Iron ore beneficiation - magnetic separation

A weak magnetic selection

China's ferromagnetic iron ore accounts for 52% of iron ore reserves (including magnetite ore accounting for 35% of China's iron ore reserves and vanadium-titanium magnetite ore accounting for 17%). The vast majority are single weak magnetic separation process, a small number of micro-fine disseminated magnetite beneficiation plant further reverse flotation of iron ore in order to obtain high-quality iron ore, and therefore highly weak magnetic field in iron ore processing Pay attention to it.

Weak magnetic separation sorting process mainly uses stage grinding-stage magnetic separation to throw qualified tailings in each grinding stage to minimize the amount of regrind in the next stage, to achieve energy saving and increase ore dressing. The goal of the factory's economic efficiency. Most magnetite ore dressing plants in China use two-stage or three-stage grinding and stage sorting process, that is, after each stage of grinding operation, a single-dissociated gangue is thrown by a magnetic separator or a dewatering and magnetic separator. Minerals and coarse concentrates will be re-selected in the next operation, which can reduce the grinding ore dressing in the next stage, save energy consumption and ball consumption in more than half, and reduce iron mineral over-grinding, which is beneficial to improve iron recovery rate. . Bengang Shantou Iron Mine Concentrator After a period of self-grinding (particle size -0.774mm accounted for 47%) CTB-1232 magnetic separator was used instead of magnetic dewatering tank for rough selection, throwing a yield of 50.25%, iron grade 6. 25% of coarse tailings, the configuration of the self-grinding machine and the second-stage ball mill changed from 1:1 to 2:1, and the annual economic benefit was 16 million yuan. After a section of ball milling (granularity 0.074mm, 53%), the Taigang Yankou Iron Ore Concentrator was rough-selected by CTB1024 magnetic separator, and the coarse tailings with a yield of 49.40% and an iron grade of 13.80% were thrown. The configuration of the two-stage ball mill is 3:2.

Fine screening and re-grinding technology is one of the effective ways to improve the grade of concentrate iron. The first to use this technology in industrial production is the Erie concentrator in the United States. In the 1970s, China first applied it at the Dagushan concentrator in Anshan Iron and Steel Co., Ltd., increasing the iron grade of concentrate from 62% to 65%. China's magnetic separation plant has been promoted and applied. The fine screening equipment used at that time was a nylon vibrating fine screen, and the screening efficiency was low. Currently, Derrick high-frequency fine screen, MVS high-frequency vibrating screen and GPS type high-frequency vibrating fine screen are widely used. As the concentrate screening equipment , the fine sieve is mainly used to screen out the coarse-grained lean bodies in the magnetic separation concentrate and re-grind the sieved products to improve the iron grade of the magnetic separation concentrate. The sifted product can be returned to the system for re-grinding, or a separate grinding machine can be used for re-grinding. A typical weak magnetic separation process is shown in Figures 1 to 3.

B strong magnetic selection

Strong magnetic separation is mainly used for sorting weak magnetic iron minerals mainly composed of hematite. In 1968, the German Humbold DP317 Jones wet magnetic separator was successfully developed and widely used in Brazil, Norway, Liberia, Canada, Spain, the United States, Sweden, etc. for the treatment of iron oxide ore. In 1975, China's Shp-type strong magnetic separator was successfully used in industrial production, rewriting the history that China's weak magnetic iron oxide ore could not be applied on a large scale without roasting. Strong magnetic separation has gradually become the main means of weak magnetic iron ore beneficiation. In recent years, with the continuous improvement of the magnetic field strength of electromagnetic strong magnetic equipment for sorting fine-grained iron ore and the successful industrial application of permanent magnet magnetic equipment, strong magnetic separation technology is playing an increasingly important role in the beneficiation of weak magnetic iron ore. The role. However, since the iron minerals embedded in the fine particles are not completely in the dissociation state of the carcass, the large amount of the living body enters the magnetic separation concentrate and the magnetic inclusions cause the quality of the iron concentrate to be not high, so the single strong magnetic separation process is used for sorting. weakly magnetic minerals iron mines less, most mines are employed as a pre-intensity magnetic separator tailing device, in addition to passing the tailings thrown in various stages of crushing grinding, the premise of ensuring metal recovery, Improve the grade of coarse concentrates as much as possible to provide high quality raw materials for subsequent operations. A small number of mines dominated by limonite and siderite are difficult to obtain high-quality iron concentrate due to the difficulty in sorting ore. It is easy to sell at low prices after simple pre-selection of strong magnetic equipment.

Figure 1 Flow chart of mineral processing principle (1)

Figure 2 Flow chart of mineral processing principle (2)

Figure 3 Flow chart of mineral processing principle (3)

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