U.S. patent application number 13/514023 was filed with the patent office on 2012-12-06 for process and system for recovery of bitumen from oil sands.
Invention is credited to Olusola B. Adeyinka, Payman Esmaeili, Brian C. Speirs.
Application Number | 20120305451 13/514023 |
Document ID | / |
Family ID | 44225536 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120305451 |
Kind Code |
A1 |
Adeyinka; Olusola B. ; et
al. |
December 6, 2012 |
Process and System For Recovery of Bitumen From Oil Sands
Abstract
A process is described for bitumen extraction from oil sands.
Solvent extraction is used, incorporating fines agglomeration to
simplify subsequent separation. A high quality bitumen product is
formed, having water and solids content that exceeds downstream
processing and pipeline requirements. An embodiment of the process
comprises combining a first solvent and a bituminous feed to form
an initial slurry, which is optionally separated into fine solids
and coarse solids. Solids are agglomerated to form an agglomerated
slurry. A low solids bitumen extract from the agglomerated slurry
is mixed with a second solvent to form a solvent-bitumen low solids
mixture, the second solvent having a similar or lower boiling point
than the first solvent. The mixture is separated to produce high
grade and low grade bitumen extracts. The first and second solvents
are recovered from the high grade bitumen extract, leaving a high
grade bitumen product.
Inventors: |
Adeyinka; Olusola B.;
(Calgary, CA) ; Speirs; Brian C.; (Calgary,
CA) ; Esmaeili; Payman; (Calgary, CA) |
Family ID: |
44225536 |
Appl. No.: |
13/514023 |
Filed: |
November 15, 2010 |
PCT Filed: |
November 15, 2010 |
PCT NO: |
PCT/US10/56727 |
371 Date: |
August 9, 2012 |
Current U.S.
Class: |
208/390 ;
196/14.52 |
Current CPC
Class: |
C10G 2300/206 20130101;
C10G 2300/301 20130101; C10G 1/04 20130101; C10G 2300/4006
20130101; C10G 2300/44 20130101; C10G 2300/80 20130101; C10G
2300/807 20130101 |
Class at
Publication: |
208/390 ;
196/14.52 |
International
Class: |
C10G 1/04 20060101
C10G001/04; C10C 3/08 20060101 C10C003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 30, 2009 |
CA |
2689,469 |
Claims
1. A process for recovery of bitumen from oil sands comprising:
combining a first solvent and a bituminous feed from oil sands to
form an initial slurry; separating the initial slurry into a fine
solids stream and a coarse solids stream; agglomerating solids from
the fine solids stream to form an agglomerated slurry comprising
agglomerates and a low solids bitumen extract; separating the low
solids bitumen extract from the agglomerated slurry; mixing a
second solvent with the low solids bitumen extract to form a
solvent-bitumen low solids mixture, the second solvent having a
similar or lower boiling point than the first solvent; subjecting
the mixture to gravity separation to produce a high grade bitumen
extract and a low grade bitumen extract; and recovering the first
and second solvent from the high grade bitumen extract, leaving a
high grade bitumen product.
2. The process of claim 1, additionally comprising recovering the
first solvent from the coarse solids stream prior to
agglomerating.
3. The process of claim 1, wherein the ratio of the first solvent
to bitumen in the initial slurry is selected to avoid precipitation
of asphaltenes during agglomeration.
4. The process of claim 3, wherein the ratio of solvent to bitumen
during agglomeration is less than 2:1.
5. The process of claim 1, wherein agglomerating solids comprises
adding an aqueous bridging liquid to the fine solids stream and
providing agitation.
6. The process of claim 1, additionally comprising adding steam to
the bituminous feed before combining with the first solvent, to
increase the temperature of the bituminous feed to a temperature of
from about 0.degree. C. to about 60.degree. C., or is from about
0.degree. C. to about 30.degree. C.
7. The process of claim 1, wherein the initial slurry is formed in
a low oxygen environment.
8. The process of claim 1, wherein the coarse solids stream is
combined with the agglomerated slurry prior to separating the low
solids bitumen extract from the agglomerated slurry.
9. The process of claim 1, wherein the first solvent comprises a
paraffinic solvent, a cyclic aliphatic hydrocarbon, or a mixture
thereof; 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; wherein the alkane comprises
heptane, iso-heptane, hexane, iso-hexane, pentane, iso-pentane, or
a combination thereof; and wherein the cyclic aliphatic hydrocarbon
comprises a cycloalkane of 4 to 9 carbon atoms.
10. The process of claim 9, wherein the distillate from a
fractionation unit has a final boiling point of less than about
180.degree. C., or less than about 100.degree. C.
11. The process of claim 1, wherein the boiling point of the second
solvent is less than 100.degree. C.
12. The process of claim 1, wherein the first solvent and second
solvent are the same.
13. The process of claim 1, wherein the agglomerated slurry is
separated into the low solids bitumen extract and agglomerates in a
solid-liquid separator, and the solid-liquid separator comprises a
secondary stage for countercurrently washing the agglomerates
separated from the agglomerated slurry.
14. The process of claim 1, wherein the first solvent recovered
from the high grade bitumen extract comprises entrained bitumen,
and is re-used for combining with the bituminous feed or for
including with the fine solids stream during agglomeration.
15. A process for recovery of bitumen from oil sands comprising:
combining a first solvent and a bituminous feed from oil sands to
form an initial slurry; separating the initial slurry into a fine
solids stream and a coarse solids stream; agglomerating solids from
the fine solids stream to form an agglomerated slurry comprising
agglomerates and a low solids bitumen extract; mixing a second
solvent with the agglomerated slurry to form a solvent-bitumen
agglomerated slurry mixture, the second solvent having a similar or
lower boiling point than the first solvent; subjecting the mixture
to separation to produce a high grade bitumen extract and a low
grade bitumen extract; recovering the first and second solvent from
the high grade bitumen extract, leaving a high grade bitumen
product; and recovering the first and second solvent from the low
grade bitumen extract, leaving a low grade bitumen product.
16. The process of claim 15, additionally comprising recovering the
first solvent from the coarse solids stream prior to
agglomerating.
17. The process of claim 15, wherein the ratio of the first solvent
to bitumen in the initial slurry is selected to avoid precipitation
of asphaltenes during agglomerating.
18. The process of claim 15, wherein agglomerating solids comprises
adding an aqueous bridging liquid to the fine solids stream and
providing agitation.
19. The process of claim 15, additionally comprising adding steam
to the bituminous feed before combining with the first solvent, to
increase the temperature of the bituminous feed to a temperature of
from about 0.degree. C. to about 60.degree. C., or is from about
0.degree. C. to about 30.degree. C.
20. The process of claim 15, wherein the initial slurry is formed
in a low oxygen environment.
21. The process of claim 15, wherein the coarse solids stream is
combined with the agglomerated slurry prior to mixing the second
solvent with the agglomerated slurry.
22. The process claim 15, wherein the first solvent comprises a
paraffinic solvent, a cyclic aliphatic hydrocarbon, or a mixture
thereof; 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; wherein the alkane comprises
heptane, iso-heptane, hexane, iso-hexane, pentane, iso-pentane, or
a combination thereof; and wherein the cyclic aliphatic hydrocarbon
comprises a cycloalkane of 4 to 9 carbon atoms.
23. The process of claim 22, wherein the distillate from a
fractionation unit has a final boiling point of less than about
180.degree. C., or less than about 100.degree. C.
24. The process of claim 15, wherein the boiling point of the
second solvent is less than 100.degree. C.
25. The process of claim 15, wherein the second solvent is
immiscible or can be rendered immiscible in the first solvent.
26. The process of claim 15, wherein the high grade bitumen extract
and the low grade bitumen extract are separated in a solid-liquid
separator, and the solid-liquid separator comprises a secondary
stage for countercurrently washing agglomerates separated from the
solvent-bitumen agglomerated slurry mixture.
27. The process of claim 15, wherein the first solvent recovered
from the high grade bitumen extract comprises entrained bitumen,
and is re-used for combining with the bituminous feed or for
including with the fine solids stream during agglomeration.
28. A process for recovery of a bitumen product from oil sands
comprising: combining a first solvent and a bituminous feed from
oil sands to form an initial slurry; agglomerating solids from
initial slurry to form an agglomerated slurry comprising
agglomerates and a low solids bitumen extract; mixing a second
solvent with the agglomerated slurry to form a solvent-bitumen
agglomerated slurry mixture, the second solvent having a similar or
lower boiling point than the first solvent; subjecting the mixture
to separation to produce a high grade bitumen extract and a low
grade bitumen extract comprising substantially all solids and
water; and recovering the first and second solvent from the high
grade bitumen extract, leaving a high grade bitumen product;
wherein the ratio of first solvent to bitumen in the initial slurry
is selected to avoid precipitation of asphaltenes during
agglomeration.
29. The process of claim 28, additionally comprising recovering
solvent from the low grade bitumen extract, leaving a low grade
bitumen product.
30. The process of claim 28, additionally comprising separating the
low solids bitumen extract from the agglomerated slurry.
31. The process of claim 28, wherein the ratio of solvent to
bitumen during agglomeration is less than 2:1.
32. The process of claim 28, additionally comprising adding steam
to the bituminous feed before combining with the first solvent, to
increase the temperature of the bituminous feed to a temperature of
from about 0.degree. C. to about 60.degree. C., or is from about
0.degree. C. to about 30.degree. C.
33. The process of claim 28, wherein the initial slurry is formed
in a low oxygen environment.
34. The process of claim 28, wherein the first solvent comprises a
paraffinic solvent, a cyclic aliphatic hydrocarbon, or a mixture
thereof; 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; wherein the alkane comprises
heptane, iso-heptane, hexane, iso-hexane, pentane, iso-pentane, or
a combination thereof; and wherein the cyclic aliphatic hydrocarbon
comprises a cycloalkane of 4 to 9 carbon atoms.
35. The process of claim 34, wherein the distillate from a
fractionation unit has a final boiling point of less than about
180.degree. C., or less than about 100.degree. C.
36. The process of claim 28, wherein the boiling point of the
second solvent is less than 100.degree. C.
37. The process of claim 28, wherein the second solvent is
immiscible or can be rendered immiscible in the first solvent.
38. The process of claim 28, wherein the high grade bitumen extract
and the low grade bitumen extract are separated in a solid-liquid
separator, and the solid-liquid separator comprises a secondary
stage for countercurrently washing agglomerates separated from the
solvent-bitumen agglomerated slurry mixture.
39. The process of claim 28, wherein the first solvent recovered
from the high grade bitumen extract comprises entrained bitumen,
and is re-used for combining with the bituminous feed or for
including with the initial slurry during agglomeration.
