U.S. patent application number 14/236052 was filed with the patent office on 2014-07-31 for method of processing tailings from solvent-based hydrocarbon extraction.
The applicant listed for this patent is Emilio Alvarez, Anjaneya S. Kovvali, Justin D. Pace, Thomas R. Palmer, David C. Rennard. Invention is credited to Emilio Alvarez, Anjaneya S. Kovvali, Justin D. Pace, Thomas R. Palmer, David C. Rennard.
Application Number | 20140209512 14/236052 |
Document ID | / |
Family ID | 47990361 |
Filed Date | 2014-07-31 |
United States Patent
Application |
20140209512 |
Kind Code |
A1 |
Alvarez; Emilio ; et
al. |
July 31, 2014 |
Method of Processing Tailings from Solvent-Based Hydrocarbon
Extraction
Abstract
Described is a method of processing a bituminous feed. The
bituminous feed is solvent extracted to form a bitumen-rich stream
and a bitumen-lean stream. Solvent is recovered from the
bitumen-rich stream to form a bitumen product. Solvent and water
are recovered from the bitumen-lean stream to form dry tailings
with a moisture content of less than 40 wt.%. The dry tailings are
separated into at least two streams, each stream having a moisture
content of less than 40 wt. %, based on at least one physical or
chemical property. At least one of the at least two streams is then
used at an oil sands mine site. In this way, the dry tailings may
be used more effectively.
Inventors: |
Alvarez; Emilio; (Missouri
City, TX) ; Rennard; David C.; (Houston, TX) ;
Palmer; Thomas R.; (Lima, NY) ; Pace; Justin D.;
(Houston, TX) ; Kovvali; Anjaneya S.; (Fairfax,
VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Alvarez; Emilio
Rennard; David C.
Palmer; Thomas R.
Pace; Justin D.
Kovvali; Anjaneya S. |
Missouri City
Houston
Lima
Houston
Fairfax |
TX
TX
NY
TX
VA |
US
US
US
US
US |
|
|
Family ID: |
47990361 |
Appl. No.: |
14/236052 |
Filed: |
August 8, 2012 |
PCT Filed: |
August 8, 2012 |
PCT NO: |
PCT/US12/49978 |
371 Date: |
January 29, 2014 |
Current U.S.
Class: |
208/390 |
Current CPC
Class: |
B08B 3/04 20130101; B08B
3/08 20130101; B07B 13/003 20130101; C10G 1/045 20130101; B07B 1/00
20130101; C10G 1/04 20130101; B07B 13/04 20130101 |
Class at
Publication: |
208/390 |
International
Class: |
C10G 1/04 20060101
C10G001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2011 |
CA |
2753811 |
Claims
1. A method of processing a bituminous feed, the method comprising:
a) solvent extracting the bituminous feed and forming a
bitumen-rich stream and a bitumen-lean stream; b) recovering
solvent from the bitumen-rich stream to form a bitumen product; c)
recovering solvent and water from the bitumen-lean stream to form
dry tailings with a moisture content of less than 40 wt. %; d)
separating the dry tailings into at least two streams, each stream
of the at least two streams having a moisture content of less than
40 wt. %, based on at least one of a physical property and a
chemical property; and e) using at least one of the at least two
streams at an oil sands mine site.
2. The method of claim 1, wherein the at least one of the physical
property and the chemical property comprises one of size, density,
dipole moment, permeability, shape, magnetism, adhesiveness,
wettability, attrition, strength, solubility, inductiveness, and
electric charge.
3. The method of claim 1, wherein step d) comprises separating the
dry tailings with a separator, wherein the separator comprises one
of a screen, a sieve, a blower, a cyclone, a centrifuge, a gravity
settler, filtration, electrostatic precipitation, magnetism, a
shaker, a grinder, milling, and rolling.
4. The method of claim 1, wherein step d) comprises separating the
dry tailings into a coarser particles stream having coarser
particles and a finer particles stream having finer particles.
5. The method of claim 4, further comprising adding water to the
coarser particles stream and pumping the coarser particles stream
into place for construction of a mine form at the oil sands mine
site, wherein the mine form comprises one of a dyke and a road.
6. (canceled)
7. The method of claim 4, wherein the finer particles stream is an
impermeable layer at the oil sands mine site.
8. The method of claim 4, further comprising depositing the coarser
particles stream over the finer particles stream to control
dusting.
9. The method of claim 1, wherein step e) comprises depositing the
at least one of the at least two streams in an oil sands mine
pit.
10. The method of claim 1, wherein step e) comprises using at least
one of the at least two streams for drainage, as foundation, for
reclamation at the oil sands mine site.
11. (canceled)
12. The method of claim 1, further comprising, prior to step d),
reducing a moisture content of the dry tailings by drying,
extraction or agglomeration.
13. (canceled)
14. The method of claim 1, further comprising mixing at least one
of the at least two streams with an additive comprising one of a
polymer, gypsum, alum, and a resin.
15. The method of claim 1, further comprising recovering at least
one heavy metal from at least one of the at least two streams,
wherein the heavy metals comprise at least one of titanium,
strontium, and vanadium.
16. (canceled)
17. The method of claim 1, further comprising grinding at least one
of the at least two streams.
18. The method of claim 1, further comprising recycling at least
one of the at least two streams into the solvent extraction of step
a).
19. The method of claim 1, further comprising combining at least
one of the at least two streams with tailings generated from an
aqueous-based bitumen extraction process.
20. The method of claim 1, wherein the dry tailings have a water:
solids mass ratio of less than 0.15:1.
