the reduced
silica geothermal brine solution to an iron removal process are different
steps.
[00102] In further embodiments, the treated brine is further treated to
remove lithium,
potassium, rubidium, and/or cesium. In some embodiments, the process for
removing lithium,
potassium, rubidium, and/or cesium occurs after the geothermal brine is
supplied to a silica
management step. In some embodiments, the process for removing lithium,
potassium,
rubidium, and/or cesium occurs after the geothermal brine is supplied to a
silica management
step. In some embodiments, the process for removing potassium, rubidium,
and/or cesium
occurs after the geothermal brine is supplied to both a silica management step
and an iron
removal process.
[00103] In some embodiments, the treated brine has a packed bed test result
that yields an
operation time at least 100% greater than an operation time of the geothermal
brine solution. In
some embodiments, the treated brine has a packed bed test result that yields
an operation time at
least 200% greater than an operation time of the geothermal brine solution. In
some
embodiments, the treated brine has a packed bed test result that yields an
operation time at least
300% greater than an operation time of the geothermal brine solution.
[00104] In another aspect, the invention provides a method for preventing
silica scale in
geothermal brine injection wells and improving injectivity of a treated brine
by selectively
removing silica and iron from a geothermal brine solution. The method includes
obtaining a
geothermal brine solution comprising silica and iron from a geothermal
reservoir. The
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geothermal brine solution is supplied to a silica management process to
produce a reduced silica
geothermal brine solution relative to the geothermal brine solution. The
reduced silica
geothermal brine solution is supplied to an iron removal process to produce a
treated brine. The
treated brine is then injected into the geothermal reservoir. Additionally,
the treated brine has a
TSS of less than about 60 ppm.
[00105] In some embodiments, the treated brine has a TSS of less than about
55 ppm. In
some embodiments, the treated brine has a TSS of less than about 50 ppm. In
some
embodiments, the treated brine has a TSS of less than about 45 ppm. In some
embodiments, the
treated brine has a TSS of less than about 40 ppm. In some embodiments, the
treated brine has a
TSS of less than about 35 ppm.
[00106] In some embodiments, the treated brine has a TSS of less than about
30 ppm. In
some embodiments, the treated brine has a TSS of less than about 25 ppm. In
some
embodiments, the treated brine has a TSS of less than about 20 ppm. In some
embodiments, the
treated brine has a TSS of less than about 15 ppm. In some embodiments, the
treated brine has a
TSS of less than about 10 ppm.
[00107] In another aspect, the invention provides a method for generating
energy from a
geothermal brine solution and improving injectivity of a treated aqueous brine
solution by
selectively removing silica and iron from a geothermal brine solution used for
energy production.
The method includes obtaining a geothermal brine solution comprising silica
and iron from a
geothermal reservoir. The geothermal brine solution is then flashed to produce
and recover heat
and energy therefrom and to produce a spent geothermal brine solution. The
spent geothermal
brine solution is then supplied to a silica management process to produce a
reduced silica
geothermal brine solution relative to the spent geothermal brine solution. The
reduced silica
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geothermal brine solution is then supplied to an iron removal process to
produce a treated
aqueous brine solution relative to the reduced silica geothermal brine
solution. The treated
aqueous brine product solution is then injected into the geothermal reservoir.
Additionally, the
treated brine has a TSS of less than about 60 ppm.
[00108] In some embodiments, the step of supplying the geothermal brine
solution to a
silica management process and the step of supplying the reduced silica
geothermal brine solution
to an iron removal process are the same step. In other embodiments, the step
of supplying the
geothermal brine solution to a silica management process and the step of
supplying the reduced
silica geothermal brine solution to an iron removal process are different
steps.
[00109] In further embodiments, the treated brine is further treated to
remove lithium,
potassium, rubidium, and/or cesium. In some embodiments, the process for
removing lithium,
potassium, rubidium, and/or cesium occurs after the geothermal brine is
supplied to a silica
management step. In some embodiments, the process for removing lithium,
potassium,
rubidium, and/or cesium occurs after the geothermal brine is supplied to a
silica management
step. In some embodiments, the process for removing potassium, rubidium,
and/or cesium
occurs after the geothermal brine is supplied to both a silica management step
and an iron
removal process.
[00110] In some embodiments, the treated brine has a TSS of less than about
55 ppm. In
some embodiments, the treated brine has a TSS of less than about 50 ppm. In
some
embodiments, the treated brine has a TSS of less than about 45 ppm. In some
embodiments, the
treated brine has a TSS of less than about 40 ppm. In some embodiments, the
treated brine has a
TSS of less than about 35 ppm. In some embodiments, the treated brine has a
TSS of less than
about 30 ppm. In some embodiments, the treated brine has a TSS of less than
about 25 ppm. In
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some embodiments, the treated brine has a TSS of less than about 20 ppm. In
some
embodiments, the treated brine has a TSS of less than about 15 ppm. In some
embodiments, the
treated brine has a TSS of less than about 10 ppm.
[00111] In another aspect, the invention provides a treated geothermal
brine composition
having a pH of about 4.0 to about 6.0 that has less than about 20 ppm by
weight of silica, less
than about 20 ppm by weight of iron, and further wherein the treated
geothermal brine
composition has TSS of less than about 30 ppm. In some embodiments, the
treated geothermal
brine composition has a TSS of less than about 25 ppm. In some embodiments,
the treated
geothermal brine composition has a TSS of less than about 20 ppm. In some
embodiments, the
treated geothermal brine composition has a TSS of less than about 15 ppm. In
some
embodiments, the treated geothermal brine composition has a TSS of less than
about 10 ppm.
Packed bed testing
[00112] The objective of packed bed testing is to simulate injectivity of
brine solutions.
This entails pumping a brine solution through a material that simulates the
region where the
brine is to be injected. Incompatibility is primarily manifested as a shorter
run time to reach a
1000 maximum psi, due to generation of suspended solids and scales that cause
an increase in
pressure across the packed bed.
[00113] In general, the packed beds should be selected such that granulated
materials,
such as rock chips, may be packed within the inner region, and such that the
flow of brine may
be allowed continuously over the granulated materials under pressures up to at
least 1000 psig
and temperatures ranging from about 80 to 110 C. The primary response factor
for the packed
bed testing is the time period, or operation time, that the brine is able to
be pumped through the
packed bed, until scaling and blockage cause the head pressure to reach 1000
psi. Long-term
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permeable flow is desired, so the longer the packed bed unit runs, the better
the potential
outcome of the brine for injecting into a reservoir. In some embodiments, the
brine can be
injected into the reservoir from which it was obtained (also sometimes
referred to as
"reinjecting"). In some embodiments, the brine can be injected into a
different reservoir than the
one from which it was obtained.
[00114] In some embodiments, the beds are packed with screened drilling
rock chips from
the well hydrothermal zone (e.g., from the well into which the brine will be
injected). In some
embodiments, the rock chips may be primarily of two types: 1) hydrothermally-
crystallized fine-
grained granitic material composed of quartz and feldspar, and 2) silica-
bonded meta-siltstone.
In some embodiments, the packed beds may be a combination of the two types of
rock chips. In
other embodiments, the packed beds may be primarily of a single type of rock
chip. In some
embodiments, the packing material is uniform in size.
[00115] In order to yield appropriate comparisons, the same type of
material and packing
should be used in both packed bed tests (i.e., for the treated and untreated
brine) for the
comparative testing. The packed beds will have brine pumped through them until
the pressure
reaches about 1000 psig at 1 LPM brine flow. Thus, the materials for the
packed beds should be
selected from materials that will allow for such pressures and temperatures
ranging from about
80 to 110 C. By comparing the packed bed tests of a treated and an untreated
brine, one can
assess whether the treatment process used has improved injectivity and reduced
scaling. If a
treated brine has a longer operation time, or the time to reach 1000 psi, then
the treated brine will
have improved injectivity. In some embodiments, the treated brine has an
operation time at least
about 50% greater than the operation time of the untreated brine solution. In
some embodiments,
the treated brine has an operation time at least about 100% greater than the
operation time of the
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untreated brine solution. In some embodiments, the treated brine has an
operation time at least
about 150% greater than the operation time of the untreated brine solution. In
some
embodiments, the treated brine has an operation time at least about 200%
greater than the
operation time of the untreated brine solution. In some embodiments, the
treated brine has an
operation time at least about 250% greater than the operation time of the
untreated brine solution.
In some embodiments, the treated brine has an operation time at least about
300% greater than
the operation time of the untreated brine solution.
[00116] TSS is also an important parameter for assessing brines. TSS can
indicate
whether brines may have minerals that could precipitate solids and generate
suspended solids,
contributing to scaling and plugging. In some embodiments, the TSS of the
treated brine will be
less than about 60 ppm. In some embodiments, the TSS of the treated brine will
be less than
about 30 ppm. In some embodiments, the TSS of the treated brine will be less
than about 25
ppm. In some embodiments, the TSS of the treated brine will be less than about
20 ppm. In
some embodiments, the TSS of the treated brine will be less than about 15 ppm.
In some
embodiments, the TSS of the treated brine will be less than about 10 ppm.
[00117] Broadly, also described herein are methods for the selective
removal of silica and
silicates (typically reported as silicon dioxide (Si02)) from solution.
Methods for the removal of
silica are commonly known as silica management. As used herein, the selective
removal of
silica generally refers to methods to facilitate the removal of silica from
solutions, such as
geothermal brines, Smackover brines, synthetic brines, and other brines
resulting from oil and
gas production without the simultaneous removal of other ions. In certain
embodiments, silica is
preferably selectively removed such that the silica can be further refined or
supplied to an
associated process, without the need for extensive purification thereof. In
some embodiments,
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the brines are brines from which energy has already been extracted. For
instance, brines from
which a power plant has already extracted energy through methods such as
flashing. Broadly
described, in certain embodiments, the methods described herein employ
chemical means for the
separation of silica. The removal of silica from solutions, such as geothermal
brines, can
prevent, reduce or delay scale formation as silica present in brines can form
scale deposits. It is
known that scale deposit formation is a common problem with geothermal brines
and therefore
the methods described herein for the selective removal of silica can be
utilized to prevent scale
formation in geothermal power equipment and also improve injectivity of
treated brines in
reservoirs. Additionally, the removal of silica from solutions, such as
geothermal brines, also
facilitates the subsequent recovery of various metals from the solution, such
as lithium,
manganese, zinc, as well as boron, cesium, potassium, rubidium, and silver. It
is understood that
the recovery of valuable metals from a geothermal brine depends upon the
concentration of a
metal in the brine, and the economics of the recovery thereof, which can vary
widely among
brines. The prevention, reduction, and/or delay of scale production in
geothermal wells and
geothermal power plant equipment can result in increased geothermal energy
production by
improving the equipment lifetime and reducing the frequency of equipment
maintenance, as well
as increase or prolong well permeability.
[00118] Typically, in geothermal power plants, heat is recovered from a
geothermal brine
through the use of one or more flash tanks. In certain embodiments, a silica
precipitate seed can
be supplied to the geothermal brine prior to the brine being supplied to the
flash tanks to remove
at least a portion of the silica present. In other embodiments, the post-flash
geothermal brine
from a geothermal plant is then fed through the silica management and iron
removal steps. In
certain embodiments, the silica precipitate seed can result in the removal of
up to 25% of the
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silica present in the brine, alternatively up to about 40% of the silica
present in the brine,
alternatively up to about 50% of the silica present in the brine,
alternatively up to about 60% of
the silica present in the brine, or alternatively greater than about 60% of
the silica present in the
brine. In certain embodiments, the silica precipitate seed can reduce the
silica concentration of
the brine to less than about 200 ppm, alternatively less than about 175 ppm,
alternatively less
than about 160 ppm, alternatively less than about 145 ppm.
[00119] The geothermal brine supplied to the flash tanks is typically
supplied at a
temperature of at least about 250 C, alternatively at least about 300 C. After
flashing of the
geothermal brine and the recovery of significant heat and energy therefrom,
the geothermal brine
can be supplied to a silica management process (as further described herein)
for the removal of
additional silica. As noted previously, the removal of silica can prevent,
reduce, or delay the
buildup of scale, thereby increasing the lifetime of the equipment and
improving injectivity of
the treated brine. Typically, the temperature of the brine has been reduced to
less than about
150 C before it is supplied to one of the silica removal processes described
herein, alternatively
less than about 125 C, alternatively less than about 120 C, alternatively less
than about 115 C,
alternatively less than about 110 C, alternatively less than about 105 C, or
alternatively less than
about 100 C.
[00120] While the removal of silica from geothermal brines in geothermal
power plants is
useful for reducing scale buildup in the power plant, supplying the brine to
one or more of the
silica removal processes described herein also has the effect of reducing the
injection
temperature of the brine to less than about 100 C, alternatively less than
about 90 C, alternatively
less than about 80 C, alternatively less than about 75 C.
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[00121] As described herein, the selective silica recovery of the present
invention can
include the use of activated alumina, aluminum salts (such as A1C13), or iron
(III) oxyhydroxides.
[00122] In certain embodiments of the present invention, the brine or
silica containing
solution can first be filtered or treated to remove solids present prior to
the selective recovery and
removal of silica.
[00123] Simulated brines can be prepared to mimic naturally occurring
brines. As
described herein, a simulated brine can be prepared to mimic the brine
composition of various
test wells found in the Salton Sea geothermal fields (Calif., U.S.).
Generally, the simulated brine
is an aqueous solution having a composition of about 260 ppm lithium, 63,000
ppm sodium,
20,100 ppm potassium, 33,000 ppm calcium, 130 ppm strontium, 700 ppm zinc,
1700 ppm iron,
450 ppm boron, 54 ppm sulfate, 3 ppm fluoride, 450 ppm ammonium ion, 180 ppm
barium, 160
ppm silicon dioxide, and 181,000 ppm chloride. Additional elements, such as
manganese,
aluminum, antimony, chromium, cobalt, copper, lead, arsenic, mercury,
molybdenum, nickel,
silver, thallium, and vanadium, may also be present in the brine. It is
understood, however, that
the methods described herein can be used to remove silica from brines and
other silica containing
solutions having silica concentrations greater than about 160 ppm. In certain
embodiments, the
brine or silica containing solution can have a silica concentration of greater
than about 400 ppm,
greater than about 500 ppm, or greater than about 600 ppm. In certain
instances, geothermal
brines can have silica concentrations of between about 400 and 600 ppm.
Selective Silica Recovery by Precipitation with Aluminum Salts
[00124] The addition of aluminum salts, such as A1C13, to brine at a pH of
between about
4 and 6, results in the formation of charged polymers, such as A11304(OH)247'-
. These charged
polymers are highly reactive with respect to silica, resulting in the
formation of amorphous
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aluminosilicate precipitates, which can be removed by filtration. In certain
embodiments, any
silica present in the brine will react with the positively charged polymer to
form an amorphous
aluminosilicate precipitate, thereby reducing the silica concentration of the
brine. In certain
embodiments, the brine can be seeded with an aluminosilicate precipitate,
which allows the silica
to attach to the seed material, thereby allowing the silica and aluminum
polymer to be removed
by conventional filtration or clarification processes. Typically, the aluminum
polymers do not
react with other components in the brine, such as lithium or iron, and thus
they stay in solution
while the silica forms the precipitate.
