(120c) CO2 Seperation from Combution Flue Gas Using Carbide Slag As CO2 Carrier

The carbonate looping process is a promising technology for CO₂ capture that uses the reversible reaction between CaO and CO₂ to produce a pure stream of CO₂ from combustion flue gas. The decay of sorbents reactivity over multiple cycles is an obstacle for realizing the carbonate looping process. In this work, the reactivity and stability of carbide slag for CO₂ capture have been examined. Comparisons with natural calcium-based sorbents, pure CaCO₃ and Ca(OH)₂ were carried out. The results show that carbide slag exhibits the highest stable reactivity among the examined natural calcium-based sorbents including limestone, shell and dolomite. The cyclic testing at severe calcination temperatures further confirms the superiority of carbide slag. XRD analysis shows that there is mayenite (Ca₁₂Al₁₄O₃₃) formed in the calcination step for carbide slag, which is the main reason for its high stability in the carbonate looping process. Experimental results show that even higher stability can be achieved if the content of Ca₁₂Al₁₄O₃₃ is increased in the calcined carbide slag. With consideration of CO₂ sorption capacity and stability, the optimum ratio of Ca₁₂Al₁₄O₃₃ to CaO is proposed.