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Speeding up methanol recovery

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October 30, 2012, 05:43 PM
Nick Duden
Speeding up methanol recovery
I need to speed up the methanol recovery from my biodiesel. Right now it takes a full 2-3 days to get all the methanol out of my bio. I usually heat about 120 gallons of bio in a tank that has 2 drum heater bands on the outside (about 2500W total). Would using an air bubbler inside of the tank speed up my process? Or will the air just lower my fuel temps and slow it down? The tank is well insulated and fuel temps get to 130-140 and stay there for a couple days while the methanol evaporates.
October 30, 2012, 07:14 PM
fabricator
You need more heat, lots more getting to 180 degrees would be good or 150 with a vacuum pump, I go to 180 degrees with constant circulation and a vacuum pump, it takes about 6 hours to demeth 350 gallons.
October 31, 2012, 05:52 PM
Nick Duden
I'm thinking about putting in some generic water heater elements. As long as they're fully submerged there shouldn't be any explosion issues I believe. Is circulation going to speed up my recovery in either case?
October 31, 2012, 07:19 PM
fabricator
Yes, circulation improves the surface area exposed to the air liquid interface and vacuum lowers the temperature methanol boils at.
October 31, 2012, 07:21 PM
fabricator
I am assuming you have a condenser that you can keep nice and cold.
November 01, 2012, 04:10 AM
Vladster
By degrees you mean F or C ?


November 01, 2012, 09:35 AM
fabricator
F
November 01, 2012, 10:15 AM
TheVol
fabricator, would you happen to have pics of your recover set up? Thanks
November 01, 2012, 02:12 PM
fabricator
This is the processor, the stainless tank on the side is the condenser, the larger stainless tank lower down is the collection tank with a reflux column on top, the vacuum pump hooks to that.

November 01, 2012, 02:57 PM
TheVol
Whoa!! Holy cow that is a really nice, clean set up! Thank you for post the pic.
November 01, 2012, 04:43 PM
Ryan P.
quote:
I am assuming you have a condenser that you can keep nice and cold.


fabricator, what method do you use to keep that condenser cold? Because I barely can. I start with water in my cooling reservoir (55gal drum) that I recirculate from at about 65F during the summer. By the time the still is up to 150F, the "cooling water" is only slightly behind at 120F. Short of hooking right into my well and just DUMPING water on the ground, I can't dump heat fast enough.

I tried adding frozen blocks of ice once the drum hits 100F, and that buys me a few degrees, but all efforts end up blowing vapor off into my methanol collection drum before I am done.

I'm considering adding a second water loop that hooks through my WVO storage drums, at least heat dumped there will be doing some GOOD for me!
November 01, 2012, 05:19 PM
fabricator
Right now I run water through it right out of the well, it keeps it cold but the pump runs almost continuously, this winter I intend to come up with a chiller based on a condenser inside a kegerator.
November 01, 2012, 05:34 PM
Ryan P.
Gotcha...we're on the same page then.

Now I am wishing more and more I had taken the time and money to run the water heating lines in my shop floor! Sure would been handy now to just tie the condenser cooler lines into the shop's slab and heat the shop with my condenser's waste heat all winter!

And I'm guessing a 28'x30' slab of 5-6" thick concrete, plus 8400 cu-ft of air above it, could hold a lot of heat!
November 01, 2012, 05:36 PM
Ryan P.
I told my wife we should put a hot tub right outside the shop. I could use the bigger heat sink for the methanol condenser and then after running it all day, I could climb into a nice 120-140 degree hot tub for an hour!
November 01, 2012, 06:39 PM
Nick Duden
What kind of a vacuum pump do you use? Right now I just vent it straight outside, only a fraction of it condenses. I just started a couple weeks ago and havent got around to building a condenser, but thats the next project. Ive already got a fuel cooler before it runs through the towers that uses a 55 gal drum resevoir, I'm sure that'll work for cooling the condenser since I'm only doing 120 gallon batches.
November 01, 2012, 06:44 PM
taralec
quote:
Originally posted by Ryan P.:
I told my wife we should put a hot tub right outside the shop. I could use the bigger heat sink for the methanol condenser and then after running it all day, I could climb into a nice 120-140 degree hot tub for an hour!


If you ever get that far Ryan,post a pic Big Grin Big Grin
November 01, 2012, 07:26 PM
fabricator
quote:
Originally posted by Ryan P.:
I told my wife we should put a hot tub right outside the shop. I could use the bigger heat sink for the methanol condenser and then after running it all day, I could climb into a nice 120-140 degree hot tub for an hour!


It's just a small Gast, 1/4 horse I think.
November 01, 2012, 08:44 PM
WesleyB
How much vacuum are you pulling during your vacuum distillation?
November 01, 2012, 09:47 PM
fabricator
You have no control over it, in the beginning the vacuum will be quite low because of the large amount of methanol you are moving, towards the end the vac will steadily rise, when it gets to around 25 your hoses will start to flatten out and you are pretty much done there is no methanol moving anymore.
November 05, 2012, 12:24 AM
Road Runner
I started with a 55 gallon barrel and did the ice block thing too, but that was when we had a 90 gallon processor. when we moved into a dedicated building, we put a ground loop in. the methanol line goes into a water cooled plumber's delight (1" copper pipe jacket with 1/2" copper pipe inside to condense methanol. it then leaves the building in pex, and runs 150 feet out and back about 5' deep. the ditch also contains a 1/2" pex 150' out an back for the plumbers delight cooling water out of a smaller 20 gallon barrel reservoir. the set up is low power, and has been run 24/7 for about 20 days without extra cooling. it's great if you have room, and can get lines buried . I'd like to see someday our catch tank in the refrigerator, but for now it has refreshments in it.

we use thomas 2650?twin piston pumps you find on ebay and surplus center.com. will do either pressure or vacuum. last ones I got were in the $60 range. They run forever. hope this helps.


powering
2 bobcats, an excavator, and a ventrac mower. looking for a diesel weedeater!