Performance of packed columns. III. Holdup for aqueous and nonaqueous systems

Abstract

AbstractTotal, static, and operating holdups have been measured for 1‐in porcelain and carbon Raschig rings and 1‐in. porcelain Berl saddles, employing aqueous solutions of calcium chloride, sorbitol, and a wetting agent as well as pure methanol and benzene. The range of variables covered by this investigation includes liquid rate, 1,000 to 10,000 1b./(hr.) (sq. ft.); viscosity, 0.6 to 185 cp.; surface tension, 23 to 86 dynes/cm.; specific gravity, 0.8 to 1.32.Equations and charts are presented for estimating holdups for all liquids. The application of holdups for estimating mass transfer coefficients, kG, and effective interfacial areas, a, is discussed.The total holdups for water, methanol, and benzene can be used to explain why mass transfer coefficients obtained by vaporization of pure liquids in packings seem to depend on gas diffusivity raised to the 0.15 power instead of the 0.67 power, as found in other mass transfer studies. The larger total holdups of nonaqueous liquids result in larger effective interfacial areas in the packing, which mask the effect of the change in gas diffusivity.