Note: Descriptions are shown in the official language in which they were submitted.
CA 02704927 2010-05-21
RECOVERY OF HYDROCARBON FROM AQUEOUS STREAMS
FIELD OF THE INVENTION
[0001] The present invention relates generally to a process for hydrocarbon
extraction
from mineable deposits, such as bitumen from oil sands, and to a system for
implementing such a
process. Processes and systems are described for recovery of hydrocarbon
associated with waste
streams produced in conventional water-based bitumen extraction processes.
BACKGROUND OF THE INVENTION
[0002] Methodologies for extracting hydrocarbon from oil sands have required
energy
intensive processing steps to separate solids and water from the products
having commercial
value.
[0003] Previously described methodologies for solvent extraction spherical
agglomeration
(SESA), have not been commercially adopted. For a description of the SESA
process, see
Sparks et al., Fuel 1992(71); 1349-1353. Such processes involved mixing a
slurry of oil sands
material with a hydrocarbon solvent (such as a high boiling point solvent),
adding a bridging liquid
(for example, water), agitating this mixture in a slow and controlled manner
to nucleate particles,
and continuing such agitation so as to permit these nucleated particles to
form larger multi-particle
spherical agglomerates for removal. A bridging liquid is a liquid with
affinity for the solid particles
(i.e. preferentially wets the solid particles) but is immiscible in the
solvent. The process was
conducted at about 50 - 80 C (see also Canadian Patent Application 2,068,895
of Sparks et al.).
The enlarged size of the agglomerates formed permits easy removal of the
solids by
sedimentation, screening or filtration.
[0004] Solvent recovery from the solids produced in previously described
processes would
be difficult, due to the nature of the solvent proposed for use in the
extraction process. The
proposed solvents in previously described processes have a low molecular
weight, high aromatic
content, and low short chain paraffin content. Naphtha was the solvent
proposed for the SESA
process, with a final boiling point ranging between 180-220 C, and a
molecular weight of 100 -
215 g/mol. With such high boiling point solvents, the recovery would be energy
intensive as
significant energy is required to vaporize the residual hydrocarbon and to
release hydrocarbon
trapped within the agglomerates.
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[0005] A methodology described by Meadus et al. in U.S. Patent No. 4,057,486,
involved
combining solvent extraction with particle enlargement to achieve spherical
agglomeration of
tailings suitable for direct mine refill. Organic material was separated from
oil sands by mixing the
oil sands material with an organic solvent to form a slurry, after which an
aqueous bridging liquid
was added in small amounts. By using controlled agitation, solid particles
from oil sands adhere to
each other and were enlarged to form macro-agglomerates of mean diameter
greater than 2 mm
from which the bulk of the bitumen and solvent was excluded. This process
permitted a significant
decrease in water use, as compared with conventional water-based extraction
processes.
Solvents used in the process were of low molecular weight, having aromatic
content, but only
small amounts of short chain paraffins. While this may have resulted in a high
recovery of
bitumen, the energy intensity required for solvent recovery would be too high
to be adopted in a
commercial application.
[0006] U.S. Patent No. 3,984,287 describes an apparatus for separating organic
material
from particulate tar sands, resulting in agglomeration of a particulate
residue. The apparatus
included a tapered rotating drum in which tar sands, water, and an organic
solvent were mixed
together. In this apparatus, water was intended to act as a bridging liquid to
agglomerate the
particulate, while the organic solvent dissolves organic materials. As the
materials combined in
the drum, bitumen was separated from the ore.
[0007] A device to convey agglomerated particulate solids for removal to
achieve the
process of Meadus et al. (U.S. Patent No. 4,057,486) within a single vessel is
described in U.S.
Patent No. 4,406,788.
[0008] A method for separating fine solids from a bitumen solution is
described in U.S.
Patent No. 4,888,108. To remove fine solids, an aqueous solution of polar
organic additive as well
as solvent capable of precipitating asphaltenes was added to the solution, so
as to form
aggregates for removal from the residual liquid. Although the method achieved
low solids content
in the resulting bitumen product with this approach, the solids content in the
bitumen product fell
short of optimal product quality of less than 400 ppm solids on a dry bitumen
basis, especially for
settling times less than 1 hour.
[0009] Others have proposed sequential use of two solvents in different
solvent extraction
schemes. For example U.S. Patent No. 3,131,141 proposed the use of high
boiling point solvent
for oil sands extraction followed by low boiling point/volatile solvent for
enhanced solvent recovery
from tailings in a unique process arrangement. U.S. Patent No. 4,046,668
describes a process of
bitumen recovery from oil sands using a mixture of light naphtha and methanol.
However, it is not
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described or suggested that a second solvent could be effectively applied to a
solvent extraction
process with simultaneous solids agglomeration without upsetting the
agglomeration process.
[0010] U.S. Patent No. 4,719,008 describes a method for separating micro-
agglomerated
solids from a high-quality hydrocarbon fraction derived from oil sands. A
light milling action was
imposed on a solvated oil sands mixture. After large agglomerates were formed,
the milling action
was used to break down the agglomerate size, but still permitted agglomerate
settling and
removal.
[0011] U.S. Patent No. 5,453,133 and U.S. Patent No. 5,882,429 describe soil
remediation
processes to remove hydrocarbon contaminants from soil. The processes employed
a solvent
and a bridging liquid immiscible with the solvent, and this mixture formed
agglomerates when
agitated with the contaminated soil. The contaminant hydrocarbon was solvated
by the solvent,
while soil particles agglomerated with the bridging liquid. In this way, the
soil was considered to
have been cleaned. Multiple extraction stages were proposed.
[0012] Canadian Patent Application 2,068,895 describes a method of
incorporating a
solvent extraction scheme into a water-based process flow sheet. The method
involved a slurry
conditioning process which allowed a hydrocarbon bitumen fraction, having high
fines content, to
be processed in a solvent extraction and solids agglomeration process to
achieve higher overall
bitumen recovery and reduced sludge volume.
[0013] The previously proposed process for agglomeration, as described by
Govier and
Sparks in "The SESA Process for the Recovery of Bitumen from Mined Oil Sands"
(Proceedings of
AOSTRA Oils Sands 2000 Symposium, Edmonton 1990, Paper 5), was of limited
practicality
partly due to the nature of the solvent which, when combined with tailings,
made solvent recovery
difficult. This process is referenced herein as the Govier and Sparks process.
The solvent
described possessed a low molecular weight and significant aromatic content,
while containing
only a small amount of short chain paraffins. Exemplary solvents were
described as varsol or
naphtha. As expected for such high boiling point solvents, bitumen recovery
was consistently high.
However, the energy intensity required for the solvent recovery was also high.
There was no
description in this document of the use of low boiling point solvents.
Further, there was no
suggestion in the Govier and Sparks process of how the process would have been
adapted to
employ a different solvent to more efficiently recover solvent, or of how
appropriate feed slurry
characteristics may have been achieved if a different solvent was employed.
[0014] Typically, a bottom sediment and water (BS&W) content, primarily
comprised of
fines, of between 0.2 - 0.5 wt% of solids in dry bitumen could be achieved
according to the Govier
and Sparks process. However, occasionally solids agglomeration would cycle
unpredictably and
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the fines content of the agglomerator discharge stream would rise
dramatically. Subsequent
settling in a clarifier or bed filtration would then be required to achieve
the desired product quality
of 0.2 - 0.5 wt% BS&W. The BS&W component prepared by the process was
comprised mostly of
solids. Bitumen products with this composition are not fungible and can only
be processed at a
site coking facility or at an onsite upgrader. This would provide limited
flexibility for sale or
processing in a remote refinery.
[0015] The above-described agglomeration processes integrated solvent
extraction and
agglomeration within the same mixing vessel, which is inefficient because
means of pre-
conditioning and conveyance of the bituminous feed into the extraction /
agglomerating unit is thus
complicated. Conventional agglomeration units are large drums designed to
integrate both the
extraction and agglomeration aspects of the process, and are bulky and
inefficient. Residence
time in such agglomeration units would be lengthy, and process kinetics
imposed restrictions on
residence time. Dissolution time, the slow agitation required, limited slurry
density, and the high
containment volume required for extraction required the residence time in the
agglomeration unit
to be lengthy, and the process slow. Further, solvent recovery was not of
concern in many
previous processes, and is not addressed in most previously described
processes.
[0016] The processing problems associated with recovery of water and bitumen
from
aqueous sources, such as from conventional water-based hydrocarbon or bitumen
extraction
processes, are largely due to the presence of fines in the streams. Aqueous
waste streams, in
particular, contain a large proportion of water, for example 60% or more by
weight, which is higher
than desired for solvent based hydrocarbon extraction processes. Recovery of
bitumen from
waste streams or intermediate streams formed in a water-based extraction
process is
environmentally prudent, and would increase the efficiency of the overall
extraction process.
Conventional attempts at de-watering streams from the water-based extraction
process are
typically undertaken only after the majority of hydrocarbon, or bitumen, has
been removed.
[0017] Aqueous streams from water based extraction process which may undergo
additional water based recovery or which may be stored as waste products
include primary
separation vessel middling streams, waste streams from secondary flotation
tails or froth
treatment, among others. Such streams have high water content, but may also
have a bitumen
content exceeding 15 wt% on a dry solids basis, which would be desirable to
recover. There is a
need for processes that can incorporate such aqueous streams into a solvent
based hydrocarbon
extraction process.
[0018] It is desirable to provide processes and systems that increase the
efficiency of oil
sands extraction, reduce water use, and/or reduce energy intensity required to
produce a
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4
commercially desirable bitumen product from oil sands. Producing a product
that is capable of
meeting or exceeding requirements for downstream processing or pipeline
transport is desirable.
[0019] Further, it is desirable to provide techniques to recover bitumen from
waste streams
arising from aqueous bitumen extraction, that can operate efficiently in the
presence of fines, or
which are largely unaffected by the presence of fines.
SUMMARY OF THE INVENTION
[0020] It is an object of the present invention to obviate or mitigate at
least one
disadvantage of previous processes and systems for hydrocarbon extraction from
mineable
deposits such as oil sands.
[0021] It is an optional object of the present invention to provide a process
or system for
recovery of hydrocarbon from waste streams, or to obviate or mitigate at least
one disadvantage
of previous methods or systems used to recover of hydrocarbon from waste
aqueous streams
arising from water-based oil sands extraction processes.
[0022] Solvent extraction processes to recover bitumen from oil sands are
described,
employing solvent extraction and sequential agglomeration of fines to
advantageously simplify
subsequent solid-liquid separation. The processes can produce at least one
bitumen product with
a quality specification of water and solids that exceeds downstream processing
and pipeline
transportation requirements and contains low levels of solids and water.
Further, systems for
implementing such processes are described.
[0023] The use of low boiling point solvents advantageously permits recovery
of solvent
with a lower energy requirement than would be expended for recovery of high
boiling point
solvents. By conducting solvent extraction and agglomeration steps
independently, shorter
residence times in the agglomeration unit can be achieved. The sequential
nature of the process
allows for flexible design of a slurry feed system which permits high
throughput from a smaller
sized agglomeration unit, as well as faster bitumen production.
[0024] When the optional step of steam pre-conditioning is employed in the
process, this
realizes the further advantage that steam not only heats the slurry or oil
sands, but adds the water
necessary for the later agglomeration process.
[0025] Advantageously, the inventive process permits formation of bitumen
products with
an acceptable composition for sale or processing at a remote refinery, and
thus these products
need not be processed by an onsite upgrader.
[0026] As a result of the process, a high quality (or high grade) bitumen
product is formed
which is able to meet and/or exceed quality specifications of low water
content and low solids
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content required for pipeline transport and downstream processing. The process
permits
premium, dry and clean bitumen to be obtained as well as a lower grade bitumen
product to be
obtained (which in certain cases may comprise primarily of asphaltenes) for
various commercial
uses. By using the process described herein, it is possible to achieve a high
grade bitumen
product, as well as lower grades of bitumen products. For example, a high
grade bitumen product
is considered to be one containing less than about 0.04 wt% solids (400 ppm),
which may be
obtained according to the instant process. Further, such a product formed by
the process
described herein may contain about 0.5 wt% or less of water + solids of the
dry bitumen product.
Water content may be less than or equal to 200 ppm in the final high grade
bitumen product. This
is an improved result compared with the 0.2 - 0.5 wt% of solids in dry bitumen
that can be
achieved according to the previously described Govier and Sparks process. Low
grade bitumen
products having more than 400 ppm solids, and more than 200 ppm water may
additionally be
obtained.
[0027] Certain embodiments of the process and system described herein
advantageously
permit recovery of hydrocarbon from waste water streams that were previously
considered too
dilute for recovery, in part due to a high fines content combined together
with a high water content
of over 60% by weight. By de-watering such aqueous waste streams containing
bitumen to the
point that the effluent contains less than 40% water, the waste stream can
then be used in a
process that employs agglomeration of fines.
