Sorption Equilibria and Kinetics of CO2, N2, and H2O on KOH-Treated Activated Carbon

The equilibria and kinetics of CO2, N2, and H2O on KOH-treated activated carbon (KOH-AC) were evaluated. The isotherms for the pure components were correlated with the Langmuir, dual-site Langmuir, Sips, and Brunauer–Emmett–Teller models. The saturated adsorption amounts followed the order qH2O > qCO2 ≫ qN2. When simulated gas composition of postcombustion CO2 capture (15 vol % CO2, 4 vol % H2O, and balanced N2) was simulated by the ideal adsorption solution theory, the adsorbed amount of H2O was much higher than those of CO2 and N2. The adsorption amount of CO2 dropped when H2O was present. The CO2 uptake curves were well correlated with a nonisothermal kinetic model because the adsorption kinetics were controlled via heat generation and transfer. At the same temperature and pressure, the adsorption rates followed the order H2O > CO2 > N2. Understanding the adsorption behaviors of flue gas including H2O is important in designing adsorptive CO2 capture processes using KOH-AC.