BHO Thermos Extraction - Points of Concern

[gunnaknow]

Always a pleasure chaps.

 

[gunnaknow]

Jump, I just did some calculations based on the vapor pressures of propane and n-butane and at -20°C, propane has a vapor pressure of 2.4 bar and n-butane has a vapor pressure of 0.5 bar. The mixture in Colibri is 22% propane and 78% n-butane. This would give a combined vapor pressure of 0.918 bar. A vapor pressure of at least 1 bar is required for the mix to act as a propellant. The boiling point mentioned in the MSDS for Newport is -11°C, so it's vapor pressure is even lower than that of Colibri. The amount of propane isn't sufficient in either brand for their mixtures to work as propellants at -20°C.

 

[jump117]

Jump, I just did some calculations

Hi Gunna!

I believe that you have offered a very successful and understandable terms !

BHO - Butane Hash Oleoresin (from dried);

BHC - Butane Hash Concrete (from un-dried).

Thanks for reminding me this topic “ Maximizing extractions” from 2010! How time flies!

 

[Gray Wolf]

Will be using safety glasses but still leery of looking down in the thermos with a flash light to see if the plant material is covered; any ball park ratio's for someone faint of heart? How much butane for 1 gram of material. Seems to simple somehow, I must be missing something. This site is like going to BHO University, lots of great professors herein, thank you all.

Here is the picture that wouldn't load. Thanks for the fix GM!

Good idea on safety glasses, but I've never needed a flash light when extracting in broad daylight. I can see down into the thermos far enough to keep track of what is going on.

 

[Gray Wolf]

Jump, I understand what you were getting at but I wouldn't have said that propane and isobutane are the propellents for n-butane. Atleast not in normal operating conditions. That could make it sound as though n-butane is the intended product for delivery and that the propane and isobutane are just added to help deliver the n-butane. I know that this isn't what you intended to mean. The truth is that all three are the propellents and they are used as a mixture because their combined vapor pressure works better together, for their intended application. Pure propane isn't suitable for use in certain products because of it's high vapor pressure and the requirement for robust containers. Pure n-butane isn't suitable for certain applications because it stops working as a propellent below -0.5C. A mixture of the two provides a good compromise for manufacturers.

By chilling the canisters down to around -20°C, we're altering the behavior of the mixture however, as the n-butane and isobutane will no longer behave as propellents, at 1 atmosphere. So we could refer to the propane as the sole propellent but only because we've changed the dynamics by chilling the cans. In an upright position, this would lead to the propane becoming depleted long before the isobutane and n-butane, leaving the can still half full and unusable, until the can temperature warmed up. However, the fact that we're injecting the gas downwards negates that problem. I'm digressing a little though. The main point is that all three are the propellents, in typical operating conditions. The point that you were getting at was correct though, which was that the propane and to a lesser extent the isobutane, will make up the majority of the initial boil off. I do enjoy our conversations.

gunna

Good points!

Colibri lists -11C as the boiling point of the 78/22% mix.

http://www.gcelectronics.com/order/msds/224.pdf

 

[gunnaknow]

That's interesting, GW. I looked at a different MSDS for Colibri the other day and the contents were listed as 78% n-butane and 22% propane. The one that you've linked to mentions the hazardous component as butane, not n-butane and it also states that the chemical composition is a blend of hydrocarbons consisting primarily of propane, iso-butane and n-butane. My calculation was based on the vapor pressures for pure n-butane and propane but the second MSDS for Colibri shows that it's not pure n-butane and propane. I don't need to bother recalculating the vapor pressure though because the boiling point is included in the second MSDS, unlike the first one that I looked at. If the boiling point is -11°C, it won't behave as a propellent unless the temperature is above this. So it clearly won't behave as a propellent if it's chilled to around -20°C in the freezer.

As it happens, the MSDS for Newport also lists the boiling point as -11°C, meaning that their compositions are the same. That doesn't come as much of a surprise because they're both manufactured by Keen Ltd.

