I run a wiped film for CBD distillation. My vacuum is typically within the range of .000375torr to .008torr. Now, as we know, the greater the vacuum, the lesser the internal vapor pressure and therefore the lesser heat required to force your compounds (in my case, the stable CBD) into a gaseous state.
Now, with a wiped film, you’re passing material over a heated evaporator to heat it up as it falls. Heat along the column doesn’t necessarily mean the heat of the material itself, and I would then think that as material reaches its boiling point on the evaporator (whether your evaporator is set at 160C or 240C) it would evaporate & condense either way. The deeper a vacuum you pull though, the tighter the differences in boiling temperature become for the compounds contained within your crude. This would mean that at an ultra-low vacuum you may be able to evaporate your compounds at a much lower temperature, but you’re evaporating everything at a much lower temperature, making it significantly harder to fractionate.
But, if material reaches its boiling point on the column and evaporates either way with minimal degradation, wouldn’t it make sense to have a vacuum at lesser strength (in the .01 to .005torr range) and run hotter temperatures? This would allow for a faster throughput (by increasing feed speed) better fractionating, and I’d think no significantly higher chance of degradation, as the material is evaporating once reaching its boiling temperature on the column either way.
I hope this is making sense – I’ve just noticed after fixing a leak in my system and running much deeper vacuum (down to .000375torr) it’s become harder to successfully fractionate, and I have to run slower, even though all my temperatures are lower.
Wondering if others have thoughts on this. Deep vacuum? Yes. Deepest possible vacuum? Doesn’t seem ideal. Perhaps a system that incorporates a nitrogen feed to control exact vacuum would be most ideal.
Edit: I mean this largely and specifically for CBD, as it’s very stable and resistant to degradation outside of oxidation.
How exactly would a lower vacuum allow you to feed faster? If your vacuum is deeper, you will distill faster when your evaporator is set at same temperature as it was before. Or do you mean that when you feed quickly at high vacuum, the quality of your product degrades? If so that may be due to other issues. I’ve had great results running at that low of vacuum and 160C.
Essentially, the deeper the vacuum, the smaller the temperature window for separation. If you view the length of the evaporator as essentially a pre-heater, with just the necessity that your oil hit the critical temperature for evaporation just before the end of the evaporator, it allows you to push your evap temps much higher – and then your feed rate much higher to keep up with the constant need for the “clearing” or continual passing of material/reduce residence time. I’ve been making 80%+ distillate at a maximum rate of 5kg/hour on a system rated for 1kg/hour. Which I know might sound insane and probably partially unbelievable, but it was achievable at a lesser vacuum running temps into 220C (again, just because your evaporator is that temperature doesn’t mean your material reaches that temperature the very moment it touches the evaporator) but much more difficult at greater levels of vacuum, as the temperature window/line between what constitutes the material you want vs the material you don’t gets substantially thinner. Essentially, I’ve had better luck at ~.05torr than at .000375torr, as the vacuum at that point is still substantial enough to dramatically lower the boiling temperature (and therefore chance for thermal degradation) without being so low that it blurs the temperature lines between fractions – allowing for substantially higher evap temperatures coupled with much higher feed rates to make up for that higher evap temp.
I see what you’re saying now. At such extreme temperature conditions as that, indeed you may well be getting heavy unwanted compounds to come over under vacuum. At 160C there isn’t as much of a risk of that happening even with very deep vacuum. Nonetheless, you ought to be able to achieve similar rates of evaporation turning the temperature lower to compensate for the vacuum. Is the difference you’re observing with the high vacuum that the oil looks different cosmetically, or that the test results are now lower?
Was saying I’ve been getting very high purity PLUS very high throughput at 220C, as I’ve dialed up the feed rate in a huge way to compensate for the higher temperatures. Essentially, although the column is 220C, it’s only being given enough residence time to heat the material to ~160C.
I’ve been finding it substantially slower with a much lower vacuum, as I can’t dial up the temp + feed rate the same without carrying undesirables over.
I am in a similar situation, I have greatly increased vacuum depth by altering my decarb/terpene removal step and replacing my diffusion pump. In the past I would distill at 160-170c around 50-300 micron. Now I distill around 130-150c anywhere from below 0.5 to about 5 micron. My vacuum is measured after the cold trap, so my values may be deceivingly low compared to a gauge in the vapor path. I find that I get generally better color at the same speed as before, or the same color and better throughput. I also find that with deeper vacuum I can get much better recovery/yield. I am now redistilling old residue and getting a good recovery (>20%) on old residue that has already been redistilled at 170C, and I attribute this to vacuum alone. Around 1 micron I have found it possible to distill as low as 115C at an uneconomically slow speed, but yielding a very light, high purity product (>98% cannabinoid on 1st pass). Running at 220C and your vacuum I would expect literally everything you feed to distill off. Turn the temp down considerably and adjust feed speed accordingly, you should see much better color. I am tempted to run my system at 220C to see if I can turn my 500g/hr system into a 5kilo/hr system. Although I am sure the color/quality wouldnt be much better than the crude was to start with haha. What distillation and vacuum system are you using to achieve such depth? I must ask those are very impressive numbers. You could easily integrate a nitrogen-based vacuum control valve to stabilize vacuum depth, although I like to assume that deeper vac is always better for THC distillation. I have heard Summit makes something along those lines but I have no experience with it.