[00125] Silica can be selectively recovered from silica containing
solutions (including
brines) by contacting them with aluminum salts, particularly aluminum halides,
such as chlorides
and bromides and maintaining a pH of between about 4 and 6, preferably between
about 4.5 and
5.5, more preferably between about 4.75 and 5.25, and even more preferably
between about 4.85
and 5.15. Generally, the brine solution, as prepared, has a measured pH of
between about 5.1
and 5.3, which is comparable to the brines of the Salton Sea, which typically
have a measured
pH of between about 4.9 and 5.1. Aluminum salt is added in a molar ratio of
aluminum salt to
silica of at least about 0.25:1, preferably at least about 0.5:1, and more
preferably at least about
1:1. In certain embodiments, the aluminum salt to silica ratio is between
about 0.5:1 and 2:1.
Optionally, the solution can be maintained at elevated temperatures. In
certain embodiments, the
solution can be at a temperature greater than about 50 C, more preferably at
least about 75 C,
and even more preferably at least about 90 C. Optionally, the silica
containing solution is
seeded with between about 0.1 and 10% by weight of an amorphous
aluminosilicate solid. In
certain embodiments, the solution is seeded with between about 1 and 2% by
weight of the
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amorphous aluminosilicate solid. In certain other embodiments, the solution is
seeded with
between about 1.25 and 1.75% by weight of the amorphous aluminosilicate solid.
[00126] The addition of, for example, aluminum chloride to an aqueous
silica solution,
such as brine, typically lowers the pH (i.e., acidifies) of the silica
containing solution as the
addition results in the production of aluminum hydroxide and hydrochloric
acid. Typically, the
pH is monitored during the process to maintain the solution at a constant pH.
In certain
embodiments, a base (for example, but not limited to, sodium hydroxide,
calcium hydroxide, and
the like) can be added to the silica containing solution to maintain the pH of
the solution between
about 4 and 6 alternatively, between about 4.5 and 5.5, and preferably at or
about 5.
[00127] In certain embodiments, the addition rate of the base is near
stoichiometric. In
certain embodiments, the equipment can be designed to include control
equipment to add the
base in a controlled process so that at least a stoichiometric amount of base
is added to the
solution, based upon the amount of silica and A1C13 present in solution.
[00128] In certain embodiments, the amorphous aluminosilicate solid used as
the seed
material is prepared in a laboratory setting. Aluminum salt can be added to a
concentrated
sodium silicate solution that may optionally be heated, neutralized to a pH of
between about 4
and 6, and stirred to form a precipitate. The precipitate is collected,
washed, and dried.
[00129] Precipitation of the amorphous aluminosilicate with an aluminum
salt is capable
of removing at least 75% of the silica present in the silica containing
solution, preferably at least
about 90%, and even more preferably at least about 95% of the silica present
in the silica
containing solution. In certain embodiments, precipitation of silica from a
silica containing
solution with an aluminum salt results in a total silica concentration in the
resulting solution of
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less than about 15 ppm, preferably less than about 10 ppm, and even more
preferably less than
about 5 ppm.
[00130] In one embodiment, the resulting amorphous aluminosilicate
precipitate is
removed from the solution by filtration, dried, and recycled as seed material
for subsequent
precipitation of silica. In other embodiments, the aluminosilicate precipitate
is supplied to a
subsequent process for recovery of silica and/or aluminum.
[00131] In certain embodiments, contacting the silica containing solution
with an
aluminum halide at a pH of between 4 and 6 results in the formation of a gel,
which can be
subsequently separated from the remaining aqueous solution by filtration,
which can be aided by
the use of a centrifuge.
[00132] In certain embodiments, precipitation occurs by adding a seed
containing solution
to the brine, contacting the mixture with aluminum chloride, and then
contacting the resulting
mixture with a base, such as limestone, NaOH or Ca(OH)2. In other embodiments,
the brine is
contacted with A1C13, and the resulting mixture is contacted with a base. In
yet other
embodiments, the brine is contacted with A1C13, the mixture is then contacted
with a seed
containing solution, and the resulting mixture is then contacted with a base.
Finally, in certain
embodiments, the brine is first contacted with A1C13, then contacted with a
base, and then the
resulting mixture is contacted with a seed containing solution.
[00133] Referring now to Figure 1, apparatus 100 for the removal of silica
from a silica
containing brine is provided. Water is provided via line 102. First water
stream 102' is supplied
to first mixer 106, where the water is mixed with base 104, for example NaOH
(caustic soda) or
Ca(OH)2 (slaked lime) or limestone to produce aqueous base stream 108. First
mixer 106 can
include any known means for mixing the base and water to form a homogeneous
stream. Second
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water stream 102" is supplied to second mixer 112 where the water is combined
with flocculant
110 to produce mixed flocculant stream 114. Exemplary flocculants include, but
are not limited
to, Magnafloc 351, Nalco 9907, 9911, 9913, 8181, 7193, 8170, and the like.
[00134] Brine 116 is supplied to third mixer 120 where it is combined with
aluminum
chloride (A1C13) containing stream 118 to produce mixed brine stream 122.
Aqueous base
stream 108 is combined with mixed brine stream 122 in fourth mixer 124 to
produce basic brine
stream 126. Basic brine stream 126 is supplied to fifth mixer 128 where it is
combined and
intimately mixed with mixed flocculant stream 114 to coagulate at least a
portion of the silica
present in brine stream 126 as an aluminosilicate solid. Mixed stream 130 with
a reduced silica
brine and solids is supplied to clarifier 132 to produce reduced silica brine
stream 134 and slurry
stream 136, which can include aluminosilicate precipitate. Clarifier 132 can
be a settling tank or
like device that can be utilized for the separation of a liquid stream from a
slurry. Slurry stream
136 can be supplied to filter 138, which separates the slurry into a solid
aluminosilicate
precipitate, which can be removed via solid removal line 140, and a
precipitate removed treated
brine stream 142. Precipitate removed treated brine stream 142 can then be
recombined with
reduced silica brine stream 134.
[00135] Fifth mixer 128 can include multiple stages. In one embodiment,
fifth mixer 128
includes three reactor stages wherein the first reactor stage includes a mixer
to facilitate intimate
mixing of the brine, and the aluminum salt, to produce a solid aluminosilicate
solid. The second
reactor stage can include means for introducing the base, such as NaOH or
Ca(OH)2 to the
reaction mixture. The second reactor stage can optionally include means for
determining the pH
of the solution, and control means, such as automated valves, operable to
control the addition of
the base to the solution to maintain a desired predetermined pH. In certain
embodiments, the
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second reactor stage can include means for adding an aluminum salt to the
solution. The third
reactor stage can include means for stabilizing the pH of the solution, and
means for supplying a
buffer to the solution. In certain embodiments, the third reactor stage can
include means for
adding an aluminum salt to the solution.
[00136] Clarifier 132 can be a vessel and can include valves and lines
configured to
facilitate the removal of an aluminosilicate slurry from the bottom of the
vessel and a low silica
concentration brine stream from a position at the midpoint or top of the
vessel. In certain
embodiments, fifth mixer 128 or clarifier 132 can include a line for supplying
a portion of the
aluminosilicate precipitate to the basic brine stream 108 as seed. In certain
embodiments, fifth
mixer 128 can include a line for supplying a low silica concentration brine
stream to brine stream
116.
[00137] The mixers used herein can each separately be a series of
continuously stirred
reactors. In certain embodiments, fourth mixer 124 can include at least one pH
meter, wherein
the feed of the aqueous base stream 108 and brine stream 112 are regulated to
maintain a desired
pH.
Selective Silica Recovery by Precipitation with Iron
[00138] In one embodiment, silica can be removed from a brine by contacting
the brine
with iron (III) hydroxide at a pH of between about 4.5 and 6, preferably
between about 4.75 and
5.5, more preferably between about 4.9 and 5.3.
[00139] A synthetic brine can be prepared having the approximate
composition provided
herein for the simulated Salton Sea reservoir, and further including about
1880 ppm manganese.
In certain embodiments, the brine will have an iron (II) salt, such as iron
(II) chloride, naturally
present in a concentration, for example, of greater than about 1000 ppm. In
other embodiments,
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an iron (II) salt or iron (III) hydroxide can be added to the brine to achieve
a certain
concentration of iron (II) salt or iron (III) hydroxide relative to the silica
or silicon containing
compounds present in the brine. In certain embodiments, the molar ratio of the
iron (II) salt or
iron (III) hydroxide to silica is at least about 1:1, preferably at least
about 4:1, more preferably at
least about 7:1 and even more preferably at least about 10:1.
[00140] When the iron in the brine or silica containing solution is iron
(II), for example
iron (II) chloride, an oxidant can be added to oxidize iron (II) salt to iron
(III) hydroxide.
Exemplary oxidants include hypohalite compounds, such as hypochlorite,
hydrogen peroxide (in
the presence of an acid), air, halogens, chlorine dioxide, chlorite, chlorate,
perchlorate and other
analogous halogen compounds, permanganate salts, chromium compounds, such as
chromic and
dichromic acids, chromium trioxide, pyridinium chlorochromate (PCC), chromate
and
dichromate compounds, sulfoxides, persulfuric acid, nitric acid, ozone, and
the like. While it is
understood that many different oxidants can be used for the oxidation of iron
(II) to iron (III), in
an embodiment, oxygen or air is used as the oxidant and lime or a like base is
used to adjust and
maintain the pH to a range of between about 4 and 7. This pH range is
selective for the
oxidation of the iron (II) salt to iron (III) hydroxide, and generally does
not result in the co-
precipitation or co-oxidation of other elements or compounds present in the
brine. In one
embodiment, the iron (II) salt can be oxidized to iron (III) by sparging the
reaction vessel with
air. Air can be added at a rate of at least about 10 cfm per 300L vessel,
preferably between about
and 50 cfm per 300L vessel. A person of skill in the art will recognize that
the cfm rate can
be adjusted based on specific operation parameters. It will be recognized by
those skilled in the
art that iron (III) hydroxide may also have a significant affinity for arsenic
(III) and (V)
oxyanions, and these anions, if present in the brine, may be co-deposited with
the silica on the
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iron (III) hydroxide. Thus, in these embodiments, steps may have to be
employed to remove
arsenic from the brine prior to silica management.
[00141] In another embodiment, iron (III) hydroxide can be produced by
adding a solution
of iron (III) chloride to the brine, which upon contact with the more neutral
brine solution, will
precipitate as iron (III) hydroxide. The resulting brine may require
subsequent neutralization
with a base to initiate precipitation of the silica. In certain embodiments,
iron (III) hydroxide can
be contacted with lime to form insoluble ferric hydroxide solids, which can be
adsorbed with
silica.
[00142] The iron (III) hydroxide contacts the silica present in the brine
to form a
precipitate. Without being bound to any specific theory, it is believed that
the silica or silicon-
containing compound attaches to the iron (III) hydroxide. In certain
embodiments, the ratio of
iron (III) hydroxide to silica is at least about 1:1, more preferably at least
about 4:1, more
preferably at least about 7:1. In other embodiments, the iron (III) hydroxide
is present in a molar
excess relative to the silica. The reaction of the iron (III) hydroxide with
silica is capable of
removing at least about 80% of the silica present, preferably at least about
90% of the silica
present, and more preferably at least about 95% of the silica present, and
typically depends upon
the amount of iron (III) hydroxide present in the solution.
[00143] In certain embodiments, the pH is monitored continually during the
reaction of
iron (III) with silica and an acid or a base is added, as needed, to maintain
the pH the desired
level, for example, between about 4.9 and 5.3. In alternate embodiments, a pH
of between about
5.1 and 5.25 is maintained. In certain embodiments, a pH of about 5.2 is
maintained.
[00144] In certain embodiments, the iron (II) salt containing solution is
sparged with air
for a period of at least about 5 minutes, alternately at least about 10
minutes, alternately at least
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about 15 minutes, and preferably at least about 30 minutes, followed by the
addition of a base,
such as calcium oxide, calcium hydroxide, sodium hydroxide, or the like, to
achieve the desired
pH for the solution. In certain embodiments, the base can be added as an
aqueous solution, such
as a solution containing between about 10 and 30% solids by weight.
[00145] In certain embodiments, a flocculant, such as the Magnafloc
products from
Ciba , for example Magnafloc 351, or a similar flocculant can be added in the
clarification step.
The flocculant can be added in an aqueous solution in amounts between about
0.005% by weight
and about 1% by weight. The flocculant can be added at a rate of at least
0.001 gpm, preferably
between about 0.001 and 1 gpm, based upon a 300L vessel. A person of skill in
the art will
recognize that the gpm can be adjusted based on specific operation parameters.
In certain
embodiments, the flocculant is a non-ionic flocculant. In other embodiments,
the flocculant is a
cationic flocculant. In certain embodiments, it is believed that non-ionic and
cationic flocculants
may be useful for use with iron precipitates. In certain embodiments, Cytec
Superfloc-N
flocculants, such as the N-100, N-100 S, N-300, C-100, C-110, C-521, C-573. C-
577 and C581
may be used for the recovery of iron and silica precipitates, according to the
present invention.
In other embodiments, flocculant products from Nalco, such as CAT-Floc,
MaxiFloc, Nalco
98DF063, Nalco 1317 Liquid, Nalco 97ND048, Nalco 9907 Flocculant, Nalco 73281,
and Nalco
9355 may be used with the present invention.
[00146] In certain embodiments, a flocculant can be added to the brine, in
addition to the
base, to facilitate the production of larger solids for easier solid/liquid
separation. In certain
embodiments, iron (III) silicate solids can be added to the solution to
increase the rate of
precipitation of silicates.
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[00147] Referring now to Figure 2, apparatus 200 for the removal of silica
from a silica
containing brine is provided. Water is provided via line 102. First water
stream 102' is supplied
to first mixer 106, where the water is mixed with base 104, for example NaOH
(caustic soda) or
Ca(OH)2 (slaked lime), to produce aqueous base stream 108. First mixer 106 can
include any
known means for mixing the base and water to form a homogeneous stream. Second
water
stream 102" is supplied to second mixer 112 where the water is combined with
flocculant 110 to
produce mixed flocculant stream 114.
[00148] Brine 216 is supplied to third mixer 224 where it is combined with
aqueous base
stream 108 and air 225 to produce mixed brine stream 226, with iron-silica
precipitates. Mixed
brine stream 226 is supplied to fourth mixer 228 where it is combined and
intimately mixed with
mixed flocculant stream 114 to further encourage precipitation of at least a
portion of the silica
present in brine stream 226. Mixed stream 230 containing a reduced silica
brine and solids is
supplied to clarifier 232 to produce reduced silica brine stream 234 and
slurry stream 236, which
can include iron-silica precipitates. Clarifier 232 can be a settling tank or
like device that can be
utilized for the separation of a liquid stream from a slurry including a
filter such as candle filters.
Slurry stream 236 can be supplied to filter 238, which separates the slurry
into a solid precipitate,
which can be removed via solid removal line 240, and a treated brine stream
242. Solids
removed via solid removal line 240 can optionally be separated from any
remaining liquid by
centrifugation. Precipitate removed treated brine stream 242 can then be
recombined with
reduced silica brine stream 234. Optionally, precipitate removed treated brine
stream 242 can be
recycled to third mixer 224, or alternatively can be combined with brine
stream 226.
[00149] Fourth mixer 228 can include multiple stages. In an embodiment,
fourth mixer
228 includes three reactor stages wherein the first reactor stage includes a
mixer to facilitate
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intimate mixing of the brine and air. In some embodiments, sufficient air is
supplied to the
reactor to oxidize at least a portion of the iron (II) present to iron (III).
