Sodium hypochlorite oxidation absorption tower

Isn’t it specified in this design description?

I don’t have this information available; I want to find out about it in advance

This is the chlor-alkali process. The reaction equation for producing sodium hypochlorite by using alkali to absorb chlorine gas is: Cl2 + 2NaOH = NaClO + NaCl + H2O + 105.8 kJ/kmol. Since this is an exothermic reaction, it is necessary to remove the heat generated during the reaction promptly; otherwise, the temperature of the absorption solution will rise. If the temperature exceeds 38°C, the following side reaction occurs: 3NaClO = NaClO3 + 2NaCl. Therefore, maintaining a certain reaction temperature helps to prevent the occurrence of such side reactions. Parameters for hypochlorite generation: NaOH content of 0.1～1.0%, effective chlorine level of ≥10%. The concentration of hypochlorite and the amount of caustic soda can be adjusted as needed by the user; the pH value cannot be used as a criterion, as the solution remains alkaline from the time of preparation until the reaction is complete

I’m extremely grateful as well. My system does not absorb chlorine; rather, it is used to oxidize and absorb various organic substances such as acetonitrile, which are responsible for the unpleasant odors in wastewater treatment plants. Theoretically, our company should be using ORP control, but it isn’t in use; therefore, we don’t know how to proceed with controlling the hyposodium oxidation absorption tower. Thank you

Fix one value and base it on the analysis results?

By adjusting the alkali concentration according to the required hypochlorous acid concentration in the system, and by calculating and controlling the amount of chlorine supplied, the production requirements can be met.

The amount of hyposodium added should be determined based on the amount of organic matter in the gas being absorbed. To check whether its oxidizing capacity meets the process requirements, a small test can be conducted. When there are many variables involved, it is necessary to automatically adjust the amount added; this also depends on the structure of the absorption tower, such as the type of spraying system, sieve plates, packing, etc., which can vary significantly； It is best to control both the pH value and ORP together; this approach is more cost-effective. Without the use of instruments, control measures become merely formalities. Manual analysis to maintain an appropriate level of alkalinity or available chlorine may also suffice. As I am not familiar with your manufacturing process, this is just for reference.

The amount of hyposodium added should be determined based on the amount of organic matter in the gas being absorbed. To check whether its oxidizing capacity meets the process requirements, a small test can be conducted. When there are many variables involved, it is necessary to automatically adjust the amount added; this also depends on the structure of the absorption tower, such as the type of spraying system, sieve plates, packing, etc., which can vary significantly； It is best to control both the pH value and ORP together; this approach is more cost-effective. Without using instruments, control measures become merely formalities. Manual analysis to maintain an appropriate level of alkalinity or available chlorine may also suffice. As I am not familiar with your manufacturing process, this is just for reference.

Dear sea friend, the waste gas treatment you mentioned should refer to a typical VOC waste gas treatment system; however, I don’t understand why your first-stage tower is a hyposodium oxidation tower We assume that your exhaust gases are acidic, so you have an alkaline washing process. But when the exhaust gases enter the first stage of sodium hypochlorite absorption, the 1% remaining free alkali in the sodium hypochlorite is instantly neutralized – wouldn’t that mean that the sodium hypochlorite itself decomposes? If your exhaust gas is alkaline, then why install a final alkali scrubber tower? It’s hard to understand why the configuration is designed this way. Furthermore, there are now online detectors for the effective chlorine content in sodium hypochlorite, which enable online monitoring; the domestically produced ones are not very expensive either.

I have the same problem exactly; I’ve learned it!