Lean TEG pH increasing gradually to 9.8
Lean TEG pH increasing gradually to 9.8
(OP)
In our gas dehydration unit last 4 months we faces problem with Lean glycol pH increasing gradully to 9.8 which creates foaming and loss of glycol. We dont have amine gas sweetening unit in our plant to suspect the pH increase due to amine. At this point I seek your kind help and advise....
What might be the possible cause of the increase in pH?
How to identify the root cause and solve the problem?
What is the possible way to bring down the pH time being?
Thank you.....
What might be the possible cause of the increase in pH?
How to identify the root cause and solve the problem?
What is the possible way to bring down the pH time being?
Thank you.....





RE: Lean TEG pH increasing gradually to 9.8
A well sized gas scrubber / filter coalescer upstream of the the glycol contactor always helps to minimise liquids entrainment / dissolution of these undesirable chemicals (and heavy hydrocarbons) into lean glycol.
RE: Lean TEG pH increasing gradually to 9.8
2) Secondly, please follow George's advice and have somebody look in the chemical dosing system. If you are using a chemical for pH adjustment and corrosion inhibition, reduce injection rate and observe the effects on glycol pH.
3) Take a sample of liquid/aqueous phase from the inlet gas knockout drum upstream of the glycol contactor and check for pH. There is no amine unit upstream, but you may be receiving some other high pH compounds/chemicals with the inlet gas stream.
4) Check if there was any change in composition of the inlet gas and the stripping gas (if your plant uses it), particularly with regards to Base components (NH3 etc.)
5) Ultimately try to submit a sample of TEG to a lab and see what are the components causing increased pH. This should give you some ideas of their origin.
Dejan IVANOVIC
Process Engineer, MSChE
RE: Lean TEG pH increasing gradually to 9.8
Plant is not new, already 9 years we never faced this problem. Once we face TEG salt contamination and we replaced the TEG and problem solved. Let me check for any changes in chemical injections.
Fresh TEG we checked pH and it is 7.2 only. No problem with fresh TEG. From chromatography gas analysis shown no any changes in the inlet gas compositions. We will check the inlet scrubber sample and TEG composition in the lab and come back to you.
Once again thank you very much for the advise.
RE: Lean TEG pH increasing gradually to 9.8
You may also try to completely switch off the chemical injection for pH control. It doesn't seem logical to maintain injection when pH is close to 10. Depending on the materials of construction, accelerated corrosion rates are possible so identifying and eliminating the causes of high alkalinity should be a priority task.
Dejan IVANOVIC
Process Engineer, MSChE
RE: Lean TEG pH increasing gradually to 9.8