The importance of current distribution and cell hydrodynamic analysis for the design of electrocoagulation reactors

Abstract

BACKGROUND: The effects of current distribution and cell hydrodynamics on the performance of an electrocoagulation (EC) reactor were studied. This analysis only considered the distributions of primary potential and current density. The hydrodynamic behavior was analyzed by means of computational fluid dynamics (CFD) using a turbulent model (k-ε). For this study, only the fluid movement between electrodes was taken into account. RESULTS:The analysis of current distribution showed the effects of cell geometry and electrode configuration on both the potential and current distributions on the anodes. Insulators placed at the edges of the electrodes produced border effects on the potential values that favored a secondary reaction and diminished the formation of aluminum clots. The CFD analysis indicated that the cell geometry arrangement generates low velocity profiles between the electrodes. From the experimental evaluation, it was observed that EC performance was improved when uniform potential and current densities were achieved with low flow velocity profiles. CONCLUSIONS: Analysis of the hydrodynamic behavior showed the impact of different hydrodynamic phenomena on both the formation of clots and the removal of the sludge formed. Likewise, it was confirmed that in optimizing energy consumption, an analysis of current distribution is a very useful tool for evaluating the arrangement of electrodes and the cell geometry.

A Comparative Analysis of 2-(Thiocyanomethylthio)-Benzothiazole Degradation Using Electro-Fenton and Anodic Oxidation on a Boron-Doped Diamond Electrode

“…For this study, two types of solutions were used: (a) a blank solution (0.02 M NaCl and 0.03 M Na 2 SO 4 ) and (b) a synthetic solution (0.02 M NaCl, 0.03 M Na 2 SO 4 , and 0.07 M TCMTB). The concentration of the blank solution was fixed to an ionic strength similar to that registered in wastewater from the paper industry [24]. The TCMTB 2…”

Velocity Simulation of an Electrochemical Reactor for Textile Wastewater Treatment

“…Reactors with distinct layouts may present different geometries (horizontal or vertical; rectangular or cylindrical), as well as size and arrangement of the electrodes, which may be presented, for instance, as rings or parallel plates [7]. In the latter case, the mixture in the reactor is exclusively hydraulic, while in the former, it is often mechanic, as seen in studies [8] [9]. The electrodes in a parallel plate reactor may also be arranged in a single channel or multiple channel configuration, in which the plates are positioned as normal and parallel to the direction of the flow, respectively [7].…”

“…The electrodes in a parallel plate reactor may also be arranged in a single channel or multiple channel configuration, in which the plates are positioned as normal and parallel to the direction of the flow, respectively [7]. Since the efficiency of the electrocoagulation process depends on the cell configuration, the fluid dynamics in the reactor also play a significant part in the outcome of the reaction [8]. The main points to be considered when analyzing the effects of hydrodynamics in the success of the reaction relate to: maximizing contact surface of the electrodes with the fluid, since it is related to the rate of metal dissolution, a consideration that is specially relevant for wastewater treatment [4]; improving the mixture, which increases both particle colliding, needed for coagulation [10] [11], as well as the contact bubble-particle, which, as previously stated, is required for flotation [4]; and finally, avoiding hydraulic phenomena such as channeling sections and stagnant zones, which causes entrapment of mud and formation of clots, respectively [6].…”

“…There have been successful studies presenting predictions of the flow profile of electrochemical reactors by CFD models, however few papers have studied configurations with multichannel multiple parallel plate electrodes [8]. CFD simulations of a rotating batch reactor for industrial wastewater treatment were used to analyze variations in the reaction time due to changes in the angular speed, and its relations to turbulence intensity and velocity field inside the electrodes zone, thus providing aids to optimize the impeller design and operation parameters [9].…”

“…The CFD analysis indicated that the cell geometry arrangement generated low velocity profiles between the electrodes, and that the low velocity improved EC performance. Also, the study showed the impact of hydrodynamic behaviour in the removal of sludge and in the formation of clots [8]. Another hydrodynamics study for a parallel plate multichannel reactor was carried out through both CFD and Residence Time Distribution (RTD), and the latter was used to describe the flow path.…”