Mineralization of CO2 from power plant flue gas by fly ash: Technology and key scientific issues

Coal-fired power generation is an important guarantee for the energy security in China, but a large amount of CO2 is emitted from flue gas. At the same time, a large amount of fly ash is also generated. The CO2 mineralization by fly ash and its product utilization are able to achieve the goals of solid waste treatment and long-term CO2 storage. At present, there are still some shortcomings in the CO2 mineralization technology by fly ash, such as low mineralization efficiency, long reaction time, and small processing capacity. The corresponding key scientific issues and technical bottlenecks need to be addressed urgently. In this paper, the basic principle of CO2 mineralization by fly ash is briefly introduced. The influencing mechanisms of different reaction conditions on alkali metal ion leaching and CO2 mineralization are analyzed. The advantages and disadvantages of three processes, namely the CO2 direct mineralization reaction process, the alkali metal pre-leaching process, and the CO2 pre-absorption process, are compared. The key technology of CO2 mineralization by fly ash is proposed, including the efficient alkali metal ion leaching, the enhanced CO2 mineralization reaction process, the intelligent equipment for fly ash mineralization CO2, and the comprehensive evaluation of mineralization effect. The physical and chemical properties of its mineralization products are clarified. And the utilization of its mineralization products is explored. Finally, three key scientific issues are summarized, including the rapid leaching of alkali metal ions from fly ash and the efficient mineralization of CO2, the multiphase mixing and reaction laws in large CO2 mineralization reactors, and the control mechanism of the mineralization product properties. The research direction of the entire chain including basic research, key technology and equipment development, and engineering application is proposed, providing a reference for the efficient mineralization of flue gas CO2 by fly ash and the utilization of its products, which is of great significance for achieving the carbon neutrality goal and utilization of solid waste. © 2024 China Coal Society. All rights reserved.