Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR TREATMENT OF MFT
USING HYDROPHILIC DRAIN PLATES
FIELD
[0001] This invention relates to the separation of bitumen from a slurry,
and more
particularly to the separation of bitumen from micro fine tailings, also known
as mature fine
tailings, or fluid fine tailings, and abbreviated herein as "MFT" or "FFT".
BACKGROUND
[0002] Tailings are a by-product of all mining operations, and in
particular in this
case, mining operations that seek to extract oil from sand. Tailings are made
up of natural
materials including water, fine clays and silts, left-over bitumen, salts and
soluble organic
compounds. They also include solvents added to bitumen during the separation
process.
Tailings are discharged and contained in large earthen structures above ground
¨ known as
tailings ponds ¨ or in former mine pits awaiting reclamation. Currently there
are hundreds of
square kilometers of tailings ponds located in the oil sands region of Western
Canada.
[0003] The larger sand particles in the tailings settle to form a
stable deposit very
quickly, while the finer clay particles and left over bitumen take years to
settle and are
known as mature fine tailings or MFT. Through treatment, the MFT in the
tailings ponds can
be reclaimed and the water reused.
[0004] The applicant has found that bitumen makes up approximately 3%
of the
MFT, which in turn is about 10% of the solid component (32.4%) in the MFT. At
this
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concentration, removal and recovery of the bitumen from the MFT is an
appealing business
opportunity since the bitumen/solid weight percent in the MFT approaches the
same levels
that exist in the mined ore. Recovering the bitumen from the MFT could provide
significant
revenue.
[0005] Research on ways to treat MFT continues, with the goal of
developing
technology that will help the fine clays settle quicker and to extract the
bitumen.
[0006] International published application No. W08500299 to Kruyer
(January 31,
1985) discloses a method of extracting bitumen from a mixture (4) such as fine
tailings.
Referring to Figure 3 of the Kruyer application, the bitumen is separated by
means of an
apertured oleophilic endless sieve (5) that is wound around a revolving
cylindrical cage (1)
having apertured sidewalls (37). The bitumen mixture tumbles inside of the
cage and
thereby is brought up to sieve speed and passes through the cage sidewall
apertures to the
sieve surface. The aqueous (water) phase of the mixture passes through the
sieve
apertures into a bath (8) from where it is removed. The oil phase/bitumen (20)
of the mixture
adheres to the oleophilic sieve and is conveyed out of the separation zone.
The bitumen is
later removed from the sieve.
[0007] U.S. Patent No. 4529496 to Kruyer discloses a method of separating
bitumen
from a mixture containing water, bitumen and particulate solids. Referring to
Figure 1 of
Kruyer, an endless mesh oleophilic conveyor belt (10) runs through the mixture
and the
bitumen adheres to the belt while the aqueous solution passes through the
apertures (16) of
the belt. The bitumen is conveyed to one or more bitumen treatment zones and
to a
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recovery zone where the bitumen is removed from the belt. A hydrophilic roller
may remove
any aqueous phase droplets on the belt.
[0008] Canadian Patent No. 2033217 to Kryuer discloses a process and
apparatus
for the recovery of bitumen from a bitumen containing mixture using two or
more nested
apertured endless belts (see Figure 1 - 34,44,45) on conveyor supports (8, 12,
23, 25) that
support these belts to form top flights approaching generally horizontal paths
above the
separating mixture and bottom flights immersed in the separating mixture.
Bitumen is
captured by and adheres to belt surfaces and is conveyed to corresponding top
flights
where it falls off into receptacles (32, 38).
[0009] Canadian Patent No. 2638596 to Kryuer discloses an apparatus
for
separating bitumen from a tailings-like mixture. The apparatus can include at
least one
endless cable (8) wrapped around at least two revolvable cylindrical members
(4,6) a
plurality of times. The cable may be wrapped around an agglomerator drum (69)
having
openings in fluid communication with the cable. Separation can be accomplished
by
oleophilic adherence to the cable, electrostatic adherence to the cable,
and/or physical
retention on the cable. This endless cable system may be useful for separation
of oil sand
slurries, mass transfer operations, and physical separations.
[0010] Canadian Patent No. 2653058 to Kruyer discloses a method for
removing
bitumen from fine tailings by means of a revolving oleophilic apertured drum
(See Figure 3a
- 301) containing oleophilic balls. The bitumen particles adhere to the balls
(321) and
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agglomerates. The bitumen is then transferred to the walls of the drum (301)
where it
passes through the openings (314) and is transferred to an oleophilic wrap
(328).
[0011] Canadian Patent No. 2666025 to Kruyer discloses a bitumen
agglomerating
and kneading apparatus allowing for bitumen to be separated from a mixture.
