Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM, APPARATUS AND PROCESS FOR
EXTRACTION OF BITUMEN FROM OIL SANDS
FIELD OF THE INVENTION
This invention relates to systems and methods for extracting hydrocarbons
from a mixture that includes solids and water. More particularly, the
invention relates
to a system and method for extracting bitumen from a hydro-transport slurry
created to
facilitate movement of bitumen contained in oil sands from a mining site to a
processing site.
BACKGROUND OF THE INVENTION
Oil sands, also referred to as tar sands or bituminous sands, are a
combination
of solids (generally mineral components such as clay, silt and sand), water,
and
bitumen. Although the term "sand" is commonly used to refer to the mineral
components of the mixture, it is well known that this term is meant to include
various
2 0 other components such as clay and silts. Technically speaking, the
bitumen is neither
oil nor tar, but a semisolid form of oil which will not flow toward producing
wells
under normal conditions, making it difficult and expensive to produce. Oil
sands are
mined to extract the oil-like bitumen which is processed further at
specialized
refineries. Conventional oil is extracted by drilling traditional wells into
the ground
2 5 whereas oil sand deposits are mined using strip mining techniques or
persuaded to
flow into producing wells by techniques such as steam assisted gravity
drainage
(SAGD) or cyclic steam stimulation (CSS) which reduce the bitumen's viscosity
with
steam and/or solvents.
3 0 Various methods and equipment have been developed over many years
for
mining oil sands and for extracting desired hydrocarbon content from the mined
solids.
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Conventional oil sand extraction processes involve the following steps:
a) Excavation of the oil sand from a mine face as a volume of ore material.
Generally,
this is done using conventional strip mining techniques and equipment.
b) Comminution of the ore material to reduce it to conveyable size for
conveying from
the mine face.
c) Combining the comminuted material with water to form a slurry. Generally,
the
slurry is formed with hot water, and, optionally other additives.
d) Pumping the slurry to a primary separation facility to separate the mineral
from the
hydrocarbon components. The pumping step is generally referred to as a "hydro-
transport" process. During the slurry formation and hydro-transport process,
large
1 5 constituents in the ore material are further reduced in size, or
ablated, and the process
of bitumen separation from the solid mineral components is commenced. These
effects are referred to as "conditioning" of the slurry.
e) Separating the bulk of the hydrocarbon (i.e. bitumen) content from the
mineral
2 0 component in one or more "primary separation vessels" (PSV) wherein the
bitumen
portion is entrained in a froth that is drawn off from the surface of the
slurry while a
significant portion of the mineral is removed as a solids or tailings stream.
f) Hydraulic transport of the tailings to a designated tailings disposal site.
g) Recovery and recycling of clarified water back to the process when released
from
the tailings slurry within the tailings disposal site.
The above separation and froth concentration steps constitute initial primary
3 0 extraction of the oil sands to separate the bitumen from the mineral
component. The
bitumen froth that results after application of the above steps is then
delivered to
secondary treatment steps that further concentrate and upgrade the bitumen to
produce
a suitable feed for upgrading to synthetic crude oil or for refining into
petroleum
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products.
Various other intervening steps are also known in the primary extraction
process such as withdrawal of a middlings layer from the PSV to further
increase the
yield of bitumen from the ore material.
As will be known to persons skilled in the art, the large-scale nature of oil
sands mining requires processing facilities of an immense size. As such, these
facilities are generally fixed in position. For this reason, transport of the
ore material
between the various above-mentioned steps generally involves the use of
trucks,
conveyors, or pipelines or various other known equipment. However, as
operations
continue, it will be appreciated that the mine face normally recedes further
away from
the permanent facilities. This, therefore, increases the transport distances
and time
resulting in increased operating and maintenance costs and environmental
impact.
There exists therefore a need to increase the efficiency of at least the
transport
and primary extraction processes to reduce operating costs. One suggestion
that has
been proposed is for having one or more of the excavating equipment to be
mobile so
as to follow the receding mine face. An example of this method is taught in
Canadian
2 0 application number 2,453,697, wherein the excavating and crushing
equipment is
made mobile so as to advance along with the mine face. The crushed ore is then
deposited onto a conveyor, which then transports the ore to a separation
facility. This
reference also teaches that the conveyor and separation facility can
periodically be
relocated to a different site once the mine face advances a sufficient
distance.
2 5 However, such relocation would involve considerable time, expense and
lost
production.
Another problem faced with respect to oil sand mining involves the fact that
sand constitutes the primary weight fraction of the mineral component of the
mined
3 0 ore material. Thus, it is desirable to separate the minerals as soon as
possible
"upstream" so as to minimize transport costs. In addition, the transport of
mineral
components results in considerable wear on the transport mechanisms, which
further
increases operating and maintenance costs. At the same time, separation of the
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bitumen and mineral components must be done in such a way as to maximize
bitumen
yield from the ore material.
Thus, there exists a need for an efficient primary extraction process to
separate
bitumen from the mineral components, preferably in proximity to the mine face
to
reduce transport costs. The present invention seeks to alleviate at least some
of the
problems associated with the prior art by providing a novel system and method
for
extracting the bitumen from a hydro-transport slurry to create an intermediate
bitumen
froth suitable for further processing. The system of the present invention is
preferably
mobile so that the primary extraction process can move with the mine face,
however,
it is also contemplated that the system can be retrofitted to existing fixed
primary
treatment facilities to improve the operational efficiency of such fixed
facilities.
