The experiments I’ve done in miners, I’ve heated first to saturate and then they cooled to crash out. So they have been exposed to heat. If heat degrades the amines then it shouldn’t be doing the Medusa still.
If it was a small amount of amines in there, how can they cover the entire surface area of a diamond to cause it Medusa out? There would have to be a large amount of the impurity in there to do so. If it’s the polymorph of the crystal it changes, then how are we 100% sure it’s an amine and not the colder temperatures?
The pattern I see is when I heat up my miner to saturate, and then let it slowly cool all the way down to the 50f range, the cloud point will show up and in those conditions the new polymorph shows up as well as it begins to crystallize. If I don’t let it get in the 50f range and keep a heater on it to stall the temp drop once it reaches 80f, it won’t Medusa out
…something to do with surface and or interfacial tensions at different temperatures?
Process engineers often express concern about amine reboiler temperatures being high enough to cause thermal degradation of the amine. However, thermal degradation is generally not a concern in amine reboilers heated with steam or heat transfer fluids.
In “DEA degradation mechanism,” Hydrocarbon Processing, October 1982, A. Meisen and M. L. Kennard discuss the fact that DEA and MDEA thermal degradation is minimal up to 400°F. Although the degradation of DEA is caused by reaction with CO2 and not temperature alone, temperature does affect the rate of degradation caused by reaction with CO2. This reference states: “Degradation increases strongly with temperature. This is not due to thermal breakdown of DEA, but it requires the presence of carbon dioxide. Design and operation of DEA units must avoid creation of elevated temperature throughout the plants. Heat transfer surfaces of DEA stripper-reboilers (especially when gas fired) are particularly prone to formation of localized hot spots. To prevent such hot spots in operating plants, DEA circulation through the stripper-reboiler should be kept high and steam (or gas) temperature kept low. In many DEA units only the bulk solution temperatures are measured. It must be remembered that the skin temperatures of heat transfer surfaces can be very much higher, particularly during process upsets. Reliance upon bulk temperatures is therefore inadequate.”
In the paper “Reduce amine plant solvent losses, Part 2” from Hydrocarbon Processing, June 1994, E. J. Stewart and R. A. Lanning mention that the thermal degradation of amines accelerates above 350°F, so the skin temperature of direct fired reboilers should be kept below 350°F. They recommend a reboiler operation with an amine bulk temperature below 260°F. This reference goes on to say: “With hot oil and steam heating systems, risk of thermal degradation is low since the heat media is usually not operated at high temperature. However, in fired-reboiler operation, the temperature of amine on the tube’s surface can easily exceed 350°F. In fired reboilers, forced circulation is often used to maintain low skin temperatures. The rule of thumb is to maintain amine skin temperatures between 300°F and 325°F, and not exceed 350°F. for these temperatures a conservative design heat flux of less than 8000 Btu/ft2 of tube area is recommended.”
Other references indicate 400°F as the thermal degradation temperature of MEA. Keep in mind that the reboiler temperature is set by the stripper operating pressure. To reduce the reboiler temperature, the stripper pressure can be reduced.
Wow. That really sounds like a reaction rate change is happening! I mean - you can limit the problem by modulating temperate. How close do you have to get to 50F for it to happen? Do you have to stay above 80F the whole time (that seems pretty warm still…) Have you done enough experiments with time and temperature to have defined the reaction rate on both sides of that equation?
If it was a really small amount of amines - and they were protonated and they were a catalyst for a different reaction during crystallization, it would not take very much at all. We’re talking less than 1% total Mols and that tips the scales. Especially if what’s in the center is not “contaminated” that would mean that the reaction is happening separately from the crystallization, perhaps concentrating in solution until a specific saturation level is high (or super saturation level is left, since crystallization).
If you cut the diamonds in half do you see any changes between the lattice on the outside and the inside?
Is anyone performing tests for these impurities so you can be certain of their amounts and type? This method of filtration has been around for years… I suppose its possible that some people were not using it and now they are using it more than before (but I don’t know why they would change, this equipment is HUGE and expensive…maybe new suppliers?)
I suppose if you had the impurity. You could separate into two different tanks. Clean up the impurity in one tank and not the other. Then run the tests side by side and see. If its the amine and it is no longer present - then you would not see the issue.
