Note: Descriptions are shown in the official language in which they were submitted.
CA 02689469 2009-12-30
PROCESS AND SYSTEM FOR RECOVERY OF BITUMEN FROM OIL SANDS
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.
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 at., 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
from recovery bitumen from oil sands using a mixture of light naphtha and
methanol. However, it is
not described or suggested that a second solvent could be effectively applied
to a solvent
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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] 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
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.
SUMMARY OF THE INVENTION
[0017] 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.
[0018] 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.
[0019] 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
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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.
[0020] 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.
[0021] 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.
[0022] 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
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.
[0023] 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
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.
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[0024] 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.
[0025] 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 from the high grade bitumen
extract, leaving a
high grade bitumen product.
[0026] 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 first 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
product; and the first and second solvent are also recovered from the low
grade bitumen extract,
leaving a low grade bitumen product.
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[0027] 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.
[0028] 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.
[0029] 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
solvent or the second solvent in a high grade bitumen extract arising from the
gravity separator
and for separating bitumen therefrom.
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[0030] 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.
[0031] 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
[0032] Embodiments of the present invention will now be described, by way of
example
only, with reference to the attached Figures.
[0033] Figure 1 is a schematic representation of an embodiment of the process.
[0034] Figure 2 illustrates an exemplary embodiment of the process consistent
with the
representation shown in Figure 1.
[0035] Figure 3 is a schematic representation of an embodiment of the process.
[0036] Figure 4 illustrates an exemplary embodiment of the process consistent
with the
representation shown in Figure 3.
[0037] Figure 5 is a schematic representation of an embodiment of the process.
[0038] Figure 6 illustrates an exemplary embodiment of the process consistent
with the
representation shown in Figure 5.
[0039] Figure 7 provides a schematic representation of an embodiment of the
system
according to the invention.
DETAILED DESCRIPTION
[0040] 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.
[0041] A process and system for recovery of bitumen from oil sands is provided
herein.
[0042] 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.
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The bituminous feed from oil sands is one that contains bitumen along with
other undesirable
components for removal 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 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.
[0043] 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.
[0044] 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
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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 product. The first and second solvent are also recovered from the low
grade bitumen
extract, leaving a low grade bitumen product.
[0045] 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.
[0046] 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.
[0047] In this embodiment of the process, the coarse solids stream is
processed
separately from the fine solids stream, and will not optionally be included
back into the mixture.
Coarse solids are processed separately to remove the solvent therefrom, or are
added back into
the slurry system or separator, for subsequent processing in an iterative
manner.
[0048] 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
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agglomerated slurry mixture, the second solvent having a similar or lower
boiling point than the
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.
[0049] In this embodiment of the process, the first solvent may be recovered
from the
coarse solids stream separately, and again there is no option to re-introduce
the coarse solids
stream into a downstream aspect of the process, for example, into the
agglomerated slurry, as
there would be in other embodiments of the process. This embodiment also
involves combining
the second solvent with the agglomerated slurry.
[0050] 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.
[0051] 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.
[0052] 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
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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
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.
[0053] 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. However, 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.
[0054] Embodiment Of A System In Which A Fine/Coarse Solids Separator And A
Gravity Separator Are Employed.
[0055] 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.
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CA 02689469 2009-12-30
[0056] In this embodiment of the system, both a fine/coarse solids separator,
and a gravity
separator are employed, consistent with the embodiment of the invention
depicted and described
previously in respect of Figure 2.
[0057] Embodiment Of A System In Which There Is No Fine/Coarse Solids
Separator
Component Upstream Of The Agglomerator.
[0058] 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.
[0059] 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.
[0060] Additional process details are described below which are generally
applicable to
most embodiments listed above, with some exceptions.
[0061] 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.
[0062] An exemplary ratio of solvent to bitumen to be selected as a target
ratio during
agglomeration is less than 2:1. A ratio of 1.5:1 or less, and a ratio of 1:1
or less, for example, a
ratio of 0.75:1, would also be considered acceptable target ratios for
agglomeration. For clarity,
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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.
[0063] 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
solvent together with the bituminous feed, and optionally with additional
additives, the bitumen
entrained within the feed is given an opportunity to become extracted into the
solvent phase prior
to 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 permit flexible
design of the slurry system and simplifies means of feeding materials into the
agglomerator.
[0064] 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.
[0065] 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
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CA 02689469 2009-12-30
feed or the solvent (or solvent/bitumen combination) used to form the initial
slurry may be
incorporated into the process.