 

[jump117]

When MSDS claims the boiling point of a mixture -11°C, that is lower boiling point of mixture of n-butane -0,5°C and isobutane -11,7 ° C,

that means that propane b.p.-42,09°C is not already present in the mixture.

At -20°C propane turned into a gaseous state, squeezed liquid butane from the can, and disappeared into the atmosphere.

Hence, the resulting volume of liquid gas in thermos would be about 22% less than the volume specified on the label.

This should be taken into account in the preliminary calculation of the volume of liquid gas.

 

[gunnaknow]

Where did you get your information from regarding it being the lower boiling point? Unless an MSDS states that the boiling point is for one of the ingredients in the mixture, or it gives the boiling point as a range, then the boiling point listed for a mixture could be the average boiling point. Sometimes this may not be the case, however, so you would need to ask the manufacturer which parameter they are using for the boiling point.

As I said before, you may get some initial propulsion out of the can at -20°C, in an upright position but as the propane concentration decreases, the vapor pressure will drop below 1 bar (atmosphere) and the remaining contents will be unusable, until the can warms up again.

If the can is facing down then even at -20°C, you will get propulsion for the entire contents of the can. The reason is quite simple. When injected downwards, the ratio of gases in the mixture remains the same from start to finish. Only in an upright position will the propane become depleted faster than the other gases. In a downward facing position, the propane is therefore able to continue exerting it's higher pressure throughout the entire discharge of the can.

This is one of the reasons why liquid feed gas stoves are more reliable in cold weather, they draw the fuel from the bottom of the tank.

Hence, the resulting volume of liquid gas in thermos would be about 22% less than the volume specified on the label.

The propane won't all boil off first and leave all of the remaining butane behind. As I'm sure that you're aware, it follows a gradient, where proportionally more propane evaporates than butane. However, the evaporative cooling quickly lowers the temperature down to where the butane is cold enough to barely evaporate. It takes longer for the evaporative cooling to bring the temperature down to where the propane will barely evaporate, so there will be considerably less of it left by that point.

gunna

 

[jump117]

Where did you get your information from regarding it being the lower boiling point? Unless an MSDS states that the boiling point is for one of the ingredients in the mixture, or it gives the boiling point as a range, then the boiling point listed for a mixture is usually the average boiling point.

I think MSDS states boiling point for one ingredient in the mixture, excluding propane from consideration.
To me it seems a reasonable explanation for claimed -11C, based on common sense.

Mathematically, the average value can be calculated by different methods.
But what is the physical meaning of this average boiling point of the mixture of three gases,
propane refuses to boil at -42C to please his neighbors in the mix?

What else, apart from the fictional solidarity with good neighbors,
can keep propane from boiling in opened vessel?

Is it possible that the liquid gases form an azeotrope with a boiling point,
which is different from the boiling points of the mixture components?

I think that at -20C and at atmospheric pressure, only n-butane and isobutane may be in a liquid state,
and at -1C there is only n-butane may stay in liquid state.

In the practice of open thermos, it means that a can should be cooled slightly below -11C,
that allows to use isobutane as a solvent together with n-butane.

Thus, propane is not included in the volume of liquid solvent,
and is not involved in the extraction of all.
Or maybe just for a very short time.

In a downward facing position, the propane continues to exert it's higher vapor pressure throughout the entire discharge of the can.

In the absence of propane, refrigerated container would have to be opened with a can opener.

 

[gunnaknow]

I think MSDS states boiling point for one ingredient in the mixture...

Yes, they do often do this and it's always annoyed me when they don't state which component or parameter they're using for the boiling point. What use is the boiling point listed if you don't know which component that it pertains to? I decided that I'd had enough of this ambiguity, so I ignored the listed boiling point and used the listed vapor pressure instead. What this tells me is that they've based the vapor pressure (and boiling point) on isobutane alone, not the mixture as a whole. I know this because the vapor pressure is listed as 3.18 -3.46 bar (at 25C), which is the same vapor pressure for isobutane. Basically, it's useless information and tells us nothing about the vapor pressure of the mixture.

