Ok, I got a real challenge to mess with. I've been given a bunch of oil that orginally came from a rehender that collects cooking grease and makes soap out of it. Supposedly, this this stuff has been cleaned and filtered. We titrated the stuff, using Fuel Miester's method and we came out to 8.5 ml of NaOH, way off the chart. Well, the resulting minibatch made 100% soap. I took a sample home and titrated with the Appleseed method and it came out to 25ml of KOH and resulting mini batch of soap. I'm trying the FATTA method now, but does anyone know what a rehender does to this stuff in order to make such high FFA? I'm guessing they burn it for a long period of time. I hear tell that they also sell some fo this stuff to be mixed for hog feed, which I find hard to believe.

Mgrant

Hi Mgrant,
The feed mix is a very common way of them getting rid of ther excess oil.

Yea, for some reason, I thought that with a such an acidic PH, the oil would give hogs some serious ulcers. Anyway, I tried the FATTA method with 2ml of acid and after two hours, the titration went from 25 down to 14. The oil got very black! I intend to let it sit all night and titrate again in the morning. Now the next question, if I want to get it to go lower, say down to 2-4, do I just add more sulfuric acid to the mix or do I need to add more acid and methanol?
Mgrant

Mgrant,
From what I have read here, give it time and titrate every couple of hours. When 2 consecutive titrations are the same, the titration will be as low as it will get. This may be because the acid has absorbed water, or because the ffa have been esterified (probably the former) Adding more acid will not have the desired effect, as the water in there will just dilute the added acid.
I have read that you can drain off the water (where wouild I have read that??) or remove the water using an inorganic salt to dry the sulphuric acid. If the H2SO4 is dried, it should continue esterifying the FFA.

Re-titrate as before to determine the "end point".
Remember, the titration will indicate the amount of caustic needed to neutralise the added H2SO4 and any remaining FFA.

Add 5 (+ titration) g/litre to the methanol and mix with the acid treated oils.

Separation should occur as it would in a single stage base reaction.

I hope I understod that correctly.

quote:

Originally posted by Tony from West Oz (The Wizard of Oz):
Mgrant,
From what I have read here, give it time and titrate every couple of hours. When 2 consecutive titrations are the same, the titration will be as low as it will get. This may be because the acid has absorbed water, or because the ffa have been esterified (probably the former) Adding more acid will not have the desired effect, as the water in there will just dilute the added acid.
I have read that you can drain off the water (where wouild I have read that??) or remove the water using an inorganic salt to dry the sulphuric acid.

that "inorganic salt" should be a sulphate to avoid any reactions with the sulphuric acid. if you add NaCl, for example, the sulphuric acid will separate the chlorine from the sodium and react with the sodium, leaving you with sodium sulphate and hydrochloric acid.

i think anhydrous sodium sulphate would be a good choice because every mole (142g) of this stuff will absorb 10 moles (180g) of water before starting to dissolve.

Well, my titration endpoint on my minibatch came to 10ml of KOH. I believe I put too much acid in, which was 4ml total, because it took around 5-6ml to cease the fizzing in my titration beaker. I didn't notice any separation during the acid stage, however the whole sample was so dark during the acid stage that any separation layer would have not been visable. So armed with my new titration endpoint, I mixed up some methoxide. After 20 minutes of mixing, I now have a nice dark glycerine layer on the bottom and a semi dark BD layer on top...about as much BD as the original oil ammount. This is a lot better than 100% soap! When I first mixed, I did notice an immediate white particulate layer, probably potassium salts from the reaction of the KOH methoxide and sulfuric acid.

I'm not in favor of using drying chemicals that would have a negative effect on either the biodiesel or by-product disposal, which is garden composting in my case. I'm sure that anhydrous sodium sulphate is nearly impossible to find in inexpensive quantaties around where I live. Perhaps silica gel might be an option. I'm more in favor is using a mechanical process, like a reflux still, to remove the water and collect the evaporated methanol for a second acid stage.

Next question, is it advisable to perform the acid stage in a separate reaction vessel or can it be done in the appleseed processor along with the base stage? I do use a separate plastic tank for glycerine settling after my base mixing process is completed, which is about two hours. But the acid reaction stage would have to remain in the reaction tank for some time till titration stabilizes, which makes me wonder what the sulfuric acid will do to the steel processor tank.

Mgrant

Just did a second minibatch, this time with 3ml of acid and left it sit overnight in a jar near a heat lamp. I left the lid on the jar to prevent the loss of methanol, but not to tight so it can release pressure. Titrated this morning at 5ml KOH. It had a small layer of liquid on the bottom of the jar, I assume this to be water. Made a minibatch out of it anyway, good separation with about the same amount of BD as oil I started with.
Mgrant

...I had some yukky oil, I mixed with ground corn, thought the pigz would eat it, not one of them would do anything but turn dey snoutz up at it... me surprized, had ta shovel it out wid da poo...

Richard

quote:

Originally posted by FlyDC8s:
...I had some yukky oil, I mixed with ground corn, thought the pigz would eat it, not one of them would do anything but turn dey snoutz up at it... me surprized, had ta shovel it out wid da poo...

Richard

you pre-treated the oil for composting - LOL

quote:

Originally posted by FlyDC8s:
...I had some yukky oil, I mixed with ground corn, thought the pigz would eat it, not one of them would do anything but turn dey snoutz up at it... me surprized, had ta shovel it out wid da poo...

Richard

Looks like Wilbur is watching what he eats...picky piggies.