Carbon Dioxide Capture Using Calcium Hydroxide Aqueous Solution as the Absorbent

Although Ca(OH)2 aqueous solution can be effectively used as an absorbent to capture CO2, its performance with highly concentrated CO2 gas mixtures has rarely been reported. Therefore, the present paper investigates the CO2-capture performance of Ca(OH)2 aqueous solution for an about 30% CO2 gas mixture. The Ca(OH)2 concentration in the solution strongly influenced the capture performance of the absorbent. The simultaneous Ca(OH)2 dissolution and CaCO3 production in the absorbent may have substantially hindered the combination of Ca2+ with CO3 2– in suspension. Therefore, a higher Ca(OH)2 concentration in suspension further reduced the CO2 absorption capacity and produced substantially agglomerated CaCO3 with low crystallinity. In contrast, the Ca(OH)2-saturated aqueous solution had the highest absorption rate and capture ratio among the six investigated absorbents. Its calculated absorption capacity of 3.05 g of CO2 [g of Ca(OH)2]−1 L–1 was 3-fold more than that of 1% Ca(OH)2 suspension solution, which confirmed Ca(OH)2-saturated aqueous solution as the most efficient absorbent for CO2 in a Ca(OH)2 aqueous solution system.