Abstract: The present invention discovers a new structural design technique which provides clearances between refractories 13 and fills the clearances with various types of refractories or refractory materials like in the past and, furthermore, uses another method to secure the heat expansion absorption function and provides a hearth structure of a rotary furnace hearth 1 able to prevent contact between the hearth structure and furnace side walls 3 and 4 caused by heat expansion of the refractories 13 and realize safe and smooth operation, that is, a hearth structure of a rotary furnace hearth laying two or more layers of refractories between side blocks 9 and 10 built at the inner circumferential end and outer circumferential end of a hearth refractory bed 7 of a rotary furnace hearth 1 and laying a powder or pellet hearth material 16 on its top surface, the hearth structure of a rotary furnace hearth 1 characterized by using refractories having a compressive strength of 0.1 to 5 MPa at 800 to 1500° C.

Abstract: A rotary furnace hearth wherein a hearth carriage carrying a hearth comprises a plurality of hearth carriages respectively having propulsion systems, wherein adjoining hearth carriages are coupled by coupling bolts and nuts via spacers interspaced in a single row in a horizontal plane, whereby even if the hearth carriages deform due to heat at the time of operation, they are structured to be able to freely deform without mutual constraint in the event of curved deformation, so the hearth carriages are maintained in individually stable states at all times.

Abstract: A reduced iron discharging screw conveyer is provided in a rotary hearth furnace and discharges reduced iron out of the rotary hearth furnace. The rotary hearth furnace produces the reduced iron by charging and heating a pellet including metallic oxide and coal material onto a rotary hearth rotating in a horizontal plane. The reduced iron discharging screw conveyer has a rotary shaft and a screw blade which is spirally formed on an outer surface of the rotary shaft. A lead angle ? of the screw blade 5a satisfies a condition of “0.46 rad ???0.79 rad”. A ratio (h/D) between height h of the screw blade and an outer diameter D of the screw conveyer is smaller than 0.2, and a ratio (t/h) between thickness t and height h of the screw blade is larger than or equal to 0.12.

Abstract: A rotary furnace hearth wherein a hearth carriage carrying a hearth comprises a plurality of hearth carriages respectively having propulsion systems, wherein adjoining hearth carriages are coupled by coupling bolts and nuts via spacers interspaced in a single row in a horizontal plane, whereby even if the hearth carriages deform due to heat at the time of operation, they are structured to be able to freely deform without mutual constraint in the event of curved deformation, so the hearth carriages are maintained in individually stable states at all times.

Abstract: The present invention discovers a new structural design technique which provides clearances between refractories 13 and fills the clearances with various types of refractories or refractory materials like in the past and, furthermore, uses another method to secure the heat expansion absorption function and provides a hearth structure of a rotary furnace hearth 1 able to prevent contact between the hearth structure and furnace side walls 3 and 4 caused by heat expansion of the refractories 13 and realize safe and smooth operation, that is, a hearth structure of a rotary furnace hearth laying two or more layers of refractories between side blocks 9 and 10 built at the inner circumferential end and outer circumferential end of a hearth refractory bed 7 of a rotary furnace hearth 1 and laying a powder or pellet hearth material 16 on its top surface, the hearth structure of a rotary furnace hearth 1 characterized by using refractories having a compressive strength of 0.1 to 5 MPa at 800 to 1500° C.

Abstract: [PROBLEMS] It is an object to provide a reduced iron discharging screw conveyer of a rotary hearth furnace, which can reduce maintenance frequency of the screw conveyer and improve operation rates of the rotary hearth furnace by extending wear life of a screw blade of the screw conveyer. [SOLVING MEANS] A reduced iron discharging screw conveyer 5 which is provided in a rotary hearth furnace and discharges reduced iron out of the rotary hearth furnace, the rotary hearth furnace producing the reduced iron by charging and heating a pellet including metallic oxide and coal material onto a rotary hearth rotating in a horizontal plane, the reduced iron discharging screw conveyer has a rotary shaft and a screw blade which is spirally formed on an outer surface of the rotary shaft. A lead angle ? of the screw blade 5a satisfies a condition of “0.46 rad???0.79 rad”. A ratio (h/D) between height h of the screw blade and an outer diameter D of the screw conveyer is smaller than 0.

Abstract: To provide a pre-heating apparatus capable of improving the installation reliability of a raw material holding gate of a pre-heating apparatus, reducing an installation cost and reducing melting electric power energy without deteriorating an operation environment while improving the pre-heating effect on raw materials by an exhaust gas, a shaft equipped with a raw material charging portion and an exhaust gas outlet at the top thereof and with a raw material holding gate at the bottom thereof is disposed in the proximity of an arc furnace, a gap is defined between the lower end portion of the shaft and the holding gate, and an outer cylinder connecting with an exhaust gas duct of the arc furnace is disposed around the outer periphery of the gap.