研究了红格钒钛磁铁矿(HCVTM)球团等温氧化动力学及其矿物学特征. 在不同的温度(1073~1373 K)和不同的时间(10~60 min)范围内,对HCVTM球团矿进行了等温氧化动力学实验. 首先分析了球团在不同温度和时间下的微观结构和矿物组成规律. 然后根据定义的氧化率,计算和分析了氧化率及其变化规律,以及矿相结构对氧化率的影响. 最后结合缩核模型、修正的氧化率函数和阿伦尼乌斯公式,计算了反应速度常数、修正系数和反应活化能,并判断了反应限制性环节. 研究表明:随温度的提高,低熔点液相增加,赤铁矿晶粒的生成、长大和再结晶,形成连续的黏结相,空隙数量减少. 随时间的增加,生成的液相促进了赤铁矿晶粒间的黏结和长大,但是晶粒间硅酸盐相和钙钛矿类物相恶化了球团结构. 同时,钙钛矿和铁板钛矿相生成. HCVTM球团矿空隙数量的减少和黏结相的生成,表现在氧化速率随时间增加而减慢. HCVTM球团氧化反应主要受扩散控制,球团氧化前期的反应活化能为13.74 kJ·mol-1,氧化后期的活化能为3.58 kJ·mol-1,氧化率函数的修正参数u2=0.03.
The isothermal oxidation kinetics and mineralogical characteristics of Hongge chromium containing vanadium and titanium magnetite (HCVTM) pellets were investigated. The experiments related to the isothermal oxidation kinetics were performed over a temperature range of 1073 to 1373 K and a time range of 10 to 60 min. First, the microstructure and variations in the mineral composition of the pellets were analyzed. Further, the oxidation rate and its change regulation were calculated and analyzed by combining the defined oxidation rate function, and the effects of the mineral phase structures on the rate of oxidation were determined. Finally, the modified oxidation rate function, Arrhenius equation, reaction rate constant, correction factor, and reaction activation energy were calculated by combining the shrinking core model, and the restrictive step in the oxidation reaction was determined. The results depict that an increase in temperature causes an increase in the low melting point liquid phase; formation, growth, and recrystallization of hematite grains; and formation of a bonding phase. Additionally, it causes a decrease in the number of interspaces. With an increase in time, the bonding and growth of hematite grains are promoted due to the generation of a liquid phase. However, the structure of pellets is observed to deteriorate due to the formation of silicate and perovskite phases. Meanwhile, perovskite, and pseudobrookite phases are also generated. Oxidation rate decreased with increasing time due to the decrease in the number of interspaces and bonding phases. In HCVTM pellets, the oxidation reaction is controlled by diffusion. The activation energy of the initial reaction is 13.74 kJ·mol-1 while that of the latter reaction is 3.58 kJ·mol-1. Further, the corrected parameter for the oxidation rate function is observed to be 0.03.