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Air-Oil Separation

Air-Oil Separation

Air-Oil Separation

I am going to use a vacuum separator to separate air from Dexron III oil at 150F and 5 psia.  A vacuum pump on the air outlet will produce the vacuum, and a PD pump on the oil will pump out the oil.  We have 60gpm oil and 50scfm air.  I have two questions - 1) how much oil vapor will carry over into the air at 5 psia (I don't have a distillation curve), and 2) Do I need a condenser to drop oil vapor out of the vacuum pump discharge (at atmospheric pressure)?  I'd appreciate any advice or references.  I can provide a P&ID if you want.

RE: Air-Oil Separation

The MSDS for this product


gives the minimum flash temperature as 352F.  I'd estimate the vapor pressure given this data at your temperature (see Thread124-27883) using the API data book correlations for vapor pressure versus temperature.

Then, once you know the vapor pressure at 150F, you can see what % oil would be in the air at your 5 psia operating pressure.  I'd do a final check to see at 50 scfm air and 60 gpm oil whether the % of oil you estimate as going into the vapor phase is a small fraction of the 60 gpm oil.  If % of oil that 'evaporates' is small, the estimate would be reasonable.  If it's not, then you'll need to do a more rigorous calculation to account for the Dexron's true boiling point curve.  Getting its true TVP curve (or at least, the first 30% or so) could be difficult but I don't expect that will be necessary.

RE: Air-Oil Separation

Thanks loads.  That's exactly what I was looking for.  I don't have an API data book, but I have a copy of Maxwell.

RE: Air-Oil Separation

Maxwell's a good source, I keep forgetting about it.

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