CA2812202C - Method and system for removing mature fine tailings of a desired density from a tailings pond - Google Patents

Method and system for removing mature fine tailings of a desired density from a tailings pond Download PDF

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Publication number
CA2812202C
CA2812202C CA2812202A CA2812202A CA2812202C CA 2812202 C CA2812202 C CA 2812202C CA 2812202 A CA2812202 A CA 2812202A CA 2812202 A CA2812202 A CA 2812202A CA 2812202 C CA2812202 C CA 2812202C
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Canada
Prior art keywords
hollow conduit
mature fine
fine tailings
desired density
pond
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CA2812202A
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French (fr)
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CA2812202A1 (en
Inventor
Rade Svorcan
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TECHNIKA ENGINEERING Ltd
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TECHNIKA ENGINEERING LTD.
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Priority to CA2812202A priority Critical patent/CA2812202C/en
Publication of CA2812202A1 publication Critical patent/CA2812202A1/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03BSEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
    • B03B9/00General arrangement of separating plant, e.g. flow sheets
    • B03B9/02General arrangement of separating plant, e.g. flow sheets specially adapted for oil-sand, oil-chalk, oil-shales, ozokerite, bitumen, or the like
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D21/00Separation of suspended solid particles from liquids by sedimentation
    • B01D21/24Feed or discharge mechanisms for settling tanks
    • B01D21/245Discharge mechanisms for the sediments
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B09DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09CRECLAMATION OF CONTAMINATED SOIL
    • B09C1/00Reclamation of contaminated soil
    • B09C1/007Reclamation of contaminated soil by removing contaminants floating on the water table

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Geology (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Soil Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Cleaning Or Clearing Of The Surface Of Open Water (AREA)
  • Treatment Of Sludge (AREA)

Abstract

A method and a system for removal of Mature Fine Tailings (MFT) out of oilsands tailings ponds, specifically enabling year-round removal of MFT which density is greater than 1.35 t/m3. It utilizes a hollow, essentially fully enclosed around its perimeter, ideally of cylindrical form structure, (henceforth called the "structure") (5) of predetermined geometry, which is placed at the pond surface as shown in Figure 2. Water and less dense MFT initially located within the structure is moved outside the structure, while the MFT of required density which is surrounding the structure enters it under the action of hydrostatic pressure as per Figure 6. Continuous MFT removal operation is enabled due to simultaneous inflow of MFT surrounding the structure so that the hydrostatic equilibrium as per Formula 1 noted herein is maintained.

Description

METHOD AND SYSTEM FOR REMOVING MATURE FINE TAILINGS OF A DESIRED
DENSITY FROM A TAILINGS POND
Field Of The Invention The invention enables continuous, year-round removal of Mature Fine Tailings (MFT) out of oilsands tailings ponds including removal of MFT which density is greater than 1.35 tones per cubic meter (t/m3).
It addresses the limitations of the current MFT removal technologies as described in the Description Of Current Art section.
- 2 -BRIEF SUMMARY
In accordance with an illustrative embodiment of the disclosure, there is provided a method comprising: selecting a desired density of mature fine tailings to be removed from an oil sands tailings pond; positioning a hollow conduit within the oil sands tailings pond such that a bottom end of the hollow conduit is open to the mature fine tailings and positioned to receive the mature fine tailings of a desired density and such that a top end of the hollow conduit is open above a free water surface of the pond, and removing the mature fine tailings of the desired density from within the hollow conduit. The mature fine tailings of the desired density fill the hollow conduit to a hydrostatically equilibrating level for balancing hydrostatic pressures inside the conduit with hydrostatic pressures outside the conduit;
The method may include adjusting a length of the hollow conduit.
The method may include coupling deflector plates to an outer surface of the hollow conduit.
The method may include coupling a buoyancy element to the hollow conduit.
The method may include selecting a desired density greater than 1.35 t/m3.
The hollow conduit may be a hollow cylindrical conduit.
The method may include pumping the mature fine tailings of the desired density from within the hollow conduit.
The method may include siphoning the mature fine tailings of the desired density from within the hollow conduit.
In accordance with another illustrative embodiment of the disclosure, there is provided a system for removing mature fine tailings of a desired density from a tailings pond. The system comprises a hollow conduit and means for removing the mature fine tailings from within the hollow conduit. The hollow conduit is configured to be positioned within the pond such that a bottom end of the hollow conduit is open to the mature fine tailings
- 3 -and positioned to receive mature fine tailings of a desired density, such that a top end of the hollow conduit is open above a free water surface of the pond, and such that the mature fine tailings of the desired density fill the hollow conduit to a hydrostatically equilibrating level for balancing hydrostatic pressures inside the hollow conduit with hydrostatic pressures outside the hollow conduit. The hollow conduit has a width or a diameter selected to allow an inflow of the mature fine tailings of the desired density into the hollow conduit to sustain a selected mature fine tailings removal capacity.
The means for removing the mature fine tailings may be any one of a pump, a siphon, an auger, a clam shell, or a shovel.
The system may further comprise at least one deflector element surrounding an outside surface of the hollow conduit, and/or a buoyancy element connected to the hollow conduit, and/or at least one support element extending from the hollow conduit to a bottom of the pond.
The hollow conduit may be a cylindrical hollow conduit, and may further comprise a wall extending between the top end and the bottom and having an adjustable section that is adjustable to change the location of the bottom end in the pond.
- 4 -BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate non-limiting embodiments of the invention, Figure 1 illustrates an example of an oil sands tailings pond;
Figure 2 illustrates the oil sands tailings pond of figure 1 with one embodiment of an MFT transfer system situated therein;
Figure 3 illustrates an example of a vertical section through an oil sands tailings pond;
Figure 4 illustrates an example of MFT density with depth in an oil sands tailings pond;
Figure 5 illustrates pumping MFT out of an oil sands tailings pond;
Figure 6 illustrates an embodiment of an MFT transfer system situated within an oil sands tailings pond;
Figure 7 illustrates side and top views of an embodiment of an MFT transfer system with adjustable side walls;
Figure 8 illustrates an embodiment of an MFT transfer system including a pump;
and Figure 9 illustrates an embodiment of an MFT transfer system including a siphon.

