(21c) Comparison of Gas Distribution Characteristics of Conventional and High Capacity Structured Packings

So called high capacity structured packings are in demand now because these packings allow retrofit of existing columns equipped with conventional corrugated sheet structured packings. A key feature of these packings is a significantly lower pressure drop, which was achieved simply by bending both ends or only bottom part of corrugations to vertical to avoid sharp change in vapor flow direction at the transitions between packing elements or layers. In addition to a smoother transition for vapor flow, the hydraulic diameter of the vertical section of flow channels is larger. This reduces vapor velocity significantly in the transition zone and creates a smoother transition for liquid too, i.e. shifts the build-up of liquid to higher vapor loads and consequently enables operation with a significantly higher capacity than achievable with conventional packings with corrugation inclination angle of 45 degrees.

A general concern related to application of high capacity structured packings is that at modest vapor loads the pressure drop may be that low that there is no intrinsic means left in a bed to suppress imported initial vapor maldistribution, which however is certain and surprisingly severe in multi-bed columns where packed beds of certain length are separated by liquid redistribution sections that consist of a liquid collecting device placed above a liquid distributor. Namely, as observed, even streamlined liquid collectors stimulate clustering of high- and low-velocity zones with strikingly large velocity range. This paper presents the results of large scale gas distribution experiments carried out to observe the gas distribution characteristics of an established high capacity structured packing (Montz-pak B1-250M), which, similar to its conventional counterpart (B1-250), required only one packing element to smooth-out a rather strongly maldistributed initial gas profile as delivered by a conventional vane-type liquid collector.