Uh did you miss the part where you do NOT need a Smelter to get Aluminium?
Sure you need a tiny bit of Molten Aluminium for making a Niobium based Crucible but that is a thing you do ONCE, since you dont ever need that much Niobium.
To get Tantalum or Niobium you need Tantalite, Columbite or Coltan. Those are the 3 Ores that contain it. If you have HBMs Nuclear Tech Mod installed it will also follow the HBM Rules of generating Coltan around the Area where the Coltass points to.