The methanation of CO2 was studied in a wall-cooled single-tube fixed-bed reactor with a nickel-based catalyst. Heat transfer and kinetic parameters were experimentally determined. Temperature profiles were recorded under different conditions: inlet gas mixtures with CO2 diluted in H-2 or N-2, tubes with diameters of 2 or 4 cm, and pressures of 1 or 4 bar at 160-200 degrees C. Modeling of CO2 conversion and temperature profiles by a two-dimensional reactor model was successfully achieved. The study is completed by modeling technical reactors for both upgrading of biogas and conversion of a CO2/H-2 feed gas free of CH4; design data of reactors for a production of 450 m(3) of synthetic natural gas per hour are given.