Mathematically, the average value can be calculated by different methods.
But what is the physical meaning of this average boiling point of the mixture of three gases,
propane refuses to boil at -42C to please his neighbors in the mix?

It's not that the propane would stop boiling, jump, it's that it's contribution to the total vapor pressure wouldn't be enough for the mixture to act as a propellant.

What else, apart from the fictional solidarity with good neighbors,
can keep propane from boiling in opened vessel?

That's a separate issue altogether. The only practical thing that would stop propane from boiling in an open vessel is for it to first lose energy through the act of boiling. As it boils, it cools down, and if the vessel is well insulated then it will eventually stop boiling. This is what I meant by evaporative cooling.

I think that at -20C and at atmospheric pressure, only n-butane and isobutane may be in a liquid state,
and at -1C there is only n-butane may stay in liquid state.

Yes, although the temperature will be rapidly dropping. As the propane evaporates it causes a loss in the energy of the liquid and it rapidly cools. So the propane will hang around for a little while. By the time that the cooling is over, much of it would be gone though.

gunna

 

[jump117]

As it boils, it cools itself down and then stops boiling. This is what I meant by evaporative cooling.

although the temperature will be rapidly dropping. As the propane evaporates it causes a loss in the energy of the liquid and it rapidly cools. So the propane will hang around for a little while. By the time that the cooling is over, most of it should be gone though.

Does it mean from your words that before cooled to the boiling point,
propane gets in a thermos in a liquid state, where continues to boil and cool?

Reducing the temperature of liquid gas in a thermos below the initial value of -20C was not observed,
and there was no sign of even weak boil around the edges.

From this I concluded that the propane completely evaporated during the injection,
when the action of its pressure visually noticeable.

I have argued that ventilation holes in lid are not necessary,
since the release of gas during soaking is virtually absent,
and the excess pressure of propane was observed only during the injection
and it easily goes passing leaky cap.

 

[Gray Wolf]

Does it mean from your words that before cooled to the boiling point,
propane gets in a thermos in a liquid state, where continues to boil and cool?

Reducing the temperature of liquid gas in a thermos below the initial value of -20C was not observed,
and there was no sign of even weak boil around the edges.

From this I concluded that the propane completely evaporated during the injection,
when the action of its pressure visually noticeable.

I have argued that ventilation holes in lid are not necessary,
since the release of gas during soaking is virtually absent,
and the excess pressure of propane was observed only during the injection
and it easily goes passing leaky cap.

I noticed some spitting during injection, which is why I added the vent holes. The difference may be the difference in terperatures and what brand of butane lighter fuel.

 

[gunnaknow]

Does it mean from your words that before cooled to the boiling point,
propane gets in a thermos in a liquid state, where continues to boil and cool?

Some of it, yes. It's only 23°C above it's boiling point, which increases the partial pressure from one atmosphere to about two atmospheres. To compare, if you take boiling water and reduce the pressure to 0.5 atmospheres with a vacuum pump, the water will boil much faster but it won't all instantly evaporate. Then you must factor in that each molecule of propane that evaporates takes energy away from it's neighbouring molecules. As the can is emptied further, the propane is exposed to an increasingly cooler environment and it begins to boil slower and slower. None the less, the propane won't hang around for very long, unless you use a considerable amount.

Reducing the temperature of liquid gas in a thermos below the initial value of -20C was not observed

It is observed through the decrease in evaporation. If the rate of evaporation decreases, it's because the temperature has also decreased. The gas escaping the thermos is taking energy with it. Energy that it absorbed from neighboring gas molecules, the air inside the thermos, the thermos walls and the plant material.

and there was no sign of even weak boil around the edges.

