Note: Descriptions are shown in the official language in which they were submitted.
"Froth Pump System and Method"
FIELD
[0001] Embodiments herein relate to the processing of bitumen. In
particular,
embodiments herein relate to an improved pump system for pumping bitumen
froth.
BACKGROUND
[0002] The extraction of bitumen from oil sands slurry involves the
gravity
separation of bitumen from solids in a gravity separation vessel known as a
flotation
cell, wherein air is added to the oil sands slurry to separate bitumen from
solids such
as sand and clays. During gravity separation in an initial primary separation
cell
(PSC), bitumen attaches to free air bubbles in the vessel and floats to the
top thereof
as a bitumen froth, while solids settle at the bottom of the vessel as PSC
tailings or
underflow. The bitumen froth is then pumped from the gravity separation vessel
to
be further processed into a saleable product, such as diluted bitumen, which
can be
refined into various hydrocarbons. The PSC underflow can be pumped to a
secondary flotation cell for further separation by adding air to the PSC
underflow to
produce a secondary bitumen froth, also known as flotation froth, at the
surface of
the secondary flotation cell. This secondary froth typically flows via a weir
system
from the top of the secondary flotation cell into a launder, pump box, and/or
surge
tank, and can be pumped back to the PSC for further recovery.
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Date Recue/Date Received 2021-09-24
[0003] Centrifugal pumps are often used to pump bitumen froth, for
example
from the PSC to storage/downstream process, or from the pump box receiving
flotation froth from the secondary flotation cell back to the PSC. However,
centrifugal
pumps can suffer from a phenomenon known as "air lock", wherein pockets of air
and low density portions of the froth can become trapped at the outer radial
extremities of the pump housing and prevent bitumen froth from being pumped
out
of the outlet of the pump.
[0004] As shown in Fig. 1, a vented impeller design, such as the
Continuous
Air Removal System by Warman , may be used to mitigate air locking in froth-
circulating centrifugal pumps by incorporating one or more openings near the
center
of the shroud of the pump impeller. The impeller is designed to promote
movement
of the low density portion of the bitumen froth, comprising air, low density
fluid, and
the like, towards the eye or center of the impeller. Holes or openings formed
through
the impeller permits the low density portion to migrate from an intake side of
the
impeller to a vent side thereof. A secondary inducer located at the vent side
of the
impeller opposite the pump inlet is configured to create low pressure near the
one or
more openings relative to the pressure on the intake side of the shroud, which
promotes the flow of the low density portion accumulated near the center of
the
impeller from the intake side to the vent side and thereafter out of the pump
via a
vent port located at the rear of the pump housing and into a vent conduit in
communication therewith. The amount of air and froth vented is controlled by a
vent
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Date Recue/Date Received 2021-09-24
control valve, such as a globe valve, positioned in-line with the vent
conduit.
Opening the vent control valve results in less flow restriction and greater
venting.
[0005]
While the use of a vented impeller and vent port can assist in
mitigating air lock, if the vent control valve is not opened enough, the pump
may
continue to become air locked due to the small amount of air expelled.
Conversely,
when the control valve is opened further to permit air to be vented at a
sufficient rate
to mitigate air lock, a significant amount of bitumen froth may also be
vented, as the
low density of highly aerated bitumen froth causes it to accumulate near the
center
of the impeller and be vented with air. This vented bitumen froth is typically
directed
back to the pump box via a standpipe. However, accumulation of froth in the
standpipe creates a back pressure to the vent port of the centrifugal pump.
Due to
the pressure head required to overcome the back pressure and transport the
vented
froth back to the pump box, which can be over 50 kPag for a typical pump box,
the
rate at which air and low density froth can be vented from the pump is
limited. The
venting rate can be increased by instead directing the vented froth to a
trench at
atmospheric pressure and grade and subsequently flushed, for example using
water,
to an emergency dump pond (EDP). While venting to an EDP at atmosphere
increases the maximum venting rate in comparison with directing the vented
froth
back to the pump box, the vented froth becomes lost product, including any
bitumen
that is vented with the air. Additionally, it may not always be practical to
vent froth to
an EDP.
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Date Recue/Date Received 2021-09-24
[0006] Moreover, vented bitumen froth can plug the vent line,
preventing
additional air from being vented from the centrifugal pump and causing further
air
locking.
