U.S. patent application number 14/113207 was filed with the patent office on 2014-03-20 for method of processing a bituminous feed with feedback control.
The applicant listed for this patent is Olusola B. Adeyinka, Emilio Alvarez, Anjaneya S. Kovvali, Thomas R. Palmer, Fritz Pierre, JR., David C. Rennard, Brian C. Speirs. Invention is credited to Olusola B. Adeyinka, Emilio Alvarez, Anjaneya S. Kovvali, Thomas R. Palmer, Fritz Pierre, JR., David C. Rennard, Brian C. Speirs.
Application Number | 20140076784 14/113207 |
Document ID | / |
Family ID | 47260151 |
Filed Date | 2014-03-20 |
United States Patent
Application |
20140076784 |
Kind Code |
A1 |
Speirs; Brian C. ; et
al. |
March 20, 2014 |
METHOD OF PROCESSING A BITUMINOUS FEED WITH FEEDBACK CONTROL
Abstract
Described herein is 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, and, solids are
agitated within the slurry to form an agglomerated slurry
comprising agglomerates and a low solids bitumen extract. In order
to control agglomeration, the slurry is analyzed and the processing
method is adjusted accordingly.
Inventors: |
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 |
Speirs; Brian C.
Adeyinka; Olusola B.
Palmer; Thomas R.
Alvarez; Emilio
Kovvali; Anjaneya S.
Rennard; David C.
Pierre, JR.; Fritz |
Calgary
Calgary
Lima
Missouri City
Fairfax
Houston
Humble |
NY
TX
VA
TX
TX |
CA
CA
US
US
US
US
US |
|
|
Family ID: |
47260151 |
Appl. No.: |
14/113207 |
Filed: |
March 9, 2012 |
PCT Filed: |
March 9, 2012 |
PCT NO: |
PCT/US12/28573 |
371 Date: |
October 21, 2013 |
Current U.S.
Class: |
208/390 |
Current CPC
Class: |
C10G 1/045 20130101;
C10G 1/047 20130101; C10G 1/04 20130101; C10G 2300/44 20130101;
C10G 33/08 20130101; C10G 2300/805 20130101; C10G 2300/1033
20130101; C10G 2300/4081 20130101 |
Class at
Publication: |
208/390 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2011 |
CA |
2741280 |
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, and agitating solids within
the slurry, to form an agglomerated slurry comprising agglomerates
and a low solids bitumen extract; c) measuring at least one
property of the agglomerated slurry, the agglomerates, or the low
solids bitumen extract; and d) comparing the at least one property
to a target range, and where the at least one property that is
measured does not fall within the target range, adjusting at least
one parameter of the method of processing the bituminous feed, for
controlling the agglomeration, wherein the at least one property
comprises a particle size distribution of the agglomerates as an
indication of agglomerate content or a density of the low solids
bitumen extract as an indication of a fines content of the low
solids bitumen extract; and wherein the at least one parameter
comprises an amount of added bridging liquid relative to an amount
of added bituminous feed, or a position at which at least a portion
of the bridging liquid is added to the slurry.
2. The method of claim 1, wherein the at least one property further
comprises one of (i) at least one property of the slurry prior to
agglomeration, (ii) at least one property of the bituminous feed,
(iii) a fines content of the low solids bitumen extract, (iv) clay
chemistry, (v) a rheological property of the agglomerated slurry,
(vi) a filtration rate of the agglomerated slurry and (vii) bitumen
content of the low solids bitumen extract.
3. (canceled)
4. The method of claim 1, wherein the at least one parameter
further comprises one of (i) an amount of added bridging liquid
relative to an amount of added bituminous feed, ii a composition of
the bridging liquid, (iii) a position at which at least a portion
of the bridging liquid is added to the slurry, (iv) an
agglomeration residence time, (v) an amount of extraction liquor
added relative to an amount of added bituminous feed, (vi) a level
of agitation provided to the slurry, and (vii) a shear environment
of the agglomeration.
5. The method of claim 1, wherein the at least one parameter
further comprises an extraction residence time.
6. The method of claim 5, wherein the extraction residence time is
greater than 5 minutes.
7. (canceled)
8. The method of claim 4, wherein the agglomeration residence time
is 1 to 5 minutes.
9. (canceled)
10. The method of claim 2, wherein the at least one property of the
bituminous feed comprises water content.
11. The method of claim 2, wherein the at least one property of the
bituminous feed comprises insoluble inorganics content.
12. The method of claim 1, wherein the adding the bridging liquid
to the slurry comprises adding a combination of at least two
different bridging liquid streams.
13. The method of claim 12, wherein the at least one parameter
comprises relative amounts of the at least two different bridging
liquid streams, recycling at least a portion of the agglomerated
slurry into step a), recycling at least a portion of the
agglomerated slurry between steps a) and b), or recycling at least
a portion of the agglomerates into step b).
