Nippon Steel Corporation

Masaharu Takahashi

Hiroshi Oda

Tetuharu Ibaraki

Shoji Imura

Shigeki Takahashi

Tetsuharu Ibaraki

Yoichi Abe

Satoshi Suzuki

Shouji Imura

The present invention provides a method and facility for preventing crumbling and powderization of green pellets when producing high strength green pellets using a powder feedstock and using the pellets in a rotary hearth reducing furnace and for efficiently reducing the same. It comprises kneading by a kneadera feedstock of a powder of a fine particle size (20 to 80 wt % having size of not more than 10 &#x3bc;m) including a metal oxide and carbon-bearing powder fed from a feed storage tankand producing green pellets by a pan type pelletizer. The green pellets are screened by a pellet screen, then dried by a pellet dryerand reduced by firing in a rotary hearth reducing furnace. At that time, the green pellets are continuously conveyed to prevent crumbling.

Metal oxide-bearing green pellets for reducing furnace, method of production of same, method of reduction of same, and reduction facility

The present invention provides a method and facility for preventing crumbling and powderization of green pellets when producing high strength green pellets using a powder feedstock and using the pellets in a rotary hearth reducing furnace and for efficiently reducing the same. It comprises kneading by a kneadera feedstock of a powder of a fine particle size (20 to 80 wt % having size of not more than 10 &#x3bc;m) including a metal oxide and carbon-bearing powder fed from a feed storage tankand producing green pellets by a pan type pelletized. The green pellets are screened by a pellet screen, then dried by a pellet dryerand reduced by firing in a rotary hearth reducing furnace. At that time, the green pellets are continuously conveyed to prevent crumbling.

Metal oxide-containing green pellet for reducing furnace, method for production thereof, method of reduction thereof, and reduction facilities

The present invention provides a method of operation and a facility for the same suppressing the generation of dioxins in the combustion exhaust gas and efficiently reclaiming heat from high temperature combustion exhaust gas when firing and reducing fines of chromium ore, iron ore, or other ore or pellets formed from dust sludge, etc. containing iron oxide or other metal oxides generated in the metal industry in a reducing rotary hearth furnace. This treats the combustion gas generated in the reducing rotary hearth furnace to make the temperature of the gas 800&#xb0; C. or higher for at least a certain time, to make the concentration of the carbon monoxide not more than 200 ppm in terms of volume ratio and to achieve a sufficiently well developed turbulent state at least at one of the inside of the exhaust gas outlet duct and the vicinity of the exhaust gas outlet duct for at least a certain time, then rapidly cooling the gas. Further, it controls the total number of moles of zinc and lead, the total number of moles of alkali metals, and the total number of moles of halogen elements contained in the combustion exhaust gas to a predetermined ratio.

Method for operating rotary hearth type reducing furnace and rotary hearth type reducing furnace facilities

There is provided a method of producing reduced iron compacts with high crushing strength, low powderization and a high reduction rate in a solid reduction-type firing reducing furnace such as a rotary hearth-type reducing furnace, as well as reduced iron compacts obtained by the method and a method of melt-reducing the reduced iron compacts in a blast furnace. In the method of producing reduced iron compacts, the atomic molar ratio of carbon to oxygen chemically combined with iron, manganese, nickel, zinc and lead, in raw material powder comprising a mixture of iron oxide-containing powder and carbon-containing powder, or the ferric oxide content of the raw material powder, is in a specified range, the compact is produced so as to give a porosity in a given range, and the compact is put on the hearth of a reducing furnace equipped with a rotating hearth and is heated for heating reduction by the heat from the combustion gas in the upper part of the furnace, for firing reduction at above a prescribed temperature.

Method of producing reduced iron compacts in rotary hearth-type reducing furnace, reduced iron compacts, and method of producing molten iron using them

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Kimitsu, Japan

Masaharu Takahashi