[0007] It is also common in conventional froth pumping systems to use a
two-
stage pump system to achieve the requisite total dynamic head (TDH) to pump
the
froth back to the PSC or to another desired location. While a two-stage pump
system
provides the requisite TDH, it is expensive due to the cost of purchasing and
maintaining multiple pumps, and introduces another point of failure in the
pump
system. Further, performance of the first pump stage can be so poor due to air
locking that even a two-stage system does not provide the required TDH
[0008] Additionally, conventional froth pumping systems require
relatively tall
pump boxes, for example over 10m tall, to provide the requisite net positive
suction
head (NPSH) for the centrifugal pump to operate without cavitating or air
locking. If
the fluid in the pump box drops below a requisite height, the pump may no
longer
have sufficient NPSH to pump effectively and will begin to experience air
locking. A
lower pump box height is desirable as the height of the PSC must be adjusted
proportionally to the height of the pump box to maintain desired gravity flow
thereto.
Increasing the height of the PSC requires additional support structure with a
commensurate cost increase.
[0009] The height of pump boxes is also increased due to the need for a
measure of surge capacity to prevent inadvertent overfilling of the pump box.
If the
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Date Recue/Date Received 2021-09-24
pump box begins to reach capacity, the flow of upstream processes may need to
be
reduced such that the pump box overflows. Such reduction of process flow
results in
less efficient operation and decreased throughput. Thus, a measure of surge
capacity is desirable to reduce the need for adjustments to upstream
processes.
[0010] It is also often required to introduce a diluent, for example
water, into
the pump box to dilute the froth therein in order to reduce the air volume
content of
the froth.
[0011] There remains a need for a froth pump system capable of
mitigating air
locking in centrifugal pumps while reducing the amount of wasted product and
addressing other disadvantages of conventional froth pumping using vented
pumps.
SUMMARY
[0012] Generally, an improved froth pump system, such as for pumping
bitumen froth, is provided. The froth pump system comprises a primary pump
such
as a centrifugal pump with a vent port, and at least one jet pump configured
to
receive a vented low density portion of the froth from the vent port and expel
a
motive fluid to impart momentum thereto. In embodiments, the at least one jet
pump
can be configured to direct the mixture of the vented portion and motive fluid
back to
the pump box, thus reducing the amount of lost product and diluent due to the
mixture being directed to an EDP.
Date Recue/Date Received 2021-09-24
[0013] The improved pump system mitigates air locking and increases the
amount of bitumen recovered while reducing the likelihood of blockage of the
vent
pipes of the pump system when compared to conventional systems using a vented
primary pump.
[0014] In a general aspect, a pump system for pumping froth
comprises:_a
primary pump comprising a pump housing having an inlet for receiving froth, a
discharge outlet, and a vent port;_an impeller located within the pump housing
configured to direct a low density portion of the froth out of the vent port
as a vented
portion and a remaining portion of the froth out of the discharge outlet;
and_at least
one jet pump comprising a jet pump housing having a motive fluid inlet for
receiving
a motive fluid, a vented portion inlet, and a jet outlet in communication with
each
other via a main bore, and a nozzle located within the main bore and in
communication with the motive fluid inlet;_wherein the vented portion inlet is
in
communication with the vent port of the primary pump.
[0015] In an embodiment, the vented portion inlet is in communication
with the
vent port via a vent conduit having a length.
[0016] In an embodiment, the pump system comprises two or more jet
pumps
[0017] In an embodiment, at least two of the two or more jet pumps are
arranged in parallel.
[0018] In an embodiment, at least two of the two or more jet pumps are
arranged in series.
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Date Recue/Date Received 2021-09-24
[0019] In an embodiment, the motive fluid is warm.
[0020] In an embodiment, a temperature of the motive fluid is about the
same
as a temperature of the vented portion.
[0021] In an embodiment, the pump system further comprises a control
valve
located upstream of the motive fluid inlet.
[0022] In an embodiment, the motive fluid is water.
[0023] In an embodiment, the motive fluid is a hydrocarbon.
[0024] In an embodiment, the froth is received at the inlet from a pump
box,
and the jet pump is configured to deliver a fluid mixture comprising the
motive fluid
and the vented portion to the pump box.
[0025] In an embodiment, the jet pump is configured to deliver the
fluid
mixture to the pump box via a line terminating under a fluid level of the pump
box.
