U.S. patent application number 14/112203 was filed with the patent office on 2014-09-18 for method of processing a bituminous feed by staged addition of a bridging liquid.
The applicant listed for this patent is Olusola B. Adeyinka, Emilio Alvarez, Lu Han, Anjaneya S. Kovvali, Thomas R. Palmer, Fritz Pierre, JR., David C. Rennard, Brian C. Speirs. Invention is credited to Olusola B. Adeyinka, Emilio Alvarez, Lu Han, Anjaneya S. Kovvali, Thomas R. Palmer, Fritz Pierre, JR., David C. Rennard, Brian C. Speirs.
Application Number | 20140262964 14/112203 |
Document ID | / |
Family ID | 47177250 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140262964 |
Kind Code |
A1 |
Han; Lu ; et al. |
September 18, 2014 |
Method of Processing a Bituminous Feed By Staged Addition of a
Bridging Liquid
Abstract
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 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. The
bridging liquid may be added in an area of relatively high shear
rates. Between stages of bridging liquid addition, agglomerates may
be removed.
Inventors: |
Han; Lu; (Herndon, VA)
; Speirs; Brian C.; (Calgary, CA) ; Adeyinka;
Olusola B.; (Calgary, CA) ; Palmer; Thomas R.;
(Lima, NY) ; Alvarez; Emilio; (Missouri City,
TX) ; Kovvali; Anjaneya S.; (Fairfax, VA) ;
Rennard; David C.; (Houston, TX) ; Pierre, JR.;
Fritz; (Humble, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Han; Lu
Speirs; Brian C.
Adeyinka; Olusola B.
Palmer; Thomas R.
Alvarez; Emilio
Kovvali; Anjaneya S.
Rennard; David C.
Pierre, JR.; Fritz |
Herndon
Calgary
Calgary
Lima
Missouri City
Fairfax
Houston
Humble |
VA
NY
TX
VA
TX
TX |
US
CA
CA
US
US
US
US
US |
|
|
Family ID: |
47177250 |
Appl. No.: |
14/112203 |
Filed: |
March 9, 2012 |
PCT Filed: |
March 9, 2012 |
PCT NO: |
PCT/US12/28565 |
371 Date: |
October 16, 2013 |
Current U.S.
Class: |
208/390 |
Current CPC
Class: |
C10G 1/045 20130101;
C10G 2300/805 20130101; C10G 2300/44 20130101; C10G 1/04
20130101 |
Class at
Publication: |
208/390 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2011 |
CA |
2,740,468 |
Claims
1. 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.
2. The method of claim 1, wherein the regions having higher shear
rates than a median shear rate within the slurry are regions
adjacent propellers used to agitate the slurry.
3. The method of claim 2, wherein the propellers comprise ports for
adding the bridging liquid to the slurry.
4. The method of claim 1, wherein the bridging liquid is one of (i)
added in at least two stages in a single agglomerator, (ii) added
continuously or intermittently in one or more agglomerators, (iii)
added in at least two agglomerators, and (iv) added in at least
three stages.
5.-6. (canceled)
7. The method of claim 1, wherein step b) comprises: i) adding a
first portion of the bridging liquid to the slurry; ii) agitating
solids within the slurry to form agglomerates; iii) removing
agglomerates from the slurry to form a solids-reduced slurry; iv)
adding a second portion of the bridging liquid to the
solids-reduced slurry; and v) agitating solids within the
solids-reduced slurry to form agglomerates.
8. The method of claim 7, one of (1) wherein steps i) to v) are
performed at least twice, (2) wherein the first portion of the
bridging liquid is added to a first agglomerator, the second
portion of the bridging liquid is added to a second agglomerator,
and agglomerates are removed to form the solids-reduced slurry
using a solid-liquid separator and (3) further comprising
comminuting removed agglomerates of step iii), wherein one of (i)
the comminuting is effected in an attrition scrubber and (ii) the
comminuting is effected in a mill.
9.-12. (canceled)
13. The method of claim 1, wherein bridging liquid added during a
first stage has one of (i) a salinity that is at least 10% higher
or lower than a salinity of a bridging liquid added during a
second, subsequent stage and (ii) 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.
14.-15. (canceled)
16. The method of claim 1, further comprising recovering the
solvent from the low solids bitumen extract to form a bitumen
product.
17. The method of claim 16, further comprising washing the
agglomerates of step c) with one of (i) the solvent recovered from
the low solids bitumen extract and (ii) a solvent, which solvent is
the same as or different from the solvent of step a), to extract
additional bitumen and to form washed agglomerates.
18. (canceled)
19. The method of claim 17, further comprising recovering solvent
from one of (i) the agglomerates, which have been separated from
the low solids bitumen extract and ii the washed agglomerates.
20. (canceled)
21. The method of claim 1, wherein the extraction liquor comprises
the solvent of step a) and bitumen in an amount of 10 to 50 wt
%.
22. The method of claim 1, further comprising, prior to step a),
contacting the bituminous feed with additional extraction liquor to
begin extraction.
