NOVELTY - The reactor system comprises a reactor (100) provided with a synthesis gas inlet (101) on one end and a methane-rich gas outlet (102) on the other end, a reaction adsorption region with a coaxial closing interlayer structure arranged between the synthesis gas inlet and the methane-rich gas outlet, an adsorbent regenerator connected with the reactor through a waste adsorbent conveying pipeline (103) and a regenerative adsorbent conveying pipeline (104), an adsorbent inlet disposed on top or upper part of each of the coaxial closing interlayer of adsorbent, and a heat exchanger.    USE - The reactor system is useful for producing methane-rich gas.    ADVANTAGE - The reactor system is capable of rapidly, energy-efficiently and economically producing the methane-rich gas with high yield and quality, and exhibits improved lifespan.    DETAILED DESCRIPTION - The reactor system comprises a reactor (100) provided with a synthesis gas inlet (101) on one end and a methane-rich gas outlet (102) on the other end, a reaction adsorption region with a coaxial closing interlayer structure arranged between the synthesis gas inlet and the methane-rich gas outlet, an adsorbent regenerator connected with the reactor through a waste adsorbent conveying pipeline (103) and a regenerative adsorbent conveying pipeline (104), an adsorbent inlet disposed on top or upper part of each of the coaxial closing interlayer of adsorbent, and a heat exchanger installed in the reactor and/or the adsorbent regenerator for transmitting the heat generated in the reaction from the reactor and/or the adsorbent regenerator. The coaxial closing interlayer structure comprises an adsorbent mandrel or a hollow pipe mandrel capable of adsorbing carbon dioxide and sulfide gas, N-coaxial closing interlayers of methanation reaction catalyst, and N-coaxial closing interlayers of adsorbent arranged to be crossed with the N-coaxial closing interlayers of methanation reaction catalyst, where N is an integer that is greater than or equal to 1. The waste adsorbent generated in the adsorbent mandrel and the coaxial closing interlayers of adsorbent are conveyed to the adsorbent regenerator by the waste adsorbent conveying pipeline. The regenerative adsorbent is recycled to the adsorbent mandrel and the coaxial closing interlayers of adsorbent by the regenerative adsorbent conveying pipeline. The sections of the coaxial closing interlayers of methanation reaction catalyst and the coaxial closing interlayers of adsorbent have regular and/or irregular closed shapes, where the regular closed shape is circle, oval, square, rectangular, prism, triangle and/or polygon. The thicknesses of the N-coaxial closing interlayers of methanation reaction catalyst and the N-coaxial closing interlayers of adsorbent are identical or different. The synthesis gas inlet is disposed on top or upper part of the reactor, and the methane-rich gas outlet is disposed on bottom part of the reactor. The side surfaces of the adsorbent mandrel, the N-coaxial closing interlayers of methanation reaction catalyst and the N-coaxial closing interlayers of adsorbent are airtight surfaces, and the upper and lower surfaces of the adsorbent mandrel, the N-coaxial closing interlayers of methanation reaction catalyst and the N-coaxial closing interlayers of adsorbent are ventilating surfaces. The sealed spaces are present at an upper side or a lower side of the adjacent adsorbent mandrel and the coaxial interlayers of methanation reaction catalyst or at an upper side or a lower side of the adjacent hollow pipe mandrel and the coaxial closing interlayers of adsorbent, and at an upper side or a lower side of the adjacent coaxial closing interlayers of methanation reaction catalyst and the coaxial closing interlayers of adsorbent. The synthesis gas or the methane-rich gas flows through the coaxial closing interlayers of methanation reaction catalyst or the coaxial closing interlayers of adsorbent along the longitudinal direction that enters or departs the sealed spaces. A material for keeping air tightness of the upper and lower surfaces is a ceramic material or metal alloy material capable of bearing a high temperature of 900 degrees C, and has sufficient mechanical strength and anti-deformation capability at the high temperature. The heat exchanger is disposed in the coaxial closing interlayers of adsorbent. A cyclone cascade, a membrane and/or a filter are installed in the reactor and/or the adsorbent for separating the gas from solid granules. The methanation reaction catalyst is low sulfur resistant or non-sulfur resistant methanation reaction catalyst. An INDEPENDENT CLAIM is included for a method for producing methane-rich gas.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a reactor system (Drawing includes non-English language text).    Reactor (100)    Synthesis gas inlet (101)    Methane-rich gas outlet (102)    Waste adsorbent conveying pipeline (103)    Regenerative adsorbent conveying pipeline. (104)