Raw ore inputted via conventional input conduit 14 is. Divided between headers 120, 121 which respectively lead to heat exchange preheaters 78, 79. Each of the headers is coupled to a divider unit 124 (FIG. 7) which may selectively route raw ore toward either the pre heaters 78, 79 or a preheater bypass conduit system 126A, 126B. Pipes 128A, 128B couple a selecting member 124 directly into a preheating assembly 78, 79 respectively. For example, raw ore 171 transmitted from selector 24 via conduit 128B enters inclined ramp 170