First post here, folks. Name is Jason. I'm actually a metal caster and found my way to you guys via some searching. While i fire a metal casting furnace on used motor oil, I was looking for a quicker way to fire a forge I was building. I'm from west texas and coal isn't something we have here. Lots of oil and natural gas, but no coal. To make things worse, propane is dumb money in my neck of the woods so I set out on firing a forge with natural gas. This thread is my adventure into what took me way too much time to solve. Hopefully this will help someone looking to do the same thing.
The Problem: As you propane burning people know, you guys can get regulators to blast out at 30psi and even 60psi and that's why you can get away with a normally aspirated propane burner or "supercharge" it with a hair dryer or compressed air line. Household natural gas pressure is only delivered at about 1psi. VERY LOW, slow and LAZY. There is no way to boost this PSI without expensive engineering. There are companies that sell natural gas forges and these can be expensive and are usually very large.
The Solution: Must create a large enough mixing chamber and an effective way to safely and smoothly deliver the collected low psi natural gas and get it to burn INSIDE an enclosed space.
Nothing I did here is new and I cannot take credit for this. The real brain child behind this is John Emmerling, His simple instructions can be found here. http://www.waynecoeartistblacksmith.com/uploads/Ribbon_Forge_Burner.pdf Thanks Wayne for posting this on your website.
On to the build and all my trials and tribulations.
This is how i WAS heating metal. Some might call it a vertical forge, but I call it a furnace. FIred with used motor oil, it has a hinging lid to allow the crucible to be lifted in and out of the heat. Used oil has the BTU's to easily reach cast iron temps and is essentially FREE to operate for long periods of time.
Here is some work on the tank itself. I thought having one end hinge would be a good idea for larger work. This haunts me later as you'll see.
2" x 2" x 6" 1/8" wall box section. Note diffuser plate with holes welded 5/8" from 2" opening on the inlet side.
Ends closed, That 1/2" lip is what secures the refractory to the body of burner housing.
Crayons mounted on plywood for burner hole pattern
Large 2" hole for inlet
Setting depth for casting
Refractory filled form and metal box
Removing the forms
Mounted in top of furnace
View inside the furnace. No METAL of burner body can protrude inside furnace!
Here is where and HOW the magic happens. The natural gas must be introduced to burner (in distance) per this
>>>> Diameter of pipe (2") X 9 = MINIMUM entrance in inches. My case 18" from burner. Reason for this is to allow
the natural gas and blown air to mix. If feeding this thing with propane, You can put it closer to the burner and shorten up the pipe.
Test firing burner outside the forge
test fire outside furnace. Shoots a nice 4ft flame
Firing inside the tank
Another view inside from the hinged side.
Full steam ahead right? Well, here is where I get a little sideways with this project. Looks like it burns great right up to the point where I close the hinged door. With the door closed, it flamed out. It became very hard to light, unstable, and just about downright scary. Lots of poofs and woofs.. I started to reconsider this hinging door and really the need for it. My openings are 4"x4" on the back and close to 6"x6" on the front. I decided to weld the back end of the tank on it. Further test firings still showed I had SOMETHING going on with this. I tried running it lean, I tried rich. I tried every blower I could find from hair dryers to large squirrel cage fans, shop vacs and paddle style fans. It is important to remember a fan is not necessarily a fan. Squirrel cage fans do not handle back pressure well. When back pressure happens to a squirrel fan, the motor slows down and stability can become an issue. Better option would be a paddle blade setup. Well, last night it finally occurred to me, what I was doing was introducing this forced air/gas mixture into a tank without a clear path to it's exit. This created a turbulent environment and made the flame highly unstable. I still hadn't added the Kaowool or Mizzou refractory cement to this as I didn't know if the burner was here to stay or would I end up on a normally aspirated propane burner. I decided last night to mock it up stuffed with 2inches of Kaowool and light it again.
As they say, the proof is in the pudding. The flame lights with ease. Turn on the air, slowly introduce the natural gas and it lets out a gentle poof and it's off to the races. It's VERY stable, and dare I say it now, REALLY HOT! I still have more work to do, adding the usual assortment of air flow valves, fine adjustment for gas control and other crap I can screw to this thing. At the moment, my fan is a whimpy microwave oven blower and the gas line is 1/2" feeding the burner. My fan is running full tilt and natural gas valve is hardly even cracked open. This is exactly what I want. Plenty of headroom to increase the heat by adding a larger fan and increasing gas flow.
And here's a small video of it running.
Stuffing this thing with the Kaowool allowed for smooth exit of airflow. PROBLEM SOLVED!
~side note~ Kaowool should be covered with Mizzou, ITC, Kast-o-lite, keeping silica out of your lungs is important.
Hopefully this might help some of you that are considering dumping your expensive propane and trying natural gas. I can already see many applications for this. It burns clean, CHEAP, lights easy, stable, could be extremely safe with the addition of flame sensors and solenoids to cut fuel in the event of a loss of the blower or even power. Compressed air could also be another option easily rigged in place of an electric motor so close to a pipe full of gas. Many question why the flame doesn't travel back up the pipe to the source. Well, the pipe remains under pressure and the pipe is a fixed size, therefore the theory is the flame has no where else to go but forward. In addition, multiple ribbon burners could be stacked, or a 3foot burner could be made just the same. Today, with the net, we stand on the shoulders of giants and each time, we get to see a little further than the last guy. So grab your man card and let's see where this takes us.