SUMMARY OF THE INVENTION
Accordingly, in some embodiments, there is provided an extraction system for
extracting bitumen from a slurry containing bitumen, solids and water
comprising:
a cyclone separation facility for separating the slurry into a solids
component
2 0 stream and a bitumen froth stream, the bitumen froth stream including
bitumen, water
and fine solids; and
a froth concentration facility for separating the bitumen froth stream into a
final bitumen enriched froth stream, and a water and fine solids stream.
In some embodiments, there is provided a process for extracting bitumen from
a slurry containing bitumen, solids and water comprising:
separating the slurry into a solids component stream and a bitumen froth
3 0 stream; and
separating the bitumen froth stream into a final bitumen froth stream and a
water and fine solids stream.
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In accordance with one aspect of the invention, there is provided a
concentrator vessel for separating a bitumen froth stream containing bitumen
froth,
water and fine solids into a final bitumen enriched froth stream and a water
and fine
solids stream, the concentrator vessel comprising:
an inlet region to receive the bitumen froth stream;
a separation region in communication with the inlet region including a
diverging channel adapted to slow the flow of the bitumen froth stream to
promote
separation of the bitumen froth from the water and fine solids, the bitumen
froth
accumulating as a froth layer atop a water layer with the fine solids settling
within the
water layer; and
a froth recovery region in communication with the separation region having an
1 5 overflow outlet to collect the bitumen froth layer as the bitumen
enriched froth stream,
and an underflow outlet to collect the water and fine solids as the water and
fine solids
stream.
In accordance with another aspect of the invention there is provided a
2 0 concentrator vessel for separating a bitumen froth stream containing
bitumen froth,
water and fine solids into a bitumen enriched froth stream and a water and
fine solids
stream. The concentrator vessel includes an inlet for receiving the bitumen
froth
stream and a separation region including a diverging channel adapted to slow
the flow
of the bitumen froth stream to promote separation of the bitumen froth from
the water
2 5 and fine solids. The concentrator vessel further includes an overflow
outlet to collect
the separated bitumen froth as the bitumen enriched froth stream and an
underflow
outlet to collect the separated water and fine solids as the water and fine
solids stream.
In accordance with another aspect of the invention there is provided a process
3 0 for separating a bitumen froth stream containing bitumen froth, water
and fine solids
into a bitumen enriched froth stream and a water and fine solids stream. The
process
involves receiving the bitumen froth stream in a concentrator vessel and
distributing
the bitumen froth stream in the concentrator vessel as a substantially uniform
and
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generally horizontal flow of the bitumen froth stream at a first flow
velocity. The
process also involves slowing the bitumen froth stream to a second flow
velocity,
slower than the first flow velocity, in a separation region of the
concentrator vessel to
promote separation of the bitumen froth from the water and fine solids. The
bitumen
froth accumulates as a bitumen froth layer atop a water layer with the fine
solids
settling within the water layer. The process also involves collecting the
bitumen froth
layer as the bitumen enriched froth stream and collecting the water layer and
fine
solids as the water and fine solids stream.
In accordance with another aspect of the invention there is provided a system
for separating a bitumen froth stream containing bitumen froth, water and fine
solids
into a bitumen enriched froth stream and a water and fine solids stream. The
system
includes receiving means for receiving the bitumen froth stream in a
concentrator
vessel and distributing means for distributing the bitumen froth stream in the
concentrator vessel as a substantially uniform and generally horizontal flow
of the
bitumen froth stream flowing at a first flow velocity. The system also
includes
slowing means for slowing the bitumen froth stream to a second flow velocity,
slower
than the first flow velocity, in a separation region of the concentrator
vessel to
promote separation of the bitumen froth from the water and fine solids. The
bitumen
froth accumulates as a bitumen froth layer atop a water layer with the fine
solids
settling within the water layer. The system also includes first collecting
means for
collecting the bitumen froth layer as the bitumen enriched froth stream and
second
collecting means for collecting the water layer and fine solids as the water
and fine
solids stream.
In accordance with another aspect of the invention there is provided a
concentrator vessel for separating a bitumen froth stream containing bitumen
froth,
water and fine solids into a bitumen enriched froth stream and a water and
fine solids
stream. The concentrator vessel includes an inlet region to receive the
bitumen froth
stream and a separation region in communication with the inlet region
including a
laterally diverging channel adapted to slow the flow of the bitumen froth
stream to
promote separation of the bitumen froth from the water and the fine solids.
The
bitumen froth accumulates as a separated bitumen froth layer atop a water
layer with
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the fine solids settling within the water layer. The concentrator vessel also
includes a
froth recovery region in communication with the separation region having an
overflow
outlet to collect the separated bitumen froth layer as the final bitumen
enriched froth
stream, and an underflow outlet to collect the water and fine solids stream.
The
laterally diverging channel is formed by first and second spaced apart
continuous
barriers. Each of the first and second spaced apart continuous barriers extend
from
respective first ends disposed proximate the inlet region to second ends
disposed
proximate the froth recovery region. The laterally diverging channel has a
first region
between the respective first ends of the first and second spaced apart
continuous
barriers and a second region between the respective second ends of the first
and
second spaced apart continuous barriers. The second region is wider than the
first
region to cause the flow of the bitumen froth stream to be slowed while a
volumetric
flow rate through the laterally diverging channel remains constant as the
bitumen froth
stream is directed from the inlet region to the froth recovery region between
the first
1 5 and second spaced apart continuous barriers.
