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Speeding up methanol recovery
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Now there is an idea, I have 50 degree water 13 feet down.
 
Location: West Michigan | Registered: April 26, 2006Reply With QuoteReport This Post
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Just ordered one of those Thomas 2650 pumps. How big are your guys' batches? At 120 gallons I can't imagine I would have as many problems cooling the methanol as some people have.
 
Location: Central IL | Registered: January 31, 2012Reply With QuoteReport This Post
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350 gallons.
 
Location: West Michigan | Registered: April 26, 2006Reply With QuoteReport This Post
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I have 375 gallon batches, but i do whole batch demething, so figure 445 gallons. those thomas pumps work great for me. I've had a couple die, but there are rebuild kits for about 20 bucks. I can never remember where I found that kit online when I need one. sometimes the capacitors will quit working, and if you ever have trouble, first check to see if things turn free, then try a new capacitor. 9 times out of ten, any time I've had trouble with these (which isn't often) it's the capacitor. capacitors can be had at just about any electric store. they will work as a compressor, but most i've seen pop off at 40 psi. not enough to pump up a tire, but great to move fuel or oil out of tanks.
I'd guess for a 120 batch, I bet you could bury a plastic 55 gallon barrel in the ground for a cooling water source, and it would be enough to do a batch every couple days. draw off the bottom, return at the top. run a downspout into it and bingo! you have a cistern. I've thought about putting our 20 gallon water tank in the fridge to give it a little help, but I just can't see using electric to do this. seems like a waste to me. If you don't want to bury something, try just using tap water if you are on city water. maybe you can hook the other end of the condenser up to the lawn sprinkler and water the garden or yard at the same time so you get the most out of the water bill.


powering
2 bobcats, an excavator, and a ventrac mower. looking for a diesel weedeater!
 
Location: morgantown wv | Registered: June 18, 2008Reply With QuoteReport This Post
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RR, what are the steps in your whole batch demeth process,I tried it a couple years ago and my yeild dropped.
 
Location: West Michigan | Registered: April 26, 2006Reply With QuoteReport This Post
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fab, I cook off any moisture in my oil after a bunch of settling. then it goes to the AE tank for 6hrs with the pump on. I don't worry too much about starting temp as long as it's over 165. I've processed as high as 200. I just have to make sure I have all the valves shut or I lose methanol. i let it sit for another 6 - 12 hrs before sending it to my base processor. before I put it over, I drain a couple of gallons off the bottom to get rid of any water. my oil is pretty good compared to others doing AE. most of the summer it was 7-8 now it's more like 5.5 naoh I had some 15 last year. I still run AE on it because it really helps my yeild, and I don't have to use as much lye. after processing at 165 for 3 hrs, the timer kicks off, and I turn on the demeth vacuum, and condensor water. I also crack open my sight glass vent a little to kind of bubble the biodiesel layer. For about the first two hours, the bubbler does nothing because I'm already to temp, and the methanol is all but making pressure to get out of the processor. The bubler valve has a check valve so it doesn't puke biodiesel.(cleaning up messes has taught me more than any book ever will.) I don't know if my sight glass location has much to do with it, but I have it coming in above the glycerin layer. I don't mix while demething. I try to keep glycerin layer as "quiet" as possible. I previously had a bubbler all the way to the bottom when this tank was only for demething for biodiesel only, and not a processor, and it seemed to mess things up. nothing scientific there, just my impressions.

most all of the methanol is gone in say 10 hrs? I usually run it 24 to 30 hrs just to get everything out I can. like I said, all this is low energy, so I don't sweat running a 500 watt vac pump an extra 20 hrs. we are talking about 375 gallons of fuel. my yield is good, usually right at 375 in/375 out, but sometimes it is 360 or so. I may be wasting some fuel here, as it is sometimes hard to see the transition from glycerin to bio in my sight glass. this is especially so if the oil titrated higher, and the bio finished up dark. After that it is off to settling tanks for a few days if I can wait, and then to the chip tanks. I've always passed 3/27, but lately my soaps have been higher, and I don't know why. I've never had to neutralize any batches before demething, though I do check them once in a while to see where I'm at. It is never more than one drop of naoh, or sulfuric one way or the other to get neutral, so I don't worry about it. my soaps before wbd from averaging 1,500 to 3,000 ppm fresh out of the processor, dropping to 400 while in settling. after wbd, it was 200 out of the processor! Lately something has changed, because my soaps are back up to the 2,000 range, and I don't know why. I suspect we've got a couple places dumping cleaner in our barrels, but I can't single that out yet. some of our tanks haven't been cleaned in two years, so that my be part of it. the processors have been, but that is about it as far as cleaning.
How much of a drop in yeild have you had? I notice my yield is slightly smaller when my AE doesn't hit my target value of 1.0 naoh, and I have to use more lye for the base step. For me, there is definitely a correlation between post ae titration, and yield. If I hit 1.0, I know I'm going to have a good yield. I know this is getting off track, but it is all tied together in my opinion.


powering
2 bobcats, an excavator, and a ventrac mower. looking for a diesel weedeater!
 
Location: morgantown wv | Registered: June 18, 2008Reply With QuoteReport This Post



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I use koh but I have the same thing if the T after the acid stage is low you are gonna have high yeild premium bio, but some batches just won't come down more than 2-3 points.
 
