Simulations and Optimization of a Reduced CO2 Emission Process for Methanol Production Using Syngas from Bi-reforming

A low CO2 emission process for methanol production using syngas generated by combined H2O and CO2 reforming with CH4 (bi-reforming) is proposed in this work. A detailed process model was developed using Aspen Plus. The operating conditions of the bi-reforming and methanol synthesis were derived from a detailed sensitivity analysis using plug flow reactor models with Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetics. A molar feed ratio of CH4:CO2:H2O of 1:1:2, instead of conventional 3:1:2 in the bi-reforming was found to be optimum and resulted in ∼99% conversion of CH4, 44% conversion of CO2, and a H2/CO ratio of 1.78 at 910 °C and 7 bar. A higher methane conversion eliminated the need for cryogenic separation of CH4. The optimum feed ratio of 1:1:2 resulted in an ∼33% higher consumption of CO2 per mole of CH4 required than the conventional process. An acid gas removal process using MDEA was used for CO2 separation, and a network of heat exchangers was configured for heat recovery. The proposed process resulted in ∼0.37 tonne of CO2 per tonne of methanol, which is ∼2–4 times lower than several published data and commercial methanol processes.