Note: Descriptions are shown in the official language in which they were submitted.
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TREATMENT OF FROTH TAILINGS FROM OIL
SANDS PROCESSING
TECHNICAL FIELD
[0001] The present disclosure relates to dewatering and consolidation of
froth tailings
from oil sands extraction processes. Residual hydrocarbons present in the
froth tailings can also
be separated and recovered.
BACKGROUND
[0002] The separation and extraction of oil and bitumen from soil, sand,
or other forms of
mineral matter is a difficult and expensive process. The commercial operations
presently used to
extract bitumen from Canadian oil sands involve crushing oil sand ore and
combining it with hot
or warm water and chemical aids such as sodium hydroxide (NaOH) to form a
slurry. The
chemical aids, together with the mechanical action of transporting the slurry
through a
hydrotransport pipeline, help to detach bitumen from oil sand particles. At
the extraction plant,
the conditioned slurry is discharged into primary separation vessels and
bitumen is separated
from solids by aeration to form a bitumen containing froth that can be skimmed
off the surface of
the water. The solids, mainly sand and some fines, together with process-
affected water, are
discharged as a tailings slurry to a tailings pond. The term fines as used
herein is consistent with
the Canadian oil sands classification system and means solid particles with
sizes equal to or less
than 44 microns (pm). Sand is considered solid particles with sizes greater
than 44 rim.
[0003] Bitumen froth is an emulsion of bitumen (about 50%-60%), water
(about 30%-
40%) and solids (about 10%-14%), mostly but not entirely mineral fines. The
components of this
emulsion are not easily separated. To reduce interfacial tension, reduce
viscosity and provide a
density difference, a diluent or solvent is added, followed by various forms
of enhanced gravity
separation. Like primary separation, froth treatment produces tailings, which
in most commercial
operations is also discharged as a separate stream to tailings ponds, where it
combines with the
tailings deposited from the primary separation cells.
[0004] The management and sustainability of tailings ponds pose
significant and growing
problems. It is estimated that tailings ponds associated with Canadian oil
sands operations now
cover an area of more than 200 km2. Reclamation efforts have had limited
success and the ponds
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continue to grow in size. The tailings ponds contain components that are toxic
to aquatic life and
the water cannot be discharged to natural waterways such as the Athabasca
River. Because of
the presence of fine particles, a gel-like layer of so-called mature fine
tailings also develops in
the ponds. It is estimated that under the action of gravity alone, this
component would take more
than a century to consolidate and settle.
[0005] Although froth tailings are a small component of the tailings
produced (2-4%)
from oil sands extraction, they contain most of the components that are
considered problematic,
including significant residues of bitumen among other hydrocarbons including
the diluent or
solvents used to extract the bitumen. Froth tailings also have somewhat
elevated concentrations
of pyrite, naturally occurring radioactive materials, and some heavy metals.
[0006] Treating the froth tailings as a separate stream before it enters
tailings ponds
would therefore confer significant environmental advantages and improvements
to current
processes. It would enable operators to apply different suites of tailings
technologies to this
stream, facilitate reclamation by removing the most toxic components, and
reduce fugitive
emissions associated with residual pollutants.
SUMMARY OF THE DISCLOSURE
[0007] Advantages of the present disclosure include processes to treat
bitumen froth
tailings to dewater the tailings to produce high solids content materials.
Additional advantageous
can include separating hydrocarbons from the tailings.
[0008] These and other advantages are satisfied, at least in part, by a
process of
consolidating bitumen froth tailings. The process comprises treating the
bitumen froth tailings,
which include fines and process water, with a highly water soluble salt.
Advantageously, the
process can include treating the bitumen froth tailings with the at least one
highly water soluble
salt or solution thereof and can optionally include either or both of at least
one polymer
flocculant or solution thereof and/or coarse particles, e.g., sand, to form a
treated tailings. The
treated tailings can include a consolidated material in the process water. The
process water can
then be advantageously separated from the consolidated material.
[0009] Implementations of the process of the present disclosure include,
for example, (i)
treating the bitumen froth tailings with at least one highly water soluble
salt to form a treated
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tailings including a consolidated material in the process water, (ii) treating
the bitumen froth
tailings with at least one highly water soluble salt and at least one polymer
flocculant to form a
treated tailings including a consolidated material in the process water, (iii)
treating the bitumen
froth tailings with at least one highly water soluble salt thereof, and coarse
particles to form a
treated tailings including a consolidated material in the process water, and
(iv) treating the
bitumen froth tailings with at least one highly water soluble salt, at least
one polymer flocculant
and coarse particles to form a treated tailings including a consolidated
material in the process
water. Each of these implementations can include aqueous solutions of the salt
and/or polymer
flocculant to treat the tailings. Each of these implementations can include
separating the process
water from the consolidated material.
[0010] In practicing aspects of the processes, bitumen froth tailings
that include
hydrocarbon, such as tar, crude oil, heavy oil, or other hydrocarbon oil,
bitumen, asphaltenes,
etc. or diluents or solvents or any combinations thereof, can be separated and
recovered. The
process can further comprise treating the tailings with a diluent to dilute
the hydrocarbon and
recovering the diluted hydrocarbon. Advantageously, the hydrocarbon separated
from the
tailings can contain a low amount of fines or has low minerals content, e.g.,
less than about 1
wt% or no more than about 0.5 wt% or no more than about 0.1 wt%.
[0011] In practicing aspects of the processes of the present disclosure
and the various
embodiments thereof, the separated process water can include the at least one
highly water
soluble salt and the process can further comprise: one or more of: (i)
recovering at least a portion
of the separated process water; (ii) recycling at least a portion of recovered
separated process
water to treat additional bitumen froth tailings; (iii) purifying at least a
portion of recovered
process water and/or (iv) concentrating the at least one highly water soluble
salt in recovered
process water to form a brine and using the brine to treat additional bitumen
froth tailings. Such
concentration can be carried out by reverse osmosis, for example.
[0012] Yet another aspect of the present disclosure includes recovering
the consolidated
materials from the tailings. Advantageously, the processes of the present
disclosure can
consolidate the solids of the tailings to produce a consolidated material
having a solids content in
excess of about 45% by weight, e.g., a solids content of greater than about
50% and higher than
about 60%, 65%, 70% and 75% by weight.
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[0013] Embodiments of the processes include one or more of the following
features
individually or combined. For example, in some embodiments the at least one
highly water
soluble salt can have a solubility in water (a salt/water solubility) of at
least about 5 g/100 g at 20
C, e.g., at least about 10 g/100 g at 20 C. In other embodiments, the at
least one highly water
soluble salt is a non-hydrolyzing salt. In still further embodiments, the at
least one highly water
soluble salt can have a monovalent cation and can include an ammonium based
salt, a phosphate
based salt, or a sulfate based salt.
