Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1999-07-13
2001-08-14
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S446000, C075S491000, C266S156000, C266S160000
Reexamination Certificate
active
06273934
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for producing metals and metal alloys, in particular although by no means exclusively iron and iron alloys, from metal oxides, such as ores and partly reduced ores, which is based on the use of a metallurgical vessel containing a molten bath.
BACKGROUND OF THE INVENTION
There are a number of known methods of smelting iron ore and partly reduced iron ore which are based on the use of a metallurgical vessel (often referred to as a “smelt reduction vessel”) containing a molten bath of iron and slag.
In general terms, these known methods require that a carbonaceous material be injected into the molten bath as a source of reductant and thermal energy. The carbonaceous material may be in solid form, such as coal, or in gaseous form, such as natural gas.
Australian patent 649,402 entitled “Smelting of Pre-reduced Iron Oxide” in the name of Zurich Branch of Midrex International BV Rotterdam discloses one particular method of smelting iron ore and partly reduced iron ore which is based on the injection of natural gas into a molten bath in a metallurgical vessel.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a more effective method of smelting iron ore and partly reduced iron ore than that disclosed in Australian patent 649,402.
According to the present invention there is provided a method of producing metals and metal alloys from metal oxides, which method comprises the steps of partially pre-reducing the metal oxides to a pre-reduction degree of at least 60% in one or more pre-reduction stages and, thereafter, completely reducing the metal oxides and melting the metal in a smelt reduction stage, and which method is characterised by carrying out at least one of the pre-reduction stages with one or more of natural gas, reformed natural gas, and partially reformed natural gas as a source of reductant.
The present invention is based in part on the realization that the use of one or more of natural gas, reformed natural gas, and partially reformed natural gas in a pre-reduction stage of a method of smelting iron ore or partly reduced iron ore enables more effective and efficient use of natural gas than in the method disclosed in Australian patent 649,402 which is based only on the use of natural gas in the smelt reduction stage of the method.
It is preferred that the pre-reduction stage(s) pre-reduce the metal oxides to a pre-reduction degree of at least 70%.
It is preferred particularly that the pre-reduction stage(s) pre-reduce the metal oxides to a pre-reduction degree of at least 80%.
It is preferred more particularly that the pre-reduction stage(s) pre-reduce the metal oxides to a pre-reduction degree of at least 90%.
It is preferred that an excess of one or more of natural gas, reformed natural gas, and partially reformed natural gas be supplied in the or each pre-reduction stage to produce a solid carbonaceous product, typically soot, and/or a solid carbon-containing product, such as iron carbide.
It is preferred particularly that the solid carbonaceous product and/or solid carbon-containing product be supplied to the smelt reduction stage.
It is preferred that the smelt reduction stage be carried out in a metallurgical vessel comprising a molten bath containing metal and slag.
It is preferred particularly that the molten bath comprise a metal layer and a slag layer.
It is preferred that the metallurgical vessel be a smelt reduction vessel which comprises bottom and/or side tuyeres/lances and/or top tuyeres/lances and that the method comprises injecting a solid and/or a gaseous carbonaceous material into the molten bath via the tuyeres/lances.
It is preferred that the solid carbonaceous material injected into the molten bath be the solid carbonaceous product and/or the solid carbon-containing product from the natural gas-operated pre-reduction stage(s).
It is preferred that the gaseous carbonaceous material be natural gas.
It is preferred particularly that the smelt reduction vessel comprises:
(i) one or more tuyeres/lances for injecting the partially reduced metal oxides from the pre-reduction stages into the molten bath; and
(ii) one or more tuyeres/lances for injecting a gas that contains oxygen into the space above the surface of the molten bath to after-burn or post-combust reaction gases, such as CO and H
2
, released from the molten bath.
It is preferred particularly that air be the oxygen-containing gas injected into the smelt reduction vessel in step ii.
It is preferred more particularly that the air be preheated to a temperature of at least 1000° C.
It is preferred that there be two pre-reduction stages.
In such a situation it is preferred particularly that the first pre-reduction stage pre-reduce the metal oxides to a pre-reduction degree of at least 11%, and the second pre-reduction stage pre-reduce the partly reduced metal oxides from the first pre-reduction stage to the selected pre-reduction degree.
It is preferred that off-gas that is discharged from the smelt reduction vessel be the source of reductant in the first pre-reduction stage.
Alternatively, it is preferred that off-gas from the second pre-reduction stage be the source of reductant in the first pre-reduction stage.
It is preferred that one or more of natural gas, reformed natural gas, and partially reformed natural gas be the source of reductant in the second pre-reduction stage.
The metal oxides may be in any suitable form. For example, the metal oxides may be in the form of ores, and the ores may be in the form of lump or fines.
It in preferred that the metal oxides be iron oxides.
According to the present invention there is also provided an apparatus for producing metals and metal alloys from metal oxides which comprises:
(i) one or more pre-reduction vessels for carrying out pre-reduction of metal oxides in at least two stages to produce pre-reduced metal oxides having a pre-reduction degree of at least 60% , preferably at least 70%, more preferably at least 80%, and typically at least 90%, with at least one of the pre-reduction vessels comprising a means for injecting one or more of natural gas, reformed natural gas, and partially reformed natural gas into the vessel for use as a source of reductant; and
(ii) a metallurgical vessel for completely reducing the partly reduced metal oxides and thereafter melting the metal, and the metallurgical vessel being adapted to contain a molten bath of metal and slag.
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Andrews Melvyn
Merchant & Gould P.C.
Technological Resouces Pty. Ltd.
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