Numerical modeling of CO2 capture in a spray tower with aqueous ammonia and full-cone atomizers

Abstract

Chemical absorption in a spray tower using aqueous ammonia is a promising method for CO₂ post-combustion capture, a key step in carbon capture and storage (CCS) approaches. However, this process is highly sensitive to atomization and subsequent droplet hydrodynamics. To investigate the impact of spray parameters on column performance, we conducted MATLAB calculations and CFD simulations focusing on droplet hydrodynamics, evaporation, and CO₂ absorption. Evaporation was calculated using an infinite conductivity model while absorption was solved using an empirical model. The effect of droplet diameter on droplet entrainment and wall deposition was revealed via the concept of droplet terminal settling velocity and droplet stopping distance. The capture efficiency for optimal parameters determined by MATLAB calculations was 67 %, which was further enhanced to 74 % by adjusting the spray angle or reducing the gas velocity. CFD simulations of the spray column underlined the necessity of two-way coupled simulations as the spray significantly affects the gas flow and causes, among other things, back-mixing behavior. Droplet stopping distances were longer than those in MATLAB calculations, with discrepancies increasing alongside the liquid-to-gas ratio. The evaporative effect was minimal, as the gas quickly became saturated.