Low Grade Iron Ore Benefication

Iron and steel industry is challenged by ever increasing commodity prices and a consequent need to reduce the capital and operation costs, besides meeting environmental regulations which get more stringent with time. The low grade iron ore has to be beneficiated for further processing.

The need for beneficiation / concentration stages is due to the fact that through simple processes of separation by size one cannot obtain products with high Fe. In general, silica, alumina and other pollutants get liberated with finer fractions. This characteristic permits the crude fraction to generate a final product with a natural segregation of impurities.

Beneficiation is processing the ore to regulate the size of the product thereby remove unwanted constituents to improve Fe. Basically the process involves crushing the rock to a fine-grain size, then mechanically removing the iron minerals from the waste material. Magnetite can be removed from the siliceous waste materials by electromagnets. Hematite requires a more sophisticated process for concentration by physical and chemical separation.

Beneficiation includes selection of effective crushing and grinding technologies, wet and dry beneficiation, and the control of moisture levels in material.

A wet beneficiation plant for producing high-grade iron ore concentrate requires screens, grinding Mills, spirals, hydrosizers/hydrocyclones, magnetic separators, Agitators, Floatation, Filters and thickeners.

Screens

The screen is a surface with multiple apertures of given dimensions. Material of mixed size presented to that surface will either pass through or be retained, according to whether the particles are smaller or larger than the governing demensions of the aperture. The efficiency of screening is determined by the degree of perfection of separation of the material into size fractions above or below the governing dimensions of the aperture.

Grinding Mills

Grinding mills with spherical Ball charge are used in mineral processing plants to grind coarse concentrates and middlings. Final concentrates and tailings are separated after grinding mills and fed with material that has already been ground and treated in one or more processing steps. In the grinding mill relatively small sized balls are used. They can be operated in both open and closed circuit. The purpose of grinding and regrinding is to reduce the ore to a size small enough to liberate and recover the valuable minerals. Closed circuit grinding minimizes over grinding of very friable ore normally found in the ore bodies of our region. The more the recirculation load the less is the over grinding of particles. For this application, 100% load is maintained. The grinding process achieves two goals, 1st the particles are crushed to achieve the liberation size for upgrading and 2nd the particles must be fine enough such that after combining them with the deslimed minus 0.150 mm fraction, the product will have the blaine needed for pelletizing.