Location: West Michigan | Registered: April 26, 2006Reply With QuoteReport This Post
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With my setup I have found that my well water is sufficient, I only need a small trickle to keep the collection vessel and the condenser cold. I think the key is the length of the condenser, mine is about 75' of 3/8" soft copper fished inside of a 1" black poly water line. Prior to this I used a medium sized chest freezer full of water and glycerin as antifreeze, it worked great but my pump wouldn't move it through my new longer condenser on the new setup so I switched to the well water and so far have not looked back.
I use a large Busche rotary vane vac pump and have found that the 3/8" line is too small and it takes too long to demeth (WBD), about 14 hours or so for a 1425 litre batch. About 120 litres or so is what I recover, I figure (never measured it) from a 1420L batch. I only let the pot temp get up to max 180F though.
Next spring I am going to swap out the 3/8" line for 5/8" and figure it should cut down the recovery time to well less then half what it is now, at least according to a vacuum guru I know Wink
It works out great, I mix the caustic in with a full fresh drum of methanol and then suck the entire amount of recovered methanol in after that, wait 20min and start the recovery all over again... The warm water exiting the condenser fills a tote 1/2 full of water and I drain the NaOH glycerin into that to keep it liquid, after 2 batches the farmer up the road comes and gets it and feeds it to his cows. Its slowly becoming easier and easier... Big Grin
Here are some pics of my setup http://biodieselpictures.com/viewtopic.php?t=743
Cheers,
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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but lately my soaps have been higher, and I don't know why.

RR, That happened to me a couple years back, turned out my titration solution was going stale, now I make a fresh batch of titrant with each new bag of caustic. Just a thought.
Cheers,
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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Jon, that is about where I'm at as well. I make up new at least once a month, or whenever I forget, and leave the lid off the container. That seems to screw up readings in a matter of a few days.


powering
2 bobcats, an excavator, and a ventrac mower. looking for a diesel weedeater!
 
Location: morgantown wv | Registered: June 18, 2008Reply With QuoteReport This Post
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quote:
Originally posted by 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!


Ryan, you can do much the same thing with a car radiator and a fan. In fact some car radiators come with the fan & electric motor all attached. Simply circulate the condenser water through the radiator suspended in your shop. Better yet find a natural gas space heater, remore the burner (or not) and the pumping will be even easier.
 
Registered: March 23, 2004Reply With QuoteReport This Post
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I just demethed partially a small 500 milliliter batch using vacuum distillation. With a vacuum pressure of about 280 millimeters mercury above zero atmospheric pressure. The still head thermometer temperature was 30 degrees centigrade ( about 86 F). If you're using vacuum in demething, depending on the pressure, the condenser has to be cold or the methanol goes out through the vacuum pump. I used ice water to cool my condenser, And ice to cool my receiving flask.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post



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the condenser has to be cold or the methanol goes out through the vacuum pump

Not just the condenser, but more importantly IMO, the collection vessel. Methanol will boil at room temperature when under a strong vacuum.
My chilled collection vessel works well at keeping the methanol from getting into the pump.
Cheers,
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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How do you chill your collection vessel? Is it on the same coolant loop as the condenser or do you use ice cold water?
 
Location: Central IL | Registered: January 31, 2012Reply With QuoteReport This Post
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Yep, I have it plumbed in parallel with the condenser. My vacuum pump is mounted on top of the vessel and it keeps it allot cooler too. Smile
Here is a pic of it if you didn't look through the link I posted above.
Its just 1/2" pex pipe secured with plastic wrap.


Then I insulated it with foil faced bubble wrap.


Cheers,
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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I've looked through your link more times than I can count. I started working on a 500 gal propane tank about 2 weeks ago and got it finished up and painted this weekend. Now I'm working on finding a collection vessel than can handle the vacuum pressure and building a condenser. I was planning on coiling up about 30' of 3/8" soft copper inside a 4"x4' piece of pvc thats water cooled but after reading your post I dont know if that will be sufficient length or diameter of copper to get the job done right.
 
Location: Central IL | Registered: January 31, 2012Reply With QuoteReport This Post
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I would agree, though 3/8" does work it is very slow for my liking. I am going to upgrade to 5/8" in the spring. I think I will keep it the same length though as it will need to cool down more volume...
If you find its difficult to wind it up small enough to fit into the 4" pipe, just get the cheap white stripe 1" poly pipe and fish the copper into that, its dirt cheap and easy to work with.
Just tape the end of the copper with electrical tape to make a smooth end and use lots of soap to lube it as you push it in, or fish a string in and pull it in with that. I laid the poly pipe out strait in my back yard, fished a string into the poly and then pulled the copper through it with the string. The whole rig coiled up very nicely when it was done.
Cheers,
Jon
 
Location: Wellington County, Ontario Canada | Registered: February 07, 2008Reply With QuoteReport This Post
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I have had good luck using flat plate heat exchangers as condensers.
 
Location: Virginia | Registered: March 17, 2007Reply With QuoteReport This Post



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So I've got kind of a dumb question. When using a vacuum pump, what keeps the methanol vapors from escaping through the pump? My initial thought would be that the pump is "sucking" the air out of the system, and any vapors would want to go through that route.
 
Location: Central IL | Registered: January 31, 2012Reply With QuoteReport This Post
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You will have vapors exiting the pump there is no way around it, the trick is to condense as much methanol as possible in front of your pump, the pump should be exhausted outside.
 
Location: West Michigan | Registered: April 26, 2006Reply With QuoteReport This Post
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