Dry goods! [Magnetic selection] of iron ore beneficiation technology

Iron ore use

Iron is the earliest found in the world, the most widely used, the most used metal, its consumption accounts for about 95% of the total metal consumption. Iron ore is mainly used for different steel industry, pig iron smelting and steel carbon content. Pig iron is usually divided according to different purposes steelmaking pig iron, foundry pig iron, pig iron alloy. Steel is divided into carbon steel and alloy steel according to the composition elements. Alloy steel is a steel that is intentionally added with an appropriate amount of one or more elements to improve or obtain certain properties on the basis of carbon steel. There are many types of elements added to steel, mainly chromium , manganese , vanadium , titanium , Nickel , molybdenum , silicon. In addition, iron ore is also used as a catalyst for the synthesis of ammonia (pure magnetite), natural mineral pigments (hematite, mirror iron ore, limonite), feed additives (magnetite, hematite, limonite) And precious stones (magnets), etc., but in small amounts. Steel products are widely used in all aspects of the national economy and people's lives, and are essential materials for social production and public life. Since the invention of the converter steelmaking method in the mid-19th century, steel has been the most important functional structural material, and it has occupied a very important position in the national economy. It is an important pillar industry for social development and the most modern industrial industry. Important and most used metal materials. Therefore, people often regard the output, variety and quality of steel as an important indicator to measure the development level of a country's industry, agriculture, national defense and science and technology.

Mineral processing method - magnetic separation

Magnetic separation is one of the main methods for selecting iron ore. Magnetic separation is divided into weak magnetic separation and strong magnetic separation . Weak magnetic separation is mainly used for sorting magnetite minerals such as magnetite and vanadium-titanium magnetite. Strong magnetic separation is mainly used for sorting with hematite. The main weak magnetic minerals, individual siderites, limonites also use strong magnetic separation equipment to simply throw the tail to restore the geological grade and then sell.

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.

Figure 1 Flow chart of mineral processing principle (1)

Figure 2 Flow chart of mineral processing principle (2)

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. There are few mines with weak magnetic iron minerals. Most mines use strong magnetic separators as pre-spinning equipment. In the various stages of crushing and grinding, the qualified tailings are thrown away. Under the premise of ensuring metal recovery rate, It is possible to improve the grade of coarse concentrate and 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.

In the sorting of weak magnetic iron ore and mixed iron ore , the use of strong magnetic separation technology to abandon the qualified tailings in advance, not only significantly reduce the amount of grinding in the next stage, the energy saving effect is significant, but also to improve and stabilize people The grade of the coarse concentrate is preliminarily removed from the slime that affects the flotation, and the flotation operation process is guaranteed to go direct. The most common beneficiation process in China's Anshan-type fine-grained (magnetic) iron ore is: a small amount of magnetite is selected by weak magnetic separation to avoid the magnetic blockage of the strong magnetic separator, and the strong magnetic separator discards the qualified tailings. The crude concentrate grade will be increased to about 45%, and the weak magnetic and strong magnetic mixed concentrate will be reverse floated to obtain high quality iron concentrate. This process has become the classic of sorting the Anshan iron ore in China. Process.

The mineral composition of the Qidashan iron ore in Anshan Iron and Steel Co., Ltd. is relatively simple, with pseudo-hematite, magnetite and quartz as the main minerals, and other mineral components are less . Qi Dashan Iron Ore Dressing Plant adopts stage grinding-rough subdivision-re-selection-magnetic separation-anion reverse flotation process, in which one section of grinding-0.074mm accounts for 60%, and the second section of grinding-0.074mm accounts for 85%. The ore of the powder ore bin is fed into a closed-circuit grinding consisting of a ball mill and a hydrocyclone, and the graded grit is returned to a section of the grinding machine, and the graded overflow is fed into the coarse subdivided cyclone to be classified into two materials. The coarse-grained material is fed into the re-election operation, and finally the re-elected concentrate is produced; the fine-grained material enters the magnetic separation operation composed of weak magnetic separation-high gradient and strong magnetic separation, and the primary mud and the secondary mud in the grinding product are taken off. . The mixed concentrate obtained by the magnetic separation operation is fed to the flotation for anion reverse flotation. The operation is a coarse and a fine three sweep, the collector is LKY, and the inhibitor is carboxymethyl starch. The fine-grained material contains 29% of iron grade. Through the weak magnetic-strong magnetic-reverse flotation combined process, 67% iron concentrate grade can be obtained, and the re-election concentrate and maglev concentrate are combined to become the final concentrate. In 2007, the production index of Qidashan Concentration Plant was: 28.26% of the original ore grade, 67.60% of the concentrate grade, 9.74% of the tailings grade, and the recovery rate of 82.73%.