21. The method of claim 1, wherein the oil sands mine site is one
of a mine site employing aqueous-based bitumen extraction and a
mine site employing solvent-based bitumen extraction.
22. (canceled)
23. The method of claim 1, wherein one of step a) comprises:
contacting the bituminous feed with a bridging liquid comprising
water, and an extraction liquor comprising a solvent; and
separating water from the bitumen-rich stream; and agitation to
form agglomerates comprising solids and water, wherein the
agglomerates are in the bitumen-lean stream.
24. (canceled)
25. The method of claim 23, wherein at least 80 wt. % of the
agglomerates of step c) are less than 2 mm.
26. The method of claim 1, wherein the solvent comprises one of an
organic solvent and a mixture of organic solvents.
27. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of Canadian
Patent Application 2,753,811 filed Sep. 29, 2011 entitled METHOD OF
PROCESSING TAILINGS FROM SOLVENT-BASED HYDROCARBON EXTRACTION, the
entirety of which is incorporated by reference herein.
FIELD
[0002] The present disclosure relates generally to the field of
hydrocarbon extraction from mineable deposits, such as bitumen from
oil sands. More particularly, the present disclosure relates to the
processing of tailings from solvent-based hydrocarbon
extraction.
BACKGROUND
[0003] Oil sands are sand deposits which, in addition to sand,
comprise clays, connate water, and bitumen. Depending on the
geographic location, bitumen may be recovered by mining and
extraction methods or by in-situ recovery methods.
[0004] Oil sands ore in a mining and extraction operation is
typically processed using mechanical and chemical techniques to
separate the bitumen from the sands. In general, water-based
extraction and solvent-based extraction are the two processes that
have been proposed or used to extract bitumen from mined oil sands.
In the case of water-based extraction, water is the dominant liquid
in the process and the extraction occurs by having water displace
the bitumen on the surface of the solids. In the case of
solvent-based extraction, the solvent is the dominant liquid and
the extraction of the bitumen occurs by dissolving bitumen into the
solvent.
[0005] The commercial application of a solvent-based extraction
process has, for various reasons, eluded the oil sands industry. A
major challenge to the application of solvent-based extraction to
oil sands is the tendency of fine particles within the oil sands to
hamper the separation of solids from the bitumen extract. Solvent
extraction with solids agglomeration is a technique that has been
proposed to deal with this challenge. The original application of
this technology was coined Solvent Extraction Spherical
Agglomeration (SESA). A more recent description of the SESA process
can be found in
[0006] Previously described methodologies for SESA have not been
commercially adopted. In general, the SESA process involves mixing
oil sands with a hydrocarbon solvent, adding a bridging liquid to
the oil sands slurry, agitating the mixture in a slow and
controlled manner to nucleate particles, and continuing such
agitation to permit these nucleated particles to form larger
multi-particle spherical agglomerates for removal. The bridging
liquid is preferably water or an aqueous solution since the solids
of oil sands are mostly hydrophilic and water is immiscible with
hydrocarbon solvents. It has been found that the bridging liquid
used in the process can be water with both a high fines and salt
content. In fact, in certain embodiments of the SESA process, it
may be preferable to have aqueous bridging liquid with either high
fines content and/or high dissolved solid content.
[0007] The SESA process described by Meadus et al. in U.S. Pat. No.
4,057,486, involves combining solvent extraction with solids
agglomeration to achieve dry tailings suitable for direct mine
refill. In the process, organic material is separated from oil
sands by mixing the oil sands material with an organic solvent to
form a slurry, after which an aqueous bridging liquid is added in
the amount of 8 to 50 wt % of the feed mixture. By using controlled
agitation, solid particles from oil sands come into contact with
the aqueous bridging liquid and adhere to each other to form
macro-agglomerates of a mean diameter of 2 mm or greater. The
formed agglomerates are more easily separated from the organic
extract compared to un-agglomerated solids. The organic extract
free agglomerates can be sintered at high temperatures to make
useful construction material. For example, halide salts such as
NaCl, KCl, and CaCl.sub.2 can be dissolved in the aqueous bridging
liquid to form agglomerates that, when sintered at elevated
temperatures, produce very strong aggregates.
[0008] The oil sands industry has become relatively adept at
handling aqueous tailings streams from water-based bitumen
extraction. These tailings are sorted by size in a variety of
operations, and bitumen and minerals can then be extracted. For
instance, settlers and cyclones are currently used for aqueous
tailings to separate particular streams by particle size
distribution; the coarser fraction can be pumped into place and
rapidly drained, making it an excellent construction material.
[0009] Oil sands tailings are unique among mining tailings in that
they comprise residual hydrocarbons. They often also comprise
metals, clays, and sands. In a water-based extraction process, oil
sand tailings comprise water. Because of this water content, the
tailings are pumpable and easily fed into separation units common
in the oil industry. In this way, metals can be extracted from the
aqueous tailings, bitumen can be skimmed from floating mats on
tailings ponds, and coarse and fines fractions can be separated by
gravity or enhanced gravity separation All of these separations of
aqueous tailings currently take place in the oil sands
industry.
[0010] While one solution to treating solid tailings could be to
wet the tailings and subject them to the same processes as aqueous
tailings this solution greatly diminishes the value of a process
that produces dry tailings in the first place.
