Pelletizing#Pelletizing of iron ore
A pellet is a hard porous ball of typically 8-18 mm in diameter, containing about 67 % -72 % Fe and various aggregates. Pellets are made from iron ore and serve in the production of pig iron as a raw material for the blast furnace process or the direct reduction.
Sifted and ground ore is rolled together with water, binder and aggregates into green pellets, which are then cured in a burning process. As the binder, bentonite is usually used, the aggregates are in accordance with the desired chemical properties of either limestone, dolomite or olivine.
The pellets can be done in three different investment types:
- Shaft furnace
- Traveling grate
Pellets are used in the production of pig iron. They have several advantages over other forms of raw materials such as iron ore concentrate or fine:
- The raw material can be transported better by the uniform shape, and store because it can not absorb moisture and will remain in heat in silos.
- In the preparation of the composition of the pellets can be well controlled, so that a single raw material is formed, which facilitates the control of the subsequent processing process.
- The porosity of the pellets in the furnace accelerates the chemical reaction, while the mechanical strength is maintained even under the thermal load. This prevents the material cakes in an oven, and the reduction gas can not freely rise through the raw material.