I have done a lot`S of processing.... and wondered why I have to use (7gram + my tritration level let`s say 3gram) = 10gram/Ltr oil ... why 7 gram... as standard... I have still have little soap in my bio after washing much and drying. What are poeple doing... 7 gra or some says 7.5 grams + tritatrion level.. ??

I have always used KOH and still will ..that natriumhydoxide is much more difficult to decilute (sorry) in methanol....

Thanks for great Forum here...

Gert.

Hello Gert

The Chemist "Neutral" (Industrial Research Chemist, PD , over 20 years Biodiesel and Alternate Fuels R&D) performed some GC tests that showed that if You want to Meet ASTM conversion it takes At Least 7g KOH mixed into 210ml methanol per litre of new oil.
If your KOH is less than 100% purity which is common, you need to adjust to compensate.

Thanks. for answer.... I think ...as you describe ... that I have to adjust the KOH as it is not 100% clean... ...

Thanks... Gert.

The reason for needing 5g NaOH (Sodium Hydroxide)or 7g KOH (Potassium Hydroxide) is that that amount of caustic is required to "catalyse" the reaction, making oil into biodiesel.

As Tilly has said, purity considerations will require that the KOH needs to be increased to account for 90% purity KOH. Similarly, if using NaOH which has degraded due to exposure to air will require test batches to determine the correct amount to use.

Soap formation in the biodiesel reaction is from 2 main causes:
1. Neutralisation fo the FFAs
2. Presence of water in the oil (including a little released during 1. above)

If you have washed your product, there should be no soap in it.
What you are seeing is likely to be biodiesel solidifying, due to the temperature of the biodiesel & the type of oil used in its manufacture. Biodiesel made from oul having a large proportion of tallow or hydrogenated palm oil makes biodiesel with high melting point esters present. These can solidify at various temperatures.

Once the biodiesel has been dried, warm it up and see if the cloudiness or solidification clears. If so, it is most likely due to high melting point methyl esters, solidifying at the ambient temperature.
This is not a bad thing as these high meltingp oint esters have a higher energy than the lower MP esters. For winter operation, you may wish to filter the high melting point esters out so that you can use the fuel at those temperatures.
Keep the solid biodiesel as it will melt when the season changes, providing a supply of high quality fuel for summer use.

I hope this helps,
Tony

Thanks for great explanation.... super...

Yes I think tha`S what is happening... I have washed the Biodiesel a lot... and there is still a little soap ( or solified biodiesel . That`S what I think it is now ) when it is clearing up.. I warm the washed biodiesel to 50 degrese Celcius and then let it sit in a drum.... when I take a sampel of it , it is clear when it is hot in the air... and when the morning comes ( after the nicgt temp) it is a little cloudi.. so ot must be the biodiesel and not soap formation. Thanks for great answer that I have been concerned about it...

Gert