Methanation of coke oven gas over Ni-Ce/γ-Al2O3 catalyst using a tubular heat exchange reactor: Pilot-scale test and process optimization

•A tubular heat exchange reactor (THER) used for COG methanation was designed.•The pilot-scale methanation test using a THER was performed.•A new COG-to-SNG process combined a THER and an adiabatic reactor was proposed.•The new COG-to-SNG process simplifies methanation production saving 6–7% energy.•The process shows high energy efficiency, low investment and CO2 emission reduction.