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There are many kinds of iron ores in the nature, so the iron beneficiation methods also vary. According to the iron ore features, different iron extraction processes used to deal with different iron ores can obtain the best mineral processing index.
Here are some common methods used in the beneficiation of iron ore:
The majority of iron minerals in the single magnetite ore are magnetite with simple composition, which is often processed by weak magnetic separation method for the beneficiation of iron ore.
For the large and medium-sized magnetic separation plant, using one stage grinding, magnetic separation method when the grinding particle size is greater than 0.2 mm. using two stage grinding, magnetic separation method when the grinding particle size is less than 0.2 mm. Using the stage grinding, magnetic separation method if the qualified tailings can be separated by rough grinding.
Dry grinding and dry magnetic separation method are often used in water-deficient area. For the rich magnetic iron ore that been diluted or the lean magnetite, using the dry magnetic separation method to remove gangue minerals. After that, the concentrate is obtained by grinding, magnetic separation.
In order to obtain high grade concentrate, using the reverse flotation or shock screen to deal with magnetite concentrate. In order to improve the recovery rate, tailings reprocessing process can be considered for further beneficiation of iron ore.
The gangue minerals of polymetallic magnetic iron contain silicate or carbonate minerals, and are often associated with polygonum cobalt pyrite, chalcopyrite and apatite. Generally, using the weak magnetic separation and flotation combined process for the beneficiation of iron ore, that is, using the weak magnetic separation to recover the iron, and using the flotation to recover sulfide or apatite.
The principle flow of polymetallic magnetic iron ore beneficiation process is divided into two types: weak magnetic separation-flotation method and floatation-weak magnetic separation method. The directions of the aggregate of magnetite and sulphide in these two processes are different. In the former process, the aggregate mainly enters the iron concentrate. In the latter process, the aggregate mainly enters the sulfide concentrate. Therefore, under the same grinding size, flotation first and magnetic separation later can obtain the iron concentrate with lower sulfide content and the sulfide concentrate with higher recovery rate.
This kind of ore is featured with self-melting, which should pay attention to maintain the self-melting of concentrate. Some of them contain high MgO content, some MgO occur in magnetite as the isomorphism, so it is difficult to separate them from iron by mechanical processing.
It includes metamorphic, sedimentary, hydrothermal and weathered typed hematite, siderite, limonite and hematite (specularite)-siderite.
This kind of ore has many kinds, and wide range of disseminated size. There are two main processes used in the beneficiation of iron ore.
Roasting magnetic separation is one of the effective methods to separate weak magnetic iron ores from fine particles to micro-fine particle (<0.02mm). When the mineral in the ore is complex and it is difficult to get good index by other mineral processing methods, the magnetization roasting magnetic separation method can be used. The vertical furnace reduction roasting has been widely used in the ore (75-20mm) , the magnetizing roaster is rarely used in the powder ore (less than 20mm). At present, strong magnetic separation, gravity separation, flotation method or combined process are often used to separate powder ores for the beneficiation of iron ore.
Flotation is one of the common methods used to separate weak magnetic iron ore from fine particle to micro-fine particle, which include positive flotation and reverse flotation wo kinds of processes. The positive flotation is suitable for quartz hematite without floating gangue, while the reverse flotation is suitable for the ore with floating gangue.
Gravity separation and strong magnetic separation are mainly used to separate coarse (20~2 mm) and medium-grain weak magnetic iron ore. The gravity separation used in the coarse and very thick (>20 mm) ore commonly include heavy media process or jigging process. The gravity separation equipment used in the medium-grain and fine-grain includes spiral concentrator, shaking table, pinched sluice and centrifugal concentrator. The strong magnetic separation equipment used in coarse and medium-grain includes high-intensity magnetic separators, the warm induction medium strong magnetic separator is used in the fine-grain particles. At present, the strong magnetic separation concentrate grade of fine ore is low and the unit of processing capacity by the gravity separation is not high, a combined process of strong magnetic separation and gravity separation is often adopted, that is, using the strong magnetic separation to discharge a large number of qualified tailings, and then using the gravity separation to further deal with strong magnetic concentrate improving the grade.
It mainly includes hydrothermal-type and sedimentary type phosphorus or sulfide containing hematite or siderite, which are often processed by gravity separation, flotation, strong magnetic separation or combined processes for the beneficiation of iron, and then the flotation is used to recover the phosphorus or sulfide.
The iron minerals in the ore are magnetite and hematite or siderite, which are often embedded in fine grains. Gangue is mainly quartz, some contain more iron silicate. The proportion of magnet in ore varies from surface to depth.
There are two kinds of magnetic iron-hematite or magnetic iron-siderite beneficiation processes used for beneficiation of iron ore.
In recent years, using the weak magnetic separation to recover magnetite and using the gravity separation, flotation or strong magnetic separation to recover weak magnetic iron, which are widely used in the beneficiation of iron ore. In this process, weak magnetic separation-flotation, flotation-weak magnetic separation and weak magnetic separation-gravity separation have been widely used for the beneficiation of iron. Through production practice, it is better to put flotation before weak magnetic separation in the weak magnetic separation-flotation process, which makes the production more stable, easy to operate and manage.
Like magnetizing roasting magnetic separation of single weak magnetic iron ore, but in the parallel process of magnetizing roasting magnetic separation and other dressing methods, the powder ore adopts the combination of weak magnetic separation and other methods. This parallel process has been in production practice. In addition, the series process of roasting magnetic separation and other methods is also studied, that is, the concentrate of roasting magnetic separation is selected by flotation, gravity separation or rotating magnetic field magnetic separation, etc., to further improve the grade of concentrate, which has not been used in the beneficiation of iron ore at present.
2) Polymetallic Magnetic Iron-Hematite or Magnetic Iron-Siderite Beneficiation Process
The iron minerals in this ore are mainly magnetite and hematite or siderite, medium to fine grain embedded. Gangue minerals are silicate and carbonate minerals or quartz. The associated components are apatite, pyrite, chalcopyrite and rare earth minerals.
The process used for beneficiation of iron ore of this kind of ore is the most complicated one in iron ore. Recovery of weak magnetic iron ore by gravity separation, flotation or strong magnetic separation and recovery of associated components by flotation.