| Vanadium-bearing titanomagnetite is a kind of multielements-coexistent iron ore,such as iron(Fe),vanadium(V)and titanium(Ti).Therefore,how to realize efficiently the utilization of vanadium-bearing titanomagnetite resource is important for promoting the continuous development of our national economy.Based on the analyses and discussion of thermodynamic calculations and the smelting processes of vanadium extraction and direct reduction,a novel process with the technologies of extracting vanadium by selective chlorination of vanadium technology is of high material adaptability,low energy consumption,and less pollution.For the extraction of vanadium,two different chlorination experiments,one for roasting of vanadium-bearing titanomagnetite ore with rich oxygen-cold forming-chlorination and the other for cold forming of vanadium slag-chlorination.are conducted.Considering the characteristics of vanadium-bearing titanomagnetite ore.coal as reduction agent are used for making pellets.Then the method of direct reduction is used for reducing the raw pellets to the metallized pellets.Finally,iron and slag are separated at an elevated temperature in the smelting separation progress.With the theoretics methods of thermodynamics and kinetics,modern analysis technologies of X-ray diffraction(XRD),optical microscopy,scanning electron microscopy-energy disperse spectroscopy(SEM-EDS),inductive coupled plasma(ICP),X-ray Fluorescence(XRF)and etc.,the study is undertaken and related research achievements are obtained as follows:(1)The thermodynamic analysis of chlorination vanadium extraction by chlorination from vanadium-bearing titanomagnetite and vanadium slag shows that vanadium extraction by chlorination and extracting vanadium from vanadium-rich resources by selective chlorination with FeClx is feasible.The higher valence of vanadium in vanadium resources,the easier for extracting vanadium by the selective chlorination.(2)The thermodynamics analysis of the compounds in vanadium resources shows that if FeCl2 or FeCl3 selected as the chlorinating agent,and when the experiment temperature is higher than 800K,the chlorination order of various metal oxides in the chlorination process is K2O>Na2O>CaO>MnO>V2O5;The stable region of VOCl3 will shrink gradually with the chlorination temperature rising,and the stable region of VOCl3 enlarges with the reduce of its part pressure.(3)Chlorination experiments show that,the extraction ratio of vanadium with FeCl3 as the chlorinating agent is higher than that of ratio with FeCl2 as the chlorinating agent under the same experimental conditions;Same conditions of chlorination temperature,chloride atmosphere and the reaction time,higher mole ratio of chlorinating agent used has a higher ratio of vanadium extraction;Same chlorinating agent.chlorinated agent ratio,chlorination temperature and reaction time,oxygen atmosphere has a higher ratio of vanadium extraction;The optimal experimental conditions in this study are 1:2 of chlorinating agent ratio,1000K of chlorination temperature,2 hours of chlorination time when vanadium slag is used as the raw material and FeCl3 is used as the chlorinating agent,in which the ratio of vanadium extraction will reach to 57%.For vanadium-bearing titanomagnetie,the optimal experimental conditions are 1:2 of chlorinating agent ratio,1100K of chlorination temperature,2 hours of chlorination time when FeCl3 is used as the chlorinating agent and the ratio of vanadium extraction will reach to 32%.(4)The thermodynamic study of vanadium-bearing titanomagnetite reduction indicates,over the temperature range of 1300 K?1600 K,oxides of iron can be reduced by fixed carbon while those of titanium can't,and the CO can't reduce them.So the separation of iron and titanium is possible by controlling the reduction reaction in the temperature range.(5)The dynamics model of vanadium-bearing titanomagnetite pellets containing carbon in the process of direct reduction is discussed.The control step link in the process of reduction and the activation energy of the reaction are determined through the model.(6)The effect of C/O,reduction temperature,and reaction time on metallized ratio of pellets is investigated in the direct reduction experiments and the direct reduction experiments with low ratio of C/O is also undertaken.The results show that ? the high metallized ratio of pellets can be achieved easily while the C/O of pellets is high;? increasing temperature is better for the increase of metallized ratio of pellets;? in the initial stage of the reaction,the metallized ratio of pellets will increase with the prolongation of time,and after that it differs with the difference of reaction atmosphere and C/O;? when the C/O of pellets is decreased,the effects of reduction temperature and reaction time on metallized ratio of pellets is the same as those of above.(7)Reaction atmosphere,melting temperature,reacting time,and the effects of carburizing on the melting are investigated in the smelting separation experiment with high temperature.The results show that ? under the protection of nitrogen,iron crystal grew up gradually with the increasing of the melting temperature in the exploration stage;? under the condition of reducing atmosphere and completed carburizing,separation of slag and iron can be realized;? by using scanning electron microscopy and analyzing the elements distribution of melting samples,it is found that metallic iron phase is the main phase in the metal sample and titanium oxide and compound oxides of Si?Al,Mg is the main phase in the slag sample;? under the condition of reducing atmosphere and limited carburizing,separation of slag and iron can be realized by improving slag composition and properly prolonging melting time.In general,not only chloride wastes can be reused but also the recovery of vanadium.titanium,and iron can be conducted efficiently using this novel process based on the technologies of extracting vanadium by selective chlorination using chloride wastes and direct reduction.Therefore?the proposed process in this study is prosperous in the future. |
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