Then you can be sure its the amine and control for amine contamination during recrystallization, etc. You could just start controlling for that. Many amines can be removed with activated carbon filtration - are people doing that and if so, does it work right away? There are other amines that are removed by bubbling using a surfactant and pulling off the scum/foam. I think carbon would be “easier” the other would require getting things wet, and then going through a lot of additional steps to get them dry again.
This is an issue I’ve been seeing from afar but not actually experienced myself firsthand. I’ve been following the science and what has been shared here.
It cools down to those temps and once it’s there it will crystallize in a new bar shape. I don’t think slow cooling is slowing down the reaction as I would be able to see a gradient on the crystal with clear to chalky. What I see is that the shape of the crystal will form in bars once I’m in the 50f temp range. Above 80f we get the usual pyramid structure we’re used to seeing. Only the rocks grown in the cold temps Medusa out after harvest. It reminds me of when I harvest pentane rocks and purge them right away. They chalk out unless I let them cure first and then purge. Maybe the bar shape structures need to slowly purge out to avoid chalking out
they say “been running the same sop for years and now medusa”
no-one has considered maybe there was something in the gas before that allowed them to run so cold with out a polymorph and now that x chemical is gone or replaced it isnt possible and demands a sop change.
honestly i hope i have this issue as it speeds things up on a cold crash to re-x
Azeotropes in general have a lower bp
So for there to be an azeotrope that has some volume the counterpart must be available in obvious numbers (doubt it ) but
I think what needs to be done is send a butane sample to a lab that tests butane quality
Years ago @SkyHighLer posted info on such lab
This is a very intriguing idea, especially with smaller stronger carboxylic acids! (e.g. citric acid)
It is hard for me to imagine the acidity of cannabinoid acids being strong enough to ionize ammonium salts, but perhaps when very little or no water is present, it can happen???
It IS technically a polymorph, since the crystals have a distinctly different structure when precipitated from Medusa-fied butane compared to the structure when precipitated from other alkanes (including clean butane), but they are both composed of pure THCa.
Using what temperatures & pressures in butane, @Waxplug1, have you been able to replicate the THCa polymorph (prism-shaped) from the medusa photos? Have you also replicated its propensity for turning chalky and crumbling? I am asking sincerely, not sarcastically.
EDIT:
I just read this as an answer to my previous question! Thank you! Any pics?!
Ah, I hadn’t read this until now, but I fully agree with the idea of using solutions to determine root cause!
I’ve said all I can about pH and water in the past, too, @EverettMarm …and I’ve come to recognize the need for common terms among the community. When we say “pH”, it also means “Lewis” concepts of electrophilic & nucleophilic in “dry” (although not necessarily anhydrous) systems, such as the “solid state pH effect” in adsorbents, I wrote about. Having a background in pure chemistry, it takes some getting used to the vernacular!
Is this a fact ? Does Medusa butane boil at a lower temp than straight n-butane ?
Finding azeotropes other than the well known
Usually used solvent ones is a tricky game
Especilly identifying them in gaseous form
But the boiling point should be easy
Just wanted to say the concept of pH - which is the -Log(|H+|) - applies to anything that can donate or accept protons. Not only water. The pH scale in non-aqueous solvents will not be 0-14, but anything that can act as a Bronsted acid (no matter how weak or strong) will have a pH scale associated with it when used as a solvent. See image below.
The pKa of a molecule is a property dependent on the solvent. It is defined as -Log of the equilibrium constant of the reaction between a protonated molecule and the solvent to form the protonated form of the solvent plus the conjugate base of the molecule.
In the context of two molecules meeting in a different solvent, their individual pKa values in water would not be very useful, since the stability of the acid and base forms will be very different. A solvent like water might be able to very heavily stabilize a conjugate base, heavily favoring the dissociation reaction of a Bronsted acid. A molecule might be more acidic or more basic in a different solvent, depending on how stable the species are in a more polar or more apolar medium.
A more useful approach when molecules do not appreciably protonate or deprotonate the solvent would be to carry out computational simulations of the protonated and deprotonated forms of each molecule within the solvent of interest, then see which one is thermodynamically more favorable. That would tell you what distribution of species to expect if you mix them in that solvent, at least after equilibrium is reached.
About the deprotonation of organic compounds, depends. An organic compound that is an extremely good Bronsted acid would be able to appreciably protonate a solvent or an excellent Bronsted base deprotonate it. This acid/base talk is all relative. Butane is not easy to deprotonate, but add Tert butyl lithium to it and it will be deprotonated.
