Note: Descriptions are shown in the official language in which they were submitted.
METHODS FOR PROCESSING A BITUMINOUS FEED
BACKGROUND
Field of Disclosure
[0001] The disclosure relates generally to the field of oil sand
processing. More
specifically, the disclosure relates to methods for processing a bituminous
feed.
Description of Related Art
[0002] This section is intended to introduce various aspects of the art,
which may be
associated with the present disclosure. This discussion is believed to assist
in providing a
framework to facilitate a better understanding of particular aspects of the
present disclosure.
Accordingly, it should be understood that this section should be read in this
light, and not
necessarily as admissions of prior art.
[0003] Modern society is greatly dependent on the use of hydrocarbon
resources for
fuels and chemical feedstocks. Hydrocarbons are generally found in subsurface
formations that
can be termed "reservoirs." Removing hydrocarbons from the reservoirs depends
on numerous
physical properties of the subsurface formations, such as the permeability of
the rock containing
the hydrocarbons, the ability of the hydrocarbons to flow through the
subsurface formations,
and the proportion of hydrocarbons present, among other things. Easily
harvested sources of
hydrocarbons are dwindling, leaving less accessible sources to satisfy future
energy needs. As
the costs of hydrocarbons increase, the less accessible sources become more
economically
attractive.
[0004] Recently, the harvesting of oil sand to remove heavy oil has
become more
economical. Hydrocarbon removal from oil sand may be performed by several
techniques. For
example, a well can be drilled to an oil sand reservoir and steam, hot air,
solvents, or a
combination thereof, can be injected to release the hydrocarbons. The released
hydrocarbons
may be collected by wells and brought to the surface. In another technique,
strip or surface
mining may be performed to access the oil sand, which can be treated with hot
water, steam or
solvents to extract the heavy oil. This other technique may be referred to as
a water-based
extraction process (WBE). The WBE is a commonly used process to extract
bitumen from
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mined oil sand. In another technique, a non-water-based extraction process can
be used to treat
the strip or surface mined oil sand. The non-water-based extraction process
may be referred to
as a solvent-based recovery process. The commercial application of a solvent-
based recovery
process has, for various reasons, eluded the oil sand industry. A major
challenge associated
with the solvent based extraction process is the tendency of fine particles
within the oil sand to
hamper the separation of solids from the heavy oil (e.g., bitumen) extracted.
The fine particles
that remain with the bitumen have an adverse impact on the transport of the
bitumen within
pipelines and have a negative impact on the downstream upgrading and/or
refining of the
bitumen. For these reasons, it is desirable to reduce the solids content of
the bitumen to a value
much less than 1 weight (wt.) %. Another major challenge to the application of
a solvent-based
recovery process for oil sand is the recovery of solvent from the bitumen-free
solids. This
solvent-based recovery process is often energy intensive and limits the
economics of the overall
solvent-based recovery process.
[0005] A
solid agglomeration process has been proposed for use in the solvent-based
recovery process. The solid agglomeration process was coined Solvent
Extraction Spherical
Agglomeration (SESA). Previously described methodologies for SESA have not
been
commercially adopted. In general, the SESA process involves mixing oil sand
with a
hydrocarbon solvent to form an oil sand slurry, adding an aqueous bridging
liquid to the oil
sand slurry to form a mixture, agitating the mixture in a slow and controlled
manner to nucleate
particles, and continuing such agitation so as to permit these nucleated
particles to form larger
multi-particle spherical agglomerates for removal. The aqueous bridging liquid
may be water
or an aqueous solution since the solids of oil sand are mostly hydrophilic and
water is
immiscible to hydrocarbon solvents. The aqueous bridging liquid preferentially
wets the solids.
With the right amount of the aqueous bridging liquid and suitable agitation of
the slurry; the
aqueous bridging liquid displaces the suspension liquid on the surface of the
solids. As a result
of interfacial forces among three phases (i.e. the aqueous bridging liquid,
the suspension liquid,
and the solids), fine particles within the solids consolidate into larger,
compact agglomerates
that are more readily separated from the suspension liquid.
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[0006]
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. Organic material is separated from oil sand by mixing
the oil sand
material with an organic solvent to form a slurry, after which an aqueous
bridging liquid is
added in an amount of 8 to 50 weight percent (wt.%) of the feed mixture. By
using controlled
agitation, solid particles from oil sand come into contact with the aqueous
bridging liquid and
adhere to each other to form macro-agglomerates with a mean diameter of 2
millimeters (mm)
or greater. The macro-agglomerates are more easily separated from the organic
solvent
compared to un-agglomerated solids. The macro-agglomerates are referred to as
macro-
agglomerates because they result from the consolidation of both fine particles
and coarse
particles that make up oil sand.
[0007]
U.S. Patent No. 4,719,008 (Sparks et al.) describes a process to apply SESA to
varying ore grade qualities by a micro-agglomeration procedure in which the
fine particles of
the oil sand are consolidated to produce micro-agglomerates with a similar
particle size
distribution to coarser grained particles of the oil sand. Using the micro-
agglomeration
procedure, the solid-liquid separation behavior of the agglomerated oil sand
will be similar
regardless of ore grade quality. The micro-agglomeration procedure occurs
within a slowly
rotating horizontal vessel. The conditions of the slowly rotating horizontal
vessel are that which
favor the formation of large agglomerates; however, a light milling action is
used to
continuously break down the micro-agglomerates. The micro-agglomerates are
formed by
obtaining an eventual equilibrium between cohesive and destructive forces.
Since
micro-agglomerates of large size can lead to bitumen recovery losses owing to
entrapment of
extracted bitumen within the agglomerated solids, the levels of bridging
liquid is kept to as low
as possible commensurate with achieving economically viable solid-liquid
separations.
[0008]
With the formation of the micro-agglomerates, the process of solid-liquid
separation using common separation devices is easier compared to the situation
where the fine
particles are un-agglomerated. Applicable separation devices include at least
one of gravity
separators, centrifuges, hydrocyclones, screens, and filters. Although the
separation devices
have been shown to be effective in separating micro-agglomerates from bitumen
extract, a
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portion of the fine solids remain un-agglomerated because they are non-wetting
with the
aqueous bridging liquid and thus remain as residual fine solids in the bitumen
extract. The
amount of the residual fine solids that remain in the bitumen extract can be
greater than 1 wt.
% on a dry bitumen basis. "Dry bitumen basis" means ignoring the presence of
water in the
bitumen extract for the purpose of calculating wt. %.
100091 Solvent deasphalting has previously been proposed as a method to
remove the
residual fine solids that remain from the bitumen extract. U.S. Patent No.
4,888,108 (Farnand)
describes a process where an aliphatic solvent, such as pentane, is added
along with a chemical
additive to the bitumen extract. The addition of the aliphatic solvent causes
asphaltenes to
precipitate onto the residual fine solids. The combination of the precipitated
asphaltenes and
the chemical additive causes the residual fine solids to aggregate so that
they can be readily
separated from the bitumen extract. Farnand describes that the most effective
chemical
additives are water-soluble organic compounds with a low miscibility with the
bitumen extract.
The organic compounds preferably comprise a carboxylic acid and/or hydroxyl
groups, and
have a weakly acidic and/or polar character. The chemical additives, such as
resorcinol,
catechol, formic acid, and maleic acid, have a synergistic effect with the
addition of the aliphatic
solvent. Less additive and aliphatic solvent was needed, when used in
combination, to obtain
the same level of solids removal as compared to when the additive or aliphatic
solvent was used
alone. Farnand theorized that the improved residual fine solids aggregation
was due to the
precipitated asphaltenes increased attraction to the residual fine solids with
the polar additives
adsorbed onto the residual fine solids surfaces.
[0010] Another method for removing the residual fine solids that remain
in the bitumen
extract is to use aliphatic solvents for the extraction of bitumen from oil
sand. U.S. Patent
Publication 2011/0127197 (Blackbourn et al.) describes the use of a C3 to C9
paraffinic solvent
for extracting bitumen from oil sand. The use of paraffinic solvent, such as
pentane, prevents
all or a portion of the asphaltenes within the bitumen from dissolving into
solution during the
solvent-based recovery process. Since the asphaltenes tend to be associated
with fine solids,
the asphaltenes that do not dissolve prevent the fine solids from dispersing
into the bitumen
extract. Blackbourn et al. described that the use of the paraffinic solvent
improved the
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separation of bitumen extract by filtration. The increased filtration rate,
compared to when an
aromatic solvent was used for bitumen extraction, was most likely due to the
fact that some of
the fine solids remained attached to the solid asphaltenes and thus were not
free to block the
filter media or the solid bed on top of the filter media. The use of
paraffinic solvent in the
solvent-based recovery process resulted in faster settling fine solids that
could be readily
separated from the majority of the bitumen extract by gravity to produce a
bitumen extract with
fine solids content of less than 0.1 wt.% on a dry bitumen basis.
[0011] The use of aliphatic solvents in a solvent-based recovery process
has been
proposed as a method to reduce the amount of residual solvent in tailings.
U.S. Patent No.
