WO2012122646A1

WO2012122646A1 - Pre-treatment of fine tailings by coarse debris removal

Info

Publication number: WO2012122646A1
Application number: PCT/CA2012/050149
Authority: WO
Inventors: Jamie Eastwood; Kenneth John Willis; William Matthew Martin; Dwayne Edwards
Original assignee: Suncor Energy Inc.
Priority date: 2011-03-14
Filing date: 2012-03-13
Publication date: 2012-09-20
Also published as: CA2772053C; CA2733873A1; CA2772053A1

Abstract

Pre-treatment techniques for pre-treating aqueous suspensions including fine solid particles include coarse debris removal prior to a chemical treatment operation. The suspension may include or be mining tailings, which may include mature fine tailings. The mining tailings may be generated from oil sands mining. The pre-treatment may include screening the tailings to remove coarse debris that would interfere with the tailings chemical treatment. The screening may be done by a screening device including a screen having and a collector body receiving the screened fluid. The screening device may include a tank screen with an inclined screen surface or an in-line screen. Several screening devices may be incorporated into a pre-treatment installation to treat parallel streams of tailings. The pre-treatment may be performed to enhance mixing of a flocculent into the screened tailings, followed by flocculation and dewatering of the tailings.

Description

PRE-TREATMENT OF FINE TAILINGS BY COARSE DEBRIS REMOVAL FIELD OF THE INVENTION

The invention generally relates to the field of the treatment of mining tailings or other aqueous suspension including fine solid particles and coarse debris. BACKGROUND

Oil sand tailings are generated from hydrocarbon extraction process operations that separate the valuable hydrocarbons from oil sand ore. 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 sands 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. A tailings pond can be 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 can be primarily water that may be recycled as process water to the extraction process. The lower stratum can contain 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 mining industry. The composition of MFT 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 addition, certain aqueous suspensions and mining tailings, such as MFT, which are retrieved from ponds or holding areas include coarse debris. The nature of the coarse debris naturally depends on the origin of the given suspension or tailings. MFT includes coarse debris of different size, shape and chemical composition. For example, MFT may include coarse debris such as biomass like wood that may be in the form of sticks and the like; petrified matter such as petrified wood; mineral lumps; solids having a density light enough to float at or near the surface of the pond; glass; plastic; metal; bitumen globules, mats or slugs. The coarse debris found in other mining tailings may include similar debris as mentioned for MFT, with the exception of bitumen materials, and may also include other debris materials such as lumps of ore or other masses depending on the geology of the ore mine, the ore extraction processing technique, or the location of the tailings pond.

In addition, aqueous suspensions and mining tailings, such as MFT, may be dewatered and solidified through chemical treatments. One chemical treatment method employs flocculation for dewatering fine tailings such as MFT. A flocculent may be added to the tailings in order to induce flocculation and the flocculated material may be deposited or provided to dewatering devices to allow water release.

In the context of subjecting aqueous suspensions or fine tailings, such as MFT, to flocculation and dewatering, the presence of coarse debris can result in several disadvantages. Firstly, the presence of coarse debris affects the fluid dynamics of the system, resulting in a fluid having two phase macroscopic behaviour, which negatively impacts chemical addition, mixing, flocculation and the overall dewatering. In addition, since coarse debris most often have different chemical and surface properties compared to the fine solid particles, the chemical treatment can be disrupted or inhibited. Additionally, coarse debris may also accumulate in or plug the tailings treatment equipment such as pipelines, flocculent injection devices, flocculation vessels, and so on. SUMMARY OF THE INVENTION

The present invention provides processes, systems, devices and techniques for pre-treating oil sands mature fine tailings (MFT), and other mining tailings and aqueous suspension including fine solid particles, in order to remove coarse debris prior to chemical enhanced dewatering. In some implementations, there is provided a process for treating oil sands mature fine tailings (MFT), including: retrieving MFT from a tailings pond; pre- treating the MFT by: providing an MFT fluid flow; screening the MFT fluid flow by passing through a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the MFT fluid flow into coarse debris and a screened MFT fluid; and collecting the screened MFT fluid in a collector body; mixing a flocculent into the screened MFT fluid to produce a mixture; depositing the mixture at a deposition site to form a flocculated tailings deposit; and allowing water to release from the flocculated tailings deposit to form dried tailings material.

The step of retrieving the MFT may include dredging. The step of providing the MFT fluid flow may include pumping the MFT through a pipeline toward the screen. The pumping may induce shear thinning of the MFT fluid flow.

The process may further include splitting the MFT into multiple MFT fluid streams prior to the pre-treating step. The step of screening may include passing each of the MFT fluid streams through a corresponding screen arranged in parallel. The process may further include adjusting or controlling flow rates of the MFT fluid streams. The flow rates of the MFT fluid streams may be adjusted or controlled to be generally equal to each other. The splitting may be performed at a lower elevation and the MFT fluid streams are transported upward to a higher elevation for the screening step. The process may further include stopping flow of one of the MFT fluid streams; and allowing allocation of the stopped flow into the other MFT fluid flow streams. The process may include cleaning a pipeline in which MFT flow has been stopped; and/or cleaning a screen to which MFT flow has been stopped.

The screening step may include providing the MFT fluid flow from an upstream section toward a downstream section of the screen. The MFT fluid flow may be provided in a generally parallel direction with a surface of the screen. The screen may be downwardly inclined in the direction of the downstream section. The process may include deflecting at least part of the oil sands tailings fluid flow coming from an inlet line towards the screen. The process may include rejecting the coarse debris from a downstream edge of the screen. The process may include discharging a stream of the screened MFT fluid from a bottom portion of the collector body through a discharge line. The process may include releasing part of the screened MFT fluid from a top portion of the collector body through an overflow line. The process may include locating the screen proximate to a perimeter of the tailings pond. The process may also include depleting MFT inventory from the tailings pond; and relocating the screen proximate to a new location proximate a tailings pond having additional MFT. The process may further include distributing the MFT fluid flow over a width of the screen by overflowing the MFT fluid flow. The overflowing may include allowing the MFT fluid flow to travel upward through a container; and passing the MFT fluid flow over a weir positioned upstream of the screen. The process may also include distributing the MFT fluid flow over the screen by accelerating the flow prior to releasing the MFT fluid onto the screen. In some implementations, there is also provided a screening device including a screen having a screening surface configured to allow material with a predetermined size that is included in an oil sands tailings fluid flow to flow through the screening surface and separate coarse debris from the oil sands tailings fluid flow, thereby splitting the oil sands tailings fluid flow into coarse debris and a screened fluid; and a collector body having side walls extending from the screening surface and configured to receive the screened fluid for a chemical tailings treatment operation.

The oil sands tailings fluid may include or be mature fine tailings (MFT).

The screen may include a plurality of screening bars, the screening bars being 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 at most the predetermined size to flow through the screen into the collector body. The screening bars may be substantially parallel to one another. The screening bars may have a flow-facing surface and side surfaces, the side surfaces extending from the flow-facing surface inwardly with a relieving angle with respect to the flow-facing surface. The flow-facing surface may be a top surface facing upward and the side surfaces extend downwardly from the top surface. The relieving angle may ranges between about 5 degrees and about 20 degrees, or may be about 8 degrees. The screen is positioned and configured such that the openings between the screening bars are unblocked in an operable screening area of the screen. The screen may include a plurality of supporting bars, the supporting bars being perpendicular to the screening bars and connected to a bottom surface of the screening bars.

The screening bars may have a length ranging between about 8 feet and 12 feet. The screening bars may have a width ranging between about ½ inches and about 2 inches, or between about 5/8 inches and about 1 inch. The screening bars may be spaced apart from each other with a distance ranging between about ½ inches and about 2.5 inches, or between about 1 and 2 inches.

The screening surface may be of rectangular shape. The predetermined size of the material flowing through the screening surface may have a maximum value for enhancing a downstream flocculation and dewatering treatment of the screened oil sands tailings. The predetermined size of the material flowing through the screening surface may have a maximum value ranging between about ¼ inches and about 6 inches. The screening surface may also be substantially parallel to the direction of the oil sands tailings fluid flow expelled from the inlet line. The screening surface may be inclined downwardly with an angle with respect to the horizontal and sufficient to allow pushing of the coarse debris down the screen and rejection over a bottom edge of the screen. The screen may have a bottom edge arranged to allow the coarse debris to be rejected. The screening surface may be inclined downwardly with an angle ranging between about 25 degrees and about 45 degrees, or with an angle of about 30 degrees. The screening surface may also be open to atmosphere.

The screening device may also include an operator platform connected to the collector body enabling an operator to clean the screening surface of some of the coarse debris. The screening device may have a side enclosure extending upwardly around the screening surface for avoiding tailings splashing laterally away from the screening surface. The screening device may include a collection area collecting the coarse debris pushed down the screening surface. The inlet line may include a wear plate receiving an initial impact of the oil sands tailings fluid flow. The wear plate may be removable. The wear plate may be positioned and configured to deflect the oil sands tailings fluid flow toward the screen in a parallel trajectory with respect to the surface of the screen.

The inlet line may include a main inlet pipe providing the oil sands tailings fluid flow into an expanded conduit located upstream of the screen and setting the direction of the oil sands tailings fluid flow before contacting the screening surface. The expanded conduit may be a box conduit being sized and configured to reduce the velocity of the oil sands tailings flow in the main inlet pipe and distribute the oil sands tailings flow over the screen. The removable wear plate may be located inside the box conduit. Te main inlet pipe may have a knife-gate valve for throttling or stopping the oil sands fluid flow toward the corresponding screen.

The screening device may include a deflector plate extending above part of the screen to ensure a deflection of the debris towards the screen. The deflector plate may be adjustable at different angles with respect to the screen. The deflector plate may be positioned at a downward angle towards the screening surface.

The screening device may also include a discharge line connected to a discharge outlet of a bottom portion of the collector body and releasing the screened fluid flow out of the collector body through the outlet. The screening device may include an overflow line connected to an overflow outlet of a top portion of the collector body and collecting the screened fluid flow overflowing the collector body through the overflow outlet.

The collector body may include an overflow collector collecting the overflowing screened fluid flow, the overflowing screened fluid flow being released from the overflow collector through the overflow outlet into the overflow line. The collector body may have a bottom portion mounted on a skid such that the screening device is relocatable. The collector body may be a tank and the screen is positioned above or at an upper part of the tank. The inlet line of the screening device may be configured to provide the tailings fluid flow, which may be oil sands tailings fluid flow, at a flow rate ranging between about 568 m³.s^"1 and about 1360 m³.s^"1.

The collector body may include a branch line branched onto the inlet line and forming an inlet opening there-between, for enabling in-line screening. The branch line and the inlet line may be configured to form a branching angle with respect to each other. The branching angle may be inclined with the direction of flow in the inlet line. The branching angle may be about 45 degrees. The branch line may have a distal portion including an abutment flange. The abutment flange may be provided with a fastening assembly for removably fastening the screen thereto.

The screen may include a plurality of supporting bars, each supporting bar projecting from the abutment flange inwardly towards the inlet opening and along the branch line, each supporting bar being operatively connected to a corresponding screening bar of the screen for supporting the corresponding screening bar. Each screening bar may be oriented along the inlet opening. Each supporting bar may be operatively connected to each corresponding screening bar by a bend. Each screening bar and each supporting bar may be cylindrical. Each screening bar may be positioned at an angle of about 45 degrees with respect to the corresponding supporting bar. The screening bars may be of different length, and the supporting bars may be of different length. The screen may include a central screening bar, and a plurality of lateral screening bars, the central screening bar being longer than the lateral screening bars. Spacings between pairs of adjacent screening bars of the screen may be different. The screen may include at least one supporting brace mounted across a plurality of corresponding supporting bars for providing reinforcement thereto. Distal extremities of the supporting bars may be welded onto an inner rim of the abutment flange. The plurality of screening bars may also extend over the inlet opening, each screening bar being oriented substantially parallel to the direction of the oil sands tailings fluid flow along the inlet line. The screening bars may be configured with respect to the oil sands tailings fluid flow for preventing coarse debris entering the branch line through the inlet opening and deflecting the coarse debris downstream along the inlet line.

The screen may include a plurality of screening bars mounted to a perimeter of the inlet opening. The inlet line and the branch line may b e configured to be under fluid pressure.

The screen may also include a central screening bar, and a plurality of lateral screening bars being spaced apart from one another with a relieving angle with respect to the central screening bar, such that adjacent screening bars diverge one from another along the direction of the oil sands tailings fluid flow along the inlet line. The central screening bar may be longer than the lateral screening bars.

The screening device may include a backflushing line branched onto the branch line, the backflushing line enabling a backflushing fluid to flow through the screen from the branch line towards the inlet line to clean the screen. The screening device may include an inspection line branched onto the inlet line or the branched line, the inspection line being configured and located for enabling inspection of the screen, plugging detection, or access to the screen for maintenance.

The screening device may include a deflector provided in the inlet line upstream of the inlet opening and configured for deflecting the oil sands tailings fluid flow toward the inlet opening. The deflector may be a deflector spool. The deflector spool may include a plurality of fins defining a deflecting angle with respect to the inlet line for deflecting the oil sands tailings fluid flow and the coarse debris towards the screen. In some implementations, there is provided a screening device including: an abutment flange for abutting against a distal end of a branch line of a lateral pipe fitting of a fluid feed system having a substantially y-joint arrangement including a main line and the branch line for splitting a fluid flow of the fluid feed system into two directions; a supporting body projecting from the abutment flange inwardly towards the main line; and a screen provided on a distal extremity of the supporting body, the screen having a screening surface being substantially parallel to a direction of flow along the main line and configured for preventing debris of predetermined size from the fluid flow, from flowing through the screening surface of the screen and into the branch line.

The screen may include at least one screening bar defining openings on either side of each bar, the openings being shaped and sized for preventing debris of predetermined size from entering the screen and flowing down the branch line. The screen may include a plurality of screening bars, the bars being spaced apart from each other so as to define openings on either side of each bar, the openings being shaped and sized for preventing debris of predetermined size from entering the screen and flowing down the branch line. The screening device may be removably insertable into the branch line so that each screening bar of the screening device is positionable substantially parallel to the direction of flow along the main line. A substantially longitudinal opening may be defined between each pair of neighbouring screening bars. Each longitudinal opening may be substantially rectangular.

The screening device may be removably insertable into the branch line so that the screening surface of the screen extends substantially along a junction interface between the main line and the branch line.

The supporting body of the screening device may include at least one supporting bar, each supporting bar projecting from the abutment flange inwardly towards the main line and being operatively connected to a corresponding screening bar of the screen for supporting said corresponding screening bar. The supporting body may include a plurality of supporting bars, each supporting bar projecting from the abutment flange inwardly towards the main line and being operatively connected to a corresponding screening bar of the screen for supporting said corresponding screening bar. The supporting body may include at least one pair of supporting bars, each pair of supporting bars projecting from the abutment flange inwardly towards the main line and being operatively connected to a corresponding screening bar of the screen for supporting said corresponding screening bar. The supporting body may include a plurality of pairs of supporting bars, each pair of supporting bars projecting from the abutment flange inwardly towards the main line and being operatively connected to a corresponding screening bar of the screen for supporting said corresponding screening bar. Each screening bar of the screen is positioned at an angle of about 45 degrees with respect to a corresponding supporting bar. The screen may include screening bars of different length, and the supporting body may include supporting bars of different length. The screen may include a central screening bar, and a plurality of lateral screening bars, the central screening bar being longer than the lateral screening bars. The central screening bar may be supported by a pair of first and second central supporting bars, and wherein the lateral screening bars are each supported by a corresponding pair of first and second lateral supporting bars, at least one of the central supporting bars being different in length than at least one corresponding lateral supporting bar so that a bend between the central screening bar and a corresponding central supporting bar be offset with a bend between an adjacent lateral screening bar and a corresponding lateral supporting bar. The central screening bar may be made integral to a corresponding central supporting bar, and wherein each lateral screening bar is made integral to a corresponding lateral supporting bar. The screening bars and the supporting bars may be cylindrical. The spacing and the numbers of screening bars on the screening surface of the screen may be variable.

