Catalytic Gasification Process with Recovery of Alkali Metal from Char

Abstract

Processes for extracting and recycling alkali metal compounds present in the char produced from the catalytic gasification of carbonaceous materials are provided involving at least contacting the char with and alkali metal hydroxide followed by carbon dioxide. Both the alkali metal hydroxide and carbon dioxide treatments serve to convert at least a portion of the insoluble alkali metal compounds in the char into soluble species which can be recovered and recycled.

1 . A process for extracting and recovering alkali metal from a char, the char comprising (i) one or more soluble alkali metal compounds and (ii) insoluble matter comprising one or more insoluble alkali metal compounds, the process comprising the steps of:
 (a) providing the char at an elevated temperature ranging from 50° C. to about 600° C.;   (b) quenching the char in an aqueous medium to fracture the char and form a quenched char slurry;   (c) contacting the quenched char slurry with an alkali metal hydroxide under suitable pressure and temperature so as to convert at least a portion of the insoluble alkali metal compounds to one or more soluble alkali metal compounds, and produce a first leached slurry comprising the soluble alkali metal compounds and a partially extracted insoluble matter;   (d) contacting the first leached slurry with carbon dioxide under suitable pressure and temperature so as to convert at least a portion of the insoluble alkali metal compounds to one or more soluble alkali metal compounds, and produce a second leached slurry comprising the soluble alkali metal compounds and a residual insoluble matter;   (e) degassing the second leached slurry under suitable pressure and temperature so as to remove a substantial portion of the excess carbon dioxide and hydrogen sulfide, if present, and produce a degassed second leached slurry;   (f) separating the degassed second leached slurry into a first liquid stream and a residual insoluble matter stream, the first liquid stream comprising a predominant portion of the soluble alkali metal compounds from the degassed second leached slurry, and the residual insoluble matter stream comprising residual soluble alkali metal compounds and residual insoluble alkali metal compounds;   (g) recovering the first liquid stream; and   (h) washing the residual insoluble matter stream with an aqueous medium to produce a first wash stream comprising substantially all of the residual soluble alkali metal compounds from the residual insoluble matter stream,   
     wherein the quenching and contacting is performed in the substantial absence of gaseous oxygen. 
   
   
       2 . The process according to  claim 1 , wherein the char is a solid residue derived from gasification of a carbonaceous material in the presence of an alkali metal. 
   
   
       3 . The process according to  claim 2 , wherein the carbonaceous material comprises one or more of coal, petroleum coke, asphaltene, liquid petroleum residue or biomass. 
   
   
       4 . The process according to  claim 1 , wherein the aqueous medium to fracture the char comprises the first wash stream. 
   
   
       5 . The process according to  claim 1 , wherein the alkali metal comprises sodium and/or potassium. 
   
   
       6 . The process according to  claim 2 , wherein the alkali metal comprises sodium and/or potassium. 
   
   
       7 . The process according to  claim 1 , wherein the alkali metal is potassium. 
   
   
       8 . The process according to  claim 1 , wherein the source of alkali metal is potassium carbonate. 
   
   
       9 . The process according to  claim 1 , wherein contacting the quenched char slurry with an alkali metal hydroxide is performed at a temperature ranging from about 100° C. up to about 300° C., a steam pressure ranging from about 25 up to about 1000 psig, and time ranging from about 1 minute up to about 180 minutes. 
   
   
       10 . A process for catalytically converting a carbonaceous composition, in the presence of an alkali metal gasification catalyst, into a plurality of gaseous products, the process comprising the steps of:
 (a) supplying a carbonaceous composition to a gasification reactor, the carbonaceous composition comprising ash;   (b) reacting the carbonaceous composition in the gasification reactor in the presence of steam and an alkali metal gasification catalyst under suitable temperature and pressure to form (i) a char comprising alkali metal from the alkali metal gasification catalyst in the form of one or more soluble alkali metal compounds and one or more insoluble alkali metal compounds, and (ii) a plurality of gaseous products comprising methane and one or more of hydrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, ammonia, and other higher hydrocarbons;   (c) removing a portion of the char from the gasification reactor;   (d) extracting and recovering a substantial portion of the alkali metal from the char according to the process of  claim 1 ; and   (e) at least partially separating the plurality of gaseous products to produce a stream comprising a predominant amount of one of the gaseous products.   
   
   
       11 . The process according to  claim 10 , wherein the carbonaceous composition comprises one or more of coal, petroleum coke, asphaltene, liquid petroleum residue or biomass. 
   
   
       12 . The process according to  claim 10 , wherein the stream comprises a predominant amount of methane. 
   
   
       13 . The process according to  claim 10 , wherein the alkali metal comprises sodium and/or potassium.