U.S. patent application number 11/366202 was filed with the patent office on 2006-09-07 for zone settling aid and method for producing dry diluted bitumen with reduced losses of asphaltenes.
Invention is credited to Jan Hendrik Beetge, Tadeusz Dabros, Hassan Hamza, Yicheng Long, Wang Sanyi, Petrus Johannes Venter, Yuming Xu, Xiaoli Yang.
Application Number | 20060196812 11/366202 |
Document ID | / |
Family ID | 36938976 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060196812 |
Kind Code |
A1 |
Beetge; Jan Hendrik ; et
al. |
September 7, 2006 |
Zone settling aid and method for producing dry diluted bitumen with
reduced losses of asphaltenes
Abstract
A method includes diluting a bitumen source, such a bitumen
froth from a hot water extraction process, with a hydrocarbon
diluent such as naphtha, contacting the bitumen with a zone
settling aid such as a polyoxyalkylate block polymer, flocculating
water and fine solids in the diluted bitumen, separating the
flocculated water and fine solids from the solvent-diluted bitumen,
and producing dry, clean diluted bitumen. Preferably, the diluted
bitumen will have less than 1.0 wt % water, but most preferably
less than 0.7 wt % water. The method may further comprise
maintaining the diluted bitumen under conditions that avoid the
precipitation of asphaltenes from the bitumen, preferably such that
the dry, clean diluted bitumen comprises essentially all, such as
greater than 96%, of the asphaltene content from the bitumen
source. Counter-current flow may be performed in a series of zone
settling stages, such as with gravity settling.
Inventors: |
Beetge; Jan Hendrik;
(Pearland, TX) ; Venter; Petrus Johannes;
(Pearland, TX) ; Sanyi; Wang; (Edmonton, CA)
; Yang; Xiaoli; (Edmonton, CA) ; Long;
Yicheng; (Calgary NW, CA) ; Xu; Yuming;
(Edmonton, CA) ; Dabros; Tadeusz; (Edmonton,
CA) ; Hamza; Hassan; (Edmonton, CA) |
Correspondence
Address: |
STREETS & STEELE
13831 NORTHWEST FREEWAY
SUITE 355
HOUSTON
TX
77040
US
|
Family ID: |
36938976 |
Appl. No.: |
11/366202 |
Filed: |
March 2, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60657758 |
Mar 2, 2005 |
|
|
|
Current U.S.
Class: |
208/435 |
Current CPC
Class: |
C10G 1/047 20130101;
C10G 1/045 20130101 |
Class at
Publication: |
208/435 |
International
Class: |
C10G 1/00 20060101
C10G001/00 |
Claims
1. A method of processing bitumen, comprising: diluting a bitumen
source with a hydrocarbon diluent to a diluent-to-bitumen ratio of
less than 1; contacting the bitumen with a zone settling aid;
flocculating water and fine solids in the diluted bitumen;
separating the flocculated water and fine solids from the diluted
bitumen; and producing a dry, clean diluted bitumen having less
than 1.0 wt % water and less than 0.5 wt % fine solids.
2. The method of claim 1, wherein the diluted bitumen has less than
0.7 wt % water and less than 0.3 wt % fine solids.
3. The method of claim 1, further comprising: maintaining the
diluted bitumen under conditions that avoid the precipitation of
asphaltenes from the bitumen.
4. The method of claim 3, wherein the dry, clean diluted bitumen
comprises essentially all of the asphaltene content from the
bitumen source.
5. The method of claim 1, wherein the step of contacting the
bitumen with a zone settling aid is performed upstream or within a
primary froth treatment vessel.
6. The method of claim 1, wherein the bitumen source is deaerated
bitumen froth.
7. The method of claim 1, wherein the bitumen source is diluted to
a diluent-to-bitumen ratio less than 0.75.
8. The method of claim 1, further comprising: passing the diluent
counter-current to the water and fine solids.
9. The method of claim 8, wherein the counter-current flow is
performed in a series of zone settling stages.
10. The method of claim 1, wherein the step of separating includes
gravity settling.
11. The method of claim 1, further comprising: aerating a slurry
containing bitumen, water and inorganic solids to form a bitumen
froth; and diluting the bitumen froth with a hydrocarbon diluent to
produce the diluted bitumen.
12. The method of claim 1, wherein the zone settling aid comprises
a polyoxyalkylate polymer having a molecular weight between about
1,000 and about 2,000,000
13. The method of claim 12, wherein the polyoxyalkylate polymer is
a reaction product of an acceptor and one or more alkyloxide
species.
14. The method of claim 13, wherein the alkyloxide species is
selected from ethylene oxide, propylene oxide, glycidol, butylene
oxide, epichlorohydrin and combinations thereof.
15. The method of claim 13, wherein the acceptor is material having
one or more active hydrogen atoms towards the oxyalkylation
reaction.
16. The method of claim 13, wherein the acceptor is Sorbitol.
17. The method of claim 13, wherein the polyoxyalkylate polymer
includes two or more block polymers selected from ethylene oxide,
propylene oxide, and butylene oxide and epichlorohydrin.
18. The method of claim 13, wherein the polyoxyalkylate polymer
includes block polymers of propylene oxide and ethylene oxide.
