Someone (Air Gas?) was trying to sell us a system. They left me a flyer with the cooling capacity of Liq N2. I’d already done the maths to figure out what I needed to remove to go from +20 to -20 so I plugged their numbers in. As it was a piece of paper, it’s probably been recycled. I’ve asked google to find a copy for me a couple of times without joy.
I suspect I was looking at direct injection of Liq N2 into the solvent. just to get a ball park on how much it would take. I told the boss that there was no way a 200l Dewar would bring 100gal down to -40C before looking at the flyer he had. I either got lucky or cheated. (which is why I’d like to find that flyer and redo the math for peer review)
Here’s what I used to size my chiller.
Ethanol = 46g/mol
has a heat capacity of 112J/mol.K
and a density of 0.7893g/cm3
1gal = 3785.41cm3 (mls)
=> density = 2990g/gal
=> 100gal = 299000g
=> 299000g/46g/mol = 6500mol.
to lower by 6500mol by 40 degrees C (or Kelvin) would be 40 * 6500 * 112 = 29,120,000J = 29,120kJ
you can then pick a time frame in which you want to remove that heat, and size your chiller (convert to BtU). Chiller guy said he got the same answer via a different route.
As I was sick and tired of minions (ok, me too) going to the freezer to get a keg of cold solvent, only to find there wasn’t one. I spec’ed dropping 100gal in an hr (sans losses, and not looking at heat transfer efficiency).
The argument was that one could walk in of a morning and suddenly realize “shit, I need to extract 100lbs of cannabis today…I’d better get some solvent chilled!”
Who the hell forgets they need to process 100lbs of cannabis? So how come they keep forgetting they need to process 15lb every day? (they don’t quite yet. which is the problem)
What that really means is I can scale to 1000gal without going back for more cold** which was the eventual Hemp target I was given when I started looking at this.
When looking at plate and frame heat exchangers, it was pointed out that a double wall separating the glycol from my food grade solvent would be a good idea, as the glycol was going to be at higher pressure than the ethanol, so any leaks would be from glycol to ethanol without that double wall.
Originally this was a three vessel setup destined for an outdoor Hemp farm.100gal each: reactor, Still, receiver, with the reactor used to cool the solvent before adding cannabis. Condenser cooling was to be provided by well water, with water then being used on plants (after cooling of course).
No CUP was involved. Filtering was an unknown. The project manager of the Hemp grow has a PhD and deep experience in filtration/particle distribution, so I figured she’d dig me out of that hole if I set the rig up on her door step and looked pathetic 
As it happens, I would have stumbled across @SamboCreeck.com’s solution just in the nick of time… Industrial Filtration Equipment Q&A
Scaling from 100lb => 1000lb was either bigger vessels or in parallel, depending on results from 100gal.
At some point, recovery from a standard still is going to become less than desirable. As recovery times increase, dwell time in the still increases. eventually you start destroying enough of your input cannabinoids that its not worth it.
But… rules changed, so plans changed. Oregon says that we can process Hemp in a licensed Cannabis facility…so lets do that instead…after some of the parts have been ordered.
Current plan is to use the Still condenser as the primary heat exchanger, and supplement with an in tank coil in the receiver. Doing the solvent “storage” and chilling in the receiver, and drawing as needed for processing in the CUP. As the receiver empties, the boiler is filled (by the CUP). done with the CUP? turn the still on. Come back in the morning to extract and cold solvent. rinse & repeat.
plans call for “trim” heat exchanger right before the CUP. using liq N2 here to chill by the CUPfull would allow solvent temp to be selected on a per run basis, not relevant for Hemp, but appropriate for boutique cannabis.
**given that I’m now using the chiller to cool the still condenser, I’ve got more heat to remove. I’m running at a vacuum and aiming at a boil temp between 25 & 35C, so there’s not a whole lot more.
Can’t wait to play with this thing!!