The new Iron Age

As global demand stretches the world’s mines to the limit, operators plan to meet the challenge with automated mega-sites the size of the UK. Jon Excell reports

In the iron ore fields of Pilbara, Western Australia, a brave new world is taking shape. Anticipating a demand for raw materials unprecedented in human history, UK giant Rio Tinto is sketching out its blueprint for the ‘Mine of the Future’, a precisely controlled network of autonomous, interlinked operations that will produce almost half a billion tonnes of iron a year.

Its developer likens it to mining’s version of a modern car plant — albeit one with a factory floor bigger than the UK. The scale of the operation may be daunting but it is the only rational response to a daunting situation.

Mining operations, which now account for about seven per cent of global energy use, are going to have to grow by an order of magnitude to meet the booming demand for commodities from the emerging economies. And the industry is going to have to innovate like never before to meet spiralling demand while minimising energy use and ensuring workforce safety.

John McGagh, Rio Tinto’s head of innovation, says this ‘unbelievable’ demand is being driven by urbanisation in India and China. ‘We’ve been digging the stuff up since the 1700s, we’ve supported about 20 per cent of the planet and now the other 80 per cent is moving through to an industrialisation phase,’ he said. ‘There are roughly 800 million people who live the kind of life that we live and 5.2 billion others that are wanting some of what we’ve got. In China we are seeing the largest land migration in history, with 400 million people leaving the land and moving into the cities.’

So what does this mean for demand? In the UK each person accounts for the use of about 400kg of steel a year while in China usage is about 200kg per person. But for the Chinese to attain living standards comparable to those in the UK, huge amounts of new infrastructure are required and initially China’s demand is expected to far exceed 400kg a head. McGagh pointed to Taiwan, where steel consumption peaked at about 1,000kg a head before starting to fall.

Meeting this challenge will require a change of mindset. ‘For 25 years until 2002 we faced declining prices for our products because the industrial consumption base in the west was seeing very little growth,’ said McGagh.

‘If you’re facing continuing decreases in your prices you’re not going to be taking risks in terms of innovation and new technology.’

But the time for innovation has arrived so Rio Tinto is setting up a series of specialist academic groups to rethink and optimise different aspects of the mining process.

Surface mining is one area ripe for development. Rio Tinto hopes to almost double its production, from 220 million tonnes to 420 million tonnes a year, in its Western Australia iron ore business. And the sheer scale of the proposed operation, coupled with the fact that fewer people want to live and work in remote areas, is leading to unprecedented levels of automation.

From autonomous drilling systems at the rock face, to fleets of autonomous trucks and driverless trains that will transport the mined minerals to the shipment point, the company is developing the building blocks for an end-to-end automated mining operation.

At the heart of this vision is a master operating system under development by a team of roboticists at Sydney University. As well as providing an ‘all-seeing’ link between every aspect of the operation, it will also enable Rio Tinto to carry out monitoring and control from a remote operations centre some 1600km away in Perth. All of these technologies will be tested this year in a Western Australia test-bed known simply as Pit-A. By the end of this year, the company hopes to control all its Pilbara operations from Perth.

Landslips are a serious danger in open-cast mines, particularly as they get deeper, and since the mine of the future will still require human workers, technology can help improve safety.

An increasingly popular technique is the use of radar scanning systems to detect potentially dangerous earth movements. For instance, the movement and surveying radar developed by South African firm Reutech Radar Systems will constantly monitor vast areas of a rock face and provide an early warning of geotechnical weakness or movement long before it can be detected by the human eye.

Jan de Beer, Reutech’s head of mining, told The Engineerthat the system will detect movements of less than a millimetre in 900m by 600m sections of slope face. Rio Tinto’s Pilbara iron ore mines use a rival slope stability radar system developed by Australian company GroundProbe.

Mining the resources that lie deeper beneath the ground such as copper, for which demand is rocketing, presents an even trickier set of engineering challenges. ‘Over the next 20 years we have to open the next tier of copper deposits and these are up to 2km deep underground,’ said McGagh. ‘We’re looking heavily at the next technological breakthroughs in the rapid development of mega underground copper deposits. We need to think about multiple,100,000-tonnes-a-day, double-shaft operations whereas the best today is 40,000 tonnes a day.’

Much of the research in this area is being carried out by a group of earth science specialists at Imperial College London. Working with £6m of Rio Tinto funding, the college’s centre for advanced mineral recovery hopes that by answering some fundamental scientific questions, it can improve a shockingly wasteful process. ‘If you’re going to mine copper, two per cent is copper mineral and the rest is waste,’ said the group’s leader Prof Jan Cilliers.

This means that in a typical underground copper mining operation 98 per cent of what is brought to the surface is waste. This is then ground into tiny, 50-micron, chunks to get the metal of the rock.

