Intro: Continous Flow Aluminum Smelter
This instructible has no photos, only drawings. This unit I Built in the late 70's for melting aluminum transmissions, bumpers and such.
The unit was about 4 ft square and 6 ft tall, would accept whole transmissions that that had been drained of oil, and automobile bumpers thru its 36" feed chute. the continuous flow of molten aluminum was poured into 1/2 ton molds.
The burner unit which is the main focus here can be scaled up or down for your particular needs. This size unit when burning uses about 7 gals used oil an hour, at 20,000 btu per lb, that's equivalent to 1.12 million btu an hr. much more than most garages need.
A 1.5" x 12" unit was placed in a barrel stove in a garage, it produced as if the barrel stove was running wide open, and burned thru in 5 mins because there was no fire brick. So be careful and have fire extinguishers handy, if you decide to build a unit like this.
Step 1: Continous Flow Smelter
This pic shows the 2 main tubes and how the holes are drilled and assembled with fuel inlet and end caps. Muffler tubing, low carbon steel tubing is fine. Size will depend heat output since size determines how fast the oil can be broken down to lighter fuels.
Step 2: Air Input
The air is provided by a blower, I have used kirby vacuums, canister vacuums in 5, 10, and 20 gal size, and commercial vane blowers salvaged from scrap yards as the blower. The size will depend on the heat output you intend to produce. the Standard exhaust tubing unit will be totally useful using the 5-10 gal vacs. Always provide a divirsion valve for the air flow for smooth startups and when restricting to a reduced heat output.
Step 3: Water Input
This tube isnt necessary for operation, but increases efficiency and reduces failure time. The unit will fail without due to a carbon build up between the 2 tubes as the oil is broken down. The carbon will be in the form of extremely heavy oil and carbon, similar to a tar but extremely heavy. The steam reacts with the carbon producing what used to be called 'water gas' made from charcoal and steam.
Failure time can be extended 5-10 times using water as without. Without the water we replaced the burner every 2 months because of reduced output, but remember we used about 30 gals a day, 5 days a week. A smaller garage heating or outdoor furnace unit would never burn that much probably all winter.
Step 4: Operation
This details the start up and operation of the unit.
The first few start ups will be tricky till you get the hang of adjustments by recognizing the need for more or less fuel, more or less air etc and when to start shutting down the propane start up torch.
When you have full air volume, and it smokes, you need less fuel, and it takes a minute or so to reduce fuel flow. But if the flame is yellow with full air flow, the fuel flow increase will be almost immediate. Air flow increase will also reduce smoke without changing fuel amount. To add steam, there is a delay and increases effective fuel input so more air has to be available, or fuel reduced.
Also you need to understand flame goes from red to yellow to blue to white to clear as the heat output increases. A clear flame may be extremely efficient, but is very dangerous since only the heat shimmer can be seen and will cause a thermite reaction very quickly, a blue flame will too, but you have a larger amount of time to remove the steel from the aluminum to prevent it.
And never place magnesium alloys into direct flame (Volkswagen motors and many semi truck frames have magnesium alloys. This warning is from experience!!!
Step 5: Water Tank Position
This depicts the water/steam tank position, it needs to be heated just as the burner does by the burner output. Placing it above the burner does this and prevents liquid water from entering the burner by using the stand pipe allowing only steam to exit the tank.
Step 6: Burner Assembly
the burner here is ready to be added to your smelter or outdoor heating unit.
there are check valves to prevent oil and water from backing up and damaging the pumps and feed lines. Spraying hot steam or oil is very dangerous! Do not use brass connections or check valves as the heat build up can follow the steel pipes back and cause the brass fitting to fail. If necessary add cooling to the valves, we directed intake air over the valves and connections just in case.
Again a diversion valve to divert excess air from the blower is preferred to reducing air intake, as reducing air intake causes the motor to work harder and overheat. A Y-branch type valve that allows the blower air a strait shot to open air and when blocked causes the air to turn down the Y is probably the best type of divert er.
Step 7: The Smelter
this is a rough drawing outlining the smelter details. you would build it with materials you salvage so no fixed dimensions are given.
The raw aluminum is placed in the chute to preheat and fall down to the grates to melt. The flame swirls like a cyclone around the metal melting it, steels and brass are raked clear as they fall free, as is the scum on the aluminum from the oxidized aluminum thats on the outside of transmissions. This scum needs an electric furnace to drive the oxygen out, so you may locate a sale for it. Any thermite reaction needs to be buried or allowed to burn out, outside the unit before it spreads to the molten aluminum. I had a 1/2" floor of aluminum that stayed in the machine, and everything else flowed out into molds thru the output tube/hole.
The last file is a Sketchup file that can be downloaded if you use sketchup.
If you make a smaller one and use it for heating a garage or outdoor furnace I would like to hear about it.
We could burn any oil product, motor oil, transmission oil, deep fry oil, etc. The oil was always mixed together, and if we ran short #3 fuel oil was used to dilute the oil we had.
A rough input/output BTU can be found since oil has 20,000 BTU per pound.
Even a fuel oil furnace doesnt use the full input rating since it only runs 5-20 mins out of an hour depending on how much heat is required to bring the heat up. realizing this this unit only needs to produce 20-40,0000 BTU/hr to heat most homes in an outdoor type furnace.
Have fun with it, and by all means be safe not sorry.