Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1998-02-11
2001-04-10
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S450000, C075S492000
Reexamination Certificate
active
06214083
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of producing liquid pig iron or liquid steel pre-products from iron-oxide-containing material, wherein fine-particulate iron-oxide-containing material is reduced to fine-particulate sponge iron by the fluidized bed method by means of a reducing gas in at least one fluidized bed reduction stage and wherein, furthermore, lumpy ore is reduced to lumpy sponge iron in a fixed bed reduction stage which is structurally separated from the fluidized bed reduction stage, and the sponge iron is charged into a melting-gasifying zone and is molten there under supply of carbon carriers and oxygen-containing gas, wherein a CO— and H
2
-containing reducing gas is generated for reducing the iron-oxide-containing material, and to a plant for carrying out the method.
2. Description of the Related Art
A method of this kind, by which it is feasible not only to process lumpy ore but also fine ore and which enables great possibilities of varying the amounts of lumpy ore and fine ore being charged in relation to the total amount of ore being charged, is known from WO-A-96/12045. In this method, the fine-particulate sponge iron produced from fine ore is briquetted for greater ease of handling and is further processed in a compact steelworks provided, for instance, with electric furnaces and converters. If necessary, the briquetted sponge iron may also be melted down in the melting-gasifying zone, particularly if surplus energy is available in the melting-gasifying zone.
A disadvantage associated with this method is the briquetting of the fine-particulate sponge iron formed from iron ore, but this is accepted in the method of WO-A-96112045, since the charging into the melting-gasifying zone of fine-particulate sponge iron constitutes a special case that is only put into practice if surplus energy is available in the melting-gasifying zone. Generally, WO-A-96/12045 requires forming briquettes from the fine-particulate sponge iron, which will then be particularly easy to handle for shipment to a compact steelworks.
SUMMARY OF THE INVENTION
The invention has as its object to further develop this known method and the plant therefor in such a way that briquetting of the fine-particulate sponge iron will no longer be necessary but wherein the further processing of the fine-particulate sponge iron will not cause difficulties of any kind. In particular, special treatment of the fine-particulate sponge iron separately from the lumpy sponge iron is to be avoided, so that no additional costs, especially costs for additional investments relating to plant components, will incur. Furthermore, the present method provides great flexibility with regard to the use of fine-particulate iron-oxide containing material and lumpy ore.
In accordance with the invention, this object is achieved by charging the fine-particulate sponge iron directly to the melting-gasifying zone in an untreated condition and in fine-particulate form and, there, is melted together with the lumpy sponge iron. As the total fine-particulate sponge iron is melted in the melting-gasifying zone or optionally is completely reduced previously, the melting-gasifying zone in accordance with the invention is designed such that the entire charge of iron-oxide-containing material, hence both the fine-particulate and the lumpy iron-oxide-containing material, can be processed at all times. According to the invention it thus suffices to feed liquid pig iron or liquid steel pre-products to a steelworks, whereby further treatment, i.e. the production of steel, is simplified considerably. As compared to the teachings of WO-A-96/12045, in accordance with the invention not only the briquetting operation but, in the steelworks, also the melting process for sponge iron are omitted.
Advantageously, fine-particulate and lumpy sponge iron are charged to the melting-gasifying zone from above, in free fall.
It is particularly advantageous if fine-particulate and lumpy sponge iron are charged to the melting-gasifying zone alternately, forming charging lentils or layers superposed in a coal bed. Each of the charging lentils or layers thus formed is either formed from fine-particulate sponge iron or from lumpy sponge iron. This offers a particular advantage with respect to the permeability, i.e. the ability to be streamed through by gas, of the piled-up material in the melting-gasifying zone, so that a complete reduction and the melting operation can proceed much more efficiently.
Suitably, fine-particulate and lumpy sponge iron are charged to the melting-gasifying zone via downpipes which project into a calming zone located above the melting-gasifying zone and terminate at a specific distance from the melting-gasifying zone. Hereby, the surface of the material of the material stream supplied into the melting-gasifying zone is maintained sufficiently small to minimize the exchange surface available for dust loss caused by entrainment of dustlike material from the melting-gasifying zone.
In accordance with a further variant, fine-particulate and lumpy sponge iron advantageously are mixed prior to being charged to the melting-gasifying zone and are charged to the melting-gasifying zone in a mixed condition, wherein, suitably, fine-particulate and lumpy sponge iron are charged in the shape of a compact material stream impacting on the melting-gasifying zone, preferably at a solid-matter porosity of above 0.7, in particular at a solid-matter porosity between 0.75 and 0.85. By this method, minimizing of the dust loss is achieved. The surface of the charged material stream is also maintained small hereby and in this way the exchange surface for the dust loss is also minimized.
Preferably, reduction of the fine-particulate iron-oxide-containing material by the fluidized bed method is carried out in two or more stages and reduction of the lumpy ore (lump ore, pellets, sinter) is carried out in a reduction shaft furnace.
A plant for carrying out the method, comprising at least one fluidized bed reactor, wherein the fine-particulate iron-oxide-containing material passes through the fluidized bed reactor streamed through by the reducing gas while forming fine-particulate sponge iron, and comprising a fixed bed reduction reactor for lumpy iron ore, a conveying duct for the lumpy sponge iron formed in the fixed bed reduction reactor departing from the fixed bed reduction reactor, and comprising a melter gasifier having the conveying duct conducting the lumpy sponge iron from the fixed bed reduction reactor opening thereinto and having feed ducts for oxygen-containing gases and carbon carriers as well as a tap for pig iron or steel prematerial and slag, respectively, as well as a reducing-gas feed duct for a reducing gas generated in the melter gasifier which enters the fixed bed reduction reactor or the fluidized bed reactor, and comprising a feed duct for reducing gas as well as an export-gas discharge duct departing from the fixed bed reduction reactor as well as from the fluidized bed reactor, is characterized in that a conveying duct for fine-particulate sponge iron formed in the fluidized bed reactor opens into the melter gasifier directly, i.e. without interposing a further treating-station.
To make it feasible to alternately charge the fine-particulate sponge iron and the lumpy sponge iron, the conveying duct for the sponge iron formed in the fixed bed reduction reactor and the conveying duct for the sponge iron formed in the fluidized bed reactor are each provided with dosing means which also enable closing of the conveying ducts.
To enable mixing of the fine-particulate and the lumpy sponge iron before charging into the melter gasifier, the conveying duct for the sponge iron formed in the fixed bed reduction reactor and the conveying duct for the sponge iron formed in the fluidized bed reactor are flow-connected with each other and from the connection of these conveying ducts a conveying duct departs which is common to the two reduction products and runs into the melter gasifier.
Preferably, a r
Andrews Melvyn
Voest-Alpine Industriean-lagenbau GmbH
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