Just below there was a discussion about "waxes" in biodiesel stored at lower temperatures. By coincidence I noticed something that might be of interest to the group. During the late summer and early fall I make and store several hundred gallons of biodiesel to use in the spring for tractor fuel on my farm. At some point as the ambient temperatures decline the fuel in the totes will gel. In early winter the fuel will pretty much gel uniformly throughout the whole container from the outside in. At this stage the fuel will cycle from gel to liquid in a narrow temperature range just above or below freezing depending on the batch. You can watch the fuel melt as the sun warms it ever so slightly. However eventually the high melt point components will solidify and settle to the bottom leaving the low melt point components on the top. Below is picture I took this morning when the temperature was zero (0) Fahrenheit, -18 Centigrade. You can see there are two layers, a lower very solid layer and an upper liquid layer. The temperature needs to be about -10 F or -23 C for the upper layer to gel.
I actually take advantage of this effect in the early spring. I will carefully pump off the upper layer to my farm tractors in the early spring and leave the lower layer until the warmer temperatures of the late spring and summer. That way I don't worry so much about gelled fuel if we get a cold snap.
In addition, each year after I empty the totes there is a white solid remaining in the bottom. Some time ago I collected some of this and as carefully as possible measured the melt point. It melted between 48 C and 54 C. This is very close to the melt point of methyl eicosane, the C-20 methyl fatty acid. With a 50 C melt point you can hold it in your hand and it doesn't melt. You might suspect that it is wax it is so solid.
Sorry when I tried to attach my photo I received an "exceeds size" error message. Does anyone know how to attach an image or where to store one for access?
Yes it seems to take a much higher tmperature to get the HMPE's to melt back into solution.
I use a chilled wood chip drum to filter the HMPE's out of my winter fuel, it works great!
I started a thread a while back about it here: http://biodiesel.infopop.cc/ev...1001332/m/4227014543
Though Graydons picture site went down so I just host them on my own site now.
Here is the fitting I made for the top of the drum, the input is through the 3/8" pipe on top, this connects to a hose which goes to the bottom of the chips, the fuel goes travels up from the bottom and out the lower pipe into the fuel tote.
In all its glory
I manage my biodiesel fuel through the winter using that method. I discovered adding kerosene and petrol to the biodiesel in the storage drum caused the HMPEs to settle out completely as the temperature dropped, leaving a clear layer to pump from through a 5µ filter into the vehicle tank. Since I started doing that I've never had winter problems from any fuel solids in the vehicle tank settling and clogging the fuel pick-up screen. As the temperature warms in the spring, the HMPEs gradually melt back into the mix, but at a higher ambient temperature than when they settled out.
The fuel storage barrel 'automatically' adjusts for the temperature the fuel needs to operate at.
John Heron, concerning the above photo, I see two lines (and valves) in the picture, one which exits the refrigerator wall, where does the second line go?
What you are saying is, the HMPE's precipitate out and then the wood chips filter & trap them. How often do you need to warm the wood chips and flush off the HMPE's or is the filter bed capacity enough for a whole season?
What is the purpose of the boot seen in the picture?
Thats the beer tap handle, a "Welly" its a local micro brewery here in Guelph, I drink so much of their beer they gave me a handle.
It's a whole lot easier to pack the oil soaked chips into used milk cartons, then just throw one into the woodstove with the burning logs when you want a quick hot burn to bring the temperature up.
Yeh, I even saved up some cartons and cardboard tubes for that but every time its time to change out the chips it seems I have a million other things I need to get done so I just end up dumping them and getting on with other important things...
I am a master procrastinator.
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