Note: Descriptions are shown in the official language in which they were submitted.
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DEVICE AND METHOD FOR SCREENING PRE-TREATMENT OF OIL SANDS
TAILINGS
FIELD OF THE INVENTION
The invention generally relates to the field of oil sands tailings treatment.
More precisely,
it provides a device and a related method for screening coarse debris from oil
sands
tailings prior to the chemical treatment of these tailings.
BACKGROUND
Oil sand tailings are generated from hydrocarbon extraction process operations
that
separate the valuable hydrocarbons from oil sand ore. All commercial
hydrocarbon
extraction processes use variations of the Clark Hot Water Process in which
water is
added to the oil sands to enable the separation of the valuable hydrocarbon
fraction from
the oil sand minerals. The process water also acts as a carrier fluid for the
mineral
fraction. Once the hydrocarbon fraction is recovered, the residual water,
unrecovered
hydrocarbons and minerals are generally referred to as "tailings".
The oil sand industry has adopted a convention with respect to mineral
particle sizing.
Mineral fractions with a particle diameter greater than 44 microns are
referred to as
"sand". Mineral fractions with a particle diameter less than 44 microns are
referred to as
"fines". Mineral fractions with a particle diameter less than 2 microns are
generally
referred to as "clay", but in some instances "clay" may refer to the actual
particle
mineralogy. The relationship between sand and fines in tailings reflects the
variation in
the oil sand ore make-up, the chemistry of the process water and the
extraction process.
Conventionally, tailings are transported to a deposition site generally
referred to as a
"tailings pond" located close to the oil sands mining and extraction
facilities to facilitate
pipeline transportation, discharging and management of the tailings. Due to
the scale of
operations, oil sand tailings ponds cover vast tracts of land and must be
constructed and
managed in accordance with regulations. The management of pond location,
filling, level
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control and reclamation is a complex undertaking given the geographical,
technical,
regulatory and economic constraints of oil sands operations.
Each tailings pond is contained within a dyke structure generally constructed
by placing
the sand fraction of the tailings within cells or on beaches. The process
water,
unrecovered hydrocarbons, together with sand and fine minerals not trapped in
the dyke
structure flow into the tailings pond. Tailings streams initially discharged
into the ponds
may have fairly low densities and solids contents, for instance around 0.5-10
wt%.
In the tailings pond, the process water, unrecovered hydrocarbons and minerals
settle
naturally to form different strata. The upper stratum is primarily water that
may be
recycled as process water to the extraction process. The lower stratum
contains settled
residual hydrocarbon and minerals which are predominately fines. This lower
stratum is
often referred to as "mature fine tailings" (MFT). Mature fine tailings have
very slow
consolidation rates and represent a major challenge to tailings management in
the oil
sands industry.
The composition of mature fine tailings is highly variable. Near the top of
the stratum the
mineral content is about 10 wt% and through time consolidates up to 50 wt% at
the
bottom of the stratum. Overall, mature fine tailings have an average mineral
content of
about 30 wt%. While fines are the dominant particle size fraction in the
mineral content,
the sand content may be 15 wt % of the solids and the clay content may be up
to 75 wt%
of the solids, reflecting the oil sand ore and extraction process. Additional
variation may
result from the residual hydrocarbon which may be dispersed in the mineral or
may
segregate into mat layers of hydrocarbon. The mature fine tailings in a pond
not only has
a wide variation of compositions distributed from top to bottom of the pond
but there may
also be pockets of different compositions at random locations throughout the
pond.
In response to economic and environmental concerns, mature fine tailings need
to be
dewatered and solidified through chemical treatments. In order to optimize
these
chemical treatments, mature fine tailings need to be screened in order to
remove solid
particles with a large particle size.
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Several devices are used to remove large solid particles from oil sands
tailings, such as
basket filters or other conventional screening devices. Prior art devices
typically require
frequent cleaning and constant monitoring. Back flushing may also be needed.
Therefore, cleaning and back flushing activities lead to unplanned downtimes
for the
screening system.