,
- 5 -Mature Fine Tailings (MFT) is a byproduct of the bitumen extraction process of oilsands mining operations. The main components of MFT are water and oilsands fines.
Numerous other ingredients are also found in MFT in smaller quantities, these are either originally found in the oilsands deposits, or are introduced into MFT through the bitumen extraction process.
The "fines" mentioned herein are solid particles smaller than approximately 44 microns which do not settle to the bottom of the pond but stay in suspension for prolonged period of time thus creating MFT.
The oilsands tailings, which are produced through the bitumen extraction process, are delivered to the tailings ponds via hydro transport installations.
Typical configuration of an oilsands tailing pond is shown in Figure 1.
Coarse fractions of the tailings such as sand settle at the bottom of the tailings pond or form a beach.
A part of water contained within the tailings creates a layer of recyclable water at the surface level of the tailings pond. This layer of recyclable water is referred to as the "water cap" (1). The rest of the water combined with fines forms MFT (2) which is located between the water cap on the top and sand deposit (3) at the bottom of the pond.
MFT behaves as Non-Newtonian, Bingham fluid. Its main physical properties are characterized by its specific gravity, shear strength and viscosity. The least dense MFT is found closer to the water cap. The MFT specific gravity, shear strength and viscosity increase with depth.
A vertical section through a typical oilsands tailing pond is shown in Figure 3. An illustration of change of corresponding MFT density with depth is shown in Figure 4. The MFT shear , ,
- 6 -strength and viscosity increase as a function of its density.
MFT needs to be removed from the tailings ponds for either one of the following reasons:
):. Meeting environmental regulations aimed at reducing the production rate of MFT
and volume of MFT accumulated through the bitumen extraction process > Tailings ponds reclaim operations > MFT transfer operations as required to support bitumen production ):. Commercial processing of MFT for recovery of valuable ingredients Description Of Current Art Currently the MFT removal operations are mostly based on utilizing:
a. Stationary submersible pumping technology, or b. Dredging technology Both technologies noted above utilize pumping device(s) placed at a predetermined depth inside the MFT deposit. The MFT is than removed by pumping and transported by hydro-transport installations.
The limitations of the Current Art are as follows:
a. Limitations utilizing stationary Submersible pumping technology Submersible pumps have been successfully used for removal of MFT of density up to approximately 1.35 t/m3. Higher density MFT is not practically pump-able utilizing unaided stationary submersible pumps because the physical properties of MFT at the pumping depth location, namely shear strength and viscosity, prevent fluid from entering the pump at a sufficient rate to avoid pump overheating and cavitation.
- 7 -In addition to this, the performance of submersible pumps is greatly compromised by pump suction plugging due to collection of various debris around the pump suction.
This debris is commonly found in MFT deposits.
b. Limitations utilizing Dredging technology Dredging technology can be utilized for removal of MFT with density higher than 1.35 t/m3, however it is not practical for use in year-round operations because of the following reasons:
= As shown in Figure 5, when pumping MFT of higher density, a more pronounced "cone" formation of lighter fluid fractions is formed around the pump suction point (4) due to physical properties of MFT. This cone formation allows penetration of smaller density MFT and water from the layers above to enter the pump therefore the required density of MFT is lost.
= In order to maintain the required density of MFT, the dredge needs to be frequently relocated to a new location, so MFT is gathered from a large area of the lake.