[0011] Outside of the oil sands mining industry, solids handling
and separation is common in the mining industry. In particular,
several mechanisms exist for the dry beneficiation of coal, as
described by Lockhart, "Dry Beneficiation of Coal", Powder
Technology 40 (1984) 17-42 and also by Dwari and Rao, "Dry
Beneficiation of Coal--A Review", Mineral Processing and Extractive
Metallurgy Review 28 (2007) 177-234. These techniques are applied
to ores, which are routinely separated and classified, and the
methods listed above, such as cyclones, sieves, magnets, etc., are
established technologies.
[0012] B. D. Sparks and F. W. Meadus, "A Combined Solvent
Extraction and Agglomeration Technique for the Recovery of Bitumen
from Tar Sands", Canadian Chemical Engineering Conference, Calgary:
Energy Processing: Tar Sands Technology, 1979 describes the
production of solid agglomerates, and refers to the storage of
these materials without containment.
[0013] U.S. Patent Publication No. 2010/0258478 Moran et al.
describes a method for separating aqueous oil sand tailings into a
bitumen rich stream and a dry mineral stream, but separation of the
dry mineral stream is not mentioned.
[0014] Newman and Arnold, in "Dry stack tailings design for the
Rosemont Copper project", Proceedings of the 14th International
Conference on Tailings and Mine Waste 2010, Vail, Colo., describe a
dry tailings project requiring a buttress and a cover requirement
for the tailings facility.
[0015] Lupo and Hall, in "Dry stack tailings--design
considerations", ibid, describe that tailings could be distributed
in a stack based on their moisture content exiting the extraction
process to reduce flow of fluid tailings and dyke strength
requirements. No separation is mentioned; instead, drier tailings
resulting from the primary process are deposited in one way while
process upset tailings are deposited in another.
[0016] U.S. Pat. No. 4,240,897 (Clarke) describes a method of
producing dry tailings and recommends that these tailings be mixed
with overburden and used as backfill for reclamation. No separation
of tailings is mentioned.
[0017] U.S. Pat. No. 7,695,612 (Erasmus) describes a method of
recovering heavy minerals from aqueous oil sands tailings.
SUMMARY
[0018] Described is a method of processing a bituminous feed. The
bituminous feed is solvent extracted to form a bitumen-rich stream
and a bitumen-lean stream. Solvent is recovered from the
bitumen-rich stream to form a bitumen product. Solvent and water
are recovered from the bitumen-lean stream to form dry tailings
with a moisture content of less than 40 wt. %. The dry tailings are
separated into at least two streams, each stream having a moisture
content of less than 40 wt. %, based on at least one physical or
chemical property. At least one of the at least two streams is then
used at an oil sands mine site. In this way, the dry tailings may
be used more effectively.
[0019] Other aspects and features of the present disclosure will
become apparent to those ordinarily skilled in the art upon review
of the following description of specific embodiments in conjunction
with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Embodiments of the present disclosure will now be described,
by way of example only, with reference to the attached figures.
[0021] FIG. 1 is a schematic illustrating a disclosed
embodiment.
[0022] FIG. 2 is a schematic illustrating a disclosed
embodiment.
[0023] FIG. 3 is a schematic illustrating a disclosed
embodiment.
[0024] FIG. 4 is a schematic illustrating a disclosed
embodiment.
DETAILED DESCRIPTION
[0025] As used herein, the term "bituminous feed" refers to a
stream derived from oil sands that requires downstream processing
in order to realize valuable bitumen products or fractions. The
bituminous feed is one that comprises bitumen along with
undesirable components. Such a bituminous feed may be derived
directly from oil sands, and may be, for example, raw oil sands
ore. Further, the bituminous feed may be a feed that has already
realized some initial processing but nevertheless requires further
processing. Also, recycled streams that comprise bitumen in
combination with other components for removal as described herein
can be included in the bituminous feed. A bituminous feed need not
be derived directly from oil sands, but may arise from other
processes. For example, a waste product from other extraction
processes which comprises bitumen that would otherwise not have
been recovered may be used as a bituminous feed. Such a bituminous
feed may be also derived directly from oil shale oil, bearing
diatomite or oil saturated sandstones.
[0026] As used herein, the term "agglomerate" refers to conditions
that produce a cluster, aggregate, collection or mass, such as
nucleation, coalescence, layering, sticking, clumping, fusing and
sintering, as examples.
[0027] As used herein, the term "dry tailings" refers to tailings
with a moisture content of less than 40 wt. %.
[0028] Dry tailings are not common in the oil sands industry. Where
produced, dry oil sands tailings have been seen as an end state
rather than as a composition suitable for further processing and
use. Additionally, solid-solid separation is not common in the oil
sands industry. As described herein, dry tailings from
solvent-based extraction may be processed for advantageous use.
[0029] As described in the summary section, the present disclosure
relates to a method of processing a bituminous feed. The bituminous
feed is solvent extracted to form a bitumen-rich stream and a
bitumen-lean stream. Solvent is recovered from the bitumen-rich
stream to form a bitumen product. Solvent and water are recovered
from the bitumen-lean stream to form dry tailings with a moisture
content of less than 40 wt. %. The dry tailings are separated into
at least two streams, each stream having a moisture content of less
than 40 wt. %, based on at least one physical or chemical property.
At least one of the at least two streams is then used at an oil
sands mine site.
[0030] Suitable solvent-based extraction processes may include
solvent-based extraction processes that uses an aqueous stream in
the extraction process. Exemplary solvent-based extraction
processes include, but are not limited to, those described in the
background section, those described below, and those described in
Canadian Patent Application Serial No. 2,724,806 ("Adeyinka et
al.") filed Dec. 10, 2010 and entitled "Process and Systems for
Solvent Extraction of Bitumen from Oil Sands".