In light of the aforementioned, there is a need for a new device and method
which would
be able to overcome at least some of the above-discussed drawbacks by
providing a
solution preventing less solid debris from plugging while requiring little to
no additional
maintenance or operations support.
SUMMARY OF THE INVENTION
The present invention responds to the above-mentioned need by providing a
screening
device and a method for screening coarse debris from oil sands tailings which
is an
improvement over known devices and/or methods.
More precisely, the present invention provides a screening device for
screening debris
from an oil sands tailings fluid flow coming from an inlet line to pre-treat
the oil sands
tailings fluid flow for chemical treatment. The screening device comprises a
screen
having a screening surface being configured to allow material with a
predetermined size
to flow through the screening surface and separate coarse debris, thereby
splitting the
tailings fluid flow into coarse debris and a screened fluid flow. The
screening device also
comprises a collector body having side walls extending from the screening
surface and
configured to receive the screened fluid flow for the chemical treatment.
According to one aspect of the screening device, the screening device may be
particularly suitable for mature fine tailings that need to be further
dewatered and dried.
According to another aspect of the screening device, the screen may comprise a
plurality
of screening bars. The screening bars may be parallel to one another and
spaced apart
from each other so as to define openings on either side of each bar, the
openings being
sized and shaped for only allowing the material of the predetermined size to
flow through
the screen towards the collector body.
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According to another aspect of the screening device, the screening bars may
have a
flow-facing surface and side surfaces extending from the flow-facing surface
with a
relieving angle for avoiding plugging of the screening surface with the coarse
debris.
According to another aspect of the screening device, the screening surface may
be
substantially parallel to the direction of the oil sands tailings fluid flow
along the inlet line.
According to another aspect of the screening device, the screening surface may
be open
to atmosphere and may comprise an operator platform connected to the collector
body
enabling an operator to clean the screening surface of some of the coarse
debris.
According to another aspect of the screening device, the collector body may
have a
bottom portion mounted on a skid such that the screening device is
relocatable. The
device may also comprise disconnection means for dismantling the screening
device into
a plurality of parts adapted for highway transport.
The present invention also provides a method for screening debris from an oil
sands
tailings fluid flow coming from an inlet line to pre-treat the oil sands
tailings fluid flow for
chemical treatment. The method comprises a step of passing the tailings fluid
flow
through a screen, the screen having a screening surface being configured to
allow
material with a predetermined size to flow through the screening surface and
separate
coarse debris, thereby splitting the tailings fluid flow into the coarse
debris and a
screened fluid flow. The method also comprises a step of collecting the
screened fluid
flow for further treatment.
While the invention will be described in conjunction with example embodiments,
it will be
understood that it is not intended to limit the scope of the invention to such
embodiments. On the contrary, it is intended to cover all alternatives,
modifications and
equivalents as may be included as defined by the present description. The
objects,
advantages and other features of the present invention will become more
apparent upon
reading of the following description and drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the screening device and the related method according to the
present
invention are represented in the following figures:
Figure 1 is a partially cut perspective view of a screening device according
to a preferred
5 embodiment of the present invention.
Figure 2 is a schematic drawing of a screen according to a preferred
embodiment of the
present invention.
Figure 3 is a cross-sectional view of a pair of screening bars according to a
preferred
embodiment of the present invention.
Figure 4 is a perspective view of a screening device according to another
preferred
embodiment of the present invention.
Figure 5 is perspective view of a screening device according to another
preferred
embodiment of the device shown on Figure 4.
Figure 6 is a schematic cross-sectional side view of a screening device
according to
another preferred embodiment of the present invention.
Figure 7 is a cross-sectional side view of an inlet line according to a
preferred
embodiment of the present invention.
Figure 8 is a top view of a screening device according to another preferred
embodiment
of the present invention.
Figure 9 is a top view of the screening device shown on Figure 8 according to
another
preferred embodiment of the present invention.
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Figure 10 is a partial schematic representation of a screening device
according to
another preferred embodiment of the present invention.
Figure 11 is a perspective view of a screen of the screening device shown in
Figure 6.
Figure 12 is a cross-sectional view of a bottom portion of the screen shown in
Figure 7.