40. A system for recovery of bitumen from oil sands comprising: a
slurry system wherein a bituminous feed is mixed with a first
solvent to form an initial slurry; an agglomerator for
agglomerating solids and producing an agglomerated slurry; a
primary solid-liquid separator for separating the agglomerated
slurry into agglomerates and a low solids bitumen extract; a
gravity separator for receiving the low solids bitumen extract and
a second solvent; and a primary solvent recovery unit for
recovering the first solvent or the second solvent in a high grade
bitumen extract arising from the gravity separator and for
separating bitumen therefrom.
41. The system of claim 40, additionally comprising a fine/coarse
solids separator in fluid communication with the slurry system for
receiving the initial slurry and separating a fine solids stream
therefrom, and wherein the agglomerator is for agglomerating the
fine solids stream therein.
42. The system of claim 40, additionally comprising a secondary
solid-liquid separator for countercurrently washing agglomerates
received from the primary solid-liquid separator.
43. The system of claim 42, wherein the primary or the secondary
solid-liquid separator comprises a gravity separator, cyclone,
screen, or belt filter.
44. The system of claim 40, additionally comprising a secondary
solvent recovery unit for recovering solvent from the agglomerates
separated in the primary solid-liquid separator.
45. The system of claim 40, additionally comprising a steam source
for pre-conditioning feed entering the slurry system.
46. The system of claim 41, additionally comprising means for
directing a coarse solids stream derived from the fine/coarse
solids separator for combination with the agglomerated slurry
arising from the agglomerator prior to entry of the slurry into the
primary solid-liquid separator.
47. The system of claim 40, wherein the slurry system comprises a
mix box, a pump, a pipeline or a combination thereof, having a feed
section for a gas blanket to provide a low oxygen environment.
48. The system of claim 40, wherein the primary solid-liquid
separator comprises a settling vessel, cyclone, or screen.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from Canadian Patent
Application 2,689,469 filed 30 Dec. 2009 entitled PROCESS AND
SYSTEM FOR RECOVERY OF BITUMEN FROM OIL SANDS, the entirety of
which is incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates generally to a process for
hydrocarbon extraction from mineable deposits, such as bitumen from
oil sands, and to a system for implementing such a process.
BACKGROUND OF THE INVENTION
[0003] Methodologies for extracting hydrocarbon from oil sands have
required energy intensive processing steps to separate solids and
water from the products having commercial value.
[0004] Previously described methodologies for solvent extraction
spherical agglomeration (SESA), have not been commercially adopted.
For a description of the SESA process, see Sparks et al., Fuel
1992(71), 1349-1353. Such processes involved mixing a slurry of oil
sands material with a hydrocarbon solvent (such as a high boiling
point solvent), adding a bridging liquid (for example, water),
agitating this mixture in a slow and controlled manner to nucleate
particles, and continuing such agitation so as to permit these
nucleated particles to form larger multi-particle spherical
agglomerates for removal. A bridging liquid is a liquid with
affinity for the solid particles (i.e. preferentially wets the
solid particles) but is immiscible in the solvent. The process was
conducted at about 50-80.degree. C. (see also Canadian Patent
Application 2,068,895 of Sparks et al.). The enlarged size of the
agglomerates formed permits easy removal of the solids by
sedimentation, screening or filtration.
[0005] Solvent recovery from the solids produced in previously
described processes would be difficult, due to the nature of the
solvent proposed for use in the extraction process. The proposed
solvents in previously described processes have a low molecular
weight, high aromatic content, and low short chain paraffin
content. Naphtha was the solvent proposed for the SESA process,
with a final boiling point ranging between 180-220.degree. C., and
a molecular weight of 100-215 g/mol. With such high boiling point
solvents, the recovery would be energy intensive as significant
energy is required to vaporize the residual hydrocarbon and to
release hydrocarbon trapped within the agglomerates.
[0006] A methodology described by Meadus et al. in U.S. Pat. No.
4,057,486, involved combining solvent extraction with particle
enlargement to achieve spherical agglomeration of tailings suitable
for direct mine refill. Organic material was separated from oil
sands by mixing the oil sands material with an organic solvent to
form a slurry, after which an aqueous bridging liquid was added in
small amounts. By using controlled agitation, solid particles from
oil sands adhere to each other and were enlarged to form
macro-agglomerates of mean diameter greater than 2 mm from which
the bulk of the bitumen and solvent was excluded. This process
permitted a significant decrease in water use, as compared with
conventional water-based extraction processes. Solvents used in the
process were of low molecular weight, having aromatic content, but
only small amounts of short chain paraffins. While this may have
resulted in a high recovery of bitumen, the energy intensity
required for solvent recovery would be too high to be adopted in a
commercial application.
[0007] U.S. Pat. No. 3,984,287 describes an apparatus for
separating organic material from particulate tar sands, resulting
in agglomeration of a particulate residue. The apparatus included a
tapered rotating drum in which tar sands, water, and an organic
solvent were mixed together. In this apparatus, water was intended
to act as a bridging liquid to agglomerate the particulate, while
the organic solvent dissolves organic materials. As the materials
combined in the drum, bitumen was separated from the ore.
[0008] A device to convey agglomerated particulate solids for
removal to achieve the process of Meadus et al. (U.S. Pat. No.
4,057,486) within a single vessel is described in U.S. Pat. No.
4,406,788.
[0009] A method for separating fine solids from a bitumen solution
is described in U.S. Pat. No. 4,888,108. To remove fine solids, an
aqueous solution of polar organic additive as well as solvent
capable of precipitating asphaltenes was added to the solution, so
as to form aggregates for removal from the residual liquid.
Although the method achieved low solids content in the resulting
bitumen product with this approach, the solids content in the
bitumen product fell short of optimal product quality of less than
400 ppm solids on a dry bitumen basis, especially for settling
times less than 1 hour.
[0010] Others have proposed sequential use of two solvents in
different solvent extraction schemes. For example U.S. Pat. No.
3,131,141 proposed the use of high boiling point solvent for oil
sands extraction followed by low boiling point/volatile solvent for
enhanced solvent recovery from tailings in a unique process
arrangement. U.S. Pat. No. 4,046,668 describes a process from
recovery bitumen from oil sands using a mixture of light naphtha
and methanol. However, it is not described or suggested that a
second solvent could be effectively applied to a solvent extraction
process with simultaneous solids agglomeration without upsetting
the agglomeration process.
[0011] U.S. Pat. No. 4,719,008 describes a method for separating
micro-agglomerated solids from a high-quality hydrocarbon fraction
derived from oil sands. A light milling action was imposed on a
solvated oil sands mixture. After large agglomerates were formed,
the milling action was used to break down the agglomerate size, but
still permitted agglomerate settling and removal.
[0012] U.S. Pat. No. 5,453,133 and U.S. Pat. No. 5,882,429 describe
soil remediation processes to remove hydrocarbon contaminants from
soil. The processes employed a solvent and a bridging liquid
immiscible with the solvent, and this mixture formed agglomerates
when agitated with the contaminated soil. The contaminant
hydrocarbon was solvated by the solvent, while soil particles
agglomerated with the bridging liquid. In this way, the soil was
considered to have been cleaned. Multiple extraction stages were
proposed.
[0013] Canadian Patent Application 2,068,895 describes a method of
incorporating a solvent extraction scheme into a water-based
process flow sheet. The method involved a slurry conditioning
process which allowed a hydrocarbon bitumen fraction, having high
fines content, to be processed in a solvent extraction and solids
agglomeration process to achieve higher overall bitumen recovery
and reduced sludge volume.
[0014] The previously proposed process for agglomeration, as
described by Govier and Sparks in "The SESA Process for the
Recovery of Bitumen from Mined Oil Sands" (Proceedings of AOSTRA
Oils Sands 2000 Symposium, Edmonton 1990, Paper 5), was of limited
practicality partly due to the nature of the solvent which, when
combined with tailings, made solvent recovery difficult. This
process is referenced herein as the Govier and Sparks process. The
solvent described possessed a low molecular weight and significant
aromatic content, while containing only a small amount of short
chain paraffins. Exemplary solvents were described as varsol or
naphtha. As expected for such high boiling point solvents, bitumen
recovery was consistently high. However, the energy intensity
required for the solvent recovery was also high. There was no
description in this document of the use of low boiling point
solvents. Further, there was no suggestion in the Govier and Sparks
process of how the process would have been adapted to employ a
different solvent to more efficiently recover solvent, or of how
appropriate feed slurry characteristics may have been achieved if a
different solvent was employed.
[0015] Typically, a bottom sediment and water (BS&W) content,
primarily comprised of fines, of between 0.2-0.5 wt % of solids in
dry bitumen could be achieved according to the Govier and Sparks
process. However, occasionally solids agglomeration would cycle
unpredictably and the fines content of the agglomerator discharge
stream would rise dramatically. Subsequent settling in a clarifier
or bed filtration would then be required to achieve the desired
product quality of 0.2-0.5 wt % BS&W. The BS&W component
prepared by the process was comprised mostly of solids. Bitumen
products with this composition are not fungible and can only be
processed at a site coking facility or at an onsite upgrader. This
would provide limited flexibility for sale or processing in a
remote refinery.
[0016] The above-described agglomeration processes integrated
solvent extraction and agglomeration within the same mixing vessel,
which is inefficient because means of pre-conditioning and
conveyance of the bituminous feed into the extraction/agglomerating
unit is thus complicated. Conventional agglomeration units are
large drums designed to integrate both the extraction and
agglomeration aspects of the process, and are bulky and
inefficient. Residence time in such agglomeration units would be
lengthy, and process kinetics imposed restrictions on residence
time. Dissolution time, the slow agitation required, limited slurry
density, and the high containment volume required for extraction
required the residence time in the agglomeration unit to be
lengthy, and the process slow. Further, solvent recovery was not of
concern in many previous processes, and is not addressed in most
previously described processes.
[0017] It is desirable to provide processes and systems that
increase the efficiency of oil sands extraction, reduce water use,
and/or reduce energy intensity required to produce a commercially
desirable bitumen product from oil sands. Producing a product that
is capable of meeting or exceeding requirements for downstream
processing or pipeline transport is desirable.
SUMMARY OF THE INVENTION
[0018] It is an object of the present invention to obviate or
mitigate at least one disadvantage of previous processes and
systems for hydrocarbon extraction from mineable deposits such as
oil sands.
[0019] Solvent extraction processes to recover bitumen from oil
sands are described, employing solvent extraction and sequential
agglomeration of fines to advantageously simplify subsequent
solid-liquid separation. The processes can produce at least one
bitumen product with a quality specification of water and solids
that exceeds downstream processing and pipeline transportation
requirements and contains low levels of solids and water. Further,
systems for implementing such processes are described.
[0020] The use of low boiling point solvents advantageously permits
recovery of solvent with a lower energy requirement than would be
expended for recovery of high boiling point solvents. By conducting
solvent extraction and agglomeration steps independently, shorter
residence times in the agglomeration unit can be achieved. The
sequential nature of the process allows for flexible design of a
slurry feed system which permits high throughput from a smaller
sized agglomeration unit, as well as faster bitumen production.
