Comparison of CO2 adsorption/desorption behaviors of a solid amine sorbent in fixed and fluidized beds

Abstract

The CO 2 adsorption and desorption behaviors, including the CO 2 adsorption capacity, CO 2 adsorption/desorption kinetics and bed pressure drops under post-combustion CO 2 capture conditions in both fluidized and fixed beds, were investigated for the first time using a solid amine sorbent in a temperature swing adsorption (TSA) experimental rig. The results show that the saturated CO2 adsorption capacities are basically the same in fluidized and fixed beds. However, the sorbent exhibits faster adsorption and desorption kinetics in a fluidized bed, as reflected by the fitted parameters of the Avrami kinetic model and the change of bed temperature during adsorption and desorption tests. Moreover, CO 2 is not a suitable fluidizing gas in a desorber as high CO 2 partial pressure inhibits the desorption process. The bed pressure drops in fluidized beds are much lower than that in fixed beds of same sorbent mass, especially at high superficial gas velocities and high sorbent loadings. By further discussion, a fluidized bed can also achieve lower equipment investment and less sorbent loading compared to multiple fixed beds in parallel. This study demonstrates the advantages of fluidized beds over fixed beds in large-scale TSA units in view of higher reactor efficiency, lower energy consumption and equipment investment.