Note: Descriptions are shown in the official language in which they were submitted.
CA 02724806 2010-12-10
PROCESSES AND SYSTEMS FOR SOLVENT EXTRACTION
OF BITUMEN FROM OIL SANDS
FIELD
[0001] Described herein are processes for hydrocarbon extraction from
mineable deposits,
such as bitumen from oil sands, and systems for implementing such processes.
BACKGROUND
[0002] Methodologies for extracting hydrocarbon from oil sands have
required energy
intensive processing steps to separate solids and water from the products
having commercial
value.
[0003] Previously described methodologies for solvent extraction
spherical agglomeration
(SESA), have not been commercially adopted. For a description of the SESA
process, see
Sparks et al., Fuel 1992(71); 1349-1353. Such processes involved mixing a
slurry of oil sands
material with a hydrocarbon solvent (such as a high boiling point solvent),
adding a bridging liquid
(for example, water), agitating this mixture in a slow and controlled manner
to nucleate particles,
and continuing such agitation so as to permit these nucleated particles to
form larger multi-particle
spherical agglomerates for removal. A bridging liquid is a liquid with
affinity for the solid particles
(i.e. preferentially wets the solid particles) but is immiscible in the
solvent. The process was
conducted at about 50 ¨ 80 C (see also Canadian Patent Application 2,068,895
of Sparks et al.).
The enlarged size of the agglomerates formed permits easy removal of the
solids by
sedimentation, screening or filtration.
[0004] Solvent recovery from the solids produced in previously described
processes would
be difficult, due to the nature of the solvent proposed for use in the
extraction process. The
proposed solvents in previously described processes have a low molecular
weight, high aromatic
content, and low short chain paraffin content. Naphtha was the solvent
proposed for the SESA
process, with a final boiling point ranging between 180-220 C, and a
molecular weight of 100 ¨
215 g/mol. With such high boiling point solvents, the recovery would be energy
intensive as
significant energy is required to vaporize the residual hydrocarbon and to
release hydrocarbon
trapped within the agglomerates.
[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
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tailings suitable for direct mine refill. Organic material was separated from
oil sands by mixing the
oil sands material with an organic solvent to form a slurry, after which an
aqueous bridging liquid
was added in small amounts. By using controlled agitation, solid particles
from oil sands adhere to
each other and were enlarged to form macro-agglomerates of mean diameter
greater than 2 mm
from which the bulk of the bitumen and solvent was excluded. This process
permitted a significant
decrease in water use, as compared with conventional water-based extraction
processes.
Solvents used in the process were of low molecular weight, having aromatic
content, but only
small amounts of short chain paraffins. While this may have resulted in a high
recovery of
bitumen, the energy intensity required for solvent recovery would be too high
to be adopted in a
commercial application.
[0006] U.S. Patent No. 3,984,287 describes an apparatus for separating
organic material
from particulate tar sands, resulting in agglomeration of a particulate
residue. The apparatus
included a tapered rotating drum in which tar sands, water, and an organic
solvent were mixed
together. In this apparatus, water was intended to act as a bridging liquid to
agglomerate the
particulate, while the organic solvent dissolves organic materials. As the
materials combined in
the drum, bitumen was separated from the ore.
[0007] A device to convey agglomerated particulate solids for removal to
achieve the
process of Meadus et al. (U.S. Patent No. 4,057,486) within a single vessel is
described in U.S.
Patent No. 4,406,788.
[0008] A method for separating fine solids from a bitumen solution is
described in U.S.
Patent No. 4,888,108. To remove fine solids, an aqueous solution of polar
organic additive as well
as solvent capable of precipitating asphaltenes was added to the solution, so
as to form
aggregates for removal from the residual liquid. Although the method achieved
low solids content
in the resulting bitumen product with this approach, the solids content in the
bitumen product fell
short of optimal product quality of less than 400 ppm solids on a dry bitumen
basis, especially for
settling times less than 1 hour.
[0009] Others have proposed sequential use of two solvents in different
solvent extraction
schemes. For example U.S. Patent No. 3,131,141 proposed the use of high
boiling point solvent
for oil sands extraction followed by low boiling point/volatile solvent for
enhanced solvent recovery
from tailings in a unique process arrangement. U.S. Patent No. 4,046,668
describes a process of
bitumen recovery from oil sands using a mixture of light naphtha and methanol.
However, it is not
described or suggested that a second solvent could be effectively applied to a
solvent extraction
process with simultaneous solids agglomeration without upsetting the
agglomeration process.
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[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
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
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a
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] A variety of system components are known for use in bitumen
extraction. The
solvent-based extraction system described by Sparks et al. (Fuel 1992; 71:1349-
1353) employs a
direct feed of oil sand into an extraction agglomerator configured as a
rotating tumbler, following
which agglomerated sand is washed in a counter-current washing system using
progressively
cleaner solvent. Solvent is recovered from washed agglomerates using a
rotating dryer.
[0017] The system described in U.S. Patent No. 4,057,486 to Meadus et al.
employs an
agglomerator configured as a rotating conical vessel, into which oil sands and
solvent are added.
This is followed by settling of agglomerates and decantation, or by screening
agglomerates to
separate of the organic phase from the agglomerates. Optional system
components such as a
fluidized bed conversion unit may be used for further processing of
agglomerates, while a
distillation unit or conversion unit may be used to further process the
organic phase.
[0018] In Canadian Patent Application 2,068,895, a system is described
which employs a
rotating drum agglomerator to combine a high fines fraction from oil sands
with solvent. Discharge
of agglomerates through a trommel screen for removing large stones is followed
by feeding
effluent to a filter via a surge hopper. Countercurrent washing through a
filter with progressively
cleaner solvent is followed by drainage of agglomerates. A rotary dryer is
employed for drying
agglomerates and for solvent recovery.
[0019] 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. It is also desirable to
produce a product
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that is capable of meeting or exceeding requirements for downstream processing
or pipeline transport.
[0020] Further, is desirable to provide systems for use in non-aqueous
extraction processes to extract hydrocarbon from oil sands.
SUMMARY
[0021] It is desirable to obviate or mitigate at least one disadvantage
of
previous processes and systems for hydrocarbon extraction from mineable
deposits such as oil sands.
[0022] Solvent extraction processes to recover bitumen from oil sands are
described, employing solvent extraction and sequential agglomeration of fines
to
advantageously simplify subsequent solid-liquid separation. The processes can
produce at least one bitumen product with a quality specification of water and
solids that exceeds downstream processing and pipeline transportation
requirements and contains low levels of solids and water. Further, exemplary
systems for implementing such processes are described.
[0023] The optional use of low boiling point solvents advantageously
permits recovery of solvent with a lower energy requirement than would be
expended for recovery of high boiling point solvents. By conducting solvent
extraction and agglomeration steps independently, shorter residence times in
the
agglomeration unit can be achieved. The sequential nature of the process
allows for flexible design of a slurry feed system which permits high
throughput
from a smaller sized agglomeration unit, as well as faster bitumen production.
[0024] When the optional step of steam pre-conditioning is employed in
the described processes, this has the further advantage that steam not only
heats the slurry or oil sands, but adds the water necessary for the later
agglomeration step.
[0025] Advantageously, the inventive processes permit 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.
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[0026] As a result of exemplary processes described herein, 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. Such processes permit
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 certain exemplary
processes 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 processes described
herein. Further, such a product formed by processes 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 according to
the processes described herein. An exemplary low grade product formed
according to processes described may be one having about 0.5 wt% of water +
solids of the dry bitumen product.
[0027] There is provided 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; separating the initial slurry into a fine solids
stream and a
coarse solids stream; agglomerating the solids from the fine solids stream to
form an agglomerated slurry comprising agglomerates and a low solids bitumen
extract, wherein agglomerating the solids comprises adding an aqueous bridging
liquid to the fine solids stream and providing agitation and wherein
separating the
initial slurry occurs before agglomerating the solids; separating the low
solids
bitumen extract from the agglomerated slurry; mixing a second solvent with the
low solids bitumen extract to form a solvent-bitumen low solids mixture, the
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CA 02724806 2014-04-17
second solvent having a similar or lower boiling point than the first solvent,
wherein the first and second solvent are the same or different from each other
and are each independently an organic solvent or a mixture of organic
solvents;
subjecting the solvent-bitumen low solids mixture to separation to produce a
high
grade bitumen extract and a low grade bitumen extract; and recovering the
first
and second solvent from the high grade bitumen extract, leaving a high grade
bitumen product.
[0028]
[0029]
[0030]
[0031] 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, wherein the first solvent is an
organic
solvent or a mixture of organic solvents; agglomerating solids from the
initial
slurry to form an agglomerated slurry comprising agglomerates and a low solids
bitumen extract, wherein agglomerating the solids comprises adding an aqueous
bridging liquid to the solids and providing agitation, wherein the ratio of
first
solvent to bituminous feed in the initial slurry is selected to avoid
precipitation of
asphaltenes during agglomeration; separating the low solids bitumen extract
from the agglomerated slurry; mixing a second solvent with the low solids
bitumen extract to form a solvent-bitumen low solids mixture, wherein the
second
solvent is a low boiling point alkane or alcohol having a lower boiling point
than
the first solvent, subjecting the solvent-bitumen low solids mixture to
separation
to produce a high grade bitumen extract and a low grade bitumen extract; and
recovering the first and second solvent from the high grade bitumen extract,
leaving a high grade bitumen product.
[0032]
[0033] There is provided herein a system 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
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separating a fine solids stream therefrom; a bridging liquid inlet in
communications with the fine solids stream to permit inflow of an aqueous
bridging liquid into the fine solids stream; an agglomerator for receiving the
fine
solids stream from the fine/coarse solids separator and the aqueous bridging
liquid, 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;
wherein
the first and second solvent are the same or different from each other and are
each independently an organic solvent or a mixture of organic solvents.
[0034] Additionally, there is provided herein a system 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 bridging liquid inlet
to permit
inflow of an aqueous bridging liquid into the initial slurry; an agglomerator
for
receiving the initial slurry and the aqueous bridging liquid, 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; wherein the first
solvent
is an organic solvent or a mixture of organic solvents, and the second solvent
is
a low boiling point alkane or alcohol having a lower boiling point than the
first
solvent.
[0035] The systems described herein may further comprise a secondary
solid-liquid separator for recovering additional bitumen product from the
agglomerates and producing solvent-wet agglomerates, and at least one solvent
recovery unit for recovering the first solvent from the solvent-wet
agglomerates
and other solids rejected from the system.
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[0036] Advantageously, non-aqueous solvent extraction of oil sands,
combined with particle enlargement through agglomeration can result in a
reduction in fresh water withdrawal from nearby rivers or other water sources,
and offers an opportunity for improved tailings management versus currently
practiced water based extraction processes.
