I recently posted on 29th March asking about 1L Dr pepper style acid/base test batch
procedure which Tilly very kindly gave me, thank you Tilly.

My original post and Tillys help

I have done a 1L test as well as a 180L batch and am a bit lost with results and thought someone could help interpret my results.

1L Test WVO (T14) - 100ml methanol - 1ml H2SO4 (98%)
Acid Stage - 11Hrs (T5.4)
Base Stage - 100ml methanol 13.8gr KOH (7.78 + 5.4)

Settled overnight, clear separation although had to use a light to see due to original feedstock being very dark. Drained glycerin and washed Dr Pepper style.
Ended up with 500ml (lost some when draining water) washed but dark red biodiesel.

27/3 Test - dissolved immediately but small qty settled out within 30 mins (estimate 10% of 3ml) Thought this was as a result of too little acid and high (5.4) FFA

180L Batch WVO (T13.5)

Did acid required calculation using :
Original_Titration_result - Desired_Titration_Result * 0.2
13.5 - 3 * 0.2 = 2.1ml * 180 = 378ml H2SO4

Added 20L methanol + 378ml H2SO4 normal methoxide carboy way over 15 mins.
Acid Stage - 8 Hrs (T4.8) I did test every 2 hrs to check was still dropping.
Base Stage - 20L methanol 2265gr KOH (7.78 + 4.8 X 180) 15 mins mixed for 90mins at 55C

Settled overnight 12hrs, again clear separation visible with light.
Site tube indicated 23L glycerin which I believe is to little if full conversion achieved.
Drained off 25L of what I assumed to be glycerin can't tell as there is no distinction between glycerin and biodiesel when draining as it is so dark, however assumed that I had drained all as site tube indicated only 23L. I managed to suck in some air when draining site tube and reopening tank valve causing agitation in tank, site tube went dark like glycerin, which told me that there was still glycerin in tank. So I started again by remixing all up and settling overnight, next day sight tube indicated 60L glycerin?

I am now very confused by what I have achieved!

Notes/Questions:
1. I now doubt the accuracy of the site tube when it come to indicating settled glycerin!
2. Should I have reheated when mixing and resettling 2nd time?
3. Is 8hrs normal to get it down to 4.8?
4. Can I get it lower?
5. I was under impression that acid/base has a higher conversion rate?
6. Site tube also indicated that I had lost about 10L of total volume?
7. Never got to required T3, stopped after 8hrs due to time constraints.
8. If I do have bad conversion, which I am sure I have, how do I reprocess, what procedure should I use to reprocess?


Any help would be appreciated.


My processor, does not show vent valve (open) and 5m coiled copper tubing rising 30cm and connected to horizontal pvc tube vented outside.

durbanboy,

sound like you did everything right. its normally much harder to determine the glycerine from the BD because that acid stage turn the BD so dark.

quote:

Notes/Questions:
1. I now doubt the accuracy of the site tube when it come to indicating settled glycerin!
yep. sight tubes will indicate the level in the tank but if the denisties are different the sight tube will be wrong.

2. Should I have reheated when mixing and resettling 2nd time?
as long as the temp is 50c or higher for the base then no addition heat is needed.

3. Is 8hrs normal to get it down to 4.8?
I usually let mine run for 12-24 hrs.
4. Can I get it lower?
yes. but it takes more time. and sometimes more acid and methanol.

5. I was under impression that acid/base has a higher conversion rate?
its does if it compared to base only on the same oil.

6. Site tube also indicated that I had lost about 10L of total volume?
7. Never got to required T3, stopped after 8hrs due to time constraints.
just let it run longer.
8. If I do have bad conversion, which I am sure I have, how do I reprocess, what procedure should I use to reprocess?
test it using the 27/3 method. it should pass. if not try 1g and 50ml/liter.

it sounds like you drained between the acid and base stages? I don't
you might try more methanol in the acid stage and less in the base stage.
maybe 120ml/L during the acid stage and 80ml in the base

-dkenny

Hello durbanboy

If you want to reprocess unwashed biodiesel, the "Standard" reprocess is 1.4g KOH (Adjusted for purity) mixed into about 35ml methanol per litre of WVO reacted after you remove the glycerine.

Thanks dkenny, Tilly for your replies.

Tilly thanks will try your reprocess figures!

dkenny, no I did not drain between stages, first drain was only after completed acid and base stages and 12 hrs settling.

I think the as dkenny says site tubes will be wrong when different density liquids are involved, this I confirmed after remixing to settle again the total volume went back up to what i thought it should be indicating that my 10L+ loss was not actual and 60L glycerin incorrect and after settling again for another 12 hrs site tube indicated another 5L glycerin. So in total about 30L glycerin

Questions:
1. Is glycerin settling from acid/base more difficult/take longer than base only?
2. Is 30L glycerin sound right on 180L wvo?

The other question still remains, with dark feedstock and dark biodiesel from acid process and unreliable site tube readings:

1. How do you establish accurately how much glycerin there is to drain?
2. And when draining how do you establish that you have now hit bio?

What procedure do you follow when draining glycerin from dark bio to make sure you get all the glycerin and little or no bio?

durbanboy,

Q1. I haven't noticed any major differences in the settling.
Q2. depends on what else is in the oil. I have had some base only batches (210L oil, 12Galmethanol) result in 20 gallons of glycerine...and others that resulted in the 13 gallons of glycerine.

I drain to and settle in a plastic cone bottom tank. I know this doesn't help you when draining from you processor. yours is a beautiful creation. I wish I could weld like that.

typically the color changes, but acid/base makes it hard to see.

-dkenny

Concerning the difference between glycerine & BD when draining, I drain through a length of clear nalgene tube. The glycerine is opaque and VERY dark, like used motor oil. The BD is also dark, but transparent, like really strong tea. Also, the viscosity is quite different. If you can, put a clear site line in the drain and put a light behind it. You'll see immediatley when the BD reaches it, also, I usually close the drain valve and let it settle a little more at that point. It's surprising how much more glycerine will settle down from the sides of the tank if you'll let it. Sometimes have to bleed off the clear section 2 or 3 times to get it all.

Sometimes the glycerine is really viscous, I bet the glycerol didn't drain out of the sight tube because it was so gooey and you dropped a good bit of BD with the glycerine. Use an eyedropper or syringe to pick up a little liqud off the top of your glycerine container, I bet there's BD there. You can siphon that off and add it to your next batch when you get to the settling stage and reclaim it.

Although Im having some AE process issues, I am getting results, including higher yield. One thing I do that makes it easier to discern the gly from the bio is a prewash. It turns the gly almost light chocoalte milk color, and the bio is darker. Maybe that would work for you also.
It really helps with washing, as I seem to have this bad habit of putting too much NAOH in.