Method of charging metal carriers to a melt-down gasifying zone

Details Method of charging metal carriers to a melt-down gasifying zone Method of charging metal carriers to a melt-down gasifying zone

1998-12-04

2001-08-21

Andrews, Melvyn (Department: 1742)

Specialized metallurgical processes, compositions for use therei

Processes

Producing or treating free metal

C075S446000, C075S492000, C075S501000, C075S502000

Reexamination Certificate

active

06277172

ABSTRACT:

The invention relates to a method of charging metal carriers, in particular sponge iron, which contain a portion of fines and are at least partially reduced and carbon carriers to a melter gasifier in which a melt-down gasifying zone is maintained, wherein the metal carriers and the carbon carriers are fed into the melter gasifier above the level of the melt-down gasifying zone and descend to the melt-down gasifying zone and travel through the same forming a metal melt, particularly forming a pig iron melt, and producing a reducing gas by coal gasification under the supply of oxygen in the lower region of the melter gasifier, and a plant for carrying out the method.
From EP-B-0 010 627 it is known to feed in particulate iron-containing material, such as pre-reduced sponge iron, through a centrally arranged charging opening in the hood of the melter gasifier from above, with the particles dropping into the melter gasifier by the effect of gravity and being moderated in the fluidized bed present within the melter gasifier. Coal in lumpy form is charged through a charging opening arranged laterally in the hood of the melter gasifier or in the dome terminating the melter gasifier toward the top, also under the influence of gravity. The reducing gas formed in the melter gasifier is withdrawn through the centrally arranged charging opening for the iron-containing material.
A process of this kind is not suitable for processing fine-particle metal carriers, in particular fine-particle sponge iron, since the fine-particle metal carriers due to the pronounced gas flow of the reducing gas formed in the melt-down gasifying zone and withdrawn through the central charging opening arranged in the hood or in the dome of the melter gasifier would be instantly carried out of the melter gasifier. Such a discharge of the fine-particle metal carriers is further favored by the temperature reigning in the upper region of the melter gasifier, i.e. in the region above the melt-down gasifying zone, which is too low to ensure a melt-down, i.e. agglomeration of the fine particles at the charging site to form bigger particles which in spite of the ascending gas stream could sink down into the melt-down gasifying zone.
From EP-A-0 217 331 it is known to introduce pre-reduced fine ore into a melter gasifier and to completely reduce and melt it by means of a plasma burner while supplying a carbon-containing reducing agent. The pre-reduced fine ore or the sponge-iron powder respectively is fed to a plasma burner provided in the lower section of the melter gasifier. A disadvantage of this method is that by supplying the pre-reduced fine ore directly in the lower meltdown region, i.e. in the region where the melt collects, complete reduction can no longer be ensured and the chemical composition necessary for further processing the pig iron cannot be achieved by any means. Moreover, the charging of major amounts of pre-reduced fine ore is not feasible due to fluidized bed or the fixed bed forming from coal in the lower region of the melter gasifier, as it is not possible to carry off a sufficient quantity of the melting products from the high-temperature zone of the plasma burner. The charging of major amounts of pre-reduced fine ore would lead to instant thermal and mechanical failure of the plasma burner.
From EP-B-0 111 176 it is known to feed a fine grain fraction of sponge iron particles into the melter gasifier through a downpipe projecting from the head of the melter gasifier into the proximity of the coal fluidized bed. At the end of the downpipe a baffle plate is provided for minimizing the velocity of the fine grain fraction, resulting in a very low exit velocity of the fine grain fraction from the downpipe. At the charging site, the temperature reigning in the melter gasifier is very low, whereby immediate melting of the supplied fine grain fraction is prevented. This and the low exit velocity from the downpipe cause a substantial portion of the supplied fine grain fraction to be carried out of the melter gasifier again together with the reducing gas generated in the same. The charging of a major amount of sponge iron particles containing a fine portion or of only a fine grain fraction is not feasible in accordance with this method.
From EP-A-0 594 557 it is known to charge a sponge iron fine grain fraction by means of a conveying gas directly into the fluidized bed formed by the melt-down gasifying zone in the melter gasifier. However, this is disadvantageous; clogging of the fluidized bed may ensue, leading to insufficient gas circulation and optionally to damming-up of gas and subsequently to eruptive outbreaks of gas, by which the clogged fluidized bed is broken up. Hereby, the gasification process for the carbon carriers and also the melt-down process for the reduced iron ore are markedly disturbed.
From EP-A-0 576 414 it is known to feed fine-particle metal carriers into the melt-down gasifying zone via dust burners. One disadvantage associated with this process is that in the melt-down gasifying zone there may result regions with an excess of metal and regions with an excess of carbon.
According to AT-B-390.622, blowing of a fine grain fraction is effected into the fixed bed of a melter gasifier, wherein the fixed bed acts like a filter. Hereby gas permeability is reduced and as a consequence thereof outbreaks of gas may occur.
From GB-A-1 090 826 a method is known in which iron ore is melted in an oxygen-fuel flame which is directed onto a melting-bed present in a melting chamber from above and the ore melt is subsequently passed into a reduction chamber and is reduced there.
The invention aims at avoiding the above-mentioned disadvantages and difficulties and has as its object to provide a method of the initially described kind and a plant for carrying out the method, with said method and plant allowing processing of fine-particulate metal carriers without the need of briquetting and wherein, on the one hand, discharge of the supplied fine particles, possibly in the pre-reduced or in the completely reduced state, by the reducing gas generated in the melter gasifier is reliably avoided and on the other hand, if necessary, a final reduction of the fine particles is ensured. A further object to be achieved in accordance with the invention is to achieve a distribution as uniform as possible of the metal carriers and the carbon carriers in the fluidized bed of the melt-down gasifying zone.
In accordance with the invention, this object is achieved in that both the carbon carriers and the metal carriers are introduced into the melter gasifier centrally above the melt-down gasifying zone, preferably gravitationally, with a central strand of metal carriers being formed which is peripherally surrounded by a jacket strand formed by the carbon carriers.
By a dense formation of a jacket, formed of carbon carriers, around the central strand of metal carriers, dust loss of the fine portion of the metal carriers, i.e. discharge of said fine portion along with the reducing gas generated in the melter gasifier, is prevented.
In accordance with a preferred embodiment, the jacket strand formed by the carbon carriers is formed by several closely adjacent strands of carbon carriers. Herein it is feasible by a suitable arrangement of the strands formed of carbon carriers to influence the structure of the fluidized bed in the melter gasifier, i.e. it is feasible to selectively charge a larger amount of carbon carriers to the central region or into the peripheral region of the fluidized bed.
Preferably, the amounts of carbon carriers and/or metal carriers charged over a unit of time are varied, wherein advantageously
the variations in the amounts of metal carriers and carbon carriers charged per unit of time are effected such that the amount of metal carriers charged is reduced and at the same time the amount of carbon carriers charged remains roughly the same or is increased, or
conversely, the amount of carbon carriers charged is reduced and at the same time the amount of metal carriers charged remains roughly the

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