The screening device may include at least one supporting brace mounted across a plurality of corresponding supporting bars for providing reinforcement to said corresponding supporting bars. The abutment flange of the device may include a ring. Extremities of supporting bars of the supporting body may be welded onto an inner rim of the ring of the abutment flange. The abutment flange may be provided with a fastening assembly for removably fastening the abutment flange onto the distal end of the branch line. The fastening assembly may include at least one hole for receiving a corresponding fastener therethrough and into a corresponding hub of the branch line. The fastening assembly may include a plurality of holes radially positioned about the abutment flange in an equally spaced manner.

There is further provided a process for screening coarse debris from an oil sands tailings fluid flow coming from an inlet line to pre-treat the oil sands tailings fluid flow for a chemical tailings treatment operation, the process including: providing the oil sands tailings fluid flow to a screening device comprising a screen and a collector body; passing the oil sands tailings fluid flow through the screen, the screen having a screening surface configured to allow material with a predetermined size to flow through the screening surface and separate the coarse debris, thereby splitting the oil sands tailings fluid flow into a coarse debris fraction and a screened oil sands tailings fluid; and collecting the screened oil sands tailings fluid in the collector body fluid for the chemical tailings treatment operation.

The screening device may be as defined, described or illustrated here-above or herein.

The chemical tailings treatment operation may include a flocculation and dewatering treatment operation. The flocculation and dewatering treatment operation may include mixing a flocculent into the screened oil sands tailings fluid to produce a mixture; depositing the mixture at a deposition site to form a flocculated tailings deposit; and allowing water to release from the flocculated tailings deposit to form dried tailings material.

There is also provided a process for screening coarse debris from a tailings fluid flow coming from an inlet line to pre-treat the tailings fluid flow for a chemical tailings treatment operation, the process including: providing the tailings fluid flow to a screening device comprising a screen and a collector body; passing the tailings fluid flow through the screen, the screen having a screening surface configured to allow material with a predetermined size to flow through the screening surface and separate the coarse debris, thereby splitting the tailings fluid flow into a coarse debris fraction and a screened tailings fluid; and collecting the screened tailings fluid in the collector body fluid for the chemical tailings treatment operation.

The screening device may be as defined, described or illustrated here-above or herein. The chemical tailings treatment operation may include a flocculation and dewatering treatment operation. The flocculation and dewatering treatment operation may include mixing a flocculent into the screened tailings fluid to produce a mixture; depositing the mixture at a deposition site to form a flocculated tailings deposit; and allowing water to release from the flocculated tailings deposit to form dried tailings material.

There is also provided a process for screening coarse debris from an aqueous suspension coming from an inlet line to pre-treat the aqueous suspension for a chemical treatment operation, the process including: providing the aqueous suspension to a screening device comprising a screen and a collector body; passing the aqueous suspension through the screen, the screen having a screening surface configured to allow material with a predetermined size to flow through the screening surface and separate the coarse debris, thereby splitting the aqueous suspension into a coarse debris fraction and a screened aqueous suspension; and collecting the screened aqueous suspension in the collector body fluid for the chemical treatment operation.

The chemical treatment operation may include a flocculation and dewatering treatment operation. The flocculation and dewatering treatment operation may include: mixing a flocculent into the screened aqueous suspension to produce a mixture; depositing the mixture at a deposition site to form a flocculated deposit; and allowing water to release from the flocculated deposit to form dried material. There is also provided a pre-treatment screening installation including: a frame; a plurality of screening devices mounted to the frame and arranged in parallel operation with respect to each other for receiving an oil sands tailings fluid flow and producing a coarse debris fraction and a screened fluid; a header mounted to the frame and in fluid communication with the screening devices for providing the oil sands tailings fluid flow to each of the screening devices; and a collector body mounted to the frame and located for receiving the screened fluid.

Each of the screening devices of the installation may be as defined, described or illustrated here-above or herein. The header may include a main pipeline; a plurality of feed pipelines for respectively providing the oil sands tailings fluid flow to the screening devices; and a branching assembly for fluidly connecting the main pipeline to the plurality of feed pipelines. The branching assembly may be configured for providing parallel flows of the oil sands tailings fluid flow to from the main pipeline to the feed pipelines. The branching assembly may include a first pipeline division splitting the main pipeline into two primary parallel pipelines, and a pair of secondary pipeline divisions each splitting one of the primary parallel pipelines into two feed pipelines. The branching assembly may be located at ground level and the feed pipelines are configured to provide the oil sands tailings fluid flow to the screening devices at an elevated location. The header may also include regulating devices for regulating the oil sands tailings fluid flow through each of the feed pipelines.

The installation may include a spillbox feed tank positioned relative to a corresponding one of the screening devices for feeding the oil sands tailings fluid flow thereto. The spillbox feed tank may include side walls defining a cavity; an inlet provided in a lower portion of the side walls for receiving the oil sands tailings fluid flow from the header and allowing the oil sands tailings fluid to flow up through the cavity; and an overflow member provided in an upper portion of the side walls for allowing the oil sands tailings fluid to spill over and onto the screening device. The overflow member may include an elongated weir extending a width of the screen and proximate thereto. The spillbox feed tank may further include a flow enhancing component for accelerating the flow prior to releasing the fluid onto the screen to distribute the fluid over the screen. The flow enhancing component may b e configuration for reducing an area through which the oil sands tailings fluid flow pass proximate upstream of the screening device. The flow enhancing component may be configured to provide sufficient flow rate to facilitate self-cleaning of the screen. The flow enhancing component may be removably mounted with respect to the spillbox feed tank.

The is also provided a process for producing a dewatered oil sands tailings material, including: retrieving oil sands tailings from a tailings pond; pre-treating the oil sands tailings by: providing an oil sands tailings fluid flow; screening the oil sands tailings fluid flow by passing through a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the oil sands tailings fluid flow into the coarse debris and a screened oil sands tailings fluid; and collecting the screened oil sands tailings fluid in a collector body; mixing a flocculent into the screened oil sands tailings fluid to produce a flocculated mixture; and dewatering the flocculated mixture at a deposition site or in a mechanical dewatering apparatus, to form the dewatered oil sands tailings material.

The screening may be performed using a screening device as defined, described or illustrated here-above or herein. The screening may also be performed using a pre-treatment screening installation as defined, described or illustrated here-above or herein.

There is also provided a process for producing a dewatered mining tailings material, including: retrieving mining tailings from a tailings pond; pre-treating the mining tailings by: providing a mining tailings fluid flow; screening the mining tailings fluid flow by passing through a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the mining tailings fluid flow into the coarse debris and a screened mining tailings fluid; and collecting the screened mining tailings fluid in a collector body; mixing a flocculent into the screened mining tailings fluid to produce a flocculated mixture; dewatering the flocculated mixture at a deposition site or in a mechanical dewatering apparatus, to form the dewatered mining tailings material.

There is also provided a process for producing a dewatered aqueous suspension material, including: pre-treating an aqueous suspension by: providing an aqueous suspension fluid flow; screening the aqueous suspension fluid flow by passing through a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the aqueous suspension fluid flow into the coarse debris and a screened aqueous suspension; and collecting the screened aqueous suspension in a collector body; mixing a flocculent into the screened aqueous suspension to produce a flocculated mixture; and dewatering the flocculated mixture at a deposition site or in mechanical dewatering apparatus, to form the dewatered aqueous suspension material.

There is also provided a method of enhancing flocculation and dewatering of an aqueous suspension including fine solid particles, by pre-treatment of the aqueous suspension by removing coarse debris therefrom. The aqueous suspension may include or be mining tailings. The aqueous suspension may also include or be mature fine tailings, which may be oil sands mature fine tailings.

The removing of the coarse debris may be performed to produce a pre-treated aqueous suspension having one phase macroscopic fluid behaviour. The removing of the coarse debris may be performed to produce a pre-treated aqueous suspension that is homogeneous. The removing of the coarse debris may be performed by screening the aqueous suspension.

The dewatering may include deposition of the pre-treated aqueous suspension subsequent to flocculation thereof.

There is also provided a method of enhancing mixing of a chemical compound into an aqueous suspension including fine solid particles, by pre-treatment of the aqueous suspension by removing coarse debris therefrom so as to produce a pre-treated aqueous suspension having one phase macroscopic fluid behaviour.

The aqueous suspension may include or be mining tailings. The aqueous suspension may also include or be mature fine tailings, which may be oil sands mature fine tailings.

The removing of the coarse debris may also ne performed to produce a pre- treated aqueous suspension that is homogeneous. The removing of the coarse debris may also be performed by screening the aqueous suspension.

The chemical compound that is mixed with the pre-treated suspension may include or be a flocculent. The method may also include adding the flocculent to the pre-treated aqueous suspension in the form of an aqueous flocculent solution, in the form of flocculent particles, and/or in the form of a dispersion of flocculent particles in a liquid medium. The flocculent may include or be a water soluble polymer. The flocculent may also induce flocculation of the pre-treated aqueous suspension sufficient to enable dewatering thereof. The dewatering may include deposition of the pre-treated aqueous suspension subsequent to flocculation thereof.

There is also provided a screening device for screening coarse debris from an oil sands tailings fluid for pre-treatment prior to a chemical tailings treatment operation. The screening device includes an inlet line to provide a flow of the oil sands tailings fluid; a screen having a screening area receiving the flow of the oil sands tailings fluid from the inlet line and allowing screened oil sands tailings fluid to pass there-through and be separated from the coarse debris; a collector body for receiving the screened oil sands tailings fluid; and wherein the screen and the inlet line are sized, positioned and configured for displacing the coarse debris out of the screening area for self-cleaning of the screening area.

The screen may have a downward angle sloping away from the inlet line in the direction of the flow to facilitate displacement of the coarse debris out of the screening area.

The inlet line may be configured to provide a flow rate to facilitate displacement of the coarse debris out of the screening area. The inlet line may be configured to provide a flow direction to facilitate displacement of the coarse debris out of the screening area. The inlet line may be configured to provide a flow pattern to facilitate displacement of the coarse debris out of the screening area.

The screen may include a downstream edge positioned so that the coarse debris drops off of the screening area. The screen may include a smooth screening surface to facilitate displacement of the coarse debris out of the screening area. The screening area may include openings absent obstructions to facilitate displacement of the coarse debris out of the screening area. The screen may include screening bars defining openings there-between and having an orientation to facilitate displacement of the coarse debris out of the screening area. The screening bars may have an orientation that is generally parallel with respect to the flow of the tailings fluid. The screening bars may have a cross- sectional shape including a relieving angle to facilitate displacement of the coarse debris out of the screening area. There is also provided a method for in-line screening in a pipeline carrying a pressurized tailings fluid flow, the method including the steps of: pumping a flow of pressurized tailings fluid along a main stream of the pipeline from a upstream location to a downstream location; branching off a slip stream of pressurized tailings fluid away from the main stream along a given junction interface; and providing a screen at the junction interface for screening pressurized tailings fluid travelling through said junction interface in order to prevent undesirable debris of the pressurized tailings fluid flow from entering into the slip stream.

Step b) may include the step of branching off the slip stream of pressurized tailings fluid away from the main stream at an angle between about 30 degrees and about 60 degrees from the main stream. Step b) may include the step of branching off the slip stream of pressurized tailings fluid away from the main stream at an angle of about 45 degrees from the main stream.

The method may further include the step of: d) varying pressure conditions at the upstream location for varying slip stream conditions of the pressurized tailings fluid at the junction interface. Step d) is done by means of at least one valve gate, or another type of valve. The pressurized tailings fluid flow may include mature fine tailings.

Step a) may include the step of pumping a feed of mature fine tailings from a tailings pond into the pipeline by means of a dredge. Pumping may be done at a rate of about 6000 gallons/minute, and wherein pressurized tailings fluid flows along the main stream and along the slip stream at rates of about 4000 gallons/minute and about 2000 gallons/minute respectively.

There is also provided a kit including an abutment flange for mounting against a distal end of a branch line of a lateral pipe fitting of a fluid feed system having a substantially y-joint arrangement including a main line and the branch line for splitting a fluid flow of the fluid feed system into two directions; a supporting body mountable onto the abutment flange for projecting from said abutment flange inwardly towards the main line; and a screen mountable onto a distal extremity of the supporting body, so that once the screening device cooperates with the lateral pipe fitting, the screen has a screening surface being substantially parallel to a direction of flow along the main line and is configured for preventing debris of predetermined size from the fluid flow, from flowing through the screening surface of the screen and into the branch line. There is also included a method of screening coarse debris from an aqueous suspension including fine solid particles, including imparting shear thinning to the aqueous suspension to reduce the viscosity thereof prior to passing the shear thinned aqueous suspension through a screen to produce a screened aqueous suspension.

The aqueous suspension may include or be mining tailings. The aqueous suspension may include or be mature fine tailings, which may be oil sands mature fine tailings.

The shear thinning may at least partially be provided by a pump. The shear thinning may be at least partially provided by wall shear forces within a pipeline.

The screened aqueous suspension may be provided to a chemical treatment operation. The chemical treatment operation may include flocculation and dewatering. The flocculation and dewatering may include mixing a flocculent into the screened aqueous suspension that is also shear thinned. There is also provided a system for treating oil sands mature fine tailings (MFT), including: a retrieval assembly for retrieving MFT from a tailings pond; a fluid transportation assembly for providing an MFT fluid flow; a screening device for screening the MFT fluid flow, the screening device including: a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the MFT fluid flow into coarse debris and a screened MFT fluid; and a collector body for collecting the screened MFT fluid. The system also includes a mixer for mixing a flocculent into the screened MFT fluid to produce a mixture; and a deposition site for receiving the mixture, allowing formation of a flocculated tailings deposit and release of water from the flocculated tailings deposit to form dried tailings material.

The retrieval assembly may include a dredge. The fluid transportation assembly may include a pipeline and at least one pump. The screening device may be as defined, described or illustrated here-above or herein. The mixer may include an in-line pipe mixer. The deposition site may include a deposition cell, which may include or be formed of sand. The deposition cell may have a sloped bottom and side walls.

The system may also include a transportation pipeline receiving the mixture from the mixer and having an outlet for depositing the mixture onto the deposition site. The mixer and the transportation pipeline may be configured and operated so as to both provide mixing prior to deposition of the mixture to facilitate dewatering.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig 1 is a partial schematic representation of a pipeline carrying a fluid flow of fine tailings and being provided with a pipe fitting including a screening device.

Fig 2 is a perspective view of the screening device shown in Fig 1 .

Fig 3 is a side elevation view of a central component of the screening device of Fig 1 .

Fig 4 is a side elevation view of a lateral component of the screening device of Fig 1 .