8,257,580 (Duyvesteyn et al.) describes a method for preparing dry, stackable
tailings. Dry,
stackable tailings may be defined as comprising less than 0.1 wt.% solvent and
from about 2
wt. % to about 15 wt. %. Water. The method involves contacting the oils sand
with a light
aromatic solvent to dissolve bitumen. The bitumen extract is then separated
from the solids in
order to produce a first solid tailings that has residual bitumen extract
entrained within. The
residual bitumen extract is removed from the tailings by washing the solids
with a light
hydrocarbon solvent to produce solvent-wet tailings where the remaining light
hydrocarbon
solvent can be readily recovered by heating and/or pressure reduction. A light
hydrocarbon
solvent may be defined as a cyclo- or iso-paraffin having between 3 and 9
carbons. The light
hydrocarbon solvent is typically an aliphatic solvent such as at least one of
propane, butane,
and pentane. Duyvesteyn et al. describes that this method has the potential
advantage of
reducing the required energy to recover the light hydrocarbon solvent from
tailings and the
potential advantage of requiring that only the washing stage needs to be
pressurized in the
solvent-based recovery process.
[0012] The above-described processes demonstrate that the use of
aliphatic solvent in a
solvent-based recovery process may reduce the amount of residual solvent in
the tailings.
However, the use of aliphatic solvent does pose challenges to the solvent-
based recovery
process. The use of aliphatic solvent may increase the chance that
asphaltenes, which have not
dissolved (i.e., undissolved asphaltenes), will be present in undesirable
locations within the
solvent-based recovery process. For example, undissolved asphaltenes may be
present in an
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extraction vessel, thereby trapping bitumen within the asphaltene and
inorganic solid pores.
Undissolved asphaltenes may be referred to as precipitated asphaltenes. The
extraction vessel
is a vessel where bitumen is extracted from oil sand. The bitumen trapped may
result in
additional losses of bitumen with the tailings. The undissolved asphaltenes
tend to foul various
components, such as piping, valves, and filters, which may result in an
increased need for
maintenance.
[0013] In view of the aforementioned disadvantages, there is a need for
improved
methods for processing a bituminous feed. For example, there is a need for a
method for using
aliphatic solvents in a solvent-based recovery process that takes advantage of
the benefits of
using aliphatic solvents while mitigating the problems that the presence of
undissolved
asphaltenes may have on the solvent-based recovery process.
SUMMARY
[0014] It is an object of the present disclosure to provide methods for
processing a
bituminous feed.
[0015] A method for processing a bituminous feed may comprise: a)
forming an oil
sand slurry, comprising a bitumen extract and solids, by contacting the
bituminous feed with a
first extraction liquor, comprising a first solvent; b) forming a rich bitumen
extract stream and
separated solids by separating the solids from the bitumen extract; c) forming
a washed solids
stream and a lean bitumen extract stream, comprising precipitated asphaltenes,
by washing the
separated solids with an aliphatic solvent; d) forming a deasphalted lean
bitumen extract stream
by separating the precipitated asphaltenes from the lean bitumen extract
stream; and e)
obtaining a bitumen product stream by removing the first solvent from at least
one of a first
portion of the rich bitumen extract stream and a first portion of the
deasphalted lean bitumen
extract stream.
[0016] A method for processing a bituminous feed may comprise: a)
forming an oil
sand slurry, comprising a bitumen extract and solids, by contacting the
bituminous feed with a
first extraction liquor comprising a first solvent; b) forming a rich bitumen
extract stream,
comprising the bitumen extract and residual fine solids, by separating the
solids from the
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bitumen extract; c) providing a hydrocarbon fluid comprising undissolved
asphaltenes; d)
forming an asphaltene-bitumen extract mixture by mixing the hydrocarbon fluid
with the rich
bitumen extract stream; e) forming a low solids bitumen extract stream by
separating
asphaltenes and the residual fine solids from the asphaltene-bitumen extract
mixture; and 0
obtaining a bitumen product stream by removing the first solvent from the low
solids bitumen
extract stream.
[0017] A method for processing a bituminous feed may comprise: a)
providing a first
extraction liquor comprising deasphalted bitumen and a first solvent; b)
forming an oil sand
slurry, comprising a bitumen extract and solids, by contacting the bituminous
feed with the first
extraction liquor; c) forming a rich bitumen extract stream by separating the
solids from the
bitumen extract; and d) obtaining a bitumen product stream by removing the
first solvent from
a first portion of the rich bitumen extract stream.
[0018] The foregoing has broadly outlined the features of the present
disclosure so that
the detailed description that follows may be better understood. Additional
features will also be
described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] These and other features, aspects and advantages of the disclosure
will become
apparent from the following description, appending claims and the accompanying
drawings,
which are briefly described below.
[0020] Figure 1 is a flow chart of a method for processing a bituminous
feed.
[0021] Figure 2 is a flow chart of a method for processing a bituminous
feed.
[0022] Figure 3 is a flow chart of a method for processing a bituminous
feed.
[0023] Figure 4 is a flow chart of a method for processing a bituminous
feed.
[0024] Figure 5 is a flow chart of a method for processing a bituminous
feed.
[0025] Figure 6 is a flow chart of a method for processing a bituminous
feed.
[0026] Figure 7 is a flow chart of a method for processing a bituminous
feed.
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[0027] Figure 8 is a flow chart of a method for processing a bituminous
feed.
[0028] Figure 9 is a flow chart of a method for processing a bituminous
feed.
[0029] It should be noted that the figures are merely examples and no
limitations on the
scope of the present disclosure are intended thereby. Further, the figures are
generally not
drawn to scale, but are drafted for purposes of convenience and clarity in
illustrating various
aspects of the disclosure.
DETAILED DESCRIPTION
[0030] For the purpose of promoting an understanding of the principles
of the
disclosure, reference will now be made to the features illustrated in the
drawings and specific
language will be used to describe the same. It will nevertheless be understood
that no limitation
of the scope of the disclosure is thereby intended. Any alterations and
further modifications,
and any further applications of the principles of the disclosure as described
herein are
contemplated as would normally occur to one skilled in the art to which the
disclosure relates.
It will be apparent to those skilled in the relevant art that some features
that are not relevant to
the present disclosure may not be shown in the drawings for the sake of
clarity.
[0031] At the outset, for ease of reference, certain terms used in this
application and
their meaning as used in this context are set forth below. To the extent a
term used herein is
not defined below, it should be given the broadest definition persons in the
pertinent art have
given that term as reflected in at least one printed publication or issued
patent. Further, the
present processes are not limited by the usage of the terms shown below, as
all equivalents,
synonyms, new developments and terms or processes that serve the same or a
similar purpose
are considered to be within the scope of the present disclosure.
[0032] Throughout this disclosure, where a range is used, any number
between or
inclusive of the range is implied.
[0033] A "hydrocarbon" is an organic compound that primarily includes
the elements
of hydrogen and carbon, although nitrogen, sulfur, oxygen, metals, or any
number of other
elements may be present in small amounts. Hydrocarbons generally refer to
components found
in heavy oil or in oil sand. However, the techniques described are not limited
to heavy oils but
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may also be used with any number of other reservoirs to improve gravity
drainage of liquids.
Hydrocarbon compounds may be aliphatic or aromatic, and may be straight
chained, branched,
or partially or fully cyclic.
[0034] "Bitumen" is a naturally occurring heavy oil material. Generally,
it is the
hydrocarbon component found in oil sand. Bitumen can vary in composition
depending upon
the degree of loss of more volatile components. It can vary from a very
viscous, tar-like, semi-
solid material to solid forms. The hydrocarbon types found in bitumen can
include aliphatics,
aromatics, resins, and asphaltenes. A typical bitumen might be composed of:
19 weight (wt.) % aliphatics (which can range from 5 wt. % - 30 wt. %, or
higher);
19 wt. % asphaltenes (which can range from 5 wt. % - 30 wt. %, or higher);
30 wt. % aromatics (which can range from 15 wt. % - 50 wt. %, or higher);
32 wt. % resins (which can range from 15 wt. % - 50 wt. %, or higher); and
some amount of sulfur (which can range in excess of 7 wt. %).
In addition, bitumen can contain some water and nitrogen compounds ranging
from less than
0.4 wt. % to in excess of 0.7 wt. %. The percentage of the hydrocarbon found
in bitumen can
vary. The term "heavy oil" includes bitumen as well as lighter materials that
may be found in
a sand or carbonate reservoir.
[0035] "Heavy oil" includes oils which are classified by the American
Petroleum
Institute ("API"), as heavy oils, extra heavy oils, or bitumens. The term
"heavy oil" includes
bitumen. Heavy oil may have a viscosity of about 1,000 centipoise (cP) or
more, 10,000 cP or
more, 100,000 cP or more, or 1,000,000 cP or more. In general, a heavy oil has
an API gravity
between 22.3 API (density of 920 kilograms per meter cubed (kg/m3) or 0.920
grams per
centimeter cubed (g/cm3)) and 10.00 API (density of 1,000 kg/m3 or 1 g/cm3).
