Eddy-current separation

When processing municipal solid wastes, an eddy current separation unit is often used to separate aluminum and other nonferrous metals from the waste stream. This is done after removal of the ferrous metals (see Fig. 1). The eddy current separator produces an electromagnetic field through which the waste passes. The nonferrous metals produce currents having a magnetic moment that is phased to repel the moment of the appHed magnetic field. This repulsion causes the nonferrous metals to be thrown out of the process stream away from nonmetallic objects (13). 

Equipment. From the appHcations standpoint, magnetic equipment falls into one of four broad categories tramp iron removal, magnetic particle separation and concentration, product cleaning, or eddy current separation on nonmagnetic metaUics. 

Eddy-current separation is usually appHed to the removal of nonferrous metaUics from product streams containing nonmetaUic or nonmagnetic materials. These include appHcations such as material recovery facUities (MRF), eg, aluminum can recovery from commingled containers both prebumed... 

Magnetic separation for ferrous materials eddy-current separation for aluminum electrostatic separation for glass from wastes free of ferrous and aluminum scrap magnetic fluid separation for uouferrous materials from processed wastes... 

Separation of the residual fractions is as follows separation of CFCs by condensation separation of expanded PS and PU foam by air classification separation of iron with a magnetic separator and separation of nonferrous metals with an eddy-current separator. 

Eddy-current separation, 75 435 of nonferrous metallics, 75 455-457 Eddy-current separator, 27 447-448 Eddy-current technique, in nondestructive evaluation, 77 420 Eddy diffusion, 9 658 Eddy viscosity, 77 779 Eddy-viscosity-based models, 77 780 Edecrin, 5 169... 

Nonessential nutrients, 17 645 Noneutectoid steels, 23 218 Nonferrous alloys, vanadium in, 25 525 Nonferrous metallics, eddy-current separation of, 15 455—451 Nonferrous metallurgy niobium in, 17 145 oxygen in, 17 762 slaked lime in, 15 63... 

Load Sampling from the 7.2 Eddy-current Separation 338... 

Figure 21 Working principle of eddy-current separator. (With permission from Ref. 16.)...

There are several designs of eddy-current separators, such as ramp separators and vertical drums. 

The performance of eddy-current separators depends on parameters such as belt speed, rotor speed, and splitter (or splitters) position. Separation is also affected by the characteristics of the feed such as particle size, shape and conductivity, size distribution, density, and moisture. In general, the capacity of eddy-current separators broadly ranges between 1 and 20 tons/hour per 1 m of belt width, depending on the material density and particle size. As electromechanical forces depend on particle size, for efficient separation solid waste stream must be classified into proper size fractions. In general, eddy-current separators process solid waste with particle size between 150 and 3 mm, and, sometimes... 

Eriez, Magnetics Europe Ltd., Eddy Current Separators, Principle and Practice , Brochure No SB 501 UK, p. 1. 

M. Lungu and Z. Schlett, Vertical Drum Eddy-current Separator with Permanent Magnets , Int. J. Mineral Processing, 63, 207-216 (2001). 

To separate aluminum from plastics, gravimetric, densiometric or electrostatic means can be employed. Gravimetric methods have been less favored, mainly because separation depends upon particle size as well as density. It is quite likely that some metal particles will be lighter than the plastic if only because of Uieir small size. On the other hand, it will always be denser. One firm which has used this approach uses an eddy current separator combined with a fluidized bed to effect removal [iS]. 

As the sand usually contains metallic elements such as flashes, pouring drops, pieces of sprue or even small parts of casting, all these have to be removed, at first by means of magnetic iron separators. If separation of the magnetic iron castings is not achieved or not possible, separation may be carried out by Eddy current separators. The residual sand lumps are then broken up. It is important not to cmsh the sand, in order to prevent the demixing of the sand and bentonite. 

A similar eddy current separator operates in the line to process the material of 4-15 mm particle size. 

Aluminum caps are the only other contaminant. Although aluminum has been widely replaced by PE, its separation still requires some development (e.g., hydrocyclones, Eddy currents, conductor/non-conductor electrostatic separation, or active metal detectors). The pilot plant is equipped with the Eddy currents separation. 

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