Research on the Influence of Limestone Particle Size on the Smelting Effect of Converter Injection Smelting Process

This study investigates the influence of limestone particle size on slag dephosphorization performance during converter injection smelting. High‐temperature calcination and slag dephosphorization experiments were conducted at 1673 K using limestone particles with average sizes of 4, 2.5, 0.84, and <0.074 mm. The decomposition characteristics, lime activity, porosity, specific surface area, and dephosphorization efficiency were compared. The lime microstructure, phase composition and slag morphology were characterized via SEM, XRD, and BET. The results indicate that 0.84 mm limestone exhibits optimal performance, with a lime activity of 350 mL, porosity of 34.42%, and specific surface area of 2.26 m 2 g −1 . The corresponding dephosphorization experiment achieved a dephosphorization rate of 85%, reducing the phosphorus content from 0.12 to 0.018 wt%. In contrast, larger particles (4 mm) showed incomplete decomposition and inferior dephosphorization (68.6%), while excessively fine particles (<0.074 mm) suffered from overburning, structural densification, and material loss. XRD and SEM analyses confirmed that the 0.84 mm slag exhibited a well‐molten state with phosphorus enriched in the Ca 3 (PO 4 ) 2 ‐Ca 2 SiO 4 solid‐solution phase, whereas the 4 mm slag contained residual free CaO, indicating incomplete slagging. The optimal particle size for converter limestone powder injection was determined to be an average of 0.84 mm.