An innovative process of blast furnace(BF) operation involving charging with low-titanium vanadium–titanium magnetite carbon composite hot briquette(LVTM-CCB) was proposed for utilizing LVTM and conserving energy. In this study, the effect of LVTM-CCB charging ratio on the softening, melting, and dripping behaviors of the mixed burden was explored systemically, and the migration of valuable elements V and Cr was extensively investigated. The results show that with increasing LVTM-CCB charging ratio, the softening interval T_(40)- T_4 increases from 146.1°C to 266.1°C, and the melting interval T_D- T_S first decreases from 137.2°C to 129.5°C and then increases from 129.5°C to 133.2°C. Moreover, the cohesive zone becomes narrower and then wider, and its location shifts slightly downward. In addition, the recovery ratios of V and Cr in dripped iron first increase and then decrease, reaching maximum values of 14.552% and 28.163%, respectively, when the charging ratio is 25%. A proper LVTM-CCB charging ratio would improve the softening–melting behavior of the mixed burden; however, Ti(C,N) would be generated rapidly in slag when the charging ratio exceeds 25%, which is not favorable for BF operation. When considering the comprehensive softening–melting behavior of the mixed burden and the recovery ratios of V and Cr, the recommended LVTM-CCB charging ratio is 20%.
The effect of sinter with different MgO contents on the softening–melting behavior of mixed burden made from chromium-bearing vanadium–titanium magnetite was investigated. The results show that with increasing MgO content in the sinter, the softening interval and melting interval increased and the location of the cohesive zone shifted downward slightly and became moderately thicker. The softening–melting characteristic value was less pronounced when the MgO content in the sinter was 2.98wt%–3.40wt%. Increasing MgO content in the sinter reduced the content and recovery of V and Cr in the dripped iron. In addition, greater MgO contents in the sinter resulted in the generation of greater amounts of high-melting-point components, which adversely affected the permeability of the mixed burden. When the softening–melting behavior of the mixed burden and the recovery of valuable elements were taken into account, proper MgO contents in the sinter and slag ranged from 2.98wt% to 3.40wt% and from 11.46wt% to 12.72wt%, respectively, for the smelting of burden made from chromium-bearing vanadium–titanium magnetite in a blast furnace.
To achieve high efficiency utilization of high-chromium vanadium–titanium magnetite(V–Ti–Cr) fines, an investigation of V–Ti–Cr fines was conducted using a sinter pot. The chemical composition, particle parameters, and granulation of V–Ti–Cr mixtures were analyzed, and the effects of sintering parameters on the sintering behaviors were investigated. The results indicated that the optimum quicklime dosage, mixture moisture, wetting time, and granulation time for V–Ti–Cr fines are 5wt%, 7.5wt%, 10 min, and 5–8 min, respectively. Meanwhile, the vertical sintering speed, yield, tumbler strength, and productivity gains were shown to be 21.28 mm/min, 60.50wt%, 58.26wt%, and 1.36 t·m-2·h-1, respectively. Furthermore, the consolidation mechanism of V–Ti–Cr fines was clarified, revealing that the consolidation of a V–Ti–Cr sinter requires an approximately 14vol% calcium ferrite liquid-state, an approximately 15vol% silicate liquid-state, a solid-state reaction, and the recrystallization of magnetite. Compared to an ordinary sinter, calcium ferrite content in a V–Ti–Cr sinter is lower, while the perovskite content is higher, possibly resulting in unsatisfactory sinter outcomes.
The optimized use of Mg O flux in the agglomeration of high-chromium vanadium–titanium magnetite was investigated systematically through sinter and pellet experiments. Mg O was added in the form of magnesite. When the content of Mg O in the sinter was increased from 1.95wt% to 2.63wt%, the low-temperature reduction degradation index increased from 80.57% to 82.71%. When the content of Mg O in the pellet was increased from 1.14wt% to 2.40wt%, the reduction swelling index decreased from 15.2% to 8.6%; however, the compressive strength of the oxidized pellet decreased dramatically and it was 1985 N with an Mg O content of 1.14wt%. This compressive strength does not satisfy the requirements for blast-furnace production. When all of the aforementioned results were taken into account, the sinter with a high Mg O content(2.63wt%) matching the pellet with a low Mg O content(less than 1.14wt%) was the rational burden structure for smelting high-chromium vanadium–titanium magnetite in blast furnaces.
