Sixteen miners have died and one is being treated in hospital following a fire at a coal mine in the Municipality of Chongqing in southwest China on Sunday 27 September 2020. The fire is understood to have broken out at the Songzao Mine on a conveyer belt used to carry coal from the excavation front to the surface. This ignited coal dust in the mine, which is more or less pure carbon, which reacted with oxygen in the atmosphere to produce deadly carbon monoxide gas (carbon usually produces carbon dioxide when it burns, but within coal mines, where there is abundant carbon, in a powdered form, and a limited supply of oxygen, then incomplete combustion often occurs, resulting in the formation of the much more deadly carbon monoxide). The cause of the incident is still being investigated, but it is understood that the mine had previously been fined for breached of safety regulations.
Coal is formed when buried organic material, principally wood, in heated and pressurized, forcing off hydrogen and oxygen (i.e. water) and leaving more-or-less pure carbon. Methane is formed by the decay of organic material within the coal. There is typically little pore-space within coal, but the methane can be trapped in a liquid form under pressure. Some countries have started to extract this gas as a fuel in its own right. When this pressure is released suddenly, as by mining activity, then the methane turns back to a gas, expanding rapidly causing, an explosion. This is a bit like the pressure being released on a carbonated drink; the term 'explosion' does not necessarily imply fire in this context, although as methane is flammable this is quite likely.
Coal is also comprised more or less of pure carbon, and therefore reacts freely with oxygen (particularly when in dust form), to create carbon dioxide and (more-deadly) carbon monoxide, while at the same time depleting the supply of oxygen. This means that subterranean coal mines need good ventilation systems, and that fatalities can occur if these break down.
China gains 70% of its energy from coal-burning power stations, which places the country under great pressure to maintain coal supplies. This has led to a poor safety record within the mining sector, particularly in the private sector, where there is a culture of seeking quick profits in poorly regulated (and sometimes officially non-existent) mines. However, the Chinese authorities have been making efforts to remedy this situation, introducing safety regulations and closing (or at least attempting to close) mines that fail to comply. Annual deaths in Chinese mines have steadily fallen from 6995 in 2002 to 316 in 2019.
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