Though wash problems weren't a main point of this thread, they've come up again in there, so...
Let's not forget that soaps (I guess I've made this point in this thread already) also cause wash problems, along with the wash problems caused by poor conversion. I think when you have emulsification (sounds like Paul did a few weeks ago, and I'm wondering if it's related to his skin/middle layer formation), it's hard to tell what causes it, without testing. It's good idea to do some sleuthing to try to figure out what caused it and to try and to determine which of the two conditions it is- soaps of poor conversion. Soapy biodiesel I've made also produced skins and middle layers that I assume were soaps. the soaps bit correlated to high initial pH and then to washing problems. And to very, very white first wash water once it did separate Maybe I'm wrong about this, but in my experience the skin formation correlates to higher pH, and to wash problems. I assume when I see a skin or a transluscent, greyish middle layer, it's a sign that a hard wash is coming. For me this means that there was water in the oil, or that I used too much catalyst, or that it was high-ffa oil (which I almost never work with unless I'm doing it to make a point to students or something). Some biodiesel I'm working with right now (we made 150-200 gallons before realizing that it emulsifies like crazy in the wash, our mistake in getting slack on doing regular quality testing) has the opposite problem, emulsifying but the pH looked like it was going to be decent fuel. I reprocessed some and a lot of glycerine dropped out on that batch, so I;'m leaning towards poor conversion rather than soaps etc as the source of the problem. I agree that we all might be talking about several different skin-forming phenomena here, though. I personally have very little experience with animal fats as feedstock, and I know that animal fats can introduce some other variables into the picture than vegetable oils. Paul, you're working with several variables that could potentially lead to either soaps or to poor conversion. My suggestion is for you to try to eliminate some of these variables by trying a trial with some very conventional processing to get a 'baseline' idea of how that oil might behave. Conventional in my mind includes: 1. DG and MG: eliminate agitation as a variable by running a long 1-hour agitation on a bucket-batch, drill/paintstirrer-agitated, maybe pulling some samples at 15-minute intervals to run tests on, to see what role agitation plays in the fuel quality. 2. DG and MG again: get the temperature up somehow. Try to make sure your small 10L batches don't lose heat so fast. I've done 2-stage in 10-liter batches and it requires a lot of reheating to remain at proper temperature. Of course it might be more crucial in two-stage acid/base, or maybe not... it seems that with singlestage some people have had problems with improper temperature as well. A hot water bath for the jugs you're using, or an immersion heater for a 5-gallon metal can, or a hotwater heater element for the same metal can, or doing a 10-liter batch in a canning kettle on a hot plate (still drill-agitated)... 3. Soaps: eliminate water as a variable and use a non- conc. aqueous process just for this trial. 4. Soaps: again, eliminate water as a variable by dewatering the oil you';re using. 5. catalyst quantity: trial and error batches, assume that you don't know what the base amount of catalyst should be for that particular oil. Work with 3.5 on up to 5 g base catalyst (for NaOH anyway) 6. conversion % again: Make sure your methanol doesn't evaporate, though in jugs it shouldn't 7. eliminate the 'glycerine draining' variable, though I can't see what difference this should make, doesn't seem harmful to me. 8 then try your entire own process, jugs, conc aqueous, low agitation, and all, with some totally different feedstock oil... Good luck! Mark At 07:11 PM 12/16/2002 +1000, you wrote: >----- Original Message ----- >From: Keith Addison <[EMAIL PROTECTED]> >Subject: Re: [biofuels-biz] skin on biodiesel > > > > Hi Paul, Michael > > > > How do you maintain the heat during the processing hour, Paul? > >Keith as this is trully a bucket method of temporary production I don't >maintain the 55 deg. The plastic bucket loses heat slowly. > > > You're using an aqueous solution of catalyst to make methoxide? > >Yes > > > Wouldn't draining off the glycerine as soon as possible also drain > > off some excess methanol? > > >By "draining off as soon as possible" I mean after the final settling after >last stirring, reaction should have gone as far as it can go by then without >further heat and stirring. Methanol excess to reaction will have dispersed >itself in both BD and glycerine. If there is to be no further reaction, the >more excess methanol that comes off in the glycerine the better. > > > And doesn't severe emulsification during washing indicate high levels > > of unconverted materials? > >That seems to be the general concensus, would say that the higher levels of >alkali ensure better reaction, this of course could be specific to my >production methods and trials, a more complete reaction process may produce >the same results with lower levels of alkali. > > >SG and viscosity testing won't necessarily give you an indication of that. > >No, the production of lower SG and viscosity was quoted as an observation of >what also happens with higher than titration indicated alkali levels. > >Regards, Paul Gobert > > > > >Biofuels at Journey to Forever >http://journeytoforever.org/biofuel.html >Biofuel at WebConX >http://webconx.green-trust.org/2000/biofuel/biofuel.htm >List messages are archived at the Info-Archive at NNYTech: >http://archive.nnytech.net/ >To unsubscribe from this group, send an email to: >[EMAIL PROTECTED] > > > >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Biofuels at Journey to Forever http://journeytoforever.org/biofuel.html Biofuel at WebConX http://webconx.green-trust.org/2000/biofuel/biofuel.htm List messages are archived at the Info-Archive at NNYTech: http://archive.nnytech.net/ To unsubscribe from this group, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
