PRE-TREATMENT OF OIL SANDS FINE TAILINGS BY DEBRIS REMOVAL

PRETRAITEMENT DE RESIDUS FINS DE SABLES BITUMINEUX PAR RETRAIT DES DEBRIS

English Abstract

The present disclosure relates to processes, systems, devices and
techniques for pre-treating an aqueous suspension including fine solid
particles
and coarse debris, in order to remove coarse debris prior to further
treatments.
The present techniques are particularly claimed and described with respect to
an aqueous suspension derived from mining operations and referred to as
mining tailings, including oil sands fine tailings, such as mature fine
tailings
(MFT).

Description

PRE-TREATMENT OF OIL SANDS FINE TAILINGS
BY DEBRIS REMOVAL
TECHNICAL FIELD
[0001] The technical field generally relates to the treatment of mine
tailings derived
from mining operations, and more particularly to techniques that can involve
screening
for removing coarse debris from oil sands fine tailings for example prior to
flocculation
and dewatering operations.
BACKGROUND
[0002] Oil sands tailings are generated from hydrocarbon extraction
process
operations that separate the valuable hydrocarbons from oil sand ore. There
are
various types of oil sands tailings, such as mature fine tailings (MFT) formed
in a
tailings pond. Tailings materials that have a high fines content can be
subjected to
dewatering operations, which can involve adding chemical additives such as
flocculants and then separating solid minerals from the water in the tailings
by
supplying the treated tailings to a sub-aerial deposition area for deposition
in thin lifts
for drying, to a dewatering device, or to a pit for settling of the mineral
solids.
[0003] Prior to addition of a flocculant or other chemical agents to
the tailings
material, the fine tailings can be screened to remove coarse debris that can
cause
issues in downstream operations. For example, Canadian patent No. 2,772,053
=
describes methods and apparatuses for removing coarse debris from fine
tailings prior
to a flocculation and dewatering operation. There is still a need for
enhancements in
terms of methods and screening apparatuses for coarse debris removal from
tailings
streams.
SUMMARY
[0004] The present disclosure provides processes, systems, devices and

techniques for pre-treating an aqueous suspension including fine solid
particles and
coarse debris, in order to remove coarse debris prior to further treatments.
The present
techniques are particularly claimed and described with respect to an aqueous
suspension derived from mining operations and referred to as mining tailings,
including
oil sands fine tailings, such as mature fine tailings (MET).
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[0005] In one aspect, there is provided a pre-treatment screening
assembly
comprising: a spillbox feed tank comprising a bottom wall and side walls
extending
upwardly from the bottom wall, thereby defining a tank cavity, an inlet
provided in the
bottom wall for receiving a tailings fluid flow into the tank cavity, and an
overflow weir
extending outwardly from an upper portion of the tank cavity; a screening
device having
a screening surface receiving the tailings fluid flow spilling over the
overflow weir of the
spillbox feed tank, the screening surface being configured to allow material
with a
predetermined size that is included in the tailings fluid flow to flow through
the
screening surface and separate coarse debris from the tailings fluid flow,
thereby
separating the tailings fluid into a coarse debris fraction and a screened
tailings fluid;
and a collector body arranged below the screening surface of the screening
device to
receive the screened tailings fluid.
[0006] In some implementations of the pre-treatment screening
assembly, the inlet
may be provided substantially centrally in the bottom wall. A width of the
overflow weir
may be smaller than a width of the screening surface. The width of the
overflow weir
may represent less than 90% of the width of the screening surface.
[0007] In some other implementations, the spillbox feed tank may
comprise a
baffle plate arranged in the tank cavity. The baffle plate may be parallel to
one of the
side walls. The spillbox feed tank may comprise two baffle plates which are
arranged in
the tank cavity in parallel relationship with two opposed side walls. The
spillbox feed
tank may further comprise an adjustable valve configured to cooperate with one
of the
inlet and the overflow weir. The spillbox feed tank may further comprise a
level sensor
for measuring a tailings fluid level in the tank cavity. The level sensor may
comprise
two pressure transmitters arranged in the tank cavity to measure the pressure
of the
tailings fluid at two distinct locations of the tank cavity. The spillbox feed
tank may
further comprise an adjustable valve configured to cooperate with one of the
inlet and
the overflow weir in response to the level measured by the level sensor.
[0008] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a spillbox feed tank comprising: a bottom wall and side walls
extending
upwardly from the bottom wall, thereby defining a tank cavity, an inlet
provided
substantially centrally in the bottom wall for receiving a tailings fluid flow
into the tank
cavity, and an overflow weir extending outwardly from an upper portion of the
tank
cavity; a screening device having a screening surface receiving the tailings
fluid flow
spilling over the overflow weir of the spillbox feed tank, the screening
surface being
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configured to allow material with a predetermined size that is included in the
tailings
fluid flow to flow through the screening surface and separate coarse debris
from the
tailings fluid flow, thereby separating the tailings fluid into a coarse
debris fraction and a
screened tailings fluid; and a collector body arranged below the screening
surface of
the screening device to receive the screened tailings fluid.
[0009] In anoth.er aspect, there is provided a pre-treatment screening
assembly
comprising: a spillbox feed tank comprising: a bottom wall and side walls
extending
upwardly from the bottom wall, thereby defining a tank cavity, an inlet for
receiving a
tailings fluid flow into the tank cavity, and an overflow weir extending
outwardly from an
upper portion of the tank cavity; a screening device having a screening
surface
receiving the tailings fluid flow spilling over the overflow weir of the
spillbox feed tank,
the screening surface being configured to allow material with a predetermined
size that
is included in the tailings fluid flow to flow through the screening surface
and separate
coarse debris from the tailings fluid flow, thereby separating the tailings
fluid into a
coarse debris fraction and a screened tailings fluid; and a collector body
arranged
below the screening surface of the screening device to receive the screened
tailings
fluid; wherein a width of the overflow weir is smaller than a width of the
screening
surface.
[0010] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a spillbox feed tank comprising: a bottom wall and side walls
extending
upwardly from the bottom wall, thereby defining a tank cavity, an inlet for
receiving a
tailings fluid flow into the tank cavity, an overflow weir extending outwardly
from an
upper portion of the tank cavity, a level sensor for measuring a tailings
fluid level in the
tank cavity, and an adjustable valve configured to cooperate with one of the
inlet and
the overflow weir in response to the level measured by the level sensor; a
screening
device having a screening surface receiving the tailings fluid flow spilling
over the
overflow weir of the spillbox feed tank, the screening surface being
configured to allow
material with a predetermined size that is included in the tailings fluid flow
to flow
through the screening surface and separate coarse debris from the tailings
fluid flow,
thereby separating the tailings fluid into a coarse debris fraction and a
screened tailings
fluid; and a collector body arranged below the screening surface of the
screening
device to receive the screened tailings fluid.
[0011] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a spillbox feed tank comprising: a bottom wall and side walls
extending
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upwardly from the bottom wall, thereby defining a tank cavity, an inlet for
receiving a
tailings fluid flow into the tank cavity, and an overflow weir extending
outwardly from an
upper portion of the tank cavity; a screening device comprising: a screening
surface
receiving the tailings fluid flow spilling over the overflow weir of the
spillbox feed tank,
the screening surface being configured to allow material with a predetermined
size that
is included in the tailings fluid flow to flow through the screening surface
and separate
coarse debris from the tailings fluid flow, thereby separating the tailings
fluid into a
coarse debris fraction and a screened tailings fluid, and a cleaning device to
remove
the coarse debris from the screening surface; and a collector body arranged
below the
screening surface of the screening surface to receive the screened tailings
fluid.
[0012] In some implementations of the pre-treatment screening
assembly, the
screening surface may define a first inclination angle with a horizontal
direction, the
cleaning device comprising a winch for adjusting the first inclination angle.
The pre-
treatment screening assembly may further comprise a debris sensor for
measuring an
amount of coarse debris on the screening surface, the winch adjusting the
first
inclination angle in response to the amount of coarse debris measured by the
debris
sensor. The pre-treatment screening assembly may further comprise a tailings
fluid
loss sensor for measuring an amount of tailings fluid losses resulting from a
running off
of the screening surface, the winch adjusting the first inclination angle in
response to
the amount of tailings fluid losses measured by the tailings fluid loss
sensor.
[0013] In some other implementations, the cleaning device may
comprise a
mechanical cleaning device to mechanically remove the coarse debris from the
screening surface. The mechanical cleaning device may comprise at least one of
a
rake and a rotating brush for going at least partially over the screening
surface.
[0014] In some other implementations, the screening device may
comprise an
upper portion having an upper screening surface defining an upper angle with a

