Note: Descriptions are shown in the official language in which they were submitted.
CA 02741280 2011-05-27
METHOD OF PROCESSING A BITUMINOUS FEED WITH FEEDBACK CONTROL
FIELD
[0001] The present disclosure relates generally to the field of hydrocarbon
extraction
from mineable deposits, such as bitumen from oil sands.
BACKGROUND
[0002] Methodologies for extracting hydrocarbon from oil sands have required
energy
intensive processing steps to separate solids from the products having
commercial value.
[0003] Solvent extraction processes for the recovery of the hydrocarbons have
been
proposed as an alternative to water extraction of oil sands. However, the
commercial
application of a solvent extraction process has, for various reasons, eluded
the oil sands
industry. A major challenge to the application of solvent extraction to oil
sands is the
tendency of fine particles within the oil sands to hamper the separation of
solids from the
hydrocarbon extract. Solids agglomeration is a technique that can be used to
deal with this
challenge.
[0004] Solids agglomeration is a size enlargement technique that can be
applied
within a liquid suspension to assist solid-liquid separation. The process
involves
agglomerating fine solids, which are difficult to separate from a liquid
suspension, by the
addition of a second liquid. The second liquid preferentially wets the solids
but is immiscible
with the suspension liquid. With the addition of an appropriate amount of the
second liquid
and a suitable agitation, the second liquid displaces the suspension liquid on
the surface of
the solids. As a result of interfacial forces between the three phases, the
fines solids
consolidate into larger, compact agglomerates that are more readily separated
from the
suspension liquid.
[0005] Solids agglomeration has been used in other applications to assist
solid-liquid
separation. For example, the process has been used in the coal industry to
recover fine coal
particles from the waste streams produced during wet cleaning treatments (see
for example,
U.S. Patent Nos. 3,856,668 (Shubert); 4,153,419 (Clayfield); 4,209,301 (Nicol
et al.);
4,415,445 (Hatem) and 4,726,810 (Ignasiak)). Solids agglomeration has also
been proposed
for use in the solvent extraction of bitumen from oil sands. This application
was coined
Solvent Extraction Spherical Agglomeration (SESA). A more recent description
of the SESA
process can be found in Sparks et al., Fuel 1992 (71); pp 1349-1353.
1
CA 02741280 2011-05-27
[0006] Previously described methodologies for SESA have not been commercially
adopted. In general, the SESA process involves mixing oil sands with a
hydrocarbon
solvent, adding a bridging liquid to the oil sands slurry, agitating the
mixture in a slow and
controlled manner to nucleate particles, and continuing such agitation to
permit these
nucleated particles to form larger multi-particle spherical agglomerates for
removal. The
bridging liquid is preferably water or an aqueous solution since the solids of
oil sands are
mostly hydrophilic and water is immiscible with hydrocarbon solvents.
[0007] The SESA process described by Meadus et al. in U.S. Patent No.
4,057,486,
involves combining solvent extraction with solids agglomeration to achieve dry
tailings
suitable for direct mine refill. In the process, organic material is separated
from oil sands by
mixing the oil sands material with an organic solvent to form a slurry, after
which an aqueous
bridging liquid is added in the amount of 8 to 50 wt% of the feed mixture. By
using controlled
agitation, solid particles from oil sands come into contact with the aqueous
bridging liquid
and adhere to each other to form macro-agglomerates of a mean diameter of 2 mm
or
greater. The formed agglomerates are more easily separated from the organic
solvent
compared to un-agglomerated solids. This process permitted a significant
decrease in water
use, as compared with conventional water-based extraction processes. The multi-
phase
mixture need only be agitated severely enough and for sufficient time to
intimately contact
the aqueous liquid with the fine solids. The patent discloses that it is
preferable that the type
of agitation be a rolling or tumbling motion for at least the final stages of
agglomeration.
These types of motion should assist in forming compact and spherical
agglomerates from
which most of the hydrocarbons are excluded. The formed agglomerates are
referred to as
macro-agglomerates because they result from the consolidation of both the fine
particles
(sized less than 44 pm) and the coarse particles (sized greater than 200 pm)
found in the oil
sands.
[0008] U.S. Patent No. 3,984,287 (Meadus et al.) and U.S. Patent No. 4,406,788
(Meadus et al.) both describe apparatuses for extracting bitumen from oil
sands while
forming macro-agglomerates for easy solid-liquid separation. U.S. Patent No.
3,984,287
(Meadus et al.) describes a two vessel agglomeration apparatus. The apparatus
comprises
a mixing vessel for agitating the oil sands, the bridging liquid, and the
solvent to form a slurry
with suspended agglomerates. The slurry is screened in order to remove a
portion of the
hydrocarbon liquid within which the bitumen product is dissolved. The
agglomerates are
then directed to a tapered rotating drum where they are mixed with additional
solvent and
2
CA 02741280 2011-05-27
bridging liquid. The additional solvent acts to wash the excess bitumen from
the
agglomerates. The additional bridging liquid allows the agglomerates to grow
by a layering
mechanism and under the increasing compressive forces produced by the tapered
rotating
drum bed depth. The compressive forces act to preferentially remove
hydrocarbon liquid
from the pores of the agglomerates such that, when optimal operating
conditions are
imposed, the pores of the agglomerates end up being filled with only the
bridging liquid, and
the solvent that remains on the surface of the agglomerates is easily
recovered. U.S. Patent
No. 4,406,788 (Meadus et al.) describes a similar apparatus to that of U.S.
Patent No.
3,984,287 (Measdus et al.), but where the extraction and agglomeration
processes occurs
within a single vessel. Within this vessel, the flow of solvent is counter-
current to the flow of
agglomerates which results in greater extraction efficiency.
[0009] The above-mentioned patents describe methods of using the fines within
oil
sands and an aqueous bridging liquid to promote the consolidation of the
coarse oil sands
particles into compact macro-agglomerates having minimal entrained
hydrocarbons and
which are easily separated from the hydrocarbon liquid by simple screening.
This macro-
agglomeration process may be suitable for oil sands feeds comprising greater
than 15 wt%
fines. For oil sands with a lesser amount of fines, the resulting agglomerates
show poor
strength and a significant amount of hydrocarbons entrained within their
pores. The inability
of the macro-agglomeration process to produce agglomerates of similar solid-
liquid
separation characteristics regardless of oil sands feed grade, is a
limitation. This limitation
can be mitigated by using a water and fine particle slurry as the bridging
liquid. U.S. Patent
No. 3,984,287 (Meadus et al.) reveals that middlings of a primary separation
vessel of a
water-based extraction process or sludge from the water-based extraction
tailings ponds may
be used as the bridging liquids with high fines content. It has been shown
that when sludge
is used as the bridging liquid, the addition of the same amount of sludge per
unit weight of oil
sands feed may result in the production of agglomerates of the same drainage
properties
regardless of oil sands quality.
[0010] U.S. Patent No. 4,719,008 (Sparks et al.) describes a process to
address the
agglomeration challenge posed by varying ore grades by means of a micro-
agglomeration
procedure in which the fine particles of the oil sands are consolidated to
produce
agglomerates with a similar particle size distribution to the coarser grained
particles of the oil
sands. Using this micro-agglomeration procedure, the solid-liquid separation
behavior of the
agglomerated oil sands will be similar regardless of ore grade. The micro-
agglomeration
3
CA 02741280 2011-05-27
process is described as occurring within a slowly rotating horizontal vessel.
The conditions
of the vessel favor the formation of large agglomerates; however, a light
milling action is
used to continuously break down the agglomerates. The micro-agglomerates are
formed by
obtaining an eventual equilibrium between cohesive and destructive forces.
Since rapid
agglomeration and large agglomerates can lead to bitumen recovery losses owing
to
entrapment of extracted bitumen within the agglomerated solids, the level of
bridging liquid is
kept as low as possible commensurate with achieving economically viable solid-
liquid
separation.
[0011] The micro-agglomeration process described in U.S. Patent No. 4, 719,008
(Sparks et al.) has several disadvantages that have thus far limited the
application of the
technology. Some of these disadvantages will now be described.
