Bitumen removal from tailings centrifuge centrate

Abstract

A process for removing residual bitumen from oil sands tailings is provided, comprising optionally diluting the tailings with sufficient water to yield a tailings feed having a solids content in the range of about 18 wt % to about 36 wt %; adding one or both of a coagulant and a flocculant to the tailings feed to form a centrifuge feed; centrifuging the centrifuge feed to produce a cake and a centrate having a solids content of less than about 3 wt %; introducing the centrate into a flotation device so that bitumen froth and cleaned centrate are formed; recycling the cleaned centrate as dilution water or discharging the cleaned centrate to a tailings pond, and further processing the bitumen froth from the flotation device either by returning it to the primary Extraction feed or by treating it in a new or existing froth treatment plant.

1 . A process for removing residual bitumen from oil sands tailings comprising:
 a) optionally diluting the tailings with sufficient water to yield a tailings feed having a solids content in the range of about 18 wt % to about 36 wt %;   b) adding one or both of a coagulant and a flocculant to the tailings feed to form a centrifuge feed;   c) centrifuging the centrifuge feed to produce a cake and a centrate having a solids content of less than about 3 wt %;   d) introducing the centrate into a flotation device so that bitumen froth and cleaned centrate are formed; and   e) recycling the cleaned centrate as dilution water in step (a) or discharging the cleaned centrate to a tailings pond.   f) further processing the bitumen froth from the flotation device.   
     
     
         2 . [Currently Amended] The process of  claim 1 , further comprising cleaning the bitumen froth in a froth cleaner to produce a cleaned froth overflow stream and a water phase underflow stream having reduced bitumen for disposal. 
     
     
         3 . The process of  claim 1 , wherein in step (a), the solids content is greater than about 30 wt %. 
     
     
         4 . The process of  claim 1 , wherein in step (b), the tailings feed and flocculant are combined within a mixer. 
     
     
         5 . The process of  claim 4 , wherein the flocculant is added in-line prior to entering the mixer. 
     
     
         6 . The process of  claim 5 , further comprising diluting the flocculant. 
     
     
         7 . The process of  claim 6 , wherein the dosage of flocculant ranges from about 400 grams to about 1,500 grams per tonne of solids in the tailings. 
     
     
         8 . The process of  claim 7 , wherein the flocculant is the form of a 0.2-0.4% solution. 
     
     
         9 . The process of  claim 8 , wherein the flocculant comprises a polyacrylamide anionic flocculant. 
     
     
         10 . The process of  claim 1 , wherein in step (b), the flocculant is fed directly to the centrifuge. 
     
     
         11 . The process of  claim 1 , wherein the centrifuge is a solid bowl decanter centrifuge. 
     
     
         12 . The process of  claim 1 , wherein after step (c), the cake is disposed in an area using a dry stacking mode of disposal. 
     
     
         13 . The process of  claim 1 , wherein the tailings comprise fluid fine tailings. 
     
     
         14 . The process of  claim 1 , wherein the flotation device comprises a separation vessel, a mechanical flotation cell, a separator equipped with aeration downpipes, or a flotation column. 
     
     
         15 . The process of  claim 1 , wherein the bitumen froth from the flotation device is further processed by mixing it with a primary extraction feed or by treating it in a new or existing froth treatment plant.