A building structure is incomplete without the right set of resources. There are many different resources involved in the construction of a building but the most important resource is the reinforced steel bar. The types of reinforced steel bar grades are Fe 415, Fe 500, Fe 550, Fe 600. The manufacture of steel begins with the steel making process, in which pig iron is purified and alloyed to make ingots.
One major part in steelmaking is the ironmaking process which is the production of iron from its ore. Normally it is done using Blast Furnaces but the problem involved was even though blast furnaces has its advantages, they are quite expensive and consumes more energy in its running and produced by-products that are not environment-friendly. As an alternative to the conventional blast furnace process, the smelting reduction process, based on smelting reduction technology was developed. The Corex process was is one such initiative.
The Alternative Ironmaking
The coal reduction process or simply COREX process was developed by Simens VAI as an environment-friendly alternative to the blast furnace. This process mainly differs from blast furnace process because unlike blast furnace which uses coke, Non-coking coal is used as the energy source and reduction agent in Corex. Also, the iron ore which contains up to 80% of lump ore can be directly supplied as input to the process.
Unlike Blast furnace which uses Nitrogen as a hot blast of air, In the corex process, pure oxygen is used as the hot blast, thereby eliminating nitrogen emissions. The most interesting feature of the Corex process is the separation of iron reduction and smelting operations into two separate reactors, which are reduction shaft and melter-gasifier, therefore it is a two-stage process.
The Iron ore is directly charged into the reduction shaft along with limestone and dolomite additives. The materials then descend in the reduction shaft by gravity. The temperatures of reduction gas are normally between 800-850C and with a pressure of 3 kg/sq cm. This reduction gas moves to the top and exits the shaft at temperatures between 250-300C. The metallization degree of the DRI and the calcination of the additives strongly depend on four factors which are:
- Reduction gas temperature.
- Reduction gas amount & quality.
- Iron-bearing burden reducibility.
- Average particle size and distribution of the solids.
The iron-bearing materials are directly reduced to above 90 % metallization in the shaft. It is termed as direct reduced iron (DRI). This DRI and partially calcined additives are discharged into the melter-gasifier from the reduction shaft via speed controlled six discharge screw conveyors.