Why is chemical dosing added to the medium-pressure steam drum instead of directly to the deaerator?
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For catalyzed external heat removal, internal heat removal, and other types of drum dosing, why not add the chemicals directly to the deaerator?
The temperature conditions vary greatly. There is a specific continuous area (upper surface).
The temperature conditions vary greatly. There is a specific continuous area (upper surface).
Firstly, the water entering the deaerator is demineralized water from the power plant, which is deoxygenated through steam heating; this water does not undergo repeated high-temperature heating, so it produces little or no harmful ions or dirt. In contrast, the water in the drum goes through repeated heating processes (which is equivalent to concentrating the liquid), and the quality of the water in the boiler varies depending on the amount of gas generated by the drum (under the same conditions, a drum that generates more gas results in lower-quality boiler water). Therefore, adding chemicals to the deaerator cannot be used to adjust the quality of the boiler water for each individual drum, leading to waste
It’s actually possible too; we can add it at the outlet of the feed water pump, and if there’s a problem with the water in a single drum boiler, we can simply switch to continuous drainage. When the unit uses cooling water, attention must be paid; using chemically treated deionized water can lead to scaling.
We add water to the drum once before starting up the plant; after that, once the quality of the deoxygenated water is strictly controlled, no more water is added! !
How do you manage to do that? Could you explain it? In our case, we add chemicals in each tank to control the quality of the boiler water, such as phosphate levels, pH value, alkalinity, and so on
Reciprocating pumps are used for adding chemicals. The more stable the pressure at the outlet of such pumps, the better for their long-term operation. The pressure at the outlet of water supply pumps is generally unstable, which can cause damage to the reciprocating pumps and hinder their long-term use. Therefore, the outlet of these pumps is usually located inside the boiler, where the pressure is more stable; pressure regulation can be achieved through control valves. If the dosing is carried out in the deaerator instead of in the drum, its effectiveness will definitely decrease, and the reason for this is obvious.
In the boiler industry as a whole, it is necessary to conduct quality analysis of the boiler water, as well as quality analysis of saturated steam and superheated steam.