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Amine Stripper Corrosion

Started by Guest_caa_*, Jul 18 2004 04:13 AM

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#1 Guest_caa_*

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Posted 18 July 2004 - 04:13 AM

We use DGA(diglycol amine) in our amine system used for removal of CO2. A simple system of an Absorber, rich amnine , lean amine heat exchanger , stripper. absorber and stripper are packed bed towers.The stripper top 6 metres is SS clad and below that is CS. We are experiencing very severe corrosion at the stripper -at the portion from below the SS cladding to @ 1 metre height. Prior to this we experienced fouling in the rich amine/lean amine exchangers causing the feed i/l temperature to the stripper to drop by 10 deg C.( 88 deg C vs 98 deg C ). We had 2 points leaking in the column @ 5mm hole - 12mm is the thickness of the CS portion. we tok a shutdown to clean the exchanger after which we got back normal temperatures and monitoring of column thickness at various locations has shown no further loss. Howevr, we still are getting leaks. The stripper feed enters at the CS zone.The water relux enters at the SS portion. It must be noted that the feed temp. was less but, we maintained column top and bottom ocnditions by increasing reboiler steam.

We checked for Heat stable salts, acid loading etc. All were very much Ok. Any ideas? I presume the info is not total, do feel free to ask

regards and thanks

#2 Art Montemayor

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Posted 18 July 2004 - 08:24 PM

caa:

As for more basic data, you haven't given:

1) Are you removing H2S or CO2 - or both?

2) What is your solution strength? Is it 70%?

3) What is your max. solution gas loading? Are you keeping it below .3 to 0.35 moles acid gas per mole of DGA?

4) How are you heating your reboiler? With low pressure steam? Or do you direct-fire it?

I would direct you to my recommended website for Amine literature and its employment in the design of a plant which I mention in my reply to Tomas in the Student Forum under his post regarding Amine absorption of CO2. Download the BR&E literature and read the article titled: "Selecting Amines for Sweetening Units". It should help you explain a lot of what is happening in your Econoline unit (Fluor E&C name for the DGA process).

I hope this helps.

Art Montemayor
Spring, Texas

#3 Guest_CAA_*

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Posted 20 July 2004 - 05:27 AM

ART,

thanks for the site reference. regarding the questions :

1) used for removing CO2 - 3 mol% of feed.

2) DGA is at 50 wt %

3) Yes. Acid gas loading @ 0.25 only.

4) We use low pressure steam in a reboiler

Also, a correction to my first post :

I mentioned that the stipper feed enters the CS zone. It enters the SS clad section of the tower at @ 3m level.

I would also like to highlight that we suspect this whole occurence of rampant corrosion having occured in a very short spell - @ 7 ~ 8 months , I believe it is linked to the loss in stripper feed temperature by 10 deg C.

The other funny part is the thrice weekly sampling of DGA never showed the Fe pickup.

regards

intu
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