Note: Descriptions are shown in the official language in which they were submitted.
81656497
TREATMENT OF OIL SAND BITUMEN TO PRODUCE LOW CALCIUM
BITUMEN
Field of the Invention
The invention relates to a method and apparatus for treatment of oil sand
bitumen to
produce a bitumen product having a low concentration of calcium.
Background
Oil sand is essentially a matrix of bitumen, mineral material and water, and
possibly
encapsulated air. The bitumen component of oil sand consists of viscous
hydrocarbons which
behave much like a solid at normal in situ temperatures and which act as a
binder for the other
components of the oil sand matrix. Oil sand will typically contain about 10%
to 12% bitumen and
about 3% to 6% water, with the remainder of the oil sand being made up of
mineral matter. The
mineral matter component in oil sand may contain about 14% to 20% fines,
measured by weight of
total mineral matter contained in the deposit, but the amount of fines may
increase to about 30% or
.. more for poorer quality deposits. Oil sand extracted from the Athabasca
area near Fort McMurray,
Alberta, Canada, averages about 11% bitumen, 5% water and 84% mineral matter,
with about 15%
to 20% of the mineral matter being made up of fines. Oil sand deposits are
mined for the purpose
of extracting bitumen from them, which is then upgraded to synthetic crude
oil.
A widely used process for extracting bitumen from oil sand is the "water
process". In this
process, aggressive thermal action and aggressive mechanical action are used
to liberate and
separate bitumen from the oil sand. An example of the water process is the hot
water process. In
the hot water process, oil sand is first conditioned by mixing it with water
at about 95°
Celsius and steam in a conditioning vessel which vigorously agitates the
resulting slurry in order to
disintegrate the oil sand. Once the disintegration of the oil sand is
complete, the slurry is separated
by allowing the sand and rock to settle out. Bitumen, with air entrained in
the bitumen, floats to the
top of the slurry and is withdrawn as a bitumen froth. The remainder of the
slurry is then treated
further or scavenged by froth flotation techniques to recover bitumen that did
not float to the top of
the slurry during the separation step. The froth is further treated to
separate solids and water from
liquid hydrocarbons. Such a process is suggested in US patent nos. 5,645,714,
and 4,533,459.
Canadian patent number 2,232,929, discloses an improvement to the hot water
process that utilizes
a paraffinic solvent to extract bitumen from the bitumen froth.
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US patent no. 6,905,593 suggests a method to remove calcium from conventional
crude oil
by extraction utilizing an aqueous mixture of and acetate ion and an alkaline
material having a pH
in the range of 3.0 to 5Ø Calcium removal from crude oils was found to be
particularly effective
within this range of pH.
Summary of the Invention
A method is provided to prepare a low calcium bitumen composition from an oil
sand
composition, the method comprising the steps of: contacting an oil sand
composition with water
and a baseic material to form a water and oil sand slurry; separating the
water and oil sand slurry
into a froth, comprising water, some mineral solids, and a bitumen
composition, and a underflow
stream comprising the majority of the mineral solids present in the oil sand
composition and a
majority of the water present in the water and oil sand slurry; contacting at
least a portion of the
bitumen composition with an acid; and separating the acid from the bitumen
wherein at least a
portion of calcium present in the bitumen composition has partitioned to the
acid.
The present invention is particularly applicable for removal of at least a
portion of calcium
from an oil sand bitumen wherein the oil sand bitumen has been treated with
caustic (or some other
base, for example, sodium carbonate or sodium silicate), as a part of a hot
water treatment system.
Use of caustic in this process can enhance this extraction of bitumen from oil
sands, but contact
with caustic has been found to increase retention of calcium in the bitumen.
Retention of calcium in
bitumen may be detrimental to performance of some bitumen upgraders. Presence
of more than 5
parts per million by weight of calcium in bitumen can be detrimental to
upgraders that utilize
contact with hydrogen and catalyst, typically at elevated temperatures and
pressures.
In one embodiment of the present invention, the hydrocarbon mixture of the
froth is
contacted with acetic acid prior to the froth being separated into a bitumen
product, a stream of
mineral solids and water and optionally a stream of asphaltenes. Addition of
acetic acid according
to this embodiment may be directly to a froth that is then treated according
to a paraffinic solvent
treatment process to separate a bitumen product from the froth. The paraffinic
solvent process may
be a process such as that disclosed in Canadian patent number 2,232,929.
In another embodiment of the present invention, a hydrocarbon solvent may be
used
according to the process disclosed in 2,232,929, and an aqueous acidic
solution may be contacted
with the solvent-diluted bitumen prior to solvent being recovered from the
solvent for recycling. At
this point in the process, the density of the phase containing the bitumen
differs from the density of
the aqueous acidic solution significantly and the majority of mineral solids
are removed, enabling
easy separation of the two phases.
