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 CO2 sorbent. Experimental CO2 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 CO2 adsorption kinetic behaviors of the sorbent under different conditions. CO2 adsorption rate increases with the increase in temperature, initial CO2 concentration and gas flow rate, as a result of the decreased CO2 diffusion resistance. A mathematical model was proposed and demonstrated to well predict the CO2 adsorption breakthrough curves in the fixed-bed column. Effects of temperature, initial CO2 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 CO2 adsorption. The results will lay the groundwork for future scale-up application of the sorbent in post-combustion CO2 capture. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.