New Insights into the Preparation of Flux Pellets from Low-Silicon, High-Alkali Iron Concentrates: Regulation Mechanisms of Liquid Phases
摘要
Aiming to address the issues of high reduction swelling index (RSI) and low compressive strength in low-silica high-alkali iron ore pellets, the thermal regime (preheating at 950 °C for 10 minutes and roasting at 1250 °C for 20 minutes) was used, and the effects of SiO2 content (2.4 to 3.7 pct) and CaO content (1.9 to 4.3 pct) on the performances of pellets were investigated in this study. Then, the compressive strength, porosity, and metallurgical properties (RI, RSI, RDI) of the pellets under varying liquid phase contents were analyzed. The results showed that when the liquid phase contents reached 11.87 ± 0.36 pct, with SiO2 and CaO contents of 2.8 and 3.3 pct, respectively, the compressive strength reached 3078 N, and the RSI, RI, and RDI were 15.18, 89.16, and 89.25 pct, respectively. As the liquid phase content increased from 6.52 ± 0.31 to 11.87 ± 0.36 pct, the K content in hematite was reduced from 6.37 to 2.57 pct and Na from 5.95 to 2.33 pct. Consequently, the growth of iron whiskers during the reduction process was suppressed, leading to a significant decrease in RSI from 100.67 to 15.18 pct. However, excessive liquid phase content inhibited hematite recrystallization and reduced pellet compressive strength. Therefore, an optimal liquid phase content of 11.87 ± 0.36 to 14.59 ± 0.37 pct is recommended, with SiO2 maintained at 2.83.2 pct and CaO at 3.3 to 3.7 pct. This study proposes a novel mechanism for optimizing the performance of high-alkali flux pellets based on liquid phase regulation, which provides theoretical guidance for the large-scale application of low-silica high-alkali pellets.