As the lifecycle of valuable mining sites wind down, with the main ore field having seen its resources depleted and stripped away, mining companies often then turn their attention to nearby sites that initially would have been more difficult or less profitable. As these operations expand, mining operators are left with a dilemma – should they extend the haulage time from the pit to the plant or build another plant at these new satellite mines?

Of course, either choice creates a host of new challenges for mine operators, and the balance between the ore that could potentially be extracted from a subsite and the cost involved in doing so can be very fine indeed. For that reason, mining companies have looked into a number of ways to keep costs down on these smaller sites.

When it comes to the crushing and screening plants required throughout the industry, using plants that are modular, scalable and relocatable can help prove the difference on smaller sites.

“Essentially, we’re quick to market, right?” says Mike Grey, CEO of mining services of Mineral Resources – which is based in Perth, Australia – speaking on the benefits that these types of crushing plants can provide. Historically, this hasn’t been the case with traditional models, which can take a considerable amount of time to obtain the required approvals for.

Then there’s the additional time taken to construct and commission a plant, which can similarly be carried out a lot faster with modular models – unlike traditional plants, they can be mobilised and set up at a mine site within a very short time frame in comparison to conventional builds. “That’s what clients are looking for these days,” Grey notes. “They don’t have the time to wait.”

Uproot the plant

Mineral Resources has spent years developing what it calls the “next revolution” of modular crushing plants, in the shape of its NextGen series. Its rapid deployment, demobilisation and relocation capabilities offer many benefits across a wide range of applications.

The company’s current modular crushing plant offerings were developed around a shortlist of requirements – being quick to market, quick to build, plug and play, and scalable to any size. They can cater for anything up to 50 million tonnes and beyond, but can start at as low as 1 million tonnes. “We just keep on adding modules,” Grey says, by way of explanation. “And, being modular, with our design there’s no in-ground services. It’s like plugging in an extension cord.”

Initially, Mineral Resources started off with trailer-mounted crushing plants, which were then followed up with semi-modular plants based on the mobile units. “We used to drive them in with wheels on, pull the wheels off and stand them up,” Grey notes.

The company later saw client demands rise due to the increasing proliferation of remote satellite pits being operated throughout Australia, where Mineral Resources is based. Many of the existing mining sites had been in operation for 50 years or so, and deposits had started to run thin at their hub sites.

“A lot of the large mines now are going to the extremities – to satellite pits,” says Grey. “And they have short lives because they’ve obviously gone to the heart of the ore body first.” These satellite mines might have a zero-to-five-year lifespan – far shorter than the larger mine sites that had been the norm in previous decades. As a result, companies are reluctant to invest in infrastructure in these new sites and are also looking for ways to minimise their environmental impact.

“That’s what essentially drove us into the NextGen I,” notes Grey. The first NextGen crushing plant was successfully installed in 2018 at a lithium project in the Pilbara and is still operating today. “The NextGen I plant is still an important component of our business and will be for some time – it has a capacity of around 12 million tonnes per annum (mpta). It is semi-modular – however, it does have in-ground services, and it certainly isn’t plug and play.”

Much work needed to be done, then, for the evolution of the NextGen II plant – the first of which was installed with a capacity of 15mtpa at a tier-one client site in the Pilbara during 2021. This involved removing the need for the foundations required by the previous model and creating a plant that doesn’t require concrete or cabling in-ground to function. “We literally could just crane [a NextGen II plant] into position and put the two cords together and turn these things on,” Grey says.

Not content to rest on its laurels, Mineral Resources is currently working on the NextGen III plant, which is set to go into production in mid-2023. They’ll offer capabilities to function at any even larger scale than the NextGen II plants, with crushers and carbon fibre screens that have been designed in-house.

The carbon fibre screens are particularly useful for a number of reasons. Mineral Resources has an innovation centre that predominantly focuses on carbon fibre products, along with polymers and ceramics, which can go hand in hand with some of the screens the company produces. By producing carbon fibre screens themselves, Mineral Resources removes its reliance on the global supply market – a notable benefit given the unpredictability of the supply chain at the moment.

