U.S. patent application number 11/123031 was filed with the patent office on 2006-11-09 for low energy process for extraction of bitumen from oil sand.
Invention is credited to George J. Cymerman, Yin Ming Samson Ng, Robert Dy Siy, Jonathan R. Spence.
Application Number | 20060249431 11/123031 |
Document ID | / |
Family ID | 37393133 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060249431 |
Kind Code |
A1 |
Cymerman; George J. ; et
al. |
November 9, 2006 |
Low energy process for extraction of bitumen from oil sand
Abstract
An improved low energy extraction process for recovering bitumen
from oil sand whereby essentially all of the thermal energy input
for processing the oil sand takes place at the slurry mixing step
as opposed to at both the slurry mixing step and the slurry
flooding step. Mined oil sand is mixed with sufficient hot slurry
water to produce an oil sand slurry having a density in the
preferred range of about 1.50 g/cc to about 1.60 g/cc and a
temperature in the preferred range of about 40.degree. C. to about
55.degree. C., more preferably greater than about 43.degree. C. The
oil sand slurry is conditioned, preferably by pumping it through a
pipeline for a sufficient length of time, and then flooded with
cold flood water to produce a diluted slurry having a density in
the range of about 1.4 g/cc to about 1.5 g/cc and a temperature
generally below 40.degree. C. and typically in the range of about
30.degree. C. to about 35.degree. C. The diluted slurry is
introduced into a gravity separation vessel where bitumen froth is
recovered.
Inventors: |
Cymerman; George J.;
(Edmonton, CA) ; Spence; Jonathan R.; (Edmonton,
CA) ; Ng; Yin Ming Samson; (Sherwood Park, CA)
; Siy; Robert Dy; (Edmonton, CA) |
Correspondence
Address: |
BENNETT JONES LLP
4500 Bankers Hall East
855 - 2nd Street SW
Calgary
AB
T2P 4K7
CA
|
Family ID: |
37393133 |
Appl. No.: |
11/123031 |
Filed: |
May 6, 2005 |
Current U.S.
Class: |
208/391 |
Current CPC
Class: |
C10G 1/047 20130101 |
Class at
Publication: |
208/391 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Claims
1. A method for recovering bitumen from oil sand, comprising: dry
mining oil sand at a mine site; mixing the oil sand with sufficient
hot slurry water to produce an oil sand slurry containing bitumen,
sand, water and entrained air, the oil sand slurry having a density
in the range of about 1.50 g/cc to about 1.65 g/cc and a
temperature in the range of about 40.degree. C. to about 70.degree.
C.; conditioning the oil sand slurry; flooding the conditioned oil
sand slurry with cold flood water to produce a diluted slurry; and
introducing the diluted slurry into a gravity separation vessel
wherein separate layers of bitumen froth, middlings and sand
tailings are formed; and separately removing bitumen froth,
middlings and sand tailings from the vessel.
2. The method as set forth in claim 1 wherein the hot slurry water
has a temperature in the range of about 70.degree. C. to about
95.degree. C.
3. The method as set forth in claim 1 wherein the oil sand slurry
has a temperature in the range of about 40.degree. C. to about
55.degree. C.
4. The method as set forth in claim 3 wherein the oil sand slurry
has a temperature greater than about 43.degree. C.
5. The method as set forth in claim 1 wherein the oil sand slurry
has a temperature in the range of about 40.degree. C. to about
50.degree. C.
6. The method as set forth in claim 1 wherein the oil sand slurry
has a temperature in the range of about 40.degree. C. to about
45.degree. C.
7. The method as set forth in claim 1 wherein caustic is added
during the mixing step.
8. The method as set forth in claim 1 wherein the conditioning step
comprises pumping the oil sand slurry through a pipeline.
9. The method as set forth in claim 8 wherein the pipeline has
sufficient length so that a slurry retention time therein is at
least 10 minutes.
10. The method as set forth in claim 1 wherein the conditioning
step comprises retaining the oil sand slurry in a tumbler or
agitation tank.
11. The method as set forth in claim 10 wherein the slurry
retention time in the tumbler and/or agitation tank is between
about 7 minutes to about 12 minutes.
12. The method as set forth in claim 1 wherein the oil sand slurry
has a density in the range of about 1.50 g/cc to about 1.60
g/cc.
13. The method as set forth in claim 1 wherein the diluted slurry
has a density in the range of about 1.4 g/cc to about 1.5 g/cc.
14. The method as set forth in claim 13 wherein the diluted slurry
has a density in the range of about 1.45 g/cc to about 1.5
g/cc.
15. The method as set forth in claim 1 wherein the cold flood water
has a temperature in the range of about 2.degree. C. to about
50.degree. C.
16. The method as set forth in claim 1 wherein the cold flood water
has a temperature in the range of about 2.degree. C. to about
27.degree. C.
17. The method as set forth in claim 1 wherein the flood water has
a temperature in the range of about 5.degree. C. to about
10.degree. C.
18. The method as set forth in claim 1 wherein the diluted slurry
has a temperature in the range of about 25.degree. C. to about
40.degree. C.