19. The method of claim 18, wherein the propylene oxide block
polymer has between 15 and 25 propylene oxide groups, and wherein
the ethylene oxide block polymer has between 5 and 15 ethylene
oxide groups per arm of a branched polymer.
20. The method of claim 19, wherein the propylene oxide block
polymer extends from the polyol, and wherein the ethylene oxide
block polymer extends from the propylene oxide block polymer.
21. The method of claim 18, wherein the polymer comprises between
10% and 50% ethylene oxide.
22. The method of claim 18, wherein the polymer comprises between
20% and 40% ethylene oxide.
23. The method of claim 18, wherein the polymer comprises between
28% and 35% ethylene oxide.
24. The method of claim 21, wherein the polymer has a molecular
weight between about 2,000 and about 2,000,000.
25. The method of claim 1, wherein the zone settling aid is an
alkoxylate polymer having the formula:
Acc-[(Ox.sub.1).sub.A1-(Ox.sub.2).sub.A2- . . .
(Ox.sub.i).sub.Ai].sub.n wherein: Acc is an acceptor; Ox.sub.1 to
Ox.sub.i are oxides, wherein each oxide is independently selected
from ethylene oxide, propylene oxide, glycidol, butylene oxide,
epichlorohydrin, and mixtures thereof, wherein A1 to Ai is between
0 and 150,000, wherein n is between about 1 and 100, and wherein
the molecular weight of the alkoxylate is between about 1000 and
about 2,000,000 g mole.sup.-1.
26. The method of claim 25, wherein the ratio of butylene oxide to
propylene oxide is between about 200:1 and about 1:200.
27. The method of claim 25, wherein the ratio of ethylene oxide to
propylene oxide is between about 200:1 and about 1:200.
28. The method of claim 25, wherein the ratio of butylene oxide to
ethylene oxide is between about 200:1 and about 1:200.
29. The method of claim 25, wherein the alkoxylate has a molecular
weight between about 2000 and about 1,000,000.
30. The method of claim 25, wherein the alkoxylate is added to the
system at a concentration of between about 1 wt. ppm and about 750
wt. ppm.
31. The method of claim 25, wherein the alkoxylate is added to the
system at a concentration of between about 25 wt. ppm and about 300
wt. ppm.
32. The method of claim 1, wherein the hydrocarbon diluent
comprises naphtha.
33. The method of claim 1, wherein the hydrocarbon diluent is
selected from aliphatics, aromatics, naphtha, gasoline, natural gas
condensate, paraffins, and combinations thereof.
34. The method of claim 13, wherein the acceptor is a low molecular
weight polyethyleneimine having a functionality range from about 4
to 14 active hydrogen atoms per molecule.
Description
[0001] This application claims priority of U.S. provisional patent
application 60/657,758 filed on Mar. 2, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to compositions and processes
for the treatment of bitumen to remove water and solids.
[0004] 2. Description of the Related Art
[0005] The Athasbasca Oil Sands Deposit is, by itself, the largest
petroleum resource in the world. These oil sands or tar sands are
located in northwestern Canada and represent the equivalent of
roughly 1.6 to 2.7 trillion barrels of oil. Presently, truck and
shovel operations first mine the oil sand and deliver it to a
crusher. In one process, bitumen separation and recovery from the
oil sand is accomplished by following what is known as the Clark
hot water extraction process. In the front end of this process, the
crushed oil sand is mixed with hot water and caustic in a rotating
tumbler or conditioned in a pipeline to produce an aqueous slurry.
The slurry is then screened to remove large rocks and the like. The
screened slurry is diluted with additional water and the product is
then temporarily retained in a primary separation vessel (PSV). In
the tumbler, bitumen globules contact and coat air bubbles that are
entrained in the slurry. In the PSV, the buoyant bitumen-coated air
bubbles rise through the slurry and form bitumen froth. The sand in
the slurry settles and is discharged from the base of the vessel,
together with some water and bitumen. This stream or portion is
referred to as the "PSV underflow" or tailings. A "middlings"
portion may also be collected, comprising water, non-buoyant
bitumen and fines, from the middle of the PSV. The froth overflows
the lip of the vessel and is recovered as the primary froth,
typically comprising 60 wt. % bitumen, 30 wt. % water and 10 wt. %
particulate solids.
[0006] The PSV underflow is introduced into a deep cone vessel,
referred to as the tailings oil recovery vessel ("TORV"). Here the
PSV underflow is contacted and mixed with a stream of aerated
middlings from the PSV. Again, bitumen and air bubbles contact and
unite to form buoyant globules that rise and form froth. This
"secondary" froth overflows the lip of the TORV and is recovered.
The secondary froth typically comprises 45 wt. % bitumen, 45 wt. %
water and 10 wt. % solids. The middlings from the TORV are
withdrawn and processed in a series of sub-aerated,
impeller-agitated flotation cells. Secondary froth, typically
comprising 40 wt. % bitumen, 50 wt. % water and 10 wt. % solids, is
produced from these cells.
[0007] The primary and secondary froth streams are typically
combined to yield a product froth stream, often comprising 60 wt. %
bitumen, 32 wt. % water and 8 wt. % solids. The water and solids in
the froth are contaminants which need to be reduced in
concentration before the froth can be treated in a downstream
refinery-type upgrading facility. This cleaning operation is
carried out using what is referred to as "froth treatment".