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Brief description of the Figure
The Figure is a process flow drawing for the process of the present invention.
Detailed Description of the Invention
Referring now to the Figure, an oil sand ore stream, 101, is contacted with
water 102, and
caustic, or another basic material, 103, in, for example, a mixer 140, to form
a water and oil sand
slurry 104. Sufficient caustic may be included so that the pH of the aqueous
phase of the water and
oil sand slurry is above about 8. The oil sand ore can be a mined bitumen ore
from a formation
such as oil sands found in the Athabasca area near Fort McMurray, Alberta,
Canada. The ratio of
oil sand ore to water may be, for example, in the range of 1 to 6 or
alternatively in the range of 1 to
2. The oil sands may contain between 75 and 95 percent by weight of mineral
solids, and may
contain between 10 and 20 percent by weight hydrocarbons. The hydrocarbon
portion of the oil
sands may have a gravity of between 7 and 10 API and may contain from 10 to
25 percent by
weight of asphaltenes. Other components of the hydrocarbon portion of the oil
sand ore may be 10
to 40 percent by weight aliphatics, 5 to 20 percent by weight aromatics, and
10 to 50 percent by
weight polar compounds. The mixer may agitate the slurry to break up solids
and to increase the
area of contact between the solids and the water. The mixer may also heat the
slurry to a
temperature of, for example, between 35 C and 90 C to enhance extraction of
hydrocarbons from
the solids. Air and chemicals such as surfactants maybe added to the slurry to
further enhance
separation of the hydrocarbons from the solids. Alternatively, liberation of
hydrocarbon from
mineral material may be accomplished in a slurry conditioning transportation
line.
The water and oil sand slurry 104 optionally may be screened in a screener 141
to remove
larger solids 106 from a remaining slurry stream 105. Caustic, or another
basic material, 103, could
optionally be added to slurry stream 105, or to the water and oil sand slurry
104, either in addition
to, or instead of being added to the mixer 140,
Slurry stream 105 may be further processed to provide an initial solids
separation in a first
separator 142 producing a first underflow stream 107, containing solids and
water with some
bitumen, and a froth stream 108. The forth stream contains a majority of the
bitumen from the oil
sands stream, along with entrained water and solids. The bitumen contained in
the froth may be a
bitumen composition having a content of calcium between, for example, 5 and
300 parts per
million by weight. Typically, the froth stream contains about 60 weight
percent bitumen, about 30
weight percent water, and about 10 weight percent mineral solids. The first
separator may include
additional steps and equipment, such as, for example, flotation cells, to
increase the bitumen
recovery and de-aerators to remove excessive air. Because of the pH of the
aqueous phase of the
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oil sand slurry is above 8, certain ions such as calcium ions, tend to remain
in the hydrocarbon
phase in complexes with, for example, naphthenates. The concentration of
calcium present in the
hydrocarbon phase mixture may be, for example, between 5 and 200 parts per
million by weight.
Processing of the oil sand ore stream to extract hydrocarbons as a froth may
include
additional steps and equipment known as the hot water process, such as the
process suggested in
US patent 4,533,459.
Froth, 108, from the first separator may be mixed with solvent 109, and, in
one
embodiment of the present invention, acetic acid 110, in a solvent-froth mixer
143. Alternatively,
acid 110 may be added before mixer 143 and after separator 142. Alternatively,
acid 110 may be
added after mixer 143. The solvent may be a hydrocarbon solvent. The
hydrocarbon solvent may
be a paraffinic solvent. The paraffinic solvent tends to reject ashphaltenes
into tailings, resulting in
a higher quality hydrocarbon product from the subsequent physical separation.
The solvent could,
in another embodiment be a naphtha solvent, in which case asphaltenes may not
be rejected into the
tailings.
The paraffinic solvent process such as the process disclosed in Canadian
patent no.
2,232,929 is capable of providing a bitumen product that is very low in
content of entrained water
and solids. Because entrained water and solids also contain calcium ions, and
the acidic extraction
process may not effectively remove calcium from such entrained water and
solids, the paraffinic
solvent process is a preferred process to separate froth into the bitumen
product and the separate
streams of solids, water, and optionally asphaltenes, but other processes
could be utilized that are
effective to separate the froth into a product bitumen that is low in solids
and water content. For
example, the naphtha solvent treatment process, optionally with additional
steps to remove a
sufficient amount of entrained solids and/or water.
The acid may be added in an amount of moles between about one and ten times
the molar
amount of calcium present in the hydrocarbon phase of the oil sand
composition. The pH of the
aqueous phase of the froth, after addition of acid, may be, for example, lower
than 8, or lower than
7.
The solvent froth mixer product, 111, is separated into a solvent diluted
bitumen 112 and
tailings 113, in a hydrocarbon enrichment separator 144.
