| Titanium slag produced by electric funace smelting from ilmenite accounts for more than 70%of total of rich titanium product.This prosess has been widespreadly applicated due to the advantages of its short flow,large capacity and less wastes.Howere,the titanium slag produced form the hard rock ilmenite ore is high in deleterious impurities and is not acceptable as a feedstock to the chloride process.Consequently,it is essential to upgrade titanium slag so it can be used for chloride process.In this work,the titanium slag with high concent impurities from Panzhihua Iron&Steel Company was taken as raw material.The mineralogy of titanium slag,oxidation-reduction behavior,acid leaching and alkali leaching were systematacially investigated by modern measure such as scanning electron microscopy,X-ray diffraction,X-ray fluorescence spectrometry.A novel process of producing rich titanium product by oxidation-reduction and fllowed acid and alkali leaching has been developed.The conclusions were as follows:(1)In the titanium slag,TiO2 concent was 72.84%,main impurities were Fe,Si,Mg,Al and Ca,especially,CaO and MgO which were up to 6.99%.The main phase present in the titanium slag were anosovite solid solution and silicate galss with mosaic structure.The averaged empirical formula of anosovite determined by SEM-EDS was(Fe0.143 Mn0.020Mg0.171)·(Ti1.212Al0.184)2O5.Fe,Mg,Mn,A1 mainly occurred in the anosovite.(2)The study of oxidation behavior shown that trivalent titanium was converted to rutile and low valence iron was converted to hematite and pseudobrookite,repectively,under the conitions of 1000? for 2h.The main phases present in the oxdized titanium slag were pseudobrookite-armalcolite solid solution,rutile,silica,hematite and silicate glass.According to the analysis of SEM and XRD,after oxidation roasting the stable structure of anosovite was destroyed;the silica in free state decomposed from the silicate glass.Fe concentrated on the edge of particle after roasting at 1000?.(3)The dynamics of titanium slag oxidation indicated that oxidation process of titanium slag followed unreacted core contraction model.The controlling step was determined by oxidation of Ti within the range of 695K?800K;within the range of 800K?1000K,interfacial chemical reaction and oxygen diffusion were the limit elements;and within range of 1000K?1200K,it was oxygen diffusion.(4)The study of reduction roasting of oxidized titanium slag shown that the phases prensent in reduced titanium slag were ferro-pseudobrookite-armalcolite solid solution,rutile,silica,silicate glass as the temperature was less than 800?;within the range of 800??900?,the phases prensent were ferro-pseudobrookite-armalcolite solid solution,ilmenite rutile,silica,silicate glass;when the temperature was above 900?,the ilmenite disappreaed,while the anosovite appeared.The ilmenite can been compounded between hematite and rutile under the reducing atmosphere at the temperature of 800?~900?.The oxidized slag was rosated in CO atmosphere,and followed leachde in hydrochloric acid solution for 7h,the TiO2 grade increased to approximately 87%.When carbon powder was used as reducing agent,the the TiO2 grade was up to above 90%after acid and alkali leaching.(5)The study of acid leaching behavior of reduced titanium slag shown that the pressure acid leaching could remove impurities effectively because Fe,Mg and other impurities dissolving in the ilmenite and ferro-pseudobrookite-armalcolite solid solution were dissolved in the hydrochloride,TiO2 grade of titanium slag increased to around 85%.The optimum acid leaching conditions:the concentration of HCl is 20%,the leaching time is 9h,the S/L ratio is 8 to 1,the temperature is 165?,the average particle size is 120?m.The leaching rate of impurities from high to low:Fe2O3>MgO>MnO>Al2O3>CaO>SiO,the leaching rates of Fe2O3 and MgO reached more than 70%,the leaching rates of MnO,Al2O3 and CaO were up to 50%,in contrast,the the leaching rates of SiO2 was down to less than 5%,which indicated that acid leaching could not remove SiO2 effectively.According to the phase analysis,the main phases present in the acid leached slag were rutile,silica and silicate glass.(6)The study of alkali leaching behavior of acid leached titanium slag shown that alkali leaching could remove the impurities of Si and Al effectively.The basic leached residue with more than 90 mass percent TiO2 and less than 1.5 mass percent(CaO +MgO)was yielded after alkali leaching at normal atmospheric pressure.Using acid pickling process treat the basic leached residue,The rich titanium product with about 95%TiO2 and less than 0.63%(CaO + MgO)was produced.According to the phase analysis,the main phase present in the basic leached residue was rutile.(7)The novel process of preparation of high quality rich titanium product from titanium slag by oxidation-reduction and followed acid and alkali leaching,pickling,open a way for titanium slag from Panzhihua Iron&Steel Company-to produce rich titanium product that contains more than 95%TiO2.In addition,the particle size could meet the requirment for chloride process.What is more,the waste acid can be recycled and utilized.The whole process is friendly to the environment. |
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