Modelling of Methanol Synthesis

Abstract

Hydrogen is a key component in the methanol (MeOH) synthesis process. It affects both the environmental and economic performance, since renewable hydrogen (usually produced by electrolysis) is the most expensive component of the process. The addition of renewable hydrogen improves the carbon balance of the process but necessitates the planning of a suitable strategy to account for the stochastic nature of renewable energy and the respective costs. For this reason, the focus of this work is the efficient hydrogen utilization in contrast to most of the past literature works that mainly focus on the conversion of the carbonaceous feedstock. Several operating parameters such as the extent of recycling, operating temperature and pressure, stoichiometric number, inlet temperature and total mass flow per tube affect the methanol yield, carbon conversion and hydrogen consumption of the process. The scope of this work is to provide insight on the effect of those parameters on the efficient hydrogen utilisation using a methanol synthesis modelling tool. The findings of this study showed that hydrogen utilisation could be considerably improved if operating at certain conditions. Lower stoichiometric numbers and mass flows per tube, inlet and cooling temperatures up to 510 K and higher operating pressures could reduce the required hydrogen per produced methanol unit. Especially the employment of recycling, could lead to substantial reduction of the associated hydrogen requirements. In particular, recycling 50 % of the residual off-gases could lead to 10 % less fresh hydrogen requirements and 90 % recycling results to 40 % less hydrogen for the production of the same amount of methanol.