19. The method as set forth in claim 1 wherein the diluted slurry
has a temperature in the range of about 30.degree. C. to 35.degree.
C.
20. The method as set forth in claim 1 comprising: heating bitumen
in the vessel by adding heated water as an underwash layer
immediately beneath the bitumen froth layer.
21. The method as set forth in claim 1 wherein the oil sand is of
about low to average grade.
22. The method as set forth in claim 1 wherein the oil sand slurry
has a density in the range of about 1.55 g/cc to about 1.60
g/cc.
23. The method as set forth in claim 1 wherein the mixing step
occurs in a mix box or cyclofeeder.
Description
[0001] The present invention relates generally to a method for
extracting bitumen from oil sand. More specifically, the present
invention relates to an improved low energy extraction process
wherein the majority of thermal energy input in the form of hot
water occurs at the slurry mixing step rather than at both the
slurry mixing step and the slurry flooding step.
BACKGROUND OF THE INVENTION
[0002] Oil sand, such as is mined in the Fort McMurray region of
Alberta, generally comprises water-wet sand grains held together by
a matrix of viscous bitumen. It lends itself to liberation of the
sand grains from the bitumen, preferably by slurrying the oil sand
in hot process water, allowing the bitumen to move to the aqueous
phase.
[0003] For many years, the bitumen in the McMurray sand has been
commercially removed from oil sand using what is commonly referred
to in the industry as the "hot water process". In general terms,
the hot water process involves the following steps: [0004] dry
mining the oil sand at a mine site that can be kilometres from an
extraction plant; [0005] conveying the as-mined oil sand on
conveyer belts to the extraction plant; [0006] feeding the oil sand
into a rotating tumbler where it is mixed for a prescribed
retention time (generally in the range of 2 to 4 minutes) with hot
water (approximately 80-90.degree. C.), steam, caustic (e.g.,
sodium hydroxide) and naturally entrained air to yield a slurry
that has a temperature typically around 80.degree. C. The bitumen
matrix is heated and becomes less viscous.
[0007] Chunks of oil sand are ablated or disintegrated. The
released sand grains and separated bitumen flecks are dispersed in
the water. To some extent bitumen flecks coalesce and grow in size.
They may contact air bubbles and coat them to become aerated
bitumen. The term used to describe this overall process in the
tumbler is "conditioning"; and [0008] diluting the slurry so
produced with additional hot water to produce a diluted slurry
having a temperature of about 65.degree. C. to about 80.degree. C.
The diluted slurry is introduced into a large, open-topped,
conical-bottomed, cylindrical vessel termed a primary separation
vessel (PSV) where the more buoyant aerated bitumen rises to the
surface and forms a froth layer. This froth layer overflows the top
lip of the PSV and is received in a launder extending around the
PSV's rim. The product is commonly called "primary froth" and
typically has a temperature of about 65.degree. C. to about
75.degree. C.
[0009] It is well understood in the industry that the quality of
the oil sand has very significant effects on the completeness of
primary bitumen recovery in the PSV and the quality of the primary
froth. For example, a "low grade" oil sand typically will contain
between about 6 to 10 wt. % bitumen with about 25 to 35 wt. %
fines. An "average grade" oil sand will typically contain at least
10 wt. % bitumen to about 12.5 wt. % bitumen with about 15 to 25
wt. % fines and a "high grade" oil sand will typically contain
greater than 12.5 wt. % bitumen with less than 15 wt. % fines.
Fines are generally defined as those solids having a size less
about 44 .mu.m. The higher fines concentrations in low to average
grade oil sand contribute to the difficulty in extracting the
bitumen.
[0010] The hot water process as described above generally assures
good bitumen recoveries for all grades of oil sand. However, the
thermal energy requirement per tonne of oil sand processed is very
high. In particular, thermal energy is required to heat the hot
process water, for steam production and for heating the hot flood
water.
[0011] Around 1990, the known conditioning step of the hot water
process was modified by eliminating the need for steam. Oil sand is
mixed with sufficient hot water to yield an oil sand slurry having
a temperature in the range of 40-55.degree. C. Mixing and
conditioning occurs in a tumbler, with retention times being
increased to within the range of about 7-12 minutes. Conditioned
slurry is flooded or diluted with additional hot water to yield a
flooded slurry temperature within the range of 50-80.degree. C.
This process is referred to as the "warm slurry extraction process"
and is disclosed in Canadian Patent No. 2,015,784.
[0012] Further in the early 1990s, there was another major
innovation in the oil sand industry, which is commonly referred to
as "pipeline conditioning". This innovation is disclosed in
Canadian Patent No. 2,029,795 and U.S. Pat. No. 5,039,227. The
bitumen extraction process using pipeline conditioning, which is
disclosed in the aforementioned patents, comprises the following
steps: [0013] supplying heated water (typically at 95.degree. C.)
at the mine site; [0014] mixing the dry as-mined oil sand with the
heated water at the mine site in predetermined portions using a
device known as a "cyclofeeder", to form an aerated slurry having a
temperature in the range of 40-70.degree. C., preferably
about50.degree. C.; [0015] screening the slurry to remove oversize
solids too large to be fed to the pipeline; [0016] pumping the
screened slurry to the extraction plant through several kilometres
of pipeline, where conditioning (i.e., lump digestion, bitumen
liberation, coalescence and aeration) occurs; and [0017] diluting
the slurry with heated flood water having a temperature in the
range of about 50.degree. C. to about 65.degree. C. and feeding the
slurry directly into a PSV for gravity separation.