The second reactor stage
can include means for introducing the base, such as NaOH or Ca(OH)2 to the
reaction mixture.
The second reactor stage can optionally include means for determining the pH
of the solution,
and control means, such as automated valves, operable to control the addition
of the base to the
solution to maintain a desired predetermined pH. In certain embodiments, the
third reactor stage
can include means for adding an aluminum salt to the solution. Optionally,
apparatus 200 can
include means for supplying air to the second and third reactor stages.
[00150] In certain embodiments, the brine is supplied to the first reactor
stage at a pH of
about 4.9 to 5.1 and a temperature of about 95-110 C where it is contacted
and sparged with air
to produce certain iron (III) oxyhydroxides. Preferably, a sparging diffuser
is utilized to
facilitate contact between the air and iron (II) contained in the brine. At a
temperature of greater
than about 90 C, the pH of the first reactor stage is controlled such that the
pH is at least about
2.5, but preferably in the range of 3.5 to 5.3. The pH is maintained by the
addition of lime or
other base to the reactor to prevent the pH becoming too acidic, which would
prevent further
oxidation of the iron (II) to iron (III).
[00151] In certain embodiments, in the second reactor stage, the lime or
other base is
added while continuing to sparge air through the brine. This provokes
precipitation of ferric ions
as oxides, hydroxides, or oxyhydroxides. Additionally, silica and other metals
are adsorbed on
the surface of the iron oxyhydroxides. The metals that adsorb on the ferric
oxyhydroxides
include arsenic, antimony, lead, and barium. The pH of the second stage of the
reactor is
maintained such that the pH of no greater than about 6, alternatively not
greater than about 5.4,
preferably not above about 5.3, and more preferably not above about 5.2.
Additional air can be
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fed to the second reactor stage through a sparger, such as an air diffuser, to
facilitate the
preparation and precipitation of iron (III) hydroxides adsorbed with silica.
[00152] In certain embodiments, the third reactor stage can serve as a
buffer tank that is
configured to maintain the pH of the solution at a pH of no greater than about
6, alternatively not
greater than about 5.4, preferably not greater than about 5.3, and even more
preferably at a pH of
not greater than about 5.2. Optionally, the third reactor stage can include an
air sparger, such as
an air diffuser, to facilitate preparation and precipitation of iron (III)
hydroxides adsorbed with
silica.
[00153] Clarifier 232 can be a vessel and can include valves and lines
configured to
facilitate the removal of an iron-silica slurry from the bottom of the vessel
and a reduced silica
concentration brine stream from a position at the midpoint or top of the
vessel. In certain
embodiments, fourth mixer 228 or clarifier 232 can include a line for
supplying a portion of the
iron-silica precipitate to the basic brine stream 216 as seed. Alternatively,
clarifier 232 can
include one or more lines configured to deliver iron (III) hydroxide
precipitate material adsorbed
with silica to one or more of the first, second, or third reactor stages. In
certain embodiments,
fourth mixer 228 can include a line for supplying a reduced silica
concentration brine stream to
basic brine stream 216.
[00154] In certain embodiments, apparatus 200 can include control means for
controlling
the addition of base to third mixer 224. In alternate embodiments, apparatus
200 can include
control means for controlling the addition of base to the second reactor
stage.
[00155] In certain embodiments, brine stream 216 can be preconditioned by
sparging the
brine stream with air prior to supplying the brine to third mixer 224.
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[00156] The mixers used herein can each separately be a series of
continuously stirred
reactors. In certain embodiments, third mixer 224 can include at least one pH
meter, wherein the
feed of the aqueous base stream 108 and brine stream 216 are regulated to
maintain a desired pH.
[00157] In certain embodiments, precipitation of silica and iron hydroxide
can be achieved
by recycling precipitate from the clarifier 232 to third mixer 224, resulting
in an increase of the
size of ferrosilicate particles. Additional recycling can also be achieved by
recycling the seeds
from clarifier 232 to first mixer 106, where base 104 is mixed with some or
all of the seeds to
promote the formation of a densified seed, which can then be fed to third
mixer 224. This
recycling step can enhance the quality of the precipitate by increasing
density of the precipitate,
thus making the design of clarifier 232 smaller and simpler. It has also
surprisingly been found
that on the introduction of these solids to the reaction vessel a minor amount
of the zinc and/or
manganese is retained in the precipitate. In certain embodiments, when seeds
are re-introduced
into third mixer 224, there is no or minimal net loss of zinc and manganese
that may be present
in the brine, and the ability of the ferrosilicate precipitate to grow and
capture silica is
unimpaired.
[00158] The rate of the addition of the air, base, and flocculant is based
upon the size of
the reactor and the concentrations of iron and silica. Generally, the rates of
addition of the
components are proportional to the other components being added and the size
of the reaction
vessels. For example, to a geothermal brine having iron and silica present,
which is supplied at a
rate of about 6 gpm (gallons per minute) to a silica removal process having an
overall capacity of
about 900 gal,, air can be added at a rate of about 100 cfm, a 20% solution of
calcium oxide in
water can be added at a rate of about 0.5 lb/min., and a 0.025% solution of
Magnafloc 351
(flocculant) at a rate of about 0.01 gpm.
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Selective Silica Recovery with Activated Alumina
[00159] Activated alumina is a known absorbent for silica. In certain
embodiments,
activated alumina is a mixture of y-A1203 and A10(OH) (boehmite).
Specifically, activated
alumina has been utilized in the removal of silica from raw water, such as
water that is fed to a
boiler. Activated alumina has not been used for the removal of silica from
brines, wherein the
removal of the silica does not also result in the removal of other ions or
compounds by the
activated alumina. Methods have not been reported for the selective removal of
silica from
brines without concurrent removal of other ions or compounds.
[00160] Activated alumina is a known absorbent for organic and inorganic
compounds in
nonionic, cationic, and anionic forms. Indeed, activated alumina is a common
filter media used
in organic chemistry for the separation and purification of reaction products.
[00161] In another embodiment of the present invention, silica can be
removed from a
brine by contacting the brine with activated alumina at a pH of between about
4.5 and 7,
alternatively between about 4.75 and 5.75, or in certain embodiments, between
about 4.8 and 5.3.
The activated alumina can have a BET surface area of between about 50 and 300
m2/g. In
certain embodiments, the brine can be combined and stirred with activated
alumina to selectively
remove the silica. In alternate embodiments, the activated alumina can be
added to the brine and
stirred to selectively remove silica and silicon containing compounds. In
certain embodiments,
the pH of the brine can be maintained at between about 4.5 and 8.5, preferably
between about
4.75 and 5.75, and more preferably between about 4.8 and 5.3, during the step
of contacting the
silica with the activated alumina. In certain embodiments, the pH can be
maintained at between
about 4.75 and 5.25. Alternatively, the pH can be maintained at between about
5.25 and 5.75.
Alternatively, the pH can be maintained at between about 5.75 and about 6.25.
A pH meter can
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be used to monitor the pH before, during, and after the contacting step. In
certain embodiments,
the pH is controlled by titrating the solution with a strong base, such as
sodium hydroxide. In an
exemplary embodiment, approximately 0.1M solution of sodium hydroxide is used
to adjust the
pH of the reaction, although it is understood that a base of higher or lower
concentration can be
employed.
[00162] Regeneration of the activated alumina can be achieved by first
washing the
alumina with a base, for example, a sodium hydroxide solution of at least
about 0.01M, followed
by the subsequent washing with an acid, for example, a hydrochloric acid
solution of at least
about 0.01M. In some embodiments, regeneration can be followed by treatment
with a sodium
fluoride solution having a pH of between about 4 and 5, to completely recover
the capacity of the
activated alumina. Optionally, the column can be rinsed with water, preferably
between 1 and 5
volumes of water, prior to contacting with sodium hydroxide.
[00163] In certain embodiments, wherein the silica containing solution can
be contacted
with the activated alumina in a column, the solution exiting the column can be
monitored to
determine loading of the activated alumina.
[00164] Figure 3 details apparatus 300 and shows an embodiment that
incorporates
removal of silica by precipitation with iron, as shown in Figure 2, followed
by removal of any
remaining silica by adsorption with activated alumina. Specifically, low
silica brine stream 234
can be supplied to first adsorbent column 344, which is charged with activated
alumina and is
operable to remove at least a portion of the silica present in the low silica
brine stream. Treated
stream 346 is then supplied to a second adsorbent column 348, which is
similarly charged with
activated alumina and is operable to remove at least a portion of the silica
present in the treated
stream, to produce product stream 350, which has a silica content that is
lower than that of the
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low silica brine stream 234. In embodiments wherein treated stream 346
includes a measurable
concentration of silica, second adsorbent column 348 is operable to produce a
product stream
350 having a lower silica concentration than that of the treated stream 346.
[00165] Referring to Figure 4, apparatus 400 for the removal of silica by
adsorption with
activated alumina is provided. A silica containing solution or silica
containing brine is supplied
via line 402 to first adsorbent column 404, which is charged with activated
alumina and is
operable to remove at least a portion of the silica present in the brine or
other solution and
produce treated stream 406 having a reduced silica content relative to that of
the stream being fed
through line 402. Treated stream 406 can then be supplied to a second
adsorbent column 408,
which can also be charged with an activated alumina adsorbent that is operable
to remove at least
a portion of the silica present in treated stream 406 to produce a product
stream 410 having a
reduced silica content relative to the silica containing solution or silica
containing brine supplied
via line 402, and in certain embodiments, relative to treated stream 406.
[00166] In certain embodiments, regenerant solution 412 can be supplied to
first adsorbent
column 404. Regenerant solution 412 can be a strong base, and can be supplied
to remove silica
adsorbed onto the activated alumina. Waste stream 414 is configured to provide
means for the
removal of the regenerant solution and any silica removed from the activated
alumina.
Optionally, as noted above, a strong acid can be supplied to first adsorbent
column 404 after the
regenerant solution and/or a sodium fluoride solution can be supplied to the
column. While
Figure 4 shows that regenerant solution 412 is supplied at the bottom of
adsorbent column 404
and flows in a counter-current flow, it is understood that the regenerant
solution can also be
supplied such that it flows in a co-current flow.
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[00167] In certain embodiments, wash water 416, such as deionized water,
can be supplied
to adsorbent column 404 and a wash water waste stream 418 can be removed from
the column.
While the wash water is shown as being supplied in a co-current flow, it is
understood that the
wash water can be supplied in a counter-current flow.
[00168] In certain embodiments, apparatus 400 can include more than two
adsorbent
columns. In certain methods wherein three or more columns are included in the
apparatus, only
two adsorbent columns are utilized at any one time. When the activated alumina
of one column
begins to lose efficiency (i.e., when silica has become adsorbed to a major
portion of the
activated alumina such that the increasing amounts of silica are not removed
by the column), that
column can be removed from service and a third column can be employed. When
the column is
removed from service, it can be regenerated, as described above, and returned
to service when
the efficiency of the second column decreases, thereby indicating the
adsorbent in the second
column is losing effectiveness. In this manner, apparatus 400 can be run
continuously as two
columns and can be employed for the removal of silica while a third column is
regenerated.
[00169] In certain embodiments, a brine, such as a geothermal brine, can be
supplied to a
process designed to remove a significant portion of silica, and optionally
iron, present in the
brine as a precursor step to the subsequent recovery of valuable components,
such as potassium,
rubidium, cesium, lithium, zinc, and manganese, and other elements. Exemplary
methods for the
reduction of the silica concentration include those described herein. The
treated brine solution
having a reduced silica concentration can then be supplied to an associated
process that is
designed to selectively remove one or more components from the treated brine.
Optionally, the
process for the removal of silica can also include the removal of iron.
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[00170] In certain embodiments, the treated brine can be supplied to a
process designed to
selectively remove and recover lithium. Certain methods for the recovery are
known in the art,
such as is described in U.S. Patent Nos. 4,116,856, 4,116,858, 4,159,311,
4,221,767, 4,291,001,
4,347,327, 4,348,295, 4,348,296, 4,348.297, 4,376,100, 4,430,311, 4,461,714,
4,472,362,
4,540,509, 4,727,167, 5,389,349, 5,599.516, 6,017,500, 6,048,507, 6,280,693,
6,555,078,
8,287,829, 8,435,468, 8,574,519, and 8,637.428. Alternatively, methods can be
employed
utilizing a lithium aluminate intercalate/gibbsite composite material, a resin
based lithium
aluminate intercalate, and a granulated lithium aluminate intercalate as
described in U.S. Patent
No. 8,637,428 and U.S. Patent Application Nos. 12/945.519 and 13/283,311.
Preferably,
recovery of lithium occurs without the co-precipitation of other metals.
[00171] For example, as shown in Figure 5, process 10 for the removal of
silica and iron
from brine, followed by the subsequent removal of lithium, is provided. In an
exemplary
embodiment, brine 12, having a silica concentration of at least about 100 ppm,
an iron
concentration of at least about 500 ppm, and a recoverable amount of lithium
or other metal, is
supplied with air 14, base stream 16, and flocculant stream 18 to a silica
removal process 20.
[00172] Silica removal process 20 can produce brine solution 26 having a
reduced
concentration of silica, and optionally iron, compared to the initial brine,
as well as a reaction by-
product stream 24 that includes silica that was previously present in the
geothermal brine.
Additionally, air/water vapor are produced and removed via line 22.
[00173] The brine solution 26 having a reduced concentration of silica and
iron can be
supplied to a lithium recovery process 28. The lithium recovery process can
include a column or
other means for contacting the brine with a extraction material suitable for
the extraction and
subsequent recovery of lithium. In certain embodiments, the extraction
material can be a lithium
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aluminate intercalate, an inorganic material with a layered crystal structure
that is both highly
selective for lithium and economically viable. Exemplary lithium intercalate
materials can
include a lithium aluminate intercalate/gibbsite composite material, a resin
based lithium
aluminate intercalate and a granulated lithium aluminate intercalate. The
gibbsite composite can
be a lithium aluminate intercalate that is grown onto an aluminum trihydrate
core. The resin-
based lithium aluminate intercalate can be formed within the pores of a
macroreticular ion
exchange resin. The granulated lithium aluminate intercalate can consist of
fine-grained lithium
aluminate intercalate produced by the incorporation of a small amount of
inorganic polymer.
[00174] The process of contacting the lithium aluminate intercalate
material with the brine
is typically carried out in a column that includes the extraction material.
The brine flows into the
column and lithium ions are captured on the extraction material, while the
water and other ions
pass through the column as geothermal brine output stream 34. After the column
is saturated, the
captured lithium is removed by flowing water supplied via line 30, wherein the
water can include
a small amount of lithium chloride present, through the column to produce
lithium chloride
stream 32. In some embodiments, multiple columns are employed for the capture
of the lithium.
[00175] As shown in Figure 6, a continuous process for the management of
silica is
provided. Silica management system 1106 includes three stirred vessels 1108,
1110, and 1112
provided in series. To first reactor 1108 is provided a geothermal brine via
line 1104. In some
embodiments, the geothermal brine has an iron content of approximately 1500
ppm and a silica
content of about 160 ppm. The brine is added at a rate of about 6 gpm. Air is
supplied via line
1140 to each reactor 1108, 1110, and 1112 and is sparged through the
geothermal brine. In some
embodiments, the air is supplied at a rate of about 100 cfm. In some
embodiments, the brine
supplied to each of the three reactors is maintained at a temperature of about
95 C.
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[00176] An aqueous calcium oxide slurry is prepared by mixing solid calcium
oxide
proved from tank 1130 via line 1132 to vessel 1134, where the solid is mixed
with water 1120
provided via line 1122. In some embodiments, the calcium oxide slurry includes
between about
15 and 25% by weight, alternatively about 20% by weight, calcium oxide, and is
supplied to
second reactor 1110 at a rate on a wet basis of about 0.5 lb/min.
