Metallurgical apparatus – Process
Reexamination Certificate
2000-03-21
2001-11-27
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Process
C266S236000, C266S241000
Reexamination Certificate
active
06322745
ABSTRACT:
The present invention relates to a direct smelting vessel for producing molten metal (which term includes metal alloys) from a metalliferous feed material such as ores, partly reduced ores and metal-containing waste streams.
The present invention relates particularly to a vessel that can be used for molten bath-based direct smelting processes.
The present invention also relates to a direct smelting process that operates in the vessel.
The term “smelting” is understood herein to mean thermal processing wherein chemical reactions that reduce metalliferous feed material take place to produce liquid metal.
The term “direct smelting process” is understood herein to mean a process that produces a molten metal directly from a metalliferous feed material, such as iron ore and partly reduced iron ore.
There is a range of known vessels that has been developed to undertake molten bath-based direct smelting processes within a gas/liquid environment of a molten bath.
One known molten bath-based direct smelting process for producing molten iron from iron ore, which is generally referred to as the Romelt process, is based on the use of a large volume, highly agitated slag bath as the medium for smelting top-charged metal oxides to metal and for post-combusting gaseous reaction products and transferring the heat as required to continue smelting metal oxides. The Romelt process includes injection of oxygen enriched air or oxygen into the slag via a lower row of tuyeres to provide slag agitation and injection of oxygen into the slag via an upper row of tuyeres to promote post-combustion. In the Romelt process the metal layer is not an important reaction medium.
Another known group of molten bath-based direct smelting processes for producing molten iron from iron ore that is also slag-based is generally described as “deep slag” processes. These processes, such as DIOS and AISI processes, are based on forming a deep layer of slag with 3 regions, namely: an upper region for post-combusting reaction gases with injected oxygen; a lower region for smelting metal oxides to metal; and an intermediate region which separates the upper and lower regions. As with the Romelt process, the metal layer below the slag layer is not an important reaction medium.
Another known bath-based direct smelting process for producing molten iron from iron ore, which relies on a molten metal layer as a reaction medium, and is generally referred to as the HIsmelt process, is described in International application PCT/AU96/00197 (WO 96/31627) in the name of the applicant.
The HIsmelt process as described in the International application comprises:
(a) forming a bath of molten iron and slag in a vessel;
(b) injecting into the bath:
(i) metalliferous feed material, typically metal oxides; and
(ii) a solid carbonaceous material, typically coal, which acts as a reductant of the metal oxides and a source of energy; and
(c) smelting the metalliferous feed material to metal in the metal layer.
The HIsmelt process also comprises post-combusting reaction gases, such as CO and H
2
, released from the bath in the space above the bath with injected oxygen-containing gas and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed materials.
The HIsmelt process also comprises forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
There are significant issues involved in constructing vessels that can contain the above-described direct smelting processes.
More particularly, for economic and safety reasons it is important that the vessels contain the direct smelting processes with minimal heat loss and be capable of withstanding the erosive/corrosive conditions that are a characteristic of the processes over long term operating campaigns.
Process containment must also be combined with means to inject and to mix reactants to form and maintain different zones in the vessels and to separate products of the processes.
Process chemistry of direct smelting processes generally requires a region of low oxygen potential to smelt metalliferous feed material and a region of high oxygen potential to combust hydrogen and carbon monoxide to obtain combustion energy. As a consequence, typically, there are wide variations in temperature and chemical composition throughout the vessels that contain direct smelting processes which place different demands on the design of vessels.
Some planned and tested direct smelting vessels include an outer steel shell and an internal lining of a refractory material, typically in the form of bricks and/or castables. It is known to use bricks of different composition and physical properties in different sections of the vessels to maximise resistance to thermal and chemical attack and erosion.
For example, refractory bricks in the base of the vessels are usually exposed to molten material that is predominantly metal whereas the refractory bricks in the mid-section of the side walls of the vessels are usually exposed to molten material that is predominantly slag and to gaseous reactants such as CO, H
2
, CO
2
and H
2
O. The bricks exposed to molten metal and the bricks exposed to molten slag require different chemical properties to resist chemical attack by metal and slag.
Moreover, in the case of vessels that operate slag-based direct smelting processes, such as the Romelt, DIOS, and AISI process, typically the slag region is agitated and the metal region is relatively undisturbed (compared with the HIsmelt process). As a consequence, the bricks exposed to the slag region require physical properties to resist erosion due to contact with agitated slag.
Furthermore, in the case of vessels that operate metal bath-based direct smelting processes, such as the HIsmelt process, typically the metal region is also agitated. As a consequence, the bricks exposed to this region require physical properties to resist erosion due to washing action of metal against the bricks.
Furthermore, in general terms, post-combustion of reaction gases generates high temperatures of the order of 2000° C. or higher and, as a consequence, the bricks exposed to the top space/transition zone/slag region in which post-combustion occurs require physical and chemical properties to withstand high temperatures.
In practice, linings of refractory materials have not been an unqualified success for a number of developing direct smelting processes.
There have been proposals to enhance the performance of refractory material linings by water cooling the linings. One particular proposal is described in Australian patent application 692405 in the name of Steel Technology Corporation in the context of a vessel for carrying out the AISI deep slag process. There have also been a limited number of proposals to use water cooled panels in place of refractory materials. On the basis of information available to the applicant these proposals have resulted in excessive heat losses and have been unsuccessful on this basis.
An object of the present invention is to provide an improved direct smelting vessel.
Another object of the present invention is to provide an improved direct smelting process that operates in the vessel.
The present invention achieves these objects by constructing a direct smelting vessel with water cooled panels in the side walls and the roof of the vessel and injection lances for oxygen-containing gas and injection lances for solids material extending into the vessel which make it possible to operate a direct smelting process in the vessel which builds-up and thereafter maintains on the water cooled panels a layer of slag which acts as an effective thermal insulation such that there are reduced heat losses from the vessel.
According to the present invention there is provided a vessel whi
Bates Cecil Peter
Burke Peter Damian
Leigh David John
Weber Margot
Weber Ralph Gottfried
Kastler Scott
Merchant & Gould P.C.
Technological Resources Pty. Ltd.
Weber Margot
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