[0026] In an embodiment, the jet pump is configured to deliver a fluid
mixture
comprising the motive fluid and the vented portion to a froth launder.
[0027] In an embodiment, the primary pump is a centrifugal pump.
[0028] In an embodiment, a diameter of the main bore of the jet pump
increases towards the jet outlet.
[0029] In an embodiment, a diameter of the main bore of the jet pump
decreases toward a constriction located along the main bore and increases from
the
constriction toward the jet outlet.
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Date Recue/Date Received 2021-09-24
[0030] In another broad aspect, a method of pumping froth comprises:
receiving the froth at a primary pump; venting a low density portion of the
froth as a
vented portion; directing a remaining portion of the froth to downstream
processes or
storage; directing the vented portion to at least one jet pump; and flowing a
motive
fluid through a nozzle of the jet pump.
[0031] In an embodiment, the step of receiving the froth comprises
receiving
the froth from a pump box, and further comprising directing a fluid mixture
comprising the motive fluid and the vented portion from the jet pump to the
pump
box.
[0032] In an embodiment, the step of directing the fluid mixture
comprises
directing the fluid mixture to a point under a fluid level of the pump box.
[0033] In an embodiment, the step of directing the fluid mixture
comprises
directing the fluid mixture to a froth launder upstream of the pump box.
[0034] In an embodiment, the method further comprises heating the
motive
fluid to a temperature of about a temperature of the vented portion.
[0035] In an embodiment, the step of directing the vented portion to at
least
one jet pump comprises directing the vented portion to two or more jet pumps.
[0036] In an embodiment, the method further comprises arranging at
least two
of the two or more jet pumps in parallel.
[0037] In an embodiment, the method further comprises arranging at
least two
of the two or more jet pumps in series.
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Date Recue/Date Received 2021-09-24
[0038] In an embodiment, the method further comprises adjusting one or
both
of pressure and rate at which the motive fluid is flowed through the nozzle
according
to a measured discharge pressure of the primary pump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Figure 1 is a cross-sectional representation of a prior art
froth pumping
system;
[0040] Figure 2A is a schematic representation of a froth pumping
system;
[0041] Figure 2B is a schematic representation of a froth pumping
system
having two jet pumps arranged in parallel;
[0042] Figure 2C is a schematic representation of a froth pumping
system
having two jet pumps arranged in series;
[0043] Figure 2D is a schematic representation of a froth pumping
system
having two vent lines and two jet pumps arranged in series along each line
[0044] Figure 3 is an elevation cross-sectional representation of an
embodiment of a centrifugal primary pump;
[0045] Figure 4A is a cross-sectional representation of an embodiment
of a
froth pumping system having a centrifugal primary pump and a jet pump;
[0046] Figure 4B is a cross-sectional representation of another
embodiment of
a froth pumping system having a centrifugal primary pump and a jet pump;
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Date Recue/Date Received 2021-09-24
[0047] Figure 4C is a cross-sectional representation of an embodiment
of a
froth pumping system having a centrifugal primary pump and two jet pumps
arranged in parallel;
[0048] Figure 4D is a cross-sectional representation of an embodiment
of a
froth pumping system having a centrifugal primary pump and two jet pumps
arranged in series; and
[0049] Figure 5 is a flow diagram illustrating the flow path of bitumen
froth in
an exemplary process incorporating the pumping system disclosed herein.
DESCRIPTION
[0050] With reference to Figs. 2A-4D, an improved pump system 10 for
pumping froth F, such as bitumen froth, is provided herein for mitigating air
locking,
while increasing the maximum venting rate and amount of bitumen recovered and
reducing the likelihood of blockage of the vent pipes of the pump system 10.
Embodiments of the pump system 10 disclosed herein are advantageous over
conventional bitumen froth pump systems as it provides increased bitumen
recovery,
increased maximum venting rate, reduced lost product, and reduced pump
maintenance costs.
