3 replies to this topic

[sealittle]

Hello,
I am a recent grad and have been working for an EPC based out of Calgary working on mainly Natural Gas Processing.

I have recently been asked by my new VP of Operations to do some work on the side.

Based on standard 32 API Oil, how can I find the True Vapor Pressure ad Reid Vapor Pressure?
The oil will be in an open tank, therefore we will be working with atmospheric conditions.

I remember doing these calculations during my undergrad but unfortunately I do not have my notes at the office yet.
If anyone could provide me with some assistance I would be deeply grateful,
Thanks!

[PaoloPemi]

detailed procedures are given in API TDB,
for a general introduction
http://www.epa.gov/t...inal/c07s01.pdf

automatic procedures are coded in simulators and process libraries but you need to characterize the composition (from a distillation curve, physical properties of mixture etc.), then a simple bubble point flash will return the desired value for true vapor pressure (which is more important from a engineering point of view), Reid gives slightly different values because it attempts to replicate the test procedure.

[sealittle]

Thank you for your reply.
I ended up using my simulator, however the values are very low. i was expecting RVP=approx 12psi,
i obtained a value of 0.21 psi. I believe the problem is associated with the poor modelling on the oil side of the simulator.
I use VMGSim v 5.
Does anybody have any suggestions?

[PaoloPemi]

if you have a distillation curve possibly you can estimate the true vapor pressure and RVP, procedures are described in API TDB (see also the above paper)
If you utilize the sofware to characterize pseudocomponents starting from a distillation curve then it should fit the provided distillation curve and you should be able to extrapolate and calculate a decent bubble point (True Vapor Pressure), the success depends from the data which you utilize to characterize the mixture, once you know the bubble point (TVP) it is easy to convert to RVP.
I use a different software (Prode Properties) and I am not familiar with the options available in your simulator, in Properties you can characterize from a distillation curve and density (plus some other options which I do not use), if that is the case with your software perhaps you have other options.