horizontal direction, and a lower portion having a lower screening surface
defining a
lower angle with the horizontal direction, the upper angle being greater than
the lower
angle. The upper angle may be at least 1.5 times greater than the lower angle.
The
cleaning device may comprise a mechanical cleaning device to mechanically
remove
the coarse debris from the lower screening surface of the screening surface.
[0015] In some other implementations, the pre-treatment screening
assembly may
further comprise a debris collection bin arranged under or close to the
screening
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device. The pre-treatment screening assembly may further comprise a debris
heater for
heating the debris collection bin. The pre-treatment screening assembly may
further
comprise a debris collection pump for pumping a tailings fluid from the debris
collection
bin and for injecting it back in the spillbox feed tank.
[0016] In some other implementations, the screening device may further
comprise
an overflow weir, the screened tailings fluid flow spilling over the overflow
weir into the
collector body. The screening surface may have a substantially concave
profile. The
cleaning device may comprise a shaker for vibrating the screening surface.
[0017] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a screening device comprising a screening surface receiving a
tailings fluid
flow, the screening surface being configured to allow material with a
predetermined
size that is included in the tailings fluid flow to flow through the screening
surface and
separate coarse debris from the tailings fluid flow, thereby separating the
tailings fluid
into a coarse debris fraction and a screened tailings fluid, the screening
surface
defining a first adjustable inclination angle with a horizontal direction; and
a collector
body arranged below the screening surface of the screening surface to receive
the
screened tailings fluid.
[0018] In some implementations, the pre-treatment screening assembly
may
further comprise a winch for adjusting the first adjustable inclination angle.
The pre-
treatment screening assembly may further comprise a debris sensor for
measuring an
amount of coarse debris on the screening surface, the winch adjusting the
first
adjustable inclination angle in response to the amount of coarse debris
measured by
the debris sensor. The pre-treatment screening assembly may further comprise a

tailings fluid loss sensor for measuring an amount of tailings fluid losses
resulting from
a running off of the screening surface, the winch adjusting the first
adjustable
inclination angle in response to the amount of tailings fluid losses measured
by the
tailings fluid loss sensor.
[0019] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a screening device comprising: a screening surface receiving a
tailings
fluid flow, the screening surface being configured to allow material with a
predetermined size that is included in the tailings fluid flow to flow through
the
screening surface and separate coarse debris from the tailings fluid flow,
thereby
separating the tailings fluid into a coarse debris fraction and a screened
tailings fluid,
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and a mechanical cleaning device configured to mechanically remove the coarse
debris from the screening surface; and a collector body arranged below the
screening
surface of the screening surface to receive the screened tailings fluid.
[0020] In some implementations of the pre-treatment screening
assembly, the
mechanical cleaning device may comprise at least one of a rake and a rotating
brush
for going at least partially over the screening surface. The screening device
may
comprise an upper portion having an upper screening surface defining an upper
angle
with a horizontal direction, and a lower portion having a lower screening
surface
defining a lower angle with the horizontal direction, the upper angle being
greater than
the lower angle. The upper angle may be at least 1.5 times greater than the
lower
angle. The mechanical cleaning device may be configured to mechanically remove
the
coarse debris from the lower screening surface of the screening surface.
[0021] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a screening device comprising: a screening surface receiving a
tailings
fluid flow, the screening surface being configured to allow material with a
predetermined size that is included in the tailings fluid flow to flow through
the
screening surface and separate coarse debris from the tailings fluid flow,
thereby
separating the tailings fluid into a coarse debris fraction and a screened
tailings fluid,
and a cleaning device configured to remove the coarse debris from the
screening
surface; a collector body arranged below the screening surface of the
screening
surface to receive the screened tailings fluid; and a debris collection bin
arranged
under or close to the screening device to collect the coarse debris removed
from the
screening surface.
[0022] In some implementations, the pre-treatment screening assembly
may
further comprise a debris heater for heating the debris collection bin. The
pre-treatment
screening assembly may further comprise a debris collection pump for pumping a

tailings fluid from the debris collection bin and for injecting it back onto
the screening
surface.
[0023] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a spillbox feed tank comprising: a bottom wall and side walls
extending
upwardly from the bottom wall, thereby defining a tank cavity, an inlet for
receiving a
tailings fluid flow into the tank cavity, and an overflow weir extending
outwardly from an
upper portion of the tank cavity; a screening device comprising a screening
surface
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receiving the tailings fluid flow spilling over the overflow weir of the
spillbox feed tank,
the screening surface being configured to allow material with a predetermined
size that
is included in the tailings fluid flow to flow through the screening surface
and separate
coarse debris from the tailings fluid flow, thereby separating the tailings
fluid into a
coarse debris fraction and a screened tailings fluid; and a collector body
arranged
below the screening surface of the screening device and having a collecting
cavity to
receive the screened fluid, the collector body comprising a discharge opening
formed in
a bottom portion of the collecting cavity for collecting and easily removing
debris that
build up in the collector body.
[0024] In some implementations of the pre-treatment screening
assembly, the
bottom portion may have a substantially conical shape. The body may have side
walls
converging toward the discharge opening. The pre-treatment screening assembly
may
further comprise a frame, the collector body being mounted to the frame so
that the
discharge opening is vertically offset relative to a ground on which the frame
stands.
[0025] In some other implementations, the screening device may have an

upstream inlet, the tailings fluid being discharged on the screening surface
over the
overflow weir at the upstream inlet, the collector body having side walls
defining at
least partially the collecting cavity and a discharge outlet for discharging
the screened
tailings fluid from the collecting cavity, the discharge outlet being formed
in one of the
side walls.
[0026] In some other implementations, the collector body may further
comprise a
deflector plate arranged in the collecting cavity. The deflector plate may
extend at least
partially over the discharge outlet. The collector body may further comprise a
vortex
breaker arranged in the collecting cavity. The collector body may have side
walls
defining at least partially the collecting cavity, the vortex breaker being
mounted to one
of the side walls. The vortex breaker may comprise a substantially cylindrical
body and
a vortex breaking core arranged in the cylindrical body. The vortex breaking
core may
have a substantially crossed-shaped section.
[0027] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a screening device comprising a screening surface receiving a
tailings fluid
flow, the screening surface being configured to allow material with a
predetermined
size that is included in the tailings fluid flow to flow through the screening
surface and
separate coarse debris from the tailings fluid flow, thereby separating the
tailings fluid
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into a coarse debris fraction and a screened tailings fluid; and a collector
body
arranged below the screening surface of the screening device and comprising: a