The Anshan Iron Mine in Anshan Iron and Steel Co., Ltd. is a typical lean red iron ore with low grade, fine grain size and complex structure . Mainly iron minerals martite, magnetite, hematite, limonite secondary minerals, siderite, gangue minerals quartz, chlorite-based phosphor, a small amount of iron amphibole, actinolite, tremolite, calcite. Donganshan Sintering Plant adopts two-stage continuous grinding-coarse subdivision-middle-mine re-grinding-re-selection-magnetic separation-anion reverse flotation process. The final grinding fineness of the second section is -0.074mm, accounting for 80%. Grinding fineness -0.074mm accounted for 71%. The overflow of the secondary grinding enters the cyclone for coarse subdivision, the coarse material is fed into the re-election operation, and finally the re-election concentrate is produced; the fine-grained material adopts the weak magnetic separation-strong magnetic-anion reverse flotation process, The grade of iron concentrate increased from 31.36% to 66.42%. The coarse-grained re-concentration concentrate and the fine-grained flotation concentrate are combined to form the final concentrate. The production index of Donganshan Sintering Plant is: 31.73% of the original ore grade, 64.80% of the concentrate grade, 16.05% of the tailings grade, and the recovery rate of 74.92%.

Baotou Steel Concentrator handles the poor oxidized ore in Bayan Obo . The iron minerals are mainly hematite and magnetite, followed by pyrite. The gangue minerals are mainly fluorite and carbonate minerals, followed by feldspar. , barite, etc. The grinding production process of Baotou Steel Concentrator is a three-stage and two closed-circuit grinding grading process, one section is rod grinding, the second section is lattice type ball mill, the third section is overflow type ball mill, and the grinding fineness is -0.174 mm accounted for 90%. Under the condition of -95%, the minerals are sorted according to the magnetic strength by simple weak magnetic separation-strong magnetic separation, and rationally grouped to obtain iron-rich weak magnetic separation and strong magnetic separation concentrate, rich in rare earth. The strong magnetic medium mine, and the removal of mineral mud and non-magnetic gangue minerals accounting for about 40% of the original ore. Weak magnetic separation and strong magnetic separation of mixed concentrates using sodium silicate as inhibitor, hydrocarbon-based sulfonic acid and carboxylic acid collector for reverse flotation, removal of fluorine, phosphorus and other carbonates, phosphate minerals, flotation The process is a rough and two fine. The ore grade was selected to be 31.85%, and the iron concentrate grade was 62.51%, and the recovery rate was 71.48%.

The main minerals in the iron ore processed by Hainan Iron and Steel Company's 1.1 million tons/year concentrator are mainly hematite (including specular iron or pseudo-hematite), a small amount of magnetite, limonite, and other small or trace metals. minerals include pyrite, copper ore, pyrrhotite and the like. The gangue minerals are mainly quartz, others are chlorite, biotite , sericite and the like. After two sections of closed ore grinding, the ore enters a weak magnetic separation condition under the condition of grinding fineness -0.074mm accounting for 90%, and the ferromagnetic tailings are selected by strong magnetic separation and weakening. After the concentrated magnetic concentrate is concentrated, the anti-flotation desulfurization and desiliconization are carried out. In the case of the original ore grade of 47.63%, the iron concentrate with a grade of 64.50% and an iron recovery rate of 71% is finally obtained.

Iron concentrate quality standard