[0037]
[0038]
[0039]
[0040] Processes and systems are described herein which may involve
the use of a lighter fraction of a hydrocarbon fluid, for example a diluent
(e.g.
natural gas condensate or naphtha), as a solvent source for solvent extraction
of
bitumen. The hydrocarbon fluid is fractionated into a heavier fraction and a
lighter fraction. The lighter fraction (with a lower boiling point) is used as
the
solvent in the extraction (as described below, more than one solvent may be
used in the extraction). The heavier fraction is recombined with the solvent
diluted bitumen product (following solvent extraction) to satisfy shipping
viscosity,
density and vapour pressure requirements. In addition, this solvent-extracted
dilbit may be further combined with other diluents or dilbit sourced from
nearby
operations (product from water-based bitumen extraction, from an in situ
bitumen
recovery process such as SAGD, or even synthetic crude from nearby
upgraders. Diluent and/or diluted bitumen can be added thereto as required to
meet pipeline specifications.
[0041] Exemplary processes are described herein for extracting bitumen
from a bituminous feed from oil sands. Such processes may comprise
fractionating a hydrocarbon fluid into a lighter fraction and a heavier
fraction;
effecting solvent extraction of the bituminous feed with the lighter fraction
as the
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CA 02724806 2013-06-06
solvent to produce solvent diluted bitumen; and combining the heavier fraction
with solvent diluted bitumen to form a high grade bitumen product.
[0042] Advantageously, in some embodiments an existing diluent pipeline
accessing an existing site for use in water based extraction processes can be
accessed for the diluent. In such an embodiment, transportation costs can be
minimized, existing storage facilities may be utilized, and other efficiencies
can
be realized by integration of a solvent extraction process with a proximal
water
based extraction process.
[0043] The solvent extraction may be, but is not limited to, one described
below or one described in the background section.
[0044] Other aspects and features will become apparent to those
ordinarily skilled in the art upon review of the following description of
specific
embodiments in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Embodiments will now be described, by way of example only, with
reference to the attached Figures.
[0046] Figure 1 is a schematic representation of an embodiment of the
process.
[0047] Figure 2 illustrates an exemplary embodiment of the process
consistent with the representation shown in Figure 1.
[0048] Figure 3 is a schematic representation of an embodiment of the
process.
[0049] Figure 4 illustrates an exemplary embodiment of the process
consistent with the representation shown in Figure 3.
[0050] Figure 5 is a schematic representation of an embodiment of the
process.
[0051] Figure 6 illustrates an exemplary embodiment of the process
consistent with the representation shown in Figure 5.
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CA 02724806 2010-12-10
[0052] Figure 7 provides a schematic representation of an embodiment of
the system
described herein.
[0053] Figure 8 illustrates an exemplary system within the scope of the
present
disclosure.
[0054] Figure 9 illustrates an exemplary ore preparation and slurry
system design for
systems described herein.
[0055] Figure 10 illustrates an agglomerator for use with exemplary
systems described
herein.
[0056] Figure 11 illustrates an optional cone settler for agglomerates
for systems
described herein.
[0057] Figure 12 illustrates a filtration unit for embodiments of systems
described herein.
[0058] Figure 13 illustrates an exemplary tailings solvent recovery unit
for use with
systems described herein.
[0059] Figure 14 illustrates a first embodiment of a system described
herein.
[0060] Figure 15 illustrates a second embodiment of a system described
herein.
[0061] Figure 16 is schematic representation of a process within the
scope of the present
disclosure.
[0062] Figure 17 illustrates an exemplary embodiment of a process
consistent with the
representation shown in Figure 16.
[0063] Figure 18 is a graph showing Thermo Gravimetric analysis (TGA)
results of a
sample described herein, in particular change in weight over time.
[0064] Figure 19 is a graph showing Thermo Gravimetric analysis (TGA)
results of a
sample described herein, in particular change in weight between 10 C and 600
C.
[0065] Figure 20 is a graph showing drying rate curve of cyclohexane
agglomerates
based on Thermo Gravimetric analysis (TGA) results of a sample described
herein.
[0066] Figure 21 is a graph showing drying rate over a temperature range
based on
Thermo Gravimetric analysis (TGA) results of a sample described herein.
[0067] Figure 22 is a graph showing moisture content of water and solvent
in
agglomerates as a function of time based on Thermo Gravimetric analysis (TGA)
results of a
sample described herein, over a 10 minute period.
DETAILED DESCRIPTION
[0068] The description below is divided into three parts. PART 1
describes processes and
systems for recovery of bitumen from oil sands, PART 2 describes systems for
solvent extraction
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of bitumen from oil sands, and PART 3 describes processes for solvent
extracting bitumen
involving fractionating a diluent.
[0069] PART 1
[0070] Processes and Systems for Recovery of Bitumen from Oil Sands.
[0071] Generally, there is provided herein a process and system for fines
capture or
agglomeration and solvent extraction of bitumen from oil sands. Processing oil
sands according to
the processes described herein may permit high throughput and improved product
quality and
value.
[0072] A process and system for recovery of bitumen from oil sands is
provided herein.
[0073] The term "bituminous feed" from oil sands refers to a stream
derived from oil sands
that requires downstream processing in order to realize valuable bitumen
products or fractions.
The bituminous feed from oil sands is one that comprises bitumen along with
other undesirable
components, which are removed in the process described herein. Such a
bituminous feed may be
derived directly from oil sands, and may be, for example, raw oil sands ore.
Further, the
bituminous feed may be a feed that has already realized some initial
processing but nevertheless
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 comprises bitumen that would otherwise not have been
recovered, may be used
as a bituminous feed. Such a bituminous feed may be also derived directly from
oil shale, oil
bearing diatomite or oil saturated sandstones.
[0074] As used herein, the term "agglomerate" refers to conditions that
produce a
cluster, aggregate, collection or mass, such as nucleation, coalescence,
layering, sticking,
clumping, fusing and sintering, as examples.
[0075] 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 a bituminous feed, to form an initial slurry and to
dissolve bitumen. This initial
slurry goes on to agglomeration. After the agglomerated slurry is formed
within the agglomerator,
a 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
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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.
[0076] Embodiment In Which Second Solvent Added Prior To Separating Low
Solids
Bitumen Extract From Agglomerated Slurry. An additional process for recovery
of bitumen
from oil sands is provided in which the second solvent is added prior to
separating low solids
bitumen extract and agglomerates from the agglomerated slurry. This embodiment
involves
combining a first solvent and a bituminous feed from oil sands to form an
initial slurry, and
subsequently separating the initial slurry into a fine solids stream and a
coarse solids stream.
Solids from the fine solids stream are agglomerated to form an agglomerated
slurry comprising
agglomerates and a low solids bitumen extract. A second solvent is then mixed
with the
agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the
second solvent
having a similar or lower boiling point than the first solvent. The mixture is
then subjected to
separation to produce a high 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.
[0077] 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.
[0078] 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
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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.
[0079] 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.
[0080] Embodiment In Which Coarse Solids Are Processed Separately From
Agglomeration Of Fine Solids Stream, And The Second Solvent Is Mixed With The
Agglomerated Slurry. A further embodiment comprises a process for recovery of
a bitumen
product from oil sands comprising: combining a first solvent and a bituminous
feed from oil sands
to form an initial slurry; separating the initial slurry into a fine solids
stream and a coarse solids
stream; recovering the first solvent from the coarse solids stream;
agglomerating solids from the
fine solids stream to form an agglomerated slurry comprising agglomerates and
a low solids
bitumen extract; mixing a second solvent with the agglomerated slurry to form
a solvent-bitumen
agglomerated slurry mixture, the second solvent having a similar or lower
boiling point than the
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.
[0081] 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.
[0082] 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
-14-
CA 02724806 2010-12-10
'
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.
[0083] 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.
[0084] Embodiment In Which Initial Slurry Is directed To Agglomeration
Without
Separation Of Coarse Solids, And In Which Second Solvent Is Introduced Prior
To Removal
Of Agglomerates. A further embodiment of the process is described herein for
recovery of a
bitumen product from oil sands. The embodiment comprises combining a first
solvent and a
bituminous feed from oil sands to form an initial slurry. Solids from the
initial slurry are
agglomerated to form an agglomerated slurry comprising agglomerates and a low
solids bitumen
extract. A second solvent is then mixed with the agglomerated slurry to form a
solvent-bitumen
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.
[0085] 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.
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CA 02724806 2010-12-10
=
[0086] Embodiment Of A System In Which A Fine/Coarse Solids Separator
And A
Gravity Separator Are Employed.
[0087] 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.
[0088] In this embodiment of the system, both a fine/coarse solids
separator, and a gravity
separator are employed, consistent with the embodiment depicted and described
previously in
respect of Figure 2.
[0089] Embodiment Of A System In Which There Is No Fine/Coarse Solids
Separator
Component Upstream Of The Agglomerator.
[0090] 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.
[0091] 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.
[0092] Additional process details are described below which are
generally applicable to
most embodiments listed above, with some exceptions.
[0093] 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,
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CA 02724806 2010-12-10
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 is assessed for an optimal
ratio of solvent to
bitumen during agglomeration, the precipitation of asphaltenes can be
minimized or avoided
beyond an unavoidable amount. Another advantage of selecting an optimal
solvent to bitumen
ratio is that when the ratio of solvent to bitumen is too high, costs of the
process may be increased
due to increased solvent requirements.
[0094] An exemplary ratio of solvent to bitumen to be selected as a target
ratio during
agglomeration is less than 2:1. A ratio of 1.5:1 or less, and a ratio of 1:1
or less, for example, a
ratio of 0.75:1, would also be considered acceptable target ratios for
agglomeration. For clarity,
ratios may be expressed herein using a colon between two values, such as
"2:1", or may equally
be expressed as a single number, such as "2", which carries the assumption
that the denominator
of the ratio is 1 and is expressed on a weight to weight basis.
[0095] Slurty System. The slurry system in which the slurry is prepared in
the system
may optionally be a mix box, a pump, 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.
[0096] 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.
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CA 02724806 2010-12-10
[0097] 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. Other methods of heating the
bituminous feed or the
solvent (or solvent/bitumen combination) used to form the initial slurry may
be incorporated into
the process.
[0098] 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.
[0099] 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.
[00100] 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
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CA 02724806 2010-12-10
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.
[00101] 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.
[00102] The steam pre-conditioning need not occur, as it is optional. Some
water may be
added at the agglomeration step if it is not added through steam pre-
conditioning. In instances
where steam pre-conditioning is used, optimally about half of the water
requirement is added as
steam, and further amounts of water can be added when the fine solids stream
is transferred into
the agglomerator.
[00103] 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.
[00104] 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.
[00105] 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
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CA 02724806 2010-12-10
=
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%.
[00106] 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.
[00107] 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.
[00108] 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.
[00109] 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.
[00110] 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.
[00111] 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.
[00112] 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.
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CA 02724806 2010-12-10
[00113] 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.
[00114] 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.
[00115] 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.
[00116] 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.
[00117] 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.
[00118] 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
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CA 02724806 2010-12-10
emulsification of the two solvents. Exemplary additives include methanoic
acid, ethylcellulose and
polyoxyalkylate block polymers.
[00119] 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.
[00120] When it is said that the first solvent and the second solvent may
have "similar"
boiling points, it is meant that the boiling points can be the same, but need
not be identical. For
example, similar boiling points may be ones within a few degrees of each
other, such as, within 5
degrees of each other would be considered as similar boiling points. The first
solvent and the
second solvent may be the same according to certain embodiments, in which
case, having
"similar" boiling points permits the solvents used to have the same boiling
point.
[00121] First Solvent. The first solvent selected according to certain
embodiments 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.
