I came across an older thread that suggested adding some of your glycerin to high titrating oil. Why would this help lower the titration value? Also, how much might your add for what would be a 30 gallon batch? 1 gallon, 5 gallons? Then, is the glycerin just left in the oil and re-titrated and processed with titration+base+22%methanol?

Also, another suggestion was to add baking soda. What does this do?

Thanks,

Grey

You can do this. Just make sure the oil is dry or it will make soap. You can heat the oil and mix in the glycerin. Then just let it settle and retitrate. Proceed as usual.
Stuart

quote:

Originally posted by sshelly:
You can do this. Just make sure the oil is dry or it will make soap. You can heat the oil and mix in the glycerin. Then just let it settle and retitrate. Proceed as usual.
Stuart

I heard that adding glycerin to wet oil was a good way to remove the water - add it cold, mix and separate off the glycerin with the water...

??

But WHY does adding glycerin lower titration?

How long should you run the processor with it in?

How much should you use for 30 gallons of oil?

Do you try to drain/remove it when finished or just leave it in for regular processing?

Grey

grey. mix up a normal batch of 30 gallons, process as normal, Drain to settling tank #1, Add 30 more gallons of (DRY)wvo to reactor, Heat. By now you should have settled gycerine in settling tank #1. Pump it all into the reactor with your heating wvo. heat to 57'C then process for an hour. Drain into settling tank #2. This is your treated oil tank. This oil will have a lower ph and will be very nice. Drain this glycerine into your glycerine storage tank. titrate this oil after pan drying a sample. ReProcess as you normally would based on titration results. Drain into settling tank #1. Repeat Process. End result... less methanol needed to be reclaimed from glycerine. more methanol used in reaction. less KOH or NAoH needed because of lowered ph. My glycerine goes straight to soap because I have removed most of the trapped methanol.
I hope this has helped you.

quote:

Originally posted by grey:
But WHY does adding glycerin lower titration?

It is the excess methoxide in the glycerin that is lowering the ph.

If glycerin lowers titration (and I don't mean to sound doubtful), why not always pump a few gallons into a batch before processing?

Grey

It's not the methoxide, it's the extra caustic (KOH or NaOH) that lowers FFA apparently. This is basically an easier version of caustic stripping (see some of Rick da Tech's posts for info on caustic stripping, an oil industry practice).

I've done this titratoin reduciton before with methanol-free glycerine, and it worked just as well as the crude methnol-containing version, so it's not the methanol that does any of this.

Also, the glycerine contains some biodiesel which I THINK will go into your oil after this type of caustic stripping, which is a good thing- you gain the otherwise lost biodiesel back, and it might act as a cosolvent to help with your next reaction (maybe).

Lastly, this method removes water from the oil because glycerine is a better solvent for water than oil is. I've done experiments about this recently and I got oil down to an unheard-of low water content of 200 ppm (as measured by lab equipment, not home methods) so I'm 100% sold on this technique being a good idea at all times.

One thing I don't know yet is what happens if there was 5% water prewash done to the batch that produced the glycerine.

Also, you'll get different results in titration reduction depending on the caustic content of the glycerine you used. Glycerine made with a lot of KOH will reduce titration on the next oil much more than glycerine made with less KOH. I also found that I got better results by doing the reaction stage-wise- meaning I add some glycerine, let it settle, remove it, add some more, and see a greater reduction in FFA that way.

There's no one answer yet to how much glycerine to use, what makes sense is to use the glycerine from the last batch I think.

Important note for newbies:
remove the glycerine before you go on to process the oil into biodiesel, or you will hinder the biodiesel reactoin because the biodiesel reaction is reversible, meaning that it's also hindered by the presence of glycerine. I wait at least a day before processing the oil into biodiesel.

It's also possible that you'll have extra soap in your biodiesel by doing this as the 'caustic stripping' reaction makes soap. I'm sure there are going to be some times when most of the soap goes into the glyceirne, but I've also seen obvious cases where high_FFA oil became thicker and had clear stuff that stuck to the sides of a plastic test bottle, like it contained soap, after doing caustic stripping to it. There might be a limit on how much you can get away with.

I haven't read the threads on caustic stripping, but...

If the principal player in the process is the caustic which is in the glycerin and no so much the glycerin itself, is not not plausible that all we are doing is letting this caustic convert some/much of the FFA to soap. This soap ends up mainly in the glycerin phase, which is pulled back out before reacting the oil.

Granted the caustic is 'free' since it was already 'paid for' during use in the previous reaction, but I'd think an acid pretreatment would be better. You convert the FFA into fuel and get higher yields. I use acid/ base, and I pay 100 times as much (per given volume of oil reacted) for the KOH as I do for sulfuric acid.

I guess I'm asking what the end goal of using glycerin as a means for lowering titration is, relative to acid/base?

Horn

Yep, that's what I was trying to say here- the caustic in the glycerine makes soap with the FFA in the oil. The thing is, it appears to me that some of that soap ends up in the glycerine, so the drawbacks aren't as huge as you might think (meaning you don't have to deal with the soap). I think that with very high-FFA oil it's possible that the soap becomes a problem because it doesn't go into the glycerine layer during the 'stripping' step as much as if you had lower-FFA oil that you did this to.