bottom wall and side walls extending from the bottom wall, thereby defining a
collecting
cavity to receive the screened fluid, a discharge opening formed in a bottom
portion of
the collecting cavity for collecting and easily removing debris that build up
in the
collector body, the side walls converging toward the discharge opening.
[0028] In some implementations of the pre-treatment screening
assembly, the
bottom portion of the collecting cavity may have a substantially conical
shape. The pre-
treatment screening assembly may further comprise a frame, the collector body
being
mounted to the frame so that the discharge opening is vertically offset
relative to a
ground on which the frame stands.
[0029] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a screening device comprising a screening surface receiving a
tailings fluid
flow, the screening surface being configured to allow material with a
predetermined
size that is included in the tailings fluid flow to flow through the screening
surface and
separate coarse debris from the tailings fluid flow, thereby separating the
tailings fluid
into a coarse debris fraction and a screened tailings fluid; and a collector
body
arranged below the screening surface of the screening device and having a
collecting
cavity to receive the screened fluid, the collector body comprising a
deflector plate
arranged in the collecting cavity.
[0030] In some implementations of the pre-treatment screening
assembly, the
collector body may have side walls defining at least partially the collecting
cavity and a
discharge outlet for discharging the screened tailings fluid from the
collecting cavity, the
discharge outlet being formed in one of the side walls, the deflector plate
extending at
least partially over the discharge outlet. The collector body may further
comprise a
vortex breaker arranged in the collecting cavity. The collector body may have
side walls
defining at least partially the collecting cavity, the vortex breaker being
mounted to one
of the side walls. The vortex breaker may comprise a substantially cylindrical
body and
a vortex breaking core arranged in the cylindrical body. The vortex breaking
core may
have a substantially crossed-shaped section.
[0031] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a plurality of spillbox feed tanks, each spillbox feed tank
comprising: a
bottom wall and side walls extending upwardly from the bottom wall, thereby
defining a
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tank cavity, an inlet for receiving a tailings fluid flow into the tank
cavity, an overflow
weir extending outwardly from an upper portion of the tank cavity, and an
adjustable
valve configured to cooperate with the overflow weir; a plurality of screening
devices,
each screening device having a screening surface receiving the tailings fluid
flow
spilling over the overflow weir of one of the spillbox feed tanks, the
screening surface
being configured to allow material with a predetermined size that is included
in the
tailings fluid flow to flow through the screening surface and separate coarse
debris from
the tailings fluid flow, thereby separating the tailings fluid into a coarse
debris fraction
and a screened tailings fluid; and a collector body arranged below the
screening
surface of the screening devices having a collecting cavity to receive the
screened
tailings fluids of the plurality of screening devices; the adjustable valves
of the spillbox
feed tanks being adjusted for the different spillbox feed tanks to have a
substantially
similar outlet flow.
[0032] In some implementations, the pre-treatment screening assembly
may
further comprise a frame, the spillbox feed tanks being mounted to the frame,
each
overflow weir defining a height relative to a ground on which the frame
stands, the
adjustable valves of the spillbox feed tanks being adjusted in response to the
height of
the overflow weir of the spillbox feed tanks. Each overflow weir may have an
adjustable
plate to modify the height of the overflow weir.
[0033] In some other implementations, the pre-treatment screening
assembly may
further comprise a frame, the spillbox feed tanks having an adjustable
mounting base
to be adjustably mounted to the frame. Each overflow weir may define a height
relative
to a ground on which the frame stands, the adjustable mounting bases being
adjusted
for the overflow weirs to have a substantially similar height. The pre-
treatment
screening assembly may comprise a single collector body.
[0034] In some other implementations, the pre-treatment screening
assembly may
comprise at least two screening devices, each screening device defining a
longitudinal
direction and having two opposed longitudinal ends, said at least two
screening
devices extending side to side substantially parallel, the pre-treatment
screening
assembly further comprising an access platform extending along the screening
devices
at one of their longitudinal ends. The pre-treatment screening assembly may
further
comprise two other screening devices, each screening device defining a
longitudinal
direction and having two opposed longitudinal ends, said at least two
screening
devices extending side to side substantially parallel, the pre-treatment
screening
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assembly further comprising a second access platform extending along said two
other
screening devices at one of their longitudinal ends, so that the pre-treatment
screening
assembly has a substantially rectangular shape.
[0035] In another aspect, there is provided a pre-treatment screening
assembly
comprising: a plurality of spillbox feed tanks, each spillbox feed tank
comprising: a
bottom wall and side walls extending upwardly from the bottom wall, thereby
defining a
tank cavity, an inlet for receiving a tailings fluid flow into the tank
cavity, and an
overflow weir extending outwardly from an upper portion of the tank cavity; at
least two
screening devices, each screening device defining a longitudinal direction and
having
two opposed longitudinal ends, said at least two screening devices extending
side to
side substantially parallel, and each screening device having a screening
surface
receiving the tailings fluid flow spilling over the overflow weir of one of
the spillbox feed
tanks, the screening surface being configured to allow material with a
predetermined
size that is included in the tailings fluid flow to flow through the screening
surface and
separate coarse debris from the tailings fluid flow, thereby separating the
tailings fluid
into a coarse debris fraction and a screened tailings fluid; an access
platform extending
along the screening devices at one of their longitudinal ends; and a collector
body
arranged below the screening surface of the screening devices having a
collecting
cavity to receive the screened tailings fluids.
[0036] In another aspect, there is provided a pre-treatment site
comprising: a pre-
treatment screening assembly according to the present disclosure; an inlet
line fluidly
connected to the pre-treatment screening assembly to discharge a tailings
fluid flow
onto the screening surface of the screening device; and a discharge line
fluidly
connected to the collector body for downstream treatment operations of the
screened
tailings fluid. The pre-treatment screening assembly may have a rectangular
shape
and comprises four screening devices, each of them constituting a corner of
the pre-
treatment screening assembly. The pre-treatment screening assembly may further

comprise two parallel platforms, said four screening devices being arranged
between
said two platforms. The pre-treatment site may further comprise at least two
pre-
treatment screening assemblies, each of them having four screening devices
arranged
between two parallel platforms, the platforms of the at least two pre-
treatment
screening assemblies being substantially parallel to each other.
[0037] In yet another aspect, there is provided a process for
screening coarse
debris from a tailings fluid flow coming from an inlet line, the process
comprising:
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providing the tailings fluid flow to a pre-treatment screening assembly
comprising a
spillbox feed tank having a bottom wall and side walls extending upwardly from
the
bottom wall, thereby defining a tank cavity, a screening device and a
collector body;
connecting the inlet line to a tailings inlet formed in the bottom wall of the
spillbox feed
tank so as to form in the tank cavity a substantially vertical tailings fluid
inlet flow; filling
the tank cavity of the spillbox feed tank with the tailings fluid flow for the
tailings fluid
flow to reach an overflow weir of the spillbox feed tank; discharging a
tailings fluid
outlet flow over the overflow weir of the tank cavity onto the screening
device, the
screening device having a screening surface configured to allow material with
a
predetermined size that is included in the tailings fluid flow to flow through
the
screening surface and separate coarse debris from the tailings fluid flow,
thereby
separating the tailings fluid into a coarse debris fraction and a screened
tailings fluid;
and collecting the screened tailings fluid into the collector body.
[0038] In some implementations, the process may further comprise
modifying at
least one of the inlet and outlet flow rates of the spillbox feed tank. The
process may
further comprise measuring a level of tailing fluid in the tank cavity. The
process may
further comprise modifying the at least one of the inlet and outlet flow rates
of the
spillbox feed tank in response to the measured level of the tailings fluid in
the tank
cavity.
[0039] In another aspect, there is provided a process for screening
coarse debris
from a tailings fluid flow coming from an inlet line, the process comprising:
providing the
tailings fluid flow to a pre-treatment screening assembly comprising a
spillbox feed tank
with a tank cavity, a screening device and a collector body; connecting the
inlet line to
a tailings inlet formed in the spillbox feed tank; filling the tank cavity of
the spillbox feed
tank with the tailings fluid flow for the tailings fluid flow to reach an
overflow weir of the
spillbox feed tank; discharging a tailings fluid outlet flow over the overflow
weir of the
tank cavity onto the screening device, the screening device having a screening
surface
configured to allow material with a predetermined size that is included in the
tailings
fluid flow to flow through the screening surface and separate coarse debris
from the
tailings fluid flow, thereby separating the tailings fluid into a coarse
debris fraction and a
screened tailings fluid; collecting the screened tailings fluid into the
collector body; and
removing the coarse debris from the screening surface.
[0040] In some implementations of the process, the screening surface
may define
a first adjustable inclination angle with a horizontal direction, the process
further
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comprising modifying the first adjustable inclination angle. The process may
further
comprise measuring an amount of coarse debris on the screening surface. The
process may further comprise measuring an amount of tailings fluid losses
resulting
from a running off of the screening surface. The screening surface may define
a first
adjustable inclination angle with a horizontal direction, the process further
comprising
modifying the first adjustable inclination angle in response to at least one
of the
measured amount of coarse debris and of the measured amount of tailings fluid
losses.
The process may further comprise placing the removed coarse debris into a
debris
collection bin. The debris collection bin may be heated. The tailings fluid
contained in
the debris collection bin may be pumped back into the spillbox feed tank. The
process
may further comprise applying vibrations to the screening surface.
[0041] In another aspect, there is provided a process for screening
coarse debris
from a tailings fluid flow coming from an inlet line and going into an outlet
line, the
process comprising: providing the tailings fluid flow to a pre-treatment
screening
assembly comprising a spillbox feed tank with a tank cavity, a screening
device and a
collector body having a discharge outlet connected to the outlet line;
connecting the
inlet line to a tailings inlet formed in the spillbox feed tank; filling the
tank cavity of the
spillbox feed tank with the tailings fluid flow for the tailings fluid flow to
reach an
overflow weir of the spillbox feed tank; discharging a tailings fluid outlet
flow over the
overflow weir of the tank cavity onto the screening device, the screening
device having
a screening surface configured to allow material with a predetermined size
that is
included in the tailings fluid flow to flow through the screening surface and
separate
coarse debris from the tailings fluid flow, thereby separating the tailings
fluid into a
coarse debris fraction and a screened tailings fluid; collecting the screened
tailings fluid
into the collector body; and deflecting the screened tailings fluid inlet flow
filling the
collector body from the discharge outlet.
[0042] In another aspect, there is provided a process for screening
coarse debris
from a tailings fluid flow coming from an inlet line, the process comprising:
providing the
tailings fluid flow to a pre-treatment screening assembly comprising at least
two
spillbox feed tanks having each a tank cavity, a screening device and a
collector body;
connecting the inlet line to a tailings inlet formed in each of the spillbox
feed tanks;
filling each tank cavity of the spillbox feed tanks with the tailings fluid
flow for the
tailings fluid flow to reach an overflow weir of each of the spillbox feed
tanks;
discharging a tailings fluid outlet flow over the overflow weir of the tank
cavity onto the
screening device, the screening device having a screening surface configured
to allow
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material with a predetermined size that is included in the tailings fluid flow
to flow
through the screening surface and separate coarse debris from the tailings
fluid flow,
thereby separating the tailings fluid into a coarse debris fraction and a
screened tailings
fluid; collecting the screened tailings fluid into the collector body; and
adjusting the
outflow rate of at least one of the tailings fluid outlet flow for the
different spillbox feed
tanks to have a substantially similar outlet flow rate.
[0043] In some implementations of the process, each overflow weir may
define a
height relative to a ground on which the pre-treatment screening assembly
stands, and
the process may further comprise modifying the height of at least one overflow
weir for
the different spillbox feed tanks to have a substantially similar outlet flow
rate. Each
spillbox feed tank may define a height relative to a ground on which the pre-
treatment
screening assembly stands, the process may further comprise modifying the
height of
at least one spillbox feed tank for the different spillbox feed tanks to have
a
substantially similar outlet flow rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] Figs. 1 and 2 are respective front and rear perspective views
of an
embodiment of a pre-treatment screening assembly;
[0045] Fig. 3 is a rear perspective view of another embodiment of a
pre-treatment
screening assembly;
[0046] Fig. 4 is a cross-section view of another embodiment of a pre-
treatment
screening assembly;
[0047] Fig. 5 is a rear perspective view of another embodiment of a
pre-
treatment screening assembly;
[0048] Fig. 6 is a rear perspective view of another embodiment of a
pre-
treatment screening assembly, the frame of the pre-treatment screening
assembly having an elevated structure;
[0049] Fig. 7 is an elevation view of an embodiment of a spillbox
feed tank;
[0050] Fig. 8 is an elevation view of another embodiment of a
spillbox feed tank;
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[0051] Fig. 9 is a side elevation view of an embodiment of a spillbox
feed tank and
a screening device;
[0052] Fig. 10 is a cross-section view of an embodiment of a screening
device;
[0053] Fig. 11 is a cross-section view of another embodiment of a
screening
device, a mechanical cleaning device being mounted to the screening device;
[0054] Fig. 12 is a side elevation view of another embodiment of a
screening
device, the screening device having a screening surface with an adjustable
inclination
angle;
[0055] Fig. 13 is a cross-section view of an embodiment of a collector
body;
[0056] Fig. 14 is a top perspective view of the collector body of
Fig. 13;
[0057] Fig. 15 is a top perspective view of other embodiments of
collector bodies;
[0058] Fig. 16 is a cross-section view of one of the collector bodies
of Fig. 15;
[0059] Fig. 17 is a perspective view of a vortex breaker;
[0060] Fig. 18 is a cross-section view of the vortex breaker of Fig.
17;
[0061] Fig. 19 is schematic view of an embodiment of a pre-treatment
site; and
[0062] Fig. 20 is schematic view of another embodiment of a pre-
treatment site.
DETAILED DESCRIPTION
[0063] Systems, processes, devices and techniques are described that
allow pre-
treating oil sands fine tailings in order to remove coarse debris prior to a
chemical
tailings treatment operation, such as chemical enhanced dewatering or other
processes.
[0064] There are provided pre-treatment screening techniques for
removing
coarse debris from oil sands fine tailings and produce screened oil sands fine
tailings,
the screened oil sands fine tailings having improved reactivity and/or
mixability with
chemicals in a subsequent chemical tailings treatment operation. The pre-
treatment
screening techniques may further produce screened oil sands fine tailings
thereby
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enabling to reduce or eliminate damage, clogging and/or plugging of downstream

