Iron ore is one of the important raw materials for the production of pig iron and steel in the iron and steel industry. There are many types of iron ore. According to the magnetic properties of the ore, it is mainly divided into strong magnetism and weak magnetism. In order to improve the efficiency and production capacity of ore dressing and meet the smelting production requirements of iron and steel plants, appropriate and technology should be selected according to the different properties of different iron ore during beneficiation to achieve better beneficiation effects.
The composition of iron ore of a single magnetite type is simple, and the proportion of iron minerals is very large. Gangue minerals are mostly quartz and silicate minerals. According to production practice research, weak magnetic separation methods are often used to separate them. In a medium-sized magnetic separation plant, the ore is demagnetized and then enters the crushing and screening workshop to be crushed to a qualified particle size, and then fed to the grinding workshop for grinding operations. If the ore size after grinding is greater than 0.2 mm, one stage of grinding and magnetic separation process is adopted; if it is less than 0.2 mm, two stages of grinding and magnetic separation process are adopted. In order to increase the recovery rate of iron ore as much as possible, the qualified tailings may be scavenged and further recovered. In areas lacking water resources, a magnetic separator can be used for grinding and magnetic separation operations.
Because magnetite is easily depleted under the effect of weathering, such ores are generally sorted by dry magnetic separator to remove part of gangue minerals, and then subjected to grinding and magnetic separation to obtain concentrate.
The magnetite in the polymetallic magnetite is sulfide magnetite, and the gangue mineral contains silicate or carbonate, and is accompanied by cobalt pyrite, chalcopyrite and apatite. This kind of ore generally adopts the combined process of weak magnetic separation and flotation to recover iron and sulfur respectively.
Process flow: the ore is fed into the magnetic separator for weak magnetic separation to obtain magnetite concentrate and weak magnetic separation tailings, and the tailings enter the flotation process to obtain iron and sulfur.
The common process flow in actual production is: the raw ore is fed into the shaft furnace for roasting and magnetization, and after magnetization, it is fed into the magnetic separator for magnetic separation.
Gravity separation and magnetic separation are mainly used to separate coarse-grained and medium-grained weakly magnetic iron ore (20~2 mm). During gravity separation, heavy medium or jigging methods are commonly used for the gravity separation of coarse and very coarse (>20 mm) ores; spiral chutes, shakers and centrifugal concentrators for medium to fine (2~0.2mm) ores, etc. Reselect method.
In magnetic separation, the strong magnetic separator of coarse and medium-grained ore is usually dry-type strong magnetic separator; the fine-grained ore is usually wet-type strong magnetic separator. Because the grade of concentrate obtained by using one beneficiation method alone is not high, a combined process is often used:
Combination of flotation and magnetic separation: the magnetite-hematite ore of qualified particle size is fed into the magnetic separator for weak magnetic separation to obtain strong magnetic iron ore and weak magnetic tailings, and the tailings are fed into the magnetic separator for weak magnetic separation. In strong magnetic separation, strong magnetic separation tailings and concentrate are obtained, and the concentrate is fed to the flotation machine for flotation to obtain flotation iron concentrate tailings.
Combined gravity separation and magnetic separation: similar to the combined flow of flotation and magnetic separation, only the flotation is replaced by gravity separation, and the products are gravity separation concentrate and tailings. These two combined methods can improve the concentrate grade.
The above are mainly the common separation methods and technological processes of strong and weak magnetic iron ore. The composition of natural iron ore is often not so simple, so in actual production, it is necessary to clarify the mineral composition, and use a single sorting method or a joint sorting method according to the corresponding mineral properties. Only in this way can the beneficiation effect be improved.
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