Electrokinetic Process And Apparatus For Consolidation Of Oil Sands Tailings

Abstract

A method is provided of treating liquid tailings using electro-kinetics by creating a variable voltage between two electrodes in the tailings. Flocculation and water release from the tailings is induced by establishing an electrical field between the two electrodes. The electrodes are connected to an electrical power source having the variable voltage to create a cathode and an anode. Compacting the flocculation solids and removing further water released from the compacting solids allows for the creation of a compacted material having a desired load bearing capacity.

1 . A method of treating liquid tailings using electro-kinetics, the method comprising the steps of:
 a. Causing at least two electrodes to come into contact with the liquid tailings;   b. Inducing flocculation of particles in the tailings and releasing water from the tailings by establishing an electrical field between said at least two electrodes, the electrodes being connected to a source of electrical power having a variable voltage to create at least one cathode and at least one anode; and   c. Compacting said flocculation solids and removing further water released from said compacting solids to create a compacted material having a minimum desired load bearing capacity.   
     
     
         2 . The method of  claim 1  wherein the tailings are at least one of oil sands extraction tailings and fly ash tailings. 
     
     
         3 . The method of  claim 1  wherein said flocculation step further comprises passing the tailings through a conduit containing the at least two electrodes. 
     
     
         4 . The method of  claim 3  in which the conduit is a canal. 
     
     
         5 . The method of  claim 3  in which the at least two electrodes are augers. 
     
     
         6 . The method of  claim 3  in which said compaction step further comprises placing said flocculated solids into a treatment cell or tailings pond and applying a second variable voltage to the flocculated solids to compact the flocculated solids through electrostriction. 
     
     
         7 . The method of  claim 6  in which the second variable voltage is created by a second pair of at least two electrodes which are placed into the treatment cell or tailings pond. 
     
     
         8 . The method of  claim 6  in which the second variable voltage applied during the compaction step is higher than the variable voltage applied during the flocculation step. 
     
     
         9 . The method of  claim 8  in which the second variable voltage is greater than 2 V DC/m . 
     
     
         10 . The method of  claim 8  in which the variable voltage during the flocculation step is between 1-2 V DC/m . 
     
     
         11 . The method of  claim 3  in which said compaction step further comprises placing said flocculated solids into a tailings pond and allowing the flocculated solids to naturally consolidate. 
     
     
         12 . The method of  claim 1  wherein said compaction step includes using electrostriction to compact the flocculated solids. 
     
     
         13 . The method of  claim 1  wherein said compaction step includes using gravity loading to further compact said flocculated solids. 
     
     
         14 . The method of  claim 12  further including the step of inserting a drain or wick into said flocculated solids to permit pore water to be expressed from said compacting solids. 
     
     
         15 . The method as claimed in  claim 13  further including the step of removing water from tailings as said solids are compacted. 
     
     
         16 . The method as claimed in  claim 15  wherein said water is pumped out of said tailings. 
     
     
         17 . The method as claimed in  claim 16  wherein said electrode includes an associated pump, electrically isolated from said electrode, to remove said water. 
     
     
         18 . The method of  claim 17  wherein the pump is located within a hollow cathode. 
     
     
         19 . The method of  claim 1  in which the tailings are located in situ at a tailings pond, the method further including the step of partitioning said tailings pond to create at least one cell, and wherein said step of causing the at least two electrodes to come into contact with the tailings comprises placing said electrodes within said cell. 
     
     
         20 . The method of  claim 19  further including the step of partitioning said tailings pond into a plurality of cells. 
     
     
         21 . The method of  claim 20  wherein said cells are formed by sheet metal pilings. 
     
     
         22 . The method of  claim 21  wherein said sheet metal pilings are electrically connected to said source of power and thereby become one of said electrodes. 
     
     
         23 . The method of  claim 1  further including the step of sampling said tailings to determine one or more electrical properties, and using said measured electrical properties to control the output from the source of power. 
     