An extra heavy
oil, in general, has an API gravity of less than 10.0 API (density greater
than 1,000 kg/m3 or 1
g/cm3). For example, a source of heavy oil includes oil sand or bituminous
sand, which is a
combination of clay, sand, water and bitumen. The recovery of heavy oils is
based on the
viscosity decrease of fluids with increasing temperature or solvent
concentration. Once the
viscosity is reduced, the mobilization of fluid by steam, hot water flooding,
or gravity is
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possible. The reduced viscosity makes the drainage or dissolution quicker and
therefore directly
contributes to the recovery rate.
[0036] The term "bituminous feed" refers to a stream derived from oil
sand 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.
Undesirable components may include but are not limited to clay, minerals,
coal, debris and
water. The bituminous feed may be derived directly from oil sand, and may be,
for example,
raw oil sand 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
sand, 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.
[0037] "Fine particles" are generally defined as those solids having a
size of less than
44 microns (pm), that is, material that passes through a 325 mesh (44 micron).
[0038] "Coarse particles" are generally defined as those solids having a
size of greater
than 44 microns (pm).
[0039] A "solvent-based recovery process" or "solvent extraction process"
or "oil sand
solvent extraction process" includes any type of hydrocarbon recovery process
that uses a
solvent, at least in part, to enhance the recovery, for example, by diluting
or lowering a viscosity
of the hydrocarbon. Solvent-based recovery processes may be used in
combination with other
recovery processes, such as, for example, thermal recovery processes. In
solvent-based
recovery processes, a solvent is injected into a subterranean reservoir. The
solvent may be
heated or unheated prior to injection, may be a vapor or liquid and may be
injected with or
without steam. Solvent-based recovery processes may include, but are not
limited to, solvent
assisted cyclic steam stimulation (SA-CSS), solvent assisted steam assisted
gravity drainage
(SA-SAGD), solvent assisted steam flood (SA-SF), vapor extraction process
(VAPEX), heated
vapor extraction process (H-VAPEX), cyclic solvent process (CSP), heated
cyclic solvent
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process (H-CSP), solvent flooding, heated solvent flooding, liquid extraction
process, heated
liquid extraction process, solvent-based extraction recovery process (SEP),
thermal solvent-
based extraction recovery processes (TSEP), and any other such recovery
process employing
solvents either alone or in combination with steam. A solvent-based recovery
process may be
a TSEP if the solvent is heated prior to injection into the subterranean
reservoir. The solvent-
based recovery process may employ gravity drainage.
[0040] "Macro-agglomeration" is the consolidation of both fine particles
and coarse
particles that make up the oil sand. Macro-agglomerates may have a mean
diameter of 2
millimeters (mm) or greater.
[0041] "Micro-agglomeration" is the consolidation of fine particles that
make up the oil
sand. Micro-agglomerates may have a mean diameter of less than 2 millimeters
(mm).
[0042] A "rich bitumen extract stream" is generally defined as a bitumen
extract stream
from which at least some solids have been removed.
[0043] A "lean bitumen extract stream" is generally defined as a bitumen
extract stream
from which a rich bitumen stream and at least some solids have been removed.
[0044] A "washed solids stream" is generally defined as a solids stream
that has been
washed using a solvent, such as but not limited to an aliphatic solvent.
[0045] A "deasphalted lean bitumen extract stream" is generally defined
as a lean
bitumen extract stream that has been deasphalted to remove some or all
asphaltenes.
[0046] A "bitumen extract" is generally defined as bitumen that has been
extracted from
oil sand.
[0047] "Residual solid fines" are generally defined as fines remaining in
a stream
following a solids separation process.
[0048] A "bitumen product stream" is generally defined as a high grade
bitumen
product that may be suitable for transport within pipelines and processing
within downstream
refineries. A high grade bitumen product stream may have a solids content of
less than 1 wt.%,
or less than 0.1 wt. %, on a dry bitumen basis.
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[0049] A "low grade bitumen product stream" is generally defined as the
result of
removing solvent from a stream containing precipitated asphaltenes, such as
precipitated
asphaltenes which have been removed from a lean bitumen extract stream, or an
asphaltene-bitumen extract mixture comprising precipitated asphaltenes, or a
precipitated
asphaltenes separated from a diluted bitumen extract stream.
[0050] The term "solvent" as used in the present disclosure should be
understood to
mean either a single solvent, or a combination of solvents.
[0051] "Solvent deasphalting" is generally defined as a method to remove
the solids
that remain in a bitumen extract from the bitumen extract.
[0052] The terms "approximately," "about," "substantially," and similar
terms are
intended to have a broad meaning in harmony with the common and accepted usage
by those
of ordinary skill in the art to which the subject matter of this disclosure
pertains. It should be
understood by those of skill in the art who review this disclosure that these
terms are intended
to allow a description of certain features described and claimed without
restricting the scope of
these features to the precise numeral ranges provided. Accordingly, these
terms should be
interpreted as indicating that insubstantial or inconsequential modifications
or alterations of the
subject matter described and are considered to be within the scope of the
disclosure.
[0053] The articles "the", "a" and "an" are not necessarily limited to
mean only one,
but rather are inclusive and open ended so as to include, optionally, multiple
such elements.
[0054] "At least one," in reference to a list of one or more entities
should be understood
to mean at least one entity selected from any one or more of the entity in the
list of entities, but
not necessarily including at least one of each and every entity specifically
listed within the list
of entities and not excluding any combinations of entities in the list of
entities. This definition
also allows that entities may optionally be present other than the entities
specifically identified
within the list of entities to which the phrase "at least one" refers, whether
related or unrelated
to those entities specifically identified. Thus, as a non-limiting example,
"at least one of A and
B" (or, equivalently, "at least one of A or B," or, equivalently "at least one
of A and/or B") may
refer, to at least one, optionally including more than one, A, with no B
present (and optionally
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including entities other than B); to at least one, optionally including more
than one, B, with no
A present (and optionally including entities other than A); to at least one,
optionally including
more than one, A, and at least one, optionally including more than one, B (and
optionally
including other entities). In other words, the phrases "at least one," "one or
more," and "and/or"
are open-ended expressions that are both conjunctive and disjunctive in
operation. For
example, each of the expressions "at least one of A, B and C," "at least one
of A, B, or C," "one
or more of A, B, and C," "one or more of A, B, or C" and "A, B, and/or C" may
mean A alone,
B alone, C alone, A and B together, A and C together, B and C together, A, B
and C together,
and optionally any of the above in combination with at least one other entity.
[0055]
Solvent deasphalting of a lean bitumen extract stream has the advantage of
controlling a location within a solvent extraction process where asphaltenes
are precipitated. It
may be desirable to limit or eliminate asphaltene precipitation within
transfer lines carrying
asphaltene containing streams between equipment used in a solvent extraction
process to
mitigate fouling. It may desirable to limit the amount of undissolved
asphaltenes within an
extraction vessel of a solvent extraction process to limit the effect
undissolved asphaltenes have
on reducing the rate by which bitumen dissolves into an extraction liquor.
There are locations
within the solvent extraction process where asphaltene precipitation may be
desirable. For
example, asphaltene precipitation may be desirable in locations within the
solvent extraction
process where the lean bitumen extract stream is mixed with a rich bitumen
extract stream to
form a combined stream. The combined stream may be deasphalted to produce a
deasphalted
bitumen extract stream and a deasphalted extraction liquor. The deasphalted
bitumen extract
stream has the advantage that residual solid fines are removed during
deasphalting to produce
reduced ash and increased API bitumen product, as compared to a bitumen
extract stream that
has not been deasphalted, when solvent is removed from the deasphalted bitumen
extract. The
deasphalted extraction liquor may have the advantage of producing an
extraction liquor that
more readily extracts bitumen from the bituminous feed than an extraction
liquor that is not
deasphalted. The deasphalted extraction liquor may have this advantage because
of the absence
of asphaltene molecules within the extraction liquor. The asphaltene molecules
may reduce the
rate of bitumen dissolution.
- 13 -
CA 2979231 2017-09-14
[0056] The solvent deasphalting described in the present disclosure may
be referred to
as controlled deasphalting. The controlled deasphalting may be combined with
aspects of other
solvent extraction processes, including but not limited to solvent extraction
with a solids
agglomeration process. Non-limiting examples of solvent extraction processes
that are solvent
extraction with solids agglomeration processes, include those described in the
background of
the present disclosure and in CA 2,724,806 ("Adeyinka et al.").
[0057] Adeyinka et al. discloses extracting bitumen from oil sand in a
manner that
employs solvent. A first solvent is combined with a bituminous feed derived
from oil sand to
form an initial slurry. The initial slurry is separated into a fines solids
stream and a coarse solids
stream, where the majority of the fine solids within the oil sand are in the
fine solids stream and
the majority of the coarse solids within oil sand are in the coarse solids
stream. The coarse
solids steam can be separated into coarse solids and a first low solids
bitumen extract stream.
Aqueous bridging liquid is added to the fine solids stream to agglomerate the
fine solids in the
stream and form an agglomerated slurry. The agglomerated slurry can be
separated into
agglomerates and a second low solids bitumen extract stream. A second solvent
can be mixed
with the first and second low solids bitumen extract streams to form 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 high grade bitumen
extracts is conducted
to produce bitumen products of commercial value.
