Highlighting the role of activated carbon particle size on CO2 capture from model flue gas

CO2 adsorption onto two particle size classes of the commercial activated carbon Filtrasorb 400, namely 600–900 μm (sample F600–900) and 900–1200 μm (sample F900–1200), was investigated at 293 K under model flue gas conditions in a fixed-bed column. Equilibrium adsorption capacity for a typical 15% CO2 postcombustion effluent was 0.7 mol kg–1 for both investigated adsorbents. In both cases, CO2 breakthrough curves showed a reduction of the characteristic breakpoint time and faster capture kinetics at higher pollutant concentration in the feed (in the range 1–15%). Dynamic adsorption data highlighted the important role played by wider micropores in determining a quicker adsorption process for finer particles. Mathematical modeling of the 15% CO2 breakthrough curve allowed identifying intraparticle diffusion as the limiting step of the adsorption process. Numerical analysis provided values of the intraparticle mass-transfer resistances equal to 1.7 and 3.3 s for F600–900 and F900–1200, respectively.