[0018] Thus, the pumping of the slurry through a pipeline, over a
certain minimum distance, to condition the slurry allows the slurry
temperature to be reduced to about 50.degree. C. without
compromising bitumen recovery. This is due to the increased
conditioning time (i.e., typically 10 minutes or greater) in the
pipeline. If a tumbler were to be used for such a slurry, it would
have to be very large, to provide a longer retention time for
conditioning to occur. Hence, by using pipeline conditioning, a
bitumen extraction process can be used with appreciably lower
thermal energy requirements per tonne of oil sand. However, thermal
energy was still needed to heat both the hot slurry water and the
hot flood water.
[0019] In an attempt to further reduce the thermal energy
requirement per tonne of oil sand, in the late 1990s a cold dense
slurrying process for extracting bitumen from oil sand was
developed, which is disclosed in Canadian patent No. 2,217,623 and
U.S. Pat. No. 6,007,708. This process is commonly referred to as
the "low energy extraction process" or the "LEE process" and
generally comprises the following steps: [0020] dry mining the oil
sand; [0021] mixing the mined oil sand with water in predetermined
proportions near the mine site to produce a slurry containing
entrained air and having a controlled density in the range of 1.4
to 1.65 g/cc and preferably a temperature in the range
20-40.degree. C.; [0022] pumping the slurry through a pipeline
having a plurality of pumps spaced along its length, preferably
adding air to the slurry as it moves through the pipeline, to
condition the slurry; [0023] diluting the slurry with flood water
and introducing the diluted slurry into the PSV to float the
aerated bitumen. The froth is maintained at a temperature of at
least 35.degree. C. in the PSV by use of a hot water underwash,
thereby assisting in removing the froth from the PSV and satisfying
downstream froth temperature needs.
[0024] Thus, in an attempt to save on energy costs, the LEE process
reduces the temperature of the slurry process water used in the
slurry preparation and conditioning stage to produce a low
temperature slurry. Thus, less thermal energy is used to heat the
slurry process water.
[0025] However, more thermal energy is also expended at the later
flooding stage, to ensure the overall PSV slurry temperature of at
least 35.degree. C. In other words, heated flood water is routinely
used to bring up the temperature of the low temperature slurry for
bitumen separation.
[0026] While the LEE process provides acceptable bitumen recovery
from high grade oil sand, bitumen recovery from low and average
grade oil sand is still appreciably less than optimal. Thus, the
range of oil sand grades which process well at the low temperature
conditions of the LEE process is limited because many low grade,
high fines ore facies do not respond well to pipeline conditioning
process at low temperatures.
[0027] It will therefore be appreciated that there exists a need
for a low energy process that will result in improved bitumen
recovery, in particular, when processing low to average grade oil
sand.
SUMMARY OF THE INVENTION
[0028] In accordance with the invention, an improved low energy
extraction process is provided for extracting bitumen from oil
sand, comprising: [0029] dry mining oil sand from a deposit at a
mine site; [0030] mixing the oil sand with sufficient hot slurry
water to produce an oil sand slurry containing bitumen, sand, water
and entrained air, the oil sand slurry having a density in the
range of about 1.50 g/cc to about 1.65 g/cc and a temperature in
the range of about 40.degree. C. to about 70.degree. C.; [0031]
conditioning the oil sand slurry; [0032] flooding the conditioned
oil sand slurry with cold flood water to dilute the slurry; [0033]
introducing the diluted slurry into a gravity separation vessel
wherein separate layers of bitumen froth, middlings and sand
tailings are formed; and [0034] separately removing bitumen froth,
middlings and sand tailings from the vessel.
[0035] Thus, broadly stated, the invention is an improved low
energy extraction process for recovering bitumen from oil sand
whereby essentially all of the thermal energy input to process the
oil sand occurs at the slurry mixing step as opposed to at both the
slurry mixing step and the slurry flooding step. By using
essentially all of the thermal energy in the form of hot slurry
water up front in the slurry mixing step, optimal slurry
conditioning occurs. Further, by using cold flood water in the
flooding step, thermal energy requirements are greatly reduced.
Thus, the invention involves a redistribution of thermal energy
input such that the majority of the thermal energy in the form of
hot process water is expended at the slurry mixing step rather than
at both the slurry mixing step and slurry flooding step.
[0036] By "slurry conditioning" is meant digestion of oil sand
lumps, liberation of bitumen from sand-fines-bitumen matrix,
coalescence of liberated bitumen flecks into larger bitumen
droplets and aeration of bitumen droplets.
