Patent ID: 8530529

Claim:
Process for the production of substitute natural gas (SNG) by the methanation of a synthesis gas derived from the gasification of a carbonaceous material, the process comprising the steps of: (a) passing the carbonaceous material through a gasification stage and withdrawing a gas containing carbon monoxide, carbon dioxide and hydrogen; (b) passing at least a portion of the gas from the gasification stage through a water gas shift stage and withdrawing a gas enriched in hydrogen; (c) passing the gas from step (b) through an acid gas removal step, withdrawing a stream of carbon dioxide and withdrawing a stream of synthesis gas containing hydrogen, carbon dioxide and carbon monoxide and with a molar ratio M=(H2−CO2)/(CO+CO2) greater than 3.00; (d) passing the synthesis gas from step (c) through a methanation section containing at least one methanation reactor and withdrawing from the methanation section a product gas containing methane; (e) adding to the methanation section of step (d) a stream having a molar ratio M=(H2−CO2)/(CO+CO2) lower than 3.00 which is selected from the group consisting of a stream derived from the gas withdrawn in step (a), a stream derived from the gas withdrawn in step (b), a stream at least partly derived from the stream of carbon dioxide withdrawn in step (c), a separate stream containing at least 80 vol % CO2, and combinations thereof.