Waste Vegetable Oil Fuels

I received a comment question on my More Stable Stand Pipe post that I though was interesting. When I answered, I sort of when off, so I thought I’d include it as a post for all.

Q: May be stupid question - but why does everyone seem to love wash tanks with holes in the bottom? Wouldn’t it be a HECK of a lot [easier and] leak proof (therefore safer) to just have no holes on the bottom and pump your water and biodiesel out of the barrels using pipe or tube inserted from the top? What am I missing?

A: Great question!! Actually I think it is an ease of use issue, not one of leaks or the risk thereof. As I have been playing with all of this stuff I have noticed that making the process easy is very important. I cut corners at first and only now do I see that the steps and suggestions found in girlMark’s book and on the http://www.biodieselcommunity.org/ page are usually spot on. Experience is an undervalued commodity. Now here is why I think this is the way to go. Along the way I’m going to call the “wash tanks with holes in the bottom” a “standpipe tank”.

Leaks: Even with my original “thread the pipe into the 3 thread deep plastic bung port” connections on my first standpipe tank. I didn’t get any leaks. I was worried, but never had any. Safety was my concern (bumping the pipes coming out the bottom, and ripping out the threads). Now that I’m using the better way explained above, that is not is concern of mine anymore. The metal standpipe tanks seem to not have this fragile connection issue, but you can’t see your product. (tradeoff)

Just Pump: Pumping sounds like a good idea, but I’ve found the less I have to pump the better. The processor design that I copied out of girlMark’s book, called the Appleseed Processor is designed to be as simple as possible. One pump does it all. I would need to buy another pump (and I have, it sits) to pump the washings out of my wash tank. The pumps I use are not self priming, and would need to be fed in order to pump liquid out and up over the edge of the barrel. This is a big issue. I bought a second, “transfer pump”, to do just that, pump out of barrels, and it is very awkward (not easy!). Two other issues are those of interface and draw point. I think that they are related. When I wash, there has always been some scum on the interface between layers: water/biodiesel and on the top (air/biodiesel interface). The standpipe tank allows you to, in a very controlled manner, avoid those scum layers. Pumps are not very controlled. You’d need to have a very steady hose end, just above the water/biodiesel scum layer (this level is different every batch), but never sucking the top scum, and this is all after getting the pump primed. Evey time you washed you’d need to lower your draw point and then pump only until the water was gone (hard to control). I pump my finished biodiesel the “pump” way, and am already looking to set up a stand pipe system for my final product.

Experience and ease: I love the idea of the Collaborative Tutorial. Everyone pipes in with experience and suggestions. This allows us all to learn faster. Try out the standpipe tank. See how it works. If you don’t like it, or find a way to make what you have in mind work, then tell us all!

Using the Standpipe Wash Tank: At the risk of boring you even further, I’ll describe how I wash. This is pretty much all taken from girlMark’s book with other collaboration along the way. FORGIVE MY FORGETTING STEPS AND MESSING UP ON HER/THEIR(Jack and Graydon too!) GREAT INSTRUCTIONS.

I pump the biodiesel out of the processor into my wash tank through the “water drain side” of the unit. There is mostly clean water from my last wash step of the last batch already in the processor. This is a free wash step as the biodiesel is pumped up through the water.

Usually that water is now milky, having taken on some bads from the biodiesel.

*I just turn on the water drain and watch until the biodiesel gets low (water mostly gone) and shut it off: no biodiesel in my water, but still some dirty water in the wash tank.

I then mist wash with hot mist (one of these days I’ll write up my method for this) until I get about 10 to 20 % of the volume of water compared to biodiesel.

I shut off the mist, and start the bubbles. I’ve made emulsion here a couple of times so be careful not to bubble too violently.

A few hours later I drain off the water (start an iterative loop at the *) and the process starts over.

Note: The hot mist becomes less and less needed. Mist washing is not as effective as bubble washing because each water drop is only used once. Mist washing does remove the bulk of the bads in the first rinse so that hopefully bubbling can occur without suds and emulsions being created. Bubble washing uses each water drop over and over until an equilibrium exists of bads (soap, glycerin, etc.) in the water and in the biodiesel. Exchanging the equilibrium-ed water with new water allows the equilibrium to be pushed further towards clean biodiesel until the water is starved for bads and the biodiesel is clean.

Another note: Somewhere in the process the biodiesel is clean enough that you could just dump in some new water, avoiding the *slow* misting (5 to 10 gallons through mist heads takes a long time!) and just start bubbling. This could save you some time.

When I feel the biodiesel is clean, I then drain just enough water out so that the “stand pipe” is an inch or two above the scum layer floating on top of the water and into the biodiesel. This puts the draw point for biodiesel well into the good stuff.

I drain biodiesel until I risk draining top scum and then I stop. There is always some biodiesel in the wash tank floating on my last wash water waiting for step one.

OK. I’m done now.

Wow! There you have it, whether you wanted it or not!