Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02783837 2012-07-26
METHODS AND APPARATUS FOR BITUMEN EXTRACTION
This application claims priority to U.S. Provisional Patent Application No.
61/511,894,
filed July 26, 2011, and U.S. Provisional Patent Application No. 61/525,557,
filed August 19,
2012. Each application is incorporated herein by reference in its entirety.
BACKGROUND
Bituminous material such as oil sands typically include sand, clay, water, and
heavy
crude oil. Many countries in the world have large deposits of oil sands,
including the United
States, Russia, and various countries in the Middle East. However, three
quarters of the world's
reserves are found in Venezuela and Canada. Oil sands may represent as much as
two thirds of
the world's total petroleum resource, but are difficult to develop because of
the expense
associated with recovering oil from oil sands.
Bitumen extraction from bituminous material such as oil sand can be a very
energy
intensive process. In the extraction of bitumen from bituminous material, the
bituminous
material is typically mined, usually by a bucket wheel excavator of dragline,
and is then
subjected to hot water extraction processing. In a typical hot water
extraction process, the
bituminous material is mixed with hot water such that the bitumen content of
the bituminous
material floats as a froth and the solid matter content of the bituminous
material sinks, thereby
making it possible to skim off the froth for further separation and eventual
refinement to finished
products. In some conventional hot water extraction processes, 87% by weight
of bitumen and
diluent naphtha are recovered from the bituminous material, with a loss of 13%
by weight being
dumped with the waste solid matter. The disposal of the solid matter involves
passing the solid
matter together with accompanying hot water to a tailings pond. The hot water
that is lost can be
1
CA 02783837 2012-07-26
at a temperature of approximately 185 F to 195 F. The loss of this hot water
considerably
reduces the overall plant thermodynamic efficiency as the heat loss must be
made up when
reheating cold water for the hot water extraction process.
In many hot water bitumen extraction processes, the tailings produced by the
process
include solid matter, hot water, and hydrocarbons not removed by the hot water
process. These
tailings can be sluiced into retaining areas, such as large ponds formed from
dams or dykes built
from tailings. When a first pond is filled, a second dam is built in the
middle of the mined out
area and this process of building dams and filling the ponds formed between
the dams is
continued until the reserve of mineable oil sands has been depleted. At this
future time, most of
the area of the mined out acreage will be covered under almost a continuous
pond including
water, oil emulsions, and clay fines gel. Environmental authorities have
determined that there
has been and will continue to be pollution impacts on the underground water
streams,
surrounding lakes, and other fresh water bodies adjacent to the mining areas.
Under this tailings
disposal system, little, if any, of the mined out land can be reclaimed and
put to useable form.
SUMMARY
Disclosed below are representative embodiments that are not intended to be
limiting in
any way. Instead, the present disclosure is directed toward novel and
nonobvious features,
aspects, and equivalents of the embodiments of the methods described below.
The disclosed
features and aspects of the embodiments can be used alone or in various novel
and nonobvious
combinations and sub-combinations with one another.
In some embodiments, a bitumen extraction method includes a step of feeding a
first
quantity of bituminous material into a first mixing drum, a step of spraying
first solvent over the
first quantity of bituminous material inside the first mixing drum, a step of
separating the first
2
CA 02783837 2012-07-26
quantity of bituminous material into a first dilbit stream and a first
tailings stream, a step of
feeding the first tailings stream into a second mixing drum, a step of
spraying first solvent over
the first tailings stream inside the second mixing drum, and a step of
separating the first tailings
stream into a second dilbit stream and a second tailings stream.
In some embodiments, a bitumen extraction system includes a first mixing drum
having a
first solvent inlet, a first dilbit outlet, and a first tailings outlet; a
first separation unit having a
second dilbit inlet in fluid communication with the first dilbit outlet, a
cleaned dilbit outlet, and a
solid materials outlet; and a second mixing drum having a first tailings inlet
in fluid
communication with the first tailings outlet, a second dilbit outlet in fluid
communication with
the first solvent inlet, and a second tailings outlet.
In at least one or more embodiments, novel features and/or advantages of the
method can
include use of a mixing drum to add solvent to bituminous material, recover
dilbit, and remove
tailings; use of multiple mixing drums in counterflow configuration; use of
one or more
hydrocyclones to carry out bitumen extraction; reducing or eliminating the
need for hot water in
bitumen extraction processing; reducing or eliminating tailings ponds
containing oil emulsions
and unstable clay fine gels; improving the thermodynamic efficiency of the
bitumen extraction
process; and improving the bitumen recovery efficiency to greater than 90%.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred and other embodiments are disclosed in association with the
accompanying
drawings in which:
Figure 1 is a flow chart detailing a method for extracting bitumen from
bituminous
material as disclosed herein;
CA 02783837 2012-07-26
Figure 2 is a process flow diagram detailing a method for extracting bitumen
from
bituminous material as disclosed herein;
Figure 3 is a flow chart detailing a method for extracting bitumen from
bituminous
material as disclosed herein;
Figure 4 is a process flow diagram detailing a method for extracting bitumen
from
bituminous material as disclosed herein;
Figure 5 is a process flow diagram detailing a method for extracting bitumen
from
bituminous material as disclosed herein;
Figure 6 is a process flow diagram detailing a method for extracting bitumen
from
bituminous material as disclosed herein;
Figure 7 is a process flow diagram detailing a method for extracting bitumen
from
bituminous material as disclosed herein;
Figure 8 is a flow chart detailing a method for extracting bitumen from
bituminous
material as disclosed herein; and
Figure 9 is a process flow diagram detailing a method for extracting bitumen
from
bituminous material as disclosed herein.
DETAILED DESCRIPTION
With reference to Figure 1, a bitumen extraction method according to some
embodiments
disclosed herein includes a step 100 of feeding bituminous material into a
mixing drum, a step
110 of spraying solvent over the bituminous material inside the mixing drum,
and a step 120 of
separating the bituminous material into a dilbit stream and a tailings stream.
The mixing drum used in step 100 can generally include any type of drum
suitable for use
in mixing together bituminous material and solvent. In some embodiments, the
mixing drum is
4
CA 02783837 2012-07-26
an enclosed drum that includes one or more inlets for feeding bituminous
material and solvent
into the drum and one or more outlets for removing various mixtures of
materials from the
mixing drum. The various inlets and outlets in the mixing drum can be located
throughout the
mixing drum. The material of the mixing drum is not limited, and may include
materials that are
generally impermeable and corrosion resistant. In some embodiments, the mixing
drum has a
generally cylindrical shape, although other shapes may be used. The mixing
drum can also vary
in size and dimensions, and the size and dimensions of the drum are generally
selected based on
the amount of bituminous material to be handled inside the mixing drum and the
bituminous
material characteristics (i.e. particle size, dissolution rate etc.).
In some embodiments, the mixing drum is a cylindrically-shaped drum oriented
such that
the axis of the cylindrically-shaped drum is generally horizontal. The
cylindrically-shaped drum
can also be slanted such that one end is higher than the other, or positioned
in a generally vertical
position. However for purposes of this discussion, the drum will be described
in the scenario
where the axis of the drum is generally horizontal.
The cylindrical drum can include one or more inlets located at various
locations
throughout the drum for feeding bituminous material inside of the drum. In
some embodiments,
the inlets are located proximate one end of the drum for the introduction of
bituminous material
into the drum. The inlets can be located around the circumference of the drum
near one end of
the drum, in the end wall of the drum (i.e., the wall perpendicular to the
ground when the axis of
the drum is positioned horizontally), or a combination of both.
The drum can also include inlets for providing solvent to the interior of the
drum. The
inlets for adding solvent into the drum can be located anywhere about the
drum, such as those
locations described above with respect to inlets for feeding bituminous
material inside of the
5
CA 02783837 2012-07-26
drum. In some embodiments, inlets are provided at various locations throughout
the drum such
that solvent can be added into the drum at various locations throughout the
drum.
In some embodiments, the various inlets and outlets included in the mixing
drum can be
sealed when mixing occurs within the mixing drum. Sealing of the inlets and
outlet can help to
ensure that materials inside the mixing drum do not leak out of the mixing
drum, and also that
any gases or vapors produced inside of the mixing drum do not leak out of the
mixing drum.
In some embodiments, one or more spray bars are positioned within the drum to
provide
solvent to the interior of the drum. In such embodiments, the spray bar passes
through an end
wall of the drum and solvent enters the interior of the drum by passing
through the spray bar and
into the drum. The spray bar can include numerous nozzles along its length
where solvent is
sprayed into the interior of the drum. In some embodiments, the spray bar is
oriented generally
parallel to the axis of the cylindrical drum, although other orientations can
be used.
In some embodiments, the interior walls of the mixing drum include a liner
that protects
the shell of the mixing drum. This liner can cover the entirety of the
interior wall of the mixing
drum or only portions of the interior of the mixing drum. Any suitable liner
material can be
used, and in some embodiments, the liner material is alloy steel or a thick
layer of rubber or any
other elastomer that is compatible with the selected solvent. This liner
material prevents wear to
the mixing drum. Any manner of securing the liner to the interior walls of the
mixing drum can
be used, and in some embodiments, the liners are bolted securely to the mixing
drums with
specially designed washers that prevent drum leakage.
The cylindrical drum can also include a mechanism for rotating the drum,
including
rotating the drum about its axis. Any manner of rotating the drum can be used,
including
6
CA 02783837 2012-07-26
hydraulic motors and tire and trunnion mechanisms. The speed at which the drum
can be rotated
can vary over a wide range of speeds.
The cylindrical drum can also include a screen liner for facilitating the
separation of
materials inside the drum. The screen liner can have any suitable shape,
including a generally
cylindrical shape. When the screen liner has a cylindrical shape, the diameter
of the screen liner
can be smaller than the diameter of the mixing drum such that the screen liner
is positioned
inside of and coaxial with the mixing drum. In some embodiments, the screen
liner can include a
plurality of coaxially aligned screens, with each screen having a different
mesh size. In this
manner, the multiple screen liner can effect a coarse and fine separation of
materials inside the
mixing drum.
The screen liner can extend along the entire length of the drum or only a
portion of the
length of the drum. In some embodiments, the screen liner is located at only
one end of the
drum, and preferably the end of the drum opposite inlets for introducing
bituminous material into
the drum. In some embodiments, the screen liner has a length that is more than
half the length of
the mixing drum. For example, the mixing drum can have an overall length of 22
meters, with
the screen liner having a length of 12 meters. In such a configuration, mixing
occurs in the
mixing drum along the first 10 meters of the mixing drum, and separation
occurs along the last
12 meters of the mixing drum. In this manner, mixing between bituminous
material and solvent
can take place along a first portion of the length of the drum while
separation occurs at the end of
the drum, after substantial mixing has taken place.
The mesh size of the screen liner can vary and be adjusted depending on the
sizes of the
material to be separated. In application, the screen effectively creates an
area between the liner
and the drum where material that passes through the liner can collect and be
removed from the
7
CA 02783837 2012-07-26
drum via a first outlet, and an area within the screen liner where bituminous
material having
bitumen extracted therefrom (i.e., tailings) remains. The material that cannot
pass through the
liner remains within this inner area can be removed from the drum via a second
(i.e., tailings)
outlet. The first outlet is therefore positioned along the drum in a position
that communicates
with the area between the liner and the drum. In some embodiments, this
location will be along
the circumference of the drum. Similarly, the second outlet can be positioned
at a location that is
in communication with the interior of the screen liner. In some embodiments,
this location will
be on an end wall of the drum. In some embodiments, the mesh size of the
screen liner is from
between 40 mesh and 200 mesh.
