Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1989-01-03
1990-06-19
Andrews, Melvyn J.
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75623, C21B 1100, C22B 3432
Patent
active
049350544
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of charging powder ore raw materials, iron ores and coal in a smelting reduction thereof.
BACKGROUND OF THE INVENTION
High Cr steel as stainless steel has been conventionally produced from ferrochromium as raw material. In view of saving energy and securing low production cost, a so-called smelting reduction method has been recently remarked, which directly obtains high Cr molten metal from Cr ores. In this method, Cr ores, coal and so on are charged into a reduction furnace of a converter type for reducing Cr so as to directly produce high Cr molten metal therefrom.
Cr raw ores are very fine in grain diameters, and ordinarily around 90% contain those having grain diameters of not more than 1 mm. Therefore, when powder Cr raw ores are charged into the reduction furnace from its top part onto the bath, they are lost up to 30% by upflowing gas.
For avoiding flying losses, an injection charging may be suggested, but special facilities are required independently therefor, and transporting pipes are easily injured by hard Cr ores. Thus, such measures could not be adopted actually.
In view of these circumstances, Cr raw ores are formed into pellets or briquets, inviting high production costs. If the ores are agglomerated, specific surface areas of the ores are made small so that a pre-heating time is made long and the reduction rate is lowered to lengthen the treatment time.
On the other hand, as an iron making method in place of the furnace production, the smelting reduction method of iron ores has been remarked as stated above in view of saving the energy and securing the low production cost.
In this smelting reduction method of iron ores, the flying loss of ores is not a big problem because the ores are coarse, but the coal as combustion fuel is scattered and lost considerably. According to the inventors'studies, why yield of the coal is inferior in the top charge method, is because the coal is broken by rapid increasing of temperature. Since the coal has volatility and the interior of the smelting furnace is at very high temperature (more than 1400.degree. C.), the coal charged by top charge method abruptly becomes high temperature and cracked, and parts of fine powders generated by the heat cracking are exhausted out of the furnace together with the exhausted gas. The flying of the coal makes unit consumption of carbonaceous materials deteriorate in the smelting reduction of the iron ores.
The present invention is to provide a method of charging ores, carbonaceous material as checking their flying losses in the smelting reduction method of Cr ores, iron ores and so on.
SUMMARY OF THE INVENTION
For accomplishing this object, in the invention, powder Cr raw ores, or iron ores and coal are charged into the furnace through a charging chute extending near a furnace mouth of the smelting furnace of the converter type or connected to the furnace body thereof, so that the flying losses of the ores and coal are checked.
In addition, the powder Cr raw ores, the iron ores and the coal are charged into the furnace while the gas is jetted toward the outside of the charging chute, thereby to enable to charge the raw materials as checking effectively the flying losses.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 to 5 concern the smelting reduction of Cr ores, and FIG. 1 explains one embodiment of the invention; FIG. 2 explains another embodiment of the invention; FIG. 3 explains a gas jetting from an end of the charging chute; FIG. 4 investigates the flying losses of grain Cr raw ores of the invention method and the comparative method; FIG. 5 investigates Cr increasing rate in the molten metal when powder Cr raw ores are charged and pelletized Cr raw ores are charged;
FIGS. 6 to 8 concern the smelting reduction of iron ores; FIG. 6 explains a further embodiment of the invention; FIG. 7 explains a still further embodiment of the invention; and FIG. 8 investigates the flying losses of grain Cr raw ores of the invention method and the comparative method.
In th
REFERENCES:
patent: 1715155 (1929-05-01), Westberg
patent: 3169055 (1965-02-01), Josefsson et al.
patent: 4430117 (1984-02-01), Spenceley et al.
Inoue Shigeru
Iwasaki Katsuhiro
Kawakami Masahiro
Kawata Hitoshi
Takahashi Kenji
Andrews Melvyn J.
Kojima Moonray
NKK Corporation
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