Figure 13 is a cross-sectional view of a screening device according to another
preferred
embodiment of the present invention.
Figure 14 is a sectional view of the screening device shown on Figure 13.
Figure 15a is a transparent top view of a deflector spool according to another
preferred
embodiment of the present invention.
Figure 15b is a sectional view of the deflector spool shown on Figure 15a.
Figure 15c is a cross-sectional view of the deflector spool shown on Figure
15b.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, the same numerical references refer to similar
elements. The
embodiments, geometrical configurations, materials mentioned and/or dimensions
shown in the above-mentioned figures are preferred and given for
exemplification
purposes only.
Moreover, although the present invention was primarily designed for screening
of an oil
sands tailings fluid flow fluid, and especially for screening mature fine
tailings (MFT), it
may be used with other types of substance(s) and/or liquid(s), for other
purposes, and in
other fields, as apparent to a person skilled in the art. For this reason,
expressions such
as "device", "screening", "screen", "line", "pipe", "oil sands", "MFT", etc.
used herein
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should not be taken as to limit the scope of the present invention and
includes all other
kinds of items and/or applications with which the present invention could be
used and
may be useful.
Referring to Figure 1, the present invention provides a screening device (2)
for screening
debris from an oil sands tailings fluid flow. The oil sands tailings fluid
flow corresponds to
any tailings derived from oil sands extraction operations and may comprise
mature fine
tailings (MFT). MFT fluid flow that is pumped from a tailings pond by means of
a dredge
or barge typically includes various kinds of debris. The term "debris"
encompasses all
kind of debris such as sticks, mineral lumps, solids floating around in the
pond, bitumen
slugs, and the like, which typically need to be screened. The oil sands
tailings fluid flow
is provided to the screening device through an inlet line (4) which is located
above a
screen (6) and distributes the tailings fluid flow on to the screen (6). The
screen (6) has a
screening surface which is substantially parallel to the direction of the oil
sands fluid flow
coming from the inlet line (4). The screen (6) separates coarse debris from
the tailings
fluid flow, thereby producing a screened fluid flow which flows through the
screen (6) and
coarse debris rejected from the screen (6). The screened, fluid flow is
collected by a
collector body (8) having side walls extending from the screening surface of
the screen
(6). The screened fluid flow contains material with a predetermined size
enabling the
material to flow through the screen (6) towards the collector body (8). The
screened fluid
flow may then be sent to downstream chemical treatments which include
flocculation and
dewatering treatments, such as those described in Canadian patent application
Nos.
2.678.818, 2.684.232 and 2.701.317.
Referring to Figures 1 and 2, the screen comprises a plurality of screening
bars (10)
which are parallel to one another. They are spaced apart from each other so as
to define
openings (12) on either side of each supporting bar (10). The space between
each
screening bar is related to a maximum value of the predetermined size of the
material
which is allowed to pass through the screen (6). The screening bars may be
spaced
apart from each other with a distance ranging between about 1/2 inches and
about 2.5
inches. Preferably, they may be spaced apart with a distance of about %
inches. The
downstream chemical treatments determine the maximum value of the
predetermined
size of the material which passes through the openings (12) of the screen (6).
The
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maximum value preferably ranges between about 3 inches and about 4 inches. The
screening bars (10) have a length ranging between about 8 feet and 12 feet and
a width
ranging between about 0.5in and about 1.5 inches. Preferably, the width of the
top
surface of the screening bars is about 3 inches. The collector body (8) is
preferably a
tank having a rectangular or square shape with a width of 5 feet.
The screen (6) also comprises a plurality of supporting bars (14) which are
perpendicular
to the screening bars (10) and connected to a bottom surface of the screening
bars (10).
The screen (6) is of rectangular shape and comprises a bottom edge (16)
designed to
reject the separated coarse debris from the screen (6) towards a collection
area. To
enhance the rejection of the coarse debris, the screening surface is inclined
downwardly
with an angle with respect to the horizontal ranging between 25 to 45 , and
preferably
30 . It allows a pushing of the coarse debris down to the bottom edge (16) of
the screen
(6). The screening device is thereby preferably self-cleaned from coarse
debris and
operates continuously.
