菱镁矿煅烧参数优化及其产物水化动力学解析

Parameters optimization of magnesite calcination and hydration dynamics of optimized sample

菱镁矿煅烧参数设计是调控产物活性的关键,产物活性及水化动力学是其利用过程中的重要特性。利用田口试验方法对菱镁矿煅烧参数进行优化。结果表明:试验优化条件为煅烧温度650℃,保温时间90 min,升温速率20℃/min及粒径大小42μm。在此优化条件下产物水化率达到58.37%(70℃水化1 h)。各煅烧参数对产物活性的影响由大到小的顺序为煅烧温度、粒度大小、保温时间、升温速率。优化产物中氧化镁晶粒较小,结晶度较低,比表面积较大(71.55 m^2/g);在优化产物水化过程中,升高温度可显著加快水化反应的进行;水化动力学过程属于化学反应控制类型,反应的表观活化能为27.94 k J/mol。在较高温度条件下,动力学过程由化学反应控制类型逐渐转变为内扩散控制类型。

Parameters are important for activity controlling during magnesite calcination. The activity and hydration dynamics of calcined samples are crucial properties. Taguchi method was used to optimize the parameters in magnesite calcination. The results show that the optimized parameters are achieved at calcination temperature of 650℃, with heating rate of 20℃/min and residence time of 90 min, and the particle size is42 μm. The optimal hydration rate reaches 58.37% after hydrating at 70℃ for 1 h. The influences of parameters on activity decrease from high to low as calcination temperature, particle size, residence time, heating rate. The optimal sample contains small crystal of MgO with high specific surface area (71.55 m2/g). During hydration, elevated temperature accelerates significantly the hydration reaction. The apparent activation energy is 27.94 kJ/mol, indicating that the dynamics is controlled by hydration reaction. Hydration dynamics changes gradually from hydration reaction controlled towards internal diffusion controlled at higher temperature.