Principles and key technologies for the large-scale ecological utilization of coal gangue

Coal is the main energy in our country and the ballast stone of energy security. As an inevitable product in the process of coal mining and coal washing, coal gangue has an annual output of more than 700 million tons, which is in urgent need of large-scale and ecological utilization to solve the problem of coal gangue as a stumbling block in enterprise development. Based on the analysis of the mechanism of ecological damage in large-scale utilization of coal gangue, the principle of large-scale ecological utilization of coal gangue was put forward, and the concrete solution of large-scale ecological utilization of environmental safety is discussed from the technical perspective. Two key technologies of large-scale ecological utilization was put forward, namely in-situ contamination control and ecological restoration of acid coal gangue mountain, and ground filling of coal gangue. The results demonstrated that: ① The key to large-scale ecological utilization of coal gangue is prevention and control of environmental contamination. Large-scale ecological utilization of coal gangue can be realized through the evaluation of the availability and economy of gangue that combined with environmental risk management. ② Realized the ecological utilization of accumulated gangue mountain by vegetation restoration based on in-situ contamination control, and developed an ecological utilization technology integrated with pollution source diagnosis, fire prevention, pollution barrier, and vegetation restoration. Based on the mechanism analysis of pollution caused by acid and heat production of gangue oxidation, thermal infrared coupled with surveying and mapping technology was uesd to locate the deep burning point (oxidation point) in gangue mountain; an oxidation inhibitor coupled with fungicide and reducing bacteria was invented, which covered with an inert materia and rolled to prevent oxygen and pollution; the fire-fighting technology combining shotcrete fire control and grouting is adopted in the spontaneous combustion area; and a fire-proof vegetation restoration technology based on local and grass irrigation was put forward, which realized in-situ contamination control and ecological restoration of acid coal gangue mountain.③ The ecological utilization of ground filling of coal gangue can be realized through the feasibility analysis of ecological utilization of ground filling, the technology of ecological utilization and the long-term monitoring of maintenance management. The key of ecological utilization is the contamination risk analysis of gangue material screening, the necessity and feasibility analysis of ground filling site selection, and environmental protection measures during the whole filling process, including safety and environmental protection measures such as anti-seepage barrier at the bottom of the site before filling, layered filling technology and soil profile reconstruction technology for fire prevention and acid control in filling, erosion control and vegetation restoration after filling. Large-scale ecological utilization of coal gangue not only solves the ecological environment problems caused by solid waste storage in mining areas, but also creates a new mode of ecological restoration in mining areas through scientific, safe, and reasonable utilization of new and dated gangue.