equipment used in the chemical tailings treatment operation.
General pre-treatment screening assembly
[0065] The general structure of a pre-treatment screening assembly
configured to
remove coarse debris from oil sands fine tailings as well an example of a
method for
removing debris from oil sands fine tailings are disclosed in the above-
mentioned
patent No. 2,772,053.
[0066] Referring to Figs. Ito 6, a known pre-treatment screening
assembly 100 as
disclosed in particular in Canadian Patent No. 2,772,053 is configured for
receiving
debris containing oil sands fine tailings and for removing coarse debris from
an oil
sands fine tailings fluid. The oil sands fine tailings are for instance
retrieved from a
tailings pond 202. An oil sands fine tailings fluid that is pumped from the
tailings pond
202 by means of a dredge or barge typically includes various kinds of debris.
Still
referring to Figs. 1 to 6, the pre-treatment screening assembly 100 generally
includes a
frame 102, at least one spillbox feed tank 110 mounted to the frame 102, at
least one
screening device 140 in fluid communication with the spillbox feed tank 110
and at
least one collector body 160.
[0067] The oil sands tailings fluid is fed to the pre-treatment
screening assembly
100 through an inlet line 104, which is connected to the spillbox feed tank
110. The
spillbox feed tank 110 then discharges the tailings fluid onto the screening
device 140.
The screening device 140 has a screening surface 142 that is configured to
separate
coarse debris from the tailings fluid, thereby producing a screened tailings
fluid which
flows through the screening surface 142 and coarse debris that are retained by
the
screening surface 142. The screened tailings fluid is collected by the
collector body
160. The screened tailings fluid may contain material with a predetermined
size
enabling the material to flow through the screening surface 142 of the
screening device
140 toward and into the collector body 160. The screened tailings fluid
collected in the
collector body 160 may then be sent to a discharge line 108 for downstream
chemical
tailings treatment operations that may include, for instance but without being
limitative,
flocculation and dewatering.
[0068] Some improvements relative to the different components of the
pre-
treatment screening assembly 100 will now be described; the improvements can
either
be considered separately or be combined together.
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Spillbox feed tank implementations
[0069] Referring now more particularly to Figs. 7 to 9, the spillbox
feed tank 110,
which is configured to feed the oil sands fine tailings fluid to the screening
device 140,
includes a tailings inlet 112, a tank cavity 114 defined by side walls 116 and
a bottom
wall 118, and an overflow weir 120. The oil sands fine tailings fluid is fed
into the tank
cavity 114 via the tailings inlet 112 and flows upward into the tank cavity
114 until
reaching the overflow weir 120, at which point the tailings fluid flows over
the overflow
weir 120 and down onto the screening device 140.
Tailings inlet formed in the bottom wall of the spillbox feed tank
[0070] In the exemplary embodiment of the spillbox feed tank 110 from
Fig. 8, the
tailings inlet 112 is formed in the bottom wall 118, for example substantially
centrally. In
the existing spillbox feed tank 110' represented for instance in Fig. 7, the
tailings inlet
112' is formed in one of the side walls 116' of the spillbox feed tank 110' so
that, when
a tailings fluid flow is introduced into the tank cavity 114' via the tailings
inlet 112', the
tailings fluid flow rebounds on the side wall opposed to the one in which the
tailings
inlet 112' is formed. This existing spillbox feed tank geometry creates an
uneven flow
distribution across the screening surface of the screening device when the
tailings fluid
flows over the overflow weir onto the screening surface. Such an arrangement
of the
tailings inlet 112' may not be satisfactory since it can lead to an overload
of one side of
the screening surface, resulting in high losses of the fine tailings fluid
running off of the
screening device on this side.
[0071] On the contrary, in the spillbox feed tank 110 represented in
Fig. 8, in which
the tailings inlet 112 is formed in the bottom wall 118 of the spillbox feed
tank 110, for
instance centrally in the bottom wall 118, the flow bias is significantly
reduced in
comparison with the spillbox feed tank 110' of Fig. 7, resulting in an
improved
screening of the tailings fluid. In the spillbox feed tank of Fig. 8, the
tailings fluid defines
a substantially vertical flow in the tank cavity 114 when introduced therein
via the
tailings inlet 112. The tailings fluid may then be discharged uniformly onto
the
screening surface 142 of the screening device 140. As a result, the used
surface area
of the screening surface 142 is increased in comparison with the spillbox feed
tank 110'
of Fig. 7, the tailings fluid overflow is reduced and thus the screening
capacity of the
pre-treatment screening assembly 100 comprising the spillbox feed tank 110 of
Fig. 8
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is improved in comparison with a pre-treatment screening assembly comprising
the
spillbox feed tank 110' of Fig. 7.
Dimensions of the overflow weir being narrower than dimensions of the
screening surface
[0072] As represented for instance in Fig. 4, the screening device 140
has an
upstream inlet 144, the tailings fluid flow being discharged onto the
screening surface
142 of the screening device 140 over the overflow weir 120 of the spillbox
feed tank
110 at the upstream inlet 144. As represented for instance in Fig. 9, the
screening
device 140 has a plurality of substantially parallel screening bars that are
spaced apart
from each other so as to define openings on either side of each screening bar.
The
screening device 140 also includes a plurality of supporting bars forming
boundaries of
the screening surface 142. The supporting bars are arranged so that the
screening
surface 142 of the screening device 140 is substantially rectangular and
defines a
length L1 and a width L2, whereas the overflow weir 120 of the spillbox feed
tank 110
defines a width W, as it is represented for instance in Figs. 2 and 9.
[0073] In some existing embodiments of the pre-treatment screening
assembly,
the width of the overflow weir substantially corresponds to the width of the
screening
surface, so that a significant quantity of the tailings fluid that is
discharged from the
spillbox feed tank on the screening device is in fact discharged on the
supporting bars
of the screening device, and thus is discharged outside the screening surface,
i.e.
outside the collector body 160. This results in significant amounts of the
tailings fluid
that are not screened by the pre-treatment screening assembly. In the shown
embodiment, as represented for instance in Fig. 9, the overflow weir 120 is
dimensioned so that its width W is narrower than the width L2 of the screening
surface
142. To this end, baffle plates 124 may be arranged in the tank cavity 114 of
the
spillbox feed tank 110, substantially parallel to the side walls 116, so as to
the reduce
the width W of the overflow weir 120 over which the tailings fluid is
discharged at the
upstream inlet 144 of the screening device 140. In some embodiments, the width
W of
the overflow weir 120 represents less than 90% of the width L2 of the
screening
surface 142.
[0074] In some other embodiments, the width W of the overflow weir 120

