Diaphragm washing tank

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This post was last edited by sunjl1981 on 2013-1-6 at 20:06. Reason for tank replacement: Recently, various parameters of our electrolysis tanks have shown a downward trend. Out of 144 electrolysis tanks, 86 of them have high concentrations and high liquid levels (concentration between 140–190 g/l); some of these tanks need to be replaced as early as two months after installation. The electrical efficiency dropped from 94.4% to 93%, and the chlorine purity dropped from 96.2% to 95.4%. Therefore, it was decided to wash the tank. Cell cleaning process: After stopping the operation at 11 a.m., hot water evaporated was used to mix with a small amount of concentrated brine. Since the shutdown was expected to be short-lived and the operation was scheduled to resume at 2:30 p.m., the cells were not sealed. Two hours after starting the cleaning process, pH test strips were used to check the acidity or alkalinity of each cell, to determine whether the water output from each cell was neutral. Testing was completed around 1:30 p.m.; at that point, heating was stopped and concentrated brine began to be added to the cells. Approximately one and a half hours later, the sodium chloride content in the electrolyte main pipeline was analyzed, and the operation was resumed only when the salt concentration was above 240 g/l. Results after tank cleaning: When the current was set at 54 KA, the changes in various parameters before and after were as follows: Cell voltage (V), concentration (g/l), chlorine purity (%), current efficiency (%). For cells with high concentration and high liquid level (140–190 g/l), the values before and after were as follows: 462, 454, 130, 110, 95.49, 6.49, 39, 6.57. There were 7 units and 31 units respectively. Problems that occurred during tank cleaning: 1. A new cell was installed on the morning of the shutdown; the gas phase data showed satisfactory results after it started operating. During tank cleaning, no action was taken regarding this cell, nor was it sealed. After restarting the system, the gas phase data for this cell became unsatisfactory – the hydrogen content reached 1.7%, and the flow rate was extremely high. Four salt water pipes were used to supply additional salt water, but the liquid level still dropped. An additional pipe was used to add water to the cell, yet the liquid level continued to fall. In the end, it was necessary to remove the cell from service. It seems that the diaphragm in this cell was damaged during cleaning, resulting in parts of it coming loose; therefore, for safety reasons, it is necessary to disconnect the new cell during cleaning. 2. When starting to add brine, the liquid level in most of the cells decreased; in some cases, the liquid level could no longer be seen, which forced the cells to be sealed in order to raise the liquid level again. This affected the time required to get the system up and running. Upon further inspection, it was found that the valves for the brine supply lines in one row of cells were not open. Therefore, it is necessary to check that all components are in place before starting the operation.