2. The combination as defined in claim 1 wherein: said furnace includes an elongated, generally tubular outer shell disposed coaxially about said furnace tube in spaced relation therewith for forming an air cooling cavity there between; said preheating enclosure is disposed interiorly of said air cooling cavity, an inner wall of said preheating enclosure being formed by said furnace tube and said raw ore preheating enclosure includes spaced apart, slotted side walls adapted to slidably, removably receive said baffles