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Recycle gas from high pressure separator is being treated in amine absorber. Treated gas then routed to recycle gas compressor (2 stage). We are observing lot of liquid accumulation in the inter stage KOD (after cooler). Liquid sample is analyzed and found that 99.7 vol% of sample contains water and remaining as amine. We are adding water to the amine system to compensate the loss through inter stage KOD.
Lean amine to absorber temperature is being varied in the range of 55 to 60 °C to maintain design DT between amine & gas. We have observed that the absorber top temperature is high when compared to bottom temperature.
Why only water is getting carried over (in huge quantities) along with the treated gas? Is the same observed in any high pressure amine absorbers.
Why temperature profile in the amine absorber is in the opposite direction? Is this related to moving of heat of absorption profile from bottom to top?

Further info:
If there is a foaming in the column the following should have happened:
1. Fluctuations in absorber bottom level; not fluctuating
2. Severe fluctuations in DP across the absorber; not fluctuating
3. Improper stripping of H2S from gas; not observed
4. Amine foaming tendency test is also done and found satisfactory.
In the case of foaming in the absorber, amine should also get carried over along with water. But this is not happening. As i said earlier amine content in the water sample is in the range of 0.3 to 0.5 wt% only.
What is the ideal delta temperature to be maintained between gas and amine?

 
Answers
20/07/2015 A: Krishna Nimesh, BPCL-Kochi Refinery, krishna.nimesh@gmail.com
Normally the LDEA Temp should be 8-10 degree Celcius more than the Recycle Gases. Try to maintain the HP Amine top temp between 40-45 degree celcius. Temperature more than 45 degree celcius will evaporate water from the LDEA solution which will frequently increase the level in inter stage cooler of Recycle Gas compressor.
Genarally foaming is a result of liquid hydrocarbon being carried over by the Recycle gases in HP Amine KOD to HP amine absorber.
27/01/2013 A: Egbert van Hoorn, Hocon B V, Egbertvh@hotmail.com
The most important reason for what is observed is foaming of the high pressure separator and/or the amine absorber.
A high top temperature of the amine absorber indicates foaming of the amine absorber.
The reason for a large quantity of water can be the interstage cooler which reduces the temperature and therefore will condense water.
The change in temperature profile is indeed due to the different way that the absorber works when foaming is occuring.
Due to the foaming, the absorption of H2S is less efficient in the bottom. More absorption moves to the top and increases the temperature in the top.
Your amine system requires to be reviewed for foaming.