14. The method of claim 1, wherein the bridging liquid is added to
the slurry in a concentration of between one of (i) 1 and 20 wt %
of the slurry and (ii) 1 and 10 wt % of the slurry.
15. (canceled)
16. The method of claim 1, further comprising separating the
agglomerates from the low solids bitumen extract.
17. The method of claim 16, further comprising recovering the
solvent from the low solids bitumen extract to form a bitumen
product.
18. 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
%.
19. The method of claim 1, wherein the bridging liquid is one of
water and an aqueous solution.
20. (canceled)
21. The method of claim 1, wherein at least 80 wt. % of the
agglomerates of step c) are between 0.1 and 1 mm.
22. The method of claim 1, wherein the agglomerated slurry has a
solids content of 20 to 70 wt %.
23. The method of claim 1, wherein the solvent comprises an organic
solvent or a mixture of organic solvents.
24. The method of claim 1, wherein the solvent comprises at least
50 wt. % cyclohexane.
25. The method of claim 1, wherein the agglomeration is effected in
one or more vessels.
26. The method of claim 1, wherein step b) comprises agitating by
mixing, shaking, or rolling.
27. The method of claim 1, wherein a ratio of the solvent to
bitumen in the agglomerated slurry is less than 2:1.
28. The method of claim 1, wherein the bituminous feed is derived
from oil sands.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Canadian patent
application number 2,741,280 filed on May 27, 2011 entitled METHOD
OF PROCESSING A BITUMINOUS FEED WITH FEEDBACK CONTROL, 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 which 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 (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.
[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.
[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 binding
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, 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 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 (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.
[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] U.S. Pat. No. 4,726,810 (Ignasiak) describes a process for
the agglomeration of coal fines within an aqueous slurry by the
addition of a bridging liquid comprising a low quality oil, such as
bitumen, and a light hydrocarbon diluent, such as kerosene. The
aqueous slurry mixture is agitated by pumping it through a pipeline
within which coal particles agglomerate and may later be separated
from the slurry by screening. The process allows for the selective
agglomeration of low-rank coal using substantially a low quality
oil.
[0020] It would be desirable to provide an alternative or improved
method for processing a bituminous feed.
SUMMARY
[0021] 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, and solids are agitated within the slurry to form an
agglomerated slurry comprising agglomerates and a low solids
bitumen extract. In order to control agglomeration, the slurry is
analyzed and the processing method is adjusted accordingly.
[0022] 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, and agitating solids within
the slurry, to form an agglomerated slurry comprising agglomerates
and a low solids bitumen extract; c) measuring at least one
property of the agglomerated slurry, the agglomerates, or the low
solids bitumen extract; and d) comparing the at least one property
to a target range, and where the at least one property that is
measured does not fall within the target range, adjusting at least
one parameter of the method of processing the bituminous feed, for
controlling the agglomeration.
[0023] 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
[0024] Embodiments of the present disclosure will now be described,
by way of example only, with reference to the attached Figures.
[0025] FIG. 1 is a flow chart illustrating a disclosed
embodiment.
[0026] FIG. 2 is a schematic illustrating a disclosed
embodiment.
[0027] FIG. 3 is a schematic illustrating a disclosed
embodiment.
[0028] FIG. 4 is a schematic illustrating a disclosed
embodiment.
[0029] FIG. 5 is a schematic illustrating a disclosed
embodiment.
[0030] FIG. 6 is a schematic illustrating a disclosed
embodiment.
[0031] FIG. 7 is a calibration curve relating bitumen content of a
bitumen extract comprised of bitumen and solvent to the measured
density of the bitumen extract.
[0032] FIG. 8 is a graph of bitumen recovery and initial filtration
rate as a function of extraction time with the agglomeration time
kept constant at 2 minutes.
[0033] FIG. 9 is a graph is a graph of bitumen recovery and initial
filtration rate as a function of agglomeration time with the
extraction time kept constant at 5 minutes.
[0034] FIG. 10 is a schematic illustrating a disclosed
embodiment.
DETAILED DESCRIPTION
[0035] The present disclosure relates to a method of processing a
bituminous feed using feedback control. 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".
[0036] Prior to describing embodiments specifically related to the
feedback control, a summary of the processes described in Adeyinka
et al. will now be provided.
[0037] Summary of Processes of Solvent Extraction Described in
Adeyinka et al.
[0038] 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.
[0039] 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 and solids are agitated within the slurry to
form an agglomerated slurry comprising agglomerates and a low
solids bitumen extract (104). At least one property of the
agglomerated slurry, the agglomerates, or the low solids bitumen
extract is measured (106). The at least one measured property is
compared to a target range. Where the at least one measured
property that is measured does not fall within the target range, at
least one parameter of the method is adjusted, for controlling the
agglomeration (108).
[0040] 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.
[0041] 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.
