Note: Descriptions are shown in the official language in which they were submitted.
CA 02610122 2013-03-18
SYSTEM FOR EXTRACTING BITUMEN FROM DILUTED PIPELINED
OIL SANDS SLURRY
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 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 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.
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
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
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
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
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a suitable feed for upgrading to synthetic crude oil or for refining into
petroleum
products.
Various other intervening steps are also known in the primary extraction
process such as withdrawal of a middlings layer from the PSV and oil recovery
from
tailings by cyclones and flotation 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
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.
However, such relocation, particularly of the separation facility including
large gravity
separation vessels 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
ore material. Thus, it is desirable to separate the minerals as soon as
possible
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"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. As well, long hydro-transport distances can
over condition
the oil sand causing bitumen recoveries to decline as the distances increase.
At the same time,
separation of the 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
According to 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 and distribute
the bitumen
froth stream as a substantially balanced flow across a separation region; the
separation region
being adapted to establish uniform, substantially horizontal flow of the
bitumen froth stream
to promote separation of the bitumen froth from the water and fine solids, the
bitumen froth
tending to move upwardly to accumulate as a froth layer atop a water layer
with the fine solids
settling within the water layer; a froth recovery region in communication with
the separation
region having an 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
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solids stream; and a flow level control means to control the level of the
water layer within the
vessel to permit the overflow outlet to collect the bitumen froth layer
despite variations in the
volume of the bitumen froth stream.
In some embodiments, there may also be 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 stream and a
bitumen froth stream,
the bitumen froth stream including bitumen froth, 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, the froth concentration
facility comprising the
concentrator vessel as described above.
In some embodiments, the extraction system of the present invention is
preferably
mobile so that the cyclone extraction facility and the froth concentration
facility can move
with the mine face at an oil sands mining site, however, it is also
contemplated that the system
can be retrofitted to existing fixed treatment facilities to improve the
operational efficiency of
such fixed facilities. In this regard, the cyclone extraction component and
the froth
concentration component may be mobile as separate units or as a combined unit.
In addition,
a water clarification facility can also be incorporated into the extraction
system for separating
the water and fine solids stream from the froth concentration facility into a
water stream and a
fine solids stream.
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BRIEF DESCRIPTION OF THE DRAWINGS
Aspects of the present invention are illustrated, merely by way of example, in
the accompanying drawings in which:
Figure 1A is a flow diagram showing a first embodiment of the system of the
present invention for extracting bitumen from a slurry containing bitumen,
solids, and
water which makes use of a cyclone separation facility having a three stage
countercurrent cyclone configuration;
Figure 1B is a flow diagram showing an alternative embodiment of the system
which employs a cyclone separation facility having two cyclone stages;
Figure 1C is a flow diagram showing a further alternative embodiment of the
system which employs a cyclone separation facility having a single cyclone
stage;
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
froth concentrator vessel defining a mobile froth concentration facility;
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;
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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
showing the underflow outlet end and the water and fine solids exit nozzle;
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; and.
Figure 8A-8C are schematic views of an alternative concentrator vessel
according to a still further embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1A, there is shown a flow diagram of an extraction system
according to an aspect of the present invention for extracting bitumen from a
conditioned oil sand 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,
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comminuting or crushing, and slurrifying oil sand ore and moving with the mine
face.
In a preferred arrangement, the system and process illustrated in Figure 1A
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.
Initially, the system of Figure 1A 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 cyclones 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 water feed 104 may be from an external water source, recycled water from
upstream or downstream processes and/or a mixture of any two or more of these
water
sources. The cyclone separation facility 102 serves to efficiently separate a
large
portion of the solids component from the bitumen component, producing a
diluted
bitumen froth stream 114 (also termed a lean bitumen froth stream), while a
large
portion of the solids component is separated as a tailings stream 128 from the
separation facility 102.
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-
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
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.
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In some aspects of the present invention, the incoming slurry 100 may be
conditioned so that aerated bitumen is liberated from the sand minerals. This
stream
may be diluted with water and/or overflow from a downstream cyclone to
maintain
cyclone feed densities in a preferred range in the order of 1200 -1320 kg/m3.
