3. The combination as defined in claim 1 wherein said heat conducting baffles are arranged in pairs vertically spaced-apart within said enclosure, each pair including: a lower, generally planar baffle adapted to be secured within said preheating enclosure in generally up wardly inclined relation therewithin, said lower baffle extending into substantial contact with said furnace tube, said lower baffle including a product output orifice for dropping raw ore passing over it, downwardly within said preheating enclosure toward the next lowermost baffle; and, an upper, generally planar baffle adapted to be se cured within said preheating enclosure in down wardly inclined relation with respect to said lower baffle, said upper baffle terminating short of said furnace tube whereby raw ore passing over it is dropped downwardly upon the lower baffle without contacting the furnace tube.