U.S. patent application number 13/646422 was filed with the patent office on 2014-04-10 for bitumen removal from tailings centrifuge centrate.
This patent application is currently assigned to SYNCRUDE CANADA LTD. in trust for the owners of the Syncrude Project. The applicant listed for this patent is SYNCRUDE CANADA LTD. IN TRUST FOR THE OWNERS. Invention is credited to OWEN NEIMAN, JONATHAN SPENCE, SIMON YUAN.
Application Number | 20140097126 13/646422 |
Document ID | / |
Family ID | 50431895 |
Filed Date | 2014-04-10 |
United States Patent
Application |
20140097126 |
Kind Code |
A1 |
SPENCE; JONATHAN ; et
al. |
April 10, 2014 |
BITUMEN REMOVAL FROM TAILINGS CENTRIFUGE CENTRATE
Abstract
A process for removing residual bitumen from oil sands tailings
is provided, comprising optionally diluting the tailings with
sufficient water to yield a tailings feed having a solids content
in the range of about 18 wt % to about 36 wt %; adding one or both
of a coagulant and a flocculant to the tailings feed to form a
centrifuge feed; centrifuging the centrifuge feed to produce a cake
and a centrate having a solids content of less than about 3 wt %;
introducing the centrate into a flotation device so that bitumen
froth and cleaned centrate are formed; recycling the cleaned
centrate as dilution water or discharging the cleaned centrate to a
tailings pond, and further processing the bitumen froth from the
flotation device either by returning it to the primary Extraction
feed or by treating it in a new or existing froth treatment
plant.
Inventors: |
SPENCE; JONATHAN; (Edmonton,
CA) ; NEIMAN; OWEN; (Fort McMurray, CA) ;
YUAN; SIMON; (Edmonton, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SYNCRUDE CANADA LTD. IN TRUST FOR THE OWNERS |
Fort McMurray |
|
CA |
|
|
Assignee: |
SYNCRUDE CANADA LTD. in trust for
the owners of the Syncrude Project
Fort McMurray
CA
|
Family ID: |
50431895 |
Appl. No.: |
13/646422 |
Filed: |
October 5, 2012 |
Current U.S.
Class: |
208/390 |
Current CPC
Class: |
C10G 1/047 20130101;
C10G 1/045 20130101 |
Class at
Publication: |
208/390 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Claims
1. A process for removing residual bitumen from oil sands tailings
comprising: a) optionally diluting the tailings with sufficient
water to yield a tailings feed having a solids content in the range
of about 18 wt % to about 36 wt %; b) adding one or both of a
coagulant and a flocculant to the tailings feed to form a
centrifuge feed; c) centrifuging the centrifuge feed to produce a
cake and a centrate having a solids content of less than about 3 wt
%; d) introducing the centrate into a flotation device so that
bitumen froth and cleaned centrate are formed; and e) recycling the
cleaned centrate as dilution water in step (a) or discharging the
cleaned centrate to a tailings pond. f) further processing the
bitumen froth from the flotation device.
2. [Currently Amended] The process of claim 1, further comprising
cleaning the bitumen froth in a froth cleaner to produce a cleaned
froth overflow stream and a water phase underflow stream having
reduced bitumen for disposal.
3. The process of claim 1, wherein in step (a), the solids content
is greater than about 30 wt %.
4. The process of claim 1, wherein in step (b), the tailings feed
and flocculant are combined within a mixer.
5. The process of claim 4, wherein the flocculant is added in-line
prior to entering the mixer.
6. The process of claim 5, further comprising diluting the
flocculant.
7. The process of claim 6, wherein the dosage of flocculant ranges
from about 400 grams to about 1,500 grams per tonne of solids in
the tailings.
8. The process of claim 7, wherein the flocculant is the form of a
0.2-0.4% solution.
9. The process of claim 8, wherein the flocculant comprises a
polyacrylamide anionic flocculant.
10. The process of claim 1, wherein in step (b), the flocculant is
fed directly to the centrifuge.
