As described in the previous papers, K
2CO
3 supported on activated carbon sorbed CO
2 from moist feed gas at 353 K to form KHCO
3 and the entrapped CO
2 was then efficiently released by steam flushing at 423 K, followed by condensation of the excess steam through a heat exchanger to afford CO
2 in high purity. In the present study, various alkali carbonates supported on activated carbon were employed to recover CO
2 from moist gases at different temperatures. Carbon dioxide can be sorbed at higher temperatures in the order of the impregnated salt, Na
2CO
3 < K
2CO
3 < Rb
2CO
3 ~ Cs
2CO
3, indicating the applicability of CO
2 sorbents from moist flue gases at temperatures of 313–393 K by selecting the type of alkali carbonate for impregnation. By employing a bench-scale apparatus packed with the sorbent, materials (CO
2, water) balance and heat balance during CO
2 sorption/release steps were measured in order to elucidate the CO
2 recovery performance. The CO
2 uptake increased in the order of the impregnated salt, Cs
2CO
3 ~ K
2CO
3 < Na
2CO
3, while heat for the CO
2 release per unit mass of recovered CO
2 decreased in the order of Na
2CO
3 > K
2CO
3 > Cs
2CO
3, providing a more energy-conservative CO
2 recovery process for moist flue gases at 313–393 K than conventional amine absorption methods.
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