Effect of Bed Height on Strength of Sinter and other Sintering Indices

Abstract

Pot sintering experiments were conducted to describe the effect of bed height on tumbler strength of sinter, reduction properties (RDI and RI) and other sintering indices. The basicity ratio, (CaO/ SiO2) and MgO of sinter were kept at 1.6 % and 2.3% level, respectively in the present pot sintering study - the values which correspond to the condition of the sintering plant. The stabilization of sinter in plant condition was simulated with the pot sintering studies through the evaluation of return fines balance. Mineralogical analysis of the sinter samples reveals the presence of a higher percentage of ferrites in sinter samples from 550 mm bed height compared to 400 mm bed height when p- and s- hematite were predominant. A higher proportion ofsecondary hematite at this bed height could be attributed to higher oxygen potential due to higher permeability of the bed height. The yield of + 10 mm sinter and its tumbler strength (TI) improved quite signi-ficantly with the increase in bed height while speed ofsintering decreased with the net result of marginal improvement in strand productivity. The reduction degr-adation index (RDI) decreases whereas reducibility index (RI) improved with the increase in bed height. Sinter produced in the lesser bed height pot had low FeO compared to that in taller bed height. And a correlation between FeO content of sinter and its RDI was established. However, these variables are inter-influenced by another variable since a lower RDI a value was achieved even at lower FeO of sinter when the flux size was narrowed down. FeO content of sinter around 8% has resulted in the best result as regards RD/. Return fines (RF) was not balanced when the sintering was conducted at lower bed height: return fines generation was about 40% higher than the return fines input; whereas, it was balanced at550 mm bed height.