BRIEF DESCRIPTION OF THE DRAWINGS
2 0 Aspects of the present invention are illustrated, merely by way of
example, in
the accompanying drawings in which:
Figure 1 is a flow diagram showing a preferred embodiment of the system of
the present invention for extracting bitumen from a slurry containing bitumen,
solids,
2 5 and water;
Figure 2 is a schematic view showing a modular, mobile extraction system
according to an aspect of the present invention incorporating a plurality of
mobile
cyclone separation stages forming a mobile cyclone separation facility and a
mobile
3 0 froth concentrator vessel defining a mobile froth concentration
facility;
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Figure 3 is a top plan schematic view showing an embodiment of a froth
concentrator vessel;
Figure 4 is side elevation view of the concentrator vessel of Figure 3;
Figure 5 is a top plan schematic view showing an alternative concentrator
vessel incorporating a turn in the diverging channel;
Figure 6 is a perspective view of a concentrator vessel according to another
embodiment;
Figure 7 is a top plan view of a concentrator vessel according to a further
embodiment;
Figures 7A is a cross-sectional elevation view taken along line 7A-7A of
Figure 7;
Figure 7B is a side elevation view taken along line 7B-7B of Figure 7;
Figure 7C is an end view of the concentrator vessel of Figure 7 showing the
overflow outlet end and the bitumen froth exit nozzle;
Figure 7D is an opposite end view of the concentrator vessel of Figure 7
2 5 showing the underflow outlet end and the water and fine solids exit
nozzle; and
Figure 7E is a detail section view taken along line 7E-7E of Figure 7 showing
details of a froth recovery weir to collect froth discharged through the
underflow
outlet.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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Referring to Figure 1, there is shown a flow diagram of an extraction system
according to an aspect of the present invention for extracting bitumen from a
slurry
that includes bitumen, solids and water. This slurry may be created by
conventional
techniques or by other techniques such as the mobile oil sand excavation and
processing system and process described in applicant's co-pending Canadian
patent
application no. 2,526,336 filed on November 9, 2005 and entitled METHOD AND
APPARATUS FOR OIL SANDS ORE MINING. This mobile oil sand excavation
and processing system is capable of excavating, comminuting or crushing, and
slurrifying oil sand ore and moving with the mine face. In a preferred
arrangement,
1 0 the system and process illustrated in Figure 1 are designed to be
mobile for movement
with the mine face and the excavation and ore processing system, however, the
present system can also be retrofitted to existing fixed froth treatment
facilities to
improve the operational efficiency of such fixed facilities.
1 5 Initially, the system of Figure 1 includes a cyclone separation
facility 102, also
referred to as a de-sanding or, more accurately, a de-mineralising facility
for treatment
of incoming slurry 100. The cyclone separation facility 102 comprises a
plurality of
hydrocyclones which aid in de-mineralizing slurry 100. A water feed 104 is
also
provided to the cyclone separation facility 102 as a water wash to the slurry
flow. The
2 0 cyclone separation facility 102 serves to efficiently separate a large
portion of the
solids component from the bitumen component, producing a bitumen rich froth
114,
while a large portion of the solids component is separated as a tailings
stream 128
from the separation facility 102.
2 5 The solids or mineral component of the incoming slurry 100 is a
significant
portion, by weight, of the excavated ore from the mine site. By way of
example,
incoming slurry 100 can have a composition within the following ranges: about
5-
15% bitumen by weight, about 40-70% solids (minerals) by weight and about 30-
75%
water by weight. In a typical slurry, the composition will be in the range of
about 7-
3 0 10% bitumen by weight, about 55-60% minerals by weight, and about 35%
water by
weight. Thus, in order to increase the efficiency of the oil sands strip
mining system,
removal of much of the solids component (minerals excluding bitumen) is
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preferentially conducted as close to the mine face as possible. This avoids
unnecessary
transport of the solids component thereby avoiding the operation and equipment
maintenance costs associated with such transport.
In one embodiment, cyclone separation facility 102 includes three cyclone
separation stages 106, 108 and 110 that are connected in series and, more
preferably,
in a counter-current arrangement (as discussed below). The cyclone separation
stages
of each comprise one or more hydrocyclones that are generally vertical units,
which
have a minimal footprint, thereby occupying a minimal area. This can be
particularly
desirable in relation to those embodiments of the present invention which are
directed
to a mobile cyclone separation facility. Suitable hydrocyclones for the
cyclone
separation stages include those manufactured by Krebs Engineers
(www.krebs.com)
under the trademark gMAX , although any hydrocyclone capable of separating a
significant amount of the solids component from a bitumen based slurry will
do. The
slurry 100 (including the bitumen and solid components of the ore) is fed to
the first
cyclone separation stage 106 wherein a first separation of the bitumen froth
and solids
is conducted in a conventional manner. Optionally, the slurry 100 is processed
by a
screening and/or comminuting unit 105 before entering the first cyclone
separation
stage 106 to ensure that solid particles in the slurry can be handled by the
cyclone.
2 0 Rejected solid particles can either be discarded after screening or
made smaller by
crushing or other suitable techniques. An exemplary sizing roller screen for
carrying
out the screening and re-sizing process is disclosed in commonly owned co-
pending
Canadian Patent application no. 2,476,194 filed July 30, 2004 and entitled
SIZING
ROLLER SCREEN ORE PROCESSING APPARATUS. In the first cyclone
2 5 separation stage 106, slurry 100 is processed in a conventional manner
to produce a
first bitumen froth 112, and a first solid tailings stream 116 which comprises
significantly less bitumen and substantially more solids than found in the
first bitumen
froth 112. Bitumen froth 112 is delivered to a froth collection stream 114,
while first
solid tailings stream 116 is pumped to a feed stream 118 of the second cyclone
3 0 separation stage 108 where a further cyclone separation process is
conducted. The
bitumen froth 120 from the second cyclone separation stage 108 is reintroduced
to the
feed stream 100 supplying the first separation stage 106. The tailings stream
122 from
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the second cyclone separation stage 106 is combined with the water feed 104 to
form
a feed 124 to the third cyclone separation stage 110. The bitumen froth 126
from the
third stage 110 is combined into the feed 118 to the second separation stage
108. The
tailings from the third stage 110 form a first tailings stream 128, which may
be
pumped to a disposal site such as a tailings pond 149.
