Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1998-08-05
2000-10-03
Warden, Jill
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75414, 75574, 75581, 266142, 266145, 266156, 266197, 266901, C22B 100
Patent
active
061267163
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a preheating apparatus for preheating iron scrap for recycling. Also, the present invention relates to a preheating process for preheating iron scrap in the preheating apparatus. Particularly, the present invention relates to a preheating apparatus for preheating iron scrap in which iron scrap is preheated in a rotary kiln type preheating furnace and a shaft furnace type preheating furnace, which are arranged in parallel with each other in the front stage of a melting furnace, and the thus preheated iron scrap is fed into the melting furnace and heated by means of arc heating or top-blowing oxygen so that the iron scrap can be melted in the furnace. Also, the present invention relates to a process for preheating iron scrap in the preheating apparatus.
BACKGROUND OF THE INVENTION
When steel is refined in an electric furnace or a converter, iron scrap to be fed into the furnace, which is a source of iron, is previously heated. In this preheating process, a large quantity of thermal energy is required. Therefore, from the viewpoint of operating cost, the preheating of iron scrap does not show much merit to reduce the cost and, further, the equipment cost is increased to provide the preheating apparatus. Recently, from the viewpoint of recycling the resource, the recycling of iron scrap has become important. In order to conduct recycling iron scrap effectively, in order to use iron scrap effectively from the viewpoint of putting it into practical use as an iron source and in order to save energy when iron scrap is used, it has been desired to develop a preheating technique for preheating iron scrap by which the total quantity of energy required for refining can be reduced as much as possible and the production cost can be reduced.
The prior art in this technical field of melting iron scrap was disclosed in "Strategy for Electric Furnace for Common Steel", which was published in November of 1994, in "Electric Furnace" issued by The Iron and Steel Institute of Japan and presented in the Twenty-seventh and Twenty-eighth Shiraishi Memorial Lectures. According to the above prior art, when iron scrap is melted, it requires a large electric power consumption, so that the operation cost is raised. According to the description of the above prior art, a cause of increase in the operation cost is a deterioration in the thermal efficiency after the step of flat bath (at the time of melting down). Concerning the method of melting iron scrap in a converter type furnace, there is a report on page 520 in vol. 78 (1992) in "Iron and Steel" (issued by the Iron and Steel Institute of Japan). According to the report, the equipment cost is increased to process a large quantity of exhaust gas and, since iron scrap is refined into molten iron, it is necessary to provide a converter in the after-process. According to the U.S. Pat. No. 4,852,858, there is disclosed a method of preheating material by the exhaust gas discharged from a refining furnace when a shaft-shaped material accommodating container is arranged in an upper portion of the metal refining furnace. However, according to the above technique, it is difficult to control the preheating condition constantly. Therefore, the refining condition tends to fluctuate greatly. As a result, it is difficult to stabilize the product quality. Japanese Examined Patent Publication (Kokoku) No. 6-46145 discloses another shaft-type preheating furnace. According to this shaft-type preheating furnace, although the thermal efficiency is high, a lower portion of the furnace is exposed to gas of high temperature. Accordingly, pieces of iron scrap are fused to each other. Therefore, it is necessary to cut off the pieces of iron scrap, which have been fused to each other, by means of oxygen cutting. Further, the following are disclosed. When water-cooled grates are provided, the charging ratio is lowered in order to ensure a space in which the water-cooled grates are operated. Therefore, the thermal efficiency is deteriorated.
Concerning
REFERENCES:
patent: 4852858 (1989-08-01), Weber
patent: 5889810 (1999-03-01), Katayama et al.
Liuyi Zhang and Franz Oeters, "Simulationsmodell zur berechnung der schrottvorwarmung mit gestufter nachverbrennung", Stahl and Eisen, vol. 110, No. 5, May 15, 1995, pp. 75-82, XP000511498, *p. 80-p. 81*.
Database WPI, Week 97530 May 1997 Derwent Publication Ltd., London, GB; AN 9713640, XP00208786 & JP 09 014865 A (NKK Corp.), Jan., 17, 1997.
"Strategy of Electric Furnace in Common Steel", Nov. 1994 p 59.
"Scrap Melting Process of Converter Type", vol. 78, No. 4, Journal of the Iron and Steel Institute of Japan, pp 520-526 Apr. 1992.
Harada Toshiya
Shigeyama Yukinori
Takeuchi Mitsugu
McGuthry-Banks Tima
Nippon Steel Corporation
Warden Jill
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