Fig 5 is a side elevational view of yet another lateral component of the screening device of Fig 1 .

Fig 6 is a cross-sectional view of a bottom portion of the screening device shown in Fig 2. Fig 7 is a partial schematic representation of a pipeline carrying a fluid flow of fine tailings and being provided with a pipe fitting including a screening device.

Fig 8 is a perspective view of the screening device shown in Fig 7. Fig 9 is a side elevation view of a central component of the screening device of Fig 7.

Fig 10 is a side elevation view of a lateral component of the screening device of Fig 7. Fig 1 1 is a side elevation view of another lateral component of the screening device of Fig 7.

Fig 12 is a cross-sectional view of a bottom portion of the screening shown in Fig 7.

Fig 13 is a partial schematic representation of a pipeline carrying a fluid flow of fine tailings and being provided with a pipe fitting including a screening device.

Fig 14 is a perspective view of the screening device shown in Fig 13.

Fig 15 is a side elevation view of a central component of the screening device of Fig 13.

Fig 16 is a side elevation view of a lateral component of the screening device of Fig 13.

Fig 17 is a cross-sectional view of the screening device shown in Fig 14.

Fig 18 is a partially cut perspective view of a screening device.

Fig 19 is a schematic drawing of a screen.

Fig 20 is a cross-sectional view of a pair of screening bars. Fig 21 is a perspective front view of screening devices included in a screening installation. Fig 22 is perspective back view of the screening installation shown in Fig 21 .

Fig 23 is a schematic cross-sectional side view of part of the screening installation shown in Fig 21 .

Fig 24 is a cross-sectional side view of part of the screening installation shown in Fig 21 including a screening device.

Fig 25 is a top view of the pipeline arrangement of a screening device.

Fig 26 is a top view of the pipeline arrangement of a screening device shown in Fig 25 as well as additional pipes.

Fig 27 is a cross-sectional view of a screening device. Fig 28 is a sectional view of the screening device shown in Fig 27.

Fig 29 is a transparent top view of a deflector spool.

Fig 30 is a sectional view of the deflector spool shown in Fig 29.

Fig 31 is a cross-sectional view of the deflector spool shown in Fig 30.

Fig 32 is a perspective front view of two screening devices included in a screening installation.

Fig 33 is a perspective back view of the screening installation of Fig 32.

Fig 34 is a perspective view of a screening device shown in Fig 32.

Fig 35 is a side view of a header and collector body of a pre-treatment installation. Fig 36 is a perspective back view of a screening installation.

Fig 37 is a perspective front view of the screening installation of Fig 36.

Fig 38 is a close up side view of a flush nozzle part of the screening installation of Fig 36. Fig 39 is a perspective back view of a collector body with flush nozzles part of the screening installation of Fig 36.

Fig 40 is a perspective view of a collector box conduit.

Fig 41 is a perspective back view of a spillbox feed tank.

Fig 42 is a perspective front view of the spillbox feed tank of Fig 41 . Fig 43 is a perspective front view partial exploded schematic of parts of a pre- treatment installation with one spillbox feed tank.

Fig 44 is a perspective front view schematic of parts of a pre-treatment installation with two spillbox feed tank.

Fig 45 is a side view of a spillbox feed tank and a screening device. Fig 46 is a side view of a spillbox feed tank and a screening device with a suspension overflowing out over the screen.

Fig 47 is a side view of a spillbox feed tank and a screening device with an attachment.

Fig 48 is a perspective isolation view of a header. Fig 49 is a process block flow diagram. Fig 50 is a graph of yield stress versus time for suspension flocculation reaction stages.

Fig 51 is another graph of yield stress versus time for suspension flocculation reaction stages. Fig 52 is a side cut view of a flocculent addition and mixer system.

Fig 53 is a block flow process diagram showing a pre-treatment installation.

Fig 54 is another block flow process diagram showing a pre-treatment installation.

Fig 55 is another block flow process diagram showing a pre-treatment installation.

DETAILED DESCRIPTION OF THE INVENTION

Systems, processes, devices and techniques are described that allow pre- treating mining tailings in order to remove coarse debris prior to a chemical tailings treatment operation, such as chemical enhanced dewatering. In some implementations, there are pre-treatment screening techniques that remove coarse debris from raw or debris containing fine tailings and provide screened fine tailings with improved reactivity and/or mixability with chemicals in a subsequent chemical tailings treatment operation. The pre-treatment screening techniques may provide screened fine tailings to reduce or eliminate damage, clogging and/or plugging of downstream equipment used in the chemical tailings treatment operation.

The pre-treatment may remove the coarse debris from fine tailings by several different methods and devices, some of which are described and illustrated herein. The pre-treatment may remove the coarse debris using a screening device, which may be implemented in a variety of ways and may have various different constructions. For instance, the screening device may be an in-line screening device, an in-line grill screen device, an open tank screening device, or another screening device configuration. The screening device may also be associated with a fluid inlet system, a fluid outlet system, and a pre-treatment installation, some implementations of which are described below.

In some implementations, the pre-treatment is used to remove coarse debris from tailings generated in oil sands mining. For instance, oil sands tailings that have developed into mature fine tailings (MFT) may be pre-treated.

In-line screening In some implementations, the screening device is for use with a lateral pipe fitting of a fluid feed system, the lateral pipe fitting having a substantially Y-joint arrangement including a main line and a branch line for splitting a fluid flow of the fluid feed system into two directions. The screening device may include an abutment flange for abutting against a distal end of the branch line; a supporting body projecting from the abutment flange inwardly towards the main line; and a screen provided on a distal extremity of the supporting body, the screen having a screening surface being substantially parallel to a direction of flow along the main line and configuration for preventing debris of predetermined size from the fluid flow, from flowing through the screening surface of the screen and into the branch line.

There may also be a kit for assembling a screening device for use with the lateral pipe fitting of a fluid feed system. The kit may include an abutment flange for mounting against a distal end of the branch line; a supporting body mountable onto the abutment flange for projecting from said abutment flange inwardly towards the main line; and a screen mountable onto a distal extremity of the supporting body, so that once the screening device cooperates with the lateral pipe fitting, the screen has a screening surface being substantially parallel to a direction of flow along the main line and is configured for preventing debris of predetermined size from the fluid flow, from flowing through the screening surface of the screen and into the branch line.

In some implementations, there is a method for in-line screening of a pipeline carrying a pressurized fluid flow. The method may include pumping a flow of pressurized fluid along a main stream of the pipeline from a upstream location to a downstream location; branching off a slip stream of pressurized fluid away from the main stream along a given junction interface; and providing a screen at the junction interface for screening pressurized fluid travelling through said junction interface in order to prevent undesirable debris of the pressurized fluid flow from entering into the slip stream.

With reference to Figs 1 to 17, some implementations employing an in-line screen will be described below.

For convenience, the following list provides numerical references for some of the corresponding components illustrated in Figs 1 to 17:

1 . in-line screening device

2. in-line screening system

3. lateral pipe fitting

5. fluid feed system

7. main line

9. branch line

1 1 . fluid flow

13. abutment flange

15. distal end (of branch line 9)

17. supporting body

19. screen

21 . distal extremity (of supporting body 17)

23. screening surface

25. direction of flow 27. debris

29. screening bar

29c. central screening bar

29s. lateral screening bar

31 . opening

33. junction interface

35. supporting bar

35c. central supporting bar

35s. lateral supporting bar

37. bend

37c. central bend

37s. lateral bend

39. supporting brace

41 . ring (of abutment flange 13)

43. extremities (of supporting bars 35)

45. inner rim (of ring 41 )

47. fastening assembly

49. hole (of abutment flange 13)

51 . fastener

53. hub (of branch line 9)

55. pipeline

57. main stream

59. upstream location

61 . downstream location

63. slip stream

Θ. angle

The in-line screening system (2) includes a pipeline arrangement and an in-line screen device (1 ) provided within one of the pipes for allowing fine tailings to pass through the pipe while deflecting and thus preventing the coarse debris (27) from flowing with the screened fine tailings. In some implementations, pre-treatment of the fine tailings includes in-line screening of a fluid flow (1 1 ) of a pipeline (55) carrying mature fine tailings, for example. The pre-treatment may include in-line screening of a pipeline (55) carrying a pressurized fluid flow (1 1 ). The method may include the steps of: pumping a flow of pressurized fluid along a main stream (57) of the pipeline (55) from a upstream location (59) to a downstream location (61 ); branching off a slip stream (63) of pressurized fluid away from the main stream (57) along a given junction interface (33); and providing a screen (19) at the junction interface (33) for screening pressurized fluid travelling through said junction interface (33) in order to prevent coarse debris in the pressurized fluid flow from entering into the slip stream (63).

MFT feed may be pumped from a tailings pond by means of a dredge or submersible pump and includes coarse debris (27). The dredge may be equipped with a cutter head or the like. The in-line screening system allows increased pumping power utilization of the dredge or submersible pump through the in-line screening system.

Various methods or components could be used in order to branch off the slip stream (63) of pressurized fluid away from the main stream (57). For example, if components such as a Y-joint fitting (3) or a corresponding lateral, are used, as exemplified in Figs 1 , 7 and 13, then the branching off of the slip stream (63) away from the main stream (57) may be done at a suitable angle (Θ), between about 30 degrees and about 60 degrees from the main stream (57). The angle (Θ) may be about 45 degrees from the main stream (57), as exemplified for example in Figs 1 , 7 and 13. Other suitable ranges of angles (Θ) may be used with the in-line screening, depending on the particular applications. The lateral pipe fitting (3) may have a substantially Y-joint arrangement including a main line (7) and a branch line (9) for splitting the fluid flow (1 1 ) of the fluid feed system (5) into at least two directions.

Although an example of carrying out this in-line screening is performed with a lateral y-joint, an alternative way of carrying out the in-line screening method would be to provide two concentric pipes fluidly connected to one another via a corresponding junction interface (33), so that a slip stream (63) may be branched out from a given pipe to the other pipe via the junction interface (33), and providing the screen (19) along the junction interface (33). Thus, it may be appreciated that various ways of branching out a corresponding slip stream (63) from a main stream (57), while providing a screening surface (23) along the junction interface (33), may be done.

Because the in-line screening is intended to be done along a pressurized pipeline circuit, so as to benefit from the drawing capabilities offered by a pumping source, such as a dredge for example, which is typically used for pumping tailings and other suspensions from a pond prior to conveying the fluid flow towards a dewatering processing system, there may be a step of varying pressure conditions at the upstream location (59) for varying slip stream conditions of the pressurized fluid at the junction interface (33). Varying pressure conditions at an upstream location (59) of the pipeline (55) can, in turn, cause corresponding pressure variations in the corresponding branch line (9) of the Y-joint fitting (3), and thus affect the amount of fluid flow (1 1 ) which is screened through the corresponding junction interface (33). The fluid flow may be controlled in this manner. Various methods and devices could be used for varying pressure conditions at the upstream location (59), such as for example, a controllable pump, a throttling knife gate valve, a sacrificial knife gate valve, or any other suitable valve.

Pumping from the tailings pond may be done at a rate of about 6000 gallons/minute. The pressurized fluid flowing as the main stream (57) and along the slip stream (63) may travel at rates of about 4000 gallons/minute and about 2000 gallons/minute, respectively.

Referring to Figs 2, 8 and 14, the in-line screening device (1 ) may include an abutment flange (13), a supporting body (17) and a screen (19). The abutment flange (13) is configured for abutting against a distal end (15) of the branch line (9). Various type and configurations of flanges may be used for connecting onto corresponding Y-fittings. The abutment flange may be, for example, an ASTM 105 N class 150 blank flange, of suitable thickness, such as 1 .5 inches. The abutment flange (13) may be in proportion with the pipe fitting (3) with which it is intended to be used, and thus, with the corresponding pipeline (55) with which it is intended to be used. As a result, the diameter of the abutment flange (13) may vary in size depending on the pipe fitting (3) and corresponding pipeline (55).

Referring now to Figs 1 and 2, and corresponding Figs 7 and 8, as well as Figs 13 and 14, the supporting body (17) may project from the abutment flange (13) inwardly towards the main line (7) and is intended for supporting the corresponding screen (19), which is meant to be provided at the junction interface (33) between the main stream (57) and the slip stream (63). The screen (19) may be provided on a distal extremity (21 ) of the supporting body (17), the screen (19) having a screening surface (23) being substantially parallel to a direction of flow (25) along the main line (7) and configured for preventing the coarse debris (27) from flowing through the screening surface (23) of the screen (19) and into the branch line (9). The screening device (1 ) may be configured so that the screen (19) and corresponding screening surface (23) do not protrude into the corresponding pipeline (55) and corresponding fluid flow (1 1 ) so as to not cause disturbance within the flow and also so as to avoid clogging or plugging of the main fluid flow (1 1 ). Ideally, the screen (19) and corresponding screening surface (23) are configured so as to be "flush" or co- planar with the pipeline wall, or in this case, along the fitting inner wall, e.g. along the junction interface (33), so as to minimize interference with the main stream (57) of pressurized fluid flow (1 1 ). The screen (19) may include at least one screening bar (29) defining openings (31 ) on either side of each bar (29), the openings (31 ) being shaped and sized for preventing the coarse debris (27) from entering the screen (19) and flowing down the branch line (9).

Referring still to Figs 1 , 2, 7, 8, 13 and 14, the in-line screen (19) may include a plurality of screening bars (29), the bars (29) being spaced apart from each other so as to define openings (31 ) on either side of each bar (29). The openings (31 ) are shaped and sized for preventing the coarse debris (27) from entering the in-line screen (19) and flowing down the branch line (9) shown in Figs 1 , 7 and 13.

Referring to Figs 2, 8 and 14, the in-line screening device (1 ) may include an odd number of screening bars (29), whether one, three, five, seven or more. The in-line screening device (1 ) may also include an even number of screening bars (29), in which case, the screening device (1 ) may include a pair of central screening bars (29c), and a suitable number of lateral screening bars (29s), depending on the total number of screening bars (29) intended to span along the junction interface (33) and the desired screening capability.

The screening surface (23) and corresponding screening openings (31 ) may be provided by corresponding screening bars (29). However, various other suitable screening components or structures could be used for carrying out the same functions, that is, for preventing the coarse debris (27) from entering the screen (19) and flowing down into the branch line (9). For example, the screening surface (23) may include a plate provided with a corresponding number of suitable screening holes, each being shaped and sized for carrying out a proper screening.

Referring to Figs 1 , 7 and 13 by way of for example, the in-line screening device (1 ) may be removably insertable into the branch line (9) so that each screening bar (29) of the in-line screening device (1 ) is positionable substantially parallel to the direction of flow (25) along the main line (7). Indeed, the in-line screening device (1 ) may be configured so that the screening surface (23), provided about the distal extremity (21 ) of the supporting body (17), does not protrude into the main stream (57), so as to avoid disturbance of the fluid flow (1 1 ) and/or possible accumulation of coarse debris (27) due to such protrusion, and/or resulting clogging. The screening surface (23) of the in-line screen (19) may also be provided along the junction interface (33) between the main stream (57) and the slip stream (63), which in the case of a lateral pipe fitting (3), is the interface between the main line (7) and the branch line (9). Referring to Figs 2, 8 and 14, a substantially longitudinal opening (31 ) may be defined between each pair of neighbouring screening bars (29), and each longitudinal opening (31 ) may be of substantially rectangular shape.

