CA3005217A1 - Pre-treatment of oil sands fine tailings by debris removal - Google Patents

Pre-treatment of oil sands fine tailings by debris removal Download PDF

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Publication number
CA3005217A1
CA3005217A1 CA3005217A CA3005217A CA3005217A1 CA 3005217 A1 CA3005217 A1 CA 3005217A1 CA 3005217 A CA3005217 A CA 3005217A CA 3005217 A CA3005217 A CA 3005217A CA 3005217 A1 CA3005217 A1 CA 3005217A1
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Canada
Prior art keywords
screening
tailings
treatment
tailings fluid
spillbox
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
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CA3005217A
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French (fr)
Inventor
Trevor Bugg
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Suncor Energy Inc
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Suncor Energy Inc
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Filing date
Publication date
Application filed by Suncor Energy Inc filed Critical Suncor Energy Inc
Priority to CA3005217A priority Critical patent/CA3005217A1/en
Priority to CA3130067A priority patent/CA3130067A1/en
Priority to CA3043713A priority patent/CA3043713C/en
Publication of CA3005217A1 publication Critical patent/CA3005217A1/en
Abandoned legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
    • B07B1/46—Constructional details of screens in general; Cleaning or heating of screens
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B13/00—Grading or sorting solid materials by dry methods, not otherwise provided for; Sorting articles otherwise than by indirectly controlled devices
    • B07B13/14—Details or accessories
    • B07B13/16—Feed or discharge arrangements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/01—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements
    • B01D29/03—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with flat filtering elements self-supporting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D35/00—Filtering devices having features not specifically covered by groups B01D24/00 - B01D33/00, or for applications not specifically covered by groups B01D24/00 - B01D33/00; Auxiliary devices for filtration; Filter housing constructions
    • B01D35/18—Heating or cooling the filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B2230/00—Specific aspects relating to the whole B07B subclass
    • B07B2230/01—Wet separation

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  • Separation Of Solids By Using Liquids Or Pneumatic Power (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)

Abstract

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

Description

PRE-TREATMENT OF OIL SANDS FINE TAILINGS
BY DEBRIS REMOVAL
TECHNICAL FIELD
[0001] The technical field generally relates to the treatment of mine tailings derived from mining operations, and more particularly to techniques that can involve screening for removing coarse debris from oil sands fine tailings for example prior to flocculation and dewatering operations.
BACKGROUND
[0002] Oil sands tailings are generated from hydrocarbon extraction process operations that separate the valuable hydrocarbons from oil sand ore. There are various types of oil sands tailings, such as mature fine tailings (MFT) formed in a tailings pond. Tailings materials that have a high fines content can be subjected to dewatering operations, which can involve adding chemical additives such as flocculants and then separating solid minerals from the water in the tailings by supplying the treated tailings to a sub-aerial deposition area for deposition in thin lifts for drying, to a dewatering device, or to a pit for settling of the mineral solids.
[0003] Prior to addition of a flocculant or other chemical agents to the tailings material, the fine tailings can be screened to remove coarse debris that can cause issues in downstream operations. For example, Canadian patent No. 2,772,053 =
describes methods and apparatuses for removing coarse debris from fine tailings prior to a flocculation and dewatering operation. There is still a need for enhancements in terms of methods and screening apparatuses for coarse debris removal from tailings streams.
SUMMARY
[0004] The present disclosure provides processes, systems, devices and techniques for pre-treating an aqueous suspension including fine solid particles and coarse debris, in order to remove coarse debris prior to further treatments.
The present techniques are particularly claimed and described with respect to an aqueous suspension derived from mining operations and referred to as mining tailings, including oil sands fine tailings, such as mature fine tailings (MET).
[0005] In one aspect, there is provided a pre-treatment screening assembly comprising: a spillbox feed tank comprising a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, an inlet provided in the bottom wall for receiving a tailings fluid flow into the tank cavity, and an overflow weir extending outwardly from an upper portion of the tank cavity; a screening device having a screening surface receiving the tailings fluid flow spilling over the overflow weir of the spillbox feed tank, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid;
and a collector body arranged below the screening surface of the screening device to receive the screened tailings fluid.
[0006] In some implementations of the pre-treatment screening assembly, the inlet may be provided substantially centrally in the bottom wall. A width of the overflow weir may be smaller than a width of the screening surface. The width of the overflow weir may represent less than 90% of the width of the screening surface.
[0007] In some other implementations, the spillbox feed tank may comprise a baffle plate arranged in the tank cavity. The baffle plate may be parallel to one of the side walls. The spillbox feed tank may comprise two baffle plates which are arranged in the tank cavity in parallel relationship with two opposed side walls. The spillbox feed tank may further comprise an adjustable valve configured to cooperate with one of the inlet and the overflow weir. The spillbox feed tank may further comprise a level sensor for measuring a tailings fluid level in the tank cavity. The level sensor may comprise two pressure transmitters arranged in the tank cavity to measure the pressure of the tailings fluid at two distinct locations of the tank cavity. The spillbox feed tank may further comprise an adjustable valve configured to cooperate with one of the inlet and the overflow weir in response to the level measured by the level sensor.
[0008] In another aspect, there is provided a pre-treatment screening assembly comprising: a spillbox feed tank comprising: a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, an inlet provided substantially centrally in the bottom wall for receiving a tailings fluid flow into the tank cavity, and an overflow weir extending outwardly from an upper portion of the tank cavity; a screening device having a screening surface receiving the tailings fluid flow spilling over the overflow weir of the spillbox feed tank, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; and a collector body arranged below the screening surface of the screening device to receive the screened tailings fluid.
[0009] In anoth.er aspect, there is provided a pre-treatment screening assembly comprising: a spillbox feed tank comprising: a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, an inlet for receiving a tailings fluid flow into the tank cavity, and an overflow weir extending outwardly from an upper portion of the tank cavity; a screening device having a screening surface receiving the tailings fluid flow spilling over the overflow weir of the spillbox feed tank, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; and a collector body arranged below the screening surface of the screening device to receive the screened tailings fluid; wherein a width of the overflow weir is smaller than a width of the screening surface.
[0010] In another aspect, there is provided a pre-treatment screening assembly comprising: a spillbox feed tank comprising: a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, an inlet for receiving a tailings fluid flow into the tank cavity, an overflow weir extending outwardly from an upper portion of the tank cavity, a level sensor for measuring a tailings fluid level in the tank cavity, and an adjustable valve configured to cooperate with one of the inlet and the overflow weir in response to the level measured by the level sensor; a screening device having a screening surface receiving the tailings fluid flow spilling over the overflow weir of the spillbox feed tank, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; and a collector body arranged below the screening surface of the screening device to receive the screened tailings fluid.
[0011] In another aspect, there is provided a pre-treatment screening assembly comprising: a spillbox feed tank comprising: a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, an inlet for receiving a tailings fluid flow into the tank cavity, and an overflow weir extending outwardly from an upper portion of the tank cavity; a screening device comprising: a screening surface receiving the tailings fluid flow spilling over the overflow weir of the spillbox feed tank, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid, and a cleaning device to remove the coarse debris from the screening surface; and a collector body arranged below the screening surface of the screening surface to receive the screened tailings fluid.
[0012] In some implementations of the pre-treatment screening assembly, the screening surface may define a first inclination angle with a horizontal direction, the cleaning device comprising a winch for adjusting the first inclination angle.
The pre-treatment screening assembly may further comprise a debris sensor for measuring an amount of coarse debris on the screening surface, the winch adjusting the first inclination angle in response to the amount of coarse debris measured by the debris sensor. The pre-treatment screening assembly may further comprise a tailings fluid loss sensor for measuring an amount of tailings fluid losses resulting from a running off of the screening surface, the winch adjusting the first inclination angle in response to the amount of tailings fluid losses measured by the tailings fluid loss sensor.
[0013] In some other implementations, the cleaning device may comprise a mechanical cleaning device to mechanically remove the coarse debris from the screening surface. The mechanical cleaning device may comprise at least one of a rake and a rotating brush for going at least partially over the screening surface.
