Jue Tang

Effects of MgO and TiO2 on the viscous behaviors and phase compositions of titanium-bearing slag

The effects of MgO and TiO2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed by Fourier transform infrared (FTIR) spectroscopy. Subsequently, main phases in the slag and their content changes were investigated by X-ray diffraction and Factsage 6.4 software package. The results show that the viscosity decreases when the MgO content increases from 10.00wt% to 14.00wt%. Moreover, the break-point temperature increases, and the activation energy for viscous flow initially increases and subsequently decreases. In addition, with increasing TiO2 content from 5.00wt% to 9.00wt%, the viscosity decreases, and the break-point temperature and activation energy for viscous flow initially decrease and subsequently increase. FTIR analyses reveal that the polymerization degree of complex viscous units in titanium-bearing slag decreases with increasing MgO and TiO2 contents. The mechanism of viscosity variation was elucidated. The basic phase in experimental slags is melilite. Besides, as the MgO content increases, the amount of magnesia–alumina spinel in the slag increases. Similarly, the sum of pyroxene and perovskite phases in the slag increases with increasing TiO2 content.

Reduction mechanism of high-chromium vanadium-titanium magnetite pellets by H2-CO-CO2 gas mixtures

The reduction of high-chromium vanadium–titanium magnetite as a typical titanomagnetite containing 0.95wt% V2O5 and 0.61wt% Cr2O3 by H2–CO–CO2 gas mixtures was investigated from 1223 to 1373 K. Both the reduction degree and reduction rate increase with increasing temperature and increasing hydrogen content. At a temperature of 1373 K, an H2/CO ratio of 5/2 by volume, and a reduction time of 40 min, the degree of reduction reaches 95%. The phase transformation during reduction is hypothesized to proceed as follows: Fe2O3 → Fe3O4 → FeO → Fe; Fe9TiO15 + Fe2Ti3O9 → Fe2.75Ti0.25O4 → FeTiO3 → TiO2; (Cr0.15V0.85)2O3 → Fe2VO4; and Cr1.3Fe0.7O3 → FeCr2O4. The reduction is controlled by the mixed internal diffusion and interfacial reaction at the initial stage; however, the interfacial reaction is dominant. As the reduction proceeds, the internal diffusion becomes the controlling step.

Optimized use of MgO flux in the agglomeration of high-chromium vanadium-titanium magnetite

The optimized use of MgO flux in the agglomeration of high-chromium vanadium-titanium magnetite was investigated systematically through sinter and pellet experiments. MgO was added in the form of magnesite. When the content of MgO in the sinter was increased from 1.95wt% to 2.63wt%, the low-temperature reduction degradation index increased from 80.57% to 82.71%. When the content of MgO in the pellet was increased from 1.14wt% to 2.40wt%, the reduction swelling index decreased from 15.2% to 8.6%; however, the compressive strength of the oxidized pellet decreased dramatically and it was 1985 N with an MgO content of 1.14wt%. This compressive strength does not satisfy the requirements for blast-furnace production. When all of the aforementioned results were taken into account, the sinter with a high MgO content (2.63wt%) matching the pellet with a low MgO content (less than 1.14wt%) was the rational burden structure for smelting high-chromium vanadium-titanium magnetite in blast furnaces.

Optimization of BF Slag for High Cr2O3 Vanadium-titanium Magnetite

In order to clarify the slag system of high Cr2O3 vanadium-titanium magnetite smelting in BF (blast furnace), the melting properties of slag samples prepared by analyticaly pure reagents were measured. By means of orthogonal test synthetic weighted score method, the optimal slag for high Cr2 O3 vanadium-titanium magnetite was obtained, which contained 10% MgO, 8% TiO2 and 15% Al2O3, with the binary basicity being 1.15. In addition, the effects of basicity, MgO, TiO2 and Al2O3 on slag melting properties were investigated by single factor test, and the results showed that, with increasing the basicity or TiO2 content, melting temperature (Tm) increased, whereas initial viscosity (η0) and highGtemperature viscosity (ηh) decreased. With increasing the MgO content, Tm decreased firstly and then increased. With increasing the Al2O3 content, Tm increased, and η0 and ηh decreased firstly and then increased.

Fundamental research on iron coke hot briquette – A new type burden used in blast furnace

In order to improve blast furnace efficiency, reduce CO2 emission and accelerate energy utilisation, a new preparation process of iron coke hot briquette (ICHB) based on the raw materials conditions in China, a new type blast furnace ironmaking burden, was experimentally investigated in this paper. The new preparation process was researched and optimised through single factor experiment and orthogonal experiment. Meanwhile, the reactivity and the post-reaction strength of ICHB prepared under the optimised conditions were tested and the effect of ICHB on the thermal performance of conventional coke was researched. In addition, softening and dripping properties of mixed burden with optimised ICHB charging was simultaneously investigated. The results showed that the optimised preparation parameters of ICHB include 15% iron ore, 65% bituminous coal, 350°C hot briquetting temperature, 1100°C carbonisation temperature and 4 hours carbonisation time. The reactivity and the post-reaction strength of ICHB prepared under the optimisation conditions are 62.4 and 10.6%, respectively. ICHB has protective effect on conventional coke and the protective effect is more obvious with 10% ICHB adding. With the increase of ICHB charging ratio, softening interval T40–T4 of mixed burden is widened while melting interval TD–TS (namely cohesive zone) is narrowed. Additionally, the permeability of mixed burden becomes better and dripping ratio is first increased then decreased. The suitable charging ratio of ICHB in mixed burden is about 30%.

