U.S. patent application number 15/165865 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 | 20160348010 15/165865 |
Document ID | / |
Family ID | 57399650 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160348010 |
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: |
57399650 |
Appl. No.: |
15/165865 |
Filed: |
May 26, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 1/045 20130101 |
International
Class: |
C10G 31/10 20060101
C10G031/10; C10G 29/20 20060101 C10G029/20; C10G 33/06 20060101
C10G033/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2015 |
CA |
2893148 |
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 a first portion of the bitumen froth; b)
subjecting the resulting first mixture to centrifugal separation in
a centrifuge to yield a first 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 1, 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.
12. The process of claim 1, wherein the solids byproduct stream
comprises asphaltenes, coarse and fine solids, residual paraffinic
solvent, and hydrocarbon.
13. The process of claim 12, 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.
14. The process of claim 13, 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.
15. The process of claim 14, wherein the powder is mixed with
bitumen, heated, and thermally upgraded in a fluid bed or delayed
coker.
16. The process of claim 14, wherein the powder is converted into a
syngas in a fluidized bed gasifier or fluid bed boiler.
17. The process of claim 14, wherein the powder is used as a fuel
for a utility boiler or stockpiled as an energy supply.
18. The process of claim 14, 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.
19. The process of claim 18, wherein the paraffinic solvent is
recycled in step (a).
20. 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.
21. The process of claim 2, wherein the decanter centrifuge is
operated to generate a g-force ranging from about 1000 to about
5000.
22. The process of claim 1, further comprising: d) mixing a
sufficient amount of naphthenic solvent with a second portion of
the bitumen froth; e) subjecting the resulting second mixture to
separation to yield a second diluted bitumen product, a water
byproduct stream, and a solids byproduct stream; and f) mixing a
portion of the second diluted bitumen product with a portion of the
dry fungible bitumen product to produce a final fungible bitumen
product.
23. A process for cleaning bitumen froth produced from an oil sands
extraction process, comprising: a) mixing a sufficient amount of
naphtha with a first portion of the bitumen froth to produce a
first diluted bitumen froth; b) mixing a sufficient amount of
paraffinic solvent with the first diluted bitumen froth to form a
second diluted bitumen froth; and c) subjecting the second diluted
bitumen froth to centrifugal separation in a centrifuge to yield a
diluted bitumen product, a water byproduct stream, and a solids
byproduct stream.
24. The process as claimed in claim 23, wherein the diluted bitumen
product has a water content of about 1.0 wt % or less.
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 suitabie
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 by-product 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
by-product 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 by-product 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 05 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.
[0033] FIG. 7 is a graph showing the water+solids content in
diluted bitumen (wt %) as a function of solvent to bitumen ratio
(wt/wt) when using either paraffinic solvent (octane) versus
naphthenic solvent (naphtha).
[0034] FIG. 8 is a graph showing the water content in diluted
bitumen (wt %) when using a mixed solvent (naphtha and octane) at
various solvent/bitumen (wt/wt) ratios.
[0035] FIG. 9 is one configuration (Configuration #1) of the
present invention where naphthenic froth treatment and paraffinic
froth treatment are combined.
[0036] FIG. 10 is another configuration (Configuration #2) of the
present invention where naphthenic froth treatment and paraffinic
froth treatment are combined.
[0037] FIG. 11 is a graph showing the water in diluted bitumen
content (wt %) when using either Configuration #1 (FIG. 9) or
Configuration #2 (FIG. 10) of combined naphtha and paraffinic froth
treatment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0038] 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.
[0039] 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 %.
[0040] 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).
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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
by-product streams, one comprising a separate water by-product
stream contaminated with trace diluent and hydrocarbon 28 in line
58; and the other comprising a solids by-product stream 30 (sands,
clays, asphaltenes) in line 80. In one embodiment, centrifugal
separation is conducted using a three-phrase decanter centrifuge
32.
[0046] 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.
[0047] 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.
[0048] The bitumen product ("dry bitumen") 44 substantially 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.
[0049] The water by-product 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 clean-up 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] With use of a three-phase decanter centrifuge, the light
phase of the troth 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
[0064] 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 DIB 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.
[0065] 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.