[0012] The micro-agglomeration process described in U.S. Patent No. 4,719,008
(Sparks et al.) requires careful control of the binding liquid to solids
ratio. If the amount of
bridging liquid added to the process is in excess of the required amount,
rapid growth of
agglomerates can lead to bitumen recovery losses owing to entrapment of
bitumen within the
agglomerated solids. However, if the amount of bridging liquid added to the
process is too
low, insufficient agglomeration increases the amount of dispersed fines in the
liquid
suspension which hampers solids-liquid separation. In U.S. Patent No.
4,719,008, a ratio
between 0.112 and 0.12 was identified as an appropriate range for bridging
liquid to solids
ratio for a particular type of low grade ore. Maintaining the ratio within a
narrow range during
the actual field operation of the agglomeration process would be a challenge.
Furthermore,
the desired amount of bridging liquid for the agglomeration process will
depend on the ore
quality and the chemistry of the fines. Because the ore quality and chemistry
will change on
a frequent basis as different mine shelves are progressed, the recipe of the
agglomeration
process may need to change accordingly in order to maintain the agglomeration
output within
an acceptable range.
[0013] In previously described SESA processes, the bridging liquid is either
added
directly to the dry oil sands or is added to the oil sands slurry comprising
the oil sands and
the hydrocarbon solvent. In the former scenario, bitumen extraction and
particle
agglomeration occurs simultaneously. For this reason, the growth of
agglomerates may
hamper the dissolution of the bitumen into the solvent, it may lead to
trapping of bitumen
within the agglomerates, and it may result in an overall increase in the
required residence
time for bitumen extraction. In the scenario where the bridging liquid is
added to the oil
4
CA 02741280 2011-05-27
sands slurry, excessive agglomeration may occur in the locations of bridging
liquid injection.
These agglomerates will tend to be larger than the desired agglomerate size
and result in an
increase in the viscosity of the slurry. A higher slurry viscosity may hamper
the mixing
needed to uniformly distribute the bridging liquid throughout the remaining
areas of the slurry.
Poor bridging liquid dispersion may result in a large agglomerate size
distribution, which is
not preferred.
[0014] An important step in the agglomeration process is the distribution of
the
bridging liquid throughout the liquid suspension. Poor distribution of the
bridging liquid may
result in regions within the slurry of too low and too high binging liquid
concentrations.
Regions of low bridging liquid concentrations may have no or poor
agglomeration of fine
solids, which may result in poor solid-liquid separation. Regions of high
bridging liquid
concentration may have excess agglomeration of solids, which may result in the
trapping of
bitumen or bitumen extract within the large agglomerates. In the process
described in U.S.
Patent No. 4,719,008 (Sparks et al.), the milling action of the rotating
vessel acts to both
breakup large agglomerates and distribute the bridging liquid throughout the
vessel in order
to achieve uniform agglomerate formation. In a commercial application, the
rotating vessel
would need to be large enough to process the high volumetric flow rates of oil
sands.
Accomplishing uniform mixing of the bridging liquid in such a large vessel
would require a
significant amount of mixing energy and long residence times.
[0015] Coal mining processes often produce aqueous slurries comprising fine
coal
particles. Solids agglomeration has been proposed as a method of recovering
these fine
coal particles, which may constitute up to 30 wt.% of the mined coal. In the
solids
agglomeration process, the hydrophobic coal particles are agglomerated within
the aqueous
slurry by adding an oil phase as the bridging liquid. When the aqueous slurry,
with bridging
liquid, is agitated, the coal particles become wetted with an oil layer and
adhere to each other
to form agglomerates. The hydrophilic ash particles are not preferentially
wetted by the oil
phase and, as a result, remain un-agglomerated and suspended in the aqueous
phase. The
agglomerated coal material, with reduced ash content, is readily separated
from the aqueous
slurry by mechanical methods such as screening.
[0016] U.S. Patent No. 4,153,419 (Clayfiled et al.) describes a process for
the
agglomeration of coal fines within an aqueous slurry by staged addition of a
bridging liquid to
the aqueous slurry. Each agglomeration stage comprises the addition of a
bridging liquid to
the slurry, agitation of the mixture, and removal of agglomerates from the
aqueous slurry.
5
CA 02741280 2011-05-27
The inventors found that performing the agglomeration process in at least two
stages yielded
higher agglomeration of the coal particles as compared to the case where the
same amount
of bridging liquid was added in one agglomeration stage.
[0017] U.S. Patent No. 4,415,445 (Van Hattem et al.) describes a process for
the
agglomeration of coal fines within an aqueous slurry by the addition of a
bridging liquid and
the addition of seed pellets that are substantially larger than the coal
fines. The presence of
seed pellets induces agglomerate growth to occur predominately by a layering
mechanism
rather than by a coalescence mechanism. Since the rate of agglomeration occurs
much
faster by layering compared to coalescence, the process described therein
allows
agglomerates to form very quickly so that, for a given residence time, a
higher throughput of
agglomerates can be obtained compared to the throughput obtainable in the
absence of
seed pellets.
[0018] U.S. Patent No. 4,726,810 (Ignasiak) describes a process for the
agglomeration of coal fines within an aqueous slurry by the addition of a
bridging liquid
comprising a low quality oil, such as bitumen, and a light hydrocarbon
diluent, such as
kerosene. The aqueous slurry mixture is agitated by pumping it through a
pipeline within
which coal particles agglomerate and may later be separated from the slurry by
screening.
The process allows for the selective agglomeration of low-rank coal using
substantially a low
quality oil.
[0019] It would be desirable to provide an alternative or improved method for
processing a bituminous feed.
SUMMARY
[0020] The present disclosure relates to a method of processing a bituminous
feed.
The bituminous feed is contacted with an extraction liquor to form a slurry. A
bridging liquid
is added to the slurry, and solids are agitated within the slurry to form an
agglomerated slurry
comprising agglomerates and a low solids bitumen extract. In order to control
agglomeration, the slurry is analyzed and the processing method is adjusted
accordingly.
[0021] In a first aspect, the present disclosure provides a method of
processing a
bituminous feed, the method comprising: a) contacting the bituminous feed with
an extraction
liquor to form a slurry, wherein the extraction liquor comprises a solvent; b)
adding a bridging
liquid to the slurry, and agitating solids within the slurry, to form an
agglomerated slurry
6
CA 02741280 2011-05-27
comprising agglomerates and a low solids bitumen extract; c) measuring at
least one
property of the agglomerated slurry, the agglomerates, or the low solids
bitumen extract; and
d) comparing the at least one property to a target range, and where the at
least one property
that is measured does not fall within the target range, adjusting at least one
parameter of the
method of processing the bituminous feed, for controlling the agglomeration.
[0022] Other aspects and features of the present disclosure will become
apparent to
those ordinarily skilled in the art upon review of the following description
of specific
embodiments in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Embodiments of the present disclosure will now be described, by way of
example only, with reference to the attached Figures.
[0024] Fig. 1 is a flow chart illustrating a disclosed embodiment.
[0025] Fig. 2 is a schematic illustrating a disclosed embodiment.
[0026] Fig. 3 is a schematic illustrating a disclosed embodiment.
[0027] Fig. 4 is a schematic illustrating a disclosed embodiment.
[0028] Fig. 5 is a schematic illustrating a disclosed embodiment.
[0029] Fig. 6 is a schematic illustrating a disclosed embodiment.
[0030] Fig. 7 is a calibration curve relating bitumen content of a bitumen
extract
comprised of bitumen and solvent to the measured density of the bitumen
extract.
[0031] Fig. 8 is a graph of bitumen recovery and initial filtration rate as a
function of
extraction time with the agglomeration time kept constant at 2 minutes.
[0032] Fig. 9 is a graph is a graph of bitumen recovery and initial filtration
rate as a
function of agglomeration time with the extraction time kept constant at 5
minutes.
[0033] Fig. 10 is a schematic illustrating a disclosed embodiment.
DETAILED DESCRIPTION
[0034] The present disclosure relates to a method of processing a bituminous
feed
using feedback control. This method may be combined with aspects of other
solvent
extraction processes, including, but not limited to, those described above in
the background
section, and those described in Canadian Patent Application Serial No.
2,724,806 ("Adeyinka
et al."), filed December 10, 2010 and entitled "Processes and Systems for
Solvent Extraction
of Bitumen from Oil Sands".
