Estudo fluidodinâmico do desprendimento de H2 em uma célula eletrolítica, utilizando o aplicativo computacional CFX.

Abstract

Most electrochemical reactors present reactions, where gas leaks, which evolve in the system in the form of bubbles. The detachment and evolution of these bubbles influence the hydrodynamics of the reactors, often improving the mass transfer between the electrode and the electrolyte solution. Consequently, due to the emission of these gases, the hydrodynamic behavior in electrochemical reactors is generally complex representing an extremely broad field for research. The main objective of this work is to study a biphasic (gas-liquid) system in order to predict the influence of the electrochemically generated hydrogen bubbles detachment inside the cathodic semi-cell, bench electrochemical geometry, available at the Electrochemical Engineering Laboratory of UFCG / CC T7DEQ. However, for this study, we adopted the hypothesis of gas injected into the semi-cell from the entire cathodic surface. With this hypothesis, it was possible to study and numerically analyze the hydrodynamic behavior of hydrogen bubbles in the Within the field of study, the concepts of computational fluid dynamics were applied from the CFX-4. Thus, in order to take into consideration the phenomena of coalescence and bubble diameter distribution, the Multiple-size-group (MUSIG) model was implemented to study the hydrodynamics of cathodic compartment. With the application of this model, it was possible to emphasize the character dimensional flow of the gas phase in the electrolytic semi-cell. However, the phase showed a behavior that was in reverse of what was expected, that is, it did not exhibit no influence from gas phase behavior. Another fact to be highlighted is that coalescence and diameter distribution of hydrogen bubbles under the conditions applied, showed no significant influence on the behavior of the fluids, although the profile of the gas curtain, generated near the catholic surface, presented a behavior similar to that observed in the experimental cell. Thus, the results presented in this work enable new avenues for the study of electrode geometries that allow the detachment of hydrogen bubbles more easily, which will provide a reduction of the electrochemically chlorine-soda overpowering process.