The cylindrical drum can further include lifting shelves (i.e., lifters) that
help to promote
mixing within the drum when the drum rotates. The height of each lifting shelf
generally
extends radially inward from the interior wall of the mixing drum, while the
length of each
lifting shelf is generally oriented parallel to the axis of the drum. In this
manner, the lifting
shelves carry a portion of the material inside of the drum up along the wall
of the drum as the
drum rotates. Eventually the lifting shelves rotate to a position where they
slant downwardly and
the lifted material falls back down towards the bottom of the drum. This
movement of the
material helps to promote mixing as discussed in greater detail below. The
lifting shelves can be
made from any suitable material, including steel, rubber, or other elastomers
compatible with the
solvents in use. Each lifting shelf can have a length that extends the entire
length of the drum or
the lifting shelves can lengths that are shorter than the length of the drum.
When in shorter
segments, various lifting shelves along the length of the drum can be offset
from other lifting
shelves located at other positions along the length of the drum.
8
CA 02783837 2012-07-26
The height of each lifting shelf can be any suitable height and the heights of
the lifting
shelves can be the same or varying throughout the drum. In some embodiments,
the placement
and height of each lifting shelf can be adjusted in order to vary the
residence time of the material
inside of the drum. Longer residence times can lead to more mixing, and
therefore adjustments
can be made to the placement and height of the lifting shelves used in order
to increase or
decrease residence time. In some embodiments, the lifting shelves can be in
the form a flute,
such as commonly used in a cement mixer, to gently knead and mix the slurry
without creating
high shear.
Retention rings may also be included within the drum to further vary residence
time. One
or more retention rings can be placed axially along the length of the drum and
will slow the
movement of material from one end of the drum to the other, thereby increasing
residence time
and promoting further mixing between materials.
In some embodiments, the mixing drum may also include a heating mechanism for
heating the material inside of the mixing drum. Any suitable type of heater
can be used to
accomplish the heating of material inside the mixing drum. In some
embodiments, the mixing
drum includes direct or indirect heating via, for example, a hot water or
steam jacket surrounding
a portion or all of the exterior of the mixing drum to thereby provide heat
from the hot water or
steam passing through the jacket through the walls of the mixing drum and to
the material inside
of the mixing drum. Use of a heater with the mixing drum can be especially
preferable when the
materials inside of the mixing drum are cold when transported into the mixing
drum. For
example, when the bituminous material transported into the mixing drum is
mined Alberta oil
sands, the temperature of the bituminous material is very cold. In some
embodiments, the heater
used in conjunction with the mixing drum is capable of heating the materials
inside of the mixing
9
CA 02783837 2012-07-26
drum to a temperature between 20 C and 75 C. The heater may be incorporated
with the mixing
drum to create a heated mixing drum (e.g., steam jacket) or the heater may be
an independent
device to raise the temperature of the bituminous material and/or solvent
prior to entering the
mixing drum. In some embodiments the heater may be upstream in the process
flow sheet either
before a primary crusher or incorporated within the primary crushing stage.
In some embodiments, the mixing drum is a trommel or a pulper. Trommels or
pulpers
generally include the closed drum configuration used for the mixing drum and
can further
include the internal screen mechanism for separating various materials inside
of the drum. Any
trommel or pulper suitable for use in mixing together and separating different
materials can be
used.
The bituminous material fed into the mixing drum can include any material that
includes
a bitumen content. In some embodiments, the bituminous material is oil sands
or tar sands. The
source of bituminous material is also not limited, and can include bituminous
material obtained
from natural deposits (such as by mining) or material that is produced by
other processes (such
as distillation bottoms produced by a distillation column). The bitumen
content of the bituminous
material can vary across a wide range and is generally dictated by the quality
of the bituminous
material being processed. For example, high quality bituminous material can
include greater
than 20% by weight bitumen, while lower quality bituminous material can
include less than 5%
by weight bitumen. Other components of the bituminous material can include,
but is not limited
to, water, clay, and sand.
Any suitable manner for feeding the bituminous material into the mixing drum
can be
used. As mentioned above, the bituminous material can be fed into the mixing
drum through one
or more inlets located at various locations throughout the mixing drum. The
bituminous material
CA 02783837 2012-07-26
can be transported to the mixing drum inlet by any manner, including through
the use of
conveyor belts, chutes, hoppers, and screw feeders. In some embodiments, the
bituminous
material is transported into the mixing drum as the mixing drum is rotating
about its axis.
In some embodiments, the bituminous material may be broken into smaller pieces
prior to
introduction into the mixing drum. Any manner of breaking up the large pieces
of bituminous
material may be used, including the use of a traditional breaker, sizer, or
crusher. In some
embodiments, the bituminous material is broken up into pieces having a size of
less than 3 inches
or, in some cases, less than 1 inch.
In some embodiments, solvent is mixed with the bituminous material prior to
and/or
during the process of breaking up larger pieces of bituminous material into
smaller pieces. The
solvent used during the breaking/crushing step can be the same solvent used in
subsequent
solvent extraction steps. In some embodiments, the solvent is a paraffinic
solvent, such as
pentane. The solvent used in the breaking/crushing step can be heated, such as
to within a range
of from 50 F to 100 F. Additionally, the apparatus used to crush the
bituminous material can
be heated using an internal or external heating mechanism.
Adding the solvent to the bituminous material can be carried out in any
suitable manner
that wets the bituminous material with solvent and begins the process of
dissolving bitumen in
the solvent. In some embodiments, the solvent is sprayed over the bituminous
material. For
example, a crushing apparatus can be configured with one or more spray nozzles
for spraying
solvent over the bituminous material before and/or as the bituminous material
passes through the
crushing mechanism (e.g., a crushing roller). In other embodiments, the
solvent and the
bituminous material can be mixed together to form solvent-wet bituminous
material prior to
being introduced into a crushing apparatus. In other words, a mixing vessel
separate from the
11
CA 02783837 2012-07-26
crushing apparatus can be provided that prepares the solvent-wet bituminous
material prior to
introducing the bituminous material into the crushing apparatus. Any suitable
mixing vessel,
including a mixing vessel having mixing blades, can be used. Adding solvent to
the bituminous
material can also be carried out on the conveyors, buckets, or chutes used to
transport the
bituminous material to the crushing apparatus.
Any suitable amount of solvent can be added to the bituminous material. In
some
embodiments, the amount of solvent added to the bituminous material is from
0.5 to 4 times the
amount of bitumen in the bituminous material on a v/v basis.
The solvent-wet bituminous material is subsequently crushed in order to reduce
the size
of clumps of bituminous material and assist with further mixing between the
solvent and the
bituminous material. Any manner of crushing the solvent-wet bituminous
material can be used,
including the use of crushing apparatus known to those of ordinary skill in
the art. Exemplary
crushing mechanisms include, but are not limited to, crushing rollers or
sizers.
In some embodiments, the solvent-wet bituminous material is crushed by passing
the
solvent-wet bituminous material through crushing rollers. The crushing rollers
can be
individually driven by electrical motors, gear motors, or with coupling and
gears counter rotating
via V-belts. Even distribution of the solvent-wet bituminous material across
the entire length of
the crushing rollers or other crushing mechanisms, the use of a favorable
angle of entry, and in
the case of crusher rollers, adjusting the speed and diameter of the crusher
rollers, can help to
ensure efficient crushing of the solvent-wet bituminous material and reduced
wear and tear on
the crushing mechanism.
Crushing rollers used to crush the solvent-wet bituminous material can also be
internally
heated to help improve disaggregation. Any suitable manner of internally
heating the crushing
12
CA 02783837 2012-07-26
rollers can used, such as through the use of steam, hot water, or electricity.
The crusher rollers
can be heated to any suitable temperature for improving disaggregation. In
some embodiments,
the crusher rollers are heated to a temperature below the boiling point
temperature of the solvent,
such as from 50 F to 100 F.
In some embodiments, the crusher rollers are provided with perforations or
holes that
deliver solvent to the surface of the crusher rollers. Providing solvent in
this manner can create a
wet film on the surface of the crusher rollers that further reduced mechanical
wear and tear on
the surface of the crusher rollers. The solvent delivered through these holes
can be heated and
can be delivered to the surface of the crusher rollers continuously or
intermittently.
In some embodiments, conveyors can be used to deliver bituminous material into
the
crushing apparatus. In instances where the bituminous material is wetted with
solvent prior to
being introduced into the crushing apparatus, the conveyors can be used to
deliver solvent-wet
bituminous material into the crushing apparatus. In instances where the
mechanism for adding
solvent to the bituminous material is incorporated into the crushing apparatus
(e.g. spray nozzles
located within the crushing apparatus and upstream of the crushing mechanism),
the conveyors
can be used to deliver dry bituminous material into the crushing apparatus.
In some embodiments, the steps of adding solvent to the bituminous material
and
crushing the solvent-wet bituminous material are repeated. Additional solvent
can be added to
the crushed solvent-wet bituminous material produced by the first solvent
addition step and the
first crushing step, followed by subjecting the crushed solvent-wet bituminous
material to a
second crushing step. Following the one or more wetting and crushing steps,
the bituminous
material can be fed into the mixing drum.
13
CA 02783837 2012-07-26
Once bituminous material has been fed into the mixing drum, a step 110 of
spraying a
solvent over the bituminous material inside the mixing drum takes place. The
solvent wets the
bituminous material and forms a slurry of material inside the mixing drum. One
aim of adding
solvent to the bituminous material inside of the drum is to promote the
dissolution of bitumen
into the solvent to thereby extract it from the bituminous material. The
rotating mixing drum,
lifting shelves, retention rings, heat and other mechanisms can be used to
promote the mixing
between the bituminous material and the solvent and the dissolution of the
bitumen in the
solvent. Eventually, a phase of bitumen diluted in solvent, also referred to
as "dilbit", and a
phase of bitumen-depleted tailings will result from the mixing of solvent and
bituminous
material inside of the mixing drum.
Any solvent capable of dissolving all or a specific part of the bitumen can be
sprayed
over the bituminous material inside of the mixing drum. Exemplary solvent
suitable for use in
step 110 include paraffinic solvents (such as propane and pentane), naphtha,
bio-diesel,
methanol, and ethanol. In some embodiments, the solvent is "dilbit," i.e.,
bitumen diluted in a
solvent. Any of these solvents mentioned above may serve as the solvent
component in the
"dilbit." In some embodiments where "dilbit" is used as the solvent sprayed
over the bituminous
material, the "dilbit" is from about 30% to about 80% solvent by volume.
In some embodiments, the amount of solvent sprayed over the bituminous
material is
based on a ratio of solvent to bitumen content in the bituminous material.
Accordingly, the
amount of solvent used can vary based on the quality of the bituminous
material (i.e., the
bitumen content of the bituminous material and the pore size in the bitumen)
and the solvent
density or solvency power. In some embodiments, the solvent to bitumen ratio
used in the
spraying step 110 is from about 0.5:1 to 4:1 on a volume basis. Using a
solvent to bitumen ratio
14
CA 02783837 2012-07-26
within this range can help to ensure that enough solvent is sprayed over the
bituminous material
to dissolve a substantial portion of the bitumen content of the bituminous
material.
When spraying solvent into the mixing drum containing bituminous material
therein, a
volume of the mixing drum will be occupied by the resulting slurry. In some
embodiments, the
amount of bituminous material and solvent into the mixing drum at one time is
controlled in
order to ensure that no greater than or no less than a specified percentage of
the internal volume
mixing drum is occupied. Over or under filling the mixing drum can negatively
impact the
mixing of the solvent and bituminous material and the dissolution of bitumen
into the solvent. In
some embodiments, from 20% to 60% of the volume inside the mixing drum is
occupied by
bituminous material and solvent.