[0014] In some other implementations, the screening device may comprise an upper portion having an upper screening surface defining an upper angle with a horizontal direction, and a lower portion having a lower screening surface defining a lower angle with the horizontal direction, the upper angle being greater than the lower angle. The upper angle may be at least 1.5 times greater than the lower angle.
The cleaning device may comprise a mechanical cleaning device to mechanically remove the coarse debris from the lower screening surface of the screening surface.
[0015] In some other implementations, the pre-treatment screening assembly may further comprise a debris collection bin arranged under or close to the screening device. The pre-treatment screening assembly may further comprise a debris heater for heating the debris collection bin. The pre-treatment screening assembly may further comprise a debris collection pump for pumping a tailings fluid from the debris collection bin and for injecting it back in the spillbox feed tank.
[0016] In some other implementations, the screening device may further comprise an overflow weir, the screened tailings fluid flow spilling over the overflow weir into the collector body. The screening surface may have a substantially concave profile. The cleaning device may comprise a shaker for vibrating the screening surface.
[0017] In another aspect, there is provided a pre-treatment screening assembly comprising: a screening device comprising a screening surface receiving a tailings fluid flow, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid, the screening surface defining a first adjustable inclination angle with a horizontal direction; and a collector body arranged below the screening surface of the screening surface to receive the screened tailings fluid.
[0018] In some implementations, the pre-treatment screening assembly may further comprise a winch for adjusting the first adjustable inclination angle.
The pre-treatment screening assembly may further comprise a debris sensor for measuring an amount of coarse debris on the screening surface, the winch adjusting the first adjustable inclination angle in response to the amount of coarse debris measured by the debris sensor. The pre-treatment screening assembly may further comprise a tailings fluid loss sensor for measuring an amount of tailings fluid losses resulting from a running off of the screening surface, the winch adjusting the first adjustable inclination angle in response to the amount of tailings fluid losses measured by the tailings fluid loss sensor.
[0019] In another aspect, there is provided a pre-treatment screening assembly comprising: a screening device comprising: a screening surface receiving a tailings fluid flow, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid, and a mechanical cleaning device configured to mechanically remove the coarse debris from the screening surface; and a collector body arranged below the screening surface of the screening surface to receive the screened tailings fluid.
[0020] In some implementations of the pre-treatment screening assembly, the mechanical cleaning device may comprise at least one of a rake and a rotating brush for going at least partially over the screening surface. The screening device may comprise an upper portion having an upper screening surface defining an upper angle with a horizontal direction, and a lower portion having a lower screening surface defining a lower angle with the horizontal direction, the upper angle being greater than the lower angle. The upper angle may be at least 1.5 times greater than the lower angle. The mechanical cleaning device may be configured to mechanically remove the coarse debris from the lower screening surface of the screening surface.
[0021] In another aspect, there is provided a pre-treatment screening assembly comprising: a screening device comprising: a screening surface receiving a tailings fluid flow, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid, and a cleaning device configured to remove the coarse debris from the screening surface; a collector body arranged below the screening surface of the screening surface to receive the screened tailings fluid; and a debris collection bin arranged under or close to the screening device to collect the coarse debris removed from the screening surface.
[0022] In some implementations, the pre-treatment screening assembly may further comprise a debris heater for heating the debris collection bin. The pre-treatment screening assembly may further comprise a debris collection pump for pumping a tailings fluid from the debris collection bin and for injecting it back onto the screening surface.
[0023] In another aspect, there is provided a pre-treatment screening assembly comprising: a spillbox feed tank comprising: a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, an inlet for receiving a tailings fluid flow into the tank cavity, and an overflow weir extending outwardly from an upper portion of the tank cavity; a screening device comprising a screening surface receiving the tailings fluid flow spilling over the overflow weir of the spillbox feed tank, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; and a collector body arranged below the screening surface of the screening device and having a collecting cavity to receive the screened fluid, the collector body comprising a discharge opening formed in a bottom portion of the collecting cavity for collecting and easily removing debris that build up in the collector body.
[0024] In some implementations of the pre-treatment screening assembly, the bottom portion may have a substantially conical shape. The body may have side walls converging toward the discharge opening. The pre-treatment screening assembly may further comprise a frame, the collector body being mounted to the frame so that the discharge opening is vertically offset relative to a ground on which the frame stands.
[0025] In some other implementations, the screening device may have an upstream inlet, the tailings fluid being discharged on the screening surface over the overflow weir at the upstream inlet, the collector body having side walls defining at least partially the collecting cavity and a discharge outlet for discharging the screened tailings fluid from the collecting cavity, the discharge outlet being formed in one of the side walls.
[0026] In some other implementations, the collector body may further comprise a deflector plate arranged in the collecting cavity. The deflector plate may extend at least partially over the discharge outlet. The collector body may further comprise a vortex breaker arranged in the collecting cavity. The collector body may have side walls defining at least partially the collecting cavity, the vortex breaker being mounted to one of the side walls. The vortex breaker may comprise a substantially cylindrical body and a vortex breaking core arranged in the cylindrical body. The vortex breaking core may have a substantially crossed-shaped section.
[0027] In another aspect, there is provided a pre-treatment screening assembly comprising: a screening device comprising a screening surface receiving a tailings fluid flow, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; and a collector body arranged below the screening surface of the screening device and comprising: a bottom wall and side walls extending from the bottom wall, thereby defining a collecting cavity to receive the screened fluid, a discharge opening formed in a bottom portion of the collecting cavity for collecting and easily removing debris that build up in the collector body, the side walls converging toward the discharge opening.
[0028] In some implementations of the pre-treatment screening assembly, the bottom portion of the collecting cavity may have a substantially conical shape. The pre-treatment screening assembly may further comprise a frame, the collector body being mounted to the frame so that the discharge opening is vertically offset relative to a ground on which the frame stands.
[0029] In another aspect, there is provided a pre-treatment screening assembly comprising: a screening device comprising a screening surface receiving a tailings fluid flow, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; and a collector body arranged below the screening surface of the screening device and having a collecting cavity to receive the screened fluid, the collector body comprising a deflector plate arranged in the collecting cavity.
[0030] In some implementations of the pre-treatment screening assembly, the collector body may have side walls defining at least partially the collecting cavity and a discharge outlet for discharging the screened tailings fluid from the collecting cavity, the discharge outlet being formed in one of the side walls, the deflector plate extending at least partially over the discharge outlet. The collector body may further comprise a vortex breaker arranged in the collecting cavity. The collector body may have side walls defining at least partially the collecting cavity, the vortex breaker being mounted to one of the side walls. The vortex breaker may comprise a substantially cylindrical body and a vortex breaking core arranged in the cylindrical body. The vortex breaking core may have a substantially crossed-shaped section.
[0031] In another aspect, there is provided a pre-treatment screening assembly comprising: a plurality of spillbox feed tanks, each spillbox feed tank comprising: a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, an inlet for receiving a tailings fluid flow into the tank cavity, an overflow weir extending outwardly from an upper portion of the tank cavity, and an adjustable valve configured to cooperate with the overflow weir; a plurality of screening devices, each screening device having a screening surface receiving the tailings fluid flow spilling over the overflow weir of one of the spillbox feed tanks, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; and a collector body arranged below the screening surface of the screening devices having a collecting cavity to receive the screened tailings fluids of the plurality of screening devices; the adjustable valves of the spillbox feed tanks being adjusted for the different spillbox feed tanks to have a substantially similar outlet flow.
[0032] In some implementations, the pre-treatment screening assembly may further comprise a frame, the spillbox feed tanks being mounted to the frame, each overflow weir defining a height relative to a ground on which the frame stands, the adjustable valves of the spillbox feed tanks being adjusted in response to the height of the overflow weir of the spillbox feed tanks. Each overflow weir may have an adjustable plate to modify the height of the overflow weir.