represents less than 85% of the width L2 of the screening surface 142. In yet
other
embodiments, the width W of the overflow weir 120 represents less than 80% of
the
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width L2 of the screening surface 142. As the width W of the overflow weir 120
is
reduced relative to the width L2 of the screening surface 142, the losses of
the tailings
fluid (i.e. the amount of the tailings fluid being discharged outside the
screening surface
142 of the screening device 140, and thus outside the collector body 160) are
reduced,
and thus the capacity of the pre-treatment screening assembly 100 is increased

compared to the pre-treatment screening assemblies in which the width of the
overflow
weir substantially corresponds to the width of the screening surface.
Control and regulation devices
[0075] As detailed above, the tailings fluid is fed into the tank
cavity 114 of the
spillbox feed tank 110 via the tailings inlet 112 and then flows over the
overflow weir
120 and down to the screening device 140 from the upstream inlet 144 (which
corresponds to an upper edge of the overflow weir 120). Referring to Fig. 4
the pre-
treatment screening assembly 100 may further comprise adjustable valves 113,
121
configured to cooperate respectively with the tailings inlet 112 and with the
overflow
weir 120. The spillbox feed tank 110 may further comprise a level sensor 126,
as
represented in Fig. 4, the level sensor 126 being configured to measure the
tailings
fluid level in the tank cavity 114 of the spillbox feed tank 110.
[0076] For instance but without being limitative, the level sensor 126
comprises
two distinct pressure transmitters that are arranged in the tank cavity 114
and that
measure the pressure of the tailings fluid at two distinct locations of the
tank cavity 114.
On the basis of a pressure difference between pressures measured by the two
distinct
pressure transmitters, the level sensor 126 determines the level of the
tailings fluid in
the tank cavity 114. For instance, the level sensor 126 can use the following
principle:
P=d*g*h, where P is the pressure difference between two vertical positions of
a fluid, d
is the density of the fluid, g is the gravitational constant and h is the
distance between
the two vertical positions at which the pressures of the fluid are measured,
to determine
the level of the tailings fluid in the tank cavity 114. The adjustable valves
113, 121 can
be actuated in response to the tailings fluid level determined by the level
sensor 126.
[0077] For instance, when the determined level is above a first pre-
determined
threshold, at least one of the following actions may be undertaken:
- the adjustable valve 121 configured to cooperate with the
overflow weir 120
will be actuated so as to increase the tailings fluid flow rate at the
overflow
weir 120 that is discharged to the screening device 140; and
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- the adjustable valve 113 configured to cooperate with the tailings inlet 112

will be actuated so as to reduce the tailings fluid flow rate at the tailings
inlet
112.
[0078] To this end, the adjustable valve 113 can be designed to
cooperate with a
pump mounted in the inlet line 104 to feed the spillbox feed tank 110 with the
tailings
fluid.
[0079] On the other hand, when the tailings fluid level determined by
the level
sensor 126 is below a second pre-determined threshold, at least one of the
following
actions may be undertaken:
- the adjustable valve 121 configured to cooperate with the
overflow weir 120
will be actuated so as to reduce the tailings fluid flow rate at the overflow
weir 120; and
- the adjustable valve 113 configured to cooperate with the tailings inlet 112

will be actuated so as to increase the tailings fluid flow rate at the
tailings
inlet 112.
[0080] Cooperation between the level sensor 126 and the adjustable
valves 113,
121 is also particularly useful to ensure that transfer pumps of the pre-
treatment
screening assembly 100, are prevented from working when the tailings fluid
level in the
tank cavity and/or in the inlet line 104 is below a pre-determined threshold,
so as not to
damage the transfer pumps. The transfer pumps may serve for instance to feed
the
spillbox feed tank 110 with the tailings fluid, to discharge the tailings
fluid on the
screening surface 142 of the screening device 140 or to make the screened
tailings
fluid circulate in the discharge line 108.
Screening device implementations
[0081] Referring again to Fig. 4, the screening device 140 has an
upstream inlet
144 at which the tailings fluid is discharged from the spillbox feed tank 110,
over the
overflow weir 120. The screening device 140 further comprises a bottom end
146, as
represented for instance in Fig. 2. The bottom end 146 is designed to
accumulate the
coarse debris received and retained by the screening surface 142, and to
easily
remove the coarse debris towards a collection area 180. To enhance the
accumulation,
and thus the rejection, of the coarse debris, the screening surface 142 may be
inclined
downwardly so as to define a first inclination angle al with respect to a
horizontal
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direction; the first inclination angle al can range between 25 degrees to 45
degrees.
For instance, the first inclination angle al measures about 30 degrees.
Adjustable inclination of the screening surface
[0082] It should be noted that the first inclination angle al may be
adjustable so as
to adapt to the nature of the tailings to be screened or perform specific
operational
steps such as maintenance operations for instance. In the shown embodiment, as

represented for instance in Fig. 12, the pre-treatment screening assembly 100
further
comprises a winch 148 that is configured to adjust the first inclination angle
al formed
by the screening surface 142 relative to the horizontal direction. As a
result, it is
possible to adapt the arrangement of the screening surface 142 of the
screening device
140 so as to alternatively enable self-cleaning of the screening surface 142
or at least
ease the discharging of the coarse debris from the screening surface 142
towards the
collection area 180, or to reduce the tailings fluid losses resulting from a
running off of
the screening surface 142. In other words, it is understood that the screening
device
140 is designed to allow a user to reduce the first inclination angle al of
the screening
surface 142, if the coarse debris loading on the screening surface 142 is
insufficient
and/or if the tailings fluid losses are excessive. A user can also increase
the first
inclination angle al of the screening surface 142 so as to increase the self-
cleaning of
the screening surface 142, for instance under heavy debris loading or when it
is
considered that the amount of the coarse debris on the screening surface 142
has
reached a pre-determined threshold.
[0083] The pre-treatment screening assembly may further comprise a
sensor
designed to evaluate the quantity of coarse debris on the screening surface.
The pre-
treatment screening assembly could further comprise a control circuit
receiving a signal
from the sensor when the quantity of coarse debris on the screening surface
measured
by the sensor has reached a pre-determined threshold, the control circuit then

actuating the winch 148 as seen on Fig. 12 ¨ or any other adapted mechanical
device -
so as to increase the value of the first inclination angle al formed between
the
screening surface and the horizontal direction. The pre-treatment screening
assembly
could further comprise an additional sensor designed to evaluate the quantity
of tailings
fluid losses resulting from a running off of the screening surface; the
control circuit
could further be designed to receive a signal from the additional sensor when
the
quantity of tailings fluid losses has reached a pre-determined threshold, the
control
circuit then actuating the winch 148 as seen on Fig. 12 ¨ or any other adapted
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mechanical device - so as to reduce the first inclination angle al formed
between the
screening surface and the horizontal direction.
[0084] In another embodiment of the screening device 140 represented
for
instance in Fig. 10, the screening surface 142 could have a concave profile,
thereby
having a varying slope decreasing from a top end 147 of the screening device
140 to a
bottom end 146 of the screening device 140. For instance, the angle formed
between
the screening surface 142 and the horizontal direction can vary between 0
degree, at
the bottom end 146 of the screening device 140, and 80 degrees, at the top end
147 of
the screening device 140. The use of a concave profile for the screening
surface 142 is
particularly efficient for the automatic removal and/or accumulation of the
coarse debris
reaching the screening surface 142, without resulting from an increase of the
tailings
fluid losses resulting from a running off of the screening surface 142.
Mechanical cleaning device
[0085] In some implementations, as represented in Fig. 11, the pre-
treatment
screening assembly 100 further comprises a mechanical cleaning device 170 that
is
configured to mechanically remove the coarse debris from the screening surface
142 of
the screening device 140. The mechanical cleaning device 170 can regularly
remove
the coarse debris from the screening surface 142 and/or when the quantity of
the
coarse debris on the screening surface 142 has reached a pre-determined
threshold.
To this end, the mechanical cleaning device 170 can cooperate with the above-
mentioned control circuit and be actuated in response to a signal sent by the
above-
mentioned sensor that is designed to evaluate the quantity of the coarse
debris on the
screening surface 142. For instance but without being limitative, the
mechanical
cleaning device 170 comprises rakes and/or rotating brushes designed to go all
over
the screening surface 142 so as to pull the coarse debris away from the
screening
surface 142; for instance, the mechanical cleaning device 170 pulls the coarse
debris
toward the collection area 180.
[0086] In some implementations, as represented in Fig. 11, the
screening device
140 comprises an upper portion 150 having an upper screening surface 151, and
a
lower portion 152 having a lower screening surface 153. The upper screening
surface
151 defines an upper angle a2 with the horizontal direction and the lower
screening
surface 153 defines a lower angle a3 relative to the horizontal, the upper
angle a2
being greater than the lower angle a3. In some implementations, the upper
angle a2
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may be comprised between 30 degrees and 60 degrees, and the lower angle a3 may

