U.S. patent application number 14/722928 was filed with the patent office on 2016-12-01 for fungible bitumen from paraffinic centrifugation.
The applicant listed for this patent is SYNCRUDE CANADA LTD. in trust for the owners of the Syncrude Project as such owners exist now and. Invention is credited to DANIEL JOHN BULBUC, DAVID HAROLD CHILDS, THADDEUS EUGENE KIZIOR, CRAIG McKNIGHT.
Application Number | 20160348008 14/722928 |
Document ID | / |
Family ID | 57397185 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160348008 |
Kind Code |
A1 |
BULBUC; DANIEL JOHN ; et
al. |
December 1, 2016 |
FUNGIBLE BITUMEN FROM PARAFFINIC CENTRIFUGATION
Abstract
A process for cleaning bitumen froth produced from an oil sands
extraction process involves mixing a sufficient amount of
paraffinic solvent with the bitumen froth; subjecting the resulting
mixture to centrifugal separation in a centrifuge to yield a
diluted bitumen product, a water byproduct stream, and a solids
byproduct stream; and processing the diluted bitumen product to
yield dry fungible bitumen product having a total water/solids
content less than about 0.5 wt %, and a recyclable paraffinic
diluent stream.
Inventors: |
BULBUC; DANIEL JOHN;
(Sherwood Park, CA) ; McKNIGHT; CRAIG; (Sherwood
Park, CA) ; KIZIOR; THADDEUS EUGENE; (Spruce Grove,
CA) ; CHILDS; DAVID HAROLD; (Edmonton, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SYNCRUDE CANADA LTD. in trust for the owners of the Syncrude
Project as such owners exist now and |
Fort McMurray |
|
CA |
|
|
Family ID: |
57397185 |
Appl. No.: |
14/722928 |
Filed: |
May 27, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 33/06 20130101;
C10G 1/045 20130101; C10G 1/047 20130101; C10G 2300/208 20130101;
C10G 2300/206 20130101; C10G 1/002 20130101; C10G 2300/308
20130101 |
International
Class: |
C10G 1/04 20060101
C10G001/04; C10J 3/46 20060101 C10J003/46; C10G 1/00 20060101
C10G001/00 |
Claims
1. A process for cleaning bitumen froth produced from an oil sands
extraction process, comprising: a) mixing a sufficient amount of
paraffinic solvent with the bitumen froth; b) subjecting the
resulting mixture to centrifugal separation in a centrifuge to
yield a diluted bitumen product, a water byproduct stream, and a
solids byproduct stream; and c) processing the diluted bitumen
product to yield dry fungible bitumen product having a total
water/solids content less than about 0.5 wt %, and a recyclable
paraffinic diluent stream.
2. The process of claim 1, wherein the centrifuge is a decanter
centrifuge.
3. The process of claim 1, further comprising processing the water
byproduct stream to recover residual bitumen and paraffinic
solvent.
4. The process of claim 3, further comprising processing the solids
byproduct stream to prepare a dry granulated powder comprising
asphaltenes and fine solids.
5. The process of claim 4, comprising optionally, mixing a
sufficient amount of the asphaltenes with the bitumen froth
following addition of the paraffinic solvent in step (a).
6. The process of claim 5, comprising optionally, subjecting the
resulting mixture to mixing in a contactor prior to centrifugal
separation in step (b).
7. The process of claim 1, wherein centrifugal separation is
conducted using a three-phrase decanter centrifuge.
8. The process of claim 7, wherein the diluted bitumen product
comprises bitumen, paraffinic solvent, and a water plus solids
content that is less than about 0.5 wt %.
9. The process of claim 8, wherein the diluted bitumen product is
transferred from the decanter centrifuge to a diluent recovery unit
for recovery of dry bitumen, light gas oil, and paraffinic
solvent.
10. The process of claim 9, wherein the dry bitumen has a total
water/solids content less than about 0.5 wt % amenable to
processing in a fluid coker or ebullating-bed hydrocracker, or to
shipping as fungible bitumen.
