Search for a command to run...
The advancement of green and low-carbon transition in the steel industry has increased the demand for high-quality direct reduced iron (DRI) as a premium feedstock for electric arc furnace steelmaking. This imposes stricter quality requirements for fired pellets utilized in gas-based shaft furnace processes. To address the poor low-temperature reduction degradation (LTD) of fired pellets produced from a single high-grade magnetite concentrate during gas-based direct reduction. This study investigates the effects of blending hematite concentrates into a magnetite concentrate base (with additions of 0, 20 wt.%, 30 wt.%, and 40 wt.%) on the characteristics of the mixed concentrates, green ball properties, firing performance, and the metallurgical performance of the resulting fired pellets under conditions simulating an HYL shaft furnace. The results indicate that the incorporation of hematite concentrate optimizes the overall particle size distribution and green ball properties. As the hematite proportion increases, the optimal preheating temperature for green balls rises, while the required roasting temperature decreases. The most significant reduction in roasting temperature, from 1225 °C to 1175 °C, is achieved with a 20 wt.% hematite addition. Regarding metallurgical properties, the addition of hematite has a minor effect on the reducibility index (RI) but substantially improves the reduction swelling index (RSI). A notable decrease in the RSI is observed at addition levels of 30% and above. Critically, the LTD is significantly enhanced. The optimal improvement is attained with a 20 wt.% hematite blend, resulting in a- LTD+6.3 mm fraction of 97.48 wt.%, a- LTD−3.2 mm fraction of only 2.18 wt.%, and a whole pellet ratio of 88.01% after reduction. Considering the comprehensive performance, a blend of hematite concentrate between 20 wt.% and 30 wt.% yields fired pellets with superior characteristics, meeting the production requirements for gas-based shaft furnace direct reduction processes. This study provides an effective technological pathway for producing high-performance DRI-grade pellets from high-grade magnetite concentrates, contributing to the green and low-carbon transformation of the iron and steel industry.