Research status and thoughts on preventing spontaneous combustion of coal in goaf using mineralization CO2 products of coal-based solid waste

QIN Botao; SHI Quanlin; JIANG Zhe; MA Zujie

doi:10.13247/j.cnki.jcumt.20250319

Abstract：Coal is a crucial energy and industrial raw material in China.During coal mining and coal-fired power generation processes,a large number of coal-based solid waste such as fly ash and coal gangue will be produced,which will seriously pollute the ecological environment for a long time.The absorption and sequestration of CO2 using substances containing alkaline com-ponents is regarded as one of the most promising carbon reduction technologies.Fly ash and gangue widely used in goaf grouting for fire prevention and extinguishing contain alkaline com-ponents such as CaO and MgO,thereby exhibiting the potential for CO2 mineral carbonation sequestration.Through the absorption and mineralization of CO2 by fly ash and coal gangue slurries,followed by the injection of mineralized products into goafs to prevent and control coal spontaneous combustion,a synergistic effect between mineral carbonation and disaster preven-tion/control can be achieved.An integrated technology for carbon sequestration via coal-based solid waste mineralization and goaf sealing for fire prevention and control is presented in this paper.The research progress of coal-based solid waste and CO2 mineralization technologies is systematically reviewed;the variation laws of the physicochemical properties and structures of coal-based solid waste after CO2 mineralization reaction are analyzed;and the inhibitory char-acteristics of mineralized products on the heating rate and heat release during coal spontaneous combustion are clarified.To further promote the development and large-scale application of the integrated technology of coal-based solid waste mineralizing CO2 and coal spontaneous combus-tion disaster prevention and control,three key challenges are identified:low reaction efficiency during the mineralization process of solid waste slurry,lack of integrated technology of CO2 mineralization-grouting for fire prevention,and insufficient understanding of the safety and en-vironmental implications of mineralized products stored in goafs.Correspondingly,the re-search directions and contents of mineralization reaction process enhancement,efficient fire prevention and extinguishing utilization of mineralized products,and long-term safe storage in goaf are proposed.There is an urgent need to study the occurrence forms and leaching patterns of calcium/magnesium elements in coal-based solid wastes,develop new technologies for effi-ciently leaching calcium and magnesium ions from slurry and rapidly dissolving CO2,innovate integrated technical equipment and intelligent control system for mineralization CO2-grouting fire prevention,elucidate the physicochemical inhibition mechanism of mineralized products on coal spontaneous combustion,and clarify the carbon sequestration stability of mineralized products as well as environmental friendliness in goaf.This integrated technology will promote the development of the entire chain of basic research-equipment research and development-engineering application,and further provide support for the low-carbon resource utilization of coal-based solid waste and the national"double carbon"goal.