Note: Descriptions are shown in the official language in which they were submitted.
CA 02740670 2011-05-20
METHOD OF PROCESSING A BITUMINOUS FEED USING AGGLOMERATION IN A
PIPELINE
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
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CA 02740670 2011-05-20
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.
[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
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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
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. The use of sludge, however, introduces other
challenges
such as the fact that the appropriate sludge may not be readily available at
the mine site.
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Furthermore, the use of sludge as the bridging liquid leads to larger
agglomerates that are
more prone to entrapment of bitumen.
[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
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] In the process described in U.S. Patent No. 4,719,008 (Sparks et al.),
the
required milling action for the micro-agglomeration process is accomplished
using a rotating
horizontal vessel. A rotating vessel must have moving seals that allow it to
interface with
other process equipment. Since a hydrocarbon solvent is a preferable solvent
for the
extraction of bitumen from the oil sands, the seals must be robust in order to
contain the
potentially flammable mixture of the oil sands slurry from the atmosphere.
Furthermore, the
presence of sand, dust and brine in the ore complicates this by exposing
potential seals to
corrosion/erosion. As such, it would be desirable to have an alternative
vessel for
agglomerating solids. Other types of common mixing systems such as
conventional mixers
and stirred vessels may allow for improved sealing; however, high-speed
stirring is a highly
inefficient method of providing the milling action required for the micro-
agglomeration
process. Furthermore, it may be difficult to maintain large agglomerates in
suspension in the
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mixing environment of a conventional mixer. Maintaining the agglomerates in
suspension is
not a requirement for rolling agglomeration.
[0013] 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
binding 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 binding 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 binding
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 binding 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.
[0014] 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
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.
[0015] 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
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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.
10016] U.S. Patent No. 3,925,189 (Wicks III) describes a process and apparatus
for
extracting hydrocarbons from oil-containing solids. Specifically, the process
involves forming
an oil-containing solid-solvent slurry and flowing the slurry within a
pipeline at a relatively
high flow velocity in order to extract the hydrocarbons from the solids. The
pipeline is
positioned uphill at an angle of between 5 to 7 degrees to the horizontal, to
increase solid
holdup and residence time in the pipeline. Wicks describes that it is
preferable to use steam
as the purge gas to remove oxygen from the oil sands, because it led to an
improvement in
the filtration rates.
[0017] 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.
[0018] 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
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the slurry, agitation of the mixture, and removal of agglomerates from the
aqueous slurry.
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.
[0019] 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.
[0020] 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.
[0021] It would be desirable to provide an alternative or improved method for
processing a bituminous feed.
SUMMARY
[0022] 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.
The slurry is then
flowed through a pipeline. Before introduction into the pipeline and/or at one
or more points
along the pipeline, a bridging liquid is added to the slurry to assist
agglomeration. Agitation
is also used to assist agglomeration. The result is an agglomerated slurry
comprising
agglomerates and a low solids bitumen extract. The agglomerates are then
separated from
the low solids bitumen extract. Performing the agglomeration in a pipeline as
opposed to in a
conventional agitating vessel may provide certain advantages, such as improved
sealing in
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CA 02740670 2011-05-20
order to contain the potentially flammable mixture of oil sands slurry from
the atmosphere,
production of smaller and more uniform agglomerates due to improved mixing of
the bridging
liquid into the oil sands slurry, and the flexibility to have a long residence
time for the
extraction and agglomeration processes since the length of the pipeline can be
readily
increased to achieve the desired residence time. Additionally, the plug flow
nature of
processing within the pipeline may allow for greater observation and control
of the
agglomeration process. Furthermore, the pipeline may have the added advantage
of
providing a means of transporting the oil sands slurry to other locations
within the mine site
as the slurry is being processed within the pipeline.
[0023] 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)
flowing the slurry
through a pipeline and adding a bridging liquid to the slurry before and/or
within the pipeline,
and agitating solids within the slurry within the pipeline to form an
agglomerated slurry
comprising agglomerates and a low solids bitumen extract; and c) separating
the
agglomerates from the low solids bitumen extract.
[0024] 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
[0025] Embodiments of the present disclosure will now be described, by way of
example only, with reference to the attached Figures.
[0026] Fig. 1 is a flow chart illustrating a disclosed embodiment.
[0027] Fig. 2 is a schematic illustrating a disclosed embodiment.