[0014] In certain embodiments, the treated tailings can have a salt-
tailings concentration
of at least 0.5 wt% of the at least one highly water soluble salt and
preferably no less than about
1 wt%, such as at least about 2 wt% and even greater than about 3 wt%, 4 wt%,
5 wt%, etc. of
the at least one highly water soluble salt. In other embodiments, treating
bitumen froth tailings
includes using a solution of one or more highly soluble salts sourced from a
natural or existing
source, e.g., seawater or a body of hypersaline water. In some embodiments,
the at least one
polymer flocculant is a polyacrylamide or co-polymer thereof The treated
tailings can have a
polymer-tailings concentration of the at least one polymer flocculant of no
less than zero and up
to about 0.001 wt%, e.g., up to about 0.003 wt%, 0.005 wt%, 0.01 wt% or 0.04
wt%.
Advantageously, the polymer flocculant forms high density flocs, e.g., having
a density greater
than the process water, which facilitates separation and dewatering of the
consolidated solids. In
other embodiments, the tailings also can be treated with coarse particles,
e.g., sand, at a sand to
fines ratio of less than 4:1, e.g., between about 2.5:1.0 to 0.5:1 or between
about 2.25:1 to about
0.75:1.
[0015] In various embodiments, treating the tailings can include
combining the bitumen
froth tailings with a solution including the at least one highly water soluble
salt and the at least
one polymer flocculant. In some embodiments, treating the tailings can include
combining a
stream of the oil sands tailing with a stream of a solution including the at
least one highly water
soluble salt and a separate stream of a solution including the at least one
polymer flocculant.
Alternatively, or in combination, treating the tailings can include combining
a stream of the
bitumen froth tailings with a stream of a solution including both the at least
one highly water
soluble salt and the at least one polymer flocculant. Coarse particles (sand)
can also be added to
the bitumen froth tailings or stream thereof and/or to any or all of the
solution streams.
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Advantageously, the streams can be mixed inline and/or with the aid of an
inline mixer. In
certain embodiments, treating the bitumen froth tailings can be carried out at
a temperature of no
more than 50 C, e.g., no more than about 40 C or 30 C. In other
embodiments, treating the
composition includes using a solution of one or more highly soluble salts
sourced from a natural
or existing source such as seawater or a body of hypersaline water.
[0016] In still further embodiments, the process water can be separated
from the
consolidated material by any one or more of decanting, filtering, vacuuming,
gravity draining,
etc. or combinations thereof. In various embodiments, separating the process
water from the
consolidated material can include mechanically dewatering the consolidated
material, e.g.,
mechanically dewatering the consolidated material by a dewatering screw. Once
separated, the
consolidated material can be transferred for further dewatering or disposal.
[0017] In practicing certain aspects of the processes of the present
disclosure and the
various embodiments thereof, the consolidated material formed in the treated
tailings according
to certain embodiments can result in a high solids content after mixing and/or
dewatering the
treated tailings in a short period of time. In some embodiments, the
consolidated material can
have a solids content of greater than about 50% and at least about 60%, 65%,
70%, 75% and
80% by weight after mixing and/or dewatering. In certain embodiments a solids
content of at
least about 70 % is achieved within about one month of gravity draining after
treating the
tailings, e.g., within about two weeks or within about one week of gravity
draining after treating
the tailings.
[0018] Additional advantages of the present invention will become readily
apparent to
those skilled in this art from the following detailed description, wherein
only the preferred
embodiment of the invention is shown and described, simply by way of
illustration of the best
mode contemplated of carrying out the invention. As will be realized, the
invention is capable of
other and different embodiments, and its several details are capable of
modifications in various
obvious respects, all without departing from the invention. Accordingly, the
drawings and
description are to be regarded as illustrative in nature, and not as
restrictive.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Reference is made to the attached drawings, wherein elements
having the same
reference numeral designations represent similar elements throughout and
wherein:
[0020] Figure 1 schematically illustrates an exemplary embodiment of a
process of
consolidating bitumen froth tailings.
[0021] Figure 2A is a picture of a vial containing bitumen froth tailings
sample.
[0022] Figure 2B is a picture of a vial containing bitumen froth tailings
after treatment
with a highly soluble salt and polymer flocculant followed by centrifugation
in accordance with
certain embodiments of the present disclosure.
[0023] Figure 3 is a picture of vials containing bitumen froth tailings
treated with a
highly soluble salt, polymer flocculant and sand.
[0024] Figure 4 is a picture of vials containing bitumen froth tailings
treated with a
highly soluble salt, polymer flocculant, sand and a diluent.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0025] The present disclosure relates to treating bitumen froth tailings
to consolidate and
dewater the tailings. As described in the background section, bitumen froth
tailings are a waste
by-product of the process of extracting bitumen from oil sands and include
process water, fines,
and hydrocarbons such as tar, crude oil, heavy oil, or other hydrocarbon oil,
bitumen,
asphaltenes, etc. or diluents or solvents or any combinations thereof. In
certain aspects, treating
the bitumen froth tailings can also include separating and recovering the
hydrocarbons from the
tailings. Advantageously, the process of the present disclosure can
consolidate the solids of the
tailings to produce consolidated material having a solids content in excess of
about 45% by
weight, e.g., a solids content of greater than about 50% and higher than about
60%, 65%, 70%
and 75% by weight.
[0026] The solids of bitumen froth tailings are classified according to
particle sizes. The
term fines as used herein is consistent with the Canadian oil sands
classification system and
means solid particles with sizes equal to or less than 44 microns (im). Sand
is considered solid
particles with sizes greater than 44 [im. Oil sands deposits include a
significant amount of fines,
e.g., 10-30 wt%. The tailings from oils sands extraction can also include a
significant amount of
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fines by weight (>5 wt%) as their solids content. Such tailings can include at
least about 10
wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt% or higher fines as their
solids content.
[0027] The terms coagulation and flocculation are often used
interchangeably in the
literature. As used herein, however, coagulation means particle aggregation
brought about by the
addition of hydrolyzing salts, whereas flocculation means particle aggregation
induced by
flocculating polymers. Hydrolyzing salts undergo hydrolysis when added to
water to form metal
hydroxides, which precipitate from the solution, trapping fines and other
minerals in the
coagulating mass. Hydrolyzing salts typically have low solubility in water and
are used as
coagulants. Aggregation induced by flocculation, in contrast, is believed to
be the result of the
polymer binding to the particles thereby tying the particles together into a
so called floc causing
aggregation of the particles.
