Conventional flotation

Where economics meets sustainability: innovation in flotation

Modern innovations to flotation cell design, alongside digital automation solutions, are elevating traditional flotation techniques to higher levels of metallurgical performance, energy efficiency, and cost-effectiveness. This allows mines to push more tonnes through and, thus, gain better results from existing concentrator plants.

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The crucial role of flotation in mineral processing

Flotation has been a cornerstone of modern mineral processing since the early 20th Century. The first patent for froth flotation was granted in 1905 to the Elmore brothers, Francis Edward and Alexander, who used a mixture of oil and air to separate sulphide ores. By the 1920s, froth flotation had become the dominant mineral separation method as larger and more efficient cells replaced earlier gravity-based jigs and shaking tables. Subsequent decades saw the introduction of reagents such as frothers and collectors, allowing improved recovery and selectivity.

Flotation works by passing air through a mineral slurry via a rotating rotor-stator. This creates bubbles that attach to hydrophilic mineral particles. Bubble-attached particles float to the froth zone at the top of the tank, where they are removed. Non-floated particles are rejected as waste. There are two main types of flotation. A forced-flotation cell uses an external air blower to introduce air into the slurry through a hollow shaft and holes in the rotor. In contrast, in self-aspirating flotation, air is drawn naturally into the slurry under suction created by the rotor’s motion.

Flotation remains indispensable in mineral processing today. However, traditional flotation systems face limitations, including high energy consumption, suboptimal recovery rates of coarser and finer particles, and throughput constraints. Modern innovations from FLS, such as WEMCO II self-aspirated flotation and nextSTEP forced-air flotation, tackle these issues through optimised equipment designs. At the same time, smart flotation solutions bring the era of digital optimisation to the flotation cell. Such innovations address the industry’s growing need to process increasing ore quantities cost-effectively while reducing environmental impact.

Innovations in mineral flotation equipment design

WEMCO II flotation cells

WEMCO II cells represent a significant leap forward in self-aspirated flotation technology. The slurry is directed below a false bottom and pumped up through a draft tube to the rotor, located high in the tank. The rotor ingests air from outside and forms bubbles, which the particles attach to. The bubble-particle aggregates then rise to the froth region, where they are recovered. The elevated rotor position means the aggregates only have a short distance to the froth.

The WEMCO II design increases shear force, creating smaller bubbles and a narrower size distribution. As a result, air control, circulation, particle suspension, and slurry-air shear are all improved for optimal attachment conditions. Continuous slurry recirculation through the draft tube also helps maximise bubble-particle attachment. Meanwhile, advanced froth stability mechanisms ensure consistent performance, even under fluctuating operating conditions. The bottom-line benefit is improved metallurgical performance with higher recovery of fine and coarse particles.

Innovative flotation retrofits and upgrades

Retrofit of existing installations extends the operational life of legacy equipment. It also simplifies the transition to higher-performance and more sustainable technology by allowing mining operations to modernise processes without extensive capital investment.

WEMCO II and nextSTEP technologies are both available as retrofit options. WEMCO II technology is compatible with existing WEMCO cells, requiring minimal downtime and providing a rapid return on investment. Meanwhile, the nextSTEP mechanism can be retrofitted to cells of all makes and models. This includes the nextSTEP Retrofit Kit to convert self-aspirated flotation machines to forced-air operation without requiring the replacement of all mechanical components. With low conversion costs of about 70% less than a complete replacement, it is ideal for converting WEMCO installations to mixedROW configurations.

In addition, FLS offers its froth recovery upgrade package to enable better control of the froth phase. Level sensors feed slurry depth and level data to actuators, which adjust the position of dart valves accordingly to maintain slurry levels in the tank. Meanwhile, radial froth crowders reduce top-of-froth surface area and increase froth movement to the nearest radial launder. This package improves recovery and grade, allows higher throughput at the same performance level, reduces reagent use, and delivers better control of froth level and surface stability.

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Smart froth flotation

Many variables influence flotation performance, requiring constant monitoring and control of the process. Smart froth flotation solutions integrate advanced sensors, machine learning algorithms, and automation to deliver unprecedented insight and optimisation capabilities.

FLS’ froth camera with LiDAR is one such smart solution that represents the next generation of mineral processing vision systems. The cameras measure froth velocity and stability and can also infer froth grade using deep neural network (DNN) technology and object detection:

DNN classifies the froth, such as barren, pulping, etc., while rejecting images affected by environmental conditions (such as direct sunlight) to eliminate false grade classifications.
Object detection provides froth-grade detection by measuring froth velocity, bubble size, colour spectra, and mass pull rate.

LiDAR is an optional add-on to the froth camera that detects the froth height above and below the tip and creates a 3D representation of the froth zone. Froth height measurements are crucial when estimating mass and volumetric pull rates.

Froth cameras are complemented by PERI online slurry analysis, which uses a solid-state, room-temperature energy dispersive x-ray fluorescence (EDXRF) detector to provide accurate, reliable and cost-effective slurry analysis.

Data and insights from both froth cameras, online slurry analysis, and other instruments can then be fed into the FLS advanced process control (APC) solution, where they are combined with AI-based data analysis technologies, model predictive control, and fuzzy logic to optimise your flotation circuit proactively.

For example, FLS APC optimises the level and airflow targets using the mass pull rate distribution and camera signals. Mass pull rate control is based on the analyser values, downstream constraints and other plant targets. This allows you to perfectly stabilise flotation cell level control, reducing variability in the cell and maximising recovery at the desired grade.

Flotation on the path to more sustainable mining

These latest innovations in conventional flotation technology help tackle some of the mining industry's most pressing challenges, including rising energy costs, declining ore grades, and tightening environmental regulations around water management, tailings, and greenhouse gas emissions.

As mining companies navigate a rapidly changing landscape, advances in conventional flotation technologies – combined with novel developments in the field of coarse particle flotation – offer a crucial pathway to achieving long-term success, capturing how engineering excellence can align economic and sustainability targets to pave the way toward a better future.