EXAMPLE 3
[0066] Experiments were conducted to compare naphthenic treatment
of bitumen froth at various solvent-to-bitumen ratios and
paraffinic (octane) treatment of bitumen froth at various
solvent-to-bitumen ratios using centrifugation. Each of the naphtha
and octane solvents and bitumen froth were first heated inside a
hot water bath at 80.degree. C. To mimic separation in a decanter
centrifuge, a benchtop Hotspin.TM. centrifuge was used. Two sets of
experiments were performed for each of naphtha as solvent and
octane as solvent. In Test 1 for naphtha, solvent-to-bitumen (S/B)
ratios (wt/wt) of 0.5, 0.7, 1.0 and 2.0 were tested. In Test 1 for
octane, solvent-to-bitumen (S/B) ratios (wt/wt) of 0.5, 1.0, 2.0
and 4.0 were tested. In Test 2 for naphtha, higher
solvent-to-bitumen (S/B) ratios (wt/wt) of 2.0, 3.0, 3.5, 4.0, 4.5
and 5.5 were tested. In Test 2 for octane, solvent-to-bitumen (S/B)
ratios (wt/wt) of 1.0, 1.2, 1.4, 1.5, 1.6, 1.8 and 2.0 and 4.0 were
tested. Froth mixtures at each solvent ratio were mixed inside a
hot water bath at 1000 rpm for 5 minutes. Froth samples (10 ml)
were collected at each S/B ratios for each solvent and subjected to
hot-spin centrifugation at 80.degree. C. and 1400 rpm for 6
minutes. The top .about.4 ml of the diluted bitumen layer from the
centrifuge tubes were drawn from each sample and analyzed using
Karl Fischer analysis. Karl Fischer is an analytical test that
measures the water content within the diluted bitumen samples.
Solids were measured by diluting the recovered hydrocarbon product
with toluene and filtering through a 1.6 micron pore size filter 55
mm in diameter. Recovered solids are then washed with excess
toluene, the filter dried and weighed for comparison to the
original mass of hydrocarbon filtered.
[0067] FIG. 7 is a plot of the water+solids content in diluted
bitumen (wt %) for each of the S/B (wt/wt) ratios tested. It can be
seen in FIG. 7 that when naphtha is used as the solvent, even at
very high S/B ratios, e.g., 5.5, the amount of water+solids in the
diluted bitumen was still fairly high, e.g., 0.9 wt %. However,
when octane was used, the comparable amount of water+solids, e.g.,
0.9 wt %, was obtained at a significantly lower S/B ratio, e.g.,
about 1.5. Furthermore, a fungible bitumen product could be
produced at much lower S/B ratios when using octane. For example,
at S/B (octane to bitumen) ratios of about 1.8 to about 2.0, the
water+solids content in the diluted bitumen was reduced to about
less than 0.2 wt %. However, an increase in S/B ratio from 2.0 to
4.0, when using octane, did not result in a further decrease in the
wt % of solids+water.
[0068] In conventional bitumen froth treatment using naphtha, a S/B
ratio (naphtha to bitumen) of 0.7 is used. Such a ratio (i.e., N/B
ratio of 0.7) generally results in a diluted bitumen product having
a total water+solids content of about 3.1 wt %. However, this
diluted bitumen product is not considered to be fungible bitumen
and must therefore be further treated. However, when using naphtha,
bitumen recovery is very good, as the hydrocarbon loss when using a
N/B ratio of 0.7 is only about 2%. On the other hand, the use of
paraffinic solvent as shown in the present invention at a S/B ratio
of 1.8 generally results in a diluted bitumen product having a
total water+solids content of about 0.1 wt %, which is considered
to be a fungible bitumen product. However, with paraffin, the
trade-off is that bitumen recovery is lower, as the hydrocarbon
loss is around 10%.
[0069] Thus, in one aspect of the present invention, paraffinic
centrifugation can be used in conjunction with a conventional
naphtha bitumen froth treatment plant which also uses
centrifugation to obtain a fungible bitumen product having a
water+solids content of about 0.5 wt % by blending products
obtained from both naphtha froth treatment and paraffinic froth
treatment of the present invention. By way of example, when using
the highlighted values in FIG. 7, i.e., N/B ratio of 07 and O/S
ratio of 1.8, to achieve 0.5 wt % water+solids in bitumen (i.e.,
fungible bitumen), one can blend 76.5% of the product from
paraffinic (e.g., octane) centrifugation with 23.5% of the product
from naphthenic centrifugation. Thus, by combining naphthenic
centrifugation with paraffinic centrifugation, a fungible product
can be produced. Furthermore, the hydrocarbon losses will be less
than when using paraffinic centrifugation alone, as there will be
an increase in hydrocarbons from 90% (paraffinic centrifugation
alone) to 91.9% (by blending the two products as discussed above)
of fungible bitumen.
EXAMPLE 4
[0070] Experiments were conducted to determine the effect on the
water content of diluted bitumen products when a mixed solvent is
used. In particular, a mixed solvent comprising a naphtha to
bitumen (N/B) ratio of 0.5 and an octane to bitumen (O/B) ratio of
1.5 for a total S/B ratio of 2.0 was tested at total solvent to
bitumen ratios of 0.7, 1.0 and 2.0 and the water content of the
resulting diluted bitumen products determined. Cold octane
(unmixed) was also tested at S/B ratios of 0.7, 1.0 and 2.0 to
determine the importance of mixing and/or temperature on removal of
water/solids from the froth. Mixing and centrifugation were
performed as described above in Example 3. Karl Fischer analysis
was used to determine the water content. The water content of the
diluted bitumen products obtained using mixed solvent and cold
octane was compared to the water content in the diluted bitumen
products from Example 3 and the results are shown in FIG. 8.
