Lean Amine over stripping - when is it considered too much? 1

[rscosta1976]

Dear all,

Can you please let me know if you have a minimum limit for H2S content on the lean amine stream?

During regeneration of amine, it is known that operators must ensure the lean loading is less than 0.1 mol/mol and in some case even lower (less than 0.05 to 0.07 mol/mol). Given such a fact and for units processing gas containing H2S and CO2, with a H2S / CO2 ratio less than 0.5, it is recommended to avoid over stripping of the amine to keep some H2S and ensure the formation of a protective FeS layer in the CS equipment.

In this case, what is the minimum amount of H2S in the lean amine stream necessary to ensure the formation of such protective FeS layer and thus minimize corrosion of the amine stripper itself (and remaining equipment in contact with high temperature lean amine)?

I would appreciate if you can share your thoughts on it.


Thank you and kind regards

 

[SJones]

There are several other parameters to consider, not least the specific amine type. Take a look at European Federation Of Corrosion Publication 46 - Corrosion In Refinery Amine Units and see if there is any assistance there.

Baker Hughes had a presentation way back that advocated the following thresholds:

0.08 mol/mol in MEA
0.02 mol/mol in DEA
0.004 mol/mol in MDEA

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[rscosta1976]

Thank you Steve. I'll also verify the document you are referring.

We have a few units running MEA, but most run MDEA and DGA. I've seen one reference stating that 300 ppm of H2S in the lean amine is the minimum recommended value for units processing acid gas with H2S/CO2 ratio below 0.5. Can you please share your thoughts on this limit?

If you allow me, I have one additional question: In Baker presentation the loading stated refers to H2S loading only? Or is it referring to the total loading (H2S + CO2)? For me this is an important detail, since we are processing gas from different sources and with different H2S/CO2 ratios, ranging from almost sweet to sour.

Again thank you for your prompt response.


Best regards,