Referring to
Figures la-d, the apparatus comprises a truncated cone containing balls (114,
117) of
several different sizes. At the narrow end of the cone is an apertured outlet
(101) that is in
contact with an endless oleophilic multiwrap cable (130) forming an apertured
oleophilic
wall. As the apparatus rotates the bitumen is agglomerated by the balls and is
separated
from the remaining fluid tailings by the revolving apertured oleophilic wall.
[0012] Canadian Patent No. 2707577 to Kruyer discloses a rotating
agglomerator (7)
for processing feedstocks of oil sand slurries, oil sand fluid tailings etc.
to increase the
bitumen particles size. The agglomerator is a drum (2) filled with a bed of
balls (4,5). The
agglomerated bitumen is separated by a revolving oleophilic apertured screen
formed from
adjacent endless cable wraps (18).
[0013] None of the above solutions to the problem of separating
bitumen from MFT
utilize hydrophilic materials that tend to repel oil. Rather, the solutions
use oleophlic
materials that have an affinity for oil.
[0014] What is needed then is a method and apparatus for treatment of
MFT using a
hydrophilic material.
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SUMMARY
[0015] The present method and apparatus for treatment of MFT using
hydrophilic
drain plates addresses some of the shortcomings of the prior art and provides
a new way to
safely and economically extract bitumen from MFT.
[0016] Accordingly then, in one aspect, there is provided, a method
for treatment of
MFT containing suspended particles of bitumen, the method comprising:
suspending at
least one vertically-oriented hydrophilic drain plate in a separation tank
containing a pool of
MFT at a starting position; removing a portion of the at least one drain plate
out of the pool
of MFT at a first rate of speed, thereby causing a boundary layer of MFT to
adhere to the
portion of the drain plate removed out of the pool; holding the portion of the
at least one
drain plate at a maximum point above a surface of the pool for a predetermined
period of
time, thereby allowing the boundary layer of MFT to begin draining back into
the pool and
allowing the suspended particles of bitumen contained within the boundary
layer of MFT to
reach a surface of the boundary layer of MFT and be deposited on the surface
of the pool
as the boundary layer of MFT drains back into the pool; returning the portion
of the at least
one drain plate to the starting position at a second rate of speed; and
removing the bitumen
particles deposited on the surface of the pool of MFT.
[0017] In further aspects of the method, the starting position for
the drain
plates is below the surface of the pool of MFT. The step of removing a portion
of the
drain plate out of the pool is accomplished by moving the drain plate relative
to the
pool or by moving the pool relative to the drain plate. Moving the pool
relative to the
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drain plate may be accomplished by raising and lowering the separation tank
containing the pool of MFT or by increasing and decreasing the volume of the
MFT
in the pool. The first rate of speed is relatively faster than the second rate
of speed.
The drain plate may be constructed from materials such as wood, cotton,
cement,
epoxy, paint, plastic and combinations thereof. The top and bottom edges of
the
drain plate should be aerodynamically shaped to reduce rupturing of the
suspended
particles of bitumen in the pool of MFT.
[0018] The step of removing the bitumen particles deposited on the
surface of
the pool of MFT in the separation tank may include causing the bitumen
particles
deposited on the surface of the pool of MFT in the separation tank to overflow
an
outlet edge of the separation tank into a collection tank thereby forming a
layer of
bitumen particles on a surface of processed MFT in the collection tank; and
removing the layer of bitumen particles on the surface of the processed MFT in
the
collection tank using a hydrophobic roller. The bitumen particles deposited on
the
surface of the pool of MFT in the separation tank may be caused to overflow
the
outlet edge of the separation tank by an inflow of MFT into the separation
tank. The
temperature of an outer surface of the hydrophobic roller may be controlled
and
adjusted by a thermal fluid circulating through the hydrophobic roller to
assist in
bonding the layer of bitumen particles on the surface of the processed MFT in
the
collection tank with the outer surface of the hydrophobic roller. At least one
drive
roller may be positioned below the surface of the processed MFT in the
collection
tank and rotated to drive the layer of bitumen particles on the surface of the
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processed MFT in the collection tank toward the hydrophobic roller. The drive
roller
is positioned near an inlet edge of the collection tank, which is positioned
adjacent
the outlet edge of the separation tank. The processed MFT is then removed from
the collection tank by overflowing a drain edge of the collection tank. The
hydrophobic roller is located in the collection tank, adjacent the drain edge
of the
collection tanks and may include an air knife to remove residual processed MFT
off
the hydrophobic roller.
