Supplementary information files for A strategy for CO₂ capture and utilization towards methanol production at industrial scale: an integrated highly efficient process based on multi-criteria assessment

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Supplementary files for article A strategy for CO₂ capture and utilization towards methanol production at industrial scale: an integrated highly efficient process based on multi-criteria assessment

CO₂ capture and utilization are an effective solution to the problem of CO₂ emissions, and a combination of ammonia-based CO₂ capture and its use for methanol production is a highly feasible strategy. However, the uses of conventional technologies have resulted in a high demand for energy, with limited use of hydrogen. To address these problems, an innovative strategy is proposed and demonstrated in this study that enhances the conventional design, i.e., to use ammonia-based CO₂ capture with double tower absorption and solvent split, along with wet hydrogen for methanol production at industrial scale. The process is further improved through a multi-criteria assessment that considered the CO₂ capture rate, NH₃ loss rate, CO₂ conversion rate, and energy saving factors, in which the latter is based on two components, namely the reboiler duty and the condenser duty. Moreover, an exergy analysis method is used to optimize the improved process, and a highly efficient integrated process is finally established. It has been found that the use of a double-tower absorption process ensures high rates of CO₂ capture and low rates of NH₃ loss. Additionally, adjusting the molar ratio of H₂ to CO₂ leads to an impressive 8% increase in the CO₂ conversion rate, reaching 25%. In terms of energy savings, the average reboiler duty was reduced from 13.39 to 11.85 MJ/kg_CO2, i.e., by 11.50%; while the condenser duty was reduced by 11.36%; both contributed to the overall energy savings. In the I-ACCMP process, the total exergy loss is 437.24 kW, of which the exergy loss of the heat exchangers accounts for 16%, and the desorption tower (DES) accounts for 48%. After optimization, the exergy loss of the heat exchangers decreases from 70.02 kW to 40.45 kW, the exergy loss of the DES decreases from 209.29 kW to 180.91 kW, and the reboiler duty is reduced from 10.60 MJ/kg_CO2 to 7.71 MJ/kg_CO2. The total exergy loss decreases from 437.24 kW to 372.68 kW, which is a reduction by 14.8%.