For an electrolyzer, there are mainly three factors that can affect its technical performance, as illustrated below.
1. Current Distribution
If an ion-exchange membrane electrolyzer is improperly designed, or the activated mesh of anode or cathode is not smooth, uneven current distribution will occur. The current distribution plays an import role in influencing current efficiency, cell voltage and the service life of membrane. As a result, the uneven current distribution will lead to uneven concentration of NaCl and NaOH, while overcurrent at some positions of the membrane and point discharge at the electrolytic cell will also take place, doing damage to the membrane. This phenomenon will be more likely to happen under high current density.
2. Electrode Coating
If the electrode coating is damaged, the cell voltage will become higher. Here are the reasons. There are mainly two kinds of damage for the coating, one is surface contamination, and the other is natural loss. The surface contamination is lead by the deposition of barium salt and manganese dioxide on the electrode surface, resulting in a lowered activity. The natural loss of coating is usually caused by the long time electrolysis.
The reverse current generated as a result of short circuit and sudden power off will corrode or oxidize the active ingredients. For example, if the polarization electricity is not supplied in time when power off, the anode and cathode will form a primary cell, and the current will be in the opposition direction when compared with normal current. This reverse current directly affects the service life of coating, and the activated electrode loses its activity, cutting down the life span of the electrolyzer. Moreover, the electrolytes in catholyte and anolyte will diffuse mutually, and water will move towards the opposite direction, resulting in bubbling of the membrane.
3. Frequent Start and Stop
If the electrolyzer starts and stops frequently, the membrane will be damaged, and the activity of electrode will also get deteriorated due to the repeated current impact, especially when the polarization device doesn’t work.
Under the condition that the dynamic electricity is cut off, light salt brine can’t be converted, and some chlorine gas exists on the top of the upper space of electrolyzer. The chlorine atom at the anode is reduced into chloride ion which penetrates to the anode side, and the salt content in the alkali will increase. At the same time, metal oxidation takes place at the cathode, forming a battery. So, the cathode is corroded, and the membrane is contaminated at the cathode side, thereby leading to enlarged membrane resistance and higher cell voltage. In addition, this effect is irreversible.