11. The process of claim 9, wherein the light gas oil is
transferred to a hydroprocessing unit.
12. The process of claim 9, wherein the paraffinic solvent is
recycled in step (a).
13. The process of claim 9, wherein the water byproduct stream
comprises water, and residual hydrocarbon, paraffinic solvent, and
fine solids.
14. The process of claim 13, wherein the water byproduct stream is
cleaned in a solvent recovery unit to yield a paraffinic solvent
stream for recycling in step (a), and a separate water and fine
solids stream for disposal in a tailings pond.
15. The process of claim 14, wherein optionally, the water
byproduct stream is passed through a disc stack centrifuge to
recover residual hydrocarbon and paraffinic solvent before cleanup
in the solvent recovery unit.
16. The process of claim 15, wherein the residual hydrocarbon is
mixed with the diluted bitumen product and transferred to the
diluent recovery unit.
17. The process of claim 16, wherein the residual paraffinic
solvent is recovered in the solvent recovery unit.
18. The process of claim 17, wherein the solids byproduct stream
comprises asphaltenes, coarse and fine solids, residual paraffinic
solvent, and hydrocarbon.
19. The process of claim 18, wherein the solids byproduct stream is
mixed with water and transferred to a flotation cell for separation
of an overflow hydrocarbon-rich with fine solids stream and an
underflow stream of clean coarse solids.
20. The process of claim 19, wherein the hydrocarbon-rich with fine
solids stream is mixed with paraffinic solvent and spray dried to
yield dry granulated powder comprising asphaltenes and fine
solids.
21. The process of claim 20, wherein the powder is mixed with
bitumen, heated, and thermally upgraded in a fluid bed or delayed
coker.
22. The process of claim 20, wherein the powder is converted into a
syngas in a fluidized bed gasifier or fluid bed boiler.
23. The process of claim 20, wherein the powder is used as a fuel
for a utility boiler or stockpiled as an energy supply.
24. The process of claim 20, wherein flashed overhead vapour
comprising paraffinic solvent and water is condensed in an OVH
condenser and decanter to separate the paraffinic solvent from the
water.
25. The process of claim 24, wherein the paraffinic solvent is
recycled in step (a).
26. The process of claim 24, wherein optionally, the water passes
through the solvent recovery unit for recovery of residual
paraffinic solvent before disposal in the tailings pond.
27. The process of claim 1, wherein the ratio of paraffinic solvent
to raw froth by weight percentage ranges from about 0.5 to about
4.5.
28. The process of claim 2, wherein the decanter centrifuge is
operated to generate a g-force ranging from about 1000 to about
5000.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to a paraffinic
bitumen froth treatment process using centrifugation to produce a
fungible bitumen product.
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.
Oil sands processing involves extraction and froth treatment to
produce diluted bitumen which is further processed to produce
synthetic crude oil and other valuable commodities. Extraction is
typically conducted by mixing the oil sand in hot water and
aerating the resultant slurry to promote the attachment of bitumen
to air bubbles, creating a lower-density bitumen froth which floats
and can be recovered in a separator such as a gravity separator or
cyclonic separator. Bitumen froth may contain about 60 wt %
bitumen, about 30 wt % water and about 10 wt % solid mineral
material, of which a large proportion is fine mineral material. The
bitumen which is present in a bitumen froth comprises both
non-asphaltenic material and asphaltenes.
[0003] Froth treatment is the process of significantly reducing the
aqueous and solid contaminants from the bitumen froth to produce a
clean diluted bitumen product (i.e., "diluted bitumen" or "dilbit")
which can be further processed to produce a fungible bitumen
product that can be sold or processed in downstream upgrading
units. It has been conventional to dilute this bitumen froth with a
hydrocarbon solvent to reduce the viscosity and density of the oil
phase, thereby accelerating the settling of the dispersed phase
impurities by gravity or centrifugation. This diluted bitumen froth
is commonly referred to as "dilfroth." It is desirable to "clean"
dilfroth, as both the water and solids pose fouling, corrosion and
erosion problems in upgrading refineries.
