Guibao Qiu

Isothermal reduction of titanomagnetite concentrates containing coal

The isothermal reduction of the Panzhihua titanomagnetite concentrates (PTC) briquette containing coal under argon atmosphere was investigated by thermogravimetry in an electric resistance furnace within the temperature range of 1250–1350°C. The samples reduced in argon at 1350°C for different time were examined by X-ray diffraction (XRD) analysis. Model-fitting and model-free methods were used to evaluate the apparent activation energy of the reduction reaction. It is found that the reduction rate is very fast at the early stage, and then, at a later stage, the reduction rate becomes slow and decreases gradually to the end of the reduction. It is also observed that the reduction of PTC by coal depends greatly on the temperature. At high temperatures, the reduction degree reaches high values faster and the final value achieved is higher than at low temperatures. The final phase composition of the reduced PTC-coal briquette consists in iron and ferrous-pseudobrookite (FeTi2O5), while Fe2.75Ti0.25O4, Fe2.5Ti0.5O4, Fe2.25Ti0.75O4, ilmenite (FeTiO3) and wustite (FeO) are intermediate products. The reaction rate is controlled by the phase boundary reaction for reduction degree less than 0.2 with an apparent activation energy of about 68 kJ·mol−1 and by three-dimensional diffusion for reduction degree greater than 0.75 with an apparent activation energy of about 134 kJ·mol−1. For the reduction degree in the range of 0.2–0.75, the reaction rate is under mixed control, and the activation energy increases with the increase of the reduction degree.

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.

Effect of burden material size on blast furnace stockline profile of bell-less blast furnace

Abstract The position and profile of the burden stockline are important parameters for blast furnace (BF) control. Theoretical calculations currently determine the position without considering the influence of different sized materials. In order to clarify the effects of different sized materials on the position and compare experimental and theoretical calculated results, a 1/15 scale cold model consisting of an actual 2500 m3 shaft and a bell-less top charging system has been built. The results indicate that (i) the chute rotary speed strongly influences the stockline peak position with different sized materials (ii) the rotary inclined angle and position of stockline peaks are approximately linear. Model predictions of the stockline with material size are poorly related to actual trial results, particularly chute rotary speed.

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.

Physical modelling of slag-foaming phenomenon resulted from inside-origin gas formation reaction

Slag foaming is a common phenomenon in the metallurgical process that negatively influence the blast furnace when smelting some special ores such as V-Ti-magnetite. Inside-origin gas plays a leading role during this foaming phenomenon. This study performed a room-temperature simulation of slag foaming from inside-origin gas. Results showed that foaming height increased with increased the amount of inside-origin gas. Higher liquid viscosity caused lower foaming height, which was opposite to the slag-foaming regularity caused by outside-origin gas. Higher surface tension benefited the suppression of the foaming phenomenon and shortened the foaming elimination time. The effect of solid particles on the foaming phenomenon was not monotonic, i.e. the maximum foaming height initially increased and then decreased with increased number of particles. Particles with better solution wettability caused higher foam because they can easily adhere onto film, thereby enhancing elasticity and extending film life. Small particle size benefited the foam. The experimental data were in accordance with the model predictions based on the estimated bubble sizes, which proved that the model developed by Zhu and Du helped predict foaming height caused by chemical reaction.

Heat recovery from hot blast furnace slag granulates by pyrolysis of printed circuit boards

Abstract Heat recovery from hot blast furnace (BF) slag is difficult to achieve but has great potential to recover energy and thereby reduce CO2 emissions. The objective of this work is to utilise the heat of hot BF slag granulates to generate combustible gas from printed circuit boards. The results showed that this is a possible process and that, after cleaning, the combustible gas could be injected into the BF as a fuel and reducing agent. The new process has advantages over the traditional process in energy saving and pollution emissions.

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.

Drying kinetics of Philippine nickel laterite by microwave heating

ABSTRACT In this study, microwave heating was used to dry nickel laterite, which contains significant quantities of free water, crystal water, and hydroxy water. The results show that the main phase of crystal water is Ca3Al6Si10O32(H2O)13, and the main phases of hydroxy water are FeO(OH) and Mg5(Al, Cr)AlSi3O10(OH)8. The microwave drying process of nickel laterite can be divided into two stages: the removal of free water and the coupled removal of free water, crystal water, and hydroxy water. The effect of particle size and microwave power output were studied, and these indicate that the drying time and specific energy consumption decrease with increasing particle diameter and microwave power. The effective diffusivity and activation energy were calculated, and these are larger in the second stage than that in the first stage. The activation energies are 27.66 and 32.80 W/g for the first and second stages, respectively. The phase transition of the product, schematic drying mechanism, and feasibility analysis of the microwave drying process are also discussed.

Effect of TiO 2 on the Viscous Behavior of High Alumina Blast Furnace Slag

The viscous behavior of molten slags has played an essential role in determining the performance and productivity of the ironmaking process. In this paper, the viscosity and free running temperature in CaO-SiO2-Al2O3-9 mass%MgO-TiO2 slag has been measured at different content of Al2O3 and Al2O3/SiO2 ratio. In addition, the slags viscous activation energy has also been calculated. The results show that the TiO2 as a basic oxide content from 1 to 5 mass% can reduce the viscosity and free running temperature, and moderate content of TiO2 in high alumina blast furnace slag remains effective for reducing viscous activation energy and free running temperature.