Characterisation driven processing of Indian sub-marginal grade of iron ore for value addition

Abstract

Iron ore resource has its own typical mineral characteristics which require definite beneficiation process to produce quality raw material. India is endowed with large reserves of high grade hematite ore. However, steady consumption of these iron ores is now a concern forcing to develop beneficiation strategies to utilize low grade iron ores. Characterization has become an integral part of mineral processing and beneficiation depends on the nature of the gangue present and its association with the ore. Different characterization aspects like mineralogy, textural relationship, liberation size, chemical analysis and grain size analysis were studied to develop the beneficiation scheme. As reflected in the National Steel Policy, the life of high grade lumpy ore as on April 2010 will be ten more years. In order to ensure longer period of ore availability, it is important to use low grade Banded Hematite Quartzite (BHQ) & Banded Hematite Jasper (BHJ) iron ores after beneficiation. Looking at the present scenario, Indian Bureau of Mines (IBM) has slashed the threshold value of Fe in hematite to 45% from 55 % (t). According to National mineral policy projections, exploitation of the low grade iron ore horizons is necessary to achieve zero waste mining. BHJ assaying up to 40% Fe (T) had upgraded above 60% Fe (T) to use effectively. Technically it is possible to enhance the quality of low grade as well as BHQ/ BHJ ironores to an acceptable grade using various techniques like Flotation, Enhanced gravity separation, WHIMS etc. In India, iron
ores are generally washed to remove the high alumina containing clayey matter. Conventionally, after washing, the lumps are directly fed to blast furnace and the fines are used after agglomerating them into sinter. However, the slimes are being rejected in the tailing ponds. These slimes in most cases contain substantial iron values in the range of 54– 58% Fe. Therefore, it is imperative to recover iron values from these slimes because of high demand on the good grade iron ores day-by-day.