Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02740468 2011-05-18
METHOD OF PROCESSING A BITUMINOUS FEED BY STAGED ADDITION OF A
BRIDGING LIQUID
FIELD
[0001] The present disclosure relates generally to the field of hydrocarbon
extraction
from mineable deposits, such as bitumen from oil sands.
BACKGROUND
[0002] Methodologies for extracting hydrocarbon from oil sands have
required energy
intensive processing steps to separate solids from the products having
commercial value.
[0003] Solvent extraction processes for the recovery of the
hydrocarbons have been
proposed as an alternative to water extraction of oil sands. However, the
commercial
application of a solvent extraction process has, for various reasons, eluded
the oil sands
industry. A major challenge to the application of solvent extraction to oil
sands is the
tendency of fine particles within the oil sands to hamper the separation of
solids from the
hydrocarbon extract. Solids agglomeration is a technique that can be used to
deal with this
challenge.
[0004] Solids agglomeration is a size enlargement technique that can
be applied
within a liquid suspension to assist solid-liquid separation. The process
involves
agglomerating fine solids, which are difficult to separate from a liquid
suspension, by the
addition of a second liquid. The second liquid preferentially wets the solids
but is immiscible
with the suspension liquid. With the addition of an appropriate amount of the
second liquid
and a suitable agitation; the second liquid displaces the suspension liquid on
the surface of
the solids. As a result of interfacial forces between the three phases, the
fines solids
consolidate into larger, compact agglomerates that are more readily separated
from the
suspension liquid.
[0005] Solids agglomeration has been used in other applications to
assist solid-liquid
separation. For example, the process has been used in the coal industry to
recover fine coal
particles from the waste streams produced during wet cleaning treatments (see
for example,
U.S. Patent Nos. 3,856,668 (Shubert); 4,153,419 (Clayfield); 4,209,301 (Nicol
et al.);
4,415,445 (Hatem) and 4,726,810(Ignasiak)). Solids agglomeration has also been
proposed
for use in the solvent extraction of bitumen from oil sands. This application
was coined
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CA 02740468 2011-05-18
Solvent Extraction Spherical Agglomeration (SESA). A more recent description
of the SESA
process can be found in Sparks et al., Fuel 1992(71); pp 1349-1353.
[0006] Previously described methodologies for SESA have not been
commercially
adopted. In general, the SESA process involves mixing oil sands with a
hydrocarbon
solvent, adding a bridging liquid to the oil sands slurry, agitating the
mixture in a slow and
controlled manner to nucleate particles, and continuing such agitation to
permit these
nucleated particles to form larger multi-particle spherical agglomerates for
removal. The
bridging liquid is preferably water or an aqueous solution since the solids of
oil sands are
mostly hydrophilic and water is immiscible with hydrocarbon solvents.
[0007] The SESA process described by Meadus et al. in U.S. Patent No.
4,057,486,
involves combining solvent extraction with solids agglomeration to achieve dry
tailings
suitable for direct mine refill. In the process, organic material is separated
from oil sands by
mixing the oil sands material with an organic solvent to form a slurry, after
which an aqueous
bridging liquid is added in the amount of 8 to 50 wt% of the feed mixture. By
using controlled
agitation, solid particles from oil sands come into contact with the aqueous
bridging liquid
and adhere to each other to form macro-agglomerates of a mean diameter of 2 mm
or
greater. The fprmed agglomerates are more easily separated from the organic
solvent
compared to un-agglomerated solids. This process permitted a significant
decrease in water
use, as compared with conventional water-based extraction processes. The multi-
phase
mixture need only be agitated severely enough and for sufficient time to
intimately contact
the aqueous liquid with the fine solids. The patent discloses that it is
preferable that the type
of agitation be a rolling or tumbling motion for at least the final stages of
agglomeration.
These types of motion should assist in forming compact and spherical
agglomerates from
which most of the hydrocarbons are excluded. The formed agglomerates are
referred to as
macro-agglomerates because they result from the consolidation of both the fine
particles
(sized less than 44 pm) and the coarse particles (sized greater than 200 pm)
found in the oil
sands.
[0008] U.S. Patent No. 3,984,287 (Meadus et al.) and U.S. Patent No.
4,406,788
(Meadus et al.) both describe apparatuses for extracting bitumen from oil
sands while
forming macro-agglomerates for easy solid-liquid separation. U.S. Patent No.
3,984,287
(Meadus et al.) describes a two vessel agglomeration apparatus. The apparatus
comprises
a mixing vessel for agitating the oil sands, the bridging liquid, and the
solvent to form a slurry
with suspended agglomerates. The slurry is screened in order to remove a
portion of the
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CA 02740468 2011-05-18
hydrocarbon liquid within with the bitumen product is dissolved. The
agglomerates are then
directed to a tapered rotating drum where they are mixed with additional
solvent and bridging
liquid. The additional solvent acts to wash the excess bitumen from the
agglomerates. The
additional bridging liquid allows the agglomerates to grow by a layering
mechanism and
under the increasing compressive forces produced by the tapered rotating drum
bed depth.
The compressive forces act to preferentially remove hydrocarbon liquid from
the pores of the
agglomerates such that, when optimal operating conditions are imposed, the
pores of the
agglomerates end up being filled with only the bridging liquid, and the
solvent that remains
on the surface of the agglomerates is easily recovered. U.S. Patent No.
4,406,788 (Meadus
et al.) describes a similar apparatus to that of U.S. Patent No. 3,984,287
(Measdus et al.),
but where the extraction and agglomeration processes occurs within a single
vessel. Within
this vessel, the flow of solvent is counter-current to the flow of
agglomerates which results in
greater extraction efficiency.
[0009] The above mentioned patents describe methods of using the
fines within oil
sands and an aqueous bridging liquid to promote the consolidation of the
coarse oil sands
particles into compact macro-agglomerates having minimal entrained
hydrocarbons and
which are easily separated from the hydrocarbon liquid by simple screening.
This macro-
agglomeration process may be suitable for oil sands feeds comprising greater
than 15 wt%
fines. For oil sands with a lesser amount of fines, the resulting agglomerates
show poor
strength and a significant amount of hydrocarbons entrained within their
pores. The inability
of the macro-agglomeration process to produce agglomerates of similar solid-
liquid
separation characteristics regardless of oil sands feed grade, is a
limitation. This limitation
can be mitigated by using a water and fine particle slurry as the bridging
liquid. U.S. Patent
No. 3,984,287 (Meadus et al.) reveals that middlings of a primary separation
vessel of a
water-based extraction process or sludge from the water-based extraction
tailings ponds may
be used as the bridging liquids with high fines content. It has been shown
that when sludge
is used as the bridging liquid, the addition of the same amount of sludge per
unit weight of oil
sands feed may result in the production of agglomerates of the same drainage
properties
regardless of oil sands quality. The use of sludge, however, introduces other
challenges
such as the fact that the appropriate sludge may not be readily available at
the mine site.
