Optimal Design Issues of a Methanol Synthesis Reactor from CO2 Hydrogenation

Methanol production through CO₂ hydrogenation was investigated in a series of fixed-bed reactors. Staging of the reactor into several smaller reactors is considered to enhance methanol production, in addition to maximizing a measure of annual profit. The degrees of freedom of the reactor system are the number of stages, the cooling medium temperature, the heat transfer area, and the volume of the stages. Depending on the objective function (OF) criteria, staging of the reactor increases the OF values to various extents. When the objective is to maximize the methanol production, the OF of a three-stage reactor system with an inlet H₂/CO₂ ratio of 2 is 2.61 % higher than in the single-stage configuration. Staging of the reactor also increases the synthesis gas conversion to methanol. However, if maximizing the annual profit is the objective, the profitability of the two-stage configuration is 2.05 % greater than in the case with one reactor, due to the higher methanol production of the staged reaction system.