Подземное тление угольных месторождений

Underground smouldering of a coal deposit

A coal seam fire is a burning of an outcrop or underground coal seam. Most coal seam fires exhibit smouldering combustion, particularly underground coal seam fires, because of limited atmospheric oxygen availability. Coal seam fire instances on Earth date back several million years. Due to thermal insulation and the avoidance of rain/snow extinguishment by the crust, underground coal seam fires are the most persistent fires on Earth and can burn for thousands of years, like Burning Mountain in Australia. Coal seam fires can be ignited by self heating of low temperature oxidation, lightning, wildfires and even arson. Coal seam fires have been slowly shaping the lithosphere and changing atmosphere, but this pace has become faster and more extensive in modern times, triggered by mining. Coal fires are a serious health and safety hazard, affecting the environment by releasing toxic fumes; reigniting grass, brush, or forest fires; and causing subsidence of surface infrastructure such as roads, pipelines, electric lines, bridge supports, buildings, and homes. Whether started by humans or by natural causes, coal seam fires continue to burn for decades, centuries, or even millennia, until one of the following occurs: either the fuel source is exhausted, a permanent groundwater table is encountered, the depth of the burn becomes greater than the ground's capacity to subside and vent, or humans intervene. Because they burn underground, coal seam fires are extremely difficult and costly to extinguish, and are unlikely to be suppressed by rainfall. There are strong similarities between coal fires and peat fires. Across the world, thousands of underground coal fires are burning at any given moment. The problem is most acute in industrializing, coal rich nations such as China.

Besides destruction of the affected areas, coal fires often emit toxic gases, including carbon monoxide and sulphur dioxide. China's coal fires, which consume an estimated 20 – 200 million tons of coal a year, make up as much as 1 percent of the global carbon dioxide emissions from fossil fuels.

In order to thrive, a fire requires fuel, oxygen, and heat. As underground fires are very difficult to reach directly, fire fighting involves finding an appropriate methodology which addresses the interaction of fuel and oxygen for the specific fire in question. A fire can be isolated from its fuel source, for example through firebreaks or fireproof barriers. Many fires, particularly those on steep slopes, can be completely excavated. In the case of near surface coal seam fires, the influx of oxygen in the air can be interrupted by covering the area or installing gas tight barriers. Another possibility is to hinder the outflow of combustion gases so that the fire is quenched by its own exhaust fumes. Energy can be removed by cooling, usually by injecting large amounts of water. However, if any remaining dry coal absorbs water, the resulting heat of absorption can lead to re ignition of a once quenched fire as the area dries. Accordingly, more energy must be removed than the fire generates. In practice these methods are combined, and each case depends on the resources available. This is especially true for water, for example in arid regions, and for covering material, such as loess or clay, to prevent contact with the atmosphere. Extinguishing underground coal fires, which sometimes exceed temperatures of 540 °C (1,000 °F), is both highly dangerous and very expensive. A jet engine unit, known as Gorniczy Agregat Gasniczy (GAG), was developed in Poland and successfully used for fighting coal fires and displacing firedamp in mines.

Time magazine reported in July 2010 that less expensive alternatives for extinguishing coal seam fires were beginning to reach the market, including heat resistant grouts and a fire smothering nitrogen foam, with other innovative solutions on the way. Hazelwood Power Station – a 2 km coal face in the Hazelwood open cut mine was set alight by a bushfire in October 2006 and again in February 2014. Thousands of residents were affected by the fire at the Hazelwood coal mine in 2014 which burned for 45 days sending smoke across the community of Morwell in Victoria. Government advised the vulnerable groups of people in South Morwell to relocate temporarily due to the danger of PM2.5 particulate matter. In May 2020 the Hazelwood Power Corporation was fined $1.56 million for occupational health and safety breaches associated with the fire.

In China, the world's largest coal producer with an annual output around 2.5 billion tons, coal fires are a serious problem. It has been estimated that some 10–200 million tons of coal uselessly burn annually, and that the same amount again is made inaccessible to mining. Some of these fires were reported burning for 3 centuries. Most of them were extinguished in 1785 These old burning hills correspond today to the Mont Salson, Bois d'Avaize and Cote Chaude in Saint Etienne, la colline du Brûlé in la Ricamarie and Le mont du Feu (Mount of fire) in Genilac. The fire in Genilac lasted 30 years from 1740. In Dudweiler, Saarland, a coal seam fire ignited around 1668 and is still burning. This so called Burning Mountain ("Brennender Berg") soon became a tourist attraction and was even visited by Johann Wolfgang von Goethe. Also well known is the so called Stinksteinwand (stinking stone wall) in Schwalbenthal on the eastern slope of the Hoher Meißner, where several seams caught fire centuries ago after lignite coal mining ceased; combustion gas continues to reach the surface.

In India, as of 2010, 68 fires were burning beneath a 58 square miles (150 km2) region of the Jharia coalfield in Dhanbad, Jharkhand. Mine fires started in this region in 1916 and are rapidly destroying the only source of prime coking coal in the country.

Coal and peat fires in Indonesia are often ignited by forest fires near deposits at the surface. It is difficult to determine when a forest fire is started by a coal seam fire, or vice versa. A fire season usually occurs every 3 to 5 years, when the climate in parts of Indonesia becomes exceptionally dry from June to November due to the El Niño–Southern Oscillation off the west coast of South America. Since 1982, fire has been a recurring feature on the islands of Borneo and Sumatra, burning large areas in 1987, 1991, 1994, 1997–1998, 2001 and 2004. increasing hospital admissions, and extending to portions of Brunei, Singapore and Malaysia. Coal outcrops are so common in Indonesia it is virtually certain these fires ignited new coal seam fires.

In 1944, Longyearbyen Mine #2 on Svalbard was set alight by sailors from the German battleship Tirpitz on its final sortie outside of Norwegian coastal waters. The mine continued to burn for 20 years, while some of the areas were subsequently mined from the reconstructed Mine #2b.

Transvaal and Delagoa Bay Collieries near Emalahleni (formerly known as Witbank), Mpumalanga has been burning since the mine was abandoned in 1953.

The 1991 film Nothing but Trouble, directed and co written by Dan Aykroyd, features a town, Valkenvania, that has an underground coal fire that has been burning for decades. The judge of the town references the constantly burning coal mine fire as the source of his hatred of financiers. In the TV show Scorpion, Season 3, Episode 23, the Scorpion team extinguishes an underground coal fire in Wyoming.