惰性气氛下CaSO4热分解动力学机理的研究

Research on the Kinetic Mechanism of Thermal Decomposition of CaSO_4 in Nitrogen Atmosphere

在升温速率为5～20 K/min 的条件下采用综合热分析仪对平均粒径为8.934 μm的 CaSO_4颗粒的分解进行研究。对于 N_2气氛中不同升温速率下 CaSO_4的热分解,采用没有任何假设或近似处理的动力学积分式和精确度很高的温度积分近似式,迭代计算得到了不同机理函数所对应的动力学参数。将升温速率外推为零,得到了理论上系统处于热平衡状态下的活化能和指前因子。同时,应用双外推法,在没有假定机理函数的情况下,得到了 CaSO_4分解的活化能随转化率的变化规律,将转化率外推为零,得到了理论上新物相形成时的活化能(992.15 kJ/mol)。将热平衡状态下的活化能与新物相形成时的活化能相比较,确定了 N_2气氛下 CaSO_4分解机理最可能是成核与生长机理。

The decomposition mechanism of calcium sulfate with average particle size of 8. 934 μm was studied using simultaneous thermalgravimetric analyzer at heating rate of 5-20 K/min. Adopting a kinetic integral expression without any approximation and a temperature integral approximation with high accuracy, all kinetic parameters of the thermal decomposition of calcium sulfate in nitrogen atmosphere corresponding to different common reaction mechanism functions were obtained by iterative calculations. When heating rate was extrapolated to zero, the activation energy and the frequency factor of decomposition in thermal equilibrium were determined. In addition, the relationship between activation energy of decomposition and conversion of calcium sulfate was obtained by double extrapolation method. Extrapolating the conversion of calcium sulfate to zero, the activation energy （992.15 kJ/mol） of the production of new product phase was obtained. By comparing the activation enery of decomposition in thermal equilibrium with that of formation of the new product phase, it was found that the mechanism of calcium sulfate decomposition in nitrogen atmosphere might be nuclear producing and growing process.