Non-perforated packings

Ito resistance coefficient for single-phase flow for non-perforated packing elements, see Eq. (3-28)... 

In packed columns, the liquid flows in counter-current to the gas, in the form of films and runlets. This applies in particular to small, non-perforated packing elements with low void fraction, e.g. e = 0.4—0.6 m m . The void space of the packing elements contains dead space, which is filled with more and more Uquid as the Uquid load ul increases. Flooding occurs when the entire column is filled with Uquid. In the case of high specific liquid loads ul and very low gas velocities uy, i.e. at very high phase flow ratios at the flooding point Xq, the so-called phase inversion occurs through the formation of bubbles, whereby the gas phase is dispersed and the Uquid now forms the continuous phase. 

Furthermore, if the wall surface of a channel is perforated, the length of the perforated channel lx is shorter, compared to non-perforated packing elements, which results in a pressure drop Apo,ix> see Fig. 3-12. 

This ratio, in turn, can be equated to the proportion of the non-perforated packing surface area (l-[Pg.142]

The concurrence between the experimental resistance coefficients for non-perforated packings with ceramic Raschig rings, and the calculation acc. to Eq. (3-28) is sufficiently good for practical applications, see Fig. 3-30. 

The non-perforated packings have the highest resistance coefficients r, see Figs. 3-9 and 3-11. They are comparable to those of modern, randomly filled lattice packings, see Figs. 3-9 and 3-7. 

A total non-perforated wall surface area of individual packing element... 

Figure 3-9. Resistance coefficient xj/ as ffinction of Reynolds number of vapour or gas Rev, valid for non-perforated Montz packing...

Friction forces are generated as a result of gas flow around the channel walls. If the walls are partially perforated, as is the case with Pall or Biatecld rings as well as lattice-type packings, the resistance coefficient Xi in Eq. (3-20) is lower, in comparison to channels with a non-perforated structure. 

Based on a simple extended channel model [34, 35], it was possible to develop a description of the dry pressure drop in random and structured packings. It was assumed that a pressure drop only occurs during gas flow through non-perforated flow channels. In the case of perforated packing elements, which are mostly used today, the proportion of deflections and cut-outs in the wall of the individual packing elements [Pg.145]

The resistance coefficient ijr of structured packings also depends on whether they are perforated, non-perforated or sHt. The resistance coefficients ijr of sKt packings have been found to be lower than those for perforated packings. 

Figure 18. Non-agitated gravity flow extractors, (a) Spray, (bj packed, and (c) perforated plate.

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