Softening-Melting Properties and Slag Evolution of Vanadium Titano-Magnetite Sinter in Hydrogen-Rich Gases

Blast furnace-basic oxygen furnace (BF-BOF) process is the predominant method for smelting vanadium titano-magnetite (VTM) in China. Hydrogen-rich (H-2-rich) gas injection in BF is considered as an important way to reduce CO2 emission under the background of low carbon metallurgy. In this paper, the softening-melting behaviors of VTM sinter in H-2-rich gases were investigated by the method of determination of its reduction softening drippinger performance under load. The experimental results indicated that the permeability of VTM sinter during the softening-melting process was improved by increasing the H-2 content of the reducing gases. The maximum pressure drop of the burden decreased gradually from 29.76 kPa to 19.97 kPa, and the total characteristic value (representing the comprehensive softening-melting property) also decreased obviously from 2357.52 kPa center dot degrees C to 630.94 kPa center dot degrees C with the increase in H-2 content. The softening interval of the samples was widened, while the melting-dripping interval increased firstly and then decreased. In that case, the position of the melting-dripping zone in BF would move downwards, which was beneficial to smelting smoothly. The thermodynamic analysis indicated that Ti- and Fe-bearing phases were more difficult to be reduced than iron oxides, and H-2-rich gas is beneficial to the reduction of that kind of oxides. Titano-magnetite will be reduced stepwise to form Fe2TiO4, and then in the order of FeTiO3 -> TiO2 -> Ti(C,N). Wustite (FeO) was an important component during the slag-forming process, whose content increased firstly and then decreased. Perovskite and silicate were the main phases in the dripping slag samples.

Automated summary

The softening-melting behaviors of VTM sinter in H-2-rich gases were investigated and it was found that increasing the H-2 content improved the permeability of the VTM sinter during the process. The maximum pressure drop and total characteristic value decreased with the increase in H-2 content, widening the softening interval of the samples. The thermodynamic analysis showed that H-2-rich gas facilitated the reduction of Fe- and Ti-bearing phases and wustite was an important component during the slag-forming process.