[0033] In some other implementations, the pre-treatment screening assembly may further comprise a frame, the spillbox feed tanks having an adjustable mounting base to be adjustably mounted to the frame. Each overflow weir may define a height relative to a ground on which the frame stands, the adjustable mounting bases being adjusted for the overflow weirs to have a substantially similar height. The pre-treatment screening assembly may comprise a single collector body.
[0034] In some other implementations, the pre-treatment screening assembly may comprise at least two screening devices, each screening device defining a longitudinal direction and having two opposed longitudinal ends, said at least two screening devices extending side to side substantially parallel, the pre-treatment screening assembly further comprising an access platform extending along the screening devices at one of their longitudinal ends. The pre-treatment screening assembly may further comprise two other screening devices, each screening device defining a longitudinal direction and having two opposed longitudinal ends, said at least two screening devices extending side to side substantially parallel, the pre-treatment screening assembly further comprising a second access platform extending along said two other screening devices at one of their longitudinal ends, so that the pre-treatment screening assembly has a substantially rectangular shape.
[0035] In another aspect, there is provided a pre-treatment screening assembly comprising: a plurality of spillbox feed tanks, each spillbox feed tank comprising: a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, an inlet for receiving a tailings fluid flow into the tank cavity, and an overflow weir extending outwardly from an upper portion of the tank cavity; at least two screening devices, each screening device defining a longitudinal direction and having two opposed longitudinal ends, said at least two screening devices extending side to side substantially parallel, and each screening device having a screening surface receiving the tailings fluid flow spilling over the overflow weir of one of the spillbox feed tanks, the screening surface being configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; an access platform extending along the screening devices at one of their longitudinal ends; and a collector body arranged below the screening surface of the screening devices having a collecting cavity to receive the screened tailings fluids.
[0036] In another aspect, there is provided a pre-treatment site comprising: a pre-treatment screening assembly according to the present disclosure; an inlet line fluidly connected to the pre-treatment screening assembly to discharge a tailings fluid flow onto the screening surface of the screening device; and a discharge line fluidly connected to the collector body for downstream treatment operations of the screened tailings fluid. The pre-treatment screening assembly may have a rectangular shape and comprises four screening devices, each of them constituting a corner of the pre-treatment screening assembly. The pre-treatment screening assembly may further comprise two parallel platforms, said four screening devices being arranged between said two platforms. The pre-treatment site may further comprise at least two pre-treatment screening assemblies, each of them having four screening devices arranged between two parallel platforms, the platforms of the at least two pre-treatment screening assemblies being substantially parallel to each other.
[0037] In yet another aspect, there is provided a process for screening coarse debris from a tailings fluid flow coming from an inlet line, the process comprising:

providing the tailings fluid flow to a pre-treatment screening assembly comprising a spillbox feed tank having a bottom wall and side walls extending upwardly from the bottom wall, thereby defining a tank cavity, a screening device and a collector body;
connecting the inlet line to a tailings inlet formed in the bottom wall of the spillbox feed tank so as to form in the tank cavity a substantially vertical tailings fluid inlet flow; filling the tank cavity of the spillbox feed tank with the tailings fluid flow for the tailings fluid flow to reach an overflow weir of the spillbox feed tank; discharging a tailings fluid outlet flow over the overflow weir of the tank cavity onto the screening device, the screening device having a screening surface configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid;
and collecting the screened tailings fluid into the collector body.
[0038] In some implementations, the process may further comprise modifying at least one of the inlet and outlet flow rates of the spillbox feed tank. The process may further comprise measuring a level of tailing fluid in the tank cavity. The process may further comprise modifying the at least one of the inlet and outlet flow rates of the spillbox feed tank in response to the measured level of the tailings fluid in the tank cavity.
[0039] In another aspect, there is provided a process for screening coarse debris from a tailings fluid flow coming from an inlet line, the process comprising:
providing the tailings fluid flow to a pre-treatment screening assembly comprising a spillbox feed tank with a tank cavity, a screening device and a collector body; connecting the inlet line to a tailings inlet formed in the spillbox feed tank; filling the tank cavity of the spillbox feed tank with the tailings fluid flow for the tailings fluid flow to reach an overflow weir of the spillbox feed tank; discharging a tailings fluid outlet flow over the overflow weir of the tank cavity onto the screening device, the screening device having a screening surface configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; collecting the screened tailings fluid into the collector body; and removing the coarse debris from the screening surface.
[0040] In some implementations of the process, the screening surface may define a first adjustable inclination angle with a horizontal direction, the process further comprising modifying the first adjustable inclination angle. The process may further comprise measuring an amount of coarse debris on the screening surface. The process may further comprise measuring an amount of tailings fluid losses resulting from a running off of the screening surface. The screening surface may define a first adjustable inclination angle with a horizontal direction, the process further comprising modifying the first adjustable inclination angle in response to at least one of the measured amount of coarse debris and of the measured amount of tailings fluid losses.
The process may further comprise placing the removed coarse debris into a debris collection bin. The debris collection bin may be heated. The tailings fluid contained in the debris collection bin may be pumped back into the spillbox feed tank. The process may further comprise applying vibrations to the screening surface.
[0041] In another aspect, there is provided a process for screening coarse debris from a tailings fluid flow coming from an inlet line and going into an outlet line, the process comprising: providing the tailings fluid flow to a pre-treatment screening assembly comprising a spillbox feed tank with a tank cavity, a screening device and a collector body having a discharge outlet connected to the outlet line;
connecting the inlet line to a tailings inlet formed in the spillbox feed tank; filling the tank cavity of the spillbox feed tank with the tailings fluid flow for the tailings fluid flow to reach an overflow weir of the spillbox feed tank; discharging a tailings fluid outlet flow over the overflow weir of the tank cavity onto the screening device, the screening device having a screening surface configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; collecting the screened tailings fluid into the collector body; and deflecting the screened tailings fluid inlet flow filling the collector body from the discharge outlet.
[0042] In another aspect, there is provided a process for screening coarse debris from a tailings fluid flow coming from an inlet line, the process comprising:
providing the tailings fluid flow to a pre-treatment screening assembly comprising at least two spillbox feed tanks having each a tank cavity, a screening device and a collector body;
connecting the inlet line to a tailings inlet formed in each of the spillbox feed tanks;
filling each tank cavity of the spillbox feed tanks with the tailings fluid flow for the tailings fluid flow to reach an overflow weir of each of the spillbox feed tanks;
discharging a tailings fluid outlet flow over the overflow weir of the tank cavity onto the screening device, the screening device having a screening surface configured to allow material with a predetermined size that is included in the tailings fluid flow to flow through the screening surface and separate coarse debris from the tailings fluid flow, thereby separating the tailings fluid into a coarse debris fraction and a screened tailings fluid; collecting the screened tailings fluid into the collector body; and adjusting the outflow rate of at least one of the tailings fluid outlet flow for the different spillbox feed tanks to have a substantially similar outlet flow rate.
[0043] In some implementations of the process, each overflow weir may define a height relative to a ground on which the pre-treatment screening assembly stands, and the process may further comprise modifying the height of at least one overflow weir for the different spillbox feed tanks to have a substantially similar outlet flow rate. Each spillbox feed tank may define a height relative to a ground on which the pre-treatment screening assembly stands, the process may further comprise modifying the height of at least one spillbox feed tank for the different spillbox feed tanks to have a substantially similar outlet flow rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] Figs. 1 and 2 are respective front and rear perspective views of an embodiment of a pre-treatment screening assembly;
[0045] Fig. 3 is a rear perspective view of another embodiment of a pre-treatment screening assembly;
[0046] Fig. 4 is a cross-section view of another embodiment of a pre-treatment screening assembly;
[0047] Fig. 5 is a rear perspective view of another embodiment of a pre-treatment screening assembly;
[0048] Fig. 6 is a rear perspective view of another embodiment of a pre-treatment screening assembly, the frame of the pre-treatment screening assembly having an elevated structure;
[0049] Fig. 7 is an elevation view of an embodiment of a spillbox feed tank;
[0050] Fig. 8 is an elevation view of another embodiment of a spillbox feed tank;
[0051] Fig. 9 is a side elevation view of an embodiment of a spillbox feed tank and a screening device;
[0052] Fig. 10 is a cross-section view of an embodiment of a screening device;
[0053] Fig. 11 is a cross-section view of another embodiment of a screening device, a mechanical cleaning device being mounted to the screening device;
[0054] Fig. 12 is a side elevation view of another embodiment of a screening device, the screening device having a screening surface with an adjustable inclination angle;
[0055] Fig. 13 is a cross-section view of an embodiment of a collector body;
[0056] Fig. 14 is a top perspective view of the collector body of Fig. 13;
[0057] Fig. 15 is a top perspective view of other embodiments of collector bodies;
[0058] Fig. 16 is a cross-section view of one of the collector bodies of Fig. 15;
[0059] Fig. 17 is a perspective view of a vortex breaker;
[0060] Fig. 18 is a cross-section view of the vortex breaker of Fig.
