Integrated process for reducing solids from the product of solvent extraction of oil sands bitumen

Abstract

A method is provided for producing a marketable bitumen product having low solids and essentially no water. The method can be integrated into existing solvent extraction processes for extracting bitumen from mined oil sand. A high-solids diluted bitumen is produced from a solvent extraction process and then mixed with a light solvent (LS) stream in at least a first mixer to produce a diluted bitumen-LS mixture. The diluted bitumen-LS mixture is subjected to separation in at least a first separator to produce low-solids diluted bitumen and high-solids asphaltene-rich tails. The LS is removed from the low-solids diluted bitumen to produce the marketable bitumen product.

What is claimed: 
     
         1 . A method of producing a marketable bitumen product having low solids and essentially no water from an oil sand/solvent slurry produced in a solvent extraction process of mined oil sand, comprising:
 (a) subjecting the oil sand/solvent slurry to a first solid-liquid separation step to produce a high-solids diluted bitumen stream and a first solids stream;   (b) mixing the high-solids diluted bitumen with a light solvent (LS) stream in at least a first mixer to produce a diluted bitumen-LS mixture;   (c) subjecting the diluted bitumen-LS mixture to separation in at least a first separator to produce low-solids diluted bitumen and high-solids asphaltene-rich tails;   (d) recovering the LS from the low-solids diluted bitumen in a diluent recovery unit to produce the marketable bitumen product;   (e) washing the high-solids asphaltene-rich tails with LS and combining the washed high-solids asphaltene-rich tails with the first solids stream to produce a second solids stream; and   (f) drying the second solids stream in a dryer to recover the LS and produce dry tailings.   
     
     
         2 . The method of  claim 1 , wherein the solvent extraction process comprises contacting mined oil sand with a high-flash point HS and a LS-rich stream to produce the oil sand/solvent slurry. 
     
     
         3 . The method of  claim 2 , wherein the first solids stream is fed to a repulper for mixing with a LS-dominant stream and subjected to a second solid-liquid separation step prior to being combined with the washed high-solids asphaltene-rich tails. 
     
     
         4 . The method of  claim 3 , wherein the second solid-liquid separation step produces a first filtrate stream and a second filtrate stream. 
     
     
         5 . The method of  claim 4 , wherein the first filtrate stream is used in the solvent extraction process as the LS-rich stream and the second filtrate stream is sent to the repulper as the LS-dominant stream. 
     
     
         6 . The method of  claim 1 , wherein in step (b), the LS is a paraffinic C 6 -C 7  solvent. 
     
     
         7 . The method of  claim 1 , wherein in step (b), the LS is a paraffinic C 5 -C 8  solvent 
     
     
         8 . The method of  claim 7 , wherein in step (b), the LS to diluted bitumen mass ratio in the diluted bitumen-LS mixture ranges from about 2.5 to about 4.0. 
     
     
         9 . The method of  claim 8 , wherein in step (c), the low-solids diluted bitumen comprises less than about 500 mg/kg solids and about 1000 mg/kg water on dry bitumen basis. 
     
     
         10 . The method of  claim 9 , wherein in step (d), the LS is recovered in the diluent recovery unit by flashing off the LS from the low-solids diluted bitumen. 
     
     
         11 . The method of  claim 10 , wherein in step (d), a first portion of the recovered LS is recycled to the first mixer, and a second portion of the recovered LS is recycled to the solvent extraction process. 
     
     
         12 . The method of  claim 11 , wherein in step (d), the marketable bitumen product comprises less than 500 mg/kg solids on dry bitumen basis. 
     
     
         13 . The method of  claim 12 , wherein the marketable bitumen product further comprises HS. 
     
     
         14 . The method of  claim 13 , wherein the HS is a light gas oil. 
     
     
         15 . The method of  claim 14 , further comprising recovering the HS. 
     
     
         16 . The method of  claim 1 , wherein the combined bitumen recovery is greater than about 90 wt %. 
     
     
         17 . The method of  claim 1 , wherein the solvent extraction process comprises contacting mined oil sand with a LS-rich stream to produce the oil sand/solvent slurry. 
     
     
         18 . The method of  claim 17 , wherein the first solid-liquid separation step comprises passing the oil sand/solvent slurry through a top-loading filter, whereby the first solids stream is a filter cake. 
     
     
         19 . The method of  claim 18 , wherein, in step (b), the LS is a paraffinic C 5 -C 8  solvent. 
     
     
         20 . The method of  claim 19 , wherein, in step (b), the LS to bitumen mass ratio in the diluted bitumen-LS mixture ranges from about 1.2 to about 2.0. 
     
     
         21 . The method of  claim 20 , wherein, in step (d), the LS is recovered in the diluent recovery unit by flashing off the LS from the low-solids diluted bitumen. 
     
     
         22 . The method of  claim 21 , wherein in step (d), a first portion of the recovered LS is recycled to the mixer, and a second portion of the recovered LS is recycled to the solvent extraction process. 
     
     
         23 . The method of  claim 1 , wherein, in step (d), the marketable bitumen product comprises less than 400 mg/kg solids on dry bitumen basis. 
     
     
         24 . The method of  claim 1 , wherein the combined bitumen recovery is greater than about 88 wt %. 
     
     
         25 . The method of  claim 1 , wherein the mixer comprises a high energy-dissipation impeller. 
     
     
         26 . The method of  claim 25 , wherein the impeller is a Rushton turbine. 
     
     
         27 . The method of  claim 26 , wherein the duration of mixing ranges from about 1 minute to about 10 minutes. 
     
     
         28 . The method of  claim 1 , wherein the separator is a gravity settler. 
     
     
         29 . The method of  claim 1 , wherein the separator is any conventional solid-liquid separator.