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A) Is it possible to recover methanol from glycerin and biodiesel together using the earlier GL-Eco design with a venturi and plumber's delight condenser?

Yes. I have done it. Works well.

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B) With properly dialed-in heat control, is that methanol going to be pure enough to use in the next batch?

Yes. It has come out at 98% pure. (I bought a hyrdometer to measure it.) But quality will depend on temp, head space in reactor, how much vacuum.

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C) In this scenario, is it necessary to neutralize the biodiesel and glycerin solution with acid? More specifically, is a very slight back reaction going to dramatically affect finished fuel quality?

The BIG Uknown. I think I am getting a back reaction with neutralizing ... but I am just starting out. Since there is no easy test for mono and diglycerides, this is tough call. (well there is a test called a CG, but not easy to come by.

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D) Is anyone using the earlier design with NaOH lye and recovering methanol from the whole batch (glycerin and biodiesel) without problems of glycerin turning to stone or other noteworthy problems?

I used Potassium and am having problems...well I am uncertain what is still suspended and what has dropped out. I tested for soap but it tests for none, however, there is still something suspended in my biodiesel. Is it mono or diglycerides? An emulsion of sorts? The unknown.

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I used Potassium and am having problems...well I am uncertain what is still suspended and what has dropped out. I tested for soap but it tests for none, however, there is still something suspended in my biodiesel. Is it mono or diglycerides? An emulsion of sorts? The unknown.

The Big D! Wow. It's an honor to get an answer from you.

I started out making biodiesel with KOH as my catalyst because I heard it was easier to work with all around. BUT I discovered like others, that once methanol has been sufficiently removed, that the KOH doesn't easily fall out but rather turned to snow in the biodiesel and remained visible.

What I'm concerned about is using NaOH and having the demethed glycerin harden up on me in my pipes. Ask me how I know. I will have to be on top of it when it shuts down and drain it within minutes. No settling overnight. I switched to NaOH for that reason. Pro's and con's for both.

I too used KOH for the same reason. However, I am thinking about going over to NaOH.

An idea to clear the pipes at the end is to use the vacuum and I already do this with KOH. One of the things that has amazed me is that if you pull a vacuum from the top like in the push/pull and open the bottom valve just a little (where you drain the glycerin) nothing comes out! Really. Air is just sucked in (or the atmosphere pushes it in - depending what side of equilibrium you want to take.) What is the point of this? Well at the end of the demething process, you got a vacuum in the tank and the pump shut down? Looking at Graham's Diagram, crack open V1 while V3,V5,V6 are closed and V4 is open - just for a second or two. Then close V4 and open V3 and reopen V1. These valve numbers are only specific to Graham's layout, however the point is that the vacuum will push the Glycerin back into the bottom of the processor. To be extra clean, you could rig up a little system of like 500ml of finished biodiesel in jar, a small hose to attach the jar to V1, and suck in the bio to really clean those pipes. You can see that I too have been working on this same concern as you.

Good luck.

Doug

PS. Have you found any posts how to remove the remaining wisps of emulsion?

Also just so you know, the centrifuge isn't magic. I mean fabricator has it working but he is using two of them for 30 hours. I ran mine (DC-20) for like 12 hours. In the first two hours it removed a bunch of glycerin, but then for the next 10, when I opened it, it revealed almost nothing inside. I am not saying it can't be used or has no effect, but I was hoping it would just whip out the soaps in a few hours. I mean if you using NaOH, demething, and gravity removes the NaOh in a few days (72 hours) seems like a real 'human effort' saver. Hey if you want to buy my setup, PM me.

Doug,

I'm getting a slight vacuum from the venturi to but I can empty the pipes by draining while hot. In my attempts at soap making, I know that hard NaOH glycerin will remain viscous at 140F.

I'm under no illusion that the centrifuge is a magic bullet. I'm planning to distill carefully and circulate to drive off the rest in a vented barrel. Methanol removal must be as complete as possible. The Biodiesel must be room temp. Then it's going to take 50 to 60 passes to draw enough soap out. The DC-20 has a very limited flow rate at 55 gph and it will take forever with all other conditions being satisfied. PABiodieselSupply has a centrifuge/motor/pump combo with 240gph flow rate which is 5x the flow for $949.00. Not a bad deal if it is indeed effective. The OC-20 would still be good for WVO filtering.

Thought?

Johno and all, why not take a sample of the bio/glyc mix and do an acid titration on the whole thing? That way you have an accurate number from a representative sample of the glyc and the bio.

My $0.02...

Just switch to NaOH... or at least try a batch. Its not that scary. Especially since its summer. I started with NaOH four years ago, tried KOH, then went back to NaOH. Not that big of a deal. I'm using the GL style appleseed with venturi and condenser and having good results with whole batch demeth, very quick separation of bio and glyc and then just settling bio for 1-5 days, depending on the batch.

Oh and the glycerine (with methanol removed), it stays hard up to 100F or so. Just be sure to drain your pipes within 30 mins of shutting down the pump.