Hydromethanation of a carbonaceous feedstock

Abstract

The present invention relates to processes for hydromethanating a carbonaceous feedstock to a methane-enriched synthesis gas and a char by-product, with catalyst recovery from the by-product char to generate a spent char, and with treatment of the spent char to generate a carbon rich portion which is ultimately recycled to the hydromethanation reactor to increase overall carbon utilization and increase yields of product gas (per unit of feedstock).

1 . A process for generating a methane-enriched raw product gas stream from a non-gaseous carbonaceous material, the process comprising the steps of:
 (a) preparing a carbonaceous feedstock from the non-gaseous carbonaceous material and a first carbon-enriched and inorganic ash-depleted char stream;   (b) introducing the carbonaceous feedstock and an alkali metal hydromethanation catalyst into a hydromethanation reactor, wherein the alkali metal hydromethanation catalyst is derived from a recycle alkali metal hydromethanation catalyst and a make-up alkali metal hydromethanation catalyst;   (c) reacting the carbonaceous feedstock in the hydromethanation reactor in the presence of carbon monoxide, hydrogen, steam and alkali metal hydromethanation catalyst to produce a methane-enriched raw product gas and a solid by-product char;   (d) withdrawing a stream of the methane-enriched raw product gas from the hydromethanation reactor as the methane-enriched raw product gas stream, wherein the methane-enriched raw product gas stream comprises methane, carbon monoxide, hydrogen, carbon dioxide, hydrogen sulfide, steam and heat energy;   (e) withdrawing a stream of the solid by-product char from the hydromethanation reactor, wherein the withdrawn solid by-product char comprises carbon and an inorganic ash, and contains an alkali metal content;   (f) treating the withdrawn solid by-product char to generate (1) a cleaned char stream depleted in at least alkali metal content, and (2) an aqueous alkali metal-enriched stream comprising one or more water-soluble alkali metal compounds, wherein the aqueous alkali metal-enriched stream comprises at least a predominant portion of the alkali metal content of the withdrawn solid by-product char;   (g) recycling at least a portion of the aqueous alkali metal-enriched stream for use as the recycle alkali metal hydromethanation catalyst;   (h) treating the cleaned char stream to generate (1) a second carbon-enriched and inorganic ash-depleted char stream, and (2) a carbon-depleted and inorganic ash-enriched char stream; and   (i) recycling at least a portion of the second carbon-enriched and inorganic ash-depleted char stream as the first carbon-enriched and inorganic ash-depleted char stream.   
     
     
         2 . The process of  claim 1 , wherein in step (h) the cleaned char stream is treated by physical beneficiation. 
     
     
         3 . The process of  claim 2 , wherein the physical beneficiation is a wet beneficiation process. 
     
     
         4 . The process of  claim 2 , wherein the physical beneficiation is a magnetic separation process. 
     
     
         5 . The process of  claim 1 , wherein the methane-enriched raw product gas stream further comprises entrained solids fines, the methane-enriched raw product gas stream is treated to removed at least a portion of the entrained solids fines to generate a removed fines stream, and at least a portion of the removed fines stream is combined with the withdrawn solid by-product char. 
     
     
         6 . The process of  claim 2 , wherein the methane-enriched raw product gas stream further comprises entrained solids fines, the methane-enriched raw product gas stream is treated to removed at least a portion of the entrained solids fines to generate a removed fines stream, and at least a portion of the removed fines stream is combined with the withdrawn solid by-product char. 
     
     
         7 . The process of  claim 1 , wherein that carbonaceous feedstock and the alkali metal hydromethanation catalyst are combined prior to introduction to the hydromethanation reactor to generate a catalyzed carbonaceous feedstock, which is introduced into the hydromethanation reactor. 
     
     
         8 . The process of  claim 2 , wherein that carbonaceous feedstock and the alkali metal hydromethanation catalyst are combined prior to introduction to the hydromethanation reactor to generate a catalyzed carbonaceous feedstock, which is introduced into the hydromethanation reactor. 
     
     
         9 . The process of  claim 7 , wherein at least a portion of the first carbon-enriched and inorganic ash-depleted char stream is combined with the catalyzed carbonaceous feedstock. 
     
     
         10 . The process of  claim 8 , wherein at least a portion of the first carbon-enriched and inorganic ash-depleted char stream is combined with the catalyzed carbonaceous feedstock.