[0004] Either a paraffinic or naphthenic type diluent may be used.
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 in naphthenic-type diluents. Aromatics
have the ability to hold asphaltenes in solution, whereas
paraffinic type diluents cause asphaltene precipitation. The use of
naphthenic type diluents results in a relatively high bitumen
recovery (generally greater than about 98%), but in a diluted
bitumen product which has relatively high water (about 2 to 4 wt %)
and solids (about 0.5 to 1.0 wt %) concentrations. The combined
water and solids concentration typically is greater than about 2.5
wt %. Due to the level of contamination, which pose fouling,
corrosion and erosion problems, the diluted bitumen is not suitable
for direct pipelining to conventional refineries, cannot be sold to
the open market, and must be upgraded using processes such as a
coker or hydroprocessing. The upgraded products are then
hydrotreated to produce synthetic crude oil.
[0005] Use of paraffinic type diluents results in a relatively
lower overall bitumen recovery (generally about 90%), but in a
bitumen product which is dry, light, and has a relatively low total
water and solids concentration (less than about 0.5 wt %). However,
paraffinic type diluents precipitate a major proportion of
asphaltenes from the bitumen froth, resulting in not only the
trapping of water and solids by the asphaltenes, but also high
asphaltenic hydrocarbon losses (about 8%) to froth treatment
tailings. There are both environmental incentives and economic
incentives for recovering all or a portion of this residual
asphaltenic hydrocarbon.
[0006] To separate the bitumen from water and solids,
naphtha-treated bitumen froth is commonly subjected to 1 g gravity
separation in inclined plate separators in series with high g
centrifugation. Paraffinic-treated bitumen froth is typically
subjected to phase separation and 1 g gravity separation, with
sufficient space needed to accommodate large gravity separation
vessels.
[0007] However, treatment processes using a naphthenic type diluent
may still result in bitumen often containing undesirable amounts of
solids and water. Product solids lead to increased wear of
downstream equipment, higher maintenance costs, and unplanned
capacity losses and outages. In addition, hydrocarbon may also be
lost to tailings due to inefficient separation. Recovery of the
solvent from the diluted bitumen product is required before the dry
fungible bitumen may be delivered to a refinery for further
processing.
[0008] Solvent and precipitated asphaltenes may also be lost to the
tailings. Since the rejected asphaltenes (7-8 wt % of the original
bitumen in froth) can be used as fuel or feedstock for various
applications, the disposal of asphaltenes in the tailings pond is
wasteful. Recovery of solvent is desirable to avoid discarding
flammable, carcinogenic solvent in a tailings pond and to minimize
expenditures for fresh solvent.
[0009] Accordingly, there is a need for a method of improving the
quality of diluted bitumen product in bitumen froth treatment
processes.
SUMMARY OF THE INVENTION
[0010] The present invention relates generally to a paraffinic
bitumen froth treatment process using a decanter centrifuge to
produce a fungible bitumen product. It was surprisingly discovered
that by using the process of the present invention, one or more of
the following benefits may be realized:
[0011] (1) The paraffinic bitumen froth treatment process of the
present invention uses a decanter centrifuge to produce a fungible
bitumen product amenable to downstream upgrading processes. Since a
decanter centrifuge is used rather than multiple large gravity
separation vessels, plot space requirements are reduced by about
70% and capital costs by about 50%.
[0012] (2) The hydrocarbon and fine solids loading on the tailings
pond from froth treatment is reduced since the decanter centrifuge
solids byproduct stream can be further processed in a flotation
cell to recover asphaltenic hydrocarbon and fine solids.
[0013] (3) Precipitated asphaltenes in the form of a dry granulated
powder are recovered and recycled at particular steps within the
process for use as feedstock or fuel for various applications
rather than being lost to tailings. This processable asphaltene
byproduct may yield a saleable hydrocarbon liquid stream at a yield
of about 40%.