[0058] The solvent extraction with solid agglomeration processes
described by
Adeyinka et al. is one suitable solvent extraction process for the processes
described in the
present disclosure. The aqueous bridging liquid of Adeyinka et al. may be
added to the slurry
(without separating the slurry into a coarse stream and a fine stream),
followed by
agglomeration. The extraction liquor that contacts the bituminous feed may
allow for complete
or near complete dissolution of the bitumen to increase overall bitumen
recovery. Complete
dissolution of the bitumen will result in fine solids dispersing into the
bitumen extract which,
if left dispersed, will hamper solid-liquid separation downstream of the
extraction process. In
contrast to the method described in U.S. Patent Publication 2011/0127197
(Blackbourn et al.),
the initial dispersing of the fine solids of Adeyinka et al. is acceptable
because the solid
- 14 -
CA 2979231 2017-09-14
agglomeration process will allow for the majority of the fine solids to be
recaptured as
agglomerates with the aqueous bridging liquid. The lean bitumen extract stream
described in
the present disclosure may be used as the second solvent in the process
described by Adeyinka
et al. The lean bitumen extract stream, which may be comprised of an aliphatic
solvent such
as but not limited to pentane, when mixed with the low solids bitumen extract,
may result in
asphaltene precipitation. The asphaltene precipitation may be referred to as
precipitated
asphaltenes. The precipitated asphaltenes aggregate with the residual solids,
forming
aggregated precipitated asphaltenes, and settle by gravity to form a high
grade bitumen extract
above a low grade bitumen extract. Solvent within the high grade bitumen
extract can be
recovered from the high grade bitumen extract overflow to form a bitumen
product with a solid
content of less than 0.1 wt. %. The low grade bitumen extract may be recycled
to other units
of the solvent extraction process to separate bitumen from the aggregated
precipitated
asphaltenes. Solvent may be recovered from the low grade bitumen extract to
produce a low
grade bitumen product with commercial value.
[0059] Figure 1 is a flow chart of a method for processing a bituminous
feed. The
method may de-asphalt a lean bitumen extract stream. Figure 5 is another flow
chart for
processing a bituminous feed.
[0060] The method may comprise forming an oil sand slurry (108) by
contacting a
bituminous feed (102) with a first extraction liquor (104), in a bitumen
extraction step (106),
(502). The oil sand slurry (108) may comprise a bitumen extract and solids.
[0061] The first extraction liquor may comprise a first solvent. The
first solvent may
be used to extract bitumen from the bituminous feed. The first extraction
liquor may comprise
a hydrocarbon solvent capable of dissolving the bitumen. The first extraction
liquor may be a
solution of a hydrocarbon solvent(s) and bitumen, where the bitumen content of
the first
extraction liquor may range between 0 and 70 wt.%, or between 0 and 50 wt.%,
or between 30
and 70 wt. %. The first extraction liquor may contain dissolved bitumen. When
the first
extraction liquor contains dissolved bitumen, the volume of the first
extraction liquor may be
increased without an increase in the required inventory of hydrocarbon
solvent(s).
- 15 -
CA 2979231 2017-09-14
[0062] A second solvent (142) may be added in the bitumen extraction step
(106). The
second solvent (142) may contact the bituminous feed (102) to help form the
oil sand slurry
(108).
[0063] The solvent extraction process may be adjusted to provide a ratio
of solvent (the
first solvent and/or the second solvent) to bitumen in the oil sands slurry
that minimizes
asphaltenes precipitation during the bitumen extraction step (106). The
presence of some
amount of precipitated asphaltenes is unavoidable. By adjusting the amount of
first and/or
second solvent flowing into a bitumen extraction vessel of the bitumen
extraction step (106), a
ratio of the first and/or second solvent to the bitumen in the bitumen
extraction vessel can be
controlled. Bitumen in the bitumen extraction vessel comes from the bituminous
feed and any
bitumen entrained in the first extraction liquor. Selecting the ratio of the
first and/or second
solvent to the bitumen may decrease the costs for processing the bituminous
feed if the ratio is
one with less solvent than bitumen. Having less first and/or second solvent
than bitumen may
lower the costs for processing the bituminous feed because of the lower first
and/or second
solvent requirements.
[0064] The ratio of the first and/or second solvent to the bitumen may be
selected as a
target ratio. The target ratio may be less than 2:1. For example but not
limited to, the target
ratio may be 1.5:1 or less, 1:1 or less, or 0.75:1. For clarity, ratios may be
expressed in the
present disclosure 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.
[0065] The first extraction liquor may be recycled to the bitumen
extraction step (106)
from a downstream step, such as but not limited to from liquid splitter (140),
as detailed below.
Residual bitumen within the first extraction liquor may increase the volume of
the first
extraction liquor. The residual bitumen within the first extraction liquor may
increase the
solubility of the first extraction liquor for additional bitumen dissolution.
[0066] Throughout this application including with reference to all
Figures, the terms
"solvent", "first solvent", "second solvent", and "third solvent" are each
considered to be a
"solvent" as defined in the present disclosure. The "solvent", "first
solvent", "second solvent",
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CA 2979231 2017-09-14
and/or "third solvent" may be the same or different from one another. As is
evident from the
description of the Figures, the "solvent", "first solvent", "second solvent",
and/or "third
solvent" may be added in different locations in the process and/or may be
added alone or as
part of a composition such as but not limited to as part of an extraction
liquor (e.g., a first
extraction liquor, a second extraction liquor). The "first solvent", "second
solvent", and/or
"third solvent" may interchangeably be referred to as a solvent. This
paragraph applies to all
of the Figures in the present disclosure.
[0067] Several types of solvents are suitable for use in the solvent
extraction process.
The solvent may comprise an organic solvent or a mixture of organic solvents.
The solvent may
comprise light aromatic compounds. The light aromatic compounds may be a light
aromatic
solvent with zero to 100% aromatic compounds. A light aromatic solvent may
have less than
16 carbon atoms per molecule. Exemplary solvents include, but are not limited
to, benzene,
toluene, naphtha and kerosene. In cases where the aromatic content of the
solvent is less than
what is needed to fully dissolve the bitumen in the bituminous feed, pre-
dissolved bitumen
within the extraction liquor can increase the solubility of the extraction
liquor towards
dissolving additional bitumen. This paragraph applies to all of the Figures in
the present
disclosure.
[0068] The solvent may comprise at least one of an open chain aliphatic
hydrocarbon,
and a cyclic aliphatic hydrocarbon. Low boiling point cycloalkanes, or mixture
of such
cycloalkanes, can substantially dissolve asphaltenes. This paragraph applies
to all of the
Figures in the present disclosure.
[0069] The solvent may comprise a paraffinic solvent. The paraffinic
solvent may be
one in which the solvent to bitumen ratio of the bitumen extract and/or the
first extraction liquor
is maintained at a level to avoid or limit precipitation of asphaltenes. The
paraffinic solvent
may comprise at least one of an alkane, a natural gas condensate, and a
distillate from a
fractionation unit (or diluent cut) containing more than 40% small chain
paraffins of 3 to 10
carbon atoms, referred to in the present disclosure as a small chain (or short
chain) paraffin
mixture. This paragraph applies to all of the Figures in the present
disclosure.
- 17 -
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[0070] Should an alkane be selected as the solvent, the alkane may
comprise at least
one of a normal alkane and an iso-alkane. The alkane may comprise at least one
of heptane,
iso-heptane, hexane, iso-hexane, pentane, and iso-pentane. This paragraph
applies to all of the
Figures in the present disclosure.
[0071] A cyclic aliphatic hydrocarbon may be selected as the solvent, it
may comprise
a cycloalkane of 4 to 9 carbon atoms. A mixture of C3-C9 cyclic and/or open
chain aliphatic
solvents may be appropriate. Exemplary cycloalkanes include at least one of
cyclohexane and
cyclopentane. 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. A mixture of
C3-C10 cyclic
and/or open chain aliphatic solvents would also be appropriate. For example,
it can be a mixture
of C3-C9 cyclic aliphatic hydrocarbons and paraffinic solvents where the
percentage of the
cyclic aliphatic hydrocarbons in the mixture is greater than 50%. This
paragraph applies to all
of the Figures in the present disclosure.
[0072] The solvent may have a final boiling point of less than 200 C
(degrees Celsius).
The solvent may have a final boiling point of less than 100 C. While it is not
necessary to use
a solvent having a boiling point of less than 200 C or less than 100 C, there
may be an extra
advantage that solvent recovery proceeds at lower temperatures, and requires a
lower energy
consumption than solvent recovery at higher temperatures.
[0073] The oil sand slurry may have a solid content in the range of 5 to
70 wt.%, 20 to
70 wt.%, or 40 to 70 wt.%. In the case of a solvent extraction process with
solids agglomeration
process, a higher solids content oil sand slurry may be desired. The higher
solids content may
increase the compaction forces that may help in the solids agglomeration
process. In other
cases, a lower solids content may be desired. The lower solids content may
reduce the mixing
energy needed in the solvent based extraction process. The oil sand slurry may
have a higher
solids content for the extraction and agglomeration processes and then be
diluted to a lower
solids content prior to solid-liquid separation. This paragraph applies to all
of the Figures in
the present disclosure.