[0066] 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
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.
[0067] 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 level of solvent recovery from tailings can be realized with
reduced energy
intensity relative to conventional processes.
[0068] 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.
[0069] 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.
[0070] 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
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CA 02689469 2009-12-30
steam, and further amounts of water can be added when the fine solids stream
is transferred into
the agglomerator.
[0071] 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.
[0072] 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.
[0073] 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%.
[0074] 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.
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CA 02689469 2009-12-30
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
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[0082] 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.
[0083] While 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 designations of first and second.
[0084] 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.
[0085] 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.
[0086] 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. 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.
[0087] 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.
[0088] 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
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CA 02689469 2009-12-30
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.
[0089] 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
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. A mixture of C4-C9 cyclic and/or open chain aliphatic solvents would be
appropriate.
[0090] Exemplary cycloalkanes include cyclohexane, cyclopentane, or a mixture
thereof.
[0091] 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.
[0092] A mixture of C4-C10 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%.
[0093] 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.
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CA 02689469 2009-12-30
[0094] 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 C1o 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.
[0095] 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
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.
[0096] 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.
[0097] 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.
[0098] 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
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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 conduced
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.
[0099] 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 conventional fractionation tower or a distillation unit.
[00100] 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.
[00101] 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.
[00102] 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 in
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
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CA 02689469 2009-12-30
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
[00103] 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.
[00104] 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.
[00105] Solvent recovery and recycle is incorporated into embodiments of the
process. For
example, the first solvent derived 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.
[00106] 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.
[00107] 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.
[00108] 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,
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CA 02689469 2009-12-30
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.
[00109] 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 from gravity separation, and generally includes water and
solids that may have
settled into the underflow in the separation process together with bitumen and
solvent. This
underflow is removed and processed separately. This leaves a high grade
extract as the overflow
of the separation process.
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 5 400 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.
[00110] 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
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CA 02689469 2009-12-30
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.
[00111] 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.
[00112] 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
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.
[00113] 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.
[00114] Figure 1 is a schematic representation of an embodiment of the process
(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
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CA 02689469 2009-12-30
conducted, leaving a high grade bitumen product. Further details of these
process steps are
provided herein.
[00115] Figure 2 outlines an embodiment of the process in which the second
solvent is
mixed with a low solids bitumen extract derived from separation of the
agglomerated slurry in a
clarifier.
[00116] 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
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.
[00117] 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.
[00118] The fine/coarse solids separator (206) may be a settling vessel,
cyclone or screen,
or any suitable separation device known in the art. 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.
[00119] 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
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CA 02689469 2009-12-30
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).
[00120] The second solvent may be one having a low boiling point. The bitumen-
containing
mixture derived 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
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.
[00121] 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).
[00122] 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.
[00123] Advantageously, the process permits 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
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CA 02689469 2009-12-30
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.
[00124] 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.
[00125] 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
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.
[00126] 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.
[00127] Figure 3 is a schematic representation of a further embodiment of the
process (30)
described herein. The combining (31) of a first solvent and a bituminous feed
from oil sand to
form 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.
[00128] Figure 4 illustrates an embodiment of the process 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.
[00129] 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
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CA 02689469 2009-12-30
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.
[00130] 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 (417a) together
with a low solids
bitumen extract 420a), all of which may be combined with the coarse solids
stream (412) and
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.
[00131] 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.
[00132] 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.
[00133] 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.
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CA 02689469 2009-12-30
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.
[00134] 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
achieving a bottom sediment and water (BS&W) content lower than about 0.5 wt%
solid in dry
bitumen.
[00135] 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 (4220 may also be added to the
secondary solid-liquid
separator (432) if needed.
[00136] 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.
[00137] 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.
[00138] 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
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CA 02689469 2009-12-30
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..
[00139] 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.
[00140] 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
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.
[00141] 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.
[00142] Figure 6 illustrates an embodiment of the invention 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.
[00143] 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
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CA 02689469 2009-12-30
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).
[00144] 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).
[00145] 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.
[00146] 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).
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CA 02689469 2009-12-30
[00147] 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).
[00148] 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
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.
[00149] 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.
[00150] 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.
[00151] 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
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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.
[00152] 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
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.
[00153] 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.
[00154] Example 1
[00155] 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.
[00156] Example 2
[00157] 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.
[00158] Example 3
[00159] 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.
[00160] 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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