Specialized metallurgical processes – compositions for use therei – Processes – Consolidating metalliferous material by agglomerating,...
Patent
1992-02-25
1994-02-15
Rosenberg, Peter D.
Specialized metallurgical processes, compositions for use therei
Processes
Consolidating metalliferous material by agglomerating,...
75773, C04B 3516
Patent
active
052862780
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
In the iron and steel industry, metallurgical dusts are produced in numerous metallurgical processes. Thus, in the manufacture of steel using known L.D.-processes, the corresponding converter steel dust is produced and is collected via suitable filtering plants. The dust has a very high metal content, iron being present in predominantly metallic or oxidic form, depending, in each case, on the method used.
The dumping of such dusts constitutes an increasingly difficult environmental and cost problem. Its high metal content argues in favour of a reutilization of the dust, and there was, therefore, also no shortage in attempts to return this dust into the steel manufacturing process.
Dusts having a high content of metallic iron and, above all, portions of pyrophoric iron, are briquetted using hot briquetting processes and are returned to the converter. Also known are the methods of direct feeding of dust into the converter and granulation processes, with the addition of binding agents. In the case of these last-mentioned methods, substances which are not very favourable for the metallurgical process, are, however, also introduced into the converter. Thus, U.S. Pat. No. 833 630 describes a process for the briquetting of brittle ores, wherein the use of a special limestone mixed with magnesium oxide and Portland cement is regarded as being essential since, otherwise, an adequate strength of the ore briquette is not obtained. The water content of 18 to 20% contained in the ore is of decisive importance for the hydraulic reaction with the Portland-cement binding agent. In this known briquetting process, the desired strength of the ore briquette is obtained solely through the reaction of the Portland cement.
A similar process is described in DE-B 1 142 442. The subject matter of this publication is a process for the briquetting of refined ores. The basic additive, in particular magnesium hydrate and/or calcium hydrate, used for the briquetting of the refined ores, constitutes a binding agent which reacts with the carbon dioxide from the air to form a carbonate and, in this way, ensures the desired strength of the ore briquette.
Metallurgical dusts which require disposal or, if possible, recycling are also produced in other metallurgical processes, such as in the manufacture of electrosteel or in the aluminium industry.
It is now the object of the present invention to provide a new process for the cold briquetting of metallurgical dusts which will overcome the disadvantages of previously known processes and which permits an advantageous reutilization of, for example, converter steel dust in the converter.
SUMMARY OF THE INVENTION
The object of the present invention is, therefore, a dry process for the cold briquetting of metallurgical dusts, in particular of converter steel dust, under high pressure and using a basic additive, which is characterized in that the dust, together with lime, dolomite, magnesite, dunite, olivine or bauxite, in each case in burnt or unburnt form and, in each case, alone or in mixtures of the aforementioned, is formed into transportable briquettes, which do not give off dust, at pressures in excess of 10,000 bar at standard temperature (20.degree. C.).
Using the cold briquetting process according to the invention, it is possible to convert metallurgical dusts, in particular converter steel dust, into transportable briquettes at standard temperature (20.degree. C.) and applying high pressures in excess of 10,000 bar, using basic additives. These briquettes can be returned, in an environmentally acceptable form, to the steel making process for the utilization of the useful substances contained therein. At the same time, the dry briquetting process according to the invention solves the environmental problem which was, previously, inseparably linked to the disposal of the metallurgical dust. In this regard, it has been proved to be particularly advantageous that, when carrying out the process according to the invention, there is no further adverse impact on the
REFERENCES:
patent: 833630 (1906-10-01), Reinke
patent: 3374085 (1968-03-01), Stone
patent: 3617254 (1971-11-01), Imperato
patent: 4105457 (1978-08-01), Pietsch
patent: 4846884 (1989-07-01), Shigematsu
I&SM, Apr. 1981; D. R. Fosnacht: "Recycling of ferrous steel plant fines, state-of-the-art"; pp. 22-26.
International Iron and Steel Institute, Committee on Environmental Affairs, (Brussels), Oct. 1987; "The management of steel industry by-products and waste"; pp. 55-69.
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