Novel sintering indexes to evaluate and correlate the crystal characteristics and compressive strength in magnetite pellets

This paper aims to develop sintering indexes to evaluate and correlate the sintering degree and compressive strength in pellets. Based on image processing techniques by using the watershed algorithm, sintering indexes, such as pellets consolidation index (CI), grain growth index (GI), and grain uniformity index (UI) are proposed for the first time to evaluate the sintering degree during the induration of pellets. The results showed that with the increase of roasting temperature from 0–1300 °C, CI and GI of ore #1 increase from 0 to 0.47 and 0 to 1.72 respectively. In contrast to ore #2, CI and GI increased from 0 to 0.41 and 0 to 1.75, respectively. CI and GI of ore #1 were higher than #2 ore under the same roasting temperature, which indicated that the Fe2O3 particles in #1 ore are easier to form sintering neck than #2. CI, GI and compressive strength of pellets have an obvious linear correlation, and the linear correlation between GI and the compressive strength of pellets is stronger with the R-Square 0.98 for #1 ore and 0.99 for ore #2.