7
CA 02741280 2011-05-27
[0035] Prior to describing embodiments specifically related to the feedback
control, a
summary of the processes described in Adeyinka et al. will now be provided.
[0036] Summary of Processes of Solvent Extraction Described in Adeyinka et
al. To extract bitumen from oil sands in a manner that employs solvent, a
solvent is
combined with a bituminous feed derived from oil sand to form an initial
slurry. Separation of
the initial slurry into a fine solids stream and coarse solids stream may be
followed by
agglomeration of solids from the fine solids stream to form an agglomerated
slurry. The
agglomerated slurry can be separated into agglomerates and a low solids
bitumen extract.
Optionally, the coarse solids stream may be reintroduced and further extracted
in the
agglomerated slurry. A low solids bitumen extract can be separated from the
agglomerated
slurry for further processing. Optionally, the mixing of a second solvent with
the low solids
bitumen extract to extract bitumen may take place, forming a solvent-bitumen
low solids
mixture, which can then be separated further into low grade and high grade
bitumen extracts.
Recovery of solvent from the low grade and/or high grade extracts is
conducted, to produce
bitumen products of commercial value.
[0037] As outlined in the summary section, and now with reference to Figure 1,
the
present disclosure relates to a method of processing a bituminous feed. The
bituminous
feed is contacted with an extraction liquor to form a slurry (102). A bridging
liquid is added to
the slurry and solids are agitated within the slurry to form an agglomerated
slurry comprising
agglomerates and a low solids bitumen extract (104). At least one property of
the
agglomerated slurry, the agglomerates, or the low solids bitumen extract is
measured (106).
The at least one measured property is compared to a target range. Where the at
least one
measured property that is measured does not fall within the target range, at
least one
parameter of the method is adjusted, for controlling the agglomeration (108).
[0038] The term "bituminous feed" refers to a stream derived from oil sands
that
requires downstream processing in order to realize valuable bitumen products
or fractions.
The bituminous feed is one that comprises bitumen along with undesirable
components.
Such a bituminous feed may be derived directly from oil sands, and may be, for
example raw
oil sands ore. Further, the bituminous feed may be a feed that has already
realized some
initial processing but nevertheless requires further processing. Also,
recycled streams that
comprise bitumen in combination with other components for removal as described
herein can
be included in the bituminous feed. A bituminous feed need not be derived
directly from oil
sands, but may arise from other processes. For example, a waste product from
other
8
CA 02741280 2011-05-27
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.
[0039] As used herein, "agglomerate" refers to conditions that produce a
cluster,
aggregate, collection or mass, such as nucleation, coalescence, layering,
sticking, clumping,
fusing and sintering, as examples.
[0040] Figure 2 is a schematic of a method of processing a bituminous feed
with
additional steps including downstream solvent recovery. Feedback control is
not illustrated in
Figure 2. The extraction liquor (202) is mixed with a bituminous feed (204)
from oil sands in
a slurry system (206) to form a slurry (208). The extraction liquor comprises
a solvent and is
used to extract bitumen from the bituminous feed. The slurry is fed into an
agglomerator
(210). Extraction may begin when the extraction liquor (202) is contacted with
the
bituminous feed (204) and a portion of the extraction may occur in the
agglomerator (210). A
bridging liquid (212) is added to the agglomerator to assist agglomeration of
the slurry.
Agitation of the slurry is also used to assist agglomeration.
[0041] The agglomerated slurry (214), comprising agglomerates and a low solids
bitumen extract, is sent to a solid-liquid separator (216) to produce a low
solids bitumen
extract (218) and agglomerates (220).
[0042] The following additional steps may also be performed. The low solids
bitumen
extract is sent to a solvent recovery unit (222) to recover solvent (224)
leaving a bitumen
product (226). The agglomerates (220) are sent to a tailings solvent recovery
unit (228) to
recover solvent (230) leaving dry tailings (232).
[0043] In one embodiment, the bituminous feed is dry oil sands, which is
contacted
with extraction liquor that free of bridging liquid in a slurry system to
produce a pumpable
slurry. The slurry may be well mixed in order to dissolve the bitumen. In this
embodiment,
the bitumen is first extracted from the bituminous feed prior to agglomeration
in order to
prevent (or limit) the agglomeration process from hampering the dissolution of
bitumen into
the extraction liquor. In another embodiment, the bridging liquid may be
directly mixed with
the bituminous feed before or at the same time as the extraction liquor so
that bitumen
extraction and agglomeration occur simultaneously. In this embodiment, the
bridging liquid is
added before or at the same time as the extraction liquor in order to minimize
the dispersion
of fines, which may reduce the solids content of the bitumen extract after the
agglomeration
process.
9
CA 02741280 2011-05-27
[0044] In one embodiment, the formed agglomerates are sized on the order of
0.1-
1.0 mm, or on the order of 0.1-0.3 mm. In one embodiment, at least 80 wt.% of
the formed
agglomerates are 0.1-1.0 mm or 0.1 to 0.3 mm in size. The rate of
agglomeration may be
controlled by a balance between intensity of agitation within the
agglomeration vessel, shear
within the vessel which can be adjusted by for example changing the shape or
size of the
vessel, fines content of the slurry, bridging liquid addition, and residence
time of the
agglomeration process.
[0045] The agglomeration of the fines within the slurry plays an important
role in the
recovery of bitumen from the oil sands. Little or no agglomeration of the
fines hampers solid-
liquid separation since fine particles interfere with the filtration process
and/or increase the
solids content of the low solids bitumen extract. However, excess
agglomeration of solids
results in entrapment of bitumen extract within the large agglomerates. Thus,
it is desirable to
control the agglomeration process with a view to achieving the desired
agglomerates, such
as agglomerates of a desired size, density, composition, other parameter, or a
combination
thereof.
[0046] The level of agglomeration will be affected by many factors among the
most
consequential are the composition of the bituminous feed (for instance as a
result of ore
quality), the amount of bridging liquid added, the method by which the
bridging liquid is
added, the residence time of the extraction and agglomeration processes, the
type and
intensity of agitation, the shear environment, the amount of any additional
solids that are
added, and the surface chemistry of the fines. .
[0047] Because the ore quality, a measure of the ore chemistry and physical
characteristics, may change on a very frequent basis as different mine shelves
are
progressed, the recipe for agglomeration may vary resulting in varying
agglomeration. Thus,
it is desirable to use a process that can be adjusted to account for feed
variation and/or the
resultant agglomeration outputs.
[0048] According to one embodiment, the bituminous feed and/or at least one of
the
agglomeration outputs (the agglomerates and the low solids bitumen extract)
are analyzed
as agglomeration proceeds. This information is then used to adjust the
process, for instance
by increasing or decreasing added solids content, adjusting the amount of
bridging liquid
added, adjusting the residence time of the extraction and/or agglomeration
processes,
adjusting intensity of agitation, or adjusting the shear environment to seek
more desired
CA 02741280 2011-05-27
output(s). These parameters may be adjusted individually or in combination in
order to
maximize the effective response of the control system.
[0049] Figure 3 illustrates one embodiment, where the following steps are
performed:
1. Measure (A) properties of the slurry (302) comprised of bituminous
feed and extraction liquor. In another embodiment, the bituminous feed may be
measured
prior to contact with the extraction liquor.
2. Combine the slurry (302) with a bridging liquid (304) and add to an
agglomerator (306).
3. Measure (B) properties of one or more outputs (308) (i.e. the
agglomerates and the low solids bitumen extract) of the agglomeration process.
The
measurement may be performed continuously.
4. Use the measurements in a controls system (310) to adjust a
parameter of the process. One option is to adjust the amount of bridging
liquid (304) that is
added to the slurry. Another option is to adjust the composition of the
bridging liquid added
to the slurry. Another option is to adjust the methods and locations of the
bridging liquid
addition in the process. Another option is to adjust the solid content of the
slurry. Another
option is to adjust the intensity of agitation of the slurry. Another option
is to adjust the
residence time of the extraction process. Another option is to adjust the
residence time of
the agglomeration process. Yet another option is to adjust the shear
environment of the
agglomeration by changing for example the size or shape of the vessel.
