Sponge Iron Plant
The main plant consists of a 4 mtr. Dia x 84 mtr. Long ported rotary kin (DR 1) and 4.8 mtr. Dia x 84 mtr.long ported rotary kin (DR 2) equipped with air injection system to provide for generation of necessary heat and reducing atmosphere required for the process. A mixture of sized iron ore and sized coal along with flux (limestone/dolomite) is charged in proportion through material handling systems into the rotary kiln. Coal acts as the reductant to romove oxygen from iron ore. The process of reduction causes micro pores in the ore body turning it porous. Directly reduced iron looks like sponge in texture due to pores and hence is called sponge iron. Iron Ore after due reduction inside the kiln is discharged to a rotary cooler of 3.5 mtr. Dia x 50 mtr long from DR1 and 3.8 x 50 mtr long from DR2 for cooling the DRI from 10000C. The DRI (metallic) and the non metaliks like unused coal, coal ash etc. discharged from the cooler and conveyed by the conveyers to a product processing building where screens and magnetic separators are provided for separation of magnetic and non magnetic elements and screening of DRI for lumps and fines. Cooling of the DRI is carried out by indirect cooling method i.e. spraying of water on the outer surface of the cooler. For the main plant the utilities like water system, compressed air system are provided. The off gas going out of the kiln is passed through a After Burning Chamber, Boiler, ESP & Stack.
The main equipment is the induction furnace. Three electrical systems with 4 nos of crucible of 8.5T and two crucibles of 10T capacity each have been set up. The Induction furnace uses about 75% to 80% of DRI. These are essentially melting units for which good quality metallics are used. The plant is equipped with 2 nos of 20/5 T cranes to facilitate charging through magnet and liquid steel handling. Liquid steel from the induction furnace is tapped at about 1600oC and after necessary homogenization in the ladle is taken to the caster for casting. The Caster is of 4 mtr. Radius with 2 strands capable of casting 10 T metal in 25 minutes. The plant is also equipped with water treatment plant and emergency cooling water system
The captive power plant was planned to utilize the sensible heat contained in the kiln waste gas of the sponge Iron Plants. It is estimated that from the quantity of energy available in the waste gas of the kilns about 42 T per hour of steam could be generated in the first power plant and 50 T per hour of steam can be generated from the second power plant. Hence,the Turbo Generator selection for the first power plant was done at 12 MW and 24 MW for the second power plant. The plant comprises of the following major units:
- Waste Heat Recovery Boilers (WHRB) 2 nos
- Atmospheric Fluidised Bed Combustion Boilers (AFBC) 2 nos
- Turbo Generator Units (TG) 2 nos