There are many factors that need to be considered when developing a flowsheet: the type of rock being crushed; the desired product; energy, water and production requirements; and the site’s climatic conditions, to name but a few. But perhaps the most significant factor – or at least the one that has the most defining impact on the final flowsheet – is whether it’s a greenfield or brownfield project.

Greenfield versus brownfield projects

Brownfield projects start with an audit of the existing plant; generally, the site’s footprint has to remain roughly the same, so the operator has certain parameters it has to work within. With that in mind, the OEM works with the miner to better understand their needs. For instance, has the desired product changed over time, does the operator want to increase its tonnage, has the ore hardness changed and can the legacy equipment still handle it, etc.

This is why it’s vital that OEMs and operators have a close working relationship founded on open, on-going communication. Over the life of the mine the characteristics of the material change; by feeding this information back to the OEM, the operator can make adjustments or changes to the equipment to improve the wear life, decrease downtime and reduce the cost per tonne. It might be as simple as changing the cone crusher liner or, in other instances, upgrading the cone crusher may make more sense commercially.

When it comes to greenfield projects, the miner has a representative sample of the material and it knows the tonnage and the product it wants to produce, so the question is: what flowsheet is required to achieve that goal? Needless to say, there are fewer constraints compared to brownfield.

There will, of course, be fluctuations in the material, but well-designed flowsheets can accommodate these.

Flowsheet optimisation

The frequency and regularity that different mines test their material to understand how it’s changed over the life of the mine varies greatly, but it is crucial if miners want to optimise equipment performance and wear life. If, after a decade of operation, the material is harder and more abrasive than the initial test samples, this could reduce wear life and change the desired product. However, if these changed material characteristics are well understood, selecting the most suitable wear components to ensure the life of these parts is prolonged is a more straightforward process.

Moreover, it’s not uncommon for the desired product to change over the life of the mine. This is particularly true in sand and aggregate operations where a quarry might have a contract to supply a special fraction for, say, 50 kms of motorway and then, once that project is complete, it might be required to deliver a different sized product for a different type of infrastructure project.

It then becomes a matter of analysing each stage of the flowsheet to determine where improvements can be made and whether the existing plant is still fit-for-purpose. At the end of the day, every portion of the flowsheet is only there to produce the best product for the next station. If two pieces of equipment are mismatched, then neither of them can really be said to be performing optimally. This becomes more important as you move further towards the downstream end of the flowsheet. Operators need to be more precise when determining the application and pay close attention to the material and what they want to achieve to avoid overloading the next station.

When it comes to flowsheet optimisation, small changes can often have significant impacts. A 5% increase in production may not sound like a lot, but, over the course of a year, that equates to a substantial boost in revenue.

Dealing with declining ore grades

Traditionally, as ore grades have declined, miners have tended to increase their tonnage using the same flowsheet. However, these days there’s an acknowledgement within the industry that this could potentially jeopardise the mine’s social licence to operate because once the site has been mined out, the community is left with a larger hole that’s more difficult to remediate.

Alternatively, operators can be more targeted and focus their efforts on identifying and then mining the higher grade ores. Moreover, new technologies and higher mineral prices have led some operators to remine their tailings. What was previously stockpiled as a waste product can now provide miners with an additional revenue stream, while also reducing waste.

Providing solutions

Developing flowsheets requires a holistic approach, one that requires OEMs to think of themselves not as suppliers of individual pieces of equipment, but, instead, as solution providers. Weir Minerals has a distinct competitive advantage when it comes to this because of its all-of mine capabilities. And, in areas where it doesn’t have the experts in-house, like in floatation, it has partnership agreements with companies like Eriez that allows it to leverage their expertise and deliver the optimal solution to its customers.

This solutions-based approach has to be site- and region-specific; ultimately, the climate – whether the mine’s located in an arid area or whether it experiences high rainfall, for instance – will influence the flowsheet design. Moreover, different mines have different concerns: the price of water and energy or the local regulations all impact flowsheet development.

OEMs need to be flexible, listen to their customers and draw on their experience and expertise to develop and implement flowsheets that produce the most valuable product at the lowest possible cost, while also minimising the impact on the environment.

Contact your local Weir Minerals representative to learn about how it can help optimise your flowsheet.