I once read on this site that a good starting point for wiped film is to gradually bring temperature up until distillate is just barely flowing. At this point you should achieve the best quality distillate for the crude you are feeding. Increase temperature until you find an adequate balance of speed and quality. This will be different depending on crude quality and distillation/vacuum systems obviously, but this is how I found my balance.
I admit it is a clever technique and quite the opposite of the way most people are doing it. It doubtlessly took a lot of tuning to get the feed rates, temperature, and vacuum all matched. Now it will take the same to get good parameter sets with deeper vacuum. Definitely with this deep of vacuum you’d have real difficulty running at 220C without just carrying over all the darkest components. Do you think you were getting excellent first pass yield running your fast method? What sort of residue to distillate ratio were you ending up with? What was the residue potency?
As they say, necessity breeds innovation. We needed faster throughput, I spent months getting it dialed in haha. I was getting fantastic first pass yield with the moderate vacuum – with very high quality. Don’t have in-house analytics yet, so I can only comment based on the one or two COAs we’ve gotten – but our 2nd pass distillate was showing 84% CBD and 93% total cannabinoid content.
But yes – at the much deeper vacuum, temperatures above 170C seem almost impossible without carrying over undesirables considering the blurring of the lines regarding temperatures used for evaporation. Much darker distillate, much slower pass. Only issue is that with the current setup, the previous “leak” technically meant the introduction of oxygen, which would certainly mean at least some measure of oxidation (but of course, how much? Likely not a ton) but it seemed that running at a more moderate vacuum with this evaporator feed strategy was much better than much deeper vacuum. Only downside is it took a lot of dialing in, with there being 6 equipment variables to account for (feed speed, feed temperature, evaporator temperature, wiper blade speed, condenser temperature, vacuum depth). But once getting it down, it was a dream. I may go back to de-greasing my feed piece to allow for that ever-so-slight leak again
Eventually, I absolutely have a setup in mind that would allow for an absolute and specific nitrogen feed to ensure a specific vacuum at all times.
That is pretty good. Definitely not as good results as the “low and slow” method, but it’s got some obvious advantages.
They make vacuum bleed valves that would let you tune it; then you’d just need to hook it up so the intake is nitrogen. You could even use the old-school ochem balloon method. However at this low of concentration I doubt the oxygen does much harm.
Oh yeah, definitely for ultra-high purity I’d still advocate for low & slow. But our current business model advocates for high CBD isolate production, so 84% distillate is definitely sufficient for our crystallization methods for high throughput. Hence, high distillate throughput takes precedent over quality if it’s 4kg/hour vs 1kg/hour. With proprietary crystallization SOP, isolate is still coming out at 99.8%+.
But yeah – If I wanted the best of both worlds, I’d do first pass with a nitrogen bleed, second pass ultra-low & slow at exact temps. Tbh I want to run a 140-150C condenser to see if I can accomplish CBD/THC separation Don’t have the right equipment for that yet though.
I was trying to post links for some German technology making the seperations of THC/CBD
(Not allowed ) that can help to acheive your objective however text me or email me if interestead
You’ve just lowered your target high purity temp, lower vac? Speed up feed or lower temps. You do not reduce everything in a solution at the same rate.
We see an example of this when the boiling point of water and ethanol form an azeotrope and evaporate at the same temp.
You are suggesting the lower vacuum is causing CBD to form an azeotrope with a heavier molecule, I’m not sure if that’s true.
Many ways to skin a cat, vac depth does alot, j attenuate for different affects. I use vac to decide to strip only heads off, or strip mains and tails from the tar fraction. But if you attain the highest vac depth and find youre pulling too much off the wall to the condenser… just speed up the flow a little, the faster refresh rate on the wall will keep the material about to exit the wiper from releasing the reds… that way deep vac and high temp can be used with increasing speed
You can use a solenoid valve to close when the vac gets too low. Vacuubrand makes a pretty good one that i have. Also digivac just came out with a super accurate one
It’s about finding a balance. My best test results came out at 205 running a medium pace. In my experience, you run for color yield and potency. But you only get to pick 2 of the 3.
There are ways to get all 3, it just requires hard work and time… its not an engineering conundrum… its just knowing how. I posted recently on the method.
I’m not saying it’s impossible I was talking more from an equal work perspective. To get all 3 you need to put in more work and it’s a question of if you can run an efficient business off of it. Honestly i prefer darker oil I can get good yields and high potency and run fast. The extra work to make it have good color is worth it for some products but I usually have an end goal in mind for when I’m doing that.
