Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1998-05-24
2001-05-22
King, Roy (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S531000, C075S549000, C266S156000, C266S157000, C266S172000
Reexamination Certificate
active
06235082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for producing liquid metal, in particular pig iron or liquid steel preproducts, from charging substances comprised of ore, in particular iron ore, and of fluxes, wherein the ore is directly reduced to sponge metal in at least one reduction zone, the sponge metal is melted along with fluxes in a melt-down gasifying zone under the supply of carbon carriers and of an oxygen-containing gas and a CO- and H
2
-containing process gas serving as a reducing gas is produced which is fed into the reduction zone and is reacted there and subsequently is withdrawn, wherein slagforming fluxes, in particular calcium carbonate, dolomite etc., by means of the process gas are calcined in a calcining zone that is separate from the reduction zone and melt-down zone and to a plant for carrying out the method.
2. Brief Description of the Related Art
It is known to admix slag formers such as CaCO
3
, dolomite etc. to the ore and effect calcination at the same time and in the same vessel as the reduction of the ore, i.e. in the reduction zone, wherein calcination is effected by means of the reducing gas. With a multistage reduction process, i.e. with a method in which several reduction zones are provided which are subsequently connected in series, complete calcination is effected only in the final reduction stage, as only in this stage the reducing gas has the temperature required for complete calcination. A disadvantage associated with this method is that the quality of the reducing gas will deteriorate, and further, that by the calcining process, which is endothermic, the reducing gas is decreased in temperature. Another disadvantage is that in the reduction of fine ore, the slagforming additions must have roughly the same grain size range so that the fluidized bed formed by the fine ore in the reduction reactor will remain largely undisturbed. Coarse-grained fluxes cannot be exploited in this manner.
From DE-A-42 40 197, a method of the initially described kind is known in which slagforming additions are treated in a separate calcining zone of a calciner, with reducing gas originating from the melter gasifier being employed for calcining purposes. In accordance with DE-A-42 40 197, the calcined fluxes are charged into the reduction reactor in the reduction zone and together with the already partially reduced ore are moved onward through the reduction shaft and finally are charged into the melter gasifier with the reduced ore.
Another disadvantage associated with this method is that the grain of the fluxes cannot be chosen freely. On the contrary, the grain or the grain size range respectively has to correspond to the grain or the grain size range respectively of the fine ore being moved through the reduction shaft. Further, an adverse effect on the reduction process, in particular on complete reduction, is to be expected, since the material and gas flow as well as the temperature profile are disturbed by the charging of the fluxes.
SUMMARY OF THE INVENTION
The invention aims at avoiding these disadvantages and difficulties and has as its object to provide a method of the initially described kind as well as a plant for carrying out the method, enabling the processing of slagforming additions of any desired grain. In particular, the reduction process for the ore is to proceed entirely undisturbed by fluxes and utilization of coarse-grained fluxes is feasible, so that a satisfactory porosity will exist in the melt-down gasifying zone.
With a method of the initially described kind, this object is achieved in that the calcining zone is connected in parallel to the reduction zone as regards the material flow and the calcined fluxes are fed into the melter gasifier directly.
If hot process gas is available in sufficient quantities, the calcining zone is suitably also connected in parallel to the reduction zone as regards the process gas flow, wherein advantageously the process gas after being discharged from the melt-down gasifying zone is purified and cooled and subsequently a portion of the process gas is fed into the reduction zone and a portion of the process gas is fed into the calcining zone.
The process gas leaving the calcining zone being still very hot, it is suitably admixed with the process gas leaving the reduction zone and advantageously is utilized for preheating and/or prereducing the ore in a prereduction zone.
In accordance with a further advantageous variant of the method, the calcining zone is connected in series to the reduction zone as regards the process gas flow, with the process gas flowing first through the reduction zone and subsequently through the calcining zone.
Since with this variant the process gas has already cooled down to some extent, advantageously an oxygen-containing gas is fed into the calcining zone and a portion of the process gas is combusted.
A plant for carrying out the method, comprising at least one reduction reactor into which the ore is conducted via a conveying duct in one direction and the reducing gas via a reducing-gas feed duct in the opposite direction, and comprising a melter gasifier into which runs a conveying duct conducting the reduction product from the reduction reactor and which is provided with feed ducts for oxygen-containing gases and carbon carriers as well as with a tap for liquid metal and slag as well as with a reducing-gas feed duct opening into the reduction reactor for a reducing gas generated in the melter gasifier, is characterized in that a calciner is provided in parallel arrangement with respect to the reduction reactor as regards the solids flow, wherein the calciner is flow-connected with the melter gasifier through a feed duct conducting the calcined materials to the melter gasifier.
Suitably, from the reducing-gas feed duct which leads to the reduction reactor, a branch duct departs and runs into the calciner.
In accordance with a preferred embodiment, a gas purifying means is provided in the reducing-gas feed duct and the branch duct departs from the reducing-gas feed duct at a position after the gas purifying means.
Another preferred embodiment is characterized in that the calciner is flow-connected with a preheating reactor for the ore through an offgas duct.
Suitably, a discharge duct for reacted reducing gas departs from the reduction reactor with a branch duct running into the calciner from said discharge duct, wherein advantageously a duct for an oxygen-containing gas opens into the calciner.
Preferably, the calciner is constructed as a shaft furnace or rotary tubular kiln or traveling grate or multiple-hearth furnace or single-stage or multistage fluidized-bed reactor or gas cyclone or as a multistage gas cyclone cascade.
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patent: 4671497 (1987-06-01), Schmitz et al.
patent: 5435832 (1995-07-01), Kepplinger et al.
patent: 5439504 (1995-08-01), Czermak et al.
patent: 5584910 (1996-12-01), Kepplinger et al.
patent: 5628260 (1997-05-01), Rongved
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patent: 394201 (1992-02-01), None
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Kepplinger Werner Leopold
Schenk Johannes-Leopold
Wurm Johann
King Roy
McGuthry-Banks Tima
Ostrolenk Faber Gerb & Soffen, LLP
Voest-Alpine Industriean-lagenbau GmbH
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