Paul & Keith, Thank you for your response.
> >Paul: > > > >I tried slaked lime on some of our high FFA crude > palm > >oil and had similar results to Keith. Leaving it > >overnight to settle gave me only about 15% recovery > of > >the oil. > > > >Part of the problem is the very high viscosity of > our > >CPO which is rather like mayonnaise even at 30 > degC. > >Things just don't settle in this goo unless you > heat > >the brew. > > If you heat it does it settle? We did. To 80C. But separation was not good: Bottom layer soap, middle layer unreacted lime, thin top layer oil. Avoiding excess Ca(OH)2 would certainly help. > >Terry's suggestion of quicklime has some merit > because > >it takes the water out of the gloop as it > esterifies > >the FFA but it still has such a low density that it > >doesn't settle for us. We probably need barium > oxide > >or maybe something made from spent nuclear fuel > rods! No offers about the procurement of nuclear waste have yet been received! > >Keith: > > > >For the same reason, we find your cold NaOH > treatment > >won't work for us. In fact our yellowy-orange > >mayonnaise turns into engine grease when we mix in > the > >NaOH solution at 30 degC. Mind you, this crude palm > >oil (CPO) titrates at 18.5 ml 0.025M NaOH/(ml of > >oil) > > That's rather an unreasonable level of FFA - what > would it be, about > 50% or something? Unless I am doing my sums incorrectly, that comes to 13% expressed as palmitic acid or 14% expressed as oleic acid. And hey, this is one of our better crude palm oils! > Could you manage to mix only 10 ml thoroughly in one > litre of oil? > Isn't the NaOH likely to get used up on only some of > the oil before > it's thoroughly mixed? That's why I took to using a > bit more water - > 40 ml/litre of oil, maybe a bit more with sticky > stuff like that. > > > at 80 degC in the oven just to see > >if anything settles out overnight. And it did! The trick was to carry out the reaction in the 70-80C range and settle it at 80C. Most of the soap floated to the top at this temperature. We got about 70% recovery of the oil after soap separation. This oil subsequently formed methyl ester without any problems. So it's thumbs up for Keith and the saponification-transesterification process! And I think it is also thumbs up for Alek's esterification-transesterification process with the same CPO. (At least with a few local modifications). Right now, the brew is in its finishing stages down in the lab. I'll let you know how it goes. > I found heating the oil made it more likely to turn > into a soapy mess > rather than just dropping out the saponified FFA. > I'd been heating it > to 55 deg C. Soap density is too similar to our oil density around 55C. 80C worked well but it still took 8 hours to get good separation at that temperature. > But with that oil you may have to resort to the > industrial caustic > refining method - 100% water (or something) and > either heat or not, > and separate it with a centrifuge. :-( That works too and we can get about 70% recovery of the oil in that saponification process also. Almost all of the water lands up with the soap and may affect its density. This could explain why the local commercial lads can make their soap sink and avoid the use of a centrifuge. > If it gets reasonably unviscous at 75-80 deg C, > maybe it's more > suited to a dual-fuel pre-heated SVO system. Not for > DIs though. Tried that. An agricutural diesel working on a fixed load with this SVO runs for about 300 hours before it croaks. Curiously, one result is the thickening of the lube-oil to a tarry viscous material. Sound familiar?. Incidentally, using the commercial de-acidifying process and a phosphoric degumming stage makes the refined SVO a much more suitable fuel. Under identical conditions, it gave over 500 hours and was only stopped because stearin precipitation in the fuel lines and filter gave problems (including spark-erosion of the piston head). > Or > for a pressure biodiesel process, or enzymes. Yes I think that you are correct. For the pressure process, my calculations indicate a general time reduction in both reaction and settling if we go to just 2 bar. This is mainly because of chemical kinetic and viscosity effects of elevated temperatures. But I have yet to test this out. Lipidases look to be quite a promising line for enzymatic ester formation but the literature available to me indicates poor yields and extended residence times. Thanks again for your response. Very much appreciated. Michael Allen Thailand __________________________________________________ Do you Yahoo!? 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