Optimization Of Kinetic Model And Process Parameters For Dimpled Tubular Crystallizer

Evaporation crystallization process is one of the most important operation units in the chemical industry. Its application is very common in the production of chemical raw material, medicines and saccharides. At present, the development and research of new crystallizers has been one of trends of industrial crystal technological development. Therefore, crystallizer, which is commonly used in the process of evaporation crystallization, was regarded as main object of study, and a new dimpled tubular crystallizer is designed in this paper, which was connected with a graphite heat exchanger to become a complete set of evaporative crystallization system using for processing industry waste water containing salt. The study of crystallization kinetics which is about the solute that is in the waste water containing salt of the crystallizer, at the same time, the parameters in the evaporation crystallization process were opimitied.The detailed contents are as followed:(1) The paper has analysed the nucleating and growing processes of crystal, studied the crystallization kinetics process and dealed with the experiment results. Then, we have obtained the solute crystallization kinetics equations in the waste water of dimpled tubular crystallizer. The Research Results Indicate:nucleate rate and growing rate are increasing as the supersaturation degree rising; as suspended density adding, nucleate rate is also increasing, but growing rate is not affected; temperature is one of the most important factors influencing nucleate and growing, and if the temperature of solution is arising, their rates are both adding.(2) In this paper, we have tested the influence of different factors on crystals got from evaporation crystallization process, and optimized each technological parameter. Results shows:①The influence of temperature:using different vapor pressure can get supersaturation solution with different temperatures; The higher crystallization feeding temperature is, the smaller particle size is. But as the temperature rising, the product yields are improved. Decreasing the temperature of cooling water could make the particle size smaller. However, the crystal yield cannot be improved substantially as the cooling water temperature falling. The influence of feeding flow:increasing feeding flow decreased the product average size for continuous process and batch process. But the product yield of continuous process got the maximum value at a certain feeding flow.The influence of time:the time of batch crystallization process would influence the product attribute. The longer the crystallization was, the bigger the particle size was. But after a certain time, the crystal growing rate would reduce.Induced crystallization:adding too much or too little crystal seed can observably affect production. Adding different size seed crystal could increase the product particle size. But only adding the appropriate size seed crystal, it can get more uniform product.