By Tirthankar Mukherjee
The causality is so commonplace that we usually forget to note how necessity continues to be the mother of invention. Thus it is no surprise that in times when mines have to get deeper to allow optimum exploitation, excavation has to be quicker to keep up with the market, costs keep ratcheting upwards, and safety concerns become mandatorily and morally paramount, miners seek succour from new technological concepts. This month, I write on some such new ideas I have read about, with the advance apology that with my grossly inadequate understanding of technical matters, my enthusiasm might have easily got the better of good judgement.
First, news from Chile, where KGHM, the world’s largest silver and eighth biggest copper producer, plans to commission and start initial production at its Sierra Gorda mine, the world’s seventh largest copper project, in the next few weeks. Sierra Gorda project is in the Atacama Desert, and the open-pit operation would produce copper, molybdenum and gold ore, while downstream processing will include crushing, grinding, flotation and drying to obtain copper and molybdenum concentrates.
So where is all the water going to come from? KGHM has built a 142-km sea water pipeline to the mine. Landlocked Mongolia can only envy Chile that it had the option, but we also have to admire the daring feat. Sierra Gorda would operate using sea water captured from the cooling systems at a thermal electricity generating plant, located on the coast. Instead of being discharged into the sea, the water would be transported to the mine and plant through a pipeline passing inland over plains and hills. That way, the pipeline itself is a marvel, but that apart, its key infrastructure includes the coastal station and two inland pump stations, with a total of 24 pumps and a pumping rate of 1 500 ℓ/s.
A senior KGHM executive told media, “Our project is located in a desert, with extremely dry conditions and scarce water reserves. That is why our top priority was securing water supply and eliminating the risk of exhausting this resource in the region.” At full capacity over a 20-year life, the amount of water used daily in the mine would be 442,000 m3. The project has been so designed that it will not discharge effluent into the environment, ensuring that the quality of groundwater is not affected. Additional precautions have been made to protect the nesting grounds of highly mobile fauna species, especially Peruvian terns and Garuma gulls.
From the Chilean desert to a claim made and elaborated on the sidelines of this year’s Prospectors and Developers Association of Canada Conference. A senior official at Quebec-based Rocmec Mining says that its patented thermal fragmentation process solves many of the problems currently being faced by deep level gold and platinum miners struggling with rapidly increasing costs, narrow veins and significant safety issues.
He was hyperbolic, arguably with proper reason. “This technology has the potential to have the same impact on the mining sector as shale gas fracking has had on the oil and gas sector. I think one day everyone will be proud to have a Dragon [the name of the machine that actually does the thermal fragmentation] in their mine.”
The technology centres on the use of extreme heat to shatter the rock within a narrow vein, instead of explosives, which makes it a great deal more efficient because it means the miner needs to extract roughly four times less rock when mining a narrow vein of gold. First a hole is drilled into vein using a long drill. Then, and I quote from the company’s website, “using a burner powered by diesel fuel, the intense heat created within the vein shatters the rock containing the precious metal contents, into small fragments. The ore bearing vein is directly extracted, greatly reducing the dilution factor and the inefficiencies associated with traditional mining methods which extract large amounts of waste rock. With this method, it’s now possible to extract a narrow mining corridor with widths of 30 cm to 1 metre.”
The first patent pertaining to the technology was filed by the group in 2002 and, most of the others were filed in 2005. The Rocmec explanation for why companies have been tardy to show interest is that many mines work on a remuneration structure that rewards the amount of tonnage milled and it takes time “to convince people that producing fewer tonnes is actually beneficial”.
The spokesman added that the mining sector is used to incremental change, and does not really like big changes, but “the tide has changed for us; what is happening (all around), the strikes, the fact that costs are rising so much is forcing people to look for new ways of doing things”. Miners cannot be very different from us and so it is true that there is a timing element to all technology. “You are currently seeing articles about the challenges of narrow vein mining, people are talking about the fact that South Africa’s mines need to change their ways or stop mining. New technology comes to the fore only when it is really needed. And, it is now really needed,” says Rocmec.
And if South African conditions are the catalyst, there are exciting reports, too, of innovative technology from there. A new fully automated low-seam mining system, which unlocks resources too difficult to mine, is able to achieve high outputs of 10,000 t a day in seams as low as 1.3 m. The first system would be operational in an underground mine by the end of this year. Supervised from a remote operating centre, the automated longwall system cuts and supports the roof automatically, with sheared coal falling onto an armoured face conveyor system for transporting from the face.
In terms of process execution, the system mimics its high-seam counterparts, but with a number of novel designs and extensive automation to allow it to provide a steep change in low-seam mining productivity. This allows low seams to be mined as efficiently as would be the case with the higher seam counterparts. “It performs all the work while keeping people out of harm’s way,” said a spokesperson of the user mine, Joy Global. Its output of three million tons a year is a considerable step up from current levels of conventional low-seam production, with the improvement likely to reach anything from 20% to 80%, depending on the seam.
All the relevant systems data is transmitted to surface where advanced monitoring is performed to predict potential equipment failures, recommend process improvement opportunities as well as defining specific maintenance needs like replacing filters, re-filling oil etc. “When that machine is operating, you don’t want to stop midshift to perform any actions. It has to run continuously between maintenance interventions,” said the spokesman.
I make no pretensions about my ability to assess the merits of any new technology regarding its global sustainability. One size will certainly not fit all, but with only 860 gigatons of the world’s 17,000 gigatons of coal resources being economically mineable, miners have to try new systems claiming to possess the potential to convert vast volumes of resources into economically viable reserves.
I do not know the relevant Mongolian statistics but most of Africa has substantial volumes of low-seam coal and 20% of China’s coal resources have seam heights below 1.5 m. All over the world, seams with heights greater than 1.5 m are depleting and much of the low-seam coal remains unexploited.
The necessity for new systems is certainly felt, so inventions cannot be far behind.