In mineral processing, froth flotation is the workhorse method for separating valuable minerals from gangue. Over the decades, several cell designs have emerged—each with its own strengths, ideal applications, and operational benefits. In this post, we’ll explore some of the most common technologies including the Denver cell, Jameson cell, WEMCO cells, direct flotation reactors, and more.
Conventional Mechanical Cells: The Denver Cell
Overview:
The Denver cell is one of the earliest and most widely used mechanically agitated flotation cells. It uses impellers (mixers) and diffusers to create air bubbles and mix them with the slurry.
When & Why to Use It:
- Robust & Proven: Ideal for many traditional ore types and long common in smaller plants and laboratory testing. Modern high-throughput rougher banks mostly use large forced-air tank cells such as the Metso TankCell and FLSmidth nextSTEP.
- Particle Size Range: Best at intermediate sizes; recovery falls off for coarse particles (above about 150 µm), which detach in the turbulence, and for ultra‐fine particles due to larger bubble sizes and less intense mixing.
- Familiar Technology: Well-understood in many processing plants, which makes troubleshooting and scale-up straightforward.
High-Intensity Reactor Flotation: The Jameson Cell
Overview:
The Jameson cell represents a shift toward intensified flotation technology. Instead of using mechanical agitation inside a large tank, the cell uses a downcomer—a vertical pipe where the slurry is mixed with air at high shear—to generate a dense foam of very fine bubbles.
When & Why to Use It:
- Fine & Ultrafine Particle Recovery: Its high turbulence and small bubble sizes (typically 0.3–0.5 mm) dramatically improve particle–bubble contact for fine particles.
- Compact & Low Maintenance: With no moving parts in the cell itself and rapid kinetics (short residence times), it’s well-suited for cleaner circuits and applications like coal, base metals, and even precious metals flotation.
- High Recovery & Efficiency: The design can replace several conventional cells, offering increased recovery and a reduced physical footprint.
Self-Aspirating Designs: WEMCO Flotation Cells
Overview:
WEMCO cells are an example of self-aspirating flotation cells. The spinning rotor creates a vortex and low pressure in the standpipe, which draws in air—eliminating the need for external air compressors.
When & Why to Use It:
- Simplicity & Reliability: Because the rotor draws in its own air, no blower is needed, which simplifies the air supply.
- Versatility in Rougher Circuits: Their design is often favored for applications where a stable froth is essential and where fluctuations in feed might otherwise cause instability.
- Suitable for Varied Particle Sizes: They perform well in both rougher and scavenger stages, particularly in environments where maintenance downtime must be minimized.
Intensified Flotation Reactors: Direct Flotation Reactors
Overview:
The Direct Flotation Reactor (DFR, from Woodgrove Technologies) is one of a class of intensified flotation machines designed to maximize bubble–particle interactions. These reactor-type cells use high shear and controlled hydrodynamics to produce ultrafine bubbles, often in a more compact unit than conventional cells.
When & Why to Use It:
- Ultra-Fine Particle Processing: They are particularly effective when dealing with ultrafine particles or ores with complex mineralogy, where conventional cells fail to recover fine valuable minerals.
- High Throughput & Short Residence Time: The reactor design supports rapid kinetics and low residence times, which can lead to enhanced recovery while using less energy.
- Innovative & Adaptable: These cells are newer than mechanical cells and columns, and their performance should be confirmed by pilot testing on the ore in question.
Other Notable Technologies
Flotation Columns:
- How They Work: Use air spargers at the bottom of a tall column to create a countercurrent flow—air bubbles rise as slurry flows downward.
- Key Points: Typically yield higher concentrate grades (due to reduced entrainment) but at lower throughput than mechanical cells.
Hybrid & Integrated Systems:
- Combining Strengths: Many modern plants now integrate several flotation technologies (e.g., using a Jameson cell as a cleaner following Denver cells in roughing circuits) to optimize both recovery and concentrate quality.
- Tailored Solutions: The choice of equipment is ultimately driven by ore characteristics, particle size distribution, and specific economic considerations.
Choosing the Right Flotation Technology
When selecting a flotation technology, consider the following factors:
- Particle Size & Ore Mineralogy: Fine or ultrafine particles often call for intensified reactors like the Jameson cell or direct flotation reactors.
- Throughput Requirements: Mechanical cells like the Denver cell can handle high throughput but may compromise on fine recovery.
- Operating Costs & Maintenance: Self-aspirating designs (e.g., WEMCO cells) need no blower, and reactor cells have no moving parts in the cell, but whole-of-life costs should be compared case by case.
- Desired Product Grade: Column flotation and intensified cells can produce higher grade concentrates due to better control over bubble generation and froth washing.
Conclusion
Each flotation technology brings a unique set of advantages to the table. Traditional Denver cells remain popular for their robustness and throughput, while the Jameson cell’s innovative downcomer design and fine bubble generation have set a new benchmark for recovering fine particles. Self-aspirating cells like WEMCO and intensified reactors are driving efficiencies and cost savings in modern plants. The ideal solution is often a hybrid approach, where multiple technologies are combined to tailor the process to the specific ore and economic requirements.
By understanding the strengths and optimal applications of each type, metallurgists and plant operators can design flotation circuits that maximize recovery, improve concentrate quality, and ultimately add value to the mineral processing operation.