Industrial electric heating furnaces – Arc furnace device – Charging or discharging
Patent
1997-10-02
1999-04-27
Hoang, Tu Ba
Industrial electric heating furnaces
Arc furnace device
Charging or discharging
373 78, 373 79, 373 84, F27D 1300
Patent
active
058987266
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a pre-heating apparatus for an arc furnace which is used for melting metallic material and for refining molten metals. Specifically, the invention relates to a pre-heating apparatus capable of preventing a non-uniform flow of an exhaust gas inside a shaft, relieving a thermal load on a gate for holding a raw material and reducing an installation cost.
BACKGROUND ART
Arc furnaces for refining include a D.C. arc furnace which causes a current to flow between an electrode disposed above metallic materials charged into the furnace and an electrode fitted to a furnace bottom or a furnace wall such as a side wall and which effects melting of the metallic materials and refines a molten metal, and an A.C. arc furnace which causes a current to flow through three electrodes disposed above the molten metal charged into the furnace, and effects melting of the metallic materials and refining of the molten metal. Exhaust gas utilization systems in the arc furnaces of these kinds generally have constructions wherein a pre-heating vessel is disposed between the arc furnace and dust collecting equipment, a bucket of the metallic materials is inserted into this pre-heating vessel and the metallic materials are pre-heated by an exhaust gas.
However, the exhaust gas duct between the arc furnace and the pre-heating vessel has a water-cooling structure because a high temperature gas generated by the arc furnace flows through this duct, and the temperature of the exhaust gas reaching the pre-heating vessel drops to an extent corresponding to the temperature drop due to water-cooling. Therefore, the retained heat of the exhaust gas cannot be efficiently utilized for pre-heating the metallic materials, and this is a critical problem from the aspect of heat efficiency. Further, the white smoke and the offensive odor that are generated when the pre-heated metallic materials are conveyed in the bucket to the arc furnace are also a critical problem from the aspect of the operating environment.
Therefore, various proposals have been made so far in order to efficiently utilize the heat of the exhaust gas for pre-heating the raw materials and to charge the pre-heated raw materials into the arc furnace without conveying them from the pre-heating vessel to the arc furnace. Japanese Unexamined Patent Publication (Kokai) No. 3-505625, for example, describes an arc furnace which pre-heats the raw materials in a pre-heating zone formed by a shaft disposed on a furnace cover and a part of a furnace body and lets the pre-heated raw materials, which are stored in the shaft, drop naturally.
In this case, however, after the raw materials stored in the shaft disposed on the furnace cover naturally drop and are then molten, or in other words, at the so-called "refining stage", the raw materials no longer exist inside the shaft, and are not pre-heated by the heat of the exhaust gas any more. Therefore, the problem of heat efficiency was still unsolved.
To solve this problem, Japanese Unexamined Patent Publication (Kokai) No. 5-500263, for example, proposes a method which disposes two sets of arc furnaces, introduces the exhaust gas into the other of the arc furnaces, which stores the raw materials inside the shaft and is in a stand-by state, so as to pre-heat the raw materials after the raw materials stored in one of the arc furnaces naturally drop and are molten by electric power supplied to this arc furnace, and pre-heats the raw materials by the other arc furnace so as to improve heat efficiency.
Japanese Unexamined Patent Publication (Kokai) No. 4-309789 proposes a method which forms the pre-heating zone in only the shaft, disposes a raw material holding gate inside the shaft, makes it possible to always store the raw materials inside the shaft and thus utilizes the heat of the exhaust gas at the refining stage.
By the way, a major portion of the energy for melting the metallic materials in the arc furnace is provided by electrical energy. When the energy efficiency for melting the metallic materials i
REFERENCES:
patent: 4736383 (1988-04-01), Meierling
Matsumoto Hiroshige
Nakayama Toshitaka
Takahashi Makoto
Tanabe Keiichi
Uchida Shinjiro
Hoang Tu Ba
Nippon Steel Corporation
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