Shan Ren

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.

Kinetics of Reduction Reaction in Micro-Fluidized Bed

Micro-fluidized bed reactor is a new research method for the reduction of iron ore fines. The reactor is operated as a differential reactor to ensure a constant gas concentration and temperature within the reactor volume. In order to understand the dynamic process of the reduction reaction in micro-fluidized bed, a series of kinetic experiments were designed. In the micro-fluidized bed, the use of shrinking core model describes the dynamic behavior of reduction of iron ore. And the apparent activation energy is calculated in the range of 700–850 °C while the initial atmosphere is 100% content of CO.

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.

Combustion Ratio of Waste Tire Particle, PC and Mixture at Blast Temperature of BF

In order to study the combustion characteristics of waste tire particle (WTP), pulverized coal (PC) and their mixture, the contents of CO, CO2 and O2 of off-gas during the combustion of WTP, PC and mixture under the condition of rich oxygen by 0–4% in blast and at 1 250 °C were measured simultaneously using synthetically infrared analyzer, and then the corresponding combustion ratio was calculated and compared. The results showed that the burning rate of WTP reached approximately 57%, which is much higher than that of PC (only about 18%) in the initial 650 s in fresh air, and then the increase of combustion rate of PC is faster than that of WTP; the combustion rate of PC improved remarkably with the addition of WTP. Meanwhile, the combustion rates of all these materials improved with the increase of oxygen content.

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.

Rules of Assimilation of Single Ore and Mixed Ores

Assimilation behaviors of 7 kinds of iron ores from Australia, Brazil, India, South Africa and China were evaluated and analyzed. On the basis of that, four ore blending principles were proposed, and seven groups of iron ore powder blending schemes were designed. The ores of different types or from different places are shown apparently different in assimilation. The assimilation of hematite in Australia, Brazil and India is relatively high, but the assimilation of magnetite in South Africa and China and specularite in China is relatively low. The assimilation of the ores has negative correlation with MgO content and binary basicity, while the assimilation of the ores has positive correlation with porosity, SiO2 and Al2O3 contents, and crystal water. The iron ores with smaller crystal size and microstruc ture looseness have relatively higher assimilation. Assimilation of mixed ores has relationship of linear, arch and “S” types to the ratio of single iron ore powder. When the charge ratio of ore is less than 25%, it possesses additivity, providing theoretical basis for optimization of ore matching.

Application of Simulated Annealing Algorithm in Sintering Burdening Optimization

Sintering burdening optimization has great value in reducing sintering cost and improving sinter qualities. Considering the nonlinear relationship between the high temperature characteristic parameters of iron ores in sintering, this article introduces the simulated annealing algorithm into burdening calculation and establishes a mathematic model of sintering burdening optimization. The initial parameters in simulated annealing algorithm are determined through tentative experiments, including initial temperature, cooling function, annealing constant and the end condition. The model can effectively reduce sintering cost and improve sinter qualities in its practical use.