Optimization of methanol synthesis under forced periodic operation in a non-isothermal fixed-bed reactor

Abstract

Methanol synthesis with a conventional Cu/ZnO/Al${}_2$O${}_3$-catalyst is typically carried out under stationary conditions. However, due to the process non-linearities, dynamic operation may improve the reactor performance. This paper numerically investigates such a potential of improvement through forced periodic operation of methanol synthesis in a non-isothermal lab-scale fixed-bed reactor. A multi-objective optimization is performed in which both the molar flow rate of methanol and the yield of methanol based on the used carbon molecules are considered as objective functions. The best possible steady state operation is then compared with the best possible periodic operation to evaluate the full potential of improvement. Focus is on periodic forcing of two inputs with same forcing frequency but different phase. Several possible input combinations are considered systematically. In particular the possibility of inlet and/or cooling temperature modulation is explored and compared. The results demonstrate a significant improvement for several input combinations through forced periodic operation.