How to prevent the oxidation of sodium sulfite solution? Are there any non-toxic and effective antioxidants?
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When using soda ash to absorb sulfur dioxide from flue gas to produce sodium sulfite, oxidation occurs; I’m not sure how to deal with this
The flue gas already contains oxygen, which makes things difficult. Unless separation is carried out through evaporation crystallization or freeze crystallization, taking advantage of the different temperature-dependent solubilities of sodium sulfate and sodium sulfite in water. Unfortunately, I don’t have my physical chemistry handbook with me, so I’ve forgotten the trend in the solubility of sodium sulfite as temperature changes.
Generally, oxidation does not occur during the absorption process, right? The reflection process, with CO2 being released, serves a protective function in itself! I think the reason for the formation of sodium sulfate is probably the presence of SO3 in the flue gas! Just personal opinion
Sodium sulfite is a substance that is prone to oxidation; since the flue gas contains oxygen, it easily oxidizes to sodium sulfate. Antioxidants such as hydroquinone are used to prevent this oxidation, with the addition amount of hydroquinone being around one in 100,000. Additionally, by changing the design of the absorption tower to make it more efficient, oxidation can be reduced. By lowering the liquid-to-gas ratio during operation, that is, by reducing the flow rate of the absorption liquid, the time that the liquid is in contact with air is decreased, which in turn helps to reduce the oxidation of sodium sulfite. These are all our experiences from the flue gas desulfurization pilot test, for your reference.
Hydroquinone is toxic and can affect the whiteness of the product after its use
That’s indeed the case; adding hydroquinone can have an antioxidant effect
I checked some information; (Na)EDTA is also useful
You forgot the boiler deaerator hydrazine hydrate