Experimental Evaluation of Aerosols Formation and Control during CO2 Absorption into Monoethanolamine Solution

Solvent loss from air emissions in form of vapor and aerosols is one of the main challenges for aqueous amine-based CO₂ absorption processes due to its negative impacts on the environment and human health as well as the operating cost. The main objective of this research is to evaluate the emissions of solvent from the absorber and the effectiveness of a water wash section to reduce these emissions. In this research, laboratory experiments were conducted to study solvent emissions, in form vapor and aerosols, from a CO₂ absorption column using 5 M MEA solution and through a water wash section. The vapor concentrations were measured using a membrane filtration device and FTIR instrument. While the particle size distribution and the concentrations of aerosols were obtained using two particle size spectrometers. In general, the aerosols formation was found to be controlled by solvent properties temperature gradient and the quality of the inlet gas specially the concentration and types of the entrapped particles. Results of our baseline experiments revealed that in the absence of CO₂ absorption, a majority of solvent emissions were in vapor form. Solvent emissions generally increased with decreasing feed CO₂ loading. The removal of MEA vapor by the water wash section was not significant (~10%), while up to 70% of the aerosol emissions were removed by the water wash. The size of aerosols increased from 52 nm in the feed gas to up to 257 nm in the effluent gas from the absorber due to particle growth and aggregation. By contrast, in the water wash section, the size of aerosols generally decreased because of the removal of larger particles.