Discussion on the issue of short-term shutdown of a single cell in ion-exchange membrane electrolyzers
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If a single-cell (single-tank) cell stops operating, and the valves for circulating brine and chlorine in that circuit cannot be fully closed (only a slight leakage occurs), what impact will this have on the cell?
It also depends on the type of electrolyzer. In the case of chlorine production electrolyzers, the hazards are relatively minimal, as there is no need to drain the liquid from them. Other types of electrolyzers do present certain hazards; one of these is damage to the ion membrane, as chlorine gas can pass through it. At the cathode, nickel deposits form, which can contaminate the ion membrane. If the liquid is not drained for a short period of time, and the temperature is increased rapidly through circulation, the impact will not be too severe
There is no major problem if no liquid is discharged, but the coating on the discharge electrode will be damaged if liquid is discharged. High-quality chlorine valves with a single chamber must be used; if there are problems, they should be replaced promptly, otherwise the losses will go far beyond the cost of just a few valves.
What kind of electrolyzers are you? In the case of Beihua Machinery, brackish water is used for replacement during single-tank shutdown; at this time, the tank is not disconnected from the system, so the problem you mentioned does not occur.
These past few days, a plan was developed: chlorine is diverted to the waste chlorine system with negative pressure applied, while hydrogen is sent to the exhaust gas system where it is replaced by nitrogen. The cathode maintains a circulating mode, while the anode maintains a single-loop circulation of brine. Pay attention to adjusting and stabilizing the temperature of the electrolytic cell in order to maintain a constant concentration of caustic soda.
Single-cell parking mode is used, with circulation of anode and cathode fluids; the saline used for circulation is diluted saline, having an alkali concentration of not less than 30, which has virtually no impact on the electrolytic cell
A short-term shutdown of a single tank has little impact; it’s sufficient to quickly identify the cause and resume operation as soon as possible. After all, the backflow brine used contains free chlorine, so the alkali concentration must not be too low.
I think there will be problems; in any case, it’s necessary to ensure that all the manual valves around the electrolyzer are in good condition in order to guarantee safety.
Doing this can reduce damage to the ion membrane. But how do you adjust the cell temperature during the shutdown cycle of each individual electrolyzer? Does a pump serve only to circulate fluid in one electrolyzer? Please specify. Internal leakage of the valves for the anode circulation brine can result in free chlorine being present in the anode solution of the electrolyzer, which can cause damage to the ion exchange membrane. The best thing to do is to replace the valve with internal leakage as soon as possible.
The single-tank parking operation is complete; fortunately, the valves are all in good condition.