Induration of Indian Low Grade Iron Ore Pellets in a Pilot Heat Hardening System

Abstract

Green pellet induration is generally conducted in travelling grate or grate kiln furnaces where drying, firing and cooling are performed by direct contact with hot gases with varying temperatures. Indian low grade goethite ore (FeO(OH)) usually contains a high amount of chemically bonded water (approx. 6%). This chemically bonded water gets suddenly released at a temperature between 350 and 450 ºC. Cracking and disintegration of some of the pellets are observed during induration. In the present investigation a suitable induration cycle has been developed for pelletization of the Indian low grade goethite ore to produce the commercial grade pellets. Green pellets with varying basicity of 0.1–0.6 were prepared in a laboratory disc pelletizer and thereafter, drying, pre-heating and firing were conducted in a tailor made laboratory scale horizontal zone furnace by varying the main process parameters such as temperature and duration of soaking. Thereafter, the experimental data were validated in a pilot pelletization system of capacity 60 kg per batch i.e. a straight grate simulator. Pellets obtained by optimizing the process parameters exhibit the properties like cold compressive strength, porosity, Reduction Degradation Index (RDI), Reducibility Index (RI) etc. in line with the commercial grade pellets.