[0051] In general, the pump system 10 comprises a primary pump 12, such
as
a centrifugal pump, and at least one jet pump 14. The centrifugal pump 12 is
configured to receive bitumen froth F from a froth source 8 such as a pump box
or
Date Recue/Date Received 2021-09-24
surge tank, vent a low density portion of the froth FL, and pump a remaining
portion
of the froth FR to a PSC or other equipment. The jet pump 14 is configured to
receive vented fluids FL from the centrifugal pump 12 and emit water or
another
suitable motive fluid FM through a nozzle therein to create a suction to draw
in the
vented portion FL from the centrifugal pump 12 and impart a motive force
thereto to
discharge it out of an outlet end of the jet pump 14. The motive fluid FM
generates a
positive pressure towards the outlet end to further assist in conveying the
discharged
bitumen-containing mixture FO of vented portion FL and motive fluid FM back to
the
pump box 8 to be stored with the rest of the bitumen froth F. The froth F is
therefore
recovered instead of disposed of, and can be pumped by the centrifugal pump 12
to
the PSC or other downstream equipment. In other embodiments the jet pump 14
can
pump the fluid mixture FO elsewhere, such as to a froth launder, storage tank,
or
another process.
[0052]
In detail, with reference to Fig. 2A and 3, the centrifugal pump 12 can
have a housing 20 with an inlet 22 located at an inlet side 24 of the pump 12
and
configured to receive bitumen froth F from a froth source 8, such as a pump
box
receiving secondary froth from a secondary flotation cell, a discharge outlet
26, and
a vent port 28 located at a rear or vent side 30 of the pump 12 opposite the
inlet side
24. An impeller 32 is rotatably mounted in the housing 20 to rotate about an
axis of
rotation X. In embodiments, the axis of rotation X is substantially aligned
with the
inlet 22 of the pump 12. The impeller 32 is operatively coupled at its axis of
rotation
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Date Recue/Date Received 2021-09-24
to a drive means 34, for example via a driveshaft 36 connected to a motor,
configured to drive the impeller 32 at sufficient speed to draw bitumen froth
F from
the bitumen froth source 8 and convey the froth F out of the discharge outlet
26 to
processing equipment downstream, such as back to a primary separation cell
(PSC).
The impeller 32 is further configured to direct a low density portion of the
froth FL,
such as a portion containing air and low density fluid, towards the vent port
28, for
example by using the impeller design as described in US Patent No. 9,879,692.
For
example, in an embodiment, the impeller can have a plurality of vanes located
at an
inlet side of an impeller shroud and configured to direct a low density
portion of the
froth FL towards an eye or center of the impeller, and a flow inducer located
at a
venting side of the shroud configured to draw the low density portion FL to
the
venting side through a plurality of openings in the shroud and direct the low
density
portion FL out of the vent port 28. The low density portion is thereby vented
from the
pump 12 as vented portion FL. As one of skill in the art would understand, the
above
described centrifugal pump 12 is merely one possible embodiment, and other
pump
designs configured to vent air and low density fluid from the pump 12 may be
used
in the pumping system 10 without deviating from the scope of the invention
described herein.
[0053]
In exemplary embodiments herein, the bitumen froth source 8 will be
assumed to be a pump box 8, and centrifugal pump 12 will be assumed to be
configured to deliver bitumen froth F from the pump box 8 back to the PSC.
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Date Recue/Date Received 2021-09-24
However, one of skill in the art would understand that embodiments of the
pumping
system 10 described herein may be used in a variety of applications to deliver
froth
F from any froth source 8 to any destination, for example to deliver froth F
from the
PSC to storage or downstream processes.
[0054]
With reference to Figs. 2A, 4A, and 4B, a jet pump 14 is located
downstream of the vent port 28 of the centrifugal pump 12 and is in
communication
therewith via vent conduit 16, and is configured to receive vented portion FL
from the
centrifugal pump 12 and provide positive pressure to convey the vented portion
FL
back to the pump box 8 or another destination. The jet pump 14 comprises a jet
pump housing 40 having a main or axial bore 46, a motive fluid inlet 48
located at a
first end 42 of the housing 40 in communication with the axial bore 44 and
connected to a motive fluid source 50, a jet pump outlet 52 in communication
with
the axial bore 46 and located at a second end 44 of the housing opposite the
first
end 42, and a vented portion inlet 54 in communication with the axial bore 46
and
configured to receive vented portion FL from the centrifugal pump 12. A nozzle
56 in
communication with the motive fluid inlet 48 is located in the axial bore 46.
A motive
fluid pump 51 can be configured to pump motive fluid FM from the motive fluid
source 50 through the nozzle 56. A control valve 49 can be located between the
motive fluid pump 51 and the motive fluid inlet 48 for controlling the flow
and/or
maximum pressure of the motive fluid.