11. The process of claim 1, wherein the centrifuge is a solid bowl
decanter centrifuge.
12. The process of claim 1, wherein after step (c), the cake is
disposed in an area using a dry stacking mode of disposal.
13. The process of claim 1, wherein the tailings comprise fluid
fine tailings.
14. The process of claim 1, wherein the flotation device comprises
a separation vessel, a mechanical flotation cell, a separator
equipped with aeration downpipes, or a flotation column.
15. The process of claim 1, wherein the bitumen froth from the
flotation device is further processed by mixing it with a primary
extraction feed or by treating it in a new or existing froth
treatment plant.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a process for removing
residual bitumen from oil sands tailings, particularly from
centrate derived from centrifugation of the tailings.
BACKGROUND OF THE INVENTION
[0002] Oil sand generally comprises water-wet sand grains held
together by a matrix of viscous heavy oil or bitumen. Bitumen is a
complex and viscous mixture of large or heavy hydrocarbon molecules
which contain a significant amount of sulfur, nitrogen and oxygen,
The extraction of bitumen from oil sand using hot water processes
yields large volumes of fine tailings composed of fine silts,
clays, residual bitumen and water. Mineral fractions with a
particle diameter less than 44 microns are referred to as
"fines."
[0003] When oil sand tailings are pumped to the deposition area,
the coarse sands settle quickly on the beach while the fine
tailings run off the beach and flow by gravity to the tailings
ponds. The low density run-off material is referred to as thin fine
tailings. The thin fine tailings suspension is typically 85% water
and 15% fine particles by weight. Dewatering of fine tailings
occurs slowly. After a few years when the fine tailings have
reached a solids content of about 30-35% and are commonly referred
to as fluid fine tailings (FFT) which typically contains about 2 wt
% bitumen.
[0004] Attempts to recover bitumen from the FFT have been largely
unsuccessful. Skimming bitumen from the tailings pond is no longer
practiced due to high operating costs and difficulties in dealing
with the froth produced. FFT may be processed for dewatering and
reclamation through decanter centrifuges, producing a cake and a
centrate (i.e., liquid stream). The centrate is usually recycled as
dilution water or discharged to the tailings pond. However,
centrate can have variable bitumen contents ranging from 0.01% to
1.9%. Higher centrate bitumen contents often result in slugs of
bitumen discharged from the centrifuges. These high bitumen
contents in centrate may cause problems for water systems during
recycle, bitumen accumulations in the centrifuge feed that
interfere with flocculation or cause mats of bitumen to form on the
surface of tailings ponds.
[0005] Accordingly, there is a need for an improved method to
remove residual bitumen from oil sands tailings centrifuge
centrate.
SUMMARY OF THE INVENTION
[0006] The current application is directed to a process for
removing residual bitumen from oil sands tailings, particularly
from centrate derived from centrifugation of the tailings. The
present invention is particularly useful with, but not limited to,
fluid fine tailings. It was surprisingly discovered that by
conducting the process of the present invention, one or more of the
following benefits may be realized:
[0007] (1) the centrate represents an easy stream to remove bitumen
due to having a relatively low solids content;
[0008] (2) the cleaned centrate may be recycled as centrifuge
dilution water, without build-up of bitumen mats or slugs which can
accumulate with time or in upset conditions; and
[0009] (3) if returned to the tailings pond, the cleaned centrate
results in less bitumen being deposited upon the surface of the
pond.
[0010] (4) the recovered bitumen has production value when returned
to the oil sand processing plant.
[0011] Thus, use of the present invention provides both
environmental and economic incentives for removing bitumen from the
centrate derived from centrifugation of oil sands tailings.
