Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1993-05-03
1994-11-15
Rosenberg, Peter D.
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75445, 75448, C22B 400
Patent
active
053644484
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process as set forth in the classifying portion of claim 1 and a reducing and smelting furnace as set forth in the classifying portion of claim 13.
A process of that kind is known from DE-A-21 32 150. In that process, the fine ore which has been subjected to pre-reduction in a pre-reducing cyclone is subjected to finishing reduction in a finishing reducing cyclone by means of the hot waste gases, essentially consisting of carbon monoxide, from a smelting and refining installation, and then fed as a solid discharge to the smelting and refining installation. In that installation, the solid discharge is melted down, with the simultaneous production of the reducing gas, by incomplete combustion of carbon in excess, and then refined by means of oxygen.
The reduction rate in the finishing reducing cyclone essentially depends on temperature. Because of what is known as the `sticking effect`, that is to say the tendency on the part of fine-grain to dust-form sponge iron to stick together at temperatures above 850.degree. C. however, it is not possible to set the optimum reducing conditions in the finishing reducing cyclone so that hitherto it is not yet technically economically possible to achieve the procedure which is basically ideal, namely high level of metallisation of the fine ore by means of reducing gas at a temperature above 850.degree. C. and subsequent smelting.
In what are known as smelting reducing processes for fine ore, fine ore is reduced in the molten condition. For that purpose, the process disclosed in EP-B1-0 063 924 provides that highly heated air or air which is enriched with oxygen is injected into the lower region of a smelting and reducing furnace which contains a column of coke, whereby high-temperature zones of between 2000.degree. and 2500.degree. C. are formed in front of the nozzles. Disposed above the injection nozzles are further nozzles through which hot pre-reduced fine ore is injected by means of hot air or oxygen. In that situation, the pre-reduced fine ore is firstly oxidised and then melted by the reaction heat in order then to undergo finishing reduction as it sinks down through the bed of coke in counterflow relationship to the hot upwardly moving gases from the high-temperature zone, and to be collected in the liquid condition in the region of the floor. The supply of heat in the lower region of the furnace must be sufficient to prevent unacceptable cooling of the liquefied iron oxide upon reduction during the downward movement in the solids bed.
Pre-reduction of the fine ore takes place in a separate pre-reducing stage or in a pre-reducing stage which is integrated in the smelting and reducing furnace, with the waste gas from the smelting furnace being used as the reducing gas.
The object of the present invent ion is to improve the level of efficiency in a process of the kind set forth in the opening part of this specification, and to permit solids reduction of fine ore above temperatures at which the `sticking effect` occurs.
The invention further seeks to provide that the total consumption of energy is reduced and excess gas is reduced or eliminated.
The invention further seeks to provide a reducing and smelting furnace for carrying out the process, which is distinguished by a low level of consumption of refractory material for the furnace lining.
The process according to the invention is characterised by the features of claim 1 while the apparatus according to the invention is characterised by the features of claim 13. Advantageous configurations of the process according to the invention and the apparatus according to the invention are set forth in the other claims.
In the process according to the invention, the fine-grain to dust-form metal oxide particles which are blown with hot reducing gas into a final reducing space are retained on a heated bulk material filter layer through which is passed the gas loaded with the particles, and undergo finishing reduction by the reducing gas flowing therepast. In that situation the `sticking effect` is
REFERENCES:
patent: 4725308 (1988-02-01), Kepplinger
patent: 4728360 (1988-03-01), Hauk
patent: 4755219 (1988-07-01), Hauk
patent: 4793855 (1988-12-01), Hauk
patent: 4995904 (1991-02-01), Hauk
Kortec AG
Rosenberg Peter D.
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