This may be a bit off the beaten path for this forum, but hopefully you folks can help.

I'm a hobby blacksmith, and I recently built an oil-burning forge. It runs great on straight WVO, but some of the potential fuel that I've recently gotten ahold of is, well, not straight WVO. It's waste restaurant grease, and judging from the look of it it's mostly animal fat. It's far too viscous to flow through my fuel line as-is, at least without preheating it enough to liquefy. So I'd like to convert it to biodiesel.

My forge uses a very simple design and has very large tolerances compared to any automobile, so I don't necessarily need anything approaching the quality of automotive biodiesel. If I were to just use 25% methanol and 6.5 g NaOH per liter of grease, with no titration and no washing, would the resulting product be particularly corrosive or potentially caustic?

It seems to me that whatever minor amount of soap or glycerine would be left in my crude biodiesel couldn't be any worse than what's in the straight WVO I've been burning. And I'm not worried about a little water unless it's going to seriously interfere with combustion. My main concerns are safety, possible damage to my forge (steel lined with ceramic fiber and high-alumina castable refractory, vinyl fuel line, 5 gallon plastic bucket for a fuel tank, soldered copper plumbing fittings and a little epoxy), and good combustion.

The issue I see would be that without a titration, the 6.5g NaOH will probably all go to soap making (animal fat is typically very high in FFA, in my experience) and all you would end up with is methanol diluted, soap contaminated oil.

But it would be thinner!

Might be easier to just warm it some (whatever is convenient), dilute it with something else, like regular diesel or kerosene, and filter out any fatty chunks that still don't dissolve or melt.

I bet the Solvent Thinning Section guys would have a good take on this.

What's the problem with titration? It literally takes 5 minutes, and you have to measure the lye anyway.

The tallow will still drop out of the BD anyway.

Like Ryan says, just warm what you have and try and use the heat of the initial oil to warm the rest in a continuous loop.

quote:

Originally posted by Tripitaka:
The tallow will still drop out of the BD anyway.

Like Ryan says, just warm what you have and try and use the heat of the initial oil to warm the rest in a continuous loop.

That depends on the temperature. If I read the original post correctly, the issue is the viscosity of the WVO. In that case biodiesel would be a good alternative.

I wouldnt waste money on something that doesnt need quality so I'd be satisfied with partial conversion in this case, ie about 12% methanol and say 4 or 5 g caustic. The mono- and diglycerides and whatever actual biodiesel is present will be enough to thin the stuff down, not to mention the methanol itself. Dont bother with washing either. Try a batch like this out and if it works go for it.

Thanks for the thoughts.

The only problem with titration is that I don't happen to have a handy way to measure pH, and I'd rather not have to worry about obtaining one. I know it wouldn't necessarily be especially hard or expensive; it's just that I'm tired of constantly needing one more thing to make it (whatever "it" is in the particular instance) perfect. At this point the imperfect but simpler solution is more appealing if it'll give satisfactory -- not necessarily optimal -- results. I don't know if that'll make any sense to you, but there it is.

Yes, viscosity is the main issue. Right now the stuff is so thick that I'll have to heat it in order to filter it -- picture 10 gallons' worth of bacon grease that's been left in the frying pan overnight. Running my exhaust through a heat exchanger to preheat the fuel would work, but it'd require reengineering, materials and a fair bit of labor, none of which I'm up for right now. (I already do this on a small scale to make the WVO atomize more readily. But my heat exchanger is at the very end of the fuel line, just before the fuel enters the airstream. Preheating the WVO in the main tank would be much more complicated.)

Thinning certainly sounds promising. Since that's the easiest solution -- kerosene and diesel are readily available -- I'll try it first. If it doesn't prove satisfactory I'll try partial conversion.

Thanks again.

4 or 5g of caustic should be enough to neutralise any acidity and give you some reaction; dont overdo the caustic without more methanol because you dont want a lot of soap.

Thanks. I have a small batch settling at home right now. (Even if I end up using a solvent, I just had to try at least one batch of BD.) We'll see how it looks tonight.

Whby not make up some small batches of BD and use that as a solvent/thinner for more grease?