Study On Recovering Iron And Simultaneous Forming Calcium Titanate By Direct Reduction From Vanadium Titanomagnetite Concentrate

Vanadium titanomagnetite is rich in reserves,which is an important source of iron and titanium resources.Both blast furnace process and non blast furnace process have the problem of low titanium content in titanium products,which is difficult to utilize.At present,it has been found that magnesium titanate or calcium titanate can be formed by adding appropriate amount of magnesium compounds in the reduction roasting process of vanadium titanomagnetite concentrate.However,the content of iron and aluminum in magnesium titanate is high,which is difficult to utilize.It is worth noting that calcium and titanium can also be combined to form calcium titanate,which is also an important functional material and widely used.In order to provide a new way for the utilization of titanium in Panxi area,a new process of recovering iron and simultaneous forming calcium titanate by direct reduction from vanadium titanomagnetite concentrate is proposed in this study.The vanadium titanomagnetite concentrate with Fe grade of 56.80%and TiO2 grade of 12.75%was used as material,the effects of different reduction conditions on the formation of calcium titanate and the reduction effect of iron in the direct reduction of vanadium titanomagnetite concentrate under the embedding coal-based method and the coal-based method a were systematically studied.Results showed that the calcium titanate can be produced by embedding coal-based method or coal-based method in the direct reduction of vanadium titanomagnetite,but the coal-based method is better than the embedding coal-based method since the lower reductant consumption,shorter roasting time,and coarser calcium titanate particles in the roasted product could be obtained in the coal-based method.It was found that the optimum conditions for the formation of calcium titanate were as follows,the dosage of CaCO3 was 18%,the dosage of graphite is 11%,the dosage of fluorite is 1%,the roasting temperature is 1400?,and the roasting time is 120min.After two-stage grinding and two-stage magnetic separation,the calcium titanate products with yield of 23.95%,iron content of 3.72%,calcium titanate conten of 75%and the reduced iron products with iron grade of 95.61%,iron recovery of 92.83%,TiO2 content 0.83%could be obtained.Then,Ilmenite was used as sample,the formation of calcium titanate and reduction mechanism of vanadium titanomagnetite concentrate was studied by thermodynamic calculation,X-ray diffraction(XRD),scanning electron microscope and energy dispersive spectrometer(SEM-EDS).The relationship between reduction atmosphere,types of calcium compounds and formation of calcium titanate and reduction of iron were also determined.Results showed that the direct reduction of vanadium titanomagnetite concentrate to produce metallic iron and calcium titanate was carried out step by step in the two roasting methods.First,CaCO3 decomposed to produce CaO,and then magnetite reduced to produce part of metallic iron.At the same time,the inclusion structure of magnetite and ilmenite was destroyed and exposed ilmenite,ilmenite would react with CaO to form calcium titanate and FeO,and then FeO was reduced to metallic iron.It is also found that the reduction atmosphere did not affect the formation of calcium titanate,but affected the purity and particle size of calcium titanate.Moreover,the mechanism of CaCO3 and CaSO4 on the formation of calcium titanate is basically same in the two roasting methods:Ca2+in CaCO3 and CaSO4 replaced Fe2+in ilmenite to form calcium titanate.However,CaCO3 and CaSO4 have different effects on iron reduction.CaCO3 could change the reduction of iron from ilmenite reduction to FeO reduction,which maked the iron reduction much easier while producing calcium titanate,while the sulfur in CaSO4 would react with iron to form FeS in the reduction atmosphere,which decreased the formation of metallic iron.