[0042] FIG. 2 is a schematic of a method of processing a bituminous
feed with additional steps including downstream solvent recovery.
Feedback control is not illustrated in FIG. 2. 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 to assist agglomeration of the slurry.
Agitation of the slurry is also used to assist agglomeration.
[0043] 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).
[0044] The following additional steps may also be performed. The
low solids bitumen extract 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).
[0045] 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. 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. In another embodiment, the bridging
liquid may be directly mixed with the bituminous feed before or at
the same time as the extraction liquor so that bitumen extraction
and agglomeration occur simultaneously. In this embodiment, the
bridging liquid is added before or at the same time as the
extraction liquor in order to minimize the dispersion of fines,
which may reduce the solids content of the bitumen extract after
the agglomeration process.
[0046] 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. The rate of agglomeration may
be controlled by a balance between intensity of agitation within
the agglomeration vessel, shear within the vessel which can be
adjusted by for example changing the shape or size of the vessel,
fines content of the slurry, bridging liquid addition, and
residence time of the agglomeration process.
[0047] The agglomeration of the fines within the slurry plays an
important role in the recovery of bitumen from the oil sands.
Little or no agglomeration of the fines hampers solid-liquid
separation since fine particles interfere with the filtration
process and/or increase the solids content of the low solids
bitumen extract. However, excess agglomeration of solids results in
entrapment of bitumen extract within the large agglomerates. Thus,
it is desirable to control the agglomeration process with a view to
achieving the desired agglomerates, such as agglomerates of a
desired size, density, composition, other parameter, or a
combination thereof.
[0048] The level of agglomeration will be affected by many factors
among the most consequential are the composition of the bituminous
feed (for instance as a result of ore quality), the amount of
bridging liquid added, the method by which the bridging liquid is
added, the residence time of the extraction and agglomeration
processes, the type and intensity of agitation, the shear
environment, the amount of any additional solids that are added,
and the surface chemistry of the fines.
[0049] Because the ore quality, a measure of the ore chemistry and
physical characteristics, may change on a very frequent basis as
different mine shelves are progressed, the recipe for agglomeration
may vary resulting in varying agglomeration. Thus, it is desirable
to use a process that can be adjusted to account for feed variation
and/or the resultant agglomeration outputs.
[0050] According to one embodiment, the bituminous feed and/or at
least one of the agglomeration outputs (the agglomerates and the
low solids bitumen extract) are analyzed as agglomeration proceeds.
This information is then used to adjust the process, for instance
by increasing or decreasing added solids content, adjusting the
amount of bridging liquid added, adjusting the residence time of
the extraction and/or agglomeration processes, adjusting intensity
of agitation, or adjusting the shear environment to seek more
desired output(s). These parameters may be adjusted individually or
in combination in order to maximize the effective response of the
control system.
[0051] FIG. 3 illustrates one embodiment, where the following steps
are performed:
[0052] 1. Measure (A) properties of the slurry (302) comprised of
bituminous feed and extraction liquor. In another embodiment, the
bituminous feed may be measured prior to contact with the
extraction liquor.
[0053] 2. Combine the slurry (302) with a bridging liquid (304) and
add to an agglomerator (306).
[0054] 3. Measure (B) properties of one or more outputs (308) (i.e.
the agglomerates and the low solids bitumen extract) of the
agglomeration process. The measurement may be performed
continuously.
[0055] 4. Use the measurements in a controls system (310) to adjust
a parameter of the process. One option is to adjust the amount of
bridging liquid (304) that is added to the slurry. Another option
is to adjust the composition of the bridging liquid added to the
slurry. Another option is to adjust the methods and locations of
the bridging liquid addition in the process. Another option is to
adjust the solid content of the slurry. Another option is to adjust
the intensity of agitation of the slurry. Another option is to
adjust the residence time of the extraction process. Another option
is to adjust the residence time of the agglomeration process. Yet
another option is to adjust the shear environment of the
agglomeration by changing for example the size or shape of the
vessel.
[0056] Measurable properties of a bituminous feed which could be
used include but are not limited to: (i) fines content, (ii)
moisture content, (iii) level of insoluble organics, (iv) quantity
of bitumen present, (v) clays content, (vi) clay chemistry, (vii)
particle size distribution, (viii) density, (ix) electrical
properties such as conductivity. Standard tests are available for
all of these measurements; for example methylene blue testing is a
well known method that can be used to quantify the quantity of
clays in the oil sands ore.
[0057] Measurable properties of the outputs of the solvent
extraction with solids agglomeration process include but are not
limited to: (i) particle size distribution of output solids, (ii)
filtration rate of slurry, (iii) fines content of the low solids
bitumen extract, (iv) bitumen content of low solids bitumen
extract, and (v) viscosity (rheology) of the slurry. The values of
these properties are strongly impacted by the solvent extraction
process and thus can be used in the control system described
herein. Other measurable properties include: (vi) hydrocarbon
content of the output solids, (vii) moisture content of
agglomerates, (viii) attrition and/or strength of the agglomerated
solids, (ix) electrical properties, and (x) yield strength of the
slurry.
