Would be nice hear your opinion about methanol removal from raw unwashed biodiesel and transfer it to waste oil.
Existing technique, named glycerin pretreatment does the job and folks happy about it.
people mixing glyc byproduct with waste oil and getting partial conversion at 60*C, and removing excess methanol and trapped biodiesel in glyc layer.
But anyone have advise how to transfer methanol from raw biodiesel to waste weg oil.
What would happen if We mix raw biodiesel and waste weg oil? does it gone work as glycerin pretreatment? It might sound ridiculious but People are awesome and do impossible things possible.
Biodiesel and WVO are miscible in all proportions so once you mix them together they will not separate.
thats why Im asking People for help.
Existing technique to remove methanol from biodiesel is water wash,
or alcohol water extraction.
however, water is not good solvent in this case because i want to use this methanol (and possibly soaps and other impurities) to next glycerin pretreatment batch. Im looking for liquid which will be immiscible wit oil ( just like water), have high affinity for methanol and do not inhibit transesterification reaction.
It would be possible to remove excess methanol by whole batch demething or removing the glycerine layer then doing vacuum distillation on the crude biodiesel upper layer, but it would be energy expensive to vacuum distill off the little bit of excess methanol in the crude biodiesel product. Glycerine pretreat using glycerine that doesn't have any methanol in it might be used for the purpose of drying waste vegetable oil some if necessary. Glycerine is miscible with methanol in all proportions, although I didn't look that fact up. Thanks
Ideally Im looking for a liquid for methanol exctraction from biodiesel.
I would use 5% of biodiesel w/w to extract methanol, then liquid and recovered methanol would go into glycerine waste oil pretreatment. I can not do it with water i think because i will ruin glycerin pretreatment.
All right then. Glycerine is not very soluble in biodiesel, but is miscible with methanol. So using pure glycerine to extract crude biodiesel with the methanol still in it would work. May or might not be practical for your application though. Methanol hydrogen bonds with the -O-H hydroxide groups, bonded to the three carbon chain that is the glycerine molecule back bone. A carbon chain with two hydroxide groups bonded to it might work, additionally. That would be two carbons, two oxygen and eight hydrogen in a molecule, might be named ethyl- diol , or ethyl glycol. I'll need to look that one up. Thanks.
Ya.. what he said.
Unless you're processing north of 1500 to 2000 gallons per week, it doesn't even remotely begin to approach something economical via money or labor..
On the other hand, if you have the "I like to tinker" bug, then distillation would be the way to go.
The best Do-it-Yourself Construction Plans on the Internet!
Waste Oil Heating - Biodiesel Systems
Biodiesel Pumps Made In The USA
I looked up the ethyl glycol I suggested might be used to extract methanol from crude biodiesel, after the glycerine layer is removed. The listed names in the CRC Handbook of Chemistry and Physics, 1975-1976 edition, are 1,2-Ethanediol, Dihydroxyethane, Ethylene Glycol, Glycol, Molecular weight 62.07, melting point -11.5 degrees centigrade, boiling point 198 degrees centigrade at atmospheric pressure. It's slightly soluble in benzene, infinitely soluble (miscible) in alcohol, soluble in ether. So ethylene glycol probably wouldn't work to extract excess methanol from crude biodiesel since I expect it would not form a separate phase (layer) if added to crude biodiesel with glycerine layer removed, just out of a processor. But demethed pure glycerine might work to do what you're saying. As I think you said, add demethed, purified glycerine to new, crude biodiesel that still has excess methanol in it to remove the excess methanol and transfer the excess methanol to the next batch in a glycerol pretreat? That might work.
Thanks for suggestion.Great work.Glycerol would work definitely.
But I have to demeth glycerol and purify, that's energy and time consuming, not worth for me.
But I believe people which using 5% water pre wash will end up with less amount of methanol than simple glycerol settling.
5% prewash extracting soaps and should extract great part of methanol in biodiesel (need to confirm first).
So that magic solvent appears to be glycerine.
There is next step now (if confirmed that 5% prewash extracts methanol better then simple settling).