[0050] Measurable properties of a bituminous feed which could be used include
but
are not limited to: (i) fines content, (ii) moisture content, (iii) level of
insoluble organics, (iv)
quantity of bitumen present, (v) clays content, (vi) clay chemistry, (vii)
particle size
distribution, (viii) density, (ix) electrical properties such as conductivity.
Standard tests are
available for all of these measurements; for example methylene blue testing is
a well known
method that can be used to quantify the quantity of clays in the oil sands
ore.
[0051] Measurable properties of the outputs of the solvent extraction with
solids
agglomeration process include but are not limited to: (i) particle size
distribution of output
solids, (ii) filtration rate of slurry, (iii) fines content of the low solids
bitumen extract, (iv)
bitumen content of low solids bitumen extract, and (v) viscosity (rheology) of
the slurry. The
values of these properties are strongly impacted by the solvent extraction
process and thus
can be used in the control system described herein. Other measurable
properties include:
(vi) hydrocarbon content of the output solids, (vii) moisture content of
agglomerates, (viii)
11
CA 02741280 2011-05-27
attrition and/or strength of the agglomerated solids, (ix) electrical
properties, and (x) yield
strength of the slurry.
[0052] Particle Size Distribution Property. The particle size distribution of
the
output solids can be measured by integrating an on-line particle size
measurement device
such as a Retsch Technology Camizer. A slip stream can be taken from the
slurry, filtered to
remove liquid, and then measured to analyze particle size distribution. The
particle size
distribution of output agglomerates may have a measured D50 of between 100
microns and
300 microns, or the agglomerates might have a measured D50 of between 300 and
1000
microns, or the agglomerates might have a measured D50 of between 1000 and
2000
microns. It is preferable that the measured D50 be between 100 and 300 microns
because
such a particle size distribution would insure good solid-liquid separation
rate while reducing
the entrapment of bitumen extract within the pores of the agglomerates.
[0053] Filtration Rate Property. The filtration rate of the slurry can be
measured by
integrating an on-line filtration device with the pipeline. A slip stream can
be taken from the
slurry and the rate of filtration can be measured, or alternatively the
filtration rate may be
directly measured if a filtration process is included in the processing of the
slurry in the solid-
liquid separator. In the case of a slip stream filtration, the filter medium
should be similar in
material and pore size to that which is used in the solid-liquid separator.
Exemplary filtration
device include, but are not limited to, lab scale chamber presses and
diaphragm filter
presses. The filtration rate of the slurry is preferably in the range of 0.2
to 1 mUcm2sec.
Higher filtration rates may be suitable; however, care should be taken to
ensure that such
filtration rates are not due to excessive channeling.
[0054] Fines Content Property. The fines content of the low solids bitumen
extract
may be measured using several methods that are well known in the art. However,
a method
that quickly measures the solid content is preferable. Such a method may
involve taking a
slip stream of the slurry and filtering it to produce a low solids bitumen
extract or directly
sampling the low solids bitumen extract from the solid-liquid separator. The
density of the
bitumen extract and a micro-filtered bitumen extract is then measured. The
bitumen extract
can be filtered through a micro-filter with a nominal pore size of 0.45
microns. Suitable
density measuring devices include vibration type liquid density meters. The
difference in
density of the bitumen extract and micro-filtered bitumen extract can be
correlated with solid
content, S by using following equation :
12
CA 02741280 2011-05-27
1 i
S = T PE
1 1
Ps PE
where Pr is the measured density of the low solids bitumen extract and PE is
the measured
density of the micro-filtered bitumen extract. ps is the solid density that
may be obtained by
experimental calibration or approximated to have a value between 2.3 to 2.6
g/cm3. The
solid content of the low solids bitumen extract is preferably less than 2 wt%,
or preferably
less than 1 wt%, or even more preferably less than 0.5 wt%.
[0055] Still another method of measuring the fines content may be an optical
method,
such as to dilute a low solids bitumen extract stream with excess solvent and
then measure
the turbidity of bitumen extract and micro-filtered bitumen extract. The
difference in turbidity
may be calibrated with fines content of the low solids bitumen extract.
[0056] Bitumen Content Property. During the extraction process as bitumen from
the oil sands dissolves into the extraction liquor, the density of the low
solids bitumen extract
increases. The bitumen content of the low solids bitumen extract can be
estimated by
measuring the density of the low solids bitumen extract. A slip stream can be
taken from the
slurry and filtered to produce the low solids bitumen extract or the low
solids bitumen extract
can be sampled from the output of the solid-liquid separator. The low solids
bitumen extract
can be filtered through a micro-filter with a nominal pore size of 0.45
microns to obtain a
solid-free bitumen extract. The density of the solid-free bitumen extract can
be measured
using an on-line density meter. The density of the bitumen extract can then be
used to
approximate the bitumen content of the solid-free bitumen extract. Figure 7 is
a calibration
curve relating bitumen content of a bitumen extract comprised of bitumen and
solvent to the
measured density of the bitumen extract. The measurement can also be used to
determine
the degree of bitumen extraction from the oil sands at different points along
the extraction
and agglomeration processes.
[0057] Viscosity Property. The particle size distribution of the oil sands
slurry has a
strong impact on the viscosity of the slurry. Slurries with a high fines
content is expected to
have a high viscosity. The slurry viscosity is expected to decrease as the
average particle
size of the slurry increases. Additionally, since a hydrocarbon phase is the
continuous fluid
in the slurry, water chemistry will have much less of an impact on the
viscosity/rheology
behavior of the slurry compared to the impact water chemistry has on the
viscosity/rheology
13
CA 02741280 2011-05-27
of water-based extraction slurries. This fact makes correlation of particle
size distribution with
rheology much simpler for the oil sands slurries described herein. Thus, in
one embodiment,
measurement of the viscosity of the slurry can be used to estimate the amount
of fines in the
oil sands slurry and therefore used to control, for example, the amount of
bridging added to
the slurry. This measurement can be obtained in a simple viscometer or in a
rheometer.
Other related tests can also be used, such as a flow rate test.
[0058] In another embodiment, measurement of the rheology of the slurry can be
used to determine the progression of the agglomeration process. For example,
after the
bridging liquid is added to the slurry and agitated, a rapid increase in the
viscosity of the
slurry may indicate excessive agglomerate growth that has led to the trapping
of a significant
amount of bitumen extract within the agglomerates. Conditions that lead to
such behavior
should be limited or avoided since they can lead to poor bitumen recovery. The
control
system described herein can be used to change process parameters, such as the
amount of
bridging liquid addition, when the viscosity of the slurry is measured to
rapidly increase. In
another example, the viscosity or rheometer measurement can be used to track
the growth of
agglomerates. In cases when the formed agglomerates are compact, the growth of
agglomerates may be accompanied by a gradual reduction in slurry viscosity or
dynamic
shear strength. Thus, the change in slurry viscosity may correlate well with
agglomerate
growth.
[0059] The viscosity of the oil sand slurry may be measured with any suitable
instrument that is well known in the art. For example, an automatic on-line
viscometer, which
takes a slip stream from the slurry and measures the viscosity, can be used.
An in-line
viscometer, such as a vibrating-type viscometer, can be used to provide
instant viscosity
measurements within the process slurry. In another example, the torque is
measured in the
agitation process, and rheological measurements could be determined in-situ.
That is, if a
mixing vessel is used for the agglomerator, the torque applied to the vessel
can be measured
as an indicator of rheological properties such as viscosity.
[0060] Various other properties of the bituminous feed, or the outputs could
be
alternatively or additionally be measured.
[0061] In another embodiment, the following steps may be performed:
1. Drill ore cores in advance of mining trucks to determine the quality of the
ore.
14
CA 02741280 2011-05-27
2. As shovels proceed through a seam, obtain further data to characterize the
ore. Send the ore to the extraction process, characterized as low, medium, or
high fines
content, or along another rating system.
3. Combine the oil sands with an extraction liquor and a bridging liquid in an
agglomerator. The extraction liquor comprises a solvent used to dissolve
bitumen. The
bridging liquid is used to assist agglomeration. The bridging liquid may be
water or a sludge
from a water-based extraction process. Suitable sludge steams include, but are
not limited
to, water-based extraction streams such as middling from primary separation,
secondary and
tertiary separation tailings, froth treatment tailings, mature fine tailings
from tailings ponds, or
a new stream resulting from passing any of these streams through a thickener,
hydrocyclone,
or other processes. For example, middlings passed through a cyclone might
generate an
overflow stream and an underflow stream. Either stream could be used in this
process as
bridging liquid. The amount of bridging liquid that is added will affect the
extent of
agglomeration. Agitation is also used to assist agglomeration.
