Study On Crystallization Process Of L-Lysine Hydrochloride

L-Lysine is one of the basic units of protein, which is one of the most important parts of biological organisms. L-Lysine can be generated by fermentation, but a long-term preservation is difficult because of the amino group. L-Lysine hydrochloride is relatively stable and easy for preservation. So L-lysine hydro-chloride is usually used in food, feed additives, and drug fields. At present, L-lysine hydrochloride is mainly used for feed industry in the homemade, because of bad mobility, poor crystal morphology, small stack-density, too deep color and asymmetry CSD etc. Products can not be used in pharmaceutical industry. Based on the above issues, this paper, L-lysine hydrochloride crystallization process has been systematically studied.The solubilities of L-lysine hydrochloride in water, methamol, ethanol, Glycol and DMSO were measured by use of the laser-monitoring dynamic method. The solubility data were correlated with Apelblat model. The metastable zone width was also measured by the laser method and the effects of cooling rate were investigated experimentally. In addition, the induction period of the super saturation water solution of L-lysine hydrochloride was measured, through which the inter surface tension between the crystal and the solution was calculated.The crystallization kinetics of L-Lysine hydrochloride in ethanol + water solution was experimentally measured by the batch dynamic method. Firstly, the solubilities of L-lysine hydrochloride was determined in ethanol + water solution. The effects of the super saturation, the agitation speed on the nucleation rate and the crystal growth rate were investigated. A size-independent model and the moment transform method were chosen to deal with the experimental data, and the model equations of the nucleation rate and the crystal growth rate in the crystallization process of L-Lysine hydrochloride were finally obtained through the least square multivariate linear regression.Aimed at solving the problems existing in the manufacture process of L-Lysine hydrochloride, efforts were carried out from two aspects, decoloration of the raw crystallization solution and the antisolvent crystallization technology. In the decoloration experiments, the effects of the operational parameters such as decoloration time, temperature and the mass of activated carbon were studied. In the antisolvent crystallization experiments, the effects of the addition rate of antisolvent, the volume of antisolvent, crystallization temperature, etc. on the purity and color-level were systematically investigated. And the experimental optimum operational conditions for the antisolvent crystallization of hydroquinone were finally obtained.