Design and operation of water-wash sections to minimize MEA emissions

Abstract

Whether in gaseous or aerosol form, mitigation of emissions from absorption-based carbon capture remains a real challenge. Among the available control technologies, water-wash is one of the most conventional and has been shown effective regarding gaseous emissions. This work aims to explore different water-wash designs and experimental conditions to observe the influence of such parameters on the aerosol mitigation capacity. For this purpose, liquid-vapour equilibria (VLE) for dilute aqueous solutions of water and monoethanolamine (MEA), loaded with CO2, were measured. An existing thermodynamic model was then validated with these data for low amine concentrations (30, 6, 3 and 0.6wt%) with CO2 loading between 0.1 and 0.4 mol CO2/mol MEA. Several simulations were carried out for coal- and natural gas-based exhaust using a model reproducing the behaviour of aerosols along the absorber and the water-wash section. Different packing heights in absorber and water-wash sections, and the presence or absence of one or more intercooling stages were studied. Although these operational changes showed significant effects on the outlet aerosol and gaseous emissions, none was able to reduce the emissions to acceptable limits.