“A steel screen typically lasts for three to five years maximum, depending on its application,” says Grey. “But in that period, you’re always maintaining them because they fatigue – they’re literally shaking themselves to bits every day. Carbon fibre just does not fatigue, does not crack, does not corrode.”

Carbon fibre is also used in other parts of Mineral Resources’ modular plants, helping to make the structures lighter and stronger, reducing the environmental impact and the reliance on steel and concrete. “Essentially, we’ve taken the NextGen II, and rather than outsourcing all the mechanical components, we’re building our own,” Grey explains. “NextGen III is going to be really exciting.”

The reward for the risk

With all of the challenges in place to develop and construct a modular plant, why are Mineral Resources and its competitors going to all this effort? Well, it’s for a variety of reasons, as there are a range of benefits that a modular, scalable and relocatable crushing plant can offer mine operators.

First and foremost is the risk reduction such plants can offer in terms of safety. “Construction is inherently a dangerous business,” Grey says. “We have so many issues around construction, and that’s predominantly driven by high-risk activities, a really transient workforce and having lots of activities in a small space.”

With modular crushing plants like the NextGen II, construction and other on-site activities are minimised. Instead, the plants are built in workshops in the form of small modules, and from there, they’re brought to the site and plugged in. On-site interaction between personnel and construction machinery is therefore minimised, and the risk of accidents is mitigated accordingly.

From an environmental perspective, then, these kinds of modular plants result in minimal disturbance to the local area, as they don’t require much in the way of construction machinery and don’t need any in-ground systems at all. “We don’t dig a hole, we don’t go around laying pipes, we don’t go putting concrete in the ground that typically never comes out,” Grey notes.

With traditional crushing plants, it has been typical practice when decommissioning a plant to simply bury its concrete foundations or leave it as is. “We take everything home,” adds Grey. “There’s nothing left in the ground, because there is nothing in the ground.”

With the NextGen plants, Mineral Resources has designed the series with a huge focus on dust mitigation in particular. “We’ve got some great reports [regarding] various standards that were well within [safe margins] in respect to our dust management,” Grey claims. Similarly, due to the design of the plants and their use of carbon fibre screens, the noise generated by their operation is far less than that of traditional crushing plants, or even other modular plants.

At the same time, with regards to improving efficiency, the power used per tonne is reduced with modular plants like NextGen II and III. This also helps from an environmental perspective – “Less power, more tonnes,” Grey notes, means “less waste”. Similarly, efficiency is also increased by making the plants maintainable. Since they’re modular, individual components can be turned off to perform maintenance procedures on while the main body keeps running.

The modular and relocatable aspects of remote operations with short-life mines or pit operations that require infrastructure only for a short time can be invaluable. On top of this, Mineral Resources operates under a build, own and operate model, removing the need to purchase a plant that will only be required for a few years. “Our clients don’t have to spend a dollar on [the plant itself],” Grey notes. “The client doesn’t have to spend the capital, we do that – we take the risk on the plant.”

The next piece of the puzzle

As to what the future can hold for modular, scalable and relocatable crushing and screening plants, Grey believes the sky’s the limit. In particular, he expects to see development into wet processing in the coming years, particularly in smaller gold operations and the like, which often struggle to get off the ground due to the capital required. Indeed, Mineral Resources is already conducting this in modular plants on its own mining sites.

“They have short lives, so I think the opportunity around relocatable gold plants, or even lithium or anything like that operating today, that’s where the future will be,” says Grey. In his opinion, the future of tier-one mining operators is already changing. As he’s made clear, these companies are seeing their main sites gradually deplete their resources and are now having to reach out several kilometres from their hubs, making use of overland conveyors and other systems that are less than ideal for many operations. These operators will want to move their crushing plants directly to the source and move the product from there.

This development isn’t likely to see itself reversed – the metals and materials that have been extracted will hardly be going back into the ground – so this trend of smaller, less profitable and shorter-living mines is here to stay. As mining operators will need to limit expenditure in order for these sites to be worth the effort, modular, scalable and relocatable crushing and screening plants are a sure fire way of achieving that goal.

This article first appeared in World Mining Frontiers magazine.