Other
cyclone feed densities may apply to specific operational or installation
requirements
for processes described herein.
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 cyclones that are generally vertical units, which
have a
minimal footprint, thereby occupying a minimal area. In alternative
embodiments,
cyclone installation may provide for mounting the cyclones on an angle. This
may
reduce the height used for installation and/or support and may direct the
underflow
streams to a common pumpbox. This may provide for reduced costs associated
with
the use of launders. This can be particularly desirable in relation to those
embodiments of the present invention which are directed to a mobile cyclone
separation facility. Suitable cyclones for the cyclone separation stages
include any
cyclone capable of separating a significant amount of the solids component
from a
bitumen based slurry, and include those manufactured by Krebs Engineers
(www.krebs.com) under the trademark gMAX , and those manufactured by sold
under the name of Cavex cyclones marketed by Weir Minerals
(www.weirminerals.com).
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. 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
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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 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 diluted froth
collection
stream 114, while first solid tailings stream 116 is pumped to a feed stream
118 of the
second cyclone 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 the second cyclone separation stage 108 is combined
with the
water feed 104 and recycled water 142 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 1A, 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 1A) 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 1A) 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 either an addition or reduction in the number of cyclone
stages used in
the process will also depend upon factors such as the desired recovery of
bitumen, the
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ease of separation of the bitumen from the mineral component, and economic
factors
involving the usual trade-off between equipment costs and the value of the
recovered
bitumen product.
In addition, it will be understood that the cyclone separation facility is
more
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.
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.
A further advantage of the multi-stage cyclone separation facility illustrated
in
Figure 1A 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 1A 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
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 minimizing
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, for example, those manufactured by Lampson International LLC) or by
providing
driven tracks on the platform(s) supporting the separation stages. Various
other
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apparatus or devices will be apparent to persons skilled in the art for
achieving the
required mobility.
By way of example, Figure 2 shows a 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
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,
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.
It will be apparent to persons skilled in the art that other arrangements of
the
cyclone separation facility and the froth concentration facility are possible
to enhance
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the mobility of the combined system. In an alternative arrangement, the
cyclone
separation facility 102, the froth concentration facility 130, and associated
auxiliary
equipment for pumping may all be positioned on a common skid such that a
single
skid operates as the smallest effective working unit of the extraction system.
Due to
the volumes of water re-circulated in the extraction process, a single skid
supporting
facilities in close proximity as an independent working unit can provide
significant
cost advantages. The skid may also include the water recover unit 140
(discussed in
more detail below).
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. As
will be
discussed below, 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 system and process contemplated herein are not limited to the three stage
countercurrent cyclone separation facility 102 illustrated, by way of example,
in
Figure 1A. The number of cyclone stages in the cyclone separation facility 102
are
primarily influenced by economics including such factors as the trade-off
between
equipment costs and the value of the recovered product.
By way of further example, Figure 1B shows an alternative embodiment of a
system for extracting bitumen having a cyclone separation facility 102 that
includes
two cyclone separation stages 106 and 108 that are connected in a counter-
current
arrangement. The cyclone separation stages each comprise one or more
hydrocyclones
that are generally vertical units, which have a minimal footprint, thereby
occupying a
minimal area. In further alternative embodiments, cyclone installation may
provide
for mounting the cyclones on an angle. This may reduce the height used for
installation and/or support and may direct the underflow streams to a common
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pumpbox. This may provide for reduced costs associated with the use of
launders.
This can be particularly desirable in relation to those embodiments of the
present
invention which are directed to a mobile cyclone separation facility.
In the facility of Figure 1B, 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 as described above.
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. Rejected solid particles can either
be
discarded after screening or made smaller by crushing or other suitable
techniques.
In the first cyclone separation stage 106, slurry 100 is processed in the
manner
described above 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 may be diluted
with wash
water 104 and pumped to a feed stream 118 of the second cyclone separation
stage
108 where a further cyclone separation process is conducted.