The screening device (1 ) may be removably insertable into the branch line (9) at a location so that the screening surface (23) of the screen (19) extends substantially along a junction interface (33) between the main line (7) and the branch line (9).

In addition, referring to Figs 2, 8 and 13, the supporting body (17) may include at least one supporting bar (35), each supporting bar (35) projecting from the abutment flange (13) towards the main line (7) and being operatively connected to a corresponding screening bar (29) of the screen (19) for supporting the corresponding screening bar (29).

The supporting body (17) may include a plurality of such supporting bars (35), each supporting bar (35) projecting from the abutment flange (13) towards the main line (7) and being operatively connected to a corresponding screening bar (29) of the screen (19) for supporting the corresponding screening bar (29). The supporting body (17) may include at least one pair of supporting bars (35) for each corresponding screening bar (29). The supporting body (17) may include a plurality of such pairs of supporting bars (35), in order to define and constitute the supporting body (17), which may be of substantially cylindrical shape, and complementary to the shape of the branch line (9).

Given that the in-line screening device (1 ) may be used with a conventional Y- joint, such as a lateral pipe fitting (3), which typically includes a branch line (9) extending at an angle (e.g. 45 degrees) from its corresponding main line (7), each screening bar (29) of the in-line screen (19) may be shaped and positioned accordingly, that is, at a corresponding angle (e.g. 45 degrees) with respect to a corresponding supporting bar (35). However, it is worth mentioning that should the screening device (1 ) be used with other types of lateral pipe fittings (3) where the branch line (9) is disposed at another angle with respect to its main line (7), then accordingly, each screening bar (29) of the screen (19) would be positioned at a corresponding angle with respect to a corresponding support bar (35) so as to be complementary to the particular configuration of the given lateral pipe fitting (37) with which the screening device (1 ) is intended to be used.

Referring to Figs 2, 8 and 14, the in-line screening device (1 ) may include screening bars (29) of different lengths, so as to span across the junction interface (33) between the main line (7) and the branch line (9) of the lateral pipe fitting (3). The screening device (1 ) may include a central screen bar (29c) and a plurality of lateral screening bars (29s), the central screening bar (29c) being longer than the lateral screening bars (29s).

Referring to Figs 3-5, 9-1 1 and 15-16, the central screening bar (29c) may be supported by a pair of first and second central supporting bars (35c), and the lateral screening bars (29s) are each supported by a corresponding pair of first and second lateral supporting bars (35s), at least one of the central supporting bars (35c) being different in length than at least one corresponding lateral supporting bar (35s) so that a bend (37c) between the central screening bar (29c) and a corresponding central supporting bar (35c) be offset with respect to a given bend (37s) between an adjacent lateral screening bar (29s) and a corresponding lateral supporting bar (35s). This may also be appreciated with reference to Figs 2, 8 and 14.

The central screening bar (29c) may be integral with a corresponding central supporting bar (35c), and each lateral screening bar (29s) may also be integral with a corresponding lateral supporting bar (35s), that is, each supporting bar (35) may be integral (i.e. made of the same material and of the same piece) with its corresponding screening bar (29), so that a corresponding screening bar (29) supported by a corresponding pair of supporting bars (35) may be easily manufactured by a suitable process, such as by cutting, or by bending an elongated bar at appropriate locations so as to form a corresponding screening bar (29) with corresponding supporting bars (35). The screening bars (29) and the supporting bars (35) are variable, and the spacing and the numbers of screening bars (29) on the screening surface (23) of the in-line screening device (1 ) are variable depending on the particular applications for which the in-line screening device (1 ) is indented. The in-line screening device (1 ) includes at least one supporting brace (39) mounted across a plurality of corresponding supporting bars (35) for providing reinforcement to said corresponding supporting bars (35). The supporting braces (39) may be provided at suitable locations along the supporting body (17) for providing additional structural reinforcement to said supporting body (17) in order to maintain structural rigidity of the in-line screening device (1 ), and also to ensure proper positioning of the screening surface (23) with respect to the junction interface (33). The supporting body (17) of the in-line screening device (1 ) is not limited to supporting bars (35), and other suitable support supporting bodies (17) may be used for the present screening device (1 ), such as a rigid shell for example, or any other suitable device that would enable to support and position a given screen surface (23) along the junction interface (33) with respect to a corresponding base, such as the abutment flange (13).

Regarding the abutment flange (13), it may include a ring (41 ) for mounting onto a corresponding distal end (15) of the branch line (9) and, where bars (35) are used for the supporting bodies (17), extremities (43) of the supporting body (17) may be welded onto an inner rim (45) of the ring (41 ) of the abutment flange (13), as exemplified in Figs 6, 12 and 17.

Referring to Figs 1 -2, 7-8 and 13-14, the abutment flange (13) may be provided with a suitable fastening assembly (47) for removably fastening the abutment flange (13) onto the distal end (15) of the branch line (9). For example, the fastening assembly (47) may include at least one hole (49) for receiving a corresponding fastener there-through and into the corresponding hub (53) of the branch line (9). The fastening assembly (47) may include a plurality of holes (49) radially positioned about the abutment flange (13) in an equally spaced manner, as also shown in Figs 6, 12 and 17. In some implementations, there is a kit for assembling an in-line screening device (1 ) for use with the lateral pipe fitting (3) of a fluid feed system (5). The kit may include an abutment flange (13) for mounting against a distal end (15) of the branch line (9); a supporting body (17) mountable onto the abutment flange (13) for projecting from the abutment flange (13) inwardly towards the main line (7); and a screen (19) mountable onto a distal extremity (21 ) of the supporting body (17), so that once the in-line screening device (1 ) cooperates with the lateral pipe fitting (3), the in-line screen (19) has a screening surface (23) being substantially parallel to a direction of flow (25) along the main line (7) and is configured for preventing coarse debris (27) from the fluid flow (1 1 ), from flowing through the screening surface (23) of the screen (19) and into the branch line (9).

As touched on above, the screening bars (29) of the in-line screening device (1 ) should be configured and located so as to provide the desired screening. Spacing of the bars (29) may be variable depending on the amount of screening required while considerations for pressure drop may also be factored in. Providing the screening bars (29) attached to an open flange connection sized for the specific lateral fitting being used allows for efficient installation of the screening device (1 ). The screening device (1 ) may also be manufactured or constructed with dimensions to match the proposed lateral fitting (3). It can simply be installed by inserting the in-line screening device (1 ) into the branch outlet with the screen face aligning with the main line flow. The desired amount of screened fluid flow may be set by throttling a downstream gate valve on the main line which helps push more fluid through the branch. As coarse debris enters the lateral and is pushed into the branch, it is stopped by the screen face. Because the bars (29) on the screen face are preferably angled at about 45 degrees to the direction of fluid flow (1 1 ), debris being screened tends to slide off the bars (29) and continue down the main line (7), thus providing the present screening device (1 ) with a "self-cleaning" functionality.

In addition, the amount and spacing of the screening bars (29) may be variable depending on the known coarse debris size and type of debris that the downstream systems and equipment can tolerate. The considerations for the amount and spacing of the screening bars (29) may include the amount and nature of chemical additive for the downstream dewatering treatment, pipeline sizes, and the intermediary equipment such as booster pumps or instrumentations that may receive the screened flow of fine tailings.

The in-line screening method and system allows efficient use of the circulation capabilities of a pumping source, so as to extract MFT from a tailings pond.

The in-line screening device (1 ) can be installed as a take-off system. The majority of the fluid ends up passing on through the main line (7) and a smaller portion passing through the branch line (9). The amount of fluid flow (1 1 ) through the branch line (9) can be controlled by restricting the downstream end of the main line (7). For example, for a given amount of gallons per minute of screened fluid being needed, there is preferably at least twice the amount of gallons per minute available. Advantageously, the screening device (1 ) does not collect debris for disposal outside of the pipeline (55), but rather it prevents debris from entering the branch line (9) of a lateral fitting (3), and does so via a "self-cleaning" feature. The device (1 ) can be used in applications requiring coarse pipeline screening and is not specific to use with mature fine tailings, or any tailings reduction operations. It should also be noted that the main line (7) may have multiple branch lines (9) each having a corresponding in-line screening device (10).

The in-line screening described herein may be used for removing coarse debris from various suspensions that include fine solid particulates and coarse debris, including mining tailings such as mature fine tailings from oil sands processing. The in-line screening can also be used for other applications within the oil and gas industry or other industries such as waste water treatment, pulp and paper, as well as dredging projects related to ponds, spillways and man-made islands or waterfronts. The in-line screening device and corresponding parts may be made of substantially rigid materials, such as metallic materials (stainless steel, etc.), hardened polymers, composite materials, and/or the like. In some circumstances, other components may be made of suitably malleable and resilient materials, such as a polymeric material (plastic, rubber, etc.), and/or the like, depending on the particular applications for which the in-line screening device and resulting pipeline or fitting are intended for and the different parameters at play.

Some implementations of the in-line screening system and device allow various advantages, such as long running times with low interruption due to line plugging, low maintenance required due to self-cleaning enabled by the strategic positioning in the feed system and design simplicity not requiring moving parts and enabling simple installation. Other advantages include the low cost and easy manufacture of the system, which can be built in-house. Pre-treatment screening installation and tank screening

Referring to Figs 21 and 22, a pre-treatment screening installation (100) may be provided. The pre-treatment screening installation (100) includes at least one screening device (102) for receiving and removing coarse debris from fine tailings. The screening devices (102) may be constructed as tank screens that are open to the atmosphere and such devices may be referred to herein as "tank screens". The pre-treatment screening installation (100) may alternatively have screening devices (102) that are constructed and configured as "in line screens" that are described above. The screening device (102) described below mainly concerns the tank screening device, although some aspects may also be relevant and applicable to the in-line screening device.

Fig 18 illustrates in greater detail the screening device (102) for screening coarse debris from the aqueous suspension or fine tailings. In some implementations, the screening device (102) is employed for screening an oil sands tailings fluid flow, which may correspond to any tailings derived from oil sands extraction operations and may include or consist of mature fine tailings (MFT) that is retrieved from a tailings pond. MFT fluid flow that is pumped from a tailings pond by means of a dredge or barge typically includes various kinds of debris. The oil sands tailings fluid flow is provided to the screening device through an inlet line (104), which may be located above a screen (106) and distributes the tailings fluid flow on to the screen (106). The screen (106) has a screening surface that may be generally parallel to the direction of the oil sands fluid flow coming from the inlet line (104). The screen (106) separates coarse debris from the tailings fluid flow, thereby producing a screened fluid flow which flows through the screen (106) and coarse debris rejected from the screen (106). The screened fluid flow is collected by a collector body (108) having side walls extending from the screening surface of the screen (106). The screened fluid flow may contain material with a predetermined size enabling the material to flow through the screen (106) toward and into the collector body (108). The screened fluid flow may then be sent to downstream chemical tailings treatment operations that may include flocculation and dewatering, such as those described in any one of Canadian patent application Nos. 2,678,818, 2,684,232 and 2,701 ,317.

Referring to Figs 18 and 19, the screen includes a plurality of screening bars (1 10) which are parallel to one another. They are spaced apart from each other so as to define openings (1 12) on either side of each screening bar (1 10). The space between each screening bar is related to a maximum value of a predetermined size of the material which is allowed to pass through the screen (106). The screening bars may be spaced apart from each other with a distance ranging between about ½ inches and about 2.5 inches. For example, they may be spaced apart with a distance of about ¾ inches. The downstream chemical treatments and the nature of the tailings or suspension and other processing parameters, determine the maximum value of the predetermined size of the material that passes through the openings (1 12) of the screen (106). The maximum value may range between about 3 inches and about 4 inches. The screening bars (1 10) may have a length ranging between about 8 feet and 12 feet and a width ranging between about 0.5 inches and about 1 .5 inches. The width of the top surface of the screening bars may be about ¾ inches. The collector body (108) may take the form of a tank having a rectangular or square shape with a width of 5 feet.

The collector body (108) may be configured as single tank below multiple screens, or there may be one or more collector body (108) for each overlying screen. The collector body (108) may have a size and configuration to enable the flow of screened fine tailings to accumulate and form a more uniform composition of the fine tailings. Thus, fluctuations in the composition of the fine tailings retrieved from the tailings pond are attenuated both by removal of the coarse debris and also by accumulating a reservoir of screened fine tailings having greater uniformity than the fine tailings piped from the pond.

The screening bars may be straight and parallel with the direction of fluid flow. It may be challenging to manufacture screening bars with ideal straightness out of metal and thus alternative materials, such as rigid polymeric materials, maybe used. Bar straightness improves the consistency of the screening. In addition, eliminating any cross-bars that are not parallel with flow direction allows reducing or eliminating accumulation of debris and the formation of debris berms that must be removed and can cause downtime. In some implementations, the surface of the screen that is functional and in contact with the fine tailings has no cross bars or other elements that would cause accumulation of debris or berm formation. It should also be noted that configurations and constructions of the screening bars for the screening tank device may also be used for other screening devices such as the in-line or grill screening devices. The screen (106) also includes a plurality of supporting bars (1 14) that may be generally perpendicular to the screening bars (1 10) and connected to a bottom surface of the screening bars (1 10). Alternatively, the screening bars (1 10) may be configured and constructed using appropriate materials with sufficient rigidity to avoid support bars, which may enhance the flow of the tailings over the screen to improve debris separation. Materials that may be used for high rigidity include rigid polymeric materials. The screen (106) may be of rectangular shape and include a bottom end (1 16) designed to reject the separated coarse debris from the screen (106) towards a collection area. To enhance the rejection of the coarse debris, the screening surface may be inclined downwardly with an angle with respect to the horizontal ranging between 25 degrees to 45 degrees, e.g. around 30 degrees. This allows a pushing of the coarse debris down to the bottom end (1 16) of the screen (106). The screening device (102) is thereby preferably self-cleaned from coarse debris and operates continuously.

Fig 20 offers a cross-sectional view of a pair of screening bars (1 10). Each screening bar may have a flow-facing surface (1 18), a surface opposite to the flow-facing surface (1 19) and side surfaces (120) extending from the flow-facing surface (1 18) and converging towards the opposite surface inwardly with a relieving angle ranging from about 5 degrees to about 20 degrees. The flow- facing surface (1 18) may be a top surface and the side surfaces (120) extend downwardly and inwardly from the top surface (1 18). The inward tapering of the side surfaces (120) provides a corresponding opening which is outwardly tapered in the downward direction. The flow-facing surface (1 18) of the screening bars is therefore in direct contact with the coarse debris (121 ) of the incoming tailings fluid flow. The space between each flow-facing surface (1 18) is related to the maximum value of the predetermined size of the material (122) which is allowed to pass between the screening bars (1 10). The presence of the relieving angle provides to the screen a functionality that decreases the risk of plugging up the screen (106) with coarse debris (121 ) or accumulation of passable material (122). However, in case of accumulation of material and plugging of the screen, an operator can perform a cleaning easily. Indeed, the screening surface may be open to the atmosphere, which allows an operator to have a permanent view of the screen. It also enables a quick and easy access to the screening surface for cleaning without requiring temporary dismantling of the device.

Referring to Fig 18, the inlet line (104) of the tank screening device (102) may include a main inlet pipe (122), a box conduit (124) extending from the main inlet pipe (122) and upstream of the screen (106). An adjustable deflector plate (126) extends from the box conduit (124) downwardly with an angle towards the screening surface to ensure deflection of the coarse debris towards the screen (106). The deflector plate (126) may be sized and configured to deflect and channel flow away from the screen discharge over a debris berm that may form in order to facilitate keeping the area clean and prevent fluid from saturating the tank base.

