Research On Dynamic Behaviors During Vanadium-Extraction Process

Vanadium resource is a kind of strategic resource for a morden industrial country, and vanadium is widely used in iron and steel industry, aerospace industry, textile industry and medical industry. Vanadium mainly exists in vanadium-titanium magnetite in nature. The vanadium-bearing hot metal is formed mainly by the reduction reaction in blast furnace, and then the vanadium in hot metal is oxidized in converter to make vanadium enrich in the vanadium slag. With the prices of vanadium containing products and iron ore increasing, more attention will be payed to vanadium extraction from hot metal. Therefore, it is important to stuy the kinetic of oxidation reaction of elements in hot metal by the converter.Based on practical condition of the70t vanadium-extraction converter of a company, a kinetic model of extracting vanadium from hot metal was established, mainly focusing on the compositions changes of the metallic bath and the slag, the temperature change of the metallic bath and the dissolved quantity of cold materials with the blowing time. Thus, parameters of the model was changed to simulate smelting process under different conditions to study the effect of the cold material, silicon content in hot metal,and oxygen supply intensity on the extracting vanadium from hot metal. The conclusions are as followed:(1) It was found that the theoretically calculated values according to the established kinetic model were well consistent with the measured data from the vanadium-extraction converter.(2) The sequence of oxidation of elements in the bath was as follewed:silicon and titanium in hot metal were oxidized rapidly during the initial stage of blowing. And vanadium started to be quickly oxidized and a small amount of carbon was oxidized during the middle stage of blowing. A transformation of the oxidation sequence of vanadium and carbon happened during the final stage of blowing and carbon started to be oxidized quickly. In addition, oxidations of manganese and chromium happened throughout the intermediate and final stage of blowing, contesting oxygen with vanadium. (3) Changes of compositions for the slag were relative to the changes of compositions for the bath. The only difference was iron oxide. The content of iron oxide reached maximum value at0.5min of blowing, and it was almost the same at the rest time.(4) The oxidation curve of vanadium was "S"-type, and the reaction rate of vanadium was slow at the initial stage of blowing because of high combination ability of silicon and titanium with oxygen, but it became fast at the middle stage of blowing, and then the reaction rate of vanadium was slow again. It showed that extending of the blowing time was unfavorable to vanadium extraction.(5) Different cold materials had different cooling effects. Oxide scale had the best cooling effect, and the second one was haft furnace, and the next one was iron of v-slag, and pig iron was at last.(6) Cold materials had influence of the temperature of bath. The temperature increased in the prior period of smelting, and then the temperature came to the lowest because of the dissoled of cold materials. Then the temperature increased quickly again because of the oxidation of elements in the bath. Using oxide scale as cold materials, the low temperature region was long. If the blowing time was too long, carbon would be oxided, and also the temperature of the bath became high in the end.(7) Hot metal with different content of silicon needed different amount of cold materials. In order to promote the extraction of vanadium from hot metal by converter, the content of silicon in hot metal should be controlled in the range of0.15%～0.25%, and the endpoint temperature of semi-steel should be controlled below1390℃.(8) When the content of carbon in hot metal was4.2%, oxygen supply intensity was8600m3/h, and the blowing timge was6min, the content of vanadium in semi-steel was less than0.03%, and the low temperature period should be longer than the present process.