[0028] _Fig. 3 is a schematic illustrating a disclosed embodiment.
[0029] Fig. 4 is a schematic illustrating a disclosed embodiment.
[0030] Fig. 5 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.
[0031] Fig. 6 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.
[0032] Fig. 7a is a schematic illustrating a disclosed embodiment.
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[0033] Fig. 7b is a schematic illustrating a disclosed embodiment.
[0034] Fig. 7c is a schematic illustrating a disclosed embodiment.
[0035] Fig. 7d is a schematic illustrating a disclosed embodiment.
[0036] Fig. 8 is a schematic illustrating a disclosed embodiment.
DETAILED DESCRIPTION
[0037] The present disclosure relates to a method of processing a bituminous
feed
using a pipeline to agglomerate solids. 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".
[0038] Prior to describing embodiments specifically related to the pipeline
agglomeration, a summary of the processes described in Adeyinka et al. will
now be
provided.
[0039] Summary of Processes of Solvent Extraction Described in Adeyinka et
al.
[0040] 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.
[0041] Pipeline Agglomeration
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
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contacted with an extraction liquor to form a slurry (102). The slurry is then
flowed through a
pipeline and a bridging liquid is added to the slurry and agitation is
provided to assist
agglomeration (104). The result is an agglomerated slurry comprising
agglomerates and a
low solids bitumen extract. The agglomerates are then separated from the low
solids
bitumen extract (106).
[0042] The term "bituminous feed" refers to a stream derived from oil sands
that
requires downstream processing in order to realize valuable bitumen products
or fractions.
The bituminous feed is one that comprises bitumen along with undesirable
components.
Such a bituminous feed may be derived directly from oil sands, and may be, for
example raw
oil sands ore. Further, the bituminous feed may be a feed that has already
realized some
initial processing but nevertheless requires further processing. Also,
recycled streams that
comprise bitumen in combination with other components for removal as described
herein can
be included in the bituminous feed. A bituminous feed need not be derived
directly from oil
sands, but may arise from other processes. For example, a waste product from
other
extraction processes which comprises bitumen that would otherwise not have
been
recovered, may be used as a bituminous feed. Such a bituminous feed may be
also derived
directly from oil shale oil, bearing diatomite or oil saturated sandstones.
[0043] 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.
[0044] Figure 2 is a schematic of a disclosed embodiment with additional steps
including downstream solvent recovery. 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 a pipeline (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 pipeline (210). The slurry (208) is flowed in the pipeline (210), and at
one or more points
along the pipeline (210), a bridging liquid (212) is added to the pipeline to
assist
agglomeration of the slurry. Alternatively or additionally, bridging liquid
may be added to the
slurry prior to the pipeline. Some form of agitation is also used to assist
agglomeration as
described below. In one embodiment, the agitation is provided by turbulent
flow in the
pipeline.
CA 02740670 2011-05-20
[0045] 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).
[0046] 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).
[0047] In one embodiment, the bituminous feed is dry oil sand, 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.
[0048] In one embodiment, agglomerates may be produced that 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 velocity within the pipeline (i.e. flow
turbulence),
fines content of the slurry, bridging liquid addition, and residence time
within the pipeline.
[0049] Figure 3 illustrates an exemplary pipeline that is segmented into three
zones.
The slurry (308), comprising the bituminous feed and the extraction liquid, is
fed into the
pipeline (310). In the extraction zone (350), bitumen extraction, which began
prior to
delivering the slurry (308) to the pipeline (310), continues. The extraction
zone (350) is
designed to provide enough residence time and agitation to dissolve the
bitumen. In the
extraction zone (350), agglomeration does not occur, or is limited because
bridging liquid is
preferably not injected into the pipeline in the extraction zone of the
pipeline.
[0050] At some point, bridging liquid (312a) is added to the pipeline (310).
Adding a
sufficient amount of bridging liquid (312a) assists agglomerate nucleation in
the nucleation
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CA 02740670 2011-05-20
zone (352). The amount of bridging liquid added within the nucleation zone may
be less or
much less than the total amount of bridging liquid needed for desired
agglomeration. In one
embodiment, the amount of bridging liquid added within the nucleation zone is
5 to 35% of
the total amount of bridging liquid added within the pipeline. In another
embodiment, the
amount of bridging liquid added within the nucleation zone is 10 to 25% of the
total amount of
bridging liquid added within the pipeline. The reduced amount of bridging
liquid added within
the nucleation zone may lower the rate of agglomerate growth and allow for
rapid dispersion
of the bridging liquid within the oil sands slurry.
