EddyFines - Eddy current separators

They purify large bulk streams and/or separate non-ferrous metals for reuse. Eddy current separators have many uses. They can handle high capacities, because the conveyor belt separates and carries away non-ferrous metals continuously and fully automatically.

An important factor for good separation is an even flow of material, supplied by a vibratory feeder or conveyor belt for example. This results in a uniform distribution across the belt, so that the material arrives as a mono-layer. This means that the supplied layer thickness is about as thick as the largest piece, and thus that there are no pieces lying one on top of the other. This is especially important with smaller fraction sizes. Goudsmit separators are robustly built so they can remain operational day and night in even the most demanding applications, such as incinerator slag reprocessing.

Application of the EddyFines 38HI include:

• recovery of fine non-ferrous metals from slag from waste incineration plants
• recovery of precious metals from scrap or electronics waste
• recovery of casting residues in the metal casting industry
• elimination of fine aluminium for the glass recycling industry
• elimination of impurities from recycled plastic streams for protection of injection moulding machines

Material

Some non-ferrous metals are more easily separated than others. This has to do with the physical properties. This table lists non-ferrous metals categorized on the basis of three factors. The first column shows the electrical conductivity of the material: a measure of how easily a material conducts electricity. The second column indicates the density of the material. This is important for the effect of gravity on the ejected piece of metal. After all, the eddy current forces generated by the eddy current magnet roller must overcome these forces. The last column shows the ratio between these two factors. The greater the electrical conductivity and the lower the density, the better a material can be separated with the eddy current technique.

Size and shape

The fraction size (i.e. the size of the particles in the flow of material) is also a very important factor for achieving good separation. Eddy currents induce repulsive forces in a piece of metal that cause it to be ejected with a certain trajectory. As a result, the non-ferrous metals have a different ejection trajectory than the other residue and inert materials in the product stream. This ultimately results in a ‘range of trajectories’ for inert and non-ferrous material. The larger the volume, the more widely‘separated’the ejection trajectories of a chunk of inert material and a non-ferrous metal object of the same volume. This is why it is easier to separate aluminium cans than small copper wires.

Size plays a role, as does the shape. For example, a ball has less air resistance than a tangle of copper wire or a bent piece of sheet metal.

Conveyor belt

We equip our EddyFines separator with 2,4 mm thin PU conveyor belts. These have a longer life time than the less long-lasting (cheaper) PVC conveyor belts, often used by our competitors.

Slide plates

Non Ferrous metals will be separated better when they lay still at the separation point of the eddy current magnet roller. Therefore the conveyor belt is supported by Stainless steel sliding plates, which ensure flat and stable transportation of the material. Competitors use conveyor belt support rollers which make materials bounce which has a negative effect on separation. They also add extra maintenance to the machine, because the bearings of the support rollers need to be changed.

Integrated drum motor

An integrated drum motor provides the drive for the conveyor belt. This provides a compact design, because there is no motor protruding from the rear of the machine. This drum motor has an IP66 protection rating, so it is well protected against dust and moisture. This means that the motor is virtually maintenance-free, which contributes to making this a robust and user-friendly machine. A fact that will surely be appreciated by your operators.

Eddy current separators have a conveyor belt system with a high-speed magnetic rotor at the end. The rotation speed of the magnets generates an induction field, creating a rapidly changing magnetic field (see animation). The separation is based on the principle that every electrically conductive particle located in an alternating magnetic field is temporarily magnetized.

Simply put: for a brief moment all metals that pass the eddy current magnet roller become magnetized themselves, causing them to be ejected. This enables us to separate a huge number of non-ferrous metals and their alloys, including aluminium, copper and brass.

The EddyFines focuses on the most difficult parts to separate, these are the small parts of 0-10+ mm and the metals that are relatively heavy, the so-called heavy non ferrous (HNF), such as: copper, gold, silver and palladium.

The EddyFines distinguishes itself by the extra large 38HI eddy current magnet roller, currently the largest on the market. This type is extremely powerful, so it can even ‘eject’ the smallest particles, just 0.5 mm across. The result: 3,500 gauss on a 2,4 mm thick belt, see the table right for comparison with the competition. The large rotor allows us to fit more magnetic pole pairs and magnet volume, resulting in pure separation of tiny NF particles.

Because the EddyFines targets smaller NF particles, it is often located at the end of a machine or production line. This machine is also often used as part of an eddy current cascade. For example, a 22HI EddyXpert may be used for the middle fraction, after which the EddyFines separates the fine fraction non-ferrous metals. These configurations provide a significantly higher separation yield.

The function of the supply segment is the uniform supply of material the creation of a mono-layer. A good supply of material is crucial for separation of the non-ferrous metals. If other material is lying on top of the non-ferrous pieces it is more difficult to eject them over the partition. Depending on your product stream, you can choose from various supply modules:

Vibratory feeder

The vibratory feeder is the most frequently chosen option. It supplies the product stream to the Eddy current as a uniform (i.e. distributed across the width) mono-layer. If your product stream still contains ferrous pieces, we can expand the vibratory feeder to include a deferrization module such as a drum magnet. This causes the material to fall evenly onto the drum and the ferromagnetic pieces are separated. The rest of the product stream (including non-ferrous metals) moves on to the conveyor belt of the middle unit. For the drum magnet there is a choice of different magnetic strengths, so we can always guarantee optimal separation.

The vibratory feeder module is not suitable for incinerator slag due to the sticking of the cementitious mass.

Conveyor belt module

The conveyor belt module has an integrated magnetic head pulley. This provides efficient removal of the pieces of ferrous metal still remaining in the supplied product stream. The magnetic head roller can be made with various types (strengths) of magnet. This always guarantees the best solution for your product stream.

One of the advantages of the conveyor belt module is that it is independently adjustable in speed. This is crucial for adjusting the ferrous separation. Another additional advantage is the integrated belt scraper that continuously cleans the belt from sticky materials such as bottom ashes. Note: for the distribution of the material, an additional spreader belt with 'material spreaders' is needed.

For the final, definitive separation of the two product streams we place a separation plate between the inert and non-ferrous streams. The parts of the separation plate that are in contact with the material are executed in manganese steel. This material is self hardening for long service life.

There are different types of end tips or plates to ensure maximum separation or purity of your product stream.

Manganese steel fines plate

This plate is often used in abrasiveproduct streams like: incineration slags or scrap metals. The tip is very sharp for precise separation. The manganese steel is a self hardening material so the tip stays sharp for a long time.

Trespa fines plate

This plate is often used in light product streams that do not have a large impact on the tip, like for example: PET flakes or rubber granulate. The plate is also sharp but the main advantage is that this material is non conductive. Therefore the separation point can be set really close to alternating magnetic Eddy current field without getting heated. This creates ëthe separation degree for these product streams.