Equipment Spotlight | DEC 2019 Eddy Current Separators

by MARY M. THORNTON

There is an ever-growing demand to maximize the recovery or removal of metal from recycling operations, especially nonferrous. The economic viability of many plants is based upon the ability to successfully recover valuable metals such as aluminum. For example, with operations processing waste plastics, successful recycling is not possible without removing ferrous and nonferrous metal contamination. This demand is driving the evolution of the eddy current separator (ECS).

Bunting is one of the world’s leading designers and manufacturers of ECS machines, magnetic separators and metal detectors with manufacturing plants located around the world. An ECS is a two-pulley conveyor system with a high-speed, multi-pole magnetic rotor positioned inside a non-metallic head pulley. In accordance with Fleming’s left-hand rule, an electric current is induced into any nonferrous metal particle entering the alternating magnetic field. This current generates its own magnetic field within the nonferrous particle that reacts with the magnetic rotor, causing it to be repelled and enabling separation.

The first ECS manufactured by Bunting dates back to the early 1990s. “Over 30 years, our technology evolved and we now offer concentric and eccentric rotor designs, featuring differing numbers of magnetic poles. Optimum separation is achieved by balancing a number of factors including, but not limited to, the particle size of the nonferrous particle, the depth of magnetic field, the number of magnetic poles, and the rotation speed of the rotor. Generally, for the separation of larger sized materials – such as aluminum cans– a deeper magnetic field with fewer magnetic poles is required. Separating smaller particles requires a shallower field, with more poles operating at a higher rotation speed,” explained Michael Wilks, global marketing director.

He added, “Waste and secondary materials aren’t typically uniform in shape or size. Subsequently, it is important to take a more holistic view of the separation objective before proposing a specific design of ECS. This includes assessing the operation of a recycling plant and the ultimate objectives there, such as end-product purity, metal content and recovery. Controlled tests at one of our test facilities confirm the level of separation possible and the projected operating parameters after installation. The use of an ECS is a key technology in the global war against waste, which Bunting’s engineers continue to develop and enhance.”

The mobile metal separator manufactured by Goudsmit Magnetics separates ferrous and nonferrous metals from bulk and recycling flows. The easy-to-position magnetic separator is designed for coarse, bulk material such as shredded wood. Ferrous items such as nails, screws, staples and hinges – as well as nonferrous materials such as door handles and strips, can also be removed from debris. The result is three separate material flows – ferrous, nonferrous and clean (inert) bulk material, which is suitable for reuse. The machine is also suitable for industrial, construction and demolition waste, refuse-derived fuels and more.

A spreading plate at the infeed point helps to break up material bulk and distributes the material over the angled feeder belt. The resulting monolayer is then ideally situated to use an overbelt magnet that pulls all iron parts from the material flow and those parts can then be diverted to the left or right. After the iron is removed, the bulk is transported to a two-meter-wide eddy current separator. At that point, a powerful 22HI rotor separates nonferrous metals from the bulk material. The capacity of the metal separator is 100 m3/hour and involves a 2000 mm wide feeder belt with speed control. The robust ferrite overbelt magnet contains material guide chutes and the eddy current separator has a 2000 mm wide 22HI rotor spinning at 3000 revolutions per minute. Both discharge belts are hydraulically height adjustable and the mobile unit is built on a single-axle trailer, suitable for public roads.

According to Erik Kuenen, international sales manager, “Goudsmit is dedicated to the design and manufacture of magnets and magnetic systems for metal separation, recycling, transport, lifting, holding and demagnetization in various branches of industry.”

The D Neo Series manufactured by IMRO Maschinenbau provides optimal nonferrous metal recovery or material purification. The powerful machine is mainly used for treating shredder material, white goods, wood, plastic, glass, household waste, IBA and bed ash and electronic scrap. “This separator stands the test when very high recovery quotas and high levels of purity are required,” noted Luis Orbezo, mechatronic engineer. The machine offers the following: a patented, infinitely variable pole system (0 – 20°), a patented, removable shell ring for easy replacement of a GFK drum shell, an infinitely variable divider, 40 poles comprising the strongest magnet material available, an ultra large diameter on the inductor pole drum, the highest magnetic strength available and a 1.4 kHz frequency.

“We produce eddy current separators with different types of rotors. Stronger magnets and higher pole changing frequencies are used for finer particles than for those used to recycle material comprising coarser particles. Optimal machine applications can be engineered with any combination of numbers, arrangement of neodymium magnets and pole system rotational speed. For more than 25 years, we’ve provided excellent solutions for all of the technical challenges in the recycling industry. No matter what your recycling requirements are, IMRO is your partner and full-service provider, always ready to assist you. Our numerous areas of expertise offer our clients a wide range of services from a single source,” Orbezo stated.

Published in the December 2019 Edition