Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1996-05-22
1999-07-20
Lazarus, Ira S.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75 101, 75 1014, 75 1035, 75 1039, 75 104, 75 1042, 75 1046, 75 1062, 75 1065, 75392, 75746, 75760, 75961, 110165A, 110218, 110250, 110344, 266205, 266215, 266227, 266229, 373 78, 373 79, 373 82, 373 83, C21B 1110, C21B 304, F23J 300, F27D 300
Patent
active
059251654
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for processing solid residues, such as slag, fly ash and filter dusts, from refuse incineration plants and an apparatus for carrying out the method.
In refuse incineration plants, approximately 30 to 35% of the amount of refuse incinerated results as slags. In this slag, up to 5% of unburnt organic constituents and about 5 to 10% of various metals, principally iron, are still present. Currently, the slag, after an appropriate mechanical treatment, is landfilled or used in civil engineering, e.g. road building as base material. Other, finer solid residues such as fly ash and boiler ash and filter dust must be disposed of separately and are taken for this purpose to special landfills. Further treatment of these wastes does not generally take place. Unburnt organic fractions and water-soluble heavy metal compounds in the slag lead to additional problems in reuse or storage, since they lead to impermissible pollution of waters.
Conversion of the solid residues from the refuse incineration plants by fusion into a vitreous state eliminates the disadvantages of the environmentally polluting crude slag. In the fusion process, the organic constituents are burnt and the heavy metals still remaining and other environmentally polluting wastes are incorporated into a water-insoluble glass matrix. The fusion operation is performed in conventional glass-melting plants, for which, however, a complex treatment of the crude slag is necessary, the iron, inter alia, having to be removed via magnetic separators and the slag having to be crushed and classified. The glass produced as granules in this method was still used in building until recently. Because of the higher requirements of environmental protection, granules of this type may no longer be readily used for building purposes, such as for road building.
Various proposals have already been made to solve these problems. For example, fundamental considerations on rendering residues inert, in particular metals and heavy metals, by melt processes can be taken from the environment!, volume 4 by Prof. Dr. Ing. Karl J. Thome-Kozmiensky from EF Verlag fur Energie und Umwelttechnik GmbH, Berlin (1990), pages 339 to 359. On page 350, separation of these heavy metals from the residual melt by density separation is suggested, reference being made to other electrofusion processes, but without giving a further description of this method.
Building on this basis, a method is disclosed in German Patent DE-C-41 17 444, in which the solid residues such as grate ash, boiler ash and filter dust from a waste incineration plant are stored temporarily in a stock bunker and are freed of ferrous scrap by a magnetic separator. This scrap is then mechanically comminuted. Obviously, to discard ferrous scrap and other relatively large parts, the slag must be substantially cooled, or cooling must at least be performed during storage. The (cooled) solid residues are then fed to a melt furnace, in which they are continuously melted with supply of energy. At the bottom of this melt furnace, the metals-enriched melt is taken off batchwise and the residual melt is taken off at a side wall of the melt furnace and cooled, which produces a vitreous product.
A similar method is disclosed by EP-A-93104418.4, in which the residues from refuse or waste incineration having a temperature between 600 and 900.degree. C. are cooled to about 80.degree. C. by discharge into water and are stored temporarily in a bunker. In a reactor, the residues are heated to a temperature of above 1000.degree. C., as a result of which the volatile metals and metal compounds escape in the gaseous state. The compounds of metallic elements, in particular heavy metals, are first oxidized and then reduced. Iron and the metals soluble in iron are collected in a melt in the reactor. From the remaining slag, an environmentally compatible product is said to form having latent hydraulic and/or pozzolanic properties, for which the slag removed from the reactor in the molten state is quenched and granulated. This
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Edlinger Alfred
Frey Ruedi
Hugentobler Ernst
Kiethe Norbert
Mayer Anton
"Holderbank" Financiere Glarus AG
Ciric Ljiljana V.
Lazarus Ira S.
Von Roll Umwelttechnik AG
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