[0014] (4) By recovering this asphaltenic hydrocarbon, diluent
losses are reduced by about 20%. Recovery and recycling of
paraffinic solvent at multiple steps within the process minimizes
expenditures for fresh solvent makeup and reduces the losses of
flammable, carcinogenic solvent in a tailings pond.
[0015] Thus, broadly stated, in one aspect of the present
invention, a process for cleaning bitumen froth produced from an
oil sands extraction process is provided, comprising: [0016] mixing
a sufficient amount of paraffinic solvent with the bitumen froth;
[0017] subjecting the resulting mixture to centrifugal separation
in a centrifuge to yield a diluted bitumen product, a water
byproduct stream, and a solids byproduct stream; and [0018]
processing the diluted bitumen product to yield dry fungible
bitumen product having a total water/solids content less than about
0.5 wt %, and a recyclable paraffinic diluent stream.
[0019] In one embodiment, the ratio of paraffinic solvent to raw
froth by weight percentage ranges from about 0.5 to about 4.5.
[0020] In one embodiment, the centrifuge is a decanter centrifuge.
In one embodiment, the decanter centrifuge is operated to generate
a g-force ranging from about 1000 to about 5000.
[0021] In one embodiment, the process further comprises processing
the water byproduct stream to recover residual bitumen and
paraffinic solvent.
[0022] In one embodiment, the process further comprises processing
the solids byproduct stream to prepare a dry granulated powder
comprising asphaltenes and fine solids.
[0023] For the purposes of the present invention, the term
"fungible bitumen" is defined as a bitumen product wherein the sum
of water and solids content is less than about 0.5 vol % to allow
the hydrocarbon product to be able to be shipped down a pipeline to
a conventional refinery.
[0024] The term "high g" decanter centrifuge is defined as a
decanter centrifuge which is operated to generate a g-force ranging
from about 1000 to about 5000.
[0025] Additional aspects and advantages of the present invention
will be apparent in view of the description, which follows. It
should be understood, however, that the detailed description and
the specific examples, while indicating preferred embodiments of
the invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention will now be described by way of an exemplary
embodiment with reference to the accompanying simplified,
diagrammatic, not-to-scale drawing:
[0027] FIG. 1 is a schematic process flow diagram of an embodiment
of the present invention for froth treatment.
[0028] FIG. 2 is a graph showing the product composition (volume
(ml) of heavy phase, light phase, and solids) as a function of spin
time (min at 1500 RPM).
[0029] FIG. 3 is a graph showing the product composition (volume
(ml) of heavy phase, light phase, and solids) as a function of spin
time (min at 1500 RPM) for two-phase (dashed line) and three-phase
(solid line) decanter centrifuges.
[0030] FIG. 4 is a graph showing the water concentration (wt %) in
the product light phase as a function of spin time (min at 1500
RPM).
[0031] FIGS. 5A-D are photographs of centrifuged paraffinic solids
with diluent to bitumen (D/B, by wt %) ratios ranging from about
1.8 to about 4.5 un-kneaded (left panel) and kneaded (right
panel).
[0032] FIG. 6 is a photograph of kneaded naphthenic cake from a
decanter centrifuge.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0033] The detailed description set forth below in connection with
the appended drawing 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 practised without these specific
details.
[0034] The present invention relates generally to a paraffinic
bitumen froth treatment process using a high g decanter centrifuge
to produce a fungible bitumen product amenable to downstream
upgrading processes. To meet specification requirements, the
fungible bitumen product must have a total water and solids
concentration of less than about 0.5 vol %.
[0035] FIG. 1 is a general schematic of a centrifuge-based froth
treatment process using centrifuges, which can be used in one
embodiment of the present invention. As used herein, the term
"centrifuge-based" process refers to an operation in which bitumen
is separated from water and solids using centrifugal acceleration
resulting from rotational movement of a suitable apparatus. In one
embodiment of the present invention, the apparatus is a decanter
centrifuge. The process generally includes three pathways yielding
one fungible bitumen product and two byproducts (contaminated water
stream and concentrated solids stream).
