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Detailed analysis of iron ore beneficiation process

Date:2018-11-14 16:17:39

There are many kinds of iron ores, and different iron ore processing technologies are quite different. Beneficiation technology is to select different beneficiation methods according to the nature of different ores to achieve the best beneficiation effect.
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The following are the common mineral processing technologies for us to summarize:
Ⅰ Magnetic ore
1. Single magnet ore
Most of the iron ore in a single magnetite ore is magnetite, which has the longest production history. Because of its simple composition, weak magnetic separation is often used.
For large and medium-sized magnetic separation plants, when the grinding particle size is greater than 0.2 mm, the first stage grinding magnetic separation is often used; when the grinding particle size is less than 0.2 mm, the second stage grinding magnetic separation is used. If the qualified tailings can be separated from rough grinding, the stage grinding magnetic separation is adopted.
In water-deficient areas, dry magnetic separation with dry grinding is used to dilute rich or poor magnetite ores. Gangue is usually removed by dry magnetic separation, the former is rich in massive ores, and the latter is concentrate obtained by grinding magnetic separation.
In order to obtain high-grade concentrate, magnetite concentrate can be treated by reverse flotation or vibrating fine screen. In order to improve the recovery rate, tailings re election process can be considered for further recovery.
2. Containing polymetallic magnetic ore
Polymetallic magnetite gangue contains silicate or carbonate minerals, often associated with pyrite or chalcopyrite and apatite. This kind of ore also has a lot of mineral processing practice. Generally, the combined process of weak magnetic separation and flotation is used to recover iron, sulfide or apatite by flotation.
Principle processes are divided into two types: weak magnetic separation-flotation and flotation-weak magnetic separation. The direction of conjoints of magnetite and sulfide in these two processes is different. In the former process, conjoints mainly enter iron concentrate; in the latter process, they mainly enter sulfide concentrate. Therefore, under the same grinding size, sulfur content can be obtained by flotation-magnetic process. Low iron concentrate and high sulphur concentrate with low recovery.
Such ores are usually self fluxing. Attention should be paid to maintaining the self fusibility of the concentrate. Others contain higher Mg, some of which are isomorphic and occur in magnetite, so it is difficult to separate them from iron by mechanical beneficiation.
Ⅱ Weak magnetic iron ore
1. Single weak magnetic iron ore
It includes hematite, siderite, limonite and hematite (mirror iron) - Siderite of sedimentary metamorphic, sedimentary, hydrothermal and weathering deposits. This kind of ore has few mineral processing practice, because there are many kinds of minerals, and the granularity is wide.
There are many mineral processing methods, and there are two common methods.
(1) roasting magnetic separation
Roasting magnetic separation is one of the effective ways to select fine particles to (0.02 mm) weak magnetic iron ore. When minerals in ores are complex and it is difficult to obtain good indexes by other methods, magnetic roasting and magnetic separation should be used. The reduction roasting of 75-20mm lump ore shaft furnace has long-term production experience, while the production practice of magnetized roasting furnace for powder ore under 20mm is less. At present, powdered ores are usually selected by strong magnetic separation, gravity separation, flotation or combined process.
(2) gravity separation, flotation, high intensity magnetic separation or combined process.
Flotation is one of the most common methods for separating fine particles to weak magnetic iron ores. There are two principles of positive flotation and reverse flotation. The former is suitable for quartz hematite without easy-to-float gangue, and the latter is suitable for gangue easy-to-float ores, both of which have production practice.
Gravity separation and high intensity magnetic separation are mainly used for gravity separation of coarse (20~2mm) and medium-sized weak magnetic iron ores, heavy medium or jigging separation of coarse and very coarse (more than 20mm) ores, and flow-film gravity separation of medium to fine ores, such as spiral concentrator, shaker, fan chute and centrifugal concentrator, for coarse and medium-sized ores. Dry magnetic induction high intensity magnetic separators are commonly used in high intensity magnetic separation. At present, because the concentrate grade of fine ore is not high and the processing capacity of gravity separation unit is low, a combined process of high intensity magnetic separation and gravity separation is often formed. A large number of qualified tailings are discarded by high intensity magnetic separation, and then the high intensity magnetic concentrate is further treated by gravity separation to improve the grade.
