Numerical Study on Reaction Characteristics of Carbon Dioxide Hydrogenation to Methanol in Habitable Confined Space Based on Heterogeneous Models

In the habitable confined space, hydrogen (H₂), the by-product of water electrolysis to provide breathing oxygen to crews, and crew’s exhaled carbon dioxide (CO₂) are the two surplus gases which should be eliminated for maintenance of atmospheric balance and protection of crew’s life safety. Catalytic synthesis of methanol (CH₃OH) from H₂ and CO₂ is one of the best ways to eliminate surplus H₂ and CO₂ in manned confined space. The conclusions drawn through reaction modeling and characteristic analysis can guide the control of the reaction process, which is conducive to maintaining the atmospheric balance in confined space. In this paper, based on the established material calculation model and temperature one-dimensional heterogeneous model, the reaction characteristics of catalytic synthesis of methanol from H₂ and CO₂ under different reaction pressures, coolant temperatures, and CO₂ to CO ratios were studied. Results show that the increase of reaction pressure, the growth of coolant temperature, and the decrease of CO₂ to CO ratio in inlet gas can all promote the increases of reaction rate, methanol synthesis rate, and the maximum temperatures of catalyst and reactant. Besides, in order to keep the catalyst maximum temperature within a reasonable reaction range (lower than 573.15 K), the reaction pressure should not be higher than 8 MPa, the coolant temperature is not higher than 538.15 K, and the ratio of CO₂ to CO is not less than 1.