Chloride level in Boiler feed water

[andygo11]

Hi, I have a question about the allowable level of chloride in boiler feed water. The water has been treated to very low oxygen level (about 6 ppb) and the PH is 12. In my option, there is no concern about the chloride because of no corrosion agents either from oxygen or low PH. Just confirm if this is true?

 

[cap1a79]

Yes, there is no chloride issue for BFW. Generally, most of chloride becomes negligible from downstream of "demineralizing" process. (Raw water --> DM plant ("demineralized") --> DM water --> Deaerator --> BFW)

Generally, to prevent corrosion in BFW, it is important to control dissolved gas(ex., CO2), oxygen level and interference between chemical injections.

Lee SiHyoung,
WorleyParsons Oman Engineering,

 

[Dhurjati Sen]

Dear andygo11,

Very interesting question.

Chloride is normally never tested in BFW. It is tested in DM water, though, where a typical analysis would show nil chlorides (chlorides as CaCO3).

Are you hinting at an upset in the DM plant?

If there is at all any chloride ingress in the BFW, it could only be removed over a period of time through blow-downs.

It would not lead to any corrosion, but there could be some scaling in the low temperature zones like the economizer, bank tubes, etc.

Regards.



DHURJATI SEN

https://www.nace.org/people/dhurjatisen

 

[EdStainless]

You can find water guidelines from various boiler manufacturers.
There will be limits on Na, Cl, and other dissolved species.
All of these limits are down in the sub-ppm range.
It doesn't take much Cl to greatly accelerate boiler tube corrosion and to destroy a steam turbine.

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P.E. Metallurgy, Plymouth Tube

 

[andygo11]

Thanks for all the answers. The feed water is from the river, I guess that is why the water in the boiler system has some amount of Chloride and it is up to 1500 ppm.

 

[EdStainless]

The raw makeup water can be from any source. That is why it get filtered, softened, goes through ion exchange, and is then degassed. Before it goes into the boiler it must be u;tra high purity.

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P.E. Metallurgy, Plymouth Tube

 

If I measured 1500 ppm chloride in my neighbourhood river I would report it to the environment regulator.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[weldstan]

andygo11,
If you have 1500ppm CL in the boiler after treatment, you have a major problem that needs to be immediately corrected.













do you

 

[bimr]

The amount of chloride in the boiler water is a function of the type of boiler and the boiler pressure. High pressure utility boilers have essentially zero chlorides.

For low pressure industrial boilers say 150 psi units, boiler water chlorides limits are set on the ideas that:
the boiler should get good fuel efficiency , and, based on both makeup and treatment dissolved solids, the total boiler water dissolved solids should not go so high that carryover, scaling and corrosion are a potential problem.
Chlorides may be maintained in the 60-200 range. The chloride concentration is controlled by boiler blowdown.

This is something that you should review with the boiler chemical program provider.