
96 Foam Fractionation: Principles and Process Design
Unfortunately, Equations 6.10 through 6.13 cannot give quantitative
estimates of the recovery and enrichment in the semi-batch process because
no information about surface and liquid uxes is given. Because the bulk
concentration of the liquid layer decreases over time, so does the surface
excess within the foam. This, in turn, impacts upon the drainage parame-
ters, from Chapter 3, m and n (as the liquid depletes, the drainage rate tends
to increase, causing a drier foam) and the foam stability (the foam becomes
less stable giving bigger bubbles). Thus, as the foam fractionation proceeds