ESTUDO DE FLUXO GASOSO DE COMPOSTOS DA GASOLINA ATRAVÉS DE SOLOS COESIVOS E NÃO COESIVOS

Abstract

The purpose of this study is to show how hydrocarbon gases behave in porous media. Two types of soil were used: one with cohesive characteristics, a Campos Elíseos silty clay, close to the REDUC refinery, and one with non-cohesive characteristics - pure silica. Tests were performed using benzene, toluene, xylene and a solution of commercial gasoline. Numerical models as stated in the theories of Stefan Maxwell and Fick were applied. Tests in non-saturated conditions were made and the parameters were later determined of advective diffusion equations of the flows. The soil used in the tests was non-saturated with air continuity in the medium, with saturation degree close to 60%. Diffusion column laboratory tests were performed using a gas chromatograph. To measure permeability a triaxial cell was used adapted specially for this study. The application of Stefan Maxwell’s theory in gaseous diffusion in the soil proved more accurate than the Fick model with multicompounds. The gas removal rate in the two types of soils used is not constant in time. In fact, the preferential removal of certain compounds results in a drop in their proportion in the non-aqueous phase liquids (NAPL). This causes a reduction in their solubility and adsorption. Permeability tests were carried out with pure air and hydrocarbon gases in a non-saturated medium. Determining gas permeabilities in the soil gave results that show the major importance of the gas characteristics in relation to the intrinsic characteristics of the soil. Lastly, it should be mentioned that, as expected, the pure silica did not present significant adsorption and the cohesive soil showed significant adsorption.