Hi, I have been asked to build a distillation unit for methanol recovery at work. We generate about 100 L of glycerol a week so I was thinking of using a stainless 200L drum and about a 5' 2" copper pipe for reflux.
I know that controlling the drum temperature isn't as important as controlling the head temp. I was thinking of having a temp probe controlling a solenoid that opens a valve and cools down the head with cool water.
I have a pretty good budget and I have to do it properly and safely. I've read through the moonshine designs but they are a little less than professional then what I am looking to build.
If anyone has any suggestions or designs that could help me it would be greatly appreciated.
I can post progress pictures as we build it for your interest as well.
Speak with Jon Heron about vacuum recovery of MeOH. Seems to be the least energy-intensive. Not sure if refluxing is so important. You have to have a chilled receiver for the MeOH to condense in - the colder the better. The receiver goes between the evaporator and the vac pump.
Ya I am planning on using vacuum as well as doing it under nitrogen. We use vacuum pumps to move around our fluids so I will just hook one up to the still.
I found a company in Toronto that makes custom stainless tanks so I am working with them to try to build some components.
When I did vacuum distillation on crude biodiesel to remove excess methanol, I used ice water to cool the condenser and ice to cool the receiving flask. I was vacuum distilling at a pressure of about 300 mm Hg. If you pull too much of a vacuum, the condenser has to be very cold, and the receiving flask has to be very cold or your methanol vapor will not condense in the condenser. The methanol vapor will go out through the vacuum pump. Cheers
That is really good to know. I found my biodiesel to contain on average about 4% methanol so wouldn't take an uneconomical amount of energy to boil off the last 4%?
I use methanol in quite a bit excess so my glycerol is containing almost 25% by volume of methanol. This is what I am planning to distill.
At what temp do you keep the head at under that pressure?
I am just now reading the (big) book "Alcohol can be a gas", mainly about small and mid scale ethanol production and all the stuff that goes into building a business around it but the still info will be the same for methanol except for the reflux column top cooling temp. There 190 proof packed column reflux still info is not directly "how to build" info but gives the general idea and rule of thumb figures on still and column design. The book does show detailed drawings of the cold water cooling coils used in the top of the column and gives some info on the type of temp control valves that cam be used to control the water flow. They also indicate that using a refrigeration type heat pump system to cool the column top coils works well as you can use the hot side of that system to add the removed heat back to the still, or heat water, or whatever.
Book is available cheapest on Ebay at around $35.00, a bit over $50.00 retail.
I neglected to write down the still head thermometer temperature at 300 mm of Hg of distilling off methanol. Sorry
I found in the CRC Handbook of Chemistry and Physics, 56th edition, that the boiling point of methanol at a pressure of 73 millimeters of mercury is 15 degrees celcius. That would be your still head thermometer temperature if you were using a vacuum pulling down to 73 mm Hg above zero pressure, in your still. So the condenser would have to be cold, not just tap water temperature. Or the methanol gas would go out through the vacuum pump without condensing in the condenser. I get about 300 millimeters Hg of vacuum from a diaphram vacuum pump for vacuum distillation.
I google searched vapor pressure methanol to get a graph. Looks like on the graph at about 300 mm Hg the boiling point is 42 degrees centigrade. I'm not sure I believe that. At 1 mm Hg the boiling point was about -44 degrees centigrade. At 1 mm of Hg the condenser would have to be pretty cold to condense the methanol before it went out through the vacuum pump as a gas. Its a lot of trouble to set up the vacuum distillation apparatus to verify this boiling point at the still head thermometer, but I'll probably do it in the next 2 days or so. How much vacuum are you planning to pull when you demeth your glycerin layer?
I have no idea yet how powerful our vacuum pumps are. I guess I will find out once I build it. The more the better, as long as I can control the condensation.
Maybe I can coil the water source through a freezer to drop it's temp. I can salt the water too to lower the temp even more. That would be something that I could build as I go if needed.
