U.S. patent application number 13/774560 was filed with the patent office on 2013-08-29 for method for extracting bitumen from an oil sand stream.
This patent application is currently assigned to SHELL CANADA ENERGY. The applicant listed for this patent is CHEVRON CANADA LIMITED, MARATHON OIL CANADA CORPORATION, SHELL CANADA ENERGY. Invention is credited to Julian Robert KIFT, Ingmar Hubertus Josephina PLOEMEN, John Patrick RINGSTROM.
Application Number | 20130220890 13/774560 |
Document ID | / |
Family ID | 49000723 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130220890 |
Kind Code |
A1 |
PLOEMEN; Ingmar Hubertus Josephina
; et al. |
August 29, 2013 |
METHOD FOR EXTRACTING BITUMEN FROM AN OIL SAND STREAM
Abstract
The present invention provides a method for extracting bitumen
from an oil sand stream that includes the steps of: providing an
oil sand stream; contacting the oil sand stream with a liquid
comprising a solvent thereby obtaining a solvent-diluted oil sand
slurry; separating the solvent-diluted oil sand slurry, thereby
obtaining a solids-depleted stream and a solids-enriched stream;
increasing the S/B weight ratio of the solids-enriched stream
thereby obtaining a solids-enriched stream having an increased S/B
weight ratio and a liquid stream; filtering the solids-enriched
stream having an increased S/B weight ratio, thereby obtaining
bitumen-depleted sand. In another embodiment, the invention is a
system for practicing this method.
Inventors: |
PLOEMEN; Ingmar Hubertus
Josephina; (Amsterdam, NL) ; RINGSTROM; John
Patrick; (Calgary, CA) ; KIFT; Julian Robert;
(Reno, NV) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHELL CANADA ENERGY;
CHEVRON CANADA LIMITED;
MARATHON OIL CANADA CORPORATION; |
|
|
US
US
US |
|
|
Assignee: |
SHELL CANADA ENERGY
Calgary
CA
MARATHON OIL CANADA CORPORATION
Calgary
CA
CHEVRON CANADA LIMITED
Calgary
CA
|
Family ID: |
49000723 |
Appl. No.: |
13/774560 |
Filed: |
February 22, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61603018 |
Feb 24, 2012 |
|
|
|
Current U.S.
Class: |
208/390 ;
196/14.52 |
Current CPC
Class: |
C10G 1/04 20130101; C10G
1/045 20130101 |
Class at
Publication: |
208/390 ;
196/14.52 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Claims
1. A method for extracting bitumen from an oil sand stream, the
method comprising at least the steps of: providing an oil sand
stream; contacting the oil sand stream with a liquid comprising a
solvent thereby obtaining a solvent-diluted oil sand slurry;
separating the solvent-diluted oil sand slurry, thereby obtaining a
solids-depleted stream and a solids-enriched stream; increasing the
solvent-to-bitumen (S/B) weight ratio of the solids-enriched stream
thereby obtaining a solids-enriched stream having an increased S/B
weight ratio and a liquid stream; and filtering the solids-enriched
stream having an increased S/B weight ratio, thereby obtaining
bitumen-depleted sand.
2. The method of claim 1, wherein the solvent comprises an
aliphatic hydrocarbon, preferably having from 3 to 9 carbon atoms
per molecule.
3. The method of claim 2, wherein the solvent comprises from 4 to 7
carbons per molecule, or a combination thereof.
4. The method of claim 1 wherein the solvent-diluted oil sand
slurry has a solvent-to-bitumen (S/B) weight ratio of from 0.5 to
4.0.
5. The method of claim 4 wherein the solvent-diluted oil sand
slurry has a solvent-to-bitumen (S/B) weight ration of from 0.7 to
3.0
6. The method of claim 5 wherein the solvent-diluted oil sand
slurry has a solvent-to-bitumen (S/B) weight ration of from 0.9 to
2.5.
7. The method of claim 1 wherein the solvent-diluted oil sand
slurry comprises from 10 to 60 vol. % of solids.
8. The method of claim 7 wherein the solvent-diluted oil sand
slurry comprises from 20 to 40 vol. % of solids.
9. The method of claim 8 wherein the solvent-diluted oil sand
slurry comprises from 25 to 35 vol. % of solids.
10. The method of claim 1 wherein the solvent is removed from the
solids-depleted stream thereby obtaining a bitumen-enriched
stream.