[00177] In silica management system 1106, brine is supplied to first vessel
1108 where the
brine is sparged with air via line 1140'. The brine is then supplied from
first vessel 1108 to
second vessel 1110. The brine in second vessel 1110 is contacted with calcium
oxide supplied
via line 1136 and is again sparged with air supplied via line 1140". The brine
is then supplied
from second vessel 1110 to third vessel 1112 where it is again sparged with
air supplied via line
1140". In some embodiments, the air to the vessels is supplied at a constant
rate. In further
embodiments, the air to the vessels is supplied at a constant rate of about
100 cfm.
[00178] After the addition of the air via line 1140' to first reactor 1108,
the pH drops. In
some embodiments, the pH drops to between about 2.3 and 3.5. Air is added to
second reactor
1110 via line 1140". In some embodiments, air is supplied at a rate of about
100 cfm and a
charge of approximately 15-25% by weight of an aqueous calcium oxide slurry at
a rate of about
0.5 lb/min., which can raise the pH in the second reactor to between about 4.8
and 6.5, and
preferably between about 5.0 and 5.5. The addition of calcium oxide sluiTy
initiates the
precipitation of iron (III) hydroxide and iron silicate. In some embodiments,
to third reactor
1112, air is added via line 1140" at a rate of about 100 cfm. Each of the
three reactors includes
means for stirring to ensure sufficient mixing of the brine, base, and air
oxidant.
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[00179] In some embodiments, the continuous addition of air and base to the
reaction
vessels results in the precipitation of the iron and silica at rates up to
about 0.5 lb/min.,
depending upon the concentration of iron and silica in the geothermal brine.
[00180] The geothermal brine, which now includes precipitates of iron (III)
hydroxide and
iron silicate, is then supplied from third vessel 1112 to clarifier 1146 via
line 1144. Water may
be added to clarifier 1146 via line 1122. In some embodiments, an aqueous
flocculant solution
of Magnafloc 351, in a concentration between about 0.005% and 1% by weight,
such as about
0.025% by weight, is prepared by supplying solid flocculant 1124 via line 1126
to flocculant
tank 1128, where the solid is contacted with water 1120 supplied via line
1122. In further
embodiments, the aqueous flocculant solution is supplied to clarifier vessel
1146 via line 1138 at
a rate of about 0.01 gpm.
[00181] Two streams are produced from clarifier 1146. First clarifier
product stream 1148
includes the geothermal brine having a reduced concentration of silica and
iron, and may be
supplied to a secondary process, such as lithium recovery. Second clarifier
product stream 1150
includes solid silica-iron waste, as well as some geothermal brine. Stream
1150 can be supplied
to filter process 1156 which serves to separate the solid silica-iron waste
1160 from the liquid
brine 1162. Alternately, a portion stream 1160 can be resupplied (not shown)
to second vessel
1110 via line 1154.
[00182] Alternate processes for the removal of silica can also be employed
as described
herein.
[00183] In certain embodiments, the treated brine solution can be supplied
to a process
designed to selectively remove and recover at least one of manganese and zinc.
In a first
embodiment, the pH of the solution can be adjusted to selectively precipitate
zinc and/or
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manganese. Following precipitation of zinc and/or manganese, the solids can be
separated from
the solution by known filtration means.
[00184] Separation of the zinc and manganese solids can be achieved by
dissolving the
solids in acid, followed by selective recovery of either zinc or manganese. In
certain
embodiments, manganese can be oxidized to precipitate a manganese solid, which
can be
separated by filtration. Zinc remaining in solution can be recovered by
electrochemical means.
[00185] Alternatively, zinc and/or manganese can be selectively removed by
extraction.
In certain embodiments, zinc and manganese can be recovered selectively or in
combination by
individual extractions, or by double extraction. In certain embodiments, zinc
and manganese can
each selectively be recovered by electrochemical means.
[00186] Known methods for the recovery of zinc that can be used for
recovery from brine
solutions are described in U.S. Patent Nos. 5,229,003, 5,358,700, 5,441,712,
6,458,184,
8,454,816, and 8,518,232.
[00187] Known methods for the recovery of manganese that can be used for
recovery
from brine solutions are described in U.S. Patent Nos. 6,682,644, 8,454,816,
8,518,232, and U.S.
Patent Publication Nos. 2003/0226761 and 2004/0149590.
[00188] Figures 7, 8, and 9 show exemplary embodiments of the present
invention. Figure
7 is an illustration of an exemplary embodiment of power production using a
geothermal brine,
followed by silica management. The brine 3101 is taken from a reservoir and
supplied to a high
pressure separator 3102. From the high pressure separator are produced two
streams, hot brine
3104 and steam 3103. The steam 3103 is then fed to a condenser 3105 to remove
salts and
entrained water whereby high pressure steam 3106 is generated and fed to a
turbine/generator
3107 to produce energy 3108. An acid 3109, preferably hydrochloric acid, is
added to the hot
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brine 3104, as the brine is a chloride brine. Other acids also can be used.
The acid/hot brine
stream 3110 is then fed to a standard pressure separator 3111. Two streams are
produced from
the standard pressure separator, a standard pressure steam 3112 and return
brine 3113. The
standard pressure steam 3112 is then fed to a condenser 3114 to remove
entrained brine whereby
clean standard pressure steam 3115 is generated and fed to turbine/generator
3107 to produce
energy 3108. The return brine 3113 is fed to an iron-silica removal process
3116 whereby iron
and silica are removed from the brine by addition of a base 3117 and an
oxidant 3118 to produce
a reduced silica and iron silica brine stream 3119. The reduced silica and
iron brine stream can
optionally be fed to a mineral extraction process 3120 whereby at least one
mineral is removed
from the reduced silica and iron brine stream. The reduced silica and iron
brine stream 3121 is
then injected into a reservoir 3122.
[00189] Figure 8 is an illustration of an exemplary embodiment of power
production using
a geothermal brine, followed by silica management. The brine 3201 is taken
from a reservoir
and supplied to a high pressure separator 3202. From the high pressure
separator 3202 are
produced two streams, high pressure steam 3203 and concentrated brine stream
3204. The high
pressure stream 3203 is then fed to a turbine/generator 3205 to produce energy
3206. The
concentrated brine stream 3204 is then fed to a high pressure crystallizer
3207 to produce a
stream 3208 that is fed to a low pressure crystallizer 3210. A high pressure
steam 3209 is
generated and fed to a turbine/generator 3205 to produce energy 3206. From the
low pressure
crystallizer 3210 is produced a low pressure steam 3211 that is fed to the
turbine/generator 3205
to produce electricity 3206 and a stream 3212 that is fed to a flash tank
3213. From the flash
tank 3213 are produced two streams, low pressure steam 3214 that is fed to a
turbine 3205 and a
stream of brine and silica solids 3215 that are fed to a primary clarifier
3216. From the primary
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clarifier 3216. seeds 3217 are recycled to the high pressure crystallizer 3207
and brine 3218 is
fed to a silica management process 3219 to remove silica by addition of a base
3220 and an
oxidant 3221. Optionally, iron may be removed, as well. From the silica
management process
3219, a reduced silica (and optionally reduced iron) brine 3222 is then fed to
a secondary
clarifier 3223 to remove silica. From the secondary clarifier 3223 the stream
3224 is fed to an
optional metal recovery process 3225. Seeds 3226 are also recycled from the
secondary clarifier
3223 to the high pressure crystallizer 3207. The reduced silica (and
optionally reduced iron)
brine 3227 is then injected into a reservoir. Stream 3228 can be supplied to
filter process 3229,
which serves to separate the solid silica-iron waste 3230 from the liquid
brine 3228. Alternately,
stream 3231 can be resupplied to second clarifier 3223.
[00190] Similarly, Figure 9 is an illustration of an exemplary embodiment
of power
production using a geothermal brine, followed by silica management. The brine
3301 is taken
from a reservoir and supplied to a high pressure separator 3302. From the high
pressure
separator 3302 are produced two streams, high pressure steam 3303 and
concentrated brine
stream 3304. The high pressure steam 3303 is then fed to a turbine/generator
3305 to produce
energy 3306. The concentrated brine stream 3304 is then fed to a high pressure
crystallizer 3307
to produce a stream 3308 that is fed to a low pressure crystallizer 3310. A
high pressure steam
3309 is generated and fed to a turbine/generator 3305 to produce energy 3306.
From the low
pressure crystallizer 3310 is produced a low pressure steam 3311 that is fed
to the
turbine/generator 3305 to produce electricity 3306 and a stream 3312 that is
fed to a flash tank
3313. From the flash tank 3313 are produced two streams, a low pressure steam
3314 that is fed
to a turbine 3305, and a stream of brine and silica solids 3315 that is fed to
a primary clarifier
3316. From the primary clarifier 3316, seeds 3317 are recycled to the high
pressure crystallizer
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3307, and the brine 3318 is fed to a secondary clarifier 3319. While the
primary clarifier 3316
removes the bulk of the solids, the secondary clarifier 3319 can further
reduced the TSS. From
the secondary clarifier 3319, two streams are produced. One stream 3320 is fed
in part to a filter
3321 or alternative solids liquid separator where silica solids 3322 are
removed. The brine
containing silica and iron 3323 is fed to a silica management process 3324,
which receives base
3325 and oxidant 3326. Optionally, iron can be removed as well. In some
embodiments, the
brine contains about 160 ppm silica and about 1600 to 2000 ppm of iron. The
reduced silica
(and optionally reduced iron) brine 3327 may be fed to an optional metal
recovery process 3328.
The reduced silica (and optionally reduced iron) brine is then injected into a
reservoir 3329.
Stream 3330 can be supplied to filter process 3331 which serves to separate
the solid silica-iron
waste 3332.
[00191] In further embodiments, the reduced silica (and optionally reduced
iron) brine is
then supplied to a process for the selective removal of lithium, potassium,
rubidium and/or
cesium.
Selective Removal of Potassium, Rubidium, and/or Cesium from Brines
[00192] Broadly described herein are methods of removing potassium,
rubidium, and/or
cesium, selectively or in combination, from brines. In some embodiments, the
methods are
operable to remove potassium, rubidium, and/or cesium, selectively or in
combination, from
brines that have already been treated to remove silica. In further
embodiments, the methods are
operable to remove potassium, rubidium, and/or cesium, selectively or in
combination, from
brines that have already been treated to remove silica and iron. As shown in
Figure 10, by
process 3400 of the present invention, a heated brine that contains potassium,
rubidium, and/or
cesium ions is contacted with a tetrafluoroborate containing solution to
produce potassium
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tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium tetrafluoroborate
precipitate in step
3410. In certain embodiments, the brine is heated to a temperature of between
about 70 to
100 C, in order to facilitate the reactivity of the potassium, rubidium,
and/or cesium ions in the
brine. In other embodiments, the brine is heated to a temperature of between
about 80 to 100 C.
In some embodiments, the brine solution is heated to a temperature of about 70
C. In some
embodiments, the brine solution is heated to a temperature of about 75 C. In
some
embodiments, the brine solution is heated to a temperature of about 80 C. In
some
embodiments, the brine solution is heated to a temperature of about 85 C. In
some
embodiments, the brine solution is heated to a temperature of about 90 C. In
some
embodiments, the brine solution is heated to a temperature of about 95 C. In
some
embodiments, the brine solution is heated to a temperature of about 100 C.
[00193] In certain embodiments, the tetrafluoroborate compound is an acid
or salt that
includes tetrafluoroborate anions. Exemplary tetrafluoroborate compounds
include fluoroboric
acid, ammonium tetrafluoroborate, alkali metal tetrafluoroborates, and
alkaline earth metal
tetrafluoroborates although it is understood that other compounds can also be
used.
[00194] In some embodiments, the brine is contacted with the
tetrafluoroborate compound
in an amount between about 10 to 80 grams per liter of brine. In some
embodiments, the brine is
contacted with the tetrafluoroborate compound in an amount between about 15 to
60 grams per
liter of brine. In some embodiments, the brine is contacted with the
tetrafluoroborate compound
in an amount between about 35 to 80 grams per liter of brine. In some
embodiments, the brine is
contacted with the tetrafluoroborate compound in an amount of at least about
10 grams per liter
of brine. In step 3410, the brine and the tetrafluoroborate compound are
contacted for between
about 30 to 60 seconds. In certain embodiments, the tetrafluoroborate compound
and the brine
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are vigorously mixed. In one embodiment, after the tetrafluoroborate compound
has been added
to the brine, the mixture is placed in a centrifuge for between about one to
five minutes. The
centrifuge speed is between about 1000-5000 revolutions per minute,
alternatively at a speed of
at least 4000 revolutions per minute. Following centrifugation of the mixture,
a precipitate layer
that includes potassium tetrafluoroborate, rubidium tetrafluoroborate, and/or
cesium
tetrafluoroborate and an aqueous layer will be present. The potassium
tetrafluoroborate,
rubidium tetrafluoroborate, and/or cesium tetrafluoroborate precipitate layer
3420 and the
aqueous layer is separated using techniques known in the art. In certain
embodiments, after
separation, the precipitate layer containing potassium tetrafluoroborate,
rubidium
tetrafluoroborate, and/or cesium tetrafluoroborate is then washed with water.
In certain
embodiments, the use of fluoroboric acid as the tetrafluoroborate compound
selectively
precipitates at least about 95% of the potassium present in the brines. As an
example, the
reaction for a brine containing potassium chloride, which is contacted with a
sodium
tetrafluoroborate solution is shown in Equation 1 below.
Eq.1 KC1(aq) + NaBF4(aq) KBF4()+ NaCl(aq)
Preparation of Potassium Chloride, Rubidium Chloride, and/or Cesium Chloride
Using Ionic
Liquids
[00195] In
another embodiment of the invention, a method for the preparation of
potassium chloride, rubidium chloride, and/or cesium chloride, selectively or
in combination,
from potassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium
tetrafluoroborate
using ionic liquids is provided. In
step 3430, potassium tetrafluoroborate, rubidium
tetrafluoroborate, and/or cesium tetrafluoroborate is supplied to an ionic
liquid solution that
contains chloride anions. In
certain embodiments of the invention, the potassium
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tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium tetrafluoroborate
is prepared using
the method described above. In some embodiments, the ionic liquid solution is
selected from the
group consisting of quaternary ammonium chlorides. In other embodiments, the
ionic liquid
solution is selected from a group of phosphonium chlorides. Exemplary ionic
liquid solutions
include tetrabutylammonium chloride (TBAC) and trihexyltetradecyl phosphonium
chloride.
