NOVELTY - Producing a methane-containing gas from a synthesis gas, comprises supplying a carbon monoxide and hydrogen containing synthesis gas for methanation to a reactor system (1) with a catalyst material, dividing process gas stream leaving the reactor system into a product gas stream and a recycled gas stream, supplying the recycled gas stream by an ejector (5) and directing for cooling in the reactor system, compressing the product gas stream, and supplying the compressed product gas to the ejector as a blowing medium.    USE - The method is useful for producing a methane-containing gas from a synthesis gas.    ADVANTAGE - The method: avoids the pressure reduction of the synthesis gas or accelerated aging of the catalyst material; and is carried out in an efficient manner at low production cost.    DETAILED DESCRIPTION - Producing a methane-containing gas from a synthesis gas, comprises supplying a carbon monoxide and hydrogen containing synthesis gas for methanation to a reactor system (1) with a catalyst material, dividing process gas stream leaving the reactor system into a product gas stream and a recycled gas stream, supplying the recycled gas stream by an ejector (5) and directing the recycled gas stream for cooling in the reactor system, compressing the product gas stream to a pressure, which is greater than the pressure of the synthesis gas, which is fed into the reactor system, and supplying the compressed product gas to the ejector as a blowing medium. The product gas stream is introduced into an input gas pipeline system and the ejector supplies the input gas from the input gas pipeline system as the blowing medium. An INDEPENDENT CLAIM is also included for a methane recovery system for carrying out the method, comprising reactor system containing the catalyst material for methanation, in which a supply line (2) for the synthesis gas is connected to the inlet of the system and a pipeline system is connected to the outlet side of the reactor system, the ejector in a recirculation line (4), in which a suction side of the ejector is connected to the piping system (3) and a pressure side of the ejector is connected at the inlet of the reactor system, at least one cooler, which is arranged in the recirculation line or between the reactor system and the ejector in the piping system, in which the piping system comprises a compressor provided in the flow direction behind the junction of the recirculation line, and the blowing agent line opening in a blowing agent input of the ejector, provided in the flow direction downstream to the compressor, is connected to the piping system or the input gas pipeline system, which is connected with the piping system for methane-containing gas.    DESCRIPTION OF DRAWING(S) - The figure 1 shows a schematic representation of a methane extraction plant for producing the methane-containing gas from synthesis gas.    Reactor system (1)    Supply line (2)    Piping system (3)    Recirculation line (4)    Ejector (5)