Alkalinity control criteria for water in medium-pressure drum boilers
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The control target for the alkalinity of water in medium-pressure drum boilers is no more than 0.4 mmol/l. What factors mainly affect alkalinity?
Your control is even tighter than that in our factory; is trisodium phosphate being added? Let me mention our control parameter for boiler water alkalinity: it should be ≤800 umol/L, which is equivalent to ≤0.8 mmol/L ； Phosphate content in boiler water: 5–15 mg/L ； Sodium content in boiler water ≤ 100 mg/L ； Sodium content in 3.5Mpa steam ≤ 15ug/L ； The total hardness of the demineralized water is ≤2 umol/L. Alkalinity control should be related to wastewater discharge, chemical addition, and the quality of the demineralized water supplied. We are not able to control it effectively, which leads to scaling in the steam turbines. Even though regulations have been established regarding wastewater discharge and chemical addition, it remains difficult to maintain proper control. Now we use water treatment agents, and this has improved things a lot, but their price is nearly 10 times higher
What type of water treatment agent have you added? Our drum also has this issue; the levels of sodium ions and silica in the steam are always above the acceptable limits
I forgot what brand it is; I’ll ask tomorrow. It’s in 25kg barrels. After some experimentation, I made a 5kg container for the additive, which is then added to the dosing tank in proportion. The water volume added to the dosing tank remains constant; what’s left is to adjust the pump output based on the analysis results
Oh, what kind of nature? Sodium hydroxide?
It’s not sodium hydroxide; there is only a product certificate with no detailed information provided. The shelf life is 1 year, it has a weakly acidic nature, and it should not come into contact with the skin. It is mainly capable of removing scale; we add it as required to keep the sodium ions in the steam at no more than 15 ug/L. When the alkalinity level becomes too high, waste water is discharged. Controlling the quality of the steam in this way is even simpler and more efficient than using trisodium phosphate.
Where are water treatment agents added?
Placed after the deaerator and before the drum, we have two dosing tanks here for adding chemicals to the drum; chemical is added manually at the top, the deoxygenated water is mixed evenly, and then it is pumped to the drum using a gear pump