If you mean regarding the propane, it can be at it's boiling point while the mixture as a whole isn't boiling. When the propane level has been reduced in the solution, it's partial pressure won't contribute enough to the total pressure and the mixture won't appear to be boiling. It's similar to a hot cup of coffee. Some of the water molecules will have more energy than the others and evaporate off but because the net energy of the coffee is lower, it isn't boiling.

I have argued that ventilation holes in lid are not necessary,
since the release of gas during soaking is virtually absent,
and the excess pressure of propane was observed only during the injection
and it easily goes passing leaky cap.

The first time that I used a thermos back in 2006, I only made one hole in the lid and it worked perfectly. Thank you for the good conversation, as always jump.

gunna

 

[jump117]

The first time that I used a thermos back in 2006

Your primacy in the application of the thermos to the butane extraction is undeniable historical fact.

I remember that I even defended your priority from foreign attacks on a UK forum.

But the most favorite memory is when you introduced me to your wonderful work.
In my opinion this topic must read every one who is going to do extraction.


jump, on 05 February 2009 - 05:45 AM, said:
what vessel do you use? I think that I’d prefer a thermos flask than coffee-press

gunnaknow, on Feb 7 2009, 02:13 AM, said:
I've been using a thermos flask for extraction, for over two years now.
Nirex has also recently started using the same method. …
Here are mine and Nirex's threads envolving the use of thermos flasks.

As you can see with my thread back in 2006, …
Gunna

jump, on Feb 7 2009, 04:43 AM, said:
It was the first idea that I've thought to myself after coffee-press reading,
it seems so obvious and ... only two independent cases since 2006.

gunnaknow, on Feb 8 2009, 07:20 AM, said:
Make that three independant cases, now that you've also thought of the idea.
Soon there'll be an army of us, at this rate.
…
Gunna

Thank you for the good conversation, as always jump.

gunna

Thank You for the lots of good conversations!

 

[gunnaknow]

Thankyou jump, that brought back some good memories! You and Nirex also came up with the idea independently of me, before finding out that I had done so a couple of years earlier. I may have been the first to discover and document the method but I don't think of myself as the originator. Every idea that we have is borrowed from things that others have done before us. Sir James Dewar had to invent the vacuum flask, someone else had to invent butane extraction and so many others had to build upon the method.

I just put those ideas together, like you and came up with the thermos method. There is really no single originator of anything, countless ideas from the ancient and recent past just converge together and lead to new ideas. We've both shared some good ideas and research with eachother and your thread has now helped to further spread the thermos and winterization methods. Now others can experiment with them and share new ideas.

gunna

 

[gunnaknow]

-

 

[gunnaknow]

-

 

[jump117]

Let's try to turn the discussion to application of gases in the extraction.

One brand of the gas mixture contains 11% propane, and the other 22%.

Which will you choose for the thermos, and which for a tube?

 

[gunnaknow]

I wouldn't necessarily say that one is better than the other. The 22% will become colder and help to stop the butane from evaporating, while the 11% will have more butane to begin with and so can allow for more evaporation of the butane, without ending up with less butane than the 22% at the end. I'm not sure that I'd choose one over the other based on whether or not you use a thermos or a tube. If you have found a reason to choose one over the other then I'd be interested to hear it.

 

[jump117]

If you have found a reason to choose one over the other then I'd be interested to hear it.

In tubes, solvent has a limited contact time with material,
the solvent must be faster to do the job more complete,
this may be provided by the higher pressure,
which rises up the boiling point and allows for gas to be in liquid state at higher temperature.
Under pressure, liquid gas is warmer and dissolves faster.

Also, the pressure moves the solvent through the densely packed material.
So, for tube I’d choose 22%, in hope that more propane gives more pressure.

Since pressure doesn’t play a role in thermos, I’d choose 11%, more liquid gas is the better.