Enhanced foam drainage using parallel inclined channels in a single-stage foam fractionation column

A single-stage vertical foam fractionation column was investigated under continuous steady-state experimental conditions. Using a simple power-law expression to describe the drainage velocity through the foam, and in conjunction with continuity arguments, a theoretical framework was developed to analyse the performance of the vertical column. A reduction in the degrees of freedom in the analysis was achieved by using a fixed feed to gas flux ratio to promote a reasonably constant surfactant recovery. It was then possible to measure the process performance by determining the change in the level of enrichment produced from a change in the gas flux, and corresponding change in the feed flux. For a constant recovery, the enrichment is directly proportional to the volume reduction (defined as the ratio of the feed volume processed to foamate volume produced in a given time). The analysis was found to be consistent with experimental data and demonstrated the need to limit the gas flux, and hence the feed flux, to relatively low values in order to produce satisfactory volume reductions, and in turn achieve high enrichment. To overcome this processing constraint, three parallel inclined channels (PIC) were used to provide an effective increase in the vessel area, and hence facilitate the release of the entrained liquid within the foam. A significant increase in the volume reduction was obtained using the inclined channel arrangement. For the same processing rate, the PIC column achieved up to a 4 fold increase in enrichment compared to the vertical column. A slight decrease in recovery, however, was observed using the PIC column.