In the embodiment illustrated in Figure 1, the three stage cyclone separation
system incorporating a counter-current process and a water feed 104 results in
a first
flow 111 (dash-dot line in Figure 1) of progressively enriched bitumen froth
from the
downstream cyclone separation stage 110 through the intermediate cyclone
separation
stage 108 to the upstream cyclone separation stage 106. At the same time,
there is an
opposite (counter-current) flow 113 (dotted line in Figure 1) of mineral
tailings from
the upstream stage 106 to the intermediate stage 108, and finally to the
downstream
stage 110. In such a facility, effectively the hydro-transported ore slurry
100 is mixed
with a counter-current wash of water to form bitumen froth stream 114 which is
then
drawn off and further processed to extract the desired hydrocarbons entrained
therein.
The counter-current water wash of the bitumen flow serves to improve the
recovery
efficiency of the bitumen. In this system, it will be understood that a three-
stage
process is preferred. However, it will be apparent to persons skilled in the
art that the
number of cyclone stages used in the process will also depend upon the grade
of the
ore supplied to the cyclone separation facility. Thus, a high grade ore may
require
fewer cyclone stages. Further, it will also be appreciated that the size or
capacity of
each cyclone stage will also be determinative of the number of stages required
for a
particular process. While wash water is shown being introduced at the
downstream
cyclone separation stage 110, it will be appreciated that wash water 104, or a
portion
thereof, can also be introduced at the other cyclone separation stages
depending on the
ore grade.
In addition, it will be understood that the cyclone separation facility is
more
3 0 efficient when operated in a water wash manner. The term "water wash"
refers to the
manner in which the slurry and water streams are supplied at opposite ends of
a multi-
stage process as discussed above. Thus, for example, water entering the
process
(either make-up or recycled) is first contacted with a bitumen-lean feed and
vice versa.
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A further advantage of the multi-stage cyclone separation facility illustrated
in
Figure 1 lies in the fact that size of the component facility may be reduced
since the
multi-stage counter-current process results in a separation efficiency roughly
equivalent to a much larger, single PSV stage system. For this reason,
embodiments of
the multi-stage facility of the present invention may be mounted on a mobile
platform
or on movable platforms and, in the result, such facility may be made moveable
along
with the oil sands mine face. However, the multi-stage cyclone separation
facility may
also be configured in a fixed arrangement.
In view of the comments above, the cyclone separation facility 102 illustrated
in Figure 1 is preferably an independently moveable facility where one desires
to
operate the facility as close to the oil sand mine face as possible. In such a
case, the
only stream requiring major transport comprises the bitumen froth stream 114
exiting
1 5 from the cyclone separation facility, with tailings optionally
deposited or stored close
to the mine face. The cyclone separation facility removes the bulk of the
solids from
the ore slurry 100 at or close to the oil sand mining site thereby avoiding
the need for
transporting such material and the various costs associated therewith.
Movement of
the cyclone separation facility 102 may be accomplished by a mobile crawler
(such as,
2 0 for example, those manufactured by Lampson International LLC) or by
providing
driven tracks on the platform(s) supporting the separation stages. Various
other
apparatus or devices will be apparent to persons skilled in the art for
achieving the
required mobility.
2 5 By way of example, Figure 2 shows a preferred setup according to an
aspect of
the invention in which each cyclone separation stage 106, 108 and 110 is
mounted on
its own independent skid 160 to form a mobile module. Positioned between each
cyclone separation stage skid 160 is a separate pump skid 162 which provides
appropriate pumping power and lines to move the froth streams and solid
tailings
3 0 streams between the cyclone separation stages. It is also possible that
any pumping
equipment or other ancillary equipment can be accommodated on skid 160 with
the
cyclone separation stage. In the illustrated arrangement of Figure 2, groups
of three
mobile modules are combinable together to form cyclone separation facilities
102,
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102', 102" to 102n as needed. Also associated with each cyclone separation
facility is
a mobile froth concentration facility 130 which will be described in more
detail
below.
Each cyclone separation facility and associated froth concentration facility
in
combination define the smallest effective working unit 200 of the extraction
system
according to the illustrated embodiment. This modular arrangement of the
extraction
system provides for both mobility of the system and flexibility in efficiently
handling
of different volumes of ore slurry. For example, mobile modules comprising
skids or
other movable platforms with appropriate cyclone stage or froth concentration
equipment on board may be assembled as needed to create additional mobile
extraction systems 200', 200" to 200n to deal with increasing ore slurry flows
provided
by hydro-transport line 101. Ore slurry from the transport line 101 is fed to
a
manifold 103 which distributes the slurry to a series of master control valves
165.
Control valves 165 control the flow of ore slurry to each mobile extraction
system 200
to 200n. This arrangement also permits extraction systems to be readily taken
off-line
for maintenance by switching flow temporarily to other systems.
