潜熱蓄熱機能を持つNi触媒を充填した固定床反応器におけるCO₂メタネーション反応の熱制御~軸方向勾配配置の効果~

抄録

This study investigates a passive type of thermal regulation for CO₂ methanation using catalyst pellets, comprising Ni catalysts supported on pellets composed of an Al–Cu–Si based microencapsulated phase change material (MEPCM, heat storage temp.: 519°C), with latent heat storage functions. The effects of catalyst bed configurations; a uniform type and multi-stage types on temperature profiles in the catalyst beds and CO₂ conversion were mainly investigated. Here, uniform type is only Ni/Al–Cu–Si MEPCM pellets were packed. The multi-stage types are with different mass fractions of Ni/MEPCM pellets and MEPCM pellets (no catalyst) in each stage. Compared to the uniform configuration, the multi-stage gradient configuration demonstrated an extended duration of temperature stagnation at around the heat storage temperature of the MEPCM and a reduction in the steady-state temperature at the inlet-side location. This effect can be attributed to the dilution of the catalyst bed with Al–Cu–Si MEPCM pellets, which suppressed the heat generated by the reaction and prevented excessive temperature increases. On the other hand, at the downstream temperature, the two-stage gradient and three-stage gradient configurations exhibited shorter durations of temperature stagnation and higher steady-state temperatures. In addition, the CO₂ conversion observed for the multi-stage gradient configurations were lower than that of the uniform configuration.