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StackCell® Flotation

Column-like performance in a substantially smaller footprint.





These compact, stackable units offer considerable savings for new installations and are ideal for expanding capacity in an existing plant.

A new high-capacity flotation technology, the StackCell®, has been developed as an alternative to both conventional and column flotation machines. This technology makes use of a pre-aerated, high-shear feed canister that provides efficient bubble-particle contacting, thereby substantially shortening the residence time required for coal flotation. Other potential advantages of the process include low air pressure requirements, low capital and installation costs, and increased flexibility in plant retrofit applications.

Recent full-scale plant trials suggest that this low-profile technology can recover and product qualities comparable to column flotation systems. Two full-scale approaches were tested including a single unit rougher application as well as a 3-stage, in-series arrangement. In the rougher application, the StackCell® was able to successfully offload an existing overloaded flotation circuit which resulted in an increase in combustible recovery in excess of 90%. For the 3-stage circuit, the metallurgical results show that the StackCells, when arranged in-series, are meeting the design requirements at an acceptable combustible recovery, product carrying capacity, and product ash content.

StackCell® technology provides an alternate means to efficiently achieve column-like performance when plant space and/or capital is limited. In particular, the small size and low weight of this new technology makes it amenable to low-cost plant upgrades where a single unit can be placed into a currently overloaded flotation circuit with minimal retrofit costs.

StackCell® features:

  • Small Footprint
  • Gravity Feed System
  • High Throughput with Low Residence Time
  • Stackable Design
  • Low Energy Input Costs
  • High Shear Bubble Generation



Principle of Operation

During operation, feed slurry enters the separator through either a bottom-fed or side-fed feed nozzle at which point low pressure air is added. The slurry travels into an internal pre-aeration sparging device that provides significant shear and contacting prior to arrival into the separation chamber. In fact, all of the necessary bubble-particle contacting is conducted in an aeration chamber prior to injection into the primary tank which is used only for the phase separation between the pulp and the froth. A liquid slurry level is maintained inside the tank so as to provide a deep froth that can be washed, thereby providing a high-grade float product. Froth is then carried into the froth launder via mass action. These separators are specifically designed to have both a small footprint and gravity-driven feed system that allows cells to be easily “stacked” in-series or placed ahead of existing conventional or column flotation cells. As such, the StackCell® successfully integrates key design characteristics of both traditional column flotation and conventional (mechanical) cells.

StackCell® Circuit Configurations


StackCell can be deployed in multiple circuit configurations. The above graphic shows possible circuits.

  • First, StackCells can be positioned in a stackable series taking advantage of the gravity flow system continuously improving grade throughout the process.
  • Second, StackCell® can be used to add capacity or be used as a rougher in a traditional Column Cell Flotation circuit or mechanical cell circuit.

Eriez Flotation StackCell® Animation:

Eriez StackCell® flotation machine decouples bubble -particle attachment and froth recovery. Attachment is optimized in a high shear single-pass collection chamber. While froth recovery and concentrate grade is maximized in a separate quiescent flotation chamber. These high rate, compact units offer considerable savings for new installations and are ideal for expanding capacity in an existing plant.





Ereiz StackCell - Minizine total cost of ownership - The Eriez StackCell ™ mechanical flotation machine uses a separate, high-energy bubble-particle contacting zone de-coupled from a larger chamber for froth/pulp phase separation. This provides an overall reduction in capital and installation costs due to a significantly smaller equipment footprint and lighter support loads when compared to conventional flotation machines. The smaller layout equates to an overall smaller plant which results in lower costs for building and site preparation.

Technical Papers and Presentations


StackCell™: A new flotation technology for decreasing cost and increasing performance - Froth flotation is the most industrially significant process for upgrading a wide range of mineral systems. Most operating concentrators have a flotation line. The majority of these operations use mechanical tank cells for the lion’s share of the flotation requirements.

Benchmarking Performance of the Two-Stage StackCell™ with Conventional Flotation for Copper Sulfide Applications - Rougher flotation in sulfide ore applications is typically performed using conventional flotation machines. The trend over the last 100 years has been for these cells to become larger in volume with cells reaching sizes of 600 m3 and in some cases even larger.

The Application of High Intensity Flotation Technology at Mt Keith Nickel Concentrator - Conventional flotation technology has historically failed to achieve high recoveries when treating <15 μm particles. The new StackCell™ flotation technology was developed to specifically target this particle size range, and was tested at pilot plant scale at Mt Keith Nickel Concentrator.

A high rate mechanical flotation cell for base metal applications Mechanical cells are the dominant unit operation in base metal rougher flotation applications worldwide. As economic demand for metals increase, and as the feasible ore grades decrease, the installed capacity of mechanical flotation units worldwide has greatly increased, adding significant capital and operating cost. One opportunity to improve this situation is to use fundamental knowledge to make the industrial flotation process more efficient.

Published Featured Articles


Improving fine particle flotation using the StackCell™ (raising the tail of the elephant curve) - For decades, the conventional flotation machine has been the accepted tool for processing sulfide ores. As plant capacity increases, machine size has evolved to as much as 600 cubic meters to keep pace with the required retention times. However, the excessively large size of these machines requires extreme floor space, foundations and power to operate. Recent work conducted by Eriez has shown that high-efficiency flotation machines which are based on focused energy input can achieve similar results with significantly less retention time, floor space and power.


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