The issue of plate efficiency in Aspen distillation column simulations
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Use Aspen to simulate the distillation process for water-methanol separation. First, DSTWU was used for design calculations, which yielded a reflux ratio of 2.5, a minimum theoretical number of plates of 5.8, and an actual theoretical number of plates of 8.7 ； The RADFRAC model is then used for verification, but to meet the separation requirements, 12 theoretical towers are necessary. Now, when designing a distillation column, data on plate efficiency is required. May I ask everyone, where should this plate efficiency be defined? If the overall tower efficiency is to be used, it can be calculated based on the viscosity of the key components according to certain methods; however, since this process is part of the etherification of light gasoline, the composition of the substances in the system is quite complex, making it impossible to find viscosity data. I wonder if Aspen can calculate the viscosity of a mixture on its own (Just as the output report can show the average molecular weight and density of the stream, similarly, regarding some parameters related to the arrangement of trays and steps, I wonder if Aspen can also handle that?) If possible, I would greatly appreciate any advice from those who are more experienced; thank you very much!
The overall tower efficiency can be calculated using empirical formulas; is it related to viscosity? I remember it having something to do with the relative volatility of the light and heavy key components. The viscosity of the mixture you’re referring to can certainly be calculated; just like properties such as molecular weight and density, as long as you specify this property in the property settings, it will appear in the results. The setup of trays is also possible; relevant parameters can be set in Tray Rating.
It can be considered as viscosity. The overall tray efficiency and the viscosity of the feed are related to the relative volatility. Reference can be made to process calculation manuals, which contain relevant simple charts and formulas.