Distribution of void fraction, ohmic resistance and current in a tall vertical gas-evolving cell

Vertical electrolysers with a narrow electrode gap are used to produce gases, e.q. Glzl Hz and Oz. The gas voidage in the solution increases with increasing height in the electrolyser and consequently the current density is expected to decrease with increasing height. Impedance and current distribution experiments were carried out in an undivided cell with two electrodes each consisting of 20 equal segments or with a segmented electrode and a one-plate electrode. It has been found that for a bubbly flow the ohmic resistance of the solution increases and the current density decreases linearly with increasing height in the cell. A relation has been presented describing the voidage in the solution as a function of the voidage and the thickness of the bubble layer both at the leading edge of the electrode and the voidage in the bulk of solution. The current distribution factor increases with increasing average current density, decreasing volumetric flow rate of liquid and decreasing distance between the anode and the cathode. Moreover, it is concluded that the change in the electrode surface area remaining free of bubbles with increasing height in the cell has practically no effect on the current distribution factor.