[0028] Recycling conventionally discarded waste water is important from an
environmental
perspective as well as from an efficiency perspective. By decreasing water
content of an
aqueous waste stream to a desirable level, the stream would become more
desirable for use in
alternative extraction processes. Recovered water may advantageously be put to
use in any
aspect of bitumen production that may incorporate recycled water. By de-
watering a waste stream
prior to attempts to remove all hydrocarbon or bitumen, steps in a
conventional aqueous process
can be omitted, thereby introducing efficiencies at certain steps in the
process.
[0029] A process for recovery of bitumen from oil sands is described herein.
In the
process, a first solvent is combined with a bituminous feed from oil sands to
form an initial slurry.
The initial slurry is separated into a fine solids stream and a coarse solids
stream. Solids from the
fine solids stream are agglomerated to form an agglomerated slurry comprising
agglomerates and
a low solids bitumen extract. The low solids bitumen extract is then separated
from the
agglomerated slurry, and a second solvent is mixed with the low solids bitumen
extract to form a
solvent-bitumen low solids mixture. The second solvent is selected to have a
similar or lower
boiling point than the first solvent. The mixture is then subjected to gravity
separation to produce
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a high grade bitumen extract and a low grade bitumen extract. The first and
second solvent can
be recovered from the high grade bitumen extract, leaving a high grade bitumen
product.
[0030] Further, described herein is a process for recovery of bitumen from oil
sands. The
process involves combining a first solvent and a bituminous feed from oil
sands to form an initial
slurry. The initial slurry is then separated into a fine solids stream and a
coarse solids stream.
Solids from the fine solids stream are agglomerated to form an agglomerated
slurry comprising
agglomerates and a low solids bitumen extract. A second solvent is then mixed
with the
agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the
second solvent
having a similar or lower boiling point than the first solvent. This mixture
is subjected to separation
to produce a high grade bitumen extract and a low grade bitumen extract. The
first and second
solvent can then be recovered from the high grade bitumen extract, leaving a
high grade bitumen
product; and the first and second solvent can also be recovered from the low
grade bitumen
extract, leaving a low grade bitumen product.
[0031] Described herein is a further process for recovery of bitumen from oil
sands
comprising combining a first solvent and a bituminous feed from oil sands to
form an initial slurry,
which is then separated into a fine solids stream and a coarse solids stream.
The first solvent is
then recovered from the coarse solids stream. Solids are agglomerated from the
fine solids
stream to form an agglomerated slurry comprising agglomerates and a low solids
bitumen extract,
and the low solids bitumen extract is then separated from the agglomerated
slurry. A second
solvent is then mixed with the low solids bitumen extract to form a solvent-
bitumen low solids
mixture, the second solvent having a similar or lower boiling point than the
first solvent. The
mixture is subjected to gravity separation to produce a high grade bitumen
extract and a low grade
bitumen extract; and the first and second solvent are separated from the high
grade bitumen
extract, leaving a high grade bitumen product.
[0032] Additionally, a process is described herein for recovery of a bitumen
product from
oil sands. The process comprises combining a first solvent and a bituminous
feed from oil sands
to form an initial slurry, and separating the initial slurry into a fine
solids stream and a coarse
solids stream. The first solvent is recovered from the coarse solids stream,
and solids are
agglomerated from the fine solids stream to form an agglomerated slurry
comprising agglomerates
and a low solids bitumen extract. Further, mixing a second solvent with the
agglomerated slurry to
form a solvent-bitumen agglomerated slurry mixture is then conducted, the
second solvent having
a similar or lower boiling point than the first solvent. The mixture is then
subjected to separation to
produce a high grade bitumen extract and a low grade bitumen extract. The
first and second
solvent are then recovered from the high grade bitumen extract, leaving a high
grade bitumen
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product; and the first and second solvent are also recovered from the low
grade bitumen extract,
leaving a low grade bitumen product.
[0033] Additionally, there is described herein a process for recovery of
bitumen from oil
sands comprising combining a first solvent and a bituminous feed from oil
sands to form an initial
slurry and agglomerating solids from the initial slurry to form an
agglomerated slurry comprising
agglomerates and a low solids bitumen extract. The low solids bitumen extract
is then separated
from the agglomerated slurry. A second solvent is then mixed with the low
solids bitumen extract
to form a solvent-bitumen low solids mixture, the second solvent having a
similar or lower boiling
point than the first solvent. The mixture is subjected to gravity separation
to produce a high grade
bitumen extract and a low grade bitumen extract; and the first and second
solvent are then
recovered from the high grade bitumen extract, leaving a high grade bitumen
product. In this
process, the ratio of first solvent to bitumen in the initial slurry is
selected to avoid precipitation of
asphaltenes during agglomeration.
[0034] Further, there is provided herein a process for recovery of a bitumen
product from
oil sands. The process involves combining a first solvent and a bituminous
feed from oil sands to
form an initial slurry, and agglomerating solids from initial slurry to form
an agglomerated slurry
comprising agglomerates and a low solids bitumen extract. A second solvent is
mixed with the
agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the
second solvent
having a similar or lower boiling point than the first solvent. The mixture is
then subjected to
separation to produce a high grade bitumen extract and a low grade bitumen
extract comprising
substantially all solids and water. The first and second solvents are then
recovered from the high
grade bitumen extract, leaving a high grade bitumen product; and similarly,
the first and second
solvents are then recovered from the low grade bitumen extract, leaving a low
grade bitumen
product. In this instance, the ratio of first solvent to bitumen in the
initial slurry is selected to avoid
precipitation of asphaltenes during agglomeration.
[0035] A system is provided for recovery of bitumen from oil sands comprising
a slurry
system wherein a bituminous feed is mixed with a first solvent to form an
initial slurry; a
fine/coarse solids separator in fluid communication with the slurry system for
receiving the initial
slurry and separating a fine solids stream therefrom; an agglomerator for
receiving a fine solids
stream from the fine/coarse solids separator, for agglomerating solids and
producing an
agglomerated slurry; a primary solid-liquid separator for separating the
agglomerated slurry into
agglomerates and a low solids bitumen extract; a gravity separator for
receiving the low solids
bitumen extract and a second solvent; and a primary solvent recovery unit for
recovering the first
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solvent or the second solvent in a high grade bitumen extract arising from the
gravity separator
and for separating bitumen therefrom.
[0036] Additionally, a system for recovery of bitumen from oil sands is
described herein,
comprising a slurry system wherein a bituminous feed is mixed with a first
solvent to form an initial
slurry; an agglomerator for receiving the initial slurry, for agglomerating
solids and producing an
agglomerated slurry; a primary solid-liquid separator for separating the
agglomerated slurry into
agglomerates and a low solids bitumen extract; a gravity separator for
receiving the low solids
bitumen extract and a second solvent; and a primary solvent recovery unit for
recovering the first
solvent or the second solvent in a high grade bitumen extract arising from the
gravity separator
and for separating bitumen therefrom.
[0037] There is described herein a process for pre-treating an aqueous
hydrocarbon-
containing feed for downstream solvent-based extraction processing for bitumen
recovery, said
aqueous hydrocarbon-containing feed comprising from 60 wt% to 95 wt% water,
from 0.1 wt% to
wt% bitumen, and from 5 wt% to 40 wt% solids, wherein said solids comprise
fines, the
process comprising: removing water from the aqueous hydrocarbon-containing
feed to produce an
effluent comprising 40 wt% water or less; and providing the effluent to a
downstream solvent-
based extraction process comprising fines agglomeration to recover bitumen.
[0038] Further, there is described herein a system for pre-treating an aqueous
hydrocarbon-containing feed for downstream solvent-based extraction processing
for bitumen
recovery, said aqueous hydrocarbon-containing feed comprising from 60 wt% to
95 wt% water,
from 0.1 wt% to 10 wt% bitumen, and from 5 wt% to 40 wt% solids, wherein said
solids comprises
fines, the system comprising: a dewatering unit for removing water from the
aqueous
hydrocarbon-containing feed to produce an effluent comprising 40 wt% water or
less; and a
conduit for providing the effluent to a downstream solvent-based extraction
process comprising
fines agglomeration to recover bitumen.
[0039] Other aspects and features of the present invention will become
apparent to those
ordinarily skilled in the art upon review of the following description of
specific embodiments of the
invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Embodiments of the present invention will now be described, by way of
example
only, with reference to the attached Figures.
[0041] Figure 1 is a schematic representation of process within the scope of
the present
disclosure.
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[0042] Figure 2 illustrates an exemplary embodiment of processes consistent
with the
representation shown in Figure 1.
[0043] Figure 3 is a schematic representation of processes within the scope of
the present
disclosure.
[0044] Figure 4 illustrates an exemplary embodiment of processes consistent
with the
representation shown in Figure 3.
[0045] Figure 5 is a schematic representation of process within the scope of
the present
disclosure.
[0046] Figure 6 illustrates an exemplary embodiment of processes consistent
with the
representation shown in Figure 5.
[0047] Figure 7 provides a schematic representation of systems within the
scope of the
present disclosure.
[0026] Figure 8 is a schematic representation of processes for preparation of
an aqueous
stream for downstream bitumen extraction, within the scope of the present
disclosure.
[0027] Figure 9 depicts an embodiment of processes according to Figure 8,
which employ
primary and secondary water separation.
[0028] Figure 10 is a schematic illustration of processes incorporating the
preparation of
an aqueous stream according to Figure 8 together with downstream steps for
recovery of bitumen
using a solvent based extraction process.
[0029] Figure 11 depicts portions of processes for extracting bitumen from an
aqueous
stream, which employ primary and secondary water separation in preparation for
entry into an
extraction process.
DETAILED DESCRIPTION
[0048] Generally, the present invention provides a process and system for
fines capture or
agglomeration and solvent extraction of bitumen from oil sands. Processing oil
sands according to
the invention permits high throughput and improved product quality and value.
[0049] A process and system for recovery of bitumen from oil sands is provided
herein.
[0050] The term "bituminous feed" from oil sands refers to a stream derived
from oil sands
that requires downstream processing in order to realize valuable bitumen
products or fractions.
The bituminous feed from oil sands is one that contains bitumen along with
other undesirable
components, which are removed in the process described herein. 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
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requires further processing according to the process described herein. Also,
recycled streams
that contain bitumen in combination with other components for removal in the
described process
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 contains 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.
[0051] As used herein, "agglomerate" refers to conditions that produce a
cluster,
aggregate, collection or mass, such as nucleation, coalescence, layering,
sticking, clumping,
fusing and sintering, as examples.
[0052] Embodiment in Which First Solvent Added Prior to Agglomeration, Second
Solvent Added After Agglomerates Removed. In one embodiment of the process, a
first
solvent is added to agglomerate the bituminous feed, but only after the
agglomerated slurry is
formed is the second solvent added to extract bitumen. This embodiment
comprises combining a
first solvent and a bituminous feed from oil sands to form an initial slurry.
The initial slurry is then
separated into a fine solids stream and a coarse solids stream. The fine
solids stream is
subjected to agglomeration to form an agglomerated slurry, which includes
agglomerates and a
low solids bitumen extract. The low solids bitumen extract is separated from
the agglomerated
slurry, and subsequently mixed with a second solvent to form a solvent-bitumen
low solids
mixture. In this embodiment, the second solvent is one having a similar or
lower boiling point than
the first solvent. The mixture is subjected to gravity separation to produce a
high grade bitumen
extract and a low grade bitumen extract. The extracts are subjected to solvent
recovery of both
the first and second extracts, leaving a low grade bitumen product and a high
grade bitumen
product.
[0053] Embodiment in Which Second Solvent Added Prior to Separating Low Solids
Bitumen Extract from Agglomerated Slurry. An additional process for recovery
of bitumen from
oil sands is provided in which the second solvent is added prior to separating
low solids bitumen
extract and agglomerates from the agglomerated slurry. This embodiment
involves combining a
first solvent and a bituminous feed from oil sands to form an initial slurry,
and subsequently
separating the initial slurry into a fine solids stream and a coarse solids
stream. Solids from the
fine solids stream are agglomerated to form an agglomerated slurry comprising
agglomerates and
a low solids bitumen extract. A second solvent is then mixed with the
agglomerated slurry to form
a solvent-bitumen agglomerated slurry mixture, the second solvent having a
similar or lower
boiling point than the first solvent. The mixture is then subjected to
separation to produce a high
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grade bitumen extract and a low grade bitumen extract. The first and second
solvent are then
recovered from the high grade bitumen extract, leaving a high grade bitumen
product. The first
and second solvent are also recovered from the low grade bitumen extract,
leaving a low grade
bitumen product.
[0054] In this embodiment of the process, the second solvent may be added
prior to
separating low solids bitumen extract from the agglomerated slurry. Thus, the
second solvent will
contact with the agglomerates and the low solids bitumen extract to form the
solvent-bitumen
agglomerated slurry mixture, which is processed further into high grade and
low grade products,
as described in further detail herein below.