[0012] In one aspect, a process for removing residual bitumen from
oil sands tailings is provided, comprising: [0013] optionally
diluting the tailings with sufficient water to yield a tailings
feed having a solids content in the range of about 18 wt % to about
36 wt %; [0014] adding one or both of a coagulant and a flocculant
to the tailings feed to form a centrifuge feed; [0015] centrifuging
the centrifuge feed to produce a cake and a centrate having a
solids content of less than about 3 wt %; [0016] introducing the
centrate into a flotation device so that bitumen froth and cleaned
centrate are formed; [0017] recycling the cleaned centrate as
dilution water or discharging the cleaned centrate to a tailings
pond; and [0018] further processing the bitumen froth from the
flotation device. The bitumen froth may be processed either by
adding it to the primary extraction feed, or by treating it in a
new or existing froth treatment plant. In either case, the
flotation bitumen froth may be first pre-cleaned by gravity removal
of a portion of the free water phase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Referring to the drawings wherein like reference numerals
indicate similar parts throughout the several views, several
aspects of the present invention are illustrated by way of example,
and not by way of limitation, in detail in the figures,
wherein:
[0020] FIG. 1 is a schematic of one embodiment of the present
invention for removing bitumen from centrate produced from the
centrifugation of oil sands tailings.
[0021] FIG. 2 is a microscopic image of centrate froth showing the
water continuous phase at the top (dark area) and the bitumen
continuous phase at the bottom (fluorescence mode, 450-490 nm
incident light).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The detailed description set forth below in connection with
the appended drawings is intended as a description of various
embodiments of the present invention and is not intended to
represent the only embodiments contemplated by the inventor. The
detailed description includes specific details for the purpose of
providing a comprehensive understanding of the present invention.
However, it will be apparent to those skilled in the art that the
present invention may be practiced without these specific
details.
[0023] The present invention relates generally to a process for
removing residual bitumen from oil sands tailings, particularly
from centrate derived from centrifugation of the tailings. As used
herein, the term "tailings" means tailings derived from oil sands
extraction operations and containing a fines fraction. The term is
meant to include fluid fine tailings (FFT) from tailings ponds and
fine tailings from ongoing extraction operations (for example,
thickener underflow or froth treatment tailings) which may bypass a
tailings pond.
[0024] FIG. 1 is a flow diagram of the process of the present
invention. In one embodiment, the tailings are primarily FFT
obtained from tailings ponds. However, it should be understood that
the fine tailings treated according the process of the present
invention are not necessarily obtained from a tailings pond, and
may also be obtained from ongoing oil sands extraction
operations.
[0025] In a tailings pond, the tailings stream separates into an
upper water layer, a middle FFT layer, and a bottom layer of
settled solids. The FFT layer may be removed from between the water
layer and solids layer via a dredge or floating barge having a
submersible pump. The FFT may then be transported to a centrifuge
plant for processing.
[0026] The FFT 10 is optionally diluted with water within a
suitable vessel such as a tank. The source of water is preferably
tailings water. Seepage of tailings water may arise from sand dike
construction rather than from the pond, and can be stored in a
water tank for use in processing. Sufficient water is added to
achieve a centrifuge feed having a solids content in the range of
about 18 wt % to about 36 wt %, preferably greater than about 30 wt
%, for the most economic usage of the centrifuge equipment.
Dilution provides a consistent feed to the centrifuge to ensure
stable machine operation. Optionally, a coagulant is introduced
into the in-line flow of FFT prior to entering a mixer. As used
herein, the term "coagulant" refers to a reagent which neutralizes
repulsive electrical charges surrounding particles to destabilize
suspended solids and to cause the solids to coagulate. Suitable
coagulants include, but are not limited to, gypsum, lime, alum,
cationic polymers, or any combination thereof. In one embodiment,
the coagulant comprises gypsum or lime. As used herein, the term
"in-line flow" means a flow contained within a continuous fluid
transportation line such as a pipe or another fluid transport
structure which preferably has an enclosed tubular construction. In
one embodiment, the dosage of the coagulant ranges from about 300
grams to about 1,500 grams per Tonne of solids in the FFT.
[0027] The FFT is then pumped from the tank into a mixer.
