Progress in reducing calcination reaction temperature of Calcium-Looping CO2 capture technology: A critical review

The calcium looping (CaL) process is a promising CO2 capture technology based on a reversible reaction, CaO(s) + CO2(g) ↔ CaCO3(s), and the forward and reverse directions of this reaction are often referred to as carbonation and calcination. Although CaO-based sorbent has the advantages of abundant reserves, low cost, and high theoretical capacity of CO2, it is limited by significant sintering of CaO grains over carbonation/calcination cycles, resulting in a rapid decline in CO2 capture performance. As an essential part of CaL technology, the CaCO3 calcination stage has a decisive influence on the sintering degree of CaO grains. In this work, a systematic understanding of fundamental aspects of the CaCO3 calcination is reviewed. The effects of calcination reaction conditions on the sintering of CaO grains and the resulting decline in CO2 capture performance during the cyclic operation were discussed. A number of efforts to reduce the calcination reaction temperature, thus slowing down CaO grains sintering, have been summarized, such as decreasing CaCO3 crystallinity, doping CaCO3 with alkali/alkaline earth salt, reducing CO2 absolute pressure, injecting steam, as well as in situ converting CO2. Finally, the future development trends for the above strategies to reduce the CaCO3 calcination temperature are also recommended. We hope this work can help and inspire researchers to make breakthroughs in this field.