[0019] In another aspect there is provided, an apparatus for
treatment of MFT
containing suspended particles of bitumen, the apparatus comprising: a
separation tank for
holding a pool of MFT; at least one hydrophilic drain plate suspended
vertically within the
separation tank at a starting position; removal means for removing a portion
of the at least
one drain plate out of the pool of MFT at a first rate of speed, thereby
causing a boundary
layer of MFT to adhere to the portion of the at least one drain plate removed
out of the pool;
holding means for holding the portion of the at least one drain plate at a
maximum point
above a surface of the pool for a predetermined period of time, thereby
allowing the
boundary layer of MFT to begin draining back into the pool and allowing the
suspended
particles of bitumen contained within the boundary layer of MFT to reach a
surface of the
boundary layer and be deposited on the surface of the pool as the boundary
layer of MFT
drains back into the pool; return means for returning the at least one drain
plate to the
starting position at a second rate of speed; and bitumen collection means for
removing and
collecting the bitumen particles deposited on the surface of the pool of MFT.
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[0020] In other aspects of the apparatus the starting position for
the drain plate is
below the surface of the pool of MFT. The drain plate is removed from the pool
by moving
the drain plate relative to the pool or by moving the pool relative to the one
drain plate. The
pool can be moved relative to the drain plate by lowering the separation tank
of by
decreasing the volume of the MFT in the pool. The first rate of speed is
relatively faster
than the second rate of speed. The hydrophilic drain plate may be constructed
from wood,
cotton, cement, epoxy, paint, plastic and combinations thereof. The top and
bottom edges
of the drain plate are aerodynamically shaped to reduce rupturing of the
suspended
particles of bitumen in the pool of MFT.
[0021] The bitumen collection means for removing and collecting the
bitumen particles
deposited on the surface of the pool of MFT in the separation tank may include
a collection
tank located adjacent the separation tank and means for causing the bitumen
particles
deposited on the surface of the pool of MFT in the separation tank to overflow
an outlet
edge of the separation tank into the collection tank thereby forming a layer
of bitumen
particles on a surface of processed MFT in the collection tank and may further
include a
hydrophobic roller located in the collection tank for removing the layer of
bitumen particles
on the surface of the processed MFT in the collection tank. A pump may be
included for
pumping MFT into the separation tank to cause the bitumen particles deposited
on the
surface of the pool of MFT in the separation tank to overflow the outlet edge
of the
separation tank into the collection tank. The hydrophobic roller may include a
temperature
control system, such as a thermal fluid circulating through the hydrophobic
roller, for
controlling the temperature of an outer surface of hydrophobic roller to
assist in bonding the
layer of bitumen particles on the surface of the processed MFT in the
collection tank with the
outer surface of the hydrophobic roller. A drive roller may be positioned for
rotation below
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the surface of the processed MFT in the collection tank for driving the layer
of bitumen
particles on the surface of the processed MFT in the collection tank toward
the hydrophobic
roller. The drive roller may be positioned near an inlet edge of the
collection tank, which is
positioned adjacent the outlet edge of the separation tank. The collection
tank includes a
drain edge for removal of the processed MFT from the collection tank by
overflowing the
drain edge of the collection tank. The hydrophobic roller is located adjacent
the drain edge
of the collection tank and may include an air knife to remove residual
processed MFT off the
hydrophobic roller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Referring to the drawings wherein like reference numerals
indicate similar
parts throughout the several views, several aspects of the multi-piece anchor
system are
illustrated by way of example, and not by way of limitation, in detail in the
figures, wherein:
[0023] Figure 1 shows a partial view of a tank containing MFT into
which one or
more drain plates are submerged;
[0024] Figure 2 shows the tank of Figure 1, wherein the drain plates
are partially
removed from the tank with bitumen adhering to the surface of the MFT on the
drain plates;
[0025] Figure 3 shows the tank of Figure 1, wherein the drain plates
are almost fully
removed from the tank;
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[0026] Figure 4 shows the tank of Figure 1, wherein the drain plates
are being
inserted back into the tank, and the bitumen is being deposited on the surface
of the MFT in
the tank;
[0027] Figure 5 shows the tank of Figure 1, wherein the drain plates are
once again
fully submerged in the tank, and a bitumen layer has been deposited on the
surface of the
MFT in the tank;
[0028] Figure 6 shows a one embodiment of a bitumen extraction
apparatus;
[0029] Figure 7 shows the extraction tank of the bitumen extraction
apparatus
shown in Figure 6;
[0030] Figure 8 shows one of the bitumen collectors of the bitumen
extraction
apparatus shown in Figure 6; and
[0031] Figure 9 shows a cross section of the bitumen collector shown
in Figure 8.
