Gold and iron ore producers recover 80 per cent of ore from the ground that is brought to surface, whereas coal mines recover only 50 per cent.
Another cost driver at the underground mines are leakages in compressed air.
For illustrative purposes, Govender used an electricity price of R1 per kWh to show how one just 10mm hole in a standard compressed air system could cost companies almost R300 000 a year.
In addition to fixing leaks in compressed air systems, “up to 40 per cent of energy can be saved by changing from pneumatic to electric systems,” he said.
Energy efficiency solutions
Compressed air comprises 17 per cent of all electricity consumed by underground mines and about 80 per cent of costs associated with typical compressed air systems are energy costs.
According to Mr Govender, one of the main cost drivers of open cast mines was diesel, particularly through the use of dump trucks. Given that 40 per cent of diesel used by these trucks was burned while idling, investing in electric trucks, stop-start technology and in-pit beneficiation methods could go some way to optimise energy usage and cutting costs.
He also said optimisation in terms of truck specifications, the gradient of mines and conserving energy on “down runs” could help to reduce operating costs.
While energy efficient solutions can easily be designed into new mines, he said reviewing hoisting and air compression methods could provide existing mines with a good starting point.
He also said existing mines stood to benefit from motor replacement strategies, where older motors were replaced with new energy efficient machines as and when they failed.