Zone settling aid and method for producing dry diluted bitumen with reduced losses of asphaltenes

Abstract

A method includes diluting a bitumen source, such a bitumen froth from a hot water extraction process, with a hydrocarbon diluent such as naphtha, contacting the bitumen with a zone settling aid such as a polyoxyalkylate block polymer, flocculating water and fine solids in the diluted bitumen, separating the flocculated water and fine solids from the solvent-diluted bitumen, and producing dry, clean diluted bitumen. Preferably, the diluted bitumen will have less than 1.0 wt % water, but most preferably less than 0.7 wt % water. The method may further comprise maintaining the diluted bitumen under conditions that avoid the precipitation of asphaltenes from the bitumen, preferably such that the dry, clean diluted bitumen comprises essentially all, such as greater than 96%, of the asphaltene content from the bitumen source. Counter-current flow may be performed in a series of zone settling stages, such as with gravity settling.

1 . A method of processing bitumen, comprising: 
 diluting a bitumen source with a hydrocarbon diluent to a diluent-to-bitumen ratio of less than 1;    contacting the bitumen with a zone settling aid;    flocculating water and fine solids in the diluted bitumen;    separating the flocculated water and fine solids from the diluted bitumen; and    producing a dry, clean diluted bitumen having less than 1.0 wt % water and less than 0.5 wt % fine solids.    
   
   
       2 . The method of  claim 1 , wherein the diluted bitumen has less than 0.7 wt % water and less than 0.3 wt % fine solids.  
   
   
       3 . The method of  claim 1 , further comprising: 
 maintaining the diluted bitumen under conditions that avoid the precipitation of asphaltenes from the bitumen.    
   
   
       4 . The method of  claim 3 , wherein the dry, clean diluted bitumen comprises essentially all of the asphaltene content from the bitumen source.  
   
   
       5 . The method of  claim 1 , wherein the step of contacting the bitumen with a zone settling aid is performed upstream or within a primary froth treatment vessel.  
   
   
       6 . The method of  claim 1 , wherein the bitumen source is deaerated bitumen froth.  
   
   
       7 . The method of  claim 1 , wherein the bitumen source is diluted to a diluent-to-bitumen ratio less than 0.75.  
   
   
       8 . The method of  claim 1 , further comprising: 
 passing the diluent counter-current to the water and fine solids.    
   
   
       9 . The method of  claim 8 , wherein the counter-current flow is performed in a series of zone settling stages.  
   
   
       10 . The method of  claim 1 , wherein the step of separating includes gravity settling.  
   
   
       11 . The method of  claim 1 , further comprising: 
 aerating a slurry containing bitumen, water and inorganic solids to form a bitumen froth; and    diluting the bitumen froth with a hydrocarbon diluent to produce the diluted bitumen.    
   
   
       12 . The method of  claim 1 , wherein the zone settling aid comprises a polyoxyalkylate polymer having a molecular weight between about 1,000 and about 2,000,000  
   
   
       13 . The method of  claim 12 , wherein the polyoxyalkylate polymer is a reaction product of an acceptor and one or more alkyloxide species.  
   
   
       14 . The method of  claim 13 , wherein the alkyloxide species is selected from ethylene oxide, propylene oxide, glycidol, butylene oxide, epichlorohydrin and combinations thereof.  
   
   
       15 . The method of  claim 13 , wherein the acceptor is material having one or more active hydrogen atoms towards the oxyalkylation reaction.  
   
   
       16 . The method of  claim 13 , wherein the acceptor is Sorbitol.  
   
   
       17 . The method of  claim 13 , wherein the polyoxyalkylate polymer includes two or more block polymers selected from ethylene oxide, propylene oxide, and butylene oxide and epichlorohydrin.  
   
   
       18 . The method of  claim 13 , wherein the polyoxyalkylate polymer includes block polymers of propylene oxide and ethylene oxide.  
   
   
       19 . The method of  claim 18 , wherein the propylene oxide block polymer has between 15 and 25 propylene oxide groups, and wherein the ethylene oxide block polymer has between 5 and 15 ethylene oxide groups per arm of a branched polymer.  
   
   
       20 . The method of  claim 19 , wherein the propylene oxide block polymer extends from the polyol, and wherein the ethylene oxide block polymer extends from the propylene oxide block polymer.  
   
   
       21 . The method of  claim 18 , wherein the polymer comprises between 10% and 50% ethylene oxide.  
   
   
       22 . The method of  claim 18 , wherein the polymer comprises between 20% and 40% ethylene oxide.  
   
   
       23 . The method of  claim 18 , wherein the polymer comprises between 28% and 35% ethylene oxide.  
   
   
       24 . The method of  claim 21 , wherein the polymer has a molecular weight between about 2,000 and about 2,000,000.  
   
   
       25 . The method of  claim 1 , wherein the zone settling aid is an alkoxylate polymer having the formula: 
       Acc-[(Ox 1 ) A1 -(Ox 2 ) A2 - . . . (Ox i ) Ai ] n   
     wherein: Acc is an acceptor; 
 Ox 1  to Ox i  are oxides, wherein each oxide is independently selected from ethylene oxide, propylene oxide, glycidol, butylene oxide, epichlorohydrin, and mixtures thereof, wherein A 1  to Ai is between 0 and 150,000, wherein n is between about 1 and 100, and wherein the molecular weight of the alkoxylate is between about 1000 and about 2,000,000 g mole −1 .  
 
   
   
       26 . The method of  claim 25 , wherein the ratio of butylene oxide to propylene oxide is between about 200:1 and about 1:200.  
   
   
       27 . The method of  claim 25 , wherein the ratio of ethylene oxide to propylene oxide is between about 200:1 and about 1:200.  
   
   
       28 . The method of  claim 25 , wherein the ratio of butylene oxide to ethylene oxide is between about 200:1 and about 1:200.  
   
   
       29 . The method of  claim 25 , wherein the alkoxylate has a molecular weight between about 2000 and about 1,000,000.  
   
   
       30 . The method of  claim 25 , wherein the alkoxylate is added to the system at a concentration of between about 1 wt. ppm and about 750 wt. ppm.  
   
   
       31 . The method of  claim 25 , wherein the alkoxylate is added to the system at a concentration of between about 25 wt. ppm and about 300 wt. ppm.  
   
   
       32 . The method of  claim 1 , wherein the hydrocarbon diluent comprises naphtha.  
   
   
       33 . The method of  claim 1 , wherein the hydrocarbon diluent is selected from aliphatics, aromatics, naphtha, gasoline, natural gas condensate, paraffins, and combinations thereof.  
   
   
       34 . The method of  claim 13 , wherein the acceptor is a low molecular weight polyethyleneimine having a functionality range from about 4 to 14 active hydrogen atoms per molecule.