Meilong Hu

Effect of cooling rate on the crystallization behavior of perovskite in high titanium-bearing blast furnace slag

The effect of cooling rate on the crystallization of perovskite in high Ti-bearing blast furnace (BF) slag was studied using confocal scanning laser microscopy (CSLM). Results showed that perovskite was the primary phase formed during the cooling of slag. On the slag surface, the growth of perovskite proceeded via the successive production of quasi-particles along straight lines, which further extended in certain directions. The morphology and structure of perovskite was found to vary as a function of cooling rate. At cooling rates of 10 and 30 K/min, the dendritic arms of perovskite crossed obliquely, while they were orthogonal at a cooling rate of 20 K/min and hexagonal at cooling rates of 40 and 50 K/min. These three crystal morphologies thus obtained at different cooling rates respectively corresponded to the orthorhombic, cubic and hexagonal crystal structures of perovskite. The observed change in the structure of perovskite could probably be attributed to the deficiency of O2−, when Ti2O3 was involved in the formation of perovskite.

Formation behavior of CaTiO3 during electrochemical deoxidation of ilmenite concentrate to prepare Fe–Ti alloy

The formation behavior of CaTiO3 during electro-deoxidization of ilmenite concentrate to prepare Fe–Ti alloy was investigated by experiments and simulation. The results indicate that the formation and decomposition of intermediate products, CaTiO3, are inevitable steps during electro-deoxidization of ilmenite concentrate. CaTiO3 can be generated through the hydrolyzation of molten salt and electrochemistry reaction during electrochemical process. The main reason for the generation of CaTiO3 is the electrochemistry reaction between Ca2+ from molten salt and TiO2 in the cathode. With the proceeding of the electro-deoxidization, CaTiO3 is further electrolyzed to form titanium sub-oxide. The current efficiency can be improved when CaTiO3 forms in the cathode by adding CaCO3 during sintering process.

Direct Electro-deoxidation of Ilmenite Concentrate to Prepare FeTi Alloy in CaCl2 Molten Salt

Abstract In order to prepare FeTi alloy using ilmenite concentrate in molten salt by electrolytic method, the electrochemical deoxidation process was studied by cyclic voltammetry and AC impedance spectroscopy. The electrolytic experiments at different time verified the electrochemical behavior. It is shown that the electrodeoxidation process for ilmenite concentrate mainly consists of two steps. Fe is reduced firstly from the ilmenite concentrate. The second step is the reduction of titanium dioxide with an intermediate product perovskite. At low voltage, the speed of electro-deoxidation process is mainly dependent on the electrochemical reaction. As the potential increases, the diffusion of ion becomes the main rate-controlling step for the electro-deoxidation of ilmenite concentrate.

Drying kinetics of Philippine nickel laterite by microwave heating

ABSTRACT In this study, microwave heating was used to dry nickel laterite, which contains significant quantities of free water, crystal water, and hydroxy water. The results show that the main phase of crystal water is Ca3Al6Si10O32(H2O)13, and the main phases of hydroxy water are FeO(OH) and Mg5(Al, Cr)AlSi3O10(OH)8. The microwave drying process of nickel laterite can be divided into two stages: the removal of free water and the coupled removal of free water, crystal water, and hydroxy water. The effect of particle size and microwave power output were studied, and these indicate that the drying time and specific energy consumption decrease with increasing particle diameter and microwave power. The effective diffusivity and activation energy were calculated, and these are larger in the second stage than that in the first stage. The activation energies are 27.66 and 32.80 W/g for the first and second stages, respectively. The phase transition of the product, schematic drying mechanism, and feasibility analysis of the microwave drying process are also discussed.

The Anodic Behavior of Electro-deoxidation of Titanium Dioxide in Calcium Chloride Molten Salt

Since Fray-Farthing-Chen (FFC) Cambridge process was proposed in 2000 for electrochemical extraction of titanium from titanium oxide, a great quantity of research has been carried out to investigate the mechanism of the electro-reduction of the process. Results show that the intermediate products of perovskite phases are inevitable during the electro-deoxidation process. In this paper, a new perspective focus on the anodic behavior was applied. The behavior of the graphite anode with different times has been investigated. Although the main anodic process in the electrolysis is the oxygen evolution by means of the CO2. The interphases of calcium species appeared on the cathode are closely related with chlorine ions in the molten CaCl2. In addition, the released CO2 from the anode is related with the formation of CaCO3 which floated on the surface of the molten salt.

