Single-alkali desulfurization for power plants
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Question: **Is it permissible to use sodium hydroxide for desulfurization? If so, 1) how should the amount of alkali added and the volume of desulfurization wastewater discharged be calculated and controlled?** How to control the pH value of the circulating spray liquid? 2) What are the requirements of environmental protection authorities regarding the discharge of desulfurization wastewater?
The single-alkali method has been applied in many small boilers, and apart from operating costs, it offers significant advantages in other aspects as well. But it needs to be used in a power plant. . . . . I’m afraid I can’t afford it. The amount of smoke is too large. The discharged wastewater must be aerated and oxidized; otherwise, the COD level will not meet the standards.
Reply to 2# sinafly, thank you. Cost is not an issue; aeration must be carried out before discharging the waste liquid. It’s just 1) **whether there are documents permitting or prohibiting single-base desulfurization?** 2) What should the Na+ concentration in the circulating fluid be? 3) What should be the pH of the circulating liquid during operation? 4) **Are there any restrictions on the sulfate emissions from the desulfurization system?**
The environmental protection authorities do not approve it; even if it is built, the local environmental agency will order you to modify the production process. I’ve seen cases where such modifications were imposed by force
Reply to 4# Qingting2004: Thank you, Qingting. This system actually uses the double-alkali method, but it cannot operate properly due to scaling inside the tower. Do you have any experience in modifying such systems to use the double-alkali method?
Reply to 5# haozhch: There isn’t any at the moment; that factory has only decided to make changes, but work hasn’t started yet
The single-alkali method and the double-alkali method are not the same; the desulfurization efficiency is certainly satisfactory, and the operation is safe and reliable. However, the operating costs are quite high, and the wastewater resulting from desulfurization is difficult to handle. Although there are no mandatory standards requiring such discharge to be prohibited, environmental authorities generally do not allow it to be discharged directly.