Bubble Effect of Anode in the Electrolytic Cell of Alkaline Chloride by the Mercury Process

Abstract

Factors influencing the "bubble effect" were analysed for graphitei anode in the electrolytic cell of alkaline chloride by the merculy proce. Saturated NaCl birine waS electrolysed using a model cell equipped with graphite anode and mercury cathode under ipractical condition. For the factorial analysis of "bubble effect" an voltage drop due ito chlorine bubbles generated from the anode and thickness of bubble dispersion layer were measuredi.
From the results, it was found that current density and brine floiw rate were highly significant, the latter being an important hydraulic factor for the large capaciity, high current density, and lower voltage cell design.The most suitable flow ratei was above 4m3 hr unit cell width (m), where "bubble effect" was below 20 mV even at i100 A dm2.
As for anodic overpotential (rrA), it depended on some factersi, for example, comb-width of anode, current density and their interactions.
In consequence, data of the complicated electrolytic system were iarranged in terms of a praetical scale "apparent current density".
After plotting rrA against "apparent current density" on logarithimic graph paper, linear Tafel relation was obtained. Some deviations from regurality may be causedi by hydraulic effect of "bubble effect". The results obtained will be confirmed quantitatively by the pilot or practical cells.