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CO2 absorption and regeneration of alkali metal-based solid sorbents
Authors:Soo Chool Lee  Bo Yun Choi  Tae Jin Lee  Chong Kul Ryu  Young Soo Ahn  Jae Chang Kim  
Affiliation:

aDepartment of Chemical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea

bDepartment of Chemical Engineering, Yeungnam University, Kyongsan 712-749, Republic of Korea

cKorea Electric Power Research Institute, Daejon 305-380, Republic of Korea

dKorea Institute of Energy Research, Daejeon 305-343, Republic of Korea

Abstract:Potassium-based sorbents were prepared by impregnation with potassium carbonate on supports such as activated carbon (AC), TiO2, Al2O3, MgO, SiO2 and various zeolites. The CO2 capture capacity and regeneration property were measured in the presence of H2O in a fixed-bed reactor, during multiple cycles at various temperature conditions (CO2 capture at 60 °C and regeneration at 130–400 °C). Sorbents such as K2CO3/AC, K2CO3/TiO2, K2CO3/MgO, and K2CO3/Al2O3, which showed excellent CO2 capture capacity, could be completely regenerated above 130, 130, 350, and 400 °C, respectively. The decrease in the CO2 capture capacity of K2CO3/Al2O3 and K2CO3/MgO, after regeneration at temperatures of less than 200 °C, could be explained through the formation of KAl(CO3)2(OH)2, K2Mg(CO3)2, and K2Mg(CO3)2·4(H2O), which did not completely converted to the original K2CO3 phase. In the case of K2CO3/AC and K2CO3/TiO2, a KHCO3 crystal structure was formed during CO2 absorption, unlike K2CO3/Al2O3 and K2CO3/MgO. This phase could be easily converted into the original phase during regeneration, even at a low temperature (130 °C). Therefore, the formation of the KHCO3 crystal structure after CO2 absorption is an important factor for regeneration, even at the low temperature. The nature of support plays an important role for CO2 absorption and regeneration capacities. In particular, the K2CO3/TiO2 sorbent showed excellent characteristics in CO2 absorption and regeneration in that it satisfies the requirements of a large amount of CO2 absorption (mg CO2/g sorbent) and fast and complete regeneration at a low temperature condition (1 atm, 150 °C).
Keywords:Carbon dioxide  Absorption  Potassium carbonate  Potassium hydrogen carbonate  Regeneration
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