23. The method of claim 1, wherein the bridging liquid is one of
water and an aqueous solution.
24. (canceled)
25. The method of claim 1, wherein at least 80 wt. % of the
agglomerates of step c) are between 0.1 and 1 mm.
26. The method of claim 1, wherein the agglomerated slurry has a
solids content of 20 to 70 wt %.
27. The method of claim 1, wherein the solvent comprises at least
one of (i) an organic solvent or a mixture of organic solvents and
(ii) a paraffinic solvent, a cyclic aliphatic hydrocarbon, or a
mixture thereof.
28. (canceled)
29. The method of claim 27, wherein the paraffinic solvent
comprises an alkane, a natural gas condensate, a distillate from a
fractionation unit, or a combination thereof containing more than
40% small chain paraffins of 5 to 10 carbon atoms.
30. The method of claim 27, wherein the alkane comprises one of (i)
normal alkane, an isoalkane, or a combination thereof and (ii)
heptane, iso-heptane, hexane, iso-hexane, pentane, iso-pentane, or
a combination thereof.
31. (canceled)
32. The method of claim 27, wherein the cyclic aliphatic
hydrocarbon comprises a cycloalkane of 4 to 9 carbon atoms, and
wherein the cycloalkane comprises cyclohexane, cyclopentane, or a
mixture thereof.
33. (canceled)
34. The method of claim 1, wherein the solvent comprises at least
50 wt. % cyclohexane.
35. The method of claim 1, wherein one of the extraction liquor
comprises residual solids and the bridging liquid comprises solid
fines, and wherein bridging liquid has a solids content of less
than 40 wt % solid fines.
36.-37. (canceled)
38. The method of claim 1, wherein a ratio of the solvent to
bitumen in the agglomerated slurry is less than 2:1.
39. The method of claim 1, wherein step b) comprises agitating by
mixing, shaking, or rolling.
40. (canceled)
41. The method of claim 1, wherein a ratio of bridging liquid plus
connate water from the bituminous feed to solids within the
agglomerated slurry is in the range of 0.02 to 0.25.
42. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Canadian patent
application number 2,740,468 filed on May 18, 2011 entitled METHOD
OF PROCESSING A BITUMINOUS FEED BY STAGED ADDITION OF A BRIDGING
LIQUID, the entirety of which is incorporated herein.
FIELD
[0002] The present disclosure relates generally to the field of
hydrocarbon extraction from mineable deposits, such as bitumen from
oil sands.
BACKGROUND
[0003] Methodologies for extracting hydrocarbon from oil sands have
required energy intensive processing steps to separate solids from
the products having commercial value.
[0004] 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.
[0005] 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.
[0006] 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. Pat. No. 3,856,668 (Shubert); U.S. Pat. No. 4,153,419
(Clayfield); U.S. Pat. No. 4,209,301 (Nicol et al.); U.S. Pat. No.
4,415,445 (Hatem) and U.S. Pat. No. 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
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.
[0007] 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.
[0008] The SESA process described by Meadus et al. in U.S. Pat. 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
formed 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 .mu.m) and the coarse
particles (sized greater than 200 .mu.m) found in the oil
sands.
[0009] U.S. Pat. No. 3,984,287 (Meadus et al.) and U.S. Pat. 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. Pat. 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 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. Pat. No. 4,406,788 (Meadus et al.) describes
a similar apparatus to that of U.S. Pat. No. 3,984,287 (Meadus 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.
[0010] 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. Pat. 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.
[0011] U.S. Pat. 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.
[0012] The micro-agglomeration process described in U.S. Pat. No.
4,719,008 (Sparks et al.) has several disadvantages that have thus
far limited the application of the technology. Some of these
disadvantages will now be described.
[0013] The micro-agglomeration process described in U.S. Pat. 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. Pat. 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.
[0014] 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.
[0015] 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 binging 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. Pat. 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.
[0016] 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 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.
[0017] U.S. Pat. No. 4,153,419 (Clayfield 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.
[0018] U.S. Pat. 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.
[0019] It would be desirable to provide an alternative or improved
method for processing a bituminous feed.
SUMMARY
[0020] 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.
[0021] 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.
[0022] 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
[0023] Embodiments of the present disclosure will now be described,
by way of example only, with reference to the attached Figures.
[0024] FIG. 1 is a flow chart illustrating a disclosed
embodiment.
[0025] FIG. 2 is a schematic illustrating a disclosed
embodiment.
[0026] FIG. 3 is a schematic illustrating a disclosed
embodiment.
[0027] FIG. 4 is a schematic illustrating a disclosed
embodiment.
[0028] FIG. 5 is a schematic illustrating a disclosed
embodiment.
[0029] FIG. 6 is a schematic illustrating a disclosed
embodiment.
DETAILED DESCRIPTION
[0030] 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 Dec.
10, 2010 and entitled "Processes and Systems for Solvent Extraction
of Bitumen from Oil Sands".
[0031] 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.
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.
Staged Addition of Bridging Liquid
[0033] As outlined in the summary section, and now with reference
to FIG. 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.
