Analysis of the reason why sodium hypochlorite is soy-red in color
Thread Content
In recent days, the sodium hypochlorite solution in the company has taken on a plum-colored appearance, with a significant amount of impurities precipitating at the bottom. Our preliminary analysis suggests the following possible causes: 1. Chlorine gas introduced into the alkaline solution causes backflow that corrodes the pipes (depending on the iron ion content in the solution)； 2. The lining material of the hyposodium reaction tank is damaged, causing corrosion to the outer wall of the reaction tank (same as above) ； 3. The exhaust gas resulting from the complete evacuation of a liquid chlorine cylinder leaves residual liquid (how to determine this?) I would like to ask everyone: has anyone encountered the same problem, and are there any other possible causes? How to solve it. Thank you!
It has also happened to us, after a large amount of chlorine entered the absorption tower. The reason was not identified, but it got better later. It has happened 2 times.
The chlorine pipelines that enter the waste gas absorption tower in our plant are all made of PVC+FRP.
We have encountered this issue before; it occurs mainly during the absorption of excess chlorine, when the pressure of chlorine gas in the pipes is too high. Our plants use iron pipes, which allows rust to get into the system, causing the sodium hypochlorite to turn red or dark red. Things returned to normal after replacement, and we switched the pipes in the towers to PVC pipes, as iron elements were the cause of the problem.
For the same reason, the issue can be resolved by using a ceramic filter for treatment.
Thank you all. The pinkish sodium hypochlorite solution is currently being analyzed, and we will be able to determine the results later! The pipes we use to enter the tower are all iron pipes; will the pressure and flow rate of residual chlorine carry iron powder in as well? Personally, I think it is the high moisture content of residual chlorine that causes corrosion in the pipes, thereby introducing iron particles!
Reply to 1# solidy66: This situation is almost certainly caused by iron ions; it should not be difficult to find out where these iron ions come from
The quality inspection report for the morning is ready; the iron ion content in the sodium hypochlorite solution is only 0.003%, so the level of iron ions should be quite low! Another situation is that the off-gases from the liquid chlorine cylinders here, when the cylinders are intact, are also used in the production of sodium hypochlorite; the formation of a brownish color is caused by the residual chlorine in the liquid chlorine cylinders during use. How is this one to be solved?
This post was last edited by solidy66 on 2010-12-7 at 12:05. I have another question: the sodium hydroxide content in the samples analyzed for quality control was 4.5%, which is significantly above the limit. The concentration of the alkaline solution we use as a raw material is 15%. Could such a high concentration of the alkaline solution also cause this phenomenon? What is the reason?
Too high a concentration of alkaline solution is not conducive to the use of chlorine to produce hyposodium; it is difficult to determine the appropriate endpoint. If other metal ions are added before reaching that endpoint, it may result in the formation of the said maroon color. It is recommended to control the moisture content in the chlorine gas, replace the pipes, and continue to pass chlorine until the endpoint is reached.
We have also encountered such problems. I’m not sure whether the chlorine gas is dried using concentrated sulfuric acid during packaging; if so, check to see if this concentrated sulfuric acid gets into the pipelines and eventually reaches the decontamination tower, causing the sodium hypochlorite to turn red.