Method for reducing rag layer volume in stationary froth treatment

Abstract

A method for reducing rag layer volume in a stationary bitumen froth treatment process is provided, comprising subjecting dilfroth having a naphtha diluent to bitumen ratio of about 0.7 to gravity settling in a splitter vessel to produce an overflow stream of raw dilbit and an underflow stream of splitter tails; mixing the splitter tails with a naphtha diluent to give a mixture having a naphtha diluent to bitumen ratio of less than about 6:1 in a scrubber feed tank; and subjecting the mixture to gravity settling and agitation in a scrubber vessel to produce an overhead stream of scrubber hydrocarbons and an underflow stream of scrubber tails.

We claim: 
     
         1 . A method for reducing rag layer volume in a stationary bitumen froth treatment process comprising:
 subjecting dilfroth having a naphtha diluent to bitumen ratio of about 0.7 to gravity settling in a splitter vessel to produce an overflow stream of raw dilbit and an underflow stream of splitter tails;   mixing the splitter tails with a naphtha diluent to give a mixture having a naphtha diluent to bitumen ratio of less than about 6:1 in a scrubber feed tank; and   subjecting the mixture to gravity settling and agitation in a scrubber vessel to produce an overhead stream of scrubber hydrocarbons and an underflow stream of scrubber tails.   
     
     
         2 . The method of  claim 1 , further comprising subjecting the raw dilbit to gravity settling and agitation in a polisher vessel at a naphtha diluent to bitumen ratio of about 0.7 to reduce and/or break rag layer and to produce an overflow stream of polished dilbit and an underflow stream of polisher sludge. 
     
     
         3 . The method of  claim 1 , further comprising diluting bitumen froth with the produced scrubber hydrocarbons to form the dilfroth. 
     
     
         4 . The method of  claim 1 , wherein the mixture has a naphtha diluent to bitumen ratio of less than 4:1. 
     
     
         5 . The method of  claim 1 , wherein the mixture has a naphtha diluent to bitumen ratio of less than or equal to 3:1. 
     
     
         6 . The method of  claim 1 , wherein agitation in the scrubber feed tank is conducted in the range of about 700 rpm to about 1300 rpm. 
     
     
         7 . The method of  claim 6 , wherein agitation in the scrubber feed tank is conducted at about 700 rpm. 
     
     
         8 . The method of  claim 1 , wherein agitation in the scrubber vessel is conducted in the range of 1 rpm to about 188 rpm. 
     
     
         9 . The method of  claim 8 , wherein agitation in the scrubber vessel is conducted at about 52 rpm to about 188 rpm. 
     
     
         10 . The method of  claim 1 , wherein agitation in the scrubber feed tank is conducted at about 1300 rpm and agitation in the scrubber vessel is conducted at about 52 rpm. 
     
     
         11 . The method of  claim 3 , wherein optionally, silicate is added to the bitumen froth. 
     
     
         12 . The method of  claim 1 , wherein optionally, water is added to the scrubber vessel.