The slot voltage has increased abnormally
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When both electrolyzers are operating normally, their total cell voltage is roughly the same; however, after one of the electrolyzers was scheduled for shutdown and restarted, it was found that its voltage was 7 V higher than that of the other electrolyzer. May I ask what caused this?
What has been done to this tank during the current reduction process and after shutdown? The voltages of the two tanks are the same before shutdown; there is no reason for one tank’s voltage to increase abnormally. It is recommended that the original poster carefully examine what problems occurred with this tank during operation, as well as what actions were taken on it after shutdown.
The total voltage is 7 volts higher; operations during shutdown are highly suspected! Was the membrane acidified by the intrusion of chlorine or salt acids, and were there any abnormal pressure differences? Is the cell voltage across the entire tank still consistent after operation?
After parking, cool down the tank and drain it, then wash the tank with pure water. Next, loosen the tightening bolts and replace the unit tank. While driving, it was discovered that the replaced unit slot was leaking again; so the cooling drain slot was adjusted and the unit slot was replaced. According to the DCS history records, during the shutdown period of this cell, the negative pressure difference remained at 1.5 hours, with the highest value reaching -2.5.
Salt acid should not have entered, as there are two automatic valves for adding acid, and both are connected to the ESD interlock; thus they cannot be opened during shutdown. Abnormalities occurred in the pressure difference during shutdown, with a negative pressure difference persisting for 1.5 hours, reaching a maximum of -2.5
During the negative pressure difference, chlorine enters the cathode, making it highly likely that chlorides are formed and nickel is deposited.
It is recommended that the poster check whether there is any internal leakage in the valve connecting the anode gas supply, open the electrolytic cell to see if the cathode mesh is deformed, and inspect for membrane leaks. There are also issues with 27 and 28, as well as whether the positive and negative values on the level gauge are indicated incorrectly, which leads to careless mistakes by the operators.
The negative pressure difference during the parking period was maintained for 1.5 hours; such a long duration caused damage to the elastic cathode mesh! How is it possible to maintain such a negative pressure difference for such a long time? Is the anode system open to the air or connected to the accident chlorine? Where does the negative pressure difference come from?