Summary of Processes of Solvent Extraction Described in Adeyinka et
al.
[0031] One method of extracting bitumen from oil sands in a manner
that employs solvent extraction with solids agglomeration is
described by Adeyinka et al. In this process, a solvent is combined
with a bituminous feed derived from oil sands to form an initial
slurry. Separation of the initial slurry into a fine solids stream
and a coarse solids stream may be followed by mixing a bridging
liquid with the fine solid stream and agglomeration of solids from
the fine solids stream to form an agglomerated slurry. The
agglomerated slurry can be separated into agglomerates and a low
solids bitumen extract. Optionally, the coarse solids stream may be
reintroduced and further extracted in the agglomerated slurry. A
low solids bitumen extract can be separated from the agglomerated
slurry for further processing. Optionally, the mixing of a second
solvent with the low solids bitumen extract to extract bitumen may
take place, forming a solvent-bitumen low solids mixture, which can
then be separated further into low grade and high grade bitumen
extracts. Recovery of solvent from the low grade and/or high grade
extracts is conducted, to produce bitumen products of commercial
value. The agglomerates may be sent to a tailings solvent recovery
unit to recover solvent and water, leaving dry tailings. Additional
details of a solvent-based extraction process are described
below.
Processing of Tailings from Solvent-Based Extraction
[0032] Dry tailings from solvent-based bitumen extraction may be
separated into at least two streams, each stream having a moisture
content of less than 40 wt. %. These streams may be suitable for
different uses. At least one stream may be suitable for use at the
oil sands mine site, or another oil sands mine site, including an
water-based bitumen extraction mine site. The separation is
effected by leveraging a physical or chemical property of the
tailings.
[0033] Characteristics to be leveraged for the dry oil sands
tailings separation may include, but are not limited to size,
density, dipole moment, permeability, shape, magnetism,
adhesiveness, wettability, attrition, strength, solubility,
inductiveness, and electric charge.
[0034] Suitable methods or devices for separating dry oil sands
tailings may include, but are not limited to a screen, a sieve, a
blower (for instance an air blower), gravity separation or enhanced
gravity separation (for instance using a cyclone, centrifuge, or
settler), filtration, electrostatic precipitation, a magnet, a
shaker, a grinder, milling, and rolling.
[0035] Separation may also be achieved naturally without using a
device, i.e. by consolidation over time. In one embodiment, the dry
tailings are rolled down an incline such as a hill or mine face.
The tailings separate themselves according to size and/or density.
Materials at the top are of a lighter density and/or a smaller
size. In another embodiment, first and second streams are separated
from one another by a sieve, screen, or a blower. In another
embodiment, the tailings are separated in a cyclone. In another
embodiment, they are separated according to their electrostatic
charge. In another embodiment, they are separated by a magnetic
field. In another embodiment, the tailings are separated by their
tendency to cling to a surface. In another embodiment, the tailings
are separated by their strength. In another embodiment, the
tailings are separated by being selectively crushed in a mill.
[0036] A first of the separated streams may be used as a
construction material while a second is used for mine backfill. In
this embodiment, the first stream may be a coarser stream. The
second stream may be comprised of a finer fraction of particles.
The separation into these streams would allow the coarser stream to
be mixed with water because it would rapidly drain. The coarser
material could subsequently be pumped into place, allowing
construction according to the general practice in the industry, for
instance for construction of a mine form at the oil sands site,
such as a dyke or a road.
[0037] At least one of the at least two streams may be used
drainage, as foundation, as a road, for reclamation, or as a dyke,
at the oil sands mine site, or is used in a deposit for growing
vegetation.
[0038] A stream of finer particle sized tailings may be separated
from a stream of coarser particle sized tailings. The finer
particles are used in the lining of a tailings cell to reduce its
permeability to water. The tailings could be placed at the bottom
of, along the walls of, and/or on the cap of a tailings
deposit.
[0039] The streams may be separated by charge or magnetism. An
incoming tailings stream is subjected to a magnetic moment or an
electrostatic charge. The portion of the incoming tailings stream
that responds to this force is captured separately from the portion
that does not respond to the force. The mineral composition of the
tailings being different, one of the tailings streams, rich in one
or more minerals, is used in a mineral extraction process to
recover the valuable minerals. Another stream is used for mine
backfill. In another embodiment, the mineral poor stream is placed
in a deposit closer to potential contact with water. The mineral
rich tailings are placed farther away from potential contact with
water. In another embodiment, the mineral rich stream is placed
under water, and the mineral poor stream is placed in or over the
water table.
[0040] The separation may be used to produce streams of differing
sizes or densities, which can be used in different capacities in
mine backfill. The lighter stream may be more prone to dusting, and
may be covered with another material, such as a coarser stream of
tailings. The heavier stream may be used as a capillary barrier. In
this application, the coarser stream has a low hydraulic wicking
potential while dry as compared to the finer stream. A material may
be selectively moved from the deposit based on its materials
properties.
[0041] The tailings may be separated into streams that differ by
their chemical composition into a chemically active stream and a
chemically inert stream. The tailings may be separated into a
stream that can be heat treated to form a cementitious material.
The tailings may be separated into a stream that can be mixed with
a chemical binder and another stream that is not mixed with a
chemical binder.
[0042] As described above, the term "dry tailings" refers to
tailings with a moisture content of less than 40 wt. %. In another
embodiment, the dry tailings may have a moisture content of less
than 30 wt. %.
