control also emanating from the refractory cover or lid 122 is the hot sand tap 128 said tap being located substantially adjacent the mother bed of the furnace 100 and having interposed between the mother bed interior of the furnace and the interior of the refractory lined cover 122 a gate valve 128a a convenient elevator 130 is provided within the circular hip surrounding the furnace support whereby each ladle may be raised into position for heating and lowered from the semi fixed cover and its ceramic plug following heating in operation the mother bed provides a combustion chamber and a holding facility for hot sand or other refractory particulate material which is to be tapped into ladles to form a secondary fluid bed by an accelerated heat transfer system in operation the fluid bed material from the mother bed once fed into the ladle is further fluidized with hot gases from the mother bed providing excellent heat transfer into the ladle when the ladle has then achieved a selected operating temperature as for example 1500 u00b0 2000 u00b0 f the hot sand is returned to the mother bed thereby conserving the heat energy flows are balanced in the system by a series of simple gate valves or ceramic plugs not shown but designed to constrict or increase the size of the duct 128 leading from the mother fluid bed to the ladle or from the fluid bed or the exhaust system sand or other bed material is thus drawn from the mother fluid bed into the correctly positioned ladle.