We are trying to model a high-vacuum short path molecular distillation unit, which is used to separate long-chained unsaturated fatty acids. Getting accurate physical properties is one challenge, characterizing the complex mixture using pseudo-components is another. But my question is: Does anyone have experience using standard unit operations models (flash units, multistage distillation units, other?) in process simulation software to model molecular distillation?
Molecular stills are simple single stage flash vaporizations as there is no fractionation via reflux return, multiple stages, etc. I have seen instances where a claim could be made for an extra fraction of an equilibrium stage (1.2 - 1.3) based on the way vapor and condendsate are routed/handles within the units. I do not believe you should count on this.
Bottom line - the unit is nothing more than an equilibrium flash where very low operating pressure and pressure drop to the condenser resulting in reduced operating temperature is the primary benefit. The biggest bang will be to gain an understanding of the thermodynamic properties of your mixture.
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