I designed a system for doing this. Removes water from oil also.
Here you go:
The best Do-it-Yourself Construction Plans on the Internet!
Waste Oil Heating - Biodiesel Systems
Biodiesel Pumps Made In The USA
Does your unit recover the methanol? If so is it pure?
Is the temperature controlled so that water doesn't contaminate the methanol? I don't see a reflux mechanism in your picture.
I want my methanol to be 100% pure to feed back into the biodiesel process.
Hey Redneck, How low is the Grand with all the lack of rain this year? Its pretty low up here...
I used to travel through Dunnville all the time, nice town.
Here are some pictures of my setup HERE.
With my old setup that was very similar (only 100l instead of 1500l) I could get 100% pure methanol recovered. With the setup in the pictures I have only been able to get 98~99% but I haven't had the time to play with it to get it to 100%. I feed all my recovered methanol into the next batch (after the methoxide goes in) and have had nothing but great success after brewing around 8500l with this setup. I use a big vacuum pump and use tap water (used to use a freezer full of antifreeze made from glycerin and water) to cool the condenser and collection vessel. My pump wasn't strong enough to circulate the antifreeze through my new 75' condenser and collection vessel lines though so I just hooked up the garden hose (well water) thinking it would be temporary, but I haven't looked back since it only takes a very small trickle of water to keep things running smooth. I bet it takes less energy to use the tap water then it did to use my old setup with the freezer. Also, the water coming out of the condenser is warm and I drain it into a tote where I also drain the demethed NaOH glycerine once its done, this keeps it liquid, the farmer up the road then comes and gets it to feed to his cattle so its a win win.
The key to pure methanol is finite temperature control of the angled pipe coming off the top of my processor as well as regulating the vacuum, an ethanol style reflux column is not necessary as there is no azeotrope with methanol and water.
There are a few things I would do differently, mainly I would have used at least a 1/2" pipe for the condenser instead of the 3/8" pipe I used, that would make a huge difference in recovery speed and give better control over the vacuum in the reactor...
Here is a doc that shows the boiling point of ethanol which is similar to methanol under vacuum if your interested. http://f1.grp.yahoofs.com/v1/w...0Atm%20Pressures.pdf
I live just north of Guelph in the Fergus/Elora area, send me a PM if you like and I will send you my number, your welcome to come by and have a look at my setup if your interested.
Hi Jon, congrats on a great setup, I bet you're pleased.
Just to recap, you're doing whole batch demeth?
What temp do you keep the methanol suction tube riser at?
What depth of vacuum do you try to maintain to demeth?
You're cooling the condenser with tap water at what temperature?
You don't lose any methanol through the vac pump?
Your MeOH collection vessel is still refrigerated? if your condenser is at tap water temp, is this still necessary?
Your boiler design works well?
It works better then my expectations, it ticks away like clock work throughout the entire dewater, brew, and demeth stage's. The demething takes about 14 hours or so and I can sleep well while it runs throughout the night. I put a flow switch on the output pipe so if the pump dies in the night or something it will kill the boiler. It uses far less biodiesel then I had anticipated too.
Hi Jon, good to hear from you.
I'm aware that Fabricator went to another boiler design after he conceived your model, so I'm glad yours works well.
Your tube-in-tube condenser is vertical but works okay?
You think it is essential to circulate the BD while you demeth?
Have you ever tried demething without circulating BD?
Your circulating pump is the yellow pump?
Your MeOH collection vessel is cooled with the same cool tap water as the condenser?
Is it possible for you to post, please, a few pictures of your settle and filter setup?
Have you ever had any problems with flour in your incoming WVO?
Phew, you'll have writers' cramp soon. I think the tap water cooling is pure serendipity.
Jon, thanks for the information. What you have built is a splendid use of all the information that is available here. More power to you. If I'm ever in your neighbourhood I would love to come and have a look-see. But don't hold your breath.
You welcome here anytime!
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