Reverse current and leakage current

The former is inevitable; different cell suppliers employ different solutions, with some using polarization rectification while others address it through materials and manufacturing processes. Does the latter refer to stray currents? Under the premise of a properly designed and balanced electrolyzer, efforts should be made to prevent salt buildup in the electrolyzer, keep the entire enclosure dry to avoid creepage, and also ensure proper grounding protection.

Do you mean that to ensure proper grounding, it is necessary to ground the area at the feed inlet of the electrolytic cell, and should grounding also be done at the liquid outlet?

Both the anode and cathode inlet and outlet liquid pipes are designed with grounding

The last edit to this post was made by nanren2 on 2018-1-21 at 22:15. As for the reason behind the reverse current, it is important to understand that during normal operation of the electrolyzer, there is a large amount of dissolved chlorine in the anode solution, while in the cathode, almost no hydrogen is dissolved due to its low solubility! When the electrolyzer stops electrolyzing, the chlorine atoms in the anode solution are reduced to chloride ions, resulting in a reduction reaction. At the cathode, however, due to the low solubility of hydrogen, there is not enough hydrogen available for the reaction to take place (that is, hydrogen and hydroxide ions losing electrons to form water). Under such electrical conditions, it is inevitable that metal oxidation occurs at the cathode electrode! Therefore, the key to eliminating reverse current is: reducing the dissolved chlorine in the anode solution and finding cathode materials that can withstand such a reverse potential! That’s how the polarized rectifier came into being. To be honest, it’s a last resort. It is to continue supplying a weak current to the electrolyzer when it is shut down, in order to maintain a forward current. One of its disadvantages is the inevitable occurrence of slight electrolysis; thus, when there are pinholes in the ion membrane, hydrogen still leaks as it would in normal operation. At this time, the amount of chlorine is low, which leads to an increase in hydrogen content in the chlorine, thereby creating safety issues! Put simply, a polarization rectifier is used to maintain a forward current during the process of replacing the chlorine dissolved in the anode solution after the electrolyzer is shut down; in other words, it serves to buy time for removing the chlorine dissolved in the anode solution of the electrolyzer! Now, Asahi Kasei’s Sigma electrolyzer has resolved the issue with the cathode material; it can withstand this reverse potential just like the original high-density version! When talking about reverse current, it is necessary to mention a characteristic related to it: the magnitude of the reverse current depends on the number of cells in series within the electrolyzer; the more cells in series, the greater the reverse current. Therefore, before finding or developing a material capable of withstanding the reverse potential for the elastic mesh in zero-gap electrolyzers, Asahi Kasei introduced an electrolyzer cell interrupter that reduces the reverse current by decreasing the number of series-connected cell units after shutting down the system. After discussing the reverse current, let’s talk about the leakage current. Leakage current refers to the current that, during operation, flows out of the electrolyzer through the electrolyte, as both the electrolyte and the pipelines are conductors. When current enters the electrolyzer from the P side, a small portion of it flows out through the electrolyte and then through the pipelines to the N side of the electrolyzer or elsewhere (where the electrolyzer pipelines are grounded). Since this current does no work, it is taken into account when calculating the current efficiency, and the leakage current is subtracted from it. I heard earlier that Beihua Ji added something to the hoses to solve this problem, but I haven’t seen any specific reports or evidence of the actual effect. I hope that Beihua Ji or the manufacturers using it can disclose more information on this! Alright, I’ve rambled on for a while now; I hope no one is annoyed!

Thank you so much! I understand the principle now!

What was mentioned above refers to the counter-voltage measures for Asahi Kasei or Kitakata-type electrolyzers; what they usually do is to keep the polarization current constant! The concept of chlorine production electrolyzers is different; in such electrolyzers, the polarization voltage is kept between 1.6 and 2.1 V, which is below the theoretical decomposition voltage for chlorine – as a result, oxygen is produced! There is a positive current without any generation of chlorine, and then the free chlorine in the saltwater is replaced, thereby avoiding back voltage!