[0037] By "hot slurry water" is meant process water having a
temperature sufficient to yield an oil sand slurry of the desired
temperature and generally refers to water that has been heated to a
temperature greater than 50.degree. C. and, more preferably, to a
temperature of between about 70.degree. C. and about 95.degree.
C.
[0038] By "cold flood water" is meant process water that has not
been heated. It is understood that the temperature of the cold
flood water can vary greatly, depending on the source of the water,
the time of year, etc. Generally speaking, however, cold flood
water will have a temperature less than 50.degree. C. and more
likely will have a temperature between about 2.degree. C. and about
27.degree. C. By way of example, recycled pond water could be used,
which typically has a temperature in the range of about 5.degree.
C. to about 10.degree. C.
[0039] Surprisingly, it was discovered that cold flood water at a
wide range of temperatures could be used to dilute the conditioned
slurry without incurring any significant losses in rejects free
bitumen recovery when compared to a process where approximately the
same temperature is maintained in the slurry mixing step and the
slurry flooding step, thereby conserving thermal energy.
[0040] In a preferred embodiment, the temperature of the hot slurry
water used in the slurry mixing step is about 75.degree. C. to
about 85.degree. C., which, when mixed with the oil sand, results
in an oil sand slurry having a temperature greater than 40.degree.
C., preferably greater than 43.degree. C., and more preferably in
the range of about 40.degree. C. to about 55.degree. C., and a
density in the range of about 1.5 g/cc to about 1.6 g/cc. Caustic
soda (NaOH) and other processing aids can be also added at this
step, if necessary or desired.
[0041] The conditioning step can be performed either by pumping the
oil sand slurry through a pipeline of sufficient length (e.g.,
typically greater than about 2.5 km), or by agitating the oil sand
slurry in a tumbler or agitation tank for a sufficient period of
time, so that liberation of bitumen from sand and subsequent
aeration of bitumen both have time to occur. Preferably,
conditioning time is about 7 to about 12 minutes when using a
tumbler and/or agitation tank and 10 minutes or more when using a
pipeline of sufficient length.
[0042] The cold flood water temperature used in the flooding step
generally ranges between 5.degree. C. and 25.degree. C., which
results in a flooded or diluted slurry having a temperature of
about 25.degree. C. to about 40.degree. C. and a density of about
1.4 g/cc to about 1.5 g/cc. More preferably, the diluted slurry
will have a density of about 1.4 g/cc to about 1.45 g/cc and a
temperature in the range of about 30.degree. C. to about 40.degree.
C., preferably, a temperature of about 35.degree. C. Use of cold
flood water for flooding eliminates the need to import heated water
from other sources, and readily available, lower quality pond water
can be used.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 is a block diagram setting forth the process in
accordance with an embodiment of the invention.
[0044] FIG. 2 is a schematic of the pilot plant used in connection
with the development of the invention.
[0045] FIG. 3 is a schematic of an industrial scale system for
practicing the process.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0046] The invention is exemplified by the following description
and examples.
[0047] A schematic of the pilot plant used in the following
examples is shown in FIG. 2. Oil sand, mixing (tumbler) water and,
optionally, caustic (NaOH) are added to tumbler 2 where the oil
sand is mixed with the water to form a slurry. Residence time of
the slurry in the tumbler is generally around 2.0 minutes. The
slurry is then screened through reject screen (not shown) having
5/16'' square openings and rejects, i.e. oil sand lumps, greater
than 5/16'' are discarded.
[0048] The slurry is then transferred to an agitated pumpbox or
mixing tank 4 to keep the slurry in suspension. Residence time of
the slurry in the agitated pumpbox or mixing tank 4 is about 5
minutes. Slurry is then pumped via Moyno 3L6 pump 6 through a
coriolis mass flow meter (not shown) to conditioning pipeline loop
8 comprised of 4-inch pipe where the slurry undergoes conditioning.
Pipeline loop 8 is approximately 40 meters in length and was
designed to provide a mean residence time of approximately 5
minutes. Thus, the total residence time of the oil sand slurry in
the tumbler, the agitated pumpbox or mixing tank, and the pipeline
is about 12 minutes.
[0049] After leaving the pipeline, the conditioned slurry is
flooded (diluted) with flood water and additional air may be added
to the diluted slurry via centrifugal pump 10 (a Warman
2''.times.1.5'' centrifugal pump, equipped with a 10 Hp motor)
situated on slurry pipeline 12 which leads to the feedwell (not
shown) of primary separation vessel (PSV) 14. The pipeline between
centrifugal pump 10 and PSV feedwell is 1.25'' in diameter and 15
meters long. Centrifugal pump 10 is typically operated at a
constant speed of 700 RPM. Air is added to the suction side of pump
10 through a 3/8'' line to a "T" junction on the 1'' slurry
pipeline 12'.
[0050] Froth underwash water is added to PSV 14 at a point beneath
the layer of bitumen froth that forms. Optionally, caustic (NaOH)
can also be added as a process aid via caustic line 16, comprising
0.25'' stainless steel tubing. In addition to this caustic line,
there are two more caustic lines 18 and 20 where NaOH can be added.
Separated bitumen froth overflows into launder 22 and is removed
into a separate froth weigh tank (not shown). This bitumen froth
from the PSV is commonly referred to as primary froth.
