Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1981-08-12
1983-04-19
Rosenberg, P. D.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75 48, 266168, 266176, C21C 700
Patent
active
043804691
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a process for continuously reducing and melting a charge of metal oxides, particularly ores and, respectively, metallic materials pre-reduced to a large extent, particularly iron sponge, if desired together with additives such as slag formers, fluxes and carbon carriers, as well as to an apparatus for performing this process.
Direct reduction processes are of considerable importance for steel production beside refining processes subsequently to a blast furnace process. With such direct reduction processes, iron sponge is, as a rule, produced in a shaft furnace or rotary kiln, which iron sponge can subsequently processed to steel by melting and alloying. It is a considerable advantage of such direct reduction processes over the blast furnace process that they are not dependent on energy carriers formed of high-grade fuels such as coke. Processing of ores by direct reduction processes is, however, disadvantageous over the combination of a blast furnace process and subsequent refining process on account of the comparatively higher total energy requirement. A drawback of the known reductive melting processes resides in the circumstance that on account of the relatively low energy produced during partial combustion effected with an excess of carbon either only coals having a high carbon content and a low content in water and volatile constituents can be used or the missing melting and reduction heat must be compensated for by supplying electrical energy.
A further disadvantageous property of these processes resides in that the effluent gases are flowing out of the melting receptacles with temperatures within the range of 1,000.degree. and 1,800.degree. C. and require a high expenditure in apparatuses for subsequent purification and utilisation, respectively.
For melting and finally reducing lumpy iron sponge within a melting receptacle it is possible to proceed such that coal dust and oxygen are subjected to partial combustion and supply the energy required for melting and reduction. Non-gasified coal particles act as reducing agent and carburizing agent. The gas generated on partial combustion and on direct reduction of the remaining iron oxides, respectively, can, after having been purified and cooled, be used for producing directly reduced iron (iron sponge) within a separated reducing shaft. The metallized product from this gas reduction aggregate shall have a very low content in residual oxygen and be supplied into the melting receptacle with a temperature between 750.degree. and 850.degree. C. Pre-reduced fine ore can, however, also be introduced into the melting receptacle together with coal dust, the iron source being molten and the remaining oxides being directly reduced within the melting receptacle. The gas thus formed and containing CO and H.sub.2 is either burned with oxygen to CO.sub.2 and H.sub.2 O when leaving the melting receptacle or is used, after having been cooled and purified, for pre-reducing fine ore in a separate fluidized bed plant. In view of no or only little melting and reducing heat being produced during the combustion with this processes, it is necessary to supply a major portion of the required energy by means of electric current. It is only by this additional supply of energy that it becomes possible to achieve the high energy concentration required with these processes.
All reductive melting processes have an essentially higher total energy consumption than the blast furnace process but also the net energy requirement (after deducting the gas credit) is, in comparison thereto, distinctly higher because the amount of direct reduction is higher or because utilisation of the chemical heat and of the sensible heat of the gas is not as ideal as with the usual pig iron technology. Additionally there arise nearly in all cases problems on account of the ash produced when burning coal because this ash is present within the effluent gas in relatively great amount and this ash is softening at the high temperatures.
The invention now aims at providing a proc
REFERENCES:
patent: 3063826 (1962-11-01), Cavanagh
patent: 3539336 (1970-11-01), Urich
patent: 3663202 (1971-05-01), Ruter
patent: 4083715 (1978-04-01), Langhammer
patent: 4116678 (1978-09-01), Lafont
Rosenberg P. D.
Voest-Alpine Aktiengesellschaft
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