K₂CO₃/Al₂O₃ for Capturing CO₂ in Flue Gas from Power Plants. Part 2: Regeneration Behaviors of K₂CO₃/Al₂O₃

The present paper is the second part of a series of papers about a systematical investigation on the application of the K2CO3/Al2O3 sorbent for capturing CO2 in flue gas. It was focused on the regeneration behaviors of K2CO3/Al2O3 in a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. The effects of operation conditions, including the regeneration temperature, gas composition, and heating rate, on the regeneration process of K2CO3/Al2O3 were thoroughly studied. The regeneration process of K2CO3/Al2O3 consists of three steps, as the temperature increases: KHCO3 is decomposed first when the temperature is lower than 180 °C; then, an intermediate product for the carbonation of K2CO3/Al2O3 is decomposed; and finally, KAl(CO3)2(OH)2 is decomposed when the temperature is higher than 250 °C. The regeneration conversion of K2CO3/Al2O3 reaches 100% in 15 min when the final temperature reaches 300 °C in N2. The effect of the gas composition of CO2 and CO2/H2O on the regeneration process is not significant. The regeneration conversion decreases from 100 to 92.8% and the reaction time decreases from 72 to 6.5 min when the heating rate increases from 5 to 80 °C/min.