Hi Todd and all Methanol recovery depends on the circumstances, whether it's worth it or not and at which stage you do it. Three options:
1. Recover from the whole batch, biodiesel, by-product and all, at some stage after processing. 2. Recover from the by-product, which contains most of the excess methanol - lose a bit in the wash-water, but use much less energy recovering the rest than you'd use in #1. But once the methanol's removed, you can't separate the by-product into FFA-glycerine-catalyst. 3. Separate the by-product (FFA-glycerine-catalyst) first, then recover the methanol from the glycerine fraction. (But I think there'll also be some in the FFA, no? Not sure, haven't checked that out yet.) So. Re #1, it seems at first the least attractive/practical option, but there's a really efficient processor (120 litres, design to be uploaded to JtF soon), properly sealed and built for pressure, which works this way. Used with acid-base, but suitablke for any process. They use a process temp of 65 deg C (150 F), with constant take-off of the methanol vapours via a condensor built into the lid; the condensed methanol is pumped back into the processor at the bottom via a sparge - little bubbles of it, they find this really optimises the methanol use. At the end of the process they simply continue to evaporate off all the excess and condense it but don't pump it back in. This is an efficient process with very low overall methanol requirements without compromising the conversion. For the process part of it you could mostly do without the condensor - the vapour condenses anyway on the undersurface of the lid and drips back in, though reintroducing it at the bottom via a sparge is better. Downside is that it's very difficult to acid-separate the by-product into FFA-glycerine-catalyst without the excess methanol, but if you don't have a need for the separated products then no matter. That also applies to #2. This is quite easy. Distilling off the methanol is not like distilling ethanol, it's already purified, all you have to do is evaporate and condense. We built a simple condensor out of a length of salvaged 3/8" (10mm) copper pipe and 32" (81cm) of plastic water pipe, 1-7/8" (48mm), with end-caps. The copper pipe is straight-through, not coiled - it won't coil that small. 1/4" (6mm) pipe will, almost, but we wanted a bigger pipe, so we made the condensor longer. There's a water inlet at the end of the plastic pipe and an outlet at the top, with hoses leading to and from a water tank and a small water pump (aquarium/fountain type, cheap) doing the work. The copper pipe emerges from the top of the plastic pipe and curves back down in a semi-circle, the end connected to a small lid in the lid of a small, 20-litre biodiesel processor with a 1.5kw heating element. The curved bit of the copper pipe is insulated. The processor lid is tight-fitting, sealed with silicon and clamped on. There are two other small lids in it, one for a temperature guage, the other for the stirrer, when required, closed when not required. Put in about 15 litres of by-product, turn on the heat. The boiling point rises as the methanol evaporates, leaving less methanol in the mixture; it's more or less all gone by the time the temp reaches about 100 deg C (212F). No need to provide for water cooling - if the tank is quite big it won't be necessary, or just take out some hot(tish) water and replace with cold. If water cooling is needed, there's a neat method I'll be uploading to JtF soon, as well as some pics of this condensor operation. Trouble with this set-up is that the electrical heat is expensive. Having established that it all works okay, I'll now dump the electrickery and use a heat-exchanger instead (fired by by-product, free heat). So we get our excess methanol back, and we're left with by-product that we can't separate. It still burns well though, but not as well as with the methanol. Would we rather have the excess methanol for re-use, or hot-burning byproduct/sawdust/milk carton logs? The logs I think, at least in winter. But it's good to have an easy choice. The by-product also makes better fuel as-is, methanol included, for use in a Turk-type burner for process heat (heat-exchangers). Anyway, our own preferances regardless, we need to have all this stuff figured out and set up for the ongoing seminars, demos, classes and so on so we can show people what their options are and how to exploit them best, reducing waste to zero and keeping costs at optimum. #3, FFA-glycerine-catalyst separation, followed by methanol recovery from the glycerine portion (mainly). http://journeytoforever.org/biodiesel_glycerin.html#separate This'll get you back your methanol, but if you want to sell the separated glycerine you'd have to use the thin-film evaporator rather than the set-up described above for raw by-product, which would wreck the glycerine, right? Or is that wrong? Presuming it's right, that's a more complex bit of kit you need, plus 85% phosphoric acid - quite a lot of it, not very cheap. Roughly, you need almost a litre per 10 litres of by-product to be separated. Plus the heat energy for distillation, whether free or not. So you'd have to work out the economics of it - is it worth it to you? There's the saving of recycling the excess methanol, but do you have a ready market for tech-grade glycerine, preferably a market for the potassium phosphates rather than just using it on the land or in the compost, which amounts to useful disposal but no cost recovery, and a good fuel use for the FFA? Or a market for it as weed-killer or whatever. So you have to figure all these variables to know when, for you, is