11. The method of claim 1 wherein the solids-enriched stream
comprises from 30 to 65 vol. % of solids.
12. The method of claim 11 wherein the solids-enriched stream
comprises from 40 to 55 vol. % of solids.
13. The method of claim 12 wherein the solids-enriched stream
comprises from 45 to 55 vol. % of solids.
14. The method of claim 1 wherein at least part of the liquid
stream is used in the step of contacting the oil sand stream with a
liquid comprising a solvent.
15. The method claim 1 wherein the solids-enriched stream having an
increased S/B weight ratio has an S/B weight ratio of from 1.5 to
8.0.
16. The method claim 15 wherein the solids-enriched stream having
an increased S/B weight ratio has an S/B weight ratio of from 2.0
to 7.0.
17. The method claim 16 wherein the solids-enriched stream having
an increased S/B weight ratio has an S/B weight ratio of from 2.2
to 6.0.
18. The method of claim 1 wherein in the step of filtering the
solids-enriched stream, a ("first") bitumen-enriched filtrate is
obtained, which is at least partly reused in the step of contacting
the oil sand stream with a liquid comprising a solvent.
19. The method of claim 18 wherein the bitumen-enriched filtrate
has an S/B weight ratio of from 1.2 to 8.0.
20. The method of claim 19 wherein the bitumen-enriched filtrate
has an S/B weight ratio of from 2.0 to 7.0.
21. The method of claim 20 wherein the bitumen-enriched filtrate
has an S/B weight ratio of from 2.2 to 6.0.
22. The method of claim 1 wherein in the step of filtering the
solids-enriched stream having an increased S/B weight ratio, a
("second") bitumen-depleted filtrate is obtained, and the
("second") bitumen-depleted filtrate is at least partly reused in
the step of increasing the solvent-to-bitumen (S/B) weight ratio of
the solids-enriched stream.
23. The method of claim 22, wherein the bitumen-depleted filtrate
has an S/B weight ratio of above 3.0.
24. The method of claim 23, wherein the bitumen-depleted filtrate
has an S/B weight ratio of above 5.0.
25. A system for performing a method for extracting bitumen from an
oil sand stream, the system comprising: a mixer for contacting an
oil sand stream with a liquid, the liquid comprising a solvent, the
mixer having an inlet for the oil sand stream and an outlet for a
solvent-diluted oil sand slurry; a solid/liquid separator for
separating the solvent-diluted oil sand slurry, the separator
having a first outlet for a solids-depleted stream and a second
outlet for a solids-enriched stream; a washer for increasing the
S/B weight ratio of the solids-enriched stream, the washer having a
first outlet for a solids-enriched stream having an increased S/B
weight ratio and a second outlet for a liquid stream; and a filter
for filtering the solids-enriched stream having an increased S/B
weight ratio, the filter having an outlet for a bitumen-depleted
sand.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/603,018 filed Feb. 24, 2012, which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for extracting
bitumen from an oil sand.
[0003] BACKGROUND TO THE INVENTION
[0004] Various methods have been proposed in the past for the
recovery of bitumen (sometimes referred to as "tar" or "bituminous
material") from oil sands as found in various locations throughout
the world and in particular in Canada such as in the Athabasca
district in Alberta and in the United States such as in the Utah
oil sands. Typically, oil sand (also known as "bituminous sand" or
"tar sand") comprises a mixture of bitumen (in this context also
known as "crude bitumen", a semi-solid form of crude oil; also
known as "extremely heavy crude oil"), sand, clay minerals and
water. Usually, oil sand contains about 5 to 25 wt. % bitumen (as
meant according to the present invention), about 1 to 13 wt. %
water, the remainder being sand and clay minerals.
[0005] As an example, it has been proposed and practiced at
commercial scale to recover the bitumen content from the oil sand
by mixing the oil sand with water and separating the sand from the
aqueous phase of the slurry formed. Disadvantages of such aqueous
extraction processes are the need for extremely large quantities of
process water (typically drawn from natural sources) and issues
with removing the bitumen from the aqueous phase (whilst emulsions
are being formed) and removing water from the bitumen-depleted
sand.
[0006] Other methods have proposed non-aqueous extraction processes
to reduce the need for large quantities of process water. Example
of such a non-aqueous extraction process are disclosed in e.g. U.S.
