Development of blast furnace quality pellet optimising blue dust, hard ore and friable ore ratio

Abstract

Three types of ore fines such as hard ore (HO), blue dust (BD) and friable ore (FO), normally available from a mine show different physical and physicochemical properties. Each of the properties of any individual ore among three may not be suitable to use independently in pelletisation. However, uses of all these three are mandatory. Ores of some poor properties may show other properties excellent. Therefore, any specific poor property of any individual ore can be modified by adding (mixing) other ore which shows that particular property excellent. In order to utilise those three ore fines in pelletisation, mixing of above three ores have been done to get good pellet properties. In industry, the fluctuation in mixing ratio often creates problem in maintaining pellet quality and consistency in spite of maintaining identical basicity and MgO content. Therefore, the required mixing ratio and pellet chemistry has also been optimised in this study. BD, FO and HO has been found to be suitable in the mixing ratio of 70:25:5 with 1.4% MgO. However, with increase in FO beyond 50%, reduction degradation index (RDI) becomes very high (25%). RDI has been decreased to very low level by increasing MgO content from 1.4 to 2% which enables to use FO up to 70% for good quality pellet preparation.