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Chemical Oxygen Demand Limit Of Boiler Feed Water

cod boiler feedwater recycle water

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#1 hiren_d

hiren_d

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Posted 22 May 2018 - 02:35 AM

Hi,

 

My question may seem impractical, but need help to avoid any confusion.

 

What is the limit of Chemical Oxygen demand of boiler feed water?

 

In IS 10496:1983, other parameters like hardness, alkalinity,pH,TDS, Silica, ammonia, iron, copper, dissolved oxygen are given but COD limit is not specified.

 

If recycle water has low COD up to 50 ppm, can we recycle it?

 

Regards,

HD



#2 Technical Bard

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Posted 23 May 2018 - 07:17 AM

It would depend on the type of boiler.  A once-through steam generator (non-waterline boiler) that is producing 0.8 quality steam can handle significantly more COD (i.e. organic material).   But an ASME drum boiler making dry steam, or superheated steam, cannot.  This water should be filtered and polished to reduce the COD.



#3 thorium90

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Posted 26 May 2018 - 12:50 PM

If the COD is high, your other parameters like TDS etc would also likely be high as well. Since TDS is a more direct indicator, and since it can be measured with an online conductivity analyser, it is commonly used as the indicator of the water quality.

Also COD is an oxygen demand, since it doesn't actually specifically say what is the item that consumes the oxygen, therefore it is only an arbitrary indicator. Similar with TDS and TSS, in that these are just a total sum but doesnt specifically say what is the actual species inside. But, COD is alot more vague than TDS and TSS so COD is not always necessarily a useful indicator of water quality.


Edited by thorium90, 26 May 2018 - 12:51 PM.





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