Hello Folks
I apparently suck at the search function. I just had a quick question about the acid esterfication.

Mainly that I can titrate my oil to determine FFA, then I am adding acid and reacting. If I test my oil for FFA again after this do I not get the effects of the acid in the titration as well? Or is the acid used. Basically do I have to modify my titration equation for the acid esterfication step.

I also have found a few different ways of doing the acid. One uses 0.5g/kg H2SO4 (so 0.5g of H2SO4 per kg of oil) the other uses a calculation based on the FFA content of the oil. Any literature/comments on this?

The methods for AE vary for sure! If you start with dry wvo you can use the formula T * .15 * ltr of oil to determine the acid requirement. If T is greater than 15 KOH use T * .1 for acid amount.
-When we check for T the total acid number of the wvo is what we determine. that is the combined value of ffa and acids from the food that has been cooked in the oil. When we check for t after AE the T value also includes the Sulfuric acid in the mix. This is one reason why there are differing ending Ts. A batch that was intitialy mixed and left to sit will have a lower T value than a batch that was mixed throughout the process. In the first case, the acid has mostly settled out.
-there is no reson to alter the T results, it will take the amount of caustic indicated to process the remaining acids in the oil wether they be from sulfuiric acid or remaining ffa's. Tom

One important thing Tom forgot to note, after you do the acid treatment, drain 2-3 liters off the bottom of the oil. If you don't, any of those heavier acids that settled out will get mixed back into the oil and you may be short of catalyst to push the conversion to completion. I keep a cubie marked "Acidic Oil" to keep the oil in and dump it in the next batch that needs AE.

Norman

-One important thing that Norman forgot to mention is after draining some crud (this only applies if the ae treatment was initialy mixed and allowed to sit) mix well prior to T to be sure any remaining acid is mixed in or you WILL be short on caustic for the base reaction.
-I don't understand the theory behind mixing the crud back into the next batch, it will have water which can negatively affect the next AE.(one would have to increase the acid amount to try and compensate for this?) Tom

Right you are, Tom, we probably both forgot something else important, like using the total volume of the batch (including methanol added) not just the original WVO when figuring the catalyst load.

I always have just added the trailings back in thinking the residual acid would be used up converting the FFa's on the next load. I pitch any water that is out of suspension as it usually is on the very bottom of the load. I will do a couple controlled experiments with the drainings and see what effect it has on the pending batch. I do not attempt to reuse any drainings from oil that has a high original T as it is usually pretty disgusting. I would say high T is 15 or over.

Norman

Alright I guess my question now is: How do I determine if the esterfication was a sucess or a failure? How do I test level of completion then if I can't really get an accurate FFA #?

-The amount of caustic required for the following base reaction is determined by T after AE! Make sure you mix everything up good before taking the sample. There is formula to determine what the ending T will be if all ffa is converted, but it is just toooo complicated for this old brain, but DD is the guy for that.
-was your AE sucessful? If T droped to 1 - 2.5 then I consider that a great reaction. The batch I did overnite started at 7 NaoH and finnished at 1 that was 160ltr of oil, 14 ltr of methanol and 150ml of sulfuric acid. Tom