An insight into the heat-management for the CO2 methanation based on free convection

This article presents a novel heat-management approach for CO2 valorization to synthetic natural gas based on free convection to the environment, without requirements of heat-exchange services. With this aim, a reactor channel was built (d = 4.6 mm, L = 250 mm) and tested at different conditions of inlet temperatures, gas hourly space velocities and pressures using an active nickel/ceria-based catalyst. After experimentation, a CFD model was developed, validated and employed for an efficient sensitive analysis of the most suitable reaction conditions. The simulation criteria were obtaining high CO2 conversion level and restricting overheating to avoid catalyst and reactor degradation. Then, the optimal conditions found by CFD modelling were successfully validated at lab-scale. The CO2 conversion level experimentally obtained was 93%, by using a decreasing temperature profile in the range of 830-495 K, operating at a pressure of 5 atm and a gas hourly space velocity of 11,520 h(-1). The proposed reactor configuration guarantees an efficient heat management along the reactor channel by using feasible conditions of pressure, temperature and flowrate for its implementation in small-scale applications, where the use of the exothermic heat is less profitable.