Current status and development trends of innovative blast furnace ironmaking technologies aimed to environmental harmony and operation intellectualization

Blast furnace (BF) ironmaking is dominant for reducing pollution emission and energy consumption in iron and steel industry. Under the increasingly strict environmental pressure, some innovative technologies of BF ironmaking for environmental protection have been developed and applied in actual operating facilities. The current state of BF ironmaking in Europe, America, Japan, and China were briefly overviewed. Moreover, some innovative BF ironmaking technologies aiming at environmental harmony and operation intellectualization in the world, such as waste gas recycling sintering, BF operation with coke oven gas injection, ferro-coke, lime coating coke, BF visualization and intellectualization, were roundly summarized. Finally, some discussion on the technologies was carried out and the development trends of BF ironmaking were pointed out. The review could provide references and supports for the progress of environment-friendly technologies of BF ironmaking, thereby promoting their practical applications and achieving sustainable development of BF ironmaking, especially for Chinese ironmaking industry.

Carbothermic Reduction Mechanism of Vanadium-titanium Magnetite

To achieve the high-efficiency utilization of vanadium-titanium magnetite (VTM), reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter, temperature, time, and carbon ratio (molar ratio of fixed carbon in coal to oxygen in iron oxides of VTM) on reduction degree were investigated. Results show that reduction degree increases with increasing volatile matter in coal, temperature, time, and carbon ratio. Phase transformation, microstructure, and reduction path were analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and FactSage 6.0. The thermoravimetry-differential scanning calorimetry-quadrupole mass spectrometer method was used for kinetic analysis of the main reduction process. Results indicate that the kinetic mechanism follows the principle of random nucleation and growth (n = 4), and the activation energy values at 600–900 and 900–1350 °C are 88.7 and 295.5 kJ/mol, respectively.

Study on Metallized Reduction and Magnetic Separation of Iron from Fine Particles of High Iron Bauxite Ore

Abstract High iron bauxite ore is a typical unmanageable polyparagenetic resource and owns high comprehensive utilization value. Separation of iron from fine particles of high iron bauxite ore by the process of metallized reduction and magnetic dressing was researched systemically. The effect of magnetic field intensity, reduction temperature, reduction time, mole ratio of fixed carbon to reducible oxygen (FC/O) and ore particles size on separation indexes was researched. The results show that, with the conditions of reduction temperature of 1,400 °C, reduction time of 180 min, FC/O of 2.0, ore particle size of –2.0 mm and magnetic field intensity of 40 KA/m, about 89.24 % of the iron could be removed from high iron bauxite ore as metallic iron. Meanwhile, 86.09 % of the aluminum is stayed in non-magnetic fraction as alumina. However, the formation of hercynite (FeAl2O4) limits the reduction rate of iron oxides to metallic iron. The lower reduction conditions and higher recovery ratio of iron could be achieved with adopting ore-coal composite agglomerates or adding catalyst.

Analysis of Gas Thermodynamic Utilization and Reaction Kinetic Mechanism in Shaft Furnace

The technology of coal gasification in shaft furnace is an effective way to develop direct reduction iron in China. In order to clarify the process of the reduction of oxidized pellets in shaft furnace by carbon monoxide or hydrogen in two ways, i. e. thermodynamics and kinetics, the gas utilization and reaction mechanism were studied by theoretical computations and isothermal thermogravimetric experiment. The results showed that the gas utilization increased with the rise of temperature when xH2/xCO⩾1 and with the increase of xCO/(xH2+xCO when temperature is less than 1073 K. The water-gas shift reaction restrains efficient utilization of gas, particularly in high temperature and hydrogen-rich gas. The gas utilization dropped with increase of carburization quantity of direct reduction iron (DRI) and oxygen potential of atmosphere. With the increase of both temperature and content of H2 in inlet gas, the reaction rate increased. At 100% H2 atmosphere, the interfacial chemical reaction is the dominant reaction restricted step. For the H2-CO mixture atmosphere, the reduction process is controlled by both interfacial chemical reaction and internal diffusion.

Optimisation study and affecting mechanism of CaO/SiO2 and MgO on viscous behaviours of titanium-bearing blast furnace slag

ABSTRACT To improve the metallurgical properties of titanium-bearing blast furnace slag, the orthogonal test was carried out and analysed by the multi-index synthetic weighted scoring method. The optimal slag compositions of titanium-bearing BF slag were CaO/SiO2 1.25, MgO 12.00 wt-%, Al2O3 11.00 wt-% and TiO2 10.00 wt-%. In addition, the CaO/SiO2 and MgO content had important effects on the break-point temperature, viscosity and activation energy of viscous flow. With an increasing CaO/SiO2 from 1.10 to 1.30, the break-point temperature increased, the slag viscosity and the activation energy of viscous flow decreased. As the MgO content grew from 6.00 to 12.00 wt-%, the viscosity decreased, while the break-point temperature and the activation energy of viscous flow first reduced and then increased. Besides, the deeply relevant mechanism was researched by Factsage 7.0, Fourier transform infrared spectroscopy and X-ray diffraction.