Potential Environmental Impact Evaluation of the Methanol Synthesis Process by Gas-to-Methanol Technology

Two methanol production process options based on gas-to-methanol (GTM) technology according to the CO₂ feed location (option 1: CO₂ is fed to the methanol synthesis unit via a reformer; option 2: CO₂ is directly fed to the methanol synthesis unit) are proposed. In this study, we simulated these two methanol synthesis process options at a steam/natural gas (S/NG) ratio of 1.5 and evaluated the environmental impact of the two options by comparing the potential environment impact (PEI) according to the recycle ratio of unreacted syngas. We simulated the process using Aspen Plus and quantitated the PEI rates using the Waste Reduction (WAR) algorithm (version 1.0). The results show that in both cases PEI rates decrease with increasing recycle ratio of the unreacted syngas and thus become environmentally friendly. Also, it was demonstrated that option 1 is more environmentally friendly than option 2, and when the recycle ratio increases from 0 to 0.9, the total rate of PEI output decreases from 176.3 to 93.4 PEI/h by 53.0% and the PEI generation rate decreases from 149.9 to 67.0 PEI/h by 44.7%.