Study On Molecular Distillation Separation Process And Application In Products Separation

Molecular distillation (MD), which is also called short path distillation, is a special separation technology with the mixtures separated without boiling. MD is also non-equilibrium and a continuous distillation process under high vacuum condition. Since the technology came out in the 30's of last century, enormous developments of application in MD had been acquired with its many virtues, especially in separation of thermal sensitive natural products. However, lack of deep fundamental studies on MD process made the application of molecular distillatory in industry restrained. Therefore, combined with mass and heat transfer in liquid film, it is important to study the separate sequence for optimizing operating conditions and enlarging equipment applications.In this paper, some operation rules were brought forward from the design point of the MD apparatus and the characteristics of mixtures, which are to be purified. First, the number of product after the separation should be the least, and the sequence of separation should be the same to the volatilities of the components in the mixture. Second, the heat sensitive substance and corrosive substance should be separated as early as possible. Meanwhile, the easiest separation step should be the first and the most difficult separation should be the last. Third, the more contained component in the mixture should be separated as early as possible. For most cases, we could consider the mixture according to the difficulty of separation as three parts, such as: easier separation part, normal part and more difficult separation part.Until now, there are few studies of molecular distillation sequences. In this paper, a new method, which can be called the dynamic programming method (DPM), was presented. This new method is consisted of by the all separators calculation. Because the number of the MD separators used in industrial applications is small, we can use the proposed DPM to calculate the whole process cost easily. Compared to the traditional distillation sequence rules, the new DPM is more convenient. In the paper, optimization of the single step MD by the differential method was also presented, by which we can design the molecular distillation flow sheet and can obtain the knowledge for the process operation.The effects of technological conditions on the process of concentrating Vitamin E by MD were studied in the paper. During the MD process optimization, the influence of operating parameters on total content and yield of effective compositions...