Do large scale Ethanol Extractors use copper condensers or just stainless steel?

If you need to prototype you could use copper. It’s quick and easy to fiddle with. I would not use it personally. The fact that side reactions may occur, copper salts may presist, and solder joints make it a less ideal choice. If your eager give it a go, there are lots of people dumping etoh through a washing machine. I refuse any of these practices, but they exist. So why not the copper?

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The washing machine is definitely not GRAS

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yea maybe, for the sake of argument im not distilling cannabinoids thru it just terpenes and ethanol. and i could redistil thru stainless steel. and all drinkable alcohol has touched a bunch of copper and there is no copper salt, salts only form after time and neglect

On the contrary, a copper still would be safe to distill etoh in. Especially if you need a still for alchol refinement. Copper shouldn’t be used in a processing vessel in that manner. Copper oxides could accumulate on surfaces, this could give your concentrate a nice statue of liberty green. Especially in the presence of co2 interacting with water in the etoh. You would be creating carbonic acid, this would attack the copper vessel. Do you need a vessel made? I employ a welder, you could message me for rates.

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Copper has been used in cookware and even water pipes for a long time, and still today. However, copper can in some uncommon instances present a metal salt/corrosion problem in cannabis chemistry, such as in hydrocarbon vapor recovery from resin, in the presence of certain resin compounds, and water. It usually doesn’t react without water present, unless there are species present that are specifically reactive with copper, such as thiols and thioethers (sulfur compounds, like the ones often needed to be removed from concentrates, which makes copper a useful tool), alkylphosphines and other phosphorous compounds (some broken parts of the “gums”, for example), and pesticides which have all sorts of weird functional groups sticking out of them that copper likes, such as alkynes and cyanides (both are triple bond groups). Copper is a catalyst capable of single-electron transfers, which makes it willing to react and assist reactions as an intermediate, but catalysis would only change the stuff that touches the copper, and not the copper itself, so since we are worried about blue & green copper salts or organometallic complexes with the soft copper ligand it is more likely being “poisoned” or irreversibly reacted with things in the resin. Although copper can be used in coupling reactions with certain carboxylic acids, I do not think the cannabinoid acids are strong enough to react with copper, even with water present… that is to say, I have never seen or heard any reliable evidence to support this idea.

Ultimately, I believe it is some very “light” compound(s) that cause the problems when water is present. I deduce this from the facts that…
A. I have never had any problems with copper distillation column packing in dry or moist distillations; that is previously dehydrated and decarboxylated resin, nor even when the distilland was slightly wet at first, and
B. From the fact that the only place I have ever seen blue & green funky copper salt corrosion from resin was inside copper tubing in recovery pumps, upon which the operators were not utilizing filter driers… so the vapor being recovered contained moisture. This was a few years ago, before people knew better what they were doing.

Oh, and the one other place I have seen copper compounds that could have possibly contaminated my cannabis resin was in the puddle of faint blue cloudy water and fusel oils leftover in a rotovap after the initial distillation of brand-new bulk190 proof ethanol. Presumably this blue color was from copper oxide present in the enormous copper stills used to make the ethanol. So there is just one more reason to pre-distill your solvents at a temperature at least 20°C cooler than that at which it will be distilled from your cannabis resin before ever using said solvents to extract cannabis!

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I used copper packing on my recovery still at 5gal scale.

Moved to copper column and condenser on my early keg based 15 gal still.

On both occasions that I tried recovering the last of the EtOH off the extracted plant material by distillation, the alcohol I got back was vividly blue. My assumption was Copper Sulphate. With the Sulphur presumably coming from proteins in the plant material (amino acids Methionine & Cystine).

So my vote would also be to stick with stainless.

Probably should have tried the GRAUS cannabis disorienter Supercritical420 & Future have been using. Washing Machine "Salad Spinner" tek

Couldn’t convince myself the wetted path was appropriate for Meds, couldn’t squeeze R&D funds to solve that from the ground up.

It never occurred to me to JUST use it for recovering the last bit of solvent. :thinking:

Looks like the CUP 15 has been ordered…

Yea, copper’s wide but limited reactivity is why it’s used spirit distillation, many conjures thats arent sulfer based are known to be affected by copper at least to a small degree. I just figured that very few cannabinoids will be volatile enough to make it over and almost all the terpenes in cannabis are found is another plant that has been distilled with copper condensers.

Any acidity will corrode copper, acid vapors can Co distill with etoh. Terpines on their own have no ph, due to non polar nature. When emulsifyed with water, or traces of water in etoh it can modify the ph. Try to test the pH of a hydrosol vs the separated oil. It proves the theory. Before you do the build get some copper and immerse it into a solution that will simulate operating. Get some copper test strips meant for aquarium use to test. Share the findings with us.

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i dont use water so its not really hydrosol right? the only acid they would be exposed to is the ethanolic carbonic acid but that should be almost entirely dissipated by this point, i wouldnt be able to pull a vacuum if there was any co2 left in solution, but i will try measuring the ph next time with universal strips

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Exactly!

So what if I have a still for reclaiming ethanol that’s all stainless steel except for the condensing coils those are copper. My builder is trying to say the stil would be 20x slower with stainless coils. Could I get some help on the subject?

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your still builder does understand the thermal transfer properties of those two metals.

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having decided that you’d prefer stainless, the trick is then to change some of the other variables in the equation. eg the ΔT , heat exchanger surface area, or flow rate.

@TheGratefulPhil was kind enough to work some of that math

edit: and thanks for bringing this up. I was aware that copper was more efficient, but was unaware of the magnitude of the difference. check the tiny condensers on the first still I built.

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Do I really have to go with stainless just on the condensing coils or can I have the condensing coils copper and everything else Stainless and still be fine?

This unit will be used for distilling ethanol out of the oil It is only a reclaim still so technically the cannabinoids in the oil which is left in the still will never pass through the Copper except for Turpines

@Champone I think cyclopath summed it up great here.

The problem isn’t the cannabinoids touching the copper, but rather what the compounds that will distill off with the etoh from the concentrate will do to the copper, possibly contaminating your ethanol and subsequently contaminating your extract that you re-use that ethanol for. I have had the misfortune of ending up with blue etoh when running a mash for my own personal vodka when I simply added baking soda to the wash in an attempt to achieve a more neutral spirit. Neither the baking soda nor the fermented wash touched the copper, but there was a reaction between the yeast nutrient I used and the baking soda which formed compounds that created copper salts, which then ended up in my ethanol. Copper salts being as toxic as they are, I decided to just scrap the ethanol and do a laborious break-down and cleaning of my still rather than try to clean up poisoned product. I have had the same blue ethanol problem when I try running too far into the tails, which probably means it is something with a higher boiling point than ethanol that co-distills that is pretty rough on copper. I wonder if that’s also what was causing the blue in cyclopath’s experience?

You can probably get away with using a copper condenser if you just distill off enough ethanol to move the product into a rotovap for finishing. Cyclopath stated that he didn’t have any issues with the color of his ethanol until he tried squeezing out the last of it from the extract. Hell, I use a copper reflux tower to re-proof my reclaim and I have had zero issues. But if I was going to invest the money into it myself, I’d rather just do it right the first time instead of having more expensive issues down the line.

I usually still it down to the last 10% then finish off in a roto. So I would be ok with copper?

I agree with doing it right the first time. My entire still is stainless except for the coil inside

depends what you mean by “coil inside”.
you using something like this?

image

We run Ethanol only and use stainless steel for everything.

It’s a bobkabob Condenser that’s the only part that is copper all the rest is stainless