Figure 3 offers a cross-sectional view of a pair of screening bars for
illustrating a
preferred technical aspect in the design of the screening bars. Each screening
bar has a
flow-facing surface (18), a surface opposite to the flow-facing surface (19)
and side
surfaces (20) extending from the flow-facing surface (18) and converging
towards the
opposite surface inwardly with a relieving angle ranging from about 5 to about
20 .
Preferably, the flow-facing surface (18) is a top surface and the side
surfaces (20)
extend downwardly and inwardly from the top surface (18). The inward tapering
of the
side surfaces (20) provides a corresponding opening which is outwardly tapered
in the
downward direction. The flow-facing surface (18) of the screening bars is
therefore in
direct contact with the coarse debris (21) of the incoming oil sands tailings
fluid flow. The
space between each flow-facing surface (18) is related to the maximum value of
the
predetermined size of the material (22) which is allowed to pass between the
screening
bars (10). The presence of the relieving angle confers to the screen a
particular design
which decreases the risk of plugging up the screen (6) with coarse debris (21)
or
accumulation of material (22). However, in case of accumulation of material
and
plugging of the screen, an operator can perform a cleaning easily. Indeed, the
screening
surface is preferably open to atmosphere which allows an operator to have a
permanent
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view of the screen. It also enables a quick and easy access to the screening
surface for
performing a cleaning without requiring complex temporary dismantling of the
device.
Referring to Figure 1, the inlet line of the screening device comprises a main
inlet pipe
(22), a box conduit (24) extending from the main inlet pipe (22) and upstream
of the
screen (6). An adjustable deflector plate (26) extends from the box conduit
downwardly
with an angle towards the screening surface to ensure a deflection of the
debris towards
the screen (6). The main inlet pipe (22) is closable, preferably with a knife-
gate valve
(28) in order to stop the oil sands tailings fluid flow from reaching the
screen. This
closing may be useful during cleaning operations, for example.
Figure 4 further illustrates an embodiment of the present invention wherein
the screening
device comprises three screening devices as described above. Indeed, the
screening
device may comprise a plurality of screening devices mounted adjacently and
operating
in parallel with respect to each other.
Referring to Figures 4, 5 and 6, the screened fluid flow collected in the
collector body (8)
is released from the collector body through at least one discharge outlet (30)
located in a
bottom portion of the collector body (8) and connected to a discharge line
(32). The
discharge line (32) sends the screened fluid flow to further treatments, such
as
flocculation and dewatering of the screened tailings. To avoid an overflowing
of the
collector body (8), the screened fluid flow is released from the collector
body into an
overflow line (34) as soon as the flow reaches at least one overflow outlet of
the collector
body (8). As Figure 4 illustrates, the collector body may comprise two types
of overflow
outlets. A first pair of overflow outlets (35) may be localised in a bottom
portion of the
collector body (35) and a second overflow outlet (36) may be localised in a
top portion of
the collector body (8) in case of an excess rise of the screened fluid flow
level. The
collector body may further comprise a spillbox (37) cooperating with the
overflow line
(34) as shown on Figure 6. When the level of the screened fluid flow
increases, it may
reach a top end of the spillbox (37) and flow down into the spillbox (37). The
overflowing
screened fluid flow is released from the spillbox through the first pair of
overflow outlets
(36). If the level of the overflowing screened fluid flow rises too rapidly in
the spillbox
because the first pair of overflow outlets (35) is not sufficient to regulate
the fluid level,
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the second overflow outlet (36) is used to release the overflowing screened
fluid flow
from the spillbox (37).
As can be seen on Figures 4 and 5, in order to improve the operation of the
screening
device, the device also comprises an operator platform (38) which is useful to
an
5 operator for monitoring the screening surface and reacting in case of
plugging. The
screening surface is preferably surrounded with a side enclosure (40) which
extends
upwardly from the collector body (8) in order to avoid tailings splashing
laterally away
from the screening surface which could be harmful to an operator. The
screening device
may be further skid-mounted (42) and semi-mobile for enabling its lifting,
dragging and
10 relocation. Preferably, no single part of the screening device exceeds
dimensional
limitations for oversized highway transport. The screening device further
comprises
disconnection means for dismantling the screening device in order to be
adapted for
transportation.
