Dispersion and conditioning techniques for thick fine tailings dewatering operations

Abstract

Techniques are described that relate to enhancing flocculation and dewatering of thick fine tailings, for example by reducing process oscillations. One example method includes dispersing a flocculant into thick fine tailings having a turbulent flow regime to produce turbulent flocculating tailings; subjecting the turbulent flocculating tailings to shear to build up flocs and increase yield stress, to produce a flocculated material having a non-turbulent flow regime; and shear conditioning the flocculated material to decrease the yield stress and produce conditioned flocculated tailings within a water release zone; and dewatering the conditioned flocculated tailings, for example by employing sub-aerial deposition. The thick fine tailings may have a Bingham Reynolds Number of at least 40,000 upon flocculant addition. Inhibiting process oscillations may include providing turbulent tailings feed, configuring a downstream pipeline assembly to reduce backpressure fluctuations and/or reducing air content in the flocculant solution, for example.

1 - 135 . (canceled) 
     
     
         136 . A method for attenuating oscillations in a flow rate of a flocculant solution comprising a flocculant injected into a flow of thick fine tailings, comprising reducing air content in the flocculant solution prior to injection. 
     
     
         137 . The method of  claim 136 , wherein reducing air content comprises reducing a viscosity of the flocculant solution sufficient to promote air liberation. 
     
     
         138 . The method of  claim 137 , wherein reducing the viscosity of the flocculant solution comprises reducing a concentration of the flocculant therein. 
     
     
         139 . The method of  claim 138 , wherein reducing the concentration of the flocculant comprises reducing by 50%. 
     
     
         140 . The method of  claim 138 , wherein reducing the concentration of the flocculant comprises reducing to between 0.1 wt % and 1 wt % flocculant per total weight of the flocculant solution. 
     
     
         141 . The method of  claim 137 , wherein reducing the viscosity is performed prior to mixing the flocculant solution in order to promote air liberation during the mixing. 
     
     
         142 . The method of  claim 141 , wherein the mixing is performed in a mixing tank. 
     
     
         143 . The method of  claim 136 , wherein the step of removing air from the flocculant solution comprises venting the flocculant solution. 
     
     
         144 . The method of  claim 143 , wherein the venting is performed at a high point along a pressurized pipeline through which the flocculant solution is supplied for addition into the thick fine tailings. 
     
     
         145 . The method of  claim 144 , wherein the venting is performed at multiple high points along the pressurized pipeline. 
     
     
         146 . The method of  claim 143 , wherein the venting is performed during line charging and is performed at different times to release built up air pockets. 
     
     
         147 . The method of  claim 136 , further comprising providing the flow of thick fine tailings with a turbulent flow regime. 
     
     
         148 . A method for treating thick fine tailings, comprising:
 preparing a flocculant solution comprising a flocculant, water and entrained air;   removing air from the flocculant solution to produce an air-depleted flocculant solution;   adding the air-depleted flocculant solution into the thick fine tailings to produce a flocculating tailings material;   shearing the flocculating tailings material to produce a conditioned flocculated tailings material that is within a water release zone wherein water separates from the conditioned flocculated tailings material; and   dewatering the conditioned flocculated tailings material.   
     
     
         149 . The method of  claim 148 , wherein removing air comprises reducing a viscosity of the flocculant solution sufficient to promote air liberation. 
     
     
         150 . The method of  claim 149 , further comprising mixing the flocculant solution after reducing the viscosity thereof in order to further promote air liberation. 
     
     
         151 . The method of  claim 148 , wherein removing air from the flocculant solution comprises venting the flocculant solution. 
     
     
         152 . The method of  claim 150 , wherein the entrained air in the flocculant solution comprises air present in a pipeline through which the flocculant solution is supplied prior to start-up; and air entrained during contacting of dry flocculant with water during preparation of the flocculant solution. 
     
     
         153 . A method for treating thick fine tailings, comprising:
 providing an in-line flow of the thick fine tailings;   adding a flocculant solution into the in-line flow of the thick fine tailings to produce an in-line flow of flocculating tailings material;   shearing the in-line flow of the flocculating tailings material to produce an in-line flow of flocculated material;   subjecting the in-line flow of the flocculated material to shear conditioning to produce a conditioned flocculated tailings material that is within a water release zone wherein water separates from the conditioned flocculated tailings material;   dewatering the conditioned flocculated tailings material; and   removing air from the flocculant solution prior to adding the flocculant solution into the in-line flow of thick fine tailings to thereby attenuate oscillations in a flow rate of the flocculant solution.   
     
     
         154 . The method of  claim 153 , further comprising:
 pumping the thick fine tailings using a first pump;   controlling the first pump based on a flow rate set point of the thick fine tailings;   pumping the flocculant solution using a second pump;   controlling the second pump based on a flow rate set point of the flocculant solution; and   regulating the flow rate set point of the flocculant solution based on flow rate, density and/or clay content of the thick fine tailings.   
     
     
         155 . The method of  claim 154 , wherein the first and second pumps have fixed rotations per minute (RPM), and wherein controlling the flocculant dosage is performed based on pre-determined optimal flocculant dosage