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Date Recue/Date Received 2021-09-24
[0055] In embodiments, the nozzle 56 is axially coincident with, or
upstream
of, the intersection between the vented portion inlet 54 and the axial bore
46, such
that vented portion FL entering the axial bore 46 from the vented portion
inlet 54 will
become entrained in the motive fluid FM discharged from the nozzle 56. In
embodiments, the nozzle 56 is a converging nozzle that reduces the pressure,
and
increases the velocity, of the motive fluid FM flowing therethrough into the
axial bore
46. The pressure reduction created by the converging nozzle 56 creates a
venturi
effect that assists in drawing vented fluid FL from the primary pump 12.
[0056] As shown in Fig. 4A, in an embodiment, the inner diameter D of
the
axial bore 46 of the jet pump 14 increases toward the second end 44. The
increase
in inner diameter D towards the outlet end 44 creates a positive pressure that
assists
in transporting the motive/vented portion mixture FO towards downstream
equipment, such as the pump box 8.
[0057] In another embodiment, with reference to Fig. 4B the inner
diameter D
of the axial bore 46 of the jet pump 14 decreases from the first end 42 of the
jet
pump to a constriction 58 located between the first end 42 and second end 44
of the
jet pump 14. The inner diameter D of the axial bore 46 can then increase from
the
constriction 58 towards the second end 44. The decrease in inner diameter D
towards the constriction 58 creates a secondary venturi effect as the motive
fluid/vented portion mixture FO flows therethrough and draws vented portion FL
and
motive fluid FM towards the second end 44 of the pump. The increase in inner
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Date Recue/Date Received 2021-09-24
diameter D towards the outlet end 44 creates a positive pressure to assist in
transporting the motive/low density portion mixture FO towards downstream
equipment, such as the pump box 8.
[0058] The size and dimensions of the jet pump 14 may be selected to
adjust
the venting capacity and available pressure head thereof. The axial bore 46
and
other internal surfaces of the jet pump 14 can be lined with a durable wear
resistant
material, for example chrome white iron, carbide weld overlays, or other wear
resistant liners, to mitigate corrosion or erosion due to the flow of motive
fluid and/or
vented portion FM, FL, FO.
[0059] In embodiments, with reference to Figs. 2B and 4C, multiple jet
pumps
14a,14b,... may be configured in parallel to further increase the venting
capacity of
the primary pump 12. Increasing the number of jet pumps 14 in parallel creates
additional suction in the vent conduit 16 and increases the rate at which
vented
portion FL may be drawn out of the vent port 28.
[0060] With reference to Figs. 2C and 4D, multiple jet pumps
14a,14b,... may
also be configured in series to increase the maximum pressure head available
to
transport the vented portion FL. Such a series configuration can be used to
transport
the vented portion FL greater distances and/or heights, such as when it is
desired to
direct the fluid mixture FO to another location besides the pump box 8 so as
to not
dilute the froth in the pump box 8.
Date Recue/Date Received 2021-09-24
[0061] As shown in Fig. 2D, the jet pumps 14a,14b,... can also be
arranged in
series on parallel venting lines to provide both greater venting rates and
maximum
pressure head.
[0062] In embodiments, the length of vent conduit 16¨ in other words
the fluid
travel distance ¨ between the primary pump 12 and the jet pump 14 can be
selected
to improve the performance of the pumping system 10. For example, reducing the
distance between the jet pump 14 and centrifugal pump 12 reduces pressure at
the
vent port 28 which allows vented portion FL to be vented from the pump 12 at a
higher rate. Reducing the length of the vent conduit 16 is also advantageous
as a
short length permits greater venting capacity while reducing the effects of
plugging
or fouling of the conduit 16. It may also be desirable to heat trace the vent
conduit 16
and other sections of the pump system to mitigate potential fouling issues.
[0063] In embodiments, the line leading from the jet pump outlet 52 to
the
pump box 8 can terminate underneath the liquid level of the pump box 8 to
provide a
siphoning effect and further assist in transporting the fluid mixture FO from
the jet
pump 14 to the pump box 8. For example, with reference to Fig. 2A to Fig. 2D,
the
line can run from the jet pump outlet 52 up over a lip of the pump box 8 and
down
into the pump box 8 below the fluid level thereof in a gooseneck fashion. An
advantage of such a design is that vented portion FL will continue to be drawn
into
the pump box 8 in the event the motive fluid pump 51 fails and motive fluid FM
is not
flowed through the jet pump 14.