The separation efficiency of the multi-stage counter-current cyclone
separation
facility allows the extraction system to be used with a variety of ores having
different
bitumen contents and solids contents. In the case of solids contents, both the
mineral
components and the fines components including silts and clays can vary. In one
variation, it is possible for the cyclone separation facility to operate with
a single
cyclone separation stage or a pair of cyclone separation stages depending on
the ore
content, however, the three stage counter-current arrangement is the preferred
arrangement for efficient separation over the widest range of ore grades.
The bitumen froth stream 114 obtained from the de-mineralizing cyclone
separation facility 102 is unique in that it contains a higher water
concentration than
normally results in other separation facilities, that is, the present system
creates a
bitumen froth stream 114 (a bitumen-lean froth stream) that is more dilute
than
heretofore known. In known separation facilities, the resulting bitumen
enriched
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stream typically has a bitumen content of about 60%, a solids content of
approximately 10%, and a water content of approximately 30%. With the system
and
process according to an aspect of the present invention, however, sufficient
water is
added as wash water 104 to create a bitumen froth stream 114 having a bitumen
content in the range of about 5-12% by weight, a solids content in the range
of about
10-15% by weight and a water content of about 60-95% by weight. It will be
understood that when the water content is in the higher concentrations (above
about
85%) the bitumen content and solids content may be below about 5% and 10%,
respectively. It will also be understood that the above concentrations are
provided
solely for illustrative purposes in one aspect of the present invention, and
that in other
variations various other concentrations will or can be achieved depending on
various
process parameters.
The present system and process create a highly diluted bitumen froth stream as
a result of washing the froth stream in a counter-current manner with water
stream
104 in order to improve bitumen recovery. The washing assists in the removal
of
solids in slurry 100. However, the increased water content of bitumen froth
stream
114 necessitates that the bitumen froth stream be further processed in an
additional
step through a froth concentration facility 130 in order to remove the wash
water.
This ensures that the final bitumen enriched froth stream 136 of the present
system is
of a composition that can be delivered to a conventional froth treatment
facility (not
shown) which operates to increase the bitumen concentration of the product to
make it
ready for further processing in an upgrade or refinery facility.
Returning to Figure 1, the bitumen froth stream 114 produced by the cyclone
separation facility 102 is delivered to a froth concentration facility
generally indicated
at 130. More specifically, the froth stream 114 is preferably pumped to a
froth
concentrator vessel 132 within the froth concentration facility 130. Froth
concentrator
vessel 132 may comprise a flotation column, a horizontal decanter, a
conventional
3 0 separation cell, an inclined plate separator (IPS) or other similar
device or system as
will be known to persons skilled in the art. In one preferred embodiment, the
froth
concentration facility comprises at least one IPS unit. It will also be
appreciated that
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the froth concentration facility 130 may comprise any number or combination of
units.
For example, in one embodiment, froth concentration facility 130 may comprise
a
separation cell and a flotation column arranged in series. In another
embodiment, the
froth concentration facility may comprise an lPS in association with a high
rate
thickener. In addition to the bitumen froth stream 114, an air feed 134 may
also be
pumped into the froth concentrator vessel 132 to assist in the froth
concentration
process. In general, however, sufficient air is entrained in the ore slurry
during the
hydro-transport process and in the froth stream during the cyclone separation
step that
addition of air is not warranted at the froth concentration step.
The froth concentrator vessels 132 described above tend to be suited to a
froth
concentration facility 130 according to an aspect of the invention that is
intended to be
fixed in place. This equipment does not tend to lend itself to being mobile
when in
operation due to its large size.
Within concentrator vessels 132, the froth is concentrated resulting in a
final
bitumen enriched froth or product stream 136 that may optionally be
transported to a
conventional froth treatment facility (not shown) to increase the bitumen
concentration of the product to make it ready for further processing in an
upgrader or
2 0 refinery facility. The froth concentration facility 130 produces a fine
solids stream
138 that comprises water and the fine solids (silt and clay) that were not
separated at
the cyclone separation facility 102. In one embodiment, chemical additives may
also
by used in the froth concentration facility 130 to enhance the separation of
fine solids
from the water.
The bitumen froth stream 114 that leaves the cyclone separation facility 102
contains bitumen at a concentration of about 5-12% by weight. As described
above,
this is a lean bitumen froth stream with a high water content. The froth
concentration
facility 130 is employed to increase the bitumen concentration in the final
bitumen
enriched froth stream 136 to about 55% to 60% by weight. When this final
product of
the extraction system is transported to a froth treatment facility (as
mentioned above),
the hydrocarbon concentration may be further increased to range from about 95%
to
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98% by weight. It should be noted that these concentrations are recited to
exemplify
the concentration process and are not meant to limit in any way the scope of
any
aspects of the present invention. It will be appreciated, for example, that
the specific
concentrations that can be achieved will depend on various factors such as the
grade
of the ore, the initial bitumen concentration, process conditions (i.e.
temperature, flow
rate etc.) and others.
In one aspect of the present invention, the froth concentration facility 130
is a
mobile facility that is used in combination with the mobile cyclone separation
facility
1 0 102 described above. As shown in Figure 2, a froth concentration
facility 130, 130',
130" to 130' is included in each mobile extraction systems 200', 200" to 200,
respectively, to provide the necessary bitumen froth concentration step.
