Role and impact of wash columns on the performance of chemical absorption-based CO2 capture process for blast furnace gas in iron and steel industries

Owing to strict environmental regulations for amine vapor emissions (generally around 1 ppmv) and demands for energy consumption reduction, wash sections in large-scale CO2 capture processes (CCPs) are receiving increasing attention. This study presents a comprehensive techno-economic analysis of a commercial-scale monoethanolamine (MEA)-based CCP containing two wash columns for the absorber and stripper for blast furnace gas (BFG) in iron and steel industries. The absorber wash column contributed slightly to improving the capture rate but did not affect the regeneration heat consumption. The contribution of the absorber wash column to the capture cost under the optimal operating condition was up to 5.4%. Furthermore, the stripper wash column improved energy efficiency of the reboiler and condenser via self-heat recuperation by approximately 1.25% and 4.44% on average, respectively. This played a critical role in enhancing the energy efficiency by recovering the partial vaporization heat of water. The maximum energy efficiency was achieved with the stripper operated under the same lean loading, indicating that the optimal lean loading for regeneration heat is the inherent thermodynamic property of the CO2/aqueous MEA system. Finally, the dimensions of absorber, stripper and wash columns were determined under the minimum capture cost for reliable and reasonable consideration.