Status and prospect of harmless disposal and resource comprehensive utilization of solid waste of coal gangue

A large amount of coal gangue generated during coal production and processing is piled up on the surface, which not only causes land occupation and soil erosion, but also causes geological disasters such as landslides and debris flows. So it has a serious impact on the ecological environment of the mining area. The cumulative stockpile of coal gangue in China has exceeded 6 billion tons, accounting for 13000 hectares of land. In 2020, the output of coal gangue in China is 729 million tons, the comprehensive utilization is 526 million tons, and the comprehensive utilization rate is 72.2%. At present, the comprehensive utilization of coal gangue in China has the characteristics of large stock and emission, highly concentrated output, low comprehensive utilization rate, extremely unbalanced regional development and small proportion of high value-added utilization. The scale and capacity of harmless disposal and resource-based comprehensive utilization of existing coal gangue obviously cannot meet the relevant national requirements for ecological environment protection and comprehensive utilization of coal under the goal of carbon peak and carbon neutral. In this regard, the large-scale harmless disposal technologies and methods of coal gangue in goaf filling, ground foundation building, subsidence pit backfilling and land reclamation are put forward. It is pointed out that the most effective methods of control the increment of coal gangue and reduce the stock of coal gangue on a large scale are the underground “mining, selection, filling and retention” integrated solid filling mining and goaf ground paste and slurry filling. The comprehensive resource utilization ways of coal gangue in power generation, building materials, resource recovery, chemical product preparation and agriculture is elaborated, and puts forward the closed cycle industrial chain model of “coal solid waste power generation-valuable element extraction-chemical products-building materials-underground filling-ground backfilling-agricultural application”. The future industrialization development direction of coal gangue with a large-scale disposal and comprehensive utilization system of “multi-channel, multi-component, multi-level+cascade recovery+ecological restoration+storage protection+underground efficient automatic filling” has been established.