Pat. No. 3,475,318 and US 2009/0301937, the teaching of which is
hereby incorporated by reference.
BRIEF SUMMARY OF THE INVENTION
[0007] In one embodiment, the present invention provides a method
for extracting bitumen from an oil sand stream, the method
comprising at least the steps of: [0008] (a) providing an oil sand
stream; [0009] (b) contacting the oil sand stream with a liquid
comprising a solvent thereby obtaining a solvent-diluted oil sand
slurry; [0010] (c) separating the solvent-diluted oil sand slurry,
thereby obtaining a solids-depleted stream and a solids-enriched
stream; [0011] (d) increasing the solvent-to-bitumen weight ratio
of the solids-enriched stream thereby obtaining a solids-enriched
stream having an increased S/B weight ratio and a liquid stream;
[0012] (e) filtering the solids-enriched stream having an increased
S/B weight ratio, thereby obtaining bitumen-depleted sand.
[0013] It has now surprisingly been found according to the present
invention that it results in significantly reduced filtration times
when compared with a process that does not apply an intermediate
step of increasing the solvent-to-bitumen weight ratio of the
solids-enriched stream (viz. step (d)).
[0014] According to the present invention, the providing of the oil
sand in step (a) can be done in various ways. Typically, before
contacting the dry oil sand (which may contain some water being
present in the oil sand) with the solvent the oil sand particles
are reduced in size, e.g. by crushing, breaking and/or grinding, to
below a desired size upper limit. Experience in large scale
operations shows that the achievable size upper limit for such size
reduction is currently about 8 inch.
[0015] The contacting in step (b) of the oil sand with the liquid
comprising a solvent thereby obtaining a solvent-diluted oil sand
slurry is not limited in any way. As an example, the liquid may be
added before, during or after the size-reducing step (if available)
of the oil sand. Further size reduction in the presence of the
liquid (comprising the solvent) may be performed; part of the size
reduction may take place by dissolution of bitumen present in the
oil sand, but further size reduction e.g. by using screens and/or
again crushers, breaker or grinders may be performed, if desired.
Typically, the solvent forms the major part of the liquid and is
preferably present in an amount of from 50 wt. % up to 100 wt. %,
preferably above 60 wt. %, more preferably above 70 wt. %, even
more preferably above 80 or even above 90 wt. %, based on the
amount of the liquid.
[0016] The solvent as used in the method of the present invention
may be selected from a wide variety of solvents, including aromatic
hydrocarbon solvents and saturated or unsaturated aliphatic (i.e.
non-aromatic) hydrocarbon solvents; aliphatic hydrocarbon solvents
may include linear, branched or cyclic alkanes and alkenes and
mixtures thereof. Preferably, the solvent in step (b) comprises an
aliphatic hydrocarbon having from 3 to 9 carbon atoms per molecule,
more preferably from 4 to 7 carbons per molecule, or a combination
thereof. Especially suitable solvents are saturated aliphatic
hydrocarbons such as propane, butane, pentane, hexane, heptane,
octane and nonane (including isomers thereof), in particular
butane, pentane, hexane and heptane. It is preferred that the
solvent in step (b) comprises at least 90 wt. % of the aliphatic
hydrocarbon having from 3 to 9 carbon atoms per molecule,
preferably at least 95 wt. %. Also, it is preferred that in step
(b) substantially no aromatic solvent (such as toluene or benzene)
is present, i.e. less than 5 wt. %, preferably less than 1 wt. %.
Herewith, the asphaltene content of the bitumen in the
bitumen-depleted sand remains relatively high when compared with
the asphaltene content of the bitumen in the original oil sand
stream.
[0017] Preferably, the particles of the solvent-diluted oil sand
slurry obtained in step (b) are screened or reduced in size to have
a diameter below 5.0 cm, preferably below 3.0 cm, more preferably
below 2.0 cm. As the screening or size reduction is performed in
the presence of solvent (rather than size reduction under dry
conditions), this helps breaking down the larger particles and
dissolving the bitumen thereby avoiding the formation of sticky
lumps. Additionally, by mixing the oil sand stream with the solvent
before the filtration (in step (e)), an increased filtration rate
is obtained.
[0018] Preferably, the solvent-diluted oil sand slurry obtained in
step (b) has a solvent-to-bitumen (S/B) weight ratio of from 0.5 to
4.0, preferably from 0.7 to 3.0, more preferably from 0.9 to 2.5.
