Modeling of Two-Phase Flow during the Electrolysis of Water in an Electrochemical Reactor in Serpentine Array

Abstract

Currently the characterization of the reaction environment within any filter-press type reactor through computational modeling is very important in the design to obtain an effective flow dispersion and therefore a uniform current and potential distribution [1]. During two-phase electrolysis such as chlorine production, water electrolysis, alumina reduction, electrocoagulation, and many other electrochemical processes appears gas release on the electrodes, H2 or O2 (bubbles), which imply a quite important electrical properties and electrochemical processes disturbance [2]. The bubbles are motion sources for the flow cells, and then hydrodynamic properties are strongly coupled with species transport and electrical performances, hence, the bubbles presence modifies the electrolysis cell performance and principally the hydrodynamics and current density distribution [3]. Therefore, this works deals with the two-phase modeling (H2O-H2) flow inside of a pre-pilot-scale continuous reactor with a stack of six cells in a serpentine array by solving the Reynolds-averaged Navier-Stokes (RANS) equations with κ-ε turbulence model (Euler-Euler approach). The hydrogen evolution reaction comes from the electrolysis of water. The electrodes were plates of aluminum, typically used in electrocoagulation processes. In order to perform a more complete flow pattern characterization, residence time distribution (RTD) studies were carried out to validate the CFD simulations in biphasic flow. The RTD simulations were calculated solving the averaged diffusion-convection equation. Close agreement between experimental and theoretical RTD simulations were attained. Finally, simulations of distribution of current and potential density distributions inside the pre-pilot-scale continuous reactor were carried out using the Bruggeman relation, observing the effect of bubble production on the distribution of potential along the electrodes.