I got some oil from a different source and was lazy to titrate it. I usually do a glycerin from last batch prewash,settle for an hour drain and add the methoxide(16% methanol, 5 grams Naoh). Usually I am able to pass the 3/27 this way and after bubbling air for a day the soap level drops significantly and was a able to get to a soap content of about 90ppm after a week of settling and was happy with it although some glycerin kept settling afterwards, by the way is there any other way except for water washing to force the glycerin out quickly?
This time since I did not pass the 3/27(and was lazy again to reprocess) I decided to add 10% kerosene to thin it and hopefully aid in settling soap and glycerin(soap levels stayed high after bubbling).
After this soap levels are still very high so I am thinking of water washing the mixed with kerosene bio. Is it a good way to solve this? Since not fully converted I might get emulations?
It has always been reported over the years that water washing biodiesel containing unconverted amounts of oil (triglycerides) will produce emulsions.
A while ago I intentionally under-converted a batch to run in my IDI van. A 10/90 test showed 0.8mls dropout. I water washed the batch and the process worked as normal with no emulsion.
Maybe it depends on the amount of unconverted oil present, but suprisingly this batch was normal.What the kerosene present would give you I have no idea. Best try is on a small sample first.
Just a slight correction,
There are three "flavors" of unconverted and partially converted oil present. Monoglycerided and diglycerides are partially converted and triglycerides are unconverted.
It is the monoglycerides and diglycerides that are said to make emulsions, not the triglycerides.
Also, if you use hard water for the wash it is a lot less likely to form an emulsion than if you use soft water.
Try hot water wash.
Agree -- and add salt (plain old NaCl table salt). It's been a long time since I had the issue, but many of us have found that saltwater is very effective in breaking an emulsion.
ytk; I see you used 16% by volume of dry methanol. Without digging through my papers, that's kind of a minimal amount to use. It's an equilibrium reaction. Using 20% methanol would shift the reaction to the right (a more complete reaction). A bigger excess of methanol would probably cause better results. If you use sodium chloride salt to break the emulsion or hot salt water, wash it afterwards to get all the salt out of the wet biodiesel. I wouldn't want salt going into my combustion chambers of my motor. Salt doesn't burn very well.
Good point, Wesley -- adequate (actually, good) washing should be an assumption in any process.
Is NaCl soluble in biodiesel? I never actually tested that and would be curious to know the answer. I believe salt is largely insoluble in oil/fat. Obviously it is highly soluble in water. I think that difference is one of the reasons it is effective in breaking emulsions, but I'm certainly no chemist. Your point secondarily emphasizes the importance of drying the fuel, because there is no question that the water used to break the emulsion contains salt -- and whether fresh or salty, water in your fuel carries a high likelihood of negative outcomes.
You're right - salt is completely insoluble in bio. It is useful for breaking emulsions as it disrupts the micelle interface.
I'm currently working on a water washing process for my room-temp method, as I want to speed up the glycerol removal process. If water washing is going to work, it should be acidic. The reason is simply that soaps are alkaline, and by acidifying the process you protonate the FFA, thus rendering it hydrophobic. The acid would have to be a weak acid, so that you don't dissolve your processor. Preliminary tests with acetic acid look good so far, but any weak acid should work, depending on what is available. I'd investigate citric (it's usually available cheaply) or sodium bisulphate (dry acid from the pool chemical section of a hardware store)
Aren't they neutralized during the reaction?
"Common Knowledge" is that by adding acid to the wash you will convert some of the soap back into FFA's which is not desirable.
I dissloved some potassium soap in water. I added a little maybe vinegar or stronger acetic acid. It was done in a small beaker. When I warmed it up a bit with a cigarette lighter free fatty acids floated to the top of the mostly water solution. Free fatty acids are less dense than water so they float on water. Acetic acid is a stronger acid than long chain free fatty acid so the proton on acetic acid swaps places with the potassium bonded to the weaker acid, free fatty acids. You can look up the boiling point of free fatty acids compared to their corresponding fatty acid methyl ester. The free fatty acid boils at a significantly higher temperature. So when fatty acids dissolve in biodiesel, it hinders vaporization of the fuel when it's injected in the combustion chamber. I expect water washing with pretty pure water is better for a wet washing method. I think as a last resort vinegar or acetic acid is useful in breaking emulsions, but that puts free fatty acids into you finished product fuel. On that subject, I made sodium or potassium soap. I put it into a large beaker. I poured some amount of muriatic acid into the beaker. I warmed it up, with stirring with a big glass rod. When it warmed up, it became free fatty acids that were very white, sodium or potassium chloride dissolved in water plus some glycerol. The free fatty acids were hard to clean out of the beaker. It kind of stuck to the container. I couldn't wash it out with the solvents I tried. I resorted to wiping it out by mechanical methods rather than chemical methods ( used an old cloth towel). I expect free fatty acids probably dissolve in biodiesel to some extent. It might be difficult to remove free fatty acids from biodiesel.
Thanks everyone,I ended up water washing it normally and it did help!
When a batch does pass the 3/27 test I only bubble air it (as suggested here!) and it does work in lowering the soap levels, it seems that some soap settles and some floats?,I collect the floating stuff, once soap stops floating I know it is pretty low in soap and test it.
Glycerin might still continue to settle after that, is there another way other then water washing to force glycerin out?
I do want to recycle the stuff left in the glycerin in the next batch and save on chemicals but it does add a lot of hassle to the process if you want to be accurate.
Thanks to you guys and your different opinions and methods I learned and still am learning how to properly make and test biodiesel!
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