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[apex]

The GSU units which I am operating use generic MDEA to remove H2S selectively over CO2 from the natural gas. The outlet H2S is somewhat more than the required which is 4 ppmv. On simulating I found that the absorption is lean end pinched w,r,t. H2S. In some articles I read that adding phosphoric acid to MDEA can improve regeneration i.e. lean loadings of MDEA & hence lower H2S ppm can be achieved in the outlet gas with reduction in steam requirement in the regenerator. I did the simulations & thermodynamically it agrees with those articles. But, I am apprehensive about operational (foaming) & corrosion problems. Anyone who has experience handling such system, please comment.

[RockDock]

The additional phosphoric acid is very low compared to the amine. In the end it is still acid/base related for corrosion. You maintain the same loadings as you would with MDEA to prevent corrosion.

 

I cannot comment on the foaming tendency of phosphoric acid, but I do not recall ever coming across an amine system that had foaming attributed to the phosphoric acid. I can imagine if the concentration of the acid is so high it forms a salt (heat stable salt), it will cause foaming. However, I don't know of any documented case of that. Your model should be able to tell you the concentration of salts. In ProMax, their is a salt analysis. You then check when that salt will precipitate.

 

I've seen a few of these units in operation without any foaming or known corrosion.

 

It is good to question any additives to your solvent. I am interested to see if anyone has experienced either of these issues.