the best stage to reclaim the methanol, if any. My guess is the bigger the operation, to more worthwhile it'll be. Home-scale? Again, if I were using the 120-litre processor I mentioned with the condensor in the lid, I'd do it that way. I may well do just that, adapting that system to our 90-litre processor set-up. Anything to add? Or change? Much more, obviously, about thin film evaporators and heat-exchangers and so on, but is this outline of the methanol-recovery options valid, think ye, o wise ones? Any opinions on Mark's tip on the flash evaporators used in the jam and jelly industry? Regards Keith >Martin, > >Thin film evaporators (industriall "wiped thin film" evaporators are used) >and vacuum are a must for glycerol. >http://www.inchem.org/documents/icsc/icsc/eics0624.htm > >Fifteen mm Hg is not an exceptionally strong vacuum. There are ~760 mm Hg >per atmosphere. However, fifteen inches would be moderate. > >I presume the thought that "you wouldn't need a lot of volume" is referring >to not needing a large mechanical unit to effect a distillation? That would >be true. But you wouldn't get much output either. The biggest limitting >factor is not just the time it takes to elevate the temp of any given >volume, but the rate of exchange ("recharge rate") required at a given flow >rate to maintain that temp. > >Not the most efficient process to be conducting with electric heat. > >And even when all things are said and done? The cost of testing and insuring >(liability) that the recovered product is food or cosmetic grade is one of >the higher costs in the entire process. Tech grade is a much less involved >matter. The glycerol recovered after alcohol recovery post FFA separation is >tech grade. The problem is that the glycerol (and water) will still have the >odour of the original feedstock unless it's descented somewhere along the >way. > >That alone causes some disconcerting problems with glycerol recovery and use >from WVO. > >Todd Swearingen > > >----- Original Message ----- >From: "Martin Klingensmith" <[EMAIL PROTECTED]> >To: <biofuel@yahoogroups.com> >Sent: Thursday, October 30, 2003 1:39 PM >Subject: [biofuel] glycerine distillation > > > > Todd, do you think a thin film evaporator could be used to distill the >glycerine? > > I just did some research of my own, and it looks like would have to keep >the glycerine below the flash point (176C) which means you'd need a vacuum >of about 15mmHg (that's a pretty strong vacuum I assume) > > > > Would you still need a high volume pump if you did something like this: > > > > <boiler>---<condensor>---<vacuum> > > |...<distilled product> > > > > The distilled glycerine would drop out and you wouldn't need a lot of >volume right? > > > > -- > > -- > > Martin Klingensmith > > http://infoarchive.net/ > > http://nnytech.net/ > > > > > > > > Appal Energy wrote: > > > > >Pieter, > > > > > >I suppose you could heat it 'til it smokes and be relatively secure in >the > > >belief that you done sumptin' wrong. (Been that. Done there.) > > > > > >I couldn't tell you precisely what temperature is the cut off point to > > >prevent degradation > > > > > >The MeOH won't evaporate until the composite liquid (alcohol and >bioidesel) > > >reaches ~160*F. (Sorry. It's an "American thang.") That would mean a temp > > >rise of ~40*F after a settled reaction - presuming that you're using an > > >insulated reactor or settling tank. > > > > > >I wouldn't suggest a pot still due to the fact that the alcohol has to >rise > > >through a thick layer of biodiesel before it can escape. A thin film > > >evaporator would be more efficient, both in fuel expended and in keeping >the > > >temp of the biodiesel elevated for a shorter period of time. > > > > > >Imagine a slightly inclined, enclosed, stainless-steel, rectangular box, > > >with the bottom being a "hot plate" that a thin film of biodiesel flows >over > > >at an adjusted rate. At the top of the box is an exhaust vent that the > > >evaporated alcohol vents out of and then into a condensor. > > > > > >That bottom "hot plate" should actually be a chamber that is filled with >a > > >circulating medium - a heat exchanger - rather than a direct form of >heat. > > >The returning, hot, biodiesel can be used to heat the reactor and or the >WVO > > >in a settling tank, in order to achieve better energy efficiency. > > > > > >Sometimes you have to build a city to handle one product. > > > > > >Todd Swearingen > > > > > > > > > > > > > > > > > > > > > > > > Biofuel at Journey to Forever: > > http://journeytoforever.org/biofuel.html > > > > Biofuels list archives: > > http://archive.nnytech.net/index.php?list=biofuel > > > > Please do NOT send Unsubscribe messages to the list address. > > To unsubscribe, send an email to: > > [EMAIL PROTECTED] > > > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > > > > > > > > > >Biofuel at Journey to Forever: >http://journeytoforever.org/biofuel.html > >Biofuels list archives: >http://archive.nnytech.net/index.php?list=biofuel > >Please do NOT send Unsubscribe messages to the list address. >To unsubscribe, send an email to: >[EMAIL PROTECTED] > >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ ------------------------ Yahoo! Groups Sponsor ---------------------~--> Rent DVDs Online - Over 14,500 titles. No Late Fees & Free Shipping. Try Netflix for FREE! http://us.click.yahoo.com/vhSowB/XP.FAA/3jkFAA/FGYolB/TM ---------------------------------------------------------------------~-> Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/index.php?list=biofuel Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! 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