Furthermore, the use of sludge as the bridging liquid leads to larger
agglomerates that are
more prone to entrapment of bitumen.
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CA 02740468 2011-05-18
[0010] U.S. Patent No. 4,719,008 (Sparks et al.) describes a process
to address the
agglomeration challenge posed by varying ore grades by means of a micro-
agglomeration
procedure in which the fine particles of the oil sands are consolidated to
produce
agglomerates with a similar particle size distribution to the coarser grained
particles of the oil
sands. Using this micro-agglomeration procedure, the solid-liquid separation
behavior of the
agglomerated oil sands will be similar regardless of ore grade. The micro-
agglomeration
process is described as occurring within a slowly rotating horizontal vessel.
The conditions
of the vessel favor the formation of large agglomerates; however, a light
milling action is
used to continuously break down the agglomerates. The micro-agglomerates are
formed by
obtaining an eventual equilibrium between cohesive and destructive forces.
Since rapid
agglomeration and large agglomerates can lead to bitumen recovery losses owing
to
entrapment of extracted bitumen within the agglomerated solids, the level of
bridging liquid is
kept as low as possible commensurate with achieving economically viable solid-
liquid
separation.
(Sparks et al.) has several disadvantages that have thus far limited the
application of the
technology. Some of these disadvantages will now be described.
[0012] The micro-agglomeration process described in U.S. Patent No.
4,719,008
(Sparks et al.) requires careful control of the bridging liquid to solids
ratio. If the amount of
bridging liquid added to the process is in excess of the required amount,
rapid growth of
agglomerates can lead to bitumen recovery losses owing to entrapment of
bitumen within the
agglomerated solids. However, if the amount of bridging liquid added to the
process is too
low, insufficient agglomeration increases the amount of dispersed fines in the
liquid
suspension which hampers solids-liquid separation. In U.S. Patent No.
4,719,008 (Sparks et
al.) a ratio between 0.112 and 0.12 was identified as an appropriate range for
bridging liquid
to solids ratio for a particular type of low grade ore. Maintaining the ratio
within a narrow
range during the actual field operation of the agglomeration process would be
a challenge.
Furthermore, the desired amount of bridging liquid for the agglomeration
process will depend
on the ore quality and the chemistry of the fines. Because the ore quality and
chemistry will
change on a frequent basis as different mine shelves are progressed, the
recipe of the
agglomeration process may need to change accordingly in order to maintain the
agglomeration output within an acceptable range.
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CA 02740468 2013-09-03
[0013] In previously described SESA processes, the bridging liquid is
either added
directly to the dry oil sands or it is added to the oil sands slurry
comprising the oil sands and
the hydrocarbon solvent. In the former scenario, bitumen extraction and
particle
agglomeration occurs simultaneously. For this reason, the growth of
agglomerates may
hamper the dissolution of the bitumen into the solvent, it may lead to
trapping of bitumen
within the agglomerates, and it may result in an overall increase in the
required residence
time for bitumen extraction. In the scenario where the bridging liquid is
added to the oil
sands slurry, excessive agglomeration may occur in the locations of bridging
liquid injection.
These agglomerates will tend to be larger than the desired agglomerate size
and result in an
increase in the viscosity of the slurry. A higher slurry viscosity may hamper
the mixing
needed to uniformly distribute the bridging liquid throughout the remaining
areas of the slurry.
Poor bridging liquid dispersion may result in a large agglomerate size
distribution, which is
not preferred.
[0014] An important step in the agglomeration process is the
distribution of the
bridging liquid throughout the liquid suspension. Poor distribution of the
bridging liquid may
result in regions within the slurry of too low and too high bridging liquid
concentrations.
Regions of low bridging liquid concentrations may have no or poor
agglomeration of fine
solids, which may result in poor solid-liquid separation. Regions of high
bridging liquid
concentration may have excess agglomeration of solids, which may result in the
trapping of
bitumen or bitumen extract within the large agglomerates. In the process
described in U.S.
Patent No. 4,719,008 (Sparks et al.), the milling action of the rotating
vessel acts to both
breakup large agglomerates and distribute the bridging liquid throughout the
vessel in order
to achieve uniform agglomerate formation. In a commercial application, the
rotating vessel
would need to be large enough to process the high volumetric flow rates of oil
sands.
Accomplishing uniform mixing of the bridging liquid in such a large vessel
would require a
significant amount of mixing energy and long residence times.
[0015] Coal mining processes often produce aqueous slurries
comprising fine coal
particles. Solids agglomeration has been proposed as a method of recovering
these fine
coal particles, which may constitute up to 30 wt.% of the mined coal. In the
solids
agglomeration process, the hydrophobic coal particles are agglomerated within
the aqueous
slurry by adding an oil phase as the bridging liquid. When the aqueous slurry,
with bridging
liquid, is agitated, the coal particles become wetted with an oil layer and
adhere to each other
to form agglomerates. The hydrophilic ash particles are not preferentially
wetted by the oil
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phase and, as a result, remain un-agglomerated and suspended in the aqueous
phase. The
agglomerated coal material, with reduced ash content, is readily separated
from the aqueous
slurry by mechanical methods such as screening.
[0016] U.S. Patent No. 4,153,419 (Clayfiled et al.) describes a
process for the
agglomeration of coal fines within an aqueous slurry by staged addition of a
bridging liquid to
the aqueous slurry. Each agglomeration stage comprises the addition of a
bridging liquid to
the slurry, agitation of the mixture, and removal of agglomerates from the
aqueous slurry.
The inventors found that performing the agglomeration process in at least two
stages yielded
higher agglomeration of the coal particles as compared to the case where the
same amount
of bridging liquid was added in one agglomeration stage.
[0017] U.S. Patent No. 4,415,445 (Van Hattem et al.) describes a
process for the
agglomeration of coal fines within an aqueous slurry by the addition of a
bridging liquid and
the addition of seed pellets that are substantially larger than the coal
fines. The presence of
seed pellets induces agglomerate growth to occur predominately by a layering
mechanism
rather than by a coalescence mechanism. Since the rate of agglomeration occurs
much
faster by layering compared to coalescence, the process described therein
allows
agglomerates to form very quickly so that, for a given residence time, a
higher throughput of
agglomerates can be obtained compared to the throughput obtainable in the
absence of
seed pellets.
[0018] It would be desirable to provide an alternative or improved method
for
processing a bituminous feed.
SUMMARY
[0019] The present disclosure relates to a method of processing a
bituminous feed.
The bituminous feed is contacted with an extraction liquor to form a slurry. A
bridging liquid
is added to the slurry in at least two stages and solids within the slurry are
agitated to form
an agglomerated slurry comprising agglomerated solids and a low solids bitumen
extract.
The bridging liquid is added to the slurry in regions having higher shear
rates than a median
shear rate within the slurry. The agglomerates are then separated from the low
solids
bitumen extract. Potential benefits may include the production of smaller and
more uniform
agglomerates. The former may lead to higher bitumen recoveries and the latter
may improve
the solid-liquid separation rate.
