Researchers from Russia's NUST MISiS National University of Science & Technology have found a way to dramatically reduce the spontaneous combustion of traces of coal found in dumps of waste rock by changing where these dumps are placed, thereby diminishing the risk of fire and improving environmental conditions in mining areas.
Known as ‘tailings’, the materials left over after the valuable ores have been extracted are often very difficult to extinguish once they catch fire, releasing toxic substances into the atmosphere for months or even years at a time. The situation is complicated by the fact that the waste products are most commonly dumped in canyons and ravines in geologically unstable areas, usually far away from any settlements and associated engineering facilities and infrastructure.
Dr. Adrian Batugin, a geophysicist and professor at the NUST MISiS’ Institute of Mining, said that he and his colleagues have discovered that tailings in geodynamically active zones burn more often than those outside them.
This, he said, led him and his fellow researchers to a hypothesis about a connection between coal dump fires and these geodynamically active areas. This hypothesis “was based on the idea that, when located in this kind of highly permeable zone, air can penetrate to the bottom of a tailing from below, ‘through’ the zone, especially if it intersects with a nearby mine,” the professor added.
Accordingly, by carefully studying a mining territory for geodynamically active areas using computer modelling, scientists are able to find suitable locations to dump tailings to reduce the risks of combustion, and the associated dangerous and ecological harm.
“Mines, their output, tailings, cities – everything is integrated in the natural geodynamic mobile system of the Earth’s crust,” Batugin said.
“Previously, it was thought that [human-made] systems could be considered ‘stationary’ on the geological time scale (given that the lifetime of a mine is insignificant compared to that of [naturally occurring] geological processes). Now, however, it has been established that there is an interaction of global and local processes, and this fact is recognised as the most important result of research in the fields of geomechanics and geodynamics. Accordingly, we are now able to retroactively see errors in the choice of engineering solutions,” the professor added.
The NUST MISiS scientists are engaged in modelling the process by which air penetrates tailings in geodynamically active areas, and hope to study in more detail how a rise in temperatures impacts and hastens the processes of air movement inside mining waste products.