[0008] While there are a variety of froth treatment processes, all
of these processes include deaeration of the combined froth product
followed by dilution with sufficient solvent, specifically naphtha,
to provide a solvent to froth ("S/F") ratio of about 0.40 (w/w).
This is done to increase the density differential between the
diluted bitumen on the one hand and the water and solids on the
other.
[0009] Kizior (U.S. Pat. No. 4,383,914) discloses that bitumen
froth may be treated in a two-stage dilution centrifuging circuit.
The naptha-diluted bitumen is treated in a battery of scroll
separators to remove coarse solids, then pumped through a battery
of disc separators to remove water and fine clay solids. In order
to obtain a disc product that is acceptable for utilization in
downstream bitumen upgrading units, Kizior states that it is
conventional to add a chemical demulsifier to the feed stream just
before it enters the disc separator. Kizior includes the use of a
low shear pump between the first and second stages of centrifugal
separation
[0010] Guymon (U.S. Pat. No. 4,968,412) discloses a process for
removal of bitumen from tar sands contaminated with clay, including
use of a solvent and centrifugal separation followed by a step of
washing residual bitumen with entrapped clay and solvent from sand
using water containing an appropriate surfactant. Guymon discloses
that the surfactant may be a primary alcohol ethoxylate, such as a
C8 to C15 alcohol with 3 to 8 ethoxylate units. It is stated that
greater than eleven ethoxylate units renders the surfactant
unusable.
[0011] Graham et al. (U.S. Pat. No. 5,143,598) discloses a
deasphaltening method of mineral fines removal wherein a
bitumen-rich solvent phase containing fines is contacted with a
solvent of limited solubility for asphaltenes. A portion of the
asphaltene content of the bitumen precipitates and in so doing acts
to agglomerate the fine mineral particles to lower the fines
content of the bitumen-rich solvent phase.
[0012] Shelfantook et al. (Canadian Patent 1,293,465) discloses a
bitumen froth treatment using a circuit comprising a plurality of
serially connected mixer and inclined plate settler units. A light
hydrocarbon diluent, such as naptha, moves counter-currently
through the circuit so that as the bitumen content of the stream
being settled diminishes, the concentration of diluent in that
stream increases. A circuit consisting of three pairs of
alternating mixers and settlers is reported as producing a bitumen
product stream of the same order of purity and same order of
recovery as obtained by dilution centrifuging. More specifically,
the bitumen product stream in Table II reports a composition
comprising 55.7% bitumen, 4.7% water, 0.7% solids, and 39.0%
naptha.
[0013] Birkholz et al. (Canadian Patent 2,232,929) discloses a
method for processing a diluted oil sand froth that contains
hydrocarbons, water, clays and coarse solids and that is withdrawn
from a lower part of a primary fluid separation vessel of a
paraffinic solvent froth treatment unit. The method includes
further diluting the underflow stream, agitating the underflow
stream at a shear level sufficient to form agglomerates of
asphaltenes and clays, and separating other hydrocarbons released
into an upper fluid layer.
[0014] Tipman et al. (Canadian Patent 2,200,899) discloses a method
for processing the underflow stream from a primary separation
vessel of a paraffinic solvent froth treatment unit. Bitumen froth
is mixed with a paraffinic diluent or solvent and fed to a primary
separation vessel. The method includes vigorously agitating the
underflow from the primary separation vessel in an agitating tank
at such a shear level that agglomerates of asphaltenes and clays
are formed. The agglomerates are then separated out in a middlings
stream from a secondary separation vessel.
[0015] Tipman et al. (Canadian Patent 2,353,109) discloses a
solvent recovery unit used to treat the underflow stream from the
last separation step in a paraffinic solvent process for separating
bitumen from oil sands froth. The paraffinic solvent process relies
upon the precipitation of asphaltenes to assist in the removal of
water and solids from the froth. Consequently, the underflow stream
from the paraffinic solvent process contains, among other things,
water, solvent, solids, precipitated asphaltenes and other
unrecovered hydrocarbons. However, the precipitated asphaltenes
trap the light diluent in the underflow stream such that the
underflow poses an environmental hazard and financial liability. A
solvent recovery process is thus used to vaporize the solvent out
of the underflow for recovery as an overhead vapor stream. While
the use of a low boiling solvent makes the recovery easier, it also
increases the operational risk of fire that can cause substantial
damage.
[0016] Mishra et al. (U.S. Pat. No. 6,019,888) discloses a bitumen
froth treatment using a diluent and an ethoxylated nonylphenol
surfactant with 4 to 13 ethoxyl groups. These surfactants have a
molecular weight between 393 (4 ethoxyl groups) and 789 (13 ethoxyl
groups) and are used at a ratio of between 1:10 (10 ppm) and
1:10,000 (1 wt %) kilograms of bitumen/diluent mix to milligram of
surfactant. Optionally, anionic or cationic flocculants may also be
used at between 1 ppm and 0.5 wt %.