[0021] When the optional step of steam pre-conditioning is employed
in the process, this realizes the further advantage that steam not
only heats the slurry or oil sands, but adds the water necessary
for the later agglomeration process.
[0022] Advantageously, the inventive process permits formation of
bitumen products with an acceptable composition for sale or
processing at a remote refinery, and thus these products need not
be processed by an onsite upgrader.
[0023] As a result of the process, a high quality (or high grade)
bitumen product is formed which is able to meet and/or exceed
quality specifications of low water content and low solids content
required for pipeline transport and downstream processing. The
process permits premium, dry and clean bitumen to be obtained as
well as a lower grade bitumen product to be obtained (which in
certain cases may comprise primarily of asphaltenes) for various
commercial uses. By using the process described herein, it is
possible to achieve a high grade bitumen product, as well as lower
grades of bitumen products. For example, a high grade bitumen
product is considered to be one containing less than about 0.04 wt
% solids (400 ppm), which may be obtained according to the instant
process. Further, such a product formed by the process described
herein may contain about 0.5 wt % or less of water+solids of the
dry bitumen product. Water content may be less than or equal to 200
ppm in the final high grade bitumen product. This is an improved
result compared with the 0.2-0.5 wt % of solids in dry bitumen that
can be achieved according to the previously described Govier and
Sparks process. Low grade bitumen products having more than 400 ppm
solids, and more than 200 ppm water may additionally be
obtained.
[0024] A process for recovery of bitumen from oil sands is
described herein. In the process, a first solvent is combined with
a bituminous feed from oil sands to form an initial slurry. The
initial slurry is separated into a fine solids stream and a coarse
solids stream. Solids from the fine solids stream are agglomerated
to form an agglomerated slurry comprising agglomerates and a low
solids bitumen extract. The low solids bitumen extract is then
separated from the agglomerated slurry, and a second solvent is
mixed with the low solids bitumen extract to form a solvent-bitumen
low solids mixture. The second solvent is selected to have a
similar or lower boiling point than the first solvent. The mixture
is then subjected to gravity separation to produce a high grade
bitumen extract and a low grade bitumen extract. The first and
second solvent can be recovered from the high grade bitumen
extract, leaving a high grade bitumen product.
[0025] Further, described herein is a process for recovery of
bitumen from oil sands. The process involves combining a first
solvent and a bituminous feed from oil sands to form an initial
slurry. The initial slurry is then separated into a fine solids
stream and a coarse solids stream. Solids from the fine solids
stream are agglomerated to form an agglomerated slurry comprising
agglomerates and a low solids bitumen extract. A second solvent is
then mixed with the agglomerated slurry to form a solvent-bitumen
agglomerated slurry mixture, the second solvent having a similar or
lower boiling point than the first solvent. This mixture is
subjected to separation to produce a high grade bitumen extract and
a low grade bitumen extract. The first and second solvent can then
be recovered from the high grade bitumen extract, leaving a high
grade bitumen product; and the first and second solvent can also be
recovered from the low grade bitumen extract, leaving a low grade
bitumen product.
[0026] Described herein is a further process for recovery of
bitumen from oil sands comprising combining a first solvent and a
bituminous feed from oil sands to form an initial slurry, which is
then separated into a fine solids stream and a coarse solids
stream. The first solvent is then recovered from the coarse solids
stream. Solids are agglomerated from the fine solids stream to form
an agglomerated slurry comprising agglomerates and a low solids
bitumen extract, and the low solids bitumen extract is then
separated from the agglomerated slurry. A second solvent is then
mixed with the low solids bitumen extract to form a solvent-bitumen
low solids mixture, the second solvent having a similar or lower
boiling point than the first solvent. The mixture is subjected to
gravity separation to produce a high grade bitumen extract and a
low grade bitumen extract; and the first and second solvent from
the high grade bitumen extract, leaving a high grade bitumen
product.
[0027] Additionally, a process is described herein for recovery of
a bitumen product from oil sands. The process comprises combining a
first solvent and a bituminous feed from oil sands to form an
initial slurry, and separating the initial slurry into a fine
solids stream and a coarse solids stream. The first solvent is
recovered from the first coarse solids stream, and solids are
agglomerated from the fine solids stream to form an agglomerated
slurry comprising agglomerates and a low solids bitumen extract.
Further, mixing a second solvent with the agglomerated slurry to
form a solvent-bitumen agglomerated slurry mixture is then
conducted, the second solvent having a similar or lower boiling
point than the first solvent. The mixture is then subjected to
separation to produce a high grade bitumen extract and a low grade
bitumen extract. The first and second solvent are then recovered
from the high grade bitumen extract, leaving a high grade bitumen
product; and the first and second solvent are also recovered from
the low grade bitumen extract, leaving a low grade bitumen
product.
[0028] Additionally, there is described herein a process for
recovery of bitumen from oil sands comprising combining a first
solvent and a bituminous feed from oil sands to form an initial
slurry and agglomerating solids from the initial slurry to form an
agglomerated slurry comprising agglomerates and a low solids
bitumen extract. The low solids bitumen extract is then separated
from the agglomerated slurry. A second solvent is then mixed with
the low solids bitumen extract to form a solvent-bitumen low solids
mixture, the second solvent having a similar or lower boiling point
than the first solvent. The mixture is subjected to gravity
separation to produce a high grade bitumen extract and a low grade
bitumen extract; and the first and second solvent are then
recovered from the high grade bitumen extract, leaving a high grade
bitumen product. In this process, the ratio of first solvent to
bitumen in the initial slurry is selected to avoid precipitation of
asphaltenes during agglomeration.
[0029] Further, there is provided herein a process for recovery of
a bitumen product from oil sands. The process involves combining a
first solvent and a bituminous feed from oil sands to form an
initial slurry, and agglomerating solids from initial slurry to
form an agglomerated slurry comprising agglomerates and a low
solids bitumen extract. A second solvent is mixed with the
agglomerated slurry to form a solvent-bitumen agglomerated slurry
mixture, the second solvent having a similar or lower boiling point
than the first solvent. The mixture is then subjected to separation
to produce a high grade bitumen extract and a low grade bitumen
extract comprising substantially all solids and water. The first
and second solvents are then recovered from the high grade bitumen
extract, leaving a high grade bitumen product; and similarly, the
first and second solvents are then recovered from the low grade
bitumen extract, leaving a low grade bitumen product. In this
instance, the ratio of first solvent to bitumen in the initial
slurry is selected to avoid precipitation of asphaltenes during
agglomeration.
[0030] A system is provided for recovery of bitumen from oil sands
comprising a slurry system wherein a bituminous feed is mixed with
a first solvent to form an initial slurry; a fine/coarse solids
separator in fluid communication with the slurry system for
receiving the initial slurry and separating a fine solids stream
therefrom; an agglomerator for receiving a fine solids stream from
the fine/coarse solids separator, for agglomerating solids and
producing an agglomerated slurry; a primary solid-liquid separator
for separating the agglomerated slurry into agglomerates and a low
solids bitumen extract; a gravity separator for receiving the low
solids bitumen extract and a second solvent; and a primary solvent
recovery unit for recovering the first solvent or the second
solvent in a high grade bitumen extract arising from the gravity
separator and for separating bitumen therefrom.
[0031] Additionally, a system for recovery of bitumen from oil
sands is described herein, comprising a slurry system wherein a
bituminous feed is mixed with a first solvent to form an initial
slurry; an agglomerator for receiving the initial slurry, for
agglomerating solids and producing an agglomerated slurry; a
primary solid-liquid separator for separating the agglomerated
slurry into agglomerates and a low solids bitumen extract; a
gravity separator for receiving the low solids bitumen extract and
a second solvent; and a primary solvent recovery unit for
recovering the first solvent or the second solvent in a high grade
bitumen extract arising from the gravity separator and for
separating bitumen therefrom.
[0032] Other aspects and features of the present invention will
become apparent to those ordinarily skilled in the art upon review
of the following description of specific embodiments of the
invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Embodiments of the present invention will now be described,
by way of example only, with reference to the attached Figures.
[0034] FIG. 1 is a schematic representation of an embodiment of the
process.
[0035] FIG. 2 illustrates an exemplary embodiment of the process
consistent with the representation shown in FIG. 1.
[0036] FIG. 3 is a schematic representation of an embodiment of the
process.
[0037] FIG. 4 illustrates an exemplary embodiment of the process
consistent with the representation shown in FIG. 3.
[0038] FIG. 5 is a schematic representation of an embodiment of the
process.
[0039] FIG. 6 illustrates an exemplary embodiment of the process
consistent with the representation shown in FIG. 5.
[0040] FIG. 7 provides a schematic representation of an embodiment
of the system according to the invention.
DETAILED DESCRIPTION
[0041] Generally, the present invention provides a process and
system for fines capture or agglomeration and solvent extraction of
bitumen from oil sands. Processing oil sands according to the
invention permits high throughput and improved product quality and
value.
[0042] A process and system for recovery of bitumen from oil sands
is provided herein.
[0043] The term "bituminous feed" from oil sands refers to a stream
derived from oil sands that requires downstream processing in order
to realize valuable bitumen products or fractions. The bituminous
feed from oil sands is one that contains bitumen along with other
undesirable components for removal in the process described herein.
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 according to the process
described herein. Also, recycled streams that contain bitumen in
combination with other components for removal in the described
process 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 contains 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.
[0044] Embodiment in which First Solvent Added Prior to
Agglomeration, Second Solvent Added after Agglomerates Removed.
[0045] In one embodiment of the process, a first solvent is added
to agglomerate the bituminous feed, but only after the agglomerated
slurry is formed is the second solvent added to extract bitumen.
This embodiment comprises combining a first solvent and a
bituminous feed from oil sands to form an initial slurry. The
initial slurry is then separated into a fine solids stream and a
coarse solids stream. The fine solids stream is subjected to
agglomeration to form an agglomerated slurry, which includes
agglomerates and a low solids bitumen extract. The low solids
bitumen extract is separated from the agglomerated slurry, and
subsequently mixed with a second solvent to form a solvent-bitumen
low solids mixture. In this embodiment, the second solvent is one
having a similar or lower boiling point than the first solvent. The
mixture is subjected to gravity separation to produce a high grade
bitumen extract and a low grade bitumen extract. The extracts are
subjected to solvent recovery of both the first and second
extracts, leaving a low grade bitumen product and a high grade
bitumen product.
[0046] Embodiment in which Second Solvent Added Prior to Separating
Low Solids Bitumen Extract from Agglomerated Slurry.
