Revealing the critical impact of CO2/(CO2+CO) ratio in different gas-to-methanol processes: Plant-wide modeling and scenario analyses

In the context of global carbon neutrality and stringent environmental constraints, gas-to-methanol (GTM) process has emerged as a pivotal pathway for sustainable methanol production. The CO2/(CO + CO2) ratios in the intermediate syngas have crucial influences on the reaction and process performances. However, the lack of consensus on the optimal CO2/(CO + CO2) ratio complicates the systematic optimization of existing GTM processes. With this challenge in mind, the reactor-level kinetic study and system-level techno-economic analysis are implemented to quantitatively investigate the feasibility, sustainability, and profitability of the different process scenarios in the range from 0.2 to 0.6. Herein, three distinct scenarios are proposed: current scenario using steam reforming technology, transitional scenario using CO2/Steam-mixed reforming technology, and future scenario using CO2/O2-mixed reforming technology. As a result, the reactor-level kinetic analysis suggests high CO2/(CO2+CO) ratios suppress the formation of byproduct dimethyl ether. Nevertheless, the system-level techno-economic analyses indicate the appropriate CO2/(CO2+CO) ratio (0.3), rather than extreme values, favors energy and exergy efficiency, carbon mitigation as well as cost saving. This study provides deep insights into the role of CO2/(CO2+CO) ratios in GTM processes and offers a scientific foundation for optimizing GTM processes.