[0017] Cymerman et al. (U.S. Pat. No. 6,746,599) discloses that
cleaned froth or "dilbit" should have less than 1.0% water and less
than 0.3% solids before being processed in an upgrading facility.
However, Cymerman explains that the ability to achieve a solution
has been constrained by various factors including the affinity
between clay and bitumen, the need to minimize bitumen losses in
the tails or sludge, the diluent-to-bitumen ratio in the dilbit
should not exceed 0.8, the equipment should be simple and
inexpensive to operate, and additives, such as demulsifiers, should
be used only sparingly. Accordingly, Cymerman discloses dilution of
bitumen froth with naptha at a naphtha/bitumen ratio of 0.5:1 to
0.8:1 and delivering this "dilfroth" into a gravity settler vessel
or "splitter." In one embodiment, Cymerman subjects the splitter
dilbit to further treatment in a "polisher" vessel having a
retention time of 5 to 24 hours. Optionally, a demulsifier is added
to the splitter dilbit treated in the polisher to produce a
polished dilbit overhead product having reduced water and solids.
Example 1 shows that the water content could be reduced from 4.57%
in the splitter overflow to 0.2% in the polisher overflow by
allowing the dilbit to settle for 26 hours in the polisher vessel
with 40 ppm demulsifier. Example 2 shows that a scrubber vessel fed
with a 5:1 ratio of naphtha/bitumen could produce a scrubber
underflow or tailings with about 1.75% bitumen.
[0018] Despite the development of these froth treatment processes,
there remains a need for an improved froth treatment process that
produces a diluted bitumen stream of higher quality, for example
having less water, less solids, and less diluent. It would be
desirable if this improved process would also increase bitumen
recovery by reducing asphaltene losses in the tailings. It would be
even further desirable if this improved process could be performed
without requiring high solvent-to-bitumen ratios, long residence
times or numerous or expensive processing units.
[0019] The present invention provides an improved froth treatment
process that meets these needs. Unlike existing processes, the
process of the present invention produces a diluted bitumen stream
with low water content analogous to a paraffinic process, without
requiring use of a paraffinic diluent, but enabling the use of
various diluents or solvents. Furthermore, the invention may
utilize a diluent-to-bitumen ratio of approximately 0.65, which is
characteristic for the conventional naphtha-based process. The use
of naphtha, or another solvent other than a paraffin, leads to
improved bitumen recovery efficiency because asphaltene
precipitation is largely avoided. The diluent-to-bitumen ratios
used in the invention are lower than the required
diluent-to-bitumen ratio of approximately 2.0 that is required for
the paraffinic process for the precipitation of asphaltenes. The
invention provides the unique and surprising result that a single
process can provide the simultaneous advantages of using any of a
variety of hydrocarbon solvents, using a low diluent-to-bitumen
ratio, and producing a diluted bitumen stream having low water
content. Accordingly, the process of this invention yields
exceptional product quality without the heretofore accompanying
disadvantage of the low space/time yield associated with high
solvent-to-bitumen ratios, nor the requirement of using only a
paraffinic diluent as is dictated by the paraffinic froth treatment
process.
SUMMARY OF THE INVENTION
[0020] The present invention provides methods of processing
bitumen. A preferred method comprises diluting a bitumen source
with a hydrocarbon diluent, contacting the bitumen with a zone
settling aid, flocculating water and fine solids in the diluted
bitumen, separating the flocculated water and fine solids from the
solvent-diluted bitumen, and producing dry, clean diluted bitumen.
Preferably, the diluted bitumen will have less than 2.0 wt % water
and less than 0.5 wt % fine solids, but most preferably less than
0.7 wt % water and less than 0.2 wt % fine solids. The method may
further comprise maintaining the diluted bitumen under conditions
that avoid the precipitation of asphaltenes from the bitumen,
preferably such that the dry, clean diluted bitumen comprises
essentially all, such as greater than 96%, of the asphaltene
content from the bitumen source. The hydrocarbon diluent is
preferably selected from aliphatic hydrocarbons, aromatic
hydrocarbons commercially available as naphtha, gasoline, natural
gas condensate, paraffins, and combinations thereof. Furthermore,
the step of contacting the bitumen with a zone settling aid may be
performed upstream of or within a primary froth treatment vessel.
In one embodiment, the bitumen source is bitumen froth from a hot
water extraction process.
[0021] In another specific embodiment, the method further comprises
passing the diluent counter-current to the water and fine solids.
This counter-current flow may be performed in a series of zone
settling stages. Optionally, the step of separating includes
gravity settling.
[0022] In still another embodiment, the method further comprises
aerating a slurry containing bitumen, water and inorganic solids to
form a bitumen froth, and diluting the bitumen froth with a
hydrocarbon diluent to produce the diluted bitumen. The method may
be performed wherein the bitumen source is diluted to a
diluent-to-bitumen ratio less than 1.
[0023] In a preferred embodiment, the zone settling aid comprises a
polyoxyalkylate polymer having a molecular weight between about
2,000 and about 2,000,000. A suitable polyoxyalkylate polymer is a
reaction product of a polyol and one or more alkyloxide species.
