【作者】 郑弢；

【导师】 许松林；

【作者基本信息】 天津大学 ， 化学工程， 2004， 硕士

【摘要】 分子蒸馏（Molecular Distillation）也称短程蒸馏（Short Path Distillation），是一种特殊的蒸馏分离技术。自上世纪三十年代问世以来，受到了人们的高度重视。近几十年来在国际上发展迅速，在工业上已得到广泛的应用。特别是随着回归自然浪潮的兴起，人们对天然产物的青睐，使得分子蒸馏技术得到了前所未有的发展。刮膜式分子蒸馏器是一种高效的分子蒸馏设备，在工业上应用较为广泛，物料在其内部刮膜器的作用下均匀分布在加热筒壁表面，使单位体积流体具有足够大的蒸发面积。同时对蒸发液膜进行不断的更新，液膜呈湍流流动，既可避免局部过热，又可强化其内部质量和热量传递过程。由于分子蒸馏是在高真空度条件下进行的非平衡连续蒸馏过程，所以解决了大量常规蒸馏技术所不能解决的问题。特别适合于分离低挥发度、高分子量、高沸点、高粘度、热敏性和具有生物活性的物料，尤其适合于对天然产物进行分离提纯。本论文旨在应用分子蒸馏小试装置，对α-亚麻酸，天然维生素E，鱼油有效成分EPA&DHA的提纯精制进行研究。通过分子蒸馏过程的各种操作参数对产品纯度与收率的影响，确定应用VKL70型刮膜式分子蒸馏设备对三种天然产物提纯精制的最佳工艺条件，为其进行工业化生产奠定了基础，对将来大规模生产上述三种产品具有重要的现实意义。本文通过对分子蒸馏器蒸发壁面的液膜流动过程进行分析，并对分子蒸馏器整体的分离过程进行物料衡算，以Langmuir-Knudsen蒸发速率理论为基础，通过对分子蒸馏器蒸发表面物质浓度的变化进行分析和求解，对原有的分子蒸馏过程模型进行了改进，结合所建立的分子蒸馏多理论级模型，讨论了系统进料速率、蒸馏温度、蒸发速率等因素对产品纯度及收率的影响，并计算得出分子蒸馏分离过程所需要的理论级数和蒸发面积。为完善分子蒸馏器的设计提供了一定的理论基础。更多还原

【Abstract】 Molecular Distillation (MD), also termed as Short Path Distillation (SPD), is a special distillation technology. It has been paid attention to by many people since it had been invented in the 30’s of last century. This technique has been gotten more and more applications internationally in the recent decades of years, and especially, it developed very quickly along with the growing-up popularity of natural products.The efficiency of wiped film molecular distillator is very high, and it has been used widely in industries. The material can be distributed into thin liquid film uniformly on the surface of evaporator, which makes the evaporation area of unit volume fluid very large. The thin-film can be renovated continuously when the rotor rotates very quickly, and the flow status in the thin-film develops into turbulent flow as well. Because of these characteristics of wiped film molecular distillator, it can not only avoid the local overheated phenomena, but also strengthen the mass and heat transfer in the liquid thin-film.MD has solved many problems that seem inextricable for conventional distillation because of the high degree of vacuum in the operation of MD. The MD technique is suitable for separating many substances that have following characteristics, low volatility, high molecular weight, high boiling point, high viscosity, heat sensitivity and biological activity, and especially suitable for the purification of natural products.The key purpose of this dissertation is to study the purification of three natural products by wiped film molecular distillation apparatus. The experiments of refining α-linolenic acid, natural Vitamin E and EPA&DHA by the VKL70 wiped film MD equipment have been discussed in this dissertation. The effects of the operating parameters on the purity and yield were studied. The optimum process conditions of refining these three natural products were obtained. This study establishes the foundation of producing these three natural products in <WP=5>industry, and has an important practical value to produce these three natural products massively in the future.The flow process of the liquid thin-film on the surface of the evaporator and the whole material balance in the process of wiped film molecular distillation have been studied in this dissertation. Based on the evaporation theory of Langmuir- Knudsen, the original distillation model has been modified by analyzing and solving the concentration of the liquid film surface. The effects of feed rate, distillation temperature and evaporation speed on the concentration and yield of product have been discussed by using the above modified mathematical model and the newly built multi-theoretical stage model. And also the theoretical stage number in the whole separation process and the required evaporation area in each stage to obtain desired purity of product have been calculated. This study provides the basic theory for new molecular distillator design.更多还原