[0055] Embodiment in Which Coarse Solids are Processed Separately From
Agglomeration of Fine Solids Stream. Additionally, another embodiment
comprises a process
for recovery of bitumen from oil sands in which a first solvent and a
bituminous feed from oil sands
are combined to form an initial slurry. The initial slurry is then separated
into a fine solids stream
and a coarse solids stream. The first solvent is recovered from the coarse
solids stream, and
solids are agglomerated from the fine solids stream to form an agglomerated
slurry comprising
agglomerates and a low solids bitumen extract. The low solids bitumen extract
is separated from
the agglomerated slurry, and mixed with a second solvent to form a solvent-
bitumen low solids
mixture. In this embodiment, the second solvent has a similar or lower boiling
point than the first
solvent. The mixture is then subjected to gravity separation to produce a high
grade bitumen
extract and a low grade bitumen extract. The first and second solvent are
recovered from the high
grade bitumen extract, leaving a high grade bitumen product.
[0056] In this embodiment of the process, the coarse solids stream is
processed
separately from the fine solids stream, to remove the solvent therefrom.
Optionally, the coarse
solids stream may be added back into the slurry system or separator, for
subsequent processing
in an iterative manner.
[0057] Embodiment in Which Coarse Solids are Processed Separately From
Agglomeration of Fine Solids Stream, and the Second Solvent is Mixed With the
Agglomerated Slurry. A further embodiment comprises a process for recovery of
a bitumen
product from oil sands comprising: combining a first solvent and a bituminous
feed from oil sands
to form an initial slurry; separating the initial slurry into a fine solids
stream and a coarse solids
stream; recovering the first solvent from the coarse solids stream;
agglomerating solids from the
fine solids stream to form an agglomerated slurry comprising agglomerates and
a low solids
bitumen extract; mixing a second solvent with the agglomerated slurry to form
a solvent-bitumen
agglomerated slurry mixture, the second solvent having a similar or lower
boiling point than the
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first solvent; subjecting the mixture to separation to produce a high grade
bitumen extract and a
low grade bitumen extract; recovering the first and second solvent from the
high grade bitumen
extract, leaving a high grade bitumen product; and recovering the first and
second solvent from
the low grade bitumen extract, leaving a low grade bitumen product.
[0058] In this embodiment of the process, the first solvent may be recovered
from the
coarse solids stream separately. Optionally, the coarse solids stream may be
added back into the
slurry system or separator, for subsequent processing in an iterative manner.
[0059] Embodiment in Which Initial Slurry is Directed to Agglomeration Without
Separation of Coarse Solids, and in Which Second Solvent is Introduced After
Agglomerates are Removed. A further embodiment of the process for recovery of
bitumen from
oil sands is described herein in which a first solvent is combined with a
bituminous feed from oil
sands to form an initial slurry. Solids in the initial slurry are agglomerated
to form an
agglomerated slurry comprising agglomerates and a low solids bitumen extract.
A low solids
bitumen extract is separated from the agglomerated slurry. A second solvent is
then mixed with
the low solids bitumen extract to form a solvent-bitumen low solids mixture,
the second solvent
having a similar or lower boiling point than the first solvent. The mixture is
then subjected to
gravity separation to produce a high grade bitumen extract and a low grade
bitumen extract. The
first and second solvent are then recovered from the high grade bitumen
extract, leaving a high
grade bitumen product. In this embodiment, the ratio of first solvent to
bitumen in the initial slurry
is selected to avoid precipitation of asphaltenes during agglomeration.
[0060] In this embodiment of the process, the step of separating the initial
slurry into a fine
solids stream and a coarse solids stream is not conducted. Thus, the
bituminous feed is
combined with the first solvent to prepare the initial slurry, which can then
be agglomerated
without the requirement for further separation. In this embodiment, the first
solvent is mixed with
the bituminous feed, but the second solvent is not introduced until after the
low solids bitumen
extract has been separated from the agglomerates. In this way, the
agglomerates need not come
into contact with the second solvent.
[0061] Embodiment in Which Initial Slurry is Directed to Agglomeration Without
Separation of Coarse Solids, and in Which Second Solvent is Introduced Prior
to Removal
of Agglomerates. A further embodiment of the process is described herein for
recovery of a
bitumen product from oil sands. The embodiment comprises combining a first
solvent and a
bituminous feed from oil sands to form an initial slurry. Solids from the
initial slurry are
agglomerated to form an agglomerated slurry comprising agglomerates and a low
solids bitumen
extract. A second solvent is then mixed with the agglomerated slurry to form a
solvent-bitumen
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agglomerated slurry mixture, the second solvent having a similar or lower
boiling point than the
first solvent. The mixture is subjected to separation to produce a high grade
bitumen extract and
a low grade bitumen extract, in which the low grade extract comprises
substantially all solids and
water. The first and second solvents are then recovered from the high grade
bitumen extract,
leaving a high grade bitumen product. The first and second solvent are
recovered from the low
grade bitumen extract, leaving a low grade bitumen product. In this
embodiment, the ratio of first
solvent to bitumen in the initial slurry is selected to avoid precipitation of
asphaltenes during
agglomeration.
[0062] In this embodiment of the process, the step of separating the initial
slurry into a fine
solids stream and a coarse solids stream is not conducted. Thus, the
bituminous feed is
combined with the first solvent to prepare the initial slurry, which is then
agglomerated without the
requirement for further separation. In this embodiment, the first solvent is
mixed with the
bituminous feed, and later, the agglomeration of solids occurs. The second
solvent is added to
the agglomerated slurry, so as to form a mixture. In this embodiment, all
components of the
agglomerated slurry are contacted by both the first and the second solvent.
Both solvents are
then recovered from each of the high grade bitumen extract and the low grade
bitumen extract.
[0063] Embodiment of a System in Which a Fine/Coarse Solids Separator and a
Gravity Separator are Employed.
[0064] A system is provided for recovery of bitumen from oil sands comprising
a slurry
system wherein a bituminous feed is mixed with a first solvent to form an
initial slurry. A
fine/coarse solids separator is included in the system, and is in fluid
communication with the slurry
system for receiving the initial slurry and separating a fine solids stream
therefrom. The system
additionally includes an agglomerator for receiving a fine solids stream from
the fine/coarse solids
separator, for agglomerating solids and producing an agglomerated slurry. A
primary solid-liquid
separator is present in the system for separating the agglomerated slurry into
agglomerates and a
low solids bitumen extract. A gravity separator is present in the system for
receiving the low solids
bitumen extract and a second solvent. A primary solvent recovery unit is
included, for recovering
the first solvent or the second solvent in a high grade bitumen extract
arising from the gravity
separator and for separating bitumen therefrom.
[0065] In this embodiment of the system, both a fine/coarse solids separator,
and a gravity
separator are employed.
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CA 02704927 2010-05-21
[0066] Embodiment of a System in Which There is no Fine/Coarse Solids
Separator
Component Upstream of the Agglomerator.
[0067] A further embodiment of a system for recovery of bitumen from oil sands
is
described herein comprising a slurry system wherein a bituminous feed is mixed
with a first
solvent to form an initial slurry. Further, the system includes an
agglomerator for receiving the
initial slurry, for agglomerating solids and producing an agglomerated slurry.
A primary solid-liquid
separator is used in the system for separating the agglomerated slurry into
agglomerates and a
low solids bitumen extract. A gravity separator is present in the system for
receiving the low solids
bitumen extract and a second solvent, and a primary solvent recovery unit for
recovering the first
solvent or the second solvent in a high grade bitumen extract arising from the
gravity separator
and for separating bitumen therefrom is also incorporated into the system.
[0068] In this embodiment of the system, there is no requirement for a
fine/coarse solids
separator, and so both fines and coarse solids may be agglomerated together in
the agglomerator.
[0069] Ratio of Solvent to Bitumen in Initial Slurry. The process may be
adjusted to
render the ratio of the first solvent to bitumen in the initial slurry 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 solvent used, can permit the control of a ratio of
solvent to bitumen in the
slurry system and agglomerator. When the solvent of the invention 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 excessive solvent use.
[0070] 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 during
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.
[0071] Slurry System. The slurry system in which the slurry is prepared in the
system
may optionally be a mix box, a pump, a pipeline, or a combination of these. By
slurrying the first
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solvent together with the bituminous feed, and optionally with additional
additives, the bitumen
entrained within the feed is given an opportunity to be extracted into the
solvent phase prior to the
downstream separation of fine and coarse solid streams and prior to
agglomeration within the
agglomeration. In some prior art processes, solvent is introduced at the time
of agglomeration,
which may require more residence time within the agglomerator, and may lead to
incomplete
bitumen dissolution and lower overall bitumen recovery. The slurry system
advantageously
permits contact and extraction of bitumen from solids within the initial
slurry, prior to
agglomeration. Forming an initial slurry prior to agglomeration advantageously
permits flexible
design of the slurry system and simplifies means of feeding materials into the
agglomerator.
[0072] Bridging Liquid. A bridging liquid is a liquid with affinity for the
solids particles in
the bituminous feed, and which is immiscible in the first solvent. In some
embodiments, the
agglomerating of solids comprises adding an aqueous bridging liquid to the
fine solids stream and
providing agitation. 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 solution 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.
[0073] Heating Bituminous Feed With Steam. According to an embodiment of the
process, steam may be added to the bituminous feed before combining with the
first solvent, to
increase the temperature of the bituminous feed to a temperature of from about
0 C to about 60
C. Steam may be of particular benefit when oil sands are mined in cold
conditions, such as
during winter time. The steam may be added to heat the oil sands or other
bituminous feed to a
temperature of from about 0 C to about 30 C. The temperatures recited here
are simply
approximate upper and lower values. Because these are exemplary ranges,
provided here
primarily for illustration purposes, it is emphasized that values outside of
these ranges may also
be acceptable. A steam source for pre-conditioning the initial slurry entering
the separator may
be an optional component of the system of the invention. Other methods of
heating the bituminous
feed or the solvent (or solvent/bitumen combination) used to form the initial
slurry may be
incorporated into the process.
[0074] During the winter, a bituminous feed may be at a low temperature below
0 C due
to low temperature of the ambient outdoor surroundings, and the addition of
steam to heat the
feed to a level greater than 0 C would be an improvement over a colder
temperature. During hot
summer conditions, the temperature of the bituminous feed may exceed 0 C, in
which case, it
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CA 02704927 2010-05-21
may not be beneficial to heat the bituminous feed. Addition of steam may be
desirable for
processing efficiency reasons, and it is possible that the upper limit of the
ranges provided may be
exceeded.
[0075] The optional step of steam pre-conditioning of the oil sands before
making contact
with solvent in the slurry system has the beneficial effect of raising the
temperature of the input
bituminous feed. The amount of steam added is lower or equal to the amount of
water required for
agglomeration. Slurrying the input feed with a low boiling point solvent is
promoted without the use
of a pressurized mixing system. Since steam pre-conditioning permits the use
of low boiling point
solvents, higher levels of solvent recovery from tailings can be realized with
reduced energy
intensity relative to conventional processes.
[0076] During the winter, incoming oil sands may be about -3 C. At this
temperature, the
separation process would require more heat energy to reach the process
temperatures between
about 0 C and 60 C, or more particularly for an exemplary processing
temperature of about 30
C. Optimally, a solvent boiling point is less than about 100 C. For a low
boiling point solvent, this
heating obtained through steam pre-conditioning is adequate to meet the
processing requirement.
For example, by heating the oil sands in a pre-conditioning step, a
temperature can be achieved
that is higher than could be achieved by heating the solvent alone, and adding
it to a cold
bituminous feed. In this way, optimal process temperatures can be achieved
without any need to
use a pressurized mixing system for solvent heating. Therefore, the steam not
only provides
water, but also some of the heating required to bring the components of the
initial slurry to a
desired temperature.
[0077] Once included as steam in a pre-conditioning step, the water content of
the initial
slurry would optimally be about 11 wt% or less, and when expressed as a
percent of solids, about
15 wt% is an upper limit to the optimal level.
[0078] The steam pre-conditioning need not occur, as it is optional. Some
water may be
added at the agglomeration step if it is not added through steam pre-
conditioning. In instances
where steam pre-conditioning is used, optimally about half of the water
requirement is added as
steam, and further amounts of water can be added when the fine solids stream
is transferred into
the agglomerator.
[0079] In embodiments in which no steam pre-conditioning is employed, a slurry
comprising the bituminous feed together with the first solvent may be prepared
within the slurry
system. Optionally, a solvent vapor could be added to the bituminous feed in
the slurry stage to
capture the latent heat at atmospheric pressure without need to pressurize the
mixing vessel.