[00122] Exemplary cycloalkanes include cyclohexane, cyclopentane, or a
mixture thereof.
[00123] 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.
[00124] 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%.
[00125] 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,
- 22 -
CA 02724806 2010-12-10
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.
[00126] The second solvent may comprise a single solvent or a solvent
system that
includes a mixture of appropriate solvents. The second solvent may be a low
boiling point, volatile,
polar solvent, which may or may not include an alcohol or an aqueous
component. The second
solvent can be C2 to C10 aliphatic hydrocarbon solvents, ketones, ionic
liquids or biodegradable
solvents such as biodiesel. The boiling point of the second solvent from the
aforementioned class
of solvents is preferably less than 100 C.
[00127] 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.
[00128] 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.
- 23 -
CA 02724806 2010-12-10
[00129] 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.
[00130] Secondary Stage of Solid-Liquid Separation to wash Agglomerates. As
a
component of the solid-liquid separator, a secondary stage of separation may
be introduced for
countercurrently washing the agglomerates separated from the agglomerated
slurry. The initial
separation of agglomerates may be said to occur in a primary solid-liquid
separator, while the
secondary stage may occur within the primary unit, or may be 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.
[00131] A secondary solid-liquid separator for countercurrently washing
agglomerates may
be included in the system or may be included as a component of a system
described herein. The
secondary solid-liquid separator may be separate or incorporated within the
primary solid-liquid
separator. The secondary solid-liquid separator may optionally be a gravity
separator, a cyclone, a
screen or belt filter. Further, a Secondary solvent recovery unit for
recovering solvent arising from
the solid-liquid separator can be included. The secondary solvent recovery
unit may be
conventional fractionation tower or a distillation unit.
[00132] 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.
[00133] 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.
[00134] Recycle and Recovery of Solvent. The process involves removal and
recovery of
solvent used in the process.
- 24 -
CA 02724806 2010-12-10
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
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
[00135] 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.
[00136] 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.
[00137] 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.
[00138] 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.
[00139] 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
- 25 -
CA 02724806 2010-12-10
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.
[00140] The first solvent recovered in the process may comprise entrained
bitumen therein,
and can thus be re-used for combining with the bituminous feed; or for
including with the fine
solids stream during agglomeration. Other optional steps of the process may
incorporate the
solvent having bitumen entrained therein, for example in countercurrent
washing of agglomerates,
or for adjusting the solvent and bitumen content within the initial slurry to
achieve the selected
ratio within the agglomerator that avoids precipitation of asphaltenes.
[00141] 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, 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 described herein, may have a low water
content that is
nearly undetectable, such as a content of 5 200 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 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.
[00142] Extraction Step is Separate from Agglomeration Step. Solvent
extraction may
be conducted separately from agglomeration in certain embodiments of the
process. Unlike prior
- 26 -
CA 02724806 2010-12-10
art processes, where the solvent is first exposed to the bituminous feed
within the agglomerator,
emobidments described herein include formation of an initial slurry in which
bitumen dissolution
into a solvent occurs prior to the agglomeration step. This has the effect of
reducing residence
time in the agglomerator, when compared to previously proposed processes which
require
extraction of bitumen and agglomeration to occur simultaneously. The instant
process is
tantamount to agglomeration of pre-blended slurry in which extraction via
bitumen dissolution is
substantially or completely achieved separately. Performing extraction
upstream of the
agglomerator permits the use of enhanced material handling schemes whereby
flow/mixing
systems such as pumps, mix boxes or other types of conditioning systems can be
employed.
[00143] 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.
[00144] 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.
[00145] When dilution of agglomerator discharge is employed in this
embodiment, the
solvent to bitumen ratio of the agglomerator feed slurry is set to obtain from
about 10 to about 90
wt% bitumen in the discharge, and a workable viscosity at a given temperature.
In certain cases,
these viscosities may not be optimal for the solid-liquid separation (or
settling) step. In such an
instance, a dilution solvent of equal or lower viscosity may be added to
enhance the separation of
the agglomerated solids in the clarifier, while improving the quality of the
clarifier overflow by
reducing viscosity to permit more solids to settle. Thus, dilution of
agglomerator discharge may
involve adding either the first or second solvent, or a separate dilution
solvent, which may, for
example, comprise an alkane.
[00146] 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
- 27 -
CA 02724806 2010-12-10
agglomerated slurry comprising agglomerates and low solids bitumen extract,
optionally
subsequently adding coarse solids stream to agglomerated slurry. Subsequently,
separation (15)
of low solids bitumen extract from agglomerated slurry occurs. Further, mixing
(16) of a second
solvent with low solids bitumen extract to extract bitumen takes place,
forming a solvent-bitumen
low solids mixture. Separation (18) of low grade bitumen extract and high
grade bitumen extracts
from the mixture occurs. Further, recovery (19) of solvent from the high grade
extract is
conducted, leaving a high grade bitumen product. Further details of these
process steps are
provided herein.
[00147] 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.
[00148] 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,
a pump or a 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.
[00149] 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.
[00150] 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
- 28 -
CA 02724806 2010-12-10
be a deep cone settler, or other device, such as thickeners, incline plate
(lamella) settlers, and
other clarification devices known in the art.
[00151] The low solids bitumen extract (220) is separated from the
agglomerated slurry
within the primary solid-liquid separator (218). This extract (220) is
subsequently combined in a
mixer (221) with a second solvent (222a). Extract (220) may optionally be sent
to a solvent
recovery unit, not shown, where the first solvent is recovered from the
extract, before the mixing
with the second solvent (222a) is undertaken within the mixer (221).
[00152] 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.
[00153] 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).
[00154] 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
- 29 -
CA 02724806 2010-12-10
recycling solvent, and maintaining an appropriate solvent:bitumen ratio within
the agglomerator to
avoid precipitation of asphaltenes.
[00155] 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
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.
[00156] For the second solvent, a low boiling point n- or iso-alkane and
alcohols or blends
are candidates. Surface modifiers may be added to the alcohol if needed. With
the alkanes,
solvent deasphalting is achieved with concurrent cleaning of the high grade
bitumen product (226)
to achieve pipeline quality. Therefore, the low grade bitumen extract (230) is
comprised
predominantly of asphaltenes or other more polar bitumen fractions.
[00157] 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.
[00158] 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.
[00159] 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.
- 30 -
CA 02724806 2010-12-10
'
,
[00160] 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.
[00161] In this embodiment, a bituminous feed (402) is provided and is
combined with a first
solvent (409a), which may have bitumen (403a) entrained therein, into slurry
system (404) to form
an initial slurry (405), optionally in the presence of steam (407) to heat the
initial slurry (405). The
initial slurry (405) is mixed and the first solvent (409a) is given time to
contact the bituminous feed
so as to extract bitumen. The slurry (405) is then directed to a separator
(406) to form a fine
solids stream (408) which is directed into an agglomerator (410). Further
arising from the
separator (406) is a coarse solids stream (412) for later processing and solid-
liquid separation.
[00162] 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.
[00163] 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.
[00164] 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
- 31 -
CA 02724806 2012-12-13
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.
[00165] The recovered first solvent (409d) arising from the primary
solvent recovery unit
(428) may be recycled for use in the process, for example when combined with
the bituminous
feed (402) in the separator (406). This recovered solvent may contain bitumen
entrained therein.
Quantities of a combination comprising recycled first solvent (409d) plus any
entrained bitumen
arising from the primary solid-liquid separator (418) or solvent recovery unit
(428) may be directed
to the agglomerator (410) for further processing. The second solvent (422b)
recovered from the
primary solvent recovery unit (428) may be also be recycled.
[00166] 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 (422g) 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.
[00167] Solvent recovered may be held in a first solvent storage (429) in
the case of the
first solvent (409d), or in a second solvent storage (445), in the case of the
second solvent (422b)
for later use in the upstream aspects of the process. High grade bitumen(431)
may be added to
the first solvent derived from first solvent storage (429), if there is a need
to alter the solvent to
bitumen ratio prior to adding a combination of solvent (409a) and bitumen
(403a) to the slurry
system (404). Further, additional first solvent (409e) make-up quantities or
second solvent (422e)
make-up quantities may be included in respective solvent storage, if the
solvent volume requires
replenishing. Additional second solvent (422f) may also be added to the
secondary solid-liquid
separator (432) if needed.
[00168] 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.
[00169] 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.
- 32 -
CA 02724806 2010-12-10
[00170] The second solvent may be a polar solvent, such as an alcohol, a
solvent with an
aqueous component, or another solvent which is immiscible in the first solvent
or which could be
rendered immiscible in the first solvent. A low boiling point n- or iso-alkane
and alcohols or blends
of these with or without an aqueous component are candidates. Surface
modifiers may be added
to the alcohol if needed. Good agglomerate strength is achieved if the
agglomerates are modified
with hydrating agents, such as a cement, a geopolymer, fly ash, gypsum or lime
during
agglomeration. Optionally, the second solvent may comprise a wetting agent in
an aqueous
solution. A further option is to employ controlled precipitation of
asphaltenes within either the
agglomerator (410) or the primary solid-liquid separator (418) by employing a
mixture of solvent
and bitumen in a ratio that avoids precipitation of asphaltenes. For example,
a ratio of solvent to
bitumen of 2:1 or less may be used within the agglomerator to control
asphaltene precipitation..
[00171] 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.
[00172] 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.
[00173] 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.
- 33 -
CA 02724806 2010-12-10
[00174] Figure 6 illustrates an embodiment similar to that depicted in
Figure 2, except that
coarse solids stream separated out of the bituminous feed is processed
separately, and not re-
combined with an agglomerated slurry.
[00175] A bituminous feed (602) is provided and combined with a first
solvent (609a),
optionally with bitumen (603a) entrained therein, in a slurry system (604) to
form an initial slurry
(605). Steam (607) may be added to the slurry system (604) to heat the initial
slurry (605). The
initial slurry (605) is then directed from the slurry system (604) to a
separator (606) for separation,
which may be a fine/coarse solids separator, in order to form a fine solids
stream (608), which is
directed into an agglomerator (610), as well as a coarse solids stream (612),
which is processed
separately from the agglomerated slurry (616) arising from the agglomerator
(610). Additional
quantities of first solvent (609b) having bitumen (603b) entrained therein,
may be added to the
agglomerator (610). A bridging liquid (614), such as water, may be added to
the agglomerator
(610), and the process of agglomeration of the solids contained within the
fine solids stream (608)
occurs by agitation within the agglomerator (610). The agglomerated slurry
(616) arising from the
agglomerator comprises agglomerates (617a) together with a low solids bitumen
extract (620a).
In this example, there is no combination with the coarse solids stream.
Instead, the agglomerated
slurry (616) itself is directed to the primary solid-liquid separator (618).
[00176] 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).
[00177] 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.
[00178] 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-
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CA 02724806 2010-12-10
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).
[00179] 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).
[00180] 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.
[00181] For the second solvent, a low boiling point n- or Ýso-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.
[00182] 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.
[00183] 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
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CA 02724806 2010-12-10
rate determining step in solvent recovery from tailings is the time required
for release of residual
solvent from the pores of the agglomerated solids. With segregation, the
solvent recovery from the
fine particles can be optimized independent of the coarse particles. The
combination of first
solvent (609f) and bitumen (609f) recovered permits separation of coarse
tailings (656), once
drained from the secondary solid liquid separator for coarse solids (652).
