Bypassing Amine Filters HELPS foaming issues in Amine Contactor, WHY?

[bac351]

Foaming problems in one of our amine vs. light gas (mainly methane, ethane, and propane) contactors has persisted for a while now. Foaming events at least twice a week. Analysis around Rich Pinch, anti-foaming agents, etc., have not seemed to help the problem. On June 2nd we decided to bypass the lean amine filters (40 micron) within the unit prior to the contactor. Since doing this, we have not seen a single foaming event within the contactor. The filters are there to help prevent foaming, but it would seem they have had the opposite effect. We believe this is ok on the process, because the whole amine system is filtered by the same micron size (40 micron) filters in the amine regeneration unit before being sent out to the other units. This is a low pressure amine system. Because the micron sizes are the same, within the unit in question, and the amine regen. unit, we would not expect there to be any difference in amine quality due to filter sizes. We do not see any foaming events in any of the other contactors across the refinery that are supplied by this amine system.

From researching literature across the web, I cannot find another situation in industry where this has happened. Has anybody ever seen this phenomena happen at their refinery? Why would bypassing these filters actually help to improve the foaming situation? Could the filters cause negative turbulence? And is there any unforeseen consequence of bypassing these local filters?

Thanks for the help

 

[EmmanuelTop]

Did you inspect/open the filters?

Dejan IVANOVIC
Process Engineer, MSChE

 

[bac351]

yes,we had to change the filters out every 12 hours because of high dP. There were gumming up pretty quick. Black nail polish looking stuff on the filters each time, not many particulates.

 

[EmmanuelTop]

The "black shoe polish" stuff are corrosion products. The fact that you are getting the filters blocked after only 12 hours of operation says one thing: your system is full of this stuff. Operating without filters means another thing: you are circulating these deposits through the entire unit and likely getting them stuck in areas where it will be very hard to get them removed from. The damage is going to reach the skies one day - you'll probably have to shutdown the entire amine system and perform thorough cleaning.

So, instead of bypassing the filters, I would keep lining them up till I clean the entire system. As for the origin of the black stuff, you need to find the key culprits of corrosion: whether is it thermal degradation of amine, operation beyond maximum recommended amine loading, incompatibility of materials, presence of contaminants in gas stream or in makeup water, etc. These could be numerous. Without proper analysis and troubleshooting, I wouldn't expect to see the problem resolved one day. It seems like the problem is definitely not of acute nature.

If there is no experience in your company to deal with these issues, considering contacting Amine Experts or other specialized consultants. Apparently there are some guys in your neighborhood:

http://aminefiltration.com/#

Dejan IVANOVIC
Process Engineer, MSChE

 

[EmmanuelTop]

Forgot to add one thing: what I think it happens when you line up the filters, is that - at some point in time - you start moving slugs of black deposits that have accumulated inside the filters into the equipment downstream, including the absorber. This could easily promote flooding and/or foaming. By bypassing the filters, you get this stuff moved in much smaller quantities so it appears the problem is mitigated.

Of course, this is just a hypothesis. For getting the real picture, one would have to do a thorough troubleshooting of the plant.

Dejan IVANOVIC
Process Engineer, MSChE

 

[georgeverghese]

Maybe the bypassing of these filters has coincided with some other event that is the real cause of the reduction in foaming? - like a reduction in gas rate (or some other upstream operating condition) at the contactor or a change in antifoam agent type or flow etc.

 

[gocougs1]

It seems to me you are probably filtering out too fine, and need coarser filters. Perhaps you are filtering out the anti-foam agent that is left over from upstream process units? I believe anti-foam agents are silicon based, so maybe some of the contaminants contain silicon.