Heating index: estimation through numerical modeling of the sintering process and its relationship with sinter quality

The temperature profile experienced by the sinter bed strongly influences iron ore sinter quality. Heating Index, defined as the area under the temperature-time curve for temperatures greater than 1200°C, is a parameter that can be derived from the sintering temperature profile. Due to the difficulty associated with bed temperature measurement during sintering, the heating index is not accurately estimated and its relationship with sinter quality is not established. It is the objective of the present work to address this. In this work, a one dimensional numerical model of the iron ore sintering process incorporating important physico-chemical processes such as coke combustion, calcination of limestone, evaporation and condensation of moisture, and melting and resolidification was developed. A good agreement between experimental temperature profiles obtained in the sinter pot and numerical temperature profiles was observed. The numerical model was used to obtain bed temperature profiles at several depths in the sinter bed which were then used to estimate the heating index at all depths. The heating index was found to increase from top to bottom in the sinter bed as the time spent by the mix at higher temperatures increases from top to bottom in the bed. The heating index values at various heights were averaged to obtain an ‘average heating index ’for the whole bed. Using pot sinter data, it was found that there exists a strong correlation between average heating index and the Tumbler Index of sinter. The correlation was found to be positive for sinter CaO levels greater than 10% and negative for CaO levels less than 10%. This study indicated that heating index can be used as a precursor to sinter quality during continuous operation at the Sinter Plants.