Optimization of Induration Cycle for Magnetite Concentrate and its Usage in Pellet-Making Process Designed for Hematite
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Optimization of Induration Cycle for Magnetite Concentrate and its Usage in Pellet-Making Process Designed for Hematite Concentrate T. Umadevi 1 & K. S. Sridhara 1 & Sah Rameshwar 1 Received: 18 September 2019 / Accepted: 21 September 2020 # Society for Mining, Metallurgy & Exploration Inc. 2020
Abstract In the magnetite iron ore pelletization process, oxidation of magnetite followed by sintering of the oxidized magnetite (hematite) is desirable. Optimum preheating time & temperature and roasting time & temperature is required to get the desired properties of the pellets with magnetite, hematite, and hematite–magnetite blend. In order to utilize the magnetite resources in a current induration furnace, which is designed for hematite resources, detailed pelletization studies have been carried out to optimize the firing cycle for magnetite concentrate as well as magnetite with hematite concentrate. Under optimum conditions, such as preheating temperature 1000–1150 °C, preheating time 10 min, roasting temperature 1250 °C and roasting time 7.5 min, the cold compression strength (CCS) of magnetite roasted pellets was 325 kg/p, and this was due to recrystallization of secondary hematite particles, and development of the strong slag bond between primary and secondary hematite particles. The strength of hematite concentrate pellets was 260 kg/p. From laboratory studies, it was found that without disturbing the induration furnace firing cycle, which is designed for hematite ore ~5%, magnetite concentrate can be used along with hematite concentrate in pellet blend and the strength of the pellets was 270 kg/p. As the magnetite concentrate increases in the blend beyond 5%, the preheating zone residence time should be increased or a supply of extra oxygen is required. Laboratory as well as plant investigation has shown that the addition of magnetite to the hematite mix blend improved the strength of the pellets compared to hematite pellet alone. Keywords Iron ore pelletization . Magnetite ore . Hematite ore . Firing cycle . Mineralogy
1 Introduction Magnetite and hematite are the two main raw materials for pellet production. Magnetite concentrates have more predominance due to the heat release by oxidation during roasting [1, 2] and may reduce energy consumption [1, 3, 4]. The most important factors influencing the properties of the fired pellets are firing temperature, fuel addition, and firing time. Comparatively, the heat consumption for producing magnetite pellet is lesser than that of hematite pellet due to the heat evolved by exothermic reaction. The optimum firing temperature of pellets within the induration furnace decides the pellet mineralogy, and pellet mineralogy in turn decides the physical and metallurgical properties of fired pellets [5]. Studies have shown that hematite pellets have poor roasting properties and
* T. Umadevi [email protected] 1
JSW Steel Limited, Bellary, India
do not achieve adequate strength until the roasting temperature is raised above 1300 °C [1, 6, 7]. But the same is not true for magneti
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