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A study was made of factors affecting the vapor‐handling capacity of perforated‐plate liquid‐vapor contacting columns. Vapor‐phase pressure drop across plates, liquid entrainment upward from plate to plate, and plate stability were investigated as functions of operational and geometric column parameters. Gas‐phase pressure drop across dry perforated plates was observed to follow functional relationships predicted from available information for single perforations. The presence of liquid on a plate increased the total pressure drop by the equivalent clear‐liquid head plus a small residue which is nearly constant for a given liquid. Entrainment was observed to be a function of column gas velocity, independent of gas velocity in the perforations. Weight rate of entrainment was also found to be proportional to the gas density, independent of liquid density, and inversely proportional to the liquid‐surface tension. For a given system, entrainment was observed to be proportional to approximately the third power of the group, gas velocity divided by the distance between the liquid surface and the plate above. The stability of perforated plates was observed to be adequate for many industrial and experimental applications, as also reported in recently published studies, but contrary to qualitative statements found in the earlier literature. Stability was found to increase with decreasing perforation diameter and decreasing total perforation area relative to column cross‐sectional area; to increase with greater gas density, liquid surface tension, and liquid wetting power; and to be virtually independent of liquid density and viscosity. Operating limits of vapor and liquid throughput are shown for a typical application of perforated plates in liquid‐vapor contacting columns.

Ind. Eng. Chem. Process Des. Dev. 1986, 25, 936-941 Park, W. K.; Mayer, R. L. T-ature-Tim-Reaction ~eovum contrdled Hydfopyfo@k?; Monsanto Research Miamisburg OH, 1981; MLM-2849. Park, W. K.; Mayer, R. L. ulha Fast Rate h)&opymlysis of Coal: Final Report; Monsanto Research: Mlamlsburg, OH 1985; MLM-3120. Taiwalkar, A. T. A Toplcal Report on Coal Hydmpym/ys/s; Instltute of Gas Techno-: Chicago, IL 1983; DOE/MC/19316-1408 (DE83006592). Woodburn, E. T.; Everson, R. C.; Kirk, A. R. M. Fuel 1974, 53, 38. DE-AC04-76DP00053. Mchrthy, J.; Ferral, J.; Charng, T.; House&n, J. Assessment of Advanced Coal OesMcatlbn RC4xW.98~; NASAlJet F'ropuklon Laboratory: Pasadena, Nettleton, M. A.; Stirling. R. Combust.Operating two or more distillation columns in parallel, with the reboiler of one serving as the condenser of the next, is known to reduce energy consumption. Similarly, introducing the feed to an extractive distillation column as a vapor, rather than as a liquid, saves energy when the major feed component is light. Combining these two concepts offers an attractive method for separating light, azeotrope-farming Organic compounds from water. As examples, the energy consumption for separating 99.9 wt % ethanol from feeds of 6 or 10 wt % was estimated for distillation trains of four or five columns. The resub indicate that the process achieves steam consumptions of only 0.94-1.47kg per kg of ethanol product, which corresponds to 2100 to 3300 kJ/kg of ethanol (6000-9400 Btu/gal).

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