In order to meet the mobility arrangement for the froth concentration facility
130, a concentrator vessel specially designed for compactness may be used with
the
current extraction system. The preferred concentrator vessel for operation in
a mobile
facility is a modified version of a horizontal decanter. The modified design
functions
to efficiently process the lean bitumen froth stream exiting from the cyclone
separation facility 102. The use of cyclone separation stages in the above
described
2 0 cyclone separation facility 102 allows the majority of the solids
material (i.e. the
mineral component) in the slurry to be removed. Such material is known to
result in
plugging of a device such as a horizontal decanter. However, since such
material is
removed by the cyclone separation facility, use of a horizontal decanter
design is
possible in the current system. As well, the horizontal decanter design lends
itself
2 5 well to modification to minimize the footprint of the concentrator
vessel. This results
in a preferred concentrator vessel having a configuration that is compact and
readily
movable, and therefore suited for incorporation into mobile embodiments of the
present invention as described above and as illustrated schematically in
Figure 2.
3 0 Referring to Figures 3 to 7D, there are shown various embodiments of a
froth
concentrator vessel 132. Vessels according to this design have been found to
reliably
handle and process froth streams with a water content ranging from about 60-
95% by
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weight, and with the majority of the solids content being fine solids with
less than
about 30% of the solids being of a particle size above about 44 microns. Such
a froth
stream composition is an example of a typical froth stream composition
produced by
cyclone separation facility 102 described above. However, the concentrator
vessel
132 is not limited to handling froth streams with the above composition.
Figures 3 and 4 are a schematic plan view and a side elevation view,
respectively, of a concentrator vessel 132 showing major features to permit an
understanding of the overall operation of the unit. The vessel includes an
inlet region
170 to receive the bitumen froth stream 114 from cyclone separation facility
102.
Inlet region 170 communicates with a separation region 172 where bitumen froth
is
concentrated by separation from the water and fine solids of the froth stream
114.
Separation region 172 preferably comprises a diverging channel adapted to slow
the
flow of the bitumen froth stream 114 to promote vertical separation of the
bitumen
froth from the water and the fine solids due to gravity. As best shown in
Figure 3, the
diverging walls 173 of the channel result in the velocity of the flow through
the
channel slowing due to there being an increasing area (wider channel) for the
flow to
move through. Arrows 175a show an initial velocity of flow volume through the
channel at a time t1 while arrows 175b show a slower flow velocity at a later
time t2 in
2 0 a wider portion of the channel. In other words, the volumetric flow
rate Q through the
channel stays constant, however, the velocity slows as the area available for
flow
increases. As flow moves through the channel, gravity and the slowing of the
flow
causes bitumen froth to accumulate as an upper froth layer 177 atop a lower
water
layer 178 with fine solids settling within the water layer. This is best shown
in the
side elevation view of Figure 4. The bitumen froth will tend to coalesce and
float on
the surface of what is primarily an aqueous flow (about 80% water by weight)
and any
remaining fine solids (silt and clay) in the stream will tend to settle within
the water
layer. Diverging channel 172 terminates in a froth recovery region 179 which
is
formed with an overflow outlet 182 to collect the bitumen froth layer as a
final
bitumen froth stream 136. An underflow outlet 184 collects the water and fine
solids
stream 138.
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Overflow outlet 182 preferably comprises at least one weir formed at a
perimeter wall 181 of the froth recovery region 179. The weir can be a
conventional
crested weir or a J-weir 188 (as best shown in Figure 4) so called because of
its shape
in cross-section. Overflow outlet 182 can be formed as a continuous weir about
the
full perimeter or a portion of the perimeter of the froth recovery region 179.
Alternatively, overflow outlet 182 can comprise a plurality of crested weir or
J-weir
sections in the perimeter wall 181 of the froth recovery region 179. The
number and
positioning of the weirs about the perimeter of froth recovery region 179 will
affect
the volumetric flow through the concentrator vessel. Any overflow outlet 182
formed
1 0 in froth recovery region 179 communicates with a froth launder 189
extending about
the perimeter of the region that collects the weir overflow and delivers the
final
bitumen enriched froth stream 136 to a product nozzle 196. Similarly,
underflow
outlet 184 in perimeter wall 181 delivers water and fine solids stream 138 to
a outflow
nozzle 198.
As best shown in Figure 4, the floor 186 of at least the separation region 172
and the froth recovery region 179 are inclined to promote flow through the
concentrator vessel and to prevent fine solids from accumulating within the
vessel.
2 0 Figure 4 also shows a preferred arrangement for inlet region 170. The
inlet
region preferably includes conditioning means in the form of an enclosure 190
about
an inlet pipe 192 for bitumen froth stream 114. The enclosure and inlet pipe
are
provided to promote a uniform velocity flow of the froth stream as the stream
enters
the separation region. Enclosure 190 and inlet pipe 192 serve to isolate the
bitumen
2 5 froth stream 114 entering the vessel at the inlet region 170 from the
separation region
172 to avoid generation of turbulence in the separation region. The bitumen
froth
stream exits enclosure 190 through a baffle plate 194 which acts to establish
substantially uniform velocity flow within the diverging channel.
3 0 Figure 5 shows schematically in plan view an alternative embodiment of
a
concentrator vessel 132 for use with various embodiments of the system of the
present
invention. In Figure 5, features that are common to the vessel of Figures 3
and 4 are
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labeled with the same reference number. The concentrator vessel of Figure 5
differs
from the vessel of Figures 3 and 4 primarily by virtue of the fact that the
diverging
channel defining the separation region 172 is formed with at least one turn
201 to
increase the length of the channel and the region available for formation of
the froth
layer and settling of the fine solids material. Turn 201 may also serve to
shorten the
overall length dimension 202 of the concentrator vessel 132 to make the vessel
more
compact and suitable for a mobile role.
