Optimized Process for Methanol Production via Bi-reforming Syngas

In this work, an optimized process for methanol production using syngas from bi-reforming is proposed. The feed ratio (CH4/CO2/H2O) in the bi-reforming step, the purge stream quantity, and the heat recovery were optimized with the overall objective to reduce direct and indirect CO2 emission in the process. The effect of the feed ratio on the rates of simultaneous reactions involved in bi-reforming (i.e., DR, SMR, and WGS) was investigated to understand the balance between the consumption and production of CO2 relative to CH4. Compared to the conventionally used feed ratio of 3:1:2, this study found that the 1:1:2 ratio resulted in 100% CH4 conversion and higher CO2 consumption per mole of CH4 in the bi-reforming step. A plant-wide heat integration approach was adopted using pinch analysis to design a network of 27 heat exchangers. The implementation of a heat exchanger network resulted in the recovery of 221 MW of heat from process streams within the plant. With complementary optimization strategies, the proposed process resulted in ∼0.31 tonnes of CO2 per tonne of methanol production, one of the lowest among the processes published in the literature.