17;
[0061] Fig. 19 is schematic view of an embodiment of a pre-treatment site; and
[0062] Fig. 20 is schematic view of another embodiment of a pre-treatment site.
DETAILED DESCRIPTION
[0063] Systems, processes, devices and techniques are described that allow pre-treating oil sands fine tailings in order to remove coarse debris prior to a chemical tailings treatment operation, such as chemical enhanced dewatering or other processes.
[0064] There are provided pre-treatment screening techniques for removing coarse debris from oil sands fine tailings and produce screened oil sands fine tailings, the screened oil sands fine tailings having improved reactivity and/or mixability with chemicals in a subsequent chemical tailings treatment operation. The pre-treatment screening techniques may further produce screened oil sands fine tailings thereby enabling to reduce or eliminate damage, clogging and/or plugging of downstream equipment used in the chemical tailings treatment operation.
General pre-treatment screening assembly
[0065] The general structure of a pre-treatment screening assembly configured to remove coarse debris from oil sands fine tailings as well an example of a method for removing debris from oil sands fine tailings are disclosed in the above-mentioned patent No. 2,772,053.
[0066] Referring to Figs. Ito 6, a known pre-treatment screening assembly 100 as disclosed in particular in Canadian Patent No. 2,772,053 is configured for receiving debris containing oil sands fine tailings and for removing coarse debris from an oil sands fine tailings fluid. The oil sands fine tailings are for instance retrieved from a tailings pond 202. An oil sands fine tailings fluid that is pumped from the tailings pond 202 by means of a dredge or barge typically includes various kinds of debris.
Still referring to Figs. 1 to 6, the pre-treatment screening assembly 100 generally includes a frame 102, at least one spillbox feed tank 110 mounted to the frame 102, at least one screening device 140 in fluid communication with the spillbox feed tank 110 and at least one collector body 160.
[0067] The oil sands tailings fluid is fed to the pre-treatment screening assembly 100 through an inlet line 104, which is connected to the spillbox feed tank 110. The spillbox feed tank 110 then discharges the tailings fluid onto the screening device 140.
The screening device 140 has a screening surface 142 that is configured to separate coarse debris from the tailings fluid, thereby producing a screened tailings fluid which flows through the screening surface 142 and coarse debris that are retained by the screening surface 142. The screened tailings fluid is collected by the collector body 160. The screened tailings fluid may contain material with a predetermined size enabling the material to flow through the screening surface 142 of the screening device 140 toward and into the collector body 160. The screened tailings fluid collected in the collector body 160 may then be sent to a discharge line 108 for downstream chemical tailings treatment operations that may include, for instance but without being limitative, flocculation and dewatering.
[0068] Some improvements relative to the different components of the pre-treatment screening assembly 100 will now be described; the improvements can either be considered separately or be combined together.

Spillbox feed tank implementations
[0069] Referring now more particularly to Figs. 7 to 9, the spillbox feed tank 110, which is configured to feed the oil sands fine tailings fluid to the screening device 140, includes a tailings inlet 112, a tank cavity 114 defined by side walls 116 and a bottom wall 118, and an overflow weir 120. The oil sands fine tailings fluid is fed into the tank cavity 114 via the tailings inlet 112 and flows upward into the tank cavity 114 until reaching the overflow weir 120, at which point the tailings fluid flows over the overflow weir 120 and down onto the screening device 140.
Tailings inlet formed in the bottom wall of the spillbox feed tank
[0070] In the exemplary embodiment of the spillbox feed tank 110 from Fig. 8, the tailings inlet 112 is formed in the bottom wall 118, for example substantially centrally. In the existing spillbox feed tank 110' represented for instance in Fig. 7, the tailings inlet 112' is formed in one of the side walls 116' of the spillbox feed tank 110' so that, when a tailings fluid flow is introduced into the tank cavity 114' via the tailings inlet 112', the tailings fluid flow rebounds on the side wall opposed to the one in which the tailings inlet 112' is formed. This existing spillbox feed tank geometry creates an uneven flow distribution across the screening surface of the screening device when the tailings fluid flows over the overflow weir onto the screening surface. Such an arrangement of the tailings inlet 112' may not be satisfactory since it can lead to an overload of one side of the screening surface, resulting in high losses of the fine tailings fluid running off of the screening device on this side.
[0071] On the contrary, in the spillbox feed tank 110 represented in Fig. 8, in which the tailings inlet 112 is formed in the bottom wall 118 of the spillbox feed tank 110, for instance centrally in the bottom wall 118, the flow bias is significantly reduced in comparison with the spillbox feed tank 110' of Fig. 7, resulting in an improved screening of the tailings fluid. In the spillbox feed tank of Fig. 8, the tailings fluid defines a substantially vertical flow in the tank cavity 114 when introduced therein via the tailings inlet 112. The tailings fluid may then be discharged uniformly onto the screening surface 142 of the screening device 140. As a result, the used surface area of the screening surface 142 is increased in comparison with the spillbox feed tank 110' of Fig. 7, the tailings fluid overflow is reduced and thus the screening capacity of the pre-treatment screening assembly 100 comprising the spillbox feed tank 110 of Fig. 8 is improved in comparison with a pre-treatment screening assembly comprising the spillbox feed tank 110' of Fig. 7.
Dimensions of the overflow weir being narrower than dimensions of the screening surface
[0072] As represented for instance in Fig. 4, the screening device 140 has an upstream inlet 144, the tailings fluid flow being discharged onto the screening surface 142 of the screening device 140 over the overflow weir 120 of the spillbox feed tank 110 at the upstream inlet 144. As represented for instance in Fig. 9, the screening device 140 has a plurality of substantially parallel screening bars that are spaced apart from each other so as to define openings on either side of each screening bar.
The screening device 140 also includes a plurality of supporting bars forming boundaries of the screening surface 142. The supporting bars are arranged so that the screening surface 142 of the screening device 140 is substantially rectangular and defines a length L1 and a width L2, whereas the overflow weir 120 of the spillbox feed tank 110 defines a width W, as it is represented for instance in Figs. 2 and 9.
[0073] In some existing embodiments of the pre-treatment screening assembly, the width of the overflow weir substantially corresponds to the width of the screening surface, so that a significant quantity of the tailings fluid that is discharged from the spillbox feed tank on the screening device is in fact discharged on the supporting bars of the screening device, and thus is discharged outside the screening surface, i.e.
outside the collector body 160. This results in significant amounts of the tailings fluid that are not screened by the pre-treatment screening assembly. In the shown embodiment, as represented for instance in Fig. 9, the overflow weir 120 is dimensioned so that its width W is narrower than the width L2 of the screening surface 142. To this end, baffle plates 124 may be arranged in the tank cavity 114 of the spillbox feed tank 110, substantially parallel to the side walls 116, so as to the reduce the width W of the overflow weir 120 over which the tailings fluid is discharged at the upstream inlet 144 of the screening device 140. In some embodiments, the width W of the overflow weir 120 represents less than 90% of the width L2 of the screening surface 142.
