I'm building an aluminum melt propane furnace in which I may also want to someday melt brass - and maybe even occasionally some cast iron. I've researched many home foundry websites and am following the advices found there but a few design details are missing. I am using a scrap 3/16" SS tank I found at a salvage yard. The tank had been cut in half by the scrap yard for crushing, but I have welded it back to its original shape. The tank is 18" in dia and I am currently planning 5" walls of 3000 deg cast refractory giving me an 8" center. I'm getting ready to cut the height of the tank to 16" not including its rounded bottom. This will leave adequate tank wall material for a 4" - 5" thick lid. I also found a nice piece of 4" schedule 40 SS pipe from which I plan to build a crucible. This will leave about 2" of space between the crucible and the refractory. Its going to be a heavy beast and so I plan to build mechanicals to help handle the lid.
My questions primarily concern the tuyere:
1.) I understand that it should enter tangentially to the inner wall of the refractory but how far up from the bottom? Some drawings I see show it at the top of the plinth (barely touching the crucible), and only one other reference that I was able to find that mentioned its location said that it should enter at the bottom 1/3 of the crucible. Is this critical?2.) Is it best to extend the tuyere into the refractory or to use a temporary mold for it and terminate the actual metal pipe at the wall of the furnace? I'll likely be using scrap SS pipe here also. I've read about it being done both ways as others have admitted to being as unsure as I am. What's optimum?
3.) Does anyone see anything wrong with the dimensions that I am planning? I am wondering if the space between the crucible wall and refractory is important and if I'm currently planning too much? If I build a larger crucible someday is 1" clearance ok?4.) The tank has a rounded bottom and a 2" hole. I suspect this is too large for a drain hole? Should I close it up to something much smaller?
5) With the diameter tank I am working with I have seen at least one reference that suggested replacing the outer one inch of refractory with one inch of Kaowool. What will this buy me? Is there any performance advantage worth the cost and hassle of working with this stuff?I haven't settled on a burner design yet but so far I am leaning to one of the blowerless designs. I'm still reading here and there is alot of good info available on the web. I thought I would get serious about the burner while the refractory is curing.
Any other comments are greatly welcomed before I do any irreversible fabbing. Thanks in advance.