基于光测法的晶种量对结晶动力学影响研究

Effect of Seed Load on Crystallization Kinetics Based on Optical Method

为进一步探究晶种添加量对于结晶动力学尤其是生长动力学的影响,以KNO3-H2O溶液为模型体系,结合光测法开展了添加晶种的间歇冷却结晶动力学实验。通过测定可反映结晶固相信息的体系透光率的变化曲线,结合溶液质量比和相对过饱和度等实测数据,借用前期所建的模型方程,拟合得到了结晶体系的成核与生长动力学参数。在此基础上,运用回代计算的方法,考察并分析了晶种添加量对于结晶成核与生长动力学的影响。结果表明:随着晶种添加量的提高,结晶体系的成核效应逐渐减弱,生长效应逐渐增强,晶体产品的粒度更趋于均匀;同时,单个晶体的线性生长速率却有所下降,从而导致产品的平均粒度减小。

To further investigate the effects of seed load on kinetics of solution crystallization, particularly crystal growth kinetics, the aqueous solution of potassium nitrate is selected and the relevant kinetic experiments of batch cooling crystallization with seed are carried out, in which the optical method is introduced and used. The curves of transmittance reflecting solid phase information are firstly determined, and the nucleation and crystal growth kinetics parameters are successfully estimated with the mass ratio and relative supersaturation data of solution using a mathematical model reported in our lab. Backward calculations with the help of the model parameters are performed, and the effects of seed load on nucleation and crystal growth kinetics are investigated and discussed in detail. The results show that the nucleation capacity decreases and crystal growth capacity increases with increasing seed load, and the size distribution of crystal products tends to become more uniform. With the increase of seed load, the linear growth rate of single crystal and the mean size of products are found reducing accordingly.