Optionally, the alkyloxide species is selected from ethylene oxide,
propylene oxide, glycidol, butylene oxide, epichlorohydrin and
combinations thereof. Optionally, the polyol is sorbitol. An
exemplary polyoxyalkylate polymer includes two or more block
polymers selected from ethylene oxide, propylene oxide, and
butylene oxide and epichlorohydrin. Glycidol would generally not
form its own block, but may be advantageously included within a
block or between blocks in order to provide branching.
[0024] In a more specific embodiment, the polyoxyalkylate polymer
includes block polymers of propylene oxide and ethylene oxide. In
yet another option, the propylene oxide block polymer has between
15 and 25 propylene oxide groups, and wherein the ethylene oxide
block polymer has between 5 and 15 ethylene oxide groups per arm of
a branched polymer. Optionally, the propylene oxide block polymer
extends from the polyol, and the ethylene oxide block polymer
extends from the propylene oxide block polymer. Optionally, the
polymer comprises between 10% and 50% ethylene oxide depending on
molecular weight and oxide composition, such as between 20% and 40%
ethylene oxide preferably between 25% and 35% ethylene oxide or
more preferably between 28% and 32% ethylene oxide. Most
preferably, the polymer has a molecular weight between about 2,000
and about 2,000,000. At the higher end of this molecular weight
range, say above, 1,000,000, it may be desirable to increase the EO
content and degree of branching through incorporation of
polyfunctional oxides such as glycidol or bis-epoxides to maintain
desireable solubility characteristics and fluid rheological
properties. Accordingly, the block polymers, especially those
having a molecular weight greater than 1,000,000, most preferably
comprise between 10% and 50% ethylene oxide, such as between 25%
and 40% ethylene oxide or between 28% and 35% ethylene oxide with a
high degree of branching built into the molecular architecture.
[0025] The zone settling aid may be an alkoxylate polymer having
the formula: Acc-[(Ox.sub.1).sub.A1-(Ox.sub.2).sub.A2- . . .
(Ox.sub.1).sub.Ai].sub.n, wherein Acc is an acceptor and Ox.sub.1
to Ox.sub.i are oxide species, wherein each oxide is independently
selected from ethylene oxide, propylene oxide, glycidol, butylene
oxide, epichlorohydrin, and combinations thereof, wherein A.sub.1
to A.sub.i is between 0 and 150,000, wherein n is between about 1
and 100, and wherein the molecular weight of the alkoxylate polymer
is between about 1000 and about 2,000,000 g moles.sup.-1. Optional
alkoxylate polymers may have a ratio of butylene oxide to propylene
oxide between about 200:1 and about 1:200, a ratio of ethylene
oxide to propylene oxide is between about 200:1 and about 1:200, or
a ratio of butylene oxide to ethylene oxide is between about 200:1
and about 1:200. Preferably, the alkoxylate has a molecular weight
between about 2000 and about 1,000,000. It is also preferred to add
the alkoxylate polymer to a froth treatment system at a
concentration of between about 1 wt. ppm and about 750 wt. ppm,
such as between about 25 wt. ppm and about 300 wt. ppm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a flow diagram of a counter-current zone settling
process for bitumen froth treatment.
[0027] FIG. 2 is a graph of the interface height as a function of
time for each column of diluted bitumen that was treated with a
zone settling aid in Example 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] The process of the present invention is suitable for
treatment of any bitumen source. Examples of commercial
significance include, without limitation, the Clark hot water
process (CHWP) and low energy extraction (LEE) processes. In a
preferred embodiment, the present invention is used to treat
bitumen froth. As used herein, reference to bitumen froth includes
a primary froth, a secondary froth, any other froth containing
bitumen, or a combined froth. Bitumen sources include, without
limitation, oil sands, crude oil and oil shale.
[0029] The present invention provides a method of processing
bitumen, wherein the bitumen is typically first diluted with a
hydrocarbon diluent, preferably at a diluent-to-bitumen ratio of
less than 1. The bitumen is contacted with a zone settling aid of
the present invention for the purpose of removing water and fine
solids in the diluted bitumen. Where the bitumen source is
deaerated bitumen froth from an oil sand process, the bitumen is
preferably contacted with a zone settling aid upstream of or within
a primary froth treatment vessel. The water and fine solids can
then be easily separated from the diluted bitumen to produce a dry,
clean diluted bitumen stream, preferably having less than 1.0 wt %
water and less than 0.5 wt % fine solids. Based on experience, 1 wt
% water is expected to be associated with 0.3 wt % solids.
[0030] In one embodiment of the invention, the method includes
maintaining the diluted bitumen under conditions that avoid the
precipitation of asphaltenes from the bitumen. In this manner, it
is possible for the dry, clean diluted bitumen to comprise
essentially all of the asphaltene content from the bitumen source,
preferably greater than 96% of the asphaltene content, and more
preferably greater than 99% of the asphaltene content.
[0031] A diluent is added to the bitumen froth to improve
separation of water in the bitumen froth from the bitumen and
diluent. A diluent, such as naptha, serves to reduce the
hydrocarbon phase viscosity and increase the density differential
between the hydrocarbon phase and the water and solids phase
(referred to as underflow). The diluent is preferably a
hydrocarbon, including, without limitation, mixed refinery products
such as naphtha, gasoline, diesel fuel, kerosene, and heating oil,
or more refined products such as butane, pentane, hexane, heptane,
octane, benzene, toluene or xylene or mixtures thereof. The
preferred diluent is naphtha.
