Condensing Butane with air

Hello friends,

I have been once again hard at work with simulations, optimizations, and calculations for the perfectly optimized BHO recovery system (okay maybe not perfect).

Has anyone heard of / played around with a high-pressure condensing system? The propane & butane mix is actually very close to what you need in a refrigerant in terms of boiling point and characteristics, I mean other than the explodey bit. Realistically you would need to compress the gas to at least 300 psi and ideally upwards of 500 psi, but there are quite a few compressing systems that would be able to achieve that. If you haven’t picked up on it yet, you could just use forced air to condense your butane back to liquid through a heat exchanger like any old HVAC system. You could use many of the same expansion valves that are used on chillers. I personally would only feel comfortable in a super controlled environment.

Also, I think it goes without saying, guys don’t use high-pressure flammable gasses to speed up recovery rates. This is more of a proof of concept… Lol

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Looked into it and yes it can be done
Quite some air condensor needed and the temp diffrance is so low it go s slow


Well, your temperature would be related to pressure. Technically you could have whatever recovery rate you wanted you just need enough pressure. If you look at this phase diagram of butane, the boiling point would be 120 C which would have a delta T of 100 degrees. I know that it’s not exactly how it works (you know ideal gas law and all that), but that you should be able to achieve much better recovery rates. You are no longer limited by heat transfer from refrigerant to chiller fluid to butane. Even the 150 MVP recovery pump would work in some sense. The boiling point is close to 75 C at 150 psi.

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We work with cold temps for a reason
In bho rigs


The heat exchangers are definitely going to cost more than the tap water alternative. Why would you want to do this?

Tap water alternative? Like running compressed butane through a heat exchange with water?

Benefits would be to expand recovery rate without spending 70 - 80 grand on a chiller. Also simplifying the system.

What you’re asking about is air cooling a compressed gas then expanding it to cool. This is the condenser side of a refrigerant system. It works much more reasonably if you use water to condense it instead of air. Also, for a reasonably sized system, trying to compress your food grade process gas to use it for cooling makes far less sense than using a refrigeration compressor to do essentially the same thing.


Propane is actually superior as a refrigerant to most of the refrigerants used today. It’s just that it’s a flammable gas and I assume companies that manufacture appliances dont use it because it would be a bad look for a company to have its product on the news being attributed to someone’s house burning down if the lines happened to leak.

But it’s more efficient than most HFCs


CO2 actually has higher COPs than 600 series refrigerants but isn’t widely adopted because common refrigeration components are only rated for 700psi and building systems for higher pressure are annoyingly more expensive than they should be. Fun fact I guess lol


Isobutane is a refrigerant itself, r600a


Yep, and butane is r600, pentane is r601, iso pentane is r601a, and propane is r290


revisit the thermal capacities of water vs air…


Specific heat is more applicable in thermal storage, no? Given high throughput (which is much more achievable in air), you aren’t even hitting very high thermal saturation points so it more or less doesn’t matter.


I’m not really understanding what your contention is, maybe I’m just missing it.

The specific heat of water is substantially higher than air (I assume this is the metric which @cyclopath was using when saying thermal capacity).

Also, specific heat is per unit mass. Getting 10 kg/minute of water is very easy. 10kg/minute of air is more challenging using the same heat exchanger.

All I’m saying is that the cost for a water pump is less than the bank of radiators, and the piping simpler.


The earth makes good use of this system, why cant we

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120C seems excessive for our target.

Yeah @SidViscous is correct that my issue was with the size of the must not fail heat exchanger.

Store heat vs remove heat or provide heat across a heat exchanger? I’m a biologist, but they read as pretty similar to me.

I think a better approach would be to remove the heat from your solvent with water, remove the heat from the water with air.

That’s my preference with ethanol recovery


Anyone making air to gas heat exchangers for condensing butane/propane?

Its winter now, the temps are always below freezing, want to take a load off the dry ice.

Any old AC condenser coil would probably work after a good cleaning


My ghetto tek plan is to put a couple ss coils in a wood plenum type box and throw a big blower on it.

Just wondering if there was a more elegant option to compare or copy.

I ran 12’ of 2" spools on a slope last winter but relied on the wind for cooling capacity, seemed to help.


You’re probably still better off putting that coil in water. Misting water on the pipe is best but it’ll only get you so cold. The BTU capacity of a single 1/2" tube in air is going to be pretty dismal, just not enough thermal mass

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