Softening–melting–dripping characteristics and evolution mechanism of vanadium-bearing titanomagnetite carbon composite briquette used as novel blast furnace burden

摘要

Vanadium-bearing titanomagnetite carbon composite briquette(VTM-CCB)was proposed as an innovative and promising blast furnace burden to realize low-carbon and high-efficiency ironmaking.To optimize the compositions of VTM-CCB based on its softening–melting–dripping characteristics,the evolution behavior and mechanisms of VTM-CCB in cohesive zone and dripping zone were investigated by conducting softening–melting tests under blast furnace conditions.The results show that the structure evolution of VTM-CCB in softening–melting process is correlated to the molten slag,metallic iron,liquid iron,and residual carbon.With the molar ratio of the fixed carbon to the reducible oxygen in iron oxides(FC/O ratio)ranging from 0.8 to 1.0,the VTM-CCB tends to form dense structure and accelerate the softening and melting.With increasing the FC/O ratio to 1.2 and 1.4,the VTM-CCB tends to form concentric circular structure,which could suppress the collapse of packed bed,shift down the location of core cohesive zone,and improve the gas permeability.Although the appropriate increase in FC/O ratio could improve the softening–melting performance of VTM-CCB,a higher FC/O ratio could also promote the precipitation of Ti(C,N),thereby thickening the molten mixtures and deteriorating the dripping behavior.Fully considering the softening–melting–dripping characteristics and permeability,the appropriate FC/O ratio of VTM-CCB should be controlled in the range of 1.0–1.2.