Modelling and Simulation of Methanation Catalytic Reactor for Renewable Electricity Storage

Storing renewable electricity in a natural gas grid is an innovative concept. Renewable energy (wind or solar power) is stored as chemical energy in existing storage capacities, which is an advantage over hydrogen. Storage and power conversion technologies for natural gas are state-of-the-art, commercial technologies unlike hydrogen. A further advantage of storage is the higher energy density of methane. Renewable natural gas substitute (SNG) can be stored, distributed and reconverted on demand in balance power. In this novel approach, renewable energies are converted via reversible solid oxide cells (RSOC) into CO and Hydrogen. Syngas (H-2 and CO) is then converted into methane. Thus, the main conversion step is methanation. Methanation synthesis is a catalytic exothermal process at temperatures of 473-673 K and high pressure from 20 to 70 bar. Syngas enters the methanation reactor with H-2/CO molar ratio of 3. The reactions considered in the proposed model are CO methanation and Water Gas Shift conversion (WGS). Modelling and simulation of the methanation catalytic reactor was developed using the Aspen Plus (TM) software considering an isothermal fixed bed reactor with steam recovery and CO methanation kinetic on Ni catalyst. The model was validated by comparing the calculated gas concentration profiles (CH4, CO, CO2 and H-2) with the recent experimental data obtained on bench-scale and with industrial data. The mean absolute percentage error was 12 %. The mixture leaving methanation reactor contained 47.3 % of CH4, 1.2 % of H-2, 6.6 % of CO2, 0.1 % of CO and 44.7 % of H2O.