[0028] In practicing aspects of the present disclosure, bitumen froth
tailings, e.g., a
suspension of particulate solids in an aqueous liquid which include fines and
process water, can
be consolidated by treating the bitumen froth tailings with one or more highly
water soluble
salt(s) or an aqueous solution thereof to destabilize and consolidate solids
in the tailings, e.g., to
destabilize and consolidate fines in the tailings. Aggregation induced by the
addition of salts is
believed to be the result of destabilizing the particles suspended in the
fluid by an alteration or a
shielding of the surface electrical charge of the particles to reduce the
inter-particle repulsive
forces that prevent aggregation. The process water can then be separated from
the consolidated
material. Advantageously, the consolidated material has a solids content of at
least 45% by
weight, e.g., a solids content of greater than about 50% by weight.
[0029] Salts that are useful in practicing the present disclosure include
salts that are
highly soluble in water. A highly water soluble salt as used herein is one
that has a solubility in
water of greater than 2 g of salt per 100 g of water (i.e., a salt/water
solubility of 2g/100g) at 20
C. Preferably the highly water soluble salt has a water solubility of at least
about 5 g/100 g at
20 C, e.g., at least about 10 g/100 g of salt/water at 20 C.
[0030] In addition, the highly water soluble salts used in the processes
of the present
disclosure are preferably non-hydrolyzing. Hydrolyzing salts undergo
hydrolysis when added to
water to form metal hydroxides, which precipitate from the solution. Such
hydrolyzing salts are
believed to form open flocs with inferior solids content and cannot be readily
recycled for use
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with additional tailings in continuous or semi-continuous processes. In
addition, hydrolyzing
salts typically have low solubility in water and are used at elevated
temperatures to ensure
sufficient solubility for aggregation, which is an energy intensive process.
See US 4,225,433
which discloses the use of lime as a coagulating agent at a temperature of 75
C.
[0031] Further, the highly water soluble salts are preferably not
carboxylate salts since
such organic acid salts tend to be more expensive than inorganic salts and can
be deleterious to
plant and/or animal life.
[0032] Highly water soluble salts that are not hydrolyzing and useful in
practicing
processes of the present disclosure include salts having a monovalent cation,
e.g., alkali halide
salts such as sodium chloride, potassium chloride; also salts with monovalent
cations such as
sodium nitrate, potassium nitrate, sodium and potassium phosphates, sodium and
potassium
sulfates, etc. are useful in practicing processes of the present disclosure.
Other monovalent
cationic salts useful in practicing processes of the present disclosure
include ammonium based
salts such as ammonium acetate (NH4C2H302), ammonium chloride (NH4C1),
ammonium
bromide (NH413r), ammonium carbonate ((NH4)2CO3), ammonium bicarbonate
(NH4HCO3),
ammonium nitrate (NH4NO3), ammonium sulfate ((NH4)2SO4), ammonium hydrogen
sulfate
(NH4HSO4), ammonium dihydrogen phosphate (NH4H2PO4), ammonium hydrogen
phosphate
((NH4)2HPO4), ammonium phosphate ((NH4)3PO4), etc. Mixtures of such salts can
also be used.
[0033] Ammonium based salts are useful for practicing the present
disclosure since
residual ammonium based salts on the consolidated material after combining the
salt with the
bitumen froth tailings are not harmful to plant life. In fact, many of the
ammonium based salts
are useful as fertilizers and are in fact beneficial to plant life, e.g.,
ammonium chloride,
ammonium nitrate, ammonium sulfate, etc. Many of the monovalent sulfate and
phosphate salts
are also useful as fertilizers. In certain embodiments of the present
disclosure, the highly water
soluble salt or salts used in the processes of the present disclosure can
preferably be non-toxic
and beneficial to plant life to aid in environmental remediation and the
restoration of mine sites.
[0034] In one aspect of the present disclosure, treating bitumen froth
tailings with a
highly water soluble salt destabilizes and consolidates solids in the
tailings. Such a process can
include mixing the bitumen froth tailings, which includes fines and process
water, with a highly
water soluble salt to consolidate the fines, and separating the process water
from the consolidated
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fines to produce a high solids content, e.g., at least 45% by weight. In
certain embodiments, the
highly water soluble salt is an ammonium based salt.
[0035] Highly water soluble salts that can be used in practicing the
present process can
also include salts having multivalent cations. Such salts include, for
example, divalent cation
salts such as calcium and magnesium cation salts, such as calcium chloride
(CaCl2), calcium
bromide (CaBr2), calcium nitrate (Ca(NO3)2), magnesium chloride (MgCl2),
magnesium bromide
(MgBr2), magnesium nitrate (Mg(NO3)2), magnesium sulfate (MgSO4); and
trivalent cation salts
such as aluminum and iron (III) cation salts, e.g., aluminum chloride (A1C13),
aluminum nitrate
(Al(NO3)3), aluminum sulfate (Al2(SO4)3), iron (III) chloride (FeC13), iron
(III) nitrate
(Fe(NO3)3), iron (III) sulfate (Fe2(SO4)3, etc. As explained above, the highly
water soluble salts
used in the processes of the present disclosure are preferably non-
hydrolyzing. Many of the
multivalent cation salts are hydrolyzing and thus less preferred for the
reasons stated above.
Moreover, experimentation with multivalent salts showed increased fouling of
containers and
formation of less cohesive consolidated materials as compared to highly water
soluble salts
having monovalent cations. In addition, some multivalent salts, such as FeCl3
and Fe2(SO4)3, are
particularly corrosive and Fe2(SO4)3 is formed from oxidizing pyrite and
results in acid mine run-
off, which make such salts less preferable for use in processes of the present
disclosure.
[0036] We found that when a sufficiently high concentration of the highly
water soluble
is included in the treated tailings, the salt can destabilize and consolidate
solids in the tailings.
For a relatively short process times with a relatively low energy input, the
salt-tailings
concentration of the at least one highly water soluble salt should preferably
be at least 0.5 wt%
and preferably no less than about 1 wt%, such as at least about 2 wt% and even
at least about 3
wt%, 4 wt%, 5 wt%, etc. The term "salt-tailings concentration" as used herein
refers to the
concentration of the highly water soluble salt(s) in the treated tailings and
is determined by
taking the percentage of the mass of highly water soluble salt(s) divided by
the combined mass
of the salt(s) plus the tailings and any water used to dilute the salt(s). For
example, combining 1
part undiluted (i.e., neat) salt to 99 parts tailings by weight results in a
salt-tailings concentration
of 1 wt%. Alternatively, treating bitumen froth tailings with an equal weight
of a 2 wt% solution
of the salt also results in a salt-tailings concentration of 1 wt% in the
treated tailings.
