Mechanical and chemical activation of CaO-based sorbents for post-combustion CO2 capture at high temperature
Type of DegreePhD Dissertation
MetadataShow full item record
The Calcium Looping (CaL) process is one of the most efficient technology for post-combustion CO2 capture. The raw material for CO2 adsorption is CaO which can be derived from limestone. The abundance and high capacity of this sorbent make the process highly favorable. Despite the advantages of CaO, regenerability remains a significant challenge. In the CaL process, CaO losses its surface area and pore structure due to the high temperature at the regeneration process. Therefore, the development of CaO-based sorbents is necessary to improve the overall efficacy of the technology. In this work, mechanical and chemical activation of CaO-based sorbents were investigated. Through the mechanical activation, ball-milling was used to synthesize high surface and porous material to increase the conversion of the sorbent in the carbonation reaction stage. Carbonation, regeneration, and cycle stability of mechanically activated Ca(OH)2 were investigated using in situ XRD technique. The results showed the overall efficacy of the process increased by 24%. Although mechanical activation of the sorbent increased the conversion initially, the cycle stability remained challenging. Chemical activation method was applied to the sorbent. Three different transient metals (Cu, Co, Fe) were selected to synthesize calcium metal oxides. The performance of these sorbents was investigated and we found that Ca2CuO3 has a decent potential to be a suitable sorbent for post-combustion CO2 capture. The sorbent showed a high regeneration kinetic even at lower temperatures compared to CaO. A decomposing process was developed for Ca2CuO3 to improve the performance of the sorbent for CO2 capture. Using hydrogen, Ca2CuO3 decomposed to CaO and Cu. The former was the active material to adsorb CO2, while the latter provided a facile heat transfer to mitigate sintering. A high stability performance was observed for the fully decomposed Ca2CuO3. Finally, the direction for future works was proposed.