Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Reexamination Certificate
1999-06-28
2001-03-27
King, Roy V. (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
C075S010150, C075S010360, C075S010380, C075S010450
Reexamination Certificate
active
06206948
ABSTRACT:
BACKGROUND TO INVENTION
This invention relates to a metal reduction and melting process, such as for example a steelmaking process, in which a metal and carbon containing burden is heated in a channel type induction furnace in order to cause the reduction and melting of the metal containing part of the burden, and apparatus for carrying out such preheating.
PRIOR ART
In a known process in this regard, i.e., that of U.S. Pat. No. 5,411,570, where the metal-containing component of the material being fed to the furnace comprises a metal ore, or a partially reduced metal ore (such as sponge iron in the case of an iron-containing burden), and the carbon-containing component coal; the material is fed substantially vertically into the furnace through one or more feed holes located along the side of the furnace in a manner so that the burden in the furnace forms a continuous longitudinally extending heap along each side of the furnace which floats on the bath of molten metal in the furnace.
In the said arrangement, the resulting gaseous products, mainly CO, and the volatile matter associated with the coal, are combusted in a cavity located in the furnace above the floating burden by burning them with oxygen, which is introduced into such area from outside the furnace.
It is also said that the gases resulting from such combustion, which are typically at a temperature in the order of 1600° C., can be utilized in the furnace for heating the burden or, where the material being fed to the furnace comprises steel scrap or cold iron, the spent carbon monoxide-related gas may be discharged through the same opening in the
OBJECT OF THE INVENTION
It is an object of the present invention to provide a metal reduction and melting process in which such combustion gases are better utilised.
SUMMARY OF THE INVENTION
According to the invention a metal reduction and melting process which involves the heating of a burden comprising a metal containing component and a carbon containing component in a channel type induction furnace in order to reduce such metal containing component, includes the step of utilising at least part of the gaseous products of such process for preheating the burden, i.e. prior to its introduction to the furnace.
It will be appreciated that if as a result of such preheating the temperature of the burden is increased beyond a predetermined value, the metal containing component in the burden will start to be reduced before the burden enters the furnace.
This will give rise to at least some gaseous reduction products being formed in the burden prior to its introduction to the furnace.
The particular temperature at which such reduction starts to take place in the burden before it enters the furnace, will of course be determined by the nature of the particular metal containing component in the burden.
Furthermore, as a result of such preheating of the burden at least some of the volatile matter associated with the carbon containing compound of the burden will also be released in the burden prior to it entering the furnace.
The aforesaid gaseous products which enter the furnace may accordingly comprise the aforesaid volatile matter together with the CO and CO
2
formed in the said reduction process.
It will be appreciated that such preheating of the burden not only gives rise to a reduced energy requirement in the overall process, but also to an increased throughput for the furnace.
Further according to the invention at least part of the aforesaid gaseous products are burnt with air and/or oxygen in the furnace and the combustion gases so produced utilised for said preheating of the burden.
Further according to the invention the burden is fed to the furnace in an elongated chamber which is provided with one or more passages extending around or through the chamber, through which passages the said combustion gases can pass in order to preheat the burden in the chamber.
Preferably the chamber and passage(s) are sealed off relative to one another so that no gaseous product can pass between them.
In a preferred form of the invention, such a passage may comprise an annular jacket which extends longitudinally around the chamber.
Further according to the invention the one or bottom end of said chamber may extend for such a distance into the furnace that it engages the heaps of burden floating on the bath of molten metal in the furnace.
In this manner the burden in the chamber is prevented from falling free Into the furnace through such end.
In one form of the invention a positive pressure may be maintained in said chamber in order to ensure that most of the gaseous products formed in the chamber will pass into the furnace.
Such a pressure may, for example, be brought about by introducing the burden to the chamber by means of a suitable lock system.
In addition, or alternatively, such positive pressure may be maintained by introducing a pressurised inert gas, such as nitrogen, to the burden prior to passing it into the chamber.
In one form of the invention at least some of the aforesaid gaseous products formed in the burden prior to its introduction to the furnace may be removed from the burden prior to the burden entering the furnace.
Thus, for example, at least some of the oxