Strengthening iron ore pellet consolidation by collaborative optimization of ore blending and high-pressure roll grinding

Iron ore pellet production is recognized as an energy-intensive and high-emission industrial process, and its energy conservation and emission reduction represent a critical component for the iron and steel industry to achieve the “dual carbon” goals. Efforts are made herein to leverage the synergistic effect of high-pressure roll grinding pretreatment and optimized ore blending, thereby reducing the pellet induration temperature while ensuring product quality, so as to provide technical support for the green transition of the iron and steel industry. A systematic laboratory experimental approach was adopted. Firstly, six types of iron concentrates were pretreated using a high-pressure roll mill under a pressure of 14 MPa, and the effects of this process on raw material particle size, specific surface area and pelletizing performance were analyzed. Subsequently, green pellets were prepared by a disc pelletizer, and the preheating and induration processes were simulated in a horizontal tube electric furnace to explore the influence law of different process parameters on pellet strength. Finally, scanning electron microscopy was employed to analyze the microstructural changes of pellets, thus revealing the synergistic strengthening mechanism.Results demonstrate that high-pressure roll grinding can significantly improve the physical properties of iron concentrates. After two passes of roll grinding treatment, the proportion of the 5 mm size fraction in the blended ore can be increased to 75.45%, which effectively enhances particle surface activity and strengthens recrystallization interface reactions, thereby improving pellet strength. Meanwhile, two passes of high-pressure roll grinding can substantially reduce the pellet induration temperature from 1 200 to 1 100 ℃. On this basis, optimized ore blending was further applied to enhance pellet consolidation efficiency. Under the optimal ore blending ratio(5 wt.% ore A, 11 wt.% ore C and 7 wt.% ore D), the minimum induration temperature of pellets can be further reduced to 1 080 ℃, with the compressive strength reaching 3 189 N/P, which far exceeds the industrial standard of 2 500 N/P. Microstructural analysis indicates that the synergistic effect of high-pressure roll grinding and optimized ore blending significantly enhances the recrystallization and intergrowth degree of hematite, reduces internal pores and cracks of pellets, and thus greatly improves structural compactness. The synergistic mechanism of high-pressure roll grinding and optimized ore blending was clarified, and the dual optimization effects of this combined technology on reducing induration temperature and improving pellet strength were quantified via laboratory data.