Maldistribution, packings, liquid random

No maldistribution of gas or liquid in three-phase processes. Regarding application of the BSR concept to gas/liquid/solid processes, an important advantage of the BSR is that adjacent strings do not (necessarily) touch. Because of the liquid surface tension, liquid will not spill over from one BSR string to another. Consequently, the initial liquid distribution is maintained throughout the BSR module. This feature is especially advantageous when incomplete catalyst wetting (which results from liquid maldistribution in traditional, randomly packed trickle-flow reactors) would lead to hot spots and decreased selectivity. 

It may be that the random or structured packing efficiency is degraded by the need to limit the bed-height space required for liquid collection redistribution, and by maldistribution and channelling in the packing [33]. 

Low liquid rates. With the aid of serrated weirs, splash baffles, reverse-flow trays, and bubble-cap trays, low liquid rates can be handled better in trays. Random packings suffer from liquid dewetting and maldistribution sensitivity at low liquid rates. 

Generally, the minimum wetting rate is at 0-5 to 2 gpm/ft2 for random packings, and 0.1 to 0.2 gpm/ft2 for structured packings (Sec. 8.2.15). It follows that point A is usually a distributor turndown limit. Regardless of which limit point A represents, it is extremely sensitive to maldistribution (Fig. 8.16b). When liquid distribution is poor, it will take more liquid to wet the entire bed, and point A will shift to the right. If distribution is very poor, point A may never be observed, and the curve will have no flat region at all. A V-shaped curve is not uncommon, and is indicative of poor distribution. 

A packed column has reasonable tolerance for a uniform or smooth variation in liquid distribution and for a variation that is totally random small-scale maldistribution). However, the impact... 

Figure 0.7 Comparing the effects of "small-scale and large-scale" maldistribution on packing HETP. (a) Comparing the effect of a simulated continuous tUt (max/ min flow ratio = 125 ) to the simulated effect of blanking a chordal area equal ts 11 percent of the tower area, (b) Comparing the effects of simulated continuous tilts (max/min flow ratios 125 and 1.5) to the effects of a situation where one-half of the distributor passes 25 percent more liquid to the other hen. (c) Comparing the effects of random maldistribution to these of zonal maldistribution. (Ae-...

Zuiderweg, F. J., and P. J. Hoek, "The Effect of Small Scale Liquid Maldistribution on the Separating Efficiency of Random Packings, I. Chem. E. Symp. Ser. 104, 1987, p. B247. 

With random packing, the degree of maldistribution u [2.2] of the liquid across the column cross section is influential due to wall effects on flow, channeling, etc., u varies in the limits... 

In Table 1 the maldistribution factors of the liquid phase for different random and corrugated structured packings are presented. 

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