
56 Foam Fractionation: Principles and Process Design
3.10 Beyond the Stable Limit of Foam
High enrichment is typically desirable during foam fractionation, and this
generally occurs under conditions of low liquid ux, low gas ux, and low
volumetric liquid fraction. However, for completeness, it is worth briey dis-
cussing the behavior of a pneumatic foam at high gas rates. As described in
Section 3.3, the equilibrium state of a pneumatic foam in a vertical column is
given by the peak of the curve in Figure3.4, and the liquid fraction increases
with increasing gas rate. In such a foam, the foam layer itself is present directly
above the bubb ...