[0051] Middlings, comprising water, bitumen and solids that collect
in the mid-section of the PSV 14, are removed to one or more
secondary flotation cells 20, each having impellers, to produce
lean bitumen flotation froth. This lean froth is then recycled back
into PSV 14 for recovery as bitumen froth.
[0052] It should be noted that the pilot plant uses a tumbler for
slurry mixing, with an average slurry mixing time of approximately
2 minutes, and a rejects screen having 5/16'' square openings.
However, when the invention is commercially practiced (see FIG. 3),
a mix box is used for slurry preparation, with 5'' openings in the
rejects screens and rejects reprocessing. Thus, the percent rejects
free bitumen recovery values obtained in the following examples
using the pilot plant more accurately reflect the values obtained
on a commercial scale.
[0053] Overall bitumen recovery is calculated as shown in equation
1 and rejects free bitumen recovery is calculated as shown in
equation 2, as follows: R o = M pf .times. X B , pf M os .times. X
B , os .times. 100 ( 1 ) R RF = M pf .times. X B , pf M os .times.
X B , os - M r .times. X B , r .times. 100 ( 2 ) ##EQU1## where
R.sub.o is the overall bitumen recovery, R.sub.RF is the rejects
free bitumen recovery, M is the mass flow rate, X is the mass
fraction, and the subscripts pf, r, os and B refer to PSV froth,
reject, oil sand and bitumen, respectively.
[0054] Two oil sand samples having different bitumen and fines
concentrations were used in the following examples. In particular,
the two oil sand samples tested were estuarine ores from the Aurora
mine in Alberta and are designated Oil Sand 1 and Oil Sand 2. The
specifications of the two samples used are given in Table 1.
TABLE-US-00001 TABLE 1 Summary of Composition, Fines and d.sub.50
Data Fines Average size wt. % < of solids Bitumen Water Solids
44 .mu.m in (d.sub.50 Oil Sand wt. % wt. % wt. % size .mu.m) Oil
Sand 1 10.4 3.5 86.0 24 124 Oil Sand 2 11.5 4.5 83.7 17 131
[0055] Table 2 summaries the operating conditions used to test the
two samples in Table 1 in the pilot plant described above.
TABLE-US-00002 TABLE 2 Operating Conditions of the Pilot Plant
Parameter Value Tumbler (RPM) 5 Tumbler Weir Height (%) 0 Mix Tank
Agitator (RPM) 275 Mix Tank Slurry Level (%) 53 Pipeline Slurry
Velocity (m/s) 4 Centrifugal Aerator Pump Speed (RPM) 700 Air/PSV
Feed Slurry Ratio (vol/vol) 0.2 Number of Flotation Cells Operating
4 Flotation Cells Impeller (RPM) 800 Air/Flotation Ratio (vol/vol)
1.42
EXAMPLE 1
[0056] Oil Sand 1 having the composition as shown in Table 1 was
tested to see what effect, if any, the redistribution of available
heat would have on the overall bitumen recovery and, in particular,
the rejects free bitumen recovery. The parameters tested and the
results for 7 separate conditions are shown in Table 3.
TABLE-US-00003 TABLE 3 Effects of Heat Redistribution Using Oil
Sand 1 Run Condition ID 1 2 3 4 5 6 7 Target Pipeline Slurry
Temperature 45 45 45 35 35 25 25 (.degree. C.) Actual Pipeline
Slurry Temperature 44 45 45 34 35 25 25 (.degree. C.) Pipeline
Slurry Density (g/cc) 1.58 1.58 1.58 1.58 1.58 1.58 1.58 Flood
Water Temperature (.degree. C.) 55 27 10 55 10 55 10 Target PSV
Temperature (.degree. C.) >45 42 <45 42 <35 >25 <25
Actual PSV Temperature (.degree. C.) 47 40 36 40 29 35 23 Target
Underwash Water 60 60 60 60 60 60 60 Temperature (.degree. C.)
Bitumen Recovery 94.2 95.7 96.5 93.7 93.7 86.9 89.4 (Overall) (%)
Bitumen Recovery (Rejects free) 98.5 98.3 98.6 97.6 97.2 94.4 93.2
(%) Rejects Bitumen Loss (%) 4.3 2.6 2.1 4.0 3.5 8.0 4.0 PSV Froth
Bitumen (%) 59.5 53.2 56.2 59.5 53.3 53.7 53.1 PSV Froth Solid (%)
16.7 14.9 15.4 16.6 16.2 14.6 16.9 PSV Middlings Bitumen (%) 0.13
0.13 0.10 0.50 1.09 2.07 4.43 PSV Tails Bitumen (%) 0.11 0.13 0.10
0.18 0.21 0.48 0.50 Flotation Unit Bitumen Recovery (%) 56.5 35.0
26.9 73.1 90.8 93.8 94.2 Flotation Tails Bitumen (%) 0.07 0.08 0.08
0.09 0.12 0.14 0.30
[0057] Run condition 1 is comparable to conditions used in the warm
slurry extraction process as described above, wherein the pipeline
slurry (i.e., oil sand slurry) temperature is between 40.degree. C.
and 55.degree. C. (preferably .about.50.degree. C.) and flood water
temperature is about 50.degree. C. to about 65.degree. C. to give a
diluted slurry (i.e., PSV temperature) having a temperature around
50.degree. C. However, as discussed above, the warm slurry
extraction process still requires considerable thermal energy, in
particular, to heat the flood water to maintain a diluted slurry
temperature of 50.degree. C.
