Flood load factor

At the flooding point, the balance of forces acting on a suspended droplet leads to correlation (2-12), which is then transposed to give the following equation for the flood load factor F v,F1 ... 

GRDC- graphical correlation, extended flood load factor Fy = f (Xp )... 

Figures 2-4a, 2-4b and 2-4c as well as the analysis of the models described in paragraph 2.2.3 provide important information on the parameters which influence the effective droplet velocity Ut. In the case of decreasing flow parameters Xpi < 10, the flood load factor F v,F1 remains virtually constant and is proportional to the reduced droplet...

Further calculations were performed, based on other methods, to determine the flood load factor Fy.n. acc. to this task definition. The results were as follows ... 

ADM = Minimum downcomer area, fT ATM = Minimum column cross-sectional area, fr CAF = Vapor capacity factor CAFo = Flood capacity factor at zero liquid load CFS = Vapor rate, actual ftVsec DT = Tower diameter, ft DTA = Approximate tower diameter, ft FF == Flood factor or design percent of flood, fractional FPL = Tray flow path length, in. 

Capacity factor based on tower area, ft/sec Capacity fector at flood, ft/sec Liquid gradient vapor load correction factor or Discharge coefficient (see accompanying table) or Gas phase loading factor, ft/sec. Equation 8-281 Eddy loss coefficient, dimensionless. Table 8-22 Wet cap pressure drop correction factor. Figure 8-115... 

The downcomer percent flood is a critical tray-loading factor. If it is over 90%, then tray flooding failure is likely. If it is below 20%, tray vapor blowthrough (downcomer side) is likely to happen. It is therefore important to keep the downcomer flood below 90% and above 20%. One more limiting downcomer flood value, the active area flood, is also important. The active area flood calculation is covered in the following section. 

Liquid load Figure 6.9a is a plot of flood F-factor against liquid load. From Eq. (6,5), it also illustrates the effect of liquid load on the flood C-factor, or CSB. As liquid load increases, CSB first rises, then declines. The decline is slow, as illustrated by the cyclohexane-n-heptane curves in Fig. 6.9a, Some of the earlier flood correlations (18-20) predict that CSB rapidly diminishes at high liquid loads (as illustrated for the butane curves in Fig. 6,9a). Later work, first reported by Gerster et al. (21) and then by many others (15,22-26), however, showed that the rapid decline (such as that for the butane system) is associated with downcomer flooding, and not with entrainment flooding. 

Overall column efficiency, fractional Overall point efficiency, gas concentrations, fractional Murphree plate efficiency, gas concentrations, fractional Eractional approach to flood E-factor for gas loading Elow parameter Gravitational constant Conversion factor... 

Figure 13-9 Correlation of the load factor (Fr = uvJuvsf at a fixed ratio of liquid to vapor mass flow rates, uvs = velocity of vapor based on the superficial area, ft/s, uvsf = velocity of the vapor based on the superficial area at the flood point, ft/s.) [W. L. Bolles and J. R. Fair, Third International Distillation Symposium, London, April 1979, No. 213 of E.F.C. Sec. 3.3, p. 35, by courtesy Institute of Chemical Engineers (London).]...

This leads to the following flood gas load factors Fv,Ff... 

By using the equations derived for the calculation of each parameter, it was possible to condense the extensive research material, which is discussed in the summary of the results of this work in Chap. 6. The end of each chapter contains example calculations to illustrate the individual correlations for determining the vapour load factor at the flooding point of the liquid hold-up as weU as the pressure drop of irrigated and dry random packing elements. The numerical examples are practice-oriented and explain the correlations mentioned before, based on the examples of different packings. 

For ordered, or structured, packings, pressure-drop estimation methods have been reviewed by Fair and Bravo [Chem. Eng. Progr, 86(1), 19 (1990)]. It is not common practice to use the packing factor approach for predicling pressure drop or flooding. For operation below the loading point, the model of Bravo et [Hydrocarbon... 

Leva [40] has correlated the data of Lubin into correction factors to apply to a non-irrigated bed pressure drop to end up vith pressure drop for a liquid-gas system in the loading to flooding range. In general this does not appear any more convenient to use than Figure 9-2 ID. 

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