Carbon Dioxide Absorption with an Aqueous Biphasic Absorbent in a Rotating Zigzag Bed

This study explored an intensive carbon dioxide (CO2) absorption process with aqueous biphasic absorbents containing diethylethanolamine (DEEA) and diethylenetriamine (DETA) in a rotating zigzag bed (RZB). The effects of the absorbent composition on the phase separation behavior and CO2 absorption performance were investigated. The dependence of the overall gas-phase volumetric mass transfer coefficient (KGa) and CO2 absorption efficiency on operating conditions with the DEEA + DETA solution was examined. Experimental results indicated that over 97% absorbed CO2 was focused on the bottom layer in the rich solution. The 4 mol/L DEEA + 1 mol/L DETA and 3.5 mol/L DEEA + 1.5 mol/L DETA solutions had much less volume of the bottom layer compared to absorbents with other compositions. Moreover, it was found that the lean solution flow rate, rotational speed of RZB, and temperature of lean solution had a positive influence on CO2 absorption. The KGa and CO2 absorption efficiency in the RZB with the 3.5 mol/L DEEA + 1.5 mol/L DETA solution reached 4.82 kmol/kPa m3 h and 98.7%, respectively, demonstrating an obvious advantage in CO2 absorption performance compared to the 5 mol/L monoethanolamine solution. An artificial neural network (ANN) model was established to predict KGa and CO2 absorption efficiency. The predicted data and experimental results were in good agreement with the deviations generally less than 10% for KGa and CO2 absorption efficiency. A comparison with a wetted-wall column revealed that the RZB could achieve higher mass transfer efficiency. In addition, the mechanism of phase separation in the DEEA + DETA solution was analyzed. This study demonstrates that the DEEA + DETA solution could be a viable absorbent for CO2 capture in RZB.