Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1999-08-12
2001-08-07
King, Roy (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
Reexamination Certificate
active
06270553
ABSTRACT:
The present invention relates generally to the production of metals and metal alloys from metal oxides.
The term “metal oxides” is understood herein to include, but is not limited to, metal oxides in ores and partially reduced ores.
The present invention relates particularly to the production of metallic iron from iron oxides in the form of ores and/or partly reduced ores.
An object of the present invention is to provide a method and a apparatus for producing metals and metal alloys which is an alternative to conventional methods and apparatus.
According to the present invention there is provided a method of producing metals and metal alloys from metal oxides, which method comprises:
(a) passing a gas at an elevated temperature through a bed of composite agglomerates that are formed from metal oxides and solid carbonaceous material and thereby reducing metal oxides in the agglomerates to metal and melting the metal; and
(b) collecting the molten metal from the agglomerates.
The present invention is based on the realization that composite agglomerates of metal oxides (such as iron oxides) and carbonaceous material (such as coal), and optionally fluxes and binders, can be produced with suitable structural properties (such as porosity and strength) and composition:
(i) to enable the agglomerates to be formed into a bed of agglomerates: and
(ii) to be an effective medium for reduction of metal oxides in the agglomerates to metal and melting of the metal in the presence of a gas at an elevated temperature.
Unlike known agglomerate-based processes for reducing iron oxides, such as the FASTMET process of Midrex Steel Corporation, which reduce iron oxides in the form of pellets to metallic iron but are operated under conditions to avoid forming molten iron, the process of the present invention deliberately operates under conditions to produce molten metal from the agglomerates.
The term “elevated temperature” is understood to mean a temperature that is above the melting point of the metal formed by the reduction of the metal oxides.
It can readily be appreciated that in any given situation the minimum elevated temperature will depend on the specific metal oxides being treated. By way of example, in the case of iron oxides, the minimum elevated temperature is of the order of 1250/1300° C.
It is preferred that the gas have some reducing potential.
The gas may be of any suitable composition.
It is preferred that the gas in part comprise CO and H
2.
It is preferred particularly that the gas be an off-gas produced in a molten bath-based smelter.
In this connection, the present invention is based on the realization that the bed is an efficient means of utilizing the sensible heat released from a molten bath-based smelter and of filtering dusts/molten material retained in off-gas produced in such a smelter.
It is preferred that the method comprises transferring at least a part of the gas released form the bed to the smelter.
In one embodiment it is preferred that the method comprises injecting a reducing gas and an oxygen-containing gas into a gas space above the surface of a molten bath in the smelter to combust a portion of the reducing gas to generate heat to maintain the bath in a molten state.
In another embodiment it is preferred that the method comprises injecting metal oxides and a solid carbonaceous material into the molten bath in the smelter and reducing the metal oxides to metal and thereafter melting the metal.
In this embodiment it is particularly preferred that the method comprises infecting an oxygen-containing gas into a gas space above the surface of molten bath in the smelter to combust a portion of combustible material in the gas space.
It is preferred that the method comprises causing splashes and/or droplets of molten metal and/or slag to be ejected upwardly from the molten bath into the gas space to form a transition zone in which heat generated by combustion of reducing gas in the gas space is transferred to the splashes and/or droplets of molten metal and/or slag and thereafter is transferred to the molten bath when the splashes and/or droplets of molten metal and/or slag fall back into the molten bath.
It is preferred particularly that the transition zone be formed by injecting a carrier gas and metal oxides and/or the carbonaceous material into the molten bath to penetrate the molten bath and cause the upward eruption of splashes and/or droplets of molten metal and/or slag.
It is preferred that the oxygen-containing gas be air.
It is preferred particularly that the air be heated.
It is preferred that the bed be located on a structure that:
(i) supports the bed;
(ii) allow gas to pass through the structure to contact the agglomerates; and
(iii) allows molten metal to drain from the bed for collection.
It is preferred that the structure comprise a water-colored grid to support the bed.
It is preferred that the structure further comprises a layer of a support medium on the grid.
The support medium may be any suitable material, such as a ceramic or refractory material.
The agglomerates may be of any suitable shape.
It is preferred that the agglomerates be in the form of pellets or briquettes.
It is preferred particularly that the agglomerates be pellets having a diameter in the range of 10-25 mm.
It is preferred that the agglomerates be formed from finely ground metal oxides and carbonaceous material.
The agglomerates may be formed by any suitable means.
The metal oxides may be any suitable metal oxides.
It is preferred that the metal oxides be iron oxides.
The carbonaceous material may be any suitable solid carbonaceous material, such as coal or coke.
It is preferred that the carbonaceous material be soft coking coal.
It is preferred that the agglomerates further comprise a flux to combine with impurities in the metal oxides and the carbonaceous material to form a molten slag which coats the molten metal and thereby inhibits oxidation of the metal.
The flux may be any suitable material, such as lime/limestone.
The relative proportions of the constituents of the agglomerates may be selected as required.
As one example, it is preferred that the proportions of metal oxides, carbonaceous material, and flux be 55%, 35%, and 10%, respectively, on a weight basis.
It is preferred that the agglomerates further comprise a binder.
The binder may be any suitable material, such as bentonite.
It is preferred that the method comprises continuously or periodically adding agglomerates to the bed to replace agglomerates consumed in the method.
It is preferred that the method comprises pre-heating agglomerates prior to adding agglomerates to the bed.
It is preferred that the method comprises controlling the addition of agglomerates to the bed to maintain a pre-determined bed depth.
In any given situation, the required bed depth will depend on a range of factors including, but not limited to, the structural properties of the agglomerates and the properties, such as temperature, of the gas.
According to the present invention there is provided an apparatus for producing metals and metal alloys from metal oxides, which apparatus comprises:
(a) a metallurgical vessel having:
i) a lower section adapted to retain a bath or molten metal,
ii) an inlet for introducing gas into the vessel;
iii) an outlet for discharging gas from the vessel; and
iv) a structure for supporting a bed of agglomerates in the vessel above the inlet, the structure being formed to allow gas flowing to the outlet to flow through the bed of agglomerates and molten metal produced by reduction to metal of metal oxides in the agglomerates to drain from the bed into the molten bath;
(b) a means for supplying gas to the vessel; and
(c) a means for supplying agglomerates to the bed.
It is preferred that the gas have some reducing potential.
It is preferred that the vessel further comprises an outlet for discharging molten metal.
It is preferred that the structure comprise a water-cooled grid to support the bed of agglomerates.
It is preferred that the structure further comprises a layer of a support medium on the grid.
REFERE
King Roy
McGuthry-Banks Tima
Merchant & Gould P.C.
Technological Resources Pty. Ltd.
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