Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1991-10-02
1993-09-21
Rosenberg, Peter D.
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
266157, F27D 314
Patent
active
052464857
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of preventing fume production during metallurigcal processes and when transporting molten metal from a metallurgical vessel, in particular a metallurgical furnace such as a blast furnace, to casting vessels. The invention further relates to apparatus which comprises at least one transporting and discharge runner, which is installed at a tapping orifice of a metallurgical furnace, and a transfer station having a swivel or tilting runner in which the molten metal flows from the discharge runner by way of a distribution system into outlet openings from which it runs off into a preferably movable casting vessel.
In metal production, particularly steel and iron manufacture, when i.a. the molten metal is transported considerable quantities of so-called "brown fume", mainly consisting of metal oxides, arise. The quantities of dust which are produced are so high that measures have to be taken to limit or eliminate them. Statutory regulations limit the permitted residual dust content to 50 mg of dust/Nm.sup.3. In order to attain these levels, according to the current state of the art (cf. German publications "Outdated plant programme of the Minister of the Interior, clean-air preservation, final report--Dust removal from foundry blast furnaces with smelting outputs of 5000 t/d and 4000 t/d" by Dipl.-Ing. Dieter Eickelpasch, Hoesch Stahl AG, Dortmund, March 1985 and "Dust removal from foundry blast furnace B with automatic minimization of the waste gas quantity" by Dr. Ing. Paul van Ackeren, Mannesmannrohrern-Werke AG, April 1983 and German publication "Steel and Iron" 104 (1984) No. 7, pages 351 ff.), the brown fume arising when iron and steel are transported is passed by means of extensive plant through filters where the iron oxide is separated and collected to be supplied then for appropriate recycling or disposal. To be able to intercept, for example, the dust arising in the tapping bay of a metallurgical furnace, in particular a blast furnace, in the first place requires the setting up of extensive, powerful extraction devices with suitable waste gas filters, pipe systems, ventilating fans, regulating devices and so on which are very expensive both to install and to operate. Furthermore, experience has shown that the extraction process leads to an intensive attraction of air to the flowing pig iron which drastically increases dust formation.
Finally, owing to impurities, not all dusts are suitable for recycling or use elsewhere and so have to be dumped, which contributes towards environmental pollution. As a whole, all the cited measures lead to considerably higher metal extraction costs.
In the past, therefore, measures have already been suggested which reduce the production of dust from the outset. Thus, it has been suggested that molten metal be transported under conditions of simultaneous oxygen displacement which may be created by dosing the flowing metal with nitrogen. In practice, however, attacking the molten metal with nitrogen in open discharge runners without additional measures has proved hardly effective since, as a result of the thermal up-current alone, the entry of oxygen could be limited only to an unsatisfactorily extent. The reduction in, for example, brown fume or in the occurrence of dust was negligible compared to the technical outlay, in particular the inert gas consumption.
For main emission sources which are difficult to access, such as the region of the tapping orifice and the transfer or inlet region into the casting vessels, no fume suppression measures are known. The aim of the present invention is therefore to improve the method and device cited in the introduction in such a manner that, for a low investment and operating cost (energy, maintenance and inert gas consumption), fumes may be extensively suppressed, the invention being specifically targetted at areas which are difficult to control, namely the tapping orifice, the transfer point with, for example, a swivel or tilting runner, the ladle inlet and the casting vessel interior.
This aim is ac
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Kahnwald, "Staubanfall beim Hochofenabstich . . . Staubemissionen" in Stahl und Eisen, 104 (1984) No. 7, pp. 351-356.
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de Haas Hans
Grutzmacher Klaus
Hammer Uwe
Krause Erhard
Lowenstein Manfred
Klockner Stahl GmbH
Rosenberg Peter D.
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