What is the appropriate pH value for desalinated water?
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The required pH level for the water at our plant’s water station is 8.5–9.2, but after standing overnight the pH drops to 7.5; we have to add ammonia to raise the pH level again. Our cooling towers operate at a pressure of 2.0 MP – what should be the appropriate pH level in those cases? This post was last edited by Welcome on 2009-2-11 21:02.]
Our process parameter is 7–8; your problem is caused by ammonia addition for adjustment. The instability resulting from such ammonia-based adjustment is particularly noticeable when desalinated water treated with ammonia is used in boilers. We have conducted experiments: desalinated water with a pH of 9, adjusted using ammonia, had its pH drop to 6–6.5 after being heated in a beaker for 30 minutes! Our boiler is suffering from corrosion on the inner wall of its furnace tubes due to this problem!
If the method of adjusting with ammonia has problems, are there any other ways to make adjustments? I guess there must be some, perhaps it’s a matter of cost or other considerations.
The pH value of our demineralized water is also kept between 8.5 and 9.2, adjusted using liquid ammonia; this is done primarily to raise the pH value for supplying water to the hydrogenation residue boilers. The pH value of the condensate water is around 8.2. Is the cooler mentioned by the poster open? Otherwise, how could it drop so quickly?
The pH value of demineralized water is generally kept between 8.5 and 9.2, with ammonia being added for adjustment.
The pH of deionized water without ammonia is acidic
Our value has always been around 6, and we haven’t noticed any issues with the equipment; it’s just that the requirements for silicate ions are quite strict
Urgent help needed on the second floor. The process parameter for our factory is 7, and it is adjusted by adding liquid ammonia; currently it remains at 9–10. After the deaerator, it drops to 7–8. There is now scaling inside the furnace tubes, and the shift supervisor cannot identify the cause. Could you please provide some guidance? Raw water ----- Multi-media filter ---- Ultrafiltration ---- Reverse osmosis ---- Mixed-bed reactor. Thank you
In general desalinated water, the pH of ion-exchanged water is moderate and may be slightly alkaline. RO water is slightly acidic.
Deionized water becomes acidic due to the dissolution of carbon dioxide.
Adding ammonia is primarily used to protect the main pipelines from corrosion, while the corrosion of boilers is prevented through measures such as using trisodium phosphate in wastewater treatment