Coal mining

Coal mining

Coal is the most abundant part of fossil energy, and coal is also the most serious energy source that pollutes the environment. Coal mining methods can be divided into open-pit mining and underground mining. Open-pit mining accounts for about 1/3 of the world, and underground mining accounts for about 2/3. Coal often coexists with methane gas (CH4), so CH4 gas is always released when coal is mined. Every 1t of coal mined will release an average of 13kg of CH4. The greenhouse effect of CH4 gas is 23 times that of CO2.

In coal mining, silicosis caused by workers inhaling silica dust is usually irreversible and fatal. The particle size of the dust produced in mechanized mining is finer than that in manual mining, and the fine-grained dust can drive straight into the deep part of the lungs of the human body, so the incidence of silicosis is higher.

Along with the underground mining of coal, a large amount of stripped matter will be produced, forming a huge rock mountain on the surface. Usually, about 0.2t of coal grindstone is produced for every 1t of coal mined. For example, the amount of coal grindstone produced in our country every year is as much as 100 million tons. The huge mining area of ​​Yanshi Mountain will encroach on a large amount of farmland, and the leaching of the rock pile by rainwater can cause water pollution. Among them, Yanshishan, which has a relatively high calorific value, will also ignite spontaneously, emitting a lot of harmful gases such as SO2, CO, and polluting the atmosphere. In addition, ground collapse above the mining area may also occur from time to time.

Poor quality coal contains a high proportion of ash, which will produce waste during sorting. Coal stored in coal mines or near the place of use and coal transportation often cause pollution. Accumulated coal will be leached by rainwater or scattered with the wind to provide dust. P. Rousseaux and others estimate that 0.05% to 0.1% of coal will be lost to the environment in this way.

When coal is burned, it produces CO2 gas that can increase the greenhouse effect of the atmosphere and also produces dust. The more energy required, the more serious the pollution caused. A 1,000MW coal-fired power station generates 6.6TW of electricity throughout the year, which consumes 6.5Mt of oxygen and 2.5Mt of coal, and releases 7.8Mt of CO2, 40,000 tons of SO2, 10,000 tons of NO2, and 6000t of dust. At the same time, 450,000 tons of solid waste will be generated.

When coal is mined, radioactive pollution may also occur. Depending on the place of origin, each ton of coal contains 1-10g of radioactive element uranium, and the amount of radioactive element thorium contained is about 2.5 times that of uranium. Therefore, the above-mentioned coal-fired power stations release an average amount of tens of tons of uranium and thorium into the environment through the atmosphere or fly ash each year. A study in the United States pointed out that the radioactive dose received by people near a coal-fired power station is a hundred times higher than that of people near a nuclear power station of the same power. Of course, the impact of coal-fired power stations on the health of the population may be more mainly from chemical pollution when coal is burned.