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[0020] In a first aspect, the present disclosure provides a method of
processing a
bituminous feed, the method comprising: a) contacting the bituminous feed with
an extraction
liquor to form a slurry, wherein the extraction liquor comprises a solvent; b)
adding a bridging
liquid to the slurry in at least two stages and agitating solids within the
slurry to form an
agglomerated slurry comprising agglomerates and a low solids bitumen extract;
said bridging
liquid being added to the slurry in regions having higher shear rates than a
median shear rate
within the slurry; and c) separating the agglomerates from the low solids
bitumen extract.
[0021] Other aspects and features of the present disclosure will
become apparent to
those ordinarily skilled in the art upon review of the following description
of specific
embodiments in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Embodiments of the present disclosure will now be described,
by way of
example only, with reference to the attached Figures.
[0023] Fig. 1 is a flow chart illustrating a disclosed embodiment.
[0024] Fig. 2 is a schematic illustrating a disclosed embodiment.
[0025] Fig. 3 is a schematic illustrating a disclosed embodiment.
[0026] Fig. 4 is a schematic illustrating a disclosed embodiment.
[0027] Fig. 5 is a schematic illustrating a disclosed embodiment.
[0028] Fig. 6 is a schematic illustrating a disclosed embodiment.
DETAILED DESCRIPTION
[0029] The present disclosure relates to a method of processing a
bituminous feed
using staged addition of a bridging liquid. This method may be combined with
aspects of
other solvent extraction processes, including but not limited to those
described above in the
background section, and those described in Canadian Patent Application Serial
No.
2,724,806 ("Adeyinka et al."), filed December 10, 2010 and entitled "Processes
and Systems
for Solvent Extraction of Bitumen from Oil Sands".
[0030] Prior to describing embodiments specifically related to the
staged addition of
bridging liquid, a summary of the processes described in Adeyinka et al. will
now be
provided.
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CA 02740468 2011-05-18
[0031] Summary of Processes of Solvent Extraction Described in
Adeyinka et
al.
[0032] To extract bitumen from oil sands in a manner that employs
solvent, a solvent
is combined with a bituminous feed derived from oil sand to form an initial
slurry. Separation
of the initial slurry into a fine solids stream and coarse solids stream may
be followed by
agglomeration of solids from the fine solids stream to form an agglomerated
slurry. The
agglomerated slurry can be separated into agglomerates and a low solids
bitumen extract.
Optionally, the coarse solids stream may be reintroduced and further extracted
in the
agglomerated slurry. A low solids bitumen extract can be separated from the
agglomerated
slurry for further processing. Optionally, the mixing of a second solvent with
the low solids
bitumen extract to extract bitumen may take place, forming a solvent-bitumen
low solids
mixture, which can then be separated further into low grade and high grade
bitumen extracts.
Recovery of solvent from the low grade and/or high grade extracts is
conducted, to produce
bitumen products of commercial value.
[0033] Staged Addition of Bridging liquid
[0034] As outlined in the summary section, and now with reference to
Figure 1, the
present disclosure relates to a method of processing a bituminous feed. The
bituminous
feed is contacted with an extraction liquor to form a slurry (102). A bridging
liquid is added
to the slurry in at least two stages and solids within the slurry are agitated
to form an
agglomerated slurry comprising agglomerated solids and a low solids bitumen
extract (104).
The bridging liquid is added to the slurry in regions having higher shear
rates than a median
shear rate within the slurry. The agglomerates are then separated from the low
solids
bitumen extract (106). Potential benefits may include the production of
smaller and more
uniform agglomerates. The former may lead to higher bitumen recoveries and the
latter may
improve the solid-liquid separation rate.
[0035] The term "bituminous feed" refers to a stream derived from oil
sands that
requires downstream processing in order to realize valuable bitumen products
or fractions.
The bituminous feed is one that comprises bitumen along with undesirable
components. Such
a bituminous feed may be derived directly from oil sands, and may be, for
example raw oil
sands ore. Further, the bituminous feed may be a feed that has already
realized some initial
processing but nevertheless requires further processing. Also, recycled
streams that
comprise bitumen in combination with other components for removal as described
herein can
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CA 02740468 2011-05-18
be included in the bituminous feed. A bituminous feed need not be derived
directly from oil
sands, but may arise from other processes. For example, a waste product from
other
extraction processes which comprises bitumen that would otherwise not have
been recovered,
may be used as a bituminous feed. Such a bituminous feed may be also derived
directly from
oil shale oil, bearing diatomite or oil saturated sandstones.
[0036] As used herein, "agglomerate" refers to conditions that
produce a cluster,
aggregate, collection or mass, such as nucleation, coalescence, layering,
sticking, clumping,
fusing and sintering, as examples.
[0037] Figure 2 is a schematic of a disclosed embodiment with
additional steps
including downstream solvent recovery. The extraction liquor (202) is mixed
with a
bituminous feed (204) from oil sands in a slurry system (206) to form a slurry
(208). The
extraction liquor comprises a solvent and is used to extract bitumen from the
bituminous
feed. The slurry is fed into an agglomerator (210). Extraction may begin when
the extraction
liquor (202) is contacted with the bituminous feed (204) and a portion of the
extraction may
occur in the agglomerator (210). A bridging liquid (212) is added to the
agglomerator (210)
to assist agglomeration of the slurry. Some form of agitation is also used to
assist
agglomeration as described below.
[0038] The agglomerated slurry (214), comprising agglomerates and a
low solids
bitumen extract, is sent to a solid-liquid separator (216) to produce a low
solids bitumen
extract (218) and agglomerates (220).
[0039] The following additional steps may also be performed. The low
solids bitumen
extract (218) is sent to a solvent recovery unit (222) to recover solvent
(224) leaving a
bitumen product (226). The agglomerates (220) are sent to a tailings solvent
recovery unit
(228) to recover solvent (230) leaving dry tailings (232).
[0040] In one embodiment, the bituminous feed is dry oil sands, which is
contacted
with extraction liquor that free of bridging liquid in a slurry system to
produce a pumpable
slurry. The slurry may be well mixed in order to dissolve the bitumen. The
bridging liquid is
then added to the slurry in order to agglomerate the fine solids within the
slurry. The rate of
agglomeration may be controlled by a balance among agitation, fines content of
the slurry,
and bridging liquid addition. In this embodiment, the bitumen is first
extracted from the
bituminous feEd prior to agglomeration in order to prevent (or limit) the
agglomeration
process from hampering the dissolution of bitumen into the extraction liquor.
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CA 02740468 2011-05-18
[0041] In one embodiment, the formed agglomerates are sized on the
order of 0.1-
1.0 mm, or on the order of 0.1-0.3 mm. In one embodiment, at least 80 wt.% of
the formed
agglomerates are 0.1-1.0 mm or 0.1 to 0.3mm in size.
