Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1982-07-09
1984-02-28
Andrews, M. J.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75 11, 75 38, 75 25, 75 26, C21B 1312
Patent
active
044340010
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for manufacturing metal from fine-grain metal oxide.
In recent years, several new processes for manufacturing metal, primarily crude iron, from particulate material containing iron oxide have been proposed and are undergoing development. One feature which is common to a number of these processes is that the iron-oxide material is partially reduced to a greater or lesser extent while in a solid state, prior to being smelted and finally reduced. A desideratum herewith is to be able to partially reduce the iron-oxide material without needing to subject the material to a preceding, conventional and expensive suction-sintering or pellet-sintering process. In this respect, the partial reduction of iron-oxide material in a fluidized bed is considered a suitable method of procedure, since it provides a particulate product which can be charged directly to the smelting and final reduction stage.
Greatly enriched concentrate as well as metallurgicaldust containing iron oxide, however, are much too fine to enable them to be satisfactorily partially reduced in practice in a fluidized bed. This is partly because the rate at which the fine material fluidizes is so low that a grid of unreasonably large area is required to enable a sufficient quantity of reduction gas to be supplied without causing the material to be blown from the bed, and partly because the fine particles of the material which is to form the fluidized bed have a great tendency to agglomerate, already at relatively low temperatures. Furthermore, such fine-grain materials require a grid with so densely located pores that the fluidizing and reduction gas must be extensively cleaned of dust, in order to prevent clogging of the pores.
Among the aforementioned proposed metal-manufacturing processes under development, primarily processes for manufacturing crude iron, is included the plasma-smelt reduction process (PSR-process), in which particulate metal-oxide material is partially reduced to 50-60% in solid phase and then injected together with slag formers and reductant into a cavity forming a melt-reduction zone in a coke-filled shaft, the partially reduced material being melted and finally reduced while supplying the requisite energy herefor with the aid of a plasma burner. The gas leaving the shaft has a high temperature and is very rich in, primarily, carbonmonoxide. Hence, in this respect the gas is well suited for use in carrying out the aforesaid partial reduction process. Such partial reduction can be carried out to advantage in a fluidized bed, provided that the particulate starting material has a suitable form with respect the particle size and particle-size distribution. As beforementioned, highly enriched concentrates and fine dusts do not lend themselves for direct use in conjuction with reduction processes carried out in a fluidized bed, which limits the possibilities of optimally utilizing the PSR-process for highly enriched concentrates and other fine-grain starting materials, among which can be mentioned dust from oxygen-gas refining processes and, for example, zinc-containing dust from electro-steel furnaces and blast furnaces, whereat these concentrates and dusts in addition to containing an oxide of Fe may also contain oxides of Ni, Co, Cr, Mo, W, Mn and Cu, which oxides could also be reduced-out and recovered, either in the form of a melt in the aforesaid shaft or, as is the case with Zn for example, in the form of a condensate obtained from the gas leaving the shaft.
According to another of said processes undergoing development, namely a German process, iron-oxide material is partially reduced to form a highly metallized product, which is then charged to the top of a reactor vessel containing a crude-iron melt, whereat oxygen gas and carbon are injected into the melt through the bottom of said vessel, for generating the energy required to melt said product. In the course hereof there is formed a hot gas which contains carbonmonoxide and hydrogen and which can be used for the partial reduction of
REFERENCES:
patent: 3936296 (1976-02-01), Campbell
patent: 3984229 (1976-10-01), Gorling
patent: 4072504 (1978-02-01), Perdahl et al.
patent: 4340420 (1982-07-01), Santen
Edstr/o/ m John O.
G/o/ rling Karl G.
Andrews M. J.
SKF Steel Engineering AB
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