Effect of inert gas injection on sinter RDI

Reduction Degradation Index (RDI) of sinter can be largely attributed to the presence of secondary hematite that is formed due the re-oxidation of magnetite formed during sinter. Inhibiting re-oxidation of magnetite during could be useful for improving (reducing) the RDI of sinter. Since, sintering is a complex process and a large number of independent variables affect sinter quality and it is challenging to obtain optimum values of all these variables. This however leads to saturation in sinter quality due to availability of very few handles. The present study, therefore, adopted a different approach to identify opportunities for improvement in high temperature properties of sinter.

An innovative approach on injecting an inert gas (nitrogen) after attaining burn through point was suggested. The hypothesis is that injection of nitrogen reduces the availability of oxygen and therefore inhibits the re-oxidation of magnetite. To evaluate the hypothesis, pot sintering experiments were conducted by injecting nitrogen gas during sintering process. A significant drop in the RDI of sinter by ~3 points in the bottom portion of the sinter has been observed. However, there is no significant difference in the RI values of sinter from the base case and nitrogen injection tests.