I went down a safety rabbit hole today and starting thinking about vapor pressure—in short, if I have a tank full of some gas, that gas will exhibit a certain pressure on the tank based on the tank’s temperature.
For context, I’m in a hot state—it is possible for the outside temp to reach 110F…if I’m using pure propane, the pressure in my solvent tank is 204 psi—no thank you.
On the other hand, n-butane sits at 47 psi when it’s in a 110F system.
Clearly, from the perspective of phase changing a hydrocarbon between liquid and gas, over and over again—n-butane is the safer choice.
However, it seems that running at such low pressures (i.e. <50psi) reduces the ability of the liquid butane from passing through various mediums (biomass, filtration, built up fats, etc). So the use of mixtures serves to improve the ability of the solvent to pass from one end of the process to another end.
This also improves one’s ability to recover (i.e. more propane = faster recovery).
Questions:
What differences have you noticed in yield and process efficiency with increasing propane concentration?
What efforts have been made to mitigate the fact that higher propane gases mixtures are problematic, pressure-wise?
What are your thoughts on the type of extracts made with propane heavy vs butane heavy solvent mixtures?
you can always back butane up with N2 if you need the pressure. usually done because solvent at -50C doesn’t have any vapor pressure. even if it’s 70% propane.
I personally prefer straight n-butane. I’ve run 70:30 (and thereabouts) and made great extract, but find the temp at which butane becomes liquid more appealing from an operational stand point.
diamond mining is safer with butane, and I’m a saucy wrench
I usually run high propane ratios on most material I process through a ETS miniMEP, which is designed with 100% propane in mind, and is certified for this. The max I have seen in my solvent tank is about 135 PSI after filling from the storage tank sitting in the sun on a 102f day.
The largest issue I have with propane isn’t the quality of product, or the pressure. It’s the mess when collecting!
Pure propane extracts are a pain in the ass to collect. Once you bleed off or vac off any remaining pressure in your collection pot, it expands making a mess. It’s a gummy sticky mess, which is difficult to transfer and clean. This adds a lot of time to my routine.
Lately I’ve had very high yielding material, and running it on only propane. Every time I go to collect, my whole collection column ends up covered in hash when it expands all the way up. Fortunately I can push it back down with nitrogen and wait for 20 minutes or so for it to melt down.
Butane extracts pour beautifully compared to propane. I have found that adding as little as 10% butane makes the collection much easier. Saves a lot of time.
All my propane heavy runs are usually about 10 minutes faster than butane heavy runs. Saves a bit of production time, but the cleanup time usually negates that.
Also, I have only had about 10% success making propane diamonds. I usually get just sugar (propane off gasses too quickly, not leaving enough solvent behind). However 70/30 Propane/n-butane make some beautiful diamonds and the sauce holds on to just about the right amount of solvent.
Overall I have good luck with all forms of post-processing of 70/30 Propane/n-butane. Good Diamonds, Budder/Crumble, Sugar, etc… About ready to give CRC a shot with propane soon.
You arent taking into account that operating pressure for ntane is usually 30 psi but you can pull full vacuum and make the total pressure differential 60 psi or more. If you cant push solvent thru material with dp>60psi there are operational problems.
propane gives a noticeable increase in recovery speed. it especially helps speed column recovery.
running cold inject butane the propane propellant helps immensely to bring psi above 0.
70/30 is a great ratio.
I used 60/20/20 from ecogreen. I ran a 7.5lb dewax column active with coil for solvent feed. The way i pushed solvent through the column was an unorthodox passive method and if my ambient temperature was cold enough i wouldn’t go pass 5psi. Typical stood around 10psi. I bottom fed and had my main ball valve open until solvent started to drip than i would close it. This prevented any vapor pressure that would heat my biomass.
