Help with problem distilling Methanol from Glyc. When I am recovering methanol from glycerine, at around 180F tank temp I am getting cavitation and getting glycerine mixed with methanol coming out of the hose to the condenser. It is contaminating my recovered methanol and forcing me to stop before full recovery. My system is a 30 gallon HW heater with 220v element running on 110. I do not circulate but I can use air from a bubbler going in the bottom. The condenser is made from 1/4" copper tubing. Any ideas of what would be causing this would be appreciated.



thanks

RCV

I have had the same problem. I posed the same question a few days ago and it seems that we are filling our tanks too full of glycerol. With my set up that is easy to do, but if you're using a water heater that may not be so easy to do.

If this is the problem, just try 2 or 3 gallons less to give a little more head space in the top of the tank.

I've also read that some see where water starts to come out of solution, but that should not start happening until the methanol is out I think.

Hopefully others may have more answers to help.

Ross

I'm getting this with both 10 and 15 gallons in a 30 gallon HW heater. It hasn't always done this but I'm not aware of any changes to cause it to start.

thanks

RCV

I had this same problem the first time I tried to recover methanol from my glycerine. I suspect that the problem is coming from heat control. I'm told and I'm seeing (by experience) that heat control during methanol recovery is crutial. The glycerine will start to foam and find its way up to your condenser if its boiling too violently.

Based on your current setup, I would heat glycerol to 155-160 and hold it there for 45 minutes to 1 hour. After the methanol flow rate slows way down, turn the heat another 8-10 degrees, hold for one hour, heat another 8-10 degrees, and so on until you can hit 190-200 without problems. My thought is to gradually bring up the glycerol temp up and make sure that the flow rate is not TOO high on the recovered methanol. If its pouring out fast, your heat is a bit high. As the concentration of methanol decreases in your glycerol, the boiling point will gradually raise. You can't just turn the heat on to 190 and let it ride. The methanol concentration is too high, therefore the boiling glycerol will be behaving too violently and carry glycerine with it up to the condenser column.

If you had the inclination to modify your set up, I would probably increase the size of your recovery tube from 1/4" to 1/2". This will allow a higher volume of vapor into the column.

Best of luck.

Keep a fire extinguisher handy!

From the photo we cannot see where your thermometer is located.
If it is at the top then what you are getting is a reading of the head temperature and 180F is WAY too hot 'cause the pot temp is considerably hotter than that.
Keep that head temp at or just above 155F and you won't be having this problem any longer.

Thanks for the reply's. I started doing something different that cured the foaming, I started adding 5ml of sulfuric acid (battery acid from auto zone)to every 5gallons of glycerine. Since then, no foaming. I had bought a rounter controller to be able to limit the current to the element but ended up using it on full power anyway.

Follow up:

I recovered approximately 9 gallons of clear liquid from 30 gallons of glycerol. I need a hygrometer to check for alcohol purity. I used a crude filter and then pumped it into my processor. Heated it to the first point where the methanol started rolling out and turned the heat off. I let the pump run for 3 hours or until the vapor recovery slowed to a drip. Repeated the process about 6 or 7 times until the stuff in the processor could heat up to 200 before boiling too violently. Each time, the temp ceiling raised a few degrees. At about 178, it took a bunch of vapor off. I need a bigger cooling water tank for the condenser. 5 gallons of water heats up VERY quick.