Research bodies turning to technology to reverse decline of deep-level mining
The outlook for South Africa’s deep-level mining sector over the next ten years is bleak should there be no drastic change in the way this type of mining is conducted, comments Mandela Mining Precinct co-director Navin Singh.
This is because of challenges around operating costs and safety of personnel, says South African Institute of Mining and Metallurgy council member William Joughin, adding that the ongoing pressure to improve safety requires a reduction in exposure of personnel at the face, which is difficult to achieve without introducing new technologies.
Deep-level gold and platinum miners were dealt another blow last month, when the National Energy Regulator of South Africa (Nersa) approved State-owned power utility Eskom’s electricity tariff increases, including a 13.8% hike to be implemented from April 1.
Minerals Council South Africa noted that, as many gold and platinum mines were already unprofitable or marginal, with electricity comprising about 25% and 17% of gold and platinum mines’ cash production costs respectively, the deep-level sector would decline further as a result of Nersa’s approval.
Even before the Nersa decision, the continued existence of deep-level mines in South Africa was questionable, which is reflected in Nedbank precious metals analysts Leon Esterhuizen’s comment to Mining Review Africa in February that Gold Fields’ South Deep mine could be the only deep-level mine with meaningful production by 2029.
“Unless operating costs are significantly reduced through new technologies, it is unlikely that mine owners will spend the capital to develop new reserves,” Joughin states, noting that, while existing high-grade, deep-level mines will probably continue with minimal capital expenditure, their production will continue to decrease as resources become depleted.
There have not been any new deep-level gold mines built in South Africa since 2003. Joughin suggests this is partly because such mines, with the exception of Harmony’s Target and Gold Fields’ South Deep, have flat-dipping, narrow reefs, which South Africa has been unable to mechanise successfully, despite extensive research in the past.
Subsequently, owners and potential investors have steered clear of developing ultra- deep deposits because, to date, there have not been any economically feasible methods to do so.
Joughin notes that, while this mechanisation challenge is not unique to deep-level mines, existing mechanised technologies need to be adapted for a deep-level environment, which includes high rock temperatures, high rock stress and seismicity.
“Reducing the exposure of workers at the mining face will provide the next step change for safety. It is, therefore, necessary to modify existing mining equipment or develop completely new machinery to operate in this environment. Ideally, no person should be allowed to work in the stopes, but this requires a great deal of research to [ensure] productive mining.”
There is no single solution to the adoption and implementation of technology, he emphasises, adding that mines vary in terms of depth of operations, orebody characteristics, infrastructure limitations and the remaining life-of-mine, which must all be taken into account when developing technology.
Even if such technologies existed and were implemented, issues pertaining to job retention and change management are also concerns, says Singh.
Further, there will always be excavations where people are exposed, in which case it is essential to ensure a cool, safe mining environment, making ongoing improvements in the management of heat and rockbursts essential, says Joughin. “If resources below 4 000 m are targeted, then major enhancements are required.”
The challenges of mining deeper and safer are not unique to South Africa. Last month, Australia’s ABC News reported that ASX-listed gold miner St Barbara, which owns Australia’s deepest gold mine – the Gwalia mine, near Leonora, in Western Australia – announced expansion plans to advance mining deeper than 2 000 m.
The media organisation further noted that gold miner Northern Star Resources had begun drilling on “what is set to be the deepest diamond drill hole in Australian mining history”. The planned depth of the Jundee hole is 3 100 m, about 90 m deeper than the previous Australian record of 3 011.5 m at Kalgoorlie-Boulder’s Super Pit gold mine in 2015.
Moreover, the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) notes: “Australia’s future minerals, energy and water resources will come from far greater depths in the onshore regions and from deep onshore plays.”
As such, the CSIRO, alongside global collaborative research organisation AMIRA International and the Australian Academy of Science, developed a 15-year roadmap to fundamentally transform the industry’s ability to find nonbulk mineral resources “under the greater part of Australia’s landmass.”
