Phenomenological behavior coupling hydrodynamics and electrode kinetics in a flow electrochemical reactor. Numerical analysis and experimental validation

Abstract

Parallel plate electrochemical reactors are frequently used in industry because its high range of applications in several electrochemical processes related with electrosynthesis, environment electrochemistry and energy storage systems. In such sense, the aim of this work is deal with the reaction environment characterization of a parallel plate flow reactor having a net-like spacer, by the employment of original experimental and theoretical techniques in order to evaluate the influence of transport phenomena on overall reactor performance. Flow distribution is analyzed by the use of automatic measurement of flow paths using image processing techniques, based on mathematical morphology theory. On the other hand, a theoretical model of current-potential distribution under intermediate kinetics control (tertiary current-potential distribution) based on numerical solution of turbulent diffusion-convection and binary electrolyte theory is proposed. In this case, concentration at electrode surface was determined in terms of dimensionless Damkhöler number, obtained from a mass balance at electrode-electrolyte interface in steady state. RTD curves obtained by image processing techniques describes correctly the fluid dynamics behavior in electrochemical reactor. Meanwhile, correspondence between calculated and experimental polarization curves using the oxidation of chloride ions to chlorine as model electrochemical reaction was made with an error values lesser than 7%, indicating a good agreement between theoretical model and experimental tests. Results founded in the parallel plate flow electrochemical reactor used here, evidenced that the methodology proposed to analyze the hydrodynamic and electrochemical behavior are adequate to its use in other electrochemical devices, particularly, when they work under intermediate kinetic and limiting current conditions.