The main inlet pipe (122) may be closable, e.g. with a knife-gate valve (28), in order to slow or stop the oil sands tailings fluid flow from reaching the screen. This closing may be useful during cleaning operations, for example. The box conduit (124) or another type of conduit may be configured and sized such that the outlet fine tailings cover a substantial portion of the screen surface area, for instance the entire width of the screen, to increase efficient utilization of the screen surface. The box conduit (124), which may also be referred to as an inlet chute, may also be seen in Fig 40.

In some implementations, the inclination of the inlet chute (124) and the screen (106) may be coordinated to enhance the distribution over the screen. For example, the inlet chute may have a steeper angle than the screen, for example by 3 degrees to 10 degrees, or by about 5 degrees. By providing a steeper angle, the flow of tailings can be further projected onto the screen, but not so much as to risk plugging the screen. The inlet chute and the screen may alternatively have the same angle.

Referring briefly to Figs 32 and 33, the pre-treatment screening installation (100) may only include two screening devices (102) with corresponding inlet lines (104). As also shown in Fig 34, the inlet line may have a cylindrical pipe conduit (127) instead of the box conduit (124) illustrated in Fig 18.

Fig 21 further illustrates an implementation where the installation (100) screening device (102) includes three screening devices. Indeed the installation (100) may include a plurality of screening devices mounted adjacently and operating in parallel with respect to each other. Referring to Fig 22, the screened fluid flow collected in the collector body (108) is released from the collector body through at least one discharge outlet (130) located in a bottom portion of the collector body (108) and connected to a discharge line (132). The discharge line (132) sends the screened fluid flow to further treatments, such as flocculation and dewatering of the screened tailings. To avoid overflowing of the collector body (108), the screened fluid flow may be released from the collector body into an overflow line (134) as soon as the flow reaches at least one overflow outlet of the collector body (108).

As Figs 21 and 23 illustrate, the collector body (108) may include two types of overflow outlets. A first pair of overflow outlets (135) may be located in a bottom portion of the collector body (108) and a second overflow outlet (136) may be located in a top portion of the collector body (108) in case of an excessive rise of the screened fluid flow level.

The collector body (108) may further include an overflow collector (137) cooperating with the overflow line (134) as shown on Fig 23. When the level of the screened fluid flow increases, it may reach a top end of the overflow collector (137) and flow down into the overflow collector (137). The overflowing screened fluid flow is released from the overflow collector through the first pair of overflow outlets (136). If the level of the overflowing screened fluid flow rises too rapidly in the overflow collector because the first pair of overflow outlets (135) is not sufficient to regulate the fluid level, the second overflow outlet (136) is used to release the overflowing screened fluid flow from the overflow collector (137).

As can be seen on Figs 21 and 22, in order to improve the operation of the screening installation, it includes an operator platform (138) which allows an operator to monitor the screening surface and reacting in case of plugging. The screening surface is preferably surrounded with a side enclosure (140) that extends upwardly from the collector body (108) in order to avoid tailings splashing laterally or forward away from the screening surface which could be harmful to an operator and reduce efficiency. The screening installation (100) may be skid-mounted (142) and semi-mobile for enabling its lifting, dragging and relocation. In some implementations, no single part of the screening device or installation exceeds dimensional limitations for oversized highway transport. The screening installation further includes disconnection means for dismantling the screening installation components in order to be adapted for transportation. Referring to Fig 24, the screening device (102) includes a wear plate (144), which may be removable, located in the conduit box (124) for receiving the initial impact of the oil sands tailings fluid flow coming from the main inlet pipe (122). The flow rate of the incoming oil sands tailings fluid flow may range from about 2500 USGPM to about 6000 USGPM (from 568 m³.s^"1 to about 1360 m³.s^"1), and the wear plate and other components may be configured and sized accordingly.

Referring to Figs 22 and 24, the conduit box (124) may also include a cleanout hatch (145) enabling cleaning and/or maintenance on the conduit (124). The cleanout hatch (145) may be a pivotable door or slidable structure for gaining access to the interior of the conduit (124). The hatch (145) may also be configured and sized to enable visual inspections and replacement of components such as the wear plate (144) that is subject to substantial erosive and abrasive forces.

Referring to Fig 35, the pre-treatment installation may include a header (146) having an elevating conduit (148), which may be vertical, and a distribution conduit (150), which may be generally horizontal. The elevating conduit (148) receives the fine tailings and transports it to an elevation to enable the fine tailings to be fed to the screening devices, while the distribution conduit (150) is fluidly connected to the elevating conduit and transports the fine tailings to multiple screening devices (not illustrated here). The distribution conduit (150) thus has multiple inlet lines (104). The header (146) of Fig 35 provides the fine tailings serially to the screening devices, due to the serial arrangement of the inlet lines (104). In such implementations of the header, valves may be provided to throttle the flow and provide balanced flow to each of the screening devices. Referring now to Fig 36, the pre-treatment installation (100), a parallel header system (152) is provided instead of the header (146) of Fig 35. Fig 36 shows the parallel header system (152) integrated into the installation (100) that includes four screening devices (102). The parallel header system (152) includes an elevating conduit (154) and a distribution conduit (156) for each of the screening devices (102). Utilizing four screening tank devices enables increased overall capacity. The parallel header system (152) provides balanced flow to each of the screening devices (102), facilitating equal flow to each of the screening devices when desired and facilitating maintenance and turn-down when one of the screening devices is brought off line. As a result, in operating conditions, no throttling of the flow is required to achieve a balanced flow. The parallel header system (152) may also be used in connection with the pre- treatment installations illustrated in the other Figures, for example instead of the serial type header. As schematically illustrated, the incoming fine tailings may be provided as a main inlet stream (158), which is split into two separate streams (160) and (162), which are each split again to feed the four elevating conduits (154) of the header (152). Valves may be provides on some or all of the pipes to allow reduced flow or to stop flow through one or more of the conduits. Referring to Fig 37, the pre-treatment installation (100) may also be designed, configured and constructed with platforms, stairways and railings that provide safe and easy access for operators.

Referring to Figs 36, 38 and 39, the installation may also include flush nozzles (164) in a bottom section of the collector body (108) to agitate small debris and/or sand that settle in the tank.

Referring now to Figs 41 to 47, the pre-treatment screening installation may include a spillbox feed tank (166) for feeding the fine tailings to the upstream end of the screen. Referring to Figs 45 to 47, the spillbox feed tank (166) includes a lower tailings inlet (168), a tank cavity (170) defined by side walls (172), and an overflow weir (174). The fine tailings are fed into the cavity (170) via the tailings inlet (168) and flow upward until reaching the overflow weir, at which point the fine tailings flow over the weir (174) and down the screen (1 14). The spillbox feed tank (166) may also have upper walls (176) that extend above the overflow weir (174) and prevent tailings from splashing out or surging over in response to increased flow rate, for example.

The spillbox feed tank (166) allows the fine tailings to be evenly distributed over the width of the screen (1 14) at the upstream inlet point. This avoids wasting screening space and thus increases throughput capacity and reduces tailings rejection back into the pond. By spreading out the flow of fine tailings the flow is not focused in the center and the deflector plate or other means of distributing the fine tailings are not as necessary.

Referring now to Fig 47, the spillbox feed tank (166) may include a flow enhancing component (178) configured to accelerate flow of the fine tailings onto the screen. The flow enhancing component (178) may function by reducing the area through which the fine tailings pass just upstream of the screen, thereby forcing an increased flowrate at the upstream part of the screen. The flow enhancing component (178) may be configured to provide sufficient flow rate to facilitate self-cleaning of the screen. The flow enhancing component (178) may be a bolt-up attachment that may be easily removed. It may be removably mounted to the screen, the spillbox or other components of the installation as needed. The flow enhancing component (178) may also be configured to provide sufficient tailings flow rate to enhance utilization of the screen area, for instance to enable the tailings to reach the downstream end of the screen. Referring to Figs 53 to 55, the pre-treatment installation (100) may be located proximate to a tailings pond (402). A dredge (400) may be used for retrieving tailings from the pond (402) and a pump (404) may pump the tailings toward the pre-treatment installation. As illustrated, the pre-treatment installation (100) may be fed with the tailings in a number of ways. Fig 53 shows a double branch configuration with four generally equal feed streams. Fig 54 shows another scenario where a double branch configuration provides four generally equal feed streams to two separate pre-treatment installations. Figs 53 and 54 may be used when the screening devices (not shown here) are of generally equal size and configuration and enable similar throughput. Fig 55 shows an alternative scenario where four feed streams are provided to the pre-treatment installation (100), but are not all equal, which may be suitable when supplying different types, sizes or configurations of screening devices. Some screening device configurations may, for example, be able to operate with higher throughputs of fine tailings. It is noted that each of the feed, branch, and main lines of Figs 53 to 55 may have flow rate measurement and/or control apparatuses, such as instruments, pumps, valves, and so on.

Other screening implementations

Figs 25 and 26 illustrate a pipeline arrangement (200) in which an in-line screening device may be provided.

An in-line screening device (1 ) as illustrated in Fig 2, for example, may be used in the pipeline arrangement (200) of Figs 25 and 26.

There may be a Y-joint arrangement (205) including an inlet line (207), and a lateral branch line (209). The expression "lateral" refers to a pipe fitting which splits the oil sands tailings fluid flow into at least two directions. The branch line (209) defines an inlet opening of the inlet line (207).The branch line (209) may be a pipe acting as a collector body as mentioned above with reference to Fig 18 for example.

Referring to Fig 26, the oil sands tailings fluid flow is pressurized and is pumped from a tailings pond or holding tank or pond into a pipeline (21 1 ). The pressurized mature fine tailings fluid flow may be supplied through the pipeline (21 1 ) to a deflector spool (212), which is better illustrated in Figs 29 to 31 . The deflector spool (212) may be connected to the inlet line (207). The mature fine tailings fluid flow is screened from its coarse debris through the branch line (209) and is pumped with a pump for downstream chemical treatments. In some implementations, an in-line screening device as illustrated in Fig 2 is in the branch line (109) of the pipeline arrangement (200), as explained in detail above.

In some implementations, as illustrated in Figs 27 and 28, a screening grill device (215) is provided. The screening grill device (215) includes a plurality of screening bars (223) may extend over the inlet opening for preventing coarse debris flowing along the inlet line (207) from entering the branch line (209) through the inlet opening. Each screening bar (223) may be oriented substantially parallel to the direction of the oil sands tailings fluid flow along the inlet line (207). Each screening bar (223) may have a substantially rectangular section. The screen (215) may include a central screening bar (223c), and a plurality of lateral screening bars (223s) being spaced apart from one another with a relieving angle with respect to the central screening bar (223c). The adjacent screening bars (223) may diverge one from another along the direction of the oil sands tailings fluid flow along the inlet line (207). 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 (215). Preferably, the central screening bar (223c) may be longer than the lateral screening bars (223s).

In some implementations, referring to Figs 25 and 26, the in-line screening system may further include a backflushing line (243) and an inspection line (245). The backflushing line (243) may be fluidly connected to the branch line (209). During possible operation downtime, a cleaning fluid, such as water, may flow through the backflushing line (243) in an opposite direction from the screened fluid flow to clean, e.g. towards the inlet line (207), for cleaning the screen (215). The screening device (203) may further include an inspection line (245). The inspection line (245) may be branched onto the inlet line (207) for enabling an inspection of the screen (215). An operator may thus have the possibility to detect plugging of the screen or carry out troubleshooting tasks. The inspection line (245) preferably provides an access to the screen (215). Referring to Figs 29 to 31 , the screening system may include a deflector spool (212) may be used upstream to the screen (215). The deflector spool (212) may include a plurality of fins (247) extending along the deflector spool (212) and forming a deflecting angle with respect to the inlet line (207). The fins may deflect the coarse debris of the incoming oil sands tailings fluid flow towards the grill screen device (215) at the intersection of the branch line (209) and into the inlet line (207).

The overall screening of the suspension or fine tailings may be performed via one or more screening tanks of an installation, one or more in-line screening devices, one or more grill screen devices, or a combination thereof.

In some implementations, there is a method for screening debris from an oil sands tailings fluid flow to pre-treat the oil sands tailings fluid flow for chemical treatment, such as flocculation and dewatering, the pre-treatment screening being enabled by one or more of the above-described systems and devices. The method includes the 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 may further include a step of collecting the screened fluid flow in a collector body prior to transporting the screened tailings for chemical treatment. The tailings fluid flow may be an oil sands mature fine tailings fluid flow.

The method may further include 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 an impact on the efficiency of the screening. The method may also include 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 in case of screening with the screening tank. The deflecting may further be performed by the deflector spool in case of the in-line screening device or the grill screen device. The method may include a step of rejecting the coarse debris from a bottom end or bottom edge of the screen towards a collection area. The method may include a step of self-cleaning of the screen. In the even of accumulations or plugging of the screen, the method may include the step of closing the inlet line during cleaning operations of the screen. The method may also include a step of discharging the screen fluid flow from a bottom portion of the collector body via a discharge line. A further step of releasing the screened 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 or conducted for a plurality of screening devices arranged in series or in parallel. Screening techniques, which should be understood to include any suitable screen, mesh or filter aided separators or other static separators used for the separation of solids from fluids.

Other coarse debris removal pre-treatment implementations

In some implementations, as described above, the pre-treatment of the fine tailings may utilize a static screening technique where the screening device includes static screening elements that retain the coarse debris and allow the fine tailings fluid to pass through. The static screening elements may include bars, mesh, filter material, and so on.

In some implementations, the pre-treatment of the fine tailings may utilize a dynamic screening technique where at least some of the screening elements are at least periodically in motion. Dynamic screening may be performed by displacing a screen, e.g. using a belt filter type configuration. The dynamic screening may displace a screen continuously or periodically and the motion may be translational as in belt-screening, back-and-forth, or rotational as in rotary drum screening. Selection of the screening technique may be done depending on the type of coarse debris, the type of suspension or tailings, the various techniques that may be used to remove the debris from the screen surface, as well as the efficiency and economics of implementing the screening technique. In some implementations, the pre-treatment of the fine tailings may utilize a separation technique other than screening to remove the coarse debris and produce a debris removed fine tailings. The separation technique may include, for example, centrifugal separation, cyclonic separation or magnetic separation where at least some of the coarse debris has magnetic properties. Selection of a separation technique may be based on the type of fine tailings, the nature of the coarse debris, and the type of chemical treatment operation to be performed on the debris removed fine tailings.

Further pre-treatment implementations In some implementations, pre-treatment for removal of coarse debris includes contacting the inlet fine tailings with a pre-treatment additive to enhance the separation of the coarse debris. The pre-treatment additive may be provided for modifying the rheological properties of the fine tailings, e.g. reducing viscosity, to facilitate the bulk tailings fluid passing through the screen. The additive may be selected to reduce forces between the coarse debris and the bulk fluid (cohesive, adsorptive, or electrostatic, for example), to aid screening and/or reduce plugging of the screen openings. The additive may be an organic or inorganic chemical, a polymeric compound, a solvent or water, and may be added to the inlet fine tailings prior to or during the pre-treatment screening. The additive may be selected to disperse, deflocculate, dilute, and/or modify the pH or electrochemical properties of the fine tailings.