This dredge relocation requirement makes it impractical to maintain MFT removal operation year-round because the majority of pond surface is covered with ice during winter months.
This "cone" formation is present at pumping of MFT of any density and pumping capacity but its influence on maintaining required pumping density, when pumping MFT of density up to 1.35 t/m3, can be mitigated by adequate engineering of the pumping system. At lower densities this "cone" becomes shallower and eventually flattens out at water level.
Description Of The Invention As shown in Figure 6 and Figure 7, the invention involves utilization of a hollow structure ("the structure") (5) which is fully enclosed around its perimeter and which has continuous solid walls up to the immersion depth "h". The structure is ideally but not necessarily of the , .
,
- 8 -cylindrical form. The structure is placed at the surface of the tailing pond and is kept on the surface by utilizing either buoyancy devices (6), or rigid supports founded at the pond bottom.
The structure has continuous essentially vertical walls penetrating the MFT
layer to a predetermined immersion depth "h", and has cross section width "D". The dimensions "h"
and "D" as shown in Figure 6 and Figure 7 are determined as the function of the MFT
physical properties, the density range which is intended for collecting ("required density") and the required MFT collecting capacity ("required capacity").
The dimensions "h" and "D" are determined utilizing hydrostatic and hydrodynamic calculations and computational fluid dynamics (CFD) methods for a specific MFT
removal project.
The dimensions "h" and "D" are determined so to prevent MFT of lower-than-required density and water to enter the confines of the structure while allowing sufficient inflow of required-density MFT to sustain the needed removal capacity.
Once the structure is installed, water and MFT of lower-than-required density originally located within the structure is moved out of the structure. Once the water and MFT of lower-than-required density are removed from within the confines of the structure, hydrostatic pressure acting on MFT surrounding structure forces MFT of required density to enter the confines of the structure and fill the structure up to the level "h1" so that hydrostatic balance is established between fluid outside and fluid inside the structure.
This hydrostatic balance at point "A" of the structure as shown in Figure 6 is defined as:
t., kl A
(4 a7- = S'o(z) Gt7-Formula 1 . .
,
- 9 -where:
4 ; - density of fluid inside the structure 4?c, - density of fluid outside the structure In summary, the step-by-step process of implementing this invention is as follows:
a. The structure (5) per Figure 6 of predetermined dimensions "D" and "h" is placed at the selected location in the tailing pond as per Figure 2.
b. Water and MFT of lower-then-required density is moved out of the structure, while MFT of the required density surrounding the structure simultaneously fills the structure under the action of hydrostatic pressure. The fill level "h1" as per the Figure 6 is determined so that the hydrostatic equilibrium per Formula 1 is maintained.
c. Once the operation of MFT removal from within the structure has started, the removed fluid is constantly being replaced by MFT of required density which is pushed into the structure by hydrostatic pressure so that the hydrostatic equilibrium per Formula us maintained. This enables continuous removal operations of MFT.
As shown in Figure 7, the design of the structure walls can be done so the immersed depth "h" can be adjusted (9) to allow for change in MFT physical properties.
MFT is removed from inside the structure and transported away utilizing either a pump (7) (such as cutter-head dredge pump) as shown in Figure 8, a siphon (8) as shown in Figure 9; or other suitable mechanical device.
This system also enables removal of organic debris contained within the MFT, as now the debris is located at or near the fluid surface.
Placing deflector elements (10) as shown in Figure 7 can further prevent lighter fluid surrounding the structure from entering it.