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Date Recue/Date Received 2021-09-24
[0064] In embodiments, as shown in Fig. 2A to Fig. 2D, a flow control
valve 49
can be located along the motive fluid line to permit adjustment of the fluid
pressure
and flow of the motive fluid FM. This in turn adjusts the rate at which vented
portion
FL is vented from the pump 12. The flow control valve can be manually
adjusted, or
automated to adjust pressure / flow rate in response to parameters of the
pumping
system such as the discharge pressure of the primary pump 12. For example, the
expected discharge pressure of the primary pump 12 can be calculated based on
froth flow and pump speed. If the measured discharge pressure of the pump 12
is
lower than the expected discharge pressure, this may be indicative of air
locking in
the primary pump 12. The flow of motive fluid FM through the jet pump 14 can
then
be increased to increase the draw of the jet pump, in turn increasing the rate
at
which vented portion FL is drawn from the primary pump 12. The flow of motive
fluid
FM can also be decreased if the measured discharge pressure is within the
expected range in order to reduce dilution of the vented portion FL.
[0065] In embodiments, the motive fluid FM can be warm water, for
example
water at a temperature of about 40 C to 95 C, which lowers the viscosity of
the
vented portion FL of the bitumen froth F. The motive fluid FM can also be
heated to
be about the same pressure as the vented portion FL. Lowering the viscosity of
the
vented portion FL further assists in mitigating plugging of the vent pipes 16,
jet pump
14, and/or equipment and conduits downstream. In other embodiments, the motive
fluid FM is a light hydrocarbon such as naphtha, paraffin solvent, tailings
water, and
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Date Recue/Date Received 2021-09-24
the like. Such motive fluids can also be warmed to provide a viscosity-
reducing
effect.
[0066] In use, with reference to Fig. 5, in an exemplary embodiment,
bitumen
froth F is pumped from a pump box 8 back to a PSC using a centrifugal pump 12.
The centrifugal pump 12 is configured to vent air and a low density portion of
the
froth F as a vented portion FL to a jet pump 14 as described above for
delivery back
to the pump box 8 or froth launder upstream of the pump box 8. Motive fluid FM
is
pumped from a motive fluid source 50 to the motive fluid inlet 48 of a jet
pump 14
and is discharged out of a nozzle 56 located within a main bore 46 of the jet
pump
14. The discharged motive fluid FM mixes with vented portion FL entering into
the jet
pump 14 and imparts momentum thereto, directing the motive fluid/vented
portion
mixture FO towards the second end 44 and out the outlet 52 of the jet pump 14.
[0067] In embodiments wherein the axial bore 46 of the jet pump 14
increases
in inner diameter D towards the second end 44, the fluid pressure of the fluid
mixture
FO increases with the inner diameter D as it flows towards the jet pump outlet
52.
The positive pressure created by the fluid mixture FO as the axial bore 46
expands
towards the outlet end 44 provides additional impetus to assist in
transporting the
fluid mixture FO to the pump box 8.
[0068] In embodiments wherein the axial bore 46 of the jet pump 14 has
a
constriction 58, as the fluid mixture FO passes through the constriction 58,
the low
pressure created by the constriction 58 draws additional vented low density
portion
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Date Recue/Date Received 2021-09-24
FL into the axial bore 46 of the jet pump. The fluid pressure of the fluid
mixture FO
increases inner diameter D of the axial bore 46 increases towards the outlet
end 44
of the jet pump 14, thus also providing additional impetus to assist in
transporting the
fluid mixture FO to the pump box 8.
[0069] Use of the jet pump 14 in the embodiments of the froth pumping
system 10 disclosed herein is advantageous over conventional systems, as
bitumen
vented from the centrifugal pump 12 that would have otherwise been disposed of
in
the EDP can now be recovered in the pump box 8. Additionally, the suction
created
by the jet pump 14 assists in drawing the vented portion FL from the
centrifugal
pump 12 while the motive fluid FM pushes the vented portion FL drawn into the
jet
pump 14 towards the jet pump outlet 52, thereby reducing the likelihood that
low
density portion of the froth F will plug the vent conduit 16 or other
components and
cause further air locking in the centrifugal pump 12.
