Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1998-09-02
2001-01-09
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S961000
Reexamination Certificate
active
06171365
ABSTRACT:
The invention relates to a method for producing liquid pig iron or liquid steel pre-products and sponge metal, in particular sponge iron, from charging substances comprising iron ore respectively metal ore, preferably in lumps and/or pellets, and optionally fluxes, wherein the charging substances are directly reduced to sponge iron in at least one first reduction zone, the sponge iron is melted in a melt-down gasifying zone under the supply of carbon carriers and oxygen-containing gas and a CO— and H
2
-containing reducing gas is produced which is fed to the first reduction zone, is reacted there and withdrawn as a top gas, and wherein the withdrawn top gas after a scrubbing operation is subjected to CO
2
elimination and optionally to heating and is supplied to at least one further reduction zone for the direct reduction of metal ore, in particular of iron ore, as a reducing gas that is at least largely free from CO
2
and after reaction with the metal ore is withdrawn as an export gas and purified in a scrubber, and a plant for carrying out the method.
Both in the scrubbing of the export gas from the first reduction zone and in the scrubbing of the export gas of the further reduction zone, sludges incur that contain iron both in oxidic form and in metallic form and optionally coal dust as well. These sludges constitute wastes or residues the metallurgical industry aims to exploit. It is known to dispose of the sludges in dumps, which can be advantageous in particular in hot climate zones, where the sludges will dry off rapidly. As the sludges do not contain any toxic substances, their disposal in dumps or landfills can be regarded as safe. If possible, the disposal of the sludges in dumps or landfills and the resulting loss of the valuable substances they contain is to be avoided and any processing of such sludges should involve as little expenditure of energy as possible while exploiting the valuable substances in an optimum manner.
A method of exploiting wastes and residues containing iron in oxidic and/or iron in metallic form or containing carbon is known from AT-B-376.241. In this method, solid particles are separated from the reducing gas as well as from the topgas exiting the direct reduction zone in cyclones and the separated solids are mixed with a binding agent, such as iron oxide dust, briquetted and fed exclusively to the melt-down gasifying zone, wherein the iron oxide dust originates in a blast furnace purification plant so that the solids incurring in the gas purification plant can be utilized as well.
A disadvantage associated with this method is that the feeding of iron oxides into the melter gasifier renders it necessary to do reduction work in order to reduce the iron oxide, whereby energy needed for the reduction process is withdrawn from the same.
From DE-A-41 23 626 it is known to agglomerate residues from the iron and steelmaking industries without distinguishing between oxidic and metallic portions, with the assistance of binding agents, slagformers and reducing agents, and to charge the agglomerates to the upper charging area of a melting aggregate, the preheating and drying of the agglomerates being effected in said charging area of the melting aggregate. The charge permeates the melting aggregate in accordance with the counter current principle, wherein it first passes into a reducing area provided inside the melting aggregate and subsequently is melted in the lower area of the melting aggregate.
This known method involves a high energy demand, as the metallic wastes or residues also have to travel through the reducing area of the melting aggregate.
From EP-A-0 623 684 it is known to collect wastes and residues containing coal dust and iron in metallic and oxidic form in three separate groups, according to their chemical composition, namely with the first group mainly containing iron in oxidic form, the second group mainly containing iron in metallic form and the third group mainly containing carbon-containing substances. Processing is effected in such a way that the substances of the first group are charged to the direct reduction zone and the substances falling into the second and third groups are charged directly into the melt-down gasifying zone.
This method has proved particularly valuable if the wastes and residues arise separately in terms of the above-mentioned different substances, i.e. in groups. Sorting of the wastes and residues from the iron and steelmaking industries, if iron in oxidic and iron in metallic form and carbon incur as mixtures, would be too expensive.
In EP-A-676 478 there is described a direct reduction process utilizing a direct reduction reactor and a melter gasifier, with the dusts separated from the reducing gas of the melter gasifier and from the topgas of the direct reduction reactor in the form of sludges being dewatered, granulated and then charged to the melter gasifier.
The invention aims at further developing the known methods in such a way as to enable the simple and efficient exploitation of the sludges incurring with the above-mentioned method of producing liquid pig iron or liquid steel pre-products and sponge metal, namely in a particularly efficient manner and at the minimum possible expenditure of energy, by directly using them for carrying out the method, wherein sorting or separation by groups according to chemical composition is, however, to be avoided.
Followed by pages 3 ff. [Translator's note: the page number refers to the German text]
Advantageously, the sludges obtained from the first reduction zone are granulated after dewatering and the granulates thus formed are charged into the melt-down gasifying zone, whereas the sludges incurring in the scrubbing of the top gas of the further reduction zone are briquetted upon dewatering and the briquettes thus formed are introduced into the first direct reduction zone.
To be able to perfectly granulate the sludges obtained from the first reduction zone—thus producing granulates of sufficient strength—such sludges are mixed with a binding agent, such as calcined lime, after dewatering. The further dewatering that is hereby effected makes it feasible to adjust a residual moisture of roughly 20%, which is particularly suitable for granulation.
The sludges from the further reduction zone are, after dewatering, commingled with dry oxidic by-products (
34
), such as rubbed-off ore parts and/or foundry dusts. Hereby a residual moisture of roughly 4% can be achieved which is advantageous for the subsequent briquetting operation. Suitably, said operation is a cold-briquetting operation.
In addition to the above-cited measures it is advantageous to scrub at least a portion of the reducing gas exiting the melt-down gasifying zone and subject any sludges separated in the process to further treatment along with the sludges from the first reduction zone.
A plant for producing liquid pig iron or liquid steel pre-products and sponge metal, in particular sponge iron, from charging substances comprising iron ore respectively metal ore, preferably in lumps and/or pellets, and optionally fluxes, comprising at least one first reduction reactor for iron ore, a melter gasifier, a feed duct for a reducing gas formed inside the melter gasifier connecting the melter gasifier with the first reduction reactor, a conveying duct for the reduction product formed inside the first reduction reactor connecting the first reduction reactor with the melter gasifier, a top-gas discharge duct departing from the first reduction reactor and provided with a first scrubber, feed ducts for carbon carriers and oxygen-containing gases opening into the melter gasifier, a tap for pig iron and slag provided at the melter gasifier and comprising at least one additional reduction reactor for receiving metal ore, in particular further iron ore, a reducing-gas feed duct leading to said reduction reactor, a top-gas discharge duct equipped with a scrubber and departing from this further reduction reactor, and comprising a discharging means for the reduction product formed in said further redu
Gr{umlaut over (u)}nbacher Herbert
Rosenfellner Gerald
Schrey G{umlaut over (u)}nter
Andrews Melvyn
Ostrolenk Faber Gerb & Soffen, LLP
Voest-Alpine Industriean-lagenbau GmbH
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