[00196] In some embodiments, potassium tetrafluoroborate, rubidium
tetrafluoroborate,
and/or cesium tetrafluoroborate is added to the ionic liquid solution in an
amount between about
35 to 80 grams per liter of brine. In some embodiments, potassium
tetrafluoroborate, rubidium
tetrafluoroborate, and/or cesium tetrafluoroborate is added to the ionic
liquid solution in an
amount between about 10 to 80 grams per liter of brine. The ionic liquid
solution and potassium
tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium tetrafluoroborate
mixture is then
heated until the potassium tetrafluoroborate, rubidium tetrafluoroborate,
and/or cesium
tetrafluoroborate is dissolved. In certain embodiments, the mixture is heated
to a temperature of
between about 70 to 100 C, alternatively between about 80 to 100 C, and
alternatively to about
90 C. In some embodiments, the mixture is stirred during the heating step. In
exemplary
embodiments, when utilizing quaternary ammonium chloride ionic liquids, the
stirring is done
intermittently, as may be necessary to dissolve all of the potassium
tetrafluoroborate, rubidium
tetrafluoroborate, and/or cesium tetrafluoroborate. In exemplary embodiments
that employ
phosphonium chloride ionic liquids, the stirring is vigorous and employed for
between about 20
and 30 minutes.
[00197] After heating the ionic liquid to dissolve the potassium
tetrafluoroborate,
rubidium tetrafluoroborate, and/or cesium tetrafluoroborate, the mixture
separates into two
distinct layers. In certain embodiments using quaternary ammonium chloride
ionic liquids,
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separation of the two layers includes a light white solid precipitate layer
that is on top of an
aqueous layer. The aqueous layer in these embodiments includes potassium
chloride, rubidium
chloride, and/or cesium chloride. In certain embodiments using phosphonium
chloride ionic
liquids, the two layers include an organic layer and an aqueous layer. The
aqueous layer in these
embodiments includes potassium chloride, rubidium chloride, and/or cesium
chloride. Equation
2 is an exemplary reaction showing the conversion of potassium
tetrafluoroborate into potassium
chloride using a quaternary ammonium chloride ionic liquid. Equation 3 is an
exemplary
reaction showing the conversion of potassium tetrafluoroborate into potassium
chloride using a
phosphonium chloride ionic liquid.
Eq. 2 KBF4 + R41\1+Cl- ¨> KC1 + R41\113F4- (R = Propyl, Butyl,
Cetyl)
Eq. 3 KBF4 + R4P+Cl- ¨> KC1+ R4P+BF4- (R= trihexyltetradecyl)
[00198] In step 3440, the aqueous layer containing potassium chloride,
rubidium chloride,
and/or cesium chloride, is isolated using appropriate separation techniques.
It will be apparent to
one of skill in the art which separation techniques may be employed to isolate
the aqueous layer.
For example, the aqueous layer containing potassium chloride is then allowed
to evaporate to
dryness, resulting in solid potassium chloride. In exemplary embodiments, the
percentage
conversion of potassium tetrafluoroborate to potassium chloride is between
about 60 to 90%. In
some embodiments, the percentage conversion of potassium tetrafluoroborate to
potassium
chloride is at least about 60%. In some embodiments, the percentage conversion
of potassium
tetrafluoroborate to potassium chloride is at least about 70%. In some
embodiments, the
percentage conversion of potassium tetrafluoroborate to potassium chloride is
at least about 80%.
In some embodiments, the percentage conversion of potassium tetrafluoroborate
to potassium
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chloride is at least about 90%. In further embodiments, the purity of the
resulting potassium
chloride is at least 98%.
[00199] As a result of the removal of potassium, rubidium or cesium, a
composition is
produced that has reduced concentrations of potassium, rubidium or cesium.
[00200] As shown in Figure 10, in some embodiments, once the potassium,
rubidium, or
cesium has been removed from the brine, the brine is injected into the ground
3450.
Preparation of Potassium Chloride, Rubidium Chloride, and/or Cesium Chloride
Using Ion
Exchange Media
[00201] Referring now to Figure 11, process 3500 details a method for the
preparation of
potassium chloride from potassium tetrafluoroborate using ion-exchange media.
Similar process
can be employed for preparation of rubidium chloride and/or cesium chloride
from rubidium
tetrafluoroborate and/or cesium tetrafluoroborate. Steps 3510 and 3520 are the
same as steps
3410 and 3420 described above for Figure 10. In step 3530, potassium
tetrafluoroborate is
supplied to an ion-exchange media mixture. The ion-exchange media mixture can
be prepared
by mixing the ion-exchange media with water. In certain embodiments of the
invention, the
potassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium
tetrafluoroborate are
prepared using the methods described herein. In some embodiments, the ion-
exchange media is
selected from quaternary ammonium functional resin beads. One exemplary resin
bead is the
DOWEX-K-21 resin bead.
[00202] In an embodiment, potassium tetrafluoroborate, rubidium
tetrafluoroborate, and/or
cesium tetrafluoroborate are added to the ion-exchange media mixture in an
amount between
about 0.5 to 10 grams of potassium tetrafluoroborate, rubidium
tetrafluoroborate, and/or cesium
tetrafluoroborate per 100g of exchange media mixture. The ion-exchange media
mixture with
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the potassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium
tetrafluoroborate is
then heated until the potassium tetrafluoroborate, rubidium tetrafluoroborate,
and/or cesium
tetrafluoroborate are dissolved. In some embodiments, the mixture is heated to
a temperature of
between about 70 to 100 C, and alternatively to about 90 C. In some
embodiments, the mixture
is heated to a temperature of between about 80 to 100 C. In some embodiments,
the mixture is
heated to a temperature of about 70 C. In some embodiments, the mixture is
heated to a
temperature of about 75 C. In some embodiments, the mixture is heated to a
temperature of
about 80 C. In some embodiments, the mixture is heated to a temperature of
about 85 C. In
some embodiments, the mixture is heated to a temperature of about 90 C. In
some
embodiments, the mixture is heated to a temperature of about 95 C. In some
embodiments, the
mixture is heated to a temperature of about 100 C. In some embodiments, the
mixture is also
stirred during the heating step. In exemplary embodiments, the mixture is
stirred vigorously
intermittently for 30 seconds at two minute intervals.
[00203] After heating the ion-exchange media mixture to dissolve the
potassium
tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium
tetrafluoroborate, the mixture
separates into an aqueous layer that includes potassium chloride, rubidium
chloride, and/or
cesium chloride and a solid ion exchange media layer. In step 3540, the
aqueous layer
containing potassium chloride, rubidium chloride, and/or cesium chloride is
isolated using
appropriate separation techniques, which will be apparent to one of skill in
the art. The aqueous
layer is then dried, resulting in solid potassium chloride, rubidium chloride,
and/or cesium
chloride. In exemplary embodiments of the invention, the percentage conversion
of potassium
tetrafluoroborate to potassium chloride is between about 60 to 90%. In some
embodiments, the
percentage conversion of potassium tetrafluoroborate to potassium chloride is
at least about 60%.
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In some embodiments, the percentage conversion of potassium tetrafluoroborate
to potassium
chloride is at least about 70%. In some embodiments, the percentage conversion
of potassium
tetrafluoroborate to potassium chloride is at least about 80%. In some
embodiments, the
percentage conversion of potassium tetrafluoroborate to potassium chloride is
at least about 90%.
[00204] As shown in Figure 11, in some embodiments, once the potassium,
rubidium, or
cesium has been removed from the brine, the brine can be injected into the
ground 3560.
[00205] Cesium can also be removed from brines using known methods, such as
through
the use of silicotitanate.
[00206] Brines that can be used in the various methods described herein can
include any
type of brine. In some embodiments, the brine is a geothermal brine. In
further embodiments,
the geothermal brine is a Salton Sea geothermal brine. In other embodiments,
the brine is a
concentrated geothermal brine. The treated brines described herein can be used
for a variety of
purposes. In some embodiments, the treated brines are used in a process to
extract minerals
remaining in the brine. In some embodiments, the treated geothermal brine is
used in a method
whereby the treated brine is injected into a geothermal reservoir.
[00207] In some embodiments, the compositions of the present invention have
improved
injectivity due to the reduction in concentration of silica, iron, potassium,
rubidium, cesium,
and/or other elements, as removal of these components of the brine reduce
scaling in the well.
EXAMPLES
EXAMPLE 1. Selective Removal of Silica Using Aluminum Salts
[00208] A simulated brine was prepared to mimic the brine composition from
exemplary
Salton Sea deep test wells (post reactor crystallizer clarifier system),
having an approximate
composition of 260 ppm (mg/kg) lithium, 63,000 ppm sodium, 20,100 ppm
potassium, 33,000
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ppm calcium, 130 ppm strontium, 700 ppm zinc, 1700 ppm iron, 450 ppm boron, 54
ppm sulfate,
3 ppm fluoride, 450 ppm ammonium ion, 180 ppm barium, 160 ppm silica (measured
as silicon
dioxide), and 181,000 ppm chloride. The silica was added to the brine as
acidified sodium
silicate solution, with the target of a concentration of about 160 ppm, the
anticipated value for
the test well brine after undergoing a clarifying process to partially remove
silica. The pH of the
simulated brine was between about 3 and 4, and was subsequently adjusted with
sodium
hydroxide or other suitable base.
[00209] To enhance separation of the aluminosilicates from the brine once
precipitated,
aluminosilicates are recycled to contact them with a fresh batch of brine.
This enhances silica
removal by increasing the size of the particles, making it easier to separate
them physically. The
amorphous aluminosilicate material was prepared by neutralizing a concentrated
sodium silicate
solution with an aluminum chloride salt. Specifically, 710 g of Na25iO3.9H20
was dissolved in
400 mL of distilled water. To the solution, 420 g of A1C13 was slowly added
while stirring to
produce a wet paste of precipitated material. The paste was dried at 60 C in
an oven overnight
and washed with Milli-Q water to remove fines to produce a solid. The
resulting solid was
relatively insoluble (relative to pure amorphous silica) and suitable for use
as a seed material for
subsequent silica removal tests.
[00210] Approximately 1.6 mL of a 0.1M solution of A1C13 was added to
approximately
60 mL of the simulated brine solution, which had an initial silica
concentration of about 160 ppm
and a pH of about 5. Approximately 1.5% by weight (relative to the total mass)
of solid
amorphous aluminosilicate was added to the solution. The A1C13 was slowly
added in an amount
equal to the molar amount of silica in solution to achieve a ratio of silica
to aluminum of about
1:1. The solution was heated to approximately 95 C and stirred constantly. The
pH was
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monitored and adjusted by titrating with sodium hydroxide or calcium hydroxide
to maintain the
starting pH of about 5. The solution was allowed to stir for approximately 10
minutes, during
which the silica and aluminum reacted to selectively precipitate on the seed
material, thereby
removing both aluminum and silica from the solution. The monomeric silica
content (i.e., non-
amorphous aluminosilicate content) dropped to approximately 25-40 ppm upon
addition of base
to maintain the pH at about 5. An additional 5-15% of the silica present
precipitated over the
next 30 minutes. Total silica removal for the process after 15 minutes of
stirring was about 95%,
resulting in a brine solution having a silica content of approximately about
10 ppm. The
aluminum concentration of the solution, after precipitation of the silica, was
between about 2-10
ppm.
EXAMPLE 2. Selective Removal of Silica Using Iron
[00211] A simulated brine was prepared to mimic the brine composition of
test wells
found in the Salton Sea, having an approximate composition of about 252 ppm
lithium, 61,900
ppm sodium, 20,400 ppm potassium, 33,300 ppm calcium, 123 ppm strontium, 728
ppm zinc,
1620 ppm iron, 201 ppm boron, 322 ppm sulfate, 3 ppm fluoride, 201 ppm barium,
57 ppm
magnesium, 1880 ppm manganese, 136 ppm lead, 6 ppm copper, 11 ppm arsenic. 160
ppm
silicon dioxide, and 181,000 ppm chloride. The simulated brine (1539.2 g) was
sparged with air
for about 60 minutes, during which time pH was measured. A calcium hydroxide
slurry having
20% solids by weight was added dropwise after 60, 90, and 120 minutes (total
weight of the
calcium hydroxide slurry added was 13.5 g; calcium hydroxide was 2.7 g dry
basis) to the
solution. The pH was monitored throughout the reaction and was initially
allowed to fall, then
adjusted to a pH of about 5 with the addition of calcium hydroxide after 60
minutes, and
maintained at about a pH of 5 thereafter. The reaction was allowed to stir
while the pH was
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maintained at about 5. Total reaction time was about 180 minutes. A white
precipitate was
collected, washed and weighed, providing a yield of about 95% recovery of the
silica present in
the brine and about 100% of the iron present in the brine.
EXAMPLE 3. Selective Removal of Silica Using Activated Alumina
[00212] A 50 mL brine solution having approximately 180 ppm dissolved
silica was
passed through a 2.5 cm diameter column filled to a depth of 20 cm and
containing
approximately 0.5 g activated alumina and about 1.2 g water. The silica
preferentially adsorbed
onto the alumina and was removed from the solution. The activated alumina had
a surface area
of about 300 m2/g and a grain size of between about 8-14 mesh (-2mm diameter).
The total bed
volume was about 102 mL. The temperature during the step of contacting the
silica containing
brine and the activated alumina was maintained between about 90 and 95 C.
[00213] The concentration of silica in the brine was monitored by measuring
monomeric
silica using the molybdate colorimetric method and using Atomic Absorption for
total silica.
Silica values were significantly lower in the exit solution due to adsorption
of the silica on the
activated alumina. Saturation of the activated alumina in the column was
indicated by a sudden
increase in silica concentration in the exit solution. A total loading of
about 1.8% by weight of
silica (Si02) on the activated alumina was achieved.
[00214] To regenerate the alumina for another cycle of silica removal, the
alumina was
first washed with 5 bed volumes of dilute water in order to remove any salt
solution remaining in
the pores. This removed only a small amount of silica from the alumina. The
alumina was then
reacted with a dilute (0.1M) sodium hydroxide solution at a temperature of
between about 50-
75 C until a desired amount of silica has been removed. The alumina was then
rinsed with
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between about 2-3 bed volumes of dilute acid to prepare the surface for the
next silica adsorption
cycle.
EXAMPLE 4. Continuous Processing of Geothermal Brine
[00215] Approximately 1.5% by weight aluminosilicate seed was added to a
brine solution
comprising about 200 mg/L Li, 75,000 mg/L Na, 24,000 mg/L K, 39,000 mg/L Ca,
156 mg/L Sr,
834 mg/L Zn, 539 mg/L B, 219 mg/L Ba, 160 mg/L Si07, and 215,500 mg/L Cl and
maintained
at about 95 C. About 1.07 mL of a 0.1M solution of A1C13 was added to
approximately 39 mL
of the brine solution such that the ratio of Si02:A1 was 1:1. About 0.45 mL of
a 1N solution of
NaOH was used to titrate the pH of the solution to about 5. The solution was
heated and stirred
for about 10 minutes to ensure complete precipitation of the aluminosilicate.
[00216] Analysis of both the feed and the output fluids during silica
removal yielded
mixed results. Comparing the results of molybdate blue calorimetry (MBC:
useful for
quantifying monomeric silica) and ICP-OES yielded silica levels that were
significantly lower
than input levels (160 mg/L).
[00217] As shown in Table 1, the results of several methods for the removal
of silica from
a brine solution were tested. Both Ca(OH)2 and NaOH were investigated, as was
NaOH along
with a 10% excess of A1C13. For the use of an excess of A1C13, the additional
A1C13 was added
approximately 2 minutes after initiation of the reaction, and additional NaOH
was titrated into
the reaction mixture to maintain a pH of about 5. Finally, NaOH and
polymerized aluminum in
the form of aluminum chlorohydrate (PAC) was also investigated, instead of
A1C13, and was
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prepared in situ by titrating NaOH into A1C13 until a pH of about 4.5 was
achieved. Additional
base was added to raise the pH to about 5.