4. Adjust one or more process parameters based on one or more output
properties. One process parameter is the amount of bridging liquid that is
added to the
slurry. Another process parameter is the solid content of the bridging liquid
added to the
slurry. Another process parameter is the methods and locations of the bridging
liquid
addition in the process. Another process parameter is the solid content of the
slurry. Another
process parameter is the intensity of agitation of the slurry. Another process
parameter is
the shear environment of the agglomerator. Another process parameter is the
residence
time of the extraction process. Yet another option process parameter is the
residence time
of the agglomeration process. Potential output properties include particle
size distribution of
the produced agglomerates, filtration rate of the slurry, solids content of
the low solids
bitumen extract, bitumen content of low solids bitumen extract, and the
viscosity of the
slurry,. The adjustments to the process parameters may be made based on the
real time
measurements of physical properties of the output(s) of the agglomeration
process, which
result in a feedback. In one embodiment, the feedback loop is a negative
feedback, since the
desired outputs of the agglomeration process may be set to one or more given
target ranges
and the input parameters may be adjusted to maintain the output parameters in
the target
range(s) regardless of type of ore feed and process upsets. The expression
"target range"
as used herein may include a range such as between X and Y, but also may
include a range
such as at least Z, or a range such as less than W.
CA 02741280 2011-05-27
[0062] In one embodiment, the characterization of fines content comprises a
methylene blue test. In another embodiment, the characterization of fines
comprises a
particle size distribution analysis. In another embodiment, the
characterization of fines
comprises viscosity/rheology tests of oil sands slurry. In another embodiment,
the ore (or
bituminous feed) is characterized by bitumen content rather than, or in
addition to, fines
content. In another embodiment, the ore (or bituminous feed) is characterized
by
spectroscopy, photoluminescence, fluorescence, or other photoactive
technology. In another
embodiment, the ore (or bituminous feed) is characterized by water chemistry
and/or
quantity. In yet another embodiment, the output solids are characterized by
particle size
distribution using sieves, laser diffraction, optical analysis, or other size
quantification
technique. In another embodiment, the hydrocarbon content of the output stream
is
measured by a bomb calorimeter, gas chromatography, photo activity such as
phosphorescence or other photon technique, particle sniffer, or other
technology. In another
embodiment, the moisture content is measured by any type of technique suitable
to measure
water content, including but not limited to a bomb calorimeter, Karl Fischer
Titration, Deen
Stark analysis, electrical conductivity, relative humidity, or any other
technique. In one
embodiment, the analysis is performed in conjunction with batch analysis at
intervals. In
another embodiment, a slip stream is sampled for analysis. In another
embodiment, on-line
analysis provides continuous information.
[0063] In another embodiment, the bridging liquid is adjusted based on a
measured
property. The following steps may be performed, with reference to Figure 4:
1. Adding the slurry (402) comprised of bituminous feed and extraction liquor
to an agglomerator (404).
2. Providing two different streams of bridging liquid (406 and 408) to the
agglomerator (404) to form an agglomerated slurry (410).
3. Based on information on the quality of the oil sand ore (or bituminous
feed)
or the quality of one or more output streams (i.e. the low solids bitumen
extract or the
agglomerates) or both, adjusting (using a control point (412)) one or both of
the flow rates of
bridging liquid.
[0064] In one embodiment, the first bridging liquid comprises water and the
second
bridging liquid comprises sludge produced from the aqueous extraction of
bitumen from oil
sands.
16
CA 02741280 2011-05-27
[0065] In another embodiment, as shown in Figure 5, first and second bridging
liquids
are mixed before they are introduced into the agglomerator. The slurry
comprised of
bituminous feed and extraction liquor (together 502) is added to an
agglomerator (504). The
first bridging liquid (506) and second bridging liquid (508) are mixed to form
a mixed bridging
liquid (514) and added to the agglomerator (504)) to form an agglomerated
slurry (510).
Based on information on the quality of the oil sand ore (or bituminous feed)
or the quality of
one or more output streams (i.e. the low solids bitumen extract or the
agglomerates) or both,
one or both of the flow rates of bridging liquids (506 and 508) are adjusted
(using a control
point (512)). In yet another embodiment, the first and second bridging liquids
are mixed in
the agglomerator.
[0066] In another embodiment, as shown in Figure 6, the properties of the
agglomeration process are adjusted through the recycling of agglomerator
output upstream
of the agglomeration process. For example, the agglomerated slurry could be
recycled
through the process to affect the residence time of the agglomeration process.
The
agglomerated solids could also be recycled through the process to increase the
solids
content of the feed slurry. Additionally, the agglomerated solids could be
recycled through
the process to provide seed particles within the bridging liquid for the
agglomeration process.
First, properties of the bituminous feed and extraction liquor (602) are
measured (A). In
another embodiment, the bituminous feed may be measured prior to contact with
the
extraction liquor. The bridging liquid (604) is added to the agglomerator
(606) to produce
outputs (608) (i.e. the agglomerates and the low solids bitumen extract) of
the agglomeration
process. One or more properties of the outputs are measured (B). The
measurements may
be performed continuously. The measurements (A and B) are used in a control
system (610)
to adjust a parameter of the process, for instance the amount and/or
composition of an input.
For instance, a portion of the agglomerated solids (611) could be recycled
back into the
process to adjust effective residence time and/or increase solids content.
[0067] In another embodimenrthe at least one property further comprises at
least
one property of the slurry prior to agglomeration.
[0068] Agitation. Agglomeration is assisted by some form of agitation. The
form of
agitation may be mixing, shaking, rolling, or another known suitable method.
The agitation of
the feed need only be severe enough and of sufficient duration to intimately
contact the
emulsion with the solids in the feed. Exemplary rolling type vessels include
rod mills and
tumblers. Exemplary mixing type vessels include mixing tanks, blenders, and
attrition
17
CA 02741280 2011-05-27
scrubbers. In the case of mixing type vessels, a sufficient amount of
agitation is needed to
keep the formed agglomerates in suspension. In rolling type vessels, the
solids content of
the feed is, in one embodiment, greater than 40 wt.% so that compaction forces
assist
agglomerate formation. The agitation of the slurry has an impact on the growth
of the
agglomerates. In the case of mixing type vessels, the mixing power can be
increased in
order to limit the growth of agglomerates by attrition of said agglomerates.
In the case of
rolling type vessels the fill volume and rotation rate of the vessel can be
adjusted in order to
increase the compaction forces used in the comminution of agglomerates. These
agitation
parameters can be adjusted in the control system described herein.
[0069] Extraction Liquor. The extraction liquor comprises a solvent used to
extract
bitumen from the bituminous feed. The term "solvent" as used herein should be
understood
to mean either a single solvent, or a combination of solvents.
[0070] In one embodiment, the extraction liquor comprises a hydrocarbon
solvent
capable of dissolving the bitumen. The extraction liquor may be a solution of
a hydrocarbon
solvent(s) and bitumen, where the bitumen content of the extraction liquor may
range
between 10 to 50 wt%. It may be desirable to have dissolved bitumen within the
extraction
liquor in order to increase the volume of the extraction liquor without an
increase in the
required inventory of hydrocarbon solvent(s). In cases where non-aromatic
hydrocarbon
solvents are used, the dissolved bitumen within the extraction liquor also
increases the
solubility of the extraction liquor towards dissolving additional bitumen.
[0071] The extraction liquor may be mixed with the bituminous feed to form a
slurry
where most or all of the bitumen from the oil sands is dissolved into the
extraction liquor. In
one embodiment, the solids content of the slurry is in the range of 10 wt% to
75 wt%, or 50 to
65 wt%. A slurry with a higher solids content may be more suitable for
agglomeration in a
rolling type vessel, where the compressive forces aid in the formation of
compact
agglomerates. For turbulent flow type vessels, such as an attrition scrubber,
a slurry with a
lower solids content may be more suitable.
