Cylindrical three-dimensional electrodes under limiting current conditions

Abstract

Three-dimensional electrodes of cylindrical geometry, with current and electrolyte flows at a right angle, can be realized with an inner or outer position of the counter electrode. Furthermore, in the case of the fluidized bed the performance of the electrode is also influenced by the position of the current feeder. For the packed bed and the fluidized bed the limiting current analysis has been applied to calculate the variation of overpotential within the bed in relation to the penetration depth of the diffusion limited current density. Results obtained for both cylindrical geometries are compared with those of a rectangular electrode. In the case of a packed bed electrode the largest penetration depth of the limiting current density is offered by the cylindrical design with the counter electrode in an outer position. For fluidized bed electrodes the situation is more complex, depending on the ratio of the solution phase to the particulate phase resistance which is a function of the resistivity and the geometric parameters. However, the configuration with an outer counter electrode is generally more advantageous.