glycerine pretreatment? - Diesel Forum

kevinj1 · 10-14-2008, 06:05 AM

I am going to use my last gylc. for pretreatment but I can't find how long to mix and settle before i do my regular process. I am starting with 40 gal wvo and 10 gal glyc. any input would be great.

Thanks Kevin

holeshotkid · 10-18-2008, 10:25 AM

Your going to love this. It actually works great to lower tritration values of the oil. Mix for two hours at 135-140 F. Let settle for about 1-2 hours and drain. You will notice that you will drain less then you put in but this is ok. Any additional fluid you gain in the processor doesn't need to be compensated with additional methoxide. If you put in 40 gal of wvo, only treat for 40 gal reguardless of how much is in the processor over 40 gal. My oil usually tritrates at 4-6 range and by doing this process, I usually end up with a tritration of 1.5-3. and in treating 60L of oil, I end up with 62-63L because of the methonal transfering from the glycerin to the wvo.

Hope this helps.

**VegasDiesel** · 10-19-2008, 06:27 PM

I'm sorry. I don't understand this. What is pretreatment? Are you talking about reusing the glycerin after a batch, by adding it to your new batch of wvo before you process it? By doing this, you titrate lower? Then what will be left over again after? Will it still be glycerin? Can you still make soap out of it etc? Thanks.

holeshotkid · 10-20-2008, 03:18 PM

Yes, glycerin pretreatment is using your glycerol from the previous batch and mixing it with your new wvo. It does a number of things including lowering the tritration value, which in turn increases your yield. It also transfers some of the methanol from the glycerin to the oil, allowing you to use slightly less methanol if you desire (I still use 20%). I have not failed a 3/27 test when using this method. When draining the pretreatment, I have consistantly observed that the glycerin is much darker and thicker then when I put it in.

**VegasDiesel** · 10-22-2008, 04:01 AM

Huh...good to know. How many times can you do this? Then is it easier to dispose of? Can you then just dump it down the drain? Or can you still make soap out of it?

holeshotkid · 10-23-2008, 11:19 AM

I only use the glycerin 1 time. After that, most of the methanol and lye or KOH are spent. I wouldn't pour it down the drain but it is suitable for soap making. Probably more so because most of the methanol has been transfered to the new oil. I use KOH so the glycerin stays liquid then I compost it. I'm looking into making a waste oil heater so I can burn the glycerin instead of just composting it.

girlmark · 10-29-2008, 12:19 PM

I do'nt think you need to mix for '2 hours'- the reaction (neutralizing FFA) that you're getting is very quick.

ToddT · 10-29-2008, 03:49 PM

How long, Mark? And is the temperature critical?

How about 1 hour at 125 degrees?

girlmark · 10-29-2008, 09:46 PM

I think it's more like 'mix long enough to get it distributed throughout the oil' rather than any specific time. I haven't done really good testing of mixing times versus processor size to see what's ideal but I just run it into a 50ish gallon processor for something like 10 minutes of mixing.

I'm basing what I suggested on the fact that FFA neutralizing is pretty instantaneous (it actually makes soap, which settles into the glycerine), so I don't see that you need a whole lot of time.

ToddT · 10-30-2008, 08:28 AM

Thanks for the reply. I see now.

For complete mixing, I'd figure the blending time based on total gallons of your oil/glycerin mixture divided by the gallons per minute of the pump times three in order to get everything mixed well.

For example, 40 gallons divided by 5 gallons per minute = 8 minutes to turn everything over once. Do that three times so that everything gets sent through the pump at least once and you have 24 minutes of mixing. If you have static mixers or a higher flowing pump, the time would be even less.

It would be important to check the gallons per minute flow rate of the pump. And remember, warmer temps will increase the flow rate significantly, particularly on a blue Harbor Freight type pump. Best way to check... time how long it takes to fill up a 5 gallon bucket and determine the gallons per minute. Don't go on what a pump is rated by the book. Go on what comes out of your pump. Viscosity, valving and lots of other things will come into play.

girlmark · 10-30-2008, 11:53 AM

Basically, there's no problem with mixing longer, and it's not all that critical how well you mix. So don't worry about it TOO much.

Dirtcheap · 03-23-2009, 09:17 PM

hey guys so let me get this straight, i just add glycerin from a previous batch to a new batch of oil , mix up let it settle and take it off the top ( how much ?) and start my next batch??? do i add it before or after my final prefiltering?? how much glycerin to how much oil? i make 40 gal batches... thanks

Dirtcheap · 03-23-2009, 09:21 PM

ohh and since there is a methanol transfer from the glycerin how hot can i heat my oil safely?? i like to heat to 140 or so... but since meth boils around 140 -145 im a little affraid

holeshotkid · 03-27-2009, 06:44 PM

Is your processor sealed or open top? You can safely heat the oil with the residual methanol in a sealed and properly vented processor without any problems so long as there is no way for your heating element to be exposed to air. In other words, no mixing or bubbling while heating. After mixing in the glycerol for a while, it will separate from the oil just like it normally does from the bd. I heat my final bd to 180-190 degrees while recovering the methonal so heating is somewhat safe as long as oxygen cannot reach the heating element. This works so well for me, the last two batches of my oil that tritrated at 3.0 ended up tritrating at 0. Yep 0. It is worth it in every way in my opinion.

holeshotkid · 03-27-2009, 06:47 PM

Dirtcheap, In reading you post again, are you under the impression that the glycerine/glycerol rises in the oil? If so, this is not the case. It will separate out and sink to the bottom of the processor with the oil rising to the top.

Hope this helps

Troy