The bitumen froth 120 produced by the second cyclone separation stage 108 is
reintroduced to the feed stream 100 supplying the first separation stage 106.
The
tailings stream 128 from the second cyclone separation stage 108 may be
optionally
mixed with fine tailing stream 144 and pumped to a disposal site such as a
tailing
pond 149. The tailings streams tend to be high density streams that are
challenging to
pump on a sustained basis. The addition of fine tailings stream 144 improves
the
pumpability of tailings stream 128. It will be noted that many of the
alternative
embodiments as described herein with respect to the illustrated embodiments of
Figure 1A may also be applied to the illustrated embodiments of Figure 1B.
A system for extracting bitumen that incorporates a cyclone separation
facility
102 that makes use of a single cyclone stage is also possible, and is
specifically
illustrated in Figure 1C. In Figure 1C, the same features as described in
previous
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embodiments are labeled with the same reference number. In this embodiment,
the
single cyclone stage 106 precludes the use of countercurrent flow between
different
stages. As in previously described embodiments, the slurry 100 is processed by
a
screening and/or comminuting unit 105 before entering the single cyclone
separation
stage 106 as feed 150 to ensure that solid particles in the slurry can be
handled by the
cyclone. The single cyclone stage produces bitumen froth 112 and solid
tailings
stream 128 which comprises significantly less bitumen and substantially more
solids
than found in bitumen froth 112. Bitumen froth 112 is delivered to a diluted
froth
collection stream 114, while solid tailings stream 128 may be optionally mixed
with
fine tailing stream 144, and directed to tailings disposal site 149. The
single stage
facility still makes use of wash water 104 and recycled water 142 to dilute
the slurry
entering the cyclone stage 106.
The diluted 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. In this
regard, 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 stream typically has a bitumen content of about 60% by
weight, a
solids content of approximately 10% by weight, and a water content of
approximately
30% by weight. 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% by weight) the bitumen content and solids
content
may be below about 5% and 10% by weight, 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 diluted bitumen froth stream 114 as a
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result of washing the froth stream with water stream 104 and/or recycled water
142 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.
Referring to Figures 1A, 1B and 1C, 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 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 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 IPS 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.
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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
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,
injected
air or other gases 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 72% 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
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
102 described above. As shown in Figure 2, a froth concentration facility 130,
130',
130" to 130n 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
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130, a concentrator vessel specially designed for compactness may be used with
the
above-described 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
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
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.
Referring to Figures 3 to 8C, 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
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.
The preferred concentrator vessel 132 has a basic structure, however, the
dimensions and proportions of the various regions of the vessel can vary.
Vessel 132
includes an inlet region to receive and distribute the bitumen froth stream as
a
substantially balanced flow across a separation region. The separation region
is
adapted to establish uniform, substantially horizontal flow of the bitumen
froth stream
which serves to promote separation of the bitumen froth from the water and
fine
solids. The substantially horizontal flow allows the bitumen froth to move
generally
upwardly due to its lower density to accumulate as a froth layer atop a water
layer
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without vector components due to flow that work against the upward movement.
Similarly, the fine solids settle within the water layer due to their higher
density. A
froth recovery region is provided in communication with the separation region
with an
overflow outlet to collect the accumulated bitumen froth layer. There is also
an
underflow outlet to collect the water and fine solids as a combined material
stream or
as separate material streams. A flow level control device, preferably in the
form of an
overflow weir is used to control the level of the water layer within the
vessel to permit
the overflow outlet to collect the bitumen froth layer despite variations in
the volume
of the bitumen froth stream.
Figures 3 and 4 are a schematic plan view and a side elevation view,
respectively, of a concentrator vessel 132 showing the major features
discussed above
arranged in an exemplary configuration 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. In this case, separation
region 172
comprises a diverging channel which serves to establish uniform, substantially
horizontal flow of the bitumen froth stream. The diverging channel also
functions to
slow the flow of the bitumen froth stream 114. Uniform, substantially
horizontal flow
and slower flow 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 tt while
arrows
175b show a slower flow velocity at a later time t2 in 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
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primarily an aqueous flow (about 85 - 90% water by weight) and any remaining
fme
solids (silt and clay) in the stream will tend to settle within the water
layer. The
diverging channel of separation region 172 ends 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.