As described above, the effect of spraying the solvent over the bituminous
material is to
create a slurry of material inside the mixing drum that can include two
phases. The first phase is
bitumen diluted in solvent ("dilbit"). The second phase is bitumen-depleted
tailings. The
bitumen-depleted tailings will generally include solvent, water, sand, clay,
and a relatively small
amount of bitumen that was not dissolved by the solvent. In some embodiments,
the bitumen-
depleted tailings can also include precipitated asphaltenes. Some or all of
the bitumen content of
the bitumen-depleted tailings can include bitumen that is occluded on the
inert material of the
tailings. While the rotation of the mixing drum can work to remove some of the
bitumen that is
stuck to the inert material (e.g., due to contact between slurry falling from
the lifting shelves with
slurry residing at the bottom of the mixing drum), the rotation of the drum
typically does not
remove all of the occluded bitumen from the inert material. Accordingly, a
relatively small
amount of bitumen remains with the bitumen-depleted tailings.
CA 02783837 2012-07-26
The rotation of the drum while the solvent is sprayed over the bituminous
material can be
any suitable speed that helps to promote mixing of the solvent and the
bituminous mater and the
create dilbit. In some embodiments, the rotational speed is kept relatively
slow in order to avoid
the dispersion of the clay component of the bituminous material. High
rotational speeds cause
clay dispersion because of high agitation and attrition breaking up clay
lenses. Clay dispersion is
undesirable because clays can become suspended in the dilbit and affect dilbit
quality, requiring
additional clay removal steps. In some embodiments, the rotational speed of
the mixing drum is
kept to less than 10 rpm in order to avoid clay dispersion, although higher
rotational speeds can
be used.
In some embodiments, the rotation of the mixing drum continues after spraying
solvent
over the bituminous material inside the mixing drum has ceased. Continuing to
rotate the mixing
drum during and after the solvent is sprayed over the bituminous material
inside the mixing drum
promotes mixing of the slurry of bituminous material and solvent and the
dissolution of the
bitumen content of the bituminous material into the solvent as described
above. In some
embodiments, the mixing of the slurry by the continued rotation of the mixing
drum during and
after solvent is sprayed over the bituminous material can continue for a
period of time sufficient
to ensure that bitumen dissolution occurs and a dilbit phase is created. The
specific period of
time of mixing can vary based on varying factors, including the bitumen
content of the
bituminous material and the amount of solvent sprayed over the bituminous
material. In
practice, the mixing drum may be a continuously operated device with a
constant feed of
bituminous material and solvent to one end and a continuous discharge of dilbt
and bitumen
depleted material at the other end, thus providing a residence time in the
drum sufficient for
dissolution and separation to occur.
16
CA 02783837 2012-07-26
The injection of solvent into the mixing drum and the subsequent mixing of the
solvent
and the bituminous material to create dilbit can, in some embodiments, create
a need for the
mixing drum to include a solvent vapor recovery system. A solvent recovery
system can be
necessary due to the volatility of some of the solvents suitable for use in
the methods described
herein. Despite being injected into the mixing drum as a liquid, portions of
such volatile solvents
may convert to a vapor phase once inside the mixing drum, and therefore
require venting from
inside the mixing drum. Any solvent vapor recovery system suitable for use
with a mixing drum
can be used, including one or more solvent vents on the mixing drum and a
solvent vapor
collection vessel connected to the one or more solvent vents.
In some embodiments, the mixing drum can be a pressurized mixing drum. A
pressurized mixing drum may be necessary in instances where the solvent
injected into the
mixing drum will not remain in a liquid state unless the mixing drum is
pressurized. For
example, the mixing drum can be a pressurized mixing drum when propane or
butane is used in
order to keep the propane and/or butane in a liquid state inside the mixing
drum. Any
mechanism suitable for pressurizing the mixing drum can be used.
In some embodiments, the solvent added to the bitumen material in the mixing
drum can
undergo pretreatment, such as heating the solvent. Additionally, heat can be
applied to the
bitumen material and solvent being mixed inside the mixing drum. In some
embodiments, the
heating of the mixing drum is accomplished by a heating source external to the
mixing drum.
The heating can be via indirect heating, including through the use of steam
via a steam jacket on
the mixing drum or direct steam injection.
The mixture of bituminous material and solvent and the creation of a slurry
having dilbit
and bitumen-depleted tailings is followed by a step 120 of separating the
dilbit from the bitumen
17
CA 02783837 2012-07-26
depleted tailings. Any technique capable of separating the dilbit from the
slurry can be used
(e.g., hydrocyclones, thickeners, clarifiers or filtration devices). As
mentioned above, a liner
screen located within the mixing drum can be used in some embodiments. The
liner screen, such
as a coaxial liner screen position at one end of the mixing drum, can have a
mesh size that is
large enough to allow the dilbit to pass through but that is small enough to
keep the bitumen-
depleted tailings within the liner screen. As the dilbit passes through the
liner screen, the dilbit
can be routed to an outlet in the mixing drum so that it can be removed from
the mixing drum
and used in subsequent steps of the process. Similarly, the bitumen-depleted
tailings that remain
within the liner screen can be transported out of the mixing drum via an
outlet in the mixing
drum. Once removed from the mixing drum, the bitumen-depleted tailings can be
subjected to
further processing, such as further contacting with solvent for additional
bitumen recovery or
solvent recovery.
Based on the mixing and separation steps, the dilbit obtained from the mixing
drum can
typically include from about 30 to about 60 wt% bitumen and from about 40 to
about 70 wt%
solvent. Relatively small amounts of solid material, such as sand, may also be
included in the
dilbit. In some embodiments, the dilbit may include from about 0 to about 3
wt% solid material.
With respect to the bitumen-depleted tailings resulting from the mixing and
separating steps, the
bitumen-depleted tailings generally include from about 50 to about 75 wt%
inert materials (such
as clay and sand), from about 0 to about 5 wt % water, from about 25 to about
40 wt% solvent,
and from about 3 to about 15 wt % bitumen.
Due to the undesirable presence of solid material such as fine solids or clays
in the dilbit,
additional steps can be taken to remove the solid material and form an
essentially pure dilbit
material. Any technique that removes solid material from the dilbit can be
used. In some
18
CA 02783837 2012-07-26
embodiments, a hydrocyclone, centrifuge, desander, switchable filter tube,
filter, polymeric
membrane, or screen is used to remove the solid material from the dilbit.
Preferably, the
hydrocyclone, centrifuge, filter, polymeric membrane, screen, etc., removes
95% or more of the
solid material in the dilbit, although removal of solid material down to any
level suitable for
subsequent processing is also acceptable. The solid material, which will
include mostly sand
particles, can then be disposed of, added back with the bitumen-depleted
tailings leaving the
mixing drum, or be recycled back into the mixing drum in the same manner as
bituminous
material is fed into the mixing drum in order to attempt to recover any
remaining bitumen that
may be occluded on the solid material. When solid material is fed back into
the mixing drum,
the solid material undergoes similar or identical processing steps as those
described above with
respect to bituminous material.
The purified dilbit obtained after solid material is removed therefrom can be
subjected to
a variety of further processing steps. In some embodiments, the dilbit is
transported to a storage
tank where it can be added to other dilbit already collected. In some
embodiments, dilbit
collected in the storage tank can be used as the solvent sprayed over the
bituminous material in
step 110. In order to ensure that the dilbit used as solvent in step 110 has a
desirable bitumen
and solvent content, additional solvent can be added to the storage tank or
bitumen can be
removed from the storage tank. For example, if the dilbit contained in the
storage tank includes
60 wt% solvent and 40 wt% bitumen but a 70% wt solvent and 30 wt% bitumen
content is
desired when the dilbit is used as solvent sprayed over the bituminous
material in the mixing
drum, then solvent can be added to the storage tank to get the dilbit in the
storage tank to the
correct composition. The solvent that is added to the storage tank can be any
of the solvents
19
CA 02783837 2012-07-26
discussed above. Any suitable manner of removing bitumen from the storage tank
can be used,
such as by distillation, flashing, gravity separation, and filtration with
polymeric membranes.
In embodiments where the dilbit is used as a solvent and sprayed over
bituminous
material transported into the mixing drum in step 110, the dilbit can
optionally be heated by a
heating mechanism prior to being sprayed over the bituminous material. In some
embodiments
and depending on the boiling point of the solvent, the dilbit is heated to a
temperature between
20 C and 120 C. Any type of heater can be used to heat the dilbit to a
temperature within this
range, including a heat exchanger.
In instances where the solvent used in step 110 is preferably not dilbit, the
dilbit in the
storage tank can be processed to separate the bitumen from the solvent, at
which point the
separated solvent can be used as the solvent sprayed over the bituminous
material in step 110.
The separated bitumen can then be transported to further processing apparatus,
such as apparatus
used to upgrade the bitumen into commercially useful lighter hydrocarbons. Any
manner of
separating the dilbit into solvent and bitumen can be used, including the use
of a froth tank or
distillation units.
As noted above, the bitumen-depleted tailings resulting from the mixing and
separating
steps can include a residual amount of solvent. Therefore, in some
embodiments, the bitumen-
depleted tailings are treated for solvent removal and recovery. Any methods
suitable for
removing solvent from tailings can be used. In some embodiments, treatment for
solvent
removal includes washing the tailings with the same solvent that is used in
the initial mixing
stage. This washing can take place in a secondary mixing drum similar or
identical to the one or
more primary mixing drums described above and used to mix bituminous material
and solvent.
In some embodiments, the additional solvent used in the washing stage is in
the vapor phase or is
CA 02783837 2012-07-26
supercritical solvent. This can help to minimize the amount of solvent
remaining in the tailings
after the washing stage. The washing with additional solvent can be carried
out in one or more
washing stages. While the washing with additional solvent can remove the
majority of the
solvent in the tailings, some trace amounts of additional solvent may remain
in the tailings.
Accordingly, the tailings can be further processed for further solvent
recovery, such as via a
column, filtration device, or by drying or flashing to remove the solvent
prior to discharge of the
tailings as a final waste.
In some embodiments, the washing of the bitumen-depleted tailings with
additional
solvent can be carried out in the same mixing drum used for spraying the
initial bituminous
material with the solvent. In such embodiments, the mixing drum will typically
include a screen
liner so that separation of the dilbit and the bitumen-depleted tailings can
be carried out within
the mixing drum. In practice, washing with a additional solvent can begin by
terminating the
spraying of solvent into the mixing drum and removing the dilbit separated
from the bitumen-
depleted tailings via the screen liner from the mixing drum. The bitumen-
depleted tailings can
remain in the mixing drum. Additional solvent is then added to the bitumen-
depleted tailings
inside the mixing drum, including adding vaporous or supercritical solvent to
the tailings.
Rotation of the drum to promote mixing between the tailings and the additional
solvent can be
carried out in a similar or identical fashion as described above. The
additional solvent displaces
the solvent out of the tailings, where it can then pass through the screen
liner located inside the
mixing drum to effect separation of the solvent from the tailings. The washed
tailings, which
now include some trace amounts of additional solvent, remain within the screen
liner and can be
processed to remove trace additional solvent from the tailings, including by
removing the tailings
21
CA 02783837 2012-07-26
from the mixing drum and heating the tailings to the point of evaporating the
trace additional
solvent.
In embodiments where the mixing drum does not include a screen liner or other
internal
separation device, the slurry can be removed from the mixing drum and then be
subjected to
separation of the dilbit from the bitumen-depleted tailings. The bitumen-
depleted tailings can
then be transported back into the same mixing drum used for the first solvent
spraying step and
be subjected to further solvent washing as described above. Any suitable
apparatus can be used
to separate the slurry, including but not limited to, a thickener. When a
thickener is used, the
slurry is received by the thickener, and the thickener separates the slurry
such that it produces a
stream of dilbit and a stream of bitumen-depleted tailings.
Figure 2 illustrates a process diagram of embodiments described above.
