Boosting ultrafine recovery through Concorde Cell™ retrofit at an Asia Pacific metallurgical operation

Improving ultrafine coal recovery in a challenging flotation environment

Recovering fine and ultrafine particles in mineral processing is inherently challenging due to slow flotation kinetics and the long residence times required for effective separation. As ore bodies continue to become more complex, an increasing proportion of valuable coal is present in finer size fractions, placing greater pressure on flotation circuits to deliver higher recovery. 

At this metallurgical coal operation in Asia Pacific, the coal preparation plant included dense medium separation for coarse coal, spirals for mid-size coal, and two parallel self-aspirated pneumatic (SAP) flotation cells treating the ultrafine fraction. Operational reviews identified that flotation recovery from the ultrafines circuit was lower than expected, resulting in combustible coal being lost to tailings and limiting overall plant yield. 

This created an opportunity to assess whether flotation performance could be improved through a targeted retrofit, rather than installing a completely new flotation circuit. 

Concorde Cell™ technology as a retrofit solution

The Concorde Cell™ is a high-intensity pneumatic flotation technology developed by Metso to specifically address the challenges associated with fine and ultrafine particle recovery. The technology enhances flotation performance by generating significantly finer air bubbles and increasing shear rate and energy dissipation, improving particle–bubble collision and attachment efficiency. 

In operation, slurry mixed with pressurised air is accelerated to supersonic velocity within the Concorde Blast Tube™, before decelerating into the flotation cell. This transition generates sonic shockwaves and high-shear vortex rings via an impingement bowl, allowing particles multiple passes through an intense collection zone. The result is faster flotation kinetics and improved recovery of ultrafine material. 

A key advantage of the Concorde Cell technology is its retrofit capability. Existing SAP flotation cells can be upgraded by replacing the original downcomers with Concorde Blast Tubes™, while retaining the flotation tank and most auxiliary equipment. 

A structured, low-risk project approach  

To de-risk the retrofit at this customer site, the operation followed a structured, stepwise evaluation methodology. This included historical performance review, laboratory testing, pilot-scale testing, metallurgical modelling, and detailed engineering and business case development. 

Results from laboratory and pilot testing consistently showed superior flotation kinetics, yield, and combustible recovery for the Concorde Cell compared with the SAP cell, providing the confidence required to proceed to plant-scale implementation. 

Retrofit implementation and plant-scale validation  

One of the two SAP flotation cells was retrofitted with Concorde Cell™ technology, while the second remained unchanged to enable direct comparison. The retrofit involved replacing SAP downcomers with Concorde Blast Tubes™, installing forced-air supply and controls, and upgrading slurry distribution components. All other infrastructure remained unchanged. 

Installation was completed during a planned maintenance shutdown, minimizing operational disruption. 

Measurable recovery and business improvements  

Plant-scale sampling campaigns demonstrated that the Concorde Cell achieved approximately 4–5% higher mass yield and around 6.4% higher combustible recovery (ad) at comparable product ash. These benefits were particularly strong in ultrafine size fractions. 

Despite the SAP cell operating with froth washing and the Concorde Cell operating without it, the Concorde Cell delivered higher recovery without compromising product quality.

Unlocking value from existing flotation infrastructure

This Asia Pacific case study demonstrates how a staged Concorde Cell™ retrofit can deliver significant improvements in ultrafine coal recovery using existing flotation infrastructure. By improving flotation kinetics through finer bubbles and high-shear conditions, the operation achieved higher recovery, strong ROI, and a clear pathway for full circuit upgrade. 

This is an abbreviation of the paper “Enhancing flotation performance through Concorde Cell retrofit of existing self-aspirated pneumatic flotation cells in a metallurgical coal application” (Chikerema, P.) at the 2026 ACPS 19th Conference, held in Hunter Valley, Australia.