Looking for the advice to remove residual alcohol after distillation

Is anyone knows the fast way to remove residual alcohol from the concentrate? Even after vacuum oven, concentrate has approximately 5400-6000 ppm of alcohol. The allowable limits in our cities between 50 - 300 ppm. I know one method using a hotplate stirrer. This method thoroughly described on skunkfarm site. First I cannot process a large volume of concentrate and second it take almost 2-3 days. I have to say that method works but makes oil slightly darker. I've heard that people use a slow cookers for it. I would appreciate the advice

Comments

  • A true problem; has been for the ages.
    You would love the machine from colorado extraction systems. Check out their website. My wife and I purchased the sprayvap and we love it. The Solventless category of Concentrates now has a new entry with this evaporative spray technology, utilizing the best solvent for this purpose-ethanol.
  • It should definitely, definitely, definitely not have that much Ethanol in it after the vacuum oven. The variables you're operating your equipment under are insufficient. Are you using a rotary evaporator prior to putting it into the vacuum oven to remove the bulk of the solvent?

  • @kris said:
    A true problem; has been for the ages.
    You would love the machine from colorado extraction systems. Check out their website. My wife and I purchased the sprayvap and we love it. The Solventless category of Concentrates now has a new entry with this evaporative spray technology, utilizing the best solvent for this purpose-ethanol.

    it looks as a normal falling-film evaporator, what are the pros?

  • Agreed that 5000 ppm ethanol sounds high for anything that's significant spent time in a vac oven.

    First suggestion is try a different lab. Some of the terps and similar compounds can cause false positives on solvent screens. Some labs are on top of this, but many are not.

    Beyond that, you need to agitate/stir under vacuum. Mild heat will def make it go faster. The darkening is due to oxidation; minimizing exposure to air (a la vacuum) and light will prevent this. You can use Roto, Eden's winterizer, or for smaller amounts even a cheap short path setup. You can purge completely even with simple setups, but it does take time.

  • Here's a method we discovered for purge residual Ethanol, post witnerization. Our residual solvent analysis consistently comes in between 54-32PPM using this method.
    http://www.catscientific.com/purge-ethanol-cannabis-oil-using-cat-mcs78-hotplate-stirrer/

  • Augold, the method you are referring to is ours. The MCS78 Hotplate Stirrer's volume limitation is 3.5 liters. we have yet to discover another method that works this well. Yes, it takes two to three days to process, and when completed you have your desired outcome, 54-32ppm

  • Add some water to the solution near the end of the extraction and boil it off as well. The water will drive off the solvent. make sure you expose the solution after to the air and keep it at a temperature of 250F for 24 hours. The last bit of water is hard to completely drive off an the oil may crackle a little when smoked but it drives off all the solvent from my experience.

  • I am using a vacuum oven from Across International and oil pump. Vacuum is close to 29.95 Hg. I was trying a different temperatures from room to up to 115F. Keep oil there for 1 day, 2 days. Result is still 5000-5600 ppm.
    I've tried the method suggested by CATScientific. I was able to remove alcohol completely. My volume of oil was 150 gr. One part of the process is decarb. the oil. My oil is already decarbed since I am baking the trim. One more decarboxilation is kind of unnecessary. Second it took 2 or 3 days, sorry I do not remember exactly of how many says I kept stirring it. Third our amber oil getting darker because of oxidation.
    DDroyd suggest to add water and boil it off. I think DDroyd is using an oil bath for that. Keep oil at 250F for 24 hours, I am sure it would remove all alcohol because it is way above water and alcohol boiling points. But then again oxidation is a problem. Everybody wants light color oil. The process definitely should be done in vacuum. Let's say we are going to mimic CATScientific process but with vacuum. One if the idea is
    using a roto evap to recoup the alcohol. Let's say after most of alcohol stopped dripping, collect it. Add water to the oil in proportion as CATScientific suggested. Start boiling the water out, continue to use roto evap. First, 120C depends on vacuum, it will be much less temperature, second it is in the vacuum. When mixture of residual alcohol stopped dripping, use the stirrer to do the rest as CATScientific suggested. But then again warm oil will be exposed to the oxygen for 2-3 days. Another issue is water/alcohol steam will go through the vacuum pump. Unless it is a fancy chemical withstand pump, it could destroy the pump. Any comments and ideas are welcome.

  • @augold said:
    I am using a vacuum oven from Across International and oil pump. Vacuum is close to 29.95 Hg. I was trying a different temperatures from room to up to 115F. Keep oil there for 1 day, 2 days. Result is still 5000-5600 ppm.
    I've tried the method suggested by CATScientific. I was able to remove alcohol completely. My volume of oil was 150 gr. One part of the process is decarb. the oil. My oil is already decarbed since I am baking the trim. One more decarboxilation is kind of unnecessary. Second it took 2 or 3 days, sorry I do not remember exactly of how many says I kept stirring it. Third our amber oil getting darker because of oxidation.
    DDroyd suggest to add water and boil it off. I think DDroyd is using an oil bath for that. Keep oil at 250F for 24 hours, I am sure it would remove all alcohol because it is way above water and alcohol boiling points. But then again oxidation is a problem. Everybody wants light color oil. The process definitely should be done in vacuum. Let's say we are going to mimic CATScientific process but with vacuum. One if the idea is
    using a roto evap to recoup the alcohol. Let's say after most of alcohol stopped dripping, collect it. Add water to the oil in proportion as CATScientific suggested. Start boiling the water out, continue to use roto evap. First, 120C depends on vacuum, it will be much less temperature, second it is in the vacuum. When mixture of residual alcohol stopped dripping, use the stirrer to do the rest as CATScientific suggested. But then again warm oil will be exposed to the oxygen for 2-3 days. Another issue is water/alcohol steam will go through the vacuum pump. Unless it is a fancy chemical withstand pump, it could destroy the pump. Any comments and ideas are welcome.