[0058] Particle Size Distribution Property.
[0059] The particle size distribution of the output solids can be
measured by integrating an on-line particle size measurement device
such as a Retsch Technology Camizer. A slip stream can be taken
from the slurry, filtered to remove liquid, and then measured to
analyze particle size distribution. The particle size distribution
of output agglomerates may have a measured D50 of between 100
microns and 300 microns, or the agglomerates might have a measured
D50 of between 300 and 1000 microns, or the agglomerates might have
a measured D50 of between 1000 and 2000 microns. It is preferable
that the measured D50 be between 100 and 300 microns because such a
particle size distribution would insure good solid-liquid
separation rate while reducing the entrapment of bitumen extract
within the pores of the agglomerates.
[0060] Filtration Rate Property.
[0061] The filtration rate of the slurry can be measured by
integrating an on-line filtration device with the pipeline. A slip
stream can be taken from the slurry and the rate of filtration can
be measured, or alternatively the filtration rate may be directly
measured if a filtration process is included in the processing of
the slurry in the solid-liquid separator. In the case of a slip
stream filtration, the filter medium should be similar in material
and pore size to that which is used in the solid-liquid separator.
Exemplary filtration device include, but are not limited to, lab
scale chamber presses and diaphragm filter presses. The filtration
rate of the slurry is preferably in the range of 0.2 to 1
mL/cm.sup.2sec. Higher filtration rates may be suitable; however,
care should be taken to ensure that such filtration rates are not
due to excessive channeling.
[0062] Fines Content Property.
[0063] The fines content of the low solids bitumen extract may be
measured using several methods that are well known in the art.
However, a method that quickly measures the solid content is
preferable. Such a method may involve taking a slip stream of the
slurry and filtering it to produce a low solids bitumen extract or
directly sampling the low solids bitumen extract from the
solid-liquid separator. The density of the bitumen extract and a
micro-filtered bitumen extract is then measured. The bitumen
extract can be filtered through a micro-filter with a nominal pore
size of 0.45 microns. Suitable density measuring devices include
vibration type liquid density meters. The difference in density of
the bitumen extract and micro-filtered bitumen extract can be
correlated with solid content, S by using following equation:
S = 1 .rho. T - 1 .rho. E 1 .rho. S - 1 .rho. E ##EQU00001##
where .rho..sub.T is the measured density of the low solids bitumen
extract and .rho..sub.E is the measured density of the
micro-filtered bitumen extract. .rho..sub.S is the solid density
that may be obtained by experimental calibration or approximated to
have a value between 2.3 to 2.6 g/cm.sup.3. The solid content of
the low solids bitumen extract is preferably less than 2 wt %, or
preferably less than 1 wt %, or even more preferably less than 0.5
wt %.
[0064] Still another method of measuring the fines content may be
an optical method, such as to dilute a low solids bitumen extract
stream with excess solvent and then measure the turbidity of
bitumen extract and micro-filtered bitumen extract. The difference
in turbidity may be calibrated with fines content of the low solids
bitumen extract.
[0065] Bitumen Content Property.
[0066] During the extraction process as bitumen from the oil sands
dissolves into the extraction liquor, the density of the low solids
bitumen extract increases. The bitumen content of the low solids
bitumen extract can be estimated by measuring the density of the
low solids bitumen extract. A slip stream can be taken from the
slurry and filtered to produce the low solids bitumen extract or
the low solids bitumen extract can be sampled from the output of
the solid-liquid separator. The low solids bitumen extract can be
filtered through a micro-filter with a nominal pore size of 0.45
microns to obtain a solid-free bitumen extract. The density of the
solid-free bitumen extract can be measured using an on-line density
meter. The density of the bitumen extract can then be used to
approximate the bitumen content of the solid-free bitumen extract.
FIG. 7 is a calibration curve relating bitumen content of a bitumen
extract comprised of bitumen and solvent to the measured density of
the bitumen extract. The measurement can also be used to determine
the degree of bitumen extraction from the oil sands at different
points along the extraction and agglomeration processes.
[0067] Viscosity Property.
[0068] The particle size distribution of the oil sands slurry has a
strong impact on the viscosity of the slurry. Slurries with a high
fines content is expected to have a high viscosity. The slurry
viscosity is expected to decrease as the average particle size of
the slurry increases. Additionally, since a hydrocarbon phase is
the continuous fluid in the slurry, water chemistry will have much
less of an impact on the viscosity/rheology behavior of the slurry
compared to the impact water chemistry has on the
viscosity/rheology of water-based extraction slurries. This fact
makes correlation of particle size distribution with rheology much
simpler for the oil sands slurries described herein. Thus, in one
embodiment, measurement of the viscosity of the slurry can be used
to estimate the amount of fines in the oil sands slurry and
therefore used to control, for example, the amount of bridging
added to the slurry. This measurement can be obtained in a simple
viscometer or in a rheometer. Other related tests can also be used,
such as a flow rate test.
