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Better blasting can save on power costs

Rocketing electricity prices are leading many mines to look at ways of reducing the energy consumed by loading, crushing and milling equipment – through better blasting techniques that deliver finer fragmentation.

Rocketing electricity prices are leading many mines to look at ways of reducing the energy consumed by loading, crushing and milling equipment – through better blasting techniques that deliver finer fragmentation.

“A 300% increase in the price paid by mines for electricity since 2008 now means that some 20 percent of a South African gold mine’s costs are accounted for by electricity,” according to Joe Keenan, managing director of explosives leader BME. “In turn, global studies estimate that about 45 percent of electricity on hard rock mines is consumed by crushing and milling equipment.”

Keenan said that conserving energy in the loading, crushing and milling stages of production has therefore become imperative, and one of the most effective ways of doing this was to improve blasting efficiency.

“In recent years, a number of mines have seen the benefit of increasing plant productivity by increasing powder factors and applying blasting products such as accurate electronic delay detonators in their blasting,” he said. “The traditional approach of trying to cut costs by reducing powder factors in blasting is giving way; in its place is the concept of blast result targets such as fragmentation outcome.”

According to Keenan, one of the problems facing mine management is that drill and blast costs are easily measured while the increased downstream energy costs caused by poor blasting results are much more difficult to quantify.

“So it is unsurprising that there tends to be greater focus on reducing drill and blast costs without realising the negative impact this has on other processes,” he said.

It is now well recognised that modern blasting techniques can reduce losses caused by ore dilution and poor liberation of minerals in the plant processes – helping to increase mine profitability and reduce overall mining costs.

Tony Rorke, technical director of BME, said there are definite energy-saving goals that these techniques can help achieve, including lower energy consumption by crushers, grinders and excavators – alongside benefits like improved mineral liberation, maximised digging rates, and increased bucket payload.

BME has been a pioneer in the field of electronic detonation, developing the AXXIS digital initiation system – which has become an industry standard and which was recently released in an updated GII version. Using the AXXIS system, electronic detonators can be programmed for ignition within milliseconds of each other, to suit operator needs and the particular geology of the rock.

“This level of timing accuracy allows for optimal interaction of the shock-waves between adjacent blastholes, so that fragmentation is enhanced,” said Rorke. “For instance, crusher throughput and power consumption are strongly influenced by blast fragmentation distribution.”

He said a reduction in coarser fragmentation increases crusher throughput and an increase in finer fragmentation results in more material by-passing the primary and secondary crushing circuits, with less energy being consumed in the crushing process.

“Similarly, feed size distribution has a significant effect on autogenous and semi-autogenous mills,” he said. “The grinding mechanism in autogenous mills is one where larger fragments are ground down whilst smaller fragments are crushed by the larger ones. If the mill-feed contains too few coarser particles, the mill efficiency and throughput drops rapidly.”

Research also shows that additional macro- and micro-fracturing within individual fragments from the blasting makes fragments easier to fracture further, using less energy in the crushing and grinding phase.

Enhancing the versatility of electronic detonation has been BME’s range of software and hardware advances. While the AXXIS system has improved safety, ease of use, robustness and accuracy of blast timing, the company also developed the BlastMap III™ computer software program – now in its third generation of improvement.

“Used together with AXXIS, BlastMap III™ gives customers optimal blast results and makes blasting much more efficient,” said Rorke. “It allows the fine-tuning of blast parameters that include vibration control, fragmentation optimisation, dilution control, heave control, and specialised blasting scenarios.”

About BME: BME is the leading supplier of explosives and services to the African mining, quarrying and construction industries. Focusing on safety, supply security and value adding technical services, BME strives to remain at the forefront of technology by regularly participating in the research and trials of new blasting techniques and products, as well as attending and presenting at technical conferences worldwide. BME has operations in Angola, Botswana, Burkina Faso, DRC, Malawi, Mali, Mauritania, Namibia, South Africa, Senegal, Sierra Leone, Swaziland, Zambia, Zimbabwe and where opportunities present themselves.