Dear Mr. Lieberman. I have an MDEA fuel gas scrubber to remove H2S. What can I do to stop the amine from carrying-over as I increase the feed gas rate? I have reduced the amine circulation rate, but this has not helped. It even made the problem worse and increased MDEA losses.
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Linda. Reducing amine circulation rate increases acid gas loading and makes the amine foam worse. Reducing amine strength would help, but this also makes amine foam-up. Best to switch from MDEA to DEA, which foams less at the same molal concentration. Improve filtration to reduce particulates. Proper oil skimming and control of heat stable salts is vital. Maintain lean amine 15°F hotter than sour fuel gas. However, never add NaOH to reduce heat stable salts. This will only make your problem worse. If you have ⅜” sieve trays, increase size of sieve holes to ½”. Perhaps your downcomer open area is too small. Increasing tray spacing will always help. Most absorbers have two to five times the number of trays required.
--Norm
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