[0069] In another embodiment, measurement of the rheology of the
slurry can be used to determine the progression of the
agglomeration process. For example, after the bridging liquid is
added to the slurry and agitated, a rapid increase in the viscosity
of the slurry may indicate excessive agglomerate growth that has
led to the trapping of a significant amount of bitumen extract
within the agglomerates. Conditions that lead to such behavior
should be limited or avoided since they can lead to poor bitumen
recovery. The control system described herein can be used to change
process parameters, such as the amount of bridging liquid addition,
when the viscosity of the slurry is measured to rapidly increase.
In another example, the viscosity or rheometer measurement can be
used to track the growth of agglomerates. In cases when the formed
agglomerates are compact, the growth of agglomerates may be
accompanied by a gradual reduction in slurry viscosity or dynamic
shear strength. Thus, the change in slurry viscosity may correlate
well with agglomerate growth.
[0070] The viscosity of the oil sand slurry may be measured with
any suitable instrument that is well known in the art. For example,
an automatic on-line viscometer, which takes a slip stream from the
slurry and measures the viscosity, can be used. An in-line
viscometer, such as a vibrating-type viscometer, can be used to
provide instant viscosity measurements within the process slurry.
In another example, the torque is measured in the agitation
process, and rheological measurements could be determined in-situ.
That is, if a mixing vessel is used for the agglomerator, the
torque applied to the vessel can be measured as an indicator of
rheological properties such as viscosity.
[0071] Various other properties of the bituminous feed, or the
outputs could be alternatively or additionally be measured.
[0072] In another embodiment, the following steps may be
performed:
[0073] 1. Drill ore cores in advance of mining trucks to determine
the quality of the ore.
[0074] 2. As shovels proceed through a seam, obtain further data to
characterize the ore. Send the ore to the extraction process,
characterized as low, medium, or high fines content, or along
another rating system.
[0075] 3. Combine the oil sands with an extraction liquor and a
bridging liquid in an agglomerator. The extraction liquor comprises
a solvent used to dissolve bitumen. The bridging liquid is used to
assist agglomeration. The bridging liquid may be water or a sludge
from a water-based extraction process. Suitable sludge steams
include, but are not limited to, water-based extraction streams
such as middling from primary separation, secondary and tertiary
separation tailings, froth treatment tailings, mature fine tailings
from tailings ponds, or a new stream resulting from passing any of
these streams through a thickener, hydrocyclone, or other
processes. For example, middlings passed through a cyclone might
generate an overflow stream and an underflow stream. Either stream
could be used in this process as bridging liquid. The amount of
bridging liquid that is added will affect the extent of
agglomeration. Agitation is also used to assist agglomeration.
[0076] 4. Adjust one or more process parameters based on one or
more output properties. One process parameter is the amount of
bridging liquid that is added to the slurry. Another process
parameter is the solid content of the bridging liquid added to the
slurry. Another process parameter is the methods and locations of
the bridging liquid addition in the process. Another process
parameter is the solid content of the slurry. Another process
parameter is the intensity of agitation of the slurry. Another
process parameter is the shear environment of the agglomerator.
Another process parameter is the residence time of the extraction
process. Yet another option process parameter is the residence time
of the agglomeration process. Potential output properties include
particle size distribution of the produced agglomerates, filtration
rate of the slurry, solids content of the low solids bitumen
extract, bitumen content of low solids bitumen extract, and the
viscosity of the slurry. The adjustments to the process parameters
may be made based on the real time measurements of physical
properties of the output(s) of the agglomeration process, which
result in a feedback. In one embodiment, the feedback loop is a
negative feedback, since the desired outputs of the agglomeration
process may be set to one or more given target ranges and the input
parameters may be adjusted to maintain the output parameters in the
target range(s) regardless of type of ore feed and process upsets.
The expression "target range" as used herein may include a range
such as between X and Y, but also may include a range such as at
least Z, or a range such as less than W.
[0077] In one embodiment, the characterization of fines content
comprises a methylene blue test. In another embodiment, the
characterization of fines comprises a particle size distribution
analysis. In another embodiment, the characterization of fines
comprises viscosity/rheology tests of oil sands slurry. In another
embodiment, the ore (or bituminous feed) is characterized by
bitumen content rather than, or in addition to, fines content. In
another embodiment, the ore (or bituminous feed) is characterized
by spectroscopy, photoluminescence, fluorescence, or other
photoactive technology. In another embodiment, the ore (or
bituminous feed) is characterized by water chemistry and/or
quantity. In yet another embodiment, the output solids are
characterized by particle size distribution using sieves, laser
diffraction, optical analysis, or other size quantification
technique. In another embodiment, the hydrocarbon content of the
output stream is measured by a bomb calorimeter, gas
chromatography, photo activity such as phosphorescence or other
photon technique, particle sniffer, or other technology. In another
embodiment, the moisture content is measured by any type of
technique suitable to measure water content, including but not
limited to a bomb calorimeter, Karl Fischer Titration, Deen Stark
analysis, electrical conductivity, relative humidity, or any other
technique. In one embodiment, the analysis is performed in
conjunction with batch analysis at intervals. In another
embodiment, a slip stream is sampled for analysis. In another
embodiment, on-line analysis provides continuous information.