Coarse tailings (656)
isolated from the tailings solvent recovery unit for coarse solids (654) can
be sent to the primary
solid-liquid separator (618) for residual fine solids removal, or may be
recycled upstream of the
process to form the initial slurry (605) in slurry system (604). The tailings
solvent recovery unit for
coarse solids (654) may be used to recover recyclable water (638) or solvent
from the secondary
solid-liquid separator for coarse solids (652). Coarse tailings (656) may also
be removed.
[00184] Figure 7 is a schematic representation of a system (70) according
to an
embodiment. 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.
[00185] PART 2
[00186] Systems for Solvent Extraction of Bitumen from Oil Sands.
[00187] Generally, described herein are systems for use in fines capture
or agglomeration
and solvent extraction of bitumen from oil sands. Processing oil sands within
systems according
to those described herein permits high throughput and improved product quality
and value.
[00188] Using non-aqueous process for extraction of bitumen from oil sands
with sequential
agglomeration of fines contained therein requires specialized systems and
equipment. Systems
developed specifically for non-aqueous extraction will serve to simplify solid-
liquid separation and
produce bitumen with a quality specification of water content and low solids
that exceeds
downstream processing and pipeline transportation requirements.
[00189] Described herein are various systems that can be used in non-
aqueous processes
for bitumen extraction. Systems are provided for processing crushed oil sand,
which may include,
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CA 02724806 2010-12-10
but are not limited to the following components: a ore preparation plant; a
slurry system; an
agglomerator which may include a discharge screening system; a primary solid-
liquid separator; a
secondary solid-liquid separator; a tailings solvent recovery unit; a rejects
solvent recovery unit; a
bitumen extract solvent recovery unit; a vent recovery system; supporting
utilities and off site
utilities; and/or an optional product cleaning plant.
[00190] A system is described herein for recovery of bitumen from oil
sands. Such a
system may comprise a slurry system in which a bituminous feed is mixed with
solvent to form an
initial slurry; an agglomerator for mixing the initial slurry and a water-
containing fluid to
agglomerate the solids from the initial slurry, producing an agglomerated
slurry; a separator unit
for separating the agglomerated slurry into agglomerates and a low solids
bitumen extract, said
separator unit comprising a countercurrent washer for solvent washing of
agglomerates with
progressively cleaner solvent; a tailings solvent recovery unit for removing
solvent from washed
agglomerates; and a solvent recovery unit for separating solvent from the low
solids bitumen
extract.
[00191] The separator unit may comprise a belt filter or a multi-stage
counterflow cyclone
for solvent washing agglomerates using progressively cleaner solvent. Further,
the separator unit
may include a gravity separator, cyclone, or screen, separating a low solids
extract from the
agglomerated slurry prior to solvent washing agglomerates. In certain
embodiments, the
separator unit may have a primary solid-liquid separator for receiving and
separating the
agglomerated slurry, as well as a secondary solid-liquid separator for
receiving underflow from the
primary solid-liquid separator. In some instances, the primary solid-liquid
separator acts as a
surge bin to smooth operating fluctuations in the composition of the
agglomerated slurry for the
secondary solid-liquid separator. The primary solid-liquid separator may be a
deep cone settler, in
which case the secondary solid-liquid separator may involve a filtration unit
for receiving underflow
from the deep cone settler for solvent washing of agglomerates.
[00192] The filtration unit, when present, may involve a belt filter for
countercurrent washing
of agglomerates.
[00193] The system may include a rejects dryer for recovering solvent from
oversized
rejects of the initial slurry.
[00194] The solvent recovery unit for separating solvent from the low
solids bitumen extract
may comprise a distillation unit, according to certain exemplary embodiments.
[00195] An optional steam source for pre-conditioning feed entering the
slurry system may
be incorporated into the system described herein.
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CA 02724806 2010-12-10
[00196] Optionally, the slurry system may be a mixing unit in which the
mixing of the initial
slurry is effected. In such instances, the mixing unit could comprise for
example: a mix box, a
pump, or a combination thereof. The slurry may thus be permitted to flow by
gravity from the
mixing unit into the agglomerator.
[00197] The slurry system can optionally be maintained in a low oxygen
environment. The
low oxygen environment may comprises a gas blanket formed from a gas that is
not reactive
under process conditions. The gas may comprise nitrogen, methane, carbon
dioxide, argon,
steam, or a combination thereof.
[00198] The agglomerator may compriss one or more rotating drums in which
the initial
slurry is subjected to agitation, or one or more tanks through which the
initial slurry is pumped.
The agglomerator may have an inlet thereon for receiving the water-containing
fluid to promote
agglomeration of fines therein.
[00199] A further system for recovery of bitumen from oil sands is
described herein, the
components of which are outlined below. The system may include a mix box in
which a
bituminous feed is mixed with solvent to form an initial slurry; an
agglomerator for mixing the initial
slurry with a water-containing fluid to agglomerate the solids from the
initial slurry, producing an
agglomerated slurry; a screen to separate oversized rejects; a rejects dryer
for receiving rejects
and recovering solvent therefrom; a separator unit comprising a deep cone
settler for separating
agglomerates and a low solids bitumen extract from the agglomerated slurry,
and a belt filter for
receiving agglomerates from deep cone settler underflow and for solvent
washing of agglomerates
using countercurrent washing with progressively cleaner solvent; a tailings
solvent recovery unit
for recovering solvent from washed agglomerates; and a solvent recovery unit
for separating
solvent from the low solids bitumen extract.
[00200] Such an exemplary system may additionally comprise a filtration
unit for washing
oversized rejects to recover bitumen. An inlet may be included on the
agglomerator for receiving
water-containing fluids to promote the agglomeration of fines therein.
[00201] A further exemplary system for recovery of bitumen from oil sands
is described
herein which includes a slurry system in which a bituminous feed is mixed with
solvent and
optionally a water-containing fluid to form an initial slurry; one or more
retention tank for receiving
and agitating the initial slurry to agglomerate solids from the initial slurry
to produce an
agglomerated slurry; a separator unit for separating agglomerates and a low
solids bitumen
extract from the agglomerated slurry, said separator unit comprising a deep
cone settler for
separating a low solids bitumen extract, and a belt filter receiving
agglomerates as underflow from
the deep cone settler for solvent washing of agglomerates using countercurrent
washing with
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CA 02724806 2010-12-10
progressively cleaner solvent; a tailings solvent recovery unit for removing
solvent from washed
agglomerates; and a solvent recovery unit for separating solvent from the low
solids bitumen
extract. In certain embodiments, agitating the initial slurry in the retention
tank occurs without
rotating the tank. Such a system may additionally comprise a conduit from the
retention tank to
the slurry system, for recirculating a portion of the agglomerated slurry. A
pump may be included,
for directing the portion of the agglomerated slurry from the retention tank
back to the slurry
system for recirculation. The exemplary system may additionally comprise an
inlet in the retention
tank for including a water-containing stream to promote agglomeration of fines
therein.
[00202] An exemplary system within the scope of the present disclosure,
includes an ore
preparation plant, a slurry system, an agglomerator, optionally a gravity
separator, a filtration unit,
a tailings solvent recovery unit, and an optional bitumen extract solvent
recovery unit. Each
component is described individually herein, followed by exemplary system
embodiments.
[00203] Ore Preparation Plant (OPP). In an overall system, mine haul trucks
deliver oil
sands ore to a receiving hopper or dump pocket installed in the OPP area. The
raw ore is then
moved through a series of conveyors and crushers to eventually provide
material of a maximum
particle size to the slurry system. An exemplary crusher is a double roll
crusher. Crushed ore is
delivered to the slurry system via a surge bin which may be proximal to the
location of the slurry
system.
[00204] Slurry System. The slurry system receives crushed ore from the
surge bin, and
promotes mixing of the crushed ore with a non-aqueous solvent so as to form a
slurry. Water may
be added to the slurry system so as to achieve the appropriate water content
for the
agglomeration stage. The slurry system has a feed section which may comprise a
hopper to
receive crushed ore from the surge bin and conveyors to move the ore to a
subsequent mixing
unit. A low oxygen environment may be achieved in the feed section through use
of a purge gas,
such as natural gas, in the interests of excluding oxygen and avoiding
explosive potential.
Because a flowable slurry is formed within the mixing unit, the slurry may be
pumped or otherwise
conveyed in a flowable manner into the agglomerator. Thus, the slurry does not
need to be further
crushed or screw-fed into the subsequent agglomeration stage. Exemplary mixing
units include a
mix box, cyclofeeder, tumbler, rotary breaker, a stirred tank or other devices
in which the mixing of
solvent slurry can be effected. The mixing unit can be configured to feed the
resulting slurry to one
or more agglomerators using a pump or by gravity. Gravity may be used to
deliver the slurry to
the agglomerator(s) in any appropriate manner, such as via chutes with flow
diverter gates. In an
embodiment described herein, flow to the agglomerator is directed only by
gravity, reducing the
energy input required to pump flowable fluids.
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CA 02724806 2010-12-10
[00205] Coarse solids or rejects, for example oversized solids which are
not further broken
down prior to entry within the slurry system, can enter the slurry system but
can be separated and
sent directly to filtration or solvent recovery instead of being forwarded on
to the agglomeration
stage. In this way, agglomeration can be optimized for appropriately sized
fines and solids. The
residence time in the mixing unit may be fixed such that complete or
substantial bitumen
dissolution occurs before the slurry is delivered to the agglomerator.
[00206] Agglomerator. Agglomeration of fines derived from the initial
slurry occurs within
an agglomerator. The initial slurry comprises bituminous components together
with solids, fines
and water. These components, together with the solvent, are subjected to
agglomeration within
the agglomerator by imparting agitation within the agglomerator. Agitation is
imparted through
such motion as tumbling, rotation, or directed flow. Within an agglomerator,
purge gas may again
be used so as to maintain a low oxygen environment within. An agglomerator may
comprise a
plurality of vessels, such as tanks or rotating drums, set up in parallel or
in series. The use of
vessels in parallel can advantageously be configured to any appropriate volume
required at a
given location. An exemplary amount of oil sand to be processed may be for
example 5000
tonnes per hour per agglomerator vessel. Thus, in a system where two
agglomerator vessels are
configured in parallel, approximately 10,000 tonnes per hour can be processed.
[00207] The agglomerator may include a discharge screening system. After
agglomeration,
streams may be screened to separate agglomerates from solvent, and
agglomerates are
processed further for bitumen recovery, while solvent with bitumen entrained
therein is further
processed through solvent recovery steps.
[00208] Agglomeration may occur in a drum-style unit, or may occur in a
shaker or within
any alternative vessel into which agitation can be introduced The agglomerator
may have an
integral trommel screen at the discharge which rotates with the agglomerator.
The screen
separates oversized reject materials, for example, solids greater than an
average particle size of
about 50mm as well as petrified wood, twigs or other material that can
potentially upset
downstream processing.