[0070] A further advantage of the pump system 10 disclosed herein is
that it
mitigates the need for a two-stage pump system, as venting air and low density
portion FL from the first pump stage (i.e. the primary pump 12) to a jet pump
14
using the system disclosed herein allows the first stage pump 12 to operate at
higher
speeds and total dynamic head (TDH). As a result, the second stage pump can be
turned down to add a reduced amount of additional head, or potentially
bypassed
altogether.
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Date Recue/Date Received 2021-09-24
[0071] Additionally, the disclosed pump system 10 reduces the need for
oversized pump boxes 8. Conventional froth pumping systems require taller pump
boxes, for example over 10m tall, to provide the requisite net positive
suction head
(NPSH) for the centrifugal pump to operate without cavitating or air locking.
Venting
to the jet pump reduces the likelihood of air locking such that required NPSH
is
lower, in turn permitting a shorter pump box to be used.
[0072] The improved operation provided by the present pumping system 10
also allows greater surge capacity to be provided by the pump box 8 due to the
reduced NPSH requirement, thus enabling a greater operational range of flow
from
upstream processes and reducing the likelihood that said upstream processes
will
be required to reduce flow to avoid overfilling of the pump box 8.
[0073] Another advantage of the present pumping system is that the
motive
fluid FM flowed through the jet pump also serves to dilute the bitumen froth F
in the
pump box 8 when the motive fluid / vented low density portion mixture FO is
returned thereto. In conventional pumping systems, diluent is added directly
to the
pump box 8 to dilute the bitumen froth F therein. Thus, less water is used
overall in
embodiments of the pumping system 10 disclosed herein compared to conventional
systems, as the motive fluid FM used for the jet pump 8 is recycled into the
process
and doubles as a diluent in the pump box 8.
Date Recue/Date Received 2021-09-24
Exam pie
[0074] In an exemplary embodiment, a bitumen froth pumping system 10
comprises a centrifugal pump 12 configured to receive and pump bitumen froth F
containing about 7.5-15% bitumen, 7.5-10% solids, and 75-85% water to a
downstream process at rate of 1000-1500 m3/hrt. The froth F comprises about 40
vol.% air. The centrifugal pump 12 suffers from significant de-rating due to
the
relatively high air content in the bitumen froth F. To counteract air locking
and
improve pump performance, the centrifugal pump 12 is configured to vent a low
density portion FL of the bitumen froth F out of a vent port 28 as vented
portion FL to
a trench, which directs the vented fluid FL to an EDP. A vent valve 29
operable to
control the volume of vented portion travelling out of the centrifugal pump 12
through
the vent port 28 may be opened to allow more vented portion FL to be vented.
However, about 1-10 m3/h of bitumen is lost to the EDP due to bitumen being
vented
together with the low density vented portion FL. Additionally, about 40m3/h of
warm
water must be continuously flowed through the trench to evacuate the vented
portion
FL to the EDP. Said water and vented portion FL, along with the bitumen
contained
therein, are lost product unless they can be separated and recovered using
further
processes at additional cost.
[0075] To address these issues, a jet pump 14 is located downstream
of, and
in communication with, the vent port 28 of the centrifugal pump 12 to assist
in
drawing vented portion FL from the centrifugal pump 12 and providing motive
force
21
Date Recue/Date Received 2021-09-24
and positive pressure to deliver the motive/vented portion mixture FO to a
pump box
8 rather than disposing of the fluid mixture in the EDP. About 150-170 m3/h at
40
kpag of warm water can be pumped through the jet nozzle 56 of the jet pump 14
as
motive fluid FM to impart a motive force to the vented portion FL. In this
particular
example, the motive fluid header pressure is 400kpag. The motive/vented fluid
mixture FO flows through the axial bore 46 of the jet pump 14 at a velocity of
about
20m/s or greater and the discharge pressure of the jet pump 14 is about 100-
125
kpag. The incorporation of the jet pump 14 in the pumping system 10 resulted
in the
recovery of about 1-10 m3/h of bitumen froth that would have otherwise been
lost to
the EDP, as well as about 20 m3/h of warm water, as warm water no longer needs
to
be continuously flowed through the trench and lost to the EDP, but is instead
recovered in the pump box 8.
[0076]
In other applications, Applicant has found that an average of 60m3/h of
vented bitumen froth was recovered by incorporating one or more jet pumps 14
downstream of the vent port 28 of the primary pump 12.
22
Date Recue/Date Received 2021-09-24