Additional water and a flocculant are introduced into the in-line
flow of the FFT at a line prior to entering the mixer. The source
of water is preferably tailings water. As used herein, the term
"flocculant" refers to a reagent which reacts with the FFT solids
to form flocs and through rearrangement reactions increases the
strength of the flocculated FFT. Flocculants useful in the present
invention are generally anionic, nonionic, cationic or amphoteric
polymers, which may be naturally occurring or synthetic, having
relatively high molecular weights. Preferably, the polymeric
flocculants are characterized by molecular weights ranging between
about 1,000 kDa to about 50,000 kDa. Suitable natural polymeric
flocculants may be polysaccharides such as dextrin, starch or guar
gum. Suitable synthetic polymeric flocculants include, but are not
limited to, charged or uncharged polyacrylamides, for example, a
high molecular weight polyacrylamide-sodium polyacrylate co-polymer
having a medium charge density (about 20-35% anionicity).
[0028] Other useful polymeric flocculants can be made by the
polymerization of (meth)acrylamide, N-vinyl pyrrolidone, N-vinyl
formamide, N,N dimethylacrylamide, N-vinyl acetamide,
N-vinylpyridine, N-vinylimidazole, isopropyl acrylamide and
polyethylene glycol methacrylate, and one or more anionic
monomer(s) such as acrylic acid, methacrylic acid,
2-acrylamido-2-methylpropane sulphonic acid (ATBS) and salts
thereof, or one or more cationic monomer(s) such as
dimethylaminoethyl acrylate (ADAME), dimethylaminoethyl
methacrylate (MADAME), dimethydiallylammonium chloride (DADMAC),
acrylamido propyltrimethyl ammonium chloride (APTAC) and/or
methacrylamido propyltrimethyl ammonium chloride (MAPTAC). The
preferred flocculant may be selected according to the FFT
composition and process conditions.
[0029] The flocculant may be supplied from a flocculant make up
system for preparing, hydrating and dosing of the flocculant.
Flocculant make-up systems are well known in the art, and typically
include a mixing skid, one or more storage tanks, and a dosing
pump. The dosage of flocculant is controlled by a metering pump. In
one embodiment, the dosage of flocculant ranges from about 400
grams to about 1,500 grams per tonne of solids in the FFT. In one
embodiment, the flocculant is in the form of a 0.2-0.4%
solution.
[0030] The additional water is provided to disperse the flocculant
into the forward flow of the FFT for better flocculation. The FFT
and diluted flocculant are further combined within the mixer. The
flocculated FFT is mixed in a manner so as to avoid overshearing
which results in floc breakage and re-suspension of the fines
within the water. Suitable mixers include, but are not limited to,
simple pipe tee mixers, in-line static mixers, dynamic mixers, and
continuous stirred-tank reactors (CSTR's). Preferably, the mixer is
a tee mixer positioned before the feed tube of the centrifuge.
Alternatively, the diluted flocculant may bypass the mixer and be
fed directly through the feed tube of the centrifuge for addition
to the FFT.
[0031] At a centrifuge plant 12, the flocculated FFT is transferred
to a centrifuge for dewatering. In one embodiment, the centrifuge
is a solid bowl decanter centrifuge. The cake 14 is collected and
transported via a conveyor, pump or transport truck to a disposal
area where the cake is stacked to maximize dewatering by natural
processes.
[0032] In one embodiment, the centrate 16 has a solids content of
less than about 3 wt %. The centrate 16 is transferred to a
flotation device at a bitumen recovery plant 18 to recover as much
bitumen from the centrate as possible in the form of froth 20.
Bitumen recovery may be accomplished using various flotation
devices including, but not limited to, a gravity separator, a
mechanical flotation cell, a separator equipped with aeration
downpipes, a flotation column, or any combination thereof.
[0033] In one embodiment, the centrate 16 may be transferred to a
gravity separator to enable quiescent separation of the bitumen
from the centrate 16. A gravity separator typically includes a
shallow cone end and a rake at the bottom of the cone for further
concentrating the bitumen froth by releasing any entrapped solids
and water. Aeration of the centrate 16 promotes the attachment of
bitumen to air bubbles, creating a lower-density bitumen froth 20
which floats to the upper portion of the gravity separator. The
resulting bitumen froth 20 overflows the weir of the vessel into a
launder extending around the rim of the gravity separator for
removal for downstream processing.