[00209] Optional Primary Solid-Liquid Separator. Following agglomeration,
agglomerates may optionally be subjected to settling for primary separation of
solids from liquid
using a gravity separator, for example by using deep cone settling. Purge gas
may be used to
maintain a low oxygen environment. Overflow from such a settler can be further
cleaned and the
solvent removed. Underflow, including agglomerates, which settle out can be
sent on to further
cleaning through washing steps which may involve, for example, belt filtration
and/or counter
current washing with progressively cleaner solvent (with less and less bitumen
entrained within the
- 40 -
CA 02724806 2010-12-10
solvent) so as to recover bitumen from agglomerates. Other exemplary gravity
separators include
a spiral classifier and a rake classifier.
[00210] The primary solid-liquid separator may act to reduce the load on
the secondary
solid-liquid separator. It may also act as a surge bin between the
agglomerator and secondary
solid-liquid separator so as to smooth out any operating fluctuations in the
output of the
agglomerator and thus improving the operation of the secondary solid-liquid
separator.
Furthermore, in the embodiment where a filtration unit is used as the
secondary solid-liquid
separator, the primary solid-liquid separator may provide a more suitable feed
to said secondary
solid-liquid separator by increasing the solids concentration of the
agglomerated slurry.
[00211] Filtration Unit. Following agglomeration, either directly or
indirectly after a settling
step in a primary solid-liquid separator, agglomerates can be drained and
washed in a low oxygen,
gas-tight filtration unit, such as a vacuum belt or pan filter. Agglomerates
are conveyed on one or
more belt filters and washed in a counter-current manner with progressively
cleaner solvent. For
example, four separate washing stages with progressively cleaner solvent may
be employed as
agglomerates progress along the belt. The final filter cake, which should be
relatively free of
bitumen may go on to further solvent removal steps before discarding as
agglomerates with a low
water content, and a residual hydrocarbon content that meets or exceeds
environmental
requirements.
[00212] In counter-current washing, solvent having bitumen entrained
therein for the earlier
stages washing can be obtained from later stages of the system. The drained
solvent from the
later stages of the counter-current washing, having entrained more bitumen
therein from the
washing step, can thus be used in earlier stages of the counter current
washing. This action
allows for washing stages to occur with progressively cleaner solvent, which
results in a more
efficient use of solvent..
[00213] Tailings Solvent Recovery Unit (TSRU). Following filtration,
solvent still
remaining in filter cake and from the rejects (separated before or after
agglomeration) can be
recovered within a tailings solvent recovery unit. By imposing a slight
vacuum, or using a gas flow
current to remove solvent vapor, the remaining amount of solvent in the solids
is encouraged to
evaporate. A purge gas may be used to create a low oxygen environment, and a
flow of vent gas
can serve the dual purpose of carrying solvent vapor away for recovery.
Exemplary TSRU include
a rotary drum dryer, a tray dryer, or a fluidized bed dryer, employing
external heating and/or
internal steam stripping. The tailings solvent recovery unit may employ
separate equipment
components. A "rejects solvent recovery unit", may be located upstream of the
agglomerator, and
is dedicated to solvent recovery from rejects and another equipment downstream
of agglomeration
- 41 -
CA 02724806 2010-12-10
and filtration which is dedicated to recovery of solvent from washed
agglomerates. In this way,
more than one TSRU may be present at different stages or locations of the
system. Following
passage through the TSRU, dried tailings derived either from rejects or from
the filter cakes, which
are adequately dried for discharge, may be forwarded to discharge conveyors
for disposal. Further
drying steps can be employed if additional water or solvent removal is
desired. Once drying is
complete, dry tailings can be sent to disposal.
[00214] Exemplary System Embodiments
[00215] In a first embodiment of a system for implementing the non-aqueous
extraction
process, a feed derived from oil sands comprising bitumen is slurrified in a
slurry system with
recycle solvent with some bitumen in it. Any water required for agglomeration
may be added in
the slurry system, and can be included as steam, or may be included in one of
the feed
components. The resulting slurry is transported to an agglomerator where
particle enlargement
through agglomeration occurs. By subjecting the slurry to mild agitation in
the presence of water in
the agglomerator, fines particles present in the slurry aggregate and form
agglomerates. Upon
discharge into a gravity separator, the agglomerates settle to the bottom of
the vessel to produce
the separator underflow. The diluted bitumen supernatant is collected as an
overflow from the
gravity separator and passes through a secondary clean-up stage, or may be
transferred directly
into a solvent recovery unit (SRU) where the non-aqueous solvent is recovered.
[00216] In this embodiment, the discharge slurry (or underflow) from the
gravity separator is
fed into a vacuum filtration unit and is washed counter-currently with
progressively cleaner solvent.
An appropriate residence time and filter arrangement is chosen to ensure that
the agglomerates,
are well drained and low in residual bitumen. The resulting solvent-wet filter
cake is then passed
into the TSRU where residual solvent is recovered and recycled to the wash
stage of the process.
Solvent is recovered from the agglomerated tailings in the TSRU by external
heating and/or
internal steam or gas stripping. The TSRU discharge may have about 15 wt%
water or less, and
residual solvent would be at levels that meet or exceed environmental
requirements. The overall
system, including the slurry system and the rejects handling unit is a unique
system and is readily
differentiated from systems and apparatuses used in conventional water based
extraction
processes.
[00217] In a further exemplary embodiment, a slurry system with re-
circulation is
employed. The system comprises a mixbox and at least one retention tank. Dry
oil sand is mixed
with solvent to form a slurry in the mixbox. The solvent used may or may not
contain bitumen
entrained therein. The resulting slurry is then directed into a retention
tank. The slurry is mixed in
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CA 02724806 2010-12-10
the tank at an appropriate mild agitation level to promote nucleation of the
fines for agglomeration.
The slurry exiting the tank may be divided into two streams, each directed to
a respective conduit.
One stream may be passed through a conduit into a separator while the other is
directed by a
conduit to be recirculated in the mixbox of the slurry system. The
recirculating flow rate could be,
for example, 0 to 60% of the nominal process flow rate. In this embodiment,
the system is may be
less maintenance intensive, as no rotating equipment is used in the
agglomeration of solids.
Capital cost savings may thus be realized due to savings in equipment costs
and the reduction of
building and foundation sizes. A steam heated filter cake conveyor located
upstream of the TSRU
dryer may be used to reduce the heating load of the system. Advantageously,
the rejects drying
drums may not be required in this embodiment.
[00218] Further embodiments of a system are described herein which
integrate a variety of
system components for use in a process for bitumen recovery from oil sands.
[00219] A non-aqueous solvent extraction process for recovery of bitumen
from oil sands
which incorporates embodiments of specialized systems described above is
provided in detail
below.
[00220] Figure 8 illustrates an exemplary system (800) within the scope of
the present
disclosure, including a slurry system; an agglomerator; a separator unit
comprising a
countercurrent washer; a tailings solvent recovery unit (TSRU); and a solvent
recovery unit (SRU).
The separator unit may optionally comprise a deep cone settler to separate low
solids bitumen (as
overflow) from agglomerates (as underflow). The countercurrent washer may
comprise a belt
filter, or a multi-stage counterflow cyclone. In the depicted exemplary system
(800), a feed (802)
is provided to a slurry system (804), together with a non-aqueous solvent
(814a) having bitumen
(816b) entrained therein, and optionally together with steam (806) to either
provide water content
for later agglomeration and/or for the purpose of heating the feed to a
temperature that is
advantageous to further downstream processing in the system. The initial
slurry (808) formed in
the slurry system is fed to an agglomerator (810) by use of pumps or by
gravity feed where the
slurry may be combined with water (812a) and a solvent (814a) in which bitumen
(816a) may be
entrained.
[00221] Upon agglomeration in the system, the agglomerated slurry (818)
is separated in
a separator unit (819), which in this instance includes a deep cone settler
(820), which separates a
low solids bitumen extract (822) from the agglomerates. The agglomerates
obtained through
separation in the deep cone settler (820) may be classified as "separator
underflow" (824) when
obtained in this way, or may simply be referenced as "extracted solids", which
can be further
processed by washing in a countercurrent washer (826). The countercurrent
washer in this
- 43 -
CA 02724806 2010-12-10
instance comprises a belt filter that incorporates countercurrent washing with
solvent with
progressively less bitumen entrained therein. From the countercurrent washer
(826), solvent
(814b) having bitumen (816b) entrained therein can be recycled for re-use in
the slurry system
(804).
[00222] After cleaning agglomerates in the countercurrent washer (826),
wet, washed
agglomerates (828) are further processed in a tailings solvent recovery unit
(830). Solvent (814c)
and water (812b) are recovered for re-use. Dry agglomerated tailings (832)
derived from the
tailings solvent recovery unit (830), are advantageously low in water content
as well as very low in
solvent content, thereby meeting or exceeding environmental standards for
solvent content. The
agglomerated tailings may be back-filled into a mine area. Solvent (814c)
recovered from the
tailings solvent recovery unit may be re-directed to the belt filter for use
in counter-current
washing, and may be combined with clean solvent (814d), having no bitumen
entrained therein, to
make up for any solvent volume losses in the system. Low solids bitumen
extract (822) may be
sent to a solvent recovery unit (834) and bitumen product (836) may be
recovered therefrom.
Further processing of the low solids bitumen extract with a solvent that may
be the same as or
different from the solvent introduced in the initial slurry can occur prior to
solvent recovery, as
described above.
[00223] In this system 800, the primary components comprise a slurry
system (804); an
agglomerator (810); a separator unit (819) comprising a deep cone settler
(820) and a
countercurrent washer (826); a solvent recovery unit (834) for removing
solvent from low solids
bitumen extract; and a tailings solvent recovery unit (830) to remove solvent
from agglomerates.
[00224] A variety of modifications and optional component configurations
are permitted and
fall within the scope of the systems described herein. Exemplary system
components are
described below with respect to Figure 9 to Figure 13. Further, Figure 14 and
Figure 15 outline
a variety of optional system configurations.
[00225] Figure 9 illustrates an exemplary ore preparation and slurry
system design (900)
for systems described herein. Raw ore (902) obtained from oil sands mining may
be processed at
or near the site of the mine, or at a remote location by conveyance into a
hopper (903) from which
ore is conveyed on conveyor belts (905, 906) to a primary crusher (907).
Further conveyance of
crushed ore on a secondary conveyor belt (909) brings crushed ore to a
secondary crusher (911),
following which a conveyor belt (913) delivers crushed ore (915) into a surge
bin (917), which may
divide crushed ore into one or more crushed ore streams (919, 920), which are
conveyed by
conveyors (923, 924) to slurry system (927). In the depicted embodiment, the
slurry system (927)
comprises a hopper (929) for receiving crushed ore from the surge bin (917),
conveyors (929,
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CA 02724806 2012-12-13
930) for conveying ore to a mix box (933). Solvent (935), and optionally water
(937), in the form of
liquid or steam or a combination thereof, are combined in the mix box (933)
with the crushed ore,
and a vent gas (939) is provided to the mix box to create a low oxygen
environment. The mixing
within the mix box permits the crushed ore to take on the consistency of a
pumpable slurry,
referenced herein as the "initial slurry" (941). One or more pumps (943a,
944a) may be used to
transport the initial slurry (941) into one or more agglomerator (943b, 944b).
