•Low-temperature steam conversion of flare gases into methane-rich mixtures.•Conversion of C2+-hydrocarbons to CH4, CO2 and H2.•Lowering net calorific value, Wobbe index and dew point temperature of the gas.•Partial conversion of C2H6 and C3H8 to reach desired gas properties.•Kinetic simulation and prediction of optimal reaction conditions. The present work aims at studying low-temperature steam conversion of model flare gas mixtures containing C2H6-C5H12 in methane excess over industrial Ni-based catalyst. It is shown that at 250–350 °C and H2O/CC2+ molar ratio of 0.7–1.0, steam conversion can be applied to convert C2+-hydrocarbons into CH4, CO2 and H2, which results in the lowering net calorific value, the Wobbe index and dew point temperature of the gas obtained. However, complete conversion is not necessary for certain applications. In these cases, kinetically controlled partial conversion of ethane and propane enables one to obtain methane-rich mixtures with desired calorific properties for various applications. This idea has been experimentally verified. Kinetic study of C2H6-C5H12 low-temperature steam conversion has been performed. A simple macrokinetic model, which included irreversible first-order kinetics for C2H6-C5H12 steam conversion and quasi-equilibrium mode for CO2 methanation, has been suggested. The model adequately describes the experimental data on the conversion of model flare gas mixtures at various temperatures and flow rates and has been applied to predict the reaction conditions which would allow one to obtain methane-rich mixtures with the desired properties for various applications.