Closed loop solvent extraction process for oil sands

Abstract

The present invention is directed to a method which includes the steps of: contacting an oil sand with a suitable solvent to generate a solvated oil sand slurry; separating solvent-diluted bitumen from the solvated oil sand slurry to generate (a) a solvent-diluted bitumen and (b) a slurry with increased solids concentration; filtering the slurry with increased solids concentration; dropping the solids into a pressure reduction vessel wherein the pressure in the pressure reduction vessel is a pressure below a vapor pressure of the solvent; and drying the solids removed from the pressure reduction vessel to produce solids having dry tailings. The method of the present invention may be used to produce a low ash bitumen product and dry tailings from oil sands.

What is claimed is: 
     
         1 . A method for extracting bitumen from an oil sand, the method comprising:
 contacting an oil sand with a solvent to generate a solvated oil sand slurry;   separating solvent-diluted bitumen from the solvated oil sand slurry to generate (a) a solvent-diluted bitumen and (b) a slurry with increased solids concentration;   filtering the slurry with increased solids concentration to produce a solids and a filtrate output;   dropping the solids into a pressure reduction vessel wherein the pressure in the pressure reduction vessel is a pressure below a vapor pressure of the solvent;   removing solids from the pressure reduction vessel; and   drying the solids removed from the pressure reduction vessel to produce solids having dry tailings.   
     
     
         2 . The method of  claim 1 , further comprising size-reducing the oil sand to produce a size-reduced oil sand feed and contacting the size-reduced oil sand feed with the solvent to generate the solvated oil sand slurry. 
     
     
         3 . The method of  claim 1  wherein the solvent is a C3 to C9 paraffinic solvent, or a mixture thereof. 
     
     
         4 . The method of  claim 1  wherein the solvent is a C5 solvent. 
     
     
         5 . The method of  claim 1  wherein the separating step is carried out in a settler. 
     
     
         6 . The method of  claim 1  further comprising producing solids and a filtrate during the filtering step. 
     
     
         7 . The method of  claim 6  further comprising drying the solids. 
     
     
         8 . The method of  claim 6  wherein at least some of the solvent in either or both of the solids and the filtrate is recovered and recycled to either or both of the contacting step and the filtering step. 
     
     
         9 . The method of  claim 6  wherein at least some of the filtrate is recycled to the contacting step. 
     
     
         10 . The method of  claim 6  further comprising heating the solids during the filtering step. 
     
     
         11 . The method of  claim 1  wherein at least some of the solvent in the solvent-diluted bitumen is recovered and recycled to either or both of the contacting step and the filtering step. 
     
     
         12 . The method of  claim 1  further comprising feeding overflow from the separating step to a second separating step. 
     
     
         13 . A method for extracting bitumen from an oil sand, the method comprising:
 reducing the size of an oil sand feed to produce a size-reduced oil sand feed;   adding to the size-reduced oil sand feed to form a slurry a solvent;   feeding the slurry to a separation device;   allowing the slurry to be separated in the separation device into a solvent-diluted bitumen and an underflow;   feeding the underflow to a filtration unit;   recovering a filtrate from the filtration unit;   recovering solids from the filtration unit;   reducing the pressure on the solids in a reduced pressure vessel to a pressure below the vapor pressure of the solvent to remove some solvent from the solids; and   recovering additional solvent from the solids from the reduced pressure vessel by drying the solids wherein dry tailings are produced.   
     
     
         14 . The method according to  claim 13 , wherein at least some of the solvent in either or both of the solids and the filtrate is recovered and recycled to either or both of the step of adding solvent to the size-reduced oil sand feed to form a slurry, and the filtration unit. 
     
     
         15 . The method according to  claim 13 , wherein at least some of the filtrate is recycled to the step of adding solvent to the size-reduced oil sand feed to form a slurry. 
     
     
         16 . The method of  claim 13  further comprising heating the solids in the filtration unit. 
     
     
         17 . The method according to  claim 13 , wherein at least some of the solvent in the solvent-diluted bitumen is recovered and recycled to either or both of the step of adding solvent to the size-reduced oil sand feed to form a slurry and the filtration unit. 
     
     
         18 . The method of  claim 13  further comprising desolventising the underflow within the filtration unit. 
     
     
         19 . The method of  claim 13  comprising adding solvent to the oil sand feed using a rotary breaker. 
     
     
         20 . The method of one of  claim 13  wherein the solvent is selected from the group consisting of C3 to C9 solvents and mixtures thereof. 
     
     
         21 . The method of  claim 13  wherein the solvent is a C5 solvent. 
     
     
         22 . The method of  claim 13  further comprising purging with an inert gas while introducing the oil sand into a hydrocarbon atmosphere. 
     
     
         23 . The method of  claim 13  further comprising feeding the solvent diluted bitumen from the separation device to a second separation device. 
     
     
         24 . The method of  claim 13  wherein the underflow fed to the filtration unit comprises about 60 to about 85% weight of solids. 
     
     
         25 . The method of  claim 13  wherein the separation device comprises a settler. 
     
     
         26 . The method of  claim 1  wherein at least a portion of solvent vapour is added above the filter bed and condenses in the filter bed. 
     
     
         27 . The method of  claim 26  further comprising the step of condensing at least a portion of the solvent vapor that was introduced above the filter bed.