[0072] The solvent used in the process may include low boiling point solvents
such
as low boiling point cycloalkanes, or a mixture of such cycloalkanes, which
substantially
dissolve asphaltenes. The solvent may comprise a paraffinic solvent in which
the solvent to
bitumen ratio is maintained at a level to avoid or limit precipitation of
asphaltenes.
[0073] 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
18
CA 02741280 2011-05-27
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.
[0074] The solvent selected according to certain embodiments may comprise an
organic solvent or a mixture of organic solvents. For example, the solvent may
comprise a
paraffinic solvent, an open chain aliphatic hydrocarbon, a cyclic aliphatic
hydrocarbon, or a
mixture thereof. Should a paraffinic solvent be utilized, it may comprise an
alkane, a natural
gas condensate, a distillate from a fractionation unit (or diluent cut), or a
combination of
these containing more than 40% small chain paraffins of 5 to 10 carbon atoms.
These
embodiments would be considered primarily a small chain (or short chain)
paraffin mixture.
Should an alkane be selected as the solvent, the alkane may comprise a normal
alkane, an
iso-alkane, or a combination thereof. The alkane may specifically comprise
heptane, iso-
heptane, hexane, iso-hexane, pentane, iso-pentane, or a combination thereof.
Should a
cyclic aliphatic hydrocarbon be selected as the solvent, it may comprise a
cycloalkane of 4 to
9 carbon atoms. A mixture of C4-C9 cyclic and/or open chain aliphatic solvents
would be
appropriate.
[0075] Exemplary cycloalkanes include cyclohexane, cyclopentane, or a mixture
thereof.
[0076] If the solvent is selected as the distillate from a fractionation unit,
it may for
example be one having a final boiling point of less than 180 C. An exemplary
upper limit of
the final boiling point of the distillate may be less than 100 C.
[0077] 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 hydrocarbons
in the mixture is
greater than 50%.
[0078] Extraction liquor may be recycled from a downstream step. For instance,
as
described below, solvent recovered in a solvent recovery unit, may be used to
wash
agglomerates, and the resulting stream may be used as extraction liquor. As a
result, the
extraction liquor may comprise residual bitumen and residual solid fines. The
residual
bitumen increases the volume of the extraction liquor and it may increase the
solubility of the
extraction liquor for additional bitumen dissolution.
[0079] The solvent may also include additives. These additives may or may not
be
considered a solvent per se. Possible additives may be components such as de-
emulsifying
agents or solids aggregating agents. Having an agglomerating agent additive
present in the
19
CA 02741280 2011-05-27
bridging liquid and dispersed in the first solvent may be helpful in the
subsequent
agglomeration step. Exemplary agglomerating agent additives include cements,
fly ash,
gypsum, lime, brine, water softening wastes (e.g. magnesium oxide and calcium
carbonate),
solids conditioning and anti-erosion aids such as polyvinyl acetate emulsion,
commercial
fertilizer, humic substances (e.g. fulvic acid), polyacrylamide based
flocculants and others.
Additives may also be added prior to gravity separation with the second
solvent to enhance
removal of suspended solids and prevent emulsification of the two solvents.
Exemplary
additives include methanoic acid, ethylcellulose and polyoxyalkylate block
polymers.
[0080] Bridging Liquid. A bridging liquid is a liquid with affinity for the
solids particles
in the bituminous feed, and which is immiscible in the solvent. Exemplary
aqueous liquids may
be recycled water from other aspects or steps of oil sands processing. The
aqueous liquid
need not be pure water, and may indeed be water containing one or more salt, a
waste
product from conventional aqueous oil sand extraction processes which may
include additives,
aqueous solutions with a range of pH, or any other acceptable aqueous solution
capable of
adhering to solid particles within an agglomerator in such a way that permits
fines to adhere to
each other. An exemplary bridging liquid is water.
[0081] The total amount of bridging liquid added to the slurry may be
controlled in
order to optimize bitumen recovery and the rate of solid-liquid separation.
The value will
depend on the measured properties described herein. By way of examples, the
total amount
of bridging liquid added to the slurry may be such that a ratio of bridging
liquid plus connate
water from the bituminous feed to solids within the agglomerated slurry is in
the range of 0.02
to 0.25, or in the range of 0.05 to 0.11. In one embodiment, the bridging
liquid to solids ratio
may be obtained by feedback control.
[0082] In one embodiment, the bridging liquid may contain fine particles
(sized less
than 44 pm) suspended therein. These fine particles may serve as seed
particles for the
agglomeration process. In one embodiment, the bridging liquid has a solids
content of less
than 40 wt.%. The bridging liquid and fines particles slurry is also referred
to herein as
sludge from a water-based extraction process. Suitable sludge steams include,
but are not
limited to, water-based extraction streams such as middling from primary
separation,
secondary and tertiary separation tailings, froth treatment tailings, mature
fine tailings from
tailings ponds, or a new stream resulting from passing any of these streams
through a
thickener, hydrocyclone, or other processes. For example, middlings passed
through a
cyclone might generate an overflow stream and an underflow stream. Either
stream could be
CA 02741280 2011-05-27
used in this process as bridging liquid. Sludge may also be produced within
the solvent
extraction with solids agglomeration process by mixing bridging liquid with
agglomerated
tailings. In this way, a portion of the agglomerated solids are recycled
through the process.
The use of bridging liquid with a significant solid content, such as that
which is described
above, may allow for greater control of the agglomeration process. Previous
work has
shown that when sludge is used as the bridging liquid, the addition of the
same amount o
sludge per unit weight of oil sands feed resulted in the production of
agglomerates of the
same drainage properties regardless of oil sands quality.
[0083] The bridging liquid may be added after the production of the oil sands
slurry or
before the production of the oil sands slurry. In the former scenario, the
bitumen is first
extracted from the bituminous feed prior to agglomeration in order to prevent
(or limit) the
agglomeration process from hampering the dissolution of bitumen into the
extraction liquor,
which may increase bitumen recovery. In the latter scenario, the bridging
liquid may be
directly mixed with the bituminous feed before or at the same time as the
extraction liquor in
order to minimize the dispersion of fines, which may reduce the solids content
of the bitumen
extract after the agglomeration process. The control system described herein
can be used to
control where in the solvent extraction with solids agglomeration process the
bridging liquid is
added based on the output of the process. The bridging liquid may comprise
less than 40
wt% solids fines. The agglomerated slurry may have a solids content of 20 to
70 wt %.
[0084] Ratio of Solvent to Bitumen for Agglomeration. The process may be
adjusted to render the ratio of the solvent to bitumen in the agglomerator at
a level that
avoids precipitation of asphaltenes during agglomeration. Some amount of
asphaltene
precipitation is unavoidable, but by adjusting the amount of solvent flowing
into the system,
with respect to the expected amount of bitumen in the bituminous feed, when
taken together
with the amount of bitumen that may be entrained in the extraction liquor
used, can permit
the control of a ratio of solvent to bitumen in the agglomerator. When the
solvent is assessed
for an optimal ratio of solvent to bitumen during agglomeration, the
precipitation of
asphaltenes can be minimized or avoided beyond an unavoidable amount. Another
advantage of selecting an optimal solvent to bitumen ratio is that when the
ratio of solvent to
bitumen is too high, costs of the process may be increased due to increased
solvent
requirements.
[0085] 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,
21
CA 02741280 2011-05-27
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.
[0086] Measurement of the solvent and bitumen content of the extraction liquor
and/or bitumen extract could occur directly or by proxy. Direct measurement of
solvent and
bitumen content could involve evaporating off the solvent and measuring the
mass of both
liquids, or use of a gas chromatograph, mass balance, spectrometer, or
titration. Indirect
measurement of solvent and bitumen content could include measuring : density,
the index of
refraction, opacity, or other properties.
[0087] Slurry System. The slurry system may optionally be a mix box, a pump,
or a
combination of these. By slurrying the extraction liquor together with the
bituminous feed,
and optionally with additional additives, the bitumen entrained within the
feed is given an
opportunity to become extracted into the solvent phase prior to agglomeration
within the
agglomerator.
