Sandwich Packings: State of the Art

Abstract

Capacity and efficiency of packed columns can be significantly improved by the application of sandwich packings. An element of such packings consists of two alternating layers of industrially available standard packings with different specific surface areas. Sandwich packings are commonly used for operating conditions between the flooding points of both layers, with a heterogeneous flow pattern established along a sandwich packing element. There are some similarities between this flow pattern and those in conventional structured packings as well as in trays. Under certain conditions, this can be used in a beneficial way. However, the application of this integrated packing type is hindered by a lack of reliable design methods. In the present article, the results of recent activities are summarized.

Experimental Investigation of the Froth Height in Columns with Sandwich Packings

“…Assuming a comparable froth height in each de‐entrainment layer (except the lowest one in which no froth regime evolves), the height of the froth regime H Fr in each sandwich stack is determined to be only 8 mm according to Flechsig et al . Whereas the experimentally obtained heights agree very well (60 mm and 61 mm), the correlation (8 mm) clearly underpredicts the experiments for the selected loads.…”

“…The comparison with an existing empirical correlation by Flechsig at al. revealed that the correlation clearly underpredicts the experimental data if column and packing dimensions, loading limits, and pressure drop level are different. However, the froth height meets the experimental results when the same pressure drop at an appropriate higher gas load is applied or the characteristics of the small‐scale column are properly considered in the correlation.…”

“…The calculated height results from the assumption, that the pressure drop of the froth regime equals the pressure drop of the flooded holdup layer, which has not been experimentally verified. Later, Flechsig et al modified this approach according to …”

“…The calculated height results from the assumption, that the pressure drop of the froth regime equals the pressure drop of the flooded holdup layer, which has not been experimentally verified. Later, Flechsig et al [3] modified this approach according to…”

Rate‐based‐Modellierung von CO2‐Absorptionskolonnen mit Anstaupackungen

“…Die Höhe des Sprudelsegments in der AN ist gleich der gesamten Höhe der AN. Die Höhe der Sprudelschicht in der AB wird durch eine empirische Korrelation berechnet, in der die Geschwindigkeiten beider Phasen, geometrische Parameter der AP und Stoffeigenschaften berücksichtigt werden : …”