Metallurgical apparatus – Means for treating ores or for extracting metals – By means applying heat to work – e.g. – furnace
Patent
1997-08-28
1999-04-27
Kastler, Scott
Metallurgical apparatus
Means for treating ores or for extracting metals
By means applying heat to work, e.g., furnace
266156, C21B 1314
Patent
active
058978291
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device of three-stage fluidized bed furnace type for reducing a fine iron ore having a wide particle-size, distribution so as to produce a directly reduced iron (DRI) to be charged into a melting furnace and, more particularly to a device of three-stage fluidized bed furnace type for reducing a fine iron ore having a wide particle size distribution in the state of stable fluidization while achieving a optimumal reduction degree and energy consumption by the use of a high-temperature reducing gas of a large CO and H.sub.2 contents, in which the reduction and degradation characteristics of the iron ore at high temperature are fully reflected.
DESCRIPTION OF THE PRIOR ART
In general, a conventional method of melting reduction includes the steps of charging an iron ore pre-reduced in a common reducing furnace to a melting furnace and reducing it into an iron while melting. In the reducing furnace, which is to reduce the iron ore in a solid state before melting it, the charged iron ore is exposed to a high-temperature reducing gas for reduction.
Such a reduction process is classified into a moving bed type process and a fluidized bed type process depending on the contact condition of the iron ore and the reducing gas. It has been known that the most effective method of reducing a fine iron ore is the fluidized bed type process where the fine iron ore having a wide particle size distribution is reduced in a reducing furnace with a reducing gas supplied through a distribution plate installed in the lower part of the furnace so as to reduce the iron ore at a fluidizing state.
An example of the fluidized bed type furnace for reducing a fine iron ore is disclosed in Japanese utility model laid-open No. Hei-1-114653, which is shown in FIG. 1. The fluidized bed type reducing furnace includes a cylindrical reducing furnace 111 and a cyclone 115, wherein the cylindrical reducing furnace 111 having a iron ore inlet hole 112, high-temperature reducing gas inlet 113, a reduced iron ore outlet 114 and a gas distributor 116 in the lower part thereof.
In the reducing furnace as described above, the fine iron ore is charged into the cylindrical reducing furnace 111 and a reducing gas is supplied to the furnace through the gas distributor 116 at an appropriate gas velocity. Then, the fine iron ore is mixed with the reducing gas and reduced in the fluidization state in which a gas ascending through the fire ore bed forms a bubbling fluidized bed with fine ore particles. The reduced iron ore is discharged through the outlet 114.
In FIG. 1, the dotted arrow represents a gas flow and the solid line a ore flow.
Generally, in such a fluidized bed type reducing furnace the fluidization in the bed should be maintained actively while the gas velocity is kept low in order to decrease the elutriated amount of the flying iron and increase gas efficiency, which leads to a problem of a conventional fluidized bed type reducing furnace in that the particle size of the iron ore is limited.
The above conventional reducing furnace can only accommodate an iron ore having the particle size of below 1 mm. But, in reality, the fine iron ore contains 50% of the iron ore having the particle size larger than 1 mm.
For that reason, the iron ore is to be classified before the reduction process and then a coarse iron ore is transferred to a shaft furnace or crushed to powder, which results in the needs of additional facilities and the increase of the number of processes units.
A twin-type fluidized bed reducing furnace to solve the above mentioned problems is disclosed in the Korean Patent Application No. 74056, by which a good-quality reduced iron can be obtained from its uniform concentration distribution and stable fluidization by properly separating the iron ore into a coarse iron ore and a medium/fine iron ore particles.
However, the above-described twin-type fluidized bed reducing furnace has two furnaces connected to each other through a circulation duct. Via the circulation duct, a large
REFERENCES:
patent: 5192486 (1993-03-01), Whipp
patent: 5370727 (1994-12-01), Whipp
patent: 5439504 (1995-08-01), Czermak et al.
patent: 5531424 (1996-07-01), Whipp
Japanese Utility Model Laid-Open No. Hei-1-114653 Abstract, Aug. 2, 1989, 1 p., English language.
Korean Patent No. 74056 Abstract, Feb. 14, 1994, 2 pp., English language.
Chung Uoo Chang
Kim Hang Goo
Kim Yong Ha
Lee Il Ock
Kastler Scott
Pohang Iron & Steel Co. Ltd.
Research Institute of Industrial Science & Technology
Voest-Alpine Industriean-lagenbau GmbH
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