Liangying Wen

Density Functional Theory Study on the Carbon-Adhering Reaction on Fe3O4(111) Surface

The density functional theory (DFT) has been employed to investigate the carbon-adhering reaction on Fe3O4(111) surface, which consists of two steps: (1) the adsorption of CO onto the Fe3O4(111) surface and (2) the second CO seizes an O atom from CO, which adsorbed on the surface, to form a CO2 molecule and the C atom left behind adheres onto the Fe3O4(111) surface. At step 1, there are five stable configurations of CO adsorbed onto Feoct2-terminated Fe3O4(111) surface and four stable formations of CO adsorbed onto the Fetet1-terminated Fe3O4(111) surface. The top configurations of these two surfaces are most stable. Moreover, a density of the state (DOS) analysis is used to investigate the bonding mechanism of CO adsorbed onto these two surfaces. The results reveal the new C-O bonds generation on two surfaces, which is important and necessary for the formation of a CO2 molecule. Besides, the transition states (TS) are searched to analyze the energy barrier in the process of CO2 desorption from two surfaces. The result indicates that the oxidation reaction of adsorbed CO molecule and surface O atom is feasible. For step 2, the result shows that the carbon-adhering reaction occurs only on the top site of Feoct2 atom and the magnetite plays a catalytic role in the carbon-adhering reaction process.

Effects of Additives on Sulfur Transformation, Crystallite Structure and Properties of Coke during Coking Of High-sulfur Coal

High-sulfur coal, as an alternative coal source, has a relatively high proportion in coal reserves. However, the feature of high sulfur content, which can cause environmental pollution and poor quality of molten iron, restrains its utilization in coking industry. Coking experiments of high-sulfur coal with Fe2O3, La2O3 and CaO as additives were carried out in order to fix the sulfur in coke. The effects of additives on sulfur distribution, crystallite structure, surface morphology and properties of coke were investigated. The results indicate that CaO can be used as sulfur-fixing agent in coking process, and CaS is the main mineralogical phase of the sulfur-contained mineral constituents in coke. Fe2O3 and La2O3 facilitate the conversion of CaO to CaS. The additives mainly influence the crystallite height and the average interlayer spacing d002 of coke. The addition of La2O3 increases the value of the crystallite height while the addition of CaO and Fe2O3 decreases it. CaO leads the pores of coke to increase with its physical action and agglomerating characteristic. Fe2O3 and C can form (Fe,C), resulting in the pulverization and erosion of the pore wall. La2O3 makes the coke surface become more compact and thinner. The reactivity of coke increases with the decrease of crystallite height and crystallite layer number.

Gas-Particle Flow and Combustion Characteristics of Pulverized Coal Injection in Blast Furnace Raceway

The two-dimensional steady-state discrete phase mathematical model is developed to analyze gas-particle flow and combustion characteristics of coal particles, as well as components concentration and temperature distribution of coal gas in the process of pulverized coal injection of blast furnace raceway. The results show that a great deal of coal gas discharges on the top of raceway away from the tuyere, and the residence time of coal particles in the region of blowpipe and tuyere is 20 ms or so and 50 ms when it reaches raceway boundary. The pressure is the highest at the bottom of raceway and the maximal temperature is about 2423 K. The char combustion is mainly carried out in the raceway and the maximum of char burn-out rate attains 3×10−4 kg/s.

Radiant Image Simulation of Pulverized Coal Combustion in Blast Furnace Raceway

The relationship between two-dimensional radiant image and three-dimensional radiant energy in blast furnace raceway was studied by numerical simulation of combustion process. Taking radiant image as radiant boundary for numerical simulation of combustion process, the uneven radiation parameter can be calculated. A method to examine thre-edimensional temperature distribution in blast furnace raceway was put forward by radiant image processing. The numeral temperature field matching the real combustion can be obtained by proposed numeric image processing technique.

Influences of CaO/SiO2/MgO/Al2O3 on the Formation Behavior of FeO-Bearing Primary-Slags in Blast Furnace

Slags play an important role in blast furnace operation, and their compositions are based on the CaO–SiO2–MgO–Al2O3 quaternary system. However, there is not a clear understanding of the effects of gangue on of the formation of FeO-bearing primary-slags process in blast furnace. In this work, the softening and dripping experiments under the blast furnace conditions are designed to explore the influences of CaO-/SiO2-/MgO-/Al2O3 on the softening and melting properties of FeO respectively. The results indicate that additions of CaO or Al2O3 decrease the starting softening temperature and no dripping behaviors are found in comparison with the base case results when only FeO is used. On the contrary, the addition of SiO2 or MgO rises the starting and ending softening temperature, as well as the dripping temperature. The lowest maximum pressure drop is obtained in the case with addition of SiO2. According to XRD analysis results, the initial phase with CaO addition in the primary-slags should be CaO·Fe3O4 and that with SiO2, MgO, Al2O3 additions are fayalite (2FeO·SiO2), magnesioferrite (MgO·FeO), hercynite (FeO·2Al2O3), respectively.

