What is the solution to the issue of free chlorine in the brine tank of an ion-exchange membrane electrolysis secondary brine filtration system?
Thread Content
Hello, sea friends! Everyone, does the saltwater tank at the secondary brine stage contain free chlorine? How should this be resolved? Please share your valuable suggestions. The brine tank here, that is, the brine storage tank located before the resin tower, occasionally contains about 0.004 PPM of free chlorine (this is not the case in the tank for the primary brine). As a result, the concentrated brine tank also sometimes contains trace amounts of free chlorine. To address this issue, the company is considering adding sodium sulfite to the brine tank used for filtering secondary brine in order to remove the free chlorine. Is this feasible? Please discuss the advantages and disadvantages. There are gifts of wealth......
Under normal circumstances, if free chlorine is present in the filtered brine tank, the plant must be shut down and the resin column stopped from operating; otherwise, the resin will be poisoned and the quality of the secondary brine cannot be guaranteed.
Here are two ideas for the original poster’s reference: 1. Has hydrochloric acid been added to the saltwater used here, and is there free chlorine in that hydrochloric acid? 2. Is the sodium chlorate content high in saltwater?
Here are two ideas for the original poster’s reference: 1. Has hydrochloric acid been added to the saltwater used here, and is there free chlorine in that hydrochloric acid? 2. Is the sodium chlorate content high in saltwater?
As mentioned above, hydrochloric acid and chlorates. If verification shows that it is sufficient to add just a little more sodium sulfite in the saline solution once
1. Has hydrochloric acid been added to the saltwater entering here, and is there free chlorine in the hydrochloric acid? Hydrochloric acid is added before the brine enters the secondary brine filtration tank; this hydrochloric acid contains 15 PPM of free chlorine. 2. Is the sodium chlorate content in the saltwater high? The sodium chlorate content in the saltwater is around 16
The chlorate level is too high. If an ion-exchange membrane has been in use for a long time, it can still be tolerated; however, if it’s only been 1–2 years since installation, it is advisable to find ways to reduce chlorate levels (e.g., by draining water or adding a decomposition tank)
It is personally recommended to add acid before the brine storage tank in the first saltwater stage, and at the same time to add a slightly excess amount of sodium sulfite before that brine storage tank; this way, there will be no free chlorine in the second saltwater.
When designing the brine tank for the secondary brine filtration in our company, pipes for adding sodium sulfite were included, but they have not been used once in all these years of system operation. Premise: Free chlorine must be absent in the saltwater after filtration; ensuring the quality of the salt is crucial. 2. Secondly, when adding the secondary brine, the free chlorine content in high-purity hydrochloric acid should be kept as low as possible.
When acid is added to adjust the pH before entering the filtered brine tank, free chlorine is generated as a result of the decomposition of chlorates in that area; adding an appropriate amount of sodium sulfite at the inlet of the pump located at the outlet of the filtered brine tank will resolve this issue.
Actually, if the ICP analysis shows that the results are satisfactory, it’s okay to have trace amounts of free chlorine; what’s important is whether the ICP results of the water coming out of the resin tower are acceptable； If reduction is desired: first, reduce the chlorate content in the brine; second, adjust the pH of the brine in the resin tower and then add sodium to make the adjustment; third, keep the free chlorine content of the acid added at less than 10 ppm