[0058] In an attempt to determine if cold flood water could be used
to conserve energy ordinarily used to heat the flood water without
a significant reduction in bitumen recovery, run conditions 2 and 3
were performed using much lower temperature flood water.
[0059] Run conditions 2 and 3 used essentially the same temperature
pipeline slurry as in run condition 1 (i.e., around 45.degree. C.).
However, run condition 2 used cold flood water at a temperature of
27.degree. C., to give a diluted slurry having a final temperature
of 40.degree. C. (i.e., actual PSV temperature), and run condition
3 used cold flood water having an even lower temperature of
10.degree. C. to give a diluted slurry temperature of 36.degree.
C.
[0060] Surprisingly, the results in Table 3, in particular, the
percent bitumen recovery (rejects free) values, show that the use
of lower flood water temperatures did not result in lower rejects
free bitumen recovery but rather the rejects free bitumen recovery
remained comparatively constant as the temperature of the flood
water decreased. Rejects free bitumen recovery was 98.5% when using
run condition 1 and 98.6% when using the coldest flood water of run
condition 3. Hence, by using cold flood water, the cost of thermal
energy is reduced without a reduction in the rejects free bitumen
recovery.
[0061] Run condition 6 uses an oil sand slurry temperature at the
lower end of the temperature range of the LEE process as described
above. Pipeline slurry temperature in this run is 25.degree. C. and
flood water temperature is around 55.degree. C. to give a diluted
slurry having a temperature around 35.degree. C. Rejects free
bitumen recovery using the LEE process at the lower temperature
range was 94.4%.
[0062] The pipeline slurry temperature in run condition 7 was also
25.degree. C., as in run condition 6. However, in this run, cold
flood water at a temperature of 10.degree. C. was used instead of
hot water to give a diluted slurry having a final temperature of
23.degree. C. Surprisingly, the use of cold flood water did not
significantly reduce the rejects free bitumen recovery (i.e., 93.2%
in run 7 versus 94.4% for run 6). Thus, the rejects free bitumen
recovery using the LEE process was not significantly affected by
the use of cold flood water.
[0063] Run condition 4 uses an oil sand slurry temperature at the
upper end of the temperature range of the LEE process. Pipeline
slurry temperature is 35.degree. C. and flood water temperature is
around 55.degree. C. to give a diluted slurry having a temperature
around 40.degree. C. Rejects free bitumen recoveries using the LEE
process at the higher temperature were improved from those in run
condition 6 (i.e., 97.6% for run 5 versus 94.4% for run 6). This is
likely due to better pipeline conditioning when higher slurry
temperatures are used.
[0064] Run condition 5 also used a pipeline slurry temperature of
35.degree. C., as in run condition 4. However, in this run, cold
flood water at a temperature of 10.degree. C., was used instead of
hot water to give a diluted slurry having a final temperature of
29.degree. C. Once again, the use of cold flood water did not
result in a decrease in rejects free bitumen recoveries; the
rejects free bitumen recoveries were the same for run conditions 4
and 5. Thus, the rejects free bitumen recoveries were not affected
by use of cold flood water to dilute the conditioned slurry.
[0065] One of the most surprising observations came from the
comparison of run condition 6 and run condition 3. The overall heat
inputs were the same for these two runs. However, the rejects free
bitumen recoveries were significantly different. Run condition 6,
using the LEE process, gave a rejects free bitumen recovery of only
94.4%. However, using essentially the same thermal energy, run
condition 3 gave a rejects free bitumen recovery of 98.6%, an
increase of more than 4%. Those in the industry will appreciate the
economic significance of such an increase in overall bitumen
recovery.
[0066] Further when comparing the results obtained in run 3 and run
6, it should also be noted that increased temperature during slurry
preparation (as in run 3) resulted in reduced reject bitumen losses
(i.e., 2.1% in run 3 versus 8.0% in run 6) and, consequently, even
greater gains in overall bitumen recovery (i.e., 96.5 % in run 3
versus 86.9 % in run 6). Yet, the process in run 3 is still a low
energy process.
[0067] In summary, the results in Table 3, and, in particular, the
comparison of runs 3 and 6, demonstrate that, by redistributing the
overall thermal energy input up front in the slurry mixing step,
improved bitumen recovery can be obtained without expending any
additional thermal energy.