be comprised between 15 degrees and 30 degrees. Optionally, the upper angle a2
may
be comprised between 40 degrees and 50 degrees, and the lower angle a3 may be
comprised between 20 degrees and 25 degrees. In some implementations, the
upper
angle a2 may be at least 1.5 times greater than the lower angle a3.
Optionally, the
upper angle a2 may be about two times greater than the lower angle a3.
[0087] The arrangement of the upper and lower portions 150, 152 of the
screening
device 140 enables to efficiently separate the liquids from the coarse debris
of the
tailings fluid, and to direct the coarse debris towards the lower portion 152,
so as to
ease their removal from the screening device 140. As represented in Fig. 11,
the
mechanical cleaning device 170 can be arranged on the lower portion 152 of the

screening device 140, so that the dimensions of the mechanical cleaning device
170
are reduced with regards to a screening device 140 having one single
inclination angle
relative to the horizontal direction, in which case the mechanical cleaning
device 170
would be dimensioned to go all over the screening surface 142. As represented
for
instance in Fig. 11, the mechanical cleaning device 170 can comprise at least
one rake
171 to remove coarse debris from the lower screening surface 153 of the lower
portion
150. The rake 171 may be mounted on a caterpillar 191 to automatically remove
coarse debris from the screening surface 142 of the screening device 140. The
mechanical cleaning device 170 may further comprise a shaker (not illustrated
in Fig.
11) designed to make the screening surface 142 vibrate so as to more easily
accumulate the coarse debris, and then to more easily remove them.
Debris collection bin
[0088] In some existing embodiments of the pre-treatment screening
assembly,
the coarse debris that are removed from the screening device are rejected in
the
tailings pond, such a coarse debris management requiring in particular from
the
screening device to be close to the tailings pond. As it is represented for
instance in
Fig. 4, the pre-treatment screening assembly 100 further comprises a debris
collection
bin 172 that is placed, for instance and without being limitative, under or in
the vicinity
of the screening device 140, so as to collect the coarse debris that are
removed from
the screening surface 142, for instance by the above described mechanical
cleaning
device 170. The coarse debris that are collected in the debris collection bin
172 can
then be hauled away at an appropriate dump location, so as to permanently be
removed from the tailings pond 202 and to reduce their long-term impact on the
tailings
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fluid dredging. The dimensions of the debris collection bin 172 are adapted so
that the
debris collection bin 172 will only need to be emptied, for instance, a few
times a
month.
[0089] Still referring to Figure 4, the pre-treatment screening
assembly 100 can
also comprise a debris heater 173 designed to heat the debris collection bin
172 so
that its content will not freeze, which would make it more complex for the
coarse debris
to be removed from the debris collection bin 173. The pre-treatment screening
assembly 100 can further comprise a debris collection pump 174, as represented
in
Fig. 4, that is designed to pump the tailings fluid from the debris collection
bin 172 and
to inject it back into the spillbox feed tank 110. The debris collection bin
172 and the
debris collection pump 174 enable to increase the quantity of the tailings
fluid that is
processed by the pre-treatment screening assembly 100.Moreover, the use of the

debris collection bin 172 enables to reduce constraints relative to the
location of the
screening device 140 close to the tailings pond 202, for debris removal
purposes.
Collector body implementations
[0090] As mentioned above, after the oil sands fine tailings fluid has
been
discharged at the upstream inlet 144 of the screening device 140, the screened
oil
sands fine tailings fluid is collected by the collector body 160. The
collector body 160
may be sized and configured to enable the flow of the screened tailings fluid
to
accumulate and form a more uniform composition of the screened tailings. Thus,
for
instance, fluctuations in the composition of the tailings retrieved from the
tailings pond
202 can be attenuated both by the removal of the coarse debris via the
screening
device 140 and also by the accumulation of the screened tailings fluid having
greater
uniformity than the tailings fluid piped from the tailings pond. In the shown
embodiment,
the collector body 160 has side walls 162 and a bottom wall 164 that define
together a
collecting cavity 166.
Design of the collector body
[0091] As represented in Figs. 1 to 6, the bottom wall 164 of the
collector body 160
may comprise a bottom discharge opening 165 designed to collect and easily
remove
debris, such as sand particles, that build up in the collector body 164 and
that have not
been removed by the screening device 140. The collector body 160 may be
designed
to favor the accumulation of debris near the bottom discharge opening 165, in
order to
ease their removal outside the collector body 160.The collector body 160 may
therefor
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have a bottom conical shape or, as represented for instance in Fig. 4, at
least one
sloped side wall 163 extending from one of the side walls 162. The sloped side
wall
163 may extend between one of the side walls 162 and the bottom wall 164.
[0092] In some other embodiments, as represented for instance in Figs.
15 and
16, the sloped side wall 163 extends only partially between two opposed side
walls
162, a substantially horizontal portion 181 extending between the sloped side
wall 163
and the side wall 162 opposed to the one from which the sloped side wall 163
extends.
In another embodiment, as represented in Fig. 16, the sloped side wall 163 is
oriented
at an inclination angle a4 with respect to the horizontal direction, the
inclination angle
a4 being comprised between 15 degrees and 75 degrees. Optionally, the
inclination
angle a4 is comprised between 30 degrees and 60 degrees. Further optionally,
the
inclination angle a4 is comprised between 40 degrees and 50 degrees.
[0093] In order to further ease the removal of the debris via the
bottom discharge
opening 165, and as it represented for instance in Fig. 3, the collector body
160 can be
elevated so that an operator can easily reach the bottom discharge opening
165, in
order to open it for removing the built-up debris. In the shown embodiment,
the frame
102 of the pre-treatment screening assembly 100 has an elevated structure, for
the
bottom discharge opening 165 of the collector body 160 to be more easily
accessible
by the operator.
Air reduction in the screened tailings
[0094] Referring to Fig. 2, the screened tailings fluid collected in
the collecting
cavity 166 of the collector body 160 is then released from the collector body
166
through at least one discharge outlet 167 that may be located in the bottom
wall 164 or
in a bottom portion of one of the side walls 162 of the collector body 160 and

connected to the discharge line 108. The discharge line 108 then sends the
screened
tailings fluid to further treatments, such as flocculation and dewatering of
the screened
tailings. The pre-treatment screening assembly 100 comprises at least one
discharge
pump 109 to make the screened tailings fluid circulate in the discharge line
108. In
some pre-treatment screening assemblies, air may be trapped within the
screened
tailings fluid flow, when the screened tailings fluid falls through the
screening device.
The formed air pockets sometimes disrupt operation of the pre-treatment
screening
assembly, for instance by disrupting the working of the discharge pump.
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[0095] So as to reduce the negative impact of the air mixing on the
pre-treatment
of the tailings, as represented in Fig. 1, the discharge outlet 167 may be
arranged in
one of the side walls 162 of the collector body 160 that extends
perpendicularly to the
upstream inlet 144 of the screening device 140 and perpendicularly to the
width L2 of
the screening surface 142. Moreover, the screening device 140 may comprise an
overflow weir 169 designed so that only top level screened tailings fluid is
collected in
the collecting cavity 166 of the collector body 160, and that less air is
transferred to the
collector body 160. As represented in Figs. 13 and 14, the pre-treatment
screening
assembly 100 comprises at least one deflector plate 168 arranged in the
collecting
cavity 166, for instance above the discharge outlet 167, so as to reduce the
circulation
of air in the discharge line 108. It should be understood that the deflector
plate 168 can
also contribute to the accumulation of the debris close to the bottom
discharge opening
165 of the collector body 160.
[0096] In an embodiment, the deflector plate 168 is oriented at an
inclination angle
a5 with respect to the horizontal direction, the inclination angle a5 being
comprised
between 20 degrees and 60 degrees. Particularly, the inclination angle a5 may
be
comprised between 30 degrees and 50 degrees. As represented in Fig. 16, the
pre-
treatment screening assembly 100 further comprises a vortex breaker 161
mounted in
an opening formed in one of the side walls 162 of the collector body 160 and
extending
at least partially in the collecting cavity 166. As represented for instance
in Figs. 16 to
18, the vortex breaker 161 comprises a substantially cylindrical body 190 and
a vortex
breaking core 192 arranged in the cylindrical body 190. In the shown
embodiment, the
vortex breaking core 192 has a crossed-shaped section: the vortex breaking
core 192
comprises two plates 194, 195 assembled together in a substantially
perpendicular
way, the two plates 194, 195 being secured to the cylindrical body 190.
Pre-treatment screening assembly implementations
[0097] It should be understood that the present description is not
limited to a pre-
treatment screening assembly 100 comprising solely one spillbox feed tank 110,
one
screening device 140 and one collector body 160, the different elements being
mounted to the frame 102. Indeed the pre-treatment screening assembly 100 may
include a plurality of screening devices mounted adjacently and operating in
parallel
with respect to each other. As represented for instance in Figs. 1 and 2, the
pre-
treatment screening assembly 100 may include four spillbox feed tanks 110,
each
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spillbox feed tank 110 having an overflow weir 120 for discharging a tailings
fluid flow
on a corresponding screening device 140.
[0098] The pre-treatment screening assembly 100 can have one single
collector
body 160 arranged below the different screening devices 140, or there may be
one or
more collector bodies 160 for each overlying screening device 140. In the
embodiment
of the pre-treatment screening assembly 100 comprising a plurality of
collector bodies
160, each collector body may have a discharge outlet 167, or the pre-treatment

