Xiang-dong Xing

Reduction Kinetics of Vanadium Titano-Magnetite Carbon Composite Pellets Adding Catalysts Under High Temperature

Experiments were carried out by adding CaF2 and NaF as catalysts in an Ar atmosphere to study the isothermal reduction kinetics of vanadium titano-magnetite carbon composite pellets under high temperature in the range from 1473 to 1673 K. The scanning electron microscope (SEM) was used to characterize the microstructure of product. By analyzing reduction mechanism, it was foundthat the rate controlling step was gas diffusion, and the activation energy was 178.39 kJ/mol without adding any catalysts. Adding CaF2 or NaF of 3% to vanadium titano-magnetite carbon composite pellets can decrease the apparent activation energy of reduction, and the decrease extent was 14.95 and 15.79 kJ/mol, respectively. In addition, temperature was an important factor influencing on reaction rate.

Reduction mechanisms of pyrite cinder-carbon composite pellets

The non-isothermal reduction mechanisms of pyrite cinder-carbon composite pellets were studied at laboratory scale under argon (Ar) atmosphere. The composite pellets as well as the specimens of separate layers containing pyrite cinder and coal were tested. The degree of reduction was measured by mass loss. The microstructures of the reduced composite pellets were characterized by scanning electron microscopy (SEM). It is found that the reduction processes of the composite pellets may be divided into four stages: reduction via CO and H2 from volatiles in coal at 673–973 K, reduction via H2 and C produced by cracking of hydrocarbon at 973–1123 K, direct reduction by carbon via gaseous intermediates at 1123–1323 K, and direct reduction by carbon at above 1323 K. Corresponding to the four stages, the apparent activation energies (E) for the reduction of the composite pellets are 86.26, 78.54, 72.01, and 203.65 kJ·mol−1, respectively.

Mechanisms of Swelling of Iron Ore Oxidized Pellets in High Reduction Potential Atmosphere

The influences of the time, temperature and atmosphere on the reduction swelling of oxidized pellets were investigated by single factor experiments. The mechanisms of reduction swelling of oxidized pellets were analyzed and investigated by SEM (scanning electron microscopy) and XRD (X-ray diffractometer) analysis. The results show that the change rules of reduction swelling index of oxidized pellets in different reduction atmospheres are very similar. With the increase of reduction time, the reduction swelling index moves up firstly and then down. When the reduction temperature is above 900 °C, α-quartz turns into α-tridymite, and the transition generates additional volume expansion effect. The reduction swelling index changes faster in H2 atmosphere than in CO atmosphere. Increasing H2 content in the reduction atmosphere is useful to decrease the reduction swelling index, but it is also easy to cause oxidized pellets cracking.

Effect of aluminum oxide on the compressive strength of pellets

Analytical-reagent-grade Al2O3 was added to magnetite ore during the process of pelletizing, and the methods of mercury intrusion, scanning electron microscopy, and image processing were used to investigate the effect of Al2O3 on the compressive strength of the pellets. The results showed that, as the Al2O3 content increased, the compressive strength of the pellets increased slightly and then decreased gradually. When a small amount of Al2O3 was added to the pellets, the Al2O3 combined with fayalite (2FeO·SiO2) and the aluminosilicate (2FeO·2Al2O3·5SiO2) was generated, which releases some iron oxide and reduces the inhibition of fayalite to the solid phase of consolidation. When Al2O3 increased sequentially, high melting point of Al2O3 particles hinder the oxidation of Fe3O4 and the recrystallization of Fe2O3, making the internal porosity of the pellets increase, which leads to the decrease in compressive strength of the pellets.

