Kinetic study on CO2 adsorption behaviors of amine-modified co-firing fly ash

Coal and biomass fly ash was impregnated with tetraethylenepentamine (TEPA) to prepare solid CO 2 sorbent. Experimental CO 2 adsorption capacities of the sorbent in fixed-bed column were fitted to several kinetic equations. The modified Avrami fractional kinetic model could accurately predict the CO 2 adsorption kinetic behaviors of the sorbent under different conditions. CO 2 adsorption rate increases with the increase in temperature, initial CO 2 concentration and gas flow rate, as a result of the decreased CO 2 diffusion resistance. A mathematical model was proposed and demonstrated to well predict the CO 2 adsorption breakthrough curves in the fixed-bed column. Effects of temperature, initial CO 2 concentration and gas flow rate on the mass transfer kinetic behaviors of the desired sorbent were investigated. The positive effect of these factors on promoting the overall mass transfer coefficient and the internal mass transfer coefficient is not significant. The external mass transfer coefficient will be remarkably reinforced with the increase in these operating parameters, due to the change in viscosity and density of the gas phase and the reduced external mass transfer resistance. Internal mass transfer process is determined as the rate-limiting step for CO 2 adsorption. The results will lay the groundwork for future scale-up application of the sorbent in post-combustion CO 2 capture.