CO2 capture by piperazine mixed with non-aqueous solvent diethylene glycol in a rotating packed bed

Abstract

In this study, a non-aqueous absorbent, 40.8wt% piperazine (PZ)/59.2wt% diethylene glycol (DEG), was proposed to capture CO2 in a rotating packed bed (RPB). It was observed that the 40.8wt% PZ could dissolve into DEG without precipitation at 20°C and regeneration energy could be reduced because the heat capacity of DEG is lower than that of water. Although the viscosity of 40.8wt% PZ/59.2wt% DEG was 7 times as much as that of 40.8wt% PZ/59.2wt% H2O, the difference in CO2 capture efficiency between these two absorbents in RPB was only 7.95% under the operation condition to satisfy 90% CO2 capture efficiency. At the rotating speed of 1600rpm, the heights of transfer unit of the proposed non-aqueous absorbent were all less than 6cm, indicating the potential of volume reduction of RPB with respect to the conventional packed column even for high viscosity absorbent. The results obtained from 23 factorial design showed that the most significant operational variable of CO2 capture efficiency for 40.8wt% PZ/59.2wt% DEG in RPB was gas flow rate, followed by liquid flow rate and temperature. Finally, the most appropriate operation conditions to achieve CO2 capture efficiency exceeding 90% were found out by path of the steepest ascent.