Zhangfu Yuan

Reduction mechanism of natural ilmenite with graphite

Abstract Reduction of Bama ilmenite concentrate containing 49.78% TiO2 and 27.96% total Fe by graphite was studied using thermogravimetric analysis system under argon gas ambient from 850 to 1 400 °C. The reduction degree of Bama ilmenite is enhanced with increasing temperature and the molar ratio of carbon to oxygen, and the reaction rate varies with temperature and reduction time simultaneously. The phase transformation, chemical composition, microstructure and morphology of reduced samples were investigated by using X-ray diffractometry, scanning electron microscopy, and energy disperse spectroscopy, respectively. The high content of impurities in Bama ilmenite evidently bates the reduction of ilmenite. Forming the enrichment zone of manganese prevents complete reduction of Fe2+. The reduction products are mostly reduced iron, rutile, reduced rutiles, Ti3O5 and pseudobrookite solid solution. The reduction kinetics was also discussed. The results show that the reduction temperature is a key factor to control reaction rate.

Effect of boron on the surface tension of molten silicon and its temperature coefficient.

The influence of boron concentration (C(B)/mass%) on the surface tension of molten silicon has been investigated with the sessile drop method under oxygen partial pressure P(O(2))=1.62x10(-25)-2.63x10(-22) MPa, and the results can be summarized as follows. The surface tension increases with C(B) in the range below 2.09 mass%, and the maximum increase rate of the surface tension is about 30 mN m(-1)(mass% C(B))(-1). The temperature coefficient of the surface tension, ( partial differential sigma/ partial differential T)C(B), was found to increase with the boron concentration in molten silicon. At the interface between molten silicon and the BN substrate, a discontinuous Si(3)N(4) layer was reckoned to form and the layer might prevent BN from dissolving into the molten silicon. Since dissolved boron from the BN substrate into the molten silicon is below 0.054 mass% and the associated increase in surface tension is below 1.5 mN m(-1), the contamination from the BN substrate on the surface tension can be ignored. The relation between the surface tension and C(B) indicates negative adsorption of boron and can be well described by combining the Gibbs adsorption isotherm with the Langmuir isotherm.

Evolution of pore and surface characteristics of silica xerogels during calcining

This paper has investigated the effect of calcining temperature (600-1000degreesC) on the mesopore, structure and surface fractal dimension of silica xerogels derived from two-step acid-base-catalyzed TEOS (tetraethyl orthosilicate) systems. Two base contents were adopted in the base step. FE-SEM (field emission gun-scanning electron microscopy) observation and XRD (X-ray diffraction) analysis indicate that gel coarsening, agglomeration and sintering occurred successively with increasing temperature, and those prepared with higher base content exhibit easier agglomeration, lower sintering temperature and weaker crystallizability. Percent mesoporosity and surface fractal dimensions evaluation via image analysis methods shows that the mesoporosity of those prepared with lower base content increases below 700degreesC and decline at higher temperatures, while the surface fractal dimension appears to decrease above 800degreesC

Jet Behavior and Metallurgical Performance of Innovated Double-Parameter Oxygen Lance in BOF

A doubleparameter oxygen lance used in a 300 t converter was designed to improve the metallurgical performance. A small-scale measurement of the jet behavior was done using a computer controlled scanning system. The experimental data on the velocity distribution at the jet centerline. the contour map of the jet velocity, the deviation of the jet centerline, and the velocity distribution of the axial section were compiled. According to the results of the small-scale measurement, the doubleparameter lance was also employed for a BOF experiment, The metallurgy indexes show that the metallurgical performance was highly promoted by use of the doubleparameter lance.

Preparation of TiCl4 with the Titanium Slag Containing Magnesia and Calcia in a Combined Fluidized Bed

This paper describes a new method for producing TiCl4 by chloridizing materials of high content CaO and MgO, in which a combined fluidized bed is used as a reactor to avoid agglomeration between particles caused by molten CaCl2 and MgCl2. The combined fluidized bed consists of at least a riser tube and a semi-circulating fluidized bed. Two kinds of high titanium slag, in which the total mass content of CaO and MgO is 2.03% and 9.09% respectively, are employed to examine the anti-agglomeration effect and the conversion of the materials when the temperature ranges are between 923.15K and 1073.15K, gas apparent velocity 0.7-1.1m.s(-1), and inlet amount of solid materials is 4.6-7.0kg.h(-1). It is found that the anti-agglomeration effect in the combined fluidized bed is satisfactory and the new method can achieve a TiCl4 production capacity of 14.0-75.4t.m(-2).d(-1) in relation to 25.0-40.0t.m(-2).d(-1) from the conventional bubble bed. Furthermore, low-temperature chloridization, for example, at 923K or 973K, can also be used to produce TiCl4 and avoid agglomeration.

