Intensification of the CO2-capturing methanol steam reforming process: A comprehensive analysis of energy, economic and environmental impacts

Abstract

The methanol (MeOH) steam reforming (MSR) process plays an important role in the MeOH-based international renewable energy supply chain. To address the challenges related to the high cost and substantial CO2 emissions linked to the state-of-the-art integrated MSR process, this study aims to propose and enhance an intensified MSR process focusing on energy utilization, economic viability and environmental impact. Aside from the MSR process, the overall scenario also includes the water–gas-shift reaction (WGS) process, CO2 capture using amine-based methods, liquefaction, and hydrogen purification through pressure-swing adsorption. Based on this study, apparent enhancements of the state-of-the-art MSR process can be achieved by adjusting key process variables, especially those related to the CO2 capture process, and by incorporating various intensification strategies, including heat integration (with feed-effluent heat exchangers) between the MSR and the WGS processes, implementing a side-draw intercooling structure of the CO2 absorber, splitting the rich solvent flow to the CO2 stripper, and employing a multi-stage CO2 stripper with vapor recompression. Compared to the state-of-the-art MSR process in the literature, the intensified MSR process produces ultra-pure hydrogen (99.99 mol%) as a main product while reduces 6.2 % of the shared cost (from 191.0 USD/t-MeOH to 179.1 USD/t-MeOH), increases the overall carbon capture rate by 3 % (from 86.73 % to 89.99 %), and reduces the direct CO2 emission by approximately 25 % (from 1.41 t-CO2/ t-MeOH to 1.06 t-CO2/ t-MeOH). Within a MeOH-based international renewable energy supply chain, these enhancements can also significantly lower the imported cost of electricity from 105.9 USD/MWh to 95.5 USD/MWh.