Is the acidic nature of the spent sodium solution due to overuse?
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This post was last edited by sunjl1981 on 2013-1-6 at 23:42. As we all know, there is a specific concentration requirement for sodium hypochlorite used for acetylene purification; too low a concentration fails to achieve the desired purification effect, while too high a concentration can pose risks. There is also a pH limit for sodium hypochlorite. The waste sodium hypochlorite from our acetylene processing unit has an acidic pH – could this be due to excessive use of this substance, that is, a concentration below the minimum required level? I would also like to ask about how to control the pH of sodium hypochlorite solutions. What is its main purpose? Is it for safety reasons or for improving purification efficiency??? This post was last edited by limingshuguang on 2008-1-15 at 09:26. ] # ， ， &
A pH value below 7 indicates acidity; although the oxidation capacity is high, excessive acidity leads to an increase in free chlorine in the gas-liquid equilibrium of the sodium hypochlorite solution, which facilitates the formation of chloroacetylene. What is chloroacetylene? You should be aware of that, right?
:):time: The person on the 2nd floor is right; you need to conduct a thorough inspection. Is the liquid alkali used to prepare sodium hypochlorite at a concentration of 1.5%? What is the pH value after mixing? If the pH value is around 8, check the effectiveness of the sodium hypochlorite sent from Tower 1 to Tower 2 after cleaning Tower 1, as well as whether the pH value is too low ； Under normal conditions, check the sulfur and phosphorus content in calcium carbide, as well as whether the hydrogen phosphide level in crude acetylene gas exceeds 500 ppm (hydrogen sulfide and similar substances should be present in very low amounts); if these levels are too high, it is necessary to adjust the concentration of sodium hypochlorite fed into the second tower.
Sodium hypochlorite is acidic in nature and prone to decomposition; it is more stable in alkaline environments, with greater alkalinity resulting in a longer storage period. If an excessive amount of chlorine gas is used in the production of sodium hypochlorite, then the pH level…
In summary, the pH value of the hyposodium solution is controlled at around 7–9, first for safety reasons and second for purification effects. Additionally, the chlorine concentration in the hypoclorite solution produced by our factory is generally within the range of 0.08% to 0.11%. This post was last edited by clq20040107 on 2008-1-15 16:44.]
It seems that no perchlorine accidents have occurred in your facility; sodium hypochlorite cannot exist in an acidic environment, as it immediately decomposes under acidic conditions to release chlorine gas, and perchlorine can lead to accidents.
Thank you all. What I’m referring to is inferior sodium hydroxide; after cleaning, S and P present in acetylene gas turn into substances such as sulfuric acid and phosphoric acid, which cause the sodium hydroxide to become acidic. My question is: once it becomes acidic, is the effective chlorine content below the minimum threshold?
It’s hard to say. Although acidic hypochlorite consumes some hypochlorite ions, in an acidic environment multiple forms of chloride ions are present in the solution. In my opinion, the best way to determine the effective chlorine content is to conduct a measurement, using the iodine titration method