[00218] Both Ca(OH)2 and NaOH were effective in both increasing the pH of
the solution,
and in removing silica, with Ca(OH)2 being slightly more effective at removing
silica than
NaOH, and removing at least about 80% of the silica present. Precipitation of
silica by
contacting with an excess of A1C13 resulted in the precipitation of nearly 87%
of silica present.
Finally, use of the PAC resulted in the removal of about 84% of the silica
present.
Table 1.
Test Condition ICP MB C
% Si02 remaining % Si02 removed % Si02 remaining % Si02 removed
in solution in solution
Ca(OH)2 17 83 19 81
NaOH 28 72 20 80
NaOH + 110% AlC13 16 84 13 87
NaOH + PAC 17 83 15 85
EXAMPLE 5. Silica Removal Process Using Aluminum Salts
[00219] Approximately 60 mL of brine containing about 160 mg/L silica at a
pH of 5 was
added to 1.07 g of amorphous aluminosilicate seed (-1.5 wt. % solids).
Approximately 1.6 mL
of a 0.1M solution of aluminum chloride (A1C13) was added to the brine
solution. The solution
was stirred, maintained at nominally 95 C, and the pH monitored. The pH
dropped to about 2.7
upon addition of the A1C13 solution. Approximately 13 mL of a saturated and
filtered Ca(OH)2
solution was added. Silica and the aluminum salt formed precipitates, yielding
a brine solution
having a silica content of about 0.23 mg/mL.
EXAMPLE 6. Packed Bed Testing
[00220] A hold-up vessel and packed bed tester (HUV-PB) were used in the
packed bed
testing. A baffled, plug-flow design with stirred sections to keep solid
particles suspended in
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solution was employed. The plug-flow design with mixing is important as it
maintains a
constant and narrow residence time distribution (RTD) while preventing
premature deposition of
suspended solids, which would bias scaling and packed-bed fouling rates.
[00221] The test set-up included brine pumping and metering equipment, a
hold-up vessel
(HUV) to provide controlled residence times similar to a full-scale injection
system, and related
controls and instrumentation.
[00222] A HUV sized for the minimum and maximum hold-up time for injection
pipelines
and wellbores was used to test the fouling rate across the packed bed. The
fouling rate was
monitored by real-time pressure drop (A P) signals at constant flow through
the packed bed.
[00223] The packing configuration and flow through the packed bed was
designed to
provide accelerated fouling compared to that occurring in the injection well.
The packed beds
were packed with screened drilling rock chips from a well hydrothermal zone.
The rock chips
were primarily of two types: 1) hydrothermally-crystallized fine-grained
granitic material
composed of quartz and feldspar and 2) silica-bonded meta-siltstone. The rock
chips were
uniformly packed to allow for the measurement of relative fouling rates under
process conditions
for each test.
[00224] The run time of each experiment depended on the behavior of the
brine across the
packed bed and the increase in pressure across the packed bed. If a pressure
drop maximum was
not reached, the test was run for up to 2 weeks before discontinuation of the
test.
[00225] A side-stream of brine was supplied to the packed bed through heat-
traced packed
bed tubing at about 10 psig from continuously flowing bypass loops. The brine
streams were
metered by positive-displacement peristaltic pumps at a controlled ratio
through a HUV to
simulate the average residence time in the injection pipeline and well
casings. The HUV was
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fitted with baffles and mixing paddles to provide plug flow without settling
of suspended solids.
The brine was then pumped under high-pressure (up to 1000 psig) through the
columns packed
with rock chips in order to simulate the reservoir formation.
[00226] During each test, data collection included brine flow rate,
temperature, pressure,
and differential pressure for each of the columns. Brine samples were
collected for chemical
analysis upstream and downstream of the beds. The tests were run until the
pressure drop (A P)
across the packed bed indicated significant plugging (approaching 1000 psig)
while the brine
flow rate through the column was maintained at a constant rate by a positive
displacement pump.
The tubes had injection brine pumped through them until the pressure reached
about 1000 psig at
1 LPM brine flow. The tests were concluded at 2 weeks, if the pressure drop of
1000 psig was
not experienced.
[00227] At the end of each test the packed bed and tubing test sections
were weighed to
determine the amount of scale deposited and the residual bulk porosity of the
packed bed was
measured. Cross-sections of the packed bed were examined by Scanning Electron
Microscopy
(SEM) and X-ray diffraction (XRD). Brine samples and deposited solids in the
tubing were also
analyzed for chemical composition.
[00228] The test runs were performed in accordance with Table 2.
Table 2.
Test 1 Untreated Brine (UB)
Test 2 Treated Brine (TB)
Test 3 50% UB : 50% TB
Test 4 Untreated Brine (UB)
Test 5 50% UB : 50% TB
Test 6 Treated Brine (TB)
Test 7 Untreated Brine (UB)
Test 8 Treated Brine (TB)
Test 9 50% UB : 50% TB
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Test 10 Untreated Brine (UB)
[00229] Treated brine was brine that had been subjected to a silica
management and iron
removal step as described in example 4 above (continuous removal of silica).
The brine was
treated by first oxidizing the Fe(II) to Fe(III) and precipitating it as
FeO(OH) with the addition of
lime (as described herein). The lithium was extracted using a granulated
sorbent based on a
lithium aluminate intercalate. Untreated brine was brine that had been flashed
for purposes of
extracting energy, but which had only a portion of silica removed, and had not
been processed to
remove iron, in a process in accordance with that described in U.S. Patent No.
5,413,718. The
untreated brine had approximately 160 mg/kg of silica. The 50:50 blends were
50:50 by
volumetric flow rate of treated and untreated brine.
Lithium extraction step
[00230] Lithium was extracted with a granular lithium aluminate sorbent
placed in two
five foot deep and 18 inch diameter columns that were run in alternating
sequences of load and
strip. Each operation was approximately two hours in duration. The sorbent was
made
according to the process described in U.S. Patent No. 8,574,519, which is
hereby incorporated by
reference in its entirety. Once the brine had passed through the columns it
was recovered in a
holding tank before a part of the flow was pumped packed bed test. The lithium
was reduced
from approximately 250 mg/kg to generally less than about 100 mg/kg and
preferably less than
about 15 ppm.
[00231] The pressure profiles of each run are shown in Figures 12-20, and
are summarized
in Table 3 below.
Table 3.
Source Packed Bed Days of Operation
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(to 1000 psi stop-point)
Average
1.38 1.67 0.97
Untreated Brine 1.34 days
(Test 1) (Test 4) (Test 7)
+15.0 4.59 +13.0
Treated Brine +10.9 days
(Test 2) (Test 6) (Test 8)
1.39 3.28 4.60
50:50 blend 3.09 days
(Test 3) (Test 5) (Test 9)
[00232] Comparing the differential pressure profiles from Figures 12, 13,
and 14 against
the differential pressure profiles from Figures 14, 15, and 16, the 50:50
brine blend run times
were equal or better than the untreated brine, which shows that the blend is
not likely to cause
scaling problems as quickly as untreated brine. The longest run times were
observed with the
treated brine as shown in Figures 18, 19, and 20, which ran long enough that
two of the runs
were terminated at two weeks. The maximum potential run time for treated
brine, Test 2, Figure
18, is not known, but an extrapolation of the trend shows it may have been as
long as 6 weeks.
The long run time of the treated brine is likely due to the lack of iron and
silica in the brine
solution. Thus, injection of treated brine appears to give the best outcome
for injectivity and
long term well permeability.
[00233] As shown in Table 4, the differences between the treated and
untreated brines
were the almost total removal of Fe, Si, and As, the significant reduction in
Li, Ba, SO4, F, and
Pb concentrations, and the increase in pH, oxygen concentration, and ORP in
the treated brine
relative to the untreated brine. Removal of Fe, Si, As, reduction in Pb
concentration, increase in
pH, oxygen. and ORP result from the silica management process.
Removal/reduction of Li is
due to the lithium extraction process. Reduction in Ba, SO4, and F
concentrations was due to
Ba504 and CaF2 precipitation during the silica management process. Since Fe
and Si are major
scaling components, the ultimate impact of the brine treatment process on
brine chemistry will
reduce the scaling potential of the depleted brine and improve injectivity.
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Table 4.
Treated brine
Analyte relative to untreated
brine
Temperature -15-20 C
pH +0.8 units
ORP +300 to 500 mV
Ca -3%
Fe -100%
Si -97%
Li -90%
As -100%
Pb -30% - 50%
Ba -60%
SO4 -55%
[00234] The chemistry of the brines were measured before and after
residence time in the
packed bed and blending in the HUV, to ensure that no major chemical reactions
were taking
place during the packed bed testing. A significant reaction would deplete the
brine in one or
more elements.
[00235] In Figures 21 through 25, the first column of each element shows
the brine
chemistry as it entered the HUV, the second column of each element shows the
brine chemistry
as it exited the HUV, and the third column shows the brine chemistry of a
sample pulled 30
minutes from the post-HUV sample. The chemistry of Test 1 (untreated brine)
was not
measured, as it terminated sooner than expected, before chemical samples could
be taken.
However, Test 4 is a repeat of the same test and the results are shown in
Figure 21, and due to
the consistency seen in the brines it is believed that Test 1 would yield
similar results.
[00236] As shown in Figures 22 and 23 for treated brines and in Figures 24
and 25 for
50:50 blend brines, it was observed in almost every case that any change in
the pre- and post-
HUV levels was small, and within the normal sample variation. The implication
of this result is
that the chemistry of the brine is stable during testing, and that there are
no major chemical
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reactions for precipitation reactions that effect brine chemistry in the
packed bed. Even in the
50:50 blend brine (Figures 24 and 25), there were no significant differences
before and after the
HUV. The 50:50 blend brine does show more variability, likely due to a small
amount of Fe
oxidation that also precipitates Si. Typical pH of the tested brines are shown
in Table 5.
Table 5.
Untreated Brine Treated Brine 50:50 Blend
Average pH 4.61 5.67 5.20
Std. Dev. 0.23 0.27 0.09
Samples 20 34 9
[00237] To evaluate the scale, cut sections of the packed beds from Tests 1
through 5 were
submitted for petrologic (mineralogical) evaluation of solids precipitated or
trapped during
packed bed testing. Scanning electron microscopy and X-ray diffraction
analyses were
conducted to characterize the chemical deposits and suspended solids that were
trapped in the
rock matrix. A sample of the unexposed matrix material was also provided in
order to compare
the fine solids with the original rock material.
[00238] Detailed SEM analyses of the scale and fine particles from the five
tests show a
variety of textures and particle morphologies. Associated spot elemental
analyses reveal the
composition of each type of fine material. The dominant type of fine material
consisted of dark
green-colored, amorphous iron silicate with subtle variations based on texture
and elemental
composition. Figures 26 through 31 show low and high magnification SEM images
from the
testing of untreated, treated and 50:50 blend brines.
[00239] Figures 26 and 27 show low and high magnification SEM images from
the testing
of untreated brines. The untreated brine used in Tests 1 and 4, showed smooth,
botryoidal
(globular textured) particles composed of relatively pure iron silicate. More
crumbly, rough-
textured, or fuzzy aggregates were composed of iron silicate with minor
calcium and aluminum.
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In places, more flaky or webby-textured surfaces were composed of iron
silicate with potassium,
aluminum, and calcium. This material could possibly represent a smectite-like
clay.
[00240] Figures 28 and 29 show low and high magnification SEM images from
the testing
of treated brines. The treated brine used in Test 2 formed a fine, cracked
crust composed of
dehydrated iron oxyhydroxide with manganese, chromium, and minor silica. In
places, trace
amounts of nickel and zinc were also present in the Fe-Mn oxyhydroxide. The Fe-
Mn
oxyhydroxide formed a thin brown coating on the drill cuttings.
[00241] Figures 30 and 31 show low and high magnification SEM images from
the testing
of 50:50 blend brines. The 50:50 blend brine used in Tests 3 and 5 formed Fe
and NaC1 deposits
in a fine solid form. These were submicron-sized crumbly deposits. The iron
chloride had a
consistent composition with minor calcium and potassium. Spot analyses also
consistently
showed minor silica with the iron chloride and it was difficult to determine
whether this was one
compound (such as eltyubyuite) or an iron-calcium-potassium chloride admixed
with opaline
silica. XRD analyses indicated minor amounts of opal-A in these two samples.
Based on how
the chloride crystals in the sample were intermixed with the other scale
material, it was possible
that the chlorides had precipitated out of solutions during mixing and
reaction. This was likely
due to the lower temperature of the treated brine when it mixes with the
untreated brine. In a real
injectivity situation, the temperatures of injectivity will be higher and this
will keep the chlorides
in solution.
[00242] A material of interest from the packed bed tests was the small
scale particles and
chemical deposits attached to the rock chip matrix. If the total rock sample
was used, the rock
matrix would dilute the scale minerals in the sample, rendering them too
dilute to be identifiable
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in the XRD scans. Therefore, the small-scale particles were washed from the
matrix rock and
concentrated to more accurately measure the mineralogy and composition of the
scale.
[00243] A
summary of the separated packed bed tube scale is shown in Table 6. Other
than halite (NaC1) precipitated in the 50:50 blend in Tests 3 and 5, all of
the major crystalline
material in the XRD patterns was attributed to minerals from the rock
fragments in the drill
cuttings. Other than trace to minor amounts of crystalline iron oxides
(magnetite, maghemite)
and iron oxyhydroxides (goethite, akaganeite), most of the chemical deposits
appeared to be
amorphous or too poorly crystalline to diffract the X-rays.
Table 6. XRD Mineralogy Relative Wt %
Salton
SAMPLE ID Sea Drill Test #1 Test #2 Test #3 Test
#4 Test #5
Cuttings
Quartz 63 31 41 0 7 17
Plagioclase 15 14 11 1 0 8
K-Feldspar 5 5 8 2 1 3
Calcite 2 2 0 0 0 1
Dolomite 1 0 0 0 0 0
Ankerite 1 0 0 0 0 0
Epidote 5 11 7 30 2 6
Barite 0 0 1 0 0 0
Pyrite 0 0 0 0 0 0
Magnetite 0 1 6 1 4 2
Maghemite 0 2 0 0 3 1
Geothite 0 0 0 0 3 0
Akaganeite 0 0 1 0 0 3
Halite 0 0 0 38 0 14
Total (Non-Clay) 91 66 74 71 20 55
Illite+ Mica 0 0 4 9 12 11
Mixed-Layer Illite- 0 0 0 0 0 0
Smectite
Chlorite 8 11 22 1 4 18
Total (Clay) 9 11 27 10 16 29
Total (Crystalline
100 76 100 81 36 84
Material)
Amorphous (Opal-A) 0 24 0 19 64 16
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GRAND TOTAL
(Crystalline and Opal- 100 100 100 100 100 100
A)
[00244] A
summary of the clay fines from the packed tube scale is shown in Table 7. The
dominant clay material was fine mica, which was likely a component of the
drill cuttings matrix.
