Process simulation was conducted to identify the technical feasibility and optimal reactor combination for a simple two-stage methanation process producing substitute natural gas (SNG). With two adiabatic fixed bed reactors in series the reaction temperature control requires high product gas recycle ratio which is much energy-consuming. An isothermal fluidized bed at 723-823 K combining a tail-end fixed bed was shown to be a high efficient one-pass methanation process. Over a Ni-Mg/Al2O3 catalyst methanation by laboratory tests in a fluidized bed exhibited obvious technical superiority over that in a fixed bed in terms of activity and carbon deposition on the spent catalyst. By noting further that the low-velocity bubbling fluidized bed leads to extremely high cross-sectional areas for large-scale industrial applications, the optimal reactor combination was proposed to be a fast fluidized bed and a clean-up fixed bed, which not only simplifies the methanation process but also reduces the reactor size and catalyst amount required. (C) 2015 Elsevier B.V. All rights reserved.