Cyclic CO_2 capture behavior of KMnO_4-doped CaO-based sorbent

摘要

This study examines the CO_2 capture behavior of KMnO_4-doped CaO-based sorbent during the multiple calcination/carbonation cycles. The cyclic carbonation behavior of CaCO_3 doped with KMnO_4 and the untreated CaCO_3 was investigated. The addition of KMnO_4 improves the cyclic carbonation rate of the sorbent above carbonation time of 257 s at each carbonation cycle. When the mass ratio of KMnO_4/CaCO_3 is about 0.5-0.8 wt.%, the sorbent can achieve an optimum carbonation conversion during the long-term cycles. The carbonation temperature of 660-710 ℃ is beneficial to cyclic carbonation of KMnO_4-doped CaCO_3. The addition of KMnO_4 improves the long-term performance of CaCO_3, resulting in directly measured conversion as high as 0.35 after 100 cycles, while the untreated CaCO_3 retains conversion less than 0.16 at the same reaction conditions. The addition of KMnO_4 decreases the surface area and pore volume of CaCO_3 after 1 cycle, but it maintains the surface area and pores between 26 nm and 175 nm of the sorbent during the multiple cycles. Calculation reveals that the addition of KMnO_4 improves the CO_2 capture efficiency significantly using a CaCO_3 calcination/carbonation cycle and decreases the amount of the fresh sorbent.