Recovering Methanol from Biodiesel
By Rick Da Tech
The GL Method
A very inventive British Tinkerer named Graham Laming has adapted the Appleseed design to the British Isle. His Ecosystem Processor has greatly reduced the methanol releases and eliminated the water wash. We can apply his technique to the Appleseed to reduce our exposure to methanol vapors and incorporate a waterless wash process Our version of the GL 1 day process will have you finished biodiesel within hours of processing without having to deal with how to dispose of the wash water.
We will convert our wash tank into a methanol removal and settling station. Process in our Appleseed as normal, using the 5% prewash to speed up separation. Then after a quick 2 hour settle, we drain our glycerin and pump the biodiesel into our freshly converted methanol removal station. Once the methanol has been removed the soap and glycerin will fall to the bottom of the drum with a few days settling time or we can filter or centrifuge the soap out quickly, or even do a fast easy water wash. There are four major components to our tank
- The heating system, consisting of a silicone band heater, insulation and a temperature gauge.
- The biodiesel circulation system, consisting of a pump and a few bits of plumbing
- The air circulation system, consisting of a condenser, a methanol collection vessel, and a venturi.
The water circulation system, consisting of a drum of water, a small pump and the condenser.
The Heating System
The biodiesel should still be hot when it is transfered into this tank. The heating system is to add heat back as it is lost through evaporation and radiation. We have chosen our 1500W 120V Band heater as the heat source. It is adjustable and simply snaps onto the drum. Then we add two layers of foil/bubble/foil insulation to keep the heat from radiating away from the drum. We add a bimetallic thermometer in order to give us the information needed to be able to adjust the temperature setting on the drum heater. The oil should be 120F or higher when we start. We should not let it get above 180F so as not to exceed the maximum operating temperature of either the venturi or the return tubing.
The Biodiesel Circulation Stystem
The biodiesel is taken from the bottom of the drum, through the pump to supply the motive for the venturi. It is then dumped back into the top of the drum. This keeps the methanol laden biodiesel near the top of the tank so it can readily evaporate.
The Air Circulation System
The air is drawn out of the top of the drum, through the condenser and into the venturi where it is mixed with the biodiesel and returned to the top of the drum. The methanol evaporates in the top of the drum and condenses in the condenser with the liquid methanol dropping into the collection vessel.
The Water Circulation System
We pump clean water from a 55 gallon drum through the condenser and back into the drum. The large mass of the water in the drum will keep the temperature from rising too much in the drum.
- Load the unwashed biodiesel into the drum.
- Turn on the biodiesel circulation pump.
- Turn on the band heater with the temperature adjustment set to mid range.
- Monitor The temperature to make sure it does not go above 180F.
- When the methanol stops draining out of the condenser, pump the biodiesel into a settling drum.
Converting a Wash Tank
The first step was to install a bimetallic thermometer. Drill a 7/8" dia hole in the side, put washers for a 7/8" bolt on both the inside and the outside. Put a bead of silicone between the washer and the drum touching the threads of the thermometer. Use a half in coupling on the inside to hold it all together. In the picture I used a conduit lock nut. A standard pipe coupling has more threads and lets you get it tighter.
The stand was part of an old test rig and worked great for this application. The tank is first plumbed with the standard stand pipe plumbing. Then add the pump, venturi and the rest of the biodiesel circulation system. To attach the return back into the tank, Drill a 1" hole near the top of the drum. I used two 3/4" 45 deg elbows and a 3/4" close nipple with two washers in between the two elbows. The venturi is added in this step.
Next we added our Plumbers Delight Condenser and hooked up the air circulation system. Then we insulated everything.
We made some minor changes in the drum. After spilling several gallons of oil on the floor out of the suction line of the venturi, it became evident that it needed to be above the liquid level. Also, we didn't need the tubing and opted instead for steel pipe between the pump and the venturi. The line enters the drum in the same way it did before. There was a bit of an alignment issue with getting it all to line up without stressing the venturi. That was resolved by changing the stand so the height of the pump could be adjusted.
The next thing we did was to rearrange the vent and condenser so that any liquid that condensed in the vent or condenser drained by gravity down to the methanol collection tank.
Then It was insulate the crap out of it. We have four layers of foil/bubble/foil on the side of the drum and a dozen layers on top. We also added foam insulation from the hardware store on the piping.
We used the tank to dewater our WVO before processing, then processed in our Appleseed as usual. After settling and draining the glycerine, the biodiesel was transfered back into the GL 1 day drum.
It took almost six hours to remove all the methanol. That was due to gradually increasing the temperature, not wanting to go above 200F. The venturi's maximum operating temperature is 200F. Once we hit 185F the methanol started to roll out of the condenser at a good rate and it only took about an hour after that before we had just over a gallon of methanol. That is about as expected indicating all the methanol was removed.
Our condenser turned out to be problematic. It was so long as to not fit our stand. Our collection vessel was in the middle of the floor and it dripped water on the floor from a bad solder joint. We also used an enormous amount of water by connecting the condenser directly to a garden hose. I didn't have the fine tunning I needed on the flow to get the most out of the water we were using.
After everything cooled down two days later, we opened up the tank and took a sample off the top. Then transfered it over to a settling tank. The GL drum was clean as a whistle, no soap anywhere, but the bio was filthy. It even had some dead bugs in it. We'll see what it looks like after three days of settling.
After a week of settling the bio in our sample jar had cleared up with the soap and trash falling to the bottom. Soap testing showed 216 ppm of soap. The 120 liter batch still had some stuff suspended in it. The top half of the 120 liters looked clean and clear and ready to use.
The experiment was a success and we will continue using the tank. There are some lessons learned that are important to mention.
- Insulate, insulate, insulate. You can't put too much insulation on the tank.
- Keep the empty space in the tank to a minimum, in our case our next tank should be a 30 gallon drum instead of the 55 gallon drum we were using.
- Mount the venturi high up. The check valve in the venturi can leak and if the venturi is below the liquid level, it can drain the tank.
- You've got to get it hot. We didn't see significant methanol until we reached 185F. Then it came out fast.
- Make sure that liquids can't puddle up in the vent plumbing. Anything condensing in the vent, must be able to drain out through the condenser into the methanol collection tank.
- A homebrew test to determine when we have removed enough methanol would be helpful. One person on infopop with the nickname Producer is using a flash point tester for this task. He has indicated that if the methanol is removed to ASTM spec levels, that the soap levels very quickly fall to under 50ppm
While we like the system and will continue to use it, there are some minor changes that need to be made. The condenser we made leaks water. It's a real mess, so we'll be looking at more condensers here in the near future. Preferably some that are easier to build and less expensive. We'll be changing the cooling water from tap water over to a closed loop system that reuses the water. A needle valve to better regulate the flow of water would be the cheap and easy fix, but I'd rather use a rain barrel to supply the water. That way I don't have to stretch 150 feet of garden hose across the yard to supply the cooling water.
In the future we are going to move from a drum to a 40 gallon water heater. Our processor is a 50 gallon water heater and by stepping down a size we will eliminate the headspace that was causing us so much trouble. The water heater comes insulated with a heating element installed so it will probably be an easier build than the drum.
If you're interested in a better integration of appleseed and GL-1 check out this processor by JoggerFogger.