The solvent diluted bitumen stream 112 may be, in some embodiments, combined
with an
acid 118. The acid may comprise mineral acids, organic acids or carboxylic
acids. The amount of
acid may be, for example, in the range of 2 to 200 percent by volume of the
amount of solvent
diluted bitumen. In an embodiment were the solvent diluted bitumen is
contacted with an acidic
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aqueous stream, the combined stream may be mixed, for example, by an in-line
mixer, or by a
pump, or by a mixing valve, and then separated by known means to separate
liquid phases, such as
hydrocyclones, settling vessels, or plate separators. A portion of the acidic
components may be,
after contact with the bitumen, salts of the acids, for example, calcium
salts.
Demulsifer(s) and/or electric field can be employed to enhance separation of
solvent-
diluted bitumen and aqueous phase in Separator 145. Separator 145 makes this
separation of the
combined acidic aqueous stream and solvent diluted bitumen stream 114 which,
in an embodiment
where either the froth or the solvent diluted bitumen is contacted with an
acid, reduced in calcium
content. Separator 145 separates the combined acid and solvent diluted bitumen
stream into a
reduced calcium solvent diluted bitumen 114 and an acid aqueous phase 115,
which could
optionally be recycled. Some make-up acid would be required to the recycled
acidic aqueous
stream, with a corresponding blow down of spent acid to remove calcium from
the system. In one
embodiment, the acid 110 used to contact froth 108 and the acid 118 used to
contact solvent-diluted
bitumen 112 are different acids, where, for example, acid 110 may be an acetic
acid solution and
acid 118 may be an hydrochloric acid solution. To produce low calcium bitumen
product, acid
employment may not be needed at both locations (110 and 118) simultaneously.
Hydrocarbon enrichment separator 144 may comprise, for example, two or three
stages of
counter current contacting of underflow from the separators with solvent such
as taught in
Canadian patent number 2,232,929.
Solvent diluted bitumen 114, or in the embodiment where acid is contacted with
the solvent
diluted bitumen and then separated, reduced calcium solvent diluted bitumen
114, may be routed to
a solvent recovery unit 147. The solvent recovery unit may be any known means
for removing
more volatile hydrocarbons from less volatile hydrocarbons, for example,
distillation. The solvent
recovery unit 147 produces a recycle solvent stream 119 and a bitumen product
stream 120.
Tailings 113 from the hydrocarbon enrichment separator 144 are then separated
into a
second recycled solvent stream 116 and a tailings solvent recovery unit
underflow stream 117 in a
tailings solvent recovery unit 146.
The second recycled solvent stream 116, may be combined with the recycled
solvent
stream 119 and additional make-up 121 go become the solvent stream 109.
Bitumen product stream 120 may then be further processed in a hydrogen
addition
upgrader 148 by contact with hydrogen 122 at elevated temperatures and
pressures to produce
upgraded products 123. The process capable of upgrading the bitumen product
may be, for
example, one using any conventional reaction apparatus. Examples of typical
reaction apparatus
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81656497
include, but are not limited to, a tubular reactor, a tower reactor and a
soaker reactor.
Although the hydrogen addition upgrader process may be conducted in a
batchwise manner,
it may also be conducted in a continuous manner. Accordingly, the bitumen and
a hydrogen-
containing gas are continuously supplied to the reaction zone in a reaction
apparatus to conduct a
partial hydroconversion and concurrent demetallization of the bitumen while
continuously
collecting the reduced calcium bitumen feedstock.
The reduced calcium bitumen feedstock may then be conveniently directly
introduced into
an ebullated bed reactor system. The ebullated bed reactor systems are well
known in the art, and
generally comprise introducing a hydrogen-containing gas and heavy hydrocarbon
feedstock into
.. the lower end of a generally vertical catalyst containing reaction vessel
wherein the catalyst is
placed in random motion within the fluid hydrocarbon whereby the catalyst bed
is expanded to a
volume greater than its static volume. Such processes are described in the
literature, e.g. U.S. Pat.
Nos. 4,913,800, 32,265, 4,411,768 and 4,941,964. Suitable processes are
commercially known
as the H-Oil Process (Texaco Development Corp.) and LC-Fining Process (ABB
Lummus Crest, Inc.).
Typically, catalyst employed in the ebullated bed are the oxides or sulfides
of a Group V1113
metal of a Group VIII metal. These include, for example, catalysts such as
cobalt-molybdate,
nickel-molybdate, cobalt-nickel-molybdate, tungsten-nickel sulfide, tungsten
sulfide, mixtures
thereof and the like, with such catalysts generally being supported on a
suitable support such as
alumina or silica-alumina.
In general, the reaction conditions in the ebullated reactor system comprise
temperatures in
the order of from about 343.degree to 482°C, preferably from about 400
to about 454.degree
C. operating pressure of from about 3550kPa (500 psig) to about 27700 kPa
(4000 psig), and
hydrogen partial pressures generally being ranging from about 3450 to 20700
kPa (500 to 3000
psia).
