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marx290 03-11-13 10:13 PM

Question About Filtering BBQ Propane
 
I'm a refrigeration hobbyist of sorts and I like using BBQ grade propane for all of my projects so far. I pass the propane through a filter when charging my systems (small stuff like dehumidifiers), and I also install an in line filter drier in the system to try to catch what water might be in there. I've noticed the stink gets filtered out too, or absorbed by the compressor oil and read in other posts that others have noticed this too.

I'm curious if anyone has a procedure for effective filtering, and maybe separating or purifying the gases in common BBQ grade propane for use in vapor compression systems?

I've been reading the thread on R-290, so maybe a link to the appropriate post?

Thanks

jeff5may 03-13-13 06:34 PM

For hobby or DIY (inexpensive) use, you have a few choices:
1. Blow torch bottles of propane
2. Cylinder exchange propane (BBQ grill tanks)
3. MAP/PRO bottles of propylene

Using option 1 or 2, you get HD-5 grade fuel propane. By the standard, it is at least 90% propane and up to 5% propylene. There is no higher standard in the USA for fuel-grade propane, so 99% propane and 1% propylene is still HD-5 grade. In reality, the gas in the bottles is nearly all propane and propylene, with a few ppm each of trace gases such as: butane, isobutane, cyclopropane methane, ethane, etc which varies by location. The propane industry works hard to keep nasty stuff out of their product. This includes water, air, acid, and generally anything not flammable and condensible.

For general-purpose hobby use, propane and propylene have very nearly the same properties in the refrigeration circuit, so a little propylene in the mix will not skew the performance of a unit. So as long as you charge slowly from the bottom of the bottle and run the exiting liquid through a filter-drier on its way into your system, you will be good to go. Just remember to stop charging before you run out of liquid in the bottle. The lighter gases, if present, will be in their gaseous state in the bottle along with the non-condensible gases.

Using option 3 is the next cheapest way to go. It is at least 99.5% propylene, at most 0.5% propane, and ppm amounts of stink oil plus even less ppm of contaminants. Propylene has even closer system properties to that of r-22 than propane. It is the next level up in off-the-shelf products in purity, and is readily available in stores that sell the torches that burn it. Again, running it through a filter-drier on its way in will remove the stink oil and any trace contaminants.

For long-term use, it is highly recommended to pony up and buy refrigerant grade gases.

marx290 03-13-13 11:27 PM

Great information! That's just what I was looking for. I know I read somewhere that BBQ grade stuff was at least 90% propane with varying amounts of other flammables mostly, and the stink oil of course. What little I've worked with it, I charge from the small Coleman bottles and then refill them from a 20 lb. tank. I didn't know some people are playing with propylene too. For the cost of it, I'll stick to the cheap propane stuff and focus on filtering it well.


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