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CA 02704927 2010-05-21
[0080] Low Oxygen for Initial Slurry. The initial slurry of the process
described herein
may optionally be formed in a low oxygen environment. A gas blanket may be
used to provide this
environment, or steam may be used to entrain oxygen away from the bituminous
feed prior to
addition of solvent. The gas blanket, when used, may be formed from a gas that
is not reactive
under process conditions. Exemplary gasses include, but are not limited to
nitrogen, methane,
carbon dioxide, argon, steam, or a combination thereof.
[0081] Separation of Fine Solids Stream and Coarse Solids Stream. The
processes
described herein may involve separation of a fine solids stream from a coarse
solids stream from
the initial slurry after it is mixed in a slurry system. This aspect of the
process may be said to
occur within a fine/coarse solids separator. An exemplary separator system may
include a
cyclone, a screen, a filter, or a combination of these. The size of the solids
separated, which may
determine whether they are forwarded to the fine solids stream versus the
coarse solids stream
can be variable, depending on the nature of the bituminous feed. Whether a
bituminous feed
contains primarily small particles and fines, or is coarser in nature may be
taken into consideration
for determining what size of particles are considered as fine solids and
directed toward
agglomeration. Notably, embodiments of the process described herein do not
require separation
of coarse and fine solids from the initial slurry. In such instances, both
coarse and fine solids will
be present in the agglomerator. When separation of coarse and fine solids is
desired, a typical
minimum size to determine whether a solid is directed to the coarse solids
stream would be about
140 microns. Fines entrainment in the coarse stream is unavoidable during this
separation. The
amount of fines entrained in the coarse solids stream is preferably less than
10wt%, for example,
less than 5wt%.
[0082] Fine/Coarse Solids Separator. A coarse solids stream derived from the
fine/coarse solids separator may be derived from the system. When the
fine/coarse solids
separator is present, the coarse solids stream may be directed for combination
with the
agglomerated slurry arising from the agglomerator prior to entry of the slurry
into the solid-liquid
separator.
[0083] The feed stream entering the agglomerator unit is pre-conditioned to
separate out
coarse particles before entry into the agglomerator unit. Thus, the stream
entering the
agglomerator is predominantly comprised of finely divided particles or a "fine
solids stream". The
slurry fraction containing predominantly coarse particles or the "coarse
solids stream" may by-
pass the agglomerator unit and can then be combined with the agglomerated
slurry before the
solid-liquid separation stage in which low solids bitumen is extracted from
the agglomerated slurry.
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CA 02704927 2010-05-21
[0084] A fine solids stream is processed separately from the coarse solids
stream, in part
because coarse solids are readily removed and need not be subjected to the
processing within the
agglomerator. The separator permits separation of a fine solids stream as a
top stream that can
be removed, while the coarse solids stream is a bottom stream flowing from the
separator.
[0085] The coarse solids fraction derived from the separator may be combined
with the
effluent arising from the agglomerator, as the coarse solids together with the
agglomerates will be
removed in a later solid-liquid separation step. This would permit recovery of
bituminous
components that were removed in the coarse solids stream.
[0086] Re-combining Coarse Solids with Agglomerated Slurry. It is optional in
the
process to utilize the coarse solids stream derived from the fine/coarse
solids separator by re-
combining it with the agglomerated slurry prior to separating the low solids
bitumen extract from
the agglomerated slurry. Alternatively, the coarse solids stream may be
processed separately, or
added back into the slurry system for iterative processing.
[0087] Agglomeration. The step of agglomerating solids may comprise adding
steam to
the bituminous feed. The addition of steam may be beneficial to the bituminous
feed because it
may begin solids nucleation prior to the step of agglomerating.
[0088] The step of agglomerating solids may comprise adding water as bridging
liquid to
the fine solids stream and providing suitable mixing or agitation. The type
and intensity of mixing
will dictate the form of agglomerates resulting from the particle enlargement
process.
[0089] Agitation could be provided in colloid mills, shakers, high speed
blenders, disc and
drum agglomerators, or other vessels capable of producing a turbulent mixing
atmosphere. The
amount of bridging liquid is balanced by the intensity of agitation to produce
agglomerates of
desired characteristics. As an example of appropriate conditions for a drum or
disc agglomerator,
agitation of the vessel may typically be about 40% of the critical drum
rotational speed while a
bridging liquid is kept below about 20 wt% of the slurry. The agitation of the
vessel could range
from 10% to 60% of the critical drum rotational speed, and the bridging liquid
may be kept
between about 10 wt% to about 20 wt% of solids contained in the slurry, in
order to produce
compact agglomerates of different sizes.
[0090] Solvents. Two solvents, or solvent systems, are sequentially employed
in this
process. The terms "first solvent" and "second solvent" as used herein should
be understood to
mean either a single solvent, or a combination of solvents which are used
together in a first
solvent extraction and a second solvent extraction, respectively. Accordingly,
the stage of the
process at which the solvent is introduced can be used to determine whether a
solvent is the first
or second solvent, as the sequential timing of the addition into the process
results in the
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CA 02704927 2010-05-21
designations of first and second. It is emphasized that the first and second
solvents are not
required to be different from each other. There are embodiments in which the
first solvent and
second solvent are the same solvent, or are combinations which include the
same solvents, or
combinations in which certain solvent ingredients are common to both the first
and second
solvents.
[0091] 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 C.
[0092] The solvents 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 included 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.
[0093] 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.
[0094] While the solvent extractions may be initiated independently, there is
no
requirement for the first solvent to be fully removed before the second
solvent extraction is
initiated.
[0095] When it is said that the first solvent and the second solvent may have
"similar"
boiling points, it is meant that the boiling points can be the same, but need
not be identical. For
example, similar boiling points may be ones within a few degrees of each
other, such as, within 5
degrees of each other would be considered as similar boiling points. The first
solvent and the
second solvent may be the same according to certain embodiments of the
invention, in which
case, having "similar" boiling points permits the solvents used to have the
same boiling point.
[0096] First Solvent. The first solvent selected according to embodiments of
the
invention may comprise an organic solvent or a mixture of organic solvents.
For example, the first
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
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CA 02704927 2010-05-21
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 first 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 first solvent, it may comprise a cycloalkane of
4 to 9 carbon
atoms.
[0097] A mixture of C4-010 cyclic and/or open chain aliphatic solvents would
also be
appropriate. For example, it can be a mixture of C4-C9 cyclic aliphatic
hydrocarbons and paraffinic
solvents where the percentage of the cyclic aliphatic hydrocarbon in the
mixture is greater than
50%. Exemplary cycloalkanes include cyclohexane, cyclopentane, or a mixture
thereof.
[0098] If the first 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 C. An exemplary
upper limit of the
final boiling point of the distillate may be less than 100 C.
[0099] Second Solvent. The second solvent may be selected to be the same as or
different from the first solvent, and may comprise a low boiling point alkane
or an alcohol. The
second solvent may have an exemplary boiling point of less than 100 C. In some
embodiments,
the second solvent can be mixed with feed into the solid-liquid separation
steps. Because the first
solvent is not used in both agglomeration and the solid-liquid separation
steps as described in
prior art, a second solvent that is miscible with the agglomerate bridging
liquid (for example,
miscible with water) can be employed at the solid-liquid separation stage. In
other words, the two
processing steps can be conducted independently and without the solid-liquid
separation
disrupting the agglomeration process. Thus, selecting the second solvent to be
immiscible in the
first solvent, and/or having the ability to be rendered immiscible after
addition, would be optional
criteria.
[00100] The second solvent may comprise a single solvent or a solvent system
that
includes a mixture of appropriate solvents. The second solvent may be a low
boiling point, volatile,
polar solvent, which may or may not include an alcohol or an aqueous
component. The second
solvent can be C2 to C10 aliphatic hydrocarbon solvents, ketones, ionic
liquids or biodegradable
solvents such as biodiesel. The boiling point of the second solvent from the
aforementioned class
of solvents is preferably less than 100 C.
[00101] Process Temperatures. The process may occur at a wide variety of
temperatures. In general, the heat involved at different stages of the process
may vary. One
example of temperature variation is that the temperature at which the low
solids bitumen extract is
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separated from the agglomerated slurry may be higher than the temperature at
which the first
solvent is combined with the bituminous feed. Further, the temperature at
which the low solids
bitumen extract is separated from the agglomerated slurry may be higher than
the temperature at
which solids are agglomerated. The temperature increase during the process may
be introduced
by recycled solvent streams that are re-processed at a point further
downstream in the process.
By recycling pre-warmed solvent from later stages of the process into earlier
stages of the
process, energy required to heat recycle stream is lower and heat is better
conserved within the
process. Alternatively, the temperature of the dilution solvent may be
intentionally raised to
increase the temperature at different stages of the process. An increase in
the temperature of the
solvent may result in a reduced viscosity of mixtures of solvent and bitumen,
thereby increasing
the speed of various stages of the process, such as washing and/or filtering
steps.
[00102] Solid-Liquid Separator. 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.
[00103] 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.
[00104] Secondary Stage of Solid-Liquid Separation to Wash Agglomerates. 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.
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CA 02704927 2010-05-21
[00105] 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
according to the
invention. 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.
[00106] The temperature for countercurrently washing the agglomerates may be
selected to
be higher than the temperature at which the first solvent is combined with the
bituminous feed.
Further, the temperature selected for countercurrently washing the
agglomerates may be higher
than the temperature at which solids are agglomerated.
[00107] 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.
[00108] Recycle and Recovery of Solvent. The process involves removal and
recovery of
solvent used in the process. 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
have 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. For
example, in steps of the
process when solvent is recovered from a low grade or high grade bitumen
extract leaving a
bitumen product, it is understood that some solvent may remain within that
product.
[00109] The system may contain a single solvent recovery unit for recovering
the first and
second solvents arising from the gravity separator. The system may
alternatively contain more
than one solvent recovery unit. For example, another solvent recovery unit may
be incorporated
before the step of adding the second solvent to recover part or all of the
first solvent.
[00110] In order to recover either or both the first solvent or the second
solvent,
conventional means may be employed. For example, typical solvent recovery
units may comprise
a fractionation tower or a distillation unit. A primary and/or secondary
solvent recovery unit may
be desirable for use in the process described herein.
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CA 02704927 2010-05-21
[00111] Solvent recovery and recycle is incorporated into embodiments of the
process. For
example, the first solvent recovered from the slurry of agglomerated solids,
which may contain
bitumen, can be recycled in the process, such as at the slurrying or
agglomerating step. Further,
the second solvent may be recovered by using a solvent recovery unit and
recycled for addition to
the low solids bitumen extract.
[00112] Solvent recovery may be controlled to ensure that the second solvent
is added at
the appropriate time. For example, the first and second solvent may be
recovered by distillation or
mechanical separation following the solid-liquid separation step.
Subsequently, the first solvent
may be recycled to the agglomeration step while the second solvent is recycled
downstream of the
agglomerating step. In the exemplary embodiment where the second solvent is
immiscible with the
first solvent, the process will occur with no upset to the agglomeration
process since interaction of
the second solvent with the bridging liquid only occurs downstream of the
agglomerating step.
[00113] Heat entrained in recycled solvent can advantageously be utilized when
the solvent
is added to the process at different stages to heat that stage of the process,
as required. For
example, heated solvent with entrained bitumen derived from washing of the
agglomerates in the
secondary solid-liquid separator may be used not only to increase the
temperature of the initial
slurry in the slurry system, but also to include a bitumen content that may be
desirable to keep the
solvent:bitumen ratio at a desired level so as to avoid precipitation of
asphaltenes from solution
during agglomeration. By including heated solvent as well as bitumen, this
addition provides an
advantage to the agglomeration process.
[00114] The first solvent recovered in the process may comprise entrained
bitumen therein,
and can thus be re-used for combining with the bituminous feed; or for
including with the fine
solids stream during agglomeration. 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 within the initial slurry to
achieve the selected
ratio within the agglomerator that avoids precipitation of asphaltenes.
[00115] Low and High Grade Bitumen Extracts and Products. Once solvent is
removed
from the low grade or high grade bitumen extracts, the resulting products may
be used for
commercial purposes. According to certain embodiments of the invention, the
low grade bitumen
extract is derived through gravity separation, and generally includes water
and solids that may
have settled into the underfiow in the separation process together with
bitumen and solvent. This
underfiow is removed and processed separately. This leaves a high grade
extract as the overflow
of the separation process.
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CA 02704927 2010-05-21
[00116] The high grade bitumen extract is considered to be of a "high grade"
in terms of
bitumen products, as it meets and may even exceed pipeline specifications. It
has been
essentially de-watered, and does not contain solids removed by gravity
separation, for example.