Referring to Fig 53, the chemical additive may be introduced into the pre- treatment system at a variety of points. The dredge (400) provides tailings from the tailings pond (402) and a pump (404) pumps the tailings flow toward one or more pre-treatment installations (100). The chemical additive may be introduce at one or more of points A, B and/or C, as illustrated. Downstream chemical treatment operations

In some implementations, the screened fine tailings are subjected to a chemical treatment operation. The screened fine tailings may be sent via pipeline to a chemical treatment unit. Various different chemical treatments may be conducted. For example, the screened fine tailings may be subjected to a chemical aided dewatering operation. Alternatively, the screened fine tailings may be subjected to a recovery process to recover one or more valuable substances included in the tailings, such as metals, hydrocarbons, residual ore, and the like. The screened fine tailings may be subjected to a chemical treatment to alter its chemistry, such as its pH or salt content, in order to prepare the tailings for reclamation, deposition, or further processing. After the pre-treatment, the screened fine tailings have a composition allowing improved mixing and processing with chemical additives. In some implementations, the dewatering operation may include chemical addition to react with the fine solid particles in the tailings followed by deposition of the tailings. The chemical addition may include addition of a flocculent, such as a long chain polymer, in the form of solid particles, an aqueous solution or a dispersion of particles in a liquid medium. Referring to Fig 49, the screened fine tailings (300) may be pumped by a pump (302) and transported by pipeline to a chemical addition device (304). A chemical additive (306), such as a flocculent, may be added to the screened tailings (300) for mixing in the chemical addition device (304). The flocculent may be added in the form of an aqueous solution where the flocculent is at least partially dissolved. The flocculated mixture (308) is then transported and deposited as a tailings deposit (310) from which release water (31 1 ) is allowed to flow.

Referring to Figs 50 and 51 , in some implementations, the screened fine tailings may be treated with a flocculent solution. Since the extent and quality of the flocculation reaction depends on the mixing of the flocculent into the fine tailings, the screened fine tailings provide improved mixability without the coarse debris, for example by presenting one phase macroscopic behavior. Thus, initial dispersion stage of the flocculent solution into the fine tailings is enhanced. In addition, the next stage of the dewatering operation includes conditioning the fine tailings by inputting a sufficient energy to cause the formation and rearrangement of flocculated fine tailing solids to increase the yield shear strength. The conditioning stage is also enhanced by the screening pre-treatment since the coarse debris would disruption both the flow dynamics and the flocculation reactions. The next stage is the water release stage. The flocculated tailings are thus subjected to sufficient energy such that the floe network structure allows water release. The input energy should not be so great as to over-shear the flocculated material. The water release stage should be attained without over-shearing the flocculated structure that can then form a generally non-flowing deposit. The flocculated fine tailings may be deposited to allow the water release and the formation of a deposit which is allowed to dry by drainage and evaporation.

Fig 52 illustrates an example of a chemical addition device (304), though it should be understood that the chemical addition device (304) may be any kind of device for mixing a chemical with the screened tailings and may be a solid- liquid mixer, liquid-liquid mixer, in-line static mixer, impeller mixer, tank mixer, T- joint mixer, Y-joint mixer, or another type of mixer. The mixer may be selected and operated to provide rapid mixing of the chemical into the screened fine tailings. One or more mixers may also be used in series or in parallel. One example implementation of a mixer configuration is shown in Fig 52. This figure illustrates a pipeline reactor design that enables rapid mixing of non- Newtonian fluids, such as MFT. The MFT (300) is supplied from an upstream pipeline into a mixing zone 312. The mixing zone 312 includes an injection device 314 for injecting the flocculent solution. The injection device may also be referred to as a "mixer". The injection device 314 may include an annular plate 316, injectors 318 distributed around the annular plate 316 and a central orifice 320 defined within the annular plate 316. The MFT accelerates through the central orifice 320 and forms a forward-flow region 324 and an annular eddy region 322 made up of turbulence eddies. The injectors 318 introduce the flocculent solution directly into the eddy region 322 for mixing with the turbulent MFT. The recirculation of the MFT eddies back towards the orifice 320 results in mixing of the flocculent solution into the MFT forward-flow. The forward-flow region 324 expands as it continues along the downstream pipe 326. For some mixer embodiments, the forward-flow region may be a vena-contra region of a jet stream created by an orifice or baffle. The main flow of the MFT thus draws in and mixes with the flocculent solution, causing dispersion of the flocculent solution, and flocculation thus commences in a short distance of pipe. The injection device 314 illustrated in Fig 52 may also be referred to as an "orifice mixer". For the mixer of Fig 52, a range of orifice diameter "d" to downstream pipe diameter "D" may be 0.25 - 0.75. In some implementations, the flocculent added to the screened fine tailings, such as screened MFT, may be a polymer flocculent with a high molecular weight. The polymer flocculent may be anionic in overall charge, e.g. approximately 30% anionicity, which may include certain amounts of cationic monomer and may be amphoteric. The polymer flocculent may be water-soluble to form a solution in which the polymer is completely dissolved. It is also possible that the polymer is mostly or partly dissolved in the solution. The polymer flocculent may be composed of anionic monomers selected from ethylenically unsaturated carboxylic acid and sulphonic acid monomers, which may be selected from acrylic acid, methacrylic acid, allyl sulphonic acid and 2- acrylamido-2-methyl propane sulphonic acid (AMPS), etc., and the salts of such monomers; non-ionic monomers selected from acrylamide, methacrylamide, hydroxy alkyl esters of methacrylic acid, N-vinyl pyrrolidone, acrylate esters, etc.; and cationic monomers selected from DMAEA, DMAEA.MeCI, DADMAC, ATPAC and the like. The polymer flocculent may also have monomers enabling interactions that results in higher yield strength of the flocculated MFT. Synthetic polymers such as thickeners maybe used, and may have hydrophobic groups to make associative polymers such that in aqueous solution the hydrophobic groups join together to limit water interactions and stick together to provide a desired shear, yield stress or viscosity response in solution and when reacted with the MFT. The polymer flocculent may also have a desired high molecular weight, for instance over 10,000,000, for certain flocculation reactivity and dewatering potential. The polymer flocculent may be generally linear or not according to the desired shear and process response and reactivity with the given MFT.

Other chemical enhanced dewatering operations may also be employed and may use organic and/or inorganic and/or organic-inorganic hybrid chemical additives. For example, the screened fine tailings may be mixed with sand and gypsum to form "consolidated tailings". A typical consolidated tailings mixture may be about 60 wt% mineral (balance is process water) with a sand to fines ratio of about 4 to 1 , and about 600 to 1000 ppm of gypsum. This combination can result in a non-segregating mixture when deposited into a tailings pond for consolidation. In another scenario, the screened fine tailings may be mixed with organic-inorganic hybrid flocculent to produce a flocculated tailings material that may be deposited and allowed to drain.

Coarse debris removal

It should thus be understood that the pre-treatment screening techniques described herein provide a screened fine tailings for improved and consistent mixing with chemicals for tailings treatment operations.

In some implementations, the pre-treatment screening removes coarse debris that would impede or inhibit chemical reactions, for instance flocculation reactions involving flocculent 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. 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 may remove bitumen masses including slugs or mats that negatively affect anionic polymeric flocculent reactions with the fine solid particles in the tailings.

In some implementations, the pre-treatment screening removes coarse debris that would have disrupted the mixing of the chemical additive and the fine tailings. For instance, the pre-treatment screening may remove coarse debris that would impede consistent mixer performance or mixer flow regime. The pre- treatment screening 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 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 may also remove coarse debris that would complicate or prevent reliable process modelling of the fluid mixing, flocculation or dewatering operations. Reliable modelling may be based on CFD modelling to predict or estimate certain reaction or fluid behaviours.

In some implementations, the pre-treatment screening removes coarse debris that would damage or clog equipment, such as the equipment illustrated in Figs 49 and/or 52. Oil sands tailings and suspensions

While several implementations have been described and illustrated herein in relation to oil sands MFT, it should be understood that the processes, systems, devices and techniques may also be used for other suspensions that include fine solid particles and coarse debris. Suspensions include mining tailings or industrial waste water, clay suspensions, sewage suspensions, cellulosic suspensions, naturally occurring sediment suspensions such as dredged seabed material, and so on.

Mining tailings may include coal tailings or other hydrocarbon tailings, metal ore tailings, red mud, kaolin slurries, phosphate tailings, and so on. The mining tailings may be retrieved from tailings ponds or provided directly from extraction facilities. The mining tailings may have a fine solids particles concentration between about 10 wt% and about 70 wt%, for example, or between about 15 wt% and about 50 wt%, or between about 20 wt% and about 40 wt%, or about 25 wt% and about 35 wt%. The mining tailings may include dispersed clay. The mining tailings may include fine solid particles that are primarily particles having various sizes up to about 44 microns. The suspension may include a solids content that is over 50 wt%, over 55 wt%, over 60 wt%, over 65 wt%, over 70 wt%, over 75 wt%, over 80 wt%, over 85 wt%, over 90 wt%, over 95 wt%, or up to 100 wt% fine solid particles with size below 44 microns. The suspension may include an amount of larger particles over 44 microns, such as sand and the like. The mining tailings may be acidic or basic or neutral, and may also include soluble compounds such as salts. The solid particles may be silicone based particles and/or carbonate based particles, for example, depending on the source of the tailings, e.g. the ore body composition.

It should be noted that while various implementations describe herein refer to MFT or fine tailings, such techniques may also be applied to other suspensions in general.

Suspensions may be aqueous suspensions including fine solid particles that are suspended in the aqueous medium and coarse debris of various types.

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. For instance, the screening device may have various shapes, sizes and configurations for receiving and screening the fine tailings. The tailings inlet may provide the fine tailings at a central point of the screen and the screen may have a generally conical construction instead of the rectangular ramp construction of the tank screening device illustrated herein. Of course, the pre- treatment installation may have various arrangements of platforms, railings, screening devices, headers and associated piping, outlets, collector bodies, and operator access and vantage points. Multiple screening devices may also be used in parallel and/or in series, and each of the screening devices may be size and configured the same or differently to provide a same or different screening operation. When screening devices are used in series, they may be configured differently so at to remove different sizes of coarse debris, e.g. a first screening device may remove the larger coarse debris and a second downstream screening device may remove smaller coarse debris, thereby producing the screened fine tailings.

Claims

1 . A process for treating oil sands mature fine tailings (MFT), comprising: retrieving MFT from a tailings pond; pre-treating the MFT by: providing an MFT fluid flow; screening the MFT fluid flow by passing through a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the MFT fluid flow into coarse debris and a screened MFT fluid; and collecting the screened MFT fluid in a collector body; mixing a flocculent into the screened MFT fluid to produce a mixture; depositing the mixture at a deposition site to form a flocculated tailings deposit; and allowing water to release from the flocculated tailings deposit to form dried tailings material.

2. The process of claim 1 , wherein the step of retrieving the MFT includes dredging.

3. The process of claim 1 or 2, wherein the step of providing the MFT fluid flow includes pumping the MFT through a pipeline toward the screen.

4. The process of claim 3, wherein the pumping induces shear thinning of the MFT fluid flow.

5. The process of any one of claims 1 to 4, further comprising: splitting the MFT into multiple MFT fluid streams prior to the pre- treating step.

6. The process of claim 5, wherein the step of screening includes passing each of the MFT fluid streams through a corresponding screen arranged in parallel.

7. The process of claim 5 or 6, further comprising: adjusting or controlling flow rates of the MFT fluid streams.

8. The process of claim 7, wherein the flow rates of the MFT fluid streams are adjusted or controlled to be generally equal to each other.

9. The process of any one of claims 5 to 8, wherein the splitting is performed at a lower elevation and the MFT fluid streams are transported upward to a higher elevation for the screening step.

10. The process of any one of claims 5 to 9, further comprising: stopping flow of one of the MFT fluid streams; and allowing allocation of the stopped flow into the other MFT fluid flow streams.

1 1 . The process of claim 10, further comprising: cleaning a pipeline in which MFT flow has been stopped; and/or cleaning a screen to which MFT flow has been stopped.

12. The process of any one of claims 1 to 1 1 , wherein the screening step includes providing the MFT fluid flow from an upstream section toward a downstream section of the screen.

13. The process of claim 12, wherein the MFT fluid flow is provided in a generally parallel direction with a surface of the screen.

14. The process of claim 12 or 13, wherein the screen is downwardly inclined in the direction of the downstream section.

15. The process of any one of claims 1 to 14, further comprising: deflecting at least part of the oil sands tailings fluid flow coming from an inlet line towards the screen.

16. The process of any one of claims 1 to 15, further comprising: rejecting the coarse debris from a downstream edge of the screen.

17. The process of any one of claims 1 to 16, further comprising : discharging a stream of the screened MFT fluid from a bottom portion of the collector body through a discharge line.

18. The process of any one of claims 1 to 17, further comprising : releasing part of the screened MFT fluid from a top portion of the collector body through an overflow line.

19. The process of any one of claims 1 to 18, further comprising: locating the screen proximate to a perimeter of the tailings pond.

20. The process of any one of claims 1 to 19, further comprising: depleting MFT inventory from the tailings pond; and relocating the screen proximate to a new location proximate a tailings pond having additional MFT.

21 . The process of any one of claims 1 to 20, further comprising: distributing the MFT fluid flow over a width of the screen by overflowing the MFT fluid flow.

22. The process of claim 21 , wherein the overflowing comprises: allowing the MFT fluid flow to travel upward through a container; and passing the MFT fluid flow over a weir positioned upstream of the screen.

23. The process of any one of claims 1 to 22, further comprising: distributing the MFT fluid flow over the screen by accelerating the flow prior to releasing the MFT fluid onto the screen.

24. A screening device comprising: a screen having a screening surface configured to allow material with a predetermined size that is included in an oil sands tailings fluid flow to flow through the screening surface and separate coarse debris from the oil sands tailings fluid flow, thereby splitting the oil sands tailings fluid flow into coarse debris and a screened fluid; and a collector body having side walls extending from the screening surface and configured to receive the screened fluid for a chemical tailings treatment operation.

25. The screening device of claim 24, wherein the oil sands tailings fluid comprises mature fine tailings (MFT).

26. The screening device of claim 24 or 25, wherein the screen comprises a plurality of screening bars, the screening bars being 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 at most the predetermined size to flow through the screen into the collector body.

27. The screening device of claim 26, wherein the screening bars are substantially parallel to one another.

28. The screening device of claim 27, wherein the screening bars have a flow- facing surface and side surfaces, the side surfaces extending from the flow- facing surface inwardly with a relieving angle with respect to the flow-facing surface.

29. The screening device of claim 28, wherein the flow-facing surface is a top surface facing upward and the side surfaces extend downwardly from the top surface.

30. The screening device of claim 28 or 29, wherein the relieving angle ranges between about 5 degrees and about 20 degrees.

31 . The screening device of claim 30, wherein the relieving angle is about 8 degrees.

32. The screening device of any one of claims 26 to 31 , wherein the screen is positioned and configured such that the openings between the screening bars are unblocked in an operable screening area of the screen.

33. The screening device of any one of claims 26 to 31 , wherein the screen includes a plurality of supporting bars, the supporting bars being perpendicular to the screening bars and connected to a bottom surface of the screening bars.

34. The screening device of any one of claims 26 to 33, wherein the screening bars have a length ranging between about 8 feet and 12 feet.

