NOVELTY - Producing (M1) synthetic natural gas involves separating syngas into first syngas, second syngas, and third syngas; methanating first syngas to produce a first effluent; mixing first effluent, with second syngas to produce a first mixed effluent; methanating first mixed effluent to produce a second effluent; mixing second effluent with third syngas to produce a second mixed effluent; methanating second mixed effluent to produce a third effluent; cooling third effluent to produce a first cooled effluent; and methanating first cooled effluent to produce a synthetic natural gas.    USE - For producing synthetic natural gas (claimed), which is used as fuel.    ADVANTAGE - The method increases the conversion and energy efficiency of the catalyst, thus reduces heat generated from the methanation reactions. The effluent produced in the method has a methane concentration, on a dry basis, of greater than or equal to 97 mol.%, thus improves product value, e.g. a heating value; and reduces the product gas recycle requirements to quench hear, of the reaction within the methanation system. The methane concentration also reduces auxiliary power consumption, capital costs, and operating costs of the methanation system.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is/are included for a system for producing synthetic natural gas comprising: a first heat exchanger adapted to heat a syngas to produce a first heated syngas; a second heat exchanger adapted to heat the first heated syngas to produce a second heated syngas; a first methanation unit adapted to methanate a first portion of the second heated syngas to produce a first effluent; a third heat exchanger adapted to cool the first effluent by transferring heat from the first effluent to a first heat recovery medium a second methanation unit, adapted to methanate a first mixture containing the first effluent and a second portion of the second heated syngas to produce a second effluent; a fourth heat exchanger adapted to cool the second effluent by transferring heat from the second effluent to a second heat recovery medium; a third methanation unit adapted to methanate a second mixture comprising the second effluent and a third portion of the second heated syngas to produce a third effluent, where the second heat exchanger heats the first heated syngas by transferring heat from a first portion of the third effluent to produce a cooled first portion of the third effluent; and a fourth methanation unit adapted to methanate the cooled first portion of the third effluent to produce a fourth effluent, where the first heat exchanger heats the syngas by transferring heat from the fourth effluent to the syngas.