Preparation of Titanium Foams Through Direct Electrolysis of the Sintered CaO-TiO2 in Molten Salt CaCl2

FFC process could be used to prepare titanium foams. The mixed oxides CaO-TiO2 with mole ratio 1:2 were sintered into CaTiO3-TiO2 mixture. CaTiO3-TiO2 was then used as cathode and electrolyzed in molten CaCl2 to prepare porous titanium. The porous titanium with the porosity of about 72.15% was first fabricated. The internal pores are in the presence of circular cavities and the pore size is in the range of 50–100 μm. Compared with the powder metallurgy technique using the space-holder this method promises to be lower cost and less processing. It is potential to fabricate titanium foams using FFC process.

Influence of TiO2 addition on the structure and metallurgical properties of coke

Cokes were produced in an electrical furnace from a coal blend containing varying levels of added TiO2. The effects of TiO2 levels on coke structure and properties were then considered. Mercury int...

Effect of basicity on the crystallization behavior of TiO2–CaO–SiO2 ternary system slag

Titanium-bearing blast furnace slag contains a considerable amount of unused titanium and thus causes both resource waste and environmental pollution. The enrichment and extraction of titanium from titanium-bearing blast furnace slag is an urgent problem to be solved. In the present work, the crystallization behavior of TiO2–CaO–SiO2 ternary system slag was investigated both theoretically and experimentally in the binary basicity (CaO/SiO2 mass ratio) range from 1.0 to 1.4. Thermodynamic calculation indicated that perovskite (CaTiO3) and sphene (CaTiSiO5) were the two main titanium-containing phases and perovskite was the first precipitated phase during the cooling process. With the increase of basicity, the mass percentage of both perovskite and wollastonite (CaSiO3) increased while that of sphene decreased. The experimental results showed good agreement with the thermodynamic calculation. Also, it was found that the crystals appeared to have hexagonal, leaf vein and dendritic shapes macroscopically, and their size reached the centimeter level. Observation of the three-dimensional topography suggested that the perovskite phase existed as dendrite with the orthorhombic crystal, and the sphene grew by taking the perovskite crystal as its nucleus and then wrapping the perovskite crystals.

Preparation of TiC by carbothermal reduction in vacuum and acid leaching using blast furnace slag bearing titania

Abstract A combined process of carbothermal reduction in vacuum and acid leaching is proposed to produce TiC from titanium bearing blast furnace (BF) slag from Pan Steel in Panzhihua city in China. Thermodynamics calculation shows that TiC can be obtained in the appropriate temperature and pressure range. Moreover, the results of the experiment indicate that TiC can be prepared by the combined process. The optimized parameters include particle size of original slag ideally below 200 mesh, reduction temperature of 1400°C, pressure of 1~10 Pa and mass ratio of slag and reduction (carbon powder) of 100/38. The x value in TiCx increases with increase of reduction degree while the maximum is 0.981. The final x is 0.957 in the pure TiC prepared by the combined process. Silicon and magnesium in the slag can be removed by evaporating, which makes silicon and titanium in the slag separate completely.

Preparation of TiC from Titanium Bearing Blast Furnace Slag by Carbothermal Reduction in Vacuum

Titanium bearing blast furnace slag, which contains 20%-30% TiO2, is a valuable secondary titanium resource. Based on the thermodynamics calculation effect of the temperature on the reduction of the slag in vacuum were studied at certain vacuum degrees. The results show that magnesium vapor and silicon monoxide vapor can be obtained at the condition of high temperature and low pressure. The purity of TiC increases with temperature increasing. When the temperature arrives at 1623K TiC can be obtained besides the reductant carbon. XRD result of the powder collected from the furnace cover show that magnesium and silicon in the titanium bearing BF slag leave the slag system during carbothermal reduction in vacuum. From the above it can be concluded that TiC can be obtained from the titanium bearing BF slag and silicon and titanium in the slag can be separated by carbothermal reduction in vacuum and acid leaching.