Effect of gas atmosphere on carbothermal reduction and nitridation of titanium dioxide

This article examined the reduction/nitridation of rutile in the He-N2, Ar-N2, and He (Ar)-H2- N2 gas mixtures, as well as pure nitrogen, in the temperature-programmed and isothermal experiments in a fixed-bed reactor. The extents of reduction and nitridation were determined from the off gas composition and LECO analysis. The off-gas composition was monitored using the infrared sensor (CO, CO2, and CH4) and dew point analyzer (H2O). The phase composition of the reduced samples was analyzed using X-ray diffraction (XRD). The temperature and gas composition had a strong effect on the rutile reduction. The reduction was the fastest in the H2- N2 gas mixture, followed by a reduction in nitrogen; the rate of reduction/nitridation in the He- N2 gas mixture was marginally higher than in the Ar-N2 gas. The rate of titania reduction/ nitridation in the He (Ar)-H2-N2 gas increased with the replacement of He (Ar) with hydrogen. The article also discusses the mechanisms of reduction/nitridation in different gas atmospheres

Phase development in carbothermal reduction and nitridation of ilmenite concentrates

The phase development in the course of carbothermal reduction and nitridation of ilmentie concentrates and synthetic rutile was studied in temperature programmed reduction (623-1873 K) and isothermal reduction experiments. Ilmenites and synthetic rutile were reduced in a tube reactor with continuously flowing hydrogen-nitrogen mixture or pure nitrogen. The rate and extent of reduction were monitored by online off-gas analysis. Samples reduced to different extent were subjected to XRD and SEM/BSE analyses. Pseudorutile and ilmenite were the main phases in ilmenite concentrates; rutile was the main phase in synthetic rutile. Pseudorutile was first converted to ilmenite and titania which occurred at temperatures below 623 K; iron oxides in ilmenite were quickly reduced to metallic iron. Titania was reduced to titanium suboxides and further to titanium oxycarbonitride. Reduction of ilmenites and synthetic rutile in hydrogen-nitrogen mixture was much faster than in pure nitrogen. The rate of conversion of titanium oxides to oxycarbonitride was affected by iron content in the ilmenites. The rate of reduction increased with increasing iron content in ilmenite (decreasing grade) when ilmenites were reduced in the hydrogen-nitrogen gas mixture, but decreased with decreasing ilmenite grade in reduction experiments in nitrogen; reduction in nitrogen was the fastest for synthetic rutile. The difference in the reduction behaviour was attributed to different chemical compositions and morphologies of ilmenites of different grades

Assessment of titanium carbide chlorination by statistical design

In present study, the effects of the process parameters on chlorination of Titanium Carbide (TiC) was studied. Besides that, process parameters were investigated by using experimental design of experiment (DOE) and statistical analysis. The chlorination of the samples was carried out at temperatures between 400 to 500°C. Effects of three parameters, namely temperature, soaking time, and molar ratio of potassium permanganate (KMnO4) to hydrochloric acid (HCl) were investigated. The interaction, on the rate of chlorination of TiC were statistically evaluated by using DOE. The weight loss (wt. %) was the main response taken into account in this paper. The results of the experimental design indicated that the main significant factor for chlorination of TiC was higher temperature, soaking time and higher molar ratio of KMnO4 to HCl. DOE results have demonstrated that the highest extent of chlorination obtained at the highest weight loss (wt. %) was about 54. 59 wt. % at 500°C with a soaking time of 180 minutes and KMnO4 to HCl molar ratio of 0. 17 respectively. The amounted to a titanium extraction of about 96. 39%. On the other hand, the lowest wt. lost was 30. 76 wt. % and this was obtained at 500°C for 120 minutes with KMnO4 to HCl molar ratio of 0. 09 respectively. The results obtained from this work will be employed as a guide for the future studies on chlorination of nitrided/carburized Malaysian ilmenite or titanium oxycarbonitride. The final aim was to produce TiCl4 at low temperatures (≤500°C) using the latter samples. The experimental values are in good agreement with calculations from the statistical model