Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1994-10-31
1996-03-19
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75572, 75581, C22B 916
Patent
active
055000320
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for continuously melting down scrap metal, in particular, bales of scrap metal containing residual plastic materials, the scrap metal being fed to a melt-down reactor and the heat required to melt the scrap being provided by direct heating from below, using burners that are located near the tapping point.
2. Description of the Related Art
The use of a shaft furnace to melt down scrap metal, in which the column of material that is to be melted is heated from below by burners, is already known from DE-PS 25 04 889. The fuel-oxygen combustion that is used in the shaft furnace for direct heating is so managed that a reducing atmosphere area is created beneath the oxidizing melt-down zone by adding large pieces of coal to the material to be melted. As a rule, relatively large amounts of plastic materials are contained in the material to be melted down, particularly when utilizing types of scrap metal that contain organic materials, such as occur, for example, when disposing of motor vehicles, or in the case of material that is to be melted down and which has been obtained by compressing bales of scrap metal, for example, from automobiles, and these lead to a relatively high concentration of injurious substances in the waste gases.
Considerable quantities of gas that contain harmful organic or inorganic substances are generated by heating melt-down reactors by burners, particularly in the case of the material that is to be melted down as referred to herein, so that large-scale and costly gas purifying facilities are required.
SUMMARY OF THE INVENTION
It is the aim of the present invention to so develop a method of the type described in the introduction hereto that scrap metal that contains plastics, in particular bales of scrap metal of the kind that result from the disposal of motor vehicles, can be melted down without the need to provide oversize gas purifying facilities. At the same time, the present invention is aimed at utilizing the pyrolysed substances contained in the material to be melted down to good effect and to minimize the energy and technical costs of the system accordingly. In order to do this, the method according to the present invention is essentially such that the process in the melt-down reactor is managed as a reducing process; such that some of the process gases are returned to the melt-down reactor as combustion gas after utilization of the sensible heat and purification; and such that the remainder is passed out as output gas. The reducing process in the interior of the melt-down reaction ensures that a process gas that contains a high proportion of chemically bound heat in addition to sensible heat is made available. The reducing management within the melt-down reactor offers the possibility of obtaining a combustion gas as process gas, which can be used subsequently as a substitute for the combustion gases that are used during the start-up phase of the melt-down reactor. Appropriate management and selection of the material to be melted down permits autothermic conduct of the process, a reducing atmosphere management of the process within the melt-down reactor then permitting a type of complete autothermic process management if, as in a preferred development, types of scrap metal with a chemically bound energy content of >0.6 kWh.t.sup.-1 are used as the working material in the melt-down reactor.
A further improvement of the energy balance can be obtained in that the sensible heat of the waste gases is used to pre-heat the combustion gases that are returned to the melt-down reactor. This type of pre-heating of the returned combustion gases makes it possible to use low-quality combustion gas to maintain the desired process parameters within the interior of the melt-down reactor.
Plant-engineering are considerably reduced with a simultaneous reduction of energy consumption are considerably reduced in that more than 20%-vol. of the process gas that is drawn off is to the melt-down reactor
REFERENCES:
patent: 3529067 (1970-09-01), Grott
patent: 3595546 (1971-07-01), Uzdavines
patent: 3615353 (1971-10-01), Mahoney
patent: 3839016 (1974-10-01), Rawlings
patent: 4715584 (1987-12-01), Hengelmolen
patent: 4925489 (1990-05-01), von Bogdandy et al.
Eberle Arwed
Kohler Herbert
Nieder Wolfgang
Perchtold Gerhard
Seirlehner Leo
Andrews Melvyn
Mercedes-Benz Aktiengesellschaft
Voest-Alpine Industriean-lagenbau GmbH
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