Hi all, Keith asked me offlist for directions for the acid number determination. Here's the info, forwarded from an offlist exchange I had with Todd Swearingen a few weeks ago, about this and other quality standards stuff... Mark
>Date: Thu, 10 Oct 2002 00:55:01 -0400 > > >Maria, > >Looking at the ASTM standards as the benchmark for home brewers, >most of the standards can be met simply by preparing and washing >the fuel well. > >A) Flash point (130*C minimum) will be relatively consistent for >all feedstocks, presuming reaction completion and the alcohol is >removed. If the alcohol is distilled or washed out this is a >non-problem. >B) Water and sediment (0.050 maximum % by volume) are >non-problems with adequate settling times, filtration and fuel >reheating to ~120*F. (I don't suggest adding any acid to clear >fuel haze, as this will increase the acid number.) >C) Free glycerin (0.020 maximum % by mass) is removed and is a >non-problem with adequate settling time and washing. >D) Total glycerin (0.240 maximum % by mass) is reduced to nil and >is a non-problem if sufficient reaction time is permitted (mono-, >di- and tri-glycerides are all cracked), sufficient caustic is >used (not excess, as this can raise the acid number by cracking >methyl esters back to FFAs) and sufficient settling time is >given. >E) Kinematic viscosity (1.9 - 6.0 mm2/s at 40*C) will also be a >non-problem if the total glycerin content (Items C & D) has been >resolved and the acid number is not elevated by imprudent use of >caustic, causing back cracking of esters to FFAs (higher >viscosity than B-100). >F) Sulfated ash (0.020 % by mass) is a non-controllable when >using straight base, as the only sulfur in the equation is >derived from the parent feedstock. When using an acid/base >process the sulfuric acid used in the esterification step is >neutralized by the base. The resulting salt is soluble in the >water wash and should be a non-problem with proper washing. >G) Sulfur (0.05% maximum by mass) - see Item F. B-100 is >essentially sulfur free. >H) Phosphorous content (0.001% maximum by mass) is a >non-controllable relative to the parent animal or plant feedstock >and is a non-problem beyond that as long as phosphoric acid is >not used to clear fuel haze. Phosphoric acid can also increase >the acid number (acid + FFAs). This is why either adequate >settling times, and slightly warmed fuel are the better options >for clearing fuel. >I) Acid number (0.80 maximum milligrams of KOH per gram of fuel) >will remain low if acids are not added to the fuel either pre, >post or during washes (either to "ease washing"(?) or clear fuel >haze) and if caustic is not used in excess, which causes higher >numbers of esters to break down to FFAs. > >Other standards, such as distillation temperature, copper strip >corrosion, cetane number and cloud point are for all practical >intents and purposes properties that will fall within ASTM >standard if the fuel is prepared and washes are conducted >properly. > >As for a poor person's method of checking acid number....It can >be conducted in the exact same manner as the titration of the >original feedstock, save for the substitution of biodiesel for >oil. Keep in mind that the assay of the KOH being used will need >to be taken into consideration. If the assay is 90% for example, >the number of milligrams of KOH per gram of oil should be >multiplied by the % purity. > >One can also assay the KOH themselves with an acid titration. But >that's a bit out of the realm of probability for most shadetree >biodieselers. > >The in house chemist (Ph.D. in chemistry) suggests that a careful >titration using the same method as the original feedstock >titration should get you within + or - 10%, perhaps + or - 5% if >one is really precise. > >You could also use other indicators such as phenophtalein to >titrate the fuel. This would reduce the margin for error from the >"pH method," as pH is really designed for aqueous solutions. > >Hope this helps. > >Todd > Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ ------------------------ Yahoo! Groups Sponsor ---------------------~--> ˇFREE Health Insurance Quotes-eHealthInsurance.com http://us.click.yahoo.com/1.voSB/RnFFAA/46VHAA/9bTolB/TM ---------------------------------------------------------------------~-> 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/