A Novel Method of Recycling CO2 for Slag Splashing in Converter

Converter off-gas, an important energy resource for steel industries, is one of the weak points in the recovery and utilization of secondary energy resources. To improve the level of recycling converter off-gas in steel plants, a novel approach to the recycle of CO2 separated from converter off-gas or other off-gas for the green slag splashing technique was developed, and the CO2 equilibrium conversion ratio of the green CO2 slag splashing under different technological conditions was calculated by the program of enthalpy (H), entropy (S), and heat capacity (C), i. e. HSC software. Furthermore, the experiments of CO2 injected into molten converter slag were carried out, and the influencing factors of the green slag splashing technique using CO2 were analyzed. The experimental results showed that the carbon content for smooth slag splashing using CO2 was about 4.0%.

Preparation of TiCl4 with multistage series combined fluidized bed

In order to solve the agglomeration problem in TiCl4 preparation, a new test in a multistage series combined fluidized bed was studied on a pilot scale. The pilot plant can make full use of titanium slag with a high content of MgO and CaO as the feedstock. Several experimental parameters such as chlorine flow and reaction temperature were discussed and the morphology and components of reaction product were analyzed. According to the results, the conversion rate of TiO2 is up to 90%. It is found that the combined fluidized bed has good anti-agglomeration ability because the accumulation of MgCl2 and CaCl2 on the surface of unreacted slag was carried out of the reactor.

Composition of off-gas produced by combined fluidized bed chlorination for preparation of TiCl4

Abstract The effects of carbon/slag molar ratio, chloride amount and temperature on equilibrium molar ratio (REq) of CO to CO2 for off-gas produced by carbochlorination of titanium slag were firstly investigated by thermodynamic calculation of equilibrium components of off-gas. The experimental CO/CO2 molar ratio (REx) was then obtained to be 0.2–0.3 by the carbochlorination experiment using a novel combined fluidized bed as chlorination reactor. To further investigate the reaction effect of the novel process mentioned above, REx, REq and corresponding reference data (RRe) were compared. The results indicate that REx is similar to RRe (0.5–1.2) but different from REq (≥4.3), which is consistent with anticipation of REx for the novel combined fluidized bed. The difference between REx and corresponding REq is mainly attributed to short retention time (about 1 s) of materials in combined fluidized bed and carbochlorination of oxide impurities contained in titanium slag, such as CaO, MgO and SiO2.

Comprehensive Utilization of Complex Titania Ore

To fully utilize Panzhihua titanium resources, a new process was proposed. In the process, Panzhihua ilmenite concentrate was first reduced in a rotary hearth furnace (RHF) to produce a titanium-rich material and iron. The titanium-rich material was then used in a new chlorination process to produce TiCl4. The comparison of different groups of experimental results or calculation results showed that the utilization ratio of material was improved by using the titanium-rich material after pretreatment other than low level titanic ilmenite directly and the combined fluidized beds (FTF) were more likely to reduce bed height and reaction time than the single fluidized beds (Single F or Single T) under the condition of the same chlorination conversion ratio. Finally, the influence of reduction temperature and the anti-agglomeration capacity of the combined fluidized bed was analyzed.

A new method for deoxidization and chlorination of refined ilmenite with high magnesia and calcia contents

Abstract A new process is proposed to utilize refined ilmenite with high magnesia and calcia contents, which is the main secondary resource from vanadium-bearing titaniferous magnetite in Panzhihua, covering about 40% of the worlds titanium. The refined ilmenite was first deoxidized to separate the iron in the ore in order to enrich the titanium. The mechanism of chlorination of the titanium-rich slag was analyzed using the HSC chemistry software. Following deoxidation, a tandem fluidized bed was applied to chlorinating the titanium-rich slag. Modeling of the tandem fluidized bed explains how this serial operation can effectively improve the convention ratio of TiO2 to TiCl4.