Bituminous
material 200 is run through a crusher 210 to reduce the size of larger pieces
of the bituminous
material 200. Once crushed, the bituminous material 200 is transported to a
mixing drum 220
that includes a spray bar 225. As the bituminous material 200 enters the
mixing drum 220,
solvent is sprayed over the bituminous material 200 via the spray bar 225. The
mixing drum 220
rotates during the spraying and a slurry is formed. The slurry generally
contains a bitumen-
enriched solvent phase and a bitumen-depleted tailings phase. A screen liner
226 inside of the
mixing drum 220 works to separate the bitumen-enriched solvent phase from the
bitumen-
depleted tailings phase 235. The bitumen enriched solvent phase 230 leaves the
mixing drum
and is sent to a separation unit 240, such as a hydrocyclone. The separation
unit 240 works to
separate any solid material from the bitumen-enriched solvent phase 230.
Accordingly, the
separation unit 240 creates a purified dilbit stream 250 and a solid materials
stream 260. The
solid materials stream 260 is routed back to the mixing drum 226 to undergo
further mixing with
22
CA 02783837 2012-07-26
solvent inside the mixing drum 220. Alternatively, the solid materials stream
260 can be added
back with the bitumen-depleted tailings phase 235. The purified dilbit stream
250 is sent to a
storage tank 270 where several different processing steps can occur. In some
instances, the dilbit
stream 250 will be suitable for use as solvent that is sprayed over bituminous
material inside of
the mixing drum 220. In some instances, the amount of solvent and bitumen in
the dilbit stream
250 will need to be adjusted, at which point bitumen 280 can be removed from
the dilbit 250 in
the storage tank 270 or solvent 290 can be added to the storage tank 270. In
still other instances,
the dilbit 250 will be separated into solvent and bitumen 280, with the
solvent being sprayed
over further bituminous material inside of the mixing drum 250 and the bitumen
280 being sent
to an upgrader.
In some embodiments, a method of extracting bitumen from bituminous material
utilizes
two or more mixing drums aligned in series. With reference to Figure 3, the
method can include
a step 300 of feeding a first quantity of bituminous material into a first
mixing drum, a step 310
of spraying solvent over the first quantity of bituminous material inside the
first mixing drum, a
step 320 of separating the first quantity of bituminous material into a first
dilbit stream and a first
tailings stream, a step 330 of feeding the first tailings stream into a second
mixing drum, a step
340 of spraying solvent over the first tailings stream inside the second
mixing drum, a step 350
of separating the first tailings stream into a second dilbit stream and a
second tailings stream, a
step 360 of feeding a second quantity of bituminous material into the first
mixing drum, and a
step 370 of spraying the second dilbit stream over the second quantity of
bituminous material
inside the first mixing drum.
In step 300, a first quantity of bituminous material is fed into a first
mixing drum. The
bituminous material and the mixing drum used in step 300 may be similar or
identical to the
23
CA 02783837 2012-07-26
bituminous material and mixing drum described in greater detail above.
Similarly, the manner of
feeding the bituminous material into the first mixing drum can be similar or
identical to the
feeding step 100 described in greater detail above. The first quantity of
bituminous material used
in step 300 can be any quantity that can be processed in the mixing drum.
Accordingly, the size
of the mixing drum can impact the size of the first quantity of bituminous
material.
In step 310, a solvent is sprayed over the first quantity of bituminous
material inside the
first mixing drum. Step 310 can be similar or identical to step 110 described
in greater detail
above, including the type and amount of solvent used, the rotation of the
mixing drum during
spraying, and the delivery of solvent via a spray bar extending through the
mixing drum.
Similarly, the result of step 310 is similar or identical to step 110
described in greater detail
above. Mixing the solvent and bituminous material results in the formation of
a slurry
containing bitumen dissolved in solvent and solvent-wet inert material (that
may or may not have
some bitumen occluded thereon). In some embodiments, the solvent sprayed over
the
bituminous material in step 310 is paraffinic solvent.
In step 320, the first quantity of bituminous material, which is now solvent
wet and in the
form of the previously described slurry, is separated into a first dilbit
stream and a first tailings
stream. The manner of separating the slurry into these two components is
similar or identical to
the separation methods described above in connection with step 120. Thus, in
some
embodiments, the mixing drum includes a liner screen that filters the dilbit
away from the
tailings. Alternatively, the slurry is removed from the mixing drum and
separated external to the
mixing drum. such as in a thickener or hydrocyclone. The separated first
dilbit stream and the
first tailings stream can be similar or identical to the dilbit and tailings
described above in step
120. Accordingly, the first dilbit stream can include primarily bitumen and
solvent and the first
24
CA 02783837 2012-07-26
tailings stream can include solvent, water, and inert materials, such as sand
and clay. As also
mentioned above in the discussion of step 120, the first dilbit stream can
further include a
relatively small amount of solid particles and the first tailings stream can
include a bitumen
content, including bitumen that remains occluded on the inert material and/or
bitumen that is
dissolved in solvent that remains with the tailings.
In step 330, the first tailings stream produced from the separation step 320
is transported
and fed in to a second mixing drum. The first tailings stream can be
transported to the second
mixing drum in any suitable manner, including through the use of conveyors,
chutes, or screw
feeders. The second mixing drum can be similar or identical to the first
mixing drum. While the
shape and orientation of the second mixing drum is not limited, in some
embodiments the second
mixing drum is a horizontally positioned cylindrical drum. As with the
previously described
mixing drum, the second mixing drum can be capable of rotating about its axis
to promote
mixing between the first tailings stream and solvent injected therein, and can
also include a
screen liner for separating materials after mixing. The size of the second
mixing drum is also not
limited, and will generally be selected based on the amount of tailings to be
processed inside of
the second mixing drum. In some embodiments, the second mixing drum is a
trommel or pulper
as described in greater detail above.
Alternatively, step 330 can be omitted. In such embodiments, the first
tailings stream can
remain in the first mixing drum, and further solvent processing of the
tailings can be carried out
in the same mixing drum used to spray first solvent over the bituminous
material. If the first
mixing drum does not include a mechanism for separating the slurry into a
dilbit stream and a
tailings stream, the slurry can be temporarily removed from the mixing drum to
separate the
slurry into a dilbit stream and a tailings stream, after which the tailings
stream can be transported
CA 02783837 2012-07-26
back into the first mixing drum. Any suitable method for separating the slurry
external to the
mixing drum can be used, including using a filter press or screening
mechanism.
In step 340, solvent is sprayed over the first tailings stream inside the
second mixing
drum (or, in embodiments where step 330 is omitted, in the first mixing drum).
The manner in
which the solvent is sprayed over the first tailings stream can be similar or
identical to the
spraying step 110 described in greater detail above. Thus, in some
embodiments, the solvent is
sprayed over the first tailings stream using a spray bar that extends into the
second mixing drum.
Any solvent described here can be used, although in some embodiments, the
solvent is dilbit.
When dilbit is used as the solvent, the amount of dilbit used in step 340 can
be based on the same
ratios discussed above in step 110. More specifically, the amount of dilbit
used in step 340 can
be based on the bitumen content of the tailings, and range from a solvent
(i.e., dilbit) to bitumen
ratio of from 0.5:1 to 9:1 on a volume basis.
When dilbit is used as the solvent in step 340, the source of the dilbit is
not limited,
although in some preferred embodiments, the source of the dilbit is downstream
processing
steps. More specifically, and as described in greater detail below, the dilbit
may be originated
from an additional mixing drum located downstream from and connected in series
with the first
and second mixing drums. For example, where a third mixing drum is connected
in series with
the first and second mixing drum, the third mixing drum can receive tailings
produced from the
second mixing drum. Treatment of these tailings in the third mixing drum with
solvent will
produce dilbit, which once separated and removed from the third mixing drum,
can be recycled
back and used as the dilbit sprayed over the tailings in the second mixing
drum. Generally
speaking, dilbit produced from a mixing drum can be used as the solvent in the
mixing drum
immediately prior in a series of mixing drums.
26
CA 02783837 2012-07-26
In step 350, the slurry produced inside of the second mixing drum by virtue of
spraying
solvent over the first stream of tailings is separated into a second dilbit
stream and a second
tailings stream. This separation step can be similar or identical to the
separation steps 330 and
120 discussed in greater detail above. Accordingly, in some embodiments, the
separation is
carried out by virtue of a liner screen inside of the second mixing drum that
filters the second
dilbit stream from the second tailings stream, while in other embodiments, the
separation is
carried out in a separation vessel (such as a thickener or hydrocyclone)
located external to the
second mixing drum. The second dilbit stream and second tailings stream
produced by the
separation step can be similar or identical in composition to the dilbit and
tailings streams
described in greater detail above. In some embodiments, the dilbit and
tailings streams are lower
in bitumen content then the dilbit and tailings stream produced in the first
mixing drum.
Once the second mixing drum has produced a second dilbit stream, a step 360 of
feeding
a second quantity of bituminous material into the first mixing drum and a step
370 of spraying
the second stream of dilbit over the second quantity of bituminous material
inside of the first
mixing drum can take place. In this manner, the overall bitumen extraction
method generates its
own solvent and becomes at least partially self-sufficient. The dilbit moves
in a counter-flow
direction to the solids and becomes more loaded with bitumen after each stage
(i.e., mixing
drum). Thus, the dilbit leaving the first mixing drum and which has passed
through one or more
downstream mixing drums reaches optimal bitumen content for further processing
or separation.
Step 360 of feeding a second quantity of bituminous material into the first
mixing drum
can be similar or identical to step 300 and 100 described in greater detail
above. Accordingly, in
some embodiments, the bituminous material is oil sands and is fed into the
first mixing drum
using conveyor belts or the like.
27
CA 02783837 2012-07-26
Step 370 of spraying the second dilbit stream over the second quantity of
bituminous
material can be similar or identical to step 310 and 110 described in greater
detail above. The
dilbit can be sprayed over the second quantity of bituminous material using a
spray bar extending
into the first mixing drum, and the first mixing drum may be rotating about
its axis as dilbit is
sprayed over the bituminous material. Additionally, the result of this step is
similar to the
spraying steps described above. A slurry is formed that include bitumen
dissolved in solvent and
solvent-wet tailings. The slurry can be separated as described above, and a
continuous process
of bitumen extraction is thus established.
In some embodiments, the second stream of dilbit is subjected to a further
separation step
prior to being sprayed over the second quantity of bituminous material inside
of the first mixing
drum. The separation step generally aims to remove any solid material from the
dilbit, such as
sand that may have filtered through the screen liner inside of the second
mixing drum. Any
suitable separation method can be used to separate solid material from the
second stream of
dilbit. In some embodiments, the separation is carried out by processing the
dilbit in a
hydrocyclone, a centrifuge, filter, clarifier, desander, or through a screen.
In some embodiments, the second stream of dilbit is heated prior to being
injected into
the first mixing drum. For example, the second dilbit stream can be heated to
a temperature in
the range of from 20 C to 40 C prior to being sprayed over bituminous material
inside of the first
mixing drum. Any suitable type of heating mechanism can be used to heat the
second dilbit
stream, including the use of a heat exchanger.
The composition of the second stream of dilbit may also be adjusted prior to
being
sprayed over the second quantity of bituminous material. Thus, in scenarios
where the dilbit
sprayed over the bituminous material has a preferred bitumen content and
solvent content,
28
CA 02783837 2012-07-26
additional solvent can be added to the dilbit prior to spraying. Other
processing steps to adjust
the composition of the dilbit can also be used, such as removing solvent or
bitumen from the
dilbit.
The first dilbit stream and any other dilbit produced by the first mixing drum
(such as
dilbit produced after spraying the second stream of dilbit over the second
quantity of bituminous
material and separating the resulting slurry) can be transported to a dilbit
storage unit. Dilbit in
the dilbit storage unit can subsequently be processed to separate the bitumen
from the solvent.