[0043] FIG. 1 illustrates an embodiment using airblowing to
separate dry tailings cyclonically. Tailings 100 may be dried 101
to form dry tailings 102. The dry tailings 102 are airblown in a
cyclone 104 for separation by particle size and/or density. The
cyclone produces a lighter stream 106 and a heavier stream 108. The
lighter stream 106 may comprise mainly clays and may be suitable as
an impermeable layer, such as a clay liner.
[0044] The heavier stream 108 may be a coarser material and may be
suitable for use as a construction material, such as for roads or
containment. In an example where both streams are used at the mine
site, as illustrated in FIG. 1, the heavier stream 108 may be used
as a containment structure 110 and the lighter stream 108 may be
used as an impermeable layer 112, for containing aqueous tailings
114.
[0045] FIG. 2 illustrates an embodiment leveraging the magnetic
dipole moment present in some of the dry tailings. Tailings 200 may
be dried 201 to form dry tailings 202. The dry tailings 202 are
separated using a magnet 204 into a higher dipole moment containing
stream 206 which may have a higher concentration of metals, and a
lower dipole moment containing stream 208. The higher dipole moment
containing stream 206 may be further processed to reclaim metals.
The lower dipole moment containing stream 208 may be used as mine
backfill.
[0046] FIG. 3 illustrates an embodiment where dry tailings 302 are
passed to a blower 304 to separate the dry tailings 302 according
to how prone they are to being carried by the wind. The coarser
fraction 306 drops out faster than the finer fraction 308. The
coarser fraction 306 may be deposited in a windy area, or on a
higher elevation than the finer fraction 308. Alternatively, the
finer fraction 308 may be placed first and then covered by the
coarser fraction 306 to reduce dusting.
[0047] FIG. 4 illustrates an embodiment where an induced dipole
moment 404 separates dry tailings 402 according to the availability
of minerals containing a dipole moment. The tailings 400 and dryer
401 are also illustrated. The material containing a higher dipole
moment 406 is more prone to acid rock drainage and may be placed in
a subaqueous environment to mitigate its oxidation. This layer may
be covered with the material containing a lower dipole moment 408.
Alternatively, the material containing a higher dipole moment 406
may be placed away from an aqueous material 410, and is insulated
with the material containing a lower dipole moment 408. The mine
pit 412 is also illustrated.
[0048] For dry sands tailings, many uses may favor a particular
fraction of the tailings rather than the whole tailings.
Furthermore, some fractions of the tailings may be preferred over
other fractions of the tailings. Examples include construction
materials for dykes or roads, as backfill within the mine, or as a
recycle stream to aid in extraction. An example of a recycle stream
aiding in the extraction process is as follows. It has been
previously shown that increasing the solids content, or more
preferably the fines content, of a slurry may improve the solvent
extraction with solids agglomeration process. Thus, a fines solids
stream produced by a process described herein may be redirected
back to the solvent extraction process to aid in solids
agglomeration. More uses can be envisioned, such as mineral
extraction from a mineral rich stream, as a pH buffer in a tailings
pond, or as an absorption stream to enhance the solids content of
fluid tailings, as described above. One example is to use the fines
streams as an impermeable layer. Such an impermeable layer can be
used as liner for mature fine tailings produced in an aqueous-based
extraction process.
[0049] The moisture content of the tailings may be reduced prior to
separation, for instance by drying, extraction, or
agglomeration.
[0050] At least one of the at least two streams may be mixed with
an additive comprising a polymer, gypsum, alum, or a resin.
[0051] At least one of the at least two streams may be mixed with
tailings generated from an aqueous-based bitumen extraction
process.
[0052] At least one of the at least two streams may be grinded.
[0053] One or more heavy metals may be recovered from at least one
of the at least two streams. The heavy metals may be titanium,
strontium, or vanadium, or a combination thereof.
[0054] At least one of the at least two streams may be recycled
into the solvent extraction of step a).
[0055] The dry tailings may have a water:solids mass ratio of less
than 0.15:1.
[0056] The oil sands mine site may be mine site employing
aqueous-based bitumen extraction or a mine site employing
solvent-based bitumen extraction.
Description of one Solvent-Based Extraction Process Using
Agglomeration:
Agglomeration.
[0057] In one embodiment, the formed agglomerates are sized on the
order of 0.1-1.0 mm, or on the order of 0.1-0.3 mm. In one
embodiment, at least 80 wt. % of the formed agglomerates are
0.1-1.0 mm, or 0.1 to 0.3 mm in size. The rate of agglomeration may
be controlled by a balance between intensity of agitation within
the agglomeration vessel, shear within the vessel which can be
adjusted by for example changing the shape or size of the vessel,
fines content of the slurry, bridging liquid addition, and
residence time of the agglomeration process. The agglomerated
slurry may have a solids content of 20 to 70 wt %.
Agitation.
[0058] Agglomeration is assisted by some form of agitation. The
form of agitation may be mixing, shaking, rolling, or another known
suitable method. The agitation of the feed need only be severe
enough and of sufficient duration to intimately contact the
emulsion with the solids in the feed. Exemplary rolling type
vessels include rod mills and tumblers. Exemplary mixing type
vessels include mixing tanks, blenders, and attrition scrubbers. In
the case of mixing type vessels, a sufficient amount of agitation
is needed to keep the formed agglomerates in suspension. In rolling
type vessels, the solids content of the feed is, in one embodiment,
greater than 40 wt. % so that compaction forces assist agglomerate
formation. The agitation of the slurry has an impact on the growth
of the agglomerates. In the case of mixing type vessels, the mixing
power can be increased in order to limit the growth of agglomerates
by attrition of said agglomerates. In the case of rolling type
vessels the fill volume and rotation rate of the vessel can be
adjusted in order to increase the compaction forces used in the
comminution of agglomerates. These agitation parameters can be
adjusted in the control system described herein.