In some embodiments, the slurry obtained in step (b) may have an
S/B weight ratio above 1.0, or even above 1.2.
[0019] Further it is preferred that the solvent-diluted oil sand
slurry obtained in step (b) comprises from 10 to 60 vol. % of
solids, preferably from 20 to 40 vol. %, more preferably from 25 to
35 vol. %.
[0020] After contacting the oil sand with the solvent in step (b),
the solvent-diluted oil sand slurry is separated in step (c),
thereby obtaining a solids-depleted stream and a solids-enriched
stream. Typically, the solvent is removed from the solids-depleted
stream obtained in step (c) thereby obtaining a bitumen-enriched
stream. This bitumen-enriched stream may be sent to a refinery or
the like for further upgrading. Preferably, the solids-enriched
stream obtained in step (c) comprises from 30 to 65 vol. % of
solids, preferably from 40 to 55 vol. %, more preferably from 45 to
55 vol. %. Typically, the solids-enriched stream obtained in step
(c) has about the same S/B weight ratio as the solvent-diluted oil
sand slurry obtained in step (b), hence from 0.5 to 4.0, preferably
from 0.7 to 3.0, more preferably from 0.9 to 2.5.
[0021] In step (d), the S/B weight ratio of the solids-enriched
stream is increased thereby obtaining a solids-enriched stream
having an increased S/B weight ratio and a liquid stream; hence,
the solids-enriched stream having an increased S/B weight ratio
obtained in step (d) has an S/B weight ratio that is higher than
the S/B ratio of the solids-enriched stream obtained in step (c).
Typically, the liquid stream obtained in step (d) will also have an
S/B weight ratio that is higher than the S/B ratio of the
solids-enriched stream obtained in step (c).
[0022] The person skilled in the art will readily understand that
step (d) can be achieved in various ways. As an example, the
solids-enriched stream obtained in step (c) may be contacted with a
stream having a higher S/B weight ratio (such a stream may include
pure solvent). Such contacting may for instance take place in
counter-current decanters, counter-current hydrocyclones or
counter-current wash columns.
[0023] According to an especially preferred embodiment of the
present invention, at least part of the liquid stream obtained in
step (d) is used in the contacting of step (b), as solvent.
[0024] Preferably, the solids-enriched stream having an increased
S/B weight ratio obtained in step (d) has an S/B weight ratio of
from 1.5 to 8.0, preferably from 2.0 to 7.0, more preferably from
2.2 to 6.0. Typically, the solids-enriched stream having an
increased S/B weight ratio obtained in step (d) has about the same
amount of solids as the solids-enriched stream obtained in step
(c), i.e. from 30 to 65 vol. % of solids, preferably from 40 to 55
vol. %, more preferably from 45 to 55 vol. %.
[0025] In step (e), the solids-enriched stream having an increased
S/B weight ratio is filtered thereby obtaining bitumen-depleted
sand. Usually, the bitumen-depleted sand is dried, thereby
obtaining a dried bitumen-depleted sand stream containing less than
500 ppmw, preferably less than 300 ppmw, of the solvent.
[0026] Typically, in step (e) one (e.g. the below-mentioned first
or second filtrate) or more filtrate streams (optionally including
one or both of the below-mentioned first and second filtrates) are
obtained as well, which may be recycled to other parts of the
process.
[0027] Preferably, in step (e) a ("first") bitumen-enriched
filtrate is obtained, which is at least partly reused in the
contacting of step (b). Typically, this bitumen-enriched filtrate
has an S/B weight ratio of from 1.2 to 8.0, preferably from 2.0 to
7.0, more preferably from 2.2 to 6.0.
[0028] Further it is preferred that in step (e) a ("second")
bitumen-depleted filtrate is obtained, which is at least partly
reused in the washing of step (d). Preferably, this
bitumen-depleted filtrate has an S/B weight ratio of above 3.0,
preferably above 5.0 and typically below 200.
[0029] The person skilled in the art will readily understand that
the filtering in step (e) can be performed in many different ways.
Although some fresh solvent may be used at the start-up of the
process of the present invention, the addition of fresh solvent
later on is preferably kept to a minimum; most of the solvent used
in the filtration step is recycled from downstream of the process.