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[0037] The highly water soluble salt(s) can be used to treat bitumen
froth tailings as a
solid, e.g., combining the salt as a powder with the tailings. Alternatively,
the salt can be used to
treat bitumen froth tailings as a solution, e.g., combining an aqueous salt
solution with the
tailings. In some aspects of the present disclosure, an aqueous solution of
the highly water
soluble salt can be prepared having a concentration of no less than about 1
wt%, e.g., greater
than about 2 wt%, 3 wt%, 5 wt%, 7 wt%, 10 wt%, 20 wt%, 30 wt% and even as
great as a 40
wt% or as an aqueous salt slurry.
[0038] In some embodiments of the present processes, it can be more
advantageous to
use a natural source of a highly soluble salt or salts such as in a natural
body of water including
such salts in sufficiently high concentration such as at least about 2 wt% and
even at least about
3 wt% or greater. For example, ocean or seawater can be used as a source of
highly soluble salts,
which can significantly improve the economics of the process under certain
conditions. The vast
majority of seawater has a salinity of between 31 g/kg and 38 g/kg, that is,
3.1-3.8%. On
average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L,
599 mM).
Seawater includes of a mixture of salts, containing not only sodium cations
and chlorine anions
(together totaling about 85% of the dissolved salts present), but also sulfate
anions and calcium,
potassium and magnesium cations. There are other ions present (such as
bicarbonate), but these
are the main components. Another natural source of highly soluble salts that
can be used as a
source of highly soluble salts includes a hypersaline body of water, e.g., a
hypersaline lake,
pond, or reservoir. A hypersaline body of water is a body of water that has a
high concentration
of sodium chloride and other highly soluble salts with saline levels
surpassing ocean water, e.g.,
greater than 3.8 wt% and typically greater than about 10 wt%. Such hypersaline
bodies of water
are located on the surface of the earth and also subsurface, which can be
brought to the surface as
a result of oil sands mining operations.
[0039] The bitumen froth tailings and salt solution or slurry should be
mixed at a ratio
sufficient to destabilize the tailings and/or cause consolidation of the
solids therein. In one
aspect of the present disclosure, the bitumen froth tailings and the salt
solution are mixed
[0040] at a ratio within a range of about 5.0:1.0 to about 1.0:5.0, e.g.,
mixed at a ratio
within a range of about 3:1 to about 1:3, such as about 1.5:1.0 to about
1.0:1.5 bitumen froth
tailings to salt solution.
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[0041] After treating the bitumen froth tailings with at least one highly
water soluble salt
the solids in the tailings can be consolidated such as by mixing followed by
gravity
sedimentation in a settling tank or by centrifugation to increase the rate of
forming a
consolidated material in the treated tailings. The consolidated material can
be separated from the
process water by decanting, filtering, electrofiltration, cross-flow
filtering, vacuuming, and/or by
mechanical dewatering, i.e., applying an external force to the consolidated
material. Once
separated, the consolidated material can be transferred for further dewatering
or disposal.
[0042] The process of the present disclosure allows for large scale
treatment of bitumen
froth tailings in a continuous or semi-continuous process. For example, the
process water
separated from an initial tailings treatment can advantageously include a
significant amount of
the one or more highly water soluble salt(s). This separated process water, or
at least a portion
thereof, can then be recovered and recycled to consolidate the solids of
additional bitumen froth
tailings by mixing the recovered process water with additional bitumen froth
tailings. The highly
water soluble salt(s) in the recovered process water can be concentrated
and/or additional highly
water soluble salt(s) added to formulate a solution from the recovered process
water for use in
treating additional bitumen froth tailings.
[0043] Although highly water soluble salts can destabilize and
consolidate solids in the
tailings, it was found that the process could be significantly improved by
including one or more
polymer flocculant(s) to the process. Including a polymer flocculant to the
process of treating
tailings with a highly water soluble salt can significantly reduce the time
for consolidation of
fines.
[0044] In addition, the processes of the present disclosure can also
include treating
bitumen froth tailings with coarse particles, e.g., particles with sizes
greater than 44 pin, such as
sand, to significantly increase the solids content. It is believed that use of
coarse particles such
as sand are needed to increase the solids content of the tailings to greater
than about 60% without
use of thermal treatments or long processing times. While treating bitumen
froth tailings with
water soluble salt(s) and coarse particles without polymer flocculant(s) can
consolidate solids in
the tailings, such a process leads to a loose consolidation.
[0045] Hence, implementation of the process of the present disclosure
include (i) treating
bitumen froth tailings with at least one highly water soluble salt to form a
treated tailings
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including a consolidated material in the process water, (ii) treating bitumen
froth tailings with at
least one highly water soluble salt and at least one polymer flocculant to
form a treated tailings
including a consolidated material in the process water, (iii) treating bitumen
froth tailings with at
least one highly water soluble salt thereof, and coarse particles to form a
treated tailings
including a consolidated material in the process water, and (iv) treating
bitumen froth tailings
with at least one highly water soluble salt, at least one polymer flocculant
and coarse particles to
form a treated tailings including a consolidated material in the process
water. Each of these
implementations can include aqueous solutions of the salt and/or polymer
flocculant to treat the
tailings. Each of these implementations can include separating the process
water from the
consolidated material. The process water can be readily separated from the
consolidated material
as, for example, by one or more of decanting, filtering, electrofiltering,
cross-flow filtering,
gravity draining, vacuuming and other evaporating techniques, etc. or
combinations thereof
and/or by one or more of a device for dewatering consolidated material such as
a centrifuge,
decanting centrifuge, dewatering screw, hydrocyclone, vacuum belt filter,
filter press or pressing
devices, etc. or combinations thereof. In addition, the separated consolidated
material can be
disposed or deposited in a containment structure which allows removal of
released water from
the consolidated material.
[0046]
Polymers that are useful in practicing the present disclosure include water
soluble
flocculating polymers such as polyacrylamides or copolymers thereof such as a
nonionic
polyacrylamide, an anionic polyacrylamide (APAM) and a cationic polyacrylamide
(CPAM),
which can contain co-monomers such as acryloxyethyltrimethyl ammonium chloride
(DAC),
methacryloxyethyltrimethyl ammonium chloride (DMC), dimethyldiallyammonium
chloride
(DMDAAC), etc. Other water soluble flocculating polymers useful for practicing
the present
disclosure include a polyamine, such as a polyamine or quaternized form
thereof, e.g.,
polyacrylamide-co-dimethylaminoethylacrylate in quaternized form, a
polyethyleneimine, a
polydiallyldimethyl ammonium chloride, a polydicyandiamide, or their
copolymers, a
polyamide-co-amine, polyelectrolytes such as a sulfonated polystyrenes can
also be used. Other
water soluble polymers such as polyethylene oxide and its copolymers can be
used. The polymer
flocculants can be synthesized in the form of a variety of molecular weights
(MW), electric
charge types and charge density to suit specific requirements. Advantageously,
the flocculating
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polymer used in practicing processes of the present disclosure do not include
use of activated
polysaccharides or activated starches, i.e., polysaccharides and starches that
have been heat
treated, in sufficient amounts to lower the density of the floc to below the
density of the process
water from which they are separated. Such activated polysaccharides and
activated starches
when used in sufficiently high dosages tend to form low density flocs which
rise to the surface of
an aqueous composition complicating removal of hydrocarbon and can hinder
removal of solids
in large scale operations involving high solids content and can also hinder
dewatering of
consolidated material.
