Fundamental Research On Reduction Of High-Impurity Ilmenite At Low-Temperature

Titanium and its compounds are important strategic metal resources in the country. As the demand for titanium products keeps growing and the stocks of domestic and foreign natural rutile keep decreasing, low-grade ilmenite is more and more important. It is necessary to learn how to make full use of ilmenite. But due to its complex crystal structure and special chemical composition, the ilmenite is hard to be smelted.There are many shortcomings in current ilmenite treatment process. This thesis studied about ilmenite from western region of Panzhihua in Sichuan Province, where has a large reserve of ilmenite with high impurity contented. By means of low-temperature metallurgy, reinforcement measures of ilmenite reduction were found. My work in this thesis can provide theoretical guidance for industrial production of low-temperature ilmenite smelting. Main results are as follows:(1) A new ilmenite treatment process as indirect magnetic roasting separation was proposed. FeTiO3can be oxidized to Fe2TiO5by O2or air, and then Fe2O3and Fe2TiO5are easier to be magnetic roasted into Fe3O4with lower concentration of CO or relatively low temperature. By ball-milling and magnetic separation, Iron fines and Titanium slag can be got.(2) Reduction of ilmenite reacts by step as:FeTiO3â†'TiO2â†'Ti3O5â†'Ti2O3. Carbon thermal reduction of ilmenite is an indirect process:FeTiO3mainly reacts with CO, which is produced by carbon gasification reaction. Under the temperature involved in this thesis, TiO2can hardly be reduced to lower valence titanium oxide, and impurity can not be reduced to elementary substance.(3) The ilmenite studied in my thesis contains higher level of impurities, and the grade of Titanium and Iron is quite low. A thermogravimetric reduction experiments in non-isothermal conditions was designed. When temperature between860℃to1100℃, interfacial chemical reaction is the rate determining step, and apparent activation energy of non-catalytic reaction is about261KJ/mol.(4) With the granularity of ilmenite refining and addition of catalyst, rate and speed of reduction elevated, both apparent activation energy and pre-exponential factor are getting lower. The effect of different catalyst (anionic group) was studied: Na2B4O7>NaF>NaCl>Na2SiO3. Interaction between catalyst and impurity is one of the causes of the different catalytic effects.(5) Compared with vertical resistance furnace, the microwave heating has the advantages of high heating efficiency and fast heating rate. Extent of carbon gasification reaction by microwave heating is much better than that of vertical resistance furnace, reduction of ilmenite is more fully, and the formation and growth of the iron grains is promoted more effectively. In kilo-level microwave reduction experiments, it is appropriate when carbon content is about20%.