[0036] In the process of the invention shown in FIG. 1, raw froth
10 is used as the feed. Raw froth 10 is initially received from an
extraction facility which extracts bitumen from oil sand using a
water extraction process known in the art. The raw froth 10, as
received, typically comprises about 60% bitumen, about 30% water
and about 10% solids, and thus, needs to be further cleaned prior
to upgrading. The raw froth 10 is pumped via froth pump 12 into
line 14. Generally, bitumen froth is deaerated in deaeration
devices known in the art prior to pumping.
[0037] A diluent 16 is introduced via pump 18 into the in-line flow
of raw froth 10. As used herein, the term "in-line" flow means a
flow contained within a continuous fluid transportation line such
as a pipe or other fluid transport structure which preferably has
an enclosed tubular construction. In one embodiment, the diluent 16
is a paraffinic solvent. As used herein, the term "paraffinic
solvent" (also known as aliphatic) means solvents containing normal
paraffins, isoparaffins and blends thereof in amounts greater than
50 wt %. Presence of other components such as olefins, aromatics or
naphthenes counteract the function of the paraffinic solvent and
hence should not be present more than 1 to 20 wt % combined and
preferably, no more than 3 wt % is present. The paraffinic solvent
may be a C4 to C20 paraffinic hydrocarbon solvent or any
combination of iso and normal components thereof. In one
embodiment, the ratio of paraffinic solvent to raw froth (by wt %)
ranges from about 0.5 to about 4.5.
[0038] Optionally, asphaltenes 20 in particulate form (i.e.,
asphaltene scavenger seed) may also be introduced via pump 22 into
the in-line flow of raw froth 10 following addition of the diluent
16. As used herein, the term "asphaltenes" means hydrocarbons,
which are the n-heptane insoluble, toluene soluble component of a
carbonaceous material such as crude oil, bitumen or coal.
Generally, asphaltenes have a density of from about 0.8 grams per
cubic centimeter (g/cc) to about 1.2 g/cc. Asphaltenes are
primarily comprised of carbon, hydrogen, nitrogen, oxygen, and
sulfur as well as trace vanadium and nickel. The carbon to hydrogen
ratio is approximately 1:1.2, depending on the source.
[0039] The mixture of raw froth 10, diluent 16, and/or asphaltenes
20 may then bypass or optionally, pass through a contactor 24
before being subjected to centrifugal separation. Mixing is
conducted for a sufficient duration in order to allow the raw froth
10, diluent 16, and/or asphaltenes 20 to combine properly. Mixer
settlers or columns are commonplace in the art and are exemplified
by apparatuses including, but not limited to, stirred liquid-liquid
extraction columns such as, for example, rotating disc contactors
and the like. In one embodiment, the rotating disc contactor 24 is
a mechanically agitated column which separates components of a
mixture by adding to the mixture a suitable liquid solvent which
dissolves or dilutes one or more components of the mixture, thereby
facilitating their separation.
[0040] The mixture of raw froth 10, diluent 16, and/or asphaltenes
20 is subjected to centrifugal separation to yield a product stream
comprising a diluted bitumen product 26 in line 36; and two
byproduct streams, one comprising a separate water byproduct stream
contaminated with trace diluent and hydrocarbon 28 in line 58; and
the other comprising a solids byproduct stream 30 (sands, clays,
asphaltenes) in line 80. In one embodiment, centrifugal separation
is conducted using a three-phrase decanter centrifuge 32.
[0041] The operation of three-phase decanter centrifuges is
commonly known to those skilled in the art and will not be
discussed in detail. Briefly, the three-phase decanter centrifuge
32 separates solids and two liquid streams from a mixture thereof.