screening assembly 100 may have a possibly larger single discharge outlet 167.
It is
thus possible to form the single discharge outlet 167 in one of the side walls
162 or
bottom walls 164 of the collector bodies 160 so as to adapt the pre-treatment
screening
assembly 100 to the location where it is installed.
Optimization of the pre-treatment screening assembly design
[0099] As represented in Fig. 5, in order to improve the operation of
the pre-
treatment screening assembly 100, said assembly 100 may include platforms,
stairways and railings 106 which allow an operator to easily and safely
monitor the pre-
treatment screening assembly 100, for example to monitor the screening
surfaces 142.
In some embodiments, as represented in Figs. 1 and 2, platforms 106 are
arranged
between two adjacent screening devices 140. When the pre-treatment screening
assembly 100 comprises four screening devices 140 arranged substantially
parallel to
each other, as represented in Fig. 5, the pre-treatment screening assembly 100
thus
comprises two substantially parallel platforms 106.
[00100] In some other embodiments, as represented in Fig. 5, the pre-
treatment
screening assembly 100 comprises one single platform 106 extending along the
four
screening devices 140, and outwardly from a respective longitudinal end 149 of
the
screening devices 140. This arrangement of the platform 106 enables to
increase the
dimensions of the screening surfaces 142 of the two adjacent screening devices
140
compared to an embodiment wherein the pre-treatment screening assembly 100
includes platforms 106 which are arranged between two adjacent screening
devices
140. Other arrangements of the platform 106 may be conceived within the
framework
of the present disclosure; for instance, the platform 106 may be arranged so
as to
overhang the screening devices 140. As represented in Fig. 1, the screening
devices
140 may comprise each an access door 157, for instance to let a user easily
access
the screening surface 142, to clean and/or repair it, whenever needed.
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[00101] In the embodiment of the pre-treatment screening assembly 100
in which
the platforms 106 are arranged between two adjacent screening devices 140, as
represented in Figs. 1 and 2, the access doors 157 of the two adjacent
screening
devices usually face each other, on each side of the corresponding platform
106. In the
embodiment of the pre-treatment screening assembly 100 comprising one single
platform 106, as represented in Fig. 5, the access doors 157 of the screening
devices
140 may be arranged at the corresponding longitudinal end 149 at which the
sole
platform 106 extends. In the embodiment of the pre-treatment screening
assembly 100
in which the platforms 106 do not extend between two adjacent screening
devices 140,
the dimensions of the screening surfaces 142 of the screening devices 140 may
be
increased. The overall screening surface of the pre-treatment screening
assembly 100
may thus be increased, and so is the pre-treatment capacity of the pre-
treatment
screening assembly 100.
Plurality of adjustable overflow weirs
[00102] In the shown embodiment from Figs. 1 and 2, the pre-treatment
screening
assembly 100 comprises a plurality of spillbox feed tanks 110, each of them
having an
overflow weir 120. In some embodiments, the overflow weirs 120 of the spillbox
feed
tanks 110 are adjustable and configured to ensure that the different spillbox
feed tanks
110 of the pre-treatment screening assembly 100 have a substantially similar
outlet
flow that is discharged on the corresponding screening device 140. In
particular, the
adjustable overflow weirs 120 may be adjustable according to an elevation of
each
spillbox feed tank 110 relative to the ground on which the frame 102 is
located. In other
words, the adjustable overflow weirs 120 enable to compensate for differences
in the
elevation of the different spillbox feed tanks 110. The adjustability of the
overflow weirs
120 may be implemented in different manners. For instance, the spillbox feed
tanks
110 may have a mounting base 130, the spillbox feed tanks 110 being mounted to
the
frame 102 of the pre-treatment screening assembly 100 via their respective
mounting
base 130. The mounting base 130 may be adjustable so as to adjust the
elevation of
the overflow weir 120.
[00103] Alternatively, the overflow weirs 120 of the spillbox feed
tanks 110 may
comprise adjustable plates that are configured to modify the elevation at
which the
tailings fluid flow will flow out of the tank cavity 114 of the spillbox feed
tank 110. It is
thus understood that the adjustable overflow weirs 120 of the spillbox feed
tanks 110
allows to more evenly discharge the tailings fluid flow on the screening
surface 142 of
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the different screening devices 140, thus improving the capacity and
efficiency of the
pre-treatment screening assembly 100.
Pre-treatment site implementations
[00104] In another aspect, there is provided a pre-treatment site for
the pre-
treatment of fine tailings, comprising several pre-treatment screening
assemblies
arranged close to a tailings pond. As represented in Fig. 19, an existing pre-
treatment
site 200' comprises six pre-treatment screening assemblies 100', each of them
having
four screening devices 140'. The four screening devices 140' of each pre-
treatment
screening assembly 100' are substantially parallel to each other so that each
pre-
treatment screening assembly 100' has a substantially rectangular shape with a
long
side 11' and a small side 12', the small side 12' of the assembly 100'
corresponding
substantially to a length of the screening devices 140. Moreover, the six pre-
treatment
screening assemblies 100' of the pre-treatment site 200' represented in Fig.
19 are
arranged side by side along their long side 11', so that the twenty-four
screening
devices 140 are arranged in a substantially parallel manner along the tailings
pond
202.
Optimized footprint pre-treatment site
[00105] The pre-treatment site 200 represented in Fig. 20c0mprise5
three pre-
treatment screening assemblies 100, each of them having four screening devices
140.
Each pre-treatment screening assembly 100 has a substantially rectangular
shape with
a long side 11 and a short side 12, the four corners of the rectangular being
constituted
by the four screening devices 140. The three pre-treatment screening
assemblies 100
are arranged side by side, their long sides 11 being substantially parallel to
each other.
The footprint of the pre-treatment site 200 represented in Fig. 20 is thus
significantly
reduced compared to the footprint of the existing pre-treatment site 200' as
represented in Fig. 19. Furthermore, thanks to an increase of the efficiency
of the pre-
treatment screening assemblies 100, the efficiency of the disclosed pre-
treatment site
200 of Fig. 20 is substantially identical or greater than the efficiency of
the existing pre-
treatment site 200' of Fig. 19.
[00106] Moreover, among many significant advantages, the reduced
footprint of the
pre-treatment site 200 compared to the pre-treatment site 200' of Fig. 19
enables to
reduce the dimensions of the inlet line 104 of the different pre-treatment
screening
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assemblies 100. Less collection areas 180 and/or less debris collection bins
172 for the
collecting of the coarse debris are also required.
Method implementations
[00107] In another aspect, there is provided a method for screening
debris from an
oil sands fine tailings fluid to pre-treat the oil sands fine tailings fluid
for chemical
treatment, such as flocculation and dewatering. The oil sands fine tailings
fluid comes
from an inlet line 104. The pre-treatment screening is enabled by one or more
of the
above-described assemblies, systems and devices.
[00108] The method includes providing a spillbox feed tank 110 with a
tailings fluid
flow, the spillbox feed tank 110 having side walls 116 and a bottom wall 118
defining
together a tank cavity 114, the spillbox feed tank 110 also comprising an
overflow weir
120. The method includes connecting the inlet line 104 to a tailings inlet 112
formed in
the bottom wall 118 of the spillbox feed tank 110 so as to form a
substantially vertical
inlet flow in the tank cavity 114. The method also includes feeding the
spillbox feed
tank 110 with the tailings fluid flow so that the tailings fluid flow reaches
the overflow
weir 120.
[00109] The method may further include adjusting at least one of the
inlet and outlet
flow rates of the tailings fluid flowing respectively to and from the spillbox
feed tank
110. In other words, the method may further include adjusting the flow rate of
the
tailings fluid introduced into the tank cavity 114 via the tailings inlet 112
and/or of the
tailings fluid going out of the tank cavity when flowing over the overflow
weir 120. It
should be noted that the adjustment may be performed in response to different
criteria,
including a measured fluid level in the tank cavity 114, a fluid losses
quantity of fluid
resulting from a running off of the screening surface 142, a measured amount
of coarse
debris on the screening surface 142, etc.
[00110] The method may thus further include measuring a level of the
ailing fluid in
the tank cavity 114. Measuring may include sensing the level of the fed
tailings with a
level sensor. Measuring may also be performed differently; for example it can
be
performed manually by an operator. Optionally, the level sensor may be
operatively
connected to a control circuit so as to monitor the level of tailings within
the tank cavity
114 and actuate certain devices, such as valves, to act in response to the
sensed level
when reaching given thresholds. The modification of the inlet and/or outlet
flow rates of
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the tailings fluid flow may be performed in response to the measured level of
the
tailings fluid in the tank cavity 114.
[00111] The method further comprises discharging the tailings fluid on a
screening
device 140, the tailings fluid being discharged over the overflow weir 120 and
down to
the screening device 140. The screening device 140 has a screening surface 142