Extraction Liquor.
[0059] The extraction liquor comprises a solvent used to extract
bitumen from the bituminous feed. The term "solvent" as used herein
should be understood to mean either a single solvent, or a
combination of solvents.
[0060] In one embodiment, the extraction liquor comprises a
hydrocarbon solvent capable of dissolving the bitumen. The
extraction liquor may be a solution of a hydrocarbon solvent(s) and
bitumen, where the bitumen content of the extraction liquor may
range between 10 and 70 wt %, or 10 and 50 wt %. It may be
desirable to have dissolved bitumen within the extraction liquor in
order to increase the volume of the extraction liquor without an
increase in the required inventory of hydrocarbon solvent(s). In
cases where non-aromatic hydrocarbon solvents are used, the
dissolved bitumen within the extraction liquor also increases the
solubility of the extraction liquor towards dissolving additional
bitumen.
[0061] The extraction liquor may be mixed with the bituminous feed
to form a slurry where most or all of the bitumen from the oil
sands is dissolved into the extraction liquor. In one embodiment,
the solids content of the slurry is in the range of 10 wt % to 75
wt %, or 50 to 65 wt %. A slurry with a higher solids content may
be more suitable for agglomeration in a rolling type vessel, where
the compressive forces aid in the formation of compact
agglomerates. For turbulent flow type vessels, such as an attrition
scrubber, a slurry with a lower solids content may be more
suitable.
[0062] The solvent used in the process may include low boiling
point solvents such as low boiling point cycloalkanes, or a mixture
of such cycloalkanes, which substantially dissolve asphaltenes. The
solvent may comprise a paraffinic solvent in which the solvent to
bitumen ratio is maintained at a level to avoid or limit
precipitation of asphaltenes.
[0063] While it is not necessary to use a low boiling point
solvent, when it is used, there is the extra advantage that solvent
recovery through an evaporative process proceeds at lower
temperatures, and requires a lower energy consumption. When a low
boiling point solvent is selected, it may be one having a boiling
point of less than 100.degree. C.
[0064] The solvent selected according to certain embodiments may
comprise an organic solvent or a mixture of organic solvents. For
example, the solvent may comprise a paraffinic solvent, an open
chain aliphatic hydrocarbon, a cyclic aliphatic hydrocarbon, or a
mixture thereof. Should a paraffinic solvent be utilized, it may
comprise an alkane, a natural gas condensate, a distillate from a
fractionation unit (or diluent cut), or a combination of these
containing more than 40% small chain paraffins of 5 to 10 carbon
atoms. These embodiments would be considered primarily a small
chain (or short chain) paraffin mixture. Should an alkane be
selected as the solvent, the alkane may comprise a normal alkane,
an iso-alkane, or a combination thereof. The alkane may
specifically comprise heptane, iso-heptane, hexane, iso-hexane,
pentane, iso-pentane, or a combination thereof. Should a cyclic
aliphatic hydrocarbon be selected as the solvent, it may comprise a
cycloalkane of 4 to 9 carbon atoms. A mixture of C.sub.4-C.sub.9
cyclic and/or open chain aliphatic solvents would be
appropriate.
[0065] Exemplary cycloalkanes include cyclohexane, cyclopentane, or
a mixture thereof.
[0066] If the solvent is selected as the distillate from a
fractionation unit, it may for example be one having a final
boiling point of less than 180.degree. C. An exemplary upper limit
of the final boiling point of the distillate may be less than
100.degree. C.
[0067] A mixture of C.sub.4-C.sub.10 cyclic and/or open chain
aliphatic solvents would also be appropriate. For example, it can
be a mixture of C.sub.4-C.sub.9 cyclic aliphatic hydrocarbons and
paraffinic solvents where the percentage of the cyclic aliphatic
hydrocarbons in the mixture is greater than 50%.
[0068] Extraction liquor may be recycled from a downstream step.
For instance, as described below, solvent recovered in a solvent
recovery unit, may be used to wash agglomerates, and the resulting
stream may be used as extraction liquor. As a result, the
extraction liquor may comprise residual bitumen and residual solid
fines. The residual bitumen increases the volume of the extraction
liquor and it may increase the solubility of the extraction liquor
for additional bitumen dissolution.
[0069] The solvent may also include additives. These additives may
or may not be considered a solvent per se. Possible additives may
be components such as de-emulsifying agents or solids aggregating
agents. Having an agglomerating agent additive present in the
bridging liquid and dispersed in the first solvent may be helpful
in the subsequent agglomeration step. Exemplary agglomerating agent
additives include cements, fly ash, gypsum, lime, brine, water
softening wastes (e.g. magnesium oxide and calcium carbonate),
solids conditioning and anti-erosion aids such as polyvinyl acetate
emulsion, commercial fertilizer, humic substances (e.g. fulvic
acid), polyacrylamide based flocculants and others. Additives may
also be added prior to gravity separation with the second solvent
to enhance removal of suspended solids and prevent emulsification
of the two solvents. Exemplary additives include methanoic acid,
ethylcellulose and polyoxyalkylate block polymers.
Bridging Liquid.
