Dgs started this discussion several days ago in an obscure part of this forum.
I have moved it to this list where more people are likely to read it and reply.
Originally posted by Dgs-
Just how important is it to dry biodiesel to less than 500ppm?
For the last few years I have used an IMB Turbo Dryer to dry my biodiesel. It is very efficient and can dry biodiesel to less than 200ppm water in a few hours.
Here in the UK most home brewers bubble and settle their biodiesel and do not dry it. I have tested many samples finished this way and the water level is always around the 600ppm region.
I have taken Johns (IMB's) lead as regards drying and will continue to dry my biodiesel to less than 200ppm simply because it is my way to get as good quality bio as possible, but this begs the question is this really essential.
The reason I ask is that to my knowledge the several hundred members on the UK forums that are using their settled and undried bio have never had a problem that can be directly connected to excess water. Some of these brewers have been using bio finished this way for around 15 years.
From the early days of biodiesel production before there were many national biodiesel standards, the accepted standard for dryness that most people worked to was "the biodiesel had to remain bright and clear at the lowest temperature the biodiesel is likely to experience."
In other words, dissolved water/ water in solution is not a problem.
For the last 15 years the "bright and clear" standard is the ONLY test I routinely perform on the biodiesel I use in my diesel engines.
I have no water or biodiesel related problems with any of the diesel engines I have used my biodiesel in.
My method of drying has changed over the years. I used to leave the biodiesel sit in 20 litre open top pails in the sun until the biodiesel was "bright and clear". I then put a top on the pail of biodiesel and placed it in storage until use.
I now pump my biodiesel into 200 litre open top drums and bubble air through it for around 24 hours and then pump the biodiesel into 200 litre closed top drums where it sits sealed until it is used.
I am currently using biodiesel that was produced about 2 years ago.
The other thing you need to keep in mind is that the ASTM and the European EN standard for dryness is quite different.
The ASTM method of testing only tests for "Free" water while the EN standard tests for both free and dissolved water.
Tilly; You are using biodiesel that was manufactured two years ago. As far as dryness of biodiesel , there is a chemical reaction called hydrolysis in esters, where water can in a way, adds itself between the methanol and the fatty acid of a biodiesel molecule. A product of this hydrolysis reaction is 1 biodiesel fatty acid ester molecule + 1 water molecule yields 1 fatty acid molecule plus one methanol alcohol molecule. Free fatty acids being present in the liquid fuel might be a problem at some level, their boiling point and vaporization temperature is much higher. Minimizing the presence of free fatty acids would be a positive quality control thing to do. So minimizing the water present especially if the biodiesel is stored a long time would be good for best quality fuel. The hydrolysis reaction is much slower without catalyst present but two years storage is a long time even for some slow reactions like hydrolysis.
Is the advice you are giving from your own personal experience?
Hi Wesley, still looking for you on TV.
You mean to say, that the water molecule donates OH- to the methyl group to reform MeOH, and the residual proton goes to the fatty acid to balance that off? I tried looking for scholarly papers on this, and the Royal Society for Chemistry had one but I could not download it.
I also use the IMB turbo dryer and have achieved very good results. Less than 200ppm if I remember correctly (DGS kindly tested it for me).
As for whether it's necessary, I'm not sure, and it is quite a faff getting it to that stage of dryness. The common rail engine is reputed to be very sensitive to any impurities, so I don't want to give mine any excuses to fail on me.
The climate here in the mother country is much more humid than where you are, so I expect that's why you can achieve a useable product just by exposing the top of your fuel to air whilst it's sitting in the pail or drum.
I'm not so sure whether just being bright and clear is sufficient. I've had bio like that in my processor that does a fair old amount of popping when I turn the elements on to warm it up as drying proceeds.