- 18 -
CA 2979231 2017-09-14
[0074] The temperature of the oil sand slurry may be at a value that is
configured to
minimize a presence of undissolved asphaltenes in the oil sand slurry. The
value may include
any number within or bounded by the range of 20-100 C. When the temperature of
the oil sand
slurry is kept at a value that minimizes the presence of undissolved
asphaltenes in the oil sand
slurry, the bitumen dissolution rate may be decreased; the viscosity of the
oil sand slurry may
be decreased. Decreasing the bitumen dissolution rate and/or the viscosity of
the oil sand slurry
may promote more effective sand digestion and agglomerate formation than
increasing the
bitumen dissolution rate and/or decreasing the viscosity of the oil sand
slurry. When the
temperature of the oil sand slurry is kept at the value that minimizes the
presence of undissolved
asphaltenes in the oil sand slurry, the solid-liquid separation may be
improved because higher
temperatures may result in a reduced slurry viscosity, which in turn, may
improve the solid-
liquid separation process. Temperatures above 100 C are generally avoided due
to the
complications resulting from high vapor pressures. This paragraph applies to
all Figures in the
present disclosure.
[0075] The method may comprise diluting the oil sand slurry (108) prior
to separating
the solids in the oil sand slurry (108) from the bitumen extract in the oil
sand slurry (108). The
oil sand slurry (108) may be diluted in a dilution step (110) to form a
diluted oil sand slurry
(147). The oil sand slurry (108) may be diluted by a second extraction liquor
(112). The oil
sand slurry (108) may be diluted by a third solvent (144). The first
extraction liquor (104) may
have a bitumen content that is the same or more than that of the second
extraction liquor (112).
The bitumen content of the second extraction liquor (112) may be between 0 and
70 wt. %.
[0076] The method may comprise forming a rich bitumen extract stream
(118) and
separated solids (116) by separating the solids from the bitumen extract,
(504). The method
may comprise forming the rich bitumen extract stream (118) and the separated
solids (116) in
a solid-liquid separator (114). Any suitable solid-liquid separator (114) may
be used. For
example and without limitation, the solid-liquid separator (114) may comprise
a gravity settler
or an enhanced gravity settler.
[0077] The method may comprise forming a washed solids stream (124) and a
lean
bitumen extract stream (126) by washing the separated solids (116) with an
aliphatic solvent
- 19 -
CA 2979231 2017-09-14
(122), (506). The separated solids (116) may be washed with the aliphatic
solvent (122) in a
washer unit (120). The aliphatic solvent (122) may be used to precipitate
asphaltenes, which
are removed from the washer unit (120) as part of the lean bitumen extract
stream (126). The
lean bitumen extract stream (122) may comprise precipitated asphaltenes.
[0078] The method may comprise forming a deasphalted lean bitumen extract
stream
(132) by separating the precipitated asphaltenes (130) from the lean bitumen
extract stream
(126), (508). The precipitated asphaltenes (130) may be separated from the
lean bitumen extract
stream (126) in a separator (128). The separator (128) may be any suitable
separator. For
example, the separator (128) may include but is not limited to a gravity
settler or an enhanced
gravity settler. At least a portion of the deasphalted lean bitumen extract
stream (132) may be
recycled as recycled deasphalted lean bitumen extract stream. The recycled
deasphalted lean
bitumen extract stream may be the second extraction liquor (112). The recycled
deasphalted
lean bitumen extract stream may be the first extraction liquor (104). Solvent
may be recovered
from the precipitated asphaltenes (130) to form a low grade bitumen stream
(not shown).
[0079] The method may comprise recycling at least a portion of the rich
bitumen extract
stream (118) as recycled rich bitumen extract stream. The recycled rich
bitumen extract stream
may be the first extraction liquor (104). The rich bitumen extraction extract
stream (118) may
be fed to a liquid splitter (140) to split the rich bitumen extract stream
(118) into a first portion
of the rich bitumen extract stream (148) and a second portion of the rich
bitumen extract stream
(104). The second portion of the rich bitumen extract stream (104) may be the
at least the
portion of the rich bitumen extract stream recycled as the recycled rich
bitumen extract stream.
The first portion of the rich bitumen extract stream (148) may be referred to
as a portion of the
rich bitumen extract stream. The second portion of the rich bitumen extract
stream 104 may be
referred to as a portion of the rich bitumen extract stream. Using at least a
portion of the rich
bitumen extract stream as the first extraction liquor may ensure that the
solvent-to-bitumen ratio
(S:B) of the initial bitumen extract obtained from dissolution of bitumen from
the bituminous
feed is less than the S:B of the lean bitumen extract. The lower S:B ratio has
the advantage of
increasing the amount of bitumen dissolution from the bituminous feed, which
may increase
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overall bitumen recovery. Additional solvent may be added to the recycled rich
bitumen extract
stream to achieve a desired S:B ratio.
[0080] The method may comprise obtaining a bitumen product stream (138)
by
removing the first solvent (136) from at least one of a portion (148) of the
rich bitumen extract
stream (118) (i.e., the first portion of the rich bitumen extract stream
(148)) and a portion (149)
of the deasphalted lean bitumen extract stream (132), (510). The bitumen
product stream (138)
may be obtained by removing solvent in a solvent recovery step (134) from at
least one of the
portion (148) of the rich bitumen extract stream (118) and a portion of the
deasphalted lean
bitumen extract stream (132). The portion (148) of the rich bitumen extract
stream (118) may
be referred to as the first portion of the rich bitumen extract stream; the
portion (149) of the
deasphalted lean bitumen extract stream may be referred to as the first
portion of the deasphalted
lean bitumen extract stream, or the second portion of the deasphalted lean
bitumen extract
stream.
[0081] The method may comprise mixing an additional solvent with the
recycled
deasphalted lean bitumen extract stream. The method may comprise mixing the
additional
solvent prior to the recycled deasphalted lean bitumen extract stream's use as
the first extraction
liquor (104) and/or the second extraction liquor (112). The first extraction
liquor and/or the
second extraction liquor (112) may comprise, in addition to the deasphalted
lean bitumen
extract stream (132), the additional solvent.
[0082] The deasphalting of the lean bitumen extract stream, of the
process depicted in
Figure 1, has the advantage of controlling the location within the solvent
extraction process
where asphaltenes are precipitated. The precipitated asphaltenes and fine
solids may be
separated from the lean bitumen extract stream in the separator (128). The
deasphalted lean
bitumen extract stream (132) may reduce the chance that asphaltene
precipitation will foul
process equipment, including but not limited to the pipelines used to recycle
the lean bitumen
extract stream (126) to upstream processes. Reducing the risk of fouling
process equipment by
asphaltene precipitation may substantially decrease the need for maintenance
of the process
equipment. The lower solid content of the deasphalted lean bitumen extract
stream (132) may
reduce the chance of plugging of process equipment by solids. For this reason,
the
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CA 2979231 2017-09-14
hydrodynamic requirements for fluid flow in pipelines and other process
equipment may be
dictated by factors other than the risk of solid settling.
[0083] The method may comprise forming an asphaltene-bitumen extract
mixture by
mixing the precipitated asphaltenes (130) with at least some of the portion of
the rich bitumen
extract stream (148) (not shown). The asphaltene-bitumen extract mixture may
be separated
from the first portion of the rich bitumen extract stream (148) to remove the
residual solids that
are within the first portion of the rich bitumen extract stream (148).
Removing the residual
solids may allow for the precipitated asphaltenes (130) from the lean bitumen
extract stream
(126) to assist with the aggregation and separation of the residual fine
solids from the first
portion of the rich bitumen extract stream (148).
[0084] The temperature and pressure of the asphaltene-bitumen extract
mixture can be
adjusted to improve the ability of the precipitated asphaltenes (130) to
aggregate the fine solids.
For example, the asphaltene-bitumen extract mixture temperature may be lowered
(i.e., the
asphaltene-bitumen extract mixture temperature may be cooled) to increase the
viscosity and
capture ability of the precipitated asphaltenes (130) and/or to reduce the
tendency of the
precipitated asphaltenes to dissolve; the asphaltene-bitumen extract mixture
temperature may
be increased (i.e., the asphaltene-bitumen extract mixture may be heated) to
reduce the tendency
of the precipitated asphaltenes to dissolve based on their thermodynamic
equilibrium.
Additional aliphatic solvent, such as but not limited to pentane, may be added
to the asphaltene-
bitumen extract mixture to precipitate additional asphaltenes that may further
help aggregate
the fine solids. Solvent may be removed from the asphaltene-bitumen extract
mixture to obtain
a low grade bitumen product stream.
