Scintigraphic Measurement of Liquid Holdup in Foam Fractionation Columns

The profile of liquid holdup in foam fractionation columns was studied as a function of time by the use of a nuclear scintigraphic imaging technique. Sodium [(99m)Tc]pertechnetate was employed as the imaging agent and served as a marker for the amount of water present in the foam during the foam fractionation of bovine serum albumin. A gamma scintigraphic camera fitted with a pinhole collimator was used to acquire the data in a dynamic manner. The greatest changes in the liquid holdup of the foam were observed in the region just above the foam-retentate interface, particularly when a gas dispersion frit with large nominal frit porosity was employed to generate the foam. Beyond these first few centimeters, the volume fraction of water in the foam did not change appreciably. This suggests that under the conditions employed, increases in foam column height would not substantially improve the performance of the foam fractionation of bovine serum albumin. In the case of foam generated with a frit of small porosity, the liquid holdup profile indicated a higher fraction of water than observed with the larger frit. The use of scintigraphic imaging can provide valuable data concerning the liquid fraction that is not easily obtained with methods previously used in the study of drainage in foam fractionation columns. Copyright 2000 Academic Press.