[0070] A bridging liquid is a liquid with affinity for the solids
particles in the bituminous feed, and which is immiscible in the
solvent. Exemplary aqueous liquids may be recycled water from other
aspects or steps of oil sands processing. The aqueous liquid need
not be pure water, and may indeed be water containing one or more
salt, a waste product from conventional aqueous oil sand extraction
processes which may include additives, aqueous solutions with a
range of pH, or any other acceptable aqueous solution capable of
adhering to solid particles within an agglomerator in such a way
that permits fines to adhere to each other. An exemplary bridging
liquid is water.
[0071] The total amount of bridging liquid added to the slurry may
be controlled in order to optimize bitumen recovery and the rate of
solid-liquid separation. By way of examples, the total amount of
bridging liquid added to the slurry may be such that a ratio of
bridging liquid plus connate water from the bituminous feed to
solids within the agglomerated slurry is in the range of 0.02 to
0.25, or in the range of 0.05 to 0.11.
[0072] The bridging liquid may be added in a concentration of less
than 50 wt % of the oil sands feed, or less 25 wt %.
[0073] In one embodiment, the bridging liquid may comprise fine
particles (sized less than 44 pm) suspended therein. These fine
particles may serve as seed particles for the agglomeration
process. In one embodiment, the bridging liquid has a solids
content of less than 40 wt. %.
Ratio of Solvent to Bitumen for Agglomeration.
[0074] The process may be adjusted to render the ratio of the
solvent to bitumen in the agglomerator at a level that avoids
precipitation of asphaltenes during agglomeration. Some amount of
asphaltene precipitation is unavoidable, but by adjusting the
amount of solvent flowing into the system, with respect to the
expected amount of bitumen in the bituminous feed, when taken
together with the amount of bitumen that may be entrained in the
extraction liquor used, can permit the control of a ratio of
solvent to bitumen in the agglomerator. When the solvent is
assessed for an optimal ratio of solvent to bitumen during
agglomeration, the precipitation of asphaltenes can be minimized or
avoided beyond an unavoidable amount. Another advantage of
selecting an optimal solvent to bitumen ratio is that when the
ratio of solvent to bitumen is too high, costs of the process may
be increased due to increased solvent requirements.
[0075] An exemplary ratio of solvent to bitumen to be selected as a
target ratio during agglomeration is less than 2:1. A ratio of
1.5:1 or less, and a ratio of 1:1 or less, for example, a ratio of
0.75:1, would also be considered acceptable target ratios for
agglomeration. For clarity, ratios may be expressed herein using a
colon between two values, such as "2:1", or may equally be
expressed as a single number, such as "2", which carries the
assumption that the denominator of the ratio is 1 and is expressed
on a weight to weight basis.
[0076] Measurement of the solvent and bitumen content of the
extraction liquor and/or bitumen extract could occur directly or by
proxy. Direct measurement of solvent and bitumen content could
involve evaporating off the solvent and measuring the mass of both
liquids, or use of a gas chromatograph, mass balance, spectrometer,
or titration. Indirect measurement of solvent and bitumen content
could include measuring : density, the index of refraction,
opacity, or other properties.
Slurry System.
[0077] The slurry system may optionally be a mix box, a pump, or a
combination of these. By slurrying the extraction liquor together
with the bituminous feed, and optionally with additional additives,
the bitumen entrained within the feed is given an opportunity to
become extracted into the solvent phase prior to agglomeration
within the agglomerator.
[0078] The resulting slurry from the slurry system may have a solid
content in the range of 20 to 65 wt %. In another embodiment, the
slurry may have a solid content in the range of 20 to 50 wt %. In
another embodiment, the slurry may have a solid content in the
range of 40 to 65 wt %. In the case of mixing type vessels, a lower
solid content may be preferred since that will assist in the proper
mixing of the bridging liquid and reduce the mixing energy needed
to keep the slurry well mixed. In the case of rolling type vessels,
a higher solid content may be preferred since that will increase
the compaction forces used in the comminution of agglomerates.
Additionally, the increased compaction forces may reduce the amount
of hydrocarbons that remain in the agglomerates and produce
stronger agglomerates.
[0079] The preferred temperature of the slurry is in the range of
20-60.degree. C. An elevated slurry temperature is desired in order
to increase the bitumen dissolution rate and reduce the viscosity
of the slurry to promote more effective sand digestion and
agglomerate formation. Temperatures above 60.degree. C. are
generally avoided due to the complications resulting from high
vapor pressures.
Residence Time.
[0080] The residence time of the extraction process may be greater
than 5 minutes, or may be greater than 10 minutes, or may be
greater than 15 minutes, or may greater than 30 minutes. Depending
on the desired level of agglomeration, the residence time of the
agglomeration process may be in the range of 15 seconds to 10
minutes. In order to maximize bitumen recovery, the residence time
of the agglomeration process may be in the range of 1 to 5
minutes.
Solid-Liquid Separator.
[0081] As described above, the agglomerated slurry may be separated
into a low solids bitumen extract and agglomerates in a
solid-liquid separator. The solid-liquid separator may comprise any
type of unit capable of separating solids from liquids, so as to
remove agglomerates. Exemplary types of units include a gravity
separator, a clarifier, a cyclone, a screen, a belt filter or a
combination thereof.
[0082] The system may contain a solid-liquid separator but may
alternatively contain more than one. When more than one
solid-liquid separation step is employed at this stage of the
process, it may be said that both steps are conducted within one
solid-liquid separator, or if such steps are dissimilar, or not
proximal to each other, it may be said that a primary solid-liquid
separator is employed together with a secondary solid-liquid
separator. When a primary and secondary unit are both employed,
generally, the primary unit separates agglomerates, while the
secondary unit involves washing agglomerates.
