Deposits of Nepheline Syenite are found in various parts of the world, major ones being in North America and parts of Europe. Sample testing had shown that a deposit in Iran would be commercially exploitable, so an initial production plant was commissioned. This utilised permanent magnetic separators for purification purposes, but it was found that in practice too much contamination was left in the product. Further tests were carried out using the Master Magnets Induced Roll machine which gave demonstrably better results.

The Induced Roll separator is an electro magnetic machine, the basic principle is that a powerful electro magnet uses a massive iron circuit to induce a magnetic field in a rotating separation roll set between fixed and adjustable magnetic poles. (See Fig. 1)

Magnetic field strengths of over 2 Tesla (20,000 gauss) can be obtained in the operating region of the separator, compared with about 1 Tesla for the best permanent magnetic separators. In operation product for treatment is fed at a controlled rate on to the roll, feebly magnetic particles are attracted to the roll face and clean product is thrown off the face at a normal trajectory. Magnetic material is discharged from the roll face at a point of lower intensity with the aid of a brush. A splitter plate between the two flows keeps them separate. To achieve optimum separation efficiency magnetic intensity, roll gap, roll speed, and splitter position are all adjustable.

Various machine configurations are available, to meet the requirements of the Iran Industrial Design Company a four roll machine was proposed, with each roll 1000mm long. The rolls were arranged in pairs, so that the total flow was split between two rolls in parallel, each of these having a secondary roll to re-treat the product. Using this layout a high degree of cleanliness was possible at a production rate of 8tph. Other configurations are available using 1, 2, or 4 rolls, with roll lengths from 500mm to 1000mm.

Test work was carried out on a laboratory scale version of the Induced Roll, this is identical in all respects to production machines, but it has a roll only 125mm long. Results obtained on this machine can therefore be directly scaled up. Test work of this nature is routinely carried out in the laboratory at Master Magnets to confirm equipment selection. The induced roll separator is now undergoing full operation within the processing plant producing clean Nephelin Syenite free of magnetic impurities.