A simple graphical method of calculating the liquid volume fraction, or wetness, of a rising pneumatic foam is presented that is deterministic, given system properties (such as the bubble size distribution and the rate at which gas is sparged to the column) and the kinematic viscosity of the interstitial fluid along with some information about the drainage behavior of the stationary foam analogue. Thus, it is shown that data for the wetness of rising columns of SDS foam (Stevenson, P.; Stevanov, C. Ind. Eng. Chem. Res. 2004, 43, 6187) can be well-predicted using an equation (Neethling, S. J.; Lee, H. T.; Cilliers, J. J. J. Phys.: Condensed Matter 2002, 14, 331) for the drainage of liquid through stationary columns of SDS foam. Further, the liquid overflow rate can be well-predicted once the liquid volume fraction is calculated. The effects of washwater added to the top of the column and bubble bursting on the equilibrium volumetric fraction have been considered theoretically. It is shown that the volumetric liquid fraction of the foam will be enhanced and the enhancement can be determined graphically. However, the rate at which liquid will be recovered from the top of the column is seen to be independent of washwater addition and bubble bursting.
Industrial & Engineering Chemistry Research Vol. 45, Issue 2, p. 803-807