Intro: Easy Dual Fuel Furnace Burner
Want to melt metal?
Want to melt metal for free with recycled oil?
Here's an easy-to-make burner that can use either propane or oil (veggie or motor). It will heat a furnace up to aluminum melting temperatures with no problem.
Step 1: The Burner
Safety talk- Yes, we're playing with fire here. Use your head. OK?
Parts for the burner:
A blower- I got mine from a surplus place. The more air it moves the more fire you can produce. Anything around this size will work. Mine's rated at 100 cfm (cubic feet per minute)
1 1/4" dia. steel pipe 18"-24" ish long. The dimensions aren't crucial. I wouldn't go with a smaller dia. though.
30" of 1/4" dia copper pipe
Hose clamp (optional)
1 male propane quick release fitting. Get this from a propane supply. Don't just use an air hose quick release.
Other stuff that you'll need:
Propane tank w/ an adjustable regulator & hose w/ female propane quick release
5 gallon bucket
Plastic valve w/ 3/8"" fittings
Clear poly tubing 3/8"
Teflon pipe tape
Drill & bits
Tap for the propane fitting
Torch & brazing rod. Doesn't have to be big, even a jewelers torch will work.
Metal cutting saw
Assorted hand tools
Step 2: Build the Burner Tube
Drill a hole about 2/3 back from the front of the steel pipe large enough to tap for the propane fitting.
Thread it and screw in the connector. Use teflon tape or pipe compound to seal it.
Now drill a second hole 90 degrees from the propane fitting that is wide enough to insert the copper tubing. You may want to file it into an oval shape to help the copper slip through. The better the fit the less brazing you'll have to do. Feed the copper tubing though until the end is flush with the front of the burner pipe.
I put a hose clamp on to secure the copper tubing and provide strain relief.
Seal the copper tubing to the steel pipe. I'd recommend brazing but you could probably get away with solder or even silicone. Only the tip of burner gets really hot.
Step 3: Attach the Blower
Now you need to attach the burner to the fan. How you attach it depends on the fan you get. For this fan I cut a piece of wood that fit snugly in the end of the fan and then drilled a hole in it that matched the outer diameter of the pipe. I put a couple screws into the block to hold it to the fan housing but just left the burner pipe as a friction fit.
I also made a sheet metal damper for more air control
Step 4: Optional Choke
You need to fire the refractory cement in a furnace very slowly the first time you use it so I made a choke to cut the air way down for a very small flame. If you want one on your burner cut a slit across the top half of the burner tube with a chop saw right next to where it meets the blower. Then cut a damper out of plywood to slide into it. I only used this for the first firing. After that I took the damper out and slid the burner tube back enough so that the slot was covered by the wood block to keep air from leaking out.
Step 5: Fuel Supply
Oil needs to be vaporized in order to burn. Some burners use oil pumps, tiny nozzles and high pressure air to vaporize the oil before it goes into the furnace. We're not doing that because then I would have to change the title of this 'ible to Complicated Dual Fuel Furnace Burner.
This burner takes the lazy approach. We use propane first to get the furnace hot enough to vaporize the oil. Once the furnace is up to temperature we turn on a gravity feed of oil to the burner. The oil drips out of the end of the copper tube, vaporizes from the heat and ignites. Once the oil burner is going you can turn the propane off and just use the cheap/free stuff.
Use a propane tank with an adjustable regulator. A BBQ tank is fine but the non adjustable regulators that come with them don't work well for this. I use a flexible hose with a quick release to the burner. You could also just plumb it together with steel pipe.
Safety First People! Make sure you use equipment that is designed for gas!
Don't cheat and use an air hose. Propane can degrade air hoses and nobody likes a gas leak.
Drill and thread a hole in a 5 gallon bucket for the 3/8" valve.. I also made a "nut" out of masonite to secure it on the inside. Attach a piece of clear tubing. If you're lucky the tubing will fit snugly over the copper tubing. If it doesn't get the right plumbing hardware and connect the two.
Fill the tank with used motor or vegetable oil. Strain it through a cloth as you pour it in. You just don't want any big chunks clogging the valve.
As long as the oil tank is higher than the burner it will feed oil to the burner nicely.
Step 6: Make Fire
Now that we have all the parts together to get our combustion on, let's mix some hydrocarbons and oxygen and generate a nice juicy exothermic reaction.
I use a torch to fight the furnace. That way I can be far away fiddling with the controls rather than sticking my face and hands near the burner as it ignites.
First turn on the fan.
Light the torch ( I use a rag soaked in WD-40 tied to a metal rod with wire) and stick it in the furnace.
Open the propane tank. Adjust to a flame that is coming out of the furnace some but not a lot. You can tell by the sound when you have a happy flame.
Once the furnace is glowing a dull red open the valve (just a little) to the oil tank. There will be quite a bit of flame from the two fuel sources. Turn off the propane tank and adjust the oil flame. There should not be any smoke if you have the oil feed adjusted correctly.
Play with your fire until you run out of oil.
Step 7: Use It!
Here are a couple of projects I've made w/ my metal casting furnace.
This was my first instructable: Entwined Valentines Hearts
The other picture is a big drill guide I made when I worked for the National Park Service
Plus some action shots
Metal casting is great fun. You should do it.
It hardly costs anything to melt metal when you're using this burner to burn waste oil.
Go here to learn how to build the rest of the furnace....
Like projects? Check out our blog- Mike and Molly's House where we chronicle our mighty projects on our mini farm.