[0071] It can be seen from FIG. 8 that comparable diluted bitumen
water content was obtained when using pure octane at a O/B ratio of
1.5 and when using mixed solvent having a N/B ratio of 0.5 and
octane having a O/B ratio of 1.5 for a total S/B ratio of 2.0.
However, the advantage is that the hydrocarbon losses were reduced.
Hence, the results suggest that the solvent used in froth treatment
can be tailored to achieve the required water content by blending
paraffinic solvent and naphtha with the benefit of being closer
operation to the 0.5 water+solids limit (for fungible bitumen) and
reduced hydrocarbon loss. It was also shown that hot octane with
mixing resulted in better water reduction than cold octane, no
mixing. Nevertheless, the water content when using cold octane, no
mixing, was still reduced to about 0.6 when cold octane was used at
a O/B ratio of 2.0.
EXAMPLE 5
[0072] In the following experiments, pure octane was added to
conventional naphtha bitumen froth treatment in two configurations.
FIG. 9 shows Configuration #1 where octane is added to 50% of a
naphtha-diluted bitumen froth (e.g., N/B ratio of 0.7) to reach a
particular octane to bitumen (O/B) ratio (e.g., 2.0). The
naphtha/octane treated froth is then mixed with the other 50% of
the naphtha-diiuted bitumen froth, to give a final diluted froth
having a total S/B ratio (e.g., 1.75). The final diluted froth is
then subjected to centrifugation. FIG. 10 shows Configuration #2
where 50% of naphtha-diluted bitumen froth (e.g., N/B ratio of 0.7)
is first centrifuged to give a diluted bitumen product and then
octane is added to the diluted bitumen product to reach an
particular octane to bitumen (O/B) ratio (e.g., 2.0). The other
non-centrifuged 50% of the naphtha-diluted bitumen froth is then
mixed with the octane-treated diluted bitumen product to give a
mixed product having a total SIB ratio (e.g., 1.64). The mixed
product is then subjected to centrifugation.
[0073] To test Configuration #1, naphtha, octane and froth were
heated inside a hot water bath at 80.degree. C. for 30 minutes.
Naphtha was mixed with froth to reach naphtha to bitumen (N/B)
ratio of 0.7. Half of the froth mixture was further diluted with
octane to reach an octane to bitumen (O/B) ratio of 2.0. The
remaining froth mixture (at 0.7N/B) was then recombined with the
asphaltene slip stream (2.0 O/B) to form a combined froth mixture
containing 1.7 S/B ratio. All streams were mixed inside the water
bath at 1000 rpm for 5 minutes prior to and after blending. Two (10
ml) froth mixture samples were taken for each individual froth
streams at 0.7 N/B and 2.0 O/B respectively, and three (10 ml) were
taken for the combined froth mixture. The (10 ml) froth samples
collected at each S/B ratio samples was then subjected to hot spin
centrifugation at 80.degree. C. and 1400 rpm for 6 minutes. The top
.about.4 ml of the diluted bitumen layer from the centrifuge tubes
were drawn from each sample and stored aside for Karl Fischer
analysis. Karl Fischer is an analytical test that measures the
amount of water content within diluted bitumen sample.
[0074] To test Configuration #2, naphtha, octane and froth were
heated inside a hot water bath at 80.degree. C. for 30 minutes.
Naphtha was mixed with froth to reach naphtha to bitumen (N/B)
ratio of 0.7. Half of the froth mixture was centrifuged and the
diluted bitumen layer was further diluted with octane to reach an
octane to bitumen (O/B) ratio of 2.0. The remaining froth mixture
(at 0.7 N/B) was then recombined with the asphaltene slip stream
(2.0 O/B) to form a combined froth stream. All streams were mixed
inside the water bath at 1000 rpm for 5 minutes prior to and after
blending. Two (10 ml) froth mixture samples were taken for each
individual froth streams at 0.7 N/B and 2.0 O/B respectively, and
three (10 ml) samples were taken for the combined froth mixture.
The (10 ml) froth samples collected at each S/B ratio was then
subjected to hot spin centrifugation at 80.degree. C. and 1400 rpm
for 6 minutes. The top .about.4 ml of the diluted bitumen layer
from the centrifuge tubes were drawn from each sample and stored
aside for Karl Fischer analysis. Karl Fischer is an analytical test
that measures the amount of water content within diluted bitumen
sample.
[0075] The results shown in FIG. 11 illustrate that there was no
benefit in centrifuging the naphtha-diluted bitumen froth prior to
the addition of octane (Configuration #2). Thus, only a single
centrifuge may be needed when treating naphtha-diluted bitumen
froth with paraffin (octane). While the final diluted bitumen
product was only of intermediate quality, under the conditions
tested herein, it is clear that a better quality product
resulted.
[0076] 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.
REFERENECES
[0077] 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.
[0078] 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.
[0079] 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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