Abstract: A process for producing a synthesis gas containing methane and using a reactor having a fuel containing carbon comprises directing gasification gases in a circulation system through a bed of fuel containing carbon to form a synthesis gas containing methane and carbon dioxide. Thereafter, the synthesis gas is cooled in a regenerator and subjected to the gas separation wherein the syngas is subjected to a gas cleansing by means of a pressure change absorption in a gas scrubber to remove most of the methane and carbon dioxide and its water content is increased. The separated gas is then heated and subsequently the portion is returned into the system together with the waste gases and fuel containing carbon. The process includes a 4-pole heater which includes the first heat exchange passage for the syngas which is cooled and a second heat exchange passage for the recirculation of the syngas and is further cooled and passed through a scrubber.