The hydrogen addition upgrader may also have other processes associated with
it. Such as
the reduced calcium bitumen may first be processed in a atmospheric and/or
vacuum distillation
unit to remove the lighter portions of the reduced calcium bitumen, with the
residual from the
distillation process going to the hydrogen addition upgrader.
The invention also includes the apparatus capable of performing the method.
Examples
Froth from a commercial oil sands facility using a water process for initial
separation of
mineral components from bitumen was heated for about one hour in an oven at 77
C. The froth
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was then homogenized for 12 minutes using a hand-held drill and paint mixer
assembly. Once
homogenized, the froth was sampled into a metal mixing vessel. The vessel was
then placed into a
temperature controlled (25 C) water bath. A paraffinic hydrocarbon solvent
containing
hydrocarbons having 5 and 6 carbons was weighed into a separate sealed
container and placed in
the same temperature controlled (25 C) water bath. Once froth and solvent were
at temperature, if
required, an acid was added to the froth. After acid was added, solvent was
added. The contents
were mixed for 10 minutes at 500 RPM. After mixing, the metal vessel contents
were transferred
into a 1000 mL graduated cylinder and the cylinder placed into the temperature
controlled (25 C)
water bath. The interface level of the settling water/solids/asphaltenes
aggregates was recorded
with respect to time. After settling, the hydrocarbon phase was sampled for
solvent-to-bitumen
ratio (S/B) determination and calcium analysis. The heavy phase was also
collected and centrifuged
at 2000 rpm for ten minutes. After centrifugation, the underflow separates
into the three phases of
hydrocarbon, water and solids. The water phase was collected and its pH
determined.
Testing was done using three types of such froth. These froths were: 1) high
calcium froth
(about 100 ppm calcium, bitumen basis), 2) mid calcium (about 16 ppm calcium)
and 3)
second high calcium forth (about 120 ppm calcium).
Chemical aids were typically added to froth in the form of stock solutions
which
contained about 5 to 20 % acid by mass. The effect of the concentration of the
acid stock
solution was tested on a limited number of acids and was not found to have any
significant
effect.
A series of screening tests were performed in order to find acids that are
effective at
removing organically bound calcium. These tests typically used mid calcium
froth (about 16
ppm calcium, bitumen basis). The results of these screening tests are shown in
table 1.
TABLE 1
Reduction in Ca
pH of water concentration with Settling Rate (% of
Chemical Added phase acid addition (`Yo, )
Standard)
H2SO4 7.2 95 55
HCI 4.5 100 30
Acetic Acid 6.8 98 85
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EDTA 7.3 25 90
Oxalic Acid 7.0 - 40 90
Citric Acid 4.0 10 100
NaHCO3 7.2 -20 100
H3PO4 5.2 50 100
From Table 1 it can be seen that acetic acid H2SO4 as well as HCl addition
were found to
produce diluted bitumen with very low Ca concentrations.
From these screening tests H2SO4, HCI, and acetic acid were found to be
effective at
removing calcium from bitumen, the other chemicals tested were not considered
effective.
Further testing was conducted with H2SO4, HO and acetic acid addition to high
calcium
froth (about 120 ppm by weight calcium).
Settling rate as a function of pH after acid addition are shown in Figure 2.
For control tests,
no chemicals were added. Acid added for each test is indicated in the figure.
Acetic acid was
added to froth as a 20 % (by mass) solution, except for the circled data
points for which glacial
(-100 %m) acetic acid was used.
While these acids had an identical pH- calcium in bitumen relation, the effect
of the pH on
the settling rate was found to depend on the type of acid added, as shown in
figure 2. A 15 to 20 %
reduction in the settling rate was found when acetic acid was added, while
when strong mineral
acids (H2SO4 or HCl) were added, the settling rate decreased 50 to 80 %,
depending on the final pH.
In another two examples, acetic acid and hydrochloric acid were added,
respectively, to a
composition of high calcium bitumen and paraffinic solvent such as stream 112
of the Figure, and
agitated. The composition was then separated into a hydrocarbon phase and an
aqueous phase by
gravity separation and calcium content of the hydrocarbon phase was
determined. In this example,
the aqueous phase separated readily from the hydrocarbon phase, and low
calcium hydrocarbon
was produced.
In another two examples, acetic acid and hydrochloric acid were added,
respectively, to a
composition of high calcium bitumen such as stream 120 of the Figure, and
agitated. The
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composition was then separated into a hydrocarbon phase and an aqueous phase
by gravity
separation and calcium content of the hydrocarbon phase was determined. In
these examples, low
calcium hydrocarbon was produced. The aqueous phase separated acceptably, but
not as quickly as
the examples wherein the acidic compositions were added to the solvent diluted
bitumen.
9
