India is the world's largest producer of sponge iron, most of which is produced primarily through the coal based method of production. Growth in the sponge iron production can be attributed largely to the popularity of secondary steelmaking route, which has shown a phenomenal growth in India. This has been mainly due to the lower investment cost of the EAF/Induction Furnace as compared with the integrated blast furnace--oxygen converter route and also because of its greater flexibility of product mix.The production of coal based sponge iron in year 2013-14 in India was 15 Million Tonne though it is hardly 55% capacity utilization of the installed capacity of more than 27 Million Tonne per Annum. The main reasons attributed for this low capacity utilization has low avaibility of Iron Ore and Non-Coking coal but with the new amendments in MMDRA Act,2015 this situation is expected to change and so shall be the capacity utilization. mix.
The process of sponge iron manufacturing involves removal of oxygen from iron ore. When that happens, the departing oxygen causes micro pores in the ore body, turning it porous. When the eventual product is observed under a microscope, it resembles a honeycomb structure, which looks spongy in texture. Hence the name sponge iron.
Sponge iron is an iron source relatively uniform in composition, and virtually free from tramp elements. It is used increasingly in Electric Arc and Induction furnaces to dilute the contaminants present in the scrap used in these processes. It has an associated energy value in the form of combined carbon, which has a tendency to increase furnace efficiency. For captive DRI production facilities, there is an added advantage that the delivery of hot DRI to the furnace can reduce energy consumption to 16 - 20%. Some of the inherent advantages of using Sponge Iron in comparison to Scrap are as under :
More Volumetric Weight : Considerably higher (10-100%) than other types of scraps.
Consistent Chemical Analysis : Avoids product quality deviations, residual element free.
Continuous Charging : Eliminates scrap recharging; consistant power loading during melting.
Reduced Flicker & Noise Level : Significant reduction in noise and flicker than that of scrap.
Reduced Nitrogen content : Lower nitrogen level (~20 ppm) for 100% DRI.
Better Bath Stirring : Highly effective bath stirring due to CO boiling.
Foamy Slag : Easy Generation of foamy slag.
Considerably higher (10-100%) than other types of scraps. Various properties of sponge iron typically sold by SSIPL are :
0.10% to 0.20% (approx.)
3-20 mm:95% Below 3 mm:5%
0-3 mm with -1mm:30% Max