[0074] In some other embodiments, the width W of the overflow weir 120 represents less than 85% of the width L2 of the screening surface 142. In yet other embodiments, the width W of the overflow weir 120 represents less than 80% of the width L2 of the screening surface 142. As the width W of the overflow weir 120 is reduced relative to the width L2 of the screening surface 142, the losses of the tailings fluid (i.e. the amount of the tailings fluid being discharged outside the screening surface 142 of the screening device 140, and thus outside the collector body 160) are reduced, and thus the capacity of the pre-treatment screening assembly 100 is increased compared to the pre-treatment screening assemblies in which the width of the overflow weir substantially corresponds to the width of the screening surface.
Control and regulation devices
[0075] As detailed above, the tailings fluid is fed into the tank cavity 114 of the spillbox feed tank 110 via the tailings inlet 112 and then flows over the overflow weir 120 and down to the screening device 140 from the upstream inlet 144 (which corresponds to an upper edge of the overflow weir 120). Referring to Fig. 4 the pre-treatment screening assembly 100 may further comprise adjustable valves 113, configured to cooperate respectively with the tailings inlet 112 and with the overflow weir 120. The spillbox feed tank 110 may further comprise a level sensor 126, as represented in Fig. 4, the level sensor 126 being configured to measure the tailings fluid level in the tank cavity 114 of the spillbox feed tank 110.
[0076] For instance but without being limitative, the level sensor 126 comprises two distinct pressure transmitters that are arranged in the tank cavity 114 and that measure the pressure of the tailings fluid at two distinct locations of the tank cavity 114.
On the basis of a pressure difference between pressures measured by the two distinct pressure transmitters, the level sensor 126 determines the level of the tailings fluid in the tank cavity 114. For instance, the level sensor 126 can use the following principle:
P=d*g*h, where P is the pressure difference between two vertical positions of a fluid, d is the density of the fluid, g is the gravitational constant and h is the distance between the two vertical positions at which the pressures of the fluid are measured, to determine the level of the tailings fluid in the tank cavity 114. The adjustable valves 113, 121 can be actuated in response to the tailings fluid level determined by the level sensor 126.
[0077] For instance, when the determined level is above a first pre-determined threshold, at least one of the following actions may be undertaken:
- the adjustable valve 121 configured to cooperate with the overflow weir 120 will be actuated so as to increase the tailings fluid flow rate at the overflow weir 120 that is discharged to the screening device 140; and - the adjustable valve 113 configured to cooperate with the tailings inlet 112 will be actuated so as to reduce the tailings fluid flow rate at the tailings inlet 112.
[0078] To this end, the adjustable valve 113 can be designed to cooperate with a pump mounted in the inlet line 104 to feed the spillbox feed tank 110 with the tailings fluid.
[0079] On the other hand, when the tailings fluid level determined by the level sensor 126 is below a second pre-determined threshold, at least one of the following actions may be undertaken:
- the adjustable valve 121 configured to cooperate with the overflow weir 120 will be actuated so as to reduce the tailings fluid flow rate at the overflow weir 120; and - the adjustable valve 113 configured to cooperate with the tailings inlet 112 will be actuated so as to increase the tailings fluid flow rate at the tailings inlet 112.
[0080] Cooperation between the level sensor 126 and the adjustable valves 113, 121 is also particularly useful to ensure that transfer pumps of the pre-treatment screening assembly 100, are prevented from working when the tailings fluid level in the tank cavity and/or in the inlet line 104 is below a pre-determined threshold, so as not to damage the transfer pumps. The transfer pumps may serve for instance to feed the spillbox feed tank 110 with the tailings fluid, to discharge the tailings fluid on the screening surface 142 of the screening device 140 or to make the screened tailings fluid circulate in the discharge line 108.
Screening device implementations
[0081] Referring again to Fig. 4, the screening device 140 has an upstream inlet 144 at which the tailings fluid is discharged from the spillbox feed tank 110, over the overflow weir 120. The screening device 140 further comprises a bottom end 146, as represented for instance in Fig. 2. The bottom end 146 is designed to accumulate the coarse debris received and retained by the screening surface 142, and to easily remove the coarse debris towards a collection area 180. To enhance the accumulation, and thus the rejection, of the coarse debris, the screening surface 142 may be inclined downwardly so as to define a first inclination angle al with respect to a horizontal direction; the first inclination angle al can range between 25 degrees to 45 degrees.
For instance, the first inclination angle al measures about 30 degrees.
Adjustable inclination of the screening surface
[0082] It should be noted that the first inclination angle al may be adjustable so as to adapt to the nature of the tailings to be screened or perform specific operational steps such as maintenance operations for instance. In the shown embodiment, as represented for instance in Fig. 12, the pre-treatment screening assembly 100 further comprises a winch 148 that is configured to adjust the first inclination angle al formed by the screening surface 142 relative to the horizontal direction. As a result, it is possible to adapt the arrangement of the screening surface 142 of the screening device 140 so as to alternatively enable self-cleaning of the screening surface 142 or at least ease the discharging of the coarse debris from the screening surface 142 towards the collection area 180, or to reduce the tailings fluid losses resulting from a running off of the screening surface 142. In other words, it is understood that the screening device 140 is designed to allow a user to reduce the first inclination angle al of the screening surface 142, if the coarse debris loading on the screening surface 142 is insufficient and/or if the tailings fluid losses are excessive. A user can also increase the first inclination angle al of the screening surface 142 so as to increase the self-cleaning of the screening surface 142, for instance under heavy debris loading or when it is considered that the amount of the coarse debris on the screening surface 142 has reached a pre-determined threshold.
[0083] The pre-treatment screening assembly may further comprise a sensor designed to evaluate the quantity of coarse debris on the screening surface.
The pre-treatment screening assembly could further comprise a control circuit receiving a signal from the sensor when the quantity of coarse debris on the screening surface measured by the sensor has reached a pre-determined threshold, the control circuit then actuating the winch 148 as seen on Fig. 12 ¨ or any other adapted mechanical device -so as to increase the value of the first inclination angle al formed between the screening surface and the horizontal direction. The pre-treatment screening assembly could further comprise an additional sensor designed to evaluate the quantity of tailings fluid losses resulting from a running off of the screening surface; the control circuit could further be designed to receive a signal from the additional sensor when the quantity of tailings fluid losses has reached a pre-determined threshold, the control circuit then actuating the winch 148 as seen on Fig. 12 ¨ or any other adapted mechanical device - so as to reduce the first inclination angle al formed between the screening surface and the horizontal direction.
[0084] In another embodiment of the screening device 140 represented for instance in Fig. 10, the screening surface 142 could have a concave profile, thereby having a varying slope decreasing from a top end 147 of the screening device 140 to a bottom end 146 of the screening device 140. For instance, the angle formed between the screening surface 142 and the horizontal direction can vary between 0 degree, at the bottom end 146 of the screening device 140, and 80 degrees, at the top end 147 of the screening device 140. The use of a concave profile for the screening surface 142 is particularly efficient for the automatic removal and/or accumulation of the coarse debris reaching the screening surface 142, without resulting from an increase of the tailings fluid losses resulting from a running off of the screening surface 142.
Mechanical cleaning device
[0085] In some implementations, as represented in Fig. 11, the pre-treatment screening assembly 100 further comprises a mechanical cleaning device 170 that is configured to mechanically remove the coarse debris from the screening surface 142 of the screening device 140. The mechanical cleaning device 170 can regularly remove the coarse debris from the screening surface 142 and/or when the quantity of the coarse debris on the screening surface 142 has reached a pre-determined threshold.
To this end, the mechanical cleaning device 170 can cooperate with the above-mentioned control circuit and be actuated in response to a signal sent by the above-mentioned sensor that is designed to evaluate the quantity of the coarse debris on the screening surface 142. For instance but without being limitative, the mechanical cleaning device 170 comprises rakes and/or rotating brushes designed to go all over the screening surface 142 so as to pull the coarse debris away from the screening surface 142; for instance, the mechanical cleaning device 170 pulls the coarse debris toward the collection area 180.
