(A) study on a continuous $co_2$ capture process using an aqueous ammonia solution

Abstract

A continuous $CO_2$ capture process using an aqueous $NH_3$ solution was investigated in this study. The experiments of continuous $CO_2$ absorption-desorption were performed using a lab-scale experimental apparatus. In order to find out the optimal operating conditions of continuous $CO_2$ capture process using an aqueous $NH_3$ solution, $CO_2$ removal efficiencies were measured under various operating conditions. The removal efficiencies were proportionally increased as the increase of $NH_3$ concentration but kept steady value above 12 wt\%. The removal efficiencies were also increased as the flow rates of gas and absorbent increase but the effects of these parameters on removal efficiencies were weaker than that of $NH_3$ concentration. As the regeneration temperature increased, the removal efficiencies increased rapidly and kept steady value at above specific temperature which defined as an optimal regeneration temperature. The optimal regeneration temperature were $87^\circ C$ for 15 wt\%, $90^\circ C$ for 12 wt\%, $93^\circ C$ for 9 wt\%, $95^\circ C$ for 6 wt\% and $97^\circ C$ for 3 wt\%. As the regeneration temperature increase, $CO_2$ loadings of both absorbents were changed from rapid decrease to steady value and the increased differences of lean and rich $CO_2$ loadings explained increased $CO_2$ removal efficiencies. Through the continuous $CO_2$ capture experiments, it could found out that the optimal operating conditions were 12 wt\% of $NH_3$ concentration, $90^\circ C$ of regeneration temperature with $CO_2$ loadings kept below 0.4.

A method based on mole fractions of vapor components at equilibrium was developed for continuous $CO_2$ capture process. It could be understood that the regeneration of $CO_2$ rich absorbent prefers the condition that the mole fraction of $NH_3$ in vapor phase at equilibrium is larger than that of $CO_2$. The mole fractions of $CO_2$ and $NH_3$ in vapor phase at actual regeneration are opposite to those at equil...