Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1994-10-27
1998-03-31
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75 103, 75 1031, 75 1032, 75961, 373 82, G22B 702
Patent
active
057333564
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to an apparatus and method for processing a contaminated free-flowing material and, in particular, for processing filter dust from steel production or garbage incineration plants.
BACKGROUND OF THE INVENTION
In a metal production or processing plant such, for example, as a steel plant, flue gas is typically guided through filters so as to minimize the amount of air pollutants being emitted into the environment. Dust particles in the flue gas may contain valuable alloying carriers (which quite often are toxic) as well as other environmentally hazardous or undesirable substances. Since the environmental laws and regulations have become increasingly stringent, the need is more urgent than before to recover valuable alloying carriers from the filter dust and to improve disposal characteristics of the toxic substances remaining therein.
By-products or end products from metal production occurring in the form of residues such, for example, as filter dust and sludge, have in the past typically been discarded in landfills. In so doing, two environmentally related parameters are not optimized. First, recoverable quantities of valuable alloying carriers and steel-improving components such, for example, as chromium, nickel, molybdenum and manganese are disposed of in a wasteful manner. Other recoverable materials so lost include lead and zinc. Second, residues containing toxic components must be disposed of in special disposal sites at great expense and at the risk of polluting the environment.
Solid residues resulting from garbage incineration include ashes, filter dust and various reaction by-products. In addition to the presence of heavy metal, these solid residues may also contain toxic organic compounds such, for example, as dioxin and furan. Furthermore, new and undesirable pollutants are generated by the incineration plains as the toxic materials contained in the garbage react and combine with other by-products, such as carbon monoxide and nitrogen oxides from a high-temperature combustion process. These new and undesirable pollutants, and oftentimes toxic substances, subsist in the incineration plant's residues including slag, filter ashes, flue gas and deposits.
There have heretofore been a number of proposals for the processing of such residues so as to resolve or minimize these problems. For example, German patent publication DE-OS 37 05 787 discloses heating of the waste dust in an oxidizing atmosphere to a temperature that is sufficient to support the formation of lead oxide vapors. The lead oxide vapors are then separated from the zinc oxide in the gas by solidifying the lead oxide, thereby recovering the lead oxide. This process, however, does not remove or recover numerous other toxic materials present in the waste dust.
German patent publication DE-OS 38 27 086 discloses a process for thermal decontamination of filter dusts and other residues and, particularly, residues from incineration plants, pyrolysis installations or varnish sludge processing plants. The process involves introducing the waste material into a crucible furnace to remove any dioxin and furan contained therein and subsequently melting the waste at temperatures of 1,400 to 1,600.degree. C. The liquid phase of the waste material is extracted and quenched while the gas phase is treated in a dust extractor.
In all of these aforedescribed processes, only a portion of the toxic or valuable materials are eliminated or recovered. Even as to those materials that are the intended subject(s) of the treatment, these toxic or valuable materials are not eliminated or recovered to a desirable or acceptable extent.
Therefore, it is an object of the present invention to provide a method and apparatus for treating contaminated free-flowing materials in which the resulting end product may be reused or disposed of in an environmentally sound manner.
SUMMARY OF INVENTION
The present invention makes use of a direct current (d.c.) or alternating current (a.c.) metallurgical vessel such, for ex
REFERENCES:
patent: 3471626 (1969-10-01), Weese et al.
patent: 4147887 (1979-04-01), Yasukawa et al.
patent: 4410996 (1983-10-01), Svensson
patent: 4940486 (1990-07-01), Sommerville et al.
patent: 5566200 (1996-10-01), Konig et al.
Konig Heribert
Rath Gero
Richter Wolfgang
Staubner Hermann
Andrews Melvyn
Mannesmann Aktiengesellschaft
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