EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

Induration of magnetite pellet is a complex physicochemical process involving oxidation, sintering and the heat transfer phenomena. Often, these phenomena happen simultaneously and influence each other while being exposed to high temperature in the induration furnace, which might results in the formation of duplex structure within the pellet having the core of magnetite and shell of oxidized magnetite (hematite). The duplex structure inside the pellet might generate structural stresses because of the difference in their crystallographic and thermal properties which may cause detrimental effects to the quality of pellets for further processing in iron making furnaces. In order to achieve good quality pellets, it is necessary to study the kinetics of each of these phenomena in isolation to have thorough understanding, identify and control the responsible process parameters during induration. In subsequent to the investigation of sintering kinetics of magnetite pellets from LKAB, this study focuses on estimating their oxidation kinetics. The reaction mechanism for oxidation of magnetite pellets and their kinetics is dependent primarily on factors such as temperature, particle size, oxygen content of the gas, etc. The isothermal oxidation kinetics considering these factors has been estimated experimentally at the pellet as well as particle scale using Thermo Gravimetric Analysis (TGA). It is found that the oxidation of magnetite pellets proceeds with two or more distinct dominant mechanisms varying with the extent of reaction. The deduced kinetic parameters will further be used to develop a mathematical model to predict the oxidation behavior of magnetite pellet during induration.