[0034] In one embodiment, the centrate 16 may be transferred to a
mechanical flotation cell which typically includes a mixer and
diffuser mechanism at the bottom of the mixing tank to introduce
air and provide mixing action, thereby intensifying the aeration of
the bitumen droplets.
[0035] In one embodiment, the centrate 16 may be transferred to a
separator equipped with aeration downpipes which combines the
centrate 16 with air in a downpipe where high shear creates the
turbulent conditions required for aeration of the bitumen droplets.
The very high interfacial surface area and intense mixing result in
rapid bitumen attachment to the air bubbles.
[0036] In one embodiment, the centrate 16 may be transferred to a
flotation column which includes air spargers to introduce air at
the bottom of a tall column while introducing the centrate above.
The countercurrent motion of the centrate 16 flowing down and the
air flowing up provides mixing action to aerate the bitumen
droplets. Counter current froth washing with water may also be
employed to produce an enhanced froth quality.
[0037] As an optional enhancement to any of the bitumen flotation
embodiments, the flotation overflow may be cleaned by removal of a
significant portion of the free water phase, using a gravity-based
froth cleaner. This is done to reduce the impact of water and
solids from the free water phase on downstream processing. The
froth cleaner is usually a simple gravity separator, fed by the
flotation overflow stream, and producing a cleaned froth overflow
stream, and a water phase underflow stream, containing only small
amounts of bitumen, to be returned to tailings for disposal. In one
embodiment, the cleaned froth 20 contains 30-40% bitumen.
[0038] Following use of any one of the above flotation devices,
froth cleaners or the like, the bitumen froth 20 is withdrawn and
transferred to either the primary extraction feed, or directly to a
froth treatment plant 22. The bitumen which is present in the
bitumen froth 20 comprises both non-asphaltenic material and
asphaltenes. Froth treatment is the process of eliminating the
aqueous and solid contaminants from the bitumen froth 20 to produce
a clean bitumen product for downstream upgrading processes. The
bitumen froth 20 is diluted with a hydrocarbon solvent to reduce
the viscosity and density of the oil phase, thereby accelerating
the settling of any dispersed phase impurities by gravity or
centrifugation.
[0039] Either a paraffinic or naphthenic type diluent may be used.
Examples of paraffinic type diluents include C4 to C8 aliphatic
compounds and natural gas condensate, which typically contains
short-chained aliphatic compounds and may also contain small
amounts of aromatic compounds. Examples of naphthenic type diluents
include toluene (a light aromatic compound) and naphtha, which may
be comprised of both aromatic and non-aromatic compounds. The
difference in the bitumen produced by use of either a paraffinic or
naphthenic type diluent can be attributed largely to the presence
of aromatics. Aromatics have the ability to hold asphaltenes in
solution, whereas paraffinic type diluents cause asphaltene
precipitation.
[0040] Recovery of the hydrocarbon solvent from the diluted bitumen
component is typically conducted in a recovery unit before the
bitumen is delivered to a refinery for further processing.
[0041] The remaining bitumen-depleted, cleaned centrate 24 may be
either recycled as dilution water in the centrifugation process or
discharged back to the tailings pond 26.
[0042] Exemplary embodiments of the present invention are described
in the following Examples, which are set forth to aid in the
understanding of the invention, and should not be construed to
limit in any way the scope of the invention as defined in the
claims which follow thereafter.
EXAMPLE 1
[0043] In a first pilot test, centrate produced from the
centrifugation of fluid fine tailings was collected in open topped
rectangular tanks prior to discharge to a settling basin. The tanks
served as gravity separators, and the froth formed on top of the
centrate within the tanks. Samples of the froth were collected and
analyzed. The froth was found to contain 57% bitumen and 9% solids.