[0083] Non-limiting methods of solid-liquid separation of an
agglomerated slurry are described in Canadian Patent Application
Serial No. 2,724,806 (Adeyinka et al.), filed Dec. 10, 2010.
Secondary Stage of Solid-Liquid Separation to Wash
Agglomerates.
[0084] As a component of the solid-liquid separator, a secondary
stage of separation may be introduced for countercurrently washing
the agglomerates separated from the agglomerated slurry. The
initial separation of agglomerates may be said to occur in a
primary solid-liquid separator, while the secondary stage may occur
within the primary unit, or may be conducted completely separately
in a secondary solid-liquid separator. By "countercurrently
washing", it is meant that a progressively cleaner solvent is used
to wash bitumen from the agglomerates. Solvent involved in the
final wash of agglomerates may be re-used for one or more upstream
washes of agglomerates, so that the more bitumen entrained on the
agglomerates, the less clean will be the solvent used to wash
agglomerates at that stage. The result being that the cleanest wash
of agglomerates is conducted using the cleanest solvent.
[0085] A secondary solid-liquid separator for countercurrently
washing agglomerates may be included in the system or may be
included as a component of a system described herein. The secondary
solid-liquid separator may be separate or incorporated within the
primary solid-liquid separator. The secondary solid-liquid
separator may optionally be a gravity separator, a cyclone, a
screen or belt filter. Further, a secondary solvent recovery unit
for recovering solvent arising from the solid-liquid separator can
be included. The secondary solvent recovery unit may be a
conventional fractionation tower or a distillation unit.
[0086] When conducted in the process, the secondary stage for
countercurrently washing the agglomerates may comprise a gravity
separator, a cyclone, a screen, a belt filter, or a combination
thereof.
[0087] The solvent used for washing the agglomerates may be solvent
recovered from the low solids bitumen extract, as described in
Canadian Patent Application Serial No. 2,724,806 (Adeyinka et al.).
A second solvent may alternatively or additionally be used as
described in Canadian Patent Application Serial No. 2,724,806
(Adeyinka et al.) for additional bitumen extraction downstream of
the agglomerator.
Recycle and Recovery of Solvent.
[0088] The process may involve removal and recovery of solvent used
in the process.
[0089] In this way, solvent is used and re-used, even when a good
deal of bitumen is entrained therein. Because an exemplary
solvent:bitumen ratio in the agglomerator may be 2:1 or lower, it
is acceptable to use recycled solvent containing bitumen to achieve
this ratio. The amount of make-up solvent required for the process
may depend solely on solvent losses, as there is no requirement to
store and/or not re-use solvent that has been used in a previous
extraction step. When solvent is said to be "removed", or
"recovered", this does not require removal or recovery of all
solvent, as it is understood that some solvent will be retained
with the bitumen even when the majority of the solvent is
removed.
[0090] The system may contain a single solvent recovery unit for
recovering the solvent(s) arising from the gravity separator. The
system may alternatively contain more than one solvent recovery
unit.
[0091] Solvent may be recovered by conventional means. For example,
typical solvent recovery units may comprise a fractionation tower
or a distillation unit. The solvent recovered in this fashion will
not contain bitumen entrained therein. This clean solvent is
preferably used in the last wash stage of the agglomerate washing
process in order that the cleanest wash of the agglomerates is
conducted using the cleanest solvent.
[0092] The solvent recovered in the process may comprise entrained
bitumen therein, and can thus be re-used as the extraction liquor
for combining with the bituminous feed. Other optional steps of the
process may incorporate the solvent having bitumen entrained
therein, for example in countercurrent washing of agglomerates, or
for adjusting the solvent and bitumen content prior to
agglomeration to achieve the selected ratio within the agglomerator
that avoids precipitation of asphaltenes.
[0093] The agglomerates may be sent to a tailings solvent recovery
unit to recover solvent and water, leaving dry tailings.
Dilution of Agglomerator Discharge to Improve Product Quality.
[0094] Solvent may be added to the agglomerated slurry for dilution
of the slurry before discharge into the primary solid-liquid
separator, which may be for example a deep cone settler. This
dilution can be carried out in a staged manner to pre-condition the
primary solid-liquid separator feed to promote higher solids
settling rates and lower solids content in the solid-liquid
separator's overflow. The solvent with which the slurry is diluted
may be derived from recycled liquids from the liquid-solid
separation stage or from other sources within the process.
[0095] When dilution of agglomerator discharge is employed in this
embodiment, the solvent to bitumen ratio of the feed into the
agglomerator is set to obtain from about 10 to about 90 wt %
bitumen in the discharge, and a workable viscosity at a given
temperature. In certain cases, these viscosities may not be optimal
for the solid-liquid separation (or settling) step. In such an
instance, a dilution solvent of equal or lower viscosity may be
added to enhance the separation of the agglomerated solids in the
clarifier, while improving the quality of the clarifier overflow by
reducing viscosity to permit more solids to settle. Thus, dilution
of agglomerator discharge may involve adding the solvent, or a
separate dilution solvent, which may, for example, comprise an
alkane.
[0096] In the preceding description, for purposes of explanation,
numerous details are set forth in order to provide a thorough
understanding of the embodiments. However, it will be apparent to
one skilled in the art that these specific details are not
required.
[0097] The above-described embodiments are intended to be examples
only. Alterations, modifications and variations can be effected to
the particular embodiments by those of skill in the art without
departing from the scope.
* * * * *