EXAMPLE 2
[0068] Oil Sand 2 having the composition as shown in Table 1 was
also tested to see what effect, if any, the redistribution of
available heat would have on the rejects free bitumen recovery. The
parameters tested and the results for 6 separate conditions are
shown in Table 4. TABLE-US-00004 TABLE 4 Effects of Heat
Redistribution Using Oil Sand 2 Run Condition ID 1 2 3 4 5 6 Target
Pipeline Slurry Temperature (.degree. C.) 45 45 35 35 25 25 Actual
Pipeline Slurry Temperature (.degree. C.) 45 44 35 35 25 25
Pipeline Slurry Density (g/cc) 1.58 1.58 1.58 1.58 1.58 1.58 Flood
Water Temperature (.degree. C.) 55 10 55 10 55 10 Target PSV
Temperature (.degree. C.) >45 <45 42 <35 >25 <25
Actual PSV Temperature (.degree. C.) 47 36 41 30 34 24 Target
Underwash Water Temperature (.degree. C.) 60 60 60 60 60 60 Bitumen
Recovery 98.0 98.6 97.4 95.7 91.6 92.6 (Overall) (%) Bitumen
Recovery (Rejects free) (%) 98.7 98.9 98.4 97.8 97.2 97.4 Rejects
Bitumen Loss (%) 0.7 0.3 0.9 2.2 5.8 4.9 PSV Froth Bitumen (%) 62.0
59.9 59.2 65.5 73.0 64.9 PSV Froth Solid (%) 15.1 15.4 16.8 17.3
13.6 14.0 PSV Middlings Bitumen (%) 0.31 0.33 0.50 0.48 1.33 1.85
PSV Tails Bitumen (%) 0.11 0.07 0.13 0.18 0.22 0.19 Flotation Unit
Bitumen Recovery (%) 95.5 69.8 87.8 87.2 95.2 90.9 Flotation Tails
Bitumen (%) 0.02 0.13 0.07 0.08 0.09 0.19
[0069] The results shown in Table 4 confirm that the use of cold
flood water when extracting bitumen from oil sand with either the
warm slurry extraction process (run condition 1) or the LEE process
(run condition 3 and 5) does not result in reduced rejects free
bitumen recovery. In fact, when one again compares run condition 5
with run condition 2, where the overall heat inputs were the same,
the use of the thermal energy up front when preparing the pipeline
slurry resulted in an increase in rejects free bitumen recovery.
Run condition 5, the LEE process at the lower temperature range,
gave a rejects free bitumen recovery of 97.2%. However, using
essentially the same thermal energy, run condition 2 gave a rejects
free bitumen recovery of 98.9%, an increase of 1.6%. Such an
increase in rejects free bitumen recovery is still economically
significant.
[0070] As was the case in example 1, increased temperature during
slurry preparation in run 2 also resulted in reduced reject bitumen
losses and therefore further gains in overall bitumen recovery
(i.e., 98.6% in run 2 versus 91.6% in run 5).
EXAMPLE 3
[0071] The effect of increasing pipeline slurry density on
extraction performance using Oil Sand 1 was determined using the
improved low energy extraction process of run condition 3 of Table
3. Results are shown in Table 5. TABLE-US-00005 TABLE 5 Effects of
Increasing Pipeline Slurry Density Using Oil Sand 1 Run Condition
ID 1 2 Target Pipeline Slurry Temperature (.degree. C.) 45 45
Actual Pipeline Slurry Temperature (.degree. C.) 44 45 Pipeline
Slurry Density (g/cc) 1.58 1.65 Flood Water Temperature (.degree.
C.) 10 10 Target PSV Temperature (.degree. C.) <45 32 Actual PSV
Temperature (.degree. C.) 36 34 Target Underwash Water Temperature
(.degree. C.) 60 60 Bitumen Recovery 96.5 95.6 (Overall) (%)
Bitumen Recovery (Rejects free) (%) 98.6 95.9 Rejects Bitumen Loss
(%) 2.1 0.3 PSV Froth Bitumen (%) 56.2 48.6 PSV Froth Solid (%)
15.4 16.4 PSV Middlings Bitumen (%) 0.10 9.20 PSV Tails Bitumen (%)
0.10 0.23 Flotation Unit Bitumen Recovery (%) 26.9 94.8 Flotation
Tails Bitumen (%) 0.08 0.59
[0072] Increasing the density of the pipeline slurry from 1.58 g/cc
to 1.65 g/cc resulted in significant increase in PSV middlings
bitumen content (from 0.1 to 9.2%). Overall bitumen recovery was
not significantly reduced due to good performance of flotation and
middlings displacement. However, in commercial practice, the
flotation system may not work as efficiently. Thus, a high middling
bitumen content may result in higher bitumen losses.
[0073] Increasing the density of the pipeline slurry from 1.58 g/cc
to 1.65 g/cc, however, resulted in a decrease in rejects free
bitumen recovery of 2.7 %. Thus, a slurry density of 1.58 g/cc
resulted in better rejects free bitumen recovery.
EXAMPLE 4
[0074] The effect of increasing pipeline slurry density on
extraction performance using Oil Sand 2 was determined using the
improved low energy extraction process of run condition 2 of Table
4. Results are shown in Table 6. TABLE-US-00006 TABLE 6 Effects of
Increasing Pipeline Slurry Density Using Oil Sand 2 Run Condition
ID 1 2 Target Pipeline Slurry Temperature (.degree. C.) 45 45
Actual Pipeline Slurry Temperature (.degree. C.) 44 45 Pipeline
Slurry Density (g/cc) 1.58 1.65 Flood Water Temperature (.degree.
