FOAM BEATING - A UNIT OPERATION

The scope of our study was to investigate the characteristics of foam beating as unit operation. The foams were beaten in a thermostated cyl indrical vessel with a vertical rotating cage from a coarse dispersion of the gas and the foaming solution. The specific foam volume (phi), the time lag in liquid drainage, the specific surface areas (A and F) of steady state foams were measured and the adsorption isotherm (Gamma ,c) of the surfactant at the air liquid surface was determined. It was shown that an optimal mixing rate exists, for which both A and F are maximal under the given conditions. Below this rate the bubble surface area (A) is less than the optimal and above this rate the liquid surf ace area has a decreasing tendency. The specific foam volume can be re gulated by changing the concentration of the surfactant. Knowing the s pecific surface area (F), the work line of the operation was construct ed and the (Gamma,c) work point was read. In the investigated cases th e concentration in the work point was near the critical micelle concen tration of the surfactant.