[0042] Figure 3 illustrates an embodiment where the bridging liquid
is added to an
agglomeration vessel at multiple locations within the vessel. As illustrated,
the bituminous
feed (302) is added to an agglomerator (304). Bridging liquid (306) is added
at multiple
stages along the flow path of the slurry. For example, multiple bridging
liquid inlet ports may
be arranged sequentially along the agglomerator. The agglomerated slurry (308)
is also
shown.
[0043] After each stage of bridging liquid addition, the slurry may be well
agitated so
that the bridging liquid comes into contact with the solids within the slurry
in order to form
agglomerates. In one embodiment, the residence time between each stage of
bridging liquid
addition is sufficient to allow agglomeration of some of the fine particles
within the slurry. The
residence time between each stage of bridging liquid addition may be greater
than 30
seconds.
[0044] After each stage of bridging liquid addition and the
resulting formation of
agglomerates, the formed agglomerates may be removed from the slurry.
Exemplary
methods for removing the agglomerates include gravity separation or screening
within the
agglomerator. Agglomerates that are larger than 1 mm are typically undesirable
due to the
increased chance of bitumen entrapment within the large agglomerates. These
large
agglomerates that are removed from the agglomerator may be separately
comminuted by
various methods known in the art to obtain agglomerates of the preferred size.
For example,
the agglomerates may be comminuted within attrition scrubbers or rod mills.
[0045] In one embodiment, the bridging liquid is added to the slurry
at relatively high
agitation or mixing energy regions in order to improve the dispersion of the
bridging liquid
within the slurry. Therefore, the bridging liquid may be added to the slurry
in regions having
higher shear rates than a median shear rate within the slurry. An example of a
region of high
shear rate within an agglomerator is adjacent the propellers of a mixing
vessel such as an
attrition scrubber. The propellers themselves may contain suitable injection
ports designed
for injecting bridging liquid, at high shear, into the slurry. In another
example, the bridging
liquid may be added to the slurry within the pumps used to transport the
slurry.
CA 02740468 2011-05-18
[0046] The staged addition of bridging liquid may be used to assist
in more uniformly
agglomerating solids. The amount of bridging liquid added at each stage of
bridging liquid
addition may be selected to obtain the desired agglomerate size.
[0047] Figure 4 illustrates an embodiment where the bridging liquid
is added to an
agglomeration vessel "continuously". As illustrated, the bituminous feed (402)
is added to an
agglomerator (404). Bridging liquid (406) is added "continuously" along the
flow path of the
slurry. As used herein "continuously" means that the bridging liquid is added
at stages
separated by residence times that are significantly shorter than the residence
time needed
for agglomerate formation. For examples, the residence times between each
bridging liquid
stage may be less than 15 seconds, or less than 5 seconds. The agglomerated
slurry (408)
is also shown.
[0048] Figure 5 illustrates an embodiment where the bridging liquid
is added to
multiple agglonierators. As illustrated, the bituminous feed (502) is added to
a first
agglomerator (504a), to which bridging liquid (506a) is added. The slurry
(503a) exists the
first agglomerator (504a) and enters the second agglomerator (504b), to which
bridging liquid
(506b) is added. The slurry (503b) exists the second agglomerator (504b) and
enters the
third agglomerator (504c), to which bridging liquid (506c) is added. The
agglomerated slurry
(508) is also shown. The use of multiple agglomerators allows for distinct
stages of
agglomeration to occur within each vessel. For example, one agglomerator may
be used for
the initial nucleation of agglomerate particles. A second agglomerator may be
used to grow
the agglomerates. A third agglomerator may be used for comminution of
agglomerates.
Since these stages of agglomeration may occur in separate vessels, the
operator may have
a greater level of control of the processes.
[0049] Figure 6 illustrates an embodiment where agglomerates are
removed from
the slurry after they form and before the injection of additional bridging
liquid. As illustrated,
the bituminous feed (602) is added to a first agglomerator (604x), to which
bridging liquid
(606x) is added. The slurry (610) exists the first agglomerator (604x) and
enters a solid-
liquid separator (612) (examples of which are described below) separating
agglomerates
(614) from the reduced-solids slurry (616). The reduced-solids slurry (616) is
fed into the
second agglomerator (604y), to which bridging liquid (606y) is added. The
agglomerated
slurry (608) is also shown. More than two agglomerators and more than one
solid-liquid
separator could be used.
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CA 02740468 2011-05-18
[0050] Exemplary methods for removing the agglomerates include, but
are not limited
to, gravity separators such as thickeners or enhanced gravity separators such
as
hydrocyclones. The agglomerates may be removed from the slurry in order to
reduce their
additional growth. It has been shown in previous studies that in order to
maximize bitumen
recovery, it is desirable to keep the agglomerates average particle size to as
low a value as
possible commensurate with achieving economically viable solid liquid
separation. If the
agglomerates were to remain within the slurry, after subsequent bridging
liquid additions, un-
agglomerated fine particles would preferentially attach to the agglomerates,
thus increasing
the chances of bitumen entrapment within the growing agglomerates.
Additionally, a portion
of the agglomerates that are removed from the agglomerators may be separately
comminuted by various methods known in the art to obtain agglomerates of the
preferred
size. For example, the agglomerates may be comminuted within attrition
scrubbers or rod
mills.
[0051] The agglomeration processes herein described may be used for
the formation
of macro-agglomerates or micro-agglomerates from the solids of the bituminous
feed.
Macro-agglomerates are agglomerates that are predominantly greater than 2 mm
in
diameter. These agglomerates comprise both the fine particles (less than 44
pm) and sand
grains of the oil sands. Micro-agglomerates are agglomerates that are
predominately less
than 1 mm in diameter and they principally comprise fine particles of the oil
sands. It has
been found that for the SESA process described above, the formation of micro-
agglomerates
are more suitable for maximizing bitumen recovery for a range of oil sands
grades.
[0052] Agitation. Agglomeration is assisted by some form of
agitation. The form of
agitation may be mixing, shaking, rolling, or another known suitable method.
The agitation of
the feed need only be severe enough and of sufficient duration to intimately
contact the
bridging liquid with the solids in the feed. Exemplary rolling type vessels
include rod mills and
tumblers. Exemplary mixing type vessels include mixing tanks, blenders, and
attrition
scrubbers. In the case of mixing type vessels, a sufficient amount of
agitation is needed to
keep the formed agglomerates in suspension. In rolling type vessels, the
solids content of
the feed is, in one embodiment, greater than 40 wt.% so that compaction forces
assist
agglomerate formation.
[0053] Extraction Liquor. The extraction liquor comprises a solvent
used to extract
bitumen from the bituminous feed. The term "solvent" as used herein should be
understood
to mean either a single solvent, or a combination of solvents.
