JOURNAL PAPER

Optimizing the performance of wet drum magnetic separators

M. Dworzanowski

Anglo American Technical Division

SYNOPSIS

The difference in the magnetic properties of minerals is the basis for magnetic separation. All minerals can be generally classified as ferromagnetic (strongly magnetic), paramagnetic (weakly magnetic) or diamagnetic (non-magnetic). Magnetic separation can be conducted dry or wet. The majority of the applications of wet magnetic separation in the mining industry are based on the wet drum magnetic separator. The wet drum magnetic separator has been in use for over 50 years and its design is based on a rotating drum installed inside a tank. Inside the drum are stationary, permanent magnets arranged in an arc to provide the magnetic field. These magnets can be of the ceramic ferrite type providing a low intensity magnetic field or of the rare earth type providing a high intensity magnetic field. Wet drum magnetic separators are generally applied in three different ways, namely to recover and recycle the medium used in dense medium separation (DMS), to remove magnetic contaminants from ores and concentrates, and to recover valuable magnetic products. Wet drum magnetic separators are applied in the following commodity areas: coal, diamonds, iron ore, chrome, platinum, heavy mineral sands, industrial minerals, and base metals. Whereas the design and operation of wet drum magnetic separators is relatively straightforward, it is very often found that the performance of wet drum magnetic separators is far from optimum. The reason for this is generally a lack of understanding of how the different design and operating variables interact and how they affect performance. This paper examines these variables, describing their importance and impact for all applications of wet drum magnetic separators. It also provides clear guidelines on how to adjust and control these variables so that optimum performance is achieved.

Keywords: Magnetic separation, ferrite and rare earth magnets, magnetite and ferrosilicon recovery, magnetic flocculation, demagnetization

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