The three-phase decanter centrifuge 32 comprises an elongated bowl
mounted for rotation along its longitudinal axis. A helical screw
conveyor is coaxially mounted within the bowl. A back drive
features a direct drive gearbox for automatically controlling the
differential speed between the bowl and the conveyor in order to
maintain a balance between liquid clarity and solids dryness,
irrespective of variations in the feed mixture. Since the bowl and
conveyor are caused to rotate at controlled different, speeds,
solids sedimented against the bowl wall are conveyed along the
inner annular surface thereof to solids discharge openings provided
at the tapered end of the bowl. The clarified liquid from which the
solids have been removed is decanted into a chamber where two
liquid phases with different specific gravities (e.g., a heavy
liquid phase, a light liquid phase) may be separated. The liquids
are separated in the liquid zone and decanted through separate
discharge systems to prevent cross-contamination. In one
embodiment, the three-phase decanter centrifuge 32 is operated to
generate a g-force ranging from about 1000 to about 5000.
[0042] The product stream comprises the diluted bitumen product 26
which contains bitumen, diluent, and trace amounts of residual
water and solids (possibly less than about 0.5 wt % total). The
diluted bitumen product 26 is transferred from the decanter
centrifuge 32 to a diluent recovery unit ("DRU") 34 via line 36.
Diluent 38 is recovered from the DRU 34 via line 40, and
transferred to line 42 where it can be combined with make-up
diluent 43 and/or diluent 16.
[0043] The bitumen product ("dry bitumen") 44 free of water and
mineral matter is recovered from the DRU 34 via line 46. As used
herein, the term "dry bitumen" refers to dry or fungible bitumen
having a solids content less than about 0.5 wt %. The dry bitumen
44 is transferred to either a storage unit 48 to be stockpiled for
future use, a unit 49 for direct sale, or a fluid coker or
ebullating-bed hydrocracker ("LC-Finer") 50 for further processing
into a synthetic crude oil product by means not shown but disclosed
in the art. In general, fluid cokers upgrade heavy hydrocarbons to
lighter products by removing carbon by thermal cracking. LC-Finers
upgrade hydrocarbons in an ebullating catalyst bed by adding
hydrogen in a hydroprocessing reaction. Virgin light gas oil
("LGO") 52 is recovered from the DRU 34 via line 54, and further
processed in downstream hydroprocessing units 56.
[0044] The water byproduct stream 28 comprises water, and residual
hydrocarbon, diluent, and fine solids. The water stream 28 exits
the decanter centrifuge 32 through line 58 and may then bypass or
optionally, pass through a high speed disc stack centrifuge 60
before being subjected to a final cleanup in a solvent recovery
unit ("SRU") 62. The disc stack centrifuge 60 may be used in the
event that the water stream 28 contains a significant amount of
bitumen, light hydrocarbon, and solids.
[0045] The operation of disk stack centrifuges is commonly known to
those skilled in the art and will not be discussed in detail.
Briefly, the disc stack centrifuge 60 separates bitumen from water
and solids using extremely high centrifugal forces. When the heavy
phase (i.e., water and solids) is subjected to such forces, the
water and solids are forced outwards against the periphery of the
rotating centrifuge bowl, while the lighter phases (i.e.,
hydrocarbon) forms concentric inner layers within the bowl. Plates
(i.e., the disc stack) provide additional surface settling area,
which contributes to speeding up separation. The bitumen and
diluent 64 is transferred from the disc stack centrifuge 60 to the
DRU 34 via line 66 for separation and processing as previously
described.
[0046] The water and residual diluent having residual hydrocarbon
contaminants (nozzle plus heavy phase water) 68 is transferred from
the disc stack centrifuge 60 to the SRU 62 via line 70. The SRU 62
separates the residual diluent from the water and fine solids by
steam stripping to produce a diluent stream 72 which may be
combined with diluent 16 prior to addition to the froth feed 10 in
line 14. The SRU 62 also produces a water and fine solids stream 74
which is disposed via pump 76 to a tailings pond 78.
[0047] The solids stream 30 comprises asphaltenes, coarse and fine
solids, residual diluent, and hydrocarbon. The solids stream 30 is
slurried with hot water upon exiting the decanter centrifuge 32
through line 80 and enters a flotation cell 82 for separation of an
overflow hydrocarbon rich with fine solids stream 84 and an
underflow stream of clean coarse solids 86. The hydrocarbon rich
with fine solids stream 84 is treated with diluent 88 in line 90
before being further combined in a mixer 92 and transferred to a
spray drier 94 which uses nitrogen 96 as the hot gas for drying.
