China Nonferrous Metallurgy

Vanadium-titanium magnetite in South Africa has the characteristics of ‘low titanium and high vanadium’. Titanium element is mainly dissolved in the lattice of magnetite. The content of TiO₂ in titanium slag produced by rotary kiln-electric furnace smelting process is similar to that of titanium concentrate， which can be applied to the production of titanium dioxide by sulfuric acid method. However， its phase composition is complex， which is very different from the acidolysis behavior of conventional titanium concentrate and acid-soluble titanium slag. At present， there are few studies on the titanium slag. In this study， the phase composition of titanium slag and the effects of various parameters in the process of ‘hydrochloric acid leaching-sulfuric acid hydrolysis-water leaching’ on its acid hydrolysis performance were investigated， and the control factors affecting its acid hydrolysis performance were analyzed. The following main conclusions were obtained. The higher the proportion of active phases such as anosovite in the slag sample， the lower the content of SiO₂ and Al₂O₃， the better the acidolysis rate. The silica gel and calcium sulfate crystallites formed by the decomposition of diopside are easy to form a passivation layer， which becomes the main limiting factor of the mass transfer process. The appropriate acid residue ratio （3. 8∶1） and sulfuric acid concentration （93%） can enhance the reaction kinetics， but excessive acid amount or curing process will inhibit mass transfer due to the increase of system viscosity. Appropriate refinement of particle size （?45 μm） can destroy the surface structure of insoluble phase， but too fine particles are easy to cause local agglomeration. When the main phase of the titanium slag is anosovite and the content of SiO₂ and Al₂O₃ is low， the acid hydrolysis rate of the titanium slag can reach 89. 96 % without curing under the conditions of particle size of ?45 μm， acid-slag ratio of 3. 8∶1 and sulfuric acid concentration of 93%. The results of this study can provide a basis and reference for the application of the titanium slag in the sulfuric acid titanium dioxide process.