Bitumen recovery from decanter centrifuge cake using diluent and bitumen froth

Abstract

The present description relates to enhanced bitumen froth treatment where decanter cake is subjected to additional processing that includes the addition of diluent and bitumen, optionally in the form of bitumen froth, followed by gravity settling or centrifugation. The resulting bitumen enriched material can then be recycled back into the froth treatment operation.

1 . A process for treating bitumen froth derived from oil sands ore, the process comprising:
 adding diluent to a bitumen froth stream to produce a diluted froth stream;   subjecting the diluted froth stream to gravity separation to produce a bitumen enriched overflow and a bitumen depleted underflow;   supplying the bitumen depleted underflow to a decanter to produce a decanter cake and a decanter overflow;   adding bitumen and an additional diluent to the decanter cake tailings to produce a diluted decanter tailings stream;   supplying the diluted decanter tailings stream to a recycle separation unit to produce a recycle bitumen stream and a tailings stream;   adding the recycle bitumen stream to the enriched overflow to produce a combined bitumen enriched stream; and   subjecting the combined bitumen enriched stream to additional separation to produce a diluted bitumen product.   
     
     
         2 . The process of  claim 1 , wherein the diluent comprises naphtha. 
     
     
         3 . The process of  claim 1 , wherein the gravity separation is performed using an inclined plate separator. 
     
     
         4 . The process of  claim 1 , further comprising adding diluent material and a secondary bitumen froth stream to the bitumen depleted underflow prior to supplying to the decanter. 
     
     
         5 . The process of  claim 4 , wherein the diluent material is first added to the secondary bitumen froth stream to produce a secondary diluted froth which is combined with the bitumen depleted underflow prior to the decanter. 
     
     
         6 . The process of  claim 4 , wherein the diluent material comprises naphtha. 
     
     
         7 . The process of  claim 1 , wherein the decanter cake is combined with a diluent stream to provide the diluent, and with a tertiary bitumen froth stream to provide the bitumen. 
     
     
         8 . The process of  claim 1 , wherein the recycle separation unit comprises a gravity settler. 
     
     
         9 . The process of  claim 8 , wherein the gravity settler comprises an inclined plate separator (IPS). 
     
     
         10 . The process of  claim 1 , wherein the recycle separation unit comprises a decanter centrifuge. 
     
     
         11 . The process of  claim 1 , wherein the additional diluent comprises naphtha. 
     
     
         12 . The process of  claim 1 , wherein the additional separation is performed in a disc centrifuge. 
     
     
         13 . The process of  claim 1 , wherein the decanter overflow is subjected to centrifugation to produce a centrifuge overflow and a centrifuge underflow. 
     
     
         14 . The process of  claim 13 , wherein the centrifuge overflow is added to the bitumen enriched overflow. 
     
     
         15 . The process of  claim 13 , wherein the centrifuge underflow is added to the tailings stream to produce a combined tailings material. 
     
     
         16 . The process of  claim 15 , wherein the combined tailings material is subjected to diluent recovery. 
     
     
         17 . The process of  claim 1 , wherein the decanter comprises a scroll centrifuge. 
     
     
         18 . The process of  claim 1 , wherein the diluted decanter tailings stream is formed to have a diluent-to-bitumen ratio between 4 and 8. 
     
     
         19 . The process of  claim 1 , wherein the diluted decanter tailings stream is formed to have a bitumen content between 8 wt % and 35 wt % prior to the recycle separation unit. 
     
     
         20 . The process of  claim 1 , wherein the temperature of the process is between 70° C. and 90° C. 
     
     
         21 . The process of  claim 1 , wherein the recycle separation unit comprises a multi-stage counter-current unit comprising at least a first gravity settler and a second gravity settler. 
     
     
         22 . The process of  claim 21 , wherein the first gravity settler receives the diluted decanter tailings stream and produces a first stage overflow as the recycle bitumen stream and a first stage underflow, the first stage underflow is combined with a diluent stream and then fed to the second stage settler to produce a second stage overflow and a second stage underflow as the tailings stream, the second stage overflow is recycled back as at least part of the bitumen and the additional diluent added to the decanter cake tailings to produce the diluted decanter tailings stream. 
     
     
         23 . A system for recovering residual bitumen from a naphtha-diluted and bitumen-enriched slurried centrifuge cake tailings, the system comprising:
 a feed inlet configured to receive the naphtha-diluted and bitumen-enriched slurried centrifuge cake tailings;   a separation chamber in fluid communication with the feed inlet and configured to effect separation to produce a bitumen enriched material and a bitumen depleted tailings material;   an upper outlet in fluid communication with the separation chamber and configured to receive an overflow of the bitumen enriched material; and   a lower outlet in fluid communication with the separation chamber and configured to receive an underflow of the bitumen depleted tailings material;   wherein the system is sized and configured such that bitumen in the naphtha-diluted and bitumen-enriched slurried centrifuge cake tailings inhibits formation of or entrapment of diluted bitumen pockets within a rag layer in the separation chamber.   
     
     
         24 . The system of  claim 23 , wherein the separation chamber comprises an inclined plate separator chamber, or a centrifuge chamber; wherein the separation chamber comprises a plurality of separation chambers fluidly connected in series or in a countercurrent configuration; or wherein the upper outlet is sized and configured for fluid communication with a line carrying a bitumen enriched overflow product stream from an inclined plate separator device that receives diluted bitumen froth in order to add a stream of the bitumen enriched material directly into the bitumen enriched overflow product stream.