12
CA 02740468 2011-05-18
[0054] In one embodiment, the extraction liquor comprises a
hydrocarbon solvent
capable of dissolving the bitumen. The extraction liquor may be a solution of
a hydrocarbon
solvent(s) and bitumen, where the bitumen content of the extraction liquor may
range
between 10 to. 50 wt%. It may be desirable to have dissolved bitumen within
the extraction
liquor in order to increase the volume of the extraction liquor without an
increase in the
required inventory of hydrocarbon solvent(s). In cases where non-aromatic
hydrocarbon
solvents are used, the dissolved bitumen within the extraction liquor also
increases the
solubility of the extraction liquor towards dissolving additional bitumen.
[0055] The extraction liquor may be mixed with the bituminous feed to
form a slurry
where most or all of the bitumen from the oil sands is dissolved into the
extraction liquor. In
one embodiment, the solids content of the slurry is in the range of 10 wt% to
75 wt%, or 50 to
65 wt%. A slurry with a higher solids content may be more suitable for
agglomeration in a
rolling type vessels, where the compressive forces aid in the formation of
compact
agglomerates. For turbulent flow type vessels, such as an attrition scrubber,
a slurry with a
lower solids content may be more suitable.
[0056] The solvent used in the process may include low boiling point
solvents such
as low boiling point cycloalkanes, or a mixture of such cycloalkanes, which
substantially
dissolve asphaltenes. The solvent may comprise a paraffinic solvent in which
the solvent to
bitumen ratio is maintained at a level to avoid or limit precipitation of
asphaltenes.
[0057] While it is not necessary to use a low boiling point solvent, when
it is used,
there is the extra advantage that solvent recovery through an evaporative
process proceeds at
lower temperatures, and requires a lower energy consumption. When a low
boiling point
solvent is selected, it may be one having a boiling point of less than. 100 C.
[0058] The solvent selected according to certain embodiments may
comprise an
organic solvent or a mixture of organic solvents. For example, the solvent may
comprise a
paraffinic solvent, an open chain aliphatic hydrocarbon, a cyclic aliphatic
hydrocarbon, or a
mixture thereof. Should a paraffinic solvent be utilized, it may comprise an
alkane, a natural
gas condensate, a distillate from a fractionation unit (or diluent cut), or a
combination of
these containing more than 40% small chain paraffins of 5 to 10 carbon atoms.
These
embodiments would be considered primarily a small chain (or short chain)
paraffin mixture.
Should an alkane be selected as the solvent, the alkane may comprise a normal
alkane, an
iso-alkane, or a combination thereof. The alkane may specifically comprise
heptane, iso-
heptane, hexane, iso-hexane, pentane, iso-pentane, or a combination thereof.
Should a
13
CA 02740468 2011-05-18
cyclic aliphatic hydrocarbon be selected as the solvent, it may comprise a
cycloalkane of 4 to
9 carbon atoms. A mixture of C4-C9 cyclic and/or open chain aliphatic solvents
would be
appropriate.
[0059] Exemplary cycloalkanes include cyclohexane, cyclopentane, or a
mixture
thereof.
[0060] If the solvent is selected as the distillate from a
fractionation unit, it may for
example be one having a final boiling point of less than 180 C. An exemplary
upper limit of
the final boiling point of the distillate may be less than 100 C.
[0061] A mixture of C4-C10 cyclic and/or open chain aliphatic
solvents would also be
appropriate. For example, it can be a mixture of C4-C9 cyclic aliphatic
hydrocarbons and
paraffinic solvents where the percentage of the cyclic aliphatic hydrocarbon
in the mixture is
greater than 50%.
[0062] Extraction liquor may be recycled from a downstream step. For
instance, as
described below, solvent recovered in a solvent recovery unit, may be used to
wash
agglomerates, and the resulting stream may be used as extraction liquor. As a
result, the
extraction liquor may comprise residual bitumen and residual solid fines.
[0063] The solvent may also include additives. These additives may or
may not be
considered a Solvent per se. Possible additives may be components such as de-
emulsifying
agents or solids aggregating agents. Having an agglomerating agent additive
present in the
bridging liquid and dispersed in the first solvent may be helpful in the
subsequent
agglomeration step. Exemplary agglomerating agent additives included cements,
fly ash,
gypsum, lime, brine, water softening wastes (e.g. magnesium oxide and calcium
carbonate),
solids conditioning and anti-erosion aids such as polyvinyl acetate emulsion,
commercial
fertilizer, humic substances (e.g. fulvic acid), polyacrylamide based
flocculants and others.
Additives may also be added prior to gravity separation with the second
solvent to enhance
removal of suspended solids and prevent emulsification of the two solvents.
Exemplary
additives include methanoic acid, ethylcellulose and polyoxyalkylate block
polymers.
[0064] Bridging Liquid. A bridging liquid is a liquid with affinity
for the solids particles
in the bituminous feed, and which is immiscible in the solvent. Exemplary
aqueous liquids may
be recycled water from other aspects or steps of oil sands processing. The
aqueous liquid
need not be pure water, and may indeed be water containing one or more salt, a
waste
product from conventional aqueous oil sand extraction processes which may
include additives,
aqueous solution with a range of pH, or any other acceptable aqueous solution
capable of
14
CA 02740468 2011-05-18
adhering to solid particles within an agglomerator in such a way that permits
fines to adhere to
each other. An exemplary bridging liquid is water.
[0065] The total amount of bridging liquid added to the slurry may be
such that a ratio
of bridging liquid to solids within the agglomerated slurry is in the range of
0.02 to 0.25, or 0.05
and 0.11. The amount of bridging liquid that makes up this ratio includes the
bridging liquid
added to the slurry and the connate water from the bituminous feed. The amount
of bridging
liquid that is added at a stage may be the same for each stage, or may be
different.
[0066] In one embodiment, the bridging liquid may contain fine
particles (sized less
than 44 pm) suspended therein. These fine particles may serve as seed
particles for the
agglomeration process. In one embodiment, the bridging liquid has a solids
content of less
than 40 wt.%. In one embodiment, the agglomerated slurry has a solids content
of 20 to 70
wt.%.
[0067] The composition of the bridging liquid, for example salinity
and/or fines
content, may be the same or different depending on which stage along the along
the slurry
flow path the bridging liquid is added. Additionally, the amount of the
bridging liquid that is
added to the slurry at each stage of bridging liquid addition may be the same
or different.
For example, the bridging liquid added during a first stage may have a
salinity that is at least
10% higher or lower than a salinity of a bridging liquid added during a
second, subsequent
stage. In another examples, the bridging liquid added during a first stage may
have a
suspended solids content that is at least 10 % higher or lower than a
suspended solids
content of a bridging liquid added during a second, subsequent stage.