[00226] Figure 10 illustrates an agglomerator for use with exemplary
systems described
herein. It is understood that the agglomerator of the system described herein
may take any
number of forms, such as having one or more rotating drums or a series of
tanks. The
agglomerator (1000) depicted in Figure 10 takes the form of a plurality of
rotating drums. Initial
slurry (941) received from the slurry system and optionally water (1020), in
the form of liquid or
steam or a combination thereof, are provided into rotating drums (1001, 1002),
which are rotated
to agglomerate fines therein. Effluent from the rotating drums will have
agglomerated particles
that may be subjected to screening for removal of oversized reject materials,
for examples, solids
greater than 50 mm as well as petrified wood, twigs or other materials that
can potentially upset
downstream processing. Screens (1003, 1004) are employed to filter out such
oversized
materials, which would be sized to permit passage of agglomerates
therethrough. Oversized
rejects in reject streams (1009, 1010) may be subjected to further processing,
such as solvent
removal (1026). Vent gas (1005, 1006) flowing out of the rotating drums (1001,
1002) may
proceed to a vent gas recovery unit (1007) in order to recover vaporized
solvent. The
agglomerated slurry arising from the agglomerators (1001,1002), having had
oversized rejects
removed with appropriately sized mesh screens (1003, 1004) which permit
agglomerates to pass
through, is optionally directed to a conveyor belt (1022) so that a stream of
agglomerated slurry
with rejects removed (1024) is directed over a distance, if required, for
further processing in a
separator unit, such as depicted in Figures 11 and 12.
[00227] Figure 11 illustrates an optional component of the separator unit.
In this
embodiment, a deep cone settler (1103) is depicted for receiving agglomerated
slurry (1009) from
the agglomerator. The cone settler permits settling of agglomerated solids to
the lower region
(1105), while a low solids bitumen extract (1107) can be drawn off as
overflow. A pump (1109) is
used to convey the overflow to further cleaning or solvent removal in a
solvent recovery unit. A
vent gas (1111a, 1111b) is provided to and removed from the cone settler to
provide a low oxygen
environment therein. One or more pumps (1113, 1114, 1115) may be used to pump
agglomerates
(1117a, 1117b, 1117c) to a countercurrent washer (1119), which may be for
example a belt filter
for effecting solvent recovery from agglomerates.
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CA 02724806 2012-12-13
[00228] Figure 12 illustrates a countercurrent washer (1200) which
includes a belt filter
system (1201) for washing of agglomerates (1117) derived from the
agglomerators or optionally
from a deep cone settler underflow. The agglomerates are conveyed along a
conveyor belt (1203),
in this instance progressing from left to right, while low solids bitumen
extracts (1205a, 1205b,
1205c, 1205d) filter through the solid cake and filter media and collects
within the tanks (1207a,
1207b, 1207c, 1207d). The low solids bitumen extracts in the tanks can be
drawn off for re-use
and pumped to an upstream stage of the belt filtration process by pumps
(1209b, 1209c, 1209d).
[00229] The belt filter may consist of one or more drainage stages where a
low solids
bitumen extract is extracted from the agglomerate slurry. The wash stages of
the belt filter may
operate countercurrently where the direction in which the agglomerates (1117)
are conveyed
along the conveyor belt (1203) is counter to the direction in which the
solvent is re-used for
washing the agglomerates. Thus, the agglomerates are washed with progressively
cleaner
solvent when conveyed along the belt (1203). Cleaner solvent is interpreted as
solvent with lesser
bitumen entrained within. Fresh solvent, coming from storage or the solvent
recovery units, has no
or minimal amounts of bitumen within. In the depicted embodiment, agglomerates
(1117)
progress from left to right, while solvent used for washing becomes cleaner as
agglomerates move
from left to right.
[00230] The low solids extract (1205d) that is filtered at the end of the
belt is the filtrate
resulting from a final drainage stage used. Once washed in the countercurrent
washing process,
a solids agglomerate filter cake of minimum bitumen content is formed. The
bitumen entrained
within the extract (1205d) collected in the final tank (1207d) is preferably
minimal. The extract
(1205d) in the tank (1207d) is pumped back with pump (1209d) to an earlier
region along the belt,
and can be used again, optionally with the addition of fresh solvent (1220),
to wash the
agglomerates at an earlier region along the belt, for example region above the
adjacent upstream
tank (1207c). The resulting low solids extract that is filtered through the
bed and filter media is
collected within a tank 1207c to be used for the next countercurrent wash of
the adjacent
upstream region. Solvent with entrained bitumen accumulated from
countercurrent washing of
agglomerates, for example, as found in tank (1207a) may be directed via pump
(1209a) to solvent
recovery (1222).
[00231] Following the solvent washing of agglomerates and final drainage
stage, The wet
agglomerates (1211) can be conveyed by conveyor (1213) to further solvent
removal in a tailings
solvent recovery unit (1215) and once dried can subsequently be sent to
storage. The wet
agglomerates (1211) once subjected to solvent removal, have a low solvent
content that meets or
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CA 02724806 2012-12-13
exceeds requisite environmental standards. For this reason, the dried
agglomerates can
eventually be used as, for example, back-fill in a spent mine.
[00232] Figure 13 illustrates an exemplary tailings solvent recovery unit
(1300) for use in
removing solvent from wet agglomerates. Following separation and washing in
the separator unit,
washed wet agglomerates (1211) can be dried in a tailings solvent recovery
unit, which may
comprise a TSRU drum (1313) comprising a dryer, an evaporator, a heater,
and/or a blower in
order to evaporate residual solvent from wet tailings. Dry agglomerates (1315)
leave the drum
(1313) and may be conveyed by means of a TSRU discharge conveyor (1317) to a
dry tailings
disposal location (1319), such as an oil sands mine location from which oil
sand recovery is
complete. Reject solids (1320), for example, oversized solids which may have
been recovered
earlier in the system, but which have been wetted with solvent may have been
previously dried for
solvent recovery in a rejects dryer (1321) may also be conveyed to dry
tailings disposal (1319),
optionally merging on a conveyor with dry agglomerates on the TSRU discharge
conveyor (1317).
[00233] Figure 13 also depicts a three phase separation unit (1310) for
use in recovery of
solvent derived from the TSRU drum (1313). In this instance, solvent derived
from agglomerated
tailings in the TSRU (1300) can be recovered and separated from water and vent
gas in a
separation unit (1327). Solvent (1323), and water (1325) can thus be separated
and reused
elsewhere in the system. The vent gas (1333) is sent to the vent gas recovery
unit to recover any
evaporated solvent. Pumps (1329, 1330) may be employed to convey solvent
(1323) and water
(1325) to other locations in the system. The tailing solvent recovery unit
(1300) may operate
under low oxygen conditions using an inert vent gas.
[00234] Figure 14 illustrates a system (1400) commensurate with a first
embodiment
described herein. A bituminous feed (1401) is mixed with a solvent (1403) and
optionally water in
a mix box (1405), and a pumpable initial slurry is formed. The initial slurry
is pumped by pump
(1407) into an agglomerator (1409) having thereon a screen (1411) to screen
for rejects. A water
containing stream may optionally be injected into the agglomerator. Screened
rejects may be
dried and the solvent recovered in the rejects dryer (1413). The agglomerated
slurry arising from
the agglomerator may be pumped into a deep cone settler (1414) via a pump box
(1445) in
communication with a pump (1417). The overflow of the deep cone settler may be
sent to a
solvent recovery unit (1426) so as to remove bitumen from solvent, thereby
forming a bitumen
product. Underflow of the deep cone settler is pumped via pump (1419) to a
belt filter (1421)
where countercurrent washing is used to remove bitumen from agglomerates with
washing along
the length of the belt filter involving progressively cleaner solvent. The
filter cake from the belt
filter is conveyed by a conveyor (1423) to a TSRU dryer (1425). Solvent
recovered in this TSRU
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CA 02724806 2010-12-10
=
dryer may have bitumen light ends entrained therein, and may be used as is, or
sent to a solvent
recovery unit (1426), to remove bitumen light ends entrained therein. The
dried agglomerates
arising from the TSRU dryer (1425) may be conveyed via conveyor (1427) to a
location for storage
of dry tailings (1429), optionally together with dried rejects from the reject
dryer (1413).
[00235] Figure 15 illustrates an exemplary embodiment of a system
described herein. A
system (1500) comprises a bituminous feed (1501) which is mixed with a solvent
(1503) and
optionally water in a mix box (1505), and an initial slurry is formed. Through
mild agitation
occurring within the slurry system (1506), the initial slurry becomes
agglomerated as it is directed
to a retention tank (1504) within the slurry system. Mild agitation causes
agglomeration of fines. A
water containing stream may optionally be injected into the retention tank to
promote
agglomeration of the fines therein. The initial slurry is held in the
retention tank (1504) where it
may be held and/or mixed for an appropriate residence time, such as 2 minutes,
for example.
Optionally, a portion (1510) of the agglomerated slurry leaving the retention
tank (1504) may be
directed to re-circulation via pump (1507) or by gravity flow, and is thus re-
directed into the mix
box (1505). Recirculation is depicted here with a dashed line to indicate the
optional nature of this
feature. Iterative recirculation may be helpful in breaking down size. The
agglomerated slurry
(1512) arising from the retention tank (1504) may be directed by a pump
(1517), as depicted, or by
gravity into a deep cone settler, or clarifier (1514). The overflow (1516) of
the clarifier (1514) may
be sent to a solvent recovery unit (1526) so as to remove bitumen from
solvent, thereby forming a
bitumen product. Underflow of the clarifier (1514) is pumped via pump (1519)
to a belt filter (1521)
where countercurrent washing is used to remove bitumen from agglomerates with
washing along
the length of the belt filter involving progressively cleaner solvent. The
filter cake from the belt
filter is then conveyed by conveyor (1523) to a TSRU dryer (1525). Solvent
recovered in this
TSRU dryer may have bitumen light ends entrained therein, and may be used as
is, or sent to a
solvent recovery unit (1526), to remove bitumen light ends entrained therein.
The dried
agglomerates arising from the TSRU dryer (1525) may be conveyed via conveyor
(1527) to a
location for storage of dry tailings (1529).
[00236] PART 3
[00237] Processes for Solvent Extracting Bitumen Involving Fractionating a
Diluent.
[00238] Generally, the processes and systems described herein involve the
use of a lighter
fraction of an available hydrocarbon fluid as a solvent source for solvent
extraction of bitumen.
The available hydrocarbon fluid may comprise a diluent (e.g. gas condensate or
naphtha). The
hydrocarbon fluid is fractionated into a heavier fraction and a lighter
fraction. Upon fractionation,
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CA 02724806 2010-12-10
the lighter fraction, which has a lower boiling point, is used as a solvent in
the extraction. As
described herein, more than one solvent may be used in the extraction. The
heavier fraction,
having a higher boiling point, is recombined with the diluted bitumen product
(following solvent
extraction) to satisfy shipping requirements. Shipping requirements may, for
example, require a
particular viscosity, vapour pressure, or other measurable parameter to be
met, which can be
achieved by addition of the heavier fraction. Further, additional diluent
and/or diluted bitumen can
be added, if needed, in order to meet shipping requirements consistent with
pipeline
specifications.
