Advanced Design and Comparative Analysis of Methanol Production Routes from CO2 and Renewable H2: via Syngas vs. Direct Hydrogenation Processes

Abstract

In this study, we propose two advanced processes, i.e., advanced syngas-to-methanol (AS2M) and direct CO2-to-methanol (DC2M) processes, for methanol production using waste CO2 and renewable H2 as feedstock. The AS2M process produces methanol from syngas after converting CO2 to CO via reverse water-gas shift and separating CO from a mixture through pressure swing adsorption. In comparison, the DC2M process directly synthesizes methanol from CO2 through direct hydrogenation. Different unit processes and recycles were synthesized to determine the optimal process configurations and operating conditions for maximizing the methanol production rate. The technoeconomic and environmental capabilities of the two proposed processes were analyzed with four evaluation criteria (carbon and energy efficiencies, CO2 reduction, and unit production cost) and compared with conventional CO2-to-methanol processes. A sensitivity analysis for various utilities and H2 supply strategies was performed to evaluate the economic feasibility and environmental benefits of the proposed systems with different design options. Our findings showed that both processes could achieve improved technical, economic, and environmental performances compared to conventional processes. In particular, the DC2M process showed the lowest unit production cost at $1.02/kg because of its simple configuration and mild operating conditions.