Tilly; I made esters via the Fisher Esterification procedure where an alcohol plus a carboxilic acid plus a catalytic quantity of strong inorganic acid produces an ester plus one molecule of water. I did make biodiesel from stearic acid ( a carboxylic acid ) plus 99.5% ethyl alcohol plus a little concentrated sulfuric acid 95-98% as a catalyist. The acid and the alcohol bond to each other by losing one water molecule during the reaction. In that reaction there is an equilibrium a forwards reaction to the right of the equation occurs while a reverse, slower reaction to the left (reactants) also occurs at the same time. The reverse reaction might qualify as being named hydrolysis. If I recall correctly the Fischer Esterification allows using anhydrous isopropyl alcohol as the alcohol to produce the biodiesel ester with different viscosity and flow properties than biodiesel made with methanol. Anhydrous isopropyl alcohol will not transesterify with vegetable oil to produce an ester product, but it will form an ester with the free fatty acid as a starting material. The general formula for the forwards and reverse equilibrium reaction for the Fischer Esterification does apply. Weak carboxilic acid (ffa's) plus dry alcohol plus strong mineral acid catalyst (H2SO4?) yields the ester (biodiesel) plus one water molecule and it's an equilibrium reaction so it goes in reverse also. Wet biodiesel stored a long time can have water add to the molecule producing a free fatty acid and an alcohol. In practical terms it might not make any difference, but on paper at least it occurs. The factor I don't know is reaction rate. So it might take a month at room temperature to break down/decompose significantly or it might take 100 years, but it does happen. In the absence of a catalyst the hydrolysis reaction rate is slower. The dryer the better (in theory) The purer the better ( catalyst has been removed).
All points taken and noted David. That is the way we were tought and we have just carried on from that thinking, but now I'm not so sure.
Bubble and settle with water content around the 600ppm for as long as some have done this method and the vehicle never shows signs of running anything but normal.
I have certainly cut down on my drying times lately.
So does this mean that the possibility exists that when we have re-tested a batch of finished bio and we note an increase in the water reading that we thought was due to the hygroscopic nature of the bio it could be actually due to the reaction you are describing.
Dgs In the hydrolysis reaction , water plus fatty acid methyl esters yields free fatty acids plus methanol but the water content decreases rather than increases. Two molecules, water and a fatty acid methyl ester react with each other to produce two different molecules, fatty acid and the alcohol (methanol). The water ceases to exist. Water is two atoms of hydrogen bonded to one atom of oxygen. If you add up the total number of atoms in octadecanoic acid methyl ester then hydroyse it with water to yield methanol plus the free fatty acid octadecanoic acid, then add up the number of atoms present in the 1 methanol molecule and one molecule of octadecanoic acid, you will see there are two hydrogen atoms and one oxygen atom extra in the products yielded and the water no longer exists. The atoms in the water in a way broke apart and reconnected or bonded to another molecular structure, the water changed into two other materials. The water is consumed in the reaction. In chemistry, except for nuclear reactions, mass is not destroyed. The three atoms that formed the water still exist but they are bonded to other atoms/elements that are not water, they are bonded to the alcohol, methanol and a free fatty acid. So the observed tested water content would decrease. The reaction is slow in the absence of a catalyst, it's faster in the presence of a strong acid and at higer temperature. Generally speaking the higher the temperature, for organic reactions like hydrolysis a ten degree celcius increase in temperature doubles the reaction rate. Without catalyst at room temperature hydolysis probably would be slow but storing wet impure biodiesel for two years might make the water a factor in causing breakdown of fatty acid methyl esters to fatty acids and methanol, the starting materials. I made ethyl biodiesel years ago. I think hydroysis might have been a factor in the contents of that small ethyl biodiesel storage bottle today. Some solid has precipated out in that bottle at room temperature.This message has been edited. Last edited by: WesleyB,
I now understand.
I've lived in various places in the US over the last 20 years. In areas where you have high humidity like the Pacific Northwest and the Sandhills along the coast in the Southeast, (similar environments to IMB's) your biodiesel can absorb water out of the air and getting it dry to start with can be difficult. I currently live in North Texas and I have no problems getting it dry enough just letting it sit in a open drum (covered with window screen to keep the bugs out).
Water in your biodiesel can affect storage.
There are a couple of articles in Make-Biodiesel.org that apply here:
Drum Vent Desiccant
Thanks for all the interesting pointers and info. I have another little problem and hope somebody can advise me what to do> Smell of fries and russian s when I drive. Is ther a way one can loose these odours? surely would appreciate any sugestions.
A catalytic converter does wonders for removing the "burnt cooking oil" smell of running biodiesel.
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