Causes to Low PH in Glycol Systems

[innocent1234]

I have encountered a EG glycol system on a refrig plant that has a low pH approximately 5. What are some of the potential causes of this low pH and perhaps some solutions to keep it in a more normal range.

Thanks

 

[ck1999]

If I am not mistake when the glycol breaks down an acid is released. Most cases an inhibitor is added to increase pH and prevent corrosion in the system. Some people use a disodium phosphate or sodium nitrite for this.


ck1999

 

[SJones]

http://www.google.co.uk/search?hl=en&q=+dehydration++glycol++maintenance&btnG=Google+Search&meta=

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[ash9144]

To state the obvious, is there a possibility you may have an exchanger leak? Watch eg tank level.

 

[monaco8774]

CO2 or H2S dissolve readily in glycol reducing the pH,also glycols oxidise readily froming corrosive organic acids.

For the first two you can only use pH control chemicals for the second you should make sure that any spent TEG is not returned to the system and that the surge tank and reboiler are adequately purged. Usually there is a fuel gas pressure blanket on the flash drum and the stripping gas to reboiler along with steam keeps the reboiler oxygen free, but if your design doesnt incorporate this or you have extended shutdown periods you may get problems.

 

[innocent1234]

Thanks for you input guys, it seems that there could be some oxygen in the inlet stream to this facility which I'm sure is causing some grief in this area. For curisosity sake, what is the tolerable limit for oxygen in the feed to a gas plant?