Promoter Characteristic Study on the K₂CO₃ Absorbents for CO₂ Capture: Mass Transfer According to Functional Group and Chain Length of Promoter

The studies on the characteristics of absorbents are important to develop process and evaluate performance. Among the absorbent studies, the overall mass transfer coefficient was used as a key data for design packing type and absorber height to achieve cost effective process. In this study, the overall mass transfer rates of the K₂CO₃ based absorbents were measured by a wetted-wall column (WWC) apparatus. Experimental conditions of temperature and pressure were maintained at 313.15 K ∼ 333.15 K and 1.15 bar, respectively. The injected CO₂ concentrations were 3 vol.% ∼ 12 vol.% (N₂ balanced). As a result of experiment, the mass transfer rates increased following the order: MEA > K₂CO₃+CL-4 > K₂CO₃+CL-2 > K₂CO₃+CL-3 > K₂CO₃+CL-1 > K₂CO₃+FG-1 > K₂CO₃+FG-2 > K₂CO₃+FG-3 at 333.15 K. In case of promoters containing hydroxyl functional groups, the equilibrium partial pressure of CO₂ increased and the slope of the flux decreased. The effect was greater than those of promoters containing increased chain length. The mass transport rate of K₂CO₃+CL-4 solution was similar to that of the commercial MEA solution.