[0047] An additional process for recovery of bitumen from oil sands
is provided in which the second solvent is added prior to
separating low solids bitumen extract and agglomerates from the
agglomerated slurry. This embodiment involves combining a first
solvent and a bituminous feed from oil sands to form an initial
slurry, and subsequently separating the initial slurry into a fine
solids stream and a coarse solids stream. Solids from the fine
solids stream are agglomerated to form an agglomerated slurry
comprising agglomerates and a low solids bitumen extract. A second
solvent is then mixed with the agglomerated slurry to form a
solvent-bitumen agglomerated slurry mixture, the second solvent
having a similar or lower boiling point than the first solvent. The
mixture is then subjected to separation to produce a high grade
bitumen extract and a low grade bitumen extract. The first and
second solvent are then recovered from the high grade bitumen
extract, leaving a high grade bitumen product. The first and second
solvent are also recovered from the low grade bitumen extract,
leaving a low grade bitumen product.
[0048] In this embodiment of the process, the second solvent may be
added prior to separating low solids bitumen extract from the
agglomerated slurry. Thus, the second solvent will contact with the
agglomerates and the low solids bitumen extract to form the
solvent-bitumen agglomerated slurry mixture, which is processed
further into high grade and low grade products, as described in
further detail herein below.
[0049] Embodiment in which Coarse Solids are Processed Separately
from Agglomeration of Fine Solids Stream.
[0050] Additionally, another embodiment comprises a process for
recovery of bitumen from oil sands in which a first solvent and a
bituminous feed from oil sands are combined to form an initial
slurry. The initial slurry is then separated into a fine solids
stream and a coarse solids stream. The first solvent is recovered
from the coarse solids stream, and solids are agglomerated from the
fine solids stream to form an agglomerated slurry comprising
agglomerates and a low solids bitumen extract. The low solids
bitumen extract is separated from the agglomerated slurry, and
mixed with a second solvent to form a solvent-bitumen low solids
mixture. In this embodiment, the second solvent has a similar or
lower boiling point than the first solvent. The mixture is then
subjected to gravity separation to produce a high grade bitumen
extract and a low grade bitumen extract. The first and second
solvent are recovered from the high grade bitumen extract, leaving
a high grade bitumen product.
[0051] In this embodiment of the process, the coarse solids stream
is processed separately from the fine solids stream, and will not
optionally be included back into the mixture. Coarse solids are
processed separately to remove the solvent therefrom, or are added
back into the slurry system or separator, for subsequent processing
in an iterative manner.
[0052] Embodiment in which Coarse Solids are Processed Separately
from Agglomeration of Fine Solids Stream, and the Second Solvent is
Mixed with the Agglomerated Slurry.
[0053] A further embodiment comprises a process for recovery of a
bitumen product from oil sands comprising: combining a first
solvent and a bituminous feed from oil sands to form an initial
slurry; separating the initial slurry into a fine solids stream and
a coarse solids stream; recovering the first solvent from the
coarse solids stream; agglomerating solids from the fine solids
stream to form an agglomerated slurry comprising agglomerates and a
low solids bitumen extract; mixing a second solvent with the
agglomerated slurry to form a solvent-bitumen agglomerated slurry
mixture, the second solvent having a similar or lower boiling point
than the first solvent; subjecting the mixture to separation to
produce a high grade bitumen extract and a low grade bitumen
extract; recovering the first and second solvent from the high
grade bitumen extract, leaving a high grade bitumen product; and
recovering the first and second solvent from the low grade bitumen
extract, leaving a low grade bitumen product.
[0054] In this embodiment of the process, the first solvent may be
recovered from the coarse solids stream separately, and again there
is no option to re-introduce the coarse solids stream into a
downstream aspect of the process, for example, into the
agglomerated slurry, as there would be in other embodiments of the
process. This embodiment also involves combining the second solvent
with the agglomerated slurry.
[0055] Embodiment in which Initial Slurry is Directed to
Agglomeration without Separation of Coarse Solids, and in which
Second Solvent is Introduced after Agglomerates are Removed.
[0056] A further embodiment of the process for recovery of bitumen
from oil sands is described herein in which a first solvent is
combined with a bituminous feed from oil sands to form an initial
slurry. Solids in the initial slurry are agglomerated to form an
agglomerated slurry comprising agglomerates and a low solids
bitumen extract. A low solids bitumen extract is separated from the
agglomerated slurry. A second solvent is then mixed with the low
solids bitumen extract to form a solvent-bitumen low solids
mixture, the second solvent having a similar or lower boiling point
than the first solvent. The mixture is then subjected to gravity
separation to produce a high grade bitumen extract and a low grade
bitumen extract. The first and second solvent are then recovered
from the high grade bitumen extract, leaving a high grade bitumen
product. In this embodiment, the ratio of first solvent to bitumen
in the initial slurry is selected to avoid precipitation of
asphaltenes during agglomeration.
[0057] In this embodiment of the process, the step of separating
the initial slurry into a fine solids stream and a coarse solids
stream is not conducted. Thus, the bituminous feed is combined with
the first solvent to prepare the initial slurry, which can then be
agglomerated without the requirement for further separation. In
this embodiment, the first solvent is mixed with the bituminous
feed, but the second solvent is not introduced until after the low
solids bitumen extract has been separated from the agglomerates. In
this way, the agglomerates need not come into contact with the
second solvent.
[0058] Embodiment in which Initial Slurry is Directed to
Agglomeration without Separation of Coarse Solids, and in which
Second Solvent is Introduced Prior to Removal of Agglomerates.
[0059] A further embodiment of the process is described herein for
recovery of a bitumen product from oil sands. The embodiment
comprises combining a first solvent and a bituminous feed from oil
sands to form an initial slurry. Solids from the initial slurry are
agglomerated to form an agglomerated slurry comprising agglomerates
and a low solids bitumen extract. A second solvent is then mixed
with the agglomerated slurry to form a solvent-bitumen agglomerated
slurry mixture, the second solvent having a similar or lower
boiling point than the first solvent. The mixture is subjected to
separation to produce a high grade bitumen extract and a low grade
bitumen extract, in which the low grade extract comprises
substantially all solids and water. The first and second solvents
are then recovered from the high grade bitumen extract, leaving a
high grade bitumen product. The first and second solvent are
recovered from the low grade bitumen extract, leaving a low grade
bitumen product. In this embodiment, the ratio of first solvent to
bitumen in the initial slurry is selected to avoid precipitation of
asphaltenes during agglomeration.
[0060] In this embodiment of the process, the step of separating
the initial slurry into a fine solids stream and a coarse solids
stream is not conducted. Thus, the bituminous feed is combined with
the first solvent to prepare the initial slurry, which is then
agglomerated without the requirement for further separation. In
this embodiment, the first solvent is mixed with the bituminous
feed, and later, the agglomeration of solids occurs. However, the
second solvent is added to the agglomerated slurry, so as to form a
mixture. In this embodiment, all components of the agglomerated
slurry are contacted by both the first and the second solvent. Both
solvents are then recovered from each of the high grade bitumen
extract and the low grade bitumen extract.
[0061] Embodiment of a System in which a Fine/Coarse Solids
Separator and a Gravity Separator are Employed.
[0062] A system is provided for recovery of bitumen from oil sands
comprising a slurry system wherein a bituminous feed is mixed with
a first solvent to form an initial slurry. A fine/coarse solids
separator is included in the system, and is in fluid communication
with the slurry system for receiving the initial slurry and
separating a fine solids stream therefrom. The system additionally
includes an agglomerator for receiving a fine solids stream from
the fine/coarse solids separator, for agglomerating solids and
producing an agglomerated slurry. A primary solid-liquid separator
is present in the system for separating the agglomerated slurry
into agglomerates and a low solids bitumen extract. A gravity
separator is present in the system for receiving the low solids
bitumen extract and a second solvent. A primary solvent recovery
unit is included, for recovering the first solvent or the second
solvent in a high grade bitumen extract arising from the gravity
separator and for separating bitumen therefrom.
[0063] In this embodiment of the system, both a fine/coarse solids
separator, and a gravity separator are employed, consistent with
the embodiment of the invention depicted and described previously
in respect of FIG. 2.
[0064] Embodiment of a System in which there is No Fine/Coarse
Solids Separator Component Upstream of the Agglomerator.
[0065] A further embodiment of a system for recovery of bitumen
from oil sands is described herein comprising a slurry system
wherein a bituminous feed is mixed with a first solvent to form an
initial slurry. Further, the system includes an agglomerator for
receiving the initial slurry, for agglomerating solids and
producing an agglomerated slurry. A primary solid-liquid separator
is used in the system for separating the agglomerated slurry into
agglomerates and a low solids bitumen extract. A gravity separator
is present in the system for receiving the low solids bitumen
extract and a second solvent, and a primary solvent recovery unit
for recovering the first solvent or the second solvent in a high
grade bitumen extract arising from the gravity separator and for
separating bitumen therefrom is also incorporated into the
system.
[0066] In this embodiment of the system, there is no requirement
for a fine/coarse solids separator, and so both fines and coarse
solids may be agglomerated together in the agglomerator.
[0067] Additional process details are described below which are
generally applicable to most embodiments listed above, with some
exceptions.
[0068] Ratio of Solvent to Bitumen in Initial Slurry.
[0069] The process may be adjusted to render the ratio of the first
solvent to bitumen in the initial slurry 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
solvent used, can permit the control of a ratio of solvent to
bitumen in the slurry system and agglomerator. When the solvent of
the invention 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 excessive solvent use.
[0070] An exemplary ratio of solvent to bitumen to be selected as a
target ratio during agglomeration is less than 2:1. A ratio of
1.5:1 or less, and a ratio of 1:1 or less, for example, a ratio of
0.75:1, would also be considered acceptable target ratios for
agglomeration. For clarity, ratios may be expressed herein using a
colon between two values, such as "2:1", or may equally be
expressed as a single number, such as "2", which carries the
assumption that the denominator of the ratio is 1 and is expressed
on a weight to weight basis.
[0071] Slurry System.
[0072] The slurry system in which the slurry is prepared in the
system may optionally be a mix box, a pump, a pipeline or a
combination of these. By slurrying the first solvent 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 the downstream separation
of fine and coarse solid streams and prior to agglomeration within
the agglomeration. In some prior art processes, solvent is
introduced at the time of agglomeration, which may require more
residence time within the agglomerator, and may lead to incomplete
bitumen dissolution and lower overall bitumen recovery. The slurry
system advantageously permits contact and extraction of bitumen
from solids within the initial slurry, prior to agglomeration.
Forming an initial slurry prior to agglomeration advantageously
permit flexible design of the slurry system and simplifies means of
feeding materials into the agglomerator.
[0073] Bridging Liquid.
[0074] A bridging liquid is a liquid with affinity for the solids
particles in the bituminous feed, and which is immiscible in the
first solvent. In some embodiments, the agglomerating of solids
comprises adding an aqueous bridging liquid to the fine solids
stream and providing agitation. 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.