[0051] At a later point, additional bridging liquid (312b) is added to the
pipeline (310)
to assist agglomerate growth, in the agglomerate growth zone (354), to a
desired size for
subsequent solid-liquid separation. In one embodiment, the bridging liquid
(312b) is added
to the agglomerate growth zone (354) at several points to assist uniform
mixing of the
bridging liquid with the slurry.
[0052] The three zones are not necessarily discrete zones. For instance,
extraction
may continue after the extraction zone, and nucleation may continue after the
nucleation
zone. ,
[0053] In another embodiment, (not shown in Figure 3) the agglomerate growth
zone
(354) may be followed by a comminution zone. The mixing energy within the
comminution
zone is increased significantly in order to comminute the undesirably large
agglomerates that
form in the agglomerate growth zone. Methods for increasing the mixing energy
include, but
are not limited to, increasing the slurry velocity within the comminution zone
and/or having
internal structures within the comminution zone of the pipeline.
[0054] Like Figure 3, Figure 4 illustrates a pipeline (410) in more detail
divided into
three zones, the extraction zone (450), the nucleation zone (452), and the
agglomerate
growth zone (454). The slurry (408), and bridging liquids (412a and 412b) are
also shown.
Measurement (456) of one or more of the properties of the slurry at a point
within the pipeline
(410) can be used to control (458) the operation downstream of the measurement
location.
One option is to adjust the amount of bridging liquid (412b) that is added.
Another option is
to adjust the velocity of the slurry in the pipeline. One possible measurement
is agglomerate
particle size distribution. This measurement can be accomplished by
integrating an online
particle size measurement device such as a Retsch Technology Camsizer. A slip
stream
can be taken from the slurry, filtered to remove liquid, and then measured to
analyze particle
12
CA 02740670 2011-05-20
size distribution. Another possible measurement is the filtration rate of the
oil sands slurry.
This measurement can be accomplished by integrating an online filtration
device with the
pipeline. A slip stream can be taken from the slurry and the rate of
filtration of that slip
stream can be measured. The filter medium should be similar to that which is
used in the
solid-liquid separator. Another possible measurement is the solids content of
the bitumen
extract. One method for accomplishing this measurement may be the measurement
of the
density of an unfiltered and micro-filtered bitumen extract. The difference in
density of these
two streams can be correlated with solid content. Yet another possible
measurement is the
power dissipation of the oil sands slurry at different points along the length
of the pipeline.
This measurement can be accomplished by measuring the static pressure along
the length of
the pipe.
[0055] Agglomerate Size. Embodiments described herein may be used for the
formation of macro-agglomerates or micro-agglomerates from the solids of the
bituminous
feed. Macro-agglomerates are agglomerates that are predominantly greater than
2 mm in
diameter. These agglomerates comprise both the fine particles (less than 44
pm) and sand
grains of the oil sands. Micro-agglomerates are agglomerates that are
predominately less
than 1 mm in diameter and they principally comprise fine particles of the oil
sands. It has
been found that for the SESA process described above, the formation of micro-
agglomerates
are more suitable for maximizing bitumen recovery for a range of oil sands
grades.
[0056] Pipeline Zones. Nominally, the pipeline will comprise two zones, an
extraction zone and an agglomeration zone. The function of the extraction zone
is to dissolve
the bitumen from the oil sands into the extraction liquor. Unlike certain
prior processes,
where the extraction liquor is first exposed to the bituminous feed within the
agglomerator, in
most of the embodiments described herein, bitumen is extracted from the oil
sands prior to
the agglomeration step in order to prevent (or limit) the agglomeration
process from
hampering the dissolution of bitumen into the extraction liquor. Thus, it is
desirable to prevent
or limit the agglomeration of particles within the extraction zone.
