Prewash problem - Diesel Forum

scbaguy · 12-14-2005, 06:20 PM

Soybean oil, titrated to .7, NaOH, 5g plus titration, 25%Methonal,

This batch I tried the "prewash". After letting the reaction run for 2 hours, I added 7.5% water to the processor, and ran it for 20 min.
I got good seperation, but on washing(mist wash), I have an "oil"layer between the bio and water. It won't mix with Bio, and wont sink in water, it has 'stuff' in it. Like pepper. It sticks to the side of the wash tank. Not creamy, just dirty.

What is it? and How do I deal with it?

Spencnaz · 12-14-2005, 06:52 PM

Sounds like an emultion was started. My question is why so much methanol? 22% is the maximum that is really required.

Can you post some pictures so we can have a look?

txcas · 12-14-2005, 08:51 PM

I saw the same thing on my first pre-wash. After the first mist wash, I swithed to the water hose and sprayed water on the bio. No emulsion after that and the layer between the water and the bio was gone after doing this. I did this 2 more times and still no emulsion. Forget about the misters and give this a shot. Spray with the water hose all over the bio and also let water run down the sides of the drum. All the dirt will move to the water layer.

dssamp · 12-14-2005, 11:24 PM

Most hot water heaters have rubber gaskets on the bungs...some are blue and some black (like when you wife hits you with a frying pan [img]/ubbthreads/images/graemlins/crazy.gif[/img] ). AND, some older hot water heaters have a rubber liner. Could be the gaskets and/or liner are coming apart from the methanol mix making what appears to be black granuals in the conversion. Or then again maybe it really is black pepper? Do you strain or filter your oil? I use furnace filters (49c each..good for a couple of batches each) and I catch a LOT of black pepper & stuff.

At any rate, my processor had black rubber gaskets. for a while. I relocated some pipes and discovered most of the rubber was eaten away..I pulled out what was left with a pair of long nosed pliers. On my next processor I heated the bungs up with a torch, THEN pulled out the gaskets...no more black junk in my biod. [img]/ubbthreads/images/graemlins/biggrin.gif[/img]

Spencnaz · 12-14-2005, 11:33 PM

That's a good point about any seasonings being in the oil.

I've been using pieces of nylon stocking on the hose barbs as a form of rough filtering before processing. It gets alot of the fines, and granular particles out of the oil.

scbaguy · 12-15-2005, 10:18 AM

I don't think it is rubber.

This is like a film. Very thin layer, looks like a dirty film dryed on the walls of something, and then came out with the BD.
I tried take pics, but they wouldn't come out where you could see the film.

I wonder if I got all the 'glycerol' drained. with the prewsh, it seemed there wasn't as clear a difference between the settled layer and the Biodiesel.

If the glycerol settled to the bottom, and some of the water from the prewash settled ontop of that, and then the Biodiesel was on top of that, If I didn't get every last bit of that "water layer" out...

I would suppose that the glycerol and water might not make to distinctly different layers, but possibly the layer might me heavier and thicker on the bottom, and thinner and more 'watery' on the top.

Assumeing this is possible, and assumeing that I didn't get the complete layer out, would that account for what I'm seeing?

And, if the above is it, why now is this 'film' not soluable in either the water, or BD?