Smelting of iron ore fines with non-metallurgical fuels and blast additives: experimental trials for ten years in low-shaft furnace

Deposits of high grade iron ores are more or less well dispersed in India. The reserves of coking coal are limited and occur over a narrow geographic region. In order to find out the possibilities of production of foundry grade iron, extensive investigations were conducted in the Low-shaft Furnace of National Metallurgical Laboratory with raw materials sent by the State Governments of Andhra Pradesh, Punjab, Maharashtra (with non-coking coals), Rajasthan, Maharashtra (with titaniferous ore and low-temperature carbonized coke); and Government of Nepal, apart from the raw materials collected by the laboratory, Trials were conducted with Assam high sulphur coal in blended coke, low-temperature carbonized coke made from Talcher coals; and limestones from Tamil Nadu and Rajasthan. For these trials, iron ore fines were smelted employing non-metallurgical fuels, such as raw coal, low-temperature carbonized coke (soft coke or char) made from wholly non-coking and nut coke (-35 + 12 mm). It was found that utilization of non-coking coals as one component burden comprising ore fines-fuel and limestone briquettes-was impracticable for technological difficulties and adverse economics. The operational complexities, wide variation in the chemical composition of pig iron produced and non-recovery of potential by-products prevented the direct utilization of lumpy non-coking coals in bedded charge. The use of iron ore fines and low-temperature carbonized coke made from wholly non-coking coals (with utilization of by-product during carbonization) enabled production of pig iron of desired analysis. Based on economic viability, it was considered that the technique was suitable for commercial adaptation in 100-150 tonnes/day furnaces of medium shaft height. (Dr. A.B. Chatterjea is Deputy Director, Ferrous Production Technology Division (low-shaft furnace Project, National Metallurgical Laboratory, Jamshedpur); Dr. B.R. Nijhawan, Ph.D. (Sheff.) FNI, FIM, Ex-Director, NML)