微细菱镁矿热分解过程及动力学

Thermal Decomposition Process and Kinetics of Microfine Magnesite

采用TG-DSC热分析技术,在不同升温速率下对高纯微细菱镁矿进行热分解动力学研究.结果表明:随着升温速率的增大,菱镁矿分解速率不断增大且最大分解速率也向高温区偏移.首先使用Hu-GaoZhang方程对不同升温速率的TG数据进行计算,确定了热分解机理函数的唯一性和活化能.进而采用双等双步法和产品形貌分析,确定其最概然机理函数为f(α)=2(1-α)1/2,热分解沿解理面向内进行,属于典型的相边界反应.最后利用Flynn-Wall-Ozawa方程求得指前因子,建立了微细菱镁矿的热分解动力学方程.用两组不同升温速率的TG数据对所建立方程进行验证,方程合理.

Thermal decomposition kinetics of highly pure micro-fine magnesite particles was studied by TG-DSC techniques at varying heating rates.The results indicate that with increase of heating rate,decomposition rate of magnesite increases gradually and maximum decomposition rate shifts to the high-temperature zone.Firstly,TG experimental data obtained at different heating rates were calculated with Hu-Gao-Zhang equation,which determined uniqueness and activation energy value of thermal decomposition mechanism function of magnesite.And then double equal-double steps method combined with morphological analysis on calcined products were adopt to determine differential form for most probable mechanism function of thermal decomposition,it is f(α)=2(1-α)1/2,and the outside-in(i.e.from cleavage surfaces to the interior of crystal)thermal decomposition of particles is a typical phase boundary reaction.Finally the pre-exponential factor was calculated by Flynn-Wall-Ozawa equation,and thermal decomposition kinetics equation of micro-fine magnesite is established.Two sets of TG data with different heating rates were used to verify the established equation and prove it is reasonable equation.