In the illustrated embodiment of Figures 3 and 4, overflow outlet 182
comprises at least one weir formed across the froth recovery region 179. The
weir
may be a conventional crested weir or a weir 188 having a J-shaped cross-
section
(as best shown in Figure 4). Overflow outlet 182 is formed as a continuous
weir
about the 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
in froth recovery region 179 communicates with a froth launder 189. In the
embodiment of Figures 3 and 4, the launder 189 extends downwardly and under
the
vessel to collect the weir overflow and deliver the final bitumen enriched
froth stream
136 to a product nozzle 196. The launder may also extend about the perimeter
of the
froth recovery region.
A flow level control device in the form of an end weir 185 is provided
adjacent the froth recovery region to control the level of the water layer 178
within the
vessel. In the illustrated embodiment, end weir 185 is an overflow weir. Use
of end
weir 185 controls the level of the water layer 178 to permit the overflow
outlet 182 to
collect the bitumen froth layer 177 despite variations in the volume of the
bitumen
froth stream. Downstream of end weir 185, water and a fine solids stream 138
flow
to an underflow outlet 198 in the form of an outflow nozzle. Opening 184 in
end weir
185 is provided to allow for passage of fine solids past the weir.
The flow level control device may be a pump or a valve arrangement to
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control the level of water layer 178 within the concentrator vessel, however,
an end
weir 185 provides for the simplest and most reliable control of the water
level. To
accommodate a wide range of flows, weir 185 is preferably configured as a
serpentine
weir to increase length within the vessel.
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.
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
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 assists in the
establishment of substantially uniform velocity flow within the diverging
channel.
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
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 defme a flow volume into which lean bitumen froth
stream
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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
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
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. An overflow weir 218 is formed at the downstream end of each channel of
the
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vessel to control the level of the water layer in the vessel as described
above with
respect to the embodiment of Figures 3 and 4. Overflow weirs 218 communicate
with
an underflow outlet to receive the water and fine solids stream 138.
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.
The
inclined floors also permit transport of settling solids through port 184 in
overflow
weir 218. The combined water and fine solids stream which passes overflow weir
218 leaves the vessel as stream 138 via an underflow outlet..
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 7E show perspective and orthographic views of further
embodiments of concentrator vessels constructed according to the design
principles
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 assist
in establishment of substantially uniform velocity flow within the diverging
channel
172 of the separation region. 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 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
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- 2 4 -
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
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.
As best seen in Figure 7 and 7E (which is a section view taken along line 7E-
7E of Figure 7), at the opposite end of the concentrator vessel, the water and
fine
solids stream exits the concentrator vessel past flow level control devices in
the form
of overflow weirs 185. The water layer overflows each weir 185 and any fine
solids
collected on the floor of the vessel move past weir 185 through underflow
outlets 184.
A J-weir 187 in communication with froth launder 189 is preferably formed
before
each weir 185 to collect bitumen froth at the end of the discharge channel.
The
rejected water and fine 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
may include a removable solids clean out box 259 so that any fine solids that
accumulate in the 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
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
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formed in the outer perimeter wall of the flow volume to promote smooth, non-
mixing 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.
In the previous embodiments of the concentrator vessel discussed above,
Figures 3 and
4 illustrate a "high aspect ratio" vessel in that separating region 172 is
relatively long in length
compared to the vessel width. Figures 5, 6 and 7 illustrate a "return flow
vessel" in that the
separation region 172 is similar in both length and width.
As a further example of the manner in which the concentrator vessel can be
configured
to suit specific layout requirements, Figures 8A-8C show an alternative vessel
which is an
example of a "low aspect ratio" vessel in that the flow stream of the
separation region 172 is
relatively wide compared to the length. This layout is particularly suited to
a mobile bitumen
extraction system.