Referring to Figure 7, the screening device comprises a removable wear plate
(44)
located preferably in the conduit box (24) for receiving the initial impact of
the oil sands
tailings fluid flow coming from the main inlet pipe (22). The flow rate of the
incoming oil
sands tailings fluid flow may be ranging from about 2500 USGPM to about 6000
USGPM
(from 568 m3.s 1 to about 1360 m3.s'1).
Figure 8 illustrates a screening device (103) according to another embodiment
of the
present invention enabling an "in-line" screening in a piping circuit. The in-
line screening
may be a y-joint arrangement (105) including an inlet line (107), and a
lateral branch line
(109). The expression "lateral" will refer to a pipe fitting which splits the
oil sands tailings
fluid flow into at least two directions. The branch line (109) defines an
inlet opening of
the inlet line (107).The branch line (109) may be a pipe acting as a collector
body as
mentioned above. The lateral branch line (109) forms a branching angle with
respect to
the inlet line (107), the branching angle being preferably about 45 degrees.
It is worth
mentioning that branching off the lateral branch line (109) from the inlet
line (107) can be
done in various ways. As can be easily understood by a person skilled in the
art, it may
be done via a conventional lateral pipe fitting or simply a y-joint.
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In this embodiment of the present invention, as illustrated on Figure 9, the
oil sands
tailings fluid flow is pressurized. The oil sands tailings fluid flow,
preferably mature fine
tailings fluid flow, is pumped from a tailings pond or holding tank into a
pipeline (111). It
is preferably pumped by means of a dredge in the tailings pond, more
preferably at a
rate of about 6000 gallons/minute. The pressurized mature fine tailings fluid
flow is
supplied through the pipeline (111) to a deflector spool (112) connected to
the inlet line
(107). The mature fine tailings fluid flow is screened from its coarse debris
through the
branch line (109) and is pumped with a pump for downstream chemical
treatments.
In one aspect of the in-line screening device (103), two types of screens may
be used.
Embodiments of the first type of screen are illustrated on Figures 10 to 12,
and
embodiments of the second type of screen are illustrated on Figures 13 and 14.
According to a preferred embodiment, referring to Figure 10, the screening
device (103)
further comprises an abutment flange (113) and a screen (115) corresponding to
the first
type of screen mentioned above. The abutment flange (113) is configured for
abutting
against a distal end (117) of the branch line (109). Flanges used for
connecting onto
corresponding y-fittings are well known in the art, and thus, need not to be
explained in
great detail herein, but it worth simply mentioning that according to a
preferred
embodiment, the abutment flange is preferably an ASTM 105 N class 150 blank
flange,
of suitable thickness, such as 1.5 inches for example. The abutment flange
(113) is
preferably in proportion with the y -joint arrangement (105) with which it is
intended to be
used. As a result, the diameter of the abutment flange (113) may vary in size
depending
on the inlet line (107) and corresponding branch line (109). The screen (115)
comprises
a least one supporting bar (119) having a distal extremity (121) extending
into a
screening bar (123). The screen may preferably comprise a plurality of
supporting bars
extending into a plurality of screening bars. The screening bars (123) and the
supporting
bars (119) may be preferably cylindrical. Each supporting bar (119) projects
from the
abutment flange (113) inwardly towards the inlet line (107) for supporting
each screening
bar (123) meant to be provided at a junction interface (125) between the inlet
line (107)
and the branch line (109). The screening bars (123) provide a screening
surface being
substantially parallel to a direction of mature fine tailings fluid flow along
the inlet line
(107). The screening surface is configured for preventing coarse debris (127)
contained
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in the incoming oil sands fluid flow, from flowing through the screening bars
(123) of the
screen (115) and into the branch line (109). A screened fluid flow is thereby
produced
and comprises material of a predetermined size allowed to flow through the
screening
bars (123). The screened fluid flow is preferably pumped into the branch line
(109). The
screen (110) and corresponding screening surface are configured so as to be
"flush"
along the inlet line (107), preferably along the junction interface (125), so
as to minimize
any interference with the pressurized oil sands fluid flow. The incoming oil
sands fluid
flow is thus split into a debris stream keeping flowing along the inlet line
(107) and a
screened fluid flow flowing along the branch line (109). The debris stream and
the
screened fluid flow preferably travel at rates of about 4000 gallons/minute
and about
2000 gallons/minute, respectively. As can be easily understood by a {person
skilled in the
art, the screening device (103) is preferably configured so that the screening
bars (123)
and corresponding screening surface do not protrude into the corresponding
inlet line
(107) so as to not cause any disturbance within the oil sands tailings fluid
flow and also,
so as to avoid any clogging or plugging of the inlet line (107). However, as
can be easily
understood by a person skilled in the art, the screening may be performed with
a plate
provided with a corresponding number of suitable screening holes, each being
shaped
and sized for carrying out a proper screening.
