Crystallization Rate and Purity of Produced Crystals

在工业结晶过程中，需要通过提纯分离工艺来获得高纯度的物质，这是一个节能的过程。在铜熔体的分离方面，由于结晶体表面含有母熔体，使纯度降低，因此选择发汗操作来提高纯度。本研究以结晶过程中的成核和生长现象为重点，探讨了结晶过程中的基本现象与晶体纯度的关系，旨在提出结晶过程中母体包裹体的新理论，以及获得高纯度的最佳条件。本文以苯-环己烷体系为研究对象，采用半间歇式结晶实验装置进行苯结晶实验，测定了在所确定的粒度范围内，苯结晶的粒度分布和纯度随时间的变化。从PSD的时间进程来看，晶体生长是以初生晶核的联合机制进行的， ...更多信息 其他和附加它们，并观察到次生核周期性产生。此外，还将擦拭操作后的晶体纯度与晶体尺寸定量地关联，以明确存在三个阶段，其中（1）通过细颗粒的附聚机理形成包含大量母熔体的小晶体，（2）形成具有低母熔体含量的中等尺寸晶体：其中认为细粒被并入大晶体中，（3）大晶体的形成，其中母熔体保持在附着于大晶体表面的细粒之间。并在对二甲苯-环己烷体系中进行了间歇实验。结果表明，初始一次成核现象对纯度有影响，同时考虑到设备中晶体生长现象，该模型还揭示了杂质排出的机理。在此基础上，从杂质夹杂和排出的机理和动力学出发，提出了高纯度结晶的最佳操作条件。少

In industrial crystallization, high purity substance is needed through purification and separation process with saving energy. Concerning separation from cutectic melt, mother melt happens to be included on the surface of crystals, to make the purity lower, and so sweating operation has been selected to improve the purity. In this study, correlation between basic crystallization phenomena and crystal purity wereinvestigated focusing nucleation and growth phenomena, to aim to propose the new theory on the mother inclusion in the process of crystallization, and optimum condition for high purification performance. In this study for the cutectic system of benzene and cyclohexane, experiments of benzene crystallization were performed using semi batch apparatus, to measure the time course of particle size distributions (PSD) and purity of crystals in the determined size range. From the time course of PSD,crystal growth was recognized to proceed by the mechanism of uniting primary nuclei wach … More other and attaching them, and secondary nuclei were observed to be produced periodically. And also crystal purity after wiping operation, was correlated quantitatively with crystal size, to make clear that there are three stages in which (1) formation of small crystals including much mother melt by the agglomeration mechanism of fineparticles, (2) formation of middle sizeone having low content of mother melt : in which find particles are thought to be incorporated into the large crystal, (3) formation of large crystals, in which mother melt are kept between the fine crystals attached to the surface of large crystal. And also batch experiments were performed in the cutectic system of paraxylene and cyclohexane. By the result, initial primary nucleation phenomena affected the purity, and also the mechanism of impurity discharge was shown by our model, considering crystal growth phenomena in the equipment. Based on the result described above, the mechanism and kinetics of impurity inclusion and discharge were considered to propose the optimum crystallization operatin condition for high purification. Less