Foaming and frothing related to system physical properties in a small perforated plate distillation column



Experimental froth heights occurring on a perforated distillation tray were correlated with the determining system physical properties under distillation conditions. A photographic technique was used to measure accurately the foam and froth heights, produced in the 4 in. square test section of a laboratory distillation column, for several points in the composition range of five binary systems. Plate design parameters and operating vapor and liquid rates were held constant throughout the experimental study.

The froth height results from this investigation (11), as well as those from studies (17) of a 6 in. distillation column, show a linear relation with the expression, UA2 ρv/(ρL — ρV), the frothing factor, for the ranges of the physical properties investigated.

The foam height results of this study indicate that the mass transfer surface tension gradient, the heat transfer gradient, and the absolute value of surface tension all contribute to foam formation and stability. Because of the complex relation between the surface tension gradient and the frothing factor in relation to the degree of foaming, as well as the effects of other influencing variables, a unique correlation of the foam height data resulting from mass transture of the effect for several of the data points.

This investigation was conducted to obtain experimental data which could provide a basis for correlation of the foam and froth heights occuring on an operating perforated distillation tray with system physical properties.