Twenty one miners have been confirmed dead following an explosion at a coal mine in the city of Qitaihi in Heilonghiang Province, China on Tuesday 29 November 2016. The incident happened at about 9.00 pm local time, and trapped a further 32 workers bellow ground, one of whom was still trapped on Saturday 3 December. Details of the incident have yet to be released, but photographs of the scene show extensive damage to surface facilities at the mine, implying the explosion was large and close to the surface, and four members of the mine's management team have been arrested, suggesting that local authorities believe there were serious breaches of health and safety regulations at the mine.
Rescue workers at the Qitaihi coal mine in Heilongjiang following the 29 November explosion. Reuters.
Coal is formed when buried organic material, principally wood, in heated and pressurised, 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.
Visible damage to surface works at the Qitaihi coal mine in Heilongjiang following the 29 November explosion. Wang Song/Xinhua.
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 dioxide, 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.
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