The high grade bitumen product formed according to embodiments of the
invention may have a
low water content that is nearly undetectable, such as a content of _< 200
ppm. The high grade
product may have a low solids content of <_ 400 ppm or lower as a result of
embodiments of the
process. The low grade bitumen product may in fact be effectively similar to a
"high grade"
product, with very low water and solids content. This may be the case for
embodiments of the
invention where low water and low solids are present in the low grade bitumen
extract emanating
from solid-liquid separation. In some embodiments, the asphaltene content of
the low grade
bitumen product are high relative to the high grade bitumen product. For
example, asphaltene
content up to 98 wt% may be realized in the low grade bitumen product if the
second solvent is
paraffinic and the amount mixed with the low solids extract causes the
precipitation of
asphaltenes. In other embodiments, the asphaltene content of both products
might in fact be
similar but the low grade bitumen product is richer in polar components of the
bitumen which are
soluble in the solvent.
[00117] Extraction Step is Separate from Agglomeration Step. Solvent
extraction may
be conducted separately from agglomeration in certain embodiments of the
process. Unlike prior
art processes, where the solvent is first exposed to the bituminous feed
within the agglomerator,
the instant invention includes formation of an initial slurry in which bitumen
dissolution into a
solvent occurs prior to the agglomeration step. This has the effect of
reducing residence time in
the agglomerator, when compared to previously proposed processes which require
extraction of
bitumen and agglomeration to occur simultaneously. The instant process is
tantamount to
agglomeration of pre-blended slurry in which extraction via bitumen
dissolution is substantially or
completely achieved separately. Performing extraction upstream of the
agglomerator permits the
use of enhanced material handling schemes whereby flow/mixing systems such as
pumps,
pipelines, mix box or other types of conditioning systems can be employed.
[00118] Because the extraction occurs upstream of the agglomeration step, the
residence
time in the agglomerator is reduced. One other reason for this reduction is
that by adding
components, such as water, some initial nucleation of particles that
ultimately form larger
agglomerates can occur prior to the slurry arriving in the agglomerator.
[00119] Dilution of Agglomerator Discharge to Improve Product Quality. The
first
solvent or second solvent or mixtures thereof 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
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CA 02704927 2010-05-21
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(s) 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. Solvents may be added at a point source of entry, or may be added
using multiple points
of entry, such as multiple injection points into the slurry.
[00120] When dilution of agglomerator discharge is employed in this embodiment
of the
invention, the solvent to bitumen ratio of the agglomerator feed slurry is set
to obtain from about
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 either the first or second solvent, or a separate
dilution solvent,
which may, for example, comprise an alkane.
[00121] Figure 1 is a schematic representation of an embodiment of processes
(10)
described herein. The combining (11) of a first solvent and a bituminous feed
from oil sand to
form initial slurry is followed by separating (12) of a fine solids stream and
coarse solids stream
from the initial slurry. Agglomerating (13) of solids from fine solids stream
then occurs to form
agglomerated slurry comprising agglomerates and low solids bitumen extract,
optionally
subsequently adding coarse solids stream to agglomerated slurry. Subsequently,
separation (15)
of low solids bitumen extract from agglomerated slurry occurs. Further, mixing
(16) of a second
solvent with low solids bitumen extract to extract bitumen takes place,
forming a solvent-bitumen
low solids mixture. Separation (18) of low grade bitumen extract and high
grade bitumen extracts
from the mixture occurs. Further, recovery (19) of solvent from the high grade
extract is
conducted, leaving a high grade bitumen product. Further details of these
process steps are
provided herein.
[00122] Figure 2 outlines an embodiment of the processes described herein, in
which the
second solvent is mixed with a low solids bitumen extract derived from
separation of the
agglomerated slurry in a clarifier.
[00123] In this embodiment, a bituminous feed (202) is provided and combined
with a first
solvent (209a), which may contain entrained bitumen (203a), in a slurry system
(204) to form an
initial slurry (205). The slurry system (204) may be any type of mixing
vessel, such as a mix box,
pump or pipeline or combination thereof, having a feed section with gas
blanket that provides a
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CA 02704927 2010-05-21
low oxygen environment. Steam (207) may be added to the slurry system (204) so
as to heat the
initial slurry (205) to a level of, for example, 0 to 60 C. The initial
slurry (205) is separated in a
fine/coarse solids separator (206) to form a fine solids stream (208), which
is directed into an
agglomerator (210), as well as a coarse solids stream (212), which later,
optionally, joins with the
agglomerated slurry (216) arising from the agglomerator (210) for further
processing. The
fine/coarse solids separator (206) may be a settling vessel, cyclone or
screen, or any suitable
separation device known in the art.
[00124] Bitumen (203b) which may be entrained in the first solvent (209b), for
example, as
derived from downstream recycling of the first solvent, may be added to the
agglomerator (210) in
order to achieve an optimal ratio of solvent to bitumen within the
agglomerator (210). Such a ratio
would be one that avoids precipitation of asphaltenes within the agglomerator
(210), and an
exemplary ratio may be less than 2:1.
[00125] An aqueous bridging liquid (214), such as water, may optionally be
added to the
agglomerator (210) in the interests of achieving good adherence of fines into
larger particles, and
the process of agglomeration of the solids contained within the fine solids
stream (208) occurs by
agitation within the agglomerator (210). The agglomerated slurry (216) arising
from the
agglomerator (210) comprises agglomerates (217a) together with a low solids
bitumen extract
(220a), all of which is optionally combined with the coarse solids stream
(212) in the event that the
coarse solids stream is directed to be combined at this stage. The slurry
(216) is then directed to
the primary solid-liquid separator (218), which may be a deep cone settler, or
other device, such
as thickeners, incline plate (lamella) settlers, and other clarification
devices known in the art.
[00126] The low solids bitumen extract (220) is separated from the
agglomerated slurry
within the primary solid-liquid separator (218). This extract (220) is
subsequently combined in a
mixer (221) with a second solvent (222a). Extract (220) may optionally be sent
to a solvent
recovery unit, not shown, where the first solvent is recovered from the
extract, before the mixing
with the second solvent (222a) is undertaken within the mixer (221).
[00127] The second solvent may be one having a low boiling point. The bitumen-
containing
mixture (223) obtained from the mixer (221) is separated in a gravity
separator (224), which may
for example be a clarifier or any other type of separator employing gravity to
separate solids and
water. Streams arising from the gravity separator (224) are directed either
toward forming a high
grade bitumen product (226) once the solvent has been extracted in a solvent
recovery unit (228),
or underflow may be removed as a low grade bitumen extract (230), which may
then optionally
have solvent removed to form a low grade bitumen product. The solvent recovery
unit (228) may
advantageously be used to recover any of the first solvent (209c) remaining
within the effluent of
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CA 02704927 2010-05-21
the gravity separator (224), in the interests of solvent recovery and re-use.
Advantageously, the
second solvent (222b) is easily removed and recovered due to its volatility
and low boiling point.
There may be bitumen entrained in recovered solvents.
[00128] The agglomerates (217b) can also be utilized, as they leave the
primary solid-liquid
separator (218) and are subsequently subjected to a separation in a secondary
solid-liquid
separator (232), permitting recovery of the first solvent (209a) and bitumen
(203a) in the process.
First solvent (209c) derived from the solvent recovery unit (228) may also be
recycled to the
secondary solid-liquid separator (232), to wash agglomerates, for example in a
belt filter using
contercurrent washing with progressively cleaner solvent. Additional
quantities of first solvent
(209d) can be used if additional volumes of solvent are needed. Tailings may
be recovered in a
TSRU or tailings solvent recovery unit (234) so that agglomerated tailings
(236) can be separated
from recyclable water (238). Either or both the recovered first solvent (209e)
derived from the
TSRU (234) and/or from the solvent recovery unit (228) may be recycled in the
secondary solid-
liquid separator (232).
[00129] A combination containing the first solvent (209a) plus bitumen (203a)
arising from
the secondary solid-liquid separator (232) can be processed with the intent of
achieving a bottom
sediment and water (BS&W) content lower than about 0.5 wt% solid in dry
bitumen. In particular,
the product would have less than 400 ppm solids. This combination may also be
recycled back
into the process by including it in the agglomerator (210) or slurry system
(204) as a way of
recycling solvent, and maintaining an appropriate solvent:bitumen ratio within
the agglomerator to
avoid precipitation of asphaltenes.
[00130] Advantageously, such processes as outlined in Figure 2 permit recovery
of both
the first solvent (209) and the second solvent (222). In one embodiment, the
first solvent (209)
may be a low boiling point solvent, such as a low boiling point cycloalkane,
or a mixture of such
cycloalkanes, which substantially dissolves asphaltenes. The first solvent may
also be a paraffinic
solvent in which the solvent to bitumen ratio is maintained at a level to
avoid precipitation of
asphaltenes.
[00131] For the second solvent, a low boiling point n- or iso-alkane and
alcohols or blends
are candidates. Surface modifiers may be added to the alcohol if needed. With
the alkanes,
solvent deasphalting is achieved with concurrent cleaning of the high grade
bitumen product (226)
to achieve pipeline quality. Therefore, the low grade bitumen extract (230) is
comprised
predominantly of asphaltenes or other more polar bitumen fractions.
[00132] Another advantage is that the process forms two different grades of
bitumen
product from the gravity separator (224). Specifically, partial product
upgrading is conducted to
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CA 02704927 2010-05-21
produce a first product of high grade bitumen product (226). The low grade
bitumen extract (230)
formed may also be processed to a low grade bitumen product after solvent
recovery, so as to
also possesses some commercial value.
[00133] This process facilitates recovery of bitumen with no need for handling
more than
one solvent in the tailings loop of the TSRU (234), thereby allowing for
simplified solvent
recovery/recycling processes.
[00134] Figure 3 is a schematic representation of a further embodiment of a
process (30)
described herein. The combining (31) of a first solvent and a bituminous feed
from oil sand to
form the initial slurry is followed by separating (32) of a fine solids stream
and coarse solids
stream from the initial slurry. Agglomerating (33) of solids from fine solids
stream then occurs to
form an agglomerated slurry comprising agglomerates and low solids bitumen
extract, optionally
subsequently adding the coarse solids stream into the agglomerated slurry.
Further, mixing (36)
of a second solvent with the agglomerated slurry occurs, to extract bitumen,
forming a solvent-
bitumen agglomerated slurry mixture. Removal (37) of agglomerates from the
mixture then
occurs. Separation (38) of high grade and low grade bitumen extracts then
occurs. Further,
recovery (39) of the solvents from the bitumen extracts is conducted, leaving
a high grade bitumen
product and a low grade bitumen product. Further details of these process
steps are provided
herein.
[00135] Figure 4 illustrates an embodiment of the processes described herein
which can be
characterized by the feature that the second solvent is mixed with the
agglomerated slurry upon
entry into the primary solid-liquid separator.
[00136] In this embodiment, a bituminous feed (402) is provided and is
combined with a first
solvent (409a), which may have bitumen (403a) entrained therein, into slurry
system (404) to form
an initial slurry (405), optionally in the presence of steam (407) to heat the
initial slurry (405). The
initial slurry (405) is mixed and the first solvent (409a) is given time to
contact the bituminous feed
so as to extract bitumen. The slurry (405) is then directed to a separator
(406) to form a fine
solids stream (408) which is directed into an agglomerator (410). Further
arising from the
separator (406) is a coarse solids stream (412) for later processing and solid-
liquid separation.
[00137] A bridging liquid (414), such as water, is added to the agglomerator
(410),
optionally together with bitumen (403b) which may be entrained in the first
solvent (409b) as
derived from downstream solvent recovery. The process of agglomeration of the
solids from the
fine solids stream (408) occurs by agitation of the agglomerator. The
agglomerated slurry (416)
arising from the agglomerator (410) comprises agglomerates (41 7a) together
with a low solids
bitumen extract 420a), all of which may be combined with the coarse solids
stream (412) and
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CA 02704927 2010-05-21
directed to a mixer (421) so as to be combined prior to entry into the primary
solid-liquid separator
(418). The agglomerated slurry (416) is mixed with the second solvent (422a)
to form a solvent-
bitumen agglomerated slurry mixture (423) within the mixer, and is then
separated within the
primary solid-liquid separator (418), which may be a deep cone settler or any
other sort of
separator. Concurrently, the second solvent (422a) can be added to the primary
solid-liquid
separator (418). The second solvent (422a) may also be added to the mixer
(421) before entry
into the primary solid-liquid separator (418). The second solvent (422a) may
be one having a low
boiling point, such as a boiling point below 100 C, and is immiscible in the
first solvent, or can be
rendered immiscible in the first solvent.
[00138] The bitumen-containing mixture within the primary solid-liquid
separator (418) is
separated and either directed toward forming high grade bitumen product (426)
once the solvent
has passed through the separator (418) to form a high grade bitumen extract
(425) and has been
extracted in a primary solvent recovery unit (428), or can be directed toward
forming a low grade
bitumen product (430). Advantageously in this embodiment, the second solvent
(422b, 422c) is
easily removed and recovered due to its volatility, low boiling point, and
optionally due to its
immiscibility in the first solvent.
