Study On Kinetics Of Pre-Reduction Process Of Molten Vanadium Slag

At present,the main smelting method of ferrovanadium in China is to transform V3+to V5+ in the slag by oxidizing and roasting the vanadium slag.Then,the product of V2O5 is prepared by means of wet leaching and secondary roasting.Finally,V2O5 is mixed with iron filings and reducing agent,and the ferrovanadium alloy is obtained after heating and refining.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 smelting process of ferrovanadium alloy with short process and green and high efficiency.At the same time,a large number of photovoltaic materials and electrolytic aluminum are produced in our country,amount 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.The pre-reduction stage mainly uses photovoltaic cutting waste PCW to reduce molten vanadium slag.This stage mainly includes the dissolving process of SiO2 in PCW,The reduction process of Si in cutting scrap to FeO in slag and the reduction process of SiC in scrap to FeO in slag.Furthermore,based on high-temperature kinetic experiments,the effects of dissolution time and different slag components on the dissolution kinetics of SiO2 in the pre-reducing slag were investigated.In addition,the effects of temperature and reaction time on the reduction process were illuminated.And then the dissolution kinetic model of SiO2,the liquid-liquid reaction kinetic model of Si and the solid-liquid reaction kinetic model of SiC were established respectively,and the restrictive links of the above three process were analyzed.The conclusions were as follows:(1)At 1550?,the content of FeO was 31.4%,26.7%and 24.5%after reduced by Si for 180,360 and 600 s,respectively.It can be seen that the reaction speed is slower with the increase of reaction time at a certain temperature.At 600 s,Si was almost completely involved in the reaction.In addition,with the increase of reaction temperature,the reaction progress completes faster.But with the increase of reaction time,there is no obvious effect on the reaction rate by temperature.The activation energy in the process of Si reducing(FeO)is obtained to be Ea=145.29 kJ/mol by high temperature experiments and kinetic model establishment.It is concluded that the limiting link of the reaction is the diffusion and mass transfer of SiO2 in slag.(2)At 1550?,the content of(FeO)was 31.3%,21.1%and 8.2%after reduced by SiC for 210,480 and 1200 s.The same conclusion can be drawn that the reaction speed is slower with the increase of reaction time at a certain temperature.At 1200 s,SiC was almost completely involved in the reaction.with the increase of reaction temperature,the reaction progress completes faster.However,with the increase of reaction time,there is no obvious effect on the reaction rate by temperature.Through the high temperature experiment of reduction kinetics and the establishment of kinetic model.The process of SiC reduction(FeO)is a first-order reaction.The activation energy is Ea=1 34.35 kJ/mol,and the limiting link is the diffusion and mass transfer of SiO2 in slag.(3)For the slag with basicity of 0.42,1600 ? and(FeO)reduction of 20%,the conversion rates of SiO2 is 0.23,0.34 and 0.39 at 30,60 and 90 s,respectively.It can be seen that the dissolution rate of SiO2 decreases with the increase of time.(4)The reduction degree of FeO in slag also has an obvious effect on the dissolution rate of SiO2 in slag.At 1600?,the dissolution rate decreased with the increase of(FeO)reduction degree.The conversion of SiO2 at 0%reduction degree is 1.51?1.70 times and 1.97?2.17 times of that at 20%and 40%reduction degree,respectively.(5)At 1600?,the limiting link in the dissolution process of SiO2 is the boundary layer chemical reaction,and the reaction coefficients are 2.30 × 10-6,2.06 × 10-6 and 1.96 × 10-6 m/s when the reduction degree of FeO is 0%,20%and 40%,respectively.This shows that the higher the degree of reduction is,the slower the dissolution rate of SiO2 is.