Any suitable manner of carrying out such a separation can be used, such as by
evaporating off
the solvent. Solvent separated from the bitumen can be collected and reused in
the process,
while bitumen can be upgraded into lighter hydrocarbon products. In some
embodiments, the
dilbit leaving the first mixing drum can be subjected to solids separation
such as the solids
separation discussed in greater detail above prior to being stored in the
dilbit storage tank. In
some embodiments, the separation process uses a hydrocyclone, centrifuge,
desander, switchable
filter tube, or screen and removes solid material such as sand that may be
contained in the dilbit
upon removal from the first mixing drum.
The first dilbit stream produced from step 320 can typically include from
about 30 to
about 60 wt% bitumen and from about 40 to about 70 wt% solvent. Relatively
small amounts of
solid material, such as sand, may also be included in the first dilbit stream.
In some
embodiments, the first dilbit stream may include from about 0 to about 3 wt%
solid material.
The first tailings stream produced from step 320 can generally include from
about 50 to about 75
wt% inert materials (such as clay and sand), from about 0 to about 5 wt %
water, from about 25
to about 40 wt% solvent, and from about 3 to about 15 wt % bitumen. The second
dilbit stream
produced from step 350 can typically include less bitumen content than the
first dilbit stream,
29
CA 02783837 2012-07-26
such as from about 20 to about 50 wt%, and the second tailings stream can
typically include less
bitumen content then the first tailings stream, such as from about 1% to about
8% wt%. When
the slurry produced from step 370 is separated into a dilbit stream and a
tailings stream, the dilbit
stream can typically have a bitumen content in the range of from 5 to 30 wt%
and the tailings can
have a bitumen content in the range of from 0 to 5wt% (or greater if a solvent
is used that
precipitates asphaltenes).
While Figure 3 includes two mixing steps carried out in two mixing drums, the
method
can include further mixing steps that utilize still additional mixing drums.
For example, the
bitumen-depleted tailings produced in the second mixing drum can be
transported to a third
mixing drum, where solvent is sprayed over the tailings, the resulting slurry
is separated, and the
separated dilbit is used in the first and/or second mixing drum. Ultimately,
any suitable number
of mixing steps and mixing drums, with the mixing drums be generally aligned
in the order
described above (i.e., mixing drum X+1 receives tailings from mixing drum X,
and mixing drum
X+1 provides a dilbit that can be used in any of the preceding mixing drums).
With reference to Figure 4, a process diagram of embodiments of the above
described
method is illustrated. A first mixing drum 400 is provided, which receives
bituminous material
410 such as oil sand. Solvent 420 (for example, dilbit) is sprayed over the
bituminous material
410 inside of the first mixing drum 400 to create a slurry that can
subsequently be separated
inside of the first mixing drum 400. The slurry is separated into a first
tailings stream 415 and a
first dilbit stream 416. The first tailings stream 415 is transported to a
second mixing drum 430.
Dilbit 440 originating from downstream processes is sprayed over the first
tailings stream 415
inside of the second mixing drum 430 to create a slurry, although in some
embodiments, fresh
solvent can be used in place of dilbit 440. The slurry is then separated into
the a second tailings
CA 02783837 2012-07-26
stream 435 and a second dilbit stream 436. The second tailings stream 435 can
either be
subjected to further bitumen extraction processing, such as in a third mixing
drum, or treated for
solvent removal and deposited as waste material. The second dilbit stream 436
is transported
first to a separation unit 470. The separation unit 470 removes solid material
that may be present
in the dilbit stream 436. The dilbit stream 436 (or a portion thereof) is then
transported back to
the first mixing drum 400, where it can be sprayed over additional bituminous
material 410 being
fed into the first mixing drum 400.
The first dilbit stream 416 leaving the first mixing drum 400 can be
transported to a
separation unit 450 that is similar to the separation unit 470. The separation
unit 450 acts to
remove solid material from the first dilbit stream 416 prior to sending the
first dilbit stream 416
to a dilbit storage unit 460. From the dilbit storage unit 460, the first
dilbit stream 416 can be
sent to further processing units, such as unit for separating the bitumen from
the solvent.
In some embodiments, systems that can be used to carry out the bitumen
extraction
methods described above include a first mixing drum, a first separation unit,
a second mixing
drum, and (optionally) a dilbit storage unit. The first mixing drum is
generally similar or
identical to the mixing drums described in greater detail above, and includes
a first dilbit inlet, a
first dilbit outlet, and a first tailings outlet. The first separation unit is
also similar or identical to
the separation units discussed above, and is generally used to separate solid
material from dilbit
that leaves the first mixing drum. The first separation unit therefore
includes a second dilbit inlet
that is in fluid communication with the first dilbit outlet of first mixing
drum. In this manner,
dilbit leaving the first mixing drum can be transported into the first
separation unit. The first
separation unit also includes a cleaned dilbit outlet for transporting cleaned
dilbit (i.e., dilbit with
less solid material than when the dilbit entered the first separation unit)
out of the first separation
31
CA 02783837 2012-07-26
unit, and a solid materials outlet for transporting separated solid material
out of the first
separation unit.
The second mixing drum is generally similar or identical to the mixing drums
described
in greater detail above, and includes a first tailings inlet. The first
tailings inlet is in fluid
communication with the first tailings outlet of the first mixing drum, and
allows for the first
tailings stream leaving the first mixing drum to be fed into the second mixing
drum. Inside the
second mixing drum the first tailings unit will be subjected to bitumen
extraction by being
sprayed with solvent that dissolves bitumen that remains with the first
tailings and subsequently
separating the dissolved bitumen from the tailings. Accordingly, the second
mixing drum also
includes a second dilbit outlet and a second tailings outlet for removing each
component from
the second mixing drum.
The second dilbit outlet of the second mixing drum is in fluid communication
with the
first dilbit inlet of the first mixing drum so that dilbit leaving the second
mixing drum can be
sprayed over bituminous material being fed into the first mixing drum. In this
manner, the
solvent needed for bitumen extraction in the first mixing drum is provided by
the dilbit produced
in the second mixing drum, and the bitumen content of the dilbit moving in a
countercurrent
direction through one or more mixing drums can be increased to an optimal
concentration for
downstream processing or separation.
The dilbit storage unit of the system includes a cleaned dilbit inlet that is
in fluid
communication with the cleaned dilbit outlet of the first separation unit. In
this manner, the
cleaned dilbit exiting the first separation unit can be transported to and
stored in the dilbit storage
unit. Dilbit in the dilbit storage unit can subsequently be transported to
downstream processing
units, such as a distillation unit for separating the solvent from the
bitumen.
32
CA 02783837 2012-07-26
The system described above can also include more than two mixing drums. Any
additional mixing drums are used in the same manner as the first two mixing
drums. For
example, a third mixing drum would receive the tailings from the second mixing
drum and can
be used to provide a dilbit stream that is used in the first and/or second
mixing drum.
In some embodiments, the bitumen extraction method and the mixing drum
configurations described above are used in conjunction with additional
downstream processing.
Typically, the downstream processing includes conducting further bitumen
extraction processing
on the bituminous material or the tailings exiting the mixing drum. By
conducting further
processing on the bituminous material or tailings, the overall extraction rate
of bitumen from the
initial bituminous material can be improved.
In some embodiments, one or more hydrocyclones are used to carry out further
bitumen
extraction on material exiting the mixing drum. More specifically, the one or
more
hydrocyclones can be used when separation of dilbit and tailings is not
carried out inside of the
mixing drums and instead the mixing drum outputs a slurry of solvent and
bituminous material.
Such a slurry is injected into a hydrocyclone, which acts to separate the
dilbit from the tailings.
The dilbit reports to the overflow stream of the hydrocyclone while the
tailings report to the
underflow of the hydrocyclone. In this manner, the mixing drum need not
include separation
apparatus (such as an internal screen). The dilbit leaving the hydrocyclone
can be sent to a
separation unit to separate the solvent from the bitumen, or can be recycled
for use as a solvent
in bitumen extraction. The tailings can be deposited back into the area from
which the
bituminous material was mined.
Figure 5 illustrates a general schematic of a mixing drum 510 having a single
hydrocyclone 520 located downstream of the mixing drum 510. In such a set up,
the
CA 02783837 2012-07-26
hydrocyclone 520 is used to separate the slurry 515 that exits the mixing drum
510 into a dilbit
stream 525 and a tailings stream 526. As shown in Figure 5, the dilbit stream
525 leaving the
hydrocylcone can be sent to a separator 530 for separating the dilbit stream
525 into solvent and
bitumen. The separator 530 can either perform a total separation, or as shown
in Figure 5, can
remove a portion of bitumen while recycling the dilbit back to the mixing drum
510. Once the
dilbit is recycled back to the mixing drum 510, it can be used in subsequent
mixing steps with
bituminous material inside of the mixing drum 510. The tailings stream 526
exits the bottom of
the hydrocyclone 520 and can be deposited as mine backfill.
Typical hydrocyclones suitable for use in the above described method and
system include
hydrocyclone separators that utilize centrifugal forces to separate materials
of different density,
size, and/or shape. The hydrocyclone will typically include a stationary
vessel having an upper
cylindrical section narrowing to form a conical base. The slurry is introduced
into the
hydrocyclone at a direction generally perpendicular to the axis of the
hydrocyclone. This
induces a spiral rotation on the slurry inside the hydrocyclone and enhances
the radial
acceleration on the tailings within the slurry. The hydrocyclone also
typically includes two
outlets. The underflow outlet is situated at the apex of the cone, and the
overflow outlet is an
axial tube rising to the vessel top (sometimes also called the vortex finder).
When the density of the solid tailings phase is greater than that of the fluid
dilbit phase,
the heavier solid particles migrate quickly towards the cone wall where the
flow is directed
downwards. Lower density solid particles migrate more slowly and therefore may
be captured in
the upward spiral flow and exit from vortex finder via the low pressure
center. Factors affecting
the separation efficiency include fluid velocity, density, and viscosity, as
well as the mass, size,
and density of the tailings particles. The geometric configuration of the
hydrocyclone can also
34
CA 02783837 2012-07-26
play a role in separation efficiency. Parameters that can be varied to adjust
separation efficiency
include cyclone diameter, inlet width and height, overflow diameter, position
of the vortex
finder, height of the cylindrical chamber, total height of the hydrocyclone,
and underflow
diameter.
The manner of transporting the slurry from the mixing drum 516 to the
hydrocyclone 520
can include any suitable mechanism for moving slurry away from the outlet of
the mixing drum
510 and into the hydrocyclone 520. In some embodiments, piping is used to
connect the outlet
of the mixing drum 510 to the inlet of the hydrocyclone 520. A pump 530 can
also be used to
ensure the movement of the slurry from the mixing drum 510 to the hydrocyclone
520.
In some embodiments, including embodiments where separation of the slurry does
not
occur inside of the mixing drum, the slurry leaving the mixing drum is sent to
a separation unit
prior to being sent to the hydrocyclone. Exemplary separation units suitable
for use in the
method include, but are not limited to, thickeners, clarifiers, or filters.
Such separation units can
be desirable when clays are present in the slurry leaving the mixing drum.
Separation units such
as thickeners can remove these clays and produce an overflow of dilbit having
reduced or
eliminated clay content. The underflow of the separation unit generally
includes the bitumen-
depleted tailings having a solvent content, and this stream can be sent to the
hydrocyclone. In
some embodiments, the bitumen-depleted tails leaving a separation unit can be
in the form a
filter cake, in which case additional solvent can be added to the filter cake
to re-slurry the
material prior to sending the tailings to the hydrocyclone.
