Mass-transfer study in a swirling flow electrochemical reactor with structured counter electrodes under single-phase and two-phase (gas-evolving) flows

This paper analyses the effect of two kinds of structures as counter electrodes on the mass-transfer performance of an electrochemical reactor under swirling flow. The arrangements used as counter electrodes were either helical-shaped structures or an expanded metal sheet. The former presents a more uniform mass-transfer distribution as the main advantage compared to a decaying swirling flow system. The best uniformity was achieved when the number of turns in the helix was higher than 9 for a 257.5 mm reactor length. The latter structured counter electrode can only be vindicated by its high value of specific surface area, increasing the space-time yield of the reactor, but with a poor performance in the mass-transfer behaviour regarding the decaying swirling flow. The effect of the volumetric flow rate on the mass-transfer distribution is scarce for both structured counter electrodes. The operation with a two-phase system showed a slightly more ineffective behaviour in comparison to the single-phase case. The use of a helical structure as a counter electrode can be recognised as an improvement in the reactor performance under swirling flow from the standpoint of the mass-transfer distribution.