Viscosity And Melt Structure Characteristics Of Vanadium Slag During Smelting Reduction Process

At present,the smelting of ferrovanadium in China is generally through the oxidation roasting of vanadium slag to complete the transformation of V3+ ions to V5+ions in the slag.Then,the products of V2O5 will be obtained after hydro-leaching and second roasting process,which is used to produce ferrovanadium alloy in the presence of iron filings and reductant by heated refined.However,the traditional process of ferrovanadium smelting has high energy consumption and serious environmental pollution,which is inconsistent with the development concept of green metallurgy.Therefore,it is of great significance to develop a new process of ferrovanadium alloy smelting with short,green and efficient process.At the same time,a large number of photovoltaic materials and electrolytic aluminum are produced in our country,a mount of photovoltaic cutting waste and aluminum ash cannot be effectively utilized.Based on the current situation and development demand of industry technology in China,the industrial secondary resources of photovoltaic cutting waste and aluminum ash were utilized as reductants in the present study,to produce ferrovanadium alloy by reducing the molten vanadium containing slag directly in two-step.This research provides process parameters for the new method of smelting ferrovanadium alloy.This process implements the green production concept of "treating waste with waste",uses the physical heat of molten vanadium slag for on-line reduction,effectively reduces production costs,promotes energy conservation and environmental improvement,the waste utilization is realized at the same time.In the process of reducing the molten vanadium slag by cutting waste,the viscosity of the slag system shows different trends with the change of compositions.Through the study of the melt structure of vanadium slag system,reveals the mechanism of the structural unit on the macroscopic viscosity.Meanwhile,a new viscosity model of the FeO-SiO2-V2O3-CaO-MnO-Cr2O3-TiO2 system and its subsystems were established.Main conclusions were listed as follows.(1)With FeO/SiO2 ratio decreased,the viscosity of the FeO-SiO2-V2O3-CaOMnO-Cr2O3-TiO2 system slag was increased when the temperatures above 1803 K,the viscosity of the slag system remained stable,and the slag fluidity was benign which can meet the needs of process production.With the FeO/SiO2 ratio decreased from 2.18 to 0.30,the viscosity of the slag system increased from 0.140 Pa·s to 0.485 Pa·s at 1823 K.(2)The change of binary basicity had little effect on the viscosity of the slag at temperatures above 1803 K.With the basicity of slag system increased from 0.3 to 0.5,the viscosity dropped only 0.101 Pa·s.When the basicity of slag system increased to 0.7,the viscosity of slag system increased slowly with the decreased of temperature,and the viscosity increased rapidly when the temperatures below 1600 K.(3)FeO-SiO2-V2O3-CaO-MnO-Cr2O3-TiO2 slag system was in molten state at 1823 K,and its viscosity change was mainly caused by the transition of the silicate structure.FeO can promote the disband of the complex silicate network in the slag system.With the FeO/SiO2 ratio decreased from 2.18 to 0.30,the total amount of simple silicate structures Q0 and Q1 decreased,the total amount of complex silicate structures Q2 and Q3 gradually increased to 97.67%.The value of n(NBO/T),which represented the degree of melt polymerization,decreased from 2.85 to 1.87.The degree of silicate polymerization was enhanced.(4)A new viscosity model of the FeO-SiO2-V2O3-CaO-MnO-Cr2O3-TiO2 system and its subsystems were established.The experimental values of the system were in good agreements with the predicted values,and the average prediction error was 11.4%.Compared with the Urbain model,the Riboud model and NPL model,prediction effect had been greatly improved.(5)The prediction error of this model for the vanadium slag system is within 15%,which Cr2O3 content was less than 5%,and the basicity less than 0.5.The average prediction error of FeO-SiO2-V2O3-Cr2O3-TiO2,FeO-SiO2-V2O3-MnO-TiO2 five-element subsystem were 14.1%and 11.2%,and for FeO-SiO2-V2O3-CaO quaternary subsystem was 13.2%.