: coal mining method
1. Waste rock discharge
Coal mines produce the largest amount of solid waste, which is also the largest industrial solid waste produced and accumulated in China, generally accounting for about 10% of coal production. The annual discharge of coal gangue in China is about1.5 ~ 200 million tons. By the end of 2002, the national coal gangue reserves were about 3.4 billion tons, covering an area of 26,000 hectares. It is the largest solid waste produced and accumulated in China's industrial solid waste. In 2004, the comprehensive utilization of coal gangue in China was 65.438+0.35 billion tons, with a utilization rate of 54%.
2. Mine water discharge
In the process of coal mine construction and production, various water sources enter the roadway and working face through different channels. In order to ensure mine safety and prevent water disasters, mine water must be discharged. According to incomplete statistics, in the process of coal mining, the mine water inflow in 2004 was about 3 billion M_, the average water inflow per ton of coal was about 2m_, and the resource utilization rate only accounted for about 22%.
3. Gas drainage and mine ventilation
Gas drainage before and during coal mining is an important measure to ensure coal mine safety. However, releasing the emitted gas into the atmosphere will have a strong greenhouse effect. The greenhouse effect of methane in gas is 20 times that of carbon dioxide. In addition, in the process of coal mine production, underground tunnels need hundreds of thousands or even millions of cubic meters of air per second. Mainly through mine ventilation. Mine ventilation also contains gas and a lot of dust. According to the relevant evaluation and estimation in recent years, the coalbed methane resource in China is 3× 106. In 2002, the output of coalbed methane in national key coal mines was 9773.37, of which the gas consumption was 5 17.49, and the utilization rate was about 5%.
4. Ecological damage caused by mining
Traditional coal mining ignores the mining, processing and utilization of other symbiotic minerals and associated minerals, resulting in a waste of resources. The coal measures in China are related to more than 20 kinds of minerals, most of which have not yet been utilized. In addition, the random storage and discarding of minerals will also cause environmental pollution and destroy the ecological environment. Coal ash mining destroyed the original mechanical balance of the crust. Cause surface subsidence and destroy the original ecosystem. This kind of destruction not only reduces or loses the original land income, but also causes the destruction of surface water conservancy facilities and the deterioration of ecological environment. The surface subsidence area caused by mining reaches 400,000 hm2 every year, with an average annual subsidence of 15000 hm2.