Isothermal methanation process and device for the preparation of synthetic natural gas

The invention discloses an isothermal methanation process for the preparation of synthetic natural gas. The process comprises methanation step, methanation heat recovery steam-making step and condensate treatment step. The purified synthesis gas is performed methanation step, wherein the methanation step adopts at least two-stage methanation, the first stage methanation adopts an adiabatic methanation reactor to perform methanation and the later methanation in each stage adopts an isothermal methanation reactor to perform methanation. The invention also discloses an isothermal methanation device used in the isothermal methanation process for the preparation of synthetic natural gas. The isothermal methanation process and the isothermal methanation device for the preparation of synthetic natural gas of the invention have the advantages of energy-saving, environmental friend and low investment.