[0085] Prior to entering the dilution step (110), the oil sand slurry
may be mixed with
an aqueous bridging liquid to form an agglomerated slurry. Mixing the oil sand
slurry with the
aqueous bridging liquid may help to agglomerate the solids within the oil sand
slurry and form
an agglomerated slurry. The agglomerates within the agglomerated slurry may be
sized on the
order of 0.1-1.0 mm, on the order of 0.1-0.5 mm or on the order of 0.1-0.3 mm.
At least 80 wt.
% of the agglomerates within the agglomerated slurry may be 0.1-1.0 mm, on the
order of 0.1-
0.5 mm or 0.1 to 0.3 mm in size. The rate of agglomeration may be controlled
by a balance
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CA 2979231 2017-09-14
between intensity of agitation within an agglomeration vessel, shear within
the vessel which
can be adjusted, for example, by changing the shape or size of the vessel,
fines content of the
slurry, bridging liquid addition, and residence time of the agglomeration
process. The
agglomerated slurry may have a solids content of 20 to 70 wt. %.
[0086] The aqueous bridging liquid may be a liquid with affinity for the
solids particles
in the bituminous feed. The aqueous bridging liquid may be a liquid that is
immiscible in the
first extraction liquor and/or the second extraction liquor. Exemplary aqueous
bridging liquids
may be water that accompany the bituminous feed and/or recycled water from
other aspects or
steps of oil sand processing. The aqueous bridging 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 in such a way
that permits fines to adhere to each other. An exemplary aqueous bridging
liquid is water. The
aqueous bridging liquid may be added to the slurry in a concentration of less
than 20 wt. % of
the slurry, less than 10 wt. % of the slurry, between 1 wt. % and 20 wt. %, or
between 1 wt. %
and 10 wt. %. The aqueous bridging liquid may comprise fine particles (for
instance less than
44 micrometer (nm)) suspended within the aqueous bridging liquid. The fine
particles
suspended may serve as seed particles for the agglomeration process. The
aqueous bridging
liquid may comprise less than 40 wt.% solid fines, or have a solids content of
20 to 70 wt. %.
[0087] The agglomeration process may be assisted by some form of
agitation. The form
of agitation may be mixing, shaking, rolling, or another known suitable
method. The agitation
of the bituminous feed (102) need only be severe enough and of sufficient
duration to intimately
contact the aqueous bridging liquid with the solids in the bituminous feed.
Exemplary rolling
type vessels include rod mills and tumblers. Exemplary mixing type vessels
include mixing
tanks, blenders, and attrition 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 bituminous feed may be greater than 40 wt. % so that
compaction
forces assist agglomerate formation. The agitation of the oil sand slurry has
an impact on the
growth of the agglomerates. In the case of mixing type vessels, the mixing
power can be
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CA 2979231 2017-09-14
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 communition of
agglomerates.
[0088] Figure 2 is a flow chart of a method for processing a bituminous
feed. The
method shown in Figure 2 may de-asphalt a diluted bitumen product stream.
[0089] The method may comprise forming an oil sand slurry (208) by
contacting a
bituminous feed (202) with a first extraction liquor (204) in a bitumen
extraction step (206),
(502). The oil sand slurry (208) may comprise a bitumen extract and solids.
The first extraction
liquor (204) may be comprised of the same components as the first extraction
liquor (104)
previously described. A second solvent (242) may be added in the bitumen
extraction step
(206). The second solvent (242) may contact the bituminous feed (202) to help
form the oil
sand slurry (208).
[0090] The method may comprise diluting the oil sand slurry (208) prior
to separating
the solids in the oil sand slurry (208) from the bitumen extract in the oil
sand slurry (208). The
oil sand slurry (208) may be diluted in a dilution step (210) to form a
diluted oil sand slurry
(247). The oil sand slurry (208) may be diluted by a second extraction liquor
(207). The oil
sand slurry (208) may be diluted by a third solvent (244). The first
extraction liquor (204) may
have a bitumen content that is the same or more than that of the second
extraction liquor (207)
as described above with reference to Figure 1.
[0091] The method may comprise forming a rich bitumen extract stream
(218) and
separated solids (216) by separating the solids from the bitumen extract (504)
in a separation
step (214) as described above with reference to Figure 1.
[0092] The method may comprise forming a washed solids stream (224) and a
lean
bitumen extract stream (226) by washing the separated solids (216) with an
aliphatic solvent
(222), (508). The separated solids (216) may be washed with the aliphatic
solvent (222) in a
washer unit (220). The aliphatic solvent (222) may be used to precipitate
asphaltenes which
are removed from the washer unit (220) as part of the lean bitumen extract
stream (226) as
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CA 2979231 2017-09-14
described above with reference to Figure 1. The lean bitumen extract stream
(226) may
comprise precipitated asphaltenes.
[0093] The method may comprise forming a diluted bitumen extract stream
(not shown)
by combining a portion of the rich bitumen extract stream (219) with a portion
of the lean
bitumen extract stream (226) in a deasphalting unit (228). The method may
comprise forming
the portion of the rich bitumen extract stream (219) that contacts the portion
of the lean bitumen
extract stream (226) to form the deasphalted bitumen extract stream in a
liquid splitter (240).
The rich bitumen extract stream (218) may be fed to the liquid splitter (240).
Once in the liquid
splitter (240), the rich bitumen extract stream (218) may be split into the
portion of the rich
bitumen extract stream (219), which contacts the portion of the lean bitumen
extract stream
(226) to form the deasphalted bitumen extract stream, and a second portion of
the rich bitumen
extract stream (204). The second portion of the rich bitumen extract stream
(204) may be used
as the first extraction liquor (204). The portion of the lean bitumen extract
stream (226) may
be mixed with the portion of the rich bitumen extract stream (219) to help
remove residual fine
solids from the portion of the rich bitumen extract stream (219). The portion
of the rich bitumen
extract stream (219) may be referred to as a first portion of the rich bitumen
extract stream. The
second portion of the rich bitumen extract stream (204) may be referred to as
a portion of the
rich bitumen extract stream.
[0094] The method may comprise forming a deasphalted bitumen extract
stream (231)
by separating precipitated asphaltenes (230) from the diluted bitumen extract
stream in the
deasphalting unit (228).
[0095] The method may comprise obtaining a bitumen product stream (238)
by
removing solvent (236) from the deasphalted bitumen extract stream (231). The
solvent (236)
may be removed from the deasphalted bitumen extract stream (231) in a solvent
recovery unit
(234). The bitumen product stream (238) may have a solids content of less than
1 wt. %, or
less than 0.1 wt. %. Solvent (236) can be removed from the deasphalted bitumen
extract stream
(231) to produce a bitumen product stream (238) with a solids content low
enough to be for
downstream refining operations.
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CA 2979231 2017-09-14
[0096] The deasphalting of the diluted bitumen extract stream, of the
process depicted
in Figure 2, has the advantage of controlling the location within the solvent
extraction process
where asphaltenes are precipitated. A majority of the solids that remain
suspended in the rich
bitumen extract stream are oleophilic solids with organic matter adsorbed on
the solids. The
solids suspended in the rich bitumen extract stream may remain suspended
because of strong
interactions with certain components of dissolved bitumen. When an aliphatic
solvent, such as
but not limited to pentane, is mixed with the rich bitumen extract stream, the
solids suspended
tend to aggregate into larger particles that can be readily separated from the
bitumen extract
stream within the rich bitumen extract stream. The solids suspended may
aggregate with
precipitated asphaltenes to form even larger aggregates. The larger aggregates
may be readily
separated from the lean bitumen extract stream in a separator (214).
[0097] A portion of the lean bitumen extract stream may not be mixed
with the rich
bitumen extract stream. This portion of the lean bitumen extract stream may be
deasphalted in
a fashion similar to what is described in the process of Figure 1 to produce a
deasphalted lean
bitumen extract stream, which can be used as part of the second extraction
liquor (207) and/or
as part of the first extraction liquor (204).
[0098] Figure 3 is a flow chart of a method for processing a bituminous
feed. The
method may de-asphalt an extraction liquor and a diluted bitumen product
stream.
[0099] The method may comprise forming an oil sands slurry (308) by
contacting a
bituminous feed (302) with a first extraction liquor (304) comprising a first
solvent in a bitumen
extraction step (306), (602). The oil sands slurry (308) may comprise a
bitumen extract and
solids. The first extraction liquor (304) may be comprised of the same
components of the first
extraction liquor (104) previously described. A second solvent (342) may be
added in the
bitumen extraction step (306). The second solvent (342) may contact the
bituminous feed (302)
to help form the oil sand slurry (308).
[00100] The method may comprise diluting the oil sands slurry (308) prior
to separating
the solids in the oil sands slurry (308) from the bitumen extract in the oil
sands slurry (308).
The oil sands slurry (308) may be diluted in a dilution step (310) to form a
diluted oil sand
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slurry (347). The oil sands slurry (308) may be diluted by a second extraction
liquor (305).
The oil sands slurry (308) may be diluted by a third solvent (344).
[00101] The method may comprise forming a rich bitumen extract stream
(318) and
separated solids (316) by separating the bitumen extract from the solids in a
separation step
(314) as described above with reference to Figure 1, (604). The separated
solids may be referred
to as residual fine solids.
