Process simulation was applied to identify optimal reactors for a two-stage methanation process.

Two adiabatic fixed beds in series require high product gas recycle ratio to control temperature.

Methanation in fluidized bed showed higher activity and less carbon deposition on spent catalyst.

Methanation could be completed through the fast reactions occurring on the catalyst surface.

Methanation in a fast fluidized bed is closed to the equilibrium and non-kinetic limited.