In the reduction zone iron oxide is reduced by carbon from the coal, with reaction mentioned below
The maximum kiln bed temperature in the reduction zone is about 1060oC with a maximum kiln gas temperature of about 1160oC. Emphasis is placed on maintaining a high ratio of carbon monoxide to carbon dioxide in the kiln bed to achieve a high degree of reduction.
Control of the rate of the heat transfer to the bed and control of the bed temperature are also critical for steady operation of the kiln, the achieve stable process chemistry and favourable reaction kinetics. The hot waste gases leave the kiln of about 800oC.
Solids are discharged from the kiln via a sealed transfer chute in to a sealed rotary cooler. Cooling is achieved by spraying water on the outside shell of the screening and magnetic separation circuits. Pores and fine DRI and char is collected separately which are nonmagnetic in mature.