I do agree that acid-base is a better method because you don't lose any of the oil, but I've done yield measurements with glycerine-caustic-stripping and haven't seen a huge reduction in yield.

The point of the process is that it's extraordinarily easy and doesn't use more chemicals.

So as GirlMark says to remove the glycerin before going on to processing, would it be removed the "normal" way...process the oil with the added glycerin for a couple of hours, then let settle for 24 hours and drain off the glycerin? If so, I'm guessing that you'll be draining about the first 5 gallons from your processor, assuming you used 5 gallons of glycerin?

Grey

I just mix glycerine with oil for a few minutes, not sure if it'd give you better results if you mixed longer.

Then I let it sit overnight or longer and then drain the glycerine the 'normal' way just like you do when you drain glycerine from biodiesel.

I haven't done any tests (such as soap test, which is also a good indicator for glycerine droplets still suspended in the oil) to see if this is a good procedure or not.

I just completed a couple of batches using the glycerine from the previous batch. The results are a bit surprising to me. Can anyone tell me what is happening here.
I start with 50 gallons of oil. I put in about 12 gallons of glycerine with the methanol still in it. It is heated to 122 degrees F. Mixed for one hour and let sit overnite with the heat still on a constand 122 degrees. The next morning I drain it off. Not easy to do as it is very thick. (KOH by the way). It is like pouring wet sand. And very black. The pump wont start and I heat the volute with a torch for a few minutes (stay away from the seal). Pump for a couple of minutes and let what is in the plumbing settle. Drain off the last bit of glycerine. I did a pan test for moisture. Small bubbles but nothing much and the oil looks very good. Oil that titrated at 3.2 now titrates at 1.8. Using a two stage base/base method on the resulting oil, I am getting very very good results. After the first stage it is good, but fails the 3/27 test. After the second stage there is no drop in the 3/27 test and the BD is lighter in color. Mist wash and dry.
My questions: 1) Why is the glycerine so thick and dark? Any ideas.
Thanks
Biodale

I am still using Sodium Hydroxide for my reaction. I was thinking about switching... Till now.
Have any of you tried this with sodium instead of potassium? If you find it is better (from my results it sounds better) post it. I was going to order a bag $150 of KOH but don't think it will work as well.
Let me/us know.

thanks

quote:

Originally posted by bioldale:

My questions: 1) Why is the glycerine so thick and dark? Any ideas.
Thanks
Biodale

The trash in the oil is sucked out into the glycerin. Stuff like flour, corn meal, cigarette butts and other stuff that your rough screening does not get out, falls in with the glycerin rather than staying suspended in the oil.

yep, agreed, that's likely to be what's going on.

If it were high-FFA oil I'd think that this was soap, but not with 3something on your titration.

the other question is, why are you even bothering? 3.2 on the titration isn't very bad oil . Did you find water in the oil?

quote:

Originally posted by girl mark:
It's not the methoxide, it's the extra caustic (KOH or NaOH) that lowers FFA apparently.

My point was that it's NOT the glycerin by itself, but the excess methoxide (Methanol and Base) leftover in the glycerin. Base being the actual component "soaping out" FFAs.

Lye stripping without water.

I had about 40 gallons of really crappy trap grease and water that I heated for several days and skimmed the liquid oil off the top. When it cooled back down to around 50 drgrees while I was allowing it one more round of settling it gelled up. so I grabbed 10 gallons of demethed glyc. that I had from last year heated the grease up and then started adding the chucks of glyc. All seemed well a few points where I added to much and it partially plugged my pump inlet. Once it melted all was good I turned the pump off and allowed it to settle under heat over night, and day then last night I tryed to drain the gly off. Well what came out was reddish colored, it thought ok it worked took out 5 gallons, then 10 then 20 then the flag went up this cant be right more out than in? so I drained 20 more it all looked the same. What was going on? So I started pokeing around in my reactor and found that the bottom was cold and most of the gly has stuck to the bottom cone. So I turned the pump on and fought for the next 2 hours getting it all out of my processor. Pumped it into a 50 gallon drum at 130 degrees and am going to let it settle today then try to pump the oil off the top and put the rest off to the side for later experiments. I did get in the first 5 gallons really thick glyc. which I put off to the side in hopes that maybe I could make it into some soap. So I will let you know what it looks like tomorrow.

One thing I forgot to put in my previous post. And this makes it even more interesting. The original amount of oil was 50 gallons. After I put in the glycerine, heated, and settled, then removed the glycerine, the total amount of good oil is 54 gallons. It seems to me if it was just the crap settling out there would be less oil not more. I probably do have some animal fats in the oil, but again, if that was settling it would make less oil.

Is it possible the glycerine (remember it is an alcohol) is esterfying some of the FFA?

Yes, I am doing this regularly now because my oil usually titrates about 8 and there is always some water in it. My experiment was to try to find a way to dry the oil without heating it. Somewhere on this site I found a post that said glycerine loved water and adding to oil was a way of drying it. I am not trying to steal this guys idea, but I cant find the post anymore. This method is doing something good, but I am not sure what.