Iron is a metal, and is not found in its pure state in nature, but is part of numerous minerals, the most used ones for obtaining iron are oxides like hematite and magnetite, also limonite, which is an iron hydroxide, and siderite or iron carbonate.

In this article we will briefly mention the processes involved in obtaining iron. After the blasting and hauling part, the ore submit to the processes mentioned below:

Crushing and grinding.

The purpose of crushing is to reduce the size of minerals. This stage of the process can be carried out dry, in machines called crushers, mostly of the gyratory type.

The milling can be wet or dry type, for this process rotating mills are used.

The difference between crushing and grinding is in the size of the materials obtained in each process: in grinding the ore is obtained in smaller particles than in the crushing.

Classification.

Separation of the material obtained in the previous processes by similar sizes, mostly a screen that separates the material by size is used, resulting in a separation of those materials that pass through a mesh and those that do not pass.

Concentration.

On this stage the separating of the objective mineral from other elements take place, the most used procedures for this purpose are:

  • Flotation: The particles of different materials are separated using reagents, causing the target mineral to float from the aqueous solution, attached to air bubbles, the other elements form the ore precipitate to the bottom of the flotation cell.
  • Magnetic separation: A material with magnetic properties such as iron can be separated from the slag by applying a magnetic field. The magnetic particles that enter this field are attracted to the lines of forces, and migrate to the region of higher density, this is the basis of the magnetic separation.

 

Pelletization.

If the ore has a low content of impurities (mainly phosphorus and sulfur), it can be used for direct loading to blast furnaces, requiring only milling and concentration treatments. But if the content of impurities is relatively high, the grinding and concentration process take place too, but a chemical pelletizing process is also required, where these impurities are significantly reduced.

Pelletization is a process consisting of the agglomeration of finely ground ore or a concentrate by the addition of additives, binders and a certain amount of water to form spherical particles which are hardened by firing in rotary kilns.

Briquetting.

For this process granular iron sponge is obtained, from the reduction of the ore in rotary kilns and passed through a roller press to mold it in the form of briquettes, which will later be used as a metal filler in electric furnaces for the manufacture of steel.

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