[0032] It is believed that the space/time yield of the process of
this invention is only limited to a diluent-to-bitumen ratio that
would provide a practical density difference to facilitate water
separation under natural gravitational conditions. Preferably, the
diluent-to-bitumen ratio is greater than or equal to 0.35. It
should be recognized that the diluent-to-bitumen ratio may vary
from a primary separation vessel to any secondary or tertiary
separation vessel that may be used in the process. Accordingly, the
diluent-to-bitumen ratio in a primary separation is preferably less
than or equal to 1. If the process includes a secondary separation,
then the diluent-to-bitumen ratio is preferably between 1 and 5.
Further still, if the process includes a tertiary separation, then
the diluent-to-bitumen ratio is preferably between 10 and 30.
Embodiments of the process that include two or more separations
will preferably involve a counter-current flow, such that the
diluted bitumen from a later separation is input into the previous
separation.
[0033] The separations are each carried out in a flotation tank or
gravity separator designed to allow separation of a bitumen froth
fraction from a water and solid fraction. Any commonly used unit
processes in mineral processing may be used, for example a
floatation tank, screens, inclined plate separator, hydraulic
classifiers, hydrocyclone separators, centrifuges, and combinations
of these units. The separations may also be carried out in multiple
vessels and/or multiple vessel types, most preferably in series,
that can accomplish a separation into at least two fractions, one
fraction having much of the bitumen and the other fraction having
much of the water and solids.
[0034] A preferred zone settling aid for use in the present
invention comprises a polyoxyalkylate having the following form:
Acc-[(Ox.sub.1).sub.A1-(Ox.sub.2).sub.A2- . . .
(Ox.sub.i).sub.Ai].sub.n, where Ox.sub.1 to Ox.sub.i are different
oxides, oxide blocks or mixed oxide blocks, and Acc is an acceptor.
Each of the oxides Ox.sub.1 to Ox.sub.i are selected from ethylene
oxide (EO), propylene oxide (PO), butylene oxide (BO),
epichlorohydrin (EPI) or mixed oxides, the mixed oxides being a
mixture of EO, PO, glycidol, BO and/or and EPI. The EO:PO, EO:BO or
PO:BO ratio may range from 200:1 to 1:200. The value of A1 to Ai
may range between 0 and 150,000. The amount of EPI added is used to
invoke incorporation of charge density through secondary reaction
with nitrogen-based organic or other carbon-chloride reactive
reagents. The value of n represents the finctionality. In certain
embodiments, the polyoxyalkylates may be derivatized.
[0035] An acceptor for the oxyalkylation reaction is a chemical
having one or more active hydrogen atoms that are easily
substituted in an epoxide reaction. This category of chemical
compounds includes any hydrogen atom that is connected to an
element other than carbon. Examples of such acceptors are water,
alcohols, polyalcohols such as glycerol, Sorbitol, pentaerythritol,
sugars such as glucose, sucrose and cellulose, amines, such as
ammonia, alkylamines, polyalkylpolyamines such as ethylene diamine,
diethylene triamine, triethylene tetra amine, hexaethylene
heptaamine, carboxylic and polycarboxylic acids, amids and
polyamids, thiols and polythiols, alkylphenol formaldehyde resins
and amine modified alkylphenol formaldehyde resins. The acceptors
result in a polymer typically having a functionality of between 1
to about 100, but the finctionality could be as high as 150,000 in
the polymeric type acceptors.
[0036] Acceptors can thus be classified as material having an
active hydrogen where an active hydrogen is defined as a hydrogen
atom bonded to an element other than carbon. These include
functional groups such as alcohols, carboxylic acids, amines,
amides, thiols and can range from being mono-functional to
polyfuctional. Specific examples of commercially significant
acceptors are water, ethylyne glycol, propylene glycol, glycerol,
TMP, pentaerythritol, ammonia, alkyl and aryl amines, polyamines
such as ethylene diamine, diethylene triamine, triethylene
tetraamine, tetraethylene pentaamine, pentaethylene hexamine,
polyethyleneimine, mono-, di-, tri and polycarboxylic acid
derivatives, monosaccharides, disaccacharides and polysaccharides
such as glucose, sucrose and cellulose. In addition
alkylphenolformaldehyde resins and amine modified
alkylphenolformaldehyde resins are also useful as acceptors for
producing zone settling aids.
[0037] Crosslinking agents may be utilized to increase the
molecular weight of the polymer through crosslinking reactions.
Suitable crosslinking agents include diepoxides, diacids,
polyacids, polyacrylic acids, isocyanates leading to the formation
of complex polyesters, complex branched ethers and complex branched
urethanes. Combinations of polyoxyalkylate polymers having
different molecular architectures can be co-reacted either in
sequence or as blends to produce complex crosslinked polymers
involving reaction with poly-epoxides, polyacids and
poly-isocyanates leading to the formation of complex
polyoxyalkylate ethers, esters and urethanes. Glycidol is also a
useful monomer to introduce branching in a propagating chain which
can be used advantageously to optimize the molecular architecture
specifically regarding molecular weight, fluid viscosity,
interfacial activities and relative solubilities.
