Experimental Study On Optimization Of Rotary Kiln Direct Reduction-Melting Separation Process For Lump Vanadium-Bearing Titanomagnetite

Vanadium-bearing titanomagnetite is an important strategic resource in China.The lump vanadium-bearing titanomagnetite exploited in South African,has the high vanadium and high titanium characteristics.It is an important complex mineral resource which contains iron,vanadium,titanium and chromium,and it also has the obvious comprehensive utilization values.The Higveld Company in the South African accounts for 40%of the world's vanadium production each year.At present,Higveld Company is being purchased by a domestic company.If the purchase is successful,the discourse power of China's vanadium smelting industry will be greatly enhanced.South Africa Higveld Company uses direct reductionfurnace smelting process of downstream rotary kiln.However,the down-stream type rotary kiln direct reduction process has some problems,such as the slow reduction rate and low metallization rate,which can seriously affect the further smelting process and lead to the low utilizations of valuable components.With improving and optimizing the existied technology,it can not only enhance the economic efficiency and alleviate the present shortage situations of mineral resources in China,but also provide the important practical experiences for the improvement and industrialization of this technology process.In this paper,the reverse-flow type rotary kiln direct reduction-smelting separation process is proposed for the lump vanadium-bearing titanomagnetite.First,under the laboratory conditions,the rotary kiln direct reduction technology parameters study on the utilizations of lump vanadium-bearing titanomagnetite is carried out,and the law of phase transition in the reduction process is also clarified.Secondly,the distribution constants of valuable components in metallized ores between titanium-bearing slag and iron melt and its influenced factors are theoretically analyzed.And the key parameters affecting the distribution constants of vanadium,chromium,silicon and titanium are acquired.Finally,the experiments on the smelting separations of metallized lump vanadium-bearing titanomagnetite are carried out,and the suitable smelting separation parameters are obtained accordingly.The conclusions are as follows:(1)Through the rotary kiln direct reduction experiments,it is found that the reduction temperature and reduction time are the most important parameters for the direct reduction process.The suitable reduction process parameters are reduction temperature 1150?,reduction time 4 h,carbon ratio 1.2,lump vanadium-bearing titanomagnetite size 8-12 mm and pulverized coal particle size<8 mm.Under these conditions,the metallization rate of reduced product is 88.61%,and the surface of reduced product has no melting phenomenon,which meets the requirements of production process.The phase transition process in the direct reduction process is Fe3O4?FeO?Fe,Fe9TiO15?Fe2.75Tio.25O4?Fe2.5Ti0.5O4?FeTiO3?Fe,vanadium and chromite oxide are reduced to oxides or carbides.(2)With the aggregated electron phase-wagner model,the thermodynamic calculations about the element distributions between titanium-bearing slag with 60wt%TiO2 and pig iron are carried out.The results show that the temperature and content of FeO in the slag are the key parameters affecting the distribution constants of vanadium,chromium,silicon and titanium.The increase of temperature,basicity and MgO content is beneficial to transfer the elements in the slag into pig iron.But the increase of content of FeO in the slag is bad for the elements spreading in the pig iron.According to the fitting relationship between the distribution ratio of vanadium and chromium in the pig iron and the content of FeO in the slag,when the content of FeO in the slag is less than 4%,it is beneficial to dissolve the vanadium and chromium into the pig iron.(3)With the thermodynamic in the smelting process of metallized lump vanadium-bearing titanomagnetite and CaO-SiO2-MgO-Al2O3-TiO2 phase diagram calculated by Factsage 7.0,it clarifies that the increase of basicity and content of MgO and FeO in the slag can both decrease the melting temperature and viscosity of titanium-bearing slag.The ideal smelting separation parameters are as follows:the basicity is 0.5-0.6,the MgO/SiO2 is 1.5?1.8,and the content of FeO in the slag is 4%.(4)Under the low basicity condition,the smelting separation parameters of metallized lump vanadium-bearing titanomagnetite contain the smelting temperature 1600?,the basicity 0.6,the carbon ratio 1.6,and the smelting time 100 min.The experimental index results are as follows:the recovery rate of Fe,V and Cr in the pig iron is 97.08%,75.57%and 98.64%,respectively.The recovery rate of TiO2 is 99.76%in the titanium-bearing slag.In this condition,if the smelting process has no crucible erosions,the grade of TiO2 is 57.11%in the slag.(5)Under the high basicity condition,the smelting separation parameters of metallized lump vanadium-bearing titanomagnetite are the smelting temperature 1600?,the basicity 1.0,the carbon ratio 1.6,and the smelting time 100 min.The experimental results are as follows:the recovery rate of Fe,V and Cr in the pig iron is 99.74%,92.53%and 99.10%,respectively.The recovery rate of TiO2 is 99.71%in the titanium-bearing slag.In this condition,if the smelting process has no crucible erosions,the grade of TiO2 is 55.06%in the slag.