Bunting laboratory-scale WHIMS installed at Wardell Armstrong’s facility in Cornwall

Wardell Armstrong, a leading global consultancy for mining and mineral processing, has acquired a laboratory-scale Wet High Intensity Magnetic Separator (WHIMS) supplied by Bunting. The laboratory WHIMS is for the consultancy’s material testing facility located in Cornwall and comes from Bunting’s range of small-scale high-intensity magnetic separators.

Bunting, which has manufacturing facilities in Redditch and Berkhamsted, is one of the world’s leading designers and manufacturers of industrial and high-intensity magnetic separators, electrostatic separators, and metal detectors for the mining and mineral processing industry.

Wardell Armstrong is a multi-disciplinary environmental, engineering, and mining consultancy providing a broad range in services to the infrastructure and energy, property and development, and mining and minerals sectors. The company’s history dates back over 185 years and it has developed a reputation for high-quality service in the UK and internationally.

For many years, Bunting and Wardell Armstrong have worked together on mining, mineral processing and environmental projects requiring material separation tests. Bunting’s Customer Experience Centre in Redditch is a world-leading testing facility for high-intensity magnetic separation, electrostatic separation, and eddy current separation.

The purchase of the laboratory WHIMS provides Wardell Armstrong with greater testing and research capabilities on-site at its Truro facility. Bunting will continue to provide support for the testing of materials on other high-intensity magnetic separators including the Rare Earth Roll and industry-leading technology such as the electrostatic separator.

Controlled material tests on laboratory-scale high-intensity magnetic separators provide vital data on the mineralogy of an ore or deposit. The electromagnetic laboratory-scale WHIMS removes fine magnetics and para-magnetics from mineral slurries. Handling minerals in a slurry or suspension is preferable for many processors, especially when beneficiation involves wet processing. Additionally, a wet process often produces a better separation for very fine materials.

The laboratory-scale WHIMS features two electromagnetic copper coils mounted either side of a canister housing a matrix, which captures magnetically-susceptible particles. The electromagnetic coils project a manually-controlled magnetic field of between 0-20,000 gauss (0-2 tesla) into the open gap of the canister housing the matrix. The level of magnetic field strength in the open gap is set in accordance with the separation objective and magnetic susceptibility of the minerals being processed. The magnetic field is intensified on the points of the matrix and there are various designs of matrix to suit different minerals applications and particle size ranges (down to <2µ).

Magnetic minerals separated on a laboratory-scale WHIMS

In operation, an initial evaluation of the test material determines the type of matrix and also the level of magnetic field required to meet the customer’s objectives. The magnetic field of the laboratory WHIMS is calibrated using the calibration graph — provided with each machine.

The graph shows the relative magnetic field (in gauss) at different current levels (in amps) with and without the matrix. The requisite level of amps to project the required magnetic field is set on the control panel. As the magnetic field rises, the increased magnetic field strength and gradient enables the capture of weaker and para magnetic minerals.

Once the matrix and magnetic field test parameters are set, the laboratory WHIMS is activated with material gravity fed in a 15-20% w/w (weight in grams/weight) suspension through the central matrix. Any residual material in the feed container is washed out into the matrix using a known volume of wash water. The non-magnetic minerals and the water flow through the matrix and are collected in a receptacle underneath. Magnetic particles are held in the matrix by the magnetic field and to remove a small proportion of non-magnetics potentially entrapped in the matrix, water is flushed through with the magnetic field still on.

The non-magnetics receptacle is then replaced for collection of the magnetics fraction — the magnetic field is turned off, which releases the magnetically trapped particles. The matrix is once again flushed through several times with water to ensure the matrix is empty. Commonly, both samples are then dried before being analysed.

The laboratory-scale WHIMS is an extremely versatile high-intensity magnetic separator used globally in mineral processing, ceramics, and by water treatment companies, as well as universities and research institutions. The WHIMS is one of several high-intensity magnetic separators in Bunting’s laboratory-scale range.

Neil Rowson, Bunting’s laboratory manager, said: “The need to process increasingly difficult deposits and recycle materials previously classed as ‘waste’ is driving a demand for high-intensity magnetic separation. Bunting already conducts extensive test work for the consultancy at our customer experience centre in Redditch, but with an increasing number of projects the consultant wanted to expand its own test capabilities.”

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Bunting-Redditch (www.bunting-redditch.com).