What is the cause of fouling in wet desulfurization equipment?
The oxidation of calcium sulfite in the process of flue gas wet desulfurization is a very important part of the desulfurization process. According to the research, when the oxidation rate of calcium sulfite in the slurry is in the range of 15~95%, it cannot produce enough gypsum varieties to make the gypsum body grow rapidly, resulting in gypsum scaling in the desulfurization tower. When the oxidation rate is less than 15%, calcium sulfate and calcium sulfite will co-precipitate, and no scaling will occur. However, a large amount of calcium sulfite is easily soluble in sulfur dioxide saturated solution to generate soluble calcium bisulfite, which is then oxidized by oxygen in the flue gas in the air to form calcium sulfate, which is attached to the tower wall and mist eliminator. Therefore, in the process of flue gas wet desulfurization, the oxidation rate of calcium sulfite in the slurry needs to be controlled by more than 95%.
Chlorogen refers to an ion present in a compound, belonging to the seventh main group of elements, with seven electrons in the outermost shell, easy to obtain electrons, and strong oxidation. In the wet desulfurization reaction, there are two main reactions: metathesis reaction and oxidation reaction. Among them, the reaction of calcium sulfite oxidation to calcium sulfate is restricted by the strong oxidation of chlorine, and the oxidation reaction is slowed down. As a result, the calcium sulfite in the slurry is supersaturated, and the supersaturated calcium sulfite is precipitated on the mist eliminator and tower wall, and is oxidized by the oxygen in the flue gas to form calcium sulfate scale.
When there is a large amount of chlorine in the slurry, the hydrogen ions in the sulfurous acid formed by sulfurous acid dissolved in water are more concentrated around the chloride, causing the reaction to lag. Part of the chemical process that should be reacted in the reaction pool of the desulfurization tower lags into the spray layer or even the defogging layer, and the calcium sulfite and calcium sulfate are precipitated in the upper area of the desulfurization tower after the reaction, and adsorbed on the mist eliminator and tower wall, and gradually form scaling.