| Vanadium extraction by converter is an important technology used in comprehensive utilization of Vanadium-titanium magnetite resources in steel industry at present, the main metallurgical effect of which is to achieve selective oxidation of carbon and vanadium by blowing oxygen and controlling the temperature, making a large number of vanadium be oxidized and enter into slag and minimizing the oxidation of carbon in molten iron. This technology has enormous importance to enterprises which smelt vanadium-titanium as the transition part between vanadium extraction and steelmaking. This paper makes research on 70t vanadium extraction converter of Chengde Jianlong Special Steel Limited Corporation fully combined with the actual production situation, aiming at three problems including the end temperature on the high side, the inaccuracy of coolant addition of each furnace and ignoring the structure optimization of coolant in the production process.In this paper, static model of 70t vanadium extraction converter of Chengde Jianlong Special Steel Limited Corporation was established and through calculating the material and heat balance of vanadium extraction converter based on the a large number of actual data of production site. Effects of different kinds of coolants on grade of vanadium slag, vanadium yield and oxidation ratio of vanadium were studied, binary and ternary structure of coolant were optimized using the verified static model and the following conclusions were obtained:(1) The transformation temperature of carbon and vanadium was calculated and the range of end-point temperature was determined below 1380℃ through integrating thermodynamics research and statistics of production site data.(2) The ability of improving the grade of vanadium slag of pig iron and oxidized scale was the best when adding single kind of coolant, grade of vanadium slag was 17.2% and 17.1% respectively. The ability of improving the oxidation ratio of vanadium of shaft furnace pellets and red mud pellets was the best when adding single kind of coolant, oxidation ratio of vanadium can reach more than 90%. Using the iron of vanadium slag can improve the vanadium yield effectively and the vanadium yield was 92.3% when only adding iron of vanadium slag.(3) The matching of 70% oxidized scale and 30% iron of vanadium slag was the best when adding two kinds of coolants together and the relevant grade of vanadium slag, oxidation ratio of vanadium, vanadium yield was 16.4%,90.0%,92.3% respectively. The formula of 70% oxidized scale and 30% shaft furnace pellets was the second best.(4) The ternary structure of coolant was further proposed based on supply condition of production site. The best ones included the formulas of 30% shaft furnace pellets,50% iron of vanadium slag and 20% pig iron; 30% shaft furnace pellets,30% iron of vanadium slag and 40% oxidized scale; 40% shaft furnace pellets,20% iron of vanadium slag and 40% oxidized scale; 30% shaft furnace pellets,30% iron of vanadium slag and 40% pig iron; 40% shaft furnace pellets,20% iron of vanadium slag and 40% pig iron and their comprehensive indexes are generally good.(5) The practice result of production site showed that the average end-point temperature declined from 1396℃ to 1367℃, average vanadium content of semi-steel declined from 0.057% to 0.034%, oxidation rate of vanadium was improved to about 90.0% significantly, and the V2O5 content of vanadium slag can stabilize around 16.5% after the static model and structure of coolant of this research applied. Several production technology indexes reached the domestic advanced level and good application effect was achieved. |
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