Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1997-09-17
2000-05-09
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75434, 420590, C21B 308
Patent
active
060598549
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for processing waste incineration residues, such as, e.g., waste incineration slags, in which the slags are subjected to a reduction process while separating metals.
2. Description of the Related Art
In connection with processes for disposing of domestic and industrial waste, it has already been proposed to reduce in the liquid state slag phases forming during combustion on grounds of the oxidizing conditions involved, in order to recover metals and/or metal alloys. However, plants arranged to permit waste incineration, as a rule, are relatively complex. Small waste incineration plants are not readily operable in an economic manner. In particular, it is to be taken into account that waste incineration slags may contain relatively high portions of heavy metals and nonferrous heavy metals. The dumping of such waste incineration slags is not readily feasible. Further processing of liquid waste incineration slags pre-supposes requirements such as suitable slag volumina, additional heating and hence additional energy feeding because of the unfavorable slag viscosity of slags forming in waste incineration.
SUMMARY AND DESCRIPTION OF THE INVENTION
The invention aims at processing waste incineration residues, such as, e.g., waste incineration slags, of various origin in an environmentally safe manner and directly producing products characterized by low contents of noxious matter and usable as raw materials for further use in steelmaking plants. At the same time, the invention aims at producing from the waste incineration slag with initially unfavorable properties synthetic blast furnace slag exhibiting good hydraulic properties. To solve these objects the process according to the invention essentially involves introducing solid waste incineration residues into a steelworks slag bath in amounts ranging from 15 to 45% by weight, based on the overall quantity, drawing off the heavy metals or heavy metal compounds, such as, e.g., Zn, Pb, Cd or Hg chlorides, which evaporate during melting of the waste incineration residues or slag, and reducing the liquid bath with aid of carbon carriers and under the formation of an iron bath, whereupon the slag phase depleted from metals is granulated and used as a mixed cement component. By the fact that solid waste incineration residues are used, waste incineration residues of various origin may be collected and used. Also, by the fact that such waste incineration residues are introduced into a liquid steelworks slag bath, a mixed slag having a basicity corresponding to that of high-quality blast furnace slag is adjusted. By adjusting the basicity to values typical of high-quality blast furnace slag, which is achieved by adding waste incineration residues to a strongly basic steel works slag, the viscosity is substantially reduced and suitable metallurgical treatment may be effected at comparatively low temperatures. The neutralization heat released during neutralization by mixing the strongly basic steelworks slag with acidic waste incineration residues at the same time allows for melting of the waste incineration residues in a manner as largely autothermic as possible such that no or only little additional energy has to be fed while simultaneously lowering the viscosity. By using a steelworks slag bath in the liquid phase it has become possible to carry out, simultaneously with the lowering of the iron oxide content of the slag by separating iron, an accordingly common or fractionated separation of metallic phases while reducing the liquid slag bath with carbon carriers under the formation of an iron bath. In this manner, an iron bath having the quality of pig iron is immediately obtained, the composition of the original steelworks slag at the same time being adjustable towards a composition of a high-quality blast furnace slag with accordingly substantially enhanced hydraulic properties. In the course of the reduction procedure, relatively high portions of heavy metals can be safely sepa
REFERENCES:
patent: 5259863 (1993-11-01), Schneider et al.
patent: 5405429 (1995-04-01), Rey et al.
patent: 5516357 (1996-05-01), Edlinger et al.
patent: 5654976 (1997-08-01), Cowx et al.
Edlinger Alfred
Mistelli Bruno
"Holderbank" Financiere Glarus AG
Andrews Melvyn
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