Removal of impurities from titanium-bearing sources and theoretical and experimental kinetic studies

This thesis work mainly evaluates methods of obtaining pure titanium hydride from different sources and methods and its theoretical and experimental kinetics using model formulation. The first route was to use Direct Reduction of Titanium Slag (DRTS) in which metallic titanium can be obtained by dehydrogenation of titanium hydride after impurities are removed. The leaching characteristics of iron removal from the reduced upgraded titanium slag was studied with mild hydrochloric and boric acids under ambient pressure and elevated pressure. Under the constraint that 1% (w/w) of titanium hydride loss is the maximum amount tolerable, 0.1 M hydrochloric acid at 140 °C was found to be the most effective condition for iron removal (87.63%). A factorial design of experiment for equation modeling with three main factors (temperature, concentration of hydrochloric, and boric acids) was performed and associated modeling results were in good agreement with experimental data. Additional study was carried out to justify the assumption, which utilized the evaluation of the effects of three empirical size distributions, the Gate-Gaudin-Schuhmann distribution, the Rosin-Rammler-Bennett distribution, and the Gamma distribution, on the fluid-solid reaction kinetics. The expressions for overall conversion rate of entire particle assemblages were derived mathematically, and calculated by a technical computing language, “MATLAB”. According to the calculation, the assumption that particle size is uniform can be valid in the determination of fluid-solid kinetics in the case where the coefficient of variation (CV) is less than 0.5. Based on the theoretical kinetic study for the effect of particle size distribution, it was assumed that the effect of particle size distribution of reduced upgraded titanium slag (UGS) does not have to be considered in the calculation of kinetics. Based on this calculation, a rate-controlling process can be found and it seems to follow interfacial reaction controlled kinetics. The activation energy of the reaction was determined to be 73.9 kJ/mole. Also, the other mechanism of the reaction-controlling process (solid-state diffusion) is suggested. An additional way of obtaining pure titanium involves the extraction of titanium from ilmenite using tannic acid. The experimental and modeling results showed the feasibility of the new process to obtain titanium.