DETAILED DESCRIPTION
[0032] The applicant's work with MFT required a supply of MFT that
was shipped to
the applicant in plastic pails. When the pails arrived and were opened, the
applicant was
surprised by the amount of bitumen stuck to the lid and walls of the pails and
concluded that
sloshing around during transit had somehow deposited this bitumen firmly on
the walls.
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This indicated that a hydrophobic material such as polyethylene could play a
roll in
extracting bitumen from MFT. The mystery was why the polyethylene sidewalls
below the
MFT surface were absolutely clear of bitumen.
[0033] The applicant considered simply dipping a plastic sheet into the
MFT,
expecting it to attract some bitumen on the surface. This did not work, so was
repeated
several times. While bitumen failed to be attracted to the sheet, the
applicant observed
bitumen globules rising to the surface right beside the sheet and flowing out
along the
surface as a surface film when the sheet was lifted out of the pool. The
applicant also
observed that when the plastic sheet was pushed back into the MFT pool, the
surface film of
bitumen bonded to the plastic and followed it below the surface, only to
reverse when the
plastic sheet was lifted back out of the MFT pool. The applicant reasoned that
if a
hydrophobic surface could be arranged to emerge continuously from the pool of
MFT, the
bitumen globules in the immediate vicinity would accompany this material to
the MFT
surface. It was thought that the bitumen would remain on the pool surface if
the
hydrophobic surface re-submerged in a distant locale from where the bitumen
was
emerging.
[0034] With this idea in mind, the applicant tried using a rotating
plastic disk and a
continuous hydrophobic belt. Both methods proved incapable of attracting and
processing
much bitumen. Next the applicant tried dipping a plastic pipe in and out of
the MFT pool
and observed that if a hydrophobic surface is rapidly inserted into the MFT
pool and
withdrawn slowly a maximum amount of bitumen can be transferred to the pool
surface from
within the MFT pool. A series of thin parallel plastic plates were fashioned
and used to dip
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in and out of the MFT pool. The bitumen collecting on the surface was removed
with a free-
floating polyethylene sheet. This system was successful in removing bitumen
from the
MFT, but eventually bitumen would adhere to the hydrophobic surface of the
plates. The
plates would have to be removed from the MFT pool and cleaned.
[0035] The applicant then realized that if a strongly hydrophilic
surface were used
instead of hydrophobic, it might be difficult for bitumen to adhere to the
surface of the plates
and some of the problems associated with using a hydrophobic material might be
avoided.
Wood was tried initially. A thin sheet of birch veneer was soaked in water for
a day to make
sure it was water saturated. The birch plate was then dipped it in and out of
the MFT. The
applicant found that in addition to the hydrophilic plate bringing small
amounts of bitumen to
the surface directly on emergence from the MFT pool, similar to what was
happening with
the hydrophobic plates, a fairly significant layer of MFT stayed on the birch
plate as it was
raised above the pool. To the applicant's surprise, when this boundary layer
began to drain
as a result of gravitational forces, bitumen in the form of globules and
surface smears began
to appear and drain towards the MFT pool, floating at the air/MFT interface
and eventually
flowing onto the surface of the MFT pool. The applicant also found that the
same relative
speed variation that was required with the hydrophobic plate, as it emerged
from and
submerged into the MFT, did not work with the hydrophilic plate. A different
relative speed
pattern was needed. The applicant found that hydrophilic plates must be
extracted rapidly
from the MFT pool. This action not only breaks through the bitumen film
floating on the
surface of the MFT pool, but primarily, the speedy movement carries the
accompanying
layer of MFT to a maximum height above the pool. The plates are then held at
the
maximum height position and the MFT layers are given time to drain and thin.
This exposes
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the entrained bitumen to the air/MFT interface where the water film
surrounding the bitumen
thins and breaks. The bitumen globules are stripped of their water cloak and
become
hydrophobic, resisting reincorporation into the water based MFT. Some bitumen
globules
drain right back to the top of the MFT pool while others slow as the MFT
around them thins
and move more slowly relative to the hydrophilic plates. Even if the MFT on
the plate thins
to the point where the bitumen globules appear to touch the plate, the
hydrophilic plate
retains a thin layer of water preventing the hydrophobic bitumen globule from
sticking to the
plate. The plate is then slowly lowered back into the MFT pool.
[0036] The
meniscus between the hydrophilic plate and the MFT is maintained by '
the MFT draining off the plates into the pool while the drain plate remains
stationary. This
MFT flow also keeps the bitumen film on the MFT pool surface away from the
plate surface.
When the plate and its accompanying water film are slowly submerged back into
the MFT
pool the meniscus between the hydrophilic plate and the MFT rises up the plate
as fast as
the plate submerges. This rising meniscus contacting the hydrophilic plate
surface moves
up like a wedge between that surface and any bitumen globules that might be
stalled there.
