Novel Sorption-Enhanced Methanation with Simultaneous CO₂ Removal for the Production of Synthetic Natural Gas

With increasing consumption of natural gas as a clean energy source and demand for efficient use of cheap and abundant coal, the production of synthetic natural gas from coal has been receiving considerable interest. In this study, the methanation reaction of coal-derived syngas for the production of synthetic natural gas was investigated using numerical simulations. In particular, the concept of a sorption-enhanced reaction, in which CO₂ removal by sorption is carried out simultaneously with the reaction, was newly applied to the methanation reaction. Effects of the operating parameters such as the fraction of catalyst and sorbent, temperature, pressure, and feed ratio (H₂/CO, H₂O/CO, and CO₂/CO) on CO conversion and purity, selectivity, and productivity of CH₄ were evaluated by computational studies. It was found that the performance of the sorption-enhanced methanation reaction is controlled by both thermodynamic equilibrium and reaction kinetics. Therefore, the reaction would require an optimal catalyst fraction, temperature, and pressure conditions for maximum efficiency. Optimal H₂/CO and H₂O/CO ratios exist considering reaction performance, and any CO₂ content in the feed reduces CH₄ productivity. Compared to the conventional methanation reaction, the sorption-enhanced methanation reaction produces CH₄ in high purity (>95%), which can be directly used for synthetic natural gas without further separation processes.