Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1998-01-20
2001-07-24
King, Roy (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S492000, C266S144000, C266S142000, C266S156000, C266S212000
Reexamination Certificate
active
06264722
ABSTRACT:
The invention relates to a process for producing molten pig iron or steel preproducts from fine-particulate iron-containing material, in particular reduced sponge iron, in a meltdown gasifying zone of a melter gasifier, in which, under the supply of carbon-containing material and oxygen-containing gas at the simultaneous formation of a reducing gas in a bed formed of solid carbon carriers, the iron-containing material is melted when passing the bed, optionally upon previous complete reduction, as well as a plant for carrying out the process. From EP-B -0 010 627 a process for producing molten pig iron or steel preproducts from particulate iron-containing material, in particular prereduced sponge iron, as well as for producing reducing gas in a melter gasifier is known, in which a fluidized bed is formed of coke particles by adding coal and by blowing in an oxygen-containing gas. The oxygen-containing gas, or pure oxygen, is injected in the lower region of the melter gasifier. The particulate iron-containing material, in particular prereduced sponge iron, and the lumpy coal are top-charged through charging openings provided in the hood of the melter gasifier, the falling particles are braked in the fluidized bed and the iron-containing particles are reduced and melted while falling through the coke fluidized bed. The melted metal covered by slag collects on the bottom of the melter gasifier. Metal and slag are drawn off through separate tap openings.
However, a process of this type is not suitable for processing fine-particle sponge iron and fine-particulate coal, since fine-particle solids particles would be immediately discharged from the melter gasifier due to the violent gas flow prevailing there. Discharging is even more favored by the temperature prevailing in the upper region of the melter gasifier, since this is too low to ensure melting of the sponge iron on the site of charging.
From U.S. Pat. No. 5,082,251 it is known to directly reduce iron-containing fine ore by fluidization by aid of a reducing gas produced from natural gas. The iron-rich fine ore is reduced by aid of a reducing gas under elevated pressure in a system comprised of fluidized bed reactors arranged in series. After this, the thus produced sponge iron powder is subjected to hot or cold briquetting. Separate melting aggregates are to be provided for further processing the sponge iron powder. The treatment of fine-particulate coal is not possible there.
From EP-B -0 111 176 is it known to produce sponge iron particles and molten pig iron from lumpy iron ore, the iron ore being directly reduced in a direct-reduction aggregate and sponge iron particles discharged from the direct-reduction aggregate being separated into a coarse-grain fraction and a fine-grain fraction. The fine grain fraction is supplied to a melter gasifier, in which the heat required for melting the sponge iron as well as the reducing gas fed to the direct-reduction aggregate are produced from the coal charged and from the oxygen-containing gas fed. In doing so, coal charging is possible, yet in lumpy form only; fine-particulate coal would be carried off the melter gasifier along with the reducing gas.
In a process according to EP-A-0 576 414 lumpy iron ore-containing charging substances are directly reduced in a reduction shaft furnace by means of the reducing gas formed in the meltdown gasifying zone. The sponge iron thus obtained is then supplied to the meltdown gasifying zone. In order to be able to additionally utilize, in that known method, fine ore and/or ore dust, such as oxidic iron fine dust incurring in a metallurgical plant, the fine ore and/or the ore dust together with coke dust is supplied to a dust burner operating into the meltdown gasifying zone and is reacted in a sub-stoichiometric combustion reaction. Such a process allows for the efficient working up of fine ore and/or ore dust incurring in a metallurgical plant up to an amount of between 20 and 30% of the overall charge and, thus, the combined processing of lumpy ore and fine ore and also the processing of coke dust. The use of coal dust would, however, be problematic, because degasification and tar formation and hence caking within the conveying tube would be caused by the hot reduced ore.
The invention aims at avoiding these drawbacks and difficulties and has as its object to provide a process of the initially defined kind as well as a plant for carrying out the process, which enable the processing of fine-particulate coal and fine-particulate iron-containing material. On the one hand, discharging of the fine particles supplied, by the reducing gas produced in the melter gasifier is to be reliably prevented and, on the other hand, possibly required complete reduction of the iron-containing material is to be ensured. In particular, the invention has as its object to provide a process by which a charge comprised of fine-particulate iron-containing material by 100% can be processed to pig iron and/or steel prematerial when charging fine-particulate coal by using a melter gasifier.
In accordance with the invention, this object with a process of the initially defined kind is achieved in that a supply duct for fine-particulate coal, such as coal dust and/or other carbon-containing materials including volatile portions, and a duct feeding an oxygen-containing gas enter in the vicinity of the reducing-gas discharge duct of the melter gasifier, the fine-particulate coal and/or other carbon-containing materials including volatile portions are reacted to fine-particulate coke upon introduction into the melter gasifier, the fine-particulate coke is discharged along with the reducing gas carried off the melter gasifier and is separated in a separating means. According to the invention, the fine-particulate coal is converted into coke in a simple manner, utilizing the discharging effect caused by the violent reducing gas flow. This fine-particle coke is substantially more readily handleable for further use, since degasification and tar formation need not be feared any longer. Other carbon-containing materials including a portion of volatile matter may, for instance, comprise synthetic shredder or fine-particle petroleum coke.
Preferably, the fine-particulate coke is supplied to the melter gasifier along with the fine-particulate iron-containing material optionally preheated and/or reduced by aid of the reducing gas, wherein, according to a preferred embodiment, in a killing zone formed above the bed a high-temperature combustion and/or gasification zone is formed under direct oxygen feeding by burning and/or gasifying the fine-particulate coke supplied to the melter gasifier, into which high-temperature combustion and/or gasification zone the fine-particulate iron-containing material is directly introduced, wherein at least surface melting of the iron-containing material and agglomerating of the same are effected by the heat released during the reaction of the fine-particulate coke.
The thus formed agglomerates have a higher rate of vertical descent on account of their increased mass. Thereby and by their enhanced form factor, i.e., by their more favorable C
w
value due to extensive sphere formation, the iron-containing material is prevented from being discharged by the reducing gas carried off the melter gasifier.
From EP-A-0 217 331 it is known to directly prereduce fine ore by fluidization and to conduct the prereduced fine ore into a melter gasifier and completely reduce and melt the same by means of a plasma burner under the supply of a carbon-containing reductant. A fluidized bed and above the same a fluidized bed of coke form within the melter gasifier. The prereduced fine ore or sponge iron powder, respectively, is supplied to a plasma burner provided in the lower section of the melter gasifier. There, it is disadvantageous that, due to the supply of prereduced fine ore directly in the lower melting region, i.e., in the region where the melt collects, complete reduction is no longer guaranteed and the chemical composition required for the further processing of the p
Kepplinger Werner Leopold
Schenk Johannes
Wallner Felix
King Roy
McGuthry-Banks Tima
Ostrolenk Faber Gerb & Soffen, LLP
Voest-Alpine
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