The bitumen globules lift away from the surface of the plate and drain down
the meniscus
arc into the bitumen film at the arc base on the surface of the MFT pool.
Eventually the
meniscus reaches the top of the submerging plate and connects over the top of
the plate
with the meniscus on the opposite side. Without the upward arc of the meniscus
on the
plate, the floating bitumen on both sides of the plate and menisci flow
together to form a
continuous floating bitumen film on top of the MFT. The slow submergence of
the
hydrophilic plate below the MFT pool surface creates a void that is filled by
the MFT flowing
in from both sides of the plate. The drag from this under surface flow of the
MFT reinforces
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the surface flow of the bitumen that has already met and connected at the
surface. This
causes the bitumen to bunch up and thicken at the surface right above the
center of the
submerged plate. As a result, lines of partially compacted bitumen, centered
above the top
edges of the hydrophilic plates remain floating on the surface of the MFT
pool. This places
the bitumen in a known position for potential removal and recovery. The slow
submergence of the plates, and the hydrophilic nature of the plates, helps
prevent bitumen
from accumulating on the plates.
[0037] Figures 1 to 5, illustrate one embodiment of the applicant's
method and
apparatus for treatment of MFT. In its basic operation, a tank 5 contains a
slurry pool 20 of
MFT, the slurry comprising suspended particles of bitumen 50. One or more
vertically-
oriented hydrophilic plates or sheets 10 are submerged in the slurry pool 20.
The plates 10
are rapidly removed from the slurry pool 20 (see Figure 2) by either raising
the plates in the
direction of arrow A, or lowering the tank 5 in the opposite direction. The
plates 10 are held
temporarily at a maximum point 30 above the slurry pool 20 (see Figure 3), and
then slowly
lowered back into the slurry pool 20 (see Figure 4) by either lowering the
plates in the
direction of arrow B or raising the tank 5 in the opposite direction. As
noted, the plates 10
may be raised and lowered or the tank 5 containing the slurry pool 20 may be
lowered and
raised relative to the plates 10. Another alternative is to raise and lower
the volume of the
MFT slurry pool 20 in the tank 5 by pumping MFT in and out of the tank.
[0038] As the plates 10 move upward out of the MFT slurry pool 20, a
boundary
layer of MFT 40 is drawn out of the slurry pool with the plates. As the MFT
boundary layer
40 begins to drain back into the slurry pool 20 (Figure 3), it thins, with the
outer layers falling
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faster than the inner layers closer to the plates 10. This allows bitumen
globules 50
entrained within the MFT boundary layer 40 to reach and remain at the surface
of the
boundary layer 40, at the air/MFT interface. As the boundary layer 40 thins
and drains back
into the slurry pool 20, the bitumen 50 accumulates as a thin film 52 on the
surface of the
slurry pool 20, directly above the plate 10, where it can be easily removed
(see Figure 5).
[0039] As shown in Figure 3, to reduce turbulence in the slurry pool
20, it is
advantageous not to completely remove the drain plates 10 from the slurry pool
20 during
the first phase of the process. It is only necessary that a portion of the
drain plate 10 be
removed, leaving another small portion in contact with the surface of the
slurry pool 20.
[0040] The exact removal and reinsertion rates of the drain plates 10
in and out of
the slurry pool 20 will vary depending on the size and composition of the
plates and the
number of plates used in the tank 5. As an example, using a drain plate 10
made of birch
and having a six inch (15 cm) vertical height, a removal rate of six inches
(15cm) per second
results in a 0.1mm thick MFT boundary layer 40 on both sides of the drain
plate, which is a
desirable thickness. In this example, it takes about 16 seconds for the
bitumen 50 to
complete forming on the surface of the MFT boundary layer 40. Therefore, a
hold time of
about 16 seconds is recommended. The formation of bitumen 50 on the outer
surface of
the MFT boundary layer 40 proceeds down the drain plate at a rate of about
1/4" (.64cm)
per second. Accordingly, a reinsertion rate of the drain plates 10 back into
the MFT pool 20
of about 0.375" (.9cm) per second has been found to be effective.
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[0041] It is important that the plates 10 be made of a hydrophilic
material to prevent
the bitumen globules 50 from adhering to the surface of the plates, thereby
keeping the
bitumen globules 50 at the air/MFT boundary so that they may be accumulated as
thin film
52 for easy removal.
[0042] Figures 6 to 9 show one embodiment of a bitumen extraction and
collection
apparatus that employs the above-described extraction mechanism. The
extraction and
collection apparatus 100 includes a primary separation tank 105 that includes
a series of
hydrophilic drain plates 110 (Figure 7) and a slurry pool of raw MFT 120 for
processing. The
extraction and collection apparatus 100 further includes two collectors 200,
into which
processed MFT and the extracted bitumen layer 52 flow, and where the bitumen
layer 52 is
removed before the processed MFT is discharged.
