Absorber Gas Wash Vessel MOC

[ashwani]

Hi,
I would like to know whether it is common to use condensate ( produced while cooling CO2 gas coming from CO2 Regenerator ) for washing Raw Synthesis Gas coming from Absorber gas outlet.

We are presently washing the Absorber outlet H2/N2 gas with BFW. We want to use the condensate from CO2 Regenerator downstream condenser to wash Absorber outlet gas. However, the condensate has pH of ~5 and the MOC of Absorber outlet gas wash vessel is Carbon Steel.

I would like to know whether the MOC of Wash Vessel in other plants (where similar condensate is used) is SS or Carbon Steel.
Thanks in advance

[Edmondson Bob]

Hi,
My experience is quite limited with this but for an amine system (sulfinol) I have seen this done without difficulty but with Benfield I think there is a need to consider possible K2CO3 contamination of the methanator and its feed/effluent exchanger and because the water is high in KHCO3 it can be corrosive to carbon steel which is not passivated by V+5-the wash vessel without wash of any kind did suffer corrosion after many years. Hopefully others will reply with their experiences.

[ashwani]

Thanks, Mr Bedmonds for sharing your experience.

Looking forward for others also to share their experience.
Regards

[Satyajit Mahapatra]

Dear Aswani,
Most of the plants use carbon steel in Absorber while the internals are stainless steel; so this is a concern off course to use CO2 rich water to use as wash water. You also need a separate high pressure pump to send water to the top of the absorber meaning some more investment. This is why BFW is used for tray washing in Absorber top.
Another point is that if you are working with Amine plant, it is a water negative plant and does not have excess water. All water is recycled to other columns and as pump sealing/flushing water which are stainless steel.
Hope this replies your concerns.
Kind regards,
Satyajit

Satyajit

[Author]

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