In some embodiments, two or more hydrocyclones aligned in series and located
downstream of the mixing drum can be used to improve the overall amount of
bitumen recovered
from the slurry. The two or more hydrocyclones can use a counter current flow
wherein dilbit
CA 02783837 2012-07-26
recovered from one hydrocyclone is recycled back and added to the slurry being
introduced to
the previous hydrocyclone. By so doing, the overall bitumen extraction
efficiency can be
improved. Any number of hydrocyclones can be used in such a system, and
calculations or
experimentation can be carried out to determine the number of hydrocyclones
necessary to
maximize bitumen extraction. In some embodiments, the number of hydrocyclones
used
depends on how efficiently the hydrocyclones are at "washing" the dilbit from
the tailings, with
additional hydrocyclones necessary when the "washing" is less efficient.
Figure 6 illustrates a system where four hydrocyclones 610, 620, 630, 640 are
aligned in
series downstream of the mixing drum 600. A pump 650, 651, 652, 653 is placed
between the
mixing drum 600 and the first hydrocyclone 610, between the first hydrocyclone
610 and the
second hydrocyclone 620, between the second hydrocyclone 620 and the third
hydrocyclone 630,
and between the third hydrocyclone 630 and the fourth hydrocyclone 640 in
order to assist in the
movement of material between each of the units. The mixing drum 600 is
provided for
producing a slurry of bituminous material and solvent, although in some
embodiments the pump
box of pump 650 can serve as both the mixing drum 600 and the pump 650 when
solvent and
bituminous material are fed directly into the pump 650. The hydrocyclones 610,
620, 630, 640
are provided for separating the slurry into dilbit and tailings. In the series
of hydrocyclones, the
tailings leaving each hydrocyclone are mixed with additional solvent (e.g.,
dilbit) and sent into
the next hydrocyclone in the series until a tailings stream substantially free
of bitumen is
produced. Simultaneously, the dilbit stream leaving each hydrocyclone is sent
to be mixed with
the tailings entering the previous hydrocyclone in the series until a dilbit
sufficiently loaded with
bitumen is produced in the first hydrocyclone in the series.
36
CA 02783837 2012-07-26
Referring still to Figure 6, in operation the method begins with introducing
bituminous
material 601 into the mixing drum 600 and spraying solvent 602 over the
bituminous material
601 inside the mixing drum 600 as described in greater detail above. The
mixing drum 600 does
not include internal separation apparatus, and therefore outputs a slurry 603
including
bituminous material and solvent. Enough solvent 602 is sprayed over the
bituminous material
601 to ensure the slurry 603 is pumpable. While not shown in Figure 6, the
slurry can be
pumped to a separation unit, such as the thickener described previously, to
remove, for example,
clays from the slurry and produce a tailings stream that is sent to the
hydrocyclones. Pump 650
pumps the slurry 603 to the first hydrocyclone 610, where the slurry 603 is
injected into the
hydrocyclone 610 at a direction generally perpendicular to the axis of the
hydrocyclone 610.
Centrifugal forces act on the slurry 603 and separate the slurry into a first
dilbit stream 611 and a
first tailings stream 612. The first dilbit stream 611 can include some of the
less dense solid
particles of the slurry 603, and therefore can be sent to a separation unit
660 that removes fine
solids from the first dilbit stream 611. In some embodiments, an objective of
the hydrocyclone
system is to have the first hydrocyclone 610 produce a first dilbit stream 611
that includes a
solids level of less than 1000 wppm.
The first tailings stream 612 leaving the first hydrocyclone 610 is
transported to the
second hydrocyclone 620. Pump 651 helps to move first tailings stream 612
towards the second
hydrocyclone 620 and can also serve as a mechanism for adding further dilbit
to the first tailings
stream 612 to ensure the first tailings stream 612 is pumpable. As discussed
in greater detail
below, the dilbit added to the first tailings stream 612 can come from the
third hydrocyclone 630.
The mixture of the first tailings stream 612 and the dilbit is transported to
and injected into the
second hydrocyclone 620 at a direction generally perpendicular to the axis of
the second
37
CA 02783837 2012-07-26
hydrocyclone 620. As with the first hydrocyclone 610, centrifugal forces act
on the first tailings
stream 612 to separate the first tailings stream into a second dilbit stream
621 and a second
tailings stream 622. Because the slurry 603 leaving the mixing drum 600 is in
a pumpable
condition by virtue of the amount of solvent 602 added to the bituminous
material 601 inside the
mixing drum 600, the second dilbit stream 621 need not be added with the
slurry 603. Instead,
the second dilbit stream 621 can be used as make-up solvent to be used inside
the mixing drum
600 and further load the second dilbit stream 621 with additional bitumen
content. Accordingly,
the second dilbit stream 621 can be transported to the mixing drum 600 and
combined with
solvent 602 entering the mixing drum 600. Alternatively, the second dilbit
stream 621 can
replace the solvent 602, thereby making the overall system generally self-
sufficient (i.e., no fresh
solvent is needed for the mixing drum 603 stage after start up).
The second tailings stream 622 is transported to the third hydrocylone 630 in
much the
same manner as the first tailings stream 612 is transported to the second
hydrocyclone 620,
including the use of a pump 652 to move the second tailings stream 622 towards
the third
hydrocyclone 630. The second tailings stream 622 can be mixed with dilbit
obtained from the
fourth hydrocyclone 640 in order to ensure that the second tailings stream 622
is pumpable.
Once transported into the third hydrocyclone 630, the second tailings stream
622 is separated
into a third dilbit stream 631 and a third tailings stream 632. As mentioned
above, the third dilbit
stream 631 is recycled back in the system to be added with the first tailings
stream 612 being
sent into the second hydrocyclone 620.
The third tailings stream 632 leaving the third hydrocyclone 630 is
transported towards
the fourth hydrocyclone 640. During the transport, the third tailings stream
632 can be mixed
with additional tailings solids that are obtained when the first dilbit stream
611 is sent to the
38
CA 02783837 2012-07-26
separation unit 660 to remove less dense solid particles that report to the
overflow in the first
hydrocyclone 610 rather than the underflow. The third tailings stream 632 can
also be mixed
with solvent to ensure the third tailings stream 632 is pumpable. The solvent
will typically be a
fresh solvent rather than a dilbit stream obtained from another hydrocyclone
in the system. Once
solvent and/or additional tailings solids are added to the third tailings
stream 632, the third
tailings stream 632 is injected into the fourth hydrocyclone 640 for
separation into a fourth dilbit
stream 641 and a fourth tailings stream 642. The fourth dilbit stream 641 can
be recycled back
to be mixed with the second tailings stream 622 being transported to the third
hydrocyclone 630.
After the fourth hydrocyclone 640, the fourth tailings stream 642 can be in a
condition
where it is sufficiently stripped of bitumen material and is therefore a final
waste product of the
system and method. The fourth tailings stream 642 can include a solvent
content, and in some
embodiments, the fourth tailings stream 642 can be sent to a solvent recovery
unit where the
solvent is removed from the tailings. Any solvent recovery unit or system can
be used to remove
the solvent from the tailings, including a belt dryer to flash recover the
solvent. Solvent can also
be recovered using wash columns, wherein the tailings are packed in a column
and solvent is
displaced out of the tailings by the introduction into the column of various
wash fluids.
As noted above, any number of hydrocyclones can be used to carry out the
bitumen
extraction. Regardless of the number of hydrocyclones used, general operating
procedures can
be followed. For example, the last hydrocyclone in the series will produce a
tailings stream that
has the lowest bitumen content of any of the tailings streams produced by the
various
hydrocyclones in the series and will not be sent to another hydrocyclone for
the purpose of
separating dilbit from the tailings. However, the tailings leaving the last
hydrocylone in the
series may include a solvent content that can be recovered using various
solvent recovery
39
CA 02783837 2012-07-26
processes. Additionally, the first hydrocyclone in the series will produce a
dilbit stream that has
the highest bitumen content of the any of the dilbit streams produced by the
various
hydrocyclones in the series, and will therefore be the dilbit stream that is
treated as a product of
the system rather than being recycled back into the system. In some
embodiments, the dilbit
from the first hydrocyclone in a series of hydrocyclones will be sent to a
separation unit to
separate solvent from the bitumen, and the separated bitumen will then be sent
to further
processing units where bitumen upgrading takes place. The solvent removed from
the bitumen
can be recycled back in the process. Furthermore, with the exception of the
dilbit stream
produced by the first hydrocyclone, the dilbit leaving each hydrocyclone in
the series will be
mixed with the tailings entering the preceding hydrocyclone in the series. As
described above, in
the case of the second hydrocyclone in the series, the dilbit can be used as
the solvent for the
mixing drum step rather than being added to the slurry produced by the mixing
drum in order to
make the overall method more self sufficient.
As noted above, dilbit from each hydrocyclone is mixed with tailings entering
the
previous hydrocyclone in order to ensure that the tailings are pumpable. In
some embodiments,
the S:B ratio used in the initial mixing drum is increased so that the dilbit
obtained from each
hydrocyclone has a suitably high amount of solvent to make the tailings
pumpable when mixed
with the dilbit. In embodiments described above where one or more mixing drums
are used to
extract bitumen, the S:B ratio can be within the range of 0.5:1 to 9:1. When
one or more
hydrocyclones are used downstream of the mixing drum, the S:B ratio used in
the mixing drum
can range from 1.5:1 to 10:1, although any S:B ratio that produces a pumpable
slurry can be
used. In addition to helping to ensure that addition of the dilbit to the
tailings makes the tailings
pumpable, the increased S:B ratio can also improve "wash" efficiency inside of
the
CA 02783837 2012-07-26
hydrocyclones (i.e., result in improved separation of dilbit and tailings).
Each hydrocyclone in
the circuit can be operated at a different S:B ratio to help accomplish these
goals.
In some embodiments, a second series of hydrocyclones can be used to remove
the
solvent from the final tailings produced by the first series of hydrocyclones.
The second series
of hydrocyclones are arranged and operated in a similar or identical manner to
the first series of
hydrocyclones. As shown in Figure 7, the final tailings 642 produced by the
first series of
hydrocyclones are mixed with a solvent mixture 721 that can be the same
solvent as used
previously to form a slurry. The mixture of solvent can be obtained from the
overflow of the
second hydrocyclone 720 in the second series of hydrocyclones. The slurry is
then injected into
a first hydrocyclone 710, which uses centrifugal force to separate a solvent
mixture 711 from a
first tailings 712. The first solvent mixture 711 of the first hydrocyclone
710 can be sent to a
separation unit 740 where primary solvent is separated, while the first
tailings 712 are sent to the
second hydrocyclone 720. Prior to being injected into the second hydrocyclone
720, the first
tailings 712 are mixed with a third solvent mixture 731 obtained from the
overflow of the third
(and in this case, final) hydrocyclone 730. The second hydrocyclone 720
produces a second
solvent mixture 721 which, as noted previously, is mixed with the final
tailings 642 from the first
series of hydrocyclones, and a second tailings stream 722, which is mixed with
fresh solvent and
injected into the third (and in this case, final) hydrocyclone 730. The third
tailings 732 produced
by the third hydrocyclone 730 have the smallest amount of solvent of any of
the tailings
produced in the second series of hydrocyclones, and the third solvent mixture
731 is mixed with
the second tailings 722.
41
CA 02783837 2012-07-26
Any of the hydrocyclones used in the methods and systems described herein can
include
an external heating source for heating the material inside of the
hydrocyclone. The heating can
be indirect heating, such as through the use of steam.