Claims (20)

Claims
1. A method comprising:
selecting a desired density of mature fine tailings to be removed from an oil sands tailings pond;
positioning a hollow conduit within the oil sands tailings pond such that a bottom end of the hollow conduit is open to the mature fine tailings and positioned to receive the mature fine tailings of a desired density and such that a top end of the hollow conduit is open above a free water surface of the pond, wherein the mature fine tailings of the desired density fill the hollow conduit to a hydrostatically equilibrating level for balancing hydrostatic pressures inside the conduit with hydrostatic pressures outside the conduit; and removing the mature fine tailings of the desired density from within the hollow conduit.
2. The method of claim 1, further comprising adjusting a length of the hollow conduit.
3. The method of claim 1, further comprising coupling deflector plates to an outer surface of the hollow conduit.
4. The method of claim 1, further comprising coupling a buoyancy element to the hollow conduit.
5. The method of claim 1, wherein selecting a desired density comprises selecting a desired density greater than 1.35 t/m3.
6. The method of claim 1, wherein the hollow conduit is a hollow cylindrical conduit.
7. The method of claim 1, wherein removing the mature fine tailings of the desired density from within the hollow conduit comprises pumping the mature fine tailings of the desired density from within the hollow conduit.
8. The method of claim 1, wherein removing the mature fine tailings of the desired density from within the hollow conduit comprises siphoning the mature fine tailings of the desired density from within the hollow conduit.
9. The method of claim 1, further comprising selecting a diameter of the hollow conduit which allows an inflow of the mature fine tailings of the desired density into the hollow conduit to sustain a selected mature fine tailings removal capacity.
10. A system for removing mature fine tailings of a desired density from a tailings pond, comprising:
a hollow conduit configured to be positioned within the pond such that a bottom end of the hollow conduit is open to the mature fine tailings and positioned to receive mature fine tailings of a desired density, such that a top end of the hollow conduit is open above a free water surface of the pond, and such that the mature fine tailings of the desired density fill the hollow conduit to a hydrostatically equilibrating level for balancing hydrostatic pressures inside the hollow conduit with hydrostatic pressures outside the hollow conduit; and means for removing the mature fine tailings from within the hollow conduit;
wherein the hollow conduit has a width or a diameter selected to allow an inflow of the mature fine tailings of the desired density into the hollow conduit to sustain a selected mature fine tailings removal capacity.
11. The system as claimed in claim 10 wherein the means for removing the mature fine tailings is a pump.
12. The system as claimed in claim 10 wherein the means for removing the mature fine tailings is a siphon.
13. The system as claimed in claim 10 wherein the means for removing the mature fine tailings is selected from a group consisting of an auger, a clam shell and a shovel.
14. The system as claimed in claim 10 further comprising at least one deflector element surrounding an outside surface of the hollow conduit.
15. The system as claimed in claim 10 wherein the hollow conduit is cylindrical hollow conduit.
16. The system as claimed in claim 15, wherein the diameter of the hollow conduit is constant.
17. The system as claimed in claim 10 wherein the hollow conduit further comprises a wall extending between the top end and the bottom and having an adjustable section that is adjustable to change the location of the bottom end in the pond.
18. The system as claimed in claim 10 further comprising a buoyancy element connected to the hollow conduit.
19. The system as claimed in claim 10 further comprising at least one support element extending from the hollow conduit to a bottom of the pond.
20. A system for removing mature fine tailings of a desired density from a tailings pond, comprising:
(a) a hollow conduit having a wall defining an open bottom end for immersion in the pond and an open top end for locating above a free water surface of the pond, and wherein the hollow conduit has a width or a diameter selected such that when the hollow conduit is positioned in the pond such that a bottom end of the conduit is open to the mature fine tailings and positioned to receive mature fine tailings of a desired density, the mature fine tailings of the desired density fill the hollow conduit to a hydrostatically equilibrating level for balancing hydrostatic pressures inside the hollow conduit with hydrostatic pressures outside the hollow conduit, and such that during the mature fine tailings removal process the mature fine tailings of the desired density are allowed to inflow into the hollow conduit to sustain a selected removal capacity;
(b) means for adjusting the conduit wall height to change the distance between the bottom end and the top end (c) means for removing the mature fine tailings from within the hollow conduit, selected from a group consisting of a pump, a siphon, an auger, a clam shell and a shovel; and (d) means for supporting the hollow conduit, selected from a group consisting of at least one of a buoyancy element connected to the hollow conduit and at least one support element extending from the hollow conduit and for contacting a bottom of the pond.
CA2812202A 2013-04-02 2013-04-02 Method and system for removing mature fine tailings of a desired density from a tailings pond Active CA2812202C (en)

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CA2812202A CA2812202C (en) 2013-04-02 2013-04-02 Method and system for removing mature fine tailings of a desired density from a tailings pond

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CA2812202A1 CA2812202A1 (en) 2014-02-11
CA2812202C true CA2812202C (en) 2016-02-16

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Publication number Priority date Publication date Assignee Title
US9127427B1 (en) 2015-02-09 2015-09-08 Technika Engineering Ltd. Recovering mature fine tailings from oil sands tailings ponds

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