Im asking now for all glycerine pretreatment pro's. Anyone done glycerine pretreatment with glycerol which have been exposed to water ( have been done 5% prewash).
many many thanks
This seems to me that it is getting very complicated. If you want to extract nearly all your methanol from the glycerol without de-mething, just use it for the prewash, in fact use it twice. First time with glycerol that you have used once before, second time with glycerol ex the last process. OK, there will still be methanol in there but very little.
I use pure glycerine in my process but only after I have de-methed and extracted all the ex-process glycerol. I then wash the bio with pure glycerine . This removes the soaps. I use the glycerine up to 10 times at @ 5%. I have had the soap level down to 10ppm by using this method.
In my opinion glycerol is too valueable to use (mixed with water) as the wash to remove methanol and soap. You cannot use this glycerol again as it is too wet.
the easiest way to economise on methanol is not to use too much in the 1st place. After a good glycerol pre-treatment where I achieve some conversion I complete the process with a maximum added amount of 12.5%
I have read several times that you use "pure glycerol" in your process.
Pure glycerol seems to be fairly expensive.
I assume you are buying it in bulk.
Where do you get your pure glycerol from and how much does it cost?
wet glycerin will hold about 60% methanol at fully saturated. wet bio will hold about 7% methanol. I know this because I have weighed and boiled off and then reweighed the products. I know this isn't helpful but just some info I learned.
Yes it is expensive but it lasts a long time. I paid £40/20 litres for the last lot, but this lasts @ 20 washes (200 litre batches) so lasts 18 months or so before it's soap level rises to the point where it is less effective.
" I use the glycerine up to 10 times at @ 5%"
Dgs, can you please explain this in more detail? Do you dilute to 5% with water?
I am not sure what you mean by "ex-process glycerol" will you please explain what you mean.
Do you mean you do not perform any water washing when you make biodiesel?
If yo do not water wash, how do you de-meth and remove all the ex-process glycerol?
Hope you are well.
This idea came from a commercial producer who is a friend of mine.
I use the glycerine at the rate of 5% per wash, so 10litres in 200. I don't use any water to dilute it. I heat the de-methed batch to 30degs and add the glycerine and compressor mix for about 30 mins. This brings the soap level down from @ 300ppm (as left overnight after de-mething) to an average of 50ppm, depending on how much the glycerine has already been used.
If I have enough time I then let the batch settle (after running the glycerine off) for a minimum of 9 days, then centrifuge it without water washing.
If i'm in a hurry to use it I still water wash, but with the soap so low I can wash really agressively from the start without fear of an emulsion. I still prefer to water wash as I always find there are mono's present which I can emulsify and remove.Not a lot but I usually get about 200mls of emulsified mono's out of a 200 litre batch which I prefer to remove.
To my knowledge glcerine, methanol and water are miscible in all proportions and there is no saturation point when these three liquids are mixed together.
I call 'ex process glycerol' the glycerol that the process has made, as opposed to the glycerine which is added. I de-meth by bubbling at @ 45 degs. As per my previous post I do not always water wash nowadays, but use a centrifuge as the final polishing tool. It seems to remove sub micron particles of glycerol, even after water washing. The settling does work well as there is seems to be no difference in the centrifuge contaminants with either method.
unless you have new data, i'm pretty sure mono's are great lubricators.
personally, i'd just leave the methanol in the final product: better yield, simplifies production, supposedly lowers emissions, improved cold weather performance.
i think soap and water (and perhaps free glyc) are the biggest contaminants to be concerned about.
From memory the total max spec for free and bonded glycerine is 2400ppm. If mono's are present then bonded glycerine will be as well.
I admire your courage when you say you would rather leave the methanol present.
Soap can certainly be removed from biodiesel containing methanol, but to my knowledge glycerol cannot be removed, only by removing the methanol first. If there is methanol present then free glycerine is also present.
You may well be correct re mono's as lubricators, however I would rather not take the chance finding out as I run 2x peugeot 2.0 hdi's on b100.
|Powered by Social Strata||Page 1 2|