Table 7. Clay XRD Mineralogy (< 4 micron size fraction, Relative Wt %)
SAMPLE ID
Rock chips Test #1 Test #2 Test #3 Test #4 Test #5
% Expandability of VS clay
25 0 35 10 0 0
(smectite interlayers)
Mica 26 67 31 35 71 44
Mixed-Layer Illite-Smectite (VS) 13 0 23 39 0 0
Kaolinite 0 0 0 0 0 18
Chlorite 61 33 46 26 29 38
TOTAL 100 100 100 100 100 100
[00245]
Total suspended solids is also an important parameter of the brine
compatibility
testing. The treated brine had lower TSS values than the untreated brine, and
even the 50:50
blend brines had less than or equal TSS to the untreated brine.
[00246] The
TSS of the untreated brine was measured using an accurate in-line method
throughout the series for tests. Those values are shown in Figure 32. The data
showed that the
TSS of the untreated brine average was about 20 ppm, but it was variable, and
sometimes
reached 50 ppm.
[00247] The
TSS were also measured on the brines used for packed bed testing, before
and after the HUV using a vacuum filtration method. The values are shown in
Figure 33. As
expected, the treated brines possessed a low TSS due to the lack of scaling
components and
filtration during processing. The untreated brine and the 50:50 blend brine
showed higher TSS,
at a similar range of values.
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[00248] Shown in Figures 34 and 35 are the results of the treated brine
(Tests 2, 6, and 8),
untreated brine (Tests 1, 4, and 7), and 50:50 brine blends (Tests 3 and 5)
analysis for percent
weight gain and residual bulk porosity.
[00249] The 50:50 blend brines performed equal to or better than the
untreated brine in
packed bed simulated well testing. This suggests that there are no major
compatibility or
reaction issues, and that reservoir permeability would not be any worse than
the untreated brine.
[00250] In addition, treated brine performed far better on the packed bed
permeability
testing than any other brine or brine blend tested. This is likely due to the
lack of scaling
compounds in the treated brine, along with a lower TSS value. The results
suggests that an
injection fluid of 100% treated brine will have the best injectivity and
permeability performance
than any other brine tested.
[00251] One improvement that can be made to the 50:50 blend brine, that may
make it
perform even better, is to provide dilution water or maintain high temperature
to prevent halite
(NaC1) from coming out of solution before injection.
EXAMPLE 7. Preparation of Treated Geothermal Brine Compositions with Reduced
Concentrations of Iron and Silica
[00252] In another example, four 20L plastic pails of geothermal brine from
the Salton
Sea, California that were subjected to silica processing, were transferred to
the reactor. The
combined sample was agitated at 80 C for 4 hours and then samples were
collected for an
elemental analysis. Table 8 shows concentrations of various elements in
samples of the
geothermal brine samples.
Table 8.
Concentration in Sample 1 Concentration in Sample 2
Element analyzed
mg/L mg/L
Arsenic <3 <3
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Concentration in Sample 1 Concentration in Sample 2
Element analyzed
mg/L mg/L
Barium 42 44
Iron 1900 1900
Lithium 310 309
Lead 130 130
Silicon 30 30
A laboratory scale stage 1 precipitation was conducted on a sample of the
adjusted geothermal
brine. The brine was sparged with air for 20 minutes, and then approximately
70% of the
required lime was added to the reaction solution. The balance of the lime was
added over the
next 20 minute period. The reaction was conducted for a total time of 150
minutes. During the
reaction period, kinetic samples were collected at set reaction times. At the
end of the reaction
period the slurry was processed in the standard manner. The Oxidation
Reduction Potential of
the solution after 20 minutes of air sparging was 200 mV. The solution pH
value was 3Ø The
solution concentrations for iron and silica were plotted against elapsed
reaction time in Figure
34. Approximately 98% of the silica precipitated and the final silica
concentration was reduced
to 6 mg/L after 65 minutes. The iron was removed by about 65% of the Fe
precipitated and the
final Fe solution concentration was 940 mg/L.
EXAMPLE 8. Preparation of Larger Scale Treated Geothermal Brine Compositions
with
Reduced Concentrations of Iron and Silica
[00253] In another example, about 69 liters of adjusted geothermal brine
was subjected to
processing on a larger scale. An insulated double walled polypropylene reactor
(-80 L) was
equipped with a polycarbonate lid that had multiple access ports for the
various pieces of
equipment and instrumentation. The overall reaction as observed at about 81 C,
following initial
sparging time of 40 minutes with an airflow of 2.25 L/min. About 84 g of dry
lime was added.
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The Si and Fe solution concentrations are plotted against reaction time in
Figure 35. Some of the
initial and final test conditions for the bulk test are summarized in Table 9.
Table 9.
Condition Initial Reading Final Reading
pH 4.43 5.33
ORP, mV -14 -293
[00254] Analysis of the data from this experiment revealed that there was
insufficient
mixing of the solution that resulted in poor suspensions of the initial
contained solids. As the
reaction progressed, the majority of these solids dissolved and released iron
and silica to
solution. The silica concentration was reduced to below 10 mg/L and iron was
removed to about
900 mg/L. Changes in the air sparging period or changes in the air flow to the
system were made
to increase the iron removal. The filtrate from the reactor was subjected to
further processing at
a temperature of about 95 C. Air was sparged into the system for about 20
minutes and then
lime was added and the pH constantly monitored. Air sparging continued. The
iron
concentration at pH 6.0 was below 50 mg/L and, therefore, the reaction was
stopped and the
reaction slurry was processed. The Si and Fe solution concentrations were
plotted against
reaction time in Figure 36. These experiments revealed that by changing the
conditions of the
treatment, one could achieve the desired levels of iron and silica removal
from the geothermal
brine.
EXAMPLE 9. Preparation of Treated Geothermal Brine Compositions with Reduced
Concentrations of Iron and Silica from Brine Treatment at a Physical Plant.
[00255] Producing treated brines with reduced silica and iron concentration
minimizes the
problems downstream during extraction of minerals like zinc and lithium from
the treated brine.
As discussed herein, the resulting brines with reduced silica and iron
concentration is much less
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likely to damage the injection wells, because all major scale-producing
elements have been
removed.
[00256] The methods and systems described herein were deployed for silica
management
of geothermal brine at two different physical plants. One physical plant
included three
rectangular continuously stirred tank reactors for iron (II) oxidation and
iron (III) oxyhydroxide
precipitation, and an inclined plate (lamella) clarifier for initial
solid/liquid separation. Another
physical plant included two cylindrical continuously stirred tank reactors and
a cylindrical
conventional rake-style clarifier. The second plant also implemented an
improved air-
sparging/agitation system for more efficient iron (II) oxidation. Because of
the decrease in
number of reactors, and the increased sparging efficiency, the total residence
time in the reactor
train could be reduced by a factor of 3. The switch to a conventional
clarifier was made in part
to minimize manual operations related to cleaning the clarifier lamella of
sticky solids, and partly
to provide data for a clarifier design that was suitable for scale up to
commercial size.
[00257] Operations using the three-reactor physical plant included feeding
brine from a
geothermal energy producer at a specified rate between 3-6 gpm. Operational
set points (pH,
sparge rate, agitation) for the three reactors were adjusted following the
experimental
observation from pilot studies. Flocculant was added initially to the
clarifier based on batch
flocculation tests, and adjusted as necessary to gain control of TSS in
overflow. The proportion
of underflow directed to recycle, and the recycle return point(s) were set as
desired for the
specific pilot campaign. Underflow advance was directed to the filter feed
tank (or thickener),
and then to pressure filter. Filtrate and thickener overflow were generally
recycled back to the
first reactor. Filter cake was periodically removed from the pressure filter
and directed to waste.
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[00258] Operations using the two-reactor physical plant were essentially
similar. Table 10
shows a comparison of the sample operating conditions at the two plants.
Table 10.
Plant Residence Feed/inlet/outlet Agitation
Sparging Clarifier Recycle
time at
nominal
gpm, min
Inlet feed was pump
controlled; advance flow via
Sparging via
gravity. Variable Inclined plate
Recycle
3- perforated
; with integral underflow
speed
reactor 120 Horizontal input near tank square U-tube
flash tank and to R-1
and
single
plant bottom below agitator blade. at bottom of
impeller floc chambers R-2
tank
Horizontal output near tank
top.
Inlet feed is pump
controlled; advance flow via Variable
gravity. speed; dual
impeller; Sparging via
40 or 20 Vertical input at tank Cylindrical
2- Recycle
lower was air injection
depending on bottom; mixed with sparge with rake and
reactor 8" Rushton into brine
underflow
position of air. separate floc
plant blade; feeds at tank to R-1
only
outflow mixing tank
Two side outlet ports; upper upper was bottom
yields 40 minute residence 8" pitched
time; lower yields 20 minute blade
residence time at 5 gpm.
[00259] Previous studies indicate that at ¨110 C the concentration of
dissolved silica in
Salton Sea geothermal brine coming out of a crystallizer clarifier is ¨116
ppm. The feed brine
composition varied depending on variations in the geothermal brine and in the
operations of the
geothermal energy producer. For example without limitations, the variations
could arise from
changes in dilution water added to the brine, or from operations related to
their flashing and
subsequent processing.
[00260] In an exemplary set-up, similar to that shown in Figure 6,
geothermal brine was
subjected to a continuous process for the management of silica. Silica
management system 1106
was carried out using two stiffed vessels 1108 and 1110 provided in series. To
first reactor 1108
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a geothermal brine was supplied via line 1104 having an iron content of
approximately 1500
ppm and a silica content of about 160 ppm. The brine is added at a rate of
about 6 gpm.
Approximately 30 cfm of air was supplied via line 1140 to each reactors 1108
and 1110, and was
sparged through the geothermal brine. The operating temperature was
approximately about 90 to
95 C in reactor 1 and 85 to 90 C in reactor 2.
[00261] After the addition of the air via line 1140' to first reactor 1108,
the pH dropped
and was around approximately about pH 4.8 to 5.4. Air was added to second
reactor 1110 via
line 1140" at a rate of about 30 cfm and a charge of approximately 10-25% by
weight of an
aqueous calcium oxide slurry at a rate of about 0.5 lb/min., which raised the
pH in the second
reactor to between about 5.0 and 5.6. The addition of the lime slurry
initiated the precipitation of
iron (III) hydroxide and iron silicate. The geothermal brine, which included
precipitates of iron
(III) hydroxide or iron oxyhydroxide and iron silicate, was then supplied from
the second vessel
1110 to clarifier 1146 via line 1144. An aqueous flocculant solution of
Magnafloc 351, in a
concentration between about 0.005% and 1% by weight, such as about 0.025% by
weight, was
prepared by supplying solid flocculant 1124 via line 1126 to flocculant tank
1128, where the
solid was contacted with water 1120 supplied via line 1122. The aqueous
flocculant solution
was supplied to clarifier vessel 1146 via line 1138 at a rate of about 0.01
gpm.
[00262] Two streams were produced from clarifier 1146. First clarifier
product stream
1148 included the geothermal brine having a reduced concentration of silica
and iron, and was
supplied to a secondary process, such as lithium recovery. Second clarifier
product stream 1150
included solid silica-iron waste, as well as some geothermal brine. The brine
was sampled
between reactors 1108 (Reactor 1) and after 1110 (Reactor 2) before as well as
after the clarifier
1146 (clarifier overflow).
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[00263] Table 11 shows the concentration of iron and silicon after silica
management
through the first reactor and after the second reactor in a physical plant.
Based on analysis of the
data collected, the iron concentration ranged from about 200 mg/L to 1000
mg/L, while the
silicon concentration ranged from about 1 to 60 mg/L.
Table 11.
From Reactor 1
Fe concentrations (mg/kg) Si concentrations (mg/kg)
Min 168 1
Max 828 43
Mode 307 10
Median 335 13
From Reactor 2
Fe concentrations (mg/kg) Si concentrations (mg/kg)
Min 180 <1
Max 833 48
Mode 297 12
Median 261 14
[00264] Samples were analyzed from the feed brine and from the clarifier
overflow to
determine the concentrations of silica and silicon. Figures 37A and 37B show
the histograms of
silicon (not Si02) concentrations in feed brine (Figure 37A) and clarifier
overflow (Figure 37B).
While the concentration of silicon in the feed brine ranged from 16-117 ppm,
the mean and
median silicon concentrations were both about 55 ppm. While the concentration
of silicon in the
treated brine from the clarifier ranged from 0-25 ppm, the mean and median
silicon
concentrations were both about 4 ppm. The Si02 concentration in the feed brine
ranged from 32
to 250 ppm, with a mean and median of 118 ppm. The silica in the clarifier
overflow ranged
from 0.4 to 53 ppm, with a mean and median of 8.6 and 7.7 ppm, respectively.
Hence, -93 % of
the feed Si02 was removed by the silica management circuit.
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[00265] Samples were analyzed from the feed brine and from the clarifier
overflow to
determine the concentrations of iron. The histograms in Figures 39A and 39B
illustrate the iron
concentrations in feed brine (Figure 39A) and clarifier overflow (Figure 39B).
While the
concentration of iron in the feed brine ranged from 638-3830 ppm, the mean and
median iron
concentrations were both about 1600 ppm. While the concentration of iron in
the treated brine
from the clarifier ranged from 0-636 ppm, the mean and median iron
concentrations were about
20 ppm and less than 1 ppm respectively.
[00266] Samples were also analyzed from another exemplary demonstration of
the
process. Figures 38A and 39B show histograms of dissolved silicon (not silica)
concentrations
in feed brine (Figure 38A) and clarifier overflow (Figure 38B). While the
concentration of
silicon in the feed brine ranged from 27-98 ppm, the mean and median silicon
concentrations
were both about 53-54 ppm. While the concentration of silicon in the treated
brine from the
clarifier ranged from 1-25 ppm. the mean and median silicon concentrations
were both about 4
ppm. The range in feed Si02 was 58 ppm to 131 ppm with mean and median of 113
ppm and
115 ppm, respectively. Si02 in the clarifier overflow ranged between 2 and 53
ppm, with a mean
and median of 8.9 and 7.8 ppm, respectively. There was similar removal
efficiency in the 95%
range. Samples were analyzed from the feed brine and from the clarifier
overflow to determine
the concentrations of iron. The histograms in Figure 40 illustrate the iron
concentrations in feed
brine (Figure 40A) and clarifier overflow (Figure 40B). While the
concentration of iron in the
feed brine ranged from 980-3830 ppm, the mean and median iron concentrations
were both about
1670 ppm. While the concentration of iron in the treated brine from the
clarifier ranged from 0-
258 ppm, the mean and median iron concentrations were about 18 ppm and 3 ppm,
respectively.
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[00267] In
another exemplary demonstration of the process, the treated brine with reduced
silica and iron concentration was fed to a lithium removal process, and the
presence of arsenic,
barium, iron, lithium, lead, and silicon was analyzed at different stages of
the operation, and the
results are shown in Table 12. Concentrations of calcium in these treated
compositions can vary
from about 30,000 ppm to about 46,000 ppm, with a median concentration of
about 36,000 ppm.
Concentrations of sodium in these treated compositions can vary from about
40,000 ppm to
about 80,000 ppm, with a median concentration of about 61,150 ppm.
Table 12.
