Exergoenvironment evaluation of carbon resource conversion and utilization via CO2 direct hydrogenation for methanol and power cogeneration

Abstract

CO2 hydrogenation technology is pivotal for achieving low-carbon and sustainable development goals by curbing carbon dioxide emissions and enabling new value chains. Traditional CO2 hydrogenation systems face challenges like excessive unreacted gas cycling and inefficient component usage. This study employed direct CO2 hydrogenation for methanol production, and integrated the chemical looping combustion (CLC) concept to enhance energy efficiency and carbon cycle utilization in methanol-electricity production. The proposed method has yielded remarkable results, attaining an exergy efficiency of 57.72 %, with CO2 equivalent emissions at 0.27 kgCO2/kgCH3OH. Furthermore, it has demonstrated a reduction of approximately 9.60 % in energy consumption and an impressive 83.63 % decrease in carbon emissions compared to the reference system. Exergoenvironmental analysis was conducted for the entire process and individual units. The results indicated superior environmental performance of the cogeneration system compared to the single-production system when the recycling ratio of unreacted gas (Ru) ranged from 1.64 to 2.72. Furthermore, CLC was identified as a key area requiring optimization within the system and determined by the values of rb,k and B˙D,k. This observation remains consistent even as Ru changes. The system showcases significant potential in thermodynamics and environmental sustainability, and lays a theoretical foundation and innovative perspective for CO2 utilization technologies.