2. Polymetallic weak magnetic iron ore
It is mainly hydrothermal or sedimentary type hematite or siderite containing phosphorus or sulphide. Such ores are generally recovered by gravity separation, flotation, high intensity magnetic separation or their combined processes, and phosphorus or sulfide are recovered by flotation.
Hydrothermal type containing apatite hematite and cupric sulphur siderite can be floatation.
Sedimentary oolitic hematite containing phosphorus can be separated from iron by flotation, but it is often difficult to concentrate into phosphorus concentrate, and the iron recovery rate decreases a lot. It can be considered that after removing large grain gangue, smelting high phosphorus pig iron and recovering steel slag and phosphate fertilizer.
The iron cap of weathered ore deposit contains limonite with non-ferrous metals, often accompanied by copper, arsenic, tin and other associated components without separate minerals. It is difficult to separate iron from ore dressing method. The chlorination roasting method is being studied. In lateritic nickel-chromium-cobalt limonite, there is no single mineral associated with the mineral. The methods of roasting ammonia leaching and segregation magnetic separation are being studied.
Ⅲ Magnetite - hematite (siderite) iron ore
1. Single magnetite - hematite (siderite) iron ore
The iron minerals in the ore are magnetite and hematite or siderite, which are mostly fine-grained; the gangue is mainly quartz, and some contain more iron silicate. The proportion of magnets in the ore varies, from the surface of the deposit to the depth of the deposit.
There are two commonly used methods for such ores:
(1) Weak magnetic separation combined with gravity separation, flotation and high intensity magnetic separation.
In recent years, the series process of recovering magnetite by weak magnetic separation and weak magnetic iron ore by gravity separation, flotation or high magnetic separation has been widely used. In this process, weak magnetic separation-flotation, flotation-weak magnetic separation and weak magnetic separation-gravity separation have been used in production; weak magnetic separation-strong magnetic separation and weak magnetic separation-strong magnetic separation-gravity separation are also under construction. Through production practice, the flotation process tends to be placed before the weak magnetic separation, which is more stable and easy to operate and manage. For the weak magnetic separation-gravity separation process, it tends to be changed to the weak magnetic separation-high magnetic separation or weak magnetic separation-high magnetic separation-gravity separation process.
(2) Parallel process of magnetizing roasting magnetic separation or other methods.
Similar to the magnetized roasting magnetic separation of single weak magnetic iron ore, but in the parallel process of magnetized roasting magnetic separation and other mineral processing methods, the weak magnetic separation is combined with other methods. This parallel process has been put into practice. In addition, the series process of roasting magnetic separation and other methods, i.e. roasting magnetic separation of concentrate by flotation, gravity separation or rotating magnetic field magnetic separation, is also studied to further improve the concentrate grade.
2. Polymetallic magnetite - hematite (siderite) iron ore
The iron minerals in this type of ore are mainly magnetite and hematite or siderite, medium to fine grain inlay; gangue minerals are silicate and carbonate minerals or fluorite; Pyrite, chalcopyrite and rare earth minerals.
The ore dressing method of such ore is the most complicated in iron ore. Generally, the combined process of weak magnetic and other methods is adopted, that is, magnetite is recovered by weak magnetic separation; weak magnetic iron is recovered by re-election, flotation or strong magnetic separation. Minerals and flotation are used to recover companion fractions.
Weak magnetic separation-flotation-strong magnetic separation, weak magnetic separation-strong magnetic separation-flotation and weak magnetic separation-re-election-flotation processes are being studied. For rare earth-containing mixed iron ore, when hematite is used as a large amount in iron ore, there is also a reduction roasting magnetic separation-flotation process, reduction roasting magnetic selection of iron minerals, and rare earth minerals after reduction roasting Flotation has improved the indicator.
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