Iron Ore Beneficiation Technology

Among the many materials used by man, a special role belongs to ferrous metals - alloys of iron with carbon and other elements. Ferrous metallurgy is based on the preliminary smelting of cast iron from ores and its subsequent conversion into steel.

Of the iron ores, the following are of industrial importance:

• Red iron ore. Content of iron oxide Fe2O3 from 60% to 70%
• Magnetic iron ore. The content of iron oxide Fe3O4 is from 55% to 60%.

Russia ranks first in the world in terms of iron ore reserves. The ores are located in the Urals, Kursk region, Western Siberia and other places.

More than 70% of iron ore in Russia is mined by open-pit mining. In open-pit mines, iron ore is mined by blasting and then sent to a beneficiation plant. At the first stage, the ore is crushed, then the ore is separated into large and small fractions on a screen and sent for enrichment. The ore mineral and waste rock are separated, obtaining a concentrate - a product with an increased content of iron oxide. Then the concentrate is mixed with fluxes - limestone or dolomite and coke.

Several methods of ore enrichment are used to obtain concentrate.

1) Flushing.

Washing is most often used for ores formed among clay and sandstone deposits. With this enrichment method, jets of liquid supplied under pressure wash out sandy or clayey waste rock, purifying the ore. Washing of brown iron ores allows increasing their iron content from 38% to 43%. The productivity of this method is not high (up to 100 t/h), which is why it was previously used in small enterprises. Now this enrichment method is used only in combination with other methods.

Washing of iron ores is the simplest method of enrichment. However, it is only possible at temperatures above 0°C. The disadvantages of washing also include the need for a large consumption of water with its subsequent purification.

2) Gravity.

The gravity enrichment method uses special suspensions that have a higher density than the density of the waste rock, but less than that of iron. During the gravity process, the waste rock floats to the surface of the suspension and is removed, and the iron precipitates to the bottom of the separator. The productivity of this enrichment method is up to 250 t/h.

3) Magnetic enrichment.

The main method of enriching iron ore is electromagnetic enrichment. This method is based on the different magnetic permeability of substances.

There are 3 types of magnetic enrichment:

• Dry.
• Wet.
• Combined (dry separation followed by wet separation).

In dry magnetic enrichment, the ore is loaded onto the drums of magnetic separators. Two types of magnetic separators are used. The diagram of a dry belt separator is shown in Fig. 8. The feed belt is fed with

In the wet method, the pulp is fed under special drums with an electromagnet that extracts ferromagnetic minerals from the pulp.

4) Flotation.

The flotation method is based on the difference in the wettability of particles. For enrichment in specialized chambers, a special liquid flotation reagent is fed into the pulp (a suspension of ore particles and water), and then air. Iron particles, combining with air bubbles, rise up into the foam cap, from which they are removed from the device. The waste rock sinks to the bottom of the installation under its own weight. Flotation allows extracting up to 90% of iron from ore, while its content in the concentrate is 60%.

Application of flotation beneficiation method:

• beneficiation of manganese ores;
• finishing of iron ore concentrates;
• additional extraction of metal from tailings after magnetic and gravitational enrichment.

For those tasks that require enrichment of non-magnetic brown and red iron ores, the ore must first be subjected to magnetizing roasting at a temperature of 600-800°C in a furnace with a reducing atmosphere. After such roasting, Fe2O3 partially transforms into Fe3O4 oxide, and then the ore is enriched in a magnetic separator.

During flotation, it is necessary to control the content of certain elements. The ARP-1C flow analyzer can be used to analyze elements in the pulp. The device allows determining elements from Ca to U directly in process flows without sampling (in transport tanks, in the pulp pipeline, etc.) in workshop conditions or at ore-control stations.