Put your crucible in the center
pop your 12in pipe to the edge of the inner wall
fill with match light charcoal
let it burn for a little bit before
popping your lid on and firing up your shop vac or hair dryer.
I have the shop vac like 4-5in away from the pipe, you gotta play with the distance depending on what your using and its power, you'll see what I mean.
Once the pipe is red hot your good too go.
Now mine gets red hot just as the charcoal runs out so i usually pop some more in there.
It's great fun and you could really end up making some useful and cool stuff check out this site
for ideas and help. I mean you could just buy one off that site but for $400 bucks and they run off propane which you could just make this one run off a, and you wouldn't have fun making something truly unique.
I would recommend adding cans to already molten aluminum because cans like to burn. Also cutting the tops and bottoms make it more pure. Start with the tops and bottoms then add the center of the cans. I've melted an old razor scooter, that was the best cause the pipe just slowly slide down as it melted. Anything
Have fun be safe.