A MATHEMATICAL MODEL FOR VOC EMISSION THROUGH A FOAM COLUMN

Abstract

A mathematical model is developed for the diffusive mass transfer of volatile organic compounds (VOC) through an aqueous foam column. The model incorporates lamella film thinning due to liquid drainage from the lamella, bubble size growth, and the VOC concentration profile as a result of the overall diffusion across the foam column. The VOC emission model compares reasonably well with the experimental data of highly stable clay aqueous foam formulation developed using surfactants, stabilizer, polymer, and clay and tested in the presence of gasoline. Foams with higher clay loading give slower liquid drainage, lower gas diffusivity in liquid, and higher diffusive mass transfer resistance for the foam column. The parametric analysis of the model shows little impact on mass transfer resistance for different initial bubble sizes. The initial foam heights and VOC concentrations, however, affect the mass transfer resistance significantly. Taller initial foam heights offer greater mass transfer resistance than smaller ones. The higher the VOC concentration in gasoline/crude oil, the greater the VOC emission, but breakthrough time is not affected.