CO_2 methanation in a bench-scale bubbling fluidized bed reactor using Ni-based catalyst and its exothermic heat transfer analysis

摘要

CO_2 methanation, as a power-to-gas technology, is considered to be an important method to secure energy supply by utilizing CO_2 and H_2 gases. In this study, a 0.2 kW CH_4 bench-scale fluidized bed reactor was used for CO_2 methanation using approximately 13 kg nickel-based catalyst to investigate the effect of temperature, gas velocity, and H_2/CO_2 ratio on CO_2 conversion, CH_4 purity, and CH_4 selectivity. Response surface methodology (RSM) was employed to design the experimental conditions to statistically evaluate the effect of operating variables. Reduced quadratic model equations for CO_2 conversion and CH_4 purity were derived, which determined the optimal conditions within the experimental conditions. The suggested conditions for the highest CO_2 conversion were 297°C, 4.66H_2/CO_2, and 4.0 U_g/U_(mf) (velocity ratio), whereas different conditions were determined for the highest CH_4 purity. Among the operating variables, temperature was the most influential factor, followed by the gas ratio. The highest CO_2 conversion and CH_4 purity were 98% and 81.6%, respectively. Additionally, the heat transfer coefficient (h_0) was found to be 115 W/m~2·°C during a 10-h continuous CO_2 methanation experiment, which is an important design factor for the further scale-up of the process.