[0075] Heating Bituminous Feed With Steam.
[0076] According to an embodiment of the process, steam may be
added to the bituminous feed before combining with the first
solvent, to increase the temperature of the bituminous feed to a
temperature of from about 0.degree. C. to about 60.degree. C. Steam
may be of particular benefit when oil sands are mined in cold
conditions, such as during winter time. The steam may be added to
heat the oil sands or other bituminous feed to a temperature of
from about 0.degree. C. to about 30.degree. C. The temperatures
recited here are simply approximate upper and lower values. Because
these are exemplary ranges, provided here primarily for
illustration purposes, it is emphasized that values outside of
these ranges may also be acceptable. A steam source for
pre-conditioning the initial slurry entering the separator may be
an optional component of the system of the invention. Other methods
of heating the bituminous feed or the solvent (or solvent/bitumen
combination) used to form the initial slurry may be incorporated
into the process.
[0077] During the winter, a bituminous feed may be at a low
temperature below 0.degree. C. due to low temperature of the
ambient outdoor surroundings, and the addition of steam to heat the
feed to a level greater than 0.degree. C. would be an improvement
over a colder temperature. During hot summer conditions, the
temperature of the bituminous feed may exceed 0.degree. C., in
which case, it may not be beneficial to heat the bituminous feed.
Addition of steam may be desirable for processing efficiency
reasons, and it is possible that the upper limit of the ranges
provided may be exceeded.
[0078] The optional step of steam pre-conditioning of the oil sands
before making contact with solvent in the slurry system has the
beneficial effect of raising the temperature of the input
bituminous feed. The amount of steam added is lower or equal to the
amount of water required for agglomeration. Slurrying the input
feed with a low boiling point solvent is promoted without the use
of a pressurized mixing system. Since steam pre-conditioning
permits the use of low boiling point solvents, higher level of
solvent recovery from tailings can be realized with reduced energy
intensity relative to conventional processes.
[0079] During the winter, incoming oil sands may be about
-3.degree. C. At this temperature, the separation process would
require more heat energy to reach the process temperatures between
about 0.degree. C. and 60.degree. C., or more particularly for an
exemplary processing temperature of about 30.degree. C. Optimally,
a solvent boiling point is less than about 100.degree. C. For a low
boiling point solvent, this heating obtained through steam
pre-conditioning is adequate to meet the processing requirement.
For example, by heating the oil sands in a pre-conditioning step, a
temperature can be achieved that is higher than could be achieved
by heating the solvent alone, and adding it to a cold bituminous
feed. In this way, optimal process temperatures can be achieved
without any need to use a pressurized mixing system for solvent
heating. Therefore, the steam not only provides water, but also
some of the heating required to bring the components of the initial
slurry to a desired temperature.
[0080] Once included as steam in a pre-conditioning step, the water
content of the initial slurry would optimally be about 11 wt % or
less, and when expressed as a percent of solids, about 15 wt % is
an upper limit to the optimal level.
[0081] The steam pre-conditioning need not occur, as it is
optional. Some water may be added at the agglomeration step if it
is not added through steam pre-conditioning. In instances where
steam pre-conditioning is used, optimally about half of the water
requirement is added as steam, and further amounts of water can be
added when the fine solids stream is transferred into the
agglomerator.
[0082] In embodiments in which no steam pre-conditioning is
employed, a slurry comprising the bituminous feed together with the
first solvent may be prepared within the slurry system. Optionally,
a solvent vapor could be added to the bituminous feed in the slurry
stage to capture the latent heat at atmospheric pressure without
need to pressurize the mixing vessel.
[0083] Low Oxygen for Initial Slurry.
[0084] The initial slurry of the process described herein may
optionally be formed in a low oxygen environment. A gas blanket may
be used to provide this environment, or steam may be used to
entrain oxygen away from the bituminous feed prior to addition of
solvent. The gas blanket, when used, may be formed from a gas that
is not reactive under process conditions. Exemplary gasses include,
but are not limited to nitrogen, methane, carbon dioxide, argon,
steam, or a combination thereof.
[0085] Separation of Fine Solids Stream and Coarse Solids
Stream.
[0086] The processes described herein may involve separation of a
fine solids stream from a coarse solids stream from the initial
slurry after it is mixed in a slurry system. This aspect of the
process may be said to occur within a fine/coarse solids separator.
An exemplary separator system may include a cyclone, a screen, a
filter or a combination of these. The size of the solids separated,
which may determine whether they are forwarded to the fine solids
stream versus the coarse solids stream can be variable, depending
on the nature of the bituminous feed. Whether a bituminous feed
contains primarily small particles and fines, or is coarser in
nature may be taken into consideration for determining what size of
particles are considered as fine solids and directed toward
agglomeration. Notably, embodiments of the process described herein
do not require separation of coarse and fine solids from the
initial slurry. In such instances, both coarse and fine solids will
be present in the agglomerator. When separation of coarse and fine
solids is desired, a typical minimum size to determine whether a
solid is directed to the coarse solids stream would be about 140
microns. Fines entrainment in the coarse stream is unavoidable
during this separation. The amount of fines entrained in the coarse
solids stream is preferably less than 10 wt %, for example, less
than 5 wt %.
[0087] Fine/Coarse Solids Separator.
[0088] A coarse solids stream derived from the fine/coarse solids
separator may be derived from the system. When the fine/coarse
solids separator is present, the coarse solids stream may be
directed for combination with the agglomerated slurry arising from
the agglomerator prior to entry of the slurry into the solid-liquid
separator.
[0089] The feed stream entering the agglomerator unit is
pre-conditioned to separate out coarse particles before entry into
the agglomerator unit. Thus, the stream entering the agglomerator
is predominantly comprised of finely divided particles or a "fine
solids stream". The slurry fraction containing predominantly coarse
particles or the "coarse solids stream" may by-pass the
agglomerator unit and can then be combined with the agglomerated
slurry before the solid-liquid separation stage in which low solids
bitumen is extracted from the agglomerated slurry.
[0090] A fine solids stream is processed separately from the coarse
solids stream, in part because coarse solids are readily removed
and need not be subjected to the processing within the
agglomerator. The separator permits separation of a fine solids
stream as a top stream that can be removed, while the coarse solids
stream is a bottom stream flowing from the separator.
[0091] The coarse solids fraction derived from the separator may be
combined with the effluent arising from the agglomerator, as the
coarse solids together with the agglomerates will be removed in a
later solid-liquid separation step. This would permit recovery of
bituminous components that were removed in the coarse solids
stream.
[0092] Re-Combining Coarse Solids with Agglomerated Slurry.
[0093] It is optional in the process to utilize the coarse solids
stream derived from the fine/coarse solids separator by
re-combining it with the agglomerated slurry prior to separating
the low solids bitumen extract from the agglomerated slurry.
Alternatively, the coarse solids stream may be processed
separately, or added back into the slurry system for iterative
processing.
[0094] Agglomeration.
[0095] The step of agglomerating solids may comprise adding steam
to the bituminous feed. The addition of steam may be beneficial to
the bituminous feed because it may begin solids nucleation prior to
the step of agglomerating.
[0096] The step of agglomerating solids may comprise adding water
as bridging liquid to the fine solids stream and providing suitable
mixing or agitation. The type and intensity of mixing will dictate
the form of agglomerates resulting from the particle enlargement
process.
[0097] Agitation could be provided in colloid mills, shakers, high
speed blenders, disc and drum agglomerators, or other vessels
capable of producing a turbulent mixing atmosphere. The amount of
bridging liquid is balanced by the intensity of agitation to
produce agglomerates of desired characteristics. As an example of
appropriate conditions for a drum or disc agglomerator, agitation
of the vessel may typically be about 40% of the critical drum
rotational speed while a bridging liquid is kept below about 20 wt
% of the slurry. The agitation of the vessel could range from 10%
to 60% of the critical drum rotational speed, and the bridging
liquid may be kept between about 10 wt % to about 20 wt % of solids
contained in the slurry, in order to produce compact agglomerates
of different sizes.
[0098] Solvents.
[0099] Two solvents, or solvent systems, are sequentially employed
in this process. The terms "first solvent" and "second solvent" as
used herein should be understood to mean either a single solvent,
or a combination of solvents which are used together in a first
solvent extraction and a second solvent extraction,
respectively.
[0100] While the stage of the process at which the solvent is
introduced can be used to determine whether a solvent is the first
or second solvent, as the sequential timing of the addition into
the process results in the designations of first and second.
[0101] It is emphasized that the first and second solvents are not
required to be different from each other. There are embodiments in
which the first solvent and second solvent are the same solvent, or
are combinations which include the same solvents, or combinations
in which certain solvent ingredients are common to both the first
and second solvents.
[0102] 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.
[0103] The solvents 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.
[0104] While the solvent extractions may be initiated
independently, there is no requirement for the first solvent to be
fully removed before the second solvent extraction is
initiated.
[0105] When it is said that the first solvent and the second
solvent may have "similar" boiling points, it is meant that the
boiling points can be the same, but need not be identical. For
example, similar boiling points may be ones within a few degrees of
each other, such as, within 5 degrees of each other would be
considered as similar boiling points. The first solvent and the
second solvent may be the same according to certain embodiments of
the invention, in which case, having "similar" boiling points
permits the solvents used to have the same boiling point.
[0106] First Solvent.
[0107] The first solvent selected according to embodiments of the
invention may comprise an organic solvent or a mixture of organic
solvents. For example, the first 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 first 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 first 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.
[0108] Exemplary cycloalkanes include cyclohexane, cyclopentane, or
a mixture thereof.
[0109] If the first 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.
[0110] 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%.
[0111] Second Solvent.
[0112] The second solvent may be selected to be the same as or
different from the first solvent, and may comprise a low boiling
point alkane or an alcohol. The second solvent may have an
exemplary boiling point of less than 100.degree. C. In some
embodiments, the second solvent can be mixed with feed into the
solid-liquid separation steps. Because the first solvent is not
used in both agglomeration and the solid-liquid separation steps as
described in prior art, a second solvent that is miscible with the
agglomerate bridging liquid (for example, miscible with water) can
be employed at the solid-liquid separation stage. In other words,
the two processing steps can be conducted independently and without
the solid-liquid separation disrupting the agglomeration process.
Thus, selecting the second solvent to be immiscible in the first
solvent, and/or having the ability to be rendered immiscible after
addition, would be optional criteria.
[0113] The second solvent may comprise a single solvent or a
solvent system that includes a mixture of appropriate solvents. The
second solvent may be a low boiling point, volatile, polar solvent,
which may or may not include an alcohol or an aqueous component.