[0043] Raw MFT 120 is pumped into the separation tank 105 through an
inlet 107 at
the base of the tank so as to minimize flow interference with the existing MFT
in the
separation tank 105. The inlet 107 may be located and shaped to actively
influence flow
patterns of the MFT pool 120, so as to assist in discharge of the extracted
bitumen layer 52
and processed MFT from the tank. The raw MFT material nominally flows from the
bottom
to the top of the separation tank 105. The raw MFT pool 120 in the separation
tank 105
occupies all of the space below, above, and between the hydrophilic drain
plates 110. The
plates 110 are mounted parallel to each other and may be joined together to
function as a
single unit.
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[0044] As described previously, to process the raw MFT pool 120 and
extract
bitumen 50, the drain plates 110 are caused to emerge and submerge continually
relative to
the raw MFT pool 120. There are four sequences in the motion of the drain
plates 110
relative to the MFT pool 120: emerge, hold, submerge and hold. This relative
movement
between the MFT pool 120 and the drain plates 110 can be achieved by holding
the
separation tank 105 steady and moving the drain plates 110, holding the drain
plates 110
steady and moving the separation tank 105, or by holding the drain plates 110
and the
separation tank 105 steady and pumping the MFT fluid in and out of the
separation tank 105
to continually flood and drain the plates.
[0045] In one example, a linear drive system using hydraulic or air
cylinders could
be used to raise and lower the drain plates 110. The speed and direction of
movement may
be controlled by mechanical flow valves, electric/fluid on/off valves or
position switches and
adjustable time delay switches. In another example, an electric linear drive
system
consisting of a threaded screw driven by a programmable stepper motor could be
used.
[0046] The applicant has found that the separation of bitumen from
the MFT is
maximized if the drain plates 110 are rapidly removed from the MFT pool 120,
held
temporarily at a maximum point above the MFT pool 120, and then slowly lowered
back into
the MFT pool, where they are again held temporarily before the process is
repeated. As
discussed above, the precise removal and reinsertion rates of the drain plates
110 in and
out of the MFT pool 120 will vary depending on the size and composition of the
plates and
the number of plates used in the separation tank 105.
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[0047] At the point in the cycle when the drain plates 110 are
completely submerged
in the raw MFT 120 the bitumen 50 that has been separated from the MFT during
the
previous cycle, is left floating on the surface of the MFT pool 120 as a thin
bitumen layer 52
The separated bitumen layer 52 concentrates in lines at the surface of the MFT
pool 120
directly above and parallel to the submerged drain plates 110. The drain
plates 110 should
be held submerged for a period of time long enough to permit removal of the
separated
bitumen layer 52 from the surface of the MFT pool 120. At this point in the
process,
additional raw MFT may be pumped into the separation tank 105, raising the
level of the
MFT pool 120 and causing the extracted bitumen layer 52 collecting on the
surface of the
MFT pool to overflow separation tank edges 108 into the two collectors 200.
The two
overflow edges 108 of separation tank 105 are at 90 degrees to the orientation
of the drain
plates 110 and the floating bitumen layer 52 on the surface of the MFT pool
120. The
opposite two barrier edges 109 of the separation tank 105 are parallel to the
drain plates
110 and must be raised somewhat higher relative to the overflow edges 108, to
direct
overflow of the separation tank 105 into the collectors 200. Those skilled in
the art will
appreciate that other methods may be used for removing the bitumen layer 52
from the
surface of the MFT pool 120, such as by mechanically wiping the surface.
[0048] Figures 8 and 9 show one of the collectors 200 used to collect
and remove
bitumen that has been separated from the MFT pool 120 in the primary
separation tank 105.
The collector 200 includes a collection tank 205 attached directly to the
primary separation
tank 105, adjacent and parallel to the overflow edge 108. The collection tank
205 includes
inlet edge 208 parallel and connected to overflow edge 108 of the separation
tank 105, and
opposite and parallel drain edge 209. While the level of the MFT pool 120 in
the separation
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tank 105 rises and falls with the relative movement of the drain plates 110
and the pumping
of MFT into the separation tank 105, the lowest fluid level of a processed MFT
pool 220 in
the collection tank 205 is controlled by the edges 108 and 208 connecting the
separation
tank 105 and collection tank 205, and the drain edges 209 of the collection
tank 205. All of
these edges 108, 208, and 209 are at the exact same level. When the fluid
level of the MFT
pool 120 in the separation tank 105 rises through a combination of inflow of
new raw MFT
120 and/or MFT volume displacement by the drain plates 110 submerging below
the
surface, the extracted bitumen layer 52 on the surface of the MFT pool 120
overflows the
edges 108 of the extraction tank 105 into the collection tanks 205 that in
turn begin to
overflow at the drain edges 209. The inlet edges 208 and overflow edges 209 of
the
collection tanks 205 are opposite and parallel to each other and perpendicular
to the
orientation of the drain plates 110. The flow of processed MFT and extracted
bitumen into
and through the collection tanks 205 is perpendicular to the collection tank
edges 208 and
209.
