Optimization of Firing Temperature for Hematite Pellets

• Published in: ISIJ International Vol. 53; no. 9; pp. 1673 - 1682
• Main Authors: Umadevi, Tekkalakote, Lobo, Naveen Frank, Desai, Sangamesh, Mahapatra, Pradipta Chandra, Sah, Rameshwar, Prabhu, Manjunath
• Format: Journal Article
• Language: English
• Published: The Iron and Steel Institute of Japan 01-01-2013
• Subjects: carbon; firing temperature; induration; iron ore pellet; microstructure; physical and metallurgical properties
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.53.1673

The heat hardening by oxidation is a process commonly used in iron ore pelletization process. The green pellets are fired in induration machine using Corex gas at JSW Steel Limited Pellet Plant. The firing temperature of induration machine strongly influences the physical and metallurgical properties of the pellet. Due to absence of exothermic reaction and poor roasting property of hematite pellet, the energy consumption of hematite pellet production is at higher side and requires higher roasting temperature. In present pelletization process, carbon burdened method is found to be more favorable technique in practice to enhance the induration of hematite pellets. Coke breeze is added in the pellet mix at JSW pellet plants to get the inherent fuel value of a hematite green ball equal to that of a magnetite pelletizing feed. The firing temperature (from corex gas) of the induration machine and carbon addition in the pellet mix is interrelated and decides physical and metallurgical properties of the pellets. At JSW Steel Pellet Plant the carbon addition varies from 0.90 to 1.50% and firing temperature varies from 1230 to 1320°C. Fluctuations in physical and metallurgical properties were observed due to deviation in carbon addition and firing temperature. Optimization of external firing temperature and coke breeze addition in the green pellet mix is necessary to get the desired properties of the pellet for iron making units. Basket trials were carried out at pellet plant induration machine by varying the external firing temperature from 1220 to 1330°C and coke breeze addition from 0.7 to 1.4%. At firing temperature of 1220, 1250, 1280, 1310 and 1330°C the optimum carbon addition 1.30, 1.20, 1.10, 0.90 and 0.70% achieved the optimum physical and metallurgical properties of the pellet for iron making units respectively.