[0086] In some implementations, as represented in Fig. 11, the screening device 140 comprises an upper portion 150 having an upper screening surface 151, and a lower portion 152 having a lower screening surface 153. The upper screening surface 151 defines an upper angle a2 with the horizontal direction and the lower screening surface 153 defines a lower angle a3 relative to the horizontal, the upper angle a2 being greater than the lower angle a3. In some implementations, the upper angle a2 may be comprised between 30 degrees and 60 degrees, and the lower angle a3 may be comprised between 15 degrees and 30 degrees. Optionally, the upper angle a2 may be comprised between 40 degrees and 50 degrees, and the lower angle a3 may be comprised between 20 degrees and 25 degrees. In some implementations, the upper angle a2 may be at least 1.5 times greater than the lower angle a3.
Optionally, the upper angle a2 may be about two times greater than the lower angle a3.
[0087] The arrangement of the upper and lower portions 150, 152 of the screening device 140 enables to efficiently separate the liquids from the coarse debris of the tailings fluid, and to direct the coarse debris towards the lower portion 152, so as to ease their removal from the screening device 140. As represented in Fig. 11, the mechanical cleaning device 170 can be arranged on the lower portion 152 of the screening device 140, so that the dimensions of the mechanical cleaning device are reduced with regards to a screening device 140 having one single inclination angle relative to the horizontal direction, in which case the mechanical cleaning device 170 would be dimensioned to go all over the screening surface 142. As represented for instance in Fig. 11, the mechanical cleaning device 170 can comprise at least one rake 171 to remove coarse debris from the lower screening surface 153 of the lower portion 150. The rake 171 may be mounted on a caterpillar 191 to automatically remove coarse debris from the screening surface 142 of the screening device 140. The mechanical cleaning device 170 may further comprise a shaker (not illustrated in Fig.
11) designed to make the screening surface 142 vibrate so as to more easily accumulate the coarse debris, and then to more easily remove them.
Debris collection bin
[0088] In some existing embodiments of the pre-treatment screening assembly, the coarse debris that are removed from the screening device are rejected in the tailings pond, such a coarse debris management requiring in particular from the screening device to be close to the tailings pond. As it is represented for instance in Fig. 4, the pre-treatment screening assembly 100 further comprises a debris collection bin 172 that is placed, for instance and without being limitative, under or in the vicinity of the screening device 140, so as to collect the coarse debris that are removed from the screening surface 142, for instance by the above described mechanical cleaning device 170. The coarse debris that are collected in the debris collection bin 172 can then be hauled away at an appropriate dump location, so as to permanently be removed from the tailings pond 202 and to reduce their long-term impact on the tailings fluid dredging. The dimensions of the debris collection bin 172 are adapted so that the debris collection bin 172 will only need to be emptied, for instance, a few times a month.
[0089] Still referring to Figure 4, the pre-treatment screening assembly 100 can also comprise a debris heater 173 designed to heat the debris collection bin 172 so that its content will not freeze, which would make it more complex for the coarse debris to be removed from the debris collection bin 173. The pre-treatment screening assembly 100 can further comprise a debris collection pump 174, as represented in Fig. 4, that is designed to pump the tailings fluid from the debris collection bin 172 and to inject it back into the spillbox feed tank 110. The debris collection bin 172 and the debris collection pump 174 enable to increase the quantity of the tailings fluid that is processed by the pre-treatment screening assembly 100.Moreover, the use of the debris collection bin 172 enables to reduce constraints relative to the location of the screening device 140 close to the tailings pond 202, for debris removal purposes.
Collector body implementations
[0090] As mentioned above, after the oil sands fine tailings fluid has been discharged at the upstream inlet 144 of the screening device 140, the screened oil sands fine tailings fluid is collected by the collector body 160. The collector body 160 may be sized and configured to enable the flow of the screened tailings fluid to accumulate and form a more uniform composition of the screened tailings. Thus, for instance, fluctuations in the composition of the tailings retrieved from the tailings pond 202 can be attenuated both by the removal of the coarse debris via the screening device 140 and also by the accumulation of the screened tailings fluid having greater uniformity than the tailings fluid piped from the tailings pond. In the shown embodiment, the collector body 160 has side walls 162 and a bottom wall 164 that define together a collecting cavity 166.
Design of the collector body
[0091] As represented in Figs. 1 to 6, the bottom wall 164 of the collector body 160 may comprise a bottom discharge opening 165 designed to collect and easily remove debris, such as sand particles, that build up in the collector body 164 and that have not been removed by the screening device 140. The collector body 160 may be designed to favor the accumulation of debris near the bottom discharge opening 165, in order to ease their removal outside the collector body 160.The collector body 160 may therefor have a bottom conical shape or, as represented for instance in Fig. 4, at least one sloped side wall 163 extending from one of the side walls 162. The sloped side wall 163 may extend between one of the side walls 162 and the bottom wall 164.
[0092] In some other embodiments, as represented for instance in Figs.
15 and 16, the sloped side wall 163 extends only partially between two opposed side walls 162, a substantially horizontal portion 181 extending between the sloped side wall 163 and the side wall 162 opposed to the one from which the sloped side wall 163 extends.
In another embodiment, as represented in Fig. 16, the sloped side wall 163 is oriented at an inclination angle a4 with respect to the horizontal direction, the inclination angle a4 being comprised between 15 degrees and 75 degrees. Optionally, the inclination angle a4 is comprised between 30 degrees and 60 degrees. Further optionally, the inclination angle a4 is comprised between 40 degrees and 50 degrees.
[0093] In order to further ease the removal of the debris via the bottom discharge opening 165, and as it represented for instance in Fig. 3, the collector body 160 can be elevated so that an operator can easily reach the bottom discharge opening 165, in order to open it for removing the built-up debris. In the shown embodiment, the frame 102 of the pre-treatment screening assembly 100 has an elevated structure, for the bottom discharge opening 165 of the collector body 160 to be more easily accessible by the operator.
Air reduction in the screened tailings
[0094] Referring to Fig. 2, the screened tailings fluid collected in the collecting cavity 166 of the collector body 160 is then released from the collector body through at least one discharge outlet 167 that may be located in the bottom wall 164 or in a bottom portion of one of the side walls 162 of the collector body 160 and connected to the discharge line 108. The discharge line 108 then sends the screened tailings fluid to further treatments, such as flocculation and dewatering of the screened tailings. The pre-treatment screening assembly 100 comprises at least one discharge pump 109 to make the screened tailings fluid circulate in the discharge line 108. In some pre-treatment screening assemblies, air may be trapped within the screened tailings fluid flow, when the screened tailings fluid falls through the screening device.
The formed air pockets sometimes disrupt operation of the pre-treatment screening assembly, for instance by disrupting the working of the discharge pump.
[0095] So as to reduce the negative impact of the air mixing on the pre-treatment of the tailings, as represented in Fig. 1, the discharge outlet 167 may be arranged in one of the side walls 162 of the collector body 160 that extends perpendicularly to the upstream inlet 144 of the screening device 140 and perpendicularly to the width L2 of the screening surface 142. Moreover, the screening device 140 may comprise an overflow weir 169 designed so that only top level screened tailings fluid is collected in the collecting cavity 166 of the collector body 160, and that less air is transferred to the collector body 160. As represented in Figs. 13 and 14, the pre-treatment screening assembly 100 comprises at least one deflector plate 168 arranged in the collecting cavity 166, for instance above the discharge outlet 167, so as to reduce the circulation of air in the discharge line 108. It should be understood that the deflector plate 168 can also contribute to the accumulation of the debris close to the bottom discharge opening 165 of the collector body 160.
[0096] In an embodiment, the deflector plate 168 is oriented at an inclination angle a5 with respect to the horizontal direction, the inclination angle a5 being comprised between 20 degrees and 60 degrees. Particularly, the inclination angle a5 may be comprised between 30 degrees and 50 degrees. As represented in Fig. 16, the pre-treatment screening assembly 100 further comprises a vortex breaker 161 mounted in an opening formed in one of the side walls 162 of the collector body 160 and extending at least partially in the collecting cavity 166. As represented for instance in Figs. 16 to 18, the vortex breaker 161 comprises a substantially cylindrical body 190 and a vortex breaking core 192 arranged in the cylindrical body 190. In the shown embodiment, the vortex breaking core 192 has a crossed-shaped section: the vortex breaking core 192 comprises two plates 194, 195 assembled together in a substantially perpendicular way, the two plates 194, 195 being secured to the cylindrical body 190.