Also, the splitting of the one or more filtrates in the first
and/or second (and optionally further) filtrates can be performed
in various ways. Typically, the first filtrate obtained in step (e)
leaves the filter cake earlier than the second filtrate obtained in
step (e).
[0030] In another aspect the present invention provides a system
for performing the method according to the present invention, the
system at least comprising:
[0031] a mixer for contacting the oil sand stream with a liquid
comprising a solvent, the mixer having an inlet for the oil sand
stream and an outlet for a solvent-diluted oil sand slurry;
[0032] a solid/liquid separator for separating the solvent-diluted
oil sand slurry, the separator having a first outlet for a
solids-depleted stream and a second outlet for a solids-enriched
stream;
[0033] a washer for increasing the S/B weight ratio of the
solids-enriched stream, the washer having a first outlet for a
solids-enriched stream having an increased S/B weight ratio and a
second outlet for a liquid stream; and
[0034] a filter for filtering the solids-enriched stream having an
increased S/B weight ratio, the filter having an outlet for a
bitumen-depleted sand.
BRIEF DESCRIPTION OF FIGURES
[0035] FIG. 1 schematically shows a process scheme of a first
embodiment of the method in accordance with the present
invention;
[0036] FIG. 2 schematically shows a process scheme of a second
embodiment of the method in accordance with the present invention;
and
[0037] FIG. 3 schematically shows a process scheme of a third
embodiment of the method in accordance with the present
invention.
[0038] For the purpose of this description, a single reference
number will be assigned to a line as well as a stream carried in
that line. Same reference numbers refer to the same or similar
elements.
DETAILED DESCRIPTION OF THE INVENTION
[0039] FIG. 1 schematically shows a simplified process scheme of a
first embodiment according to the present invention for extracting
bitumen (i.e. in the context of the invention a bituminous and/or
extremely heavy crude oil like material) from an oil sand stream.
The process scheme is generally referred to with reference number
1. The process scheme 1 shows a crusher 2, a de-oxygenation unit 3,
a mixer 4, a solid/liquid separator (such as a settler) 5, a washer
6, a filter 7, a dryer 8, a clarifier 9, a SRC (solvent recovery
column) 11, and a fresh solvent source 12.
[0040] During use of the process scheme of FIG. 1, an oil sand
stream 10 is provided and fed to the mixer 4. Typically, before
entering the mixer 4, the oil sand stream 10 has been crushed (e.g.
in crusher 2) or treated otherwise, to reduce the size of the
larger oil sand lumps to below a pre-determined upper limit.
Experience in large scale operations shows that the achievable size
upper limit for such size reduction is currently about 8 inch.
Further, the oil sand stream is usually de-oxygenated (e.g. in
de-oxygenation unit 3), in particular when a non-aqueous solvent is
subsequently used for the bitumen extraction.
[0041] In the embodiment of FIG. 1, the oil sand stream 10 is
contacted in the mixer 4 with solvent stream 60 (preferably
containing an aliphatic hydrocarbon solvent and a certain amount of
bitumen) recycled from downstream of the process (and with stream
80 which is further discussed below) thereby obtaining a
solvent-diluted oil sand slurry 20. Usually, in the mixer 4 (or in
a separate unit, if needed), the particles of the solvent-diluted
oil sand slurry obtained are reduced in size, typically to have a
diameter below 5.0 cm. Any undesired materials (such as rocks and
woody material) that may hinder downstream processing may be
removed by using screens or the like (preferably in the presence of
solvent) and the remaining oil sand particles are reduced in size
in the presence of the solvent, e.g. by crushing, breaking and/or
grinding. Typically the contacting step in mixer 4 is executed at
about ambient temperatures, preferably at a temperature in the
range from 0-40.degree. C., preferably 5-25.degree. C., and at
about atmospheric pressure.
[0042] The slurry stream 20 exiting the mixer 4 is fed (using a
pump) into the settler 5 and allowed to settle, thereby obtaining
(as an overflow) a solids-depleted stream 30 and (as an underflow)
a solids-enriched stream 40. The solids-depleted stream 30 may be
further processed in clarifier 9 to remove fines; the overflow of
the clarifier 9 may be sent as stream 100 to a SRC 11, whilst the
underflow 110 of the clarifier 9 may be combined with the
solids-enriched stream 50 having an increased S/B weight ratio
(discussed below) and/or with the solids-enriched stream 40 (not
shown). In the SRC 11, solvent is removed from the overflow 100 of
the clarifier 9 thereby obtaining a bitumen-enriched stream 120;
the solvent recovered in the SRC 11 may be recycled in the process,
e.g. as wash solvent stream 130 to the filter 7.
