Equilibrium and kinetic aspects for catalytic methanation focusing on CO2 derived Substitute Natural Gas (SNG)

The production of Substitute Natural Gas (SNG) can be a key component of indigenous energy supply towards a low carbon future. In the present work, state of the art catalytic processes for SNG production based on CO and CO2 methanation are presented. Equilibrium based simulations are performed for both CO and CO2 methanation in order to define the optimum process parameters. A special focus is given on SNG derived from CO2 and hydrogen via power to gas process, which combines energy storage, Carbon Capture and Utilisation (CCU) with SNG production. Three kinetic models for CO2 methanation at 10 atm, 17 atm and 20 atm from the literature are compared. The quality of SNG produced is evaluated depending on the different operating pressure and temperature of CO2 derived SNG process. Low pressure bulk methanation (< 20 atm) cannot meet today's grid specifications without any additional measures taken such as blending with fossil natural gas or additional process equipment. Although heating value and Wobbe Index can be fulfilled, the maximum allowed hydrogen content remains a critical issue. Optimum process scheme and conditions for a dry hydrogen mole fraction lower than 2%vol in the final SNG are presented.