Hello Andreas, Bill Just to add that it can be difficult to remove the water content from animal fats in used oil. Andreas, you raise a good point with water-soluble contaminants (which can also throw out titration results). In some severe cases I've found it useful to wash the oil first - a hot bubblewash: heat the oil to about 70 deg C, add 50% of water at near boiling point, bubblewash for half an hour or longer while maintaining heat at 70 deg C, settle and cool, drain off water, then dry oil as usual. This has the advantage of removing the water-solubles, whereas, as you say, simply heating the oil to remove the water will leave them behind, and possibly some water with them. But it's quite energy-intensive. I like Girl Mark's advice here - find better oil!
>Bill, > >you are right (in principle) - allthough this process is dangerous because: > >- Water in oil can suddenly start boiling (like a mini-explosion) and spit >oil around. To avoid this keep stirring the oil. >- Water on the bottom (where it usually is because of the higher density) >underlies a higher pressure then at the top - thus the boiling point rises >according to the height of oil above. So the boiling point may not be 10 >degrees Celsius but above. >- If mixtures of water and other substances occur (in our case e.g. salt or >sugar solved from the french fries etc.) the boiling point is significantly >above 100 degrees. > >This and the fact that you need (some, not much) more energy to heat up to >the boiling point you usually prefer to just heat the oil to 60 - 70 >degrees and then wait for the water to separate (which it usually does in >about the same amount as if you would boil it). If it does not, you will >have the same problems removing it by vaporiszing because in this case the >oil will be additionaly impurified with all the stuff that has been solved >in the water and that's now left behind because the vapour is pure water... One point on energy use in comparing the two main dewatering methods is that heating to 60-70 deg C and settling loses the heat, whereas with boiling it off, while using lots of energy, you can at least catch it "on the way down" and start processing the oil once it's cooled to 55 deg C, saving some of the extra energy. But more heat carries the danger of creating more FFAs, which adds to boiling being the less preferred method. >Hope this helps... Me too! :-) Best Keith >Andreas Ohnsorge > > > > > "William Clark" > > <eufclark To: ><biofuel@yahoogroups.com> > > @bellsouth.net> cc: > > Subject: Re: >[biofuel] steam versus oil heating for commercial plants > > 23.05.2003 04:21 > > Please respond > > to biofuel > > > >Hello Andreas, > >Perhaps you could help me with a chemistry question. When water boils, the >temperature of a solution will not exceed 100 deg. C until all water is >boiled off, correct? If oil containing water is heated, does this still >apply? More to the point, can the absence of water be determined by a rise >in oil temp beyond 100 deg. C? I truly have no clue if any of this is >right. >Your help or others would be most appreciated. > >Bill Clark <snip> ------------------------ Yahoo! Groups Sponsor ---------------------~--> Get A Free Psychic Reading! Your Online Answer To Life's Important Questions. http://us.click.yahoo.com/Lj3uPC/Me7FAA/uetFAA/FGYolB/TM ---------------------------------------------------------------------~-> 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/
