Research progress of CO₂ storage technology by mineralization of coal-based solid waste

The goal of “carbon peak and carbon neutrality” is China’s responsibility as a major country to maintain global ecological security, and it is also an important way to achieve high-quality development and ecological civilization construction. CO₂ emission reduction is imperative.As a result of the energy resource endowment pattern of “rich in coal, poor in oil and less gas”, the main energy in China is still coal with high carbon emission intensity. Coal is an important energy and raw material for high energy-consuming industries such as electric power, iron and steel and coal chemical industry. it plays an important role in the process of achieving the goal of “double carbon”. The coal industry achieves carbon peak through low-carbon transformation, which is the inherent requirement of the high-quality development of coal industry. It is also an important starting point for the implementation of the national “double carbon” strategic goal. Compared with the traditional natural mineralization raw materials, coal-based solid waste mineralization and storage CO₂ has the advantages of rich raw materials, friendly products, low energy consumption and rapid reaction. At the same time, it can produce high value-added products for chemical industry, construction and other fields. The characteristics of main coal-based solid waste coal gangue, fly ash, desulphurization gypsum, gasification slag and furnace bottom slag in China are introduced, the main CO₂ emission sources and production in China are analyzed, and the in-situ and ex-situ CO₂ mineralization technologies according to different mineralization and storage locations and direct and indirect carbonation technologies according to mineralization mechanism are reviewed. The research progress of CO₂ mineralization and storage technology using coal-based solid waste as raw material is reviewed, and it is found that this technology has harsh reaction conditions, high cost, small treatment scale, and the research is still in the laboratory stage. This paper briefly describes the mineralization and storage technology of CO₂ with coal-based solid waste as carrier and goaf as storage source, which mainly includes two technologies: construction of functional filling body and preparation of negative carbon filling material. The existing problems and future research direction of coal-based solid waste mineralization and storage of CO₂ are analyzed. For the CO₂ mineralization technology with coal-based solid waste as raw material, the technological process should be optimized, the reaction cost should be reduced, and the research on industrialization promotion should be further strengthened. aiming at the CO₂ mineralization and storage technology with coal-based solid waste as carrier and goaf as storage source, the research on deep mineralization mechanism, storage risk assessment and long-term stability should be strengthened in the future, so as to improve the storage scale and long-term stability of CO₂. On this basis, the slurry filling material is prepared from coal-based solid waste, with water as carrier, pump as power and pipeline as channel, the filling material and CO₂ are transported to the goaf for mineralization reaction, and combined with microbial induced calcium carbonate precipitation (MICP) technology, the mining fissures in rock mass are closed to realize CO₂ mineralization and storage.