[00139] The agglomerates (417b) can also be processed as they leave the
primary solid-
liquid separator (418) and are subsequently subjected to a separation in a
secondary solid-liquid
separator (432), permitting recovery of the second solvent (422d), first
solvent (409c) and any
bitumen entrained therein in the process. Residual solvent in the tailings may
be recovered in a
TSRU or tailings solvent recovery unit (434) so that agglomerated tailings
(436) may be
separated, and optionally water (438) used in the process may be recovered and
recycled.
[00140] The recovered first solvent (409d) arising from the primary solvent
recovery unit
(428) may be recycled for use in the process, for example when combined with
the bituminous
feed (402) in the separator (406). This recovered solvent may contain bitumen
entrained therein.
Quantities of a combination comprising recycled first solvent (409d) plus any
entrained bitumen
arising from the primary solid-liquid separator (418) or solvent recovery unit
(428) may be directed
to the agglomerator (410) for further processing. The second solvent (422b)
recovered from the
primary solvent recovery unit (428) may be also be recycled.
[00141] Secondary recovery of bitumen occurs within the secondary solid-liquid
separator
(432). The separated low grade bitumen extract (450) may be subjected to
separation within a
secondary solvent recovery unit (444), which may be a distillation unit, to
recover and recycle the
second solvent (422d) and to arrive at a low grade bitumen product (430). The
low grade bitumen
product (430) possesses some commercial value, as it can be processed further
with the intent of
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CA 02704927 2010-05-21
achieving a bottom sediment and water (BS&W) content lower than about 0.5 wt%
solid in dry
bitumen.
[00142] Solvent recovered may be held in a first solvent storage (429) in the
case of the
first solvent (409d), or in a second solvent storage (445), in the case of the
second solvent (422b)
for later use in the upstream aspects of the process. High grade bitumen(431)
may be added to
the first solvent derived from first solvent storage (429), if there is a need
to alter the solvent to
bitumen ratio prior to adding a combination of solvent (409a) and bitumen
(403a) to the slurry
system (404). Further, additional first solvent (409e) make-up quantities or
second solvent (422e)
make-up quantities may be included in respective solvent storage, if the
solvent volume requires
replenishing. Additional second solvent (422f) may also be added to the
secondary solid-liquid
separator (432) if needed.
[00143] This embodiment of the process forms different grades of bitumen
product and
advantageously permits recovery and/or recycling of both the first solvent and
the second solvent.
[00144] In this embodiment, the first solvent may be a low boiling point
cyclic aliphatic
solvent, such as a low boiling point cycloalkane, or a mixture of such
cycloalkanes, which
substantially dissolves asphaltenes. The first solvent may also be a
paraffinic solvent in which the
solvent to bitumen ratio is maintained at a level to avoid precipitation of
asphaltenes.
[00145] The second solvent may be a polar solvent, such as an alcohol, a
solvent with an
aqueous component, or another solvent which is immiscible in the first solvent
or which could be
rendered immiscible in the first solvent. A low boiling point n- or iso-alkane
and alcohols or blends
of these with or without an aqueous component are candidates. Surface
modifiers may be added
to the alcohol if needed. Good agglomerate strength is achieved if the
agglomerates are modified
with hydrating agents, such as a cement, a geopolymer, fly ash, gypsum or lime
during
agglomeration. Optionally, the second solvent may comprise a wetting agent in
an aqueous
solution. A further option is to employ controlled precipitation of
asphaltenes within either the
agglomerator (410) or the primary solid-liquid separator (418) by employing a
mixture of solvent
and bitumen in a ratio that avoids precipitation of asphaltenes. For example,
a ratio of solvent to
bitumen of 2:1 or less may be used within the agglomerator to control
asphaltene precipitation..
[00146] The embodiment depicted in Figure 4 results in enhanced liquid
drainage during
agglomerate washing when the second solvent comprises predominantly of polar
component,
such as an alcohol. Further, enhanced solvent recovery may be achieved, which
results in a more
environmentally benign tailings stream.
[00147] The product upgrading of low grade bitumen product (430) can be
undertaken to
produce a low grade product with some commercial value. If the commercial
value involves
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CA 02704927 2010-05-21
alternate fuel applications, it would be possible to have a residual alcohol
content remaining in the
low grade bitumen product (430) from the second solvent. Generally, the low
grade bitumen
product (430) is comprised predominantly of asphaltenes or other more polar
bitumen fractions.
[00148] Figure 5 is a schematic representation of an additional embodiment of
the process
(50) described herein. The combining (51) of a first solvent and a bituminous
feed from oil sand to
form initial slurry is followed by separating (52) of a fine solids stream and
coarse solids stream
from the initial slurry. Recovery (54) of the first solvent from the coarse
solids stream is then
conducted. Agglomerating (53) of solids from the fine solids stream then
occurs to form
agglomerated slurry comprising agglomerates and low solids bitumen extract. In
this embodiment,
the coarse solids stream is not optionally added to the agglomerated slurry,
as the coarse solids
stream is processed separately. Subsequently, separation (55) of low solids
bitumen extract from
agglomerated slurry occurs. Further, mixing (56) of a second solvent with low
solids bitumen
extract to extract bitumen takes place, forming a solvent-bitumen low solids
mixture. Separation
(58) by gravity of low grade and high grade bitumen extracts from the mixture
then occurs.
Further, recovery (59) of the solvents is conducted, leaving a high grade
bitumen product. Further
details of these process steps are provided herein.
[00149] Figure 6 illustrates an embodiment similar to that depicted in Figure
2, except that
coarse solids stream separated out of the bituminous feed is processed
separately, and not re-
combined with an agglomerated slurry.
[00150] A bituminous feed (602) is provided and combined with a first solvent
(609a),
optionally with bitumen (603a) entrained therein, in a slurry system (604) to
form an initial slurry
(605). Steam (607) may be added to the slurry system (604) to heat the initial
slurry (605). The
initial slurry (605) is then directed from the slurry system (604) to a
separator (606) for separation,
which may be a fine/coarse solids separator, in order to form a fine solids
stream (608), which is
directed into an agglomerator (610), as well as a coarse solids stream (612),
which is processed
separately from the agglomerated slurry (616) arising from the agglomerator
(610). Additional
quantities of first solvent (609b) having bitumen (603b) entrained therein,
may be added to the
agglomerator (610). A bridging liquid (614), such as water, may be added to
the agglomerator
(610), and the process of agglomeration of the solids contained within the
fine solids stream (608)
occurs by agitation within the agglomerator (610). The agglomerated slurry
(616) arising from the
agglomerator comprises agglomerates (617a) together with a low solids bitumen
extract (620a).
In this example, there is no combination with the coarse solids stream.
Instead, the agglomerated
slurry (616) itself is directed to the primary solid-liquid separator (618).
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CA 02704927 2010-05-21
[00151] The low solids bitumen extract (620) is separated from the
agglomerated slurry
(616) within the primary solid-liquid separator (618). This extract (620) is
subsequently combined
in a mixer (621) with a second solvent (622a). Extract (620) may optionally be
sent to a solvent
recovery unit, not shown, where all of the first solvent contained therein is
recovered from the
extract, before mixing with the second solvent within the mixer (621).
[00152] The second solvent may be one having a low boiling point. The solvent-
bitumen
low solids mixture (623) derived from the mixer (621) is separated in a
gravity separator (624), and
streams arising from the gravity separator (624) are directed either toward
forming a high grade
bitumen product (626) once the solvent has been extracted in a solvent
recovery unit (628), or
toward forming a low grade bitumen extract (630). The solvent recovery unit
(628) may
advantageously be used to recover the majority of the first solvent (609c)
remaining within the
effluent, or overflow, of the gravity separator (624), in the interests of
solvent recovery and re-use.
Streams derived from the gravity separator (624) include high grade bitumen
extract (625), and
low grade bitumen extract (630) as underflow. Advantageously, the second
solvent (622b) is
easily removed and recovered due to its volatility and low boiling point.
[00153] The separated agglomerates (617b) can also be utilized, as they leave
the primary
solid-liquid separator (618) and are subsequently subjected to a separation in
a secondary solid-
liquid separator (632), permitting recovery of the first solvent (609c) and
bitumen (603c) entrained
therein in the process. Solvent (609d) derived from the solvent recovery unit
(628) may also be
recycled to the secondary solid-liquid separation separator (632). Additional
quantities of the first
solvent (609e) may be added to the secondary solid-liquid separator, if
desired, for example for
washing purposes. Tailings may be recovered in a TSRU or tailings separation
recovery unit
(634) so that agglomerated tailings (636) can be separated from recyclable
water (638). Either or
both the recovered first solvent (609g or 609d)) derived from the TSRU (634)
and/or from the
solvent recovery unit (628) may be recycled in the secondary solid-liquid
separator (632).
[00154] A combination containing the first solvent (609c) plus bitumen (603c)
arising from
the secondary solid-liquid separator (632) can be processed with the intent of
achieving a bottom
sediment and water (BS&W) content lower than about 0.5 wt% solid in dry
bitumen. In particular,
the product may have less than 400 ppm solids. This combination containing the
first solvent plus
bitumen may also be recycled back into the process by including it in the
agglomerator (610) or
slurry system (604).
[00155] Advantageously, the process permits recovery of both the first solvent
and the
second solvent. In one embodiment, the first solvent may be a low boiling
point solvent, such as a
low boiling point cycloalkane, or a mixture of such cycloalkanes, which
substantially dissolves
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CA 02704927 2010-05-21
asphaltenes. The first solvent may also be a paraffinic solvent in which the
solvent to bitumen ratio
is maintained at a level to avoid precipitation of asphaltenes.
[00156] For the second solvent, a low boiling point n- or iso-alkane and
alcohols or blends
are candidates. Surface modifiers may be added to the alcohol if needed. With
the alkanes,
solvent deasphalting is achieved with concurrent cleaning of the high grade
bitumen product (626)
to achieve pipeline quality. Therefore, the low grade bitumen extract (630) is
comprised
predominantly of asphaltenes or other more polar bitumen fractions.
[00157] In this embodiment, the coarse solid stream (612) derived from the
separator (606)
is kept segregated from the agglomerated slurry (616). Thus, the separator
(606) can be reduced
in size compared to the approach described with respect to Figure 2, as only
quick settling solids
are removed. These coarse solids may form the majority of the particulate,
especially for high
grade oil sands, and will exhibit high drainage rates in the secondary solid-
liquid separator for
coarse solids (652). The non-agglomerated nature of the coarse solids allows
for efficient solvent
recovery of both first solvent (609f) and bitumen (603f) entrained therein.
[00158] The agglomerated slurry (616) may thus enter a reduced size primary
solid-liquid
separator (618) and can be processed as described above in the secondary
liquid-solid separator
(632) and TSRU (634). Agglomerated tailings (636) can be removed using the
TSRU (634). The
rate determining step in solvent recovery from tailings is the time required
for release of residual
solvent from the pores of the agglomerated solids. With segregation, the
solvent recovery from the
fine particles can be optimized independent of the coarse particles. The
combination of first
solvent (609f) and bitumen (609f) recovered permits separation of coarse
tailings (656), once
drained from the secondary solid liquid separator for coarse solids (652).
Coarse tailings (656)
isolated from the tailings solvent recovery unit for coarse solids (654) can
be sent to the primary
solid-liquid separator (618) for residual fine solids removal, or may be
recycled upstream of the
process to form the initial slurry (605) in slurry system (604). The tailings
solvent recovery unit for
coarse solids (654) may be used to recover recyclable water (638) or solvent
from the secondary
solid-liquid separator for coarse solids (652). Coarse tailings (656) may also
be removed.
[00159] Figure 7 is a schematic representation of a system (70) according to
an
embodiment of the invention. The system comprises a slurry system (71) in
which a bituminous
feed is mixed with a first solvent to form an initial slurry. A separator (73)
is present, in which a
fine solids stream and a coarse solids stream are separated from the initial
slurry. An
agglomerator (75) is present in the system, for receiving fine solids stream
from separator, and in
which agglomerated slurry is formed. A primary solid-liquid separator (77) is
included in the
system (70) for receiving the agglomerated slurry, and separating it into
agglomerates and a low
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CA 02704927 2010-05-21
solids bitumen extract. A gravity separator (78) is included for receiving the
low solids bitumen
extract and a second solvent. Further, a primary solvent recovery unit (79) is
also included in the
system (70) for recovering first and/or second solvent arising from primary
solid-liquid separator,
leaving bitumen product.
[00160] Aspects of the present invention which generally relate to a process
and system for
recovery of hydrocarbon associated with or entrained within an aqueous stream.