The second solvent can be C.sub.2 to C.sub.10 aliphatic hydrocarbon
solvents, ketones, ionic liquids or biodegradable solvents such as
biodiesel. The boiling point of the second solvent from the
aforementioned class of solvents is preferably less than
100.degree. C.
[0114] Process Temperatures.
[0115] The process may occur at a wide variety of temperatures. In
general, the heat involved at different stages of the process may
vary. One example of temperature variation is that the temperature
at which the low solids bitumen extract is separated from the
agglomerated slurry may be higher than the temperature at which the
first solvent is combined with the bituminous feed. Further, the
temperature at which the low solids bitumen extract is separated
from the agglomerated slurry may be higher than the temperature at
which solids are agglomerated. The temperature increase during the
process may be introduced by recycled solvent streams that are
re-processed at a point further downstream in the process. By
recycling pre-warmed solvent from later stages of the process into
earlier stages of the process, energy required to heat recycle
stream is lower and heat is better conserved within the process.
Alternatively, the temperature of the dilution solvent may be
intentionally raised to increase the temperature at different
stages of the process. An increase in the temperature of the
solvent may result in a reduced viscosity of mixtures of solvent
and bitumen, thereby increasing the speed of various stages of the
process, such as washing and/or filtering steps.
[0116] Solid-Liquid Separator.
[0117] 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.
[0118] 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.
[0119] Secondary Stage of Solid-Liquid Separation to Wash
Agglomerates.
[0120] 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 conduced completely separately
in a secondary solid-liquid separator. By "countercurrently
washing", it is meant that a progressively cleaner solvent is used
to wash bitumen from the agglomerates. Solvent involved in the
final wash of agglomerates may be re-used for one or more upstream
washes of agglomerates, so that the more bitumen entrained on the
agglomerates, the less clean will be the solvent used to wash
agglomerates at that stage. The result being that the cleanest wash
of agglomerates is conducted using the cleanest solvent.
[0121] 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 according to the invention. 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.
[0122] The temperature for countercurrently washing the
agglomerates may be selected to be higher than the temperature at
which the first solvent is combined with the bituminous feed.
Further, the temperature selected for countercurrently washing the
agglomerates may be higher than the temperature at which solids are
agglomerated.
[0123] 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.
[0124] Recycle and Recovery of Solvent.
[0125] The process involves removal and recovery of solvent used in
the process.
In this way, solvent is used and re-used, even when a good deal of
bitumen in 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.
For example, in steps of the process when solvent is recovered from
a low grade or high grade bitumen extract leaving a bitumen
product, it is understood that some solvent may remain within that
product
[0126] The system may contain a single solvent recovery unit for
recovering the first and second solvents arising from the gravity
separator. The system may alternatively contain more than one
solvent recovery unit. For example, another solvent recovery unit
may be incorporated before the step of adding the second solvent to
recover part or all of the first solvent.
[0127] In order to recover either or both the first solvent or the
second solvent, conventional means may be employed. For example,
typical solvent recovery units may comprise a fractionation tower
or a distillation unit. A primary and/or secondary solvent recovery
unit may be desirable for use in the process described herein.
[0128] Solvent recovery and recycle is incorporated into
embodiments of the process. For example, the first solvent derived
from the slurry of agglomerated solids, which may contain bitumen,
can be recycled in the process, such as at the slurrying or
agglomerating step. Further, the second solvent may be recovered by
using a solvent recovery unit and recycled for addition to the low
solids bitumen extract.
[0129] Solvent recovery may be controlled to ensure that the second
solvent is added at the appropriate time. For example, the first
and second solvent may be recovered by distillation or mechanical
separation following the solid-liquid separation step.
Subsequently, the first solvent may be recycled to the
agglomeration step while the second solvent is recycled downstream
of the agglomerating step. In the exemplary embodiment where the
second solvent is immiscible with the first solvent, the process
will occur with no upset to the agglomeration process since
interaction of the second solvent with the bridging liquid only
occurs downstream of the agglomerating step.
[0130] Heat entrained in recycled solvent can advantageously be
utilized when the solvent is added to the process at different
stages to heat that stage of the process, as required. For example,
heated solvent with entrained bitumen derived from washing of the
agglomerates in the secondary solid-liquid separator, may be used
not only to increase the temperature of the initial slurry in the
slurry system, but also to include a bitumen content that may be
desirable to keep the solvent:bitumen ratio at a desired level so
as to avoid precipitation of asphaltenes from solution during
agglomeration. By including heated solvent as well as bitumen, this
addition provides an advantage to the agglomeration process.
[0131] The first solvent recovered in the process may comprise
entrained bitumen therein, and can thus be re-used for combining
with the bituminous feed; or for including with the fine solids
stream during agglomeration. 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 within the initial slurry to
achieve the selected ratio within the agglomerator that avoids
precipitation of asphaltenes.
[0132] Low and High Grade Bitumen Extracts and Products.
[0133] Once solvent is removed from the low grade or high grade
bitumen extracts, the resulting products may be used for commercial
purposes. According to certain embodiments of the invention, the
low grade bitumen extract is derived from gravity separation, and
generally includes water and solids that may have settled into the
underflow in the separation process together with bitumen and
solvent. This underflow is removed and processed separately. This
leaves a high grade extract as the overflow of the separation
process. The high grade bitumen extract is considered to be of a
"high grade" in terms of bitumen products, as it meets and may even
exceed pipeline specifications. It has been essentially de-watered,
and does not contain solids removed by gravity separation, for
example. The high grade bitumen product formed according to
embodiments of the invention may have a low water content that is
nearly undetectable, such as a content of .ltoreq.200 ppm. The high
grade product may have a low solids content of .ltoreq.400 ppm or
lower as a result of embodiments of the process. The low grade
bitumen product may in fact be effectively similar to a "high
grade" product, with very low water and solids content. This may be
the case for embodiments of the invention where low water and low
solids are present in the low grade bitumen extract emanating from
solid-liquid separation. In some embodiments, the asphaltene
content of the low grade bitumen product are high relative to the
high grade bitumen product. For example, asphaltene content up to
98 wt % may be realized in the low grade bitumen product if the
second solvent is paraffinic and the amount mixed with the low
solids extract causes the precipitation of asphaltenes. In other
embodiments, the asphaltene content of both products might in fact
be similar but the low grade bitumen product is richer in polar
components of the bitumen which are soluble in the solvent.
[0134] Extraction Step is Separate from Agglomeration Step.
[0135] Solvent extraction may be conducted separately from
agglomeration in certain embodiments of the process. Unlike prior
art processes, where the solvent is first exposed to the bituminous
feed within the agglomerator, the instant invention includes
formation of an initial slurry in which bitumen dissolution into a
solvent occurs prior to the agglomeration step. This has the effect
of reducing residence time in the agglomerator, when compared to
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, pipelines, mix box or
other types of conditioning systems can be employed.
[0136] Because the extraction occurs upstream of the agglomeration
step, the residence time in the agglomerator is 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 slurry arriving in the
agglomerator.
[0137] Dilution of Agglomerator Discharge to Improve Product
Quality.
[0138] The first solvent or second solvent or mixtures thereof 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(s) 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.
[0139] When dilution of agglomerator discharge is employed in this
embodiment of the invention, the solvent to bitumen ratio of the
agglomerator feed slurry 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 either the first or
second solvent, or a separate dilution solvent, which may, for
example, comprise an alkane.
[0140] FIG. 1 is a schematic representation of an embodiment of the
process (10) described herein. The combining (11) of a first
solvent and a bituminous feed from oil sand to form initial slurry
is followed by separating (12) of a fine solids stream and coarse
solids stream from the initial slurry. Agglomerating (13) of solids
from fine solids stream then occurs to form agglomerated slurry
comprising agglomerates and low solids bitumen extract, optionally
subsequently adding coarse solids stream to agglomerated slurry.
Subsequently, separation (15) of low solids bitumen extract from
agglomerated slurry occurs. Further, mixing (16) of a second
solvent with low solids bitumen extract to extract bitumen takes
place, forming a solvent-bitumen low solids mixture. Separation
(18) of low grade bitumen extract and high grade bitumen extracts
from the mixture occurs. Further, recovery (19) of solvent from the
high grade extract is conducted, leaving a high grade bitumen
product. Further details of these process steps are provided
herein.
[0141] FIG. 2 outlines an embodiment of the process in which the
second solvent is mixed with a low solids bitumen extract derived
from separation of the agglomerated slurry in a clarifier.
[0142] In this embodiment, a bituminous feed (202) is provided and
combined with a first solvent (209a), which may contain entrained
bitumen (203a), in a slurry system (204) to form an initial slurry
(205). The slurry system (204) may be any type of mixing vessel,
such as a mix box, pump or pipeline or combination thereof, having
a feed section with gas blanket that provides a low oxygen
environment. Steam (207) may be added to the slurry system (204) so
as to heat the initial slurry (205) to a level of, for example, 0
to 60.degree. C. The initial slurry (205) is separated in a
fine/coarse solids separator (206) to form a fine solids stream
(208), which is directed into an agglomerator (210), as well as a
coarse solids stream (212) which later, optionally, joins with the
agglomerated slurry (216) arising from the agglomerator (210) for
further processing.
[0143] Bitumen (203b) which may be entrained in the first solvent
(209b), for example, as derived from downstream recycling of the
first solvent, may be added to the agglomerator (210) in order to
achieve an optimal ratio of solvent to bitumen within the
agglomerator (210). Such a ratio would be one that avoids
precipitation of asphaltenes within the agglomerator (210), and an
exemplary ratio may be less than 2:1.
[0144] The fine/coarse solids separator (206) may be a settling
vessel, cyclone or screen, or any suitable separation device known
in the art. An aqueous bridging liquid (214), such as water, may
optionally be added to the agglomerator (210) in the interests of
achieving good adherence of fines into larger particles, and the
process of agglomeration of the solids contained within the fine
solids stream (208) occurs by agitation within the agglomerator
(210). The agglomerated slurry (216) arising from the agglomerator
(210) comprises agglomerates (217a) together with a low solids
bitumen extract (220a), all of which is optionally combined with
the coarse solids stream (212) in the event that the coarse solids
stream is directed to be combined at this stage. The slurry (216)
is then directed to the primary solid-liquid separator (218), which
may be a deep cone settler, or other device, such as thickeners,
incline plate (lamella) settlers, and other clarification devices
known in the art.
[0145] The low solids bitumen extract (220) is separated from the
agglomerated slurry within the primary solid-liquid separator
(218). This extract (220) is subsequently combined in a mixer (221)
with a second solvent (222a). Extract (220) may optionally be sent
to a solvent recovery unit, not shown, where the first solvent is
recovered from the extract, before the mixing with the second
solvent (222a) is undertaken within the mixer (221).
[0146] The second solvent may be one having a low boiling point.