[0057] The function of the agglomeration zone is to agglomerate the solids to
the
amount commensurate with achieving economically viable solid-liquid
separation. For most
of the embodiments described herein, micro-agglomerates are preferred because
they allow
for good solid-liquid separation without entrapping a significant amount of
the bitumen extract
within the agglomerates. The extraction of the bitumen prior to the
agglomeration process
13
CA 02740670 2011-05-20
has the effect of reducing the required residence time in the agglomeration
zone, when
compared to certain previously proposed processes which require extraction of
bitumen and
agglomeration to occur simultaneously. The reduced residence time of the
agglomeration
zone allows for agglomerates of smaller particle size distribution to form.
[0058] The agglomeration zone may comprise a nucleation zone, an agglomerate
growth zone, and a comminution zone. The agglomeration process is initiated
within the
nucleation zone. The amount of bridging liquid added within the nucleation
zone may be less
or much less than the total amount of bridging liquid needed for desired
agglomeration. The
amount of bridging liquid added within the nucleation zone may be 5 to 35% of
the total
amount of bridging liquid added within the agglomeration zone. In another
embodiment, the
amount of bridging liquid added within the nucleation zone is 10 to 25% of the
total amount of
bridging liquid added within the agglomeration zone. The reduced amount of
bridging liquid
added within the nucleation zone may lower the rate of agglomerate growth and
allow for
rapid dispersion of the bridging liquid within the oil sands slurry. Following
the nucleation
zone, additional bridging liquid is added within the agglomeration growth zone
in order to
grow the agglomerates to the desired size and reduce the amount of fine solids
dispersed
within the bitumen extract. The bridging liquid may be added to the
agglomerate growth zone
at several points to assist uniform mixing of the bridging liquid within the
slurry. A
comminution zone may follow the agglomerate growth zone in order to comminute
the
undesirably large agglomerates that may form in the agglomerate growth zone.
The
comminution may be effected by, for example, increasing the velocity within
the comminution
zone or having internal structures within the comminution zone.
[0059] Velocity within Pipeline. The nature of slurry flow within a horizontal
pipeline
depends on the ratio of the average flow velocity of the slurry within the
pipeline to the
limiting settling velocity of the slurry. When the average flow velocity is
greater than the
limiting settling velocity, the slurry flow within the pipeline is homogenous
with no average
concentration changes across the pipe. At any velocity below the limiting
settling velocity,
the slurry flow becomes heterogeneous with the concentration of the solids
increasing
towards the bottom of the pipe. For an average flow velocity that is
heterogeneous but
where the slurry velocity remains greater than 40% of the limiting settling
velocity, the solids
that are deposited at the bottom of the pipe can flow by bouncing and rolling
along the pipe.
This type of flow is called saltation flow. The average flow velocity that is
below that which is
14
CA 02740670 2011-05-20
needed for saltation flow is usually avoided since pipeline plugging will
occur as solids are
continuously injected into the pipeline.
[0060] The limiting settling velocity for a slurry is best determined by
conducting tests
with the slurry flowing within a pipeline test rig. In the absence of such
tests, the limiting
settling velocity, VL can be estimated using the following equation proposed
by R Durand:
PS - Pr
VL = FL FgD
Pr
where, g is the acceleration due to gravity, D is the diameter of the
pipeline, ps is the
density of the solids within the slurry, and p, is the density of the liquid
of the slurry. FL is a
parameter that is dependent upon the particle size distribution and the solids
volume
concentration within the slurry. For a slurry with mixed particle size, such
as that expected
for oil sands slurries as described herein, FL has been measured to have
values within the
range of 0.5 to 1.5.
[0061] In the extraction zone, the average flow velocity within the pipeline
can be that
needed for saltation flow or greater. It is preferable that the slurry flow be
homogenous or
mildly heterogeneous. However, this not necessary since the extraction liquor
will digest the
oil sands lumps even under low agitation conditions. The average flow velocity
within the
extraction zone may be 1 to 5 m/sec. In another embodiment, the average flow
velocity
within the extraction zone may be 2 to 3 m/sec.
[0062] In the agglomeration zone, it is desired that the slurry flow be a
homogenous
type slurry flow. The homogenous flow will allow for proper mixing of the
bridging liquid.
Additionally, this type of flow will ensure that most, if not all, of the
solids remain in the
turbulent flow regime of slurry such that they are consistently exposed to the
high shear
forces needed to prevent (or limit) excessive growth of the agglomerates and
non-uniformity
of agglomerate size. The average flow velocity within the agglomeration zone
may be greater
than 2 m/sec. In another embodiment, the average flow velocity within the
agglomeration
zone may be 3 to 6 m/sec.
