Steam drum PH issue

The pH value of the water in a drum boiler can be fine-tuned by adding phosphates

Depending on the pressure class of the boiler, medium and low-pressure boilers are generally treated with phosphates for fine tuning; there is also a treatment process called coordinated phosphating, aimed at preventing alkali embrittlement.

Ammonia water needs to be added in the early stages of using the device; generally, phosphates are sufficient later on

We fine-tune by adding phosphate solution

Isn’t the pH value of water in a drum boiler already alkaline? Then why add phosphates?

I’m not sure what size of boiler this guy is referring to; boilers with a capacity of less than 1000 T/h can all have their pH value adjusted by adding phosphates. The phosphates are added inside the boiler’s drum, with the difference lying in the amount added. The greater the boiler’s evaporation rate, the higher its pressure level, and the better the quality of the feedwater, the less phosphates need to be added. For a boiler with a capacity of 1000 T/h, the amount required is between 0.3–0.5 mg/l. For furnaces with a capacity of over 1000 T/h, the method of adding NaOH or full volatilization treatment (using only ammonia and hydrazine) is generally employed. As for the coordinated phosphate treatment mentioned by someone upstairs, it is a misconception regarding water treatment inside the furnace; practice has shown that this approach leads to severe corrosion in the boiler’s evaporation system.

Generally, hydrazine is used for chemical deoxygenation in the boiler feedwater pipeline, which also affects the pH to a certain extent. Additionally, phosphates are added to the drum for scale removal, and this also helps to regulate the pH

What is the purpose of phosphates added to the steam drum, and how much is usually added?

Additional info: We have three drum vessels, A, B, and C, powered by one phosphate pump; however, only one of them has a low pH level, ranging between 8 and 9, while the pH of the water supplied is between 7 and 8.

We use a phosphate pump to inject water into the drum simultaneously with the feed water, adjusting the pH value of the mixture to 7-8

Adding phosphates to the drum is mainly to prevent scaling.

1 Add phosphates; there are two types of such salts: sodium hydrogen phosphate and sodium dihydrogen phosphate. Adjust the ratio of the two based on experience, and add them to the drum to regulate the pH value of the liquid in the drum. 2 Remove some of the phosphates. There are two ways: in-line and between-row.

The addition is intended to balance the pH level, and it also helps to remove substances that tend to cause scaling, such as heavy metals and calcium and magnesium ions; the pH is adjusted through intermittent and continuous discharge.

The phosphate we added is H3PO4-10H2O

Ammonia water is added first, followed by hydrazine.

Add phosphates, such as sodium hydrogen phosphate and disodium hydrogen phosphate.

Phosphates are added, and the pH is controlled between 7 and 8 through sequential and intermittent addition

What we add here is phosphate, specifically trisodium phosphate.

Add trisodium phosphate to adjust the pH; if adjustment is not possible, an appropriate amount of sodium hydroxide can be added.