Magnetic Separation

摘要

Large-scale magnetic separation processes became viable with the advance of commercial permanent magnets in the 1940s. Magnetite ores could then be efficiently processed at low cost. Weakly magnetic, relatively high-value minerals could be processed by the turn of the 19th century with low-capacity electromagnetic separators and from the 1930s with induced roll electromagnetic separators. Thirty years later, high-intensity magnetic separators for high-capacity processing of non-magnetite iron ores became available, complementing other beneficiation methods. Shortly thereafter, high-gradient versions of high-intensity magnetic separators were developed, impacting the kaolin clay processing industry and later some other minerals applications. More recently, a further version of the high-gradient magnetic separator (HGMS) type has benefitted the non-magnetite iron ore industry. In 1981, the first high-intensity magnetic separator based on powerful rare-earth magnets was developed and with further advances changed the industrial minerals industry. Superconducting magnets for ore processing were introduced in commercial scale in the early 1980s and later generations changed the kaolin clay processing industry again. The paper will give an overview of the historical developments of magnetic separation for minerals, the impact on the ore processing industry as well as major application examples. An overview of designs is included, but detailed explanations of the operational features and comparisons will be given only as examples because some technologies tend to replace prior art and the interested reader may easily find plenty of literature on such subjects. Other important magnetic separation uses, such as removal of tramp iron, metals recycling and filtration of waste water are not included.