     
         24 . The method of  claim 1  further including the step of measuring the electrical properties of said tailings over time and adjusting said variable voltage across said electrodes in response to changes detected in said measured electrical properties. 
     
     
         25 . The method of  claim 24  wherein the at least two electrodes are used to induce a variable voltage during the compaction step to cause electrostriction of the flocculated fluids and the variable voltage applied during the electrostriction step is higher than the variable voltage applied during the flocculation step. 
     
     
         26 . The method of  claim 23  wherein said electrical properties vary as said solids compaction process progresses, and said voltage is varied as said compaction progresses. 
     
     
         27 . The method of  claim 1  wherein said source of power is at least one transformer. 
     
     
         28 . The method of  claim 27  wherein said at least one transformer is operatively connected to a computer to permit the power from said transformer to be controlled. 
     
     
         29 . The method of  claim 28  wherein said controller includes a remote access controller. 
     
     
         30 . The method of  claim 1  wherein said predetermined load bearing capacity of said compacted solids is about 5 kPa or more. 
     
     
         31 . The method of  claim 1  wherein the flocculation of the solids within the tailings is induced by one or more of an AC, DC or EM-induced electrical field. 
     
     
         32 . The method of  claim 31  in which the flocculation of the solids within the tailings is induced by alternating current and in which the anode and cathode are operating 180° out of phase with each other. 
     
     
         33 . The method of  claim 1  wherein said electrical field gradient can have any range, but the preferred embodiment ranges from about 0.3 volt per centimeter to about 4 volt per centimeter. 
     
     
         34 . The method of  claim 22  wherein said electrical field gradient is a substantially uniform field between said electrodes. 
     
     
         35 . An electrode for use in a method of compacting solids in an oil sands extraction tailings pond, the electrode comprising:
 a. A connector to electrically connect said electrode to a source of power;   b. An electrically conductive body having a size and shape to permit said body to be inserted into said tailings pond and to extend below and above said tailings; and   c. A means to electrically isolate a portion of said electrode which extends above said tailings pond.   
     
     
         36 . The electrode of  claim 35  wherein said body is hollow and includes openings to permit water to pass into said electrode. 
     
     
         37 . The electrode of  claim 36  wherein said openings are screened to prevent solids from passing into said hollow electrode. 
     
     
         38 . The electrode of  claim 37  further including a pump located with said electrode to remove said water from within said hollow body. 
     
     
         39 . The electrode of  claim 38  wherein said pump is electrically isolated from said electrode. 
     
     
         40 . A conveyor for use in a method of flocculating tailings, the conveyor comprising:
 a. A conduit defining a tailings reservoir through which tailings may pass, the conduit having an intake opening and a discharge opening;   b. First and second electrodes connected to a power source, the first and second electrodes at least partially placed within the tailings reservoir;   c. A water extraction outlet within the tailings reservoir for removing released water; and   d. A means to cause the tailings to pass through the tailings reservoir from the intake opening to the discharge opening.   
     
     
         41 . The conveyor of  claim 40  wherein the first and second electrodes are a pair of augers. 
     
     
         42 . The conveyor of  claim 41  wherein the means to cause the tailings to pass through the tailings reservoir are the pair of augers. 
     
     
         43 . The conveyor of  claim 40  wherein the means to cause the tailings to pass through the tailings reservoir is a pump in fluid connection with the tailings reservoir. 
     
     
         44 . The conveyor of  claim 40  in which the first and second electrodes each have hollow core to allow released water to travel from the anode to the cathode. 
     
     
         45 . A method of treating a layer of a tailings pond comprising the steps of: providing a cable electrode which can be submerged to a desired depth; positioning the electrode within the tailings pond at the depth of the layer to be treated; positioning at least one other electrode at the same depth at a location remote from the first electrode; connecting the electrodes to a source of power and encouraging flocculation to occur at the depth that the electrodes are submerged within the tailings pond.