Without bitumen recovery, discharge of the centrate into the
Mildred Lake Settling Basin resulted in the formation of a large
visible mat of bitumen.
EXAMPLE 2
[0044] In a second pilot test, six samples of froth which formed in
the centrate tank of an Andritz A14 centrifuge were taken. The
analyses of the froth samples are set out in Table 1. The froth
samples had considerably poorer froth quality compared to the first
centrifuge pilot. The present FFT centrifuge prototype samples had
bitumen contents ranging from 8.5 wt % to 28.4 wt %, with solids
contents from 11.4 wt % up to 18.9 wt %.
TABLE-US-00001 TABLE 1 Date Sep. 28, Sep. 28, Sep. 28, Sep. 28,
Sep. 29, Sep. 29, 2011 2011 2011 2011 2011 2011 Time 10:23 13:40
15:28 16:55 14:57 15:49 Bitumen, wt % 11.7 17.0 15.8 8.5 22.7 28.4
Water, wt % 68.6 66.9 65.0 72.2 60.9 56.3 Solids, wt % 16.8 15.8
18.9 18.3 11.4 12.4 Solids <5.5 55.1 60.9 62.7 54.6 55.9 56.2
.mu.m, % Solids <44 96.5 97.8 98.3 96.9 96.3 96.4 .mu.m, %
Solids d50, 4.6 3.8 3.6 4.7 4.5 4.5 .mu.mm
[0045] As shown in FIG. 2, the froth samples were mostly
water-continuous. The bitumen continuous phase was found to have 30
vol % of degraded bitumen, with mostly dendrites and sheets ranging
from 100 .mu.m to 150 .mu.m. The bitumen continuous phase was also
found to contain a high amount of dispersed water droplets that
were less than 10 .mu.m in size. Both water continuous and bitumen
continuous phases were observed, with the dispersed water drops in
the bitumen continuous phase showing up as dark circles.
[0046] Further characterization tests were conducted on the bitumen
from the centrate froth samples (Table 2). The bitumen was
separated from the centrate froth samples using a combination of
Dean Stark extraction with toluene, followed by removal of the
toluene with the standard rotary evaporator method. The bitumen
asphaltenes and MCR characterization data fall within the range of
normally expected values.
TABLE-US-00002 TABLE 2 Date Sep. 28, Sep. 28, Sep. 28, Sep. 28,
Sep. 29, Sep. 29, 2011 2011 2011 2011 2011 2011 Time 10:23 13:40
15:28 16:55 14:57 15:49 Extraneous 0.3 0.3 0.2 0.2 0.5 0.5 Matter,
wt % C5 Asphaltene 15.1 15.3 15.0 13.8 16.2 16.6 Content, wt %
Micro-carbon 12.9 12.8 12.6 12.6 13.4 13.8 Residue, wt %
EXAMPLE 3
[0047] The centrate froth samples were also processed using the 1 G
and Cold Spin tests, as detailed below, to evaluate the simulated
froth treatment processability in inclined plate settler and
centrifuges.
[0048] Summary of Cold Spin Test
[0049] The cold spin test was performed as follows: [0050] Collect
a froth sample in a 250 ml jar, and add naphtha to achieve a
naphtha to bitumen ratio (N/B) of 0.7; [0051] Heat to 80.degree.
C., then mix for 10 minutes on a shaker table; [0052] Centrifuge
for 10 minutes at 2000 RPM; and [0053] Take a 1 gram sample of
hydrocarbon layer, and determine water content with a Karl Fischer
Titration.
