Keith, As always, I'm wonderfully impressed with your filing system for a summary on a topic. I agree that the viscometer test will not provide an absolute test for the completion of the esterification reaction, unless one runs a detailed calibration curve for a particular oil against results from a GC. And, also, a cheap viscometer will not produce results as good as a more sophisticated instrument.
However, a relative measure of the quality of a batch process may still be the best method of obtaining feedback on an inherently variable process. Without some convenient, cheap feedback method, how is a small volume producer able to understand the effect of the reaction parameters? We have seen here on this listserve that it is not practical to have contracted analysis of every batch, nor to support an in-house laboratory. Do you suggest a better method of quality control? Note that the viscometer method, even with a cheap instrument, got me to within 8/100 of 1% of the required ASTM level of total glycerin for the one sample I had tested. If I had not been so cheap with the methanol, going from 18% used in my usual reaction to, say, 22%, the reaction might have gone to near completion. My goal is to help the small producer find a way to make an acceptable biodiesel. Can we find ways to guide people towards a better product, or will it be a series of roadblocks for everyone without nearly unlimited time and money? I suspect that those limited number of current commercial producers wish us to believe that few, if any, others can make quality biodiesel. I don't believe that myself. Tom Leue In a message dated 11/14/03 5:08:37 AM, [EMAIL PROTECTED] writes: > Hello Tom > > Nice to hear from you again. I hope you're fully recovered now after > your accident. > > >Randall, > > > >I've been producing biodiesel for the past 6 years, until recently. I have > a > >scientific peer reviewed paper that shows an almost complete correlation > >between the quality (completeness) of the reaction and the > >viscosity. So, viscosity > >is the best indicator of the quality of the reaction. A cheap ($5.99) > >viscosity tester can be obtained from harbor freight). This is the > >best and most > >indicative test. > > A lot of people disagree with that. I presume you're talking of the > paper by De Filippis et al? "Transesterification Processes for > Vegetable Oils: A Simple Control Method for Methyl Ester Content". > You can find it here: > http://www.veggiepower.org.uk/report1.htm > > For a start, they weren't using a cheap $5.99 Marsh funnel-type > viscometer but a Hoeppler micro-viscometer, Haake's MicroVisco 2 - > this thing: > http://www.thermo.com/eThermo/CDA/Products/Product_Detail/1,1075,10000 > 01067494-108-X-108-1000000008451,00.html > > Not quite the same thing. And yes, it matters when you're trying to > distinguish the very small differences in viscosity between > glycerides and methyl ester accurately enough to be sure that your > reaction has gone far enough towards completion to fall within the > quality standards: "Total glycerine (free glycerine and unconverted > glycerides combined) - 0.240% by mass, max." (ASTM D-6751). > > A funnel viscometer (or a PET bottle and a straw) won't get you near > that, maybe within 5%, not good enough. The "almost" in "almost > complete correlation" is rather critical. > > This is what Mark (Girl Mark) said about viscosity tests as a quality > measure: "What this test won't tell you: Again, mono- and > diglycerides foul it up. The viscosity of MG and DG are close enough > to biodiesel that home-scale viscosity measurements can't detect > them, and, again, in unwashed fuel the methanol gives us even more > inaccuracies to worry about. I do not recommend this test unless > you're a fuels lab." > > She said much the same thing about the other "quality test" popular > with some people, specific gravity (density). > > We say much the same: > > http://journeytoforever.org/biodiesel_make2.html#visco > Viscosity testing > "... a useful comparative indicator of biodiesel quality. > Unfortunately, and despite claims to the contrary, that's all it is > -- a comparative indicator: this batch is better than that batch. > Even at the laboratory or industrial level, viscosity testing alone > cannot tell you if the process has gone far enough before reaching > equilibrium -- in other words that there are not unacceptably high > levels of harmful unreacted and partly reacted materials in your > fuel..." > > Aleks Kac said this in a message to the Biofuel list: "I've seen bio > with a SG 0.885 g/l (excellent) and have a kinematic viscosity of > 10.5 cSt (horrible) but an acceptable cetane number of ~50!" > > The De Filippis paper on viscosity testing was discussed at the > Biodiesel list when it was first posted. Here's what Todd Swearingen > said about it: > > >Date: Tue, 21 May 2002 12:36:15 -0400 > >Subject: Re: [Biodiesel] Quality testing > >Reply-To: [EMAIL PROTECTED] > > > >If only curves and viscosity worked that way. They might get you > >ballpark,Ê inside of 5% or a little less, depending upon the > >precision of the person graphing the curve or the number of > >experiments conducted. But a 2-5% uncompleted reaction will still > >leave you with a wash tank, barrel or carboy filled with a mess > >and a "fuel" that wants to strangle an engine on early morning > >starts and spits out higher volumes of white smoke compared to > >completely reacted biodiesel. > > > >They are also referring to more precision equipment than what has > >been relied upon in previous conversations here or at the Maui > >board, which further reduces any shoddiness in margin > >calculations. > > > >Many industrial processes include in-line viscometers to let > >operators and technicians know when they are at different levels > >of a given process. This eliminates the need for as many "grab > >samples" as use to be conducted. But they are only relied upon as > >indicators, not absolutes, and almost invariably there are other > >factors that are added to their processes after taking such > >initial measurements which insure that the desired result has > >been reached. These generally include prolonged dwell time and/or > >temp and pressure modifications with a final "grab sample" > >submitted for analysis to "seal the deal" of product integrity. > > > >Todd Swearingen > > > >----- Original Message ----- > >From: hcr_ii <[EMAIL PROTECTED]> > >To: <[EMAIL PROTECTED]> > >Sent: Tuesday, May 21, 2002 12:00 PM > >Subject: [Biodiesel] Quality testing > > > >>Seems that you might be able to test quality based on an accurate > >>measure of viscosity after all. > >> > >>"......They then used gas chromatography (GC)(the same analysis used > >>by large fuel companies) to determine %methyl esters, %mono, di, and > >>triglycerides still in the samples. They also measured the density > >>and viscosity of the mixtures at 20 and 37.8 C. Using the results > >>from the GC they developed correlation curves between % conversion > >>and the density and viscosity of the esters. So all you have to do is > >>measure the viscosity or density at 20 or 37.8 C to figure your % > >>conversion." > >> > >>You will find the source on the Maui board. > > And about funnel and PET bottle-and-straw viscometers: > > "Our resident chemist is more inclined to compare your viscometer > with the "taste, smell and feel method" of determining whether or not > a reaction has gone to completion. A better "shadetree" indicator of > reaction completion for those without GC or LGC - which is almost > everyone who has ever made or will ever make biodiesel - is what > takes place in the wash." > > Indeed. > > I have to say that viscosity testing doesn't seem to have helped you > much with quality Tom, and just where it would be expected not to > help - glycerin content: > > http://archive.nnytech.net/sgroup/biofuels-biz/3152/1/ > Date: 2003-07-28 > From: [EMAIL PROTECTED] > Subject: [biofuels-biz] Almost ASTM Fuel > >My results were good, but not quite good enough. There are 14 > >parameters tested under the ASTM standard. I passed 13 of them. The > >last one was Total Glycerin: this is basically a measure of the > >completeness of the overall reaction, breaking down the oil into > >methylesters. The standard is no more than 0.25% total glycerine > >from unreacted oil. My results came back at 0.33% total glycerine. > >That is 7/1000 off of the standard. Everything else met the > >specifications. > > It was Aleks who first told you about viscosity testing, on the > Biofuel list just two years ago, but he didn't suggest it as a > biodiesel quality test, he was discussing your problems with burning > biodiesel in your mother's furnace. Here are the archive links to > that discussion: > > http://archive.nnytech.net/index.php?view=9541&list=BIOFUEL > From: [EMAIL PROTECTED] > Date: 2001-11-04 > Subject: Here in the frozen North > > http://archive.nnytech.net/index.php?view=9546&list=BIOFUEL > From: "Aleksander <kac" <[EMAIL PROTECTED]> > Date:Ê Mon Nov 5, 2001Ê 6:05am > Subject:Ê Biodiesel for heating was:Here in the frozen North... > > http://archive.nnytech.net/index.php?view=9566&list=BIOFUEL > From: [EMAIL PROTECTED] > Date:Ê Mon Nov 5, 2001Ê 10:38pm > Subject:Ê Re: [biofuel] Biodiesel for heating was:Here in the frozen > North... > > http://archive.nnytech.net/index.php?view=9573&list=BIOFUEL > From: "Aleksander <kac" <[EMAIL PROTECTED]> > Date:Ê Tue Nov 6, 2001Ê 6:18am > Subject:Ê Re: Biodiesel for heating - viscosity > > http://archive.nnytech.net/sgroup/biofuel/9580/1/ > From: [EMAIL PROTECTED] > Date:Ê Tue Nov 6, 2001Ê 12:58pm > Subject:Ê Re: [biofuel] Re: Biodiesel for heating - viscosity > > http://archive.nnytech.net/index.php?view=9581&list=BIOFUEL > From: "Aleksander <kac" <[EMAIL PROTECTED]> > Date:Ê Tue Nov 6, 2001Ê 1:33pm > Subject:Ê Re: Biodiesel for heating - viscosit > > I think viscosity testing (and SG) can give people a false sense of > confidence in the quality of their homebrew, and helps to enshrine > some rather dubious practices as acceptable, or even as standard, > though they do not help to achieve a quality product and more likely > hinder it. > > Best > > Keith > > > > >Tom Leue > > > >In a message dated 11/11/03 9:07:16 AM, [EMAIL PROTECTED] writes: > > > > > > > Greetings, > > > > > > I would appreciate learning if there is a fairly simple and affordable > > > Fuel Quality test system for the home producer of biodiesel. > > > > > > Randal Son > > > "Resist Convenience" > > ----------------------------- Homestead Inc. www.yellowbiodiesel.com [Non-text portions of this message have been removed] ------------------------ Yahoo! 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