GUO Pei-min
钢铁研究学报(英文版)
The activity model of CaO-FeO-SiO2-WO3 quarternary system was established according to the coexistence theory of slag structure and the reduction thermodynamics of scheelite was discussed by applying this model. The activities of SiO2 and WO3 decrease, while that of CaO increases with increasing the basicity of slag. Among SiC, [C] and [Si] reactants, the reducing capability of SiC is the strongest, while that of [C] is the poorest at a high temperature (about 1873 K). It is advantageous to increase the yield of tungsten by increasing the content of [Si] or [C]. Oxidizability of slag has a significant effect on the yield of tungsten. Controlling of basicity and oxidizability of slag can prevent the oxidation loss of tungsten.
关键词:
activity model;scheelite;thermodynamics;direct reduction
GUO Pei-min
钢铁研究学报(英文版)
The deoxidation kinetics of hematite ore with various particle sizes with hydrogen at low temperature and reduction mechanisms were studied using the thermogravimetric analysis. Under the same temperature, after particle size of powder becomes thinner from 107.5μm to 2μm, the surface area of powder and the contact area between powder and gas increase, which makes the deoxidation process of hematite accelerate about 8 times, and the apparent activation energy of deoxidation reaction drops to 36.9 kJ/mol from 78.3 kJ/mol because of activity of ore powder improved with refining gradually. Under the same reaction rate, the reaction temperature of 6.5μm powder decreases about 80℃ than that of 107.5μm powder. Thinner diffusion layer also helps accelerate the reaction with powder refining. The higher the temperature, the greater peak of deoxidation rate is; under the same temperature, the greater the particle size, the smaller the peak of deoxidation rate is; both inner diffuse and interface chemical reaction play an important role in the whole reaction process.
关键词:
iron oxide;low temperature;deoxidation kinetics;thermogravimetric analysis (TGA);reduction mechanism
PANG Jian-ming
,
GUO Pei-min
,
ZHAO Pei
钢铁研究学报(英文版)
The reduction-degree of the sample increases and the utilization ratio of gas decreases when the reaction lasts longer time, which indicates that the reaction is faster at the beginning of reduction, while it becomes slower in subsequent process. The higher the reaction temperature, the higher the utilization ratio of gas and the reduction-degree are, but the difference of utilization ratio among the different temperatures becomes smaller with time. The utilization ratio of gas can reach about 8% and the reduction-degree is 80% for 20 min reduction at 850 ℃, indicating that the reduction reaction by CO is very fast at high temperature. The higher the reaction temperature, the higher the apparent reaction rate constant is, but the difference of apparent reaction rate constant among the different temperatures becomes bigger. The apparent activation energy is about 5911 kJ/mol in the fluidized bed experiment. The increase of reduction-degree with gas velocity shows quite good linearity, indicating that at high temperature even higher velocity of reducing gas can be used to improve the productivity of reactor when CO is used as reducing gas. With the increase of charge height, the metallization ratio and the reduction-degree decrease, but the utilization ratio of gas increases.
关键词:
CO
,
fluidized bed
,
fine powder
,
iron ore
,
reduction-degree