Arsenic Barium Iron Lithium Lead Silicon Potassium Manganese Zinc
Sampling
ppm ppm ppm ppm ppm ppm ppm
ppm ppm
Silica Min 8 0 990 144 49 27 10,990 889
288
Management Max 30 244 2085 387 110 61 25,990 1558 540
Inlet Median 13 198 1673 248 92 54 17,920
1349 472
Silica Min 0 51 0 122 43 1 9,063 695
208
Management Max 3 516 258 354 90 25 24,350 1556 552
Outlet Median 0 154 3 251 78 4 18,480 1366
476
Brine Outlet Min 0 52 0 16 41 0 16,860
953 434
from Max <1 191 72 287 86 4 29,325 1803
614
Lithium
Extraction Median <1 120 1 45 65 3 21,020 1483 515
Column 1
Brine Outlet Min 0 0 0 5 26 0 10,640
753 309
from Max 1 348 331 341 92 12 33,850 2111
678
Lithium
Extraction Median <1 108 1 46 73 3 19,920 1427 499
Column 2
EXAMPLE 10. Selective Removal of Potassium Using Ammonium Tetrafluorob orate
[00268]
Approximately 100 grams of geothermal brine was heated to about 90 C in a
water bath. Approximately 3.5 grams of ammonium tetrafluoroborate was added to
the brine.
White potassium tetrafluoroborate precipitate formed almost immediately. The
mixture was
vigorously shaken for 30 seconds and then transferred to centrifuge tubes and
centrifuged at
4000 rpm for 4 minutes. Two layers formed, a clear aqueous layer and a white
potassium
tetrafluoroborate precipitate layer. The clear aqueous layer was decanted off
and the potassium
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tetrafluoroborate precipitate was washed with deionized water at room
temperature. The
potassium tetrafluoroborate precipitate yield was 2.4 grams.
EXAMPLE 11. Selective Removal of Potassium Using Fluoroboric Acid
[00269]
Approximately 100 grams of geothermal brine was heated to about 90 C in a
water bath. Approximately 5.0 grams of fluoroboric acid (as 48% by weight
solution) was added
to the brine. A white potassium tetrafluoroborate precipitate formed almost
immediately. The
mixture was vigorously shaken for 30 seconds and then centrifuged at 4000 rpm
for four
minutes. Two layers were formed, a clear aqueous layer and a solid white
potassium
tetrafluoroborate precipitate layer. The clear aqueous layer was decanted off
and the potassium
tetrafluoroborate precipitate layer was washed with deionized water. The
potassium
tetrafluoroborate precipitate yield was 2.65 grams.
EXAMPLE 12. Selective Removal of Potassium Using Modified DOWEX-K-21 resin
beads
[00270]
Approximately 100 grams of water was added to 40 grams of Dowex-K-21 ion
exchange resin beads containing chloride ions. To this, 8 grams of potassium
tetrafluoroborate
was added and the resulting solution was heated to about 90 C in a water bath
for approximately
30 minutes. The solution was stirred occasionally during heating. All
potassium
tetrafluoroborate dissolved in the first 5 minutes of the reaction. The clear
solution was decanted
off and the tetrafluoroborate terminated Dowex-K-21 resin beads (modified
resin beads) were
separated from the clear solution. Approximately 50 grams of geothermal brine
was heated to
about 90 C in a water bath. Approximately 40 grams of the modified resin beads
were added to
the brine. The mixture was vigorously shaken for 1 minute and then continued
heating at 90 C
in a water bath. A white potassium tetrafluoroborate precipitate formed within
5 minutes.
Heating continued for 5 more minutes. The liquid with the precipitate was
collected in a
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centrifuge tube. The liquid with the precipitate was then centrifuged at 4000
rpm for 4 minutes.
The potassium tetrafluoroborate precipitate yield was 0.4 grams.
EXAMPLE 13. Potassium Chloride Conversion using Tetrabutylammonium Chloride
[00271] Approximately 0.55 grams of tetrabutylammonium chloride (TBAC) was
dissolved in about 10 mL of water in a test tube and heated to about 85 C.
Potassium
tetrafluoroborate (approximately 0.25 grams), prepared using the methods
described above, was
added to the solution and heated with occasional stirring until completely
dissolved. A lighter
white precipitate formed and floated to the surface of the solution. After
five minutes, the white
precipitate was separated from the aqueous layer of the solution. The aqueous
layer was allowed
to evaporate to dryness, producing solid potassium chloride. The reaction
yielded 90 mg of
potassium chloride.
EXAMPLE 14. Potassium Chloride Conversion Using Trihexyltetradecyl Phosphonium
Chloride
[00272] Approximately 1.03 grams of trihexyltetradecyl phosphonium chloride
was added
to about 5 grams of water and heated to about 90 C. Approximately 1.02 grams
of potassium
tetrafluoroborate, prepared using the methods described above, was added to
the solution and
stirred vigorously for about 30 minutes. Two layers were formed, an aqueous
layer and an
organic layer. The two layers were separated and the aqueous layer was allowed
to evaporate to
dryness, producing solid potassium chloride. The reaction yielded 0.5 grams of
potassium
chloride.
EXAMPLE 15. Potassium Chloride Conversion Using DOWEX-K-21 Resin Beads
[00273] Approximately 8 grams of DOWEX-K-21 resin beads were added to 100
grams
of water and heated to 90 C. 1.0 gram of potassium tetrafluoroborate was added
to the solution
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and the solution was shaken vigorously for 30 seconds every two minutes, for
approximately 10
minutes. All of the potassium tetrafluoroborate was dissolved in solution
after 10 minutes. The
resulting aqueous layer was separated from the resin beads and allowed to
evaporate to dryness,
producing solid potassium chloride. This reaction yielded 0.58 grams of
potassium chloride.
EXAMPLE 16. Potassium Chloride Conversion Using Trihexyltetradecyl Phosphonium
Chloride
[00274] Approximately 4.1 grams of potassium tetrafluroborate was added to
7.3 grams of
water. To this suspension was added approximately 16.8 grams of
trihexyltetradecyl
phosphonium chloride. The resulting mixture was vigorously agitated at 90 C
for 2 to 10
minutes. The resulting mixture was separated using a separatory funnel. The
potassium chloride
concentration in the final solution was approximately 23 wt.%. X-ray powder
diffraction
confirmed the presence of potassium chloride.
EXAMPLE 17. Selective Removal of Potassium and Rubidium from a Reduced Silica
Feed
Using Fluoroboric Acid
[00275] A geothermal brine that had been subjected to a silica management
process and
had reduced silica content was heated to about 90 C in a water bath.
Fluoroboric acid (as 48%
by weight solution) was added to the reduced silica geothermal brine, as shown
in Table 13. A
white potassium tetrafluoroborate precipitate formed almost immediately. The
mixtures were
vigorously shaken for 30 seconds and then centrifuged at 4000 rpm for four
minutes. Two layers
were formed; a clear aqueous layer and a solid white potassium
tetrafluoroborate precipitate
layer. The clear aqueous layer was decanted off and the potassium
tetrafluoroborate precipitate
layer was washed with deionized water. The clear aqueous layer was analyzed
using ICP-OES.
The results are shown in Table 14.
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Table 13.
Sample g XBF4/kg Brine brine wt. (g) brine, mL HBF4
wt. (g)
1 0 10 8.33 0
2 0.96 10 8.33 0.02
3 4.8 10 8.33 0.1
4 12 10 8.33 0.25
24 10 8.33 0.5
6 36 10 8.33 0.75
7 48 10 8.33 1
8 60 10 8.33 1.25
9 72 10 8.33 1.5
Table 14.
Fe K Li Mn Pb Rb Si Zn
Sample
(mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg)
1 0.2 19667 256 1417 93 287 4 531
2 N.D. 18167 249 1433 89 280 4 537
3 N.D. 17000 247 1400 89 264 5 520
4 N.D. 13917 248 1392 90 234 5 529
5 0.17 8417 23 1283 85 179 5 489
6 N.D. 3500 249 1425 83 123 6 537
7 N.D. 925 235 1358 72 55 6 507
8 0.18 392 251 1425 76 37 9 524
9 0.13 362 266 1508 74 32 11 565
N.D. indicates that the levels were below detectable limits.
EXAMPLE 18. Selective Removal of Potassium and Rubidium from a Reduced Silica
Feed
Using Fluoroboric Acid
[00276] A geothermal brine that had been subjected to a silica management
process and
had reduced silica content was heated to about 90 C in a water bath.
Fluoroboric acid (as 48%
by weight solution) was added to the reduced silica geothermal brine, as shown
in Table 15. A
white potassium tetrafluoroborate precipitate formed almost immediately. The
mixtures were
vigorously shaken for 30 seconds and then centrifuged at 4000 rpm for four
minutes. Two layers
were formed; a clear aqueous layer and a solid white potassium
tetrafluoroborate precipitate
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layer. The clear aqueous layer was decanted off and the potassium
tetrafluoroborate precipitate
layer was washed with deionized water. The clear aqueous layer was analyzed
using ICP-OES.
The results are shown in Table 16.
Table 15.
g XBF4/Kg Brine brine wt. (g) brine, mg/Kg HBF4 wt. (g)
1 0 50 41.7 0
2 2.16 50 41.7 0.23
3 5.57 50 41.7 0.58
4 8.06 50 41.7 0.84
12.96 20 41.7 0.54
6 17.52 20 41.7 0.73
7 22.56 20 41.7 0.94
8 25.44 20 41.7 1.06
Table 16.
Fe K Li Mn Pb Rb Si Zn
Sample
(mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg,/kg) (mg/kg)
1
<MQL 21917 131 <MQL <MQL <MQL 1.31 1.31
2 <MQL 19000 121 0.93 <MQL <MQL
2.01 2.01
3 <MQL 17958 125 0.44 <MQL <MQL
1.38 1.38
4 <MQL 16792 130 0.62 <MQL <MQL
1.30 1.30
5 <MQL 14292 134 1.64 <MQL <MQL
1.33 1.33
6 <MQL 11125 121 0.62 <MQL <MQL
1.23 1.23
7 <MQL 9208 127 0.48 <MQL <MQL
1.30 1.30
8
<MQL 7017 115 <MQL <MQL <MQL 1.23 1.23
<MQL or less than Method Quantification Limit indicates that the levels were
below detectable
limits of the method.
EXAMPLE 19. Selective Removal of Potassium and Rubidium from a Reduced Silica
Brine
Using Ammonium Tetrafluoroborate
[00277] A
geothermal brine that had been subjected to a silica management process and
had reduced silica content was heated to about 90 C in a water bath. Ammonium
tetrafluoroborate was added to the reduced silica geothermal brine, as shown
in Table 17. A
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white potassium tetrafluoroborate precipitate formed almost immediately. The
mixtures were
vigorously shaken for 30 seconds and then centrifuged at 4000 rpm for four
minutes. Two layers
were formed; a clear aqueous layer and a solid white potassium
tetrafluoroborate precipitate
layer. The clear aqueous layer was decanted off and the potassium
tetrafluoroborate precipitate
layer was washed with deionized water. The clear aqueous layer was analyzed
using ICP-OES.
The results are shown in Table 18.
Table 17.
Sample g XBF4/Kg Brine Brine wt. (g)
Brine, mL NH4BF4 wt. (g)
1 0 10 8.33 0
2 0.48 10 8.33 0.01
3 2.4 10 8.33 0.05
4 4.8 10 8.33 0.1
12 10 8.33 0.25
6 24 10 8.33 0.5
7 38.4 10 8.33 0.8
Table 18.
Fe K Li Mn Pb Rb Si Zn
Sample
(mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg)
1 <MQL 19417 235 1883 83 191 2.6 507
2 <MQL 18083 220 1817 78 183 2.6 465
3 <MQL 18167 224 1833 79 181 2.8 473
4 <MQL 17583 220 1800 78 178 2.9 469
5 <MQL 16083 230 1892 83 173 3.1 499
6 <MQL 9917 260 2017 93 135 3.8 531
7 <MQL 1542 218 1783 79 42 7.8 455
<MQL or less than Method Quantification Limit indicates that the levels were
below detectable
limits of the method.
EXAMPLE 20. Selective Removal of Potassium and Rubidium from a Reduced Silica
Brine
Using Calcium Tetrafluoroborate
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[00278] Reduced silica brine was heated to about 90 C in a water bath.
Calcium
tetrafluoroborate was added to the reduced silica brine, as shown in Table 19.
A white potassium
tetrafluoroborate precipitate formed almost immediately. The mixtures were
vigorously shaken
for 30 seconds and then centrifuged at 4000 rpm for four minutes. Two layers
were formed; a
clear aqueous layer and a solid white potassium tetrafluoroborate precipitate
layer. The clear
aqueous layer was decanted off and the potassium tetrafluoroborate precipitate
layer was washed
with deionized water. The clear aqueous layer was analyzed using ICP-OES. The
results are
shown in Table 20.
Table 19.
Sample g XBF4/Kg Brine brine wt. (g) brine, L Ca(BF4)2 wt. (g)
1 0 10 8.33 0
2 2 10 8.33 0.02
3 10 10 8.33 0.1
4 25 10 8.33 0.25
50 10 8.33 0.5
6 75 10 8.33 0.75
7 100 10 8.33 1
Table 20.
Sample Fe K Li Mn Pb Rb Si Zn
(mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg)
1 <MQL 14833 109 0.1 15 242 10.7 0.91
2 <MQL 14833 106 0.1 16 239 2.7 0.96
3 <MQL 14292 107 0.1 16 229 4.4 0.95
4 <MQL 12208 106 0.1 16 209 1.6 0.99
5 <MQL 10292 111 0.2 16 113 0.8 1.14
6 <MQL 5688 110 0.2 16 142 1.0 1.20
7 <MQL 2483 111 0.3 16 99 1.1 1.34
EXAMPLE 21. Selective Removal of Cesium from a Reduced Silica Brine Using
Crystalline
Silicotitanate
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[00279] A reduced silica brine was heated to about 90 C in a water bath.
One gram of
crystalline silicotitanate was added to 100 grams of reduced silica brine and
allowed contact for
3 hours, at pH 3, 5, and 8. The crystalline silicotitanate uptake of cesium
was measured. Uptake
efficiency at pH 8 was 35.11%, at pH 5 was 77.46%, and pH 3 was 73.53%. The
concentration
of Cs was measured using atomic absorption spectroscopy. The uptake efficiency
is measured
by analyzing the initial concentration in the brine solution prior to contact
with the CST sorption
media and again after contact.
[00280] As is understood in the art, not all equipment or apparatuses are
shown in the
figures. For example, one of skill in the art would recognize that various
holding tanks and/or
pumps may be employed in the present method.
[00281] The singular forms "a," "an" and "the" include plural referents,
unless the context
clearly dictates otherwise.
[00282] "Optional" or "optionally" means that the subsequently described
event or
circumstances may or may not occur. The description includes instances where
the event or
circumstance occurs and instances where it does not occur.
[00283] Ranges may be expressed herein as from about one particular value,
and/or to
about another particular value. When such a range is expressed, it is to be
understood that
another embodiment is from the one particular value and/or to the other
particular value, along
with all combinations within said range.
[00284] Throughout this application, where patents or publications are
referenced, the
disclosures of these references in their entireties are intended to be
incorporated by reference into
this application, in order to more fully describe the state of the art to
which the invention
pertains, except when these reference contradict the statements made herein.
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[00285] As used herein, recitation of the term about and approximately with
respect to a
range of values should be interpreted to include both the upper and lower end
of the recited
range.
[00286] Although the present invention has been described in detail, it
should be
understood that various changes, substitutions, and alterations can be made
hereupon without
departing from the principle and scope of the invention. Accordingly, the
scope of the present
invention should be determined by the following claims and their appropriate
legal equivalents.
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