The voltage of the Woody cell is high
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This post was last edited by liuzhaohua on 2015-6-18 at 15:58. The resin tower is in regeneration mode; the voltage of all electrolytic cells has suddenly increased, reaching a level 10 V higher than normal (for 146 cells). Alkali production has decreased slightly, and the purity of chlorine gas has dropped. An inspection of the saline system revealed no abnormalities; it is suspected that there is a leak inside the outlet valve of the resin regeneration tower. After closing the manual valve, the voltage in the tank decreased slowly, but it was still about 5-6 volts higher than normal. The voltage increased while the resin tower was under acid cleaning. Later, the system was shut down and the two units were taken apart for inspection – no bubbling was observed, and the membranes appeared yellowish, suggesting the presence of many impurities. After cleaning the tanks, the system was restarted, and the voltages of both units decreased slightly while increasing slightly as well; the alkali production remained roughly the same as before. Has the membrane been contaminated by calcium and magnesium, causing irreversible damage? Why does only the slot voltage increase while other parameters remain roughly the same? Are there any remedies or ways to further determine the cause? Please help analyze it
It’s likely that calcium and magnesium have entered the system, which will also lead to a decrease in chlorine purity. It seems there’s no other way except to replace the membrane. How long has the membrane been in operation?
Given the situation with the ion membrane, it’s likely that it has been contaminated by heavy metals. Washing it with water twice while the system is stopped will result in a slight decrease in the cell voltage, and the current efficiency of the ion membrane will definitely decline as well.
It must be contaminated by calcium and magnesium ions. Calcium and magnesium ions enter the ion membrane from the sulfonic acid side; due to their valence of two, their entry rate is slower than that of sodium ions. When calcium and magnesium ions penetrate the membrane, they react with hydroxide ions that have diffused back from the cathode to form precipitates (in crystalline form). The current efficiency decreases, and the cell voltage increases. Washing with water can remove the crystals, while also leaving voids in the membrane. Also, you mentioned acid washing; in that case, the pH level inside the anode chamber is likely to be low. If it’s too low, the membrane can be acidified, and the carboxyl groups will turn into the -COOH form, preventing the membrane from functioning. At the same time, the membrane resistance increases, and the slot voltage rises sharply. Regarding calcium and magnesium ions, magnesium ions have a greater impact on the cell voltage, while calcium ions have a greater impact on current efficiency. So it’s possible that there is a significant accumulation of magnesium ions. It is recommended to monitor the operation on a continuous basis, as well as to analyze the quality of the saline solution, including the purity of hydrochloric acid and the quality of pure water. I hope you can find out the cause soon :)
Why do calcium and magnesium ions enter the ion membrane more slowly than sodium ions?
Internal leakage of the valve, with impurity ions entering the system after desorption – a typical accident. Early detection and proper handling minimized the impact. The vehicle should have been stopped at that time to deal with the issue; continuing to clean it would have resulted in less impact.
Because calcium and magnesium ions are divalent. . The ion membrane is formed by electrostatic bonds between the fixed ions SO3- and COO-, along with the positively charged counterion Na+. During the exchange, the ion Na+ is exchanged with Na+ of the same charge in the aqueous solution
Exchange ideas and improve together :)
If it is dealt with too late, even parking the vehicle to clean the film will not yield good results, and it will be impossible to return to the previous condition.