    I use a Rotary Evaporator to remove the bulk of the ethanol in my solution and then use an AI Oven @ 29.95Hg for the tails. I only dry on a hotplate prior to distillation, and even then it can still be done under vacuum in an oven with a suitable beaker. I would never allow any of my processes to take "days". You have an oven and someone taught you how to winterize, but they neglected to give you the procedure end to end. I would use a diaphragm pump for bulk solvent evaporation unless you're used to using a rotary vane pump for volatiles and hate pump oil. I recommend the Adixen ACP 15 for larger units and the Vacuubrand MD 4C for Evaporators but that's typically 10L and above. Vacuubrand makes a 2 head pump that may be suitable for a 5L benchtop evaporator. Welch also makes good diaphragm pumps.

  • Thank you ThomasWR.
    You are right regarding the process. I've never knew the complete process. I just simply follow the instruction from skunkfarm site of how to make cannabis oil. It is definitely something missing there. Instruction is very simple there. Mix cruide oil with alcohol 1 to 10-15, freeze it for 48-72 hours, filtered few times and evaporate the alcohol. Put it on the shelf in the pan for 2 days for a dry run, and use it.
    For 10L evaporator I am using a diaphragm pump. It is a cheap pump. It was cost only $700 and able to create vacuum not deeper than 26.5-27 Hg. It maybe not enough for evaporation. I do not know that. The evap bath is set to 54C and 70 rpm. After evaporation I pour the oil into the pans and place them on the warm pad with fan above for the 24 hrs for a dry run. Than I place the pans in vacuum oven. Since I read somewhere that the diaphragm pump is not able to create a deep vacuum, I am using a rotary vane pump. It does create 29.95Hg. Lately i made a very interesting observation. I had a rotary vane pump before, even few of them and I could set the oven for 115F for 24 or even 48 hours. After 24 hours oil was good, clean but tasteless. With the current pump if I increase the temperature higher than ambient, after 24 hours oil has a hint of nasty, like burnt taste. So, currently I do not even use the oven heating feature. I think something in the oil got burnt.

  • I would love to read a comparison/contrast between the Colorado Extraction Systems machine and the Eden Labs vacuum distillation machine, for ethanol only extraction. We are considering purchasing the 100 gallon Eden Labs machine. What are the pros and cons of these two systems? Thanks very much in advance!

  • So we follow similar processes to our fellow hydrocarbon extractors. After the rotovap to pour onto oilslick or pyrex dish and keep the film thin. More surface area for the ethanol to purge off. We also take the dish out every couple hours and agitate (if its a lot of oil in the pyrex and cannot get a thin film). Its not the best due to oxidation but this gets most of the ethanol out. Would be ideal to have a battery operated mixer that goes into the vac oven.

  • edited October 2017

    Thats a ton of residual ethanol in your oil. Plate the oil thinner and pull full vacuum in an oven at 70C for 30-60 minutes. There should be way <300 ppm after that, if you don't pre-decarb the plant material this is an ideal time to decarb the oil.

  • Buy a rota vape machine and you will be good to go
  • Magnetic Stirrer with hot plate is also useful for the distilation. These are well for their heavy duty and robust constructions.
    newmeditech.com/products/lab-equipments-products/magnetic-stirrer-hot-plate/

  • I do things a little different. For medical grade I want cold processed full spectrum with no separation or decarboxylation. I use a magnetic mixer for a few minutes just capturing all the trichomes and that is all I want. 98 proof is out there, I use 94 proof, filter and evaporate in a slow churn until it gets to the consistency I want. I am after the thca and I do not heat the mixture at all. 90% of everything I want is in the ball and stem of the cannabis trichomes. Lots of thca and phytocannabinoids still in the leaf, but that's ok, produces a nice pure honeyish oil you can do anything with. A dab will blast you if that is what you want my peeps like it in controlled mg coconut oil caps with thca, which is non psychoactive.
    Are you good at chemistry as you can get 90 % pure with centrifugal partition chromatography

    If you want full spectrum to dab with alcohol, distill then magnetic mixer with hot plate. If you want to do volume get a heavy duty mixer that will go up to 300 C and you can run 2 liters at a time, if you want to run more volume get two mixers. Two liters is a lot, like a a half kilo of flower. Which is no problem, 4 to 6 hours once you get it down.
    peace and good health to all

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