In the concentrator vessel embodiment of Figure 5, there is an outer perimeter
wall 204 and a floor which define a flow volume into which bitumen froth
stream 114
is introduced after passing through inlet region 170. Diverging channel 172 is
formed
by at least one barrier within the outer perimeter wall. In the illustrated
embodiment,
the at least one barrier comprises a pair of diverging plates 206 that define
a first
section of the diverging channel 172 between opposed inner surfaces 208 of the
plates, and a second section of the diverging channel after turn 201 between
the outer
surfaces 210 of the plates and the perimeter wall 204 of vessel. Turn 201 is
formed
between the ends 212 of the plates and the outer perimeter wall. In the
embodiment
of Figure 5, the froth recovery region 179 is adjacent the outer perimeter
wall of the
flow volume. The pair of diverging plates 206 are positioned centrally
adjacent inlet
region 170 to form a central diverging channel which divides into two channels
at
turns 201 on opposite sides of the flow volume. At turn 201, flow from the
first
section of diverging channel 172 is split into two separate flows with each
flow
reversing course through substantially 180 degrees toward inlet region 170 in
the
second section of the diverging channels. This reversing of the flow at each
turn 201
requires slowing and turning of the flow which provides additional opportunity
for the
bitumen froth layer to form on the water layer of the flow. End wall section
212 of
perimeter wall 204 where the flow reverses tends to create a stagnant zone
defining a
portion of the froth recovery region for the present vessel for removal of the
accumulated bitumen froth layer. End wall section 212 is therefore formed with
an
3 0 overflow outlet in the form of an overflow weir that empties into
launder 189 for
collection and recovery of the separated froth. Side wall sections 214 of the
perimeter
wall define additional froth recovery regions. One or more additional overflow
outlets
CA 02567702 2006-11-09
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for bitumen froth into launder 189 may be formed in side wall sections 214.
The
overflow outlets of the side wall or end wall sections may be the crest weir
or J-weir
arrangements previously described in the discussion of Figure 4 or a
combination of
both. The use of end wall section 212 and side wall sections 214 to provide
overflow
outlets for the enriched bitumen froth provides an opportunity to collect the
bitumen
enriched froth product in stages so that the product is recovered as it is
produced.
This minimizes "slip" between the froth layer and the underlying water layer
which is
important to avoid bitumen being entrained back into the water layer. The
enriched
bitumen froth collected in launder 189 exits from the launder as final product
stream
136.
The concentrator vessel 132 of Figure 5 may also include an inclined floor
formed in the separation region and the froth recovery region to induce flow
from the
inlet region to the overflow and underflow outlets. The inclined floor of the
flow
chamber provides a path for collection of rejected water and fine solids and
enhances
removal of these components without re-entrainment of the bitumen froth layer.
An
underflow outlet 184 in each end wall section 218 of the perimeter wall
collects the
combined water and fine solids stream which is discarded as stream 138.
2 0 The concentrator vessel 132 of Figure 5 optionally includes a central
barrier
220 extending between the pair of diverging barriers 208 to form a pair of
diverging
channels adjacent the inlet region.
Figures 6 to 7D show perspective and orthographic views of concentrator
vessels constructed according to the design features discussed above. In each
embodiment, inlet region 170 is formed with an enclosure 190 and baffle plate
194 to
prevent turbulent flow created when bitumen froth stream 114 is delivered into
the
inlet region by inlet pipe 192 from disturbing the flow in diverging channel
172. Flow
exits the inlet region through baffle plate 194 which tends to establish
substantially
uniform velocity flow within the diverging channel 172. As best shown in
Figure 7A,
which is a cross-sectional view taken along line 7A-7A of Figure 7, and Figure
7B,
which is a side elevation view taken along line 7B-7B of Figure 7, the floor
186 of
diverging channel 172 defining the first separation region before turn 201 and
the
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floor 188 of the second separation region after turn 201 are sloped to promote
flow
through the concentrator vessel and to ensure that fine solids that settle in
the water
layer continue to be transported along the sloped floor by gravity towards the
underflow outlets 184. By way of example, floors 186 and 188 may have a slope
of
about 3-3.5%, but other inclines are also possible.
Adjacent perimeter walls 230 is the froth recovery region of the concentrator
vessels. Perimeter walls 230 are formed with overflow outlets in the form of
crested
weirs or J weirs to allow the bitumen enriched froth layer collecting atop the
water
1 0 layer to overflow from the concentrator vessel into froth launder 189.
As best shown
in Figure 7B, froth launder 189 is formed with a sloped floor 256 that
delivers the
collected bitumen enriched froth to one or more product nozzles 196. Figure
7C,
which is an end view of the concentrator vessel, shows product nozzle 196 at a
low
point in the launder to ensure efficient collection of the bitumen enriched
froth stream.
At the opposite end of the concentrator vessel, the water and fine solids
stream
exits the concentrator vessel through underflow outlets 184 formed in end
walls 185
of the discharge channels. End walls 185 are preferably formed with a J weir
187 to
collect bitumen froth at the end of the discharge channel. The rejected water
and fine
2 0 solids stream is collected in a discharge section 258 and discharged
through outflow
nozzle 198. As best shown Figure 7D, which is an end view of the concentrator
vessel, the discharge section is formed with a sloped floor and outflow nozzle
198 is
at a low point in discharge section. Discharge section 258 preferably includes
a
removable solids clean out box 259 so that any fine solids that accumulate in
the
2 5 discharge section can be periodically removed.
As shown in the embodiment of Figure 6, the concentrator vessel 132 may
optionally include flow re-direction means in the form of vanes 250 to promote
smooth flow through turns 201 in the diverging channels. Vanes 250 are adapted
to
3 0 re-direct the flow through turns 201 to maintain smooth flow lines and
prevent mixing
of the. Alternatively, the flow re-direction means may also comprise rounded
corners
formed in the outer perimeter wall of the flow volume to promote smooth, non-
mixing
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- 2 0 -
flow through turns 201.
