Please help analyze the feed situation of the vacuum distillation tower, experts
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In a vacuum distillation column, feed is usually introduced at the bottom of the column. However, we encountered a case where the feed was introduced at the 4th plate from the top, and there was no steam stripping at the bottom either. Could experts help analyze what the function of the 4 plates below the feed inlet is? Can these 4 trays be simulated using Aspen? In Aspen simulations, is it generally required that there be a gas phase entering at the bottom of the tower in order to carry out calculations?
This situation can be simulated; the feed should be a gas-liquid mixture, and after entering the tower the gas and liquid are separated. The function of the tower is to carry out flash separation
This post was last edited by dajihuangxz on 2019-12-2 08:31. Hello, thank you for your reply. But I still don’t quite understand what you mean. If by \"the feed should be in a gas-liquid phase, with gas and liquid separated after entering the tower, and the function of the tower is to carry out flash separation,\" you are referring to an overall vacuum distillation tower, then it’s understandable. But what I asked about were the 4 trays below the feed inlet, because flashing occurs at the feed inlet and above it after the material enters the tower; the trays below the feed inlet have no heat source, and the pressure there is higher than that of the feed tray – so how can flashing continue there?
The vacuum distillation column mentioned in the question does not have a stripping section; rather, separation is achieved through flash evaporation as the gas-liquid stream enters the column. The four trays below the feed inlet facilitate gas-liquid exchange, and the pressure decreases as one moves downward in the column. There is a pressure drop across the trays of the vacuum distillation column, and although the difference in pressure between adjacent trays is small, it still exists. Therefore, flash evaporation still occurs in the four trays below the feed inlet
This post was last edited by dajihuangxz on 2019-12-2 09:55. Understood, thanks