Referring to Figures 8A-8C, a "low aspect ratio" froth concentration vessel
132
comprises an inlet region 170A to receive the bitumen froth stream 114 from
the cyclone
separation facility 102 via a gravity flow channel. As illustrated in Figure
8a the inlet region
170A connects via system of splitters and distribution channels to distribute
the bitumen froth
stream 114 equally both in volumetric and composition across the length of the
inlet region
170B. It will be noted that a first hydraulic jump 301, distribution channels
302, a second
hydraulic jump 304 and fan distributors 306 illustrated in Figure 8A and 8C
are only examples
of various devices and techniques available to persons skilled in the art for
distributing the
bitumen froth feed 114.
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The inlet region 170B may incorporate perforated distribution plates to
stabilize the
incoming bitumen froth 114 into the separation region 172. As illustrated in
Figure 8B, the
separation region 172 may be subdivided by parallel vertical baffles 308 such
that the
geometry for each flow channel is the same. The vertical baffles 308 result in
channel
Reynolds numbers of about 175,000 and turbulence intensities in the order of
25% from the
mean flow.
In the separation zone 172, aerated bitumen droplets tend to move upwardly to
float on
the surface of a water layer 178. The droplets coalesce into a bitumen froth
177 which
overflows by gravity into overflow outlet 182. The overflow outlet illustrated
in Figures 8B
and 8C are a plurality of J-weirs 188 configured to span the width of the
froth concentration
vessel 132. Each segment of the J-weir 188 collects bitumen froth 177 from a
specific portion
of the froth concentration vessel 132 and transfers the bitumen froth 177 into
the froth
collection launder 310 below the froth concentration vessel 132 as best shown
in Figure 8C.
The bitumen froth collected in the froth collection launder 310 exits from the
froth
concentration vessel as final product stream 136. Other locations for the
froth collection
launder 310 may be applied to specific layout considerations.
The froth concentrator vessel 132 illustrated in Figure 8C includes an
inclined floor
from the inlet region 170B to the underflow outlet region 312. The inclined
floor slope may be
in the range of from about 3 to 7% or in the range of about 3-3.5% in the
direction of the flow
stream and assists gravity in transferring settling fine solids to be
discharged via the underflow
outlet 184. Located at the low point of the separation region 172, the
underflow outlet 184 is a
slotted orifice spanning the width of the froth concentration vessel and
discharges settled fine
solids with a portion of the water into the underflow collection launder 314.
Other apparatuses
such as valves can be applied in lieu of the slotted orifice and/or the
underflow outlet 184 can
be segregated for subsequent water treatment operations.
The bulk of the water entering into the underflow region exits the froth
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concentration vessel 132 via an overflow weir 185. In order to control the
water level
upstream of the weir within the operational tolerances for the J-weir to
collect
bitumen froth, the overflow weir 185 illustrated in Figure 8B may be a long
crested or
serpentine weir specified to limit the water level while permitting
significant
variations in the water flow rate due to feed fluctuations in the volume and
composition of bitumen froth feed 114. The overflow weir 185 discharges into
the
underflow collection launder 314 and combines with the underflow outlet 184
discharge as the water and fine solids stream 138 from the froth concentrator
vessel
132. Note in this arrangement that the water and fine solids streams are
readily
separable for handling in different downstream processes, if desired.
Referring back to Figure 1A or 1B, 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
stream 128 produced by the cyclone separation facility 102. As shown in Figure
1A-
1C, water stream 142 may be recycled into the water feed 104 that is supplied
to the
cyclone separation facility 102 to create a blended water stream. This serves
to reduce
the amount of new water required by the system by recycling and reusing water.
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 hydrocyclone unit. A
suitable
hydrocyclone for the water separation step is a 50mm Mozley hydrocyclone as
marketed by Natco. Removal 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
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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
amenable 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.
In a further aspect of the present invention, as shown in Figure 1A-1C, 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 1A-1C, 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.
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
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shown in Figure 1A-1C 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
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
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
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
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.
