Problems with making BioDiesel

[BlueRose]

Hi guys

I would really need your help ...

I have allready made 150 L of BioDiesel (3 batches of 50L) and car preforms perfect, but with last batch I have some problems.

Friend of mine brought to me some oil (it may be really old) to make BioDiesel from it. So i started do do everything as before. I put the oil in tank heat it up to 80-90 °C to get rid of the water. Drain 50L of oil and clean the tank so that it was dray. I have taken the sample of oil and make titration I get the number 0,4 so i knew i need to put 5,4g of NaOH per liter of oil in side. In total i put in 280g of NaOH just to be safe I add more.
I have 4 bottles to mix methanol each 2,5 L here i made something different than before. I didn't mix NaOH in all for of them i only mix it in 2 of them.

So I have 2 bottles of 2,5 L of methanol and 140g of NaOH in each and 2 bottles with only methanol.

I heated the oil to 55°C and first add bottles with NaOH and after that I added the rest of methanol. Again to be sure I added 0,5L of methanol. I mix and let the glycerol settle for 10h ( during the nigh). Drain the glycerol and start washing the BioDiesel with water by air bubbles. I forgot to turn up the temperature to 65°C so i got emulsion. But when i turned the temperature to 80°C emulsion was gone.

But allready i knew that something is not O.K. because the color of wet biodiesel during washing was not as it should be. It was a bit more white than normally.

After drying Biodiesel the color was much darker allmost brown insted of a slightly yellow as i think it should be.

On left is the biodiesel from last batch on left from previous


When I did a test of how clean the biodiesel is ( 50% water and 50% BioDiesel) this is the result I got

water is crystal Clean but the middle layer i did not get before.

So can Any one please tell me what went wrong

Is it because the oil was to old
or because there was still some water in the oil
or was because I put 2 times 2,5L methanol with 140g of NaOH and after 2 times 2,5L of methanol (total 10l) insted of 4 times 2,5 and 70g NaOH
or because i had an emulsion
or because extra 10g of NaOH an 0,5L of methanol
or because .....

All so i would like to know how to fix it. I heard someting with salt but i don't know if this is the case.

[julianf]

My guess -

The layer may be mono / di glycerides, due to slightly unconverted product.

You really need to do a 90/10 test (23/7 etc) to check your conversion, before going onto the wash.

The wiki will tell you all about the 90/10 test.

[therecklessengineer]

Yes, I'd agree with Julian.

[Julian]

Agree with above, a 3/27 test is a must.

I know it's difficult to judge colours on a PC monitor but the previous batch bio is very yellow.  Your current batch, although it looks a bit wet, is more of a usual colour.

It's probably safer to under dose the NaOH, than to over dose, especially with higher titrating oils ... you can always reprocess, but having too much catalyst around is likely to promote emulsions.

Not sure about the white intermediate layer being mono/diglycerides.  It could well be, but it could also be an emulsion (although the water phase looks very clear).  Try adding a little vinegar or straight acid if you have any, and see if it splits completely after a gentle shake.

If you feel the bio is tending towards a darker brown than it should be, it's possible you didn't remove all the glycerin.  That being the case, I believe traces can help promote emulsions in subsequent washes.

[Jonzeyboy43]

Mine ends up that yellow colour usually

[willbuild]

What amount of time had passed from shaking the 50/50 test to taking the picture?
You can try a dr pepper test (how to is on wiki) using 1 ltr or 0.5 of the bio.
If glyc falls out there is unconverted oil. if no glyc falls out do another 50/50 test and see if white layer is less or disappears

[Tony]

Try the 50:50 with boiling water from the kettle. If that white layer is mono/diglycerides then with boiling water it won't be so thick and perhaps not present at all.

If it is mono/diglycerides don't worry too much, it's perfectly usable fuel if the water layer is clear, but more susceptible to absorbing atmospheric moisture (giving emulsion that can contribute to filter blocking) and in winter months earlier waxing.

Taken years of pain to get to those conclusions... if only I knew then what I know now!

[willbuild]

I just tried a 50/50 test one with hot water and another with cold. the water in the cold test is cloudy and the hot one is crystal clear and both have a thin layer of white?

[BlueRose]

Okay ...

So did 4/45 test and get out 0,2 (4%) drop out so i don't know if this is much or not. The result was very cloudy.



How ever at temperature 43°C the test was clear



Problems with color are because it is still wet. The problem is because i am using air bubbles to dray the biodiesel an the water which came out of bio diesel was over the air bubbles so it was cleaning the biodiesel insted of drying. Tomorrow i will dray it again and share the results.

For the 50/50 test: well after 4 days it is like this



I did tray adding salt and it reduse white layer and left me wit small amount with white layer. On other forum i found that the Na from salt should react with di/mo glycerides and form soap. But just to think it through soap dissolves in water so why the white layer. I will tray it with boiled water and tray to ad HCl.

Again questions

Way i am still getting drop out. I did titration and ewerthing what to do to get 100% conversion.
And how to get rid of di/ mono glycerides.
Was the idea to first "shock the oil wit half of methanol and all of NaOH and then ad the rest of methanol good or bead idea.

[Julian]

You should be able to get a complete pass.  The time to do the 3/27 test is during processing, so you can reprocess until you obtain a 100% conversion.

Depending on your car and engine type, a 96% conversion could be quite acceptable.  the result of you 3/27 test looks quite white, usually they tend to be a straw colour.  I've never tried heating a 3/27 above the 20°C at which it's supposed to be carried out, so I'm not sure what that indicates.  I'd guess the 4% unreacted oil may dissolve into the methanol, giving you a false pass.

What forum said that salt would react mono and di glycerides?  My chemistry is very poor, but I'd be surprised if that were the case.,  Far more likely the white layer is an emulsion and the salt is breaking it.  Try adding quite a bit of acid, I'm sure you'll find it will split completely.

If you are happy with the 96% conversion, I wouldn't worry too much about the emulsion.  You could decant off the bio, bubble with air only to remove the methanol and then leave to settle for a week or so.