[00239] Diluted bitumen is also referred to as "dilbit" herein. Dilbit is
bitumen diluted by a
diluent, for example a natural gas condensate or naphtha. The bitumen is
diluted for easier
transport by pipeline.
[00240] A process is described herein for extracting bitumen from a
bituminous feed from
oil sands. The process comprises fractionating a hydrocarbon fluid into a
lighter fraction and a
heavier fraction; effecting solvent extraction of the bituminous feed with the
lighter fraction as the
solvent to produce solvent diluted bitumen; and combining the heavier fraction
with solvent diluted
bitumen to form a high grade bitumen product.
[00241] The hydrocarbon fluid may be, for example, a diluent, a natural
gas condensate,
naphtha, a C5+ natural gas condensate, mixtures of these, and optionally other
fluids that may
possess appropriate qualities under certain temperature and pressure
conditions.
[00242] The lighter fraction may have a boiling point of less than 100 C,
and/or may
comprise hydrocarbons with a boiling point less than 100 C, but greater than
50 C. The lighter
fraction may comprise one or more C5 to C8 hydrocarbons, and in certain
embodiments may
comprises a single hydrocarbon. The lighter fraction comprises a C4 or lighter
hydrocarbon, for
example under certain circumstances or conditions. For example, if
fractionating is conducted
under pressure and temperature conditions permitting the lighter fraction to
remain liquid, then C4
or lighter hydrocarbons could comprise the lighter fraction.
[00243] Di!bit or diluent may be combined with the high grade bitumen
product to form a
mixed product. If used, the dilbit may be derived from any appropriate source,
such as from a
water-based bitumen extraction operation. The dilbit may be derived from a
paraffinic froth
treatment operation, for example. Further, the dilbit may be derived from an
in situ bitumen
production operation, such as SAGD, SA-SAGD, LASER, or CSS. Optimally, the
dilbit, when
used, has less than 300 ppm filterable solids on a bitumen basis.
[00244] The mixed product produced according to the process is
advantageously fungible.
For example, the mixed product may have less than 300 ppm filterable solids on
a bitumen basis.
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CA 02724806 2010-12-10
[00245] In the process, effecting solvent extraction may comprise
agglomerating solids.
Further, effecting solvent extraction may comprise recycling the solvent.
[00246] In the process described, fractionating may comprise solvent
removal by vaporizing
and condensing the lighter fraction, flashing to create a pressure drop and
vaporize the lighter
fraction. Optionally, using membrane separation based on solvent molecular
size would be a
possible method of fractionating. Further, fractionating may involve solvent
removal by
vaporization followed by condensation of the lighter fraction at or below the
boiling point of the
lighter fraction.
[00247] Effecting solvent extraction may comprise combining a first
solvent and the
bituminous feed to form an initial slurry; separating the initial slurry into
a fine solids stream and a
coarse solids stream; agglomerating solids from the fine solids stream to form
an agglomerated
slurry comprising agglomerates and a low solids bitumen extract; separating
the low solids
bitumen extract from the agglomerated slurry; mixing a second solvent 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; subjecting the mixture to gravity
separation to produce a high
grade bitumen extract and a low grade bitumen extract; and recovering the
first and second
solvent from the high grade bitumen extract, leaving the high grade bitumen
product; wherein the
first solvent or the second solvent comprises the lighter fraction.
[00248] Optionally, effecting solvent extraction may comprise combining a
first solvent and
the bituminous feed to form an initial slurry; separating the initial slurry
into a fine solids stream
and a coarse solids stream; agglomerating solids from the fine solids stream
to form an
agglomerated slurry comprising agglomerates and a low solids bitumen extract;
mixing a second
solvent with the agglomerated slurry to form a solvent-bitumen agglomerated
slurry mixture, the
second solvent having a similar or lower boiling point than the 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 the
high grade bitumen
product; and recovering the first and second solvent from the low grade
bitumen extract, leaving a
low grade bitumen product; wherein the first solvent or the second solvent
comprises the lighter
fraction.
[00249] Additionally, effecting solvent extraction may comprise combining
a first solvent and
the bituminous feed 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; separating the low solids
bitumen extract from the
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CA 02724806 2010-12-10
agglomerated slurry; mixing a second solvent 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, subjecting the mixture to gravity separation to produce a high grade
bitumen extract and a
low grade bitumen extract; and recovering the first and second solvent from
the high grade
bitumen extract, leaving the high grade bitumen product; wherein the first
solvent or the second
solvent comprises the lighter fraction.
[00250] Optionally, the effecting of solvent extraction may comprise
combining a first
solvent and the bituminous feed to form an initial slurry; separating the
initial slurry into a fine
solids stream and a coarse solids stream; recovering the first solvent from
the coarse solids
stream; agglomerating solids from the fine solids stream to form an
agglomerated slurry
comprising agglomerates and a low solids bitumen extract; mixing a second
solvent with the
agglomerated slurry to form a solvent-bitumen agglomerated slurry mixture, the
second solvent
having a similar or lower boiling point than the 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 the high grade
bitumen product; and
recovering the first and second solvent from the low grade bitumen extract,
leaving a low grade
bitumen product; wherein the first solvent or the second solvent comprises the
lighter fraction.
[00251] The effecting of solvent extraction may optionally comprise
combining a first solvent
and the bituminous feed to form an initial slurry; agglomerating solids from
the initial slurry to form
an agglomerated slurry comprising agglomerates and a low solids bitumen
extract; separating the
low solids bitumen extract from the agglomerated slurry; mixing a second
solvent 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, subjecting the mixture
to gravity separation to
produce a high grade bitumen extract and a low grade bitumen extract; and
recovering the first
and second solvent from the high grade bitumen extract, leaving the high grade
bitumen product;
wherein the ratio of first solvent to bitumen in the initial slurry is
selected to avoid precipitation of
asphaltenes during agglomeration; wherein the first solvent or the second
solvent comprises the
lighter fraction.
[00252] The effecting of solvent extraction may comprise combining a first
solvent and the
bituminous feed to form an initial slurry; agglomerating solids from initial
slurry to form an
agglomerated slurry comprising agglomerates and a low solids bitumen extract;
mixing a second
solvent with the agglomerated slurry to form a solvent-bitumen agglomerated
slurry mixture, the
second solvent having a similar or lower boiling point than the first solvent;
subjecting the mixture
to separation to produce a high grade bitumen extract and a low grade bitumen
extract comprising
- 51 -
CA 02724806 2010-12-10
substantially all solids and water; and recovering the first and second
solvent from the high grade
bitumen extract, leaving the high grade bitumen product; and recovering the
first and second
solvent from the low grade bitumen extract, leaving a low grade bitumen
product; wherein the ratio
of first solvent to bitumen in the initial slurry is selected to avoid
precipitation of asphaltenes during
agglomeration; wherein the first solvent or the second solvent comprises the
lighter fraction.
[00253] Other methods of solvent extraction, in addition to or as an
alternative to those
mentioned above may be used in the process, such as prior methods described
herein in the
background section.
[00254] The first solvent and the second solvent, if used in effecting
solvent extraction may
comprise the lighter fraction. The first solvent and the second solvent may
comprises at least 50%
by weight of the lighter fraction. Further, the first solvent and the second
solvent may comprises
at least 90% by weight of the lighter fraction. Optionally, the ratio of the
first solvent to bitumen in
the initial slurry may be less than 2:1, and can be selected to limit
precipitation of asphaltenes
during agglomeration.
[00255] The initial slurry described in the solvent extraction steps
described above may be
formed in a low oxygen environment under a gas blanket. Optionally, the first
solvent used in
solvent extraction may have a boiling point of less than 100 C. The second
solvent, when used in
solvent extraction, may have a boiling point of less than 100 C. Indeed, it is
envisioned that the
first solvent and the second solvent are possibly the same solvent, and may
comprise the lighter
fraction.
[00256] Where applicable, the agglomerated slurry may be separated into
low solids
bitumen extract and agglomerates in a solid-liquid separator. The solid-liquid
separator may
comprise a gravity separator, a cyclone, a screen, a belt filter or a
combination thereof. Further,
the solid-liquid separator may comprise a secondary stage for countercurrently
washing the
agglomerates separated from the agglomerated slurry. Where applicable, the
secondary stage for
countercurrently washing the agglomerates may comprise a gravity separator, a
cyclone, a
screen, a belt filter, or a combination thereof.
[00257] The process for solvent extracting bitumen involving fractionating
a diluent may be
used with a process or system described in PART I, or PART 2 above, but need
not be limited to
these processes or systems. The processes described herein may be used with
another process
or system of solvent extraction including, but not limited to, those described
in the background
section.
[00258] Processes and systems are described herein which involves the use
of a lighter
fraction of a hydrocarbon fluid, for example a diluent (e.g. gas condensate or
naphtha), as a
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CA 02724806 2010-12-10
solvent source for solvent extraction of bitumen. The diluent stream is
fractionated into a heavier
fraction and a lighter fraction. The lighter fraction (with a lower boiling
point) is used for as the
solvent in the extraction (as described below more than one solvent may be
used in the
extraction). The heavier fraction is recombined with the diluted bitumen
product (following solvent
extraction) to satisfy shipping viscosity requirements and diluent and/or
dilbit can be added thereto
as required to meet pipeline specifications.
[00259] Fractionation. Fractionation may involve separating of fluids
according to any
appropriate methodology. Fractionating may comprise vaporizing a liquid, and
subsequently
condensing specific boiling point ranges to separate different hydrocarbons,
or different
hydrocarbon mixtures according to a pre-selected boiling point. In addition,
similar separation
might be achieved through flashing (pressure drop - some light ends turn to
vapor); or even
membrane separation, where separation is based on molecular size, which may
give similar
results to fractionation based on boiling points
[00260] Figure 16 is schematic representation of an exemplary process
(1600) within the
scope of the present disclosure where the solvent is obtained from
fractionating a hydrocarbon
fluid. The process of shown in Figure 16 involves fractionating the
hydrocarbon fluid into a lighter
fraction and a heavier fraction (1602). It is conceivable for more than two
fractions to be formed.
The lighter fraction is used as the solvent in a solvent extraction process
for extracting bitumen
from a bituminous feed, so as to produce solvent diluted bitumen (1604). The
heavier fraction is
added to the solvent diluted bitumen stream (1606) to create a mixture.
Optionally, diluent and/or
dilbit or synthetic crude may be added to the mixture of the heavier fraction
and the solvent diluted
bitumen (1608), if desired, to meet fungible requirements.
[00261] As discussed further below, the hydrocarbon fluid may be a
diluent, for example
natural gas condensate or naphtha. A primary criteria of the hydrocarbon fluid
is that it must be
capable of being fractionated to produce at least a fraction suitable for use
as a solvent in solvent
extraction of bitumen. Suitable solvents include, but are not limited to,
those described above in
PARTI and those previously described or known, such as those described in the
background
section.