[0063] In the agglomerate growth zone, the average flow velocity should not be
too
high a velocity so that the shear forces subject the agglomerates to severe
attrition that
prevents agglomerate growth. However, such severe attrition may be desired
within the
nucleation zone and in the comminution zone. In the nucleation zone, the
severe attrition can
CA 02740670 2011-05-20
be used to rapidly disperse the bridging liquid. In the comminution zone, the
severe attrition
can be used to reduce the size of the larger agglomerates. Erosion of the
pipeline and
excessive pressure drop will limit the average flow velocity within all zones
making up the
agglomeration zone.
[0064] Residence Time. An advantage of the pipeline agglomeration process
described herein is the flexibility to have a long residence time for the
extraction and
agglomeration processes since the length of the pipeline can be readily
increased to achieve
the desired residence time. 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.
Figure 5 (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. In contrast, as Figure
6 (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 led 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,
[0065] The results plotted in Figure 5 and Figure 6 suggest that it is
preferable for the
residence time of the extraction zone to be greater or much greater than the
residence time
of the agglomeration zone. The residence time of the extraction zone 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. The residence time of the agglomeration zone may be
in the range
of 30 seconds to 10 minutes. In one embodiment, the residence time of the
agglomeration
zone may be in the range of 1 to 5 minutes. The residence time of the
nucleation zone within
the agglomeration zone may be less than 30 seconds. For embodiments where the
agglomeration zone comprises a comminution zone, the residence time within the
agglomeration may be extended beyond 5 minutes to provide the required
residence time for
the comminution. zone.
[0066] Geometry of Pipeline. It is desirable to have the pipeline diameter of
the
extraction zone to be constant and as large as possible commensurate with
keeping the
slurry flow above the saltation velocity. Exemplary pipeline diameters are in
the range of 0.5
16
CA 02740670 2011-05-20
to 1.5 m. These pipeline diameters are similar in size to those of the
hydrotransport pipelines
used in the water-based extraction process. Since the total pipeline length
may comprise
mostly the extraction zone, attempts should be made to minimize erosion within
this portion
of the pipeline.
[0067] For the agglomeration zone of the pipeline, it is desirable to have
homogenous or close to homogenous type flow in order to ensure or promote
uniform
agglomerate formation and growth. In one embodiment, the homogenous slurry
flow can be
accomplished by reducing the pipeline diameter of the agglomeration zone (as
seen in
Figure 7a) in order to increase the average flow velocity of the slurry and
reduce the limiting
settling velocity. In Fig. 7a, the slurry (708a), the extraction zone (750a),
and the
agglomeration zone (754a) are shown. In one embodiment, the pipeline diameter
in the
agglomeration zone may be 0.25 to 1.5 m. In another embodiment, the homogenous
slurry
flow can be accomplished by incorporating a recycle loop with the
agglomeration zone as
shown in Figure 7b. In Fig. 7b, the slurry (708b), the extraction zone (750b),
and the
agglomeration zone (754b) are shown. The recycle loop (755) would act to
increase the
average flow velocity within the agglomeration zone. In yet another
embodiment, as shown in
Figure 7c, the pipeline of the agglomeration zone (754c) can be configured at
angles to the
horizontal. The configuration of the pipeline at angles will have the effect
of reducing the
limiting settling velocity of the slurry. By way of example, the pipeline may
be angled 50 to
450 to horizontal.
[0068] The above described methods of promoting homogenous or near
homogenous slurry flow may be employed separately or in combination in order
to maximize
effectiveness. Additionally, the pipeline of the agglomeration zone may
comprise internal
structures to promote homogenous slurry flow. Exemplary structures include
intermittently
spaced static mixers as shown in Figure 7d. In Figure 7d, the static mixers
(756) are shown
within the agglomeration zone (754d). It is preferable that static mixers, or
the like, be
included in the pipeline in such a way that they can be readily replaced since
such devices
may be subject to high rates of erosion. Other potential internal structures
will be readily
known by those skilled in the art.
[0069] Control Methods. The plug flow nature of processing the bituminous feed
within the pipeline may allow for greater observation and control of the
agglomeration
process. For example, measurement of one or more of the properties of the
slurry at a point
17
CA 02740670 2011-05-20
or multiple points within the pipeline can be used to control the operation
downstream of the
measurement location. One option is to adjust the amount of bridging liquid
that is added.