South Africa has historically led the way in the development of technologies for cooling deep-level mines and managing rockbursts and seismicity, notes Joughin.
However, he stresses that locally, mining methods remain “primitive” because of the challenges asso- ciated with the orebody geometry.
Additionally, local research and development into mining technologies had completely tapered off by 2015, adds Joughin. The lack of research was one of the core issues discussed at the 2015 Mining Phakisa – the government-led industry engagement meant to develop a long-term mining strategy – which would eventually lead to the establishment of the Mandela Mining Precinct, officially launched last year.
Nevertheless, South Africa, and other mining jurisdictions worldwide have made inroads in enhancing the longevity of deep-level extraction, as shallow ore reserves have dwindled.
Last year, the Council for Scientific and Industrial Research (CSIR) presented some of its research on limiting the impact of fall-of-ground incidents, which account for 40% of mining fatalities. The presentation included information on ground-penetrating radar (GPR), which can be used to improve roof-bolting applications and detecting potential faults in a hanging wall.
The research also noted the CSIR’s work on three-dimensional (3D) mapping technologies, which could be integrated in real time into an existing mine plan, and described plans to mount the GPR on a robotic platform to accelerate underground 3D surveys.
Similarly, the CSIRO is developing deep earth imaging tools, which will use “smart analytics and algorithms to simulate geological models and properties, which allow for subtle patterns to be identified and interpreted, thus, more precisely imaging subsurface rock properties”.
The organisation is building new analytical software tools based on rock physics and drawing on predictive technology, machine learning, geological uncertainty analysis and geoscience modelling to manage real-time or near-real-time data streams.
The idea is to boost mineral and resource exploration, and fully exploit the continent’s mineral wealth using deep earth imaging to explore beyond the exposed or shallow crust.
Cooling, Drones & Drills
South African mineral and metallurgical research company Mintek noted in its 2017/18 yearly results that it had instituted a mine cooling optimisation project at a local deep-level mine.
“The ultimate aim . . . is to use Mintek’s sophisticated process modelling and real- time optimisation technologies to optimise the operation of the mine’s refrigeration plant, maximising inventory build-up of cooling water during Eskom’s off-peak periods,” Mintek explains.
This would minimise the need to use the plant during peak hours, where electricity can be up to six times more expensive, thereby reducing costs.
Noting that deep-level mines are inherently energy-intensive consumers, the organisation explains that the refrigeration and ventilation systems account for a substantial share of mines’ energy costs – “so any energy savings here can have a big impact”.
Mintek states that control of the refrigeration process is highly interactive and notoriously difficult, with several prior attempts of advanced process-control vendors at auto- matic control failing as a consequence.
“As this is a completely new process area for Mintek’s measurement and control division, the system was offered on a three-month trial basis to enable the client . . . to evaluate the benefits,” Mintek notes. The client was convinced of the performance after three days and chose to proceed with first-phase implementation.
“Discussions are currently under way to expand the system further,” states Mintek.
Meanwhile, the CSIRO’s technology arm, Data61, is competing in the US Defense’s Advanced Research Projects Agency’s three-year subterranean challenge, which explores new approaches to rapidly map, navigate and search underground environments.
Data61’s robotics and autonomous systems group is “drawing on decades of experience in developing robots and sensing and communications systems for challenging environments like underground mines and caves” to compete for $4.5-million in funding.
Meanwhile, the Mining Precinct has initiated the Isidingo Drill Challenge. Singh explains that equipment manufacturers and designers were challenged to develop a concept for a lighter, quieter, faster and safer drilling machine.
“Three companies were selected to develop their concepts into prototypes within the next six months,” he adds.
“For example, a more efficient drill may improve drilling and, thus, blasting, but, if the cleaning systems are not simultaneously changed, then all that we are doing is moving the constraint from one area to another.”
Singh and Joughin recognise that, while a technological revolution in mining is necessary, it is only a part of a greater solution, which must incorporate aspects relating to human capital and effective systems management.