10 Tonne Electro Overbands for Russian Coal Plant

By chameleon | 17 February 2015

Magnetic Separation is a key stage of any screening, crushing and sorting plant and MK Vega-Po LLC (“Radex”), of St Petersburg in Russia, purchased six (6) Electro Overband Magnets for their coastal coal processing complex in Nakhodka on the Trudny Peninsula, approximately 85km (53 miles) east of Vladivostok in Russia.

9000 tph Coal Processing Plant

Radex started work on the Nakhodka project in early 2013 and their task was focused on integrating new equipment into an existing coal processing plant specifically for the screening, crushing and removal of magnetic tramp metal prior to feeding the loading vessels. The end specification of the coal dictated that all the output product needed to be have a maximum ferromagnetic content of 0.5 kg per 10,000 tonnes (0.000005%), which also could be no more than 50mm in size in any one dimension. Magnetic Separators would remove tramp metal and protect the screens, crushers and conveyors and guarantee the high output specification of the coal at two locations on each of the three process lines.

The finished plant receives around 9000 tph of coal, which is then split into three (3) lines each handling 3000 tph. At the first stage of the process, material can either be fed directly onto the output conveyor feeding the loading vessel or into the screening and crushing plant. The material that is fed through the screening and crushing plant immediately passes under the first Electro Overband Magnet. This removes large tramp iron such as digger teeth, blasting caps and tramp metal to protect the roller screen. After the screening stage, material under 50mm (approximately 95% of the main infeed) in size is fed straight to the main output conveyor feeding the loading vessel, whilst between 150 and 250 tph of 50-300mm coal (between 5% and 8% of the main infeed) is conveyed to an impact crusher. After crushing, the material is returned to the original screening stage, after passing under a second Electro Overband Magnet. This removes any metal that has been liberated or introduced during the crushing process.

Technical Product Information: Electro Overband Magnets

Removing Metal Contamination with Electro Overband Magnets

The selected Electro Overband Magnets are designed to operate and separate tramp ferrous metal where the operating gap (the distance between the magnet and the conveyed material) is high. The increased magnetic power of the Electro Overband Magnet enables the extraction of ferrous metals even from material conveyed along deep troughed conveyors.

An Electro Overband Magnet consists of a coil, wound of aluminium wire, centrally located inside a mild steel fabricated box and mounted around a solid steel core. When powered, the coil produces a magnetic field that is focused and projected downwards by the steel core and a thick steel back plate. All the Electro Overband Magnets for the Nakhodka project are oil cooled, where the coil is efficiently maintained at an optimum working temperature by recirculating oil inside the stainless steel box. Oil cooled Electro Overband Magnets produce higher magnetic fields that other designs such as those where the coil is cooled using air.

The Bunting engineering team used a computer model to assess applications where there are set separation objectives and this enables the size, type and design of the Electro Overband Magnet to be considered in detail. Other parameters, such as operating at potentially low temperatures around minus 20 degrees centigrade, had to be considered when finalising the design. The high strength magnetic field meant that ferrous metal would be attracted and propelled up onto the magnet at speed with a high impact force and so the whole base plate of all the Electro Overband Magnets was made out of wear resistant manganese steel.

Largest Electro Overband Magnets Built by Bunting

Radex ordered the Electro Overband Magnets in two (2) stages, with an initial order for two (2) placed in May 2013 and a second order for (4) placed in February 2014. All the equipment was designed and built by at Bunting’s UK manufacturing and test facility in Redditch, near Birmingham, UK.

The initial order in May and despatched in July 2013, for the first line processing 3000 tonnes per hour of coal, was for

One model 200 OCW 45 Electro Overband Magnet
One model 105 OCW 45 Electro Overband Magnet

Both were supplied with transformers. The model 200 OCW 55 was positioned over the 2m wide main infeed conveyor running at 3 m/sec prior to the roller screen, with the model 105 OCW 45 situated on the 1.2m wide return conveyor post crushing of the oversize fraction. Both Electro Overband Magnets are positioned inline over the head pulley. Separated tramp ferrous metals is lifted and then discharged away from and out of the natural trajectory of the coal. Electro Overband Magnets used in the inline orientation generally achieve a better separation performance than when positioned across the conveyor belt as the conveyor belt flattens as it passes over the head pulley, breaking the surface of and opening the conveyed material and enabling the more effective removal of tramp metal, especially when located at the bottom of the burden.

The Model 200 OCW 45 is one of the largest Electro Overband Magnets ever manufactured by Bunting. The Electro Overband Magnet weighed approximately 10 tonnes and drew up to 15.6 kW from the 17.5kW transformer rectifier set. The overall dimensions of the Overband Magnet, including the running gear, are 4.3m long by 2.67m wide and 2.07m high. The Model 105 OCW 45 weighed approximately 5.6 tonnes with overall dimensions of 3.275m long by 2m wide and 1.49m high and drawing up to 8.7kW from a 9kW transformer rectifier.

Following the successful installation of the first two (2) Electro Overband Magnets, Radex placed a second order in February 2014 which was despatched to Russia on June 2014 for the second and third screening and crushing lines, replicating the equipment purchased for the first line.

The plant is now fully operational, processing over 9000 tonnes per hour of coal and maintaining the high quality specification of the final coal product.