Integrated calcium looping technologies for enhanced CO₂ valorisation—A critical review

The calcium looping (CaL) process stands out as a promising technology for carbon dioxide (CO₂) capture, which exhibits two essential phases: carbonation and calcination. CaL process has several advantages over conventional systems such as availability of abundant and low cost CaO sorbents, reduced environmental impact, lower greenhouse emissions and energy requirements. CaL offers easy and innovative schemes to integrate renewable energy such as concentrated solar power, oxy-fuel and chemical looping process and steam dilution to further enhance the overall efficiency of the system. The review first focuses on summarizing the characteristics and operational parameters of these process integrated CaL facilities while highlighting key experimental findings. The examination of innovative sorbent materials utilized within integrated CaL processes has been addressed, emphasizing pathways directed towards enhancing reaction efficacy, energy conservation, and holistic sustainability attained via process integration and intensification. Meanwhile, strategies to overcome the limitation of CaL process in terms of rapid sintering of sorbent particles over time have also been discussed. Further, the approaches for integrating CaL into industrial plants such as power, cement and steel plants have been identified and compared to realize significant reduction of energy penalty compared to conventional system. The impact of multivariate latent variable (LV) modeling on the integrated CaL process has been examined. Based on the review, CaL showed equivalent or better performance in reducing CO₂ emissions (global warming potential or climate change impact indicator) in comparison to alternative scenarios.