Enhanced Techniques for Dewatering Thick Fine Tailings

Abstract

Techniques for dewatering thick fine tailings may include flocculant dosing on a clay basis and then subjecting the flocculated tailings to dewatering, for instance by pipelining the flocculated material from flocculant addition to a deposition site. The thick fine tailings can be pre-treated by removing hydrocarbons and shear-thinning prior to flocculant addition.

1 . A process for treating thick fine tailings, comprising:
 determining clay content of the thick fine tailings;   providing a flow of the thick fine tailings;   injecting an aqueous solution of a flocculant into the flow of the thick fine tailings at an in-line injecting location and mixing the flocculant into the flow to produce a flocculated tailings flow comprising water and flocs, wherein the flocculant is dosed in accordance with the clay content of the thick fine tailings;   pipelining the flocculated tailings flow from the in-line injection location to a dewatering site; and   dewatering the flocculated tailings at the dewatering site to allow water to separate from the flocs.   
     
     
         2 . The process of  claim 1 , wherein the dewatering comprises separating water from the flocs by drainage. 
     
     
         3 . The process of  claim 1 , wherein the dewatering comprises forming a thickened lower layer comprising the flocs and an upper layer comprising separated water. 
     
     
         4 . The process of  claim 1 , wherein the clay content of the thick fine tailings is above 80% on a total solids basis. 
     
     
         5 . The process of  claim 1 , wherein the thick fine tailings has a clay-to-water ratio (CWR) between 0.2 and 0.4 and a sands-to-fine ratio (SFR) below 1. 
     
     
         6 . The process of  claim 1 , wherein determining the clay content of the thick fine tailings comprises conducting a methylene blue test. 
     
     
         7 . The process of  claim 1 , wherein determining the clay content of the thick fine tailings comprising using an estimate based on viscosity measurement of the thick fine tailings. 
     
     
         8 . The process of  claim 1 , further comprising shearing the thick fine tailings to produce a sheared-thinned fine tailings prior to determining the clay content thereof. 
     
     
         9 . The process of  claim 8 , wherein determining the clay content of the thick fine tailings comprises estimating the clay content based on viscosity measurement of the shear-thinned thick fine tailings. 
     
     
         10 . The process of  claim 1 , wherein the flocculant comprises an anionic polymer flocculant. 
     
     
         11 . The process of  claim 1 , wherein the flocculant comprises a 30% anionic sodium polyacrylamide-polyacrylate polymer flocculant. 
     
     
         12 . The process of  claim 1 , further comprising removing hydrocarbons from the thick fine tailing prior to injecting the aqueous solution of the flocculant. 
     
     
         13 . The process of  claim 1 , further comprising thinning the thick fine tailings to produce a thinned tailings material, removing hydrocarbons from the thinned tailings material to produce a hydrocarbon-depleted tailings, and then injecting the aqueous solution of the flocculant to the hydrocarbon-depleted tailings. 
     
     
         14 . The process of  claim 13 , wherein the hydrocarbons comprise bitumen. 
     
     
         15 . The process of  claim 1 , wherein the thick fine tailings comprise mature fine tailings (MFT) retrieved from a tailings pond. 
     
     
         16 . The process of  claim 1 , wherein the thick fine tailings comprises tailings derived from an oil sands extraction operation. 
     
     
         17 . A process for treating thick fine tailings, comprising:
 determining clay content of the thick fine tailings;   providing a flow of the thick fine tailings;   adding a flocculant into the flow of the thick fine tailings and mixing the flocculant into the flow to produce a flocculated tailings comprising water and flocs, wherein   the flocculant is dosed in accordance with the clay content of the thick fine tailings;   subjecting the flocculated tailings to shear conditioning up to and past a peak yield strength of the flocculated tailings to produce a conditioned tailings that is in a water release zone; and   dewatering the conditioned tailings to allow water to separate from the flocs.   
     
     
         18 . The process of  claim 17 , wherein the flow of the thick fine tailings is provided via a feed pipeline to a flocculant addition point, the flocculant is added in-line into the flow of the thick fine tailings at the flocculant addition point to form an in-line flow of the flocculated tailings, the in-line flow of the flocculated tailings is transported via a pipeline directly from the flocculant addition point to at least one discharge to impart the shear conditioning, the conditioned tailings are discharged via the at least one discharge into a deposition site, and the dewatering occurs in the deposition site. 
     
     
         19 . The process of  claim 17 , wherein the clay content of the thick fine tailings is above 80% on a total solids basis, and the thick fine tailings has a clay-to-water ratio (CWR) between 0.2 and 0.4. 
     
     
         20 . The process of  claim 17 , further comprising shearing the thick fine tailings to produce a sheared-thinned fine tailings prior to determining the clay content thereof, removing hydrocarbons from the shear-thinned fine tailings to produce a hydrocarbon-depleted tailings, and adding the flocculant to the hydrocarbon-depleted tailings.