[00262] Figure 17 illustrates a system where solvent is sourced from a
diluent stream and
used in the solvent extraction process. In this embodiment, diluent (1702)
from a diluent pipeline
(1704) is fractionated in a fractionation unit (1706). A lighter fraction
(1708) and a heavier fraction
(1710) are formed. The lighter fraction (1708) is used as the solvent in
solvent extraction of
bitumen (1712). The bitumen feed (1713) is also shown. The solvent extraction
(1712) may be as
described above in PARTI, or may be another solvent extraction process
including, but not limited
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CA 02724806 2010-12-10
to, those described in the background section. Solvent extraction (1712)
includes the associated
solvent recycling (not shown). From the solvent extraction (1712), a solvent
diluted bitumen with
low levels of fine solids (1714) is obtained. The heavier fraction (1710) and
the solvent diluted
bitumen (1714) are combined to form product (1715). If the product (1715) has
a filterable solids
content that is higher than a desirable level, the product (1715) may be
combined with diluent
and/or dilbit (1716) to form a mixed product (1718). A product requirement
where the filterable
solids content, on a bitumen basis, must not exceed a level of 300 ppm of
filterable solids can be
met according to the process described. This requirement may be one typically
needed for
downstream refineries. Thus, by adding a diluent containing bitumen but having
a solids content
measurably less than 300 ppm, the resulting product stream can result in an
overall solids content
below the 300 ppm level. By combining such streams, the solids content is
reduced to a level that
can meet the 300 ppm limit and render the stream appropriate for downstream
refineries.
[00263] The dilbit may be from a water-based extraction process, for
example PFT or an in
situ operation, such as SAGD. The dilbit (1716) has less than 300ppm
filterable solids on a
bitumen basis. The mixed product (1718) is more likely achieve its fungibility
requirement of less
than 300 ppm of filterable solids in cases where the mass of bitumen in dilbit
(1716) available from
a water-based extraction operation exceeds the mass of bitumen from product
(1715) by a
significant amount, so that the combination of streams results in an
appropriate result. For
example, a level factor of from at least a 2-fold different, for example, a 2-
fold, 3-fold, 4-fold, or 5-
fold minimum difference in filterable solids is appropriate, thus making it
quite simple to produce a
mixed product (1718) that meets fungible requirements. An example of this is
when the filterable
solids content of a product is 1000 ppm, but it is desirable to reduce to 300
ppm. The dilbit used
may have a filterable solids content of 100 ppm, resulting in a 10-fold
difference between the
filterable solids content of the two streams.
[00264] A "diluent" as used herein means a hydrocarbon fluid that could be
used to dilute
bitumen or heavy oil to reduce its viscosity for easier transportation.
Natural gas condensate is
one common diluent. Natural gas condensate is a low-density mixture of
hydrocarbon liquids that
are present as gaseous components in the raw natural gas produced from natural
gas fields. The
condensate condenses out of the raw gas if the temperature is reduced to below
the hydrocarbon
dew point temperature of the raw gas. Natural gas condensate is also referred
to as simply
condensate, or gas condensate, or sometimes natural gasoline because it
comprises
hydrocarbons within the gasoline boiling range. Another common diluent is
naphtha. Naphtha is
is a mixture of C5 to C13 hydrocarbons which may include about 15 to 40 wt.%
of C6 to C11
aromatic compounds and the balance mostly a mixture of C5 to C11 aliphatic
hydrocarbons,
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CA 02724806 2010-12-10
including mixed paraffins and mixed olefins. Naphtha may have a final boiling
point of around 175
C.
[00265] In one embodiment, the diluent is a C5+ gas condensate with at
least five carbons
including, among other components, pentane and hexane. The diluent may have
similar
properties to heptane. C5+ gas condensates are hydrocarbon mixtures
predominantly comprising
C5, C6, and heavier hydrocarbons, are often produced in natural gas processing
plants, and can
be sold as commodity as such condensates can often be processed to
transportation fuels.
[00266] The lighter fraction, while composed primarily of 05 to C8
molecules may optionally
employ C4 and lighter molecules, should the process temperature and pressure
allow for such
hydrocarbon components remain as liquid. For example, in one embodiment, the
lighter fraction
may have a boiling point of from 30 to 50 C, or may comprise hydrocarbons
having a boiling point
in this range. For example, if pressurized systems are employed, such lower
boiling point liquids
(below 50 C) may be used, such as butane (C4).
[00267] In the PFT process, which is water-based, diluent may be used to
dilute the
bitumen product after removal of solvent, thus making the product of a PFT
extraction operation
easier to transport. Therefore, in such a PFT process, diluent is on hand.
Using this diluent in a
nearby solvent extraction operation would be advantageous since an independent
solvent source
would not be required. An example of where diluent is used to dilute the
product of a PFT process
will now be provided. Processes for extracting bitumen from mined oil sands
commonly employ
the steps of bitumen extraction, bitumen froth separation, and froth
treatment. An example of
such a process will now be provided, although different processes exist. Oil
sand is supplied from
a mine, mixed with water, and separated from rocks and debris. The slurry is
conditioned by
adding air, and optionally chemical additives such as caustic (sodium
hydroxide). The slurry is
sent to a primary separation cell/vessel (PSV) where the aerated bitumen
droplets separate from
most of the solids to form bitumen froth. The bitumen froth comprises bitumen,
water and fine
solids (also referred to as mineral solids). A typical composition of bitumen
froth is about 60 wt%
bitumen, 30 wt% water, and 10 wt% solids. A paraffinic solvent is combined
with the bitumen froth
and further separation occurs in a Froth Separation Unit (FSU). The lighter
fraction from the FSU
is sent to a Solvent Recovery Unit (SRU) to recover solvent for reuse. The
bitumen product
stream from the SRU is combined with a diluent to form dilbit for transport.
The dilbit formed in
the water-based extraction process described above may be combined with the
dilbit formed in the
solvent-bases extraction process.
[00268] Where a stand alone solvent extraction operation is envisioned,
the expensive PFT
process could be replaced by additional gravity separation vessels such as
inclined plate settlers.
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CA 02724806 2010-12-10
The solvent extraction bitumen product will contain almost no water, removing
some separation
considerations such as solids stabilized emulsions.
[00269] The combination of higher diluent use and blending with a diluted
water-based
extraction product (dilbit) enables the product of the solvent extraction to
be shipped without
additional product cleaning. A range of blending options can be used. For
example, a very high
diluent amount could be used with the solvent extracted bitumen to have very
low density and
viscosity, allowing particles to easily settle. Less diluent would be required
in the water-based
dilbit stream, as the combined stream could still meet shipping requirements
[00270] In the solvent-based extraction process described above in the
background section,
the proposed solvent was naphtha having a final boiling point of about 180-220
C. With such high
boiling point solvents, the recovery of solvent from the solvent-washed ore
would be energy
intensive as all of the water would necessarily be evaporated in order to
recover all the solvent.
However, if a lighter solvent is used, as proposed herein, the boiling point
will be lower, and
therefore the energy requirements to remove the solvent can potentially be
less
[00271] In a solvent-based process, recovering high boiling point solvent
requires that water
be first evaporated, which adds to the cost. On the other hand, if a lighter
fraction is used in a
solvent extraction process, recovering the solvent can be less energy
intensive. As an example,
water requires 2257 kj/kg to change phase at 100 C; while a light hydrocarbon
(for instance
cyclohexane, boiling point = 80.7 C) would require approximately 356 kj/kg.
As a result, use of
lower boiling point solvents reduces both the sensible heat required to raise
the temperature of the
solids and fluid to a high final boiling point, as well as giving a
significant reduction in the heat of
vaporization required by keeping the required temperature below 100 C For
example, a
temperature of about 80 C can be used to remove the bulk of the solvent
without evaporating
water that would be present in an aqueous extraction process, thereby reducing
costs. Some
hydrocarbon liquids are known to form azeotropes with water (requires that
water and
hydrocarbon both boil at the same temperature, which may be lower than 100
C). Tailoring the
fractionation operation to produce low boiling point solvents that do not form
an azeotrope in the
operating range is a further enhancement of the process.
[00272] Thermo Gravimetric Analysis (TGA) can be used to determine changes
in weight
in relation to change in temperature of a sample of unwashed tailings (low
grade ore -
agglomerated) with cyclohexane . The method was 600/10C, 30', Air, 10-21689 #2
Air. The
results are shown in Figure 18 to Figure 21. The initial weight of the sample
was 62.40193 mg.
The solvent free mass was estimated to be 60.34511 mg (no mass spectrometry
analysis was
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CA 02724806 2010-12-10
performed, but rather a guess was made as to when all the solvent left the
sample). The final
weight of the sample was 57.71024 mg.
[00273] Figure 18 is a graph showing Thermo Gravimetric analysis (TGA)
results of a
sample in which a sample of unwashed tailings changes in weight over time. The
lines
representing the solvent free mass and the final weight are indicated as
dashed lines on the chart.
[00274] Figure 19 is a graph showing Thermo Gravimetric analysis (TGA)
results of the
same sample, illustrating change in weight relating to change in temperature
from 10 to 600 C.
[00275] Figure 20 is a graph showing a drying rate curve for cyclohexane
agglomerates
based on Thermo Gravimetric analysis (TGA) results of the sample. The chart
illustrates the rate
of change (mg/minute) depending on the ratio "X", which is free solvent
(mg)/dry solids (mg). In
this instance, Xc appears to be about 0.01 mg/mg. Xe appears to be negligible
(about 0.0 mg/mg).
The rate of about 1 mg solvent per minute is employed in a constant rate
regime. The kd is about
121 (mg solvent/min)/(mg solvent/mg dry solid) for these conditions.
[00276] Figure 21 is a graph showing drying rate based on Thermo
Gravimetric analysis
(TGA) results of the sample, showing rate (mg/min) changes over a temperature
range.
[00277] Figure 22 is a graph showing the moisture content of water and
solvent remaining
within agglomerates as a function of time based on Thermo Gravimetric Analysis
(TGA) results.
These data illustrate that at a point in time following 8 minutes of drying,
the agglomerates
reached the desired 400 ppm (0.04%) of residual solvent with only about 60% of
it initial water
content being lost. At the 8 minute point, solvent content was reduced from
about 5% to about
0.04%, while water content was reduced from about 5% to about 2%, representing
a reduction of
about 60%. The reduction in solvent content over that period of time was
considerably greater.
Values are expressed on a weight basis.
[00278] Another specification that may be used on the light solvent is to
limit the vapour
pressure or lower boiling point so that the extraction can operate without the
need for
pressurization. The boiling point must be higher than the desired operating
temperature, but lower
than 100 C to avoid excess water evaporation.
[00279] In PARTI, a first solvent and a second solvent are discussed and
it is mentioned
that they may be the same solvent. The lighter fraction as discussed herein in
PART3 may be the
first solvent, the second solvent, both, or part of one of both of the first
and second solvents. The
higher boiling point cut from the fractionator may be used as the second
solvent, or as a diluent for
shipping requirements.
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[00280] EXAMPLES
[00281] In the preceding description, for purposes of explanation,
numerous details are set
forth in order to provide a thorough understanding of the embodiments
described herein. However,
it will be apparent to one skilled in the art that these specific details are
not necessarily required in
practice.
[00282] The examples below describe embodiments intended to exemplify only
certain
embodiments. 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.
[00283] Example 1
[00284] 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
product suitable for transportation via a common carrier pipeline and
processing in a remote
refinery.
[00285] Example 2
[00286] 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
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CA 02724806 2010-12-10
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.
[00287] Example 3
[00288] 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.
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