Effects of iron compounds on pyrolysis behavior of coals and metallurgical properties of resultant cokes

The utilization of highly reactive and high-strength coke can enhance the efficiency of blast furnace by promoting indirect reduction of iron oxides. Iron compounds, as the main constituent in iron-bearing minerals, have aroused wide interest in preparation of highly reactive iron coke. However, the effects of iron compounds on pyrolysis behavior of coal and metallurgical properties of resultant cokes are still unclear. Thus, three iron compounds, i.e., Fe3O4, Fe2O3 and FeC2O4 • 2H2O, were adopted to investigate their effects on coal pyrolysis behavior and metallurgical properties of the resultant cokes. The results show that iron compounds have slight effects on the thermal behavior of coal blend originated from thermogravimetric and differential thermogravimetric curves. The apparent activation energy varies with different iron compounds ranging from 94.85 to 110.11 kJ/mol in the primary pyrolysis process, while lower apparent activation energy is required for the secondary pyrolysis process. Iron compounds have an adverse influence on the mechanical properties and carbon structure of cokes. Strong correlations exist among coke reactivity, coke strength after reaction, and the content of metallic iron in cokes or the values of crystallite stacking height, which reflect the dependency of thermal property on metallic iron content and carbon structure of cokes.

Cold model of coal gas component concentration distribution in blast furnace raceway

Primary distribution of coal gas in blast furnace raceway has an important effect on blast furnace ironmaking process. The coal gas component concentration distribution was studied experimentally using a three-dimensional cold model. The results showed that CH4 concentration diminishes along with the height increasing on vertical section of raceway, and the concentration is the highest in the bottom of raceway. CH4 concentration increases gradually along the raceway depth with the lowest concentration value in front of the tuyere. The distribution of CH4 concentration has different characteristics in different raceway zones.

Simulation and Investigation on Physical Properties of Continuous Casting Slab AH36 at High Temperature

During the continuous casting process, physical properties of slab for continuous casting at high temperature have an important effect on the slab quality in different part and the curve establishment of external target temperature for slab. It has significance to simulate and investigate the physical behaviors of slab at high temperature during the continuous casting process. Investigation existent in this field is scarce around the world. Continuous casting process is a complicated cooling process in unsteady state that sometimes the external temperature of slab will rise. In allusion to temperature rise and temperature drop, the paper simulated and investigated the physical properties of slab AH36 at high temperature under conditions of different temperatures and different temperature variation velocities, such as thermal expansion property, differential thermal analysis curve (DSC), isobaric thermal capacity (CP) and so on. Results of the investigation have provided a scientific data base for a further study on continuous casting technology and quality control for steel AH36.

Interaction mechanism between coal combustion products and coke in raceway of blast furnaces

The interaction mechanism between the combustion products of pulverized coal injected and coke in the raceway of blast furnace was studied through thermodynamic calculation and experiments. The results indicated that additives significantly affected the melting property of coal ash in high temperature zone. Although the unburnt char, raw coal ash, and catalyzed coal ash failed to wet the coke surface, the wettability of the catalyzed coal ash on the coke was greater than that of the raw coal ash. Since the unburnt char had weak reaction with the coke surface, it showed little influence on the surface morphology of the coke. The interaction between the raw coal ash and the coke gave rise to the increase in the pore size on the coke surface. However, the raw coal ash only affected the coke surface and the entrances of the pores owing to its poor fluidity. After being melted, the catalyzed coal ash was expected to immerge into the inside part of the coke and then react with the coke, resulting in an expansion and increase of coke cavities. The raw coal ash and the unburnt char reduced the coke reactivity, while the catalyzed coal ash improved the coke reactivity. Thereinto, the coal ash containing Fe2O3 exhibited a larger influence on the reactivity than that containing CaO.

Thermal Simulation on Mechanical Properties of Steel Q345 for Continuous Casting Slab

The modeling of solidification in Continuous Casting demands the mechanical properties of steels at high temperature. These mechanical properties parameters provide the design data for the target surface temperature curve and dynamic control modeling of secondary cooling system, and are used to research hot delivery and crack mechanisms of cast slab. The properties parameters of steels can be obtained by physics simulation experiment. Following processing parameters in Continuous Casting, the stress-strain curves and mechanical properties of steel Q345 were tested and analyzed. Then the curves of relationships between the yield strength, tensile strength, reduction of area, Young’s modulus, plastic modulus of steel Q345 and temperature were obtained. We found the strength of steel Q345 cast slab felled down basically; the ductility was decreased below 700°C, in the range of 725°C-900°C and 1275°C-melting point. The plastic modulus was analyzed with the different temperatures and the different strains in detail. The parameters of mechanical properties for steel Q345 were obtained for using in elastic-plasticity stress model.