Liquid hold-up, in packed

Total liquid hold-up in packed bed, h[ = static hold-up, hg, plus operating hold-up, ho [64, 66]. 

Jesser, B. W. and J. C. Elgin, Studies of Liquid Hold-up in Packed Towers, Trans. Amer. Inst. Chem. Engr., 39, No. 3 277 (1943). 

Otake, T. and K. Okada, Liquid Hold-up in Packed Towers, Operating and Holdup Without Gas Flow, Soc. Chem. Engrs. Qapan) 17, No. 7, 176 (1953). 

Ortiz-Arroyo, A. Larachi, F. Iliuta, I. Method for inferring contact angle and for correlating static liquid hold-up in packed beds. Chem. Eng. Sci. 2003, 58 (13), 2835-2855. 

Liquid hold up in a tower represents the liquid held in the void spaces of the packing during operating conditions. At flooding, essentially all of the voids are filled with liquid. 

Gayler, R., Roberts, N. W. and Pratt, H. R. C. Trans. Inst. Chem. Eng. 31 (1953) 57. Liquid-liquid extraction. Part IV. A further study of hold-up in packed columns. 

Fig. 8.15. Experimentally determined liquid hold-up in katapak-S packing. (From Ref. [21].)...

R. Gayler, N. W. Roberts, H. R. C. Pratt, Liquid-Liquid Extraction. A further Study of Hold-up in Packed Columns. Trans. Am. Inst. 

The study under pressure with countercurrent flow has shown that the operating pressure has no effect on hold-up. In fact for a liquid flow rate of 4.63 kg/rrPs and constant gas velocity of 0.037 m/s, liquid hold-up is 0.21 for pressure ranging between 0.1 and 1.3 MPa. This result is in agreement with the conclusions of Van Gelder el al. [1] concerning the influence of pressure on liquid hold-up in a packed column operating with cocurrent flow. Larachi el al. [4] report the same observations in a fixed bed column with cocurrent flow. 

In addition to these pressure drop models, models to represent spreading of liquid in packed beds because of spatial variation in flow resistance are needed. In a randomly packed bed, the void fraction is not uniform. This implies that some flow channels formed within a packed bed offer less resistance to flow than other channels of equal cross-sectional area. Liquid will tend to move toward channels of lower resistance, leading to higher liquid hold-up in such channels. Thus, even if the initial liquid distribution is uniform, inherent random spatial variation of the bed leads to non-uniform liquid flow. Yin et al. (2000) assumed that the dispersion coefficient for liquid phase volume fraction is linearly proportional to the adverse gradient of... 

Alix, R, and Raynal, L. (2008), Liquid distribution and liquid hold-up in modern high capacity packings, Chemical Engineering Research Design, 86(6) 585-591. 

Kolar.V., Broz.Z. and J.Tichy. "Liquid hold-up in gas-liquid countercurrent flow through a bed of packing". Coll.Czech. Chem.Comm. 35 (1970) 3344. 

Mohunta,D.M. and G.S.Laddha, "Prediction of liquid hold-up in random packed beds". Chem.Engng.Sci. 20 (1965) 1069. 

Pendulum Pulsator. Technical Information - ENVIMAC Engineering GmbH, 46149 Oberhausen Gayler R, Roberts NW, Pratt HRC. Liquid-Liquid Extraction Part IV. A Father Study of Hold-Up in Packed Columns. Trans. Inst. Chem. Engrs. 31(1953), p. 57-68... 

Piret et al. measured liquid holdup in a column of 2J-ft diameter and 6-ft packed height, packed with graded round gravel of lj-in. size, the total voidage of the bed being 38.8%. The fluid media, air and water, were in countercurrent flow. The liquid holdup was found to increase markedly with liquid flow rate, but was independent of gas flow rate below the loading point. Above the loading point, an increase of liquid hold-up with gas flow rate was observed. 

Specchia, V., and Baldi, G., Pressure drop and liquid hold-up for two-phase concurrent flow in packed beds. Chem. Eng. Sci. 32, 515-523 (1977). 

The liquid hold-up is appreciably lower in a packed column than a plate column. This can be important when the inventory of toxic or flammable liquids needs to be kept as small as possible for safety reasons. 

An estimate of the amount of liquid held up in the packing under operating conditions is needed to calculate the total load carried by the packing support. The liquid hold-up will depend on the liquid rate and, to some extent, on the gas flow-rate. The packing manufacturers design literature should be consulted to obtain accurate estimates. As a... 

Relative Kga valid for all systems controlled by mass transfer coefficient (Kg) and wetted area (a) per unit volume of column. Some variation should be expected when liquid reaction rate is controlling (not liquid diffusion rate). In these cases liquid hold-up becomes more important. In general a packing having high liquid hold-up which is clearly greater than that in the falling film has poor capacity. 

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