The bitumen-containing mixture derived from the mixer (221) is
separated in a gravity separator (224), which may for example be a
clarifier or any other type of separator employing gravity to
separate solids and water. Streams arising from the gravity
separator (224) are directed either toward forming a high grade
bitumen product (226) once the solvent has been extracted in a
solvent recovery unit (228), or underflow may be removed as a low
grade bitumen extract (230), which may then optionally have solvent
removed to form a low grade bitumen product. The solvent recovery
unit (228) may advantageously be used to recover any of the first
solvent (209c) remaining within the effluent of the gravity
separator (224), in the interests of solvent recovery and re-use.
Advantageously, the second solvent (222b) is easily removed and
recovered due to its volatility and low boiling point. There may be
bitumen entrained in recovered solvents.
[0147] The agglomerates (217b) can also be utilized, as they leave
the primary solid-liquid separator (218) and are subsequently
subjected to a separation in a secondary solid-liquid separator
(232), permitting recovery of the first solvent (209a) and bitumen
(203a) in the process. First solvent (209c) derived from the
solvent recovery unit (228) may also be recycled to the secondary
solid-liquid separator (232), to wash agglomerates, for example in
a belt filter using contercurrent washing with progressively
cleaner solvent. Additional quantities of first solvent (209d) can
be used if additional volumes of solvent are needed. Tailings may
be recovered in a TSRU or tailings solvent recovery unit (234) so
that agglomerated tailings (236) can be separated from recyclable
water (238). Either or both the recovered first solvent (209e)
derived from the TSRU (234) and/or from the solvent recovery unit
(228) may be recycled in the secondary solid-liquid separator
(232).
[0148] A combination containing the first solvent (209a) plus
bitumen (203a) arising from the secondary solid-liquid separator
(232) can be processed with the intent of achieving a bottom
sediment and water (BS&W) content lower than about 0.5 wt %
solid in dry bitumen. In particular, the product would have less
than 400 ppm solids. This combination may also be recycled back
into the process by including it in the agglomerator (210) or
slurry system (204) as a way of recycling solvent, and maintaining
an appropriate solvent:bitumen ratio within the agglomerator to
avoid precipitation of asphaltenes.
[0149] Advantageously, the process permits recovery of both the
first solvent (209) and the second solvent (222). In one
embodiment, the first solvent (209) may be a low boiling point
solvent, such as a low boiling point cycloalkane, or a mixture of
such cycloalkanes, which substantially dissolves asphaltenes. The
first solvent may also be a paraffinic solvent in which the solvent
to bitumen ratio is maintained at a level to avoid precipitation of
asphaltenes.
[0150] For the second solvent, a low boiling point n- or iso-alkane
and alcohols or blends are candidates. Surface modifiers may be
added to the alcohol if needed. With the alkanes, solvent
deasphalting is achieved with concurrent cleaning of the high grade
bitumen product (226) to achieve pipeline quality. Therefore, the
low grade bitumen extract (230) is comprised predominantly of
asphaltenes or other more polar bitumen fractions.
[0151] Another advantage is that the process forms two different
grades of bitumen product from the gravity separator (224).
Specifically, partial product upgrading is conducted to produce a
first product of high grade bitumen product (226). The low grade
bitumen extract (230) formed may also be processed to a low grade
bitumen product after solvent recovery, so as to also possesses
some commercial value.
[0152] This process facilitates recovery of bitumen with no need
for handling more than one solvent in the tailings loop of the TSRU
(234), thereby allowing for simplified solvent recovery/recycling
processes.
[0153] FIG. 3 is a schematic representation of a further embodiment
of the process (30) described herein. The combining (31) of a first
solvent and a bituminous feed from oil sand to form initial slurry
is followed by separating (32) of a fine solids stream and coarse
solids stream from the initial slurry. Agglomerating (33) of solids
from fine solids stream then occurs to form an agglomerated slurry
comprising agglomerates and low solids bitumen extract, optionally
subsequently adding the coarse solids stream into the agglomerated
slurry. Further, mixing (36) of a second solvent with the
agglomerated slurry occurs, to extract bitumen, forming a
solvent-bitumen agglomerated slurry mixture. Removal (37) of
agglomerates from the mixture then occurs. Separation (38) of high
grade and low grade bitumen extracts then occurs. Further, recovery
(39) of the solvents from the bitumen extracts is conducted,
leaving a high grade bitumen product and a low grade bitumen
product. Further details of these process steps are provided
herein.
[0154] FIG. 4 illustrates an embodiment of the process which can be
characterized by the feature that the second solvent is mixed with
the agglomerated slurry upon entry into the primary solid-liquid
separator.
[0155] In this embodiment, a bituminous feed (402) is provided and
is combined with a first solvent (409a), which may have bitumen
(403a) entrained therein, into slurry system (404) to form an
initial slurry (405), optionally in the presence of steam (407) to
heat the initial slurry (405). The initial slurry (405) is mixed
and the first solvent (409a) is given time to contact the
bituminous feed so as to extract bitumen. The slurry (405) is then
directed to a separator (406) to form a fine solids stream (408)
which is directed into an agglomerator (410). Further arising from
the separator (406) is a coarse solids stream (412) for later
processing and solid-liquid separation.
[0156] A bridging liquid (414), such as water, is added to the
agglomerator (410), optionally together with bitumen (403b) which
may be entrained in the first solvent (409b) as derived from
downstream solvent recovery. The process of agglomeration of the
solids from the fine solids stream (408) occurs by agitation of the
agglomerator. The agglomerated slurry (416) arising from the
agglomerator (410) comprises agglomerates (417a) together with a
low solids bitumen extract 420a), all of which may be combined with
the coarse solids stream (412) and directed to a mixer (421) so as
to be combined prior to entry into the primary solid-liquid
separator (418). The agglomerated slurry (416) is mixed with the
second solvent (422a) to form a solvent-bitumen agglomerated slurry
mixture (423) within the mixer, and is then separated within the
primary solid-liquid separator (418), which may be a deep cone
settler or any other sort of separator. Concurrently, the second
solvent (422a) can be added to the primary solid-liquid separator
(418). The second solvent (422a) may also be added to the mixer
(421) before entry into the primary solid-liquid separator (418).
The second solvent (422a) may be one having a low boiling point,
such as a boiling point below 100.degree. C., and is immiscible in
the first solvent, or can be rendered immiscible in the first
solvent.
[0157] The bitumen-containing mixture within the primary
solid-liquid separator (418) is separated and either directed
toward forming high grade bitumen product (426) once the solvent
has passed through the separator (418) to form a high grade bitumen
extract (425) and has been extracted in a primary solvent recovery
unit (428), or can be directed toward forming a low grade bitumen
product (430). Advantageously in this embodiment, the second
solvent (422b, 422c) is easily removed and recovered due to its
volatility, low boiling point, and optionally due to its
immiscibility in the first solvent.
[0158] The agglomerates (417b) can also be processed as they leave
the primary solid-liquid separator (418) and are subsequently
subjected to a separation in a secondary solid-liquid separator
(432), permitting recovery of the second solvent (422d), first
solvent (409c) and any bitumen entrained therein in the process.
Residual solvent in the tailings may be recovered in a TSRU or
tailings solvent recovery unit (434) so that agglomerated tailings
(436) may be separated, and optionally water (438) used in the
process may be recovered and recycled.
[0159] The recovered first solvent (409d) arising from the primary
solvent recovery unit (428) may be recycled for use in the process,
for example when combined with the bituminous feed (402) in the
separator (406). This recovered solvent may contain bitumen
entrained therein. Quantities of a combination comprising recycled
first solvent (409d) plus any entrained bitumen arising from the
primary solid-liquid separator (418) or solvent recovery unit (428)
may be directed to the agglomerator (410) for further processing.
The second solvent (422b) recovered from the primary solvent
recovery unit (428) may be also be recycled.
[0160] Secondary recovery of bitumen occurs within the secondary
solid-liquid separator (432). The separated low grade bitumen
extract (450) may be subjected to separation within a secondary
solvent recovery unit (444), which may be a distillation unit, to
recover and recycle the second solvent (422d) and to arrive at a
low grade bitumen product (430). The low grade bitumen product
(430) possesses some commercial value, as it can be processed
further with the intent of achieving a bottom sediment and water
(BS&W) content lower than about 0.5 wt % solid in dry
bitumen.
[0161] Solvent recovered may be held in a first solvent storage
(429) in the case of the first solvent (409d), or in a second
solvent storage (445), in the case of the second solvent (422b) for
later use in the upstream aspects of the process. High grade
bitumen (431) may be added to the first solvent derived from first
solvent storage (429), if there is a need to alter the solvent to
bitumen ratio prior to adding a combination of solvent (409a) and
bitumen (403a) to the slurry system (404). Further, additional
first solvent (409e) make-up quantities or second solvent (422e)
make-up quantities may be included in respective solvent storage,
if the solvent volume requires replenishing. Additional second
solvent (422f) may also be added to the secondary solid-liquid
separator (432) if needed.
[0162] This embodiment of the process forms different grades of
bitumen product and advantageously permits recovery and/or
recycling of both the first solvent and the second solvent.
[0163] In this embodiment, the first solvent may be a low boiling
point cyclic aliphatic solvent, such as a low boiling point
cycloalkane, or a mixture of such cycloalkanes, which substantially
dissolves asphaltenes. The first solvent may also be a paraffinic
solvent in which the solvent to bitumen ratio is maintained at a
level to avoid precipitation of asphaltenes.
[0164] The second solvent may be a polar solvent, such as an
alcohol, a solvent with an aqueous component, or another solvent
which is immiscible in the first solvent or which could be rendered
immiscible in the first solvent. A low boiling point n- or
iso-alkane and alcohols or blends of these with or without an
aqueous component are candidates. Surface modifiers may be added to
the alcohol if needed. Good agglomerate strength is achieved if the
agglomerates are modified with hydrating agents, such as a cement,
a geopolymer, fly ash, gypsum or lime during agglomeration.
Optionally, the second solvent may comprise a wetting agent in an
aqueous solution. A further option is to employ controlled
precipitation of asphaltenes within either the agglomerator (410)
or the primary solid-liquid separator (418) by employing a mixture
of solvent and bitumen in a ratio that avoids precipitation of
asphaltenes. For example, a ratio of solvent to bitumen of 2:1 or
less may be used within the agglomerator to control asphaltene
precipitation.
[0165] The embodiment depicted in FIG. 4 results in enhanced liquid
drainage during agglomerate washing when the second solvent
comprises predominantly of polar component, such as an alcohol.
Further, enhanced solvent recovery may be achieved, which results
in a more environmentally benign tailings stream.
[0166] The product upgrading of low grade bitumen product (430) can
be undertaken to produce a low grade product with some commercial
value. If the commercial value involves alternate fuel
applications, it would be possible to have a residual alcohol
content remaining in the low grade bitumen product (430) from the
second solvent. Generally, the low grade bitumen product (430) is
comprised predominantly of asphaltenes or other more polar bitumen
fractions.
