Solvent emissions control in large scale chemical absorption CO₂ capture plant

Solvent emissions is a serious problem in the industrialization of the amine scrubbing process. To design pollutant control equipment for a 2 million tons/year CO₂ capture plant, a bench and a pilot facility were tested to investigate the aerosol emissions. And three Aspen models were built to study vapor emission and design emissions control measurement. The emissions assessment showed the treated flue gas after the absorber was about to discharge 1078 mg/Nm³ aerosol-type solvent and 1055 mg/Nm³ vapor-type solvent. The experimental results of particle size distribution indicated that improving the growth of the submicron droplets before the water wash and demister was the key to control aerosol emissions. Three control methods were compared by simulation, the best control measure was the combination of dry bed and water wash section, and the drain-out water is feed to the top of the dry bed. Considering the economy and control efficiency, the packing height of the water wash section is 2.5 m, and the scrubbing flow rate is 5000 Nm³/h. The extra cooling for the dry bed is not necessary and uneconomic. Under this countermeasure, the vapor emissions solvent is as low as 1.27 mg/Nm³ without additional freshwater for the water wash section.