[0078] In another embodiment, the bridging liquid is adjusted based
on a measured property. The following steps may be performed, with
reference to FIG. 4:
[0079] 1. Adding the slurry (402) comprised of bituminous feed and
extraction liquor to an agglomerator (404).
[0080] 2. Providing two different streams of bridging liquid (406
and 408) to the agglomerator (404) to form an agglomerated slurry
(410).
[0081] 3. Based on information on the quality of the oil sand ore
(or bituminous feed) or the quality of one or more output streams
(i.e. the low solids bitumen extract or the agglomerates) or both,
adjusting (using a control point (412)) one or both of the flow
rates of bridging liquid.
[0082] In one embodiment, the first bridging liquid comprises water
and the second bridging liquid comprises sludge produced from the
aqueous extraction of bitumen from oil sands.
[0083] In another embodiment, as shown in FIG. 5, first and second
bridging liquids are mixed before they are introduced into the
agglomerator. The slurry comprised of bituminous feed and
extraction liquor (together 502) is added to an agglomerator (504).
The first bridging liquid (506) and second bridging liquid (508)
are mixed to form a mixed bridging liquid (514) and added to the
agglomerator (504)) to form an agglomerated slurry (510). Based on
information on the quality of the oil sand ore (or bituminous feed)
or the quality of one or more output streams (i.e. the low solids
bitumen extract or the agglomerates) or both, one or both of the
flow rates of bridging liquids (506 and 508) are adjusted (using a
control point (512)). In yet another embodiment, the first and
second bridging liquids are mixed in the agglomerator.
[0084] In another embodiment, as shown in FIG. 6, the properties of
the agglomeration process are adjusted through the recycling of
agglomerator output upstream of the agglomeration process. For
example, the agglomerated slurry could be recycled through the
process to affect the residence time of the agglomeration process.
The agglomerated solids could also be recycled through the process
to increase the solids content of the feed slurry. Additionally,
the agglomerated solids could be recycled through the process to
provide seed particles within the bridging liquid for the
agglomeration process. First, properties of the bituminous feed and
extraction liquor (602) are measured (A). In another embodiment,
the bituminous feed may be measured prior to contact with the
extraction liquor. The bridging liquid (604) is added to the
agglomerator (606) to produce outputs (608) (i.e. the agglomerates
and the low solids bitumen extract) of the agglomeration process.
One or more properties of the outputs are measured (B). The
measurements may be performed continuously. The measurements (A and
B) are used in a control system (610) to adjust a parameter of the
process, for instance the amount and/or composition of an input.
For instance, a portion of the agglomerated solids (611) could be
recycled back into the process to adjust effective residence time
and/or increase solids content.
[0085] In another embodiment, the at least one property further
comprises at least one property of the slurry prior to
agglomeration.
[0086] Agitation.
[0087] 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
emulsion 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. The agitation of the slurry has an impact on the growth
of the agglomerates. In the case of mixing type vessels, the mixing
power can be increased in order to limit the growth of agglomerates
by attrition of said agglomerates. In the case of rolling type
vessels the fill volume and rotation rate of the vessel can be
adjusted in order to increase the compaction forces used in the
comminution of agglomerates. These agitation parameters can be
adjusted in the control system described herein.
[0088] Extraction Liquor.
[0089] 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.
[0090] 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.
[0091] 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 vessel, 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.
[0092] 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.
[0093] 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.
[0094] 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.
[0095] Exemplary cycloalkanes include cyclohexane, cyclopentane, or
a mixture thereof.
[0096] 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.
[0097] 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
hydrocarbons in the mixture is greater than 50%.
[0098] 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. The residual bitumen increases the volume of the extraction
liquor and it may increase the solubility of the extraction liquor
for additional bitumen dissolution.
[0099] 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 include 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.
[0100] Bridging Liquid.
[0101] 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 solutions 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.
[0102] The total amount of bridging liquid added to the slurry may
be controlled in order to optimize bitumen recovery and the rate of
solid-liquid separation. The value will depend on the measured
properties described herein. By way of examples, the total amount
of bridging liquid added to the slurry may be such that 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, or in the range of 0.05 to 0.11. In one embodiment, the
bridging liquid to solids ratio may be obtained by feedback
control.