Cilliers’ team aims to acquire the scientific knowledge that could help turn this wasteful equation on its head. The vision is to carry out extraction and processing deep underground, avoiding the need to hoist waste to the surface and reducing the energy required to break the rock.

One step towards achieving this will be acquiring a greater understanding of the dynamics of block caving. This exploits the natural fractures of rock to make it break under its own weight and stress and is becoming the preferred approach for large underground mines.

The dynamics of rock fracture during block caving are not well understood, and improved knowledge in this area could make the process safer and more efficient. But acquiring this knowledge is tricky, particularly if you are developing a mine from scratch.

‘Often you’re going from a large, open-cast mine to an underground mine and by then you’ve got a lot of information on the rock dynamics,’ said Cilliers. ‘However, if you’re starting from scratch the amount of rock you have to do experiments on is very small. So we’re going to go right down to the atomic scale and ask “how do atoms break apart in a solid piece of material?” We will then build that fundamental model up into to a tens of kilometres model for an entire ore body.’

This work, which will involve huge amounts of computer modelling and rock analysis on some of the most powerful scientific instruments available, will link in with a parallel project studying the development of new in-situ sensing techniques.

Cilliers group is working closely on this area with the team at the new Rio Tinto centre for sensing and materials at Australia’s Curtin Technology University.

‘We will drill holes to get rock samples and then use those holes to sense the shape and distribution of the ore body — this will feed into knowledge of ore body model,’ said Cilliers.

He added that much of the sensing technology required will be borrowed from the oil and gas industry, which, surprisingly, does has have a history of technology transfer with the mining business. ‘We believe that a lot of technology from the oil industry will be transferrable to hard rock mining, particularly sensing technology for oil field sensing using 3D and 4D seismic sensors,’ said Cilliers.

He believes the oil industry will also benefit from this dialogue. ‘One would expect in the future to see tech transfer from mining industry to oil industry,’ he said. ‘For instance, the extraction of oil from tar sand uses technology very close to mining rather than to oil extraction.’

The improved understanding will lead to better exploitation of diminishing resources. ‘There’s only so much mineral to mine in the world,’ said Cilliers. ‘We cannot afford any more to leave chunks of mineral behind. We have to mine every last scrap because the world needs it. Our vision of the mine of the future is that we extract every ounce of metal that we can from an ore body.’

To achieve the vision of extracting metals deep underground some enormous improvements to existing techniques will be required, and Cilliers’ team is also investigating the science that could make this possible.

‘The vision is that instead of hoisting all this waste to the surface we treat it like an oil mine, where you pump down steam on the one side and extract the oil on the other side,’ said Cilliers. ‘In the case of copper we could pump down some acid, dissolve the metal and pump up a liquid solution rather than all the rock. This could have great benefits but nobody has tried it before and we don’t know if it’s possible.’

To achieve it the group will have to bring about step-change improvements in the understanding of how liquid flows through rocks. Cilliers said such knowledge could help advance the science of heap leaching — a critical mining process that uses a leach solution to dissolve and extract metals in ore. ‘We’re going to go right down to fundamentals and observe the flow around individual rocks and scale it up into larger models. To be able to mathematically model the mass transfer characteristics of very chaotic and very random leach piles is an important key.’

Rio Tinto’s McGagh agrees. ‘One of the real breakthroughs would be in-situ leaching. It’s not beyond the bounds of reason to believe that we can in-situ leach and basically send down a barren liquor and bring back a heavily cooper or nickel laden liquor, but there are enormous technical and environmental issues. Every kilowatt you put in you’ve got to pull out, you’ve got to cool the place and where do you put the waste?’

Meanwhile, Cilliers’ team is studying the science of another important technique: froth flotation. This 100-year-old process uses bubbles to pick up fine mineral particles and separate them from waste rock. Cilliers believes that if this process could be optimised to pick up larger particles, a large proportion of the energy used during rock crushing, which accounts for five per cent of global mining’s energy use, could be saved. ‘Generally we grind down to 75 microns to liberate the minerals,’ he said. ‘If we can do that more effectively at a coarser grind size that will also have benefit.’

With mining accounting for seven per cent of the world’s energy use and demand set to rocket, perhaps the biggest challenge for the mine of the future is not just meeting the demand, but ensuring it keeps energy use near to current levels.

McGagh is quietly optimistic. ‘We’re fighting some fundamental dynamics,’ he said. ‘The ore bodies are getting deeper, the haul distances are getting further and the mineralogy is getting more complex. The fundamental challenge for the mining business is to fight those physical things and we will do everything we possibly can to hold the energy equation at is is now. It’s impossible to predict, but that’s why they call it innovation.’