Adsorption properties and performance of CPO-27-Ni/alginate spheres during multicycle pressure-vacuum-swing adsorption(PVSA)CO₂ capture in the presence of moisture

CPO-27-Ni/alginate spheres have been prepared and evaluated for post-combustion CO₂ capture using both dry and moist synthetic flue-gas in a multicycle pressure-vacuum swing adsorption (PVSA) cycle. Single component equilibrium isotherms of the adsorbent spheres give estimated CO₂/N2 and H₂O/CO₂ selectivities of 24 and 7 at 323 K for the actual gas composition (around 9 kPa H₂O, 28 kPa CO₂, rest N2, ptot=200 kPa). The PVSA cycle used consists of four steps; an adsorption step, a counter-current blowdown step, a counter-current purge step and, finally, a counter-current pressurization step. The results from single column testing show that the presence of moist in the flue gas reduces the CO₂ working capacity somewhat (around 15%), however, even when beginning the cyclic PVSA run with an adsorbent completely saturated with water, an apparent steady state performance is reached in which the CO₂ working capacity still is significant and stable over more than 100 cycles. The results are interpreted as a consequence of the counter-current blowdown and purge steps carried out in dry nitrogen.