Within the spray drier 94, the asphaltene-diluent mixture is pumped
through high delta P atomizing nozzles to form a spray pattern of
fine droplets. As these droplets form, any diluent is flashed off,
leaving behind asphaltenes and fine solids in the form of dry
granulated powdered solids 98 at the bottom of the spray drier 94.
The solids 98 may be transferred to a storage unit 100 to be
stockpiled for various future uses.
[0048] In one embodiment, the solids 98 may be combined with
diluent 110 prior to addition to the froth feed 10 in line 14
(i.e., as asphaltene scavenger seed 20). The diluent 110 can be a
combination of water with paraffinic or aromatic diluent.
[0049] In one embodiment, the solids 98 may be combined with
bitumen 112 in a mixer 114, heated in a heater 116, and thermally
upgraded in a fluid bed or delayed coker 118.
[0050] In one embodiment, the solids 98 may be injected into a
fluidized bed gasifier or fluid bed boiler 120 which converts the
solids 98 into a syngas which can be further processed to produce a
synthetic natural gas or to produce liquid fuels.
[0051] In one embodiment, the solids 98 may be used as fuel for
utility boilers which convert water into steam for electricity
generation and process applications.
[0052] In one embodiment, the solids 98 may be directed to a land
storage facility 122 to be stockpiled for future use as an energy
supply.
[0053] The flashed overhead vapour comprising diluent and water 124
is condensed in an overhead exchanger system comprising an OVH
condenser 126 and decanter 128 to separate the diluent 130 from the
water 132. The diluent 130 is transferred via pump 134 into line
136 which connects with line 42 going to the diluent storage tank
16. The diluent 130 may be combined with diluent 72 from the SRU 62
prior to routing to the diluent storage tank 16. The water 132 may
bypass or optionally, be pumped via pump 138 to pass through the
SRU 62 for recovery of any residual diluent before disposal in the
tailings pond 78.
Example 1
[0054] Experiments were conducted to investigate the ability of a
three-phase decanter centrifuge to separate a light phase product
having a water content below about 2.0 wt % from naphthenic diluted
froth. To mimic separation in a decanter centrifuge, a benchtop
Hotspin.TM. centrifuge was run at particular speeds and spin times.
Samples of naphthenic diluted froth contained bitumen (44 wt %),
naphtha (26 wt %), water (22 wt %), and solids (8 wt %), with the
N:B ratio being about 0.6. The samples were maintained at
80.degree. C. and spun at 1500 rpm for 1, 2, 4, and 8 mins. Two
samples were prepared for each spin time. The reported values are
the average values between the two samples at each spin time.
[0055] Three distinguishable interfaces between light phase, heavy
phase and solids were achieved in each sample after each
centrifugation interval. The separated heavy phase became less
turbid when spun longer, while the overall combined volume of heavy
phase and solids remained relatively constant. FIG. 2 shows the
volumes of each of the three phases in the samples. The volume of
the light phase remained relatively constant with increasing spin
times. For each spin time, the volume of light phase was about 77%
of the total volume. In contrast, the volume of solids increased
with longer spin times up to 4 min, after which the samples
stabilized. Increasing the residence time appeared to aid in
clarifying the heavy phase since its turbidity decreased with spin
time. The fact that the light phase volume remained constant with
spin time is of interest when comparing the operation of a
two-phase decanter to that of a three-phase decanter. A two-phase
decanter separates only the solids from the liquid phase, meaning
that the product is a combination of the light phase and heavy
phase. In contrast, a three-phase decanter separates all three
phases independently.