According to another preferred embodiment, Figure 11 illustrates screening
bars (123)
which define openings (129) on either side of each bar (123). The openings
(129) are
shaped and sized for preventing coarse debris (127) from entering the screen
(110) and
flowing down the branch line (109). Preferably, the screening device (103) may
comprise
an odd number of screening bars (123), in which case, the screen (110) would
comprise
a central screening bar (123c), and a suitable number of lateral screening
bars (123s),
depending on the total number of screening bars (123) intended to span along
the
junction interface (125) and the desired screening capability, as can be
easily
understood by a person skilled in the art. The central screening bar (123c)
may be
longer than the lateral screening bars (123s). The central screening bar
(123c) is
supported by a pair of first and second central supporting bars (119c), and
the lateral
screening bars (123s) are each supported by a corresponding pair of first and
second
lateral supporting bars (1 19s), at least one of the central supporting bars
(123c) being
different in length than at least one corresponding lateral supporting bar
(119s) so that a
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bend (131c) between the central screening bar (123c) and a corresponding
central
supporting bar (119c) be offset with respect to a given bend (131 s) between
an adjacent
lateral screening bar (123s) and a corresponding lateral supporting bar
(119s). The
screen (110) further comprises at least one supporting brace (133) mounted
across a
plurality of corresponding supporting bars (119) for providing reinforcement
to said
corresponding supporting bars (119). The supporting braces (133) are
preferably
provided at suitable locations along the supporting bars (119) for providing
additional
structural reinforcement and rigidity to the screen (110), and also to ensure
proper
positioning of the screening surface with respect to the junction interface
(125).
Figure 11 and 12 illustrate the abutment flange (113) according to an
embodiment of the
screening device. The abutment flange may comprise a ring (135) for mounting
onto the
corresponding distal end (117) of the branch line (109), as is well known in
the art, and
according to a preferred embodiment of the present invention, where the
extremities
(137) of the supporting bars (119) are welded onto an inner rim (139) of the
ring (135) of
the abutment flange (113). Preferably also, the abutment flange (113) is
provided with a
suitable fastening assembly for removably fastening the abutment flange (113)
onto the
distal end (117) of the branch line (109). For example, the fastening assembly
may
comprise at least one hole (141) for receiving a corresponding fastener
therethrough and
into a corresponding hub (143) of the branch line (109), as is well known in
the art.
Preferably also, the fastening assembly (47) comprises a plurality of holes
(141) radially
positioned about the abutment flange (113) in an equally spaced manner as
shown on
Figure 12.
