Numerical Model to Analyze the Physicochemical Mechanisms Involved in CO₂ Absorption by an Aqueous Ammonia Droplet

CO₂ is the main anthropogenic greenhouse gas and its reduction plays a decisive role in reducing global climate change. As a CO₂ elimination method, the present work is based on chemical absorption using aqueous ammonia as solvent. A CFD (computational fluid dynamics) model was developed to study CO₂ capture in a single droplet. The objective was to identify the main mechanisms responsible for CO₂ absorption, such as diffusion, solubility, convection, chemical dissociation, and evaporation. The proposed CFD model takes into consideration the fluid motion inside and outside the droplet. It was found that diffusion prevails over convection, especially for small droplets. Chemical reactions increase the absorption by up to 472.7% in comparison with physical absorption alone, and evaporation reduces the absorption up to 41.9% for the parameters studied in the present work.