[0103] 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. %. The bridging liquid and fines
particles slurry is also referred to herein as sludge from a
water-based extraction process. Suitable sludge steams include, but
are not limited to, water-based extraction streams such as middling
from primary separation, secondary and tertiary separation
tailings, froth treatment tailings, mature fine tailings from
tailings ponds, or a new stream resulting from passing any of these
streams through a thickener, hydrocyclone, or other processes. For
example, middlings passed through a cyclone might generate an
overflow stream and an underflow stream. Either stream could be
used in this process as bridging liquid. Sludge may also be
produced within the solvent extraction with solids agglomeration
process by mixing bridging liquid with agglomerated tailings. In
this way, a portion of the agglomerated solids are recycled through
the process. The use of bridging liquid with a significant solid
content, such as that which is described above, may allow for
greater control of the agglomeration process. Previous work has
shown that when sludge is used as the bridging liquid, the addition
of the same amount o sludge per unit weight of oil sands feed
resulted in the production of agglomerates of the same drainage
properties regardless of oil sands quality.
[0104] The bridging liquid may be added after the production of the
oil sands slurry or before the production of the oil sands slurry.
In the former scenario, 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, which may increase bitumen
recovery. In the latter scenario, the bridging liquid may be
directly mixed with the bituminous feed before or at the same time
as the extraction liquor in order to minimize the dispersion of
fines, which may reduce the solids content of the bitumen extract
after the agglomeration process. The control system described
herein can be used to control where in the solvent extraction with
solids agglomeration process the bridging liquid is added based on
the output of the process. The bridging liquid may comprise less
than 40 wt % solids fines. The agglomerated slurry may have a
solids content of 20 to 70 wt %.
[0105] Ratio of Solvent to Bitumen for Agglomeration.
[0106] 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.
[0107] 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.
[0108] Measurement of the solvent and bitumen content of the
extraction liquor and/or bitumen extract could occur directly or by
proxy. Direct measurement of solvent and bitumen content could
involve evaporating off the solvent and measuring the mass of both
liquids, or use of a gas chromatograph, mass balance, spectrometer,
or titration. Indirect measurement of solvent and bitumen content
could include measuring density, the index of refraction, opacity,
or other properties.
[0109] Slurry System.
[0110] 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.
[0111] The resulting slurry from the slurry system may have a solid
content in the range of 20 to 65 wt %. In another embodiment, the
slurry may have a solid content in the range of 20 to 50 wt %. In
another embodiment, the slurry may have a solid content in the
range of 40 to 65 wt %. In the case of mixing type vessels, a lower
solid content may be preferred since that will assist in the proper
mixing of the bridging liquid and reduce the mixing energy needed
to keep the slurry well mixed. In the case of rolling type vessels,
a higher solid content may be preferred since that will increase
the compaction forces used in the comminution of agglomerates.
Additionally, the increased compaction forces may reduce the amount
of hydrocarbons that remain in the agglomerates and produce
stronger agglomerates.
[0112] The preferred temperature of the slurry is in the range of
20-60.degree. C. An elevated slurry temperature is desired in order
to increase the bitumen dissolution rate and reduce the viscosity
of the slurry to promote more effective sand digestion and
agglomerate formation. Temperatures above 60.degree. C. are
generally avoided due to the complications resulting from high
vapor pressures.
[0113] Residence Time.
[0114] The residence time of the extraction and agglomeration
processes has a strong impact on the bitumen extract and
agglomerated solids. Batch experiments within a mixing vessel were
conducted to test the affects of residence time. FIG. 8 (as
described further below) shows that the bitumen recovery and the
initial liquid filtration rate increases as the extraction time
increases for batch experiments conducted with the agglomeration
time kept constant at 2 minutes. Thus, increasing the residence
time of the extraction process may result in an increase in both
the bitumen recovery and the rate of solid-liquid separation. In
contrast, as FIG. 9 (as described further below) shows, the bitumen
recovery reaches a maximum and then decreases as the agglomeration
time increases for batch experiments conducted with the extraction
time kept constant at 5 minutes. The decrease in recovery beyond
the maximum recovery is most likely due to excessive agglomerate
growth that leads to entrapment of the bitumen extract within the
agglomerates. However, this growth of agglomerates does result in
an increase in the initial filtration rate as the agglomeration
time increases.
[0115] The results plotted in FIG. 8 and FIG. 9 demonstrate the
impact that residence time of the extraction and agglomeration
processes have on the bitumen extract and agglomerated solids.
[0116] As shown in FIG. 10, the recycle loops, (1020) and (1022)
can be used in the control system described herein to adjust the
effective residence time within the slurry system (1005) and
agglomerator (1006). First, properties of the bituminous feed and
extraction liquor (1002) are measured (A). In another embodiment,
the bituminous feed may be measured prior to contact with the
extraction liquor. The bridging liquid (1004) is added to the
slurry system (1005) and the slurry is passed to the agglomerator
(1006) to produce outputs (1008) (i.e. the agglomerates and the low
solids bitumen extract) of the agglomeration process. One or more
properties of the outputs (1008) are measured (B).
