Pressure drop irrigated packed column

A new generalised correlation for pressure drop in packed columns, similar to Figure 11.44, has been published by Leva (1992), (1995). The new correlations gives a better prediction for systems where the density of the irrigating fluid is appreciably greater than that of water. It can also be used to predict the pressure drop over dry packing. 

Mackowiak J. Pressure Drop in Irrigated Packed Columns. Chem. Eng. Processing vol. 29 (1991) no. 

Table 4-4a. Determination of pressure drop in irrigated packed column in operating range up to flooding point. List of test points and relative mean aqueous systems acc. to Table 2-2, for approx. 1 bar, 293/313 K... 

In the case of larger-diameter packing elements, e.g. in absorption with a mostly mass transfer resistance in one phase, the liquid flow is mostly turbulent, with Rcl > 12.3. Here, Eqs. (5-2) and (5-6) lead to the following equations for calculating the pressure drop of irrigated packed columns with any type of column internal ... 

I. Iliuta, F. Larachi, Mechanistic model for structured-packing containing columns Irrigated pressure drop, liquid holdup and packing fractional wetted area, Ind. Eng. Chem. Res. 40 (2000) 5140-5146. 

When designing a packed column, it is also important to calculate the pressure drop of the irrigated packing Ap/H per 1 m packed bed height and the respective hquid hold-up hL. In recent years, these have become important technical-economic parameters. They allow the assessment of packed columns in terms of their suitabihty for the rectification of temperature-sensitive mixtures and for aU gas/Hquid systems, i.e. for absorption, desorption, cooling and preheating of gas as well as for absorption using slow chemical reactions, where the residence time of the hquid must be known. 

It is important to know the total pressure drop Ap of the irrigated packed bed when designing packed columns for gas/liquid systems in counter-current flow of the phases. In absorption as weU as desorption processes, the total pressure drop Ap of the packing determines the blower capacity and thus the major part of the operating costs of the process. In rectihcation, the sum of the top pressure pT and the total pressure drop Ap gives the bottom pressure pw, which determines the bottom temperature tw- The bottom temperature, in turn, determines the effective temperature difference, at a given heating medium temperature, at which the reboiler in the distillation column must be operated. 

Table 4-1 contains a Kst of some important studies [ 1-21,25,41-48] on the pressure drop of irrigated packings in columns with conventional packing elements, such as Raschig rings, Pall rings and Intalox saddles. The work can be divided into three groups. 

An accurate determination of the pressure drop of irrigated packings acc. to the above model can only be guaranteed if the correlations for predicting the resistance coefficient v f for the respective column size are known, see Sect 3.2.3. 

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