[0043] The solids-enriched stream 40 exiting the settler 5 is fed
into the washer 6 and contacted with a solvent containing stream.
The washer 6 may be any device for increasing the S/B weight ratio
of the solids-enriched stream 40 and usually is a counter-current
decanter, a counter-current hydrocyclone or a cyclowash
hydrocyclone. A suitable washer is for example Krebs CycloWash
obtainable from FLSmidth A/S (Valby, Denmark).
[0044] In the embodiment of FIG. 1, a filtrate stream 90 obtained
in the filter 7 is used for increasing the S/B weight ratio in the
washer 6; it goes without saying that other streams may be used as
well, instead or in addition (including pure solvent), to increase
the S/B weight ratio of the solids-enriched stream 40. Used liquid
is removed from the washer 6 as (an overflow) stream 60 and reused
as solvent in the mixer 4. Further a solids-enriched stream 50
having an increased S/B weight ratio is removed from the washer 6
(optionally combined with stream 110 from the clarifier 9) and fed
to the filter 7 for filtration.
[0045] In the filter 7, the solids-enriched stream 50 having an
increased S/B weight ratio is filtered, thereby obtaining a
bitumen-depleted sand stream 70; typically this bitumen-depleted
sand stream 70 is the "filter cake" as used in the filter 7. This
bitumen-depleted sand stream 70 may be sent to a dryer 8 and
removed as dried stream 140; this dried stream 140 would in the art
be referred to as "tailings". The dried stream 140 can be used for
land reclamation. Of course, if needed, further removal of solvent
from the dried stream 140 may be performed. A recovered solvent
stream 150 may be recycled from the dryer 8 to e.g. the filter
7.
[0046] In the embodiment of FIG. 1, a first bitumen-enriched
filtrate (removed as stream 80) and a second bitumen-depleted
filtrate (removed as stream 90) are obtained as well in the filter
7. It goes without saying that further filtrate streams may be
generated in the filter 7. The first bitumen-enriched filtrate 80
is recycled to the mixer 4 and the second bitumen-depleted filtrate
90 is sent to the washer 6; in FIG. 1 an optional additional
solvent stream 170 is shown, which may combined with stream 90 (or
directly fed into washer 6). The solvent stream 170 may originate
from e.g. recycled solvent stream 150 or from fresh solvent stream
160 (both discussed below).
[0047] As shown in the embodiment of FIG. 1, a stream 160 of fresh
solvent may be fed from the fresh solvent unit 12 to the filter 7,
instead of or in addition of recycled solvent streams 130 (from the
SRC 11) and 150 (from the dryer 8); of course other sources of
solvent recycle streams may be used as well.
[0048] FIGS. 2 and 3 schematically show a simplified process scheme
of a second and third embodiment according to the present invention
for extracting bitumen from oil sand.
[0049] In FIG. 2, recycling of a filtrate stream (90 in FIG. 1)
from the filter 7 to the washer 6 does not take place and the full
filtrate 80 is sent to the mixer 4. Fresh solvent 170 (for example
originating from stream 160) alone may be used for increasing the
S/B weight ratio in washer 6.
[0050] In FIG. 3 recycling of a filtrate stream (80 in FIG. 1) from
the filter 7 to the mixer 4 does not take place.
[0051] The person skilled in the art will readily understand that
many modifications may be made without departing from the scope of
the invention.
[0052] The present invention is described below with reference to
the following Examples, which are not intended to limit the scope
of the present invention in any way.
EXAMPLE 1
[0053] A 753.3 g sample of an Athabasca oil sand (having a bitumen
content of 9.7 wt. %; the particles having a diameter below 5.0
cm), 104.7 g solvent (n-pentane; "S1") and 188 g of diluted bitumen
were mixed for 2.5 minutes under ambient conditions using a mixer
at 500 rpm to obtain a slurry having a target S/B weight ratio of
1.6. The diluted bitumen as used in this Example was bitumen
(containing 11 wt. % asphaltenes) diluted with n-pentane. The
purpose of adding diluted bitumen was to adjust the solids volume
fraction of the slurry to about 37 vol. % to mimic the actual
bitumen extraction process (see in this respect also the recycle
streams 60 and 80 in the Figures).
