MDEA Properties

Hello,

I would be interested in knowing if you have received a reply about your questions regarding MDEA. I am currently trying to size some control valves and could use information regarding critical and vapor pressures.

Thank you,

Greg Fitzgerald

I have some client data that suggests vapor pressure isn't a significant factor in sizing the let-down valve. Their valve operated from about 700 psig to under 50 psig. The valve was a linear trim and I had a percentage open. Doing some playing around with valve sizing assuming a) a 'low' vapor pressure and b) a vapor pressure equal to the inlet pressure (worse case to account for dissolved gases and the acid gas that break out during the dP), the difference in required Cv was about 2.4, a significant difference.

The valve was running right about where a 'low' vapor pressure calculation predicted the Cv should be. My recommendation would be to pick a critical pressure (1000 psia) where the valve sizing isn't affected.

I don't have any vapor pressure data for 35% MDEA, your viscosity estimate looks correct. If you google Gas/Spec MDEA you can get some information for MDEA properties with vapor pressure for 100% and 50% MDEA. I'd check the vapor pressure data they have for 50 wt% at your temperature and if it backcalculates based on an ideal solution (not a great assumption for amine/water I know) you should be able to use the same approach to check the vp for your solution.

Thank you very much. I found this to be most helpful.

"the difference in required Cv was about 2.4"

That should have been, the difference in required Cv was a factor of about 2.4.