Progress in research of CO₂ fixation and sequestration by coal mine solid waste mineralization and co-disposal of pollution and carbon reduction

The goal of “double carbon”strategy has put forward new requirements for the transformation and upgrading of the coal industry and the development trend of green and low-carbon. The coal-based energy structure and high intensity coal mining cause solid waste in mining areas to occupy land space, destroy the ecological environment and emit greenhouse gases, which has become one of the prominent problems restricting the green and low-carbon development of the coal industry. Based on the concept of “waste utilization and carbon sequestration, where it comes from”, exploring a new solid waste disposal path of harmless, reduced, resource-based and low carbonization in mining areas, and innovating and developing key technologies that integrate solid waste disposal in mining areas, full utilization of underground space, and CO₂ capture, utilization and storage (CCUS), which are urgent demands of green and low carbon development in mining area under the goal of “double carbon”. The research shows that important progress has been made in the resource utilization path and disposal technology of solid waste such as coal gangue, fly ash, furnace bottom slag and coal gasification slag in the underground space filling mining and settlement control, coal mine fire prevention, building materials and agriculture, which provides the basis and insights for the research of solid waste fixed CO₂ storage in mining areas. However, it is urgent to strengthen the research on the engineering technology of solid waste CO₂ fixed storage in mining area. The solid waste in mining area has great potential and engineering feasibility for fixing and storing CO₂. At present, a new technical system of solid waste disposal and coal-based CCUS is being formed in mining area. Solid waste and CO₂-based gas-liquid-solid three-phase materials mineralization strengthening, high efficiency mineralization carbon fixation and product control, mineralization carbon fixation filling in underground space and CO₂ sealing, the evaluation of CO₂ potential and carbon removal in goaf, and the evaluation of CO₂ environment and safety in goaf will constitute the core connotation of solid waste disposal - coal-based CCUS-goaf filling technology system. Solid waste disposal in mining area-CCUS based coal-goaf filling technology is the key to realizing the waste free mine circular economy model of “coal production and processing-solid waste disposal in mining area-efficient mineralization carbon sequestration and CO₂ storage-underground space filling and utilization-ground subsidence prevention and ecological restoration in mining area” in the future. The research and development of filling and sealing functional materials under the solid waste CO₂ base in mining area is an important breakthrough. Moreover, the research and application of integrated technologies such as solid waste disposal in mining areas, coal-based CCUS, goaf filling, underground space utilization, and ecological restoration and protection in mining areas provide a new development idea for the construction of green and low-carbon mines.