[0047] The amount of polymer(s) used to treat tailings should preferably
be sufficient to
flocculate the solids in the tailings and any added sand. The amount of
polymer(s) used to treat
tailings can be characterized as a concentration based on the total weight of
the tailings or as a
dosage based on the weight percent of the solids in the tailings.
[0048] In some embodiments of the present disclosure, the concentration
of the one or
more polymer flocculant(s) in the treated tailings has a polymer-tailings
concentration of no less
than zero and up to about 0.001 wt%, e.g., up to than about 0.003 wt%, 0.005
wt% or up to about
0.01 wt%. For relatively short processing times, consolidation of the
fines/sand mixture can be
obtained at polymer-tailings concentrations no less than about 0.04 wt%. The
term "polymer-
tailings concentration" as used herein refers to the concentration of the
flocculating polymer(s) in
the treated tailings and is determined by taking the percentage of the mass of
the polymer(s)
divided by the combined mass of the polymer(s) plus the tailings and any water
used to dissolve
the polymer(s). For example, combining 1 part undiluted (i.e., neat) polymer
to 9999 parts
tailings by weight results in a polymer-tailings concentration of 0.01 wt%.
Alternatively,
treating bitumen froth tailings with an equal weight of a 0.02 wt% solution of
the polymer also
results in a polymer-tailings concentration of 0.01 wt%. In certain
embodiments, bitumen froth
tailings is treated with at least one polymer flocculant to yield a polymer-
tailings concentration
of up to about 0.02 wt%, such as up to about 0.03 wt%, 0.04 wt%, 0.05 wt%, and
even at least
about 0.07 wt%, 0.09 wt%, 0.1 wt%, 0.2 wt%, etc. The amount of polymer
flocculant can be
used in greater concentrations. However, after certain high concentrations it
becomes difficult to
dissolve the flocculant, the solution becomes too viscous and the process is
less economical.
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[0049] In some embodiments of the present disclosure, the concentration
of the one or
more polymer flocculant(s) in the treated tailings has dosage (weight of the
flocculant(s) to
weight of the solids in the tailings) of up to about 0.005 wt%, e.g., up to
about 0.01 wt% and
preferably up to about 0.015 wt%, 0.020 wt%, 0.025 wt%, 0.03 wt%, or 0.04 wt%.
[0050] It was observed that the amount of polymer flocculant can be
reduced if the salt-
tailings concentration is increased. While the reason for this effect is not
clear, a very low
polymer-tailings concentration of up to about 0.001 wt%, e.g., up to about
0.003 wt%, 0.005,
wt%, 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt %, for example, can
achieve reasonably
fast consolidation of solids in bitumen froth tailings if the salt-tailings
concentration is increased.
[0051] Coarse particles useful for practicing processes according to the
present disclosure
are preferably sand and when used in treating tailings the amount of such
particles are preferably
in a sand to fines ratio (SFR ratio) of less than 4:1, e.g., between about
2.5:1.0 to 0.5:1 or
between about 0.75:1 and 2.25:1. The SFR ratio is calculated by determining
the amount of sand
added to an estimated amount of solid fines in the tailings on a weight basis.
It is believed that
the use of coarse particles facilitates packing of the consolidated fines
which advantageously
increases the solids content and can even form a jammed structure of
consolidated solids, i.e. a
structure in which generally individual particles of the consolidated solid
can no longer move
freely relative to other particles.
[0052] Treating bitumen froth tailings with at least one highly water
soluble salt and
optionally with either or both of at least one polymer flocculant and/or sand
can be carried out in
a number of ways. In certain embodiments, treating the bitumen froth tailings
includes
combining and/or mixing the various components. In addition, the at least one
salt can be added
directly to the tailings either as an undiluted powder or as a solution; the
at least one polymer
flocculant can be added directly to the tailings either as an undiluted
material or as a solution,
and the sand can be added to the tailings directly or with the salt and/or
polymer or solutions
thereof. The salt and polymer can be combined in a single solution, with or
without sand, and
combined with the tailings. The order of combining the salt, polymer and sand
to the tailings can
give equivalent results and optimization of the process will depend on the
scale and equipment
used in the process.
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[0053] However, it tends to be more convenient to first prepare one or
more solutions
including the one or more highly water soluble salt(s) and the one or more
polymer flocculant(s)
followed by combining the one or more solutions with the bitumen froth
tailings and sand. In
certain embodiments, an aqueous solution of one or more highly water soluble
salt(s) can be
prepared having a concentration of no less than about 0.5 wt% or 1 wt%, e.g.,
at least about 2
wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 10 wt%, 20 wt%, 30 wt% and even as
great as a 40
wt% or as an aqueous salt slurry for use in treating the tailings. The one or
more polymer
flocculant(s) can also be included in the aqueous solution of the salt(s) and
can have a
concentration of no less than zero and up to about 0.001 wt%, e.g., up to
about 0.003 wt%, 0.005
wt%, 0.01 wt%, 0.04 wt%, 0.05 wt %, 0.1 wt%, 0.2 wt%, 0.4 wt%, for example.
The aqueous
solution of the highly water soluble salt(s) and polymer flocculant(s) can be
used to treat the
bitumen froth tailings and can be combined with such tailings at a ratio of
between 5.0:1.0 and
1.0:5.0, such as 3: to 1:3 and at a ratio between 1.5:1.0 to 1.0:1.5 of
bitumen froth tailings to
aqueous solution. Sand can be combined with the tailings before, during, or
after combining the
tailings with the salt(s) and polymer(s) solutions.
[0054] Because highly water soluble salts and polymer flocculants that
are preferably
water soluble are used in the process of the present disclosure, the
temperature of the treated
tailings need not be elevated above ambient to practice the process. In
certain embodiments,
treating the bitumen froth tailings according to the various embodiments
herein can be carried
out at a temperature of no more than 50 C, e.g., no more than about 40 C or
30 C.
Advantageously, the processes of the present disclosure can be practiced
without addition of a
significant amount of an alkali metal hydroxide salt(s), such as lithium,
sodium or potassium
hydroxide, e.g., less than 0.05 wt% or without any addition of such salts.
