Study Of Liquid Flow Characteristics And Structure Optimization Of Wiped Film Molecular Distillation

Wiped film molecular distillation technology is especially suitable for the separation and purification of heat sensitive and high value added natural products with the advantages of good film forming and low pressure loss.The liquid film flow and distribution characteristics of the material on the evaporating wall are important factors affecting the internal working efficiency of the whole equipment,and it is of great significance to study the flow characteristics and structure optimization of the internal liquid membrane of the molecular distillation unit.This paper,with the main purpose of developing a new molecular distillation unit with 0.2m~2 evaporation area,firstly collects and analyzes the relevant documents and data and determines the research program of the paper.Then,a three-dimensional model of distributor and multi-layer scraper is established based on the model of the literature,and the influence of the two on the flow characteristics of liquid film is analyzed.On this basis,the influence of process,structure and other parameters on the liquid flow is discussed.Finally,a set of Chinese unit with molecular distillation is designed,and the main conclusions obtained from this paper are as follows:(1)In the simulation study of the distributor,the paper proposes five optimization models and compares the flow characteristics of liquid film through the analysis of different parameters(speed,feed speed,viscosity,feed location)model in the case under liquid phase and the velocity distribution.The study shows that the average variance of intermediate feed liquid is 94%less than that of traditional side feed,and the distribution efficiency is improved,which avoids the disadvantages of uneven distribution and coking.And for the distributor structure,the performance of distributor with traditional triangle groove is better than that of the new type of inclined slot when feeding on one side,while the inclined slot shows the superior performance in the middle feed.(2)In the simulation study of multi-layer scraper,it is found that the material liquid spirals downward with the motion of the rotor,and the head wave constantly gathes and decomposes along the axial direction of the rotor,increasing the frequency of the exchange between the head wave and the liquid film.(3)In addition,it is found that increasing the speed,surface tension and reducing the contact Angle are beneficial to the decomposition of the head wave and the spreading of liquid film.Appropriate increase stagger angle between the layers of scraper can decrease the thickness of liquid film,enhance the turbulent effect,but excessive stagger Angle makes uniformity of liquid membrane.Besides,the setting of layer spacing can promote the decomposition and update of the head wave and has a certain optimal value suitable for the scraper film.(4)In this paper,a detailed design and strength check of the molecular distillation apparatus is carried out,and the modal analysis of the new rotor mechanism in the motion process is investigated.On this basis,the process flow of the molecular distillation is designed and the design and selection of related equipment are completed.Finally,this paper explores and studies the operation and separation process in the experiment,and lays a foundation for the experimental verification and application development of molecular distillation.