Quote:
Originally Posted by AC_Hacker
If we had a method that was dialed in for removal of water and any other potentially corrosive agents, and that could be implemented by a vapor-compression hobbyist, we would be making a major contribution to our community.
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I think I'm extraordinarily lucky with my source of Propane. In WA our Propane is just Propane. It's not very wet, it has no significant proportion of Butane or other major contaminants (read as it checks out with accurate P/T measurements). From what I read, this is very much the exception rather than the rule. In most places I think the major challenge is going to be separating the Butane and other HC fractions.
This might be easier in countries that have snow, as if you keep the cylinder below about -15C the Butane should stay liquid and allow you to draw off the propane *slowly* as a vapor. This will still require a small-displacement compressor (like a small fridge compressor) to move the propane into another bottle. If I get my bottle chiller up and going I could experiment with this, as I have a bottle of 60/40 Propane/Iso-Butane I mixed up for use in my car.
The circulation of the liquid through a filter/drier certainly removes a significant proportion of the mercaptan and moisture. Decanting the gas slowly as a vapor also leaves a significant proportion of the mercaptan in the bottle. The colder the bottle and the slower the vapor withdrawal the cleaner the gas appears to get.
Ethyl Mercaptan is an alcohol. Synthetic oils are alcohol based. Moisture causes them to break down into alcohols and acids. For this reason, filter/driers are geared to absorb alcohols also, so they do a pretty good job of removing the general impurities I see in my Propane.
At the moment, I'm struggling to come up with a method for "purifying" the Propane that does not rely on a compressor, condenser and 2 valve bottle.