Propane burner build: The Mule

If anybody wants some used kiln bricks I have a good supply. I share my shop with a guy that builds and services kilns and he is always taking apart kilns. I used a bunch to build my furnace. Two layers of bricks and half a bag of castable refractory we had laying around. Works like a champ.

Kilns get up to about 2300F inside and stay well under 200F on the outside with one layer. We a have a glass blowing furnace going that has 2 layers of brick and some brushed on refractory. That thing runs 24/7 for up to a year at a time at about 2000F and the outside surface is around 140F.

The bricks are light weight and wouldn't be that expensive to ship. I think they are about $5 each new. If you are near St Pete, Fl you could come and fill your trunk with them if I tell him to save some.

In reply to jgrewe:

I know I'm late to this, but is that offer still valid?

Sure, most are 3x4x9 when new. They will have the ends cut at angles to make specific size "round" kilns. I think they are usually 8 or 10 sided. They will have grooves in one of the faces to hold the heating elements. They are easy to cut with a hand saw. Give me an idea of how many you might want and I'll have him put some aside next time he tears down a kiln

Here is mine with the lid off to give you ideas.

In reply to jgrewe:

pm sent

This came in Friday, looks fresh.

RevRico picked up a bag today w/ some other goods. Good guy that Rev.

Keg build is still a few weeks out at least, need to clean out garage and finish a few other projects. Being retired again, things should progress smoothly after that.

Just a bump for myself while renewing pics after the Photobucket fuster cluck

Update: Did make progress... but not enough to finish this year.

Rods for securing refractory.

1" Inswool was a last minute decision. Better to have than not. Glued in w/ Clearco 444 spray adhesive. Similar installation on the keg base.

Drier mix. Rammed mix w/ 2X2 on the inner and outer circumferences but not over the wool. Old pneumatic jitterbug sander used as table shaker to remove entrained air, it worked quite well. 

1" PVC pipe guide to hold center. Mineralac and beam clamp FTW. Ran outta 1/4" all thread, so compromise.

Surfaces covered w/ plastic, air dry at 60°F for 36 hours. Cooler nights brought in halogen work lights to maintain temps. Gradually raised temps 60-70-80 degrees w/ moving the lamps closer. Held 95-100° for 48 hours w/ lamps (90-110°F recommended). 

October temps went from August to November overnight. Needed two more weeks of good temps to finish walls, cure and dry out w/ burner but temps never came back. Keg and lid moved inside house for the winter. One minor glitch, it appeared as if the Inswool was pushing up through the refractory but it was actually mineral crystals, looked exactly like wool. Surfaces are covered w/ plastic now at 70°.

No major berkeley ups yet... but there's still time as they say.

Tentative schedule to finish is May or later. Gimme 70° days again!

Burner update 10/24/20

Rather pleased with the overall performance of the burner, glad I built it like this.

Changed out the 1 x 3/4" bell reducer for a straight 3/4" SS coupling on the flare end. The 1 x 3/4" bell would work well using it as a forge burner or for other shop use but not necessarily in the furnace. 

Could have cast a socket with flare molded in the furnace refractory for fitting the 3/4" pipe end but the refractory would degrade over time and need replaced or recast. The 3/4" coupling will be used as a sacrificial/ consumable piece. SS was chosen over BMI or steel for better durability. A 3/4 x 8" SS nipple replaced the previous black nipple. 

At first the burner lit w/ the 3/4 coupling flare outside the furnace but burnt back in the pipe. First time that ever happened. Ground the threads out w/ a carbide burr, not happy yet. Ground a slight taper to the end of the coupling and bingo, she lit but at higher pressure. Once warmed up some I was able to lower the gas pressure to 2 PSI and adjust the choke down. 

And yes, I know the burner will act differently in the furnace but I'm not doing a flarectomy when all set up to cure refractory outside. 

There is about 12 hours run time on this SS coupling as shown.

Lowest fire I could get, that is with the 0.023 MIG tip and choke cut way down. I could never get the 0.030 orifice down this low. The refractory was warmed to over 185°F w/ lamps during dryout. Not throwing too much heat at it to start. The needle valve came into play also for fine tuning. 

Primary air cut back at 2 PSI gas pressure.

That ain't a lot of primary air.

Monitored furnace bore temp w/ a digital kiln pyrometer from Skutt. Gradually increased temp over 8 hours w/ burner adjustments. The pyrometer reads to 2500°F, once reached I ran over two hours longer so maybe 2700-2800° final.

She's cherry. 

Result

Keg foundry furnace build is here