35. The screening device of any one of claims 26 to 34, wherein the screening bars have a width ranging between about ½ inches and about 2 inches.

36. The screening device of claim 35, wherein the width of each of the screening bars has a width between about 5/8 inches and about 1 inch.

37. The screening device of any one of claims 26 to 36, wherein the screening bars are spaced apart from each other with a distance ranging between about ½ inches and about 2.5 inches.

38. The screening device of claim 37, wherein the supporting bars are spaced apart from each other with a distance between about 1 inch and about 2 inches.

39. The screening device of any one of claims 24 to 38, wherein the screening surface is of rectangular shape.

40. The screening device of any one of claims 24 to 39, wherein the predetermined size of the material flowing through the screening surface has a maximum value for enhancing a downstream flocculation and dewatering treatment of the screened oil sands tailings.

41 . The screening device of any one of claims 24 to 40, wherein the predetermined size of the material flowing through the screening surface has a maximum value ranging between about ¼ inches and about 6 inches.

42. The screening device of any one of claims 24 to 41 , wherein the screening surface is substantially parallel to the direction of the oil sands tailings fluid flow expelled from the inlet line.

43. The screening device of any one of claims 24 to 42, wherein the screening surface is inclined downwardly with an angle with respect to the horizontal and sufficient to allow pushing of the coarse debris down the screen and rejection over a bottom edge of the screen.

44. The screening device of claim 43, wherein the screen has a bottom edge arranged to allow the coarse debris to be rejected.

45. The screening device of claim 43 or 44, wherein the screening surface is inclined downwardly with an angle ranging between about 25 degrees and about 45 degrees.

46. The screening device of claim 45, wherein the screening surface is inclined downwardly with an angle of about 30 degrees.

47. The screening device of any one of claims 24 to 46, wherein the screening surface is open to atmosphere.

48. The screening device of claim 47, including an operator platform connected to the collector body enabling an operator to clean the screening surface of some of the coarse debris.

49. The screening device of any one of claims 24 to 48, further comprising a side enclosure extending upwardly around the screening surface for avoiding tailings splashing laterally away from the screening surface.

50. The screening device of any one of claims 24 to 49, further comprising a collection area collecting the coarse debris pushed down the screening surface.

51 . The screening device of any one of claims 24 to 50, wherein the inlet line includes a wear plate receiving an initial impact of the oil sands tailings fluid flow.

52. The screening device of claim 51 , wherein the wear plate is removable.

53. The screening device of claim 51 or 52, wherein the wear plate is positioned and configured to deflect the oil sands tailings fluid flow toward the screen in a parallel trajectory with respect to the surface of the screen.

54. The screening device of any one of claims 24 to 53, wherein the inlet line further comprises a main inlet pipe providing the oil sands tailings fluid flow into an expanded conduit located upstream of the screen and setting the direction of the oil sands tailings fluid flow before contacting the screening surface.

55. The screening device of claim 54, wherein the expanded conduit is a box conduit being sized and configured to reduce the velocity of the oil sands tailings flow in the main inlet pipe and distribute the oil sands tailings flow over the screen.

56. The screening device according to claim 55, wherein the removable wear plate is located inside the box conduit.

57. The screening device according to any one of claims 54 to 56, wherein the main inlet pipe has a knife-gate valve for throttling or stopping the oil sands fluid flow toward the corresponding screen.

58. The screening device according to any one of claims 24 to 57, further including a deflector plate extending above part of the screen to ensure a deflection of the debris towards the screen.

59. The screening device of claim 58, wherein the deflector plate is adjustable at different angles with respect to the screen.

60. The screening device of claim 59, wherein the deflector plate is positioned at a downward angle towards the screening surface.

61 . The screening device of any one of claims 24 to 60, further comprising a discharge line connected to a discharge outlet of a bottom portion of the collector body and releasing the screened fluid flow out of the collector body through the outlet.

62. The screening device of any one of claims 24 to 61 , further comprising an overflow line connected to an overflow outlet of a top portion of the collector body and collecting the screened fluid flow overflowing the collector body through the overflow outlet.

63. The screening device of claim 62, wherein the collector body includes an overflow collector collecting the overflowing screened fluid flow, the overflowing screened fluid flow being released from the overflow collector through the overflow outlet into the overflow line.

64. The screening device of any one of claims 24 to 63, wherein the collector body has a bottom portion mounted on a skid such that the screening device is relocatable.

65. The screening device of any one of claims 24 to 64, wherein the collector body is a tank and the screen is positioned above or at an upper part of the tank.

66. The screening device of any one of claims 24 to 65, wherein the inlet line is configured to provide the oil sands tailings fluid flow at a flow rate ranging between about 568 m³.s^"1 and about 1360 m³.s^"1.

67. The screening device of claim 24, wherein the collector body comprises a branch line branched onto the inlet line and forming an inlet opening therebetween, for enabling in-line screening.

68. The screening device of claim 67, wherein the branch line and the inlet line are configured to form a branching angle with respect to each other.

69. The screening device of claim 68, wherein the branching angle is inclined with the direction of flow in the inlet line.

70. The screening device of claim 69, wherein the branching angle is about 45 degrees.

71 . The screening device of any one of claims 67 to 70, wherein the branch line has a distal portion including an abutment flange.

72. The screening device of claim 71 , wherein the abutment flange is provided with a fastening assembly for removably fastening the screen thereto.

73. The screening device of any one of claims 67 to 72, wherein the screen comprises a plurality of supporting bars, each supporting bar projecting from the abutment flange inwardly towards the inlet opening and along the branch line, each supporting bar being operatively connected to a corresponding screening bar of the screen for supporting the corresponding screening bar.

74. The screening device of claim 73, wherein each screening bar is oriented along the inlet opening.

75. The screening device of claim 74, wherein each supporting bar is operatively connected to each corresponding screening bar by a bend.

76. The screening device of claim 74 or 75, wherein each screening bar and each supporting bar are cylindrical.

77. The screening device of any one of claims 73 to 76, wherein each screening bar is positioned at an angle of about 45 degrees with respect to the corresponding supporting bar.

78. The screening device of any one of claims 73 to 77, wherein the screening bars are of different length.

79. The screening device of any one of claims 73 to 78, wherein the supporting bars are of different length.

80. The screening device of any one of claims 73 to 79, wherein the screen includes a central screening bar, and a plurality of lateral screening bars, the central screening bar being longer than the lateral screening bars.

81 . The screening device of any one of claims 73 to 80, wherein spacings between pairs of adjacent screening bars of the screen are different.

82. The screening device of any one of claims 73 to 81 , wherein the screen includes at least one supporting brace mounted across a plurality of corresponding supporting bars for providing reinforcement thereto.

83. The screening device of any one of claims 73 to 82, wherein distal extremities of the supporting bars are welded onto an inner rim of the abutment flange.

84. The screening device of any one of claims 73 to 83, wherein the plurality of screening bars extends over the inlet opening, each screening bar being oriented substantially parallel to the direction of the oil sands tailings fluid flow along the inlet line.

85. The screening device of any one of claims 73 to 84, wherein the screening bars are configured with respect to the oil sands tailings fluid flow for preventing coarse debris entering the branch line through the inlet opening and deflecting the coarse debris downstream along the inlet line.

86. The screening device of any one of claims 67 to 70, wherein the screen comprises a plurality of screening bars mounted to a perimeter of the inlet opening.

87. The screening device of any one of claims 67 to 85, wherein the inlet line and the branch line are configured to be under fluid pressure.

88. The screening device of any one of claims 67 to 86, wherein the screen includes a central screening bar, and a plurality of lateral screening bars being spaced apart from one another with a relieving angle with respect to the central screening bar, such that adjacent screening bars diverge one from another along the direction of the oil sands tailings fluid flow along the inlet line.

89. The screening device of claim 88, wherein the central screening bar is longer than the lateral screening bars.

90. The screening device of any one of claims 67 to 89, further including a backflushing line branched onto the branch line, the backflushing line enabling a backflushing fluid to flow through the screen from the branch line towards the inlet line to clean the screen.

91 . The screening device of any one of claims 67 to 90, further including an inspection line branched onto the inlet line or the branched line, the inspection line being configured and located for enabling inspection of the screen, plugging detection, or access to the screen for maintenance.

92. The screening device of any one of claims 67 to 91 , further including a deflector provided in the inlet line upstream of the inlet opening and configured for deflecting the oil sands tailings fluid flow toward the inlet opening.

93. The screening device of claim 92, wherein the deflector is a deflector spool.

94. The screening device of claim 93, wherein the deflector spool includes a plurality of fins defining a deflecting angle with respect to the inlet line for deflecting the oil sands tailings fluid flow and the coarse debris towards the screen.

95. A screening device comprising: an abutment flange for abutting against a distal end of a branch line of a lateral pipe fitting of a fluid feed system having a substantially y- joint arrangement including a main line and the branch line for splitting a fluid flow of the fluid feed system into two directions; a supporting body projecting from the abutment flange inwardly towards the main line; and a screen provided on a distal extremity of the supporting body, the screen having a screening surface being substantially parallel to a direction of flow along the main line and configured for preventing debris of predetermined size from the fluid flow, from flowing through the screening surface of the screen and into the branch line.

96. The screening device of claim 95, wherein the screen includes at least one screening bar defining openings on either side of each bar, the openings being shaped and sized for preventing debris of predetermined size from entering the screen and flowing down the branch line.

97. The screening device of claim 95 or 96, wherein the screen includes a plurality of screening bars, the bars being spaced apart from each other so as to define openings on either side of each bar, the openings being shaped and sized for preventing debris of predetermined size from entering the screen and flowing down the branch line.

98. The screening device of claim 96 or 97, wherein the screening device is removably insertable into the branch line so that each screening bar of the screening device is positionable substantially parallel to the direction of flow along the main line.

99. The screening device of any one of claims 96 to 98, wherein a substantially longitudinal opening is defined between each pair of neighbouring screening bars.

100. The screening device of claim 99, wherein each longitudinal opening is substantially rectangular.

101 . The screening device of any one of claims 95 to 100, wherein the screening device is removably insertable into the branch line so that the screening surface of the screen extends substantially along a junction interface between the main line and the branch line.

102. The screening device of any one of claims 95 to 101 , wherein the supporting body includes at least one supporting bar, each supporting bar projecting from the abutment flange inwardly towards the main line and being operatively connected to a corresponding screening bar of the screen for supporting said corresponding screening bar.

103. The screening device of any one of claims 95 to 102, wherein the supporting body includes a plurality of supporting bars, each supporting bar projecting from the abutment flange inwardly towards the main line and being operatively connected to a corresponding screening bar of the screen for supporting said corresponding screening bar.

104. The screening device of any one of claims 95 to 103, wherein the supporting body includes at least one pair of supporting bars, each pair of supporting bars projecting from the abutment flange inwardly towards the main line and being operatively connected to a corresponding screening bar of the screen for supporting said corresponding screening bar.

105. The screening device of any one of claims 95 to 104, wherein the supporting body includes a plurality of pairs of supporting bars, each pair of supporting bars projecting from the abutment flange inwardly towards the main line and being operatively connected to a corresponding screening bar of the screen for supporting said corresponding screening bar.

106. The screening device of any one of claims 96 to 105, wherein each screening bar of the screen is positioned at an angle of about 45 degrees with respect to a corresponding supporting bar.

107. The screening device of any one of claims 95 to 106, wherein the screen includes screening bars of different length.

108. The screening device of any one of claims 95 to 107, wherein the supporting body includes supporting bars of different length.

109. The screening device of any one of claims 95 to 108, wherein the screen includes a central screening bar, and a plurality of lateral screening bars, the central screening bar being longer than the lateral screening bars.

1 10. The screening device of claim 109, wherein the central screening bar is supported by a pair of first and second central supporting bars, and wherein the lateral screening bars are each supported by a corresponding pair of first and second lateral supporting bars, at least one of the central supporting bars being different in length than at least one corresponding lateral supporting bar so that a bend between the central screening bar and a corresponding central supporting bar be offset with a bend between an adjacent lateral screening bar and a corresponding lateral supporting bar.

1 1 1 . The screening device of claims 109 or 1 10, wherein the central screening bar is made integral to a corresponding central supporting bar, and wherein each lateral screening bar is made integral to a corresponding lateral supporting bar. 12. The screening device of any one of claims 96 to 1 1 1 , wherein the screening bars and the supporting bars are cylindrical. 13. The screening device of any one of claims 96 to 1 12, wherein the spacing and the numbers of screening bars on the screening surface of the screen are variable. 14. The screening device of any one of claims 96 to 1 12, wherein the screening device includes at least one supporting brace mounted across a plurality of corresponding supporting bars for providing reinforcement to said corresponding supporting bars. 15. The screening device of any one of claims 95 to 1 14, wherein the abutment flange includes a ring. 16. The screening device of any one of claims 95 to 1 15, wherein extremities of supporting bars of the supporting body are welded onto an inner rim of the ring of the abutment flange. 17. The screening device of any one of claims 95 to 1 16, wherein the abutment flange is provided with a fastening assembly for removably fastening the abutment flange onto the distal end of the branch line. 18. The screening device of any one of claims 95 to 1 17, wherein the fastening assembly includes at least one hole for receiving a corresponding fastener therethrough and into a corresponding hub of the branch line. 19. The screening device of any one of claims 95 to 1 18, wherein the fastening assembly includes a plurality of holes radially positioned about the abutment flange in an equally spaced manner.

120. A process for screening coarse debris from an oil sands tailings fluid flow coming from an inlet line to pre-treat the oil sands tailings fluid flow for a chemical tailings treatment operation, the method comprising: providing the oil sands tailings fluid flow to a screening device comprising a screen and a collector body; passing the oil sands tailings fluid flow through the screen, the screen having a screening surface configured to allow material with a predetermined size to flow through the screening surface and separate the coarse debris, thereby splitting the oil sands tailings fluid flow into a coarse debris fraction and a screened oil sands tailings fluid; and collecting the screened oil sands tailings fluid in the collector body fluid for the chemical tailings treatment operation.

121 . The process of claim 120, wherein the screening device is as defined in any one of claims 24 to 1 19.

122. The process of claim 120 or 121 , wherein the chemical tailings treatment operation comprises a flocculation and dewatering treatment operation.

123. The process of claim 122, wherein the flocculation and dewatering treatment operation comprises: mixing a flocculent into the screened oil sands tailings fluid to produce a mixture; depositing the mixture at a deposition site to form a flocculated tailings deposit; and allowing water to release from the flocculated tailings deposit to form dried tailings material.

124. A process for screening coarse debris from a tailings fluid flow coming from an inlet line to pre-treat the tailings fluid flow for a chemical tailings treatment operation, the method comprising: providing the tailings fluid flow to a screening device comprising a screen and a collector body; passing the tailings fluid flow through the screen, the screen having a screening surface configured to allow material with a predetermined size to flow through the screening surface and separate the coarse debris, thereby splitting the tailings fluid flow into a coarse debris fraction and a screened tailings fluid; and collecting the screened tailings fluid in the collector body fluid for the chemical tailings treatment operation.

125. The process of claim 124, wherein the screening device is as defined in any one of claims 24 to 1 19.

126. The process of claim 124 or 125, wherein the chemical tailings treatment operation comprises a flocculation and dewatering treatment operation.