[0049] The collectors 200 each include a subsurface drive roller 210
that rotates in a
direction away from the separation tank 105 to provide a hydraulic drag force
that induces
the lines of extracted bitumen 52 on the surface of the processed MFT pool
220, along with
a small amount of subsurface processed MFT, to flow quickly towards the
overflow edge
209 of the collection tank 205, carrying with it the lines of extracted
bitumen 52 on the
surface. Subsurface drive roller 210 is preferably hydrophilic so as to limit
any buildup of
bitumen that might occur on the roller surface.
[0050] The flow of surface bitumen 52 is slowed by blocking the flow
with the edge
of a slowly rotating, hydrophobic collector roller 300. Collector roller 300
may be cylindrical
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CA 02847386 2014-03-26
in shape and may also be hollow to accommodate a thermal fluid 330 that may be
used to
control the temperature of the surface of the roller. The floating extracted
bitumen layer 52
is pressured to accumulate and spread out at the nip edge 310 of the collector
roller 300
along its axis by drag forces caused by the moving layer of MFT generated by
the drive
rollers 210 and flowing beneath the bitumen layer 52. The applicant has found
that multiple
drive rollers 210 rotating in the same direction can enhance the flow of
bitumen layer 52
towards the collector roller 300, while two parallel drive rollers 210,
rotating in opposite
directions, can be used to accumulate and hold the extracted bitumen layer 52
on the
surface between the rollers.
[0051] The rotating drive roller 210 is positioned near the inlet
edge 208 of the
collection tank 205, and below the minimum level of the MFT pool 220 as
determined by
inlet and drain edges 208, 209. The rotation speed of drive roller 210 is
adjusted to
establish enough force on the floating bitumen layer 52 so as to cause it to
spread out in a
continuous layer along the nip edge 310, where collector cylinder 300 contacts
the surface
of the MFT pool 220. The speed of collector roller 300 must be adjusted so
that it rotates as
fast as possible without creating turbulence at the fluid surface of the
collection tank 205.
The subsurface flow of the MFT pool 220 is needed to provide a drag force on
the surface
bitumen layer 52 to press the bitumen into a continuous layer accumulated at
and parallel to
the nip edge 310 of the bitumen collector roller 300. The speed of the
subsurface drive
roller 210 must be limited so that it does not create turbulence at the fluid
surface of the
collection tank 205.
CA 02847386 2014-03-26
[0052] The bitumen collector roller 300 is positioned between the
subsurface drive
roller 210 and the drain edge 209, with the lowest point of the bitumen
collector roller 300
being below the level of the drain edge 209. This allows the collector roller
300 to block the
surface bitumen layer 52 from overflowing the drain edge 209 even when fluid
levels in the
collection tanks 205 reach their minimum. At the nip point 310 on the
collection roller 300
the blocked bitumen layer 52 is squeezed between the surface of collection
roller 300 and
the MFT pool 220 by rotation of the collection roller 300. As the collection
roller 300 rotates
the bitumen layer 52 is pressed against the surface of the collection roller
300 where it
forms a continuous isolating layer 54 between the collection roller 300 and
the water based
MFT pool 220. As long as the bitumen layer 64 remains continuous, the surface
of collector
roller 300 will never be exposed to the water based MFT pool 220.
[0053] At the nip point 310, the temperature of the surface of the
bitumen collector
roller 300 may be controlled by the thermal fluid 330 circulating
therethrough. The level of
the fluid 330 in the roller 300 may be controlled to further influence the
surface area of the
collector cylinder 300 that is to be affected. Temperature control of the
surface of collector
roller 300 can assist in bonding the isolated bitumen layer 54 to the surface
of the roller. As
the collector roller 300 and its attached layer of bitumen 54 complete their
rotation through
the MFT pool 220 at an exit point 320, they emerge carrying some residual MFT.
An air
knife 340 may be located at this point to blow the residual MFT off the
surface of the
bitumen layer 54, back into the MFT pool 220 for discharge. The air
temperature and flow
rate are controlled in the air knife 340 to enhance retention of the bitumen
layer 54 on the
collector roller 300 while at the same time allowing maximum removal of
residual MFT by
the air knife 340.
