Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1999-04-07
2001-07-24
King, Roy (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S550000, C075S446000, C075S491000, C075S961000
Reexamination Certificate
active
06264725
ABSTRACT:
This is a national stage of Application No. PCT/AT97/00214, filed Oct. 6, 1997, which claims priority to Austrian Patent Application No. A1779/96 filed on Oct. 8, 1996.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for producing liquid pig iron or steel preproducts from fine-particulate iron oxide carriers and lumpy iron-containing material, such as partially and/or completely reduced sponge iron, in a meltdown gasifying zone of a melter gasifier, in which the iron-containing material, optionally upon previous complete reduction, is melted in a bed formed of solid carbon carriers, under the supply of carbon-containing material and oxygen-containing gas while simultaneously forming a reducing gas, wherein fine-particulate iron oxide carriers, such as iron-containing fine ore and ore dust and oxidic iron fine dust, are introduced into a reducing gas stream leaving the melter gasifier, the reducing gas is freed from the fine-particulate material formed therefrom, the separated fine-particulate material is introduced into the meltdown gasifying zone by means of a dust burner via a dust recirculation line and the reducing gas is used for reducing the iron-oxide-containing material, and a plant for carrying out the process.
2. Brief Description of the Related Art
A process of this type of known from EP-A-0 576 414. The known process allows to charge larger amounts of fine ore and/or ore dust, such as oxidic iron fine dust accumulating in a metallurgical plant, in addition to lump ore. The oxidic fine particles introduced into the reducing gas stream are conveyed into the meltdown gasifying zone of the melter gasifier via a dust recirculation line. The dust recirculation line is comprised of a dust sluice and a pneumatic conveying system as well as of a dust bumer, the dust sluice overcoming the pressure difference between the melter gasifier and the solids separator, for example a cyclone, which, in tum, frees the reducing gas from the fine particles.
However, a problem arises from the fact that the oxidic fine particles introduced into the meltdown gasifying zones have to be reduced yet. In order not to impair the meltdown and gasifying process in the meltdown gasifying zone, i.e. the generation of reducing gas, the amount of such oxidic fine particles that can be processed according to the known process is not very large.
SUMMARY OF THE INVENTION
The object of the invention is to prevent these disadvantages and difficulties and to solve the technical problem of further developing the process described above to the effect that large amounts of fine ore and/or ore dust, such as oxidic iron fine dust accumulating in a metallurgical plant, can be charged without disturbing the meltdown gasifying process and without involving a large number of apparatus.
According to the invention, this problem is solved by conveying the separated fine-particulate material in the dust recirculation line via a fluidized bed sluice formed by the separated fine-particulate material and by reducing gas to the dust burner and reducing it thereby.
In this way, the fine-particulate iron oxide carriers introduced into the reducing gas stream, such as fine ore, are prereduced to a high degree during transport via the dust recirculation line, the required plant components being easy to implement in respect of design and cost. The high degree of prereduction of the fine-particulate iron oxide carriers allows to process very large amounts of such iron oxide carriers without impairing the meltdown and gasifying process in any way.
A variant which optimally uses the reducing gas supplied to the dust recirculation line is characterized in that the fluidized bed sluice comprises a counterflow fluidized bed zone formed by the separated fine-particulate material and penetrated by reducing gas in counterflow to said material, and a parallel-flow fluidized bed zone formed by the separated fine-particulate material and penetrated by reducing gas in parallel flow with said material, preferably in a substantially larger amount than in the counterflow fluidized bed zone, in which zones the fine-particulate material is reduced.
To ensure a certain extent of reduction of the fine-particulate iron oxide carriers already in the reducing gas stream, the fine-particulate iron ore is advantageously introduced into the reducing gas stream, shortly after the latter has left the melter gasifier, the fine-particulate iron ore being expediently blown into the reducing gas stream, preferably after the latter has been cooled to 800 to 900° C.
The ensure an optimum contact of the individual fine particles with the reducing gas, immediately after entry of the fine particles into the reducing gas stream, a central material jet formed by the fine-particulate iron ore and a carrier gas, is introduced into the reducing gas according to a preferred embodiment and at least one gas jet formed by a secondary gas is directed against the material jet, the gas jet atomizing the material jet and the fine particles being uniformly distributed within the reducing gas.
The gas jet preferably imparts to the material jet a torque about the axis of the material jet and the fine particles leave the material jet due to centrifugal forces, thereby disintegrating the same.
A good contact of the fine particles with the reducing gas can also be ensured by blowing the fine-particulate iron ore into the reducing gas stream in a direction opposite to the flow of the latter.
A plant for carrying out the process by means of a melter gasifier with a supply duct for feeding carbon-containing material, a reducing gas duct including a solids separator for drawing off the reducing gas generated and a duct for feeding oxygen-containing gas, as well as with a slag and iron melt tap, wherein a lower section of the melter gasifier for collecting the molten pig iron or steel prematerial and the liquid slag, a central section located thereabove for accommodating a bed of solid carbon carriers and, following thereupon, an upper section as a killing space are provided, and a reduction vessel for iron-oxide-containing material, wherein the reduction vessel is connected with the melter gasifier via the reducing gas duct and a duct conveying the at least partially reduced material (sponge iron) from the reduction vessel to the melter gasifier and a conveying duct for fine-particulate iron ore runs into the reducing gas duct, and comprising a dust recirculation means departing from the solids separator and opening into the melter gasifier by means of a dust bumer, characterized in that the dust recirculation means is comprised of at least one fluidized bed reactor into which a duct feeding reducing gas runs.
According to a preferred embodiment, the dust recirculation means is comprised of a counterflow fluidized bed reactor and a downstream parallel-flow fluidized bed reactor, a duct feeding reducing gas running both into the counterflow and into the parallel-flow fluidized bed reactors.
The conveying duct for fine-particulate iron ore preferably opens into the starting region of the reducing gas duct, i.e. shortly after the connection of the latter to the melter gasifier.
A preferred embodiment is characterized in that the conveying duct for fine-particulate iron ore is comprised of a blow-in nozzle projecting through the wall of the reducing gas duct, said blow-in nozzle including a central tube conducting fine particles and a carrier gas and, at the mouth of the central tube, being provided with at least one nozzle which is connected to a gas duct for feeding a secondary gas, the longitudinal axes of the nozzles enclosing an angle with the longitudinal central axis of the central tube, the angle advantageously ranging between 20° and 60°.
The longitudinal axis of the nozzle is preferably skew to the longitudinal central axis of the central tube, wherein, upon projection of the longitudinal axis of the nozzle perpendicular to a plane laid through the longitudinal central axis of the central tube and the nozzle mouth, an angle ranging between
Nagl Michael
Stockinger Josef
King Roy
McGuthry-Banks Tima
Ostrolenk Faber Gerb & Soffen, LLP
Voest-Alpine Industriean-lagenbau GmbH
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