8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

Tata Steel Kalinganagar is a green field 3MTPA integrated steel plant operating via the BF-BOF route. The sinter plant at Tata Steel Kalinganagar was commissioned in January 2016. The sintering machine area is 496m2 with state-of-the-art cooler design and advanced high intensity mixing-granulation systems. Among the challenges faced in the ramp up, two key issues that were of major concern in the sinter making process was alkali management due to use of unbeneficiated high alkali ores in pile making and the control of high temperature property of sinter (Reduction Degradation Index, RDI). Due to limited availability and logistic issues of supply to Kalinganagar from Tata Steel’s captive iron ore mines at Joda and Noamundi, it was decided to use unbeneficiated iron ore from Khondbond, Odisha. In terms of ore chemistry, Khonbond ore had high alumina and alkali content (0.3% K2O as compared to 0.05% for beneficiated ores from Joda and Noamundi). High alkali content leads to higher coke rate, low productivity and affects the furnace lining in the blast furnace. Studies on alkali flushing capabilities of the blast furnace were carried out and based on this, the permissible limit of sinter alkali was determined and threshold for usage of Khondbond ores in base mix pile was fixed. Permissible limit of sinter RDI is 30, as desired by blast furnace operators at Tata Steel India. Though commissioning of sinter plant at Kalinganagar was carried out in Jan’16, measurement of sinter RDI began in the month of May’16, and was found to be higher than the specified limit of 30%. Sinter RDI varied between 24 and 46 at different regimes of operating parameters and iron ore fines. Based on data analysis, trials were carried out to control the sintering process – in terms of heat input and burn through temperatures. FeO content of sinter at high alumina input conditions was fixed at 9% minimum to maintain sinter RDI below 30 by considering sinter alumina 2.8% max, with reference to past data at TSK. FeO below 9% needs an action on fuel rate to increase in steps after considering the burn through point and sinter RDI. It was also critical to control the burn through point so as to minimize on strand cooling which is detrimental due to the formation of secondary hematite, known to reduce sinter strength. Crushing fineness of solid fuel and flux also needed improvement for efficiency of solid fuel consumption and consistency in sinter quality.