Cryogenic liquefied natural gas (LNG) is used as a source of refrigeration and methane in the production of dry sulfur-free, methane-enriched synthesis gas or fuel gas. Raw syngas is indirectly and directly contacted with cryogenic liquefied natural gas (LNG) and cooled thereby below the dew point. Water is thereby condensed out and separated from the process gas stream. Further, the liquid LNG vaporizes and increases the methane content of the dewatered synthesis gas. Cold liquid absorbent solvent contacts the dry CH.sub.4 -enriched synthesis gas in an absorption column and absorbs the acid gases e.g. H.sub.2 S and COS and optionally H.sub.2 S+COS+CO.sub.2. In a preferred embodiment, the rich solvent absorbent is regenerated in a stripping column and the released acid gases are sent to a Claus unit for the production of elemental sulfur. In a second embodiment, the regenerated lean liquid absorbent solvent may be mixed with the dry, purified synthesis gas leaving from the top of the absorption tower. This mixture is then directly and optionally indirectly contacted with additional cryogenic liquid LNG. The CH.sub.4 content of the synthesis or fuel gas is thereby increased to a value in the range of about 10 to 80 mole %. By means of a decanter, dry, sulfur-free methane-enriched syngas product is separated from liquid absorbent solvent. The liquid absorbent solvent is then recycled to the absorption column.