Bank more buck through cyclone optimisation

In mineral processing, the most consequential equipment is not always the most complex. Dense medium cyclones and hydrocyclones are, by design, straightforward devices – one inlet, two exits, and a set of operating principles that are easy to grasp. But that simplicity is deceptive. When these units sit at the centre of a beneficiation circuit, even marginal inefficiencies can translate into millions of rands in lost revenue, misplaced product and wasted energy every year.

Multotec's webinar, Bank More Buck Through Cyclone Optimisation, presented by Ernst Bekker, Cyclone Process Specialist, makes the case that understanding how a cyclone works is only the beginning. Bekker draws on real-world examples across coal, diamond and copper processing to show what underperformance actually costs – and why sustainable optimisation demands a whole-of-circuit view, not just a unit-level inspection.

Why do "simple" devices carry such significant optimisation risk?

A cyclone has no moving parts and an operating principle that can be explained in minutes. That simplicity is a trap. Psychologists Justin Kruger and David Dunning identified that a little knowledge can produce a lot of confidence – and in cyclone optimisation, that dynamic plays out with real financial consequences.

The risk is compounded by the cyclone's position in the process:

• Dense medium cyclones and hydrocyclones sit at the centre of a wider circuit
• Decisions made at that point ripple outward
• Diagnoses based on incomplete information – or a general internet search – are unlikely to address the real cause

What does cyclone inefficiency actually cost – in coal, diamonds and copper?

The financial impact of cyclone underperformance is best understood through specific examples – and the numbers are difficult to ignore.

• Coal: On a 300 tonne per hour plant, inefficiency means coal is physically discarded – representing lost revenue, wasted energy and a measurable impact on the communities that depend on that energy supply.
• Diamonds: At a Lesotho mine renowned for producing some of the world's largest diamonds, each particle spends only seconds inside the dense medium cyclone. Dividing the sale value of those stones by the seconds spent in the cyclone puts the cost of a poor decision into immediate perspective
• Copper: A small deviation in hydrocyclone overflow size distribution on a 122 tonne per hour plant translated into a loss of R2 410 per hour – roughly R14 million per year. The difference between efficient and inefficient was barely visible on a graph.

The pattern across all three commodities is consistent: the losses are rarely dramatic in isolation, but they are cumulative; and more importantly, they are avoidable.

Why is inspecting the cyclone only the starting point for optimisation?

Inspecting the cyclone is the logical first step – but it is only that. Once the unit itself has been assessed, the real work begins.

The next layer is understanding the factors that influence cyclone performance: feed rate, slurry density, pressure, and size distribution. These variables don't originate inside the cyclone – they are determined by the equipment and conditions upstream. A cyclone that appears to be underperforming may, in fact, be responding correctly to a poorly controlled feed.

From there, the view needs to widen further. Auxiliary equipment, pump behaviour, sump levels and screen performance all play a role. In a milling circuit, the grind and cut point matter too. The cyclone is only as good as the circuit in which it operates – and optimisation that stops at the unit boundary will always leave some value unrealised.

What does a whole-of-circuit approach to cyclone optimisation look like in practice?

Whole-of-circuit optimisation means starting at the cyclone and deliberately stepping back through every layer of the process until the true source of underperformance is identified.

For a dense medium cyclone, that means beginning with a physical inspection of the unit, then examining the factors that govern or influence its performance – medium density, feed pressure and volumetric flow. From here the view widens to include screen performance, pump operation and overall feed rates. For a hydrocyclone in a milling circuit, the same logic applies, with additional consideration given to mill feed rate, grind size, sump level control and the performance of downstream flotation equipment.

The question at each step is the same: is the problem originating at the cyclone, or is the cyclone simply reflecting a problem that lies elsewhere in the circuit?

What role do suppliers and metallurgists play in cyclone optimisation?

Cyclone optimisation is not the sole responsibility of the supplier, nor of the metallurgist on site – it requires both, working from a shared understanding of the full process.

The risk of operating in silos is well documented. A metallurgist who understands the basic operating principles of a cyclone may diagnose a problem confidently – but incorrectly. A supplier who focuses only on the unit they supply, without understanding the broader circuit, will offer solutions that are incomplete at best. In both cases, the mine carries the cost.

The shared responsibility is clear: suppliers must bring deep process knowledge, not just product knowledge. Metallurgists must look beyond the data they are given and ask what it means in the context of the full circuit. Together, that is what genuine optimisation looks like.

Closing thought

Cyclones may be simple in design, but their impact on process performance – and on the bottom line – is anything but. The difference between a plant that extracts full value from its ore body and one that consistently leaves money on the table often comes down to how well these units are understood, monitored and optimised within their broader circuit context.

For more information on cyclone optimisation, contact Multotec. You can also watch the complete webinar here.