Rethinking recovery: Why combining leading-edge grinding and flotation technologies changes the game

First published on International Mining, April 2026.

Across global mineral processing operations, recovery remains one of the most persistent and costly challenges. As orebodies become more complex and head grades decline, mines are increasingly dealing with finer mineral dissemination and more difficult liberation characteristics. In many cases, valuable minerals are not fully liberated at conventional grind sizes, leading to losses in tailings. At the same time, operations are under pressure to reduce energy consumption, water usage and overall operating costs. The result is a difficult balancing act: chasing higher recovery by pushing throughput without escalating energy intensity or capital expenditure.

In numerous plants, recovery challenges are not caused by a single piece of equipment but by a misalignment between grinding performance and flotation capability. With increasingly changing conditions, grinding circuits may not produce the optimal particle size distribution for effective flotation, while flotation circuits struggle to recover ultrafine particles efficiently. This disconnect often results in incremental fixes rather than structural improvements.

Why common fixes often fall short

Across the industry, operators are experimenting with a range of fixes, but most only scratch the surface when it comes to addressing recovery losses. Many operators look to increase flotation capacity as a way to improve recovery. However, by pushing throughput, many particles are not sufficiently liberated, which directly impacts recovery. While fine particles are often already well liberated, they are still difficult to recover in flotation due to their higher specific surface area, greater water film surface area, lower mass and momentum, and higher surface energy.

Simply expanding flotation volume does not address these underlying challenges. Furthermore, while adding more flotation cells may seem like a straightforward solution, the assumption that increased residence time will improve fine particle recovery overlooks their fundamentally different flotation kinetics.

As a result, increasing flotation capacity adds complexity, footprint and capital cost, without guaranteeing improved recovery.

Another common strategy is to intensify grinding in conventional ball mills to achieve finer particle sizes. While this can improve liberation to some extent, it comes at a significant energy penalty. Ball mills are inherently less efficient in the ultrafine range and pushing them harder often results in escalating power consumption, higher media wear and increased production of slimes. Excessive slimes can negatively affect flotation selectivity and stability, undermining the intended recovery gains.

Some operations focus primarily on reagent optimization, adjusting chemical regimes to improve fine particle recovery. While chemistry plays an important role, it cannot compensate for inadequate liberation. Over-reliance on reagents may increase operating costs and create downstream impacts in water treatment or concentrate quality.

In other cases, plants upgrade either the grinding or flotation circuit independently. Although this may improve performance in one stage, it frequently shifts the bottleneck elsewhere in the process. Without aligning liberation and recovery mechanisms, the full benefit is rarely realised.

An integrated solution: HIGmill™ + Concorde Cell™

A more effective approach is to treat grinding and flotation as a unified recovery system. One approach is to combine a HIGmill™, - Opens in a new window one of Metso’s vertical stirred mill offerings, with a Concorde Cell™ - Opens in a new window to create a coordinated solution designed specifically to address fine and ultrafine grinding/liberation and recovery challenges.

The HIGmill™ delivers energy-efficient fine and ultrafine grinding, producing a tightly controlled particle size distribution while minimising overgrinding and slime generation. Its vertical design enhances grinding efficiency and reduces footprint compared to traditional regrind technologies. By generating improved liberation at lower specific energy consumption, it prepares the material for optimal downstream recovery.

While it can handle a wide range of particle sizes, the Concorde Cell™ is engineered to maximise flotation performance for fine and ultrafine particles. Its high-shearing environment accelerates flotation kinetics of otherwise elusive particles, enabling improved recovery in a compact space with reduced residence time, optimizing footprint and CAPEX compared to other flotation technologies. When paired with the HIGmill™, the flotation stage receives a feed that is not only sufficiently liberated but also ideally conditioned for high-intensity separation.

The synergy lies in process alignment. Instead of compensating for grinding limitations in flotation, or vice versa, the two technologies, which are both designated as Metso Plus offerings, are designed to complement each other, improving overall circuit efficiency and reducing the cost per recovered tonne while providing a more sustainable solution.

Finding the sweet spot

The combined solution is particularly effective in applications where fine mineral liberation is critical. Operations processing fine-grained sulphide ores, such as copper, zinc, or nickel, often benefit significantly from improved ultrafine grinding and enhanced fine particle recovery. Refractory gold operations, where ultra-fine liberation is essential to unlock value, are another strong candidate. Industrial minerals, where particle size needs to fit a tight range, could benefit from this solution as well. Across ore types, the Concorde Cell™ provides higher concentrate grades consistently, increasing rejection of impurities and optimizing both the logistics and sustainability of the circuit.

The combination also performs well in regrind circuits targeting higher concentrate grades or in brownfield operations where footprint constraints limit expansion options. Because both technologies are compact and energy-efficient, they offer advantages in space-constrained or energy-sensitive environments, but also for tailings reprocessing applications.

However, the solution is not universal. In ores that are already coarse liberated at primary grind sizes, additional ultrafine grinding may offer limited incremental benefit. Similarly, if recovery losses are primarily driven by water quality, reagent interactions, or upstream process variability, the root cause may lie elsewhere. A structured technical evaluation is therefore essential before implementation.

Evaluating suitability: A structured approach

Determining whether the HIGmill™ and Concorde™ combination is appropriate requires a data-driven assessment. Mineralogical analysis should confirm whether recovery losses are linked to incomplete liberation together with high losses in fine particles or another aspect of the process. Energy audits can reveal inefficiencies in existing regrind circuits, while flotation kinetics studies can highlight underperformance in the fine particle fraction. Tailings analysis often provides valuable insights into the quantity and characteristics of valuable minerals being lost.

Pilot testing or integrated test work can then quantify the potential uplift in recovery and energy efficiency. By evaluating grinding and flotation performance together rather than independently, operators can define recovery potential more accurately and make better-informed investment decisions. This integrated approach also supports reliable equipment sizing and selection, improving the overall plant layout and ensuring a fit-for-purpose process design.

Final considerations

As orebodies become more complex and sustainability expectations rise, incremental recovery improvements are no longer sufficient. Adding capacity or increasing energy consumption to chase marginal gains is becoming economically and environmentally unsustainable. The more effective strategy is to optimize the entire recovery chain, from liberation to separation.

Combining the HIGmill™ and Concorde Cell™ represents a shift from isolated equipment upgrades and new installations to integrated process engineering. By aligning ultrafine grinding efficiency with high-intensity flotation capability, operations can improve recovery while controlling energy intensity and footprint.

Ultimately, the key question is not whether to grind finer or float harder, but how to design a system in which both stages work in synergy. For operations facing fine particle recovery challenges, this integrated approach may provide the step-change improvement needed to unlock additional value, efficiently, sustainably and predictably.