[0088] The resulting slurry from the slurry system may have a solid content in
the
range of 20 to 65 wt%. In another embodiment, the slurry may have a solid
content in the
range of 20 to 50 wt%. In another embodiment, the slurry may have a solid
content in the
range of 40 to 65 wt%. In the case of mixing type vessels, a lower solid
content may be
preferred since that will assist in the proper mixing of the bridging liquid
and reduce the
mixing energy needed to keep the slurry well mixed. In the case of rolling
type vessels, a
higher solid content may be preferred since that will increase the compaction
forces used in
the comminution of agglomerates. Additionally, the increased compaction forces
may reduce
the amount of hydrocarbons that remain in the agglomerates and produce
stronger
agglomerates.
[0089] The preferred temperature of the slurry is in the range of 20-60 C. An
elevated slurry temperature is desired in order to increase the bitumen
dissolution rate and
reduce the viscosity of the slurry to promote more effective sand digestion
and agglomerate
formation. Temperatures above 60 C are generally avoided due to the
complications
resulting from high vapor pressures.
[0090] Residence Time. The residence time of the extraction and agglomeration
processes has a strong impact on the bitumen extract and agglomerated solids.
Batch
experiments within a mixing vessel were conducted to test the affects of
residence time.
22
CA 02741280 2011-05-27
Figure 8 (as described further below) shows that the bitumen recovery and the
initial liquid
filtration rate increases as the extraction time increases for batch
experiments conducted
with the agglomeration time kept constant at 2 minutes. Thus, increasing the
residence time
of the extraction process may result in an increase in both the bitumen
recovery and the rate
of solid-liquid separation. In contrast, as Figure 9 (as described further
below) shows, the
bitumen recovery reaches a maximum and then decreases as the agglomeration
time
increases for batch experiments conducted with the extraction time kept
constant at 5
minutes. The decrease in recovery beyond the maximum recovery is most likely
due to
excessive agglomerate growth that leads to entrapment of the bitumen extract
within the
agglomerates. However, this growth of agglomerates does result in an increase
in the initial
filtration rate as the agglomeration time increases.
[0091] The results plotted in Figure 8 and Figure 9 demonstrate the impact
that
residence time of the extraction and agglomeration processes have on the
bitumen extract
and agglomerated solids.
[0092] ,As shown in Figure 10, the recycle loops, (1020) and (1022) can be
used in
the control system described herein to adjust the effective residence time
within the slurry
system (1005) and agglomerator (1006). First, properties of the bituminous
feed and
extraction liquor (1002) are measured (A). In another embodiment, the
bituminous feed may
be measured prior to contact with the extraction liquor. The bridging liquid
(1004) is added to
the slurry system (1005) and the slurry is passed to the agglomerator (1006)
to produce
outputs (1008) (i.e. the agglomerates and the low solids bitumen extract) of
the
agglomeration process. One or more properties of the outputs (1008) are
measured (B).
The measurements may be performed continuously. The measurements (A and B) are
used
in a control system (1010) to adjust a parameter of the process, for instance
the amount
and/or composition of an input. For instance, a portion of the agglomerated
solids (1022) or
a portion of the slurry prior to agglomeration (1020) could be recycled back
into the process
to adjust effective residence time and/or increase solids content.
[0093] The results plotted in Figure 8 and Figure 9 also suggest that it is
preferable
for the residence time of the extraction process be greater or much greater
than the
residence time of the agglomeration process. The extraction process may occur
in the slurry
system and the agglomeration process may occur in the agglomerator. The
residence time of
the extraction process may be greater than 5 minutes, or may be greater than
10 minutes, or
may be greater than 15 minutes, or may greater than 30 minutes. Depending on
the desired
23
CA 02741280 2011-05-27
level of agglomeration, the residence time of the agglomeration process may be
in the range
of 15 seconds to 10 minutes. In order to maximize bitumen recovery, the
residence time of
the agglomeration process may be in the range of 1 to 5 minutes.
[0094] Solid-Liquid Separator. As described above, the agglomerated slurry may
be separated into a low solids bitumen extract and agglomerates in a solid-
liquid separator.
The solid-liquid separator may comprise any type of unit capable of separating
solids from
liquids, so as to remove agglomerates. Exemplary types of units include a
gravity separator,
a clarifier, a cyclone, a screen, a belt filter or a combination thereof.
[0095] 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.
[0096] Non-limiting methods of solid-liquid separation of an agglomerated
slurry are
described in Canadian Patent Application Serial No. 2,724,806 (Adeyinka et
al.), filed
December 10, 2010.
[0097] Secondary Stage of Solid-Liquid Separation to Wash Agglomerates. As a
component of the solid-liquid separator, a secondary stage of separation may
be introduced
for countercurrently washing the agglomerates separated from the agglomerated
slurry. The
initial separation of agglomerates may be said to occur in a primary solid-
liquid separator,
while the secondary stage may occur within the primary unit, or may be
conducted
completely separately in a secondary solid-liquid separator. By
"countercurrently washing", it
is meant that a progressively cleaner solvent is used to wash bitumen from the
agglomerates. Solvent involved in the final wash of agglomerates may be re-
used for one or
more upstream washes of agglomerates, so that the more bitumen entrained on
the
agglomerates, the less clean will be the solvent used to wash agglomerates at
that stage.
The result being that the cleanest wash of agglomerates is conducted using the
cleanest
solvent.
[0098] 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
24
CA 02741280 2011-05-27
primary solid-liquid separator. The secondary solid-liquid separator may
optionally be a
gravity separator, a cyclone, a screen or belt filter. Further, a secondary
solvent recovery
unit for recovering solvent arising from the solid-liquid separator can be
included. The
secondary solvent recovery unit may be a conventional fractionation tower or a
distillation
unit.
[0099] 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.
[00100] The solvent used for washing the agglomerates may be solvent recovered
from the low solids bitumen extract, as described with reference to Figures 2
to 4. A second
solvent may alternatively or additionally be used as described in Canadian
Patent Application
Serial No. 2,724,806 (Adeyinka et al.) for additional bitumen extraction
downstream of the
agglomerator.
[00101] Recycle and Recovery of Solvent. The process may involve removal and
recovery of solvent used in the process.
[00102] In this way, solvent is used and re-used, even when a good deal of
bitumen is
entrained therein. Because an exemplary solvent:bitumen ratio in the
agglomerator may be
2:1 or lower, it is acceptable to use recycled solvent containing bitumen to
achieve this ratio.
The amount of make-up solvent required for the process may depend solely on
solvent
losses, as there is no requirement to store and/or not re-use solvent that has
been used in a
previous extraction step. When solvent is said to be "removed", or
"recovered", this does not
require removal or recovery of all solvent, as it is understood that some
solvent will be
retained with the bitumen even when the majority of the solvent is removed.
[00103] The system may contain a single solvent recovery unit for recovering
the
solvent(s) arising from the gravity separator. The system may alternatively
contain more than
one solvent recovery unit.
[00104] Solvent may be recovered by conventional means. For example, typical
solvent recovery units may comprise a fractionation tower or a distillation
unit. The solvent
recovered in this fashion will not contain bitumen entrained therein. This
clean solvent is
preferably used in the last wash stage of the agglomerate washing process in
order that the
cleanest wash of the agglomerates is conducted using the cleanest solvent.
[00105] The solvent recovered in the process may comprise entrained bitumen
therein, and can thus be re-used as the extraction liquor for combining with
the bituminous
CA 02741280 2011-05-27
feed. Other optional steps of the process may incorporate the solvent having
bitumen
entrained therein, for example in countercurrent washing of agglomerates, or
for adjusting
the solvent and bitumen content prior to agglomeration to achieve the selected
ratio within
the agglomerator that avoids precipitation of asphaltenes.
[00106] Dilution of Agglomerator Discharge to Improve Product Quality. Solvent
may be added to the agglomerated slurry for dilution of the slurry before
discharge into the
primary solid-liquid separator, which may be for example a deep cone settler.
This dilution
can be carried out in a staged manner to pre-condition the primary solid-
liquid separator feed
to promote higher solids settling rates and lower solids content in the solid-
liquid separator's
overflow. The solvent with which the slurry is diluted may be derived from
recycled liquids
from the liquid-solid separation stage or from other sources within the
process.
[00107] When dilution of agglomerator discharge is employed in this
embodiment, the
solvent to bitumen ratio of the feed into the agglomerator is set to obtain
from about 10 to
about 90 wt% bitumen in the discharge, and a workable viscosity at a given
temperature. In
certain cases, these viscosities may not be optimal for the solid-liquid
separation (or settling)
step. In such an instance, a dilution solvent of equal or lower viscosity may
be added to
enhance the separation of the agglomerated solids in the clarifier, while
improving the quality
of the clarifier overflow by reducing viscosity to permit more solids to
settle. Thus, dilution of
agglomerator discharge may involve adding the solvent, or a separate dilution
solvent, which
may, for example, comprise an alkane.
[00108] In the preceding description, for purposes of explanation, numerous
details
are set forth in order to provide a thorough understanding of the embodiments.
However, it
will be apparent to one skilled in the art that these specific details are not
required.
[00109] Control Systems. Embodiments of the disclosure can be represented as a
computer program product stored in a machine-readable medium (also referred to
as a
computer-readable medium, a processor-readable medium, or a computer usable
medium
having a computer-readable program code embodied therein). The machine-
readable
medium can be any suitable tangible, non-transitory medium, including
magnetic, optical, or
electrical storage medium including a diskette, compact disk read only memory
(CD-ROM),
memory device (volatile or non-volatile), or similar storage mechanism. The
machine-
readable medium can contain various sets of instructions, code sequences,
configuration
information, or other data, which, when executed, cause a processor to perform
steps in a
method according to an embodiment of the disclosure. Those of ordinary skill
in the art will
26
CA 02741280 2011-05-27
appreciate that other instructions and operations necessary to implement the
described
implementations can also be stored on the machine-readable medium. The
instructions
stored on the machine-readable medium can be executed by a processor or other
suitable
processing device, and can interface with circuitry to perform the described
tasks.
[00110] The above-described embodiments are intended to be examples only.
Alterations, modifications and variations can be effected to the particular
embodiments by
those of skill in the art without departing from the scope, which is defined
solely by the claims
appended hereto.
[00111] Batch Experiments. Experiments were conducted to test the effects of
varying residence time on the extraction and agglomeration processes. The
initial liquid
drainage rate of the formed agglomerates and bitumen recovery from the oil
sands were
used as the experimental measurements to determine the effectiveness of the
solvent
extraction with solids agglomeration process. The agglomerates were also
visually inspected
for their size and uniformity.
[00112] Medium grade Athabasca oil sand was used in these experiments. The oil
sands had a bitumen content of 9.36 wt% and a water content of 4.66 wt%. The
percentage
of fines (< 44 m) that make up the solids was approximately 25 wt%. The oil
sands were
kept at -20 C until they were ready for use. A solution of cyclohexane and
bitumen was
used as the extraction liquor. The percentage of bitumen in the extraction
liquor was 24
wt%. Distilled. water was used as the bridging liquid. For each experiment a
total of 350g of
oil sands, 235.07g of extraction liquor, and a total of 16.8g of water were
used. This
composition translated to a solids content of 50 wt% and a water to solids
ratio of 0.11 for the
agglomerated slurry.
[00113] A Parr reactor (series 5100) (Parr Instrument Company, Moline, IL,
USA) was
used as the extractor and agglomerator. The reactor vessel was made of glass
that permits
direct observation of the mixing process. A turbine type impeller powered by
an explosion
proof motor of 0.25 hp was used. The mixing and agglomeration speed of the
impeller were
set to 1500 rpm. This rotation speed allowed the slurry to remain fluidized at
all conditions of
the experiments. The agglomeration experiments were conducted at room
temperature (22
C).
[00114] The agglomerated solids produced in these experiments were treated in
a
Soxhlet extractor combined Ah Dean-Stark azeotropic distillation, to determine
the material
contents of the agglomerated slurry. Toluene was used as the extraction
solvent. The oil
27
CA 02741280 2011-05-27
sand solids were dried overnight in an oven (100 C) and then weighed to
determine the
solids content of the agglomerated slurry. The water content was determined by
measuring
the volume of the collected water within the side arm of the Dean-Stark
apparatus. The
bitumen content of the agglomerated slurry was determined by evaporating the
toluene and
residual cyclohexane from an aliquot of the hydrocarbon extract from the
Soxhlet extractor.
[00115] The initial liquid drainage rate was calculated by measuring the time
needed
to drain 50 mL of bitumen extract above the bed of agglomerated solids.
[00116] The effects of extraction residence time on the solvent extraction
with
solids agglomeration process. 350g of oil sands and 235.07g of extraction
liquor were
placed into the Parr reactor vessel. The solids and solvent were mixed at 1500
rpm for a
given extraction residence time to homogenize the mixture and to extract the
bitumen that
was in the oil sands. The extraction times tested were 0.5, 1, 2, 5, 15, and
30 minutes. After
the extraction time elapsed, 16.8g of water was quickly pored into the vessel
through a
sample port. The mixture was then mixed at 1500 rpm for an additional 2
minutes to
agglomerate the solids.
[00117] After the agglomeration process, the impeller was turned off and the
agglomerates were allowed to settle for over 1 minute. The supernatant
(bitumen extract)
was poured into a separate container and the wet solids were transferred to a
Buchner
funnel. The solids rested on a filter paper with a nominal pore size of 170
m. The filter's
effective area was approximately 8 cm2. The solids bed height was 10.8 cm. A
portion of the
collected supernatant was poured on top of the solids until a liquid height of
1.9 cm formed
above the solids surface. A light vacuum was then applied to the Buchner
funnel and the
initial drainage rate of the liquid was recorded.
[00118] The remaining supernatant was poured onto the solid bed and allowed to
filter
through. 211 mL of pure cyclohexane was then filtered through the solid bed in
order to
wash the agglomerates. The solid bed was then allowed to drain of liquid under
a light
vacuum for about 30 seconds. The bitumen content of the washed solids was then
measured
to determine the bitumen recovery of the solvent extraction process.
[00119] Figure 8 plots the bitumen recovery and the initial liquid filtration
rate as a
function of the extraction residence time. The figure shows that the bitumen
recovery and the
initial liquid filtration rate increases as the extraction time increases for
batch experiments
conducted with the agglomeration time kept constant at 2 minutes.
28
CA 02741280 2011-05-27
[00120] The effects of agglomeration residence time on the solvent extraction
with solids agglomeration process. 350g of oil sands and 235.07g of extraction
liquor
were placed into the Parr reactor vessel. The solids and solvent were mixed at
1500 rpm for
minutes to fully homogenize the mixture and to fully extract the bitumen that
was in the oil
5 sands. After 5 minutes of mixing, 16.8g of water was quickly pored into the
vessel through a
sample port. The mixture was then mixed at 1500 rpm for a given agglomeration
residence
time to agglomerate the solids. The agglomeration times tested were 0.5, 1, 2,
5, 15, and 30
minutes.
[00121] After the agglomeration process, the impeller was turned off and the
agglomerates were allowed to settle for over 1 minute. The supernatant
(bitumen extract)
was pored into a separate container and the wet solids were transferred to a
Buchner funnel.
The solids rested on a filter paper with a nominal pore size of 170 m. The
filter's effective
area was approximately 8 cm2. The solids bed height was 10.8 cm. A portion of
the
collected supernatant was poured on top of the solids until a liquid height of
1.9 cm formed
above the solids surface. A light vacuum was then applied to the Buchner
funnel and the
initial drainage rate of the liquid was recorded.
[00122] The remaining supernatant was poured onto the solid bed and allowed to
filter
through. 211 ml- of pure cyclohexane was then filtered through the solid bed
in order to
wash the agglomerates. The solid bed was then allowed to drain of liquid under
a light
vacuum for about 30 seconds. The bitumen content of the washed solids was then
measured
to determine the bitumen recovery of the solvent extraction process.
[00123] Figure 9 plots the bitumen recovery and the initial liquid filtration
rate as a
function of the agglomeration residence time. The figure shows that the
bitumen recovery
reaches a maximum and then decreases as the agglomeration time increases for
batch
experiments conducted with the extraction time kept constant at 5 minutes. The
decrease in
recovery beyond the maximum recovery is most likely due to excessive
agglomerate growth
that lead to entrapment of the bitumen extract within the agglomerates.
However, this growth
of agglomerates does result in a continuous increase in the initial filtration
rate as the
agglomeration time increases.
29