According to another aspect of the in-line screening, a second type of screen
(115) is
provided. Referring to Figures 13 and 14, the plurality of screening bars
(123) may
extend over the inlet opening for preventing coarse debris flowing along the
inlet line
(107) from entering the branch line (109) through the inlet opening. Each
screening bar
(123) may be oriented substantially parallel to the direction of the oil sands
tailings fluid
flow along the inlet line (107). Preferably, each screening bar (123) may have
a
substantially rectangular section. More preferably, the screen (115) may
comprise a
central screening bar (123c), and a plurality of lateral screening bars (123s)
being
spaced apart from one another with a relieving angle with respect to the
central
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screening bar (123c). The adjacent screening bars (123) may diverge one from
another
along the direction of the oil sands tailings fluid flow along the inlet line
(107). Thereby,
the screen has a diverging configuration which avoids pinch points along the
direction of
fluid flow along the inlet line and therefore reduces the risks of plugging of
the screen
(115). Preferably, the central screening bar (123c) may be longer than the
lateral
screening bars (123s).
According to another preferred embodiment, the in-line screening device (103)
may
further comprise a backflushing line (143) and an inspection line (145) as
illustrated on
Figures 8 and 9. The backflushing line (143) may be preferably branched onto
the
branch line (109). During possible operation downtime, a cleaning fluid, such
as water,
may flow through the backflushing line (143) in an opposite direction from the
screened
fluid flow to clean (e.g. towards the inlet line (107)) for cleaning the
screen (115). The
screening device (103) may further preferably comprise an inspection line
(145). The
inspection line (145) may be branched onto the inlet line (107) for enabling
an inspection
of the screen (115). An operator may thus have the possibility to detect
plugging of the
screen or carry out troubleshooting tasks. The inspection line (145)
preferably provides
an access to the screen (115).
According to another embodiment of the screening device (103), a deflector
spool (112)
may be used upstream to the screen (115). As shown on Figure 15, the deflector
spool
(112) preferably comprises a plurality of fins (147) extending along the
deflector spool
(112) and forming a deflecting angle with respect to the inlet line (107). The
fins may
deflect the coarse debris of the incoming oil sands tailings fluid flow
towards the screen
(115) at the intersection of the branch line (109) and into the inlet line
(107).
According to another embodiment, the screening may be performed within the
screening
tank, the in-line screening device or a combination thereof.
The present invention also provides a method for screening debris from an oil
sands
tailings fluid flow coming from an inlet line to pre-treat the oil sands
tailings fluid flow for
chemical treatment, the screening being made according to the above-mentioned
embodiments of the screening device. The method comprises the step of passing
the
tailings fluid flow through a screen (6, 110), the screen having a screening
surface being
CA 02733873 2011-03-14
configured to allow material with a predetermined size to flow through the
screening
surface and separate coarse debris, thereby splitting the tailings fluid flow
into the coarse
debris and a screened fluid flow as better shown on Figure 1 and 6. The method
further
comprises a step of collecting the screened fluid flow in a collector body (8,
109) for
5 further chemical treatment. As previously mentioned, the oil sands tailings
fluid flow may
be a mature fine tailings fluid flow.
The method may further comprise a step of providing the oil sands tailings
fluid flow in a
direction substantially parallel to the screening surface along the inlet
line. The direction
of the incoming fluid flow has a considerable impact on the efficiency of the
screening.
10 The method may also comprise a step of deflecting the oil sands tailings
fluid flow
coming from the inlet line towards the screen. This deflecting may be
performed by the
adjustable deflector plate (26) in case of screening with the screening tank
as illustrated
on Figures 1 to 7. The deflecting may further be performed by the deflector
spool (112)
in case of the in-line screening as illustrated on Figures 8 to 15. According
to another
15 preferred embodiment, the method may comprise a step of rejecting the
coarse debris
from a bottom edge of the screen towards a collection area. Even if the screen
used in
the present method is a self-cleaning screen, a plugging with coarse debris
may occur.
That is the reason why the method may also comprise a step of closing the
inlet line
during cleaning operations of the screen.
According to another aspect of the method, a step of discharging the screen
fluid flow
from a bottom portion of the collector body into a discharge line may be
performed. A
further step of releasing the screen fluid flow from a top portion of the
collector body into
an overflow line may also be performed. The steps of the method may be
repeated for a
plurality of screens adjacent to each other and operating in parallel.
The description and drawings of the screening device and method are intended
to help
the understanding of the invention rather than to limit its scope. It will be
apparent to one
skilled in the art that various modifications may be made to the invention
without
departing from what has actually been invented.
