Operational strategies for industrial-scale methanol synthesis via CO2 hydrogenation under varying load conditions

Methanol is an important bulk chemical and versatile energy carrier that enables large-scale renewable energy imports due to its storability and compatibility with existing infrastructure. However, producing methanol from a fluctuating renewable hydrogen supply requires large storage capacities or load-flexible operation of the methanol synthesis process. This raises the question of how the methanol synthesis loop can be operated at part-load down to 10% without unduly shortening the catalyst lifetime. In this study, we used a one-dimensional, pseudo-homogeneous reactor model for industrial-scale methanol synthesis and integrated it into a steady-state process simulation of the entire synthesis loop. Our results demonstrate that decreasing the load increases both the hot spot temperature in the reactor and the water partial pressure. To prevent accelerated catalyst deactivation through sintering and hydrothermal sintering, we have developed operational strategies to enable load flexibility while mitigating critical operating conditions such as increased hot spot temperatures and water partial pressures. The main strategy identified for this purpose involves the combined adjustment of various operating parameters such as loop pressure and coolant temperature. Furthermore, integrating additional flexibility measures, including the stoichiometric number, purge ratio, condenser temperature, and recycling of purified methanol to the reactor inlet, reduces the required extent of pressure and temperature variation. These findings demonstrate that flexible part-load operation of methanol synthesis reactors down to 10% load is feasible without increasing catalyst deactivation.