configured to allow material with a predetermined size to flow through the
screening
surface 142 and separate the coarse debris, thereby splitting the tailings
fluid into
coarse debris and a screened tailings fluid. In some implementations, the
method may
include evenly discharging the tailings fluid flow along a width L2 of the
screening
device 140 so as to maximize a screening surface efficiency. Optionally, the
method
may include discharging the tailings fluid flow onto at most 80% of the width
of the
screening surface 142. Further optionally, the method may include discharging
the
tailings fluid flow onto at most 85% of the width screening surface 142. Still
further
optionally, the method may include discharging the tailings fluid flow onto at
most 90%
of the width screening surface 142. The method may further comprise removing
the
coarse debris from the screening surface 142.
[00112] As detailed above, the screening surface 142 is oriented at a first
inclination
angle al with respect to a horizontal direction. The method may further
comprise
adjusting the first inclination angle al of the screening surface 142.
[00113] The method may further comprise at least one of:
- measuring an amount of coarse debris on the screening surface 142;
- measuring a fluid level in the tank cavity 114; and
- measuring an amount of tailings fluid losses resulting from a running off
of
the screening surface 142.
[00114] For instance, the first inclination angle al of the screening
surface 142 may
be modified in response to at least one of the measured amount of coarse
debris, the
measured fluid level in the tank cavity and the measured amount of tailings
fluid losses.
The method may further comprise collecting the removed debris in a debris
collection
bin 172 which may be located near the screening device 140. The method may
further
comprise heating the debris collected in the debris collection bin 172. The
method may
further comprise pumping the tailings fluid contained in the debris collection
bin 172
back into the spillbox feed tank 110, so as to reduce the amount of oil sands
tailings
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fluid losses resulting from a running off of the screening surface 142.
Depending on the
time of the year, the pumping of the tailings fluid in the debris collection
bin 172 may be
performed with or without the heating of the debris collection bin 172.
[00115] The method may further comprise applying vibrations to the
screening
surface 142. Thanks to the vibrations, the coarse debris retained by the
screening
surface 142 may be more easily removed from the screening surface 142. The
method
may further include collecting the screened tailings fluid in a collector body
160 prior to
transporting the screened tailings fluid for chemical treatment via a
discharge line 108.
The collector body 160 may comprise a discharge outlet 167 connected to the
discharge line 108. The method may further include deflecting a screened
tailings fluid
flow upstream of the collector body 160 from the discharge outlet 167.
Deflection may
reduce the amount of air flowing with the screened tailings fluid flow in the
discharge
line 108.
[00116] The method may include providing a pre-treatment screening
assembly 100
comprising at least two spillbox feed tanks 110 having each a tank cavity 114.
The
method may include adjusting the outflow rate of the tailings fluid flow
discharged over
the overflow weir 120 of at least one spillbox feed tank 110 of the different
spillbox feed
tanks 110 to have a substantially similar outlet flow rate between the
different spillbox
feed tanks 110. Each overflow weir 120 defines a height relative to a ground
on which
the pre-treatment screening assembly 100 stands. The method may further
comprise
adjusting the height of at least one overflow weir 120 from the plurality of
spillbox feed
tanks 110 to obtain a substantially similar outlet flow rate between the
different spillbox
feed tanks 110. Each spillbox feed tank 110 defines a height relative to a
ground on
which the pre-treatment screening assembly 100 stands. The method may further
comprise adjusting the height of at least one spillbox feed tank 110 from the
plurality of
spillbox feed tanks 110 to have a substantially similar outlet flow rate
between the
spillbox feed tanks 110.
[00117] The steps of the method may be repeated or conducted for a
plurality of
pre-treatment screening assemblies 100 arranged in series or in parallel.
[00118] It should be understood that the pre-treatment screening
techniques
described herein provide screened tailings for improved and consistent mixing
with
chemicals in downstream tailings treatment operations.
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[00119] In some implementations, the pre-treatment screening assembly
removes
coarse debris that would impede or inhibit chemical reactions, for instance
flocculation
reactions involving flocculant and fine solid particles in the tailings. The
pre-treatment
process may remove coarse debris having different chemical or inertial
properties
compared to the fine solid particles that are not removed.
[00120] In certain applications, the fine solid particles include clay
and may have a
certain shape, size and surface characteristics that are considered for the
chemical
selection and process design for the chemical treatment operation, and can
bestow
certain macroscopic fluid properties. In one example, the pre-treatment
screening
assembly may remove bitumen masses including slugs or mats that negatively
affect
anionic polymeric flocculant reactions with the fine solid particles in the
tailings.
[00121] In some implementations, the pre-treatment screening assembly
removes
coarse debris that would have disrupted the mixing of the chemical additive
and the
fine tailings. For instance, the pre-treatment screening assembly may remove
coarse
debris that would impede consistent mixer performance or mixer flow regime.
The pre-
treatment screening assembly may also remove coarse debris that would cause
two
phase macroscopic fluid behaviour, thereby providing screened fine tailings
having one
phase macroscopic fluid behaviour. The pre-treatment screening assembly may
remove coarse debris so that the resulting pre-treated tailings fluid is
homogeneous, or
does not contain a substantial amount of settling solid particles. The pre-
treatment
screening assembly may also remove coarse debris that would complicate or
prevent
reliable process modelling of the fluid mixing, flocculation or dewatering
operations.
[00122] In some implementations, the pre-treatment screening assembly
removes
coarse debris that would damage or clog equipment.
[00123] While several implementations have been described and
illustrated herein
in relation to oil sands fine tailings, it should be understood that the
processes,
systems, devices and techniques may also be used for any other aqueous
suspensions
that include solid particles and coarse debris. Such aqueous suspensions may
comprise mining tailings resulting from mining operations, such as mature fine
tailings.
[00124] In the preceding description, the same numerical references
refer to similar
elements. Furthermore, for the sake of simplicity and clarity, not all figures
contain
references to all the components and features, and references to some
components
and features may be found in only one figure, and components and features of
the
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present disclosure which are illustrated in other figures can be easily
inferred
therefrom.
[00125] Finally, while the description and drawings describe and
illustrate certain
implementations and examples of the pre-treatment techniques, the components,
geometries, arrangements and/or configurations may have various other
characteristics, features and co-operations as those presented herein.
[00126] Several alternative embodiments and examples have been
described and
illustrated herein. The embodiments of the invention described above are
intended to
be exemplary only. A person of ordinary skill in the art would appreciate the
features of
the individual embodiments, and the possible combinations and variations of
the
components. A person of ordinary skill in the art would further appreciate
that any of
the embodiments could be provided in any combination with the other
embodiments
disclosed herein. It is understood that the invention may be embodied in other
specific
forms without departing from the central characteristics thereof. The present
examples
and embodiments, therefore, are to be considered in all respects as
illustrative and not
restrictive, and the invention is not to be limited to the details given
herein. Accordingly,
while the specific embodiments have been illustrated and described, numerous
modifications come to mind. The scope of the invention is therefore intended
to be
limited solely by the scope of the appended claims.
[00127] Any publications, including patents, patent applications and
articles,
referenced or mentioned in this specification are herein incorporated in their
entirety
into the specification, to the same extent as if each individual publication
was
specifically and individually indicated to be incorporated herein. In
addition, citation or
identification of any reference in the description of some embodiments of the
invention
shall not be construed as an admission that such reference is available as
prior art to
the present invention.
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Representative Drawing