Pressure drop structured packings

For ordered, or structured, packings, pressure-drop estimation methods have been reviewed by Fair and Bravo [Chem. Eng. Progr, 86(1), 19 (1990)]. It is not common practice to use the packing factor approach for predicling pressure drop or flooding. For operation below the loading point, the model of Bravo et [Hydrocarbon... 

Norton Intalox Structured Packing Pressure Drop Coefficient F for Type 2T Packing... 

The channel model This model attributes packed-column pressure drop to the resistance to flow in a multitude of parallel channels. The channels may have bends in them or may have contractions and enlargements. Liquid flows down the walls of the channel, thus consuming some of the available cross-section area. This in turn increases the pressure drop. The channel model has been applied both for random and structured packings (e.g., 3,62,736,78,91,92,93a), A popular application of this model is the Bravo et al. (91) correlation for structured-packing pressure drop ... 

FIGURE 5.8-14 Geometric factors for estimating structured packing pressure drop (Ref. 24). 

Vacuum systems. Packing pressure drop is much lower than that of trays because the packing open area approaches the tower cross-sectional area, while the tray s open area is only 8 to 15 percent of the tower cross-sectional area. Also, the tray liquid head, which incurs substantial pressure drop (typically about 50 mm of the liquid per tray), is absent in packing. Typically, tray pressure drop is of the order of 10 mbar per theoretical stage, compared to 3 to 4 mbar per theoretical stage with random packings and about one-half of that with structured packings. 

As shown by the equations in Section 12.1, column plate height is affected by many parameters, including flow velocity, particle diameter, packing nonuniformity, diffusivities, degree of retention, stationary phase structure, temperature, pressure drop, and pressure. Some of these parameters are interdependent, such as diffusivity and temperature also velocity and pressure drop. Finding a minimum with respect to all of these parameters is an extended task we shall not attempt here. However, we can readily uncover some simple rules for optimizing a few of the major parameters. First we choose flow velocity. 

Boston inside-out method. 172-177, 198 Bravo, et al. rfructured packing pressure drop, 447, 499, 500 Bravo Fair et al. mass transfer random packing, 528-530 structured packings, 474, 529, 531, 532 Brown-Martin method, 109 Bryoden method, 161, 162, 175, 176. 179... 

Figure 2-5 illustrates a typical section of Intalox packing 2T for use in a small diameter column. As with random dumped packings, pressure drop is determined for structured packings using an air/water system at atmospheric pressure and ambient temperature. Figure 2-6 is a plot of the pressure drop for Intalox Structured packing 2T. These curves have... 

Refitting of a tray-type column is desired to increase loading, increase efficiency, and/or decrease pressure drop. Structured packing is pariicularly applicable in this case. 

Sepn. Purif., 3, 19 (1989)] takes holdup into account and applies to random as well as structured packings. It is somewhat cumbersome to use and requires three constants for each packing type and size. Such constants have been evaluated, however, For a number of commonly used packings. A more recent pressure drop and holdup model, suitable for extension to the flood point, has been pubhshed by Rocha et al. [Jnd. Eng. Chem. Research, 35, 1660 (1996)]. This model takes into account variations in surface texturing of the different brands of packing. 

Representative pressure drop data for random and structured packings are given in Figs. 14-52-14-54. 

Efficiency and pressure drop data for Siilzer BX metal gauze structured packing and for three test mixtures are shown in Fig. 14-7.5. For the ethyl benzene/styrene test mixture, the effect of operating pressure is shown. The high viscosity mixture, propylene glycoL/ethylene... 

Lucas and Porter (U.S. Patent 3,370,401, 1967) developed a fiber-bed scrubber in which the gas and scrubbing liquid flow vertically upward through a fiber bed (Fig. 17-55). The beds tested were composed of knitted structures made from fibers with diameters ranging From 89 to 406 [Lm. Lucas and Porter reported that the fiber-bed scrubber gave substantially higher efficiencies than did venturi-type scrubbers tested with the same dust at the same gas pressure drop. In similar experiments, Semrau (Semrau and Lunn, op. cit.) also found that a fiber-bed contactor made with random-packed steel-wool fibers gave higher efficiencies than an orifice contactor. However, there... 

Once packing heights are determined in other sections from HETP (distillation) or Koa (absorption), the height allowances for the internals (from Figure 1) can be added to determine the overall column height. Column diameter is determined in sections on capacity and pressure drop for the selected packing (random dumped or structured). 

Table 7 show s ranges of pressure drop for design. Pressure drop sets the allowable vapor flow rate. The flood pressure drop, for random or structure packings, is given in Reference 15 as ... 

Tlie flood pressure drop for structured packing, already shown in the subsection on random dumped packings, is repeated here ... 

Structured packing used as a vapor distributor for random packed bed dislodged and blown sideways. High pressure drop. Hold down not provided. Design eiTor. 

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