Process for the production of spongy metal

Details Process for the production of spongy metal Process for the production of spongy metal

1998-08-19

2001-05-22

King, Roy (Department: 1742)

Specialized metallurgical processes, compositions for use therei

Processes

Producing or treating free metal

C075S450000, C075S479000, C075S487000, C075S492000

Reexamination Certificate

active

06235081

ABSTRACT:

This application is the national phase under 35 U.S.C. §371 of prior PCT International Application No. PCT/AT97/00044 which has an International filing date of Dec. 15, 1997 which designated the United States of America, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing sponge metal, in particular sponge iron, from charging materials consisting of metal ore or iron ore respectively, preferably in lumps and/or pellets, and optionally fluxes, wherein a CO— and H
2
-containing feedgas from a gas source which is compressed and optionally subjected to CO
2
elimination and heating is supplied to a reduction zone to serve as a reducing gas and after reaction with the metal ore is withdrawn from the reduction zone as an export gas for further use by a consumer. The present invention is also directed to a plant for carrying out the method.
A method of this type is known from AT-B-396.255 and from DE-C-40 37 977. With these known methods, the gas source is formed by a first reduction zone, in which iron ore is directly reduced to sponge iron, wherein the sponge iron is melted in a meltdown 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containing reducing gas is produced which is fed to the first reduction zone, is reacted there and withdrawn as a feedgas for the further reduction zone. According to AT-B-396.255, the feedgas prior to being fed to the further reduction zone is subjected to CO
2
elimination by a reformer and at the same time is heated; in accordance with DE-C-40 37 977, CO
2
elimination is effected by a CO
2
scrubber.
With these known methods, export gas withdrawn from the further reduction zone is subjected to scrubbing and is subsequently mixed with the export gas from the first reduction zone, and the mixed gas thus formed is subjected to CO
2
elimination and heating. This gas mixture is then supplied to the further reduction process to serve as a reducing gas. It thereby becomes feasible to exploit a portion of the reductants still present in the export gas from the further reduction zone, as the export gas is supplied to the further reduction process as a recycle reducing gas.
Often, there is a requirement for the export gas from the further reduction zone to be available for an external consumer, f.i. as a fuel gas. The export gas from the further reduction zone will then not be recycled. In this case, provisions must therefore be made to ensure that a sufficient amount of reducing gas will be available at any time to enable steady operation of the reduction process. In particular, the supply to the further reduction zone of a sufficient amount of reducing gas is to be ensured even with different operating states of the entire plant, f.i. even in the event of a failure.
SUMMARY OF THE INVENTION
With a method of the initially described kind this object is achieved in that into the reduction zone a CO— and H
2
-containing feedgas is fed from at least two gas sources to serve as a reducing gas and that a breakdown of one of the gas sources is compensated for by recycling at least a portion of the export gas from the reduction zone, wherein said export gas is subjected to compression, to CO
2
elimination and optionally to heating and is supplied to the reduction zone along with the feedgas from the other intact gas source(s).
The special feature of this method is that if at least two gas sources are provided, the direct reduction process in the further reduction zone can be continued even in case of a breakdown of one of the gas sources. Actually the breakdown of one of the gas sources would normally cause too small an amount of reducing gas to be fed to the further reduction zone, which leads to difficulties and may possibly cause the disruption of the continuously progressing direct reduction process in this further reduction zone. In accordance with the invention this is avoided by recycling at least a portion of the export gas from the further reduction zone.
If export gas from the further reduction zone is to be recycled, preferably said gas will first of all be pre-compressed in order to level out differences of pressure and pre-compressed and in the pre-compressed state will be admixed to the reducing gas from the intact gas source and subjected to further compression along with the same. In that case, compression of the recycled export gas to the pressure level required for the further direct reduction process takes place in stages, thus allowing it to get by with not too expensively designed compressors (in terms of capacity).
Other possible gas sources apart from a plant with a first reduction zone where iron ore is directly reduced to sponge iron and the sponge iron melted in a meltdown gasifying zone under the supply of carbon carriers and oxygen-containing gas would be coal gasification processes and blast furnace processes, so that at least one gas source could also be a coal gasification means or a blast furnace.
A plant for carrying out the method according to the invention, with a reduction reactor for producing sponge metal, in particular sponge iron, from charging materials consisting of metal ore or iron ore respectively, preferably in lumps and/or pellets, and optionally fluxes, with a reducing-gas feed duct and an ore feed duct leading to said reduction reactor, an export-gas discharge duct departing from this reduction reactor and a discharging means for the reduction product formed in said reduction reactor, wherein from a gas source dispensing a CO— and H
2
-containing feedgas a feedgas duct conducting the feedgas dispensed by the gas source runs into the reducing-gas feed duct via a compressor and optionally a CO
2
elimination plant and optionally a gas heater, characterized in that at least a second gas source dispensing a CO— and H
2
-containing gas likewise runs into the reducing-gas feed duct via a feedgas duct equipped with a compressor and optionally via a CO
2
elimination plant as well as optionally a gas heating plant and that a conveying duct for at least a portion of the export gas formed in the reduction reactor is adapted to be flow-connectable with the reducing-gas feed duct of the reduction reactor via the compressors, which are connectable in series via a connection duct, and via a CO
2
elimination plant and optionally a heating means.
The compressors that are anyway provided for the two gas sources being optionally switchable from a parallel to a serial connection, there is no need for a separate compressor for the recycled gas if recycling the export gas, so that enormous savings in terms of capital expenditures will result.
Herein suitably the two feedgas ducts departing from the gas sources can be cut off individually by means of valves prior to running into one each of the compressors and are connectable via a connection duct.
A preferred embodiment is characterized in that at least one gas source is formed by a first reduction reactor for iron ore, preferably in lumps and/or pellets, a melter gasifier, a feed duct for a reducing gas connecting the melter gasifier with the first reduction reactor, a conveying duct for the reduction product formed in the first reduction reactor connecting the first reduction reactor with the melter gasifier, an export-gas discharge duct departing from the first reduction reactor, feed ducts for oxygen-containing gases and carbon carriers opening into the melter gasifier and a tap for pig iron and slag provided at the melter gasifier, wherein the export-gas discharge duct departing from the first reduction reactor serves as a feedgas duct.
Preferably, two gas sources are formed in the same way by first reduction reactors having one melter gasifier each and through feedgas ducts are flow-connected with the reducing-gas feed duct of the further reduction reactor via one compressor each.


REFERENCES:
patent: 2653088 (1953-09-01), Pike
patent: 5238487 (1993-08-01), Hauk et al.
patent: 5676732 (1997-10-01), Viramontes-Brown et al.
patent: 39

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