Passive thermal management of CO2 Methanation using phase change material with high thermal conductivity

CO₂ methanation is a promising technology for fuel decarbonization. Since methanation is an exothermic reaction, thermal management of the reactor is an important issue. This study investigated the effect of applying metallic phase change material(PCM) for reactor thermal management. In this study, Zn-30 %Al alloy(melting point: 429–509 °C)-based PCM composites were mixed with catalysts in a bench scale reactor, then steady-state and transient methanation were examined. The results at steady state indicated peak temperature was reduced from 464 °C to 411 °C compared to conventional single-catalyst condition. This corresponded to 38 % reduction in the temperature difference between peak and base temperature. Furthermore, temperature distribution in the whole reactor was homogenized, achieving a dispersion of the local thermal stress. This was due to high thermal conductivity of metallic PCM. Then, transient thermal management of PCM was evaluated. Periods for temperature increase between 430 and 450 °C, including PCM melting point, was prolonged 45 min compared to the condition without PCM. This resulted 71 % suppression of exothermic speed. This was due to complex effects of latent heat and high thermal conductivity of metallic PCM, offering thermal buffer in case of catalyst thermal runaway. These results showed the introduction of metallic PCM into methanation reactor provides novel thermal management.