[0117] The measurements may be performed continuously. The
measurements (A and B) are used in a control system (1010) to
adjust a parameter of the process, for instance the amount and/or
composition of an input. For instance, a portion of the
agglomerated solids (1022) or a portion of the slurry prior to
agglomeration (1020) could be recycled back into the process to
adjust effective residence time and/or increase solids content.
[0118] The results plotted in FIG. 8 and FIG. 9 also suggest that
it is preferable for the residence time of the extraction process
be greater or much greater than the residence time of the
agglomeration process. The extraction process may occur in the
slurry system and the agglomeration process may occur in the
agglomerator. The residence time of the extraction process may be
greater than 5 minutes, or may be greater than 10 minutes, or may
be greater than 15 minutes, or may greater than 30 minutes.
Depending on the desired level of agglomeration, the residence time
of the agglomeration process may be in the range of 15 seconds to
10 minutes. In order to maximize bitumen recovery, the residence
time of the agglomeration process may be in the range of 1 to 5
minutes.
[0119] Solid-Liquid Separator.
[0120] 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.
[0121] 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.
[0122] 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.
[0123] Secondary Stage of Solid-Liquid Separation to Wash
Agglomerates.
[0124] 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.
[0125] 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 a
conventional fractionation tower or a distillation unit.
[0126] 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.
[0127] 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.
[0128] Recycle and Recovery of Solvent.
[0129] The process may involve removal and recovery of solvent used
in the process.
[0130] 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 has 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.
[0131] 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.
[0132] 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.
[0133] 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.
[0134] Dilution of Agglomerator Discharge to Improve Product
Quality.
[0135] 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.
[0136] 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.
[0137] 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.
[0138] Control Systems.
[0139] Embodiments of the disclosure can be represented as a
computer program product stored in a machine-readable medium (also
referred to as a computer-readable medium, a processor-readable
medium, or a computer usable medium having a computer-readable
program code embodied therein). The machine-readable medium can be
any suitable tangible, non-transitory medium, including magnetic,
optical, or electrical storage medium including a diskette, compact
disk read only memory (CD-ROM), memory device (volatile or
non-volatile), or similar storage mechanism. The machine-readable
medium can contain various sets of instructions, code sequences,
configuration information, or other data, which, when executed,
cause a processor to perform steps in a method according to an
embodiment of the disclosure. Those of ordinary skill in the art
will appreciate that other instructions and operations necessary to
implement the described implementations can also be stored on the
machine-readable medium. The instructions stored on the
machine-readable medium can be executed by a processor or other
suitable processing device, and can interface with circuitry to
perform the described tasks.
[0140] 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.
[0141] Batch Experiments.
[0142] Experiments were conducted to test the effects of varying
residence time on the extraction and agglomeration processes. 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 solids agglomeration process. The agglomerates were
also visually inspected for their size and uniformity.
[0143] 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.
[0144] 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.).
[0145] 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.
[0146] 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.
[0147] The Effects of Extraction Residence Time on the Solvent
Extraction with Solids Agglomeration Process.
[0148] 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 a given extraction residence time to
homogenize the mixture and to extract the bitumen that was in the
oil sands. The extraction times tested were 0.5, 1, 2, 5, 15, and
30 minutes. After the extraction time elapsed, 16.8 g 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.
[0149] 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.
[0150] 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.
[0151] FIG. 8 plots the bitumen recovery and the initial liquid
filtration rate as a function of the extraction residence time. The
figure shows that the bitumen recovery and the initial liquid
filtration rate increases as the extraction time increases for
batch experiments conducted with the agglomeration time kept
constant at 2 minutes.
[0152] The Effects of Agglomeration Residence Time on the Solvent
Extraction with Solids Agglomeration Process.
[0153] 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
minutes of mixing, 16.8 g of water was quickly pored into the
vessel through a sample port. The mixture was then mixed at 1500
rpm for a given agglomeration residence time to agglomerate the
solids. The agglomeration times tested were 0.5, 1, 2, 5, 15, and
30 minutes.
[0154] 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 .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.
[0155] 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.
[0156] FIG. 9 plots the bitumen recovery and the initial liquid
filtration rate as a function of the agglomeration residence time.
The figure shows that the bitumen recovery reaches a maximum and
then decreases as the agglomeration time increases for batch
experiments conducted with the extraction time kept constant at 5
minutes. The decrease in recovery beyond the maximum recovery is
most likely due to excessive agglomerate growth that lead to
entrapment of the bitumen extract within the agglomerates. However,
this growth of agglomerates does result in a continuous increase in
the initial filtration rate as the agglomeration time
increases.
* * * * *