CaF_2-SiO_2-CaO渣系的非等温挥发行为

Non-isothermal Analysis on the Evaporation Behavior of CaF_2-SiO_2-CaO System Slag

使用同步热分析仪,以10K/min的升温速率对CaF2-SiO2-CaO三元渣系的失重率进行测定,采用非等温热分析方法对渣系挥发反应动力学进行了研究,确定了渣系挥发的反应机理函数f(α),分析了挥发反应机理,并对建立的动力学模型进行验证.结果表明,渣系挥发性与其液相线及物相组成密切相关,而碱度对其影响较小;引起渣系成分改变的挥发过程可分为1373～1573K和1573～1773K两个阶段,前者属三维扩散型机理函数,其微分形式为f(α)=3/2(1-α)4/3[(1-α)-1/3-1]-1,后者属随机成核和随后生长型机理函数,其微分形式为f(α)=1/4(1-α)[-ln(1-α)]-3.70%CaF2-30%SiO2渣系2个阶段的反应活化能分别为550.10和376.16kJ/mol,指前因子1gA分别为16.55和8.4.实验结果与模型计算结果吻合很好.

The weight loss rate of CaF2-SiO2-CaO system was measured by a simultaneous thermal analyzer and platinic crucible at the heating rate of 10 K/min,and the thermal volatile kinetics studied using a non-isothermal approach.The conversion function f（α） and volatile kinetic parameters of slag were determined by the TG curves,kinetics model established verified,and its evaporation mechanism analyzed.The results indicated that the weight loss rate was closely related to the liquidus and phase of slag.But the volatility had no significant correlation with basicity.The evaporation causing the change composition of slag could be divided into two stages in 1373～1573 and 1573～1773 K.The former belonged to three-dimensional diffusion with differential form f（α）=3/2（1-α）4/3[（1-α）-1/3-1]-1,the latter to random nucleation and growth with differential form f（α）=1/4（1-α）[-ln（11-α）]-3.For the 70% CaF2-30% SiO2 slag system,the activation energy at two stages was 550.10 and 376.16 kJ/mol,and the frequency factor lgA 16.55 and 8.4,respectively.The experimental results were in good agreement with the kinetic model.