Quasistatic Model for Foam Fractionation

A simple model is presented for foam fractionation. The basis of the model is that the liquid fraction profile across the foam column is known quasistatically at any instant in time, and only varies gradually as the foam column height itself varies. Using suitable boundary conditions, the model provides a relation between liquid flux through the foam column and instantaneous foam column height. The flux of surface active material through the column can then also be determined. The model makes it possible to explore how design and operational parameters of a fractionation system influence performance. Indeed the model clarifies that tall columns enrich surfactant, but high velocities of air through the column are detrimental to enrichment. Having larger bubbles in the column helps enrichment though, despite reducing specific surface area and thereby despite reducing the total amount of surface active material adsorbed.