Estudo computacional de uma proposta de um dissipador de gases em um reator Upflow Anaerobic Sludge Blanket

Abstract

The Upflow Anaerobic Sludge Blanket reactors are anaerobic treatment units and having an upflow sludge bed, which generally degrades the organic matter present in wastewater. This treatment system is very widespread in sewage treatment sewage in Brazil. Yet studies are needed of the hydrodynamic behavior of the reactor, to propose changes for improvement in processes efficiencies. In this context arises the computational fluid dynamics tool that aims to reproduce numerically the phenomena being widely used to reproduce and document flow. The programs were adopted to simulate the COMSOL Multiphysics® and ANSYS®/CFX for hydrodynamic simulation of phase separator of the UASB. The hydrodynamic study computational phase separator showed that the gas stream has great influence on the flow of the reactor and this gas stream may result in a recirculation zone which can reach the entire volume of the reactor. To avoid losses of biogas dissolved in the treated effluent alternative geometry has been proposed to increase the exchange of gases at the outlet of the reactor. The tapered stepped structure was prepared and analyzed using CFD tool. With the ANSYS®/CFX was determined that the flow characteristics to permit the evaluation of this new proposal. The characteristics evaluated were mixing speed, pressure, liquid fraction, energy dissipation, flow velocity, kinetic energy and yet was made a section normal to the steps for determining the liquid fraction on the stairs, the pressure and velocity all is relative to height . The study showed geometry characteristics which enables increased mass transfer, allowing more gas exchange and power dissipation.