Such aqueous
streams may be ones having in excess of 60% water. Such streams may be ones
produced or
rejected from water-based bitumen extraction processes, or may be streams that
are directly
derived from oil sands which include a high water content, but which were not
necessarily
intended for a water-based bitumen extraction process. Certain rejected
streams from water-
based bitumen extraction processes (or "waste streams"), as well as
intermediate streams
produced in the extraction process which were not intended as waste, may be
relatively high in
water content, and thus can advantageously be processed further through non-
aqueous solvent
extraction once the water content of the high water stream streams is reduced
to a level
acceptable within the non-aqueous solvent extraction process, such as for
example reduced
below 40% water.
[00161] Recovery of bitumen from relatively high fines aqueous feed streams
may involve
using a combination of non-aqueous solvent extraction and agglomeration of
solids. Non-aqueous
solvent extraction and agglomeration processes can employ aqueous feed
streams, provided the
water content is not so high as to negatively impact the agglomeration aspect.
Aqueous feed
streams may be used, despite a high fines content, and in this way, such
aqueous streams that
may have previously been considered difficult to recover because of the fines
content, can be
effectively utilized. High fines content is a characteristic previously
considered problematic in
conventional methods for extracting hydrocarbon from aqueous feed streams. For
example, waste
streams arising from water-based methods of hydrocarbon recovery, which may
have previously
been directed to tailings ponds, can be used in the solvent extraction
processes described herein,
provided the water content is in an appropriate range to permit use of the
stream without causing
excessive dilution to the solvent extraction process thereby impeding
efficient agglomeration of
fines. Thus, waste streams arising from conventional extraction processes,
intermediate streams
from conventional extraction processes, or any bituminous aqueous stream can
be used in the
solvent extraction process if pre-conditioned to achieve desired
characteristics. The process is
described herein for utilization of streams that are high in water content,
which may require
concentration through pre-treatment in order to be effectively used in such an
extraction process.
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CA 02704927 2010-05-21
[00162] Hydrocarbon-containing streams bearing levels of water that are not in
excess of a
level that would be of detriment to a non-aqueous extraction process (such as
streams containing
less than about 40 wt% water), can be fed directly into the non-aqueous
extraction processes as
described herein, without the need for concentration through a water removal
pre-treatment
process. Such streams that already contain water at a lower, acceptable level
for non-aqueous
extraction, are encompassed in the processes described herein.
[00163] One embodiment provides a process for pre-treating an aqueous
hydrocarbon-
containing feed for downstream solvent-based extraction processing for bitumen
recovery, the
aqueous hydrocarbon-containing feed comprising from 60 wt% to 95 wt% water,
from 0.1 wt% to
wt% bitumen, and from 5 wt% to 40 wt% solids, wherein the solids comprise
fines, the process
comprising: removing water from the aqueous hydrocarbon-containing feed to
produce an effluent
comprising 40 wt% water or less; and providing the effluent to a downstream
solvent-based
extraction process comprising fines agglomeration to recover bitumen. The step
of removing
water from the aqueous hydrocarbon-containing feed may comprise: flowing the
aqueous
hydrocarbon-containing feed into a primary water separation system to remove
water from the
aqueous hydrocarbon-containing feed, producing a reduced-water stream of from
30 wt% to 60
wt% solids, and recycled water; and removing water from the reduced-water
stream using a
secondary water separation system to produce an effluent comprising 40 wt%
water or less. The
primary water separation system may comprise a clarifier, a settler, a
thickener or a cyclone.
Flocculant may be added to the aqueous hydrocarbon-containing feed in the
clarifier. A solvent or
flocculant may be mixed with the aqueous hydrocarbon-containing feed prior to
water separation
in the clarifier. The solvent may be mixed with the aqueous hydrocarbon-
containing feed with a
solvent:bitumen ratio of less than about 2:1. A low boiling point cycloalkane
solvent may be mixed
with the aqueous hydrocarbon-containing feed. The secondary water separation
system may
comprise a centrifuge with filtering capacity, a shale shaker, or one or more
clarifiers. The
aqueous hydrocarbon-containing feed may comprise effluent of a froth
separation unit. The
aqueous hydrocarbon-containing feed may comprise tailings from a tailings
solvent recovery unit.
[00164] One embodiment provides a system for pre-treating an aqueous
hydrocarbon-
containing feed for downstream solvent-based extraction processing for bitumen
recovery, the
aqueous hydrocarbon-containing feed comprising from 60 wt% to 95 wt% water,
from 0.1 wt% to
10 wt% bitumen, and from 5 wt% to 40 wt% solids, wherein the solids comprises
fines, the system
comprising: a dewatering unit for removing water from the aqueous hydrocarbon-
containing feed
to produce an effluent comprising 40 wt% water or less; and a conduit for
providing the effluent to
a downstream solvent-based extraction process comprising fines agglomeration
to recover
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CA 02704927 2010-05-21
bitumen. The dewatering unit may comprise: a primary water separation system
to remove water
from the aqueous hydrocarbon-containing feed, producing a reduced-water stream
and recycled;
and a secondary water separation system for receiving the reduced-water stream
and removing
water therefrom to produce an effluent comprising 40 wt% water or less.
[00165] There are many sources of aqueous hydrocarbon-containing feed streams
in
excess of 60 wt% water which can be subjected to processing as described
herein, so that
hydrocarbon may be extracted. Such streams that are referred to as aqueous
hydrocarbon-
containing feed streams may interchangeably be referenced herein as "high
water content
streams". The variety of aqueous hydrocarbon-containing feed streams which
could be used as
feed streams in the processes described herein possess over 60 wt% water.
Thus, possible
streams for processing according to the processes described include streams
derived from
conventional froth treatment processes, either as intermediates of the froth
treatment process, or
as an end-product or waste product of aqueous oil sands extraction processes.
For example,
streams that may normally have been considered waste streams in a conventional
aqueous
extraction process can now be subjected to processing, and recovery of
hydrocarbon. Such
streams need not be designated as waste streams per se, but may be
intermediate streams which
would have normally proceeded to further processing within an aqueous
extraction or froth
treatment process. Aqueous streams need not be derived from a water-based
extraction process,
but may contain water for other reasons, such as steam exposure, water-
heating, or due to mixing
of water with oil sands that have not yet been subjected to any extraction
process, but which have
been rendered aqueous for alternative reasons..
[00166] Depending on the froth treatment conducted and ore grade, bitumen
content in a
feed arising from such process streams may exceed 15 wt% bitumen on a dry
solids basis.
Although such a feed may comprise hydrocarbon of a predominantly lower grade,
its bitumen
content may be comparable to or higher than the original oil sands ore for the
same solids
throughput. However, in the integration of the non-aqueous solvent extraction
and agglomeration
process described herein with a conventional process, it is problematic that,
except for oversized
rejects, other potential feed streams have a very large proportion of water.
This large proportion
of water is higher than the optimum needed for effective fines agglomeration
in the process. An
advantage of the utilization of high water content streams, as described
herein is that pre-
conditioning of such streams can reduce water content to permit such streams
to be used as feed
streams in a non-aqueous solvent extraction process, thereby addressing this
challenge. The
treatment process for waste streams according to embodiments described herein
permits aqueous
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CA 02704927 2010-05-21
streams with high fines content to be used as feed streams for the non-aqueous
solvent extraction
process, so as to permit successful recovery of bitumen that would have
otherwise been lost.
[00167] Typical aqueous hydrocarbon-containing feed streams for use in the de-
watering
process include, but are not limited to middlings derived from a primary
separation vessel (PSV),
paraffinic froth treatment (PFT) tailings, floatation tails which may not yet
have been directed to a
tailings pond, and/or mature fine tailings (MFT), which may have already been
present in a tailings
pond. Appropriate aqueous hydrocarbon-containing feed streams may be ones
containing
bitumen and/or other hydrocarbon components, which may or may not include
bitumen.
[00168] Feed streams arising as waste from conventional oil sands processing
techniques
are particularly attractive for pre-conditioning as described herein, to
reduce water content prior to
use as a feed in an agglomeration process. If conventional feed streams were
fed directly into an
agglomeration process, without pre-treatment as described herein, there is the
problem that
(except for oversize rejects) such feed streams would provide excessive
dilution and decrease
effectiveness and/or efficiency of the agglomeration process. The pre-
conditioning process
described herein would not previously have been considered as an effective way
to recover waste
water, nor would it have been viewed as an optimal way to recover bitumen that
would have
otherwise been lost. By pre-treating a waste stream in this way, in
preparation for subsequent
recovery in an extraction process, both a reduction in waste and an increase
in recovery of
bitumen can be realized.
[00169] Advantageously, the middlings from a primary separation vessel used in
a
conventional water-based extraction process may be processed less efficiently
on the assumption
that further hydrocarbon components can be recovered in downstream solvent-
based extraction
processes. This results in an energy saving at this step, as not all bitumen
need be removed in a
water based bitumen extraction process.
[00170] A mixer may be used as the aqueous stream enters a primary water
separation
system or vessel. One or more points of entry of the hydrocarbon-containing
feed stream may be
used on the way to such a primary separation vessel, so as to allow turbulence
to occur. As an
exemplary embodiment, multiple injection points of an aqueous hydrocarbon-
containing feed are
used on the way to the primary separation vessel.
[00171] Flocculants or other additives, such as coagulants or pH modifiers may
be added to
the aqueous hydrocarbon-containing feed streams. Typically, a pH of 8.5 is
achieved, and a drop
in pH may be achieved. Thus, pH may be modified from a level above pH 7 to a
level below pH 7.
A reduction in pH may reduce surface activities of the clays, which may result
in precipitation of
fines. A non-aqueous solvent may be added to the aqueous hydrocarbon-
containing feed
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CA 02704927 2010-05-21
streams, for example a solvent may be used which may be lighter or heavier
than water. When
solvent is present, deriving recycled water may be accomplished in an
appropriate way so that the
recycled water may be recovered separately from the solvent. Further, small
quantities of solvent
may adhere to solids and thus sink to the bottom in a dewatering unit,
permitting concentration of
solids in the underflow.
[00172] In the primary water separation step for water removal, a clarifier, a
settler,
thickener, or a cyclone may be used in single or multiple units which may be
in communication in
serial, or employed in parallel. Thus, the dewatering unit may comprise one or
more of such units.
The resulting effluent may contain from 30 wt% to 60wt% solids. The
hydrocarbon content of the
effluent arising from this stage of the process is enriched, relative to the
initial aqueous feed. A
doubling of the hydrocarbon content, or a further enriched content, may be
achieved. However,
the effluent from this stage is still pumpable so as to permit transport and
movement through to
further aspects of the process. The content of solids may in fact be above a
level of 60wt%, and
water content could be lower that 40%, provided the effluent from the
underflow derived from the
primary water separation is still pumpable.
[00173] When present, a secondary water separation system of the dewatering
unit may be
employed. Similar types of apparatuses may be employed in such secondary
separation, or a
filter, filter centrifuge, centrifuge, or vibration filter may be employed.
The system may employ a
single dewatering unit, or the dewatering unit may comprise individual
components, such as
primary water separation system and a secondary water separation system. Each
of the primary
and secondary water separation systems may have multiple individual components
operating in
parallel or in serial.
[00174] A feed stream comprising bitumen, water and solids with or without
residual solvent
is pre-conditioned according to the process described herein. The feed stream
may be derived
from a mixture of oilsand, oversized rejects stream, and high water content
streams or blends
thereof. An exemplary high water content stream may be one derived from a
primary separation
vessel middling stream, or from secondary flotation tails and/or froth
treatment tailings from a
water-based extraction process. Such feed streams or blends thereof are
processed via a single
or dual staged water separation system (WSS) in order to be adequately pre-
conditioned for use
as a feed stream in the non-aqueous solvent extraction and agglomeration
processes described
herein, as depicted for example in Figure 1 to Figure 6.
[00175] Figure 8 is a schematic representation of the process (800) in which
an aqueous
bituminous feed stream is conditioned according to the invention. The initial
aqueous bituminous
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CA 02704927 2010-05-21
feed (830) is one derived from oil sands extraction processes, for example, it
may be a waste
stream derived from frothing in a conventional extraction process.
Advantageously, the feed may
have high fines content, as such fines can be subsequently removed. The feed
(830) contains
60% to 95% water on a weight basis, and also contains from 0.1 wt% to 10 wt%
bitumen, and
from 5 wt% to 40 wt% solids. The step of water removal (832) is conducted in
any manner that
would be acceptable so as to achieve an effluent (834) having about 40% water,
or less, by
weight. This effluent goes on to downstream solvent extraction (836), for
example using a
process that involves agglomeration of fines.
[00176] Figure 9 represents processes (900) for pre-treating a bituminous feed
(902) with
water content of from 60 wt% to 95 wt% water, with from 0.1 wt% to 10 wt%
bitumen, and with 5
wt% to 40 wt% solids.