In some embodiments, the downstream processing utilizes one or more packed
columns
for conducting further bitumen extraction on the bitumen-depleted tailings
produced by the
upstream mixing drum (or mixing drums). In such embodiments, the downstream
processing
generally includes introducing the bitumen-depleted tailings into one or more
packed columns,
followed by passing solvent through the tailings packed in the column(s). As
the solvent passes
through the packed column(s), the solvent dissolves bitumen remaining in the
tailings and carries
it through and out of the column as a bitumen laden solvent. In some
embodiments, the solvent
used in the packed column is the same solvent used in the upstream mixing
drums, such as a
paraffinic solvent.
With reference to Figure 8, the downstream processing method can include a
step 800 of
loading bitumen-depleted tailings in a column, a step 810 of feeding a first
quantity of solvent
into the column, a step 820 of collecting bitumen-enriched solvent exiting the
column, and
optionally, a step 830 of feeding the bitumen-enriched solvent into the
column.
With reference to the step 800 of loading bitumen-depleted tailings in a
column, the
bitumen-depleted tailings generally include the tailings produced by the
upstream mixing drum
or drums. In embodiments where multiple mixing drums are used upstream of the
column, the
tailings can come from the last mixing drum in the series of mixing drums.
The column into which the tailings are loaded can be any type of column
suitable for
carrying out bitumen. In some embodiments, the column has a generally vertical
orientation.
The vertical orientation may include aligning the column substantially
perpendicular to the
42
CA 02783837 2012-07-26
ground, but also may include orientations where the column forms angles less
than 90 with the
ground. In some embodiments, the column can oriented at an angle anywhere
within the range
of from about 1 to 90 with the ground. In a preferred embodiment, the
column is oriented at an
angle anywhere within the range of from about 15 to 90 with the ground.
The material of construction for the vertical column is also not limited. Any
material that
will hold the bitumen material within the column can be used. The material may
also preferably
be a non-porous material such that various solvents fed into the column may
only exit the
column from one of the ends of the vertical column. The material can be a
corrosive-resistant
material so as to withstand the potentially corrosive components fed into the
column as well as
any potentially corrosive materials.
The shape of the column is not limited to a specific configuration. Generally
speaking,
the column can have two ends opposite one another, designated a top end and a
bottom end. The
cross-section of the column can be any shape, such as a circle, oval, square,
rectangle, or the like.
In some embodiments, the cross-section of the column changes along the height
of the column,
including both the shape and size of the column cross-section. The column can
be a straight line
column having no bends or curves along the height of the vertical column.
Alternatively, the
column can include one or more bends or curves. In some embodiments, the
column is free of
obstructions, such as platforms of stages.
A wide variety of dimensions can be used for the column, including the height,
inner
cross sectional diameter and outer cross sectional diameter of the column. In
some
embodiments, the ratio of height to inner cross sectional diameter ranges from
0.25:1 to 15:1.
The tailings can be loaded in the column according to any suitable method. For
example,
in some embodiments, the tailings are generally loaded in the column by
introducing the tailings
43
CA 02783837 2012-07-26
into the column at the top end of the column. The bottom end of the column can
be blocked,
such as by a removable plug or by virtue of the bottom end of the column
resting against the
floor. In some embodiments, a metal filter screen at the bottom end of the
column can be used to
maintain the bitumen material in the vertical column. In such configurations,
introducing the
tailings at the top end of the column fills the column with tailings.
In some embodiments, the tailings loaded into the column by pouring the
bitumen
material into the top end of the column. In one example, tailings can be
transported to the
column via a conveyor having one end positioned over the top end of the
column. In such a
configuration, the tailings fall into the column after it is transported over
the end of the conveyor
positioned over the column. Manual methods of loading tailings into the column
can also be
used, such as mechanical or manual shoveling the tailings into column. For
larger diameter
columns, automatic distribution systems can be used, such as the systems
disclosed in U.S. Pat.
Nos. 4,555,210 and 6,729,365.
The amount of tailings loaded in the column may be such that the tailings
substantially
fill the column. In some embodiments, the tailings may be added to the column
to occupy 90%
or more of the volume of the column. In some embodiments, the tailings may not
be filled to the
top of the column so that room is provided to feed solvent into the column.
Generally speaking, the loading of tailings into the column as described above
will lead
to a well packed column. That is to say, the tailings will settle into the
vertical column in
manner that results in minimal void spaces within vertical column. If the
vertical column is not
well packed (i.e., includes too many void spaces or overly large void spaces),
solvent added to
the column to dissolve and extract bitumen (a step of the method described in
greater detail
below) will flow through the vertical column too quickly. When solvent passes
through the
44
CA 02783837 2012-07-26
tailings too quickly, an insufficient amount of solvation of bitumen occurs
and a generally poor
extraction process results.
In some embodiments, additional steps may be taken to ensure a packed column
of
tailings and thereby promote sufficient solvation of bitumen when solvent is
passed through the
tailings loaded in the column. In some embodiments, the size of individual
pieces of the tailings
can be reduced prior to loading the tailings into the column. Reducing the
size of the pieces of
the tailings may help the pieces of the tailings settle closer to each other
in the column and avoid
the formation of void spaces or overly large void spaces. The pieces of
tailings can be reduced
in size by any suitable procedure, such as by crushing or grinding the pieces.
In some
embodiments, the pieces are reduced in size based on the diameter of the
column used. In some
embodiments, the pieces are reduced to a size that is 15% or less than the
diameter of the
column. For example, when the column has a diameter of 40 inches, the pieces
can be reduced
to a size of 6 inches or less. For commercial operation the material is
usually reduced to
nominally 8 inches or less for ease of handling and to ensure dissolution
within adequate
retention time.
In other embodiments, the tailings can be packed down once it is loaded in the
column in
order to reduce or eliminate void spaces. Any method of packing down the
tailings may be used.
In some embodiments, a piston or the like is inserted into the top end of the
vertical column and
force is applied to the piston to move the piston downwardly into the column
in order to pack
down the tailings. The piston may apply pressure downwardly on the tailings
loaded in the
column as a consistent application of downward pressure or as a series of
downward blows.
Alternatively, a vibration device, such as the device disclosed in U.S. Pat.
No. 3,061,278 can be
used to pack down the tailings. Packing down of the tailings can also be
performed manually.
CA 02783837 2012-07-26
Additionally, packing may be allowed to occur under its own weight, including
after solvent has
been added to the tailings. After solvent has been added to the tailings and
the bitumen has
become partially solvated, the mixture of solvent and tailings can compact and
slump down
under its own weight. After the tailings are packed down once, additional
tailings can be added
to the column to take up the space in the column created by the packing. The
packing down of
tailings and adding of further tailings can be repeated one or more times.
In step 810, a first quantity of solvent is fed into the column. One objective
of adding
solvent to the column is to dissolve the bitumen content of the tailings
loaded in the column. Put
another way, the solvent is added to the column to reduce the viscosity of the
bitumen and allow
it to flow through and out of the column. Without the solvent, the bitumen
content of the tailings
at room temperature may have a viscosity in the range of 100,000 times that of
water and will
not flow through the column. The addition of the solvent reduces the viscosity
of the bitumen to
a flowable state and allows it to travel out of the column with the first
solvent.
Accordingly, the solvent used in step 810 can be any suitable solvent for
dissolving or
reducing the viscosity of the bitumen in the bitumen material. In some
embodiments, the first
solvent includes a hydrocarbon solvent. The solvent can be the same solvent as
is used when
mixing solvent and bituminous material in the upstream mixing drum. In some
embodiments,
the solvent is a paraffinic solvent, such as pentane.
The solvent added into the column need not be 100% solvent. Other components
can be
included with the solvent when it is added into the column. In some
embodiments, the solvent
added into the column include a bitumen content. The solvent might include a
bitumen content
when the solvent added into the column in step 810 is solvent that has already
been used to
extract bitumen. As described in greater detail below, solvent that passes
through tailings in a
46
CA 02783837 2012-07-26
column may exit the column as bitumen-enriched solvent, and this bitumen-
enriched solvent
may be used to carry out step 810 being performed on a different column packed
with tailings.
For example, bitumen-enriched solvent collected from the bottom of a first
column as described
in greater detail below may be added to bitumen material loaded in a second
column in order to
carry out step 810 in the second column.
The solvent can be fed into the column in a wide variety of ways. For example,
in some
embodiments, solvent is injected into the tailings loaded in the column at
various locations along
the height of the column. Such injection may be accomplished through the use
of column side
injectors that are spaced along the height of the column and extend through
the side wall of the
column and into the interior of the column where the tailings are loaded.
Injection of solvent at
various locations along the height of the column can also be accomplished by
using a single pipe
that extends down into the column and includes various locations along the
length of the pipe
where solvent can exit the pipe. The pipe can be positioned down the center of
the column or off
to the side of the column.
In configurations such as those described above, the solvent may be injected
into the
column beginning with the lowest injection positions first and moving upwardly
through the
column. Injecting solvent into the column in this manner and in this order
helps to ensure
percolation of solvent through the column and prevents the column from
plugging up as
described in greater detail below.
In some embodiments, the amount of solvent added to the column is based on a
ratio of
solvent to bitumen content in the tailings on a v/v basis (herein referred to
as "S:B") In some
embodiments, the S:B ratio is greater than 1.
47
CA 02783837 2012-07-26
As discussed above, the solvent can be injected into the column starting from
the bottom
of the column and moving upwards to the top of the column. Injecting the
solvent into the
column in this manner may beneficially prevent the column from plugging by
ensuring that the
S:B ratio does not fall below 1 at any location inside the column. If solvent
is added at the top of
the column at an S:B ratio of 1, a portion of the solvent may flow down the
column to a location
where the S:B ratio is below 1 and therefore does not sufficiently reduce the
viscosity of the
bitumen to flow through the column. This may result in the column plugging up.
By
introducing the solvent at an S:B ratio of at least 1 at the bottom of the
column and subsequently
and sequentially adding solvent at higher positions along the column at an S:B
ratio greater than
1, portions of the injected solvent may not be able to flow downwardly to a
location in the
column where the S:B ratio is not greater than 1 and plug the column.
Accordingly, the manner
of injecting the solvent into the column described in greater detail above may
avoid problems
related to column plugging.
If the column does become plugged due to the S:B ratio falling below 1 at a
location
within the column, steps can be taken to unplug the column. More specifically,
the location of
the plug can be identified and additional solvent can be injected into the
column at the injection
point just below the plug (when the column is operated in a downward flow
mode). The
additional solvent injected into the column can be injected into the column in
such a manner as
to close off the bottom of the column and force the solvent to flow upwardly
though the column.
For example, increasing the flow rate and pressure of the injected solvent may
result in closing
off the bottom of the column. The upwardly moving solvent may then displace
and dissolve the
bitumen phase causing the plug due to the viscosity issues.
48
CA 02783837 2012-07-26
The solvent fed into the column flows downwardly through the tailings loaded
in the
column. The solvent flows downwardly through the height of the column via
small void spaces
in the tailings. The solvent may travel the flow of least resistance through
the tailings. As the
solvent flows through the tailings, the solvent can dissolve bitumen contained
in the tailings and
thereby form bitumen-enriched solvent. In some embodiments, 90%, preferably
95%, and most
preferably 99% or more of the bitumen in the tailings is dissolved in the
solvent and becomes
part of the bitumen-enriched solvent phase.
The bitumen-enriched solvent that flows downwardly through the height of the
column
may exit the column at, for example, the bottom end of the column.
Accordingly, a step 820 of
collecting the bitumen-enriched solvent exiting the column is performed. Any
method of
collecting the bitumen-enriched solvent can be used, such as by providing a
collection vessel at
the bottom end of the column. The bottom end of the column can include a metal
filter screen
having a mesh size that does not permit bitumen material to pass through but
which does allow
for bitumen-enriched solvent to pass through and collect in a collection
vessel located under the
screen. Collection of bitumen-enriched solvent can be carried out for any
suitable period of
time. In some embodiments, collection is carried until the bitumen-enriched
solvent phase
substantially or completely stops exiting the column. In some embodiments,
collection is carried
out for from 2 to 60 minutes.
