Microscopic simulation of CO2 hydrogenation to methane in a fixed-bed catalytic reactor

"Power-to-Gas" technology offers a significant opportunity to address energy challenges and reduce the greenhouse effect, with the CO2 methanation process at its core. Fixed-bed reactor models were developed using the discrete element method and simulated in conjunction with computational fluid dynamics. The distribution and variations in temperature, mass concentration, and reaction rate within the reactor were analysed. The effects of reactor diameter, heat transfer coefficient, feed flow rate, feed composition, and feed temperature on CO2 conversion and reactor temperature were discussed. Special attention was given to the changes in the temperature and location of hot spots within the reactor. The results revealed that material and temperature distributions within the catalyst were non-uniform. As the reactor diameter increased, the hot spot temperature also rose, and the hot spot location shifted toward the upper part of the reactor. Increasing the heat transfer coefficient effectively reduced the bed temperature and enhanced the CO2 conversion. However, a higher feed flow rate led to an increased reactor hot spot temperature and a corresponding decrease in CO2 conversion rate. The presence of CH4 and H2O in the feed reduced both the hot spot temperature and CO2 conversion, and caused the hot spot position to shift downward. While the feed temperature influenced the bed hot spot temperature, it did not significantly impact the CO2 conversion rate.