Carbon dioxide absorption with aqueous amine solutions promoted by piperazine and 1-methylpiperazine in a rotating zigzag bed

Abstract

In order to overcome the drawback of short liquid resistance time in rotating packed bed (RPB), a multi-stage rotating zigzag bed (RZB) was employed to enhance carbon dioxide (CO2) absorption process with blended aqueous amine solutions containing diethylenetriamine (DETA) + piperazine (PZ) or DETA + 1-methylpiperazine (1-MPZ) as absorbents. The effects of different operating parameters on the CO2 absorption efficiency, overall gas-phase volumetric mass transfer coefficient (KGa) and height of mass transfer unit in the RZB were investigated. Experimental results indicated that increase of the promoter concentration, lean solution flow rate and rotational speed were conducive to gas–liquid mass transfer and CO2 absorption. It was found that both PZ and 1-MPZ were effective promoters, while PZ exhibited better performance. Meanwhile, comparison of CO2 absorption performance between one stage and two stages revealed that two stages had higher CO2 absorption efficiency due to extended residence time of absorbents and CO2 in the RZB. A comparison with RPB demonstrated that the RZB could achieve higher mass transfer and CO2 absorption efficiencies with smaller rotor volume and less absorbent consumption. The maximum CO2 absorption efficiency and KGa reached 99.3% at a gas flow rate of 1.5 m3/h and 7.43 kmol/kPa m3 h at an inlet gas CO2 concentration of 2% respectively in the RZB with DETA + PZ system, suggesting that RZB may be an effective device for CO2 absorption.