The concentrator vessel embodiment of Figure 7 includes a froth layer flow
enhancement means 135 to prevent formation of stagnant regions in the froth
layer. In
the illustrated embodiment, the froth layer flow enhancement means takes the
form of
a rotatable paddle element which is operated to urge the froth layer into
movement in
any stagnant zones that may develop so as to urge the froth layer toward an
overflow
outlet.
1 0 In some situations, bitumen froth may become entrained in the rejected
water
and fine solids flow that exits the concentrator vessel through underflow
outlets 184.
To address this issue, a weir may be provided in the discharge section 258,
the weir
being adapted to permit any bitumen froth that exits the underflow outlet and
collects
atop the water layer in the discharge section to overflow back into the froth
launder.
An example of such an arrangement is best shown in Figure 7E which is a detail
view
taken along line 7E-7E. The top of end wall 185 defines a weir 255 which
allows any
bitumen froth that rises to the surface of the underflow water to overflow
into J weir
187 on the opposite side of the end wall for delivery to the froth launder.
Referring back to Figure 1, in a further embodiment of the system of the
present invention, the water and fine solids stream 138 produced by froth
concentration facility 130 is diverted to an optional water recovery facility
140 which
separates the fine solids stream 138 into a water stream 142 and a
concentrated fine
solids stream 144. The fine solids stream 144 is preferably combined with the
solids
2 5 stream 128 produced by the cyclone separation facility 102. As shown in
Figure 1,
water stream 142 may be recycled into the water feed 104 that is supplied to
the
cyclone separation facility 102. Water recovery facility 140 may include any
known
equipment 141 for separating water from solids such as, for example, a
thickener or a
cyclone stage. Preferably, water recovery equipment 141 is specifically
designed to
separate small sized solids particles (silt and clay) since much of the larger
sized solid
particles have been removed upstream in the cyclone separation facility 102.
The most
appropriate equipment for this step will often be a high gravity cyclone unit.
Removal
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of fine solids from water stream 142 avoids the accumulation of the such
solids within
the system and permits recycling of the water. Water recovery facility 140 is
preferably mobile and may comprise a water recovery unit mounted on its own
independently movable platform 166 (see Figure 2) or incorporated into the
same
movable platform as froth concentration facility 130.
The slurry 100 that is fed to cyclone separation facility 102 is generally
formed
using heated water. In conventional bitumen extraction equipment such as
primary
separation vessels (PSV), where bubble attachment and flotation are used for
bitumen
extraction, temperature can affect the efficiency of the extraction process.
In
embodiments of the present invention, the extraction process is not as
temperature
sensitive since the cyclone equipment provides solid/liquid separation based
on
rotational effects and gravity. Extraction efficiency tends to be maintained
even as
temperature drops making the cyclone extraction process more amendable to
lower
temperature extraction. This has energy saving implications at the cyclone
separation
facility 102 where wash water feed 104 or recycled water stream 140 do not
have to
be heated to the same extent as would otherwise be necessary to maintain a
higher
process temperature.
2 0 In a further aspect of the present invention, as shown in Figure 1,
the cyclone
separation stage 102 may optionally be provided with a "scalping" unit shown
at 146.
The scalping unit 146 may comprise, for example, a pump box or the like which
serves to remove any froth formed in the slurry feed 100 during the hydro-
transport
process. It will be appreciated that removal of such bitumen rich froth
further
increases the recovery efficiency of the three-stage counter-current
separation stages.
The froth stream 148 generated by the scalping unit 146 is combined into the
froth
stream 114 resulting from the cyclone separation facility 102. The remaining
slurry
from the scalping unit 146 then comprises the feed 150 to the cyclone
separation
facility. As illustrated in Figure 1, if a scalping unit 146 is used, the
froth stream 120
from the second cyclone separation stage 108 is fed downstream of the scalping
unit
146.
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In a further optional embodiment, the ore slurry 100 may be provided with any
number of known additives such as frothing agents and the like prior to being
fed to
the cyclone separation stage 102. An example of such additives is provided in
US
patent number 5,316,664. As mentioned above, the solids components stream 128
shown in Figure 1 is transported to a tailings disposal site 149. In a
preferred
embodiment, the solids stream (which may comprise solely the solids component
stream 128 from the cyclone facility 102 or a combined solids stream including
the
fine solids stream 144 from the water recovery unit 140) is pumped to a
tailings pond
where the solids are allowed to settle thereby allowing the water to be drawn
off. In
1 0 one embodiment, a rheology modifier or other such additive may be added
to the
solids stream in order to enhance settlement of the solids material. An
example of
such an additive is described in PCT publication WO/2004/9698 19 to Ciba
Specialty
Chemicals Water Treatments Limited. The solids stream may be passed through
various known equipment such as belt filters, stacking cyclones and the like
prior to
1 5 deposit into tailings disposal site 149.
Throughout the above discussion, various references have been made to
pumping, transporting, conveying etc. various materials such as slurries,
froth and
tailings and others. It will be understood that the various equipment and
infrastructure
2 0 such as pumps, conveyor belts, pipelines etc. required by these
processes will be
known to persons skilled in the art and, therefore, the presence of such
elements will
be implied if not otherwise explicitly recited.
Although the present invention has been described in some detail by way of
2 5 example for purposes of clarity and understanding, it will be apparent
that certain
changes and modifications may be practised within the scope of the appended
claims.