[0068] General Experimental Observations. Preliminary batch tests of
solvent
extraction have shown that bitumen recovery increased by as much as five
percentage
points when the bridging liquid was added into the process vessel at
intermittent time
intervals during the agglomeration process compared to the case where all the
bridging liquid
was added at the beginning of the agglomeration process. The improved bitumen
recovery
performance demonstrated by the staged bridging liquid addition is also
supported by
observations made during batch testing of the solids agglomeration process
within a mixing
vessel. In these tests, a translucent organic fluid was used as the continuous
phase with
sand and clay as the solids, and water as the bridging liquid. When the water
was added all
at once to the slurry comprising the organic fluid and solids, large
agglomerates quickly
formed and began to segregate from the slurry. The slurry remained segregated
until
sufficient mixing energy was applied to the slurry to break up the initially
formed
CA 02740468 2011-05-18
agglomerates and disperse the water. The particle size distribution of the
agglomerates
formed in this suboptimal case was found to be broad with a significant amount
of
agglomerates being outside the size range for optimal bitumen recovery and
solid-liquid
separation. For the tests where the water was added gradually and near the
mixing
impellers for increased mixing energy, the water rapidly dispersed and minimal
segregation
of agglomerates was observed. The particles size distribution of these
agglomerates was
found to be narrow, and as a result the bridging liquid can be used more
efficiently to obtain
the desired agglomerate size.
[0069] .Ratio of Solvent to Bitumen for Agglomeration. The process
may be
adjusted to render the ratio of the solvent to bitumen in the agglomerator at
a level that
avoids precipitation of asphaltenes during agglomeration. Some amount of
asphaltene
precipitation is unavoidable, but by adjusting the amount of solvent flowing
into the system,
with respect to the expected amount of bitumen in the bituminous feed, when
taken together
with the amount of bitumen that may be entrained in the extraction liquor
used, can permit
the control of a ratio of solvent to bitumen in the agglomerator. When the
solvent is assessed
for an optimal ratio of solvent to bitumen during agglomeration, the
precipitation of
asphaltenes can be minimized or avoided beyond an unavoidable amount. Another
advantage of selecting an optimal solvent to bitumen ratio is that when the
ratio of solvent to
bitumen is too high, costs of the process may be increased due to increased
solvent
requirements.
[0070] An exemplary ratio of solvent to bitumen to be selected as a
target ratio during
agglomeration is less than 2:1. A ratio of 1.5:1 or less, and a ratio of 1:1
or less, for example,
a ratio of 0.75:1, would also be considered acceptable target ratios for
agglomeration. For
clarity, ratios may be expressed herein using a colon between two values, such
as "2:1", or
may equally be expressed as a single number, such as "2", which carries the
assumption
that the denominator of the ratio is 1 and is expressed on a weight to weight
basis.
[0071] Slurry System. The slurry system may optionally be a mix box,
a pump, or a
combination of these. By slurrying the extraction liquor together with the
bituminous feed,
and optionally with additional additives, the bitumen entrained within the
feed is given an
opportunity to become extracted into the solvent phase prior to agglomeration
within the
agglomerator.
[0072] Solid-Liquid Separator. As described above, the agglomerated
slurry may
be separated into a low solids bitumen extract and agglomerates in a solid-
liquid separator.
16
CA 02740468 2011-05-18
The solid-liquid separator may comprise any type of unit capable of separating
solids from
liquids, so as to remove agglomerates. Exemplary types of units include a
gravity separator,
a clarifier, a cyclone, a screen, a belt filter or a combination thereof.
[0073] The system may contain a solid-liquid separator but may
alternatively contain
more than one. When more than one solid-liquid separation step is employed at
this stage of
the process, it may be said that both steps are conducted within one solid-
liquid separator, or
if such steps are dissimilar, or not proximal to each other, it may be said
that a primary solid-
liquid separator is employed together with a secondary solid-liquid separator.
When a
primary and secondary unit are both employed, generally, the primary unit
separates
agglomerates, while the secondary unit involves washing agglomerates.
[0074] Non-limiting methods of solid-liquid separation of an
agglomerated slurry are
described in Canadian Patent Application Serial No. 2,724,806 (Adeyinka et
al.), filed
December 10, 2010.
[0075] Secondary Stage of Solid-Liquid Separation to Wash
Agglomerates. As a
component of the solid-liquid separator, a secondary stage of separation may
be introduced
for countercurrently washing the agglomerates separated from the agglomerated
slurry. The
initial separaticm of agglomerates may be said to occur in a primary solid-
liquid separator,
while the secondary stage may occur within the primary unit, or may be
conduced completely
separately in a secondary solid-liquid separator. By "countercurrently
washing", it is meant
that a progressively cleaner solvent is used to wash bitumen from the
agglomerates.
Solvent involved in the final wash of agglomerates may be re-used for one or
more upstream
washes of agglomerates, so that the more bitumen entrained on the
agglomerates, the less
clean will be the solvent used to wash agglomerates at that stage. The result
being that the
cleanest wash of agglomerates is conducted using the cleanest solvent.
[0076] A secondary solid-liquid separator for countercurrently washing
agglomerates
may be included in the system or may be included as a component of a system
described
herein. The secondary solid-liquid separator may be separate or incorporated
within the
primary solid-liquid separator. The secondary solid-liquid separator may
optionally be a
gravity separator, a cyclone, a screen or belt filter. Further, a secondary
solvent recovery
unit for recovering solvent arising from the solid-liquid separator can be
included. The
secondary solvent recovery unit may be conventional fractionation tower or a
distillation unit.
17
CA 02740468 2011-05-18
[0077] When conducted in the process, the secondary stage for
countercurrently
washing the agglomerates may comprise a gravity separator, a cyclone, a
screen, a belt
filter, or a combination thereof.
[0078] The solvent used for washing the agglomerates may be solvent
recovered
from the low solids bitumen extract, as described with reference to Figures 2
to 4. A second
solvent may alternatively or additionally be used as described in Canadian
Patent Application
Serial No. 2,724,806 (Adeyinka et al.) for additional bitumen extraction
downstream of the
agglomerator.
[0079] Recycle and Recovery of Solvent. The process may involve
removal and
recovery of solvent used in the process.
[0080] In this way, solvent is used and re-used, even when a good
deal of bitumen is
entrained then3in. Because an exemplary solvent:bitumen ratio in the
agglomerator may be
2:1 or lower, it is acceptable to use recycled solvent containing bitumen to
achieve this ratio.
The amount of make-up solvent required for the process may depend solely on
solvent
losses, as there is no requirement to store and/or not re-use solvent that
have been used in a
previous extraction step. When solvent is said to be "removed", or
"recovered", this does not
require removal or recovery of all solvent, as it is understood that some
solvent will be
retained with the bitumen even when the majority of the solvent is removed.
[0081] The system may contain a single solvent recovery unit for
recovering the
solvent(s) arising from the gravity separator. The system may alternatively
contain more than
one solvent recovery unit.
[0082] Solvent may be recovered by conventional means. For example,
typical
solvent recovery units may comprise a fractionation tower or a distillation
unit. The solvent
recovered in this fashion will not contain bitumen entrained therein. This
clean solvent is
preferably used in the last wash stage of the agglomerate washing process in
order that the
cleanest wash-of the agglomerates is conducted using the cleanest solvent.
