Aluminum Nozzle Melted at 1400 C
I set up to run at 4" w.c.
It only took one minute to get a sustained flare.
Looking down the aluminum throat is pretty.
You can see the thermocouple with the business end right under the nozzle holes.
At about 10 minutes into the burn and 1250 C I saw a drip forming and thought that was the aluminum melting, I pulled out the drip with my poker and discovered that it was iron. A nail had reached the reaction zone, melted and dripped through one of the the nozzle holes. At this temp the aluminum was still solid and the aluminum outside of the barrel was running around 350 C,
At 1380 C I saw a shower of sparks coming down through the nozzle holes. Sparks looked like a 4th of July sparkler. I checked with the poker and the aluminum was soft. Moments later the temp passed 1400C and the aluminum collapsed.
I'll send a picture of the nasty results when everything cools down.
So I think that this thick walled aluminum tube might work below 1200 C. It may be better to keep things down around 1000 anyway to avoid creating abrasive and nozzle obstructing clinkers.
Copper is a better conductor, melts at a higher temperature and is physically more durable. It is the preferred tuyere for ancient and modern smelters and a good choice for a gasifier if it wasn't so expensive.
Kristijan's thick-walled steel pipe looks pretty attractive and Dave gets 100 hours out of a simple pipe cast into a block of refractory. Maybe Andy's idea of aluminum filled stainless would transfer enough heat away to slow the oxidation of the stainless while it protects the aluminum from direct heat?
Thanks for the warnings/guesses. I needed to see it for myself.