Furnace (part VI)

(A used vegetable oil furnace)

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One of the things that the human race has in common appears to be an insatiable appetite for three things... sugar, salt, and OIL. The last of these is an interesting one, particularly because it comes in many forms - vegetable oil, olive oil... and the list goes on.

The deep fried junk that we have for lunch and dinner creates gallons and gallons of dirty used cooking oil at the back of restaurants which we would rather not see. But in actual fact this dirty liquid makes an extremely powerful fuel (aided by burnt potato bits) which just makes sense in a furnace!

Used cooking oil... a free & environmentally friendly fuel

A brand new crucible - beautiful!

Vegetable oil has the potential to burn very ferociously under the right circumstances. It was thus decided that the old tin-can crucibles would be absolutely out-of-the-question. New idea? An old fire extiguisher!

This poor old extinguisher was just slowly karking it at the back of a church, so I decided to empty out the powder and take to it with an angle grinder. There on the left, we have ourselves a beautiful new thick-walled crucible.

To modify the furnace to take used vegetable oil, some sort of feeding mechanism was needed. After a bit of deep thought, I came up with this mechanism using a few old scrap pieces of copper tubing and joiners, complete with a ball valve to control oil flow.

The large steel tube at the base is an air inlet, once again for the purposes of providing oxygen to the base of the furnace. However, as seen in the next slide, it'll also have a much-needed second function.

Oil feeder tube

Schematic of oil feeding physics

When the oil tank (not pictured) is mounted above the feeder tube, the oil is brought down to the ball valve by the force of gravity. If the valve is open, the oil continues to flow around the bend and into the steel tube. At the same time, highly compressed air is blown into the steel tube, hopefully atomizing the oil particles and resulting in a fine mist of oil at the output.

This fine vegetable oil mist (sounds delightful...) turns out to be remarkably flammable and serves as an ideal furnace fuel.

In order to increase the pressure of the air right at the point where the oil arrives in the steel tube, a steel nozzle (pictured) was fashioned out of sheet metal and shaped into a cone.

This cone fits snugly inside the steel tube and directs a jet of air right into the oil outlet.

Steel nozzle for pressurizing air

The new furnace setup

Putting all the parts together, we have here the completely trial setup for this brand-spanking new feeder tube.

On the top of the ladder there is the oil tank (inverted orange juice carton) whose tube connects to the feeder mechanism. The old furnace is back, with the original air inlet replaced with the steel air tube. At the inlet of the steel tube, I've used the output of a vaccuum cleaner (not pictured) to provide the pressurized air.

It took quite a while for everything to set into place and function as designed. For instance, the ball valve had to be moved very delicately. If it was too open, too much oil would flow and the ignition source (I used some cardboard and BBQ bricks) would be drenched and put out.

Upon first light, however, the furnace burned magnificently...

First light! The oil burning furiously away!

An over-excited furnace gobbling up some oil

One of the most interesting things one notices from using a used vegetable oil furnace is the smell which eminates immediately from the fire. A subtle blend of KFC chicken nuggets, spring rolls, potato chips and McBurgers with a whiff of burnt pig fat. Yuck. I bet you get fat just inhaling this stuff.

Of the many things that could be improved with this setup, one of the more concerning was the proximity of the plastic oil hose to the fire itself. Hmm...

Here the furnace is cooling off after an intense session! This little guy has survived many things and has many stories to tell.

Notice all the burnt bits of god-knows-what strewn about on the bricks. Just absolute chaos. Interesting to also note that the grass around this area was dead the next day. Now are you concerned about what goes in your McDonalds deluxe burger?

A scorched earth



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