Study on improving the performance of vanadium-titanium magnetite oxidized pellets with limonite

To improve the compressive strength of vanadium-titanium magnetite oxidized pellets, this study systematically investigated the effects of limonite addition on the quality of green pellets, compressive strength of fired pellets, metallurgical properties, and bentonite dosage ratio through comprehensive pelletizing experiments. The underlying mechanism of limonite in strengthening the compressive strength of vanadium-titanium magnetite oxidized pellets was elucidated through analysis of volume changes and phase composition during the roasting process. Experimental results demonstrate that limonite significantly enhances both green pellet and fired pellet quality. With increasing limonite content, the compressive strength of green pellets, drop resistance frequency, and compressive strength of fired pellets exhibited a progressive improvement. Notably, when the limonite addition reached 9%, the fired pellets achieved a compressive strength of 3514 N/pellet. The study further revealed that increasing limonite content reduced T₁₀, T₄₀, and softening temperature range while expanding the melting temperature range, with the Reduction Swelling Index (RSI) remaining relatively stable. When substituting bentonite with limonite, green pellet quality showed a gradual decline, and the compressive strength of fired pellets initially increased before decreasing, though remaining consistently higher than baseline values. Appropriate limonite addition was found to enhance low-melting-point phases and porosity in pellets, promote faster and more uniform magnetite oxidation rate, optimize pore distribution with reduced cracks, and ultimately improve fired pellet strength. These findings provide critical insights for optimizing vanadium-titanium magnetite pellet production through strategic limonite utilization.