Patent ID: 8328890

Claim:
A process for generating a plurality of gaseous products from a carbonaceous feedstock and recovering a methane product stream, the process comprising the steps of: (a) supplying a carbonaceous feedstock, an oxygen-rich gas stream, an alkali metal gasification catalyst, and steam to a catalytic gasifier; (b) reacting the carbonaceous feedstock in the catalytic gasifier in the presence of steam, hydrogen, carbon monoxide, the oxygen-rich gas stream and the alkali metal gasification catalyst, and at a temperature of from about 450° C. to about 800° C. and pressure of from about 400 psig to about 1000 psig, to form a first gas stream comprising a plurality of gaseous products comprising methane, carbon dioxide, hydrogen, carbon monoxide and hydrogen sulfide, wherein the first gas stream comprises at least 50 mol % methane plus carbon dioxide based on the moles of methane, carbon dioxide, carbon monoxide and hydrogen in the first gas stream; (c) optionally reacting at least a portion of the carbon monoxide and at least a portion of the hydrogen present in the first gas stream in a catalytic methanator in the presence of a sulfur-tolerant methanation catalyst to produce a methane-enriched first gas stream; (d) removing a substantial portion of the carbon dioxide and a substantial portion of the hydrogen sulfide from the first gas stream (or the methane-enriched first gas stream if step (c) is present) to produce a second gas stream comprising a substantial portion of the methane from the first gas stream (or the methane-enriched first gas stream if step (c) is present); (e) optionally, if the second gas stream comprises hydrogen and greater than about 100 ppm carbon monoxide, reacting the carbon monoxide and hydrogen present in the second gas stream in a catalytic methanator in the presence of a methanation catalyst to produce a methane-enriched second gas stream; and (f) recovering the second gas stream (or the methane-enriched second gas stream if step (e) is present), wherein: (i) at least one of step (c) and step (e) is present, (ii) the second gas stream (or the methane-enriched second gas stream if step (e) is present) is the methane product stream, or the second gas stream (or the methane-enriched second gas stream if step (e) is present) is purified to generate the methane product stream; (iii) a solid char product is produced in step (b), which is periodically withdrawn from the catalytic gasifier; and (iv) carbon monoxide in the first gas stream is subjected to a water-gas shift reaction in the presence of an aqueous medium to convert a portion of the carbon monoxide to carbon dioxide and to increase the fraction of hydrogen in the first gas stream.