[0034] 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 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.
[0035] 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.
[0036] FIG. 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.
[0037] 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).
[0038] 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).
[0039] 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.
[0040] 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 0.3 mm in size.
[0041] FIG. 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] FIG. 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.
[0047] FIG. 5 illustrates an embodiment where the bridging liquid
is added to multiple agglomerators. 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.
[0048] FIG. 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.
[0049] 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.
[0050] 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 .mu.m)
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.
Agitation
[0051] 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.
Extraction Liquor
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.degree. C.
[0057] 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 cyclic
aliphatic hydrocarbon be selected as the solvent, it may comprise a
cycloalkane of 4 to 9 carbon atoms. A mixture of C.sub.4-C.sub.9
cyclic and/or open chain aliphatic solvents would be
appropriate.
[0058] Exemplary cycloalkanes include cyclohexane, cyclopentane, or
a mixture thereof.
[0059] 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.degree. C. An exemplary upper limit
of the final boiling point of the distillate may be less than
100.degree. C.
[0060] A mixture of C.sub.4-C.sub.10 cyclic and/or open chain
aliphatic solvents would also be appropriate. For example, it can
be a mixture of C.sub.4-C.sub.9 cyclic aliphatic hydrocarbons and
paraffinic solvents where the percentage of the cyclic aliphatic
hydrocarbon in the mixture is greater than 50%.
[0061] 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.
[0062] 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.
Bridging Liquid
[0063] 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
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.
[0064] 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.
[0065] In one embodiment, the bridging liquid may contain fine
particles (sized less than 44 .mu.m) 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. %.
[0066] 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.
General Experimental Observations
[0067] 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 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.
Ratio of Solvent to Bitumen for Agglomeration
[0068] 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.
[0069] 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.
Slurry System
[0070] 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.
Solid-Liquid Separator
[0071] As described above, the agglomerated slurry may be separated
into a low solids bitumen extract and agglomerates in a
solid-liquid separator. 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.
[0072] 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 primary and secondary units are both employed,
generally, the primary unit separates agglomerates, while the
secondary unit involves washing agglomerates.
[0073] 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 Dec. 10, 2010.
Secondary Stage of Solid-Liquid Separation to Wash Agglomerates
[0074] 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 separation 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 conducted 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.
[0075] 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.
[0076] 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.
[0077] The solvent used for washing the agglomerates may be solvent
recovered from the low solids bitumen extract, as described with
reference to FIGS. 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.
Recycle and Recovery of Solvent
[0078] The process may involve removal and recovery of solvent used
in the process.
[0079] In this way, solvent is used and re-used, even when a good
deal of bitumen is entrained therein. 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.
[0080] 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.
[0081] 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.
[0082] 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.
Extraction Step May be Separate from Agglomeration Step
[0083] 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.
[0084] 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.
Dilution of Agglomerator Discharge to Improve Product Quality
[0085] 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.
[0086] 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 agglomerator discharge may involve adding the solvent, or a
separate dilution solvent, which may, for example, comprise an
alkane.
Potential Advantages
[0087] 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. Pat. No. 4,153,419).
[0088] 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.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] 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.
Batch Experiments
[0093] 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.
[0094] 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 .mu.m)
that make up the solids was approximately 25 wt %. The oil sands
were kept at -20.degree. 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 350 g of oil sands, 235.07 g of extraction
liquor, and a total of 16.8 g 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.
[0095] A Parr reactor (series 5100) (Parr Instrument Company,
Moline, Ill., 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.degree. C.).
[0096] 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.degree.
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.
[0097] 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.
Experiment 1
Agglomeration by Adding all the Bridging Liquid at One Stage
[0098] 350 g of oil sands and 235.07 g 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, 16.8 g of water was quickly poured into the vessel through
a sample port. The mixture was then mixed at 1500 rpm for an
additional 2 minutes to agglomerate the solids.
[0099] 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 poured 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 .mu.m. The
filter's effective area was approximately 8 cm.sup.2. The solids
bed height was 10.8 cm. A portion of the collected supernatant was
poured 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/(cm.sup.2 sec).
[0100] 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%.
Experiment 2
Agglomeration by Adding all the Bridging Liquid at One Stage
[0101] 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/(cm.sup.2 sec). However, the bitumen recovery
for this extraction process dropped to 83.8%.
Experiment 3
Agglomeration by Using Staged Addition of Bridging Liquid to Solids
Slurry
[0102] 350 g of oil sands and 235.07 g 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 poured into the vessel through
a sample port and the mixture was mixed for 30 seconds.
Subsequently, 5.6 g of water was poured into the vessel and the
mixture was mixed for an additional 30 seconds. Lastly, 5.6 g of
water was poured into the vessel and the mixture was mixed for 1
minutes. All mixing was done at room temperature.
[0103] 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 poured 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 .mu.m. The
filter's effective area was approximately 8 cm.sup.2. The solids
bed height was 10.8 cm. A portion of the collected supernatant was
poured 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/(cm.sup.2 sec).
[0104] 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 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%.
[0105] 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.
* * * * *