Development of roasting-leaching route to produce iron ore concentrate at par with the composition of medium/high grade iron ore from low grade iron ore and iron ore slimes suitable for steel making

摘要

India occupies sixth position in ore resource base and ranks fourth with respect to world iron ore production1'1. One of the most immediate technological challenges facing the industry is to deal with the problem of processing high alumina content low grade iron ore, alumina rich iron ore fines and slimes. The draft steel policy of 2012 of India envisages to reach a production capacity of 300 MT per year of crude quality steel by 2025-26. In order to achieve the goal of National Steel Policy, our steel industry needs a large quantity of iron ore containing 62-64% Fe and low percentage of alumina and silica. The existing reserves of hematite (averaging around 63% Fe) may not last beyond 29-30 years at the present rate of consumption. Due to increased demand and continuous depletion of high grade iron ore, it has become necessary to develop technology to effectively beneficiate iron ore slime and low grade iron ore comprising of high percentage of alumina and silica. In present investigation an attempt has been made to develop roasting-leaching route to remove alumina and silica from very low grade iron ore (~35%Fe& 10.75%A1) and iron ore slime (~55%Fe& 6%A1), making use of different percentages of sodium carbonate salt (6 to 15%) as an additive for different durations of roasting, followed by water leaching and dilute acid leaching to get iron ore concentrate at par with medium or high grade iron ore. The iron ore concentrate so produced is highly suitable for producing low phosphorous steel in an electric arc / induction furnace.