Up to 5% magnetics: Bunting magnets used to remove steel from old landfill

Cross belt overband magnet (Source: Bunting Magnetics Europe Ltd.)

Berkhamsted, UK — Bunting Magnetics Europe Ltd has supplied one cross belt overband magnet and five magnetic pulleys to Gloucester based Wheatway of for installation on mobile screens owned and used by Cotswold Recycling Company Limited. Cotswold Recycling has a two-year project for re-processing landfill on an old site near Reading, Berkshire.

The landfill originated from industrial and commercial waste and is being reworked and the area cleansed to enable the building of houses. The landfill site had approximately 400,000 tonnes of material that required processing. Originally closed in the mid 1990’s, the site had been used for industrial and commercial tipping for over 15 years.

Tower structure with cross belt overband magnet

One issue facing Cotswold Recycling was efficiently removing any steel and ferrous metals from the material. The company was already working closely with Wheatway, who specialises in providing engineered solutions and spares to the crushing, screening and recycling industry. Initially, Wheatway designed a tower structure incorporating a cross belt overband magnet.  This was positioned between two screens and separated ferrous metals by lifting them off a 800mm wide connecting conveyor belt inclined at 30º.

The Bunting cross belt overband magnet was a twin-pole design, rather than mono-pole, resulting in a far superior level of separation.  Although there was an excellent level of separation, Wheatway then considered how to make a more flexible and mobile solution as the mobile screens were constantly being repositioned.  Wheatway contacted Bunting and then purchased five magnetic pulleys, one for each of the mobile screens.

Axial magnetic field produced

The magnetic pulleys replaced the head pulleys of the conveyors on the output of the screens. Bunting manufactured the magnetic pulley by mounting strong permanent ferrite magnets onto a steel carrier that is then encased by a tightly fitting stainless steel shell. The magnets produce an axial magnetic field that rotates with the normal motion of the pulley. This enables entrapped material to be freed and reduces the carryover of non-magnetic material into the reclaimed ferrous metals. The magnetic pulley is a simple and very effective way to separate ferrous metals, especially when the particle sizes are below 50mm and can be designed to be retrofitted on most conveyors.

For the installation, Wheatway designed a stainless steel splitter plate, which was then bolted onto the existing framework without any need for any additional holes or modification of the screen frame.  All the screened material would then pass up the belt and any ferrous metals would be attracted to the pulley and discarded under the pulley, whilst all non-magnetic materials continued to cascade under a normal trajectory out and away into a separate pile.

Working remarkably well

Wheatway designed the retrofit to ensure that there was no reworking of the framework and utilised existing holes and fittings. This meant that a team of three people, including Colin Smith of Wheatway and Richard Cooper of Cotswold Recycling, was able to install all the magnetic pulleys and the chutes in one day. Each magnetic pulley is fitted underneath a 900mm wide conveyor belt carrying approximately 50 tonnes per hour of minus 40mm material and, depending on the area of the landfill being processed, removes up to 5 per cent magnetics. The magnetics are then passed on for further processing to recover, clean and reuse the steel and other ferrous metals.

Richard Cooper of Cotswold Recycling commented on the Bunting equipment, stating: “The magnetic pulleys are very good and are working remarkably well, especially considering what’s going over them.”

Source: Bunting Magnetics Europe Ltd