Attrition Cells/Scrubbers

Attrition Cells are designed to scrub the surfaces of particulates, liberate deleterious materials and break down pretend particulates associated with durability, such as hard-pan clays. The top size of the feed is typically of up to 12mm (1/2”). Surface contaminants, such as clays, oxides and chemicals, are removed by particle-on-particle attrition generated by a series of rotating paddles inside the Attrition Cells that have been sized to suit the application.  

This style of scrubber is ideal for industrial (frac, glass, sports) and mineral sands to meet turbidity and colour test requirements. They also allow more efficient downstream separation, such as in flotation and electrostatic/electromagnetic separation. Attrition Cells can handle high plasticity clays in high shear and aggressive scrubbing environments.

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Why McLanahan Attrition Cells

Attrition Cells are one of the many feed preparation types of equipment offered by McLanahan. We test material in our applications laboratory to evaluate the most appropriate process for the application, whether it’s surface contamination or durability issues. Multiple configurations of Attrition Cells are available, including a variety of sizes and shapes, as well as unique adjustable internal geometry.  

Fabricated and serviced by local teams, Attrition Scrubbers are designed to be robust, having heavy-duty direct-drive gear boxes that eliminate the slip often associated with V-belt driven units. They also feature field-replaceable rubber liners, shaft protection and individually replaceable paddles.

McLanahan’s Applications Research Laboratory performs lab-scale testing of samples to determine the effectiveness of the process. This ensures the selection of the most efficient operating configuration, and the appropriate size and quantity of cells required in the field.

McLanahan has more than 30 years of experience with Attrition Cells and many units installed in a variety of applications. Our experienced geological and process engineering staff can assist with your applications needs to ensure efficiency and profitable production. 

How Attrition Cells Work

Attrition Cells are typically fed by Separators™, Hydrosizers™, or Dewatering Screens to present the material at a high density to achieve the best scrubbing action possible. Operating densities vary depending on the application but are typically in the range of 72-75% solids by weight. To maintain correct operating density, dilution water is automatically added at rising power draw. In the event of excessive power draw, the motor shuts off to protect the motor, gearbox and shaft/paddles.

Attrition Cells are configured to provide the most efficient performance, producing a high shear environment in which particle-on-particle scrubbing scours their surface and liberates deleterious materials. Due to the higher levels of materials passing through the unit too quickly to be fully processed, multiple Attrition Cells are used in series.

Material enters the Attrition Cell at the bottom and by displacement passes up through the tank, being subject to high velocity axial and radial motion to best provide particle-on-particle scrubbing action. The material overflows the Attrition Cell at the top and passes through to the next cell in the series, where the scrubbing is repeated. A series of weirs is provided to increase or decrease the total volume being processed in an Attrition Cell. Retention time is based on test-work and can vary between one and eight minutes. Greater retention times may end in diminishing returns for the energy consumed and capital investment. 

In cases of severe contamination, interstage washing is used. In this type of application, the materials can be diluted and processed through a pump and Separator™ or other methods, and are then directed to the next stage for further attritioning.

Most commonly used is a 1.7m3 unit with multiple units in series. These can be round, square or octagonal. Larger units are available; however, multiple smaller units are preferred due to their efficiency.

Applications For Attrition Cells

As a part of an integrated process utilising Hydrosizers™, Hydrocyclone/Separators™ and attrition technologies, Attrition Scrubbers can be used in glass sand, frac sand, mineral sand, clay, iron ore, and sand and gravel production, as well as in the preparation of flotation feeds and reagent washing.

Attrition Cell Features & Benefits

  • Direct drive shaft eliminates V-Belt slippage
  • Field-replaceable natural rubber liners and paddles allow shell liners, baffles, paddles and shaft protection to be replaced in the field – no need for factory rebuilds
  • Adjustable hubs allow paddle sets to be reoriented within the Attrition Cell
  • Up-front testing provides the greatest confidence in capital expenditure

Frequently Asked Questions

What retention time do I need?

The typical retention time for clay removal is two to five minutes, but specifications and individual requirements vary. The only real way of determining how long the retention time needs to be is to test the materials.

How long will the components last?

As with all mineral processes, you can design based on best principles and practices. Experience shows that particle shape, size and mineralogy affect wear life and sometimes materials of construction have to vary to suit. No manufacturer can guarantee wear life, but advanced knowledge of the materials being handled can help with selection of materials and thicknesses to help maximise your wear life.

Can I add caustic or acidic fluids?

In certain applications it is necessary to add chemicals to improve the performance of the attrition process. Certain materials of construction are adversely affected by different chemistries, so it is important to consult the factory before purchase and/or before the use of additional chemistry.

Are the paddles externally accessible?

McLanahan does not employ the use of side access to Attrition Cells for safety reasons. Extraction of the shaft assembly allows more controlled and more complete access to the assembly to evaluate any wear or damage. This allows the maintenance crew to remove/replace worn components with the greatest level of safety (worn components often have sharp edges). Reaching inside the vessel and indexing the shaft rotation can lead to uncontrolled exposure to sharp surfaces and accidental engagement. Inspection of internal surfaces can also be carried out with the shaft assembly removed.