The iron ore tailings in China have characteristics such as low grade, small particle size, fine grain size of iron-containing mineral intercalation, complex symbiosis, easy to slime, etc. It causes difficulties to iron tailings re-processing. Under the condition of increasing shortage of iron resources and increasing dependence on foreign countries, it is especially important in strengthening iron tailings re-processing.
Different iron ore tailings re-processing technologies are according to different ore characteristics. The common iron re-processing technologies are single magnetic separation technology, gravity-magnetic separation combined technology, flotation-magnetic separation combined technology, and flotation-magnetic-gravity separation combined technology.
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Iron exists in magnetite, hematite, and limonite with weak magnetic separation in part of iron tailings. The gangue minerals are main quartz, calcite, and other minerals without magnetic. Therefore, iron in tailings can be recovered depending on the magnetic differences. Because of the characteristics of iron tailings, if the indexes of magnetic separation are not ideal, fine grinding can be used for monomer dissociation of iron minerals to increase magnetic separation effort. Magnetic separation is simple without extra pollution, which is wildly used in iron ore tailings re-processing at present.
The iron grade of iron tailings is low. Therefore, pre-concentrating can be used to increase iron grade and remove a number of tailings. Considering the production cost and technology, pre-grinding is not applied for iron ore tailings. Gravity separation can be used for iron pre-concentrating since iron density is greater than gangue minerals. In gravity separation, spiral chute has the characteristics such as small area occupied, without power, large capacity, stable processing course, etc. The spiral chute can be used in pro-concentrating. The coarse concentrates are fine grinded. Strong magnetic minerals are recovered by weak magnetic separation. The tailings of weak magnetic separation are recovered by strong magnetic separation.
Flotation-magnetic separation combined technology can concentrate iron minerals in magnetic separation and increasing iron grade in the flotation process. Desliming and purification can be accomplished at the same time, optimizing the flotation environment. The common flotation technologies of iron tailings are positive anion flotation, anion verse flotation, and cation verse flotation.
Positive anion flotation is suitable for simple iron oxide ores. Cation verse flotation is suitable for complex iron ores. If the feeding grade requirement is high, a stage concentrating is added before flotation to reach good flotation indexes.
Applied flotation-magnetic-gravity separation combined technology in iron recovery, gravity is used as pre-concentrating to increasing ore grade before magnetic separation, and desliming at the same time, increasing magnetic recovery rate. Flotation is used as supplementary means. It can collect interlocked minerals to increase the recovery rate of the whole operation.