3.3 Blasting

Effective blasting has long been recognised as an opportunity to enhance efficiency and productivity on mine sites. Improvements in resource characterisation, combined with smart blasting, ore sorting and waste removal, can significantly reduce the energy required in the comminution process while at the same time increasing product throughput.

Improve resource characterisation

The level of ore concentration variability and other characteristics of rock types significantly influence :mine to mill’ design and operational efforts to minimise total energy usage. Typically, geologists’ predictions about the ore body and mineral processing performance from observations at the core scale are different from the reality faced by engineers. Geometallurgy helps to address this difference by first performing many smaller volume (lower cost) tests and then using the data obtained to construct a three-dimensional (3D) geometallurgical model of the ore body. Footnote 7 The 3D geometallurgical model is used to inform a ‘smart’ blasting approach that targets the sections of the ore body with the highest ore grade concentration. Footnote 8 Leading companies, which have partnered with the CRC ORE, have shown that this process can reduce business-as-usual trends in energy use per tonne of metal by 10-50%. Footnote 9

3D geometallurgical models of the ore body can also enable the optimal design of mine-to-mill circuits and the integration of energy efficiency into the measurement and accounting of energy use per unit of métal produced. For example, the Sustainable Minerals Institute at the University of Queensland, in partnership with Anglo Platinum, has developed the ‘Geology-Mine-Plant Management Tool’ to optimise energy use, water use and greenhouse gas emissions across the whole geology-mine-plant extraction process.

Selective smart blasting

Conventional blasting is focused on the entire region of a mine to achieve the top size that can be transported in haul trucks and processed through the primary crusher. Footnote 10 Selective or smart blast design technology uses geometallurgical data to target relatively high ore concentration sections of the ore body with greater blast energy. This significantly improves the grade of ore being fed to the crusher and grinding mill. Footnote 11 The net total energy consumed at the crushing and grinding stages is reduced because:

  • a reduction in the feed size to the primary crusher requires less energy to crush the ore to the same product size
  • additional macrofracturing and microfracturing within individual fragments from the blasting makes fragments easier to fracture further in the crushing and grinding phases Footnote 12
  • an increased percentage of relatively small mineral ore particles can bypass stages of crushing, decreasing the percentage of total tonnes crushed.

Research has been undertaken to consider blasting techniques that can achieve energy savings through the crushing and grinding process. Footnote 13 Savings of up to 30% have been reported. Footnote 14 Software packages are also available to assist in designing effective blasting techniques, including analysing and evaluating energy, scatter, vibration, damage and cost. Research by Aditya Birla Minerals Limited found that modifications to the blasting patterns at Aditya Birla mine would result in energy and cost savings (Box 9).

Box 9: Altering blast patterns at Aditya Birla mine

The Birla Nifty copper mine is in the Great Sandy Desert region of the East Pilbara in Western Australia, about 1,250 km north of Perth and 350 km east of Port Hedland. In conducting an energy-efficiency assessment at the Birla Nifty mine site, Aditya Birla Minerals Limited examined opportunities to modify the blasting pattern to produce a more optimally blasted rock size for crushing and grinding.

Studies estimate that altering the blast pattern would save around 25,000 GJ of energy for an estimated cost saving of $900,000/year. The investment return for the project was less than a two-year simple payback.

Source: Aditya Birla Minerals Ltd—Opportunity C, EEO Opportunities Register, 2011, http://eex.gov.au/opportunities-register/aditya-birla-minerals-ltd-opportunity-c/.

Ore sorting and waste removal

Gangue usually occurs in the ore body as large clumps that contain little or no valuable mineral. It is usually harder than the valuable minerals because it usually contains a high concentration of silicates.

Ore sorting and rejection of gangue can help the progressive upgrade of ore concentration in the ore body undergoing comminution. This enables the mill to process material at a very high concentration of ore grade, without low-grade material and gangue driving down the average. The sorting criteria should also be integrated with the mine plan and blast design (selective blasting and screening) to ensure that only the right parts of the ore body are sent to the sorting section, and that they are blasted into a size distribution suited to sorting. Footnote 15

Once mined, gangue can be rejected by progressively processing the ore using a series of separation devices. Such devices include ore-sorting devices, screens, density separators (such as heavy media circuits or drum separators) and magnetic separators. Optical, radiometric, X-ray and laser ore-sorting devices can also be used for gangue rejection. The effectiveness of each device depends on the ore’s texture, which is defined by properties including mineralogy, mineral grain size, mineral shape and the association between minerals. Footnote 16 A better understanding of ore texture is critical in the selection of a separation device. Footnote 17

Footnotes

Footnote 7
AR Bye, The application of multi-parametric block models to the mining process, South African Institute of Mining and Metallurgy International Conference: Platinum Surges Ahead, Sun City South Africa, 2006.

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Footnote 8
A Bye, Case studies demonstrating value from geometallurgy initiatives 1st International Geometallurgy Conference (GeoMet 2011), 2011.

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Footnote 9
CRC ORE, 2010-11 annual report: transforming resource extraction, CRC ORE, St Lucia, Queensland, Australia, 2011.

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Footnote 10
MS Powell, AR Bye, Beyond mine-to-mill: circuit design for energy efficient resource utilisation, Proceedings of 10th Mill Operators Conference Australasian Institute of Mining and Metallurgy Adelaide, Australia, 12-14 October 2009, pp. 357-364.

Return to footnote 10 referrer

Footnote 11
AR Bye, Case studies demonstrating value from geometallurgy initiatives, 1st International Geometallurgy Conference (GeoMet 2011), 2011.

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Footnote 12
K Nielsen, J Kristiansen, Blasting-crushing-grinding: optimisation of an integrated comminution system, Proceedings of FRAGBLAST 5: Fragmentation ay Blasting, Montreal, Canada, 25-29 August 1996, pp. 269-277.

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Footnote 13
J Eloranta, L Workman, ‘Saving money from the start: a look at the effects of blasting on crushing and grinding efficiency and energy consumption’ Pit a Quarry, 2004, 96(8):30.

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Footnote 14
Ibid.

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Footnote 15
MS Powell, AR Bye, Beyond mine-to-mill; see footnote 10 for details.

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Footnote 16
L Vink, ‘Textures of the Hilton North deposit, Queensland, Australia and their relationships to liberation’, PhD thesis, University of Queensland, Brisbane 1997.

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Footnote 17
MS Powell, AR Bye, Beyond mine-to-mill; see footnote 10 for details.

Return to footnote 17 referrer

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