Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1999-07-27
2001-06-05
Kastler, Scott (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S503000, C075S504000, C266S173000
Reexamination Certificate
active
06241804
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for producing iron briquettes and/or cold iron sponge, in which charge materials which contain lumpy material containing iron oxide are introduced into the reduction zone of a reduction reactor, then a hot reduction gas flows through the charge materials, which are reduced to hot iron sponge which passes through a gas feed zone, which is downstream of the reduction zone and in which reduction gas is introduced into the reduction reactor, which gas, after it has flowed through the reduction zone, is extracted from the reduction reactor as a top gas, in which process to produce cold iron sponge, hot iron sponge is cooled in a cooling zone downstream of the gas feed zone as a result of cooling gas being passed through it and is discharged from the shaft furnace in a product-discharge zone downstream of the cooling zone. The invention also relates to an installation for carrying out the process.
2. Brief Discussion of the Related Art
Numerous processes for producing iron sponge are known from the prior art, and corresponding installations are commercially available. Processes for producing iron briquettes, and corresponding installations, are also known.
U.S. Pat. No. 3,748, 120 has disclosed a process and a device for reducing iron oxide to form metallic iron. In this process, iron oxide is reduced to form iron sponge in a direct reduction reactor, by reduction gas being passed through, and the iron sponge is cooled by cooling gas being passed through and is discharged from the reduction reactor.
SUMMARY OF THE INVENTION
In DE-C 29 35 707 C2, as well as in U.S. Pat. No. 4,439,233, in order to produce iron sponge, iron oxide is again reduced to form iron sponge in a direct reduction reactor, by reduction gas being passed through. However, the iron sponge is not cooled, but rather is discharged from the reduction reactor in the hot state and is subjected to a hot-briquetting operation.
Processes and installations of the type described above have the drawback that they are each only able to produce one type of product, i.e. either iron sponge or iron briquettes.
After it has been produced, iron sponge is processed further as quickly as possible, for example in a melt-down gasifier or an electric arc furnace, to produce liquid pig iron or steel, and is not usually a product which can be used commercially.
Iron briquettes are used for the same purposes as iron sponge, but unlike the latter can be stored for an unlimited period and therefore constitute a product which can be used commercially.
In order, in a reduction reactor for producing iron sponge, to avoid standstills which may occur, for example, when a steel works which is linked to the reactor is unable to accommodate any iron sponge, it has hitherto been necessary to provide a plurality of product hoppers, each with a storage capacity of approximately 5000 t or more. If the buffer capacity of the product hoppers is insufficient, the reduction reactor may have to be shutdown, since otherwise iron sponge would have to be stored in the open air, and the iron sponge would not be protected from environmental influences, such as for example rain.
Both the set-up costs and the operating costs of product hoppers constitute a considerable economic burden on a metallurgical plant. Both the loss of production caused by shutting down the reduction reactor and starting it up again and the resultant costs are undesirable and reduce the economic efficiency of a metallurgical plant.
Therefore, the object of the present invention is to provide a process for the reduction of iron oxide which makes it unnecessary to set up and operate product hoppers. If iron sponge cannot be processed further immediately, the intention is that it should no longer be necessary to shutdown the reduction reactor, thus avoiding production losses. Furthermore, it is intended for it to be possible to convert existing installations for the production of iron sponge in a simple, inexpensive manner.
According to the invention, this object is achieved by the fact that to produce iron briquettes, hot iron sponge is discharged from the shaft furnace in a removal zone, which is arranged between the gas feed zone and the cooling zone, and is subjected to a briquetting operation.
Lumpy material containing iron oxide is understood to mean both lump ore and iron ore pellets.
The process according to the invention makes it possible, for the first time, to choose to produce iron briquettes and/or cold iron sponge, since a single process is able to deliver two different types of product; cold iron sponge is understood here to mean iron sponge at a temperature of approximately 30 to 100° C. This flexibility makes both product hoppers and any need to shutdown the reduction reactor in which the process is being carried out superfluous.
According to one embodiment of the process according to the invention, the production of cold iron sponge can be interrupted temporarily. This ensures that cold iron sponge is not “over produced”. In situations where the capacity of the reduction reactor to produce iron sponge is greater than the requirements of a linked steel works, this excess capacity can be sold in the form of iron briquettes.
According to a further embodiment of the process according to the invention, the production of iron briquettes can also be interrupted, for example in order to use the entire production capacity to produce iron sponge.
Advantageously, the hot iron sponge which is discharged from the removal zone is still at a temperature of from 600 to 1000° C., preferably 650 to 850° C., during the briquetting.
The hot iron sponge is therefore briquetted in the hot state. Consequently, the addition of binders, which is required for cold briquetting, can be largely eliminated. Compared to hot briquetting of cold iron sponge, this process also has the advantage that there is no need to employ additional energy to heat the iron sponge.
According to an advantageous embodiment of the process according to the invention, the hot iron sponge is briquetted under an inert-gas atmosphere or under a reducing atmosphere, in order to protect the iron from being reoxidized during the briquetting operation.
Preferably, the inert gas or reducing gas used is nitrogen, top gas, flue gas or mixtures of these gases. Large volumes of each of these gases are available in metallurgical plants; top gas, as a partially reacted reduction gas, is particularly suitable for use as an inert gas. If appropriate, the CO
2
and H
2
O levels in the top gas and/or flue gas are reduced to a sufficient extent for there no longer to be any risk of reoxidation of the briquetted iron or iron which is to be briquetted, before the top gas and/or flue gas is/are used as inert gas.
According to one embodiment of the process according to the invention, during the production of iron briquettes, small quantities of cold iron sponge are discharged from the shaft furnace at recurring intervals, in the product discharge zone. This avoids agglomeration of the iron sponge particles in the cooling zone and product discharge zone, and the production of cold iron sponge can be resumed at any time.
The invention also relates to an installation for producing iron briquettes and/or cold iron sponge from charge materials which contain lumpy material containing iron oxide, having a reduction reactor, which is aligned essentially vertically, for iron oxide, with an upper reduction zone and a lower cooling zone, and having a device for introducing material which contains iron oxide into the reduction zone, having a gas feed zone, which is arranged beneath the reduction zone, and a reduction gas feed line, which connects the gas feed zone to a reduction gas source, having a discharge device, which is arranged beneath the cooling zone, for discharging reduction product from the reduction reactor, having a top-gas discharge line for removing the reacted reduction gas from the reduction reactor, and having a device for introducing and extracting a cool
Kastler Scott
Ostrolenk Faber Gerb & Soffen, LLP
Voest-Alpine Industriean-lagenbau GmbH
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