[0054] The slurry was then transferred to a 1400 ml settle tube and
allowed to settle for 10 minutes, after which a solids-depleted
stream (supernatant liquid; stream 30 in Figures) having an S/B
weight ratio of 1.5 was removed. The solids-enriched fraction
remaining in the settle tube was transferred to a tumbler (Reax 20,
obtainable from Heidolph (Schwabach, Germany), at 15 rpm setting)
and contacted (whilst mixing) during 5 minutes with 149 g fresh
solvent ("S2") and transferred again to the settle tube and allowed
to settle, wherein the supernatant liquid (stream 60 in the
Figures; having an S/B weight ratio of 2.8) was removed. The
resulting solids-enriched stream (stream 50 in the Figures) had an
increased S/B weight ratio.
[0055] The solids-enriched stream having an increased S/B weight
ratio was transferred to a filtration vessel (diameter of the
filter was 78 mm), allowed to settle, and the surface of the filter
cake levelled (height of the filter cake was about 9 cm). The
supernatant liquid on top of the filter cake was pushed through the
filter cake until only a thin (1 mm) layer of supernatant liquid
remained (the pressure drop across the filter cake was 0.8
bar).
[0056] 81.3 g of fresh solvent was added as a wash solvent on top
of the filter cake and pushed through the filter cake until only a
thin (1 mm) layer of supernatant liquid remained. The collected
filtrate (including the supernatant liquid on top of the filter
cake) had an S/B weight ratio of 2.8. The time taken for the
filtration was 16 seconds.
EXAMPLE 2
[0057] Following the same procedure and equipment of Example 1, a
756.6 g sample of the same Athabasca oil sand as used in Example 1
was treated, whilst using the amounts and S/B weight ratios as
indicated in Table 1. The time taken for the filtration was 23
seconds.
COMPARATIVE EXAMPLES 1 AND 2
[0058] In order to show the effect of the intermediate contacting
step (step (d)) according to the present invention and the
resulting increased S/B weight ratio of the solids-enriched stream
(stream 50 in the Figures, which is the filter feed stream) on the
filtration time, Comparative Examples 1 and 2 were performed (see
Table 1 for amounts and S/B weight ratios used). In Comparative
Examples 1 and 2 the same Athabasca oil sand was used, but no
contacting step was performed to increase the S/B weight ratio (as
in step (d); but the other steps were kept the same); hence in
Comparative Examples 1 and 2 the filtration step was performed with
the same S/B weight ratio as during the contacting step.
[0059] Table 1 below shows the results obtained for Examples 1 and
2 and Comparative Examples 1 and 2. The "delta p" is the pressure
difference across the filter cake as applied by pressurized
nitrogen above the filter cake. "t1" represents the time from
beginning of feeding of the solids-enriched stream having an
increased S/B weight ratio until any liquid on top of the filter
cake was filtered through the bed and the top surface of the filter
cake became visible.
TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 C. Ex. 1 C. Ex. 2 Oil sand [g]
753.3 756.8 751.1 753.4 Solvent S1 [g] 104.7 145.1 101.2 145.6
Target S/B weight ratio of 1.6 2.35 1.6 2.35 slurry Actual S/B
weight ratio of 1.5 2.1 1.3 2.1 stream 30 S/B weight ratio of
stream 60 2.8 4.35 -- -- S/B weight ratio of stream 50 2.8 4.35 1.3
2.1 (filter feed) Solvent S2 [g] 149.0 167.3 -- -- Wash solvent for
filtration 81.3 153.8 82.4 153.2 [g] Delta p [bar] 0.8 0.8 0.8 0.8
Collected filtrate [g] 170.9 244.8 167.2 253.6 t1 [s] 16 22 49 49
S/B weight ratio of collected 2.8 5.3 1.5 2.7 filtrate
[0060] As can be learned from the Examples, the Examples 1 and 2
according to the present invention resulted in a significantly
reduced filtration time (t1 in Table 1) when compared with
Comparative Examples 1 and 2 wherein no washing step was used. This
means that according to the present invention the filtration can be
performed faster; also lower filter CAPEX (Capital Expenses) is
needed.
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