Pre-treatment screening assembly implementations
[0097] It should be understood that the present description is not limited to a pre-treatment screening assembly 100 comprising solely one spillbox feed tank 110, one screening device 140 and one collector body 160, the different elements being mounted to the frame 102. Indeed the pre-treatment screening assembly 100 may include a plurality of screening devices mounted adjacently and operating in parallel with respect to each other. As represented for instance in Figs. 1 and 2, the pre-treatment screening assembly 100 may include four spillbox feed tanks 110, each spillbox feed tank 110 having an overflow weir 120 for discharging a tailings fluid flow on a corresponding screening device 140.
[0098] The pre-treatment screening assembly 100 can have one single collector body 160 arranged below the different screening devices 140, or there may be one or more collector bodies 160 for each overlying screening device 140. In the embodiment of the pre-treatment screening assembly 100 comprising a plurality of collector bodies 160, each collector body may have a discharge outlet 167, or the pre-treatment screening assembly 100 may have a possibly larger single discharge outlet 167.
It is thus possible to form the single discharge outlet 167 in one of the side walls 162 or bottom walls 164 of the collector bodies 160 so as to adapt the pre-treatment screening assembly 100 to the location where it is installed.
Optimization of the pre-treatment screening assembly design
[0099] As represented in Fig. 5, in order to improve the operation of the pre-treatment screening assembly 100, said assembly 100 may include platforms, stairways and railings 106 which allow an operator to easily and safely monitor the pre-treatment screening assembly 100, for example to monitor the screening surfaces 142.
In some embodiments, as represented in Figs. 1 and 2, platforms 106 are arranged between two adjacent screening devices 140. When the pre-treatment screening assembly 100 comprises four screening devices 140 arranged substantially parallel to each other, as represented in Fig. 5, the pre-treatment screening assembly 100 thus comprises two substantially parallel platforms 106.
[00100] In some other embodiments, as represented in Fig. 5, the pre-treatment screening assembly 100 comprises one single platform 106 extending along the four screening devices 140, and outwardly from a respective longitudinal end 149 of the screening devices 140. This arrangement of the platform 106 enables to increase the dimensions of the screening surfaces 142 of the two adjacent screening devices compared to an embodiment wherein the pre-treatment screening assembly 100 includes platforms 106 which are arranged between two adjacent screening devices 140. Other arrangements of the platform 106 may be conceived within the framework of the present disclosure; for instance, the platform 106 may be arranged so as to overhang the screening devices 140. As represented in Fig. 1, the screening devices 140 may comprise each an access door 157, for instance to let a user easily access the screening surface 142, to clean and/or repair it, whenever needed.
[00101] In the embodiment of the pre-treatment screening assembly 100 in which the platforms 106 are arranged between two adjacent screening devices 140, as represented in Figs. 1 and 2, the access doors 157 of the two adjacent screening devices usually face each other, on each side of the corresponding platform 106. In the embodiment of the pre-treatment screening assembly 100 comprising one single platform 106, as represented in Fig. 5, the access doors 157 of the screening devices 140 may be arranged at the corresponding longitudinal end 149 at which the sole platform 106 extends. In the embodiment of the pre-treatment screening assembly 100 in which the platforms 106 do not extend between two adjacent screening devices 140, the dimensions of the screening surfaces 142 of the screening devices 140 may be increased. The overall screening surface of the pre-treatment screening assembly 100 may thus be increased, and so is the pre-treatment capacity of the pre-treatment screening assembly 100.
Plurality of adjustable overflow weirs
[00102] In the shown embodiment from Figs. 1 and 2, the pre-treatment screening assembly 100 comprises a plurality of spillbox feed tanks 110, each of them having an overflow weir 120. In some embodiments, the overflow weirs 120 of the spillbox feed tanks 110 are adjustable and configured to ensure that the different spillbox feed tanks 110 of the pre-treatment screening assembly 100 have a substantially similar outlet flow that is discharged on the corresponding screening device 140. In particular, the adjustable overflow weirs 120 may be adjustable according to an elevation of each spillbox feed tank 110 relative to the ground on which the frame 102 is located. In other words, the adjustable overflow weirs 120 enable to compensate for differences in the elevation of the different spillbox feed tanks 110. The adjustability of the overflow weirs 120 may be implemented in different manners. For instance, the spillbox feed tanks 110 may have a mounting base 130, the spillbox feed tanks 110 being mounted to the frame 102 of the pre-treatment screening assembly 100 via their respective mounting base 130. The mounting base 130 may be adjustable so as to adjust the elevation of the overflow weir 120.
[00103] Alternatively, the overflow weirs 120 of the spillbox feed tanks 110 may comprise adjustable plates that are configured to modify the elevation at which the tailings fluid flow will flow out of the tank cavity 114 of the spillbox feed tank 110. It is thus understood that the adjustable overflow weirs 120 of the spillbox feed tanks 110 allows to more evenly discharge the tailings fluid flow on the screening surface 142 of the different screening devices 140, thus improving the capacity and efficiency of the pre-treatment screening assembly 100.
Pre-treatment site implementations
[00104] In another aspect, there is provided a pre-treatment site for the pre-treatment of fine tailings, comprising several pre-treatment screening assemblies arranged close to a tailings pond. As represented in Fig. 19, an existing pre-treatment site 200' comprises six pre-treatment screening assemblies 100', each of them having four screening devices 140'. The four screening devices 140' of each pre-treatment screening assembly 100' are substantially parallel to each other so that each pre-treatment screening assembly 100' has a substantially rectangular shape with a long side 11' and a small side 12', the small side 12' of the assembly 100' corresponding substantially to a length of the screening devices 140. Moreover, the six pre-treatment screening assemblies 100' of the pre-treatment site 200' represented in Fig.
19 are arranged side by side along their long side 11', so that the twenty-four screening devices 140 are arranged in a substantially parallel manner along the tailings pond 202.
Optimized footprint pre-treatment site
[00105] The pre-treatment site 200 represented in Fig. 20c0mprise5 three pre-treatment screening assemblies 100, each of them having four screening devices 140.
Each pre-treatment screening assembly 100 has a substantially rectangular shape with a long side 11 and a short side 12, the four corners of the rectangular being constituted by the four screening devices 140. The three pre-treatment screening assemblies 100 are arranged side by side, their long sides 11 being substantially parallel to each other.
The footprint of the pre-treatment site 200 represented in Fig. 20 is thus significantly reduced compared to the footprint of the existing pre-treatment site 200' as represented in Fig. 19. Furthermore, thanks to an increase of the efficiency of the pre-treatment screening assemblies 100, the efficiency of the disclosed pre-treatment site 200 of Fig. 20 is substantially identical or greater than the efficiency of the existing pre-treatment site 200' of Fig. 19.
[00106] Moreover, among many significant advantages, the reduced footprint of the pre-treatment site 200 compared to the pre-treatment site 200' of Fig. 19 enables to reduce the dimensions of the inlet line 104 of the different pre-treatment screening assemblies 100. Less collection areas 180 and/or less debris collection bins 172 for the collecting of the coarse debris are also required.
Method implementations
[00107] In another aspect, there is provided a method for screening debris from an oil sands fine tailings fluid to pre-treat the oil sands fine tailings fluid for chemical treatment, such as flocculation and dewatering. The oil sands fine tailings fluid comes from an inlet line 104. The pre-treatment screening is enabled by one or more of the above-described assemblies, systems and devices.
[00108] The method includes providing a spillbox feed tank 110 with a tailings fluid flow, the spillbox feed tank 110 having side walls 116 and a bottom wall 118 defining together a tank cavity 114, the spillbox feed tank 110 also comprising an overflow weir 120. The method includes connecting the inlet line 104 to a tailings inlet 112 formed in the bottom wall 118 of the spillbox feed tank 110 so as to form a substantially vertical inlet flow in the tank cavity 114. The method also includes feeding the spillbox feed tank 110 with the tailings fluid flow so that the tailings fluid flow reaches the overflow weir 120.
