I have seen other people post about making a “still” to clean the used IPA. So I tried it with a pressure cooker and a coil of copper pipe in a cooler for the condenser.
Well that attempt worked but was very slow. And if you used to much heat the IPA would boil and run dirty IPA into the condenser. It also was very slow and not be worth the time.
So I had an idea to use a vacuum pump to see if it would speed things up. First attempt I put the pump pulling the vapor from the pressure cooker. That made the pump get very hot so I moved the pump to pull from the condenser. That worked pretty good, still not fast but it may be worth it. What happens is pulling the vacuum keeps the IPA from boiling and it keeps all hoses and the pressure cooker lid tightly sealed. So basically you use a lot of heat on the pressure cooker and that speeds things up.
I did not measure the speed or timing yet but will do so next time. What was left over in the pressure cooker was a thick molasses. I had been doing clear and black resin. I need to find a way to clean that out of the pressure cooker.
A professional solution takes about 2~3 hours for 10 liters. I read you didn’t measure it you but state it took too long so how many hours approximately?
A vacuum on top is only needed for higher temperature boiling solvents (such as TPM) as IPA boils at a lower temperature than water.
Pro solutions use special bags (they need to survive high temperatures) that retain all the impurities after the recycling and then you just remove the bag and throw it away with any cleaning need.
Also be careful with home made solutions (and cheap ones) due to all the dangers involved.
I was thinking of some plastic bags. Just need to find what will standup to IPA and heat. The vacuum pump lets me keep the heat on without it boiling the dirty IPA into the condenser. My guess is I get 1.5 liter or more in one hour.
Doesn’t the vacuum pump mean the boiling temperature of the IPA is reduced, so you don’t need heat?
I guess it depends on what you call vacuum. I have an refrigeration pump that goes down to 200Torr or so. That causes any moisture in the refrigeration system to evaporate at room temperature.
I would guess the boiling temp is reduced. My vacuum pump is a Thomas 107CAB18-H which is a diaphragm type pump that does not need oil. It only pulls 23 inches. I would guess it would work without heat but that would provide very slow results. What I find is I can keep the heat on full and it does not spit out dirty resin. So it really speeds up the results with the high heat. Don’t know if the IPA will damage the pump diaphragm yet.
Well I tried a plastic bag so I could do an easy clean up and that test run failed. The plastic bag leaked a little and it would pull the bag with the vacuum so the dirty IPA would get into the vacuum inlet. I think my pan that the bag sits in needs to also get supplied by the vacuum to keep the bag from pulling off the sides of my pan.
Did another test of my unit. I made a stand to hold a 1 gallon storage bag and put that in my pot. What I find running my vacuum pump is that 27 inches of vacuum makes the IPA boil violently. When I reduce the vacuum to about 15 inches it seemed to work better. But I see the IPA does not produce much vapor because I see my clear hose going into the pump fills with IPA and then pulls that IPA out and it builds again. When I vent a little vacuum in my pot then it pulls the IPA consistently. So not sure if I need larger dia. hoses and condenser to make things run better. I will have to watch the MOON SHINERS show to get more ideas about the design.
Grab one of the cheap 3 gallon moonshine stills off eBay or Amazon. Make sure by confirming with the seller that the still is made of the type of stainless steel that will heat with an induction cooktop. While you’re shopping online grab a single-burner induction cooktop which allows you to set the cook temperature in either C or F degrees. Be sure the cooktop is of sufficient diameter so that the chosen still will fit on it.
Induction cooktop with temp control is key here because the cheap resistive burners put out way too much heat and will burn the resin while distilling, and you’ll have impure distillate plus a burnt-on mess at the bottom of the pot (voice of experience) that you will spend hours scraping and hacking with metal implements to remove.
Fill the still pot with your dirty IPA, set the burner to 83C or slightly higher but not too much higher. If you get it too high then it boils off some of the resin components and will taint or cloud the distillate. Not a huge problem, you can just re-distill the distillate at the correct temp and it will come out clean.
Note that pure IPA boils at 82.6C (180.68deg F) but with the resin impurities this will require a somewhat higher temp. There is enough slop in the accuracy of most cooktops you can get by setting to 180F but definitely experiment with the temp setpoint until you get clear distillate.
Once the IPA is boiled off, it will stop distilling and you can switch off the heat. After letting the pot cool, you will discover a gelatin-like puck in the bottom of the pot. If you haven’t set your temp too high, you will be able to just slide this out into a metal pan and set outside in the sun for a few weeks to dry to solid. Then you can dispose of it properly.
Remember IPA is a fire hazard so definitely do this at your own risk. Distill outside away from people and structures.
Thanks. Never thought about induction heating. I did see a different type of distillation that uses a 3 or 4 inch tube and a copper pipe coil in that tube that your run the cold water through. I was running my vapor thought the copper tube but I think that restricts the flow to much.