BaO对铁酸钙等温还原动力学的影响研究

Research of effect of Bao on the isothermal reduction kinetics of calcium ferrite

为研究铁酸钙的还原性能和动力学特征,本文在1 123~1 273 K温度范围内,30%H+70%N(体积分数)气氛条件下,采用等温热重法进行BaO质量分数分别为0%、2%、4%、8%的还原试验;并借助X射线衍射仪及扫描电子显微镜对还原前、后样品的物相组成和微观形貌进行分析。结果表明:BaO与铁酸钙在高温下发生固溶,形成铁酸钙和铁酸钡固溶相(简称“CFBF”),其以颗粒状存在于铁酸钙内部;当BaO质量分数一定时,不同温度下铁酸钙的最大还原度差别不大,均处于0.95和1;当温度不变时,随着BaO质量分数由0%增加至8%,铁酸钙的还原度逐渐降低,表观活化能由41.2 kJ/mol增大至77.9 kJ/mol;ln-ln法和Sharp法分析表明,CF的还原符合F1和R2模型,含BaO铁酸钙还原过程模型函数前期(还原度小于0.5)、后期(还原度大于0.5)为F1模型。

To study the reduction properties and kinetic characteristics of calcium ferrate, in the temperature range of 1 123~1 273 K,under the atmospheric conditions of 30%H+70%N(volume fraction),the reduction test of BaO mass fractions of 0%,2%,4% and 8%,respectively, is carried out by isothermal weight method.X-ray diffractometer and scanning electron microscopy are used to analyze the phase composition and microscopic morphology of samples before and after restoration.The results show that the solid solution of BaO and calcium ferrate occurred at high temperature forms calcium ferrate and barium ferrate solid solution phase( "CFBF"),which exists in the interior of calcium ferrate in the form of particles.When the BaO mass fraction is fixed, the maximum reduction degree of calcium ferrite at different temperatures does not differ much, both at 0.95 and 1;when the temperature is unchanged, as the BaO mass fraction increases from 0% to 8%,the reduction degree of calcium ferrite gradually decreases, and the apparent activation energy increases from 41.2 kJ/mol to 77.9 kJ/mol.Ln-ln method and Sharp method analysis show that the reduction of CF conforms to the F1 and R2 models, and the model function of the BaO calcium ferritate reduction process function is F1 model in the early stage(the reduction degree is less than 0.5)and the later stage(the reduction degree is greater than 0.5).