[00177] The bituminous feed (902) is passed into a primary water separation
system or
PWSS (904). In the PWSS, a portion of the water contained in the feed (902) is
recovered as
recycled water (906). The remaining portion is a reduced-water stream (908),
which is then fed
into a secondary water separation system or SWSS (910) to produce an effluent
(912) having the
consistency of a pumpable slurry, containing predominantly fine solids and
hydrocarbon, and
having a water content of up to 40 wt%. More recycled water (906) is recovered
from the
secondary water separation system (910). The effluent (912) of the secondary
water separation
system, having the consistency of a pumpable slurry, may be combined with
oversized rejects
(914) and/or recycled extract liquor (916) in proportions which permit the
water content of the
resulting slurry (918) to remain within the desired level for fines
agglomeration or capture in later
downstream processing.
[00178] The primary water separation system (904) may preferably be a
clarifier unit or
cyclone which takes advantage of inherent or induced high settling
characteristics of the high
water content feeds. In contrast to conventional extraction processes in which
additives are
employed to disperse fines in water and prevent slime coating of bitumen,
flocculants or
coagulants may optionally be used to induce the aggregation of fines and
hydrocarbons within the
clarifier. Large quantities of recycled water low in total suspended solids
may thus be recovered.
Advantageously, by recovering water at this stage, efficiencies are
introduced, due to the reduced
volume forwarded for downstream processing.
[00179] The secondary water separation unit (910) may be a filtering device
that can
provide centrifugal or vibrational force for phase separation. A slurry of
coarse solids may be
added to the secondary water separation system to promote efficient
dewatering. In exemplary
embodiments, the secondary water separation system (910) may comprise a
centrifuge with
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CA 02704927 2010-05-21
filtering capacity, or a shale shaker. It may be possible in certain
embodiments that the dewatering
achieved in the secondary water separation system is enough to allow for
direct feed of the
effluent (912), without addition of oversize rejects or oil sands, into the
non-aqueous solvent
extraction processes described herein, and as depicted for example in Figure 1
to Figure 6.
[00180] Optionally, solvent (920) may be added to the bituminous feed (902)
entering the
primary water separation system (904) so as to dissolve bitumen and decrease
the feed density
sufficiently for selective phase separation under gravity or for application
of a centrifugal force
field. If solvent is added, an exemplary solvent:bitumen ratio is less than
2:1.
[00181] As a further option, a flocculant (922) with selective reactivity for
the fines may be
added to aggregate clays contained in the bituminous feed (902) thus promoting
faster settling or
drainage. The flocculant may be added prior to entry of the feed (902) into
the primary water
separation system (904), via a mixer (921) or may be added directly into the
primary water
separation system. The resulting reduced-water stream (908) resulting from the
primary water
separation system (904) is passed through the secondary water separation
system (910) and the
effluent (912) may be subsequently combined with the oversize rejects (914) to
produce a slurry
(918) ready for processing via the non-aqueous solvent extraction process
described herein, as
depicted for example in Figure 1 to Figure 6.
[00182] Conventional oil sands processing may include a flotation separation
step, resulting
in the formation of a froth. Asphaltene content in froth is typically about 5%
to 15%. To separate
the asphaltenes from the hydrocarbons targeted for recovery, the froth can be
mixed with a
solvent and subjected to one or more settling stages. An aqueous froth may be
mixed with a
solvent for precipitation of asphaltenes and is then subjected to one or more
settling stages. The
solvent can be, for example, a paraffinic hydrocarbon solvent having a chain
length between about
and about 8 carbons. An exemplary solvent may be a mixture of pentane and
hexane. This
solvent is typically recovered from waste streams and recycled, to avoid
release to the
environment. Separation of the solvent can occur, for example, in a tailings
solvent recovery unit
(TSRU). Conventionally, the solvent is recycled and the tailings that exit the
TSRU are disposed
of as a waste product.
[00183] The bituminous feed (902) may comprise froth treatment tailings
derived from an
aqueous bitumen extraction of oil sands. A stream of effluent arising from a
froth separation unit
(FSU) underflow may be used as the bituminous feed (902) in the process
described herein.
Further, the bituminous feed (902) may comprise tailings from a tailings
solvent recovery unit
(TSRU). Advantageously, when FSU tailings are employed as the bituminous feed
(902) in the
instant process, this would allow exclusion of the TSRU from conventional
froth treatment
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CA 02704927 2010-05-21
processes, since residual solvent recovery would occur in a later step of the
non-aqueous
extraction process described herein, as depicted for example in Figure 1 to
Figure 6. Thus, in a
conventional process that would typically treat effluent from froth separation
using TSRU, the use
of the effluent as the bituminous feed (902) negates the requirement for
recovery of solvent in a
conventional tailing solvent recovery unit.
[00184] The resulting slurry (918) may be combined with any other appropriate
bituminous
feed as an additional feed source (930) for later downstream processing in a
process (932)
capable of separating fines out of a high fines content aqueous bituminous
feed, such as one
capable of agglomerating tailings (934) while forming a hydrocarbon product
(936).
[00185] Figure 10 is a schematic illustration of a process (1000)
incorporating the
preparation of a waste water stream according to Figure 8 together with
downstream steps for
recovery of bitumen. An aqueous bituminous feed is derived (1030) from oil
sands extraction and
has from 60 wt% to 95 wt% water, from 0.1 wt% to 10 wt% bitumen, and from 5
wt% to 40 wt%
solids. This feed is potentially derived from waste streams recovered from
froth treatment, but
may also be derived from intermediate streams from any aqueous oil sands
extraction process.
Further, an aqueous stream meeting these criteria that has not been prepared
through an
aqueous extraction process may nevertheless be used as a feed stream.
[00186] Water is removed (1032) from the aqueous hydrocarbon-containing feed
having 60
wt% to 95 wt% water, resulting in an effluent comprising 40% water or less,
which goes on to be
used (1034) as bituminous feed either alone or in combination with further
bitumen containing
sources. Other bitumen containing sources may include oversized rejects or
recycled extract
liquor, or any source of bitumen. The resulting mixture should have the
consistency of a
pumpable slurry. This mixture, including the effluent having less than 40%
water, is now used as
the feed for further processing. Ina subsequent step, a first solvent is added
(1012) to the
bituminous feed to form an initial slurry. Fine solids and coarse solids are
separated (1014) as a
fine solids stream and a coarse solids stream from the initial slurry. Fine
solids are agglomerated
(1016) from the fine solids stream to form a slurry comprising agglomerates
and low solids
bitumen extract. A low solids bitumen extract is separated (1018) from the
aggregated slurry. A
second solvent is added (1020) to the low solids bitumen extract to recover a
new bitumen extract
essentially free of solids. In this way, a hydrocarbon product is derived from
a bitumen-containing
waste water stream.
[00187] Figure 11 depicts an embodiment of the process described herein,
employing
primary and secondary water separation prior to entry into a non-aqueous
solvent extraction
process employing agglomeration for recovery of bitumen. Figure 11 outlines an
embodiment of
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CA 02704927 2010-05-21
the process in which a waste stream containing a high fines content, but also
high in water (60
wt% to 95 wt% water) is pre-treated and utilized as a bituminous feed in a
process to recover the
bitumen contained therein.
[00188] In Figure 11, the bituminous feed (1172) is passed into a primary
water separation
system or WSS (1174). In the primary water separation system, a portion of the
water contained in
the feed (1172) is recovered as recycled water (1176). The remaining portion
is a reduced-water
stream (1178), which is then fed into a secondary water separation system
(1180) to produce an
effluent (1182) having the consistency of a pumpable slurry, containing
predominantly fine solids
and hydrocarbon, and having a water content of up to 40 wt%. More recycled
water (1176) is
recovered from the secondary water separation system (1180). The effluent
(1182) of the
secondary water separation system, having the consistency of a pumpable
slurry, may be
combined with oversized rejects (1184) and/or recycled extract liquor (1186)
in proportions which
permit the water content of the resulting slurry (1188) to remain within the
desired level for fines
capture in later downstream processing. This slurry (1188) is thus used as a
bituminous feed in
subsequent processing steps for bitumen recovery.
[00189] The primary water separation system (1174) may preferably be a
clarifier unit which
takes advantage of inherent or induced high settling characteristics of the
high water content
feeds. In contrast to conventional extraction processes in which additives are
employed to
disperse fines in water and prevent slime coating of bitumen, flocculants or
coagulants may
optionally be used to induce the aggregation of fines and hydrocarbons within
the clarifier. Large
quantities of recycled water low in total suspended solids may thus be
recovered.
Advantageously, by recovering water at this stage, efficiencies are
introduced, due to the reduced
volume forwarded for downstream processing.
[00190] The secondary water separation unit (1180) may be a filtering device
that can
provide centrifugal or vibrational force for phase separation. A slurry of
coarse solids may be
added to the secondary water separation system to promote efficient
dewatering. In exemplary
embodiments, the secondary water separation system (1180) may comprise a
centrifuge with
filtering capacity, or a shale shaker. It may be possible in certain
embodiments that the dewatering
achieved in the secondary water separation system is enough to allow for
direct feed of the
effluent (1182), without addition of oversize rejects or oil sands, into the
remainder of the
processing steps.
[00191] Optionally, solvent (1190) may be added to the bituminous feed (1172)
entering the
primary water separation system (1174) so as to dissolve bitumen and decrease
the feed density
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sufficiently for selective phase separation under gravity or for application
of a centrifugal force
field. If solvent is added, an exemplary solvent:bitumen ratio is less than
2:1.
[00192] As a further option, a flocculant (1192) with selective reactivity for
the fines may be
added to aggregate clays contained in the bituminous feed (1172) thus
promoting faster settling or
drainage. The flocculant may be added prior to entry of the feed (1172) into
the primary water
separation system (1174), via a mixer (1191) or may be added directly into the
primary water
separation system. The resulting reduced-water stream (1178) resulting from
the primary water
separation system (1174) is passed through the secondary water separation
system (1180) and
the effluent (1182) may be subsequently combined with the oversize rejects
(1184) to produce a
slurry (1188) ready for processing via the subsequent solvent extraction and
agglomeration
processing, for example as described herein and depicted in Figure 1 to Figure
6.
[00193] The resulting slurry (1188) may be combined with any other appropriate
feed
source as a bituminous feed.
[00194] In the preceding description, for purposes of explanation, numerous
details are set
forth in order to provide a thorough understanding of the embodiments of the
invention. However,
it will be apparent to one skilled in the art that these specific details are
not required in order to
practice the invention.
[00195] Example 1
[00196] Approximately 500 g of low grade oil sands (comprising 22 wt% fines)
was mixed
with 300 g cyclohexane as a first solvent (loaded with bitumen up to 40 wt%)
using an impeller in a
mixing vessel at 30 C. Sand grains greater than 1 mm were removed by
screening. The
remaining slurry was passed into an agglomerator where 30 ml of water was
added. Agglomerates
of sizes ranging from 0.1 mm to 1 cm were formed. The agglomerated slurry was
allowed to settle
for 30 minutes and a first supernatant was collected for water and solids
content analysis. Solids
content determined by ashing ranged between 5,000 - 20,000 ppm on a dry
bitumen basis for this
first supernatant while water content by Karl Fischer analysis was generally
less than 1000 ppm.
Portions of the first supernatant were mixed with normal pentane as a second
solvent above the
critical solvent to bitumen ratio to effect precipitation of asphaltene at 30
C. After settling for 30
minutes, a second supernatant was collected and analyzed for solids and water
content. The
sediment from the settling test comprised predominantly of asphaltenes and
less than 20 wt%
solids and was treated as the lower grade bitumen extract. Solids and water
contents of the
second supernatant were determined to be less than 400 ppm and 200 ppm on a
dry bitumen
basis, respectively. The second supernatant was a dry, clean and partially de-
asphalted bitumen
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product suitable for transportation via a common carrier pipeline and
processing in a remote
refinery.
[00197] Example 2
[00198] In another experiment similar to the one described in Example 1, a
mixture of 30%
cyclohexane and 70% heptane, by volume, was used in agglomeration as the first
solvent. For the
first supernatant, solids content determined by ashing range between 5,000 -
10,000 ppm on a
dry bitumen basis while water content by Karl Fischer analysis was generally
less than 1,000 ppm.
Portions of the first supernatant were mixed with normal pentane as a second
solvent above the
critical solvent to bitumen ratio to effect precipitation of asphaltene at
room temperature. The
solids and water content of the resulting second supernatant was determined to
be less than 400
ppm and 200 ppm on a dry bitumen basis after 30 minutes of settling.
[00199] Example 3
[00200] In another experiment similar to the one described in Example 1,
normal heptane
loaded with 40 % bitumen was used as extraction solvent (the first solvent).
Solids content of the
first supernatant was determined to be less than 400 ppm on a dry bitumen
basis after 30 minutes
of settling. Water content was less than 200 ppm. The resulting product,
having less than 400
ppm of filterable solids was a high grade bitumen product.
[00201] The above-described embodiments of the invention 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 of the invention,
which is defined solely by
the claims appended hereto.
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