[0083] The solvent recovered in the process may comprise entrained
bitumen
therein, and can thus be re-used as the extraction liquor for combining with
the bituminous
feed. Other optional steps of the process may incorporate the solvent having
bitumen
entrained therein, for example in countercurrent washing of agglomerates, or
for adjusting
the solvent and bitumen content prior to agglomeration to achieve the selected
ratio within
the agglomerator that avoids precipitation of asphaltenes.
18
CA 02740468 2011-05-18
[0084] . Extraction Step may be Separate from Agglomeration Step.
Solvent
extraction may be conducted separately from agglomeration in certain
embodiments of the
process. Unlike certain prior processes, where the solvent is first exposed to
the bituminous
feed within the agglomerator, certain embodiments described herein include
contact of the
extraction liquor with the bituminous feed prior to the agglomeration step.
This has the effect
of reducing residence time in the agglomerator, when compared to certain
previously
proposed processes which require extraction of bitumen and agglomeration to
occur
simultaneously. The instant process is tantamount to agglomeration of pre-
blended slurry in
which extraction via bitumen dissolution is substantially or completely
achieved separately.
Performing extraction upstream of the agglomerator permits the use of enhanced
material
handling schemes whereby flow/mixing systems such as pumps, mix boxes or other
types of
conditioning systems can be employed. Additionally, performing extraction
upstream of the
agglomerator prevents the agglomeration process from hampering the dissolution
of bitumen
into the extraction liquor.
[0085] Because the extraction may occur upstream of the agglomeration step,
the
residence time in the agglomerator may be reduced. One other reason for this
reduction is
that by adding components, such as water, some initial nucleation of particles
that ultimately
form larger agglomerates can occur prior to the agglomerator.
[0086] .Dilution of Agglomerator Discharge to Improve Product
Quality. Solvent
may be added to the agglomerated slurry for dilution of the slurry before
discharge into the
primary solid-liquid separator, which may be for example a deep cone settler.
This dilution
can be carried, out in a staged manner to pre-condition the primary solid-
liquid separator feed
to promote higher solids settling rates and lower solids content in the solid-
liquid separator's
overflow. The solvent with which the slurry is diluted may be derived from
recycled liquids
from the liquid-solid separation stage or from other sources within the
process.
[0087] When dilution of agglomerator discharge is employed in this
embodiment, the
solvent to bitumen ratio of the feed into the agglomerator is set to obtain
from about 10 to
about 90 wt% bitumen in the discharge, and a workable viscosity at a given
temperature. In
certain cases, these viscosities may not be optimal for the solid-liquid
separation (or settling)
step. In such an instance, a dilution solvent of equal or lower viscosity may
be added to
enhance the separation of the agglomerated solids in the clarifier, while
improving the quality
of the clarifier overflow by reducing viscosity to permit more solids to
settle. Thus, dilution of
19
CA 02740468 2011-05-18
agglomerator discharge may involve adding the solvent, or a separate dilution
solvent, which
may, for example, comprise an alkane.
[0088] Potential Advantages. There may be advantages of embodiments
described
herein, for instance as compared to SESA. It is believed that adding the
bridging liquid at
multiple stages along the flow path of oil sands slurry can lead to an
agglomeration process
that is more controllable and yield agglomerates of more uniform size. It is
also believed that
adding the bridging liquid at multiple stages along the flow path of oil sands
slurry will reduce
the overall energy requirement of the agglomeration process. Similar
advantages have been
realized in the agglomeration of coal fine particles (see U.S. Patent No.
4,153,419).
[0089] The high energy requirements of solids agglomeration process is a
well known
limitation. Embodiments described herein are expected to reduce the total
energy needed to
form the agglomerates. The reduction in energy is due to the lower power
requirement
needed for the agglomeration process. The reduction in power, in turn, is due
to the staged
addition of bridging liquid. Since the bridging liquid is added in stages, the
viscosity of the oil
sands does not increase as much as it would if all the bridging liquid was
added at once. A
reduction in the power requirement means that that the torque requirements of
motors used
in certain types of agglomeration vessel can be reduced. In the case of
rotating type
vessels, the required amount of milling can be reduced. Furthermore, the wear
of the
internals of the vessels will be dramatically reduced due to a reduction in
the required mixing
intensity.
[0090] Without intending to be bound by theory, it is believed that
staged addition of
bridging liquid helps balance the rate of agglomeration with the rate of
mixing. In the
presence of a significant amount of bridging liquid, the agglomeration of the
solids occur at a
rate that is much more rapid than the rate of mixing of the slurry. In fact,
the agglomeration
process itself tends to hamper mixing by increasing the effective viscosity of
the slurry. The
staged addition of the bridging liquid may modulate the rate of agglomeration
at any
particular location in the vessel. Thus, the mixing of the slurry can match
the agglomeration
process to ensure that the slurry remains relatively homogeneous. The addition
of bridging
liquid in high mixing energy regions of the slurry assist bridging liquid
dispersion throughout
the slurry. Additionally, removing the agglomerates from the slurry after each
stage of
bridging liquid addition reduces the viscosity of the slurry and prevents (or
limits) excessive
growth of the formed agglomerates.
CA 02740468 2011-05-18
[0091] Another potential advantage of certain embodiments is the
shifting of the
growth of agglomerates to a layering mechanism rather than a coalescence
mechanism.
The layering mechanism refers to agglomerate growth where the individual fine
particles
stick on the surface of already formed agglomerates. The coalescence mechanism
refers
agglomerate growth where two or more agglomerates stick together. The layering
mechanism should result in more compact agglomerates with less bitumen extract
entrapped
therein. In the cases where the formed agglomerates remain in the slurry,
these
agglomerates act as seed particles and shift the agglomeration process to more
of a layering
mechanism than a coalescence mechanism, which may dominate the agglomerate
growth
mechanism if all the bridging liquid was introduced in a single stage.
[0092] In the preceding description, for purposes of explanation,
numerous details
are set forth in order to provide a thorough understanding of the embodiments.
However, it
will be apparent to one skilled in the art that these specific details are not
required.
[0093] The above-described embodiments are intended to be examples
only.
Alterations, modifications and variations can be effected to the particular
embodiments by
those of skill in the art without departing from the scope, which is defined
solely by the claims
appended hereto.
[0094] Batch Experiments. Experiments were conducted to test the
effectiveness of
using staged addition of bridging liquid in order to agglomerate oil sand
solids within a slurry.
The initial liquid drainage rate of the formed agglomerates and bitumen
recovery from the oil
sands were used as the experimental measurements to determine the
effectiveness of the
solvent extraction with agglomeration process. The agglomerates were also
visually
inspected for their size and uniformity.
