D

FIG. 14-49 Common third-generation random packings. (a) Intalox metal tower packing (IMTP). (b) Cascade mini-ring (CMR) (plastic). (c) Nutter ring (metal). (d) Raschig Super-Ring (metal). (Parts a, b, courtesy of Koch-Glitsch LP; part c, courtesy of Sulzer Chemtech; part d, courtesy of Rashig AG.)

packing size). This improves drainage, and therefore capacity, but at the expense of reduced gas-liquid contact, and therefore efficiency.

A recent development followed the realization that liquid drainage was restricted at the element-to-element transition rather than inside elements (Lockett and Billingham, IChemE Symp. Ser. 152, London, 2006). This means that the liquid accumulation leading to flood initiates at the transition region. A fourth generation of structured packing started, in which the main body of each element has layers inclined at 45°, but the ends of each element are almost vertical to permit drainage at this end region (Fig. 14-50d; but keep in mind that successive elements are rotated 90° rather than continuous, as shown in Fig. 14-50d). These S-shaped or high-capacity packings offer greater capacity compared to equivalent 45° inclined packings with efficiency the same with some (Pilling and Haas, Topical Conference Proceedings, p. 132, AIChE Spring Meeting, New Orleans, March 10-14, 2002; McNulty and Sommerfeldt in "Distillation: Horizons for the New Millennium," Topical Conference Proceedings, p. 89, AIChE Spring Meeting, Houston, Tex., March 1999) and lower with others [Olujic et al., Chem. Eng. and Proc., 42, p. 55 (2003)].

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