ICL is making significant upgrades to its magnetic separators at the Boulby mine in North Yorkshire, England, with the company having decided to replace an existing single air-cooled Overband Electromagnet with four modern ElectroMax Overband Magnets that have been designed and built by Bunting-Redditch.

The ElectroMax Overband Magnets are a major improvement over the previous model, providing a more efficient and effective way to separate magnetic materials from non-magnetic materials, according to Bunting-Redditch. This upgrade will help ICL improve its mining operations, resulting in higher quality minerals and a more efficient production process, the company says.

ICL Boulby is the largest employer in the East Cleveland and the North York Moors National Park and will continue to be part of the region’s economic and social landscape for decades to come. In 1968, ICL Boulby, then known as Cleveland Potash, started underground mining of potash and salt. By 2017, the mining company had mined 1 Mt of polyhalite at Boulby.

The project to upgrade the magnetic separators at Boulby started in May 2023 when Bunting’s Technical Sales Engineer, Tom Higginbottom, undertook an on-site review of the existing installation. Material transported on three feed conveyors converged onto one conveyor where the in-situ Overband Electromagnet, installed many years previously, was failing to capture some tramp ferrous metal including small bolts and heavy steel bars. The tramp metal damages processing equipment such as crushers and screens, resulting in significant repair costs and costly production downtime.

In operation, Overband Magnets sit over conveyors to magnetically attract and remove tramp ferrous metal from the mined material. A heavy-duty rubber belt rotates around two large pulleys mounted either side of the central electromagnetic block and transports captured ferrous metal away from the magnet face and into a separate collection area.

The underground location of the Overband Magnet meant any replacement had to be air and not oil cooled. Even the switchgear had to be oil-free.

Bunting’s applications engineers assessed the project and compared new designs of air-cooled Overband Magnets with the installed unit. At a suspension height of 450 mm, the new overbands would have over double the gauss, the unit of measurement of magnetic induction, also known as magnetic flux density. However, the force density factor, which relates to the rate of change in gauss and the ability to lift a ferrous metal part, was over four times higher.

Bunting’s engineers concluded that the optimum solution was to install four air-cooled ElectroMax-Plus Overband Magnets instead of a single large unit. Three of the ElectroMax-Plus Overband Magnets would remove tramp ferrous metal on the three feed conveyors, with the fourth replacing the existing Overband Magnet where the conveyors merged the material into a single stream.

The suspension height of all four ElectroMax-Plus Overband Magnets (model EMAX-X-140) is between 400 and 450 mm across a 1,400-mm wide conveyor belt. Each Overband Magnet weighs 3.3 t and measures 950 mm long, 1,641 mm wide (with the motor to drive the self-cleaning belt), and 764 mm high. The ElectroMax Overband Magnets also feature bearing rotation sensors, belt tracking switches and bespoke guarding.

Higginbottom said: “Working closely with the engineering team at ICL Boulby and understanding the application and installation was the key to determining the best solution.”

The order for all four ElectroMax Overband Magnets was placed in September 2023 with delivery agreed for January 2024.