Designing mines out of the energy squeeze

Designing mines out of the energy squeeze

Gone are the days when mines could design their energy systems based simply on peak requirements, according to SRK principal mining engineer Noddy McGeorge; a completely new philosophy is now required.

“Today’s mine energy designs need to address higher risks, better efficiencies and smarter application,” said McGeorge. “This means putting energy decisions in the driving seat of mine planning; this could include altering production plans to meet the needs of load balancing, exploring energy recovery systems and installing more secure power sources on-site.”He said this process required a detailed understanding of load requirements for each production process on a mine, so that management could estimate variability over time and incorporate these variations in its designs.

“Savings can be valuably found where energy usage is highest,” he said. “A good example is in fuel consumption in open pit operations; about 70% of diesel consumed is used in elevating waste material to be dumped – so any design innovations that reduce the amount or position of waste can help cut the diesel bill.”McGeorge emphasised the need for innovative solutions, as most of the 15% energy savings so far achieved by South African mines – when Eskom required the mining sector to limit its usage – were focused on lighter consumption areas such as water heating and lighting.

US research showed that most energy in open pit mines was consumed in mill and concentrator operations, followed by waste rock removal and ore excavation. In a typical hard rock underground mine, ventilation accounted for almost 42% of cumulative energy per tonne hoisted, well ahead of hoisting activities at 13% and drilling at 9%. In deep mines with high rock temperatures, cooling is also a significant energy factor.

“A new design philosophy must acknowledge that a mine is its own energy network, and all activities must be planned so that they contribute to balancing this network,” he said. “The strategy of load shifting has shown substantial results, with some mines saving up to 25% of their energy usage by shifting load away from areas of the workplace when not occupied by workers at that time.

”A realistic goal for mines was to halve their energy consumption without impacting productivity, he said, a challenge that could be met by using benchmarking and proper power management. The benchmark approach considers possible energy savings in each mining process – from extraction and materials handling to beneficiation and processing – and across a range of mineral commodities. Consumption targets can then be compared between four categories: current usage; best practice usage; practical minimum usage; and theoretical minimum usage.

“Technology and automation are strong components of the modern design philosophy, allowing real-time monitoring and controlling of energy infrastructure,” said McGeorge. “It should be remembered, however, that increased use of technology will raise energy consumption – so it must be more productive. Also, applying new technology to an old mine design is possible, but is likely not to achieve optimal results.”

Inside Mining - Designing mines out of the energy squeeze

Norman McGeorge - Principal Mining Engineer

SRK Africa