Such strongly alkali
salts tend to require elevated temperatures to be effective.
[0055] In practicing aspects of the present disclosure, bitumen froth
tailings, e.g., a
suspension of particulate solids in an aqueous liquid which include fines and
process water, can
be consolidated by treating the bitumen froth tailings with at least one
highly water soluble salt
or aqueous solutions thereof and can optionally include either or both of (i)
at least one polymer
flocculant, e.g., a water soluble flocculating polymer, or aqueous solutions
thereof, and/or (ii)
coarse particles, e.g., sand to form a treated tailings. Treating tailings in
this manner can cause
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destabilization and consolidation of the solids, e.g., fines and sand, in the
treated tailings to form
a consolidated material, which can settle under gravity relatively quickly, in
the process water.
The process water can then be readily separated from the consolidated
material.
[0056] The treated tailings and/or consolidated material can be further
dewatered to
further separate the process water from the consolidated material and, in some
instances, further
consolidate the solids. In some embodiments, the consolidated material formed
in the treated
tailings can be separated from the process water by any one or more of
decanting, filtering, e.g.,
electrofiltering, cross-flow filtering, gravity draining, vacuuming and other
evaporating
techniques, etc. or combinations thereof and/or by any one or more of a
mechanical dewatering,
i.e., applying an external force to the consolidated material, with a device
for dewatering
consolidated material such as by applying a centrifuge, decanting centrifuge,
dewatering screw,
hydrocyclone, filter press, pressing device, etc. or combinations thereof. In
one aspect of the
processes of the present disclosure, the process water can be separated from
the consolidated
material by passing a stream of treated tailings through a cross-flow filter,
e.g., a porous or
slotted pipe, which filters and dewaters the treated tailings stream to
separate the process water
from the consolidated material. In another aspect of the processes of the
present disclosure, the
process water can be separated from the consolidated material by gravity
draining to achieve a
solids content of at least about 70% within about a month after treating the
tailings, e.g., within
about two weeks or within about one week of gravity draining after treating
the tailings.
[0057] The consolidated material formed in the treated tailings can
advantageously have
a high solids content, e.g., a solids content of greater than about 50% and at
least about 60%,
65%, 70% and 75% by weight. In addition, the consolidated material formed in
the treated
tailings according to certain embodiments can result in a high solids content
after mixing and/or
dewatering the treated tailings in a short period. In embodiments of the
present disclosure, the
consolidated material can have a solids content of greater than about 50% and
at least about
60%, 65%, 70%, 75% and 80% by weight after mixing and/or dewatering. In
certain
embodiments a solids content of at least about 70 % is achieved within about
one month of
gravity draining after treating the tailings, e.g., within about two weeks or
within about one week
of gravity draining after treating the tailings.
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[0058] In an embodiment of the present disclosure, the process includes
mixing the
bitumen froth tailings with a highly water soluble salt, e.g., an ammonium
based salt, a water
soluble polymer, e.g., a polyacrylamide, and sand, e.g., in a sand to fines
ratio of between 0.75:1
and 2.25:1 to form a treated tailings including a consolidated material having
a high solids
content, e.g., a solids content of greater than about 50% by weight, e.g., at
least about 60%, 65%,
70 wt% or higher.
[0059] Another advantage of the processes of the present disclosure is
the recovery of
materials from tailings that include rare earth elements. For example, certain
tailings can include
valuable minerals that include rare earth elements. A rare earth element
(REE), as defined by
IUPAC, is one of a set of seventeen chemical elements in the periodic table,
specifically the
fifteen lanthanides, as well as scandium and yttrium. Scandium and yttrium are
considered rare
earth elements because they tend to occur in the same ore deposits as the
lanthanides and exhibit
similar chemical properties. Many of the REE are used in electronic devices,
magnets, high
performance coatings. Such REE include cerium (Ce), dysprosium (Dy), erbium
(Er), europium
(Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium
(Nd),
praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium
(Tb), thulium
(Tm), ytterbium (Yb) and yttrium (Y).
[0060] REE in aqueous fines are typically in the form of an ion or oxide.
For example,
zirconium can be present as zircon, ZrSiO4, titanium can be present as the
minerals ilmenite,
leucoxene and rutile. Coal ash and coal cleaning wastes contain rare earth
elements. Fire clay
coal ash has unusually high concentrations of Yttrium and zirconium. Oil sands
tailings also
contain REE.
[0061] The processes of the present disclosure are useful in recovering
REE. It is
believed that in some tailings, REEs absorb on the surface of clays in
tailings. In other tailings,
REEs are included also among the solids of the tailings but can also be in the
process water.
Absorbed REEs can be exchanged with the highly water soluble salts of the
present disclosure,
e.g., ammonium based salts due to an exchange of ammonium ions for the REE
ions. REEs from
the solids of the tailings can be obtained by leaching the solids with acid
followed by extraction
and precipitation or by caustic decomposition followed by acid leaching.
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[0062] Another aspect of processes of the present disclosure includes
consolidating an
aqueous composition including fines and process water, e.g., tailings, which
include REE
materials by treating the composition with at least one highly water soluble
salt, e.g., an
ammonium based salt such as ammonium sulfate, to form a treated composition
including a
consolidated material in process water which includes the REE materials in the
process water
and/or among the consolidated materials. In one aspect of the present
disclosure, the treated
composition consolidates the fines and also separates REE materials from the
solids and into the
process water. The process water can then be separated from the consolidated
material and the
REE materials can be recovered from the separated process water. The REE
materials can be
recovered from the process water by precipitation, e.g., using oxalic acid, or
extraction. Other
methods for recovering REE from the process water include mineral processing
and physical
beneficiation, deep eutectic solvents/ionic liquids extraction, acid
dissolution, high temperature
phase separations, use of REE selective sorbents, photophoresis, in-situ brine
injection and
extraction, reactive grinding, etc. In other aspect of the present disclosure,
the treated
composition consolidates the fines and REEs are among the consolidated
materials. The process
water can then be separated from the consolidated material. The consolidated
material can then
be leached with acid, e.g., nitric acid, sulfuric acid, etc., followed by
extraction with solvent
and/or ion exchange resins and precipitated. Alternatively, the consolidated
material can then be
treated with a caustic reagent such as sodium hydroxide to decompose certain
of the materials to
form hydroxides of the REEs followed by leaching in acid, e.g., HC1.