[0167] FIG. 5 is a schematic representation of an additional
embodiment of the process (50) described herein. The combining (51)
of a first solvent and a bituminous feed from oil sand to form
initial slurry is followed by separating (52) of a fine solids
stream and coarse solids stream from the initial slurry. Recovery
(54) of the first solvent from the coarse solids stream is then
conducted. Agglomerating (53) of solids from the fine solids stream
then occurs to form agglomerated slurry comprising agglomerates and
low solids bitumen extract. In this embodiment, the coarse solids
stream is not optionally added to the agglomerated slurry, as the
coarse solids stream is processed separately. Subsequently,
separation (55) of low solids bitumen extract from agglomerated
slurry occurs. Further, mixing (56) of a second solvent with low
solids bitumen extract to extract bitumen takes place, forming a
solvent-bitumen low solids mixture. Separation (58) by gravity of
low grade and high grade bitumen extracts from the mixture then
occurs. Further, recovery (59) of the solvents is conducted,
leaving a high grade bitumen product. Further details of these
process steps are provided herein.
[0168] FIG. 6 illustrates an embodiment of the invention similar to
that depicted in FIG. 2, except that coarse solids stream separated
out of the bituminous feed is processed separately, and not
re-combined with an agglomerated slurry.
[0169] A bituminous feed (602) is provided and combined with a
first solvent (609a), optionally with bitumen (603a) entrained
therein, in a slurry system (604) to form an initial slurry (605).
Steam (607) may be added to the slurry system (604) to heat the
initial slurry (605). The initial slurry (605) is then directed
from the slurry system (604) to a separator (606) for separation,
which may be a fine/coarse solids separator, in order to form a
fine solids stream (608), which is directed into an agglomerator
(610), as well as a coarse solids stream (612), which is processed
separately from the agglomerated slurry (616) arising from the
agglomerator (610). Additional quantities of first solvent (609b)
having bitumen (603b) entrained therein, may be added to the
agglomerator (610). A bridging liquid (614), such as water, may be
added to the agglomerator (610), and the process of agglomeration
of the solids contained within the fine solids stream (608) occurs
by agitation within the agglomerator (610). The agglomerated slurry
(616) arising from the agglomerator comprises agglomerates (617a)
together with a low solids bitumen extract (620a). In this example,
there is no combination with the coarse solids stream. Instead, the
agglomerated slurry (616) itself is directed to the primary
solid-liquid separator (618).
[0170] The low solids bitumen extract (620) is separated from the
agglomerated slurry (616) within the primary solid-liquid separator
(618). This extract (620) is subsequently combined in a mixer (621)
with a second solvent (622a). Extract (620) may optionally be sent
to a solvent recovery unit, not shown, where all of the first
solvent contained therein is recovered from the extract, before
mixing with the second solvent within the mixer (621).
[0171] The second solvent may be one having a low boiling point.
The solvent-bitumen low solids mixture (623) derived from the mixer
(621) is separated in a gravity separator (624), and streams
arising from the gravity separator (624) are directed either toward
forming a high grade bitumen product (626) once the solvent has
been extracted in a solvent recovery unit (628), or toward forming
a low grade bitumen extract (630). The solvent recovery unit (628)
may advantageously be used to recover the majority of the first
solvent (609c) remaining within the effluent, or overflow, of the
gravity separator (624), in the interests of solvent recovery and
re-use. Streams derived from the gravity separator (624) include
high grade bitumen extract (625), and low grade bitumen extract
(630) as underflow. Advantageously, the second solvent (622b) is
easily removed and recovered due to its volatility and low boiling
point.
[0172] The separated agglomerates (617b) can also be utilized, as
they leave the primary solid-liquid separator (618) and are
subsequently subjected to a separation in a secondary solid-liquid
separator (632), permitting recovery of the first solvent (609c)
and bitumen (603c) entrained therein in the process. Solvent (609d)
derived from the solvent recovery unit (628) may also be recycled
to the secondary solid-liquid separation separator (632).
Additional quantities of the first solvent (609e) may be added to
the secondary solid-liquid separator, if desired, for example for
washing purposes. Tailings may be recovered in a TSRU or tailings
separation recovery unit (634) so that agglomerated tailings (636)
can be separated from recyclable water (638). Either or both the
recovered first solvent (609g or 609d)) derived from the TSRU (634)
and/or from the solvent recovery unit (628) may be recycled in the
secondary solid-liquid separator (632).
[0173] A combination containing the first solvent (609c) plus
bitumen (603c) arising from the secondary solid-liquid separator
(632) can be processed with the intent of achieving a bottom
sediment and water (BS&W) content lower than about 0.5 wt %
solid in dry bitumen. In particular, the product may have less than
400 ppm solids. This combination containing the first solvent plus
bitumen may also be recycled back into the process by including it
in the agglomerator (610) or slurry system (604).
[0174] Advantageously, the process permits recovery of both the
first solvent and the second solvent. In one embodiment, the first
solvent may be a low boiling point solvent, such as a low boiling
point cycloalkane, or a mixture of such cycloalkanes, which
substantially dissolves asphaltenes. The first solvent may also be
a paraffinic solvent in which the solvent to bitumen ratio is
maintained at a level to avoid precipitation of asphaltenes.
[0175] For the second solvent, a low boiling point n- or iso-alkane
and alcohols or blends are candidates. Surface modifiers may be
added to the alcohol if needed. With the alkanes, solvent
deasphalting is achieved with concurrent cleaning of the high grade
bitumen product (626) to achieve pipeline quality. Therefore, the
low grade bitumen extract (630) is comprised predominantly of
asphaltenes or other more polar bitumen fractions.
[0176] In this embodiment, the coarse solid stream (612) derived
from the separator (606) is kept segregated from the agglomerated
slurry (616). Thus, the separator (606) can be reduced in size
compared to the approach described with respect to FIG. 2, as only
quick settling solids are removed. These coarse solids may form the
majority of the particulate, especially for high grade oil sands,
and will exhibit high drainage rates in the secondary solid-liquid
separator for coarse solids (652). The non-agglomerated nature of
the coarse solids allows for efficient solvent recovery of both
first solvent (609f) and bitumen (603f) entrained therein.
[0177] The agglomerated slurry (616) may thus enter a reduced size
primary solid-liquid separator (618) and can be processed as
described above in the secondary liquid-solid separator (632) and
TSRU (634). Agglomerated tailings (636) can be removed using the
TSRU (634). The rate determining step in solvent recovery from
tailings is the time required for release of residual solvent from
the pores of the agglomerated solids. With segregation, the solvent
recovery from the fine particles can be optimized independent of
the coarse particles. The combination of first solvent (609f) and
bitumen (609f) recovered permits separation of coarse tailings
(656), once drained from the secondary solid liquid separator for
coarse solids (652). Coarse tailings (656) isolated from the
tailings solvent recovery unit for coarse solids (654) can be sent
to the primary solid-liquid separator (618) for residual fine
solids removal, or may be recycled upstream of the process to form
the initial slurry (605) in slurry system (604). The tailings
solvent recovery unit for coarse solids (654) may be used to
recover recyclable water (638) or solvent from the secondary
solid-liquid separator for coarse solids (652). Coarse tailings
(656) may also be removed.
[0178] FIG. 7 is a schematic representation of a system (70)
according to an embodiment of the invention. The system comprises a
slurry system (71) in which a bituminous feed is mixed with a first
solvent to form an initial slurry. A separator (73) is present, in
which a fine solids stream and a coarse solids stream are separated
from the initial slurry. An agglomerator (75) is present in the
system, for receiving fine solids stream from separator, and in
which agglomerated slurry is formed. A primary solid-liquid
separator (77) is included in the system (70) for receiving the
agglomerated slurry, and separating it into agglomerates and a low
solids bitumen extract. A gravity separator (78) is included for
receiving the low solids bitumen extract and a second solvent.
Further, a primary solvent recovery unit (79) is also included in
the system (70) for recovering first and/or second solvent arising
from primary solid-liquid separator, leaving bitumen product.
[0179] In the preceding description, for purposes of explanation,
numerous details are set forth in order to provide a thorough
understanding of the embodiments of the invention. However, it will
be apparent to one skilled in the art that these specific details
are not required in order to practice the invention.
Example 1
[0180] Approximately 500 g of low grade oil sands (comprising 22 wt
% fines) was mixed with 300 g cyclohexane as a first solvent
(loaded with bitumen up to 40 wt %) using an impeller in a mixing
vessel at 30.degree. C. Sand grains greater than 1 mm were removed
by screening. The remaining slurry was passed into an agglomerator
where 30 ml of water was added. Agglomerates of sizes ranging from
0.1 mm to 1 cm were formed. The agglomerated slurry was allowed to
settle for 30 minutes and a first supernatant was collected for
water and solids content analysis. Solids content determined by
ashing ranged between 5,000-20,000 ppm on a dry bitumen basis for
this first supernatant while water content by Karl Fischer analysis
was generally less than 1000 ppm. Portions of the first supernatant
were mixed with normal pentane as a second solvent above the
critical solvent to bitumen ratio to effect precipitation of
asphaltene at 30.degree. C. After settling for 30 minutes, a second
supernatant was collected and analyzed for solids and water
content. The sediment from the settling test comprised
predominantly of asphaltenes and less than 20 wt % solids and was
treated as the lower grade bitumen extract. Solids and water
contents of the second supernatant were determined to be less than
400 ppm and 200 ppm on a dry bitumen basis, respectively. The
second supernatant was a dry, clean and partially de-asphalted
bitumen product suitable for transportation via a common carrier
pipeline and processing in a remote refinery.
Example 2
[0181] In another experiment similar to the one described in
Example 1, a mixture of 30% cyclohexane and 70% heptane, by volume,
was used in agglomeration as the first solvent. For the first
supernatant, solids content determined by ashing range between
5,000-10,000 ppm on a dry bitumen basis while water content by Karl
Fischer analysis was generally less than 1,000 ppm. Portions of the
first supernatant were mixed with normal pentane as a second
solvent above the critical solvent to bitumen ratio to effect
precipitation of asphaltene at room temperature. The solids and
water content of the resulting second supernatant was determined to
be less than 400 ppm and 200 ppm on a dry bitumen basis after 30
minutes of settling.
Example 3
[0182] In another experiment similar to the one described in
Example 1, normal heptane loaded with 40% bitumen was used as
extraction solvent (the first solvent). Solids content of the first
supernatant was determined to be less than 400 ppm on a dry bitumen
basis after 30 minutes of settling. Water content was less than 200
ppm. The resulting product, having less than 400 ppm of filterable
solids was a high grade bitumen product.
[0183] The above-described embodiments of the invention 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 of the
invention, which is defined solely by the claims appended
hereto.
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