Another option is to adjust the velocity of the slurry in the pipeline.
Another option is to adjust
the solid content of the bridging liquid added to the slurry. Another option
is to adjust the
methods and locations of the bridging liquid addition along the pipeline. Yet
another option is
to reduce the solid content of the slurry. One possible measurement is
agglomerate particle
size distribution. This measurement can be accomplished by integrating an
online particle
size measurement device such as a Retsch Technology Camsizer. A slip stream
can be
taken from the slurry, filtered to remove liquid, and then measured to analyze
particle size
distribution. Another possible measurement is the filtration rate of the oil
sands slurry. This
measurement can be accomplished by integrating an online filtration device
with the pipeline.
A slip stream can be taken from the slurry and the rate of filtration of that
slip stream can be
measured. The filter medium should be similar to that which is used in the
solid-liquid
separator. Another possible measurement is the solids content of the bitumen
extract. Those
skilled in the art will know that this measurement can be quickly accomplished
in numerous
ways. One method for accomplishing this measurement may be the measurement of
the
density of an unfiltered and micro-filtered bitumen extract. The difference in
density of these
two streams can be correlated with solid content. Yet another possible
measurement is the
power dissipation of the slurry at different points along the length of the
pipeline. This
measurement can be accomplished by measuring the static pressure along the
length of the
pipe.
[0070] 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.
[0071] 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.
18
CA 02740670 2011-05-20
[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] In another embodiment, it may desirable to use hydrocarbon solvents
that
preferentially precipitate asphaltenes from the bitumen. The precipitated
asphaltenes may
agglomerate with the oileophilic solids within the slurry which can help to
produce a bitumen
extract with less entrained fine particles.
[0074] 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.
[0075] 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.
[0076] Exemplary cycloalkanes include cyclohexane, cyclopentane, or a mixture
thereof.
[0077] 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.
[0078] 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
19
CA 02740670 2011-05-20
paraffinic solvents where the percentage of the cyclic aliphatic hydrocarbon
in the mixture is
greater than 50%.
[0079] 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.
[0080] The solvent may also include additives. These additives may or may not
be
considered a solvent per se. Possible additives may be components such as de-
emulsifying
agents or solids aggregating agents. Having an agglomerating agent additive
present in the
bridging liquid and dispersed in the first solvent may be helpful in the
subsequent
agglomeration step. Exemplary agglomerating agent additives include cements,
fly ash,
gypsum, lime, brine, water softening wastes (e.g. magnesium oxide and calcium
carbonate),
solids conditioning and anti-erosion aids such as polyvinyl acetate emulsion,
commercial
fertilizer, humic substances (e.g. fulvic acid), polyacrylamide based
flocculants and others.
Additives may also be added prior to gravity separation with the second
solvent to enhance
removal of suspended solids and prevent emulsification of the two solvents.
Exemplary
additives include methanoic acid, ethylcellulose and polyoxyalkylate block
polymers.
[0081] 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 salts,
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 the pipeline in such a way that permits
fines to adhere to
each other. An exemplary bridging liquid is water.
[0082] The bridging liquid may be added to the slurry in a concentration of
less than
20 wt% of the slurry. In another embodiment, the bridging liquid is added to
the slurry in a
concentration of less than 10 wt% of the slurry. In one embodiment, the
bridging liquid is
added in a concentration of between 1 wt% and 20 wt% or between 1 wt% and 10
wt%. In
one embodiment, the bridging liquid comprises fine particles (for instance
less than 44 pm)
suspended therein. These fine particles may serve as seed particles for the
agglomeration
CA 02740670 2011-05-20
process. The bridging liquid may comprise less than 40 wt% solid fines. The
agglomerated
slurry may have a solids content of 20 to 70 wt%.
[0083] Ratio of Solvent to Bitumen for Agglomeration. The process may be
adjusted to render the ratio of the solvent to bitumen in the pipeline at a
level that avoids or
limits 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.
[0084] 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.
[0085] For the embodiment where precipitation in the pipeline is preferred a
solvent
to bitumen ratio of at least 2:1 or greater is desired.
[0086] 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
pipeline. 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 30
to 50 wt%. 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.