[0063] The process of the present disclosure allows for large scale
treatment of bitumen
froth tailings in a continuous or semi-continuous process with further
recovering, recycling and
purifying at least a portion of the process water in the tailings. When non-
hydrolyzing, highly
water soluble salts are used in the processes of the present disclosure, the
process water separated
from an initial treated tailings can advantageously include a significant
amount of the one or
more highly water soluble salt(s) initially used to treat the tailings.
[0064] In practicing aspects of the processes of the present disclosure
and the various
embodiments thereof, the separated process water can include the at least one
highly water
soluble salt and the process can further comprise one or more of: (i)
recovering at least a portion
of the separated process water; (ii) recycling at least a portion of recovered
separated process
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water to treat additional bitumen froth tailings; and/or (iii) purifying at
least a portion of
recovered process water. In some implementations, the recovered separated
process water, which
includes the highly soluble salts(s), can be processed to concentrate the
highly soluble salts(s) in
the water. For example, a reserve osmosis system, which generates desalted
water and a waste
brine, can be used to generate a brine which includes the highly soluble
salts(s) from recovered,
separated process water from the treated bitumen froth tailings. This brine
can then be used to
treat additional bitumen froth tailings and the process can be carried out in
a continuous or semi-
continuous manner.
[0065] Figure 1 schematically illustrates such an exemplary continuous or
semi-
continuous process. As shown in the figure, bitumen froth tailings is treated
with one or more
highly water soluble salt(s) by combining a stream of the salt(s) (101a),
which can be as an
aqueous solution, with a stream of tailings (103a). Optionally, the tailings
can also be treated
with one or more polymer flocculant(s) by combining a stream of the
flocculants(s) (102a),
which can be as an aqueous solution, with the tailings stream (103a).
Alternatively, the salts(s)
and flocculant(s) can be combined together as a solution to treat the tailings
as a stream thereof.
Coarse particles (sand) can also be added to the bitumen froth tailings or
stream thereof and/or to
any or all of the solution streams.
[0066] The streams of salt(s) and polymer(s) can be sourced from holding
areas 101 and
102 and the streams of tailings and sand can be sourced from holding areas 103
and 105,
respectively. Alternatively, the froth tailings and/or the stream of sand can
be sourced directly
from an oil sands extraction or separation operation.
[0067] For this embodiment, the stream of salt(s) (101a) and polymer(s)
(102a) and
tailings stream (103a) are carried to mixing device 107. (Optionally, a stream
of sand can be
added to the streams of salt(s) and polymer(s) (105a) or to tailings stream
(105b), for example).
Mixing device 107 can be an inline mixer, a mixing tank, ribbon mixer or other
mixing device
that can mix streams 101a, 102a, 103a and 105a. For this embodiment, the
bitumen froth tailings
are combined with the salt(s) and polymer(s) as solutions followed by addition
of sand to treat
the tailings. However, the bitumen froth tailings can be treated with an
aqueous solution
including both the salt(s) and polymer(s. In addition, the order can be
changed, e.g., the sand can
be combined with the bitumen froth tailings (105b) followed by mixing with the
salt(s) and
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polymer(s) solution or solutions. The sand can be added as a wet or dry
stream. In some
embodiments, the combination of the streams in a line can cause sufficient
mixing to eliminate
the need for a separate mixing device, e.g., inline mixing, and the combined
streams can be
carried directly to a mechanical dewatering device to separate consolidated
material from process
water.
[0068]
As shown in the embodiment of Figure 1, after mixer 107, the treated tailings,
which include a consolidated material and process water, is transferred to a
solids/liquid
separator 109, e.g., dewatering device, to separate the process water from the
consolidated
material.
Such devices include, for example, one or more of a decanting, filtering,
electrofiltering, cross-flow filtering, gravity draining, or vacuuming device
or combination
thereof and/or by one or more of a device for dewatering consolidated material
such as a
centrifuge, decanting centrifuge, dewatering screw, hydrocyclone, vacuum belt
filter, filter press
or pressing devices, etc. or combinations thereof.
[0069]
A stream of separated process water (111) can be recovered and collected in a
tank or pond and a stream of separated consolidated material (113) can be
recovered. For this
embodiment, the recovered process water (111) includes the process water from
the tailings and
from stream 101a and thus includes residual salt(s) from the one or more
highly water soluble
salt(s) and can possibly include residual polymer(s) from the one or more
polymer flocculant(s.
There are also highly water soluble salts that are constituents of the
original tailings and these
become part of the recovered process water. In some embodiments, the recovered
process water
(111) can then be transferred to a water purifying system 115 to purify at
least a portion of the
recovered process water (117) which can be used for other operations or
discharged. Water
purifying systems that can be used for embodiments of the processes of the
present disclosure
include reverse osmosis systems, vacuum distillation systems, electrodialysis,
filtration systems,
etc. The remaining, non-purified recovered process water, which includes the
one or more
highly water soluble salt(s) from stream 101a and potentially highly water
soluble salt(s) that are
constituents of the original tailings (119) can be recycled back to the
treatment process. For this
embodiment, at least a portion of the non-purified recovered process water can
be recycled back
to holding tank 101 and deficiency in the concentration of the salt(s) or
polymer(s) can be
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corrected by adding additional highly water soluble salt(s) or polymer
flocculant(s) from one or
more make-up tanks such as make-up tanks 121 and 122.
[0070] In certain implementations of the process of the present
disclosure, at least a
portion, if not all, of recovered process water stream 111 can be recovered
and purified with a
reverse osmosis system. Such a system can concentrate the at least one highly
soluble salt in the
recovered portion of separated process water 111 to form a brine. At least a
portion, if not all, of
the brine can be cycled back to salt / polymer flocculant storage 101 and/or
102 to treat
additional tailings. Such a reverse osmosis system can concentrate the at
least one highly soluble
salt to a concentration of greater than about 2 wt% such as greater than about
4 wt%, 5 wt%, 6
wt%, 7wt% and higher such that the salt-tailings concentration in salt
/polymer flocculant storage
containers can be at an equilibrium of about 2wt% to about 7 wt%, and values
therebetween, or
higher. Thus, the salt concentration of the highly water soluble salt in
storage 101 can be
maintained at a range of about 2 wt % to about 7 wt%, and values therebetween,
depending on
the amount of process water subject to reverse osmosis system and cycled back
to the process.
The aqueous solution stream including the at least one highly water soluble
salt and the at least
one polymer flocculant can be combined with the tailings stream 103a at a
ratio within a range of
about 5.0:1.0 to about 1.0:5.0, e.g., combined at a ratio within a range of
about 3:1 to about 1:3,
such as about 1.5:1.0 to about 1.0:1.5.
