Preparation of high-proportion vanadium-titanium pellet and design of burden structure based on basicity matching

To increase the proportion of vanadium-titanium pellets in blast furnace burden and alleviate the deterioration of high-temperature performance caused by matching high pellet ratios with high-basicity sinter, a burden design strategy based on basicity matching was proposed. Fluxed vanadium-titanium pellets with different basicities were prepared under the boundary conditions of maintaining the iron grade, slag basicity, w（MgO）/w（Al₂O₃） ratio, and thermal regime. Their cold strength, reduction disintegration, reducibility, and softening-melting behavior were systematically evaluated. The results show that, with increasing pellet basicity （from 0.13 to 0.62）, the mass fraction of CaO in the pellet increases from 0.32% to 2.13%, and the compressive strength reaches 2 714.6 N per pellet. At a pellet basicity of 0.62, the reduction degradation index （I_{RD<3.15 mm}） decreases to 1.60%, indicating good low- and medium-temperature the reduction degradation resistance. However, the reduction swelling index （I_RS） reaches 17.84%. For a single pellet bed, the softening-melting behavior deteriorates with increasing basicity, and the gas permeability index （S value） increases from 340.60 to 2 000.27 kPa·℃. In the composite burden composed of basic sinter, acid sinter, Baima pellets, and vanadium-titanium pellets, however, a clear synergistic slagging effect occurs between sinter and pellets. At a total pellet ratio of 59% and a vanadium-titanium pellet basicity of 0.47, the composite burden exhibits the best high-temperature performance, with a softening interval of 75 ℃, a melting-dripping interval of 130 ℃, and the lowest S value of 1 372.91 kPa·℃. Ore-blending calculations indicate that, while maintaining the slagging regime, the pellet ratio can be increased from 55% to 61%, the vanadium-titanium ore proportion increases by 3.44 percentage points, the mass fraction of TiO₂ in the slag is increased to 23.15%, and the ore-blending cost decreases by 38.10 yuan/t（hot metal）. These results provide a basis for optimizing high-proportion vanadium-titanium pellet burden and for the low-cost and efficient utilization of vanadium-titanium magnetite.