Mining in focus
Diesel-driven equipment contributes to the amount of diesel particulate matter ( DPM ) circulating the underground environment . A good ventilation system is required to prevent the DPM from becoming a potential hazard .
underground mines is a result of the geothermal gradient , where the temperature normally increases from about 25˚C to 30 ° C per kilometre . The conduction of heat by different rock types is determined by the mineral composition and density of the rock . Dense rock , like the igneous rocks of the Bushveld Complex in South Africa , conduct heat more effectively than the clastic sediments such as the quartzite and shale of the country ’ s coalfields . “ A secondary source of heat , especially in trackless mining operations , stems from the engines of underground vehicles and equipment ,” says Steenkamp .
The rock type will also determine the hazards associated with mining it and the ventilation remedial measures . In coal mines , the dust has to be suppressed and safely ventilated , along with methane , to prevent explosions .
In gold mines , the silica dust needs to be suppressed and sufficient fresh air supplied to the working face . Silicosis and other lung diseases can directly be ascribed to the dust generated in underground mining operations .
According to Steenkamp , the layout of a mine needs to take the ventilation and cooling requirements into consideration . In bord-and-pillar operations , for example , the layout of the mine advance resembles a Christmas tree , as this is the most effective layout for mining advances , ventilation , and cooling flow .
Ventilation regimes
In underground mining operations , there are two main ventilation regimes — an upcast and a downcast — where air is either ‘ sucked ’ out of the mine or forced down into the operations .
Booster fans will also be installed , and ventilation walls built to aid effective ventilation and cooling . The placement of the ventilation shaft , the diameter of the shaft , and the specifications of the extraction fans need to be done with great care , as it will usually need to last the entire production life of the mine . Sinking secondary ventilation shafts or replacing / upgrading / refurbishing is expensive and almost always results in a period of operations being halted or severely limited .
Steenkamp says that the introduction of prototype platinum cell electric vehicles , instead of traditional machines in underground mines , will affect the ventilation requirements significantly . Traditional mining methods make use of diesel-driven equipment that not only increases the temperatures but generates a range of noxious gases that
[ 22 ] MINING MIRROR JULY 2018