HELP : Depressuring calculation of an amine absorber

[volpi]

I am performing the depressuring calculation of an amine absorber (HP) in order to determine the minimum design temperature of the vessel and therfore to confirm the material selection.
I am using the Depres Unit of PRO II software. I have already size the BDV orifice size for the fire case, according to API 520. I have now to calculate the cold blowdown case but I don't know what must be the initial conditions and the thermodynamic to be used. Please note that I have no specification regarding this subject :
- Initial temperature = normal operating temperature or minimum ambient temperature?
- Model = User defined without heat input (Twall = Tin the vessel) or Rigorous model (Twall = Tin the vessel at the beginning of the depressurization and is then calculated according to heat exchange between metal and gas in side).

I know that my question can have different answers since it depends of the depressurization philosophy but I would appreciate to have your advice since I do not want to determine exactely the minimum design temperature but only to confirm material selection.

Thanks,

 

[MortenA]

If your vessel can sit still at PAHH for a while then i believe that you must use lowest ambient temperature for cold blow down.

Best regards

Morten