[0056] FIG. 3 shows the product composition (volume (ml) of heavy
phase, light phase, and solids) as a function of spin time (min at
1500 RPM) expected using two-phase (dashed line) and three-phase
(solid line) decanter centrifuges. Given that the residence time in
a centrifuge is a function of feed rate, the product from the
two-phase decanter centrifuge has a higher solids and water content
at higher feed rates. In contrast, the product from the three-phase
decanter centrifuge is independent of feed rate, implying that the
three-phase decanter centrifuge may produce a more consistent
product over a wider feed rate envelope compared to a two-phase
decanter centrifuge.
[0057] The amount of water present in the separated light phase was
measured using Karl Fisher titration. The water content (wt %) in
the light phase after the tested spin times (min at 1500 RPM) is
shown in FIG. 4. While the bulk of the light phase separated
immediately, the water content continued to decrease with
increasing spin times. The water concentration in the light phase
was below the standard froth treatment water specification of about
2.0 wt % after only one minute of spin time. In comparison, the
water content for a two-phase decanter is substantially higher
since the heavy phase (water) is not separated from the light
phase.
[0058] With use of a three-phase decanter centrifuge, the light
phase of the froth separated from the heavy phase and solids
relatively quickly, while the solids separated from the heavy phase
over a longer time frame. After initial separation, the water
content of the light phase was less than about 2.0 wt %.
Volumetrically, a significant amount of the solids were removed
from the light phase. Based on these results, a three-phase
decanter centrifuge is suitable for producing a light phase which
meets froth treatment product specifications of less than about 2.0
wt % water.
Example 2
[0059] An experiment was conducted to assess the feasibility of a
three-phase decanter centrifuge to convey separated solids in a
paraffinic diluted froth treatment process. Pentane
(C.sub.5H.sub.12) and undiluted froth were mixed in diluent to
bitumen (D/B) ratios of about 1.8, 2.8, 3.5, and 4.5 by weight.
These samples were poured into 8 oz jars and cold spun (room
temperature) for 20 minutes at about 2,000 RPM. After spinning in
the centrifuge, the liquid phase was poured out leaving only the
solids. FIGS. 5A-D show these solids at the various D/B ratios
before and after kneading with a lab spoon to simulate conveyance
in a decanter centrifuge. For comparison, kneaded naphthenic cake
is shown in FIG. 6. For each solid, the relative cohesive property,
adhesion to the beaker and lab spoon, and shear strength were
inspected.
[0060] It was expected that separating paraffinic solids trapped in
viscous medium might be challenging in a decanter centrifuge.
However, it was observed that the paraffinic solids became more
brittle and lost their cohesive or gummy texture with increasing
D/B ratios (FIGS. 5A-D) in comparison to the naphthenic solids
which were more cohesive and gummy (FIG. 6). These preliminary
observations indicate suitability of a paraffinic solvent to froth
ratio in the range of about 1.8 to about 4.5 by weight, and that
the conveyability of the paraffinic solids may be comparable to the
conveyability of the naphthenic solids processed by decanter
centrifuges in froth treatment.
[0061] 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.
REFERENCES
[0062] All publications mentioned herein are incorporated herein by
reference (where permitted) to disclose and describe the methods
and/or materials in connection with which the publications are
cited. The publications discussed herein are provided solely for
their disclosure prior to the filing date of the present
application. Nothing herein is to be construed as an admission that
the present invention is not entitled to antedate such publication
by virtue of prior invention. Further, the dates of publication
provided may be different from the actual publication dates, which
may need to be independently confirmed. [0063] Hassan, A.; Hassan,
A.; Viswanathan, K.; Borsinger, G. G.; Anthony, R. G. Bitumen
extraction and asphaltene removal from heavy crude using high
shear. United States Patent Application Publication No. US
2011/0266198, published Nov. 3, 2011. [0064] Tipman, R.; Long, Y.;
and Shelfantook, W. E. Solvent process for bitumen separation from
oil sands froth. Canadian Patent No. 2,149,737, issued Mar. 2,
1999; U.S. Pat. No. 5,876,592, issued Mar. 2, 1999; Canadian Patent
No. 2,217,300, issued Aug. 20, 2002; U.S. Pat. No. 6,214,213,
issued Apr. 10, 2001.
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