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CA 02847386 2014-03-26
[0054] The collector roller 300 and its attached layer of bitumen 54
continue to rotate
past the exit point 320 and on though to an extraction point 350 where the
bitumen layer 54
is scraped off the surface by a hot rigid scraping knife 360 that removes and
heats the
bitumen beyond its flow point. The bitumen drips off the knife and is
collected in a pan or
trough 370 where it is pumped or drained off into collection tanks. It is not
necessary that
the bitumen layer 54 be completely removed from the surface of the collector
roller 300,
since a remaining thin layer of bitumen can enhance bonding with the floating
bitumen layer
52 when the collection roller 300 again rotates through to the nip point 310.
[0055] The flow of processed MFT in the MFT pool 220 continues
through the
collection tanks 205 below the collector roller 300 as long as the level of
the MFT pool 120
in the separation tank 105 remains above the overflow edges 108. The MFT pool
220 in the
collection tank 205 ebbs and flows with the cycling of the collection plates
110 in and out of
the MFT pool 120 in the separation tank 105 and with the inflow of raw MFT
into the
separation tank 105. However, bitumen collection in the collection tanks 205
runs at a
steady but much slower pace than bitumen extraction in the extraction tank
105, and the
collector roller 300 is prevented from rotating if there is a lack of bitumen
at the nip point
310. A colour sensor may be installed at the nip point 310 to detect a reduced
density of the
bitumen layer 52 to thereby signal a shutdown of the collector roller 300.
[0056] The applicant has found that the hydrophilic drain plates 10,
110 should be
thin to provide the most surface area for each unit of weight. The drain
plates should be
rigid and stable so an equal distance between the plates can be maintained to
promote
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CA 02847386 2014-03-26
uniform MFT flow patterns. The plates should have high tension and compressive
strength,
so that mounting points can be well spaced to minimize interference with MFT
flow between
the plates. The surfaces of the plates should be smooth or uniformly rough to
prevent those
surfaces from adversely influencing drain patterns of the draining MFT and
bitumen film.
The material used to construct the drain plate should be non-corrosive or at
least be
protected from corrosion.
[0057] The applicant has found that wood is an excellent hydrophilic
surface for use
in constructing drain plates 10, 110. Baltic birch veneer is a good example.
Cotton is
another common hydrophilic material, which can be made into a sock and fitted
over a rigid
support plate. A simple open square weave fabric called muslin was used by the
applicant
over a plastic support plate. Tests suggest that muslin could survive a year
without decay
breakdown in this environment. Cement is another product that is hydrophilic
but has no
strength in thin sheets. Cement bonds well in thin layers to corrosion
resistant aluminum.
Early work by the applicant suggests that if a cement-coated aluminum plate is
used, a
slightly thicker layer of cement than needed should be applied and the extra
sanded off
using ultra fine grit moving parallel to the drain pattern so as to create a
smooth hydrophilic
surface with only minor imperfections aligned with the drain flow direction.
Epoxy coatings
and paints are also a good option for coating structural drain plates 10, 110
to protect them
from corrosion. The coatings must be hydrophilic, smooth, and durable, with
any imperfects
aligned with the drain flow direction. Plastics, such as polyethylene, can
also be
manufactured to have hydrophilic characteristics. Solid plastic drain plates
would have the
smoothness desired and would work well in the temperature and chemical
environment
23
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CA 02847386 2014-08-01
encountered in the above-describe process. Of course, combinations of the
above-
mentioned materials could also be used for constructing the hydrophilic drain
plates.
[0058] The applicant has found that both the top and bottom edges of
the drain
plates 10, 110 should be constructed to have aerodynamic curved surfaces to
prevent a
sharp edge impacting a bitumen particle/globule suspended in the MFT and
initiating
bitumen build up on the drain plates that would eventually need to be
physically removed.
The previous detailed description is provided to enable any person skilled in
the art
to make or use the method and apparatus for treatment of MFT using hydrophilic
plates.
Various modifications to those embodiments will be readily apparent to those
skilled in the
art, and the generic principles defined herein may be applied to other
embodiments without
departing from the scope of the method and apparatus for treatment of MFT
described
herein. Thus, the present method and apparatus for treatment of MFT is not
intended to be
limited to the embodiments shown herein, but is to be accorded the full scope
consistent
with the claims, wherein reference to an element in the singular, such as by
use of the
article "a" or "an" is not intended to mean "one and only one" unless
specifically so stated,
but rather "one or more". All structural and functional equivalents to the
elements of the
various embodiments described throughout the disclosure that are known to
those of
ordinary skill in the art are intended to be encompassed by the elements of
the claims.
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