[0095] Medium grade Athabasca oil sand was used in these
experiments. The oil
sands had a bitumen content of 9.36 wt% and a water content of 4.66 wt%. The
percentage
of fines (< 44 ttm) that make up the solids was approximately 25 wt%. The oil
sands were
kept at -20 C until they were ready for use. A solution of cyclohexane and
bitumen was
used as the extraction liquor. The percentage of bitumen in the extraction
liquor was 24
wt%. Distilled water was used as the bridging liquid. For each experiment a
total of 350g of
oil sands, 235.07g of extraction liquor, and a total of 16.8g of water were
used. This
composition translated to a solids content of 50 wt% and a water to solids
ratio of 0.11 for the
agglomerated slurry.
21
CA 02740468 2011-05-18
[0096] A Parr reactor (series 5100) (Parr Instrument Company, Moline,
IL, USA) was
used as the extractor and agglomerator. The reactor vessel was made of glass
that permits
direct observation of the mixing process. A turbine type impeller powered by
an explosion
proof motor of 0.25 hp was used. The mixing and agglomeration speed of the
impeller were
set to 1500 rpm. This rotation speed allowed the slurry to remain fluidized at
all conditions of
the experiments. The agglomeration experiments were conducted at room
temperature
(22 C).
[0097] The agglomerated solids produced in these experiments were
treated in a
Soxhlet extractor combined with Dean-Stark azeotropic distillation, to
determine the material
contents of the agglomerated slurry. Toluene was used as the extraction
solvent. The oil
sand solids were dried overnight in an oven (100 C) and then weighed to
determine the
solids content of the agglomerated slurry. The water content was determined by
measuring
the volume of the collected water within the side arm of the Dean-Stark
apparatus. The
bitumen content of the agglomerated slurry was determined by evaporating the
toluene and
residual cyclohexane from an aliquot of the hydrocarbon extract from the
Soxhlet extractor.
[0098] The initial liquid drainage rate was calculated by measuring
the time needed
to drain 50 mL of bitumen extract above the bed of agglomerated solids.
[0099] Experiment 1: agglomeration by adding all the bridging liquid
at one
stage. 350g of oil sands and 235.07g of extraction liquor were placed into the
Parr reactor
vessel. The solids and solvent were mixed at 1500 rpm for 5 minutes to
homogenize the
mixture and to extract the bitumen that was in the oil sands. After 5 minutes
of mixing, 16.8g
of water was quickly pored into the vessel through a sample port. The mixture
was then
mixed at 1500 rpm for an additional 2 minutes to agglomerate the solids.
[00100] After the agglomeration process, the impeller was turned off
and the
agglomerates were allowed to settle for over 1 minute. The supernatant
(bitumen extract)
was pored into a separate container and the wet solids were transferred to a
Buchner funnel.
The solids rested on a filter paper with a nominal pore size of 170 tim. The
filter's effective
area was approximately 8 cm2. The solids bed height was 10.8 cm. A portion of
the
collected supernatant was pored on top of the solids until a liquid height of
1.9 cm formed
above the solids surface. A light vacuum was then applied to the Buchner
funnel and the
initial drainage rate of the liquid was recorded. The initial drainage rate
for solids
agglomerated by adding all the bridging liquid at one stage to the solids
slurry was 0.35
mL/(cm2sec).
22
CA 02740468 2011-05-18
[00101] The remaining supernatant was poured onto the solid bed and
allowed to filter
through. 211 mL of pure cyclohexane was then filtered through the solid bed in
order to
wash the agglomerates. The solid bed was then allowed to drain of liquid under
a light
vacuum for about 30 seconds. The bitumen content of the washed solids was then
measured
to determine the bitumen recovery of the solvent extraction process. The
bitumen recovery
from this solvent extraction with solids agglomeration process was 87 %.
[00102] Experiment 2: agglomeration by adding all the bridging liquid
at one
stage. The same conditions as Experiment 1 was repeated with the agglomeration
time
extended to 15 minutes instead of 2 minutes. The initial drainage rate for
solids
agglomerated by adding all the bridging liquid at one stage and extending the
agglomeration
time increased to 1.6 mL/(cm2sec). However, the bitumen recovery for this
extraction
process dropped to 83.8%
[00103] Experiment 3: agglomeration by using staged addition of
bridging liquid
to solids slurry. 350g of oil sands and 235.07g of extraction liquor were
placed into the Parr
reactor vessel. The solids and solvent were mixed at 1500 rpm for 5 minutes to
fully
homogenize the mixture and to fully extract the bitumen that was in the oil
sands. After 5
minute of mixing, 5.6 g of water was pored into the vessel through a sample
port and the
mixture was mixed for 30 seconds. Subsequently, 5.6 g of water was pored into
the vessel
and the mixture was mixed for an additional 30 seconds. Lastly, 5.6 g of water
was pored
into the vessel and the mixture was mixed for 1 minutes. All mixing was done
at room
temperature.
[00104] ,After the agglomeration process the impeller was turned off
and the
agglomerates were allowed to settle for over 1 minute. The supernatant
(bitumen extract)
was pored into a separate container and the wet solids were transferred to a
Buchner funnel.
The solids rested on a filter paper with a nominal pore size of 170 m. The
filter's effective
area was approximately 8 cm2. The solids bed height was 10.8 cm. A portion of
the
collected supernatant was pored on top of the solids until a liquid height of
1.9 cm formed
above the solids surface. A light vacuum was then applied to the Buchner
funnel and the
initial drainage rate of the liquid was recorded. The initial drainage rate
for solids
agglomerated by adding bridging liquid in three separate stages to the solids
slurry was 1.04
mL/(cm2sec).
[00105] ,The remaining supernatant was poured onto the solid bed and
allowed to filter
though. 211 mL of pure cyclohexane was then filtered through the solid bed in
order to wash
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CA 02740468 2011-05-18
the agglomerates. The solid bed was then allowed to drain of liquid under a
light vacuum for
about 30 seconds. The bitumen content of the washed solids was then measured
to
determine the bitumen recovery of the solvent extraction process. The bitumen
recovery from
this solvent extraction with solids agglomeration process was 86.3 %.
[00106] The drainage rate of the agglomerates formed by using staged
addition of the
bridging liquid was approximately 3 times greater than that of agglomerates
formed when all
the bridging liquid is added in one stage (compare Experiment 3 to Experiment
1). The
drainage rate of the single stage agglomeration process can be increased by
extending the
agglomeration time (see Experiment 2) in order to form larger agglomerates.
However, the
larger agglomerates results in a reduction in the bitumen recovery. In
contrast, the staged
addition of bridging liquid resulted in an increase in drainage rate without a
significant
reduction in bitumen recovery. Visual inspection of Experiment 3 agglomerates
did not
reveal significantly larger agglomerates compared to the agglomerates of
Experiment 1. This
suggests that the faster drainage rate of the agglomerates formed by staged
addition of
bridging liquid is due to more uniform agglomerates rather than larger
agglomerates.
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