Experimental and Theoretical Study of CO2 Absorption with Piperazine-Promoted Potassium Carbonate Solution in Hollow Fiber Membrane Contactors

Potassium carbonate is an economical absorbent for CO2, separation from flue gases. In this study, potassium carbonate as absorbent and piperazine as promoter were applied to absorb CO2, from a gas mixture using a hollow fiber membrane contactor in experimental scale. Also, a mathematical model has been presented to find the CO2, concentration profile in different phases and to analyze the process. Effects of concentration of potassium carbonate and piperazine and other parameters such as liquid and gas flow rates were experimentally observed and studied. Effects of membrane wetting on absorption recovery and piperazine concentration on effective length of the module have been analyzed using the mathematical model. Experimental results show that CO2, recovery can rise up to 1.6 times and CO2, recovery can reach to 90% by adding 0.03 M piperazine to 5 wt % aqueous solution of potassium carbonate. The results of the mathematical model at high gas flow rates reveal that CO2, recoveries are considerably higher (up to 8 times) for promoted potassium carbonate solution compared to aqueous potassium carbonate in membrane contactors. Also, a high reaction rate of piperazine can prevent sharp reduction of recovery at low wetting fractions.