Modelagem matemática da volatilização de sulfeto de hidrogênio a partir de superfícies líquidas quiescentes expostas ao escoamento atmosférico

Abstract

In this study the volatilization of hydrogen sulfide dissolved in the liquid from a tank with quiescent free surface was studied by numerical solution of transport equations. Quiescent surfaces are present in Wastewater Treatment Plants – WWTP, for example, sedimentation tank. Hydrogen sulphide is typically pursued as the marker for odour due to its very low detection and recognition thresholds and its considerable emission rate. To evaluate the volatilization of gases dissolved in the liquid from surfaces quiescent the finite volumes method (MVF) was used to solve the mass conservation equations, momentum and chemical species with the used of the computational dynamic fluid program ANSYS-CFX. The flow was considered isothermal. The results obtained by the numerical simulations are compared with simulations made by other authors to validate the mathematical model. Studies had shown the volatilization of a gas dissolved in the water in free surface quiescent was linked to the parameters as Reynolds number (Re), Schmidt number (Sc), the liquid tank with aspect ratio (depth/length) and Henry number (KH) of the substance. In the current study the overall mass transfer coefficient (KL) values extends further down stream as the Re number increases. The presence of the recirculation in the phase liquid was also larger to increased of the Renumber. To Re = 702,07, KL stayed among 3,08×10-6m/s and 4,04 ×10-6m/s; to Re = 970,38, KL stayed among 3,24×10-6m/s and 4,30 ×10-6m/s and to Re = 1220,11, KL stayed among 4,10×10-6m/s and 5,36 ×10-6m/s.