I'm demething my bio and cant get the temperature past 145*F or so. There is plenty of methanol that comes out, but how can I tell if I removed all the methanol? After a few hours it stops coming out, but I need to get hotter to remove all the methanol or will it all come out at 145*F, well below the boiling point of methanol
140F is quite low to be producing any methanol. Is your temp gauge accurate?. Where are you measuring?.
Typically maximum production seems to occur at around a liquid temp of 80C (176F) where it stays for a long time as the boiling methanol stops the temperature from rising any further until the bulk methanol is out. As the boiling subsides the temperature starts to rise again.
The temp gauge is a cheap one, it could be off. Its got a probe about 3/4 of the way into the heated fuel.I noticed on our methanol recovery from glycerin it works best around 176, but even as low as 120F the methanol is evaporating from the fuel. Ive taken temp readings with a infrared thermometer on the outside of the tank (removed the insulation)and the tank was never more than 140F. Is it possible for all the methanol to be removed at that low of a temp? Or will some residual methanol require a higher temperature to evaporate?
Are you WBD with glycerin in the bio? Approx. 40 % of the total methanol you use can be taken out without any problems if doing a WBD. That's my experiance anyway. We use 11 1/2 gallons and demeth 4 1/2 gal out of the whole batch.
As far as temperature of the bio and glycerin to demeth, methanol will start flowing at 130 F as soon as the suction starts flowing vapours thru the condenser. Within 3 hrs we will have 4 1/2 gal methanol and the temp of the batch is at most 170. I think you can get it done with lower temps but takes longer.
If you are doing Whole Batch Demeth check this out to see how much methanol you can remove. this forum in the UK has great info on all bio diesel areas.
Mister Dean, Sir; Relative to whole batch demething, since the reaction is an equilibrium, and with the catalyst present, doesn't the reaction reverse during demething, making monoglycerides, which can be removed later.This message has been edited. Last edited by: WesleyB,
WBD theory and practice don't seem to agree. There have been no reverse reactions reported. This may be because it is quite difficult to demeth too far unless using a vacuum. JMO and experience.
I don't WBD due to the fact my demething tank doesnt have a cone bottom and would make glycerin drainage difficult. My reasoning for demething the fuel isnt to recover the methanol. I use wood chips to dry wash, and demeth the fuel before going through the chips. I demeth the glycerin at a later stage in a separate system altogether. I considered WBD but at the time I designed the operation I wasn't quite sold on the idea.
I took the trouble to read the link you posted and it means what? I certainly see no indication of reverse reaction and it was a batch of bio sans glycerol and definitely not WBD.
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