Congregated electron phase and Wagner model applied in titanium distribution behavior in low-titanium slag

Abstract For studying the carbon thermal reduction rules of titanium in hot metal and providing a theoretical basis for the blast furnace (BF) hearth protection, the distribution behavior of titanium between low-titanium slag system of CaO–SiO 2 – MgO–Al 2 O 3 –TiO 2 and hot metal was studied using analytical reagents in a temperature range from 1350 °C to 1600 °C. Through high temperature melting, rapid quenching, chemical analysis and thermodynamic model calculating, the results showed that the increase of reaction temperature, which improved the titanium distribution L (Ti) and lowered the system activity coefficient γ sys , leads to the rise of equilibrium constant. Combined with Wagner and congregated electron phase models, the data obtained in distribution experiments were used to fit out the Gibbs free energy formula of titanium carbothermic reduction. Finally, the relations between the contents of Si and Ti in hot metal and the titanium load to reach the minimum w (Ti) for the formation of TiC were given.

Reduction of Pyrite Cinder Pellets Mixed with Coal Powder

Direct reduction of pyrite cinder in a rotary hearth furnace (RHF) was studied under the condition of laboratory simulation. Effects of reduction temperature, reduction time, molar ratio of carbon to oxygen, and CaO addition on metallization rate as well as compressive strength of the pellets after reduction were discussed. The results showed that the metallization rate and compressive strength were 93.9% and 2160 N per pellet respectively under the conditions of the reduction temperature of 1200 °C, the reduction time of 16 min, and the molar ratio of carbon to oxygen (xc/xo) of 1.0; adding 2. 5 % CaO was beneficial to sulfur enrichment in slag phase of pellet, and metallization rate increased slightly while compressive strength decreased.

Investigation on Co-Combustion Kinetics of Anthracite and Waste Plastics by Thermogravimetric Analysis

In order to effectively recycle resource for the benefit of the global environment, the utilization of waste plastics as auxiliary injectant for blast furnaces is becoming increasingly important. Combustion kinetics of plasticscoal blends with 0, 10%, 20% and 40% waste plastics (WP) are investigated separately by thermogravimetric analysis (TGA) from ambient temperature to 900 °C in air atmosphere. These blends are combusted at the heating rates of 5, 10 and 20 °C/min. The results indicate that, with the increase of waste plastics content, the combustion processes of blends could be divided into one stage, two stages and three stages. The waste plastics content and heating rates have important effects on the main combustion processes of blends. With the increase of waste plastics content, the ignition temperature and the final combustion temperature of blends tend to decrease, while the combustion reaction becomes fiercer. With the increase of the heating rate, the ignition temperature, the mass loss rate of the peaks and the final combustion temperature of blends combustion tend to increase. The Flynn-Wall-Ozawa (FWO) iso-conversional method is used for the kinetic analysis of the main combustion process. The results indicate that, when the waste plastics content varied from 0 to 40%, the values of activation energy increase from 126. 05 to 184. 12 kJ/mol.

Strengthening Reduction Process of Vanadium Titanao‐Magnetite with CaF2 Added at High Temperature

Experiments were carried out by adding CaF2 as catalyst in a Ar atmosphere to study the isothermal reduction kinetics of vanadium titano-magnetite carbon composite pellets under high temperature in the range from1473 to 1673K. By analyzing reduction mechanism, it was found that the rate controlling step was gas diffusion, and the activation energy was 178.39kJ•mol−1 without adding any catalysts. Adding CaF2 of 3% to vanadium titano-magnetite carbon composite pellets can decrease the apparent activation energy of reduction, and the decrease extent was 14.95kJ•mol−1. In addition, temperature is an important factor influencing on reaction rate.

Thermodynamic Analysis of Titanium Behavior in Hot Metal and Titanium Load Foundation

Distribution behavior of titanium between CaO-SiO2-MgO-Al2O3-TiO2 and hot metal was studied between 1350 °C to 1600 °C. Experimental results indicate that the reaction temperature influenced the activity coefficients of titanium and resulted in the variation of equilibrium constant. Finally, the Gibbs free energy formula of titanium carbothermic reduction was fit out using the thermodynamic model of Wagner and congregated electron phase models.