[0054] Summary of a 1 G Test
[0055] The 1 G test was performed as follows: [0056] Collect a
froth sample in a 1 litre jar, and add naphtha to achieve a 0.7
N/B; [0057] Heat to 80.degree. C., then mix for 20 minutes on a
shaker table; [0058] Further mix with a baffled tank/impeller mixer
at 700 RPM for 10 minutes; [0059] Place the jar in a 80.degree. C.
water bath, and allow to settle for 2 hours; [0060] At 0, 1, 3, 5,
7, 10, 15, 20, 30, 60, 90, 120 minute marks, collect 1 gram
samples, and determine water contents with a Karl Fischer
Titration. The 1-G tests of the froth samples showed no froth
separation at all, possibly due to the high water and emulsion
content of the centrate froth samples. In the Cold Spin tests, it
was found that an average of 1% water remaining in the diluted
bitumen, which falls within the range of 1% to 2% expected for
normally separating froths (Table 3). The water content in the
diluted bitumen samples ranged from 0.25% to 3%. The tests indicate
that the froth would likely be difficult to process in the inclined
plate settlers, but may be treatable with a centrifuge-based froth
treatment process with naphtha dilution. This behavior is
consistent with the 30% degraded bitumen observed in the microscopy
evaluations.
TABLE-US-00003 [0060] TABLE 3 Date Sep. 28, Sep. 28, Sep. 28, Sep.
28, Sep. 29, Sep. 29, 2011 2011 2011 2011 2011 2011 Time 10:23
13:40 15:28 16:55 14:57 15:49 Cold Spin 0.88 0.73 0.65 0.95 0.65
1.13 Test Actual Naphtha/ Bitumen Ratio Cold Spin 0.8 0.47 0.56
0.25 3.01 1.1 Water in Diluted Bitumen, wt %
EXAMPLE 4
[0061] During the second pilot test, nine 1 m.sup.3 totes of FFT
centrifuge centrate were collected for evaluation in a test loop.
The centrate was circulated through a flow loop through an aerator,
and transferred to an open topped tank where froth was removed.
Three tests were performed, one with "normal" centrate and two with
"off-spec" centrate containing a higher amount of solids and
bitumen. Samples were collected for analysis, and a complete
material balance was performed and shown in Table 4. These results
indicate that the froth qualities are very "lean" at less than 10%
bitumen content, potentially indicating the need for froth cleaning
(i.e. removal of the free water phase) prior to further processing.
Recovery of centrate bitumen is expected to have its highest
production potential during periods of "off-spec" FFT centrifuge
operation, when the centrate contains more bitumen
TABLE-US-00004 TABLE 4 Mass balances of centrate bitumen flotation
tests Bitumen Water Solids Bitumen Water Solids Test# Centrate Name
Content % Content % Content % Recovery % Recovery % Recovery % CC-1
off-spec Feed 0.99 90.55 8.45 100.00% 100.00% 100.00% Froth 4.32
85.55 10.14 36.60% 7.95% 10.09% Free bitumen 13.02 76.81 10.17
0.41% 0.03% 0.04% Tailings 0.68 91.02 8.30 62.99% 92.02% 89.87%
CC-2 off-spec Feed 1.02 91.44 7.54 100.00% 100.00% 100.00% Froth
4.94 84.96 10.11 43.82% 8.41% 12.14% Free bitumen 7.41 82.86 9.73
0.12% 0.02% 0.02% Tailings 0.63 92.09 7.28 56.06% 91.58% 87.84%
CC-3 on-spec Feed 0.06 99.66 0.28 100.00% 100.00% 100.00% Froth
7.31 80.14 12.55 45.17% 0.30% 16.70% Free bitumen 5.16 90.64 4.20
0.47% 0.01% 0.08% Tailings 0.03 99.73 0.24 54.36% 99.69% 83.21%
[0062] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention,
and without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions. Thus, the present invention is not
intended to be limited to the embodiments shown herein, but is to
be accorded the full scope consistent with the claims, wherein
reference to an element in the singular, such as by use of the
article "a" or "an" is not intended to mean "one and only one"
unless specifically so stated, but rather "one or more". All
structural and functional equivalents to the elements of the
various embodiments described throughout the disclosure that are
known or later come to be known to those of ordinary skill in the
art are intended to be encompassed by the elements of the claims.
Moreover, nothing disclosed herein is intended to be dedicated to
the public regardless of whether such disclosure is explicitly
recited in the claims.
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