Selection of Optimal Operating Conditions for a Continuous CO₂-Capture Process Using an Aqueous Ammonia Solution

Abstract

The optimal conditions of the absorbent concentration, rich CO2 loading, and regeneration temperature in a continuous CO2-capture process using a 3−27 wt % aqueous NH3 solution were experimentally studied and compared to vapor−liquid equilibrium of a CO2−NH3−H2O system. The dependence of CO2 removal efficiency upon the NH3 concentration and regeneration temperature was well-explained by the regeneration critical condition, which was defined using mole fractions of CO2, NH3, and H2O in the vapor phase at equilibrium. The optimal conditions were 12 wt % NH3 concentration, 0.36 rich CO2 loading, and a 90 °C regeneration temperature. Use of the vapor−liquid equilibrium data of the CO2−NH3−H2O system at regeneration conditions can be employed as a method to select the optimal operating conditions of a regeneration system and can provide guidelines for the design and operation of a CO2-capture process using aqueous NH3 solution.