Improvement of iron ore pellets metallurgical properties by their fluxing by lime

Abstract

Fluxed iron ore pellets, obtained by application of raw limestone are widely used in the iron ore share of blast furnace charge. Decomposition of the raw limestone in the process of the pellets burning requires considerable energy. The purpose of the work was to study quality variation of raw and burned pellets, as well as metallurgical properties variation, caused by substitution of limestone by burned and slaked lime. Physical simulation of the pelletizing process and pellets burning process was done. In the process of the experiment simulation of total and partial substitution of limestone by lime as well as with partial substitution of limestone by slaked lime was accomplished. Diagrams of plasticity and strength of raw and burned pellets at various shares of limestone, burned and slaked lime presented. It was shown that the strength during reducing RDI-1 (ISO 4696-1) has a tendency to increase when application of lime. Increase of Index RDI+6,3 value accounted for 3.6% (abs.) at application of quicklime and slaked lime correspondently. Index RDI−3,15 value decreased by 1.06% (abs.) and 0.88% (abs.) and that of index RDI−0,5 – by 0.75% (abs.) and 0.8% (abs.) at application of quicklime and slaked lime correspondently. It was assumed that application of slaked lime can contribute to bentonite share decrease and thus to total iron content increase. It was established that application of lime enables to decrease heat consumption for pellets burning. Application of slaked lime instead of limestone in the process of pellets production results in an increase of their strength during reducing and compression strength. This effect enables to reach a higher efficiency in the process of such pellets usage in blast furnace charge or in the process of their metallization, comparing with the usage of pellets fluxed by limestone.