[0038] The resulting polymer that is useful as a zone settling aid
has a molecular weight of between about 1000 and about 2,000,000,
preferably between about 2000 and about 1,000,000.
[0039] The zone settling aid may be formulated with a carrier, such
as kerosene, naphtha, hydrocarbon, or any other suitable diluent or
diluent mixture, including, without limitation, water or methanol.
The concentration of the carrier in the formulation may range from
between 0 to about 99 wt. %.
[0040] A particularly preferred zone settling aid is a
polyoxyalkylate polymer based on sorbitol. Such a polymer may be
referred to as a "star polymer." The polyoxyalkylate polymer
includes two or more block polymers selected from ethylene oxide,
propylene oxide, and butylene oxide. Optionally, the
polyoxyalkylate polymer includes block polymers of propylene oxide
and ethylene oxide, for example where the propylene oxide block
polymer has between 15 and 25 propylene oxide groups, and wherein
the ethylene oxide block polymer has between 5 and 15 ethylene
oxide groups. In one embodiment, the propylene oxide block polymer
extends from the polyol, and wherein the ethylene oxide block
polymer extends from the propylene oxide block polymer. Still
further, the polymer may comprise between 10% and 50% ethylene
oxide, between 20% and 40% ethylene oxide, between 25% and 35%
ethylene oxide, or between 28% and 32% ethylene oxide. Suitably,
these polymers preferably have a molecular weight between about
1,000 and about 2,000,000. The exact makeup of the polymer
determines the relative solubility of the polymer and its ability
to settle and remove water and solids.
[0041] Now referring to FIG. 1, a flow diagram of a suitable
counter-current zone settling process for bitumen froth treatment
is shown. In a Clark Hot Water Process, a conditioned bitumen
slurry 12 is fed into a primary separation vessel (PSV) 14. Bitumen
becomes attached to air bubbles and forms a froth that exits the
PSV in an overflow stream 16. The PSV will also typically produce a
middlings stream 18 and an underflow or tailings stream 20, either
or both of which may be further processed in a tailings oil
recovery vessel (TORV) 22 to produce a secondary froth stream 24.
Regardless of the exact content or processing scheme, a bitumen
froth stream 26 is delivered for processing in a froth treatment
system 28.
[0042] The froth treatment system 28, as shown, includes three zone
settling vessels 30, 32, 34, that are operated with the water and
solids 36 from the dearated froth passing in counter-current flow
to a hydrocarbon diluent, such as aliphatics, aromatics, naphtha,
gasoline, natural gas condensate, and combinations thereof. A
source of clean hydrocarbon diluent 38 is introduced into the third
stage settling vessel 34. If desirable, the hydrocarbon diluent may
be mixed in a mixing vessel 40 prior to entry into the vessel 34 to
assure efficient contact between the hydrocarbon diluent and any
bitumen remaining the tailings. Similar mixing vessels 40 may be
used prior to the other settling vessels 30, 32.
[0043] In each of the vessels 30, 32, 34, the hydrocarbon diluted
bitumen 42 is buoyant and rises to the top of the vessel to be
withdrawn. At the same time, the water and solids 36 sink within
the vessel to be withdrawn from the bottom. By passing the water
and solids 36 successively from vessel 30 to vessel 32 to vessel
34, the tailings become more and more concentrated with less and
less bitumen. By passing the hydrocarbon diluent from vessel 34 to
vessel 32 to vessel 30, the bitumen content of the hydrocarbon
increases and the overall bitumen recovery is maximized. While any
number of vessels or stages may be used, three stages is generally
sufficient. Finally, the tailings 44 are first treated in a diluent
recovery unit prior to being discarded and the dry and clean
diluted bitumen stream 46 is transferred to a bitumen upgrading
facility.
[0044] In accordance with the present invention, a zone settling
aid is added to the froth treatment process. While the zone
settling aid may be beneficially added at any one or more points in
the process, the zone settling aid is preferably added to the
primary froth treatment vessel 30, to mixer 40 just before the
vessel 30, to the froth stream 26, or even to the diluted bitumen
recycle stream being returned to vessel 30. The use of the zone
settling aid improves separation efficiency of the water and solids
out of the diluted bitumen. The improved separation results in
greater overall bitumen recovery (especially greater asphaltene
recovery), higher quality (drier and cleaner) diluted bitumen 46,
greater processing rates through a given set of zone settling
vessels, and lower bitumen content in the tailings 44. Other
advantages of the process may become apparent over time through
expanded use of the zone settling aids. It is foreseen that
optimization of a zone settling aid may involve injection at any,
or even each stage.
EXAMPLE 1
[0045] A bitumen froth containing approximately 60% bitumen, 30%
water and 10% solids was mixed with a hydrocarbon diluent
consisting of 30% toluene and 70% heptane to simulate naphtha. The
diluent to bitumen ratio (D:B) of the diluted bitumen was 0.75 and
the temperature of the mixture was 50.degree. C.
