3 replies to this topic

[cjdean]

I am working on a project that is installing a propane refrigeration system in a gas processing plant. The engineering company has designed a system running at 0 psig suction to the compressor to achieve the required refrigeration to -40 F. I do not have any experience operating propane refrigeration systems at near vacuum pressure, and was concerned about potential contamination with oxygen, moisture, or other inerts. The engineering company has stated that this is very typical and they even have one plant operating subatmospheric at -60 F without issues.

Does anyone here have experience running propane refrigeration systems at or very near vacuum levels that could provide some input on this issue? One option we may have would be to switch to propylene refrigerant, as that would raise the suction pressure by ~4 psi at the same operating temperatures. However, the local operations group would prefer to stay with propane if possible.

Thanks for your input!

Caleb

[Bobby Strain]

I have been in the process engineering business for more than 40 years. Believe me, what you were told is news to me! Good luck.

Bobby

[Robert Montoya]

Cjdean; is typical work with vacuum pressure there is not problem with contamination. The pressure is around 9 psia or -5 psig.
The most important is that the vessel upstream the inlet compressor should have a heat source in order to avoid the accumulation of liquid refrigerant due the low temperature work.

[Art Montemayor]

Caleb:

I've been involved in refrigeration - especifically the refrigeration and liquefaction of gases - since coming out of university in 1960, and my experience has been exactly the same as Bobby Strain's. I don't know who you are dealing with as a mechanical refrigeration packager or what compressor you have selected, but my personal stance on this issue was formed a lot of years ago: I wouldn't accept this type of process design because of the potential hazard.

I also consider this type of design as a cheap, low-cost option, with minimum concern for operational problems, and simply a design that major, serious processing companies would not accept. This opinion was formed a lot of years ago and I have never had reason to change my mind. I fully agree with your stance on this topic and I frankly wouldn't care how many other processes are working with sub-atmospheric suction conditions using hydrocarbon refrigerants. The most important process in the world has to be YOUR process and you have a right to protect it and ensure the welfare and safety of your men and equipment. Good luck.