Magnetic separation - Theory and modeling

The magnetic separation of ores underwent rapid industrial development at the beginning of the 20th ^e century, with separators operating mainly in the dry process. It wasn't until the 1960s-1970s that the first high-tonnage industrial applications of magnetic field separation were developed. In this case, the wet process is used, enabling finer particles to be treated than in the dry process. The most notable example is the Jones-type carousel separator.

Over the past two decades, the performance of magnetic separation has improved, and the technique has become increasingly used in the recovery of raw materials. This has been due, on the one hand, to the development of ceramic permanent magnets with high specific energy, which have found applications in low- and high-intensity dry process separation, but also to the appearance of separators that use a ferromagnetic extraction matrix placed in the intense field produced by a copper or superconducting coil. The materials to be treated are then subjected, in the matrix, to magnetic energy gradients sufficient to separate particles of low magnetic susceptibility and small particle size. This is known as high-gradient magnetic separation (HGMS), and separation is carried out wet. The carrier liquid for solid particles is usually water.

The phenomena occurring within the extraction matrix of high-gradient, high-magnetic-field separators initially lead to the retention of at least some of the particles transported by the liquid introduced into the system. Over time, the matrix becomes progressively saturated and loses its effectiveness more or less rapidly, thus limiting the separator's performance. The matrices generally used are in the form of toothed plates, balls, foam or iron wool, which complicates the determination of the various flows and magnetic forces involved.

The complete study of the subject includes the articles :

• J 3 220 "Magnetic separation: theory and modeling" (this article) ;

• J 3 221 "Low and high intensity magnetic separation" ;

• J 3 222 "High gradient magnetic separation (HGMS) and high field" ;

• J 3 223 "Magnetic separation: economics and special applications" ;

• Doc. J 3 224 "Magnetic separation. Find out more".