[0071] The process of the present disclosure can also include steps to
recover residual
hydrocarbon, e.g., tar, crude oil, heavy oil, or other hydrocarbon oil,
bitumen, asphaltenes, etc.
from the bitumen froth tailings. As explained earlier, bitumen froth tailings
typically include a
low amount of residual bitumen. The bitumen froth tailings can also include
residual asphaltenes
depending on the oil sands extraction process as well as other hydrocarbons,
such as tar, crude
oil, heavy oil, or other hydrocarbon oil, etc. and/or diluents or solvents
from the oil sands
extraction operation.
[0072] The process of the present disclosure can further include adding
an organic
diluent to the bitumen froth tailings to dilute hydrocarbon therein and to
promote separation and
recovery of the hydrocarbon. Organic diluents useful for the processes of the
present disclosure
are soluble or mix readily with the hydrocarbon but are immiscible with water.
Organic diluents
useful for the processes of the present disclosure aid in diluting the
hydrocarbon separated from
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the composition to reduce the viscosity thereof. Such organic diluents
include, for example,
aromatic hydrocarbons such as benzene, toluene, xylene, non-aromatic
hydrocarbons such as
pentanes, hexanes, cyclohexane, heptanes, mixtures of hydrocarbons such as
naphtha, e.g., light
or heavy naphtha, kerosene and paraffinic diluents, etc. Hydrocarbon separated
from the treated
tailings can then be recovered by any number of processes useful for
recovering hydrocarbon
separated from solids and an aqueous mixture such as by skimming, decanting,
distilling,
centrifuging, etc. using such devices such as decanters, distillation columns,
pressure separators,
centrifuges, open tank, hydrocyclones, settling chambers or other separators,
etc.
[0073] It is believed that when a polymer flocculant is used to treat the
tailings, the
polymer acts in concert with the salt(s) to sequester solids, particularly
fines, and to minimize
emulsion formation in the treated composition. The organic diluent(s) aid in
separating the
hydrocarbon and lowers the viscosity of viscous hydrocarbons separated from
the composition,
which aids in recovering the hydrocarbons. Advantageously, the hydrocarbon
separated from the
tailings can contain a low amount of fines or has low minerals content, e.g.,
less than about 1
wt% or no more than about 0.5 wt% or no more than about 0.1 wt%. The
determination of fines
content can be assessed by detecting for mineral matter content in the
separated hydrocarbon by
infrared spectroscopy, x-ray diffraction, ash content or by an equivalent
method.
[0074] In addition, the consolidated solids can be recovered. The
recovered consolidated
solids can include residual highly water soluble salt(s) from the treatment of
the tailings. When
the salt used in treating the tailings is beneficial to plant life, such as an
ammonium based salt or
sulfate based salt or phosphate based salt, the residual salt can act as a
fertilizer with the
consolidated solids.
[0075] EXAMPLES
[0076] The following examples are intended to further illustrate certain
preferred
embodiments of the invention and are not limiting in nature. Those skilled in
the art will
recognize, or be able to ascertain, using no more than routine
experimentation, numerous
equivalents to the specific substances and procedures described herein.
[0077] Bitumen Froth Tailings
[0078] A portion of a bitumen froth tailings (FT) sample obtained from an
oil sands
extraction operation was poured into a glass jar and the picture shown in
Figure 2A taken a few
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minutes later. There was a degree of settling and some sand was visible at the
bottom of the jar.
The fines remained suspended. A sample of the stirred and remixed material was
taken and its
solids content determined to be 12.6% by drying in a vacuum oven.
[0079] Treatment of Bitumen Froth Tailings With Highly Water Soluble Salt
and
Polymer Flocculant
[0080] In an initial consolidation experiment, equal weights of a 5%
ammonium sulfate
solution containing 0.1% polyacrylamide (PAM) and froth tailings were mixed in
a vial then
centrifuged at 3000 rpm for 30 secs, to accelerate settling. The result is
shown in Figure 2B. It
can be seen that the solids consolidate to give a bottom layer in contact with
an apparently clear
supernatant. It appears that there is a layer of black material at the surface
of the clear water, but
this is simply a reflection of the bottom mineral layer in the meniscus.
[0081] The supernatant liquid was removed with a pipette and the solids
content of the
consolidated material was determined to be 38.7% by drying.
[0082] Treatment of Bitumen Froth Tailings With Highly Water Soluble Salt
and
Polymer Flocculant and Sand
[0083] Additional treatment of froth tailings samples with a salt
solution, polymer and
sand were performed in two additional ways. First, sand was added to a froth
tailings sample to
give a solids ratio (sand to froth tailings solids) of 1:1. Salt (ammonium
sulfate) and polymer
(polyacrylamide) were then added as solids and the mixture stirred. The amount
of salt and
polymer added gave a salt concentration of 2.5% and a polymer concentration of
0.05%,
respectively, in the final mixture. The vial was then centrifuged at 3000 rpm
for 30 secs, to
accelerate settling. The result is shown in the vial on the left in Figure 3.
The result obtained with
the addition of an equal weight of the 5% ammonium sulfate solution containing
0.1%
polyacrylamide polymer to the froth tailings/sand mixture is shown in the
right-hand vial. A
consolidated material was obtained using both methods.
[0084] The solids content of the consolidated material at the bottom of
the froth
tailings/solution vial (right hand vial in Figure 3) was determined to be
53.9%.
[0085] Treatment of Bitumen Froth Tailings With Highly Water Soluble Salt
and
Polymer Flocculant and Sand and Diluent
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24
[0086] A further set of experiments involved the simultaneous removal of
residual
hydrocarbon from the froth tailings, principally bitumen, using a diluent. The
results are shown
in Figure 4. The vial on the left was obtained by mixing froth tailings with
an equal weight of a
5% ammonium sulfate solution containing 0.1% polyacrylamide (PAM) and some
naphtha. No
sand was used. The vial on the right included sand, with the proportion of
sand to froth tailings
(FT) solids being 1:1. Without sand, the hydrocarbon layer appeared to contain
some emulsified
clays/hydrocarbons. The material obtained using sand appeared much cleaner.
This was
confirmed using infrared spectroscopy.
[0087] Only the preferred embodiment of the present invention and
examples of its
versatility are shown and described in the present disclosure. It is to be
understood that the
present invention is capable of use in various other combinations and
environments and is
capable of changes or modifications within the scope of the inventive concept
as expressed
herein. Thus, for example, those skilled in the art will recognize, or be able
to ascertain, using
no more than routine experimentation, numerous equivalents to the specific
substances,
procedures and arrangements described herein. Such equivalents are considered
to be within the
scope of this invention, and are covered by the following claims.
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