[00102] The method may comprise forming a washed solids stream (324) and
a lean
bitumen extract stream (326) by washing the separated solids (316) with an
aliphatic solvent
(322). The separated solids (316) may be washed with the aliphatic solvent
(322) in a washer
unit (320). The aliphatic solvent (322) may be used to precipitate
asphaltenes, which are
removed from the washer unit (320) as part of the lean bitumen extract stream
(326) as
described above with reference to Figure 1.
[00103] The method may comprise combining at least a portion of the rich
bitumen
extract stream (318) with at least a portion of the lean bitumen extract
stream (326) in a
deasphalting unit (328) to form a diluted bitumen extract stream (not shown).
Additional
aliphatic solvent may be added to the diluted bitumen extract stream to
precipitate asphaltenes,
forming a deasphalted bitumen extract stream (329) and separated asphaltenes
(330). The
deasphalted bitumen extract (329) may be separated by a splitter (327) into a
deasphalted
extraction liquor (332) and a diluted bitumen product stream (331). The
deasphalted extraction
liquor (332) can be used as the first extraction liquor (304) for adding to
the bituminous feed
(302) and/or as the second extraction liquor (305) for adding to the oil sand
slurry (308).
[00104] The deasphalting unit (328) may separate the diluted bitumen
extract stream
with a separator. The separator (328) may separate the deasphalted bitumen
extract stream into
a deasphalted extraction liquor (332) and a diluted bitumen product stream
(331).
[00105] The method may comprise obtaining a bitumen product stream (338)
by
removing a first solvent (336) from the diluted bitumen product stream (331).
The solvent
(336) may be removed from the diluted bitumen product stream (331) in a
solvent recovery unit
(334). The bitumen product stream (338) may have a solids content of less than
1 wt. %, or
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less than 0.1 wt. %. Solvent can be removed from the diluted bitumen product
stream (331) to
produce the bitumen product stream (338) with a substantially low solids
content. The
substantially low solids content may render the bitumen suitable for
downstream refining
operations.
[00106] The method may comprise obtaining a low grade bitumen product
stream by
removing the first solvent from the precipitated asphaltenes to obtain a low
grade bitumen
product stream. The precipitated asphaltenes may be mixed with the rich
bitumen extract
stream.
[00107] The deasphalting of the diluted bitumen extract stream, of the
process depicted
in Figure 3, has the advantage of controlling the location within the solvent
extraction process
where asphaltenes are precipitated. Precipitated asphaltenes and fine solids
may be readily
separated from the diluted bitumen extract stream in the separator (327). The
deasphalted
bitumen extract stream (329) can be separated into the deasphalted extraction
liquor and the
diluted bitumen product stream with both streams having favorable properties.
The diluted
bitumen product stream has the advantage that residual solid fines are removed
during the
deasphalting process and results in a low ash bitumen product. The deasphalted
extraction
liquor has the advantage of being an extraction liquor that may more readily
dissolve bitumen
from the bituminous feed due to the absence of asphaltene molecules that
reduce the rate of
bitumen dissolution. The use of a deasphalted extraction liquor can result in
an increase in
bitumen recovery from a bituminous feed. The deasphalted extraction liquor has
the advantage
of limiting fouling by asphaltene precipitation within the process equipment
pipelines used to
transfer the deasphalted extraction liquor to the bituminous feed. The lower
solid content of
the deasphalted extraction liquor may also reduce the chance of catastrophic
plugging of
process equipment, including pipelines, by settling solids. The deasphalted
bitumen may have
an asphaltene content of less than 15 wt.%, less than 10 wt.%, or less than 5
wt.%. The
deasphalted bitumen may have an undissolved (precipitated) asphaltene content
of less than 1
wt.%, less than 0.5 wt.%, or less than 0.2 wt.%. To achieve these undissolved
(precipitated)
asphaltene contents, the deasphalted bitumen may be subjected, for instance,
to gravity
separation.
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[00108] Figure 4 is a flow chart of a method for processing a bituminous
feed. The
method may de-asphalt and solvent extract with solids agglomeration.
[00109] The method may comprise forming an oil sands slurry (408) by
contacting a
bituminous feed (402) with a first extraction liquor (404) comprising a first
solvent in a bitumen
extraction step (406). The oil sands slurry (408) may comprise a bitumen
extract and solids.
The first extraction liquor (404) may be comprised of the same components of
the first
extraction liquor (104) previously described. A second solvent (442) may be
added in the
bitumen extraction step (406). The second solvent (442) may contact the
bituminous feed (402)
to help form the oil sand slurry (408).
[00110] The method may comprise diluting the oil sands slurry (408) prior
to separating
the solids in the oil sands slurry (408) from the bitumen extract in the oil
sands slurry (408).
The oil sands slurry (408) may be diluted in a dilution step (410) to form a
diluted oil sand
slurry (447). The oil sands slurry (408) may be diluted by a second extraction
liquor (407).
The oil sands slurry (408) may be diluted by a third solvent (444).
[00111] An aqueous bridging liquid (445) may be added to the oil sand
slurry (408) as
part of an agglomeration step (446) to agglomerate the solids in the slurry
and form an
agglomerated slurry (448). As described above, the aqueous bridging liquid may
wet the solids
and displace the suspension liquid on the surface of the solids. The aqueous
bridging liquid
may be referred to as a bridging liquid. As a result of interfacial forces
among three phases (i.e.
the aqueous bridging liquid, the suspension liquid, and the solids), fine
particles within the
solids may consolidate into larger, compact agglomerates that are more readily
separated from
the suspension liquid.
[00112] The method may comprise forming a rich bitumen extract stream
(418) and
separated solids (416) by separating the bitumen extract from the solids in a
separation step
(414) as described with reference to Figure 1. The separated solids may be
referred to as
residual solids.
[00113] The method may comprise forming a washed agglomerated solids
stream (424)
and a lean bitumen extract stream (426) by washing the separated solids (416)
with an aliphatic
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solvent (422) in a washer unit (420). The aliphatic solvent (422) may be used
to precipitate
asphaltenes removed from the washer unit (420) as part of the lean bitumen
extract stream (426)
as described above with reference to Figure 1.
[00114] The method may comprise forming a diluted bitumen extract stream
by
combining a portion (419) of the rich bitumen extract stream (418) with a
portion of the lean
bitumen extract stream (426) in a deasphalting unit (428). The method may
comprise forming
the portion of the rich bitumen extract stream (419) that contacts the portion
of the lean bitumen
extract stream (426) in a liquid splitter (440) such as the liquid splitter
(240) previously
described with respect to Figure 1. The liquid splitter (440) may function in
the same way as
the liquid splitter (240) previously described with respect to Figure 1 to
split the rich bitumen
extract stream (218) into the portion of the rich bitumen extract stream
(419), which contacts
the portion of the lean bitumen extract stream (426), and a second portion of
the rich bitumen
extract stream (404). The second portion of the rich bitumen extract stream
(404) may be the
same as the second portion of the rich bitumen extract stream (204) discussed
with respect to
Figure 1. The portion of the lean bitumen extract stream (426) may be mixed
with the portion
of the rich bitumen extract stream (418) to help remove residual fine solids
from the portion of
the rich bitumen extract stream (418). The portion of the rich bitumen extract
stream (419) may
be referred to as a first portion of the rich bitumen extract stream. The
second portion of the
rich bitumen extract stream (404) may be referred to as a portion of the rich
bitumen extract
stream.
[00115] The second portion of the rich bitumen extract stream (404) may
not be mixed
with the rich bitumen extract stream. The second portion of the rich bitumen
extract stream
(404) may be deasphalted, in a fashion similar to what is described with
respect to Figure 1, to
produce a deasphalted lean bitumen extract stream. The deasphalted lean
bitumen extract
stream may be used as part of the second extraction liquor (407).
[00116] The method may comprise separating the diluted bitumen extract
stream, in a
solid-liquid separation step, to form a low solids bitumen extract stream
(431), settled solids
and undissolved asphaltenes (430).
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[00117] The method may comprise obtaining another bitumen product stream
(438) by
removing the first solvent (436) from the low solids bitumen extract stream
(431). The solvent
(436) may be removed from the low solids bitumen extract stream (431) in a
solvent recovery
unit (434). The another bitumen product stream (438) may have a solids content
of less than 1
wt. %, or less than 0.1 wt. %. Solvent can be removed from the low solids
bitumen extract
stream (431) to produce the another bitumen product stream (438) with a
substantially low
solids content. The substantially low solids content may render the bitumen
suitable for
downstream refining operations.
[00118] Solvent extraction with solid agglomeration process is one
suitable solvent
extraction process for use with the processes described in the present
disclosure. The portion
of the rich bitumen extract stream may be recycled so that it is used as the
first extraction liquor.
Using a portion of the rich bitumen extract stream as the first extraction
liquor ensures that the
S:B of the initial bitumen extract obtained from dissolution of bitumen from
the bituminous
feed is less than the S:B of the bitumen extract. The lower S:B ratio has the
advantage of
increasing the amount of bitumen dissolution from the bituminous feed, which
may increase
overall bitumen recovery. However, the complete or near complete dissolution
of the bitumen
will result in fine solids dispersing into the bitumen extract which, if left
dispersed, will hamper
solid-liquid separation downstream of the solvent extraction process.
