The burner I built is similar in construction to a tiger torch. I use a 20 pound propane bottle without a pressure regulator , just a small valve in the line.
As you can see the pot is made from standard pipe, so is the bottom of it.
The outside shield is standard steel pipe also.
I start by adding aluminum shavings to get a layer of melted aluminum in the pot and then add the Pistons.
Any steel that is in the Pistons will stay in the bottom of the pot and the ash can be skimmed of the top before pouring it into the pipe mould.
I have a long handle on the pot to lift the pot from the burner& pour the aluminum into the pipe moulds, that are sitting on 3/4 to 1 inch thick steel to absorb the heat.
Caution do not stand the pipes on concrete.
The aluminum shafting will be easily be removed from the pipe mould when cooled.providing there was no large burrs on the inside of the pipe.
I takes a lot of heat , be careful and do it outside.