The dispersed phase holdup for spray columns can be related to the phase flow rates by the following equation, derived originally for packed columns [5] and applied subsequently to pulsed [10] and rotary annular columns [11]: ▪ In this expression, v 0 is the characteristic velocity identified as the mean relative velocity of the droplets extrapolated to essentially zero flow rates. Differentiation of the above equation, treating x as the independent variable, gives expressions which have been used to correlate flood point data in terms of n 0 [10, 11]. It has also been shown that the limiting holdup at the flood point is dependent only on the phase flow ratio and is independent of the physical properties of the system. In the case of spray columns, it has been found possible to predict v 0 on the basis of the normal correlation of the free falling velocity for spheres, assuming the droplet size to be given by H ayworth and T reybal's relationship [6]. The entire flooding curve can thus be predicted for any system in terms of its physical properties and the dispersed phase nozzle geometry.