[00109] The method may further include adjusting at least one of the inlet and outlet flow rates of the tailings fluid flowing respectively to and from the spillbox feed tank
110. In other words, the method may further include adjusting the flow rate of the tailings fluid introduced into the tank cavity 114 via the tailings inlet 112 and/or of the tailings fluid going out of the tank cavity when flowing over the overflow weir 120. It should be noted that the adjustment may be performed in response to different criteria, including a measured fluid level in the tank cavity 114, a fluid losses quantity of fluid resulting from a running off of the screening surface 142, a measured amount of coarse debris on the screening surface 142, etc.
[00110] The method may thus further include measuring a level of the ailing fluid in the tank cavity 114. Measuring may include sensing the level of the fed tailings with a level sensor. Measuring may also be performed differently; for example it can be performed manually by an operator. Optionally, the level sensor may be operatively connected to a control circuit so as to monitor the level of tailings within the tank cavity 114 and actuate certain devices, such as valves, to act in response to the sensed level when reaching given thresholds. The modification of the inlet and/or outlet flow rates of the tailings fluid flow may be performed in response to the measured level of the tailings fluid in the tank cavity 114.
[00111] The method further comprises discharging the tailings fluid on a screening device 140, the tailings fluid being discharged over the overflow weir 120 and down to the screening device 140. The screening device 140 has a screening surface 142 configured to allow material with a predetermined size to flow through the screening surface 142 and separate the coarse debris, thereby splitting the tailings fluid into coarse debris and a screened tailings fluid. In some implementations, the method may include evenly discharging the tailings fluid flow along a width L2 of the screening device 140 so as to maximize a screening surface efficiency. Optionally, the method may include discharging the tailings fluid flow onto at most 80% of the width of the screening surface 142. Further optionally, the method may include discharging the tailings fluid flow onto at most 85% of the width screening surface 142. Still further optionally, the method may include discharging the tailings fluid flow onto at most 90%
of the width screening surface 142. The method may further comprise removing the coarse debris from the screening surface 142.
[00112] As detailed above, the screening surface 142 is oriented at a first inclination angle al with respect to a horizontal direction. The method may further comprise adjusting the first inclination angle al of the screening surface 142.
[00113] The method may further comprise at least one of:
- measuring an amount of coarse debris on the screening surface 142;
- measuring a fluid level in the tank cavity 114; and - measuring an amount of tailings fluid losses resulting from a running off of the screening surface 142.
[00114] For instance, the first inclination angle al of the screening surface 142 may be modified in response to at least one of the measured amount of coarse debris, the measured fluid level in the tank cavity and the measured amount of tailings fluid losses.
The method may further comprise collecting the removed debris in a debris collection bin 172 which may be located near the screening device 140. The method may further comprise heating the debris collected in the debris collection bin 172. The method may further comprise pumping the tailings fluid contained in the debris collection bin 172 back into the spillbox feed tank 110, so as to reduce the amount of oil sands tailings fluid losses resulting from a running off of the screening surface 142.
Depending on the time of the year, the pumping of the tailings fluid in the debris collection bin 172 may be performed with or without the heating of the debris collection bin 172.
[00115] The method may further comprise applying vibrations to the screening surface 142. Thanks to the vibrations, the coarse debris retained by the screening surface 142 may be more easily removed from the screening surface 142. The method may further include collecting the screened tailings fluid in a collector body 160 prior to transporting the screened tailings fluid for chemical treatment via a discharge line 108.
The collector body 160 may comprise a discharge outlet 167 connected to the discharge line 108. The method may further include deflecting a screened tailings fluid flow upstream of the collector body 160 from the discharge outlet 167.
Deflection may reduce the amount of air flowing with the screened tailings fluid flow in the discharge line 108.
[00116] The method may include providing a pre-treatment screening assembly 100 comprising at least two spillbox feed tanks 110 having each a tank cavity 114.
The method may include adjusting the outflow rate of the tailings fluid flow discharged over the overflow weir 120 of at least one spillbox feed tank 110 of the different spillbox feed tanks 110 to have a substantially similar outlet flow rate between the different spillbox feed tanks 110. Each overflow weir 120 defines a height relative to a ground on which the pre-treatment screening assembly 100 stands. The method may further comprise adjusting the height of at least one overflow weir 120 from the plurality of spillbox feed tanks 110 to obtain a substantially similar outlet flow rate between the different spillbox feed tanks 110. Each spillbox feed tank 110 defines a height relative to a ground on which the pre-treatment screening assembly 100 stands. The method may further comprise adjusting the height of at least one spillbox feed tank 110 from the plurality of spillbox feed tanks 110 to have a substantially similar outlet flow rate between the spillbox feed tanks 110.
[00117] The steps of the method may be repeated or conducted for a plurality of pre-treatment screening assemblies 100 arranged in series or in parallel.
[00118] It should be understood that the pre-treatment screening techniques described herein provide screened tailings for improved and consistent mixing with chemicals in downstream tailings treatment operations.
[00119] In some implementations, the pre-treatment screening assembly removes coarse debris that would impede or inhibit chemical reactions, for instance flocculation reactions involving flocculant and fine solid particles in the tailings. The pre-treatment process may remove coarse debris having different chemical or inertial properties compared to the fine solid particles that are not removed.
[00120] In certain applications, the fine solid particles include clay and may have a certain shape, size and surface characteristics that are considered for the chemical selection and process design for the chemical treatment operation, and can bestow certain macroscopic fluid properties. In one example, the pre-treatment screening assembly may remove bitumen masses including slugs or mats that negatively affect anionic polymeric flocculant reactions with the fine solid particles in the tailings.
[00121] In some implementations, the pre-treatment screening assembly removes coarse debris that would have disrupted the mixing of the chemical additive and the fine tailings. For instance, the pre-treatment screening assembly may remove coarse debris that would impede consistent mixer performance or mixer flow regime.
The pre-treatment screening assembly may also remove coarse debris that would cause two phase macroscopic fluid behaviour, thereby providing screened fine tailings having one phase macroscopic fluid behaviour. The pre-treatment screening assembly may remove coarse debris so that the resulting pre-treated tailings fluid is homogeneous, or does not contain a substantial amount of settling solid particles. The pre-treatment screening assembly may also remove coarse debris that would complicate or prevent reliable process modelling of the fluid mixing, flocculation or dewatering operations.
[00122] In some implementations, the pre-treatment screening assembly removes coarse debris that would damage or clog equipment.
[00123] While several implementations have been described and illustrated herein in relation to oil sands fine tailings, it should be understood that the processes, systems, devices and techniques may also be used for any other aqueous suspensions that include solid particles and coarse debris. Such aqueous suspensions may comprise mining tailings resulting from mining operations, such as mature fine tailings.
[00124] In the preceding description, the same numerical references refer to similar elements. Furthermore, for the sake of simplicity and clarity, not all figures contain references to all the components and features, and references to some components and features may be found in only one figure, and components and features of the present disclosure which are illustrated in other figures can be easily inferred therefrom.
[00125] Finally, while the description and drawings describe and illustrate certain implementations and examples of the pre-treatment techniques, the components, geometries, arrangements and/or configurations may have various other characteristics, features and co-operations as those presented herein.
[00126] Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while the specific embodiments have been illustrated and described, numerous modifications come to mind. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.
[00127] Any publications, including patents, patent applications and articles, referenced or mentioned in this specification are herein incorporated in their entirety into the specification, to the same extent as if each individual publication was specifically and individually indicated to be incorporated herein. In addition, citation or identification of any reference in the description of some embodiments of the invention shall not be construed as an admission that such reference is available as prior art to the present invention.
CA3005217A 2018-05-17 2018-05-17 Pre-treatment of oil sands fine tailings by debris removal Abandoned CA3005217A1 (en)

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