[0046] A first zone settling aid (AST-3) was prepared from a
polyethylene amine acceptor having on average nine active hydrogen
atoms, a first propylene oxide block of about 1451 daltons per
branch, and a second ethylene oxide block of about 435 daltons per
branch. The resulting polyoxyalkylate has a molecular weight of
about 17,000 daltons. The first zone settling aid was mixed with
diluted bitumen at 50 ppm and 100 ppm concentrations,
separately.
[0047] A second zone settling aid (AST-2) was prepared from a triol
acceptor having three active hydrogen atoms that were used to
prepare a sequential polymer having three branches. Each branch had
a first propylene oxide block of about 3000 daltons, a 50/50
mixture of ethylene oxide and propylene oxide block of about 3000
daltons, and a third propylene oxide block of about 3000 daltons.
This second zone settling aid was mixed with diluted bitumen at a
100 ppm concentration.
[0048] The mixture was then placed in a glass column where the
height of an interface between the oil and tailing phases could be
observed and measured. These phases were allowed to settle for 25
minutes to determine a settling rate and the water content of the
hydrocarbon phase. The water content in a blank of the diluted
bitumen was about 3.95% throughout the column with no detectable
settling over a period of 25 minutes. The dry, clean diluted
bitumen contained 0.34% water when treated with 100 ppm of the
first zone settling aid, 0.58% water when treated with 50 ppm of
the first zone settling aid, and 0.60% water when treated with 50
ppm of the second zone settling aid. The water content as a
function of fluid level is provided in Table 1. TABLE-US-00001
TABLE 1 Effects of chemical addition on dehydration at three levels
of fluid Blank AST-3 AST-3 AST-2 Chemical dosage (ppm) 0 50 100 50
KF. H2O % Oil phase 3.95 0.58 0.34 0.598 160 mm from the bottom
3.65 0.65 14.6 0.582 80 mm from the bottom 3.9 36.42 15.2 41.3
[0049] Upon placing the mixtures into columns, the initial
interface heights were between 300 and 350 mm. FIG. 2 was prepared
by measuring the interface height of each column over a 25 minute
period. As shown, the interface of the blank was unchanged. The
first zone settling aid (AST-3) brought about a 12.6 mm/min drop of
the interface with a 50 ppm addition and 5.6 mm/min drop with a 100
ppm addition, while the second zone settling aid (AST-2) brought
about a settling rate similar to the 50 ppm addition of the first
zone settling aid (AST-3).
EXAMPLE 2
[0050] A zone settling aid according to the invention was prepared
with a sorbitol acceptor having six active hydrogen atoms, a first
PO block of about 1000 daltons for each of the six branches, and a
second EO block of about 300 daltons per branch. The total
molecular weight of the zone settling aid was about 7,800
daltons.
[0051] A 404 gram sample of bitumen froth was 60% bitumen (246
grams bitumen), 30% water and 10% solids. The froth was heated to
85.degree. C. and stirred for three minute to homogenize the
sample. To achieve a diluent:bitumen ratio of 0.65, about 160 grams
of naphtha was heated to 85.degree. C. and added to the froth with
stirring for two minutes at 1000 RPM with a paint stirrer. Then,
0.57 ml of a 10% solution of the zone settling aid was added to the
diluted bitumen with three minutes of stirring. Upon settling,
about 300 grams of dry, diluted bitumen was removed from the top of
the settler for a recovery of about 182 grams of bitumen. The
diluted bitumen had a water content of 0.608% determined by Karl
Fischer titration.
[0052] A second stage settler was simulated by adding back 118
grams of naphtha to the underflow remaining in the bottom of the
vessel with stirring for 3 minutes. It was determined that 69 grams
bitumen was in the second stage vessel with 446 grams naphtha for
D:B ratio of about 2.47. Upon settling, about 200 grams of dry,
diluted bitumen was removed from the top of the second stage
settler and determined to contain about 58 grams of bitumen.
Accordingly, the first and second stages recovered about 97.3% of
the available bitumen.
[0053] A third stage settler was simulated by adding 142 grams
naphtha to the remaining underflow. This provided a D:B ratio of
about 24 in the third stage.
[0054] The terms "comprising," "including," and "having," as used
in the claims and specification herein, shall be considered as
indicating an open group that may include other elements not
specified. The term "consisting essentially of," as used in the
claims and specification herein, shall be considered as indicating
a partially open group that may include other elements not
specified, so long as those other elements do not materially alter
the basic and novel characteristics of the claimed invention. The
terms "a," "an," and the singular forms of words shall be taken to
include the plural form of the same words, such that the terms mean
that one or more of something is provided. For example, the phrase
"a solution comprising a phosphorus-containing compound" should be
read to describe a solution having one or more
phosphorus-containing compound. The term "one" or "single" shall be
used to indicate that one and only one of something is intended.
Similarly, other specific integer values, such as "two," are used
when a specific number of things is intended. The terms
"preferably," "preferred," "prefer," "optionally," "may," and
similar terms are used to indicate that an item, condition or step
being referred to is an optional (not required) feature of the
invention.
[0055] It will be understood from the foregoing description that
various modifications and changes may be made in the preferred
embodiment of the present invention without departing from its true
spirit. It is intended that this description is for purposes of
illustration only and should not be construed in a limiting sense.
The scope of this invention should be limited only by the language
of the following claims.
* * * * *