Flood-packings correlation

The Kiefer and Gill correlation. Zenz (76) discovered that packing pressure drop at the flood point decreases as the packing capacity increases. A similar observation was reported by Strigle and Rukovena (15,77) and Ma kowiak (736). Kister and Gill (60) applied this principle to derive a simple flood point correlation... 

The pressure drop/flooding rate correlation, Figure 15.4, is next used to determine G, the vapor mass rate per unit column cross-sectional area. The information needed includes the packing factor of the selected packing material, the L/V ratio and the fluid properties (vapor and liquid densities and liquid viscosity), and a pressure drop within the acceptable range. The column cross-sectional area and diameter are then calculated from G and V. These calculations should be carried out at different column heights since the vapor and liquid rates and properties may vary. 

Figure 13-6 The Eckert flood velocity correlation. (Fp = packing factor, ft"1 see Table 13-7. g = acceleration of gravity, ft/s2. Gvsf = mass velocity of the vapor, superficial, flood, lb/s-ft2. wL = liquid mass flow rate, lb/s. wv = vapor mass velocity, lb/s. pv = density of vapor, lb/ft3. pL = density of liquid, lb/ft3. p, = viscosity of vapor, lb/ft-s. pw — viscosity of water, lb/ft-s.) [J. S. Eckert, Chem. Eng. Prog.. 63(3) 39 (1949), by courtesy American Institute of Chemical Engineers.]...

The first group of flooding point correlations is based on the assumption that, in accordance with visual observations, droplets are formed in the void spaces of the packing elements, which then fall down into the packing elements situated below, see Sect. 2.2.1. 

Fig. 23. Pressure drop and flooding correlation for various random packings (95). ip = p- o IP-l (standard acceleration of free fall) = 9.81 m/s, p, = liquid viscosity ia mPa-s numbers on lines represent pressure drop, mm H2O /m of packed height to convert to ia. H2O /ft multiply by 0.012. Packing...

Flooding and Loading Since flooding or phase inversion normally represents the maximum capacity condition for a packed column, it is desirable to predict its value for new designs. The first generalized correlation of packed-column flood points was developed by Sherwood, Shipley, and Holloway [Ind. Eng. Chem., 30, 768 (1938)] on the basis of laboratory measurements primarily on the air-water system. 

The packing factor (F) is an important design variable in determining the capacity of any packing design from a flooding, or pressure drop standpoint. This-factor was first described by Sherwood in 1938. The empirical correlation is ... 

Kaiser [140] presents a correlation analysis for flooding in packed towers that is more analytical in the performance approach. It is based on single phase hydraulics. It would have been helpful for the article to present a comparison of results tvith the other more conventional techniques. 

Revised Packed Tower Pressure Drop Correlation Constants for Towers Operating Below Flooding Region... 

Packed towers should operate near 70% of the flooding rate given by the correlation of Sherwood, Lobo, et al. 

The pressure drop through packed columns, and the flooding conditions, can be estimated from the generalized correlation of Leva (1992), shown in Fig. 13-5. The pressure gradient in millimeters of water per meter of packed height is the parameter on the curves, and interpolation is usually necessary to determine the pressure drop (note that the pressure... 

A useful graphical correlation for flooding rates was first presented by Sherwood et a/.(60) and later developed by Lobo el al.(6l> for random-dumped packings, as shown in Figure 4.17 in which ... 

Figure 4.17. Generalised correlation for flooding rates in packed towers(6l)...

Mozenski and Kucharski [2] examined the pressure-drop, overload limit, and flooding limit of a column (0.5 m diameter) packed with Pall rings (35 mm diameter) and Bialecki rings (35 mm and 50 mm diameter) sprayed with propylene carbonate up to 15 bar. Some specific correlations have been proposed and compared with literature data for atmospheric pressure, particularly with the use of the Sherwood diagram for loading-and flooding capacities. 

Figure 6.2-1. Generalized flooding-and pressure-drop-correlations for packings versus flow parameter.

The correlation of Eckert (Fig. 13.37) combines a pressure drop relation and safe flow rates insofar as staying away from the flooding point is concerned. A flooding line corresponds to pressure drops in excess of 2 in. water/ft. In use, a pressure drop is selected, and the correlation is applied to find the corresponding mass velocity G from which the tower diameter then is calculated. Another correlation recommended by a manufacturer of packings appears in Figure 13.40. Example 13.16 compares these correlations for a specific case they do not compare any more closely than could be expected from the scatter of flooding data. 

For low-capacity random packings, such as the small first-generation packings and those smaller than 1-in diameter (Fp > 60 ft-1), calculated flood pressure drops are well in excess of the upper pressure drop curve in Fig. 14-55. For these packings only, the original Eckert flood correlation Chem. Eng. Prog. 66(3), 39 (1970)] found in pre-1997 editions of this handbook and other major distillation texts is suitable. 

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