Effect of operating parameters of potassium carbonate supported on gamma alumina (K2CO3/γ-Al2O3) on CO2 capture capacity using depressurized regeneration

Potassium carbonate (K2CO3) loaded at 17% by weight (wt.%) on a gamma alumina (gamma-Al2O3) support was prepared by impregnation and then employed to adsorb carbon dioxide (CO2) under a turbulent fluidized bed regime in a glass riser-sorber. The spent K2CO3/gamma-Al2O3 sorbent was regenerated in situ by depressurization at 0.8 or 2 atm for 2 or 20 min. The CO2 sorption occurred by both chemical sorption and physical adsorption and the total sorption capacity was not significantly dependent on the sorbent regeneration time (2 or 20 min) or regeneration cycles (1-3), but was strongly dependent upon the regeneration pressure, being better at 0.2 than at 0.8 atm. There was no detectable formation of inactive species. such as KAI(CO3)(OH)(2) H2O), on the regenerated sorbent and the meso-pore type IV surface area was not affected by the number of regeneration cycles. Rather the relocation of water on the sorbent surface in the hydrothermal treatment after sorbent regeneration is hypothesized to have played an important role in the CO2 capture capacity. This was because the accumulation of water near the pore entrance rather than deep inside the pore reduced the average pore diameter and increased the average pore volume when regenerated at 0.8 atm, but not at 0.2 atm. The regenerated sorbent (at 0.2 atm for 2 min) had a CO2 capture capacity of about 95% of that of the fresh adsorbent. As the result of the short regeneration time, the depressurization regeneration unit can be much more compact than the conventional heat regeneration unit. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.