Dispersion of the fine
solids prior to solid agglomeration is acceptable because the solid
agglomeration process will
allow for the majority of the fine solids to be recaptured as agglomerates
with the bridging
liquid. The temperature, pressure, solvent composition, extraction liquor
composition(s),
and/or S:B of the bitumen extract may be configured to minimize the presence
of undissolved
asphaltenes. The temperature, pressure, solvent composition, extraction liquor
composition(s),
and/or S:B of the bitumen extract may be configured to minimize the presence
of undissolved
asphaltenes by keeping a value of the temperature, pressure, solvent
composition, extraction
liquor composition(s), and/or S:B of the bitumen extract at a value that
minimizes the presence
of undissolved asphaltenes.
[00119] The residual solids that remain in the rich bitumen extract
stream may be
removed by mixing a portion of the rich bitumen extract stream with some or
all of the lean
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bitumen extract stream. The increased S:B ratio of the diluted bitumen extract
stream may
cause the residual solids to aggregate with or without accompanying asphaltene
precipitation.
The aggregated fine solids may readily be separated from the diluted bitumen
extract stream in
a separator (428). The solvent can be removed from the diluted bitumen extract
stream to
produce a bitumen product stream with a solid content of less than 0.1 wt.%.
The underflow
stream from the separation process may be recycled upstream of the separation
process in order
to recover residual bitumen extract from the solid agglomerates. For example,
the underflow
comprised of undissolved asphaltenes may be recycled and mixed with the rich
bitumen extract
stream to assist with the aggregation of the fine solids. In cases when
precipitated asphaltenes
are aggregated with the fine solids, the solvent can be recovered from the
underflow extract
stream to produce a low grade bitumen product with commercial value.
[00120] Figures 6 and 8 are a flow charts of a method for processing a
bituminous feed.
[00121] The method may comprise forming an oil sand slurry (808) by
contacting a
bituminous feed (802) with a first extraction liquor (804), in a bitumen
extraction step (806),
(602), as described above with reference to Figure 1. The oil sand slurry
(808) may comprise
a bitumen extract and solids, as described above with reference to Figure 1.
The first extraction
liquor (804) may comprise a first solvent, as described above with reference
to Figure 1.
[00122] The method may comprise forming a rich bitumen extract stream
(818) and
separated solids (816) by separating the solids from the bitumen extract,
(604), as described
above with reference to Figure 1. The method may comprise forming the rich
bitumen extract
stream (818) and the separated solids (816) in a solid-liquid separator (814),
as described above
with reference to Figure 1.
[00123] The method may comprise providing a hydrocarbon fluid (850)
comprising
undissolved asphaltenes (606). The hydrocarbon fluid (850) may be any suitable
hydrocarbon
fluid for increasing the solvent to bitumen ratio and to precipitate
asphaltenes as described
above with reference to Figure 1.
[00124] The method may comprise forming an asphaltene-bitumen extract
mixture (852)
by mixing the hydrocarbon fluid (850) with the rich bitumen extract stream
(818), (608). The
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hydrocarbon fluid (850) may be mixed with the rich bitumen extract stream
(818) in a mixer
(851). The mixer (851) may be any suitable mixer to combine the two streams.
[00125] The method may comprise forming a low solids bitumen extract
stream (854)
by separating asphaltenes and residual fine solids (856) from the asphaltene-
bitumen extract
mixture (852), (610). The method may comprise forming the low solids bitumen
extract stream
(854) and the asphaltenes and residual fine solids (856) in a solid-liquid
separator (853), as
described above with reference to Figure 1.
[00126] The method may comprise obtaining a bitumen product stream (858)
by
removing the first solvent (860) from the low solids bitumen extract stream
(854), (612), as
described above with reference to Figure 1. The bitumen product stream (858)
may be obtained
by removing the first solvent (860) in a solvent recovery step (862).
[00127] Figures 7 and 9 are flow charts of a method for processing a
bituminous feed.
[00128] The method may comprise providing an extraction liquor (904)
comprising
deasphalted bitumen and a first solvent, in a solvent extraction step (906),
(702), as described
above with reference to Figure 1.
[00129] The method may comprise forming an oil sand slurry (908) by
contacting the
bituminous feed (902) with the extraction liquor (904), (704), as described
above with reference
to Figure 1. The oil sand slurry (908) may comprise a bitumen extract and
solids.
[00130] The method may comprise forming a rich bitumen extract stream
(918) by
separating the solids (916) from the bitumen extract (706), as described above
with reference
to Figure 1. The rich bitumen extract stream (918) may be separated from the
solids (916) in a
solid-liquid separator (914), as described above.
[00131] The method may comprise obtaining a bitumen product stream (962)
by
removing the first solvent (964) from a portion of the rich bitumen extract
stream (918) (708),
as described above (708) with reference to Figure 1. The bitumen product
stream (962) may
be obtained by removing the first solvent (964) in a solvent recovery step
(968).
[00132] The deasphalted bitumen within the first extraction liquor may
have several
advantages. The deasphalted bitumen may be more readily able to dissolve
bitumen from the
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bituminous feed. The deasphalted bitumen may be more readily able to dissolve
bitumen from
the bituminous feed due to a reduced amount of asphaltene content. The reduced
amount of
asphaltene content can reduce a rate of bitumen dissolution. Therefore, the
deasphalted bitumen
may increase bitumen dissolution in the first extraction liquor. Therefore,
the deasphalted
bitumen may result in an increase in bitumen recovery from a bituminous feed.
The deasphalted
bitumen may have the advantage of limiting fouling by asphaltene
precipitation. The
deasphalted bitumen may limit fouling by asphaltene precipitiation within the
process
equipment pipelines used to transfer the deasphalted bitumen to the bituminous
feed because
of the lower asphaltene content of the deasphalted bitumen. The deasphalted
bitumen may
reduce the chance of catastrophic plugging of process equipment, including
pipelines, by
settling solids. The lower solid content of the deasphalted bitumen may allow
for this reduction.
The deasphalted bitumen may allow for the removal of residual solid fines
during deasphalting
to produce reduced ash and increased API bitumen product, as compared to a
bitumen extract
stream that has not been deasphalted, when solvent is removed from the
deasphalted bitumen.
The deasphalted bitumen may have an asphaltene content of less than 15 wt.%,
less than 10
wt.%, or less than 5 wt.%. The deasphalted bitumen may have an undissolved
(precipitated)
asphaltene content of less than 1 wt.%, less than 0.5 wt.%, or less than 0.2
wt.%. To achieve
these undissolved (precipitated) asphaltene contents, the deasphalted bitumen
may be
subjected, for example but not limited to, to gravity separation.
[00133] Examples
[00134] A bituminous feed of oil sand (10.3 wt.% bitumen, 3.5 wt.% water,
27.8 wt.%
fines) was mixed with a pentane-bitumen extraction liquor (first extraction
liquor) at 1500 rpm
for 15 minutes at room temperature in a mixing vessel (bitumen extraction
step) to form an oil
sand slurry. The oil sand slurry was 50 wt.% solids and at a solvent-to-
bitumen ratio of 0.8.
After 15 minutes of mixing, water was added as a bridging liquid and adjusted
to achieve a final
water-to-solids ratio of 0.08. The oil sand slurry was mixed at 1500 rpm for 2
minutes to achieve
microagglomerates via spherical agglomeration. The agglomerated slurry was
filtered (solid-
liquid separation step), followed by washing of the separated solids with
pentane (aliphatic
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CA 2979231 2017-09-14
solvent) using a wash ratio of 0.7 mL of solvent/g of solids. Two tests were
performed according
to the above procedure.
[00135] Test 1: The bitumen of the pentane-bitumen extraction liquor
(first extraction
liquor) was a non-deasphalted bitumen comprising approximately 18 wt.%
asphaltenes.
[00136] Test 2: The bitumen of the pentane-bitumen extraction liquor
(first extraction
liquor) was a partially deasphalted bitumen comprising approximately 9 wt. %
asphaltenes.
[00137] Bitumen recovery was determined by the Dean-Stark method. In the
Dean-Stark
method, a weighed sample is separated into bitumen, water, and solids by
refluxing toluene.
Condensed toluene and co-distilled water are continuously separated in a trap
designed to
recycle the solvent through an extraction thimble, dissolving the bitumen
present in the sample,
while the water is retained in the trap. Once the three components have been
physically
separated, they can be determined by various means. Test 1, using a partially
deasphalted
bitumen (first extraction liquor), had a total bitumen recovery of 85%. Test
2, using a
deasphalted bitumen (first extraction liquor), had a total bitumen recovery of
90%. This result
strongly suggests that a deasphalted bitumen has the advantage of producing an
extraction
liquor that more readily extracts bitumen from the bituminous feed.
[00138] The scope of the claims should not be limited by particular
embodiments set
forth herein, but should be construed in a manner consistent with the
specification as a whole.
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