[Biofuel] Geeky process question
Hi Bob; I notice you are very sharp on the chemistry so I have a question for you regarding the biodiesel process. Copying to list as well. I am wondering if in these processes where you have two phases that separate does the separation proceed over time by an exponential decay? I mean if I measured the amount of say glycerine that comes out per unit of time would it be described by a function something like Y= X(1-e^-t/tc) where Y would be the amount of glycerine at a given time, X is the total amount which will ever settle out, t is the time interval and tc some time constant for the reaction conditions? If this IS the case then what factors would dictate tc?? Where I am going with this is that in electronics we use this formula to describe the charging of a capacitor. Basically after a period of time equal to five time constants there is already 99% of the maximum you will ever get in the capacitor. I am trying to determine a cutoff point for settling in order to optimize the process in terms of time, without raising contamination levels in the final product unduely. Am I on the right track here? Sorry but I am not trained in chemistry. Joe ___ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
Re: [Biofuel] Geeky process question
Say Joe, Wouldn't be appropraite if you put Bob Allen - Geeky process question in the heading? fredOn 1/9/06, Joe Street [EMAIL PROTECTED] wrote: Hi Bob;I notice you are very sharp on the chemistry so I have a question foryou regarding the biodiesel process. Copying to list as well.I amwondering if in these processes where you have two phases that separate does the separation proceed over time by an exponential decay?I meanif I measured the amount of say glycerine that comes out per unit oftime would it be described by a function something like Y= X(1-e^-t/tc) where Y would be the amount of glycerine at a given time, X is the totalamount which will ever settle out, t is the time interval and tc sometime constant for the reaction conditions?If this IS the case then what factors would dictate tc??Where I am going with this is that inelectronics we use this formula to describe the charging of acapacitor.Basically after a period of time equal to five timeconstants there is already 99% of the maximum you will ever get in the capacitor.I am trying to determine a cutoff point for settling inorder to optimize the process in terms of time, without raisingcontamination levels in the final product unduely.Am I on the righttrack here?Sorry but I am not trained in chemistry. Joe___Biofuel mailing listBiofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.orgBiofuel at Journey to Forever:http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages):http://www.mail-archive.com/biofuel@sustainablelists.org/ ___ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
Re: [Biofuel] Geeky process question
Howdy Joe, to be honest I have never given thought to the kinetics of phase separation, although your intuitive guess at an exponential rate for the process certainly seems reasonable. Variables would include viscosities of both phases, the difference in densities of the phases, and maybe the difference in the polarities of the phases, and I would bet most importantly, temperature. The variables are not completely independent as viscosity is a function of temperature, even the densities may vary differently as a function of temperature. Further, unless you have essentially infinite partition coefficients, you will always have some of each dissolved in the other. and one more thing, the two phases are not homogeneous, the glycerin phase also contains the unreacted methanol, and alkaline catalyst, small amounts of mono and diglycerides, etc. If I were to approach the problem, I would certainly do it empirically. take crude reaction mixture after it had cooled to room temperature (to control for temperature which is an important variable), remix it, then put it in a burette, and monitor phase separation over time. All that having been said, does it really matter that much, considering that good washing will remove any of the glycerin cocktail not separated by gravity? Hi Bob; I notice you are very sharp on the chemistry so I have a question for you regarding the biodiesel process. Copying to list as well. I am wondering if in these processes where you have two phases that separate does the separation proceed over time by an exponential decay? I mean if I measured the amount of say glycerine that comes out per unit of time would it be described by a function something like Y= X(1-e^-t/tc) where Y would be the amount of glycerine at a given time, X is the total amount which will ever settle out, t is the time interval and tc some time constant for the reaction conditions? If this IS the case then what factors would dictate tc?? Where I am going with this is that in electronics we use this formula to describe the charging of a capacitor. Basically after a period of time equal to five time constants there is already 99% of the maximum you will ever get in the capacitor. I am trying to determine a cutoff point for settling in order to optimize the process in terms of time, without raising contamination levels in the final product unduely. Am I on the right track here? Sorry but I am not trained in chemistry. -- Bob Allen http://ozarker.org/bob Science is what we have learned about how to keep from fooling ourselves - Richard Feynman ___ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