In some embodiments, the bitumen-enriched solvent collected in step 820
contains from
about 10 wt% to about 60 wt% bitumen and from about 40 wt% to about 90 wt%
first solvent.
Minor amounts of non-bitumen material can also be included in the bitumen-
enriched solvent
phase.
49
CA 02783837 2012-07-26
In some embodiments, the flow of solvent through the column and the removal of
bitumen-enriched solvent phase is aided by adding a pressurized gas into the
column either
before or after solvent is fed into the column. Applying a pressurized gas
over the tailings
loaded in the column can facilitate the separation of the bitumen-enriched
solvent from the non-
bitumen components of the tailings loaded in the vertical column. Once
liberated and having a
much reduced viscosity due to the addition of the solvent, the bitumen-
enriched solvent phase
can be pushed out of the column either by the continual addition of
pressurized gas or by feeding
additional solvent into the column. The addition of additional solvent or
bitumen-enriched
solvent collected in step 820 can displace the liberated bitumen-enriched
solvent from the
tailings by providing a driving force across a filtration element (i.e., the
non-bituminous
components of the tailings). Any suitable gas may be used. In some
embodiments, the gas is
nitrogen, carbon dioxide or steam. The gas can also be added over the tailings
loaded in the
vertical column in any suitable amount. In some embodiments, 1.8 m3 to 10.6 m3
of gas per ton
of tailoings is used. This is equivalent to a range of about 4.5 liters to 27
liters of gas per liter of
tailings. In certain embodiments, 3.5 m3 of gas per ton of tailings is used.
After collecting bitumen-enriched solvent, a step 830 of feeding the collected
bitumen-
enriched solvent back into the column can optionally be performed. The bitumen-
enriched
solvent phase can be fed into the column in a similar or identical manner as
described above with
respect to feeding a first quantity of solvent into the column. The bitumen-
enriched solvent may
be fed back into the column "as is" or may be diluted with additional solvent
prior to feeding the
bitumen-enriched solvent back into the column. The amount of bitumen-enriched
solvent phase
fed into the column is not limited. In some embodiments, the bitumen-enriched
solvent fed into
CA 02783837 2012-07-26
the column is approximately 0.5 to 3.0 times the amount of bitumen by volume
contained in the
original bitumen material.
In some embodiments, the bitumen-enriched solvent fed into the column behaves
much
like the first quantity of solvent fed into the column. The bitumen-enriched
solvent flows
downwardly through the column, dissolving additional bitumen still contained
in the column and
forcing any entrapped bitumen-enriched solvent out of the column. The bitumen-
enriched
solvent eventually may exit the column, where it may be collected in a similar
or identical
manner to the collection step 820 described above.
The steps of collecting bitumen-enriched solvent and feeding bitumen-enriched
solvent
back into the column can be repeated one or more times in order to remove
greater amounts of
bitumen from the tailings loaded in the column. In some examples, the steps of
collecting the
bitumen-enriched solvent and feeding the bitumen-enriched solvent into the
column are repeated
until less than 1 wt% bitumen of the bitumen material is remaining in the
column.
In some embodiments, more than one column is provided for carrying out the
extraction
of bitumen from tailings. The columns can generally be aligned in parallel and
can each receive
a portion of the tailings produced in the mixing drums upstream. The bitumen-
enriched solvent
produced from each of the columns can be combined for further use or
processing. Similarly, the
tailings leaving each of the columns after bitumen extraction can be combined
for further
processing or disposal.
In some embodiments, the bitumen-enriched solvent obtained from processing the
tailings in the columns can be used as the solvent that is sprayed over
bituminous material in the
upstream mixing drums. Alternatively, the bitumen-enriched solvent can be
separated into a
solvent phase and a bitumen phase. The bitumen-enriched solvent can also be
divided such that
51
CA 02783837 2012-07-26
some of the bitumen-enriched solvent is used upstream in the mixing drums, and
a remaining
portion is separated into solvent and bitumen.
In some embodiments, the tailings remaining in the column after solvent has
been passed
therethrough contain a trace amount solvent. Accordingly, further drying steps
can be carried
out in order to remove and recover the trace amount of solvent. Any suitable
drying apparatus
can be used. The drying apparatus generally operates by heating the tailings
to the point of
evaporating the solvent. The evaporated solvent can be collected, condensed,
and reused. The
dried tailings can be disposed of.
With reference to Figure 9, a system 900 including packed columns downstream
of the
mixing drums is illustrated. The system 900 generally includes a mineral sizer
920, a first pulper
930, a first thickener 940, a second pulper 950, a second thickener 960, a
wash column 970, and
a dryer 980. While the system 900 includes, for example, two pulpers, other
embodiments of the
system can have fewer or more pulpers. The system 900 will generally include
one thickener
paired with each pulper. The system 900 can also include multiple wash
columns. In some
embodiments, the system 900 includes four wash column aligned in parallel.
In operation, system 900 begins with bituminous material 910, such as the
bituminous
material described above, being transported into the mineral sizer 920.
Solvent 915, such as the
solvent described above, can be injected into the mineral sizer 920 at the
same time as the
bituminous material 910 (as shown in Figure 9) and/or can be mixed with the
bituminous
material 910 prior to its introduction into the mineral sizer 920. The mineral
sizer 920 works to
reduce the size of large clumps of material that may be present in the
bituminous material 910,
and the solvent 915 helps to begin the process of dissolving bitumen while
reducing the wear on
the mineral sizer.
52
CA 02783837 2012-07-26
A slurry 925 of bituminous material and solvent exits the mineral sizer 920
and is
transported to the first pulper 930. In the first pulper 930, solvent is
sprayed over the slurry 925
as described in greater detail above. The solvent sprayed over the slurry 925
in the pulper 930
can be a fresh stream of solvent, or, as shown in Figure 9, can be recycle
dilbit 961 obtained
from the downstream second thickener 960. In some embodiments, the solvent
used in the first
pulper 930 is the same solvent used in the mineral sizer 915 and as will be
used in the second
pulper 950. When dilbit 961 is used, the solvent component of the dilbit can
be same solvent
used throughout the rest of the system 900.
A first pulper slurry 935 is produced as a result of the mixing of solvent and
bituminous
material in the first pulper 930. In some embodiments, separation of the first
pulper slurry 935
into a dilbit stream and a bitumen-depleted slurry can be carried out inside
of the pulper.
However, as shown in Figure 9, the first pulper slurry 935 leaves the first
pulper 930 and is
transported to a first thickener 940. The first thickener 940 operates to
separate the first pulper
slurry 935 into a dilbit stream 941 and a bitumen-depleted slurry stream 942.
The dilbit stream
941 can be sent to further processing apparatus where the solvent component of
the dilbit stream
941 is separated from the bitumen component. The bitumen-depleted slurry
stream 942 is
transported to a second pulper 950.
The second pulper 950 operates in much the same way as the first pulper 930.
Solvent is
sprayed over the bitumen-depleted slurry stream 942 in order to dissolvent
additional bitumen
content. The solvent can be clean solvent, or, as shown in Figure 9, can be
dilbit 972 obtained
from the downstream wash column 970. In some embodiments, the solvent used in
the second
pulper 950 (including the solvent component of the dilbit 972) is the same
solvent as used
throughout the system 900.
53
CA 02783837 2012-07-26
A second pulper slurry 955 is produced as a result of the mixing of solvent
and bitumen-
depleted slurry in the second pulper 950. In some embodiments, separation of
the second pulper
slurry 955 into a dilbit stream and a bitumen-depleted slurry can be carried
out inside of the
pulper. However, as shown in Figure 9, the second pulper slurry 955 leaves the
second pulper
950 and is transported to a second thickener 960. The second thickener 960
operates to separate
the second pulper slurry 955 into a dilbit stream 961 and a bitumen-depleted
slurry stream 962.
The dilbit stream 961 can be sent to further processing apparatus where the
solvent component of
the dilbit stream 941 is separated from the bitumen component, or can be
recycled back for use
in the first pulper 930. The bitumen-depleted slurry stream 962 is transported
to one or more
downstream wash columns 970.
The bitumen depleted slurry stream 962 is loaded in the one or more wash
columns 970,
where solvent 971 is passed through the bitumen-depleted slurry stream 962 in
order to dissolve
additional bitumen and remove the bitumen from the bitumen-depleted slurry
stream 962 in the
form of a dilbit stream 972. The solvent 971 used in the wash column 972 can
be the same
solvent used through the system 900. In some embodiments, multiple wash cycles
are carried
out and can include recycling dilbit 972 back through the wash column 970.
Once a sufficient
number of wash cycles have been carried out, the dilbut 972 can be sent to
separation apparatus
for separating solvent from bitumen, or, as shown in Figure 9, can be recycled
back for use in the
second pulper 950.
The solvent washing that takes place in the wash column 970 ultimately
produces a
solvent-wet tailings phase 973 that can be removed from the wash column 970
and sent to a
dryer for removal of the trace amount of solvent included in the tailings
phase 973. In some
embodiments, the dryer 980 can operate by heating the tailings phase 973 to a
temperature above
54
CA 02783837 2012-07-26
the boiling point temperature of the solvent component, thereby causing the
solvent to evaporate
and exit the dryer 980 as a solvent vapor 981. The solvent vapor 981 can then
be sent to a
condenser for condensing the vapor back to a liquid so that it might be reused
in the system 900.
Once the solvent has been evaporated from the tailings, a dry tailings phase
982 can be
discharged from the dryer and disposed of.
Several advantages can be realized by using the methods and systems described
herein.
Specifically, the use of a single solvent where the solvent is paraffinic can
provide numerous
advantages over other solvent bitumen extraction techniques, including those
techniques using
more than one type of solvent. Firstly, the use of paraffinic solvent can
increase the throughput
of the method by a factor of 2 or greater. Improved throughput can be realized
due to the use of
the lighter paraffinic solvent that is capable of solvating the bitumen
material faster than heavier
solvents and results in reduced viscosity dilbit, which can be recovered from
the solids easier.
The paraffinic solvent can also advantageously precipitate asphaltenes,
further eliminating the
heavy viscosity component. In some instances, the paraffinic solvent causes
the asphaltenes to
precipitate into the solids, and more specifically onto the finer clays. The
precipitated
asphaltenes are captured by finer clays while the dilbit passes through and
out of the bitumen
material for successful bitumen extraction. The precipitation of asphaltene
can also be beneficial
by allowing for the upgrading of bitumen extracted in the dilbit using
conventional upgrading
processing equipment (i.e., specialized upgrading equipment capable of
handling asphaltenes as
well as bitumen is not required).
The systems and methods that use a single solvent instead of two different
types of
solvents can also be advantageous from a capital expenditure (CAPEX)
perspective. Single
solvent systems typically only require a single distillation unit for the
separation and recovery of
CA 02783837 2012-07-26
the single solvent. Single solvent systems, including single solvent systems
using a paraffinic
solvent, also tend to require smaller distillation units as compared to when
heavier solvents are
used. Operating expenditures (OPEX) are also reduced when using a single
solvent system
versus a two solvent system. For example, lower heating duty is required for
removing a single,
relatively light, solvent from the tailings. Finally, environmental advantages
can result from the
single solvent system. Carbon dioxide emissions and fugitive solvent loses can
be reduced when
a single solvent system is used in lieu of a system that uses two different
types of solvents.
In view of the many possible embodiments to which the principles of the
disclosed
invention may be applied, it should be recognized that the illustrated
embodiments are only
preferred examples of the invention and should not be taken as limiting the
scope of the
invention. Rather, the scope of the invention is defined by the following
claims. We therefore
claim as our invention all that comes within the scope and spirit of these
claims.
56