127. The process of claim 126, wherein the flocculation and dewatering treatment operation comprises: mixing a flocculent into the screened tailings fluid to produce a mixture; depositing the mixture at a deposition site to form a flocculated tailings deposit; and allowing water to release from the flocculated tailings deposit to form dried tailings material.

128. A process for screening coarse debris from an aqueous suspension coming from an inlet line to pre-treat the aqueous suspension for a chemical treatment operation, the method comprising: providing the aqueous suspension to a screening device comprising a screen and a collector body; passing the aqueous suspension through the screen, the screen having a screening surface configured to allow material with a predetermined size to flow through the screening surface and separate the coarse debris, thereby splitting the aqueous suspension into a coarse debris fraction and a screened aqueous suspension; and collecting the screened aqueous suspension in the collector body fluid for the chemical treatment operation.

129. The process of claim 128, wherein the screening device is as defined in any one of claims 24 to 1 19.

130. The process of claim 128 or 129, wherein the chemical treatment operation comprises a flocculation and dewatering treatment operation.

131 . The process of claim 130, wherein the flocculation and dewatering treatment operation comprises: mixing a flocculent into the screened aqueous suspension to produce a mixture; depositing the mixture at a deposition site to form a flocculated deposit; and allowing water to release from the flocculated deposit to form dried tailings material.

132. A pre-treatment screening installation comprising: a frame; a plurality of screening devices mounted to the frame and arranged in parallel operation with respect to each other for receiving an oil sands tailings fluid flow and producing a coarse debris fraction and a screened fluid; a header mounted to the frame and in fluid communication with the screening devices for providing the oil sands tailings fluid flow to each of the screening devices; and a collector body mounted to the frame and located for receiving the screened fluid.

133. The installation of claim 132, wherein each of the screening devices is as defined in any one of claims 24 to 1 19.

134. The installation of claim 132 or 133, wherein the header comprises: a main pipeline; a plurality of feed pipelines for respectively providing the oil sands tailings fluid flow to the screening devices; and a branching assembly for fluidly connecting the main pipeline to the plurality of feed pipelines.

135. The installation of claim 134, wherein the branching assembly is configured for providing parallel flows of the oil sands tailings fluid flow to from the main pipeline to the feed pipelines.

136. The installation of claim 135, wherein the branching assembly comprises a first pipeline division splitting the main pipeline into two primary parallel pipelines, and a pair of secondary pipeline divisions each splitting one of the primary parallel pipelines into two feed pipelines.

137. The installation of claim 136, wherein the branching assembly is located at ground level and the feed pipelines are configured to provide the oil sands tailings fluid flow to the screening devices at an elevated location.

138. The installation of any one of claims 134 to 137, wherein the header further comprises regulating devices for regulating the oil sands tailings fluid flow through each of the feed pipelines.

139. The installation of any one of claims 132 to 138, further comprising: a spillbox feed tank positioned relative to a corresponding one of the screening devices for feeding the oil sands tailings fluid flow thereto, the spillbox feed tank comprising: side walls defining a cavity; an inlet provided in a lower portion of the side walls for receiving the oil sands tailings fluid flow from the header and allowing the oil sands tailings fluid to flow up through the cavity; and an overflow member provided in an upper portion of the side walls for allowing the oil sands tailings fluid to spill over and onto the screening device.

140. The installation of claim 139, wherein the overflow member comprises an elongated weir extending a width of the screen and proximate thereto.

141 . The installation of claim 139 or 140, wherein the spillbox feed tank further comprises a flow enhancing component for accelerating the flow prior to releasing the fluid onto the screen to distribute the fluid over the screen.

142. The installation of claim 141 , wherein the flow enhancing component is configuration for reducing an area through which the oil sands tailings fluid flow pass proximate upstream of the screening device.

143. The installation of claim 141 or 142, wherein the flow enhancing component is configured to provide sufficient flow rate to facilitate self- cleaning of the screen.

144. The installation of any one of claims 141 or 142, wherein the flow enhancing component is removably mounted with respect to the spillbox feed tank.

145. A process for producing a dewatered oil sands tailings material, comprising: retrieving oil sands tailings from a tailings pond; pre-treating the oil sands tailings by: providing an oil sands tailings fluid flow; screening the oil sands tailings fluid flow by passing through a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the oil sands tailings fluid flow into the coarse debris and a screened oil sands tailings fluid; and collecting the screened oil sands tailings fluid in a collector body; mixing a flocculent into the screened oil sands tailings fluid to produce a flocculated mixture; and dewatering the flocculated mixture at a deposition site or in a mechanical dewatering apparatus, to form the dewatered oil sands tailings material.

146. The process of claim 145, wherein the screening is performed using a screening device as defined in any one of claims 24 to 1 19.

147. The process of claim 145, wherein the screening is performed using a pre-treatment screening installation as defined in any one of claims 132 to 144.

148. A process for producing a dewatered mining tailings material, comprising: retrieving mining tailings from a tailings pond; pre-treating the mining tailings by: providing a mining tailings fluid flow; screening the mining tailings fluid flow by passing through a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the mining tailings fluid flow into the coarse debris and a screened mining tailings fluid; and collecting the screened mining tailings fluid in a collector body; mixing a flocculent into the screened mining tailings fluid to produce a flocculated mixture; dewatering the flocculated mixture at a deposition site or in a mechanical dewatering apparatus, to form the dewatered mining tailings material.

149. The process of claim 148, wherein the screening is performed using a screening device as defined in any one of claims 24 to 1 19.

150. The process of claim 148, wherein the screening is performed using a pre-treatment screening installation as defined in any one of claims 132 to 144.

151 . A process for producing a dewatered aqueous suspension material, comprising: pre-treating an aqueous suspension by: providing an aqueous suspension fluid flow; screening the aqueous suspension fluid flow by passing through a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the aqueous suspension fluid flow into the coarse debris and a screened aqueous suspension; and collecting the screened aqueous suspension in a collector body; mixing a flocculent into the screened aqueous suspension to produce a flocculated mixture; and dewatering the flocculated mixture at a deposition site or in mechanical dewatering apparatus, to form the dewatered aqueous suspension material.

152. The process of claim 151 , wherein the screening is performed using a screening device as defined in any one of claims 24 to 1 19.

153. The process of claim 151 , wherein the screening is performed using a pre-treatment screening installation as defined in any one of claims 132 to 144.

154. A method of enhancing flocculation and dewatering of an aqueous suspension comprising fine solid particles, by pre-treatment of the aqueous suspension by removing coarse debris therefrom.

155. The method of claim 154, wherein the aqueous suspension comprises mining tailings.

156. The method of claim 154 or 155, wherein the aqueous suspension comprises oil sands mature fine tailings (MFT).

157. The method of any one of claims 154 to 156, wherein the removing of the coarse debris is performed to produce a pre-treated aqueous suspension having one phase macroscopic fluid behaviour.

158. The method of any one of claims 154 to 157, wherein the removing of the coarse debris is performed to produce a pre-treated aqueous suspension that is homogeneous.

159. The method of any one of claims 154 to 158, wherein the removing of the coarse debris is performed by screening the aqueous suspension.

160. The method of any one of claims 154 to 159, wherein the dewatering comprises deposition of the pre-treated aqueous suspension subsequent to flocculation thereof.

161 . A method of enhancing mixing of a chemical compound into an aqueous suspension comprising fine solid particles, by pre-treatment of the aqueous suspension by removing coarse debris therefrom so as to produce a pre- treated aqueous suspension having one phase macroscopic fluid behaviour.

162. The method of claim 161 , wherein the aqueous suspension comprises mining tailings.

163. The method of claim 161 or 162, wherein the aqueous suspension comprises oil sands mature fine tailings (MFT).

164. The method of any one of claims 161 to 163, wherein the removing of the coarse debris is performed to produce a pre-treated aqueous suspension that is homogeneous.

165. The method of any one of claims 161 to 164, wherein the removing of the coarse debris is performed by screening the aqueous suspension.

166. The method of any one of claims 161 to 165, wherein the chemical compound comprises a flocculent.

167. The method of any one of claims 161 to 166, further comprising adding the flocculent to the pre-treated aqueous suspension in the form of an aqueous flocculent solution.

168. The method of any one of claims 161 to 166, further comprising adding the flocculent to the pre-treated aqueous suspension in the form of flocculent particles.

169. The method of any one of claims 161 to 166, further comprising adding the flocculent to the pre-treated aqueous suspension in the form of a dispersion of flocculent particles in a liquid medium.

170. The method of any one of claims 161 to 169, wherein the flocculent comprises a water soluble polymer.

171 . The method of any one of claims 161 to 170, wherein the flocculent induces flocculation of the pre-treated aqueous suspension sufficient to enable dewatering thereof.

172. The method of claim 171 , wherein the dewatering comprises deposition of the pre-treated aqueous suspension subsequent to flocculation thereof.

173. A screening device for screening coarse debris from an oil sands tailings fluid for pre-treatment prior to a chemical tailings treatment operation, the screening device comprising: an inlet line to provide a flow of the oil sands tailings fluid; a screen having a screening area receiving the flow of the oil sands tailings fluid from the inlet line and allowing screened oil sands tailings fluid to pass there-through and be separated from the coarse debris; a collector body for receiving the screened oil sands tailings fluid; and wherein the screen and the inlet line are sized, positioned and configured for displacing the coarse debris out of the screening area for self-cleaning of the screening area.

174. The screening device of claim 173, wherein the screen has a downward angle sloping away from the inlet line in the direction of the flow to facilitate displacement of the coarse debris out of the screening area.

175. The screening device of claim 173 or 174, wherein the inlet line is configured to provide a flow rate to facilitate displacement of the coarse debris out of the screening area.

176. The screening device of any one of claims 173 to 175, wherein the inlet line is configured to provide a flow direction to facilitate displacement of the coarse debris out of the screening area.

177. The screening device of any one of claims 173 to 176, wherein the inlet line is configured to provide a flow pattern to facilitate displacement of the coarse debris out of the screening area.

178. The screening device of any one of claims 173 to 177, wherein the screen comprises a downstream edge positioned so that the coarse debris drops off of the screening area.

179. The screening device of any one of claims 173 to 178, wherein the screen comprises a smooth screening surface to facilitate displacement of the coarse debris out of the screening area.

180. The screening device of any one of claims 173 to 179, wherein the screening area comprises openings absent obstructions to facilitate displacement of the coarse debris out of the screening area.

181 . The screening device of any one of claims 173 to 179, wherein the screen comprises screening bars defining openings there-between and having an orientation to facilitate displacement of the coarse debris out of the screening area.

182. The screening device of claim 181 , wherein the screening bars have an orientation that is generally parallel with respect to the flow of the oil sands tailings fluid.

183. The screening device of claim 181 or 182, wherein the screening bars have a cross-sectional shape including a relieving angle to facilitate displacement of the coarse debris out of the screening area.

184. A method for in-line screening in a pipeline carrying a pressurized tailings fluid flow, the method including the steps of: a) pumping a flow of pressurized tailings fluid along a main stream of the pipeline from a upstream location to a downstream location; b) branching off a slip stream of pressurized tailings fluid away from the main stream along a given junction interface; and c) providing a screen at the junction interface for screening pressurized tailings fluid travelling through said junction interface in order to prevent undesirable debris of the pressurized tailings fluid flow from entering into the slip stream.

185. The method of claim 184, wherein step b) includes the step of branching off the slip stream of pressurized tailings fluid away from the main stream at an angle between about 30 degrees and about 60 degrees from the main stream.

186. The method of claim 184 or 185, wherein step b) includes the step of branching off the slip stream of pressurized tailings fluid away from the main stream at an angle of about 45 degrees from the main stream.

187. The method of any one of claims 184 to 186, wherein the method further includes the step of: d) varying pressure conditions at the upstream location for varying slip stream conditions of the pressurized tailings fluid at the junction interface.

188. The method of claim 187, wherein step d) is done by means of at least one valve gate.

189. The method of any one of claims 184 to 188, wherein the pressurized tailings fluid flow comprises mature fine tailings.

190. The method of any one of claims 184 to 189, wherein step a) includes the step of pumping a feed of mature fine tailings from a tailings pond into the pipeline by means of a dredge.

191 . The method of any one of claims 184 to 190, wherein pumping is done at a rate of about 6000 gallons/minute, and wherein pressurized tailings fluid flows along the main stream and along the slip stream at rates of about 4000 gallons/minute and about 2000 gallons/minute respectively.

192. A kit comprising: an abutment flange for mounting against a distal end of a branch line of a lateral pipe fitting of a fluid feed system having a substantially y- joint arrangement including a main line and the branch line for splitting a fluid flow of the fluid feed system into two directions; a supporting body mountable onto the abutment flange for projecting from said abutment flange inwardly towards the main line; and a screen mountable onto a distal extremity of the supporting body, so that once the screening device cooperates with the lateral pipe fitting, the screen has a screening surface being substantially parallel to a direction of flow along the main line and is configured for preventing debris of predetermined size from the fluid flow, from flowing through the screening surface of the screen and into the branch line.

193. A method of screening coarse debris from an aqueous suspension comprising fine solid particles comprising imparting shear thinning to the aqueous suspension to reduce the viscosity thereof prior to passing the shear thinned aqueous suspension through a screen to produce a screened aqueous suspension.

194. The method of claim 193, wherein the aqueous suspension comprises mining tailings.

195. The method of claim 193 or 194, wherein the aqueous suspension comprises oil sands mature fine tailings (MFT).

196. The method of any one of claims 193 to 195, wherein the shear thinning is at least partially provided by a pump.

197. The method of any one of claims 193 to 196, wherein the shear thinning is at least partially provided by wall shear forces within a pipeline.

198. The method of any one of claims 193 to 197, wherein the screened aqueous suspension is provided to a chemical treatment operation.

199. The method of claim 198, wherein the chemical treatment operation comprises flocculation and dewatering.

200. The method of claim 199, wherein the flocculation and dewatering comprise mixing a flocculent into the screened aqueous suspension that is also shear thinned.

201 . A system for treating oil sands mature fine tailings (MFT), comprising: a retrieval assembly for retrieving MFT from a tailings pond; a fluid transportation assembly for providing an MFT fluid flow; a screening device for screening the MFT fluid flow, the screening device comprising: a screen configured to allow material with a predetermined size to flow there-through and separate coarse debris, thereby splitting the MFT fluid flow into coarse debris and a screened MFT fluid; and a collector body for collecting the screened MFT fluid; a mixer for mixing a flocculent into the screened MFT fluid to produce a mixture; and a deposition site for receiving the mixture, allowing formation of a flocculated tailings deposit and release of water from the flocculated tailings deposit to form dried tailings material.

202. The system of claim 201 , wherein the retrieval assembly comprises a dredge.

203. The system of claim 201 or 202, wherein the fluid transportation assembly comprises a pipeline and at least one pump.

204. The system of any one of claims 201 and 203, wherein the screening device is as defined in any one of claims 24 to 94.

205. The system of any one of claims 201 to 204, wherein the mixer comprises an in-line pipe mixer.

206. The system of any one of claims 201 to 205, wherein the deposition site comprises a deposition cell comprising sand and having a sloped bottom and side walls.

207. The system of any one of claims 201 to 206, further comprising a transportation pipeline receiving the mixture from the mixer and having an outlet for depositing the mixture onto the deposition site.

208. The system of claim 207, wherein the mixer and the transportation pipeline are configured and operated so as to both provide mixing prior to deposition of the mixture to facilitate dewatering.