Simulation Of Wiped Film Molecular Distillation Process For Seal Oil Fatty Acids

Seal oil is rich in ω-3 polyunsaturated fatty acids such as EPA, DPA and DHA, which have an important effect on human’s health. The separation or enrichment of these three kinds of medicinal components is necessary due to the low content of them in the crude product. Molecular distillation technology is an effective separation method to concentrate medicinal components from seal oil, due to it operates under low pressure and at relatively low temperature with short residence time, and can effectively minimize the risk of thermal decomposition of the materials. Some scholars have begun to study the wiped film molecular distillation process for the separation of non-esterified seal oil fatty acids, in order to protect the biological activity and the medicinal value of the medicinal components. The effects of evaporator temperature and feed rate on the evaporation process are examined. However, the design of wiped film molecular distiller and the optimization of the separation process are mostly based on experience due to the insufficient theoretical research and a further study between the separation process and operating parameters. Therefore, it is significant that studying the wiped film molecular distillation process with non-esterified seal oil fatty acids.The vapor pressure data of EPA and other ω-3 polyunsaturated fatty acids are needed in order to calculate the evaporation rate, which is used for the simulation of wiped film molecular distillation process of seal oil fatty acids. The vapor pressure data can only be obtained by estimating due to the purity of EPA and other co-3 polyunsaturated fatty acids is very low and the experimental error is very large. However, there is no feasible estimate method can be utilized for calculating the vapor pressure data due to the lacking of critical parameters and basic data. In this work, a new and simple correlation of vapor pressure and temperature with four-parameter is proposed based on the experimental data of wiped film molecular distillation and the latest model used for estimating the vapor pressure data of fatty acids. The accuracy of the equation is verified by back-calculating the normal boiling point of seal oil fatty acids, and the absolute errors are less than 1.5 K.In this work, a 1-D mathematical model of wiped film molecular distillation process is proposed based on the model founded by Guillermo et al. and the rationality of the model is verified by the simulation of the separation of DBP-DBS binary mixture. According to seal oil is a multi-component liquid mixture with non-ideality, and there are a variety of resistances on the evaporation rate, a corrected evaporation rate equation is founded by using the device parameters, operating conditions and material properties based on the equation proposed by Kawala and Stephan. The modified equation is used for calculating the evaporation rate in the simulation of wiped film molecular distillation process for the separation of medicinal components from the non-esterified seal oil fatty acids. The simulation is performed with a binary system and a multi-component system respectively. The results show that, as the evaporator temperature increased, the mass fraction of residue decreased but the mole fraction of medicinal components in the residue increased when the feed rate is constant. As the feed rate increased, the mass fraction of residue increased but the mole fraction of medicinal components in the residue reduced when the evaporator temperature is invariable. The simulated results agree well with the experimental values and the applicability and reliability of the model and the corrected evaporation rate equation are verified. Taking into account the calculated quantity and complexity and the magnitude of simulation errors, the binary system is considered to be the better simulation system and can be used for further researching of the non-esterified seal oil fatty acids.