C.) 10 10 Target PSV Temperature (.degree. C.) <45 32 Actual PSV
Temperature (.degree. C.) 36 35 Target Underwash Water Temperature
(.degree. C.) 60 60 Bitumen Recovery 98.6 95.3 (Overall) (%)
Bitumen Recovery (Rejects free) (%) 98.9 96.5 Rejects Bitumen Loss
(%) 0.3 2.3 PSV Froth Bitumen (%) 59.9 63.6 PSV Froth Solid (%)
15.4 15.4 PSV Middlings Bitumen (%) 0.33 7.77 PSV Tails Bitumen (%)
0.07 0.19 Flotation Unit Bitumen Recovery (%) 69.8 94.0 Flotation
Tails Bitumen (%) 0.13 0.59
[0075] Increasing the density of the pipeline slurry from 1.58 g/cc
to 1.65 g/cc resulted in significant increase in PSV middlings
bitumen content (from 0.33 to 7.77%). Further, the rejects free
bitumen recovery was reduced from 98.9% to 96.5%. Once again, a
slurry density of 1.58 g/cc resulted in better bitumen
recovery.
EXAMPLE 5
[0076] The effect of decreasing pipeline slurry density on
extraction performance using Oil Sand 2 was determined using a
target pipeline slurry temperature of 27.degree. C. Results are
shown in Table 7. TABLE-US-00007 TABLE 7 Effects of Decreasing
Pipeline Slurry Density Using Oil Sand 2 Run Condition ID 1 2
Target Pipeline Slurry Temperature (.degree. C.) 27 27 Actual
Pipeline Slurry Temperature (.degree. C.) 27 26 Pipeline Slurry
Density (g/cc) 1.58 1.49 Flood Water Temperature (.degree. C.) 47 4
Flooded Slurry Density (g/cc) 1.46 1.46 Actual PSV Temperature
(.degree. C.) 32 27 Target Underwash Water Temperature (.degree.
C.) N/A 47 Bitumen Recovery 95.5 92.8 (Overall) (%) Bitumen
Recovery (Rejects free) (%) 98.6 96.6 Rejects Bitumen Loss (%) 3.2
4.0 PSV Froth Bitumen (%) 59.7 54.9 PSV Froth Solid (%) 13.5 14.0
PSV Middlings Bitumen (%) 0.64 2.69 PSV Tails Bitumen (%) 0.13 0.29
Flotation Unit Bitumen Recovery (%) 90.1 95.3 Flotation Tails
Bitumen (%) 0.09 0.15
[0077] Decreasing the density of the pipeline slurry from 1.58 g/cc
to 1.49 g/cc resulted in a reduction of rejects free bitumen
recovery from 98.6% to 96.6%. Again, a slurry density of 1.58 g/cc
resulted in better overall bitumen recovery.
[0078] Turning now to FIG. 3, a schematic is shown of an industrial
scale system for practicing the invention.
[0079] More particularly, oil sand is surface mined and fed into a
primary crusher 30 of the double roller type, to reduce the
oversize to less than 24''. The crushed oil sand is carried by
conveyer to surge pile 34 of oil sand. Oil sand from surge pile 34
is fed by conveyer 36 to a mix box 38, comprising a plurality of
inclined plates 40. Hot slurry water is also added to the mix box
to form an oil sand slurry. Mixing can also occur in a cyclofeeder
as is known in the art.
[0080] Product slurry 54 leaves the bottom outlet 56 of mix box 38
and passes through screen 42 and, optionally, more hot slurry water
is added. Product slurry enters a pump box 52 and rejects 44 are
fed to an impact crusher 46 and screened again through screen 48.
Oversize rejects 58 are discarded but screened material enters pump
box 50, where more hot slurry water is added and then oil sand
slurry is pumped into pump box 52.
[0081] Oil sand slurry in pump box 52 is then pumped by a series of
pumps 60 through conditioning pipeline 62 and, optionally, air,
frother and other process aids may be added. Conditioned oil sand
slurry is then pumped via pump through a second section 66 of
pipeline where cold flood water is added and, optionally, more air
is added. Diluted slurry is then introduced into primary separation
vessel 68 and retained under quiescent conditions, to allow the
solids to settle and the bitumen froth to float to the top. A froth
underwash of hot water is added directly beneath the layer of
bitumen froth to aid in the separation. Bitumen froth, which is
called primary froth, is removed from the top of the primary
separation vessel 68 and then deaerated in froth deaerator 72. Once
deaerated, primary froth is retained in froth tank 74.
[0082] Middlings from primary separation vessel 68 are removed and
undergo flotation in flotation cells 70 to produce secondary froth.
Secondary froth is recycled back to the primary separation vessel
68. Tailings, the solids, water, etc. that collects at the bottom
of the primary separation vessel 68 are removed and deposited into
tailings pond 76.
* * * * *