21
CA 02740670 2011-05-20
Temperatures above 60 C are generally avoided due to the complications
resulting from high
vapor pressures.
[0087] Solvent Slurry Transport. In the mining of oil sands, the distance that
mined
oil sands must travel from the mine to the extraction plant and subsequently
to a disposal site
necessitates significant energy expenditure and cost. The processing of
bituminous feed by
conducting solvent extraction with solid agglomeration in a pipeline, as
described herein, has
the advantage of providing a means of transporting the oil sands as a slurry
to other
locations within the mine site while the slurry is being processed within the
pipeline. A similar
benefit is realized within the hydrotransport lines of water-based extraction
facilities. In the
case of water-based extraction facilities, it is generally more cost effective
and less energy
intensive to transport oil sands by pipeline than by dry solid transport
methods such as trucks
and/or conveyors. Similar cost and energy saving may be realized in the case
of solvent
slurry transport.
[0088] Figure 8 illustrates a mine facilities layout where slurry systems
(802a, 802b,
and 802c)) are located close to the mine face to receive oil sands (804a,
804b, and 804c) by
trucks and/or conveyors. Pipelines (806a, 806b, and 806c) are then used to
conduct the
solvent extraction with solids agglomeration process while transporting the
slurry to a central
facility (808) where the remaining processes of solvent extraction, as
outlined in Figure 2,
may occur. As illustrated in Figure 8, optional equipment (808) such as a
drum, a clarifier,
and an inclined plate separator may also be used. The central facility may
include a solid-
liquid separator (812) (such as a belt filter), a tailings solvent recover
unit (814), and a clean
solvent storage (816), the operations of which are described above. The
bitumen product
(818) may be pipelined to a plant. The coarse solids (820) may be sent to a
pit. The location
of central facilities may be dictated by various factors such as the footprint
of the facilities,
tailings disposal requirements, and other considerations.
[0089] 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.
[0090] 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
22
CA 02740670 2011-05-20
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.
[0091] 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.
[0092] 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.
[0093] A secondary solid-liquid separator for countercurrently washing
agglomerates
may be included in the system or may be included as a component of a system
described
herein. The secondary solid-liquid separator may be separate or incorporated
within the
primary solid-liquid separator. The secondary solid-liquid separator may
optionally be a
gravity separator, a cyclone, a screen or belt filter. Further, a secondary
solvent recovery
unit for recovering solvent arising from the solid-liquid separator can be
included. The
secondary solvent recovery unit may be a conventional fractionation tower or a
distillation
unit.
(0094] 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.
23
CA 02740670 2011-05-20
[0095] The solvent used for washing the agglomerates may be solvent recovered
from the tow 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
pipeline.
[0096] Recycle and Recovery of Solvent. The process may involve removal and
recovery of solvent used in the process.
[0097] 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 pipeline
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.
[0098] 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.
[0099] Solvent may be recovered by conventional means. For example, typical
solvent recovery units may comprise a fractionation tower or a distillation
unit.
[00100] The solvent recovered in the process may comprise entrained bitumen
therein, and can thus be re-used for combining with the bituminous feed. Other
optional
steps of the process may incorporate the solvent having bitumen entrained
therein, for
example in countercurrent washing of agglomerates, or for adjusting the
solvent and bitumen
content prior to agglomeration to achieve the selected ratio within the
pipeline.
[00101] Dilution of Pipeline 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.
24
CA 02740670 2011-05-20
[00102] When dilution of pipeline discharge is employed in this embodiment,
the
solvent to bitumen ratio of the feed into the pipeline 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
pipeline discharge may involve adding the solvent, or a separate dilution
solvent, which may,
for example, comprise an alkane.
[00103] Potential Advantages. There may be advantages of embodiments described
herein, for instance as compared to SESA. Solids nucleation and extraction in
the pipeline is
expected to improve bitumen recovery due to full bitumen dissolution in the
pipeline as well
as to increase control of the agglomeration process. It is expected that
embodiments will
improve the distribution of bridging liquid within the slurry in order to
produce a narrower
particle size distribution for the agglomerates. Agglomerates that are more
uniform in size
may have higher drainage rates for solid-liquid separation methods such as
filtration and
screening. It is also expected that embodiments will improve the sealing
required to contain
the potentially flammable mixture of oil sands slurry from the atmosphere.
Additionally, since
the length of a, pipeline can be readily extended, the residence time needed
for
agglomeration within the pipeline can be increased at a lower cost as compared
to what
would be needed for other agglomeration vessels. Additionally, the pipeline
has the added
advantage of providing a means of transporting the oil sands slurry to other
locations within
the mine site as the slurry is being processed within the pipeline.
[00104] Rotating type vessels, such as the vessel described in U.S. Patent No.
4,719,008 (Sparks et al.), need to be large in order to process the high
volumetric flow rates
of oil sands. These large vessels have a low surface to volume ratio, which in
turn increases
the difficulty of uniformly mixing the bridging liquid within the slurry. In
contrast, a pipeline
generally has relatively a high surface to volume ratio. This characteristic
of the pipeline
agglomeration vessel may make it easier to inject the bridging liquid into the
slurry in such a
way to allow for uniform mixing of the bridging liquid.
[00105] In contrast to other agglomeration vessels, a pipeline may enable plug
flow, or
close to plug flow, behavior of the agglomeration process. For this reason,
the pipeline may
CA 02740670 2011-05-20
comprise different zones along the length of the pipe, each accomplishing a
different result,
as described above with reference to Figures 3 and 4. In general, the plug
flow (or near plug
flow) behavior of the agglomeration process within a pipeline may allow for
greater flexibility
in observing and controlling the agglomeration process itself. For example,
measurement of
one or more of the properties of the slurry at a point or multiple points
within the pipeline can
be used to control the operation downstream of the measurement location. Since
the ore
quality and chemistry of the oil sands will change on a frequent basis as
different mine
shelves are progressed, the recipe of the agglomeration process may need to
change
accordingly. Thus, having greater control of the agglomeration process, as
described herein,
will help the agglomeration outputs to remain within acceptable ranges
regardless of feed
changes.
[00106] Rotating type vessels, such as the vessel described in U.S. Patent No.
4,719,008 (Sparks et al.), must have moving seals that allow it to interface
with other process
equipment. Since a hydrocarbon solvent is a preferable solvent for the
extraction of bitumen
from the oil sands, the seals must be robust in order to contain the
potentially flammable
mixture of oil sands slurry from the atmosphere. Furthermore, the materials
being processed,
such as sand and brine, accelerate the corrosion and erosion of seals. Since
the pipeline
itself has no moving parts, sealing is expected to be a much easier task for
said pipeline.
However, the pumps used in the process may need to be specially designed.
[00107] Unlike certain prior process, where the extraction liquor is first
exposed to the
bituminous feed within the agglomerator, in most of the embodiments described
herein
bitumen is extracted from the oil sands prior to the agglomeration step. The
decoupling of the
extraction and agglomeration processes may yield certain advantages. For
example, the
experimental results plotted in Figures 5 and 6 suggest that the rate of
bitumen recovery and
solid-liquid separation can increase by extending the extraction residence
time while keeping
the agglomeration residence time low. Thus, it may be beneficial to have the
extraction
residence time be as much as 30 minutes or greater. An advantage of the
pipeline
agglomeration process described herein is that such long residence time in the
extraction
zone of the pipeline is economically feasible since the length of the pipeline
can be readily
increased to achieve the desired residence time.
[00108] In the mining of oil sands, the distance that mined oil sands must
travel from
the mine to the extraction plant and subsequently to a disposal site
necessitates significant
26
CA 02740670 2011-05-20
energy expenditure and cost. The processing of bituminous feed by conducting
solvent
extraction with solid agglomeration in a pipeline, as described herein, has
the advantage of
providing a means of transporting the oil sands as a slurry to other locations
within the mine
site while the slurry is being processed within the pipeline. It is believed
the solvent slurry
transport, described herein can provide a more cost effective and less energy
intensive
method to transport oil sands within the mine site rather than by the dry
solid transport
methods such as trucks and/or conveyors.
[00109] 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.
[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
27
CA 02740670 2011-05-20
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 with Dean-Stark azeotropic distillation, to
determine the material
contents of the agglomerated slurry. Toluene was used as the extraction
solvent. The oil
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 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 pored 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
28
CA 02740670 2011-05-20
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 5 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.
[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
5 minutes to fully homogenize the mixture and to fully extract the bitumen
that was in the oil
sands. After 5 minute 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 pored 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 6 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
29
CA 02740670 2011-05-20
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,
