Problems with the efficiency of packed towers
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Hello, everyone: When using ASPEN for the simulation of column processes, plate columns can utilize the Murphree efficiency or overall column efficiency to account for the difference between the theoretical number of plates and the actual number of plates. As for the packed tower, is it necessary to input the Murphree efficiency or overall tower efficiency in order to adjust the theoretical plates and actual plates (although there are no theoretical plates in a packed tower either), or is such adjustment already included in the equivalent plate height HETP provided as input for tower diameter verification? I’ve been troubled by this question. Because I have looked at some ASPEN tower design documents from chemical engineering design competitions, some teams use the O’Connell method to calculate the tower efficiency (as shown in the figure), and update the actual number of trays as well as the feed tray (this approach is used for both packed towers and theoretical trays). However, some teams do not do this, which is why this question has persisted. If a packed tower requires correction using the tower efficiency, what methods do we generally use to estimate this efficiency in the absence of actual parameters?
Unlike tray towers, which have a clear distinction between the theoretical number of plates and the actual number of plates, packed towers typically use the equivalent theoretical plate height HETP to describe the mass transfer efficiency. When simulating a packed tower, it is often not necessary to enter the Murphree efficiency or the overall tower efficiency separately. The input equivalent theoretical plate height HETP has already taken into account the mass transfer efficiency. If it is necessary to estimate the mass transfer efficiency of a packed tower, it can be calculated using empirical data or equations provided in the literature, or by employing tower efficiency estimation methods such as O’Connell’s method. In the absence of specific parameters, estimation can be made by referring to known tower efficiency data under similar process conditions. .