Anhydrous sulfuric acid is colored, while the material in question is dark red in color
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Recently, the material produced from ammonium sulfate has taken on a dark red color, with the intensity of this color varying at times; it is thought that this is caused by ferric ions in concentrated sulfuric acid. However, experiments showed that when gas before desulfurization was passed through the acid, no color change occurred, while when gas after desulfurization was passed through the acid, it turned dark red. This raises another question: it is possible that the gas is carrying sulfocyanate ions from the desulfurization solution, but there were no changes in the desulfurization process itself, and no such color changes occurred before; so what is the cause of this issue? The reason has not yet been identified
It must be caused by liquid in the desulfurization zone; it contains phenols
We have a similar situation here; we don’t use pre-desulfurization, and after crude benzene processing, we use alkaline desulfurization. Is your desulfurization process based on ammonia? We are vaporizing ammonia to introduce concentrated ammonia gas into ammonium sulfate; I made adjustments to the ammonia vaporization process and things improved a bit. I need to check the COD value of the ammonia solution
It can be considered from the following aspects: 1. Check whether the oil content of the remaining ammonia water before it enters the ammonia vaporization tower is high, and whether the oil removal process is effective enough to meet the requirements； 2. What is the set temperature for the ammonia vaporization tower, and is it too high? ； 3. What is the pressure drop in the ammonia vaporization tower, and is it too high? The reason for considering these aspects is mainly that phenolic substances are the primary factor causing the reddish tint in ammonium sulfate. The remaining ammonia water contains certain phenolic substances; those with a boiling point of ≤230°C are monophenols (also known as volatile phenols), including phenol, cresol, and xylene. This substance vaporizes along with ammonia during the distillation process and enters the ammonium sulfate system, especially when the oil removal effect is poor and the operating temperature of the ammonia vaporization tower is high. We once analyzed the ammonia vapor and confirmed the presence of phenolic substances in it.
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Does ammonium sulfide turn dark red right after coming out of the centrifuge, or does it change color after being left in contact with air for a while?
If it is caused by volatile phenols, it is possible to measure the levels of volatile phenols in the remaining ammonia water before and after the ammonia distillation tower.