Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1998-07-01
2001-01-30
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S571000, C075S573000, C266S044000
Reexamination Certificate
active
06179896
ABSTRACT:
The invention relates to a method of producing molten pig iron or steel pre-products from an ore which in at least one reduction zone is reduced to partially and/or completely reduced sponge iron which is melted down in a melt-down gasifying zone of a melter gasifier under supply of carbon-containing material and oxygen and while simultaneously forming a reducing gas in a bed formed of solid carbon carriers, optionally upon previous complete reduction.
A method of this kind is known for instance from EP-A-0 576 414. There, the sponge iron partially or completely reduced from lump ore in a shaft furnace from the shaft furnace passes into the bed formed of solid carbon carriers in the melter gasifier via discharge worms, namely in roughly uniform distribution. The reducing gas formed in the melt-down gasifying zone flows upward through the bed of solid carbon carriers which exhibits a specific gap volume and it melts the sponge iron charged into the bed. To be effective, this method requires a certain minimum gap volume of the bed of solid carbon carriers.
A method of the kind initially described is further known from EP-A-0 594 557, for instance, according to which fine ore is reduced to sponge iron by the fluidized bed method. Herein, the partially or completely reduced sponge iron through forced conveyance realized by means of injectors passes into the bed formed of solid carbon carriers, in roughly uniform distribution. Here, too, the reducing gas formed in the melt-down gasifying zone flows upward through the bed of solid carbon carriers which exhibits a specific gap volume and it melts the sponge iron charged into the bed. For this method to be effective, a certain minimum gap volume of the bed of solid carbon carriers is necessary.
When using solid carbon carriers having a broad range of grain sizes or having a fines content, the gap volume of the bed, which is necessary for uniform gas distribution, is limited from the outset. If, in such a bed of solid carbon carriers, sponge iron is charged in a uniformly distributed manner and if, moreover, the sponge iron is partially of a rather fine-grained nature, i.e. is provided with a fines portion, the gap volume of the bed of solid carbon carriers is decreased and satisfactory flowing of gas through the bed will no longer be ensured. Inside the bed, a localized passage may be formed through which the reducing gas forming in the bed will flow upward, in which case, however, large areas of the bed will no longer be flown through by gas at all, or not sufficiently.
The invention aims at avoiding these disadvantages and difficulties and has as its object to provide a method of the initially described kind, in which effective formation of reducing gas will be ensured by satisfactory gas flow through the entire bed even at a low gap volume of the bed of solid carbon carriers and at the same time efficient melting of the charged sponge iron will take place. In accordance with the invention, this object is achieved in that at least the sponge iron is in contrast to the prior art no longer charged to the bed of solid carbon carriers in a uniformly distributed manner but is charged to the melt-down gasifying zone discontinually, under formation of areas of piled-up sponge iron which are embedded in the bed of carbon carriers and which are superposed and which are separated by solid carbon carriers, wherein each of the areas of piled-up sponge iron while sparing a cross section zone of the melt-down gasifying zone extends over the cross section of the same and wherein the reducing gas forming in the melt-down gasifying zone flows past the areas of piled-up sponge iron under melting of the same and upwards through the cross section zones that are free from sponge iron and formed from carbon carriers, and flows through the said zones.
In this way, no decrease will be caused in the gap volume by the sponge iron being charged, so that the bed of solid carbon carriers can be thoroughly flown through by gas at all times even at a small gap volume and in spite of charging dust-like sponge iron. Between the areas of piled-up sponge iron there will thus remain areas of the bed of solid carbon carriers which can be thoroughly flown through by gas, thus ensuring that sufficient amounts of reducing gas will be formed by gasification of the carbon carriers in any event.
According to a preferred embodiment, the sponge iron is charged to the melt-down gasifying zone under formation of circular areas of piled-up sponge iron, wherein advantageously the sponge iron is charged to the melt-down gasifying zone under formation of a single area of piled-up sponge iron per cross section level and with the area of piled-up sponge iron extending centrally over the cross section and forming a cross section zone shaped like a circular ring, which is free from sponge iron.
According to another preferred embodiment, the sponge iron is charged to the melt-down gasifying zone under formation of several areas of piled-up sponge iron that lie in a plane and are arranged at a distance from each other and thus between the areas of piled-up sponge iron yield cross section zones that are free from sponge iron.
Further it is also possible to charge the sponge iron to the melt-down gasifying zone under formation of an area of piled-up sponge iron having the shape of a circular ring lying in a plane, wherein advantageously the sponge iron is charged to the melt-down gasifying zone under formation of cross section zones that are free from sponge iron and lie outside and inside the area of piled-up sponge iron that is shaped like a circular ring.
Preferably, in addition, the solid carbon carriers are also charged to the melt-down gasifying zone non-continuously, namely by reducing the quantity or by interrupting such charging during the charging of the sponge iron.
Suitably, the charging of solid carbon carriers is stopped during the charging of the sponge iron, then the charging of the sponge iron is stopped for a specific period and for a specific period only solid carbon carriers are charged, whereupon, in turn, only sponge iron is charged for a specific period, and so on.
To ensure that the bed of solid carbon carriers in the lower area of the melt-down gasifying zone will be flown through by gas in a satisfactory manner, the areas of piled-up sponge iron are advantageously formed so as to slope gently towards their edges.
Suitably, the sponge iron is formed from fine ore in a fluidized bed process.
According to yet another embodiment, the sponge iron is formed from lump ore in a shaft furnace.
REFERENCES:
patent: 4564389 (1986-01-01), Yamaoka et al.
patent: 5759232 (1998-06-01), Takahashi et al.
patent: 0195770 (1986-09-01), None
patent: 0217331 (1987-04-01), None
patent: 0576414 (1993-12-01), None
patent: 0594557 (1994-04-01), None
Kepplinger Leopold Werner
Schenk Johannes-Leopold
Wallner Felix
Andrews Melvyn
Deutsche Voest-Alpine Industrieanlagenbau GmbH
Ostrolenk Faber Gerb & Soffen, LLP
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