Extraction of oil sand bitumen with two solvents

Abstract

A process for extracting bitumen from oil sand using a combination of heavy solvent and light solvent is provided comprising contacting mined oil sand with a non-flammable heavy solvent (HS) to produce a dense oil sand slurry; mixing the dense slurry with a light solvent (LS) to give a heavy solvent to light solvent (HS/LS) mass ratio of about 70/30 to 50/50 and subjecting the diluted oil sand slurry to a first stage solid-liquid separation to produce a first liquids stream containing bitumen and a first solids stream; mixing the solids stream with a mixed solvent having a HS/LS mass ratio of about 75/25 to 55/45 and subjecting the diluted solids stream to a second stage solid-liquid separation to produce a second liquids stream and a second solids stream; rinsing the solids stream with a countercurrent flow of LS to recover the HS and produce spent solids; and drying the spent solids to LS concentration of less than 160 g/tonne solids.

What is claimed is: 
     
         1 . A process for extracting bitumen from oil sand, comprising:
 (a) contacting mined oil sand with a non-flammable heavy solvent (HS) to produce a dense oil sand slurry;   (b) mixing the dense slurry with a light solvent (LS) to give a heavy solvent to light solvent (HS/LS) mass ratio of 70/30 to 50/50 and subjecting the diluted oil sand slurry to a first stage solid-liquid separation to produce a first liquids stream containing bitumen of the highest concentration and a first solids stream;   (c) mixing the solids stream with a mixed solvent having a HS/LS mass ratio of 75/25 to 55/45 and subjecting the diluted solids stream to a second stage solid-liquid separation to produce a second liquids stream and a second solids stream;   (d) reusing the second liquids stream after removing its LS component in step (a);   (e) rinsing the second solids stream with a countercurrent flow of LS to recover the HS and produce spent solids; and   (f) drying the spent solids to LS concentration of less than 160 mg/kg solids.   
     
     
         2 . The process of  claim 1 , wherein the recovered HS from step (e) that is rich in LS is reused in either the first-stage separation [step (b)], the second-stage separation [step (c)], or both. 
     
     
         3 . The process of  claim 1 , wherein the HS is a non-volatile, high-flash point virgin light gas oil, distilled from oil sand bitumen, having a boiling range of about 220-480° C. 
     
     
         4 . The process of  claim 1 , wherein the LS is mixed C 6 -C 7 , produced from an oil sand bitumen upgrading unit, having a boiling range of about 66-101° C. 
     
     
         5 . The process as claimed in  claim 3 , wherein the boiling range is about 220-330° C. 
     
     
         6 . The process as claimed in  claim 4 , wherein boiling range is about 85-101° C. 
     
     
         7 . The process of  claim 1 , wherein the diluted oil sand slurry is transported to the first-stage separation though a pipeline. 
     
     
         8 . The process of  claim 1 , wherein the ratio of HS/LS continuously varies from the first to the last separation stage to optimize bitumen recovery and separation rate. 
     
     
         9 . The process of  claim 1 , wherein a dryer removes and recovers about 99.9% of LS from the spent solids. 
     
     
         10 . The process of  claim 1 , wherein the oil sand contains at least about 40% fines in solids and bitumen recovery is at least about 95%. 
     
     
         11 . The process of  claim 1 , further comprising:
 (g) integrating the process with an existing water-based extraction process to maximize economic return, minimize total energy input and convert wet tailings produced from the water-based extraction process to trafficable solids.   
     
     
         12 . A process for extracting bitumen from oil sand using a combination of heavy solvent and light solvent, comprising:
 (a) contacting mined oil sand with a non-flammable heavy solvent (HS) to produce a dense oil sand slurry;   (b) mixing the dense slurry with a light solvent (LS) to give a heavy solvent to light solvent (HS/LS) mass ratio of about 70/30 to 50/50 and subjecting the diluted oil sand slurry to a first stage solid-liquid separation to produce a first liquids stream containing bitumen and a first solids stream;   (c) mixing the solids stream with a mixed solvent having a HS/LS mass ratio of about 75/25 to 55/45 and subjecting the diluted solids stream to a second stage solid-liquid separation to produce a second liquids stream and a second solids stream;   (d) rinsing the solids stream with a countercurrent flow of LS to recover the HS and produce spent solids; and   (e) drying the spent solids to LS concentration of less than 160 g/tonne solids.   
     
     
         13 . The process of  claim 12 , wherein the recovered HS from step (d) that is rich in LS is reused in either the first-stage separation [step (b)], the second-stage separation [step (c)], or both. 
     
     
         14 . The process of  claim 12 , wherein the HS is a non-volatile, high-flash point virgin light gas oil, distilled from oil sand bitumen, having a boiling range of about 220-480° C. 
     
     
         15 . The process of  claim 12 , wherein the LS is mixed C 6 -C 7 , produced from an oil sand bitumen upgrading unit, having a boiling range of about 66-101° C. 
     
     
         16 . The process as claimed in  claim 14 , wherein the boiling range is about 220-330° C. 
     
     
         17 . The process as claimed in  claim 15 , wherein boiling range is about 85-101° C. 
     
     
         18 . The process of  claim 12 , wherein the diluted oil sand slurry is transported to the first-stage separation though a pipeline. 
     
     
         19 . The process of  claim 12 , wherein the ratio of HS/LS continuously varies from the first to the last separation stage to optimize bitumen recovery and separation rate. 
     
     
         20 . The process of  claim 12 , wherein a dryer removes and recovers about 99.9% of LS from the spent solids. 
     
     
         21 . The process of  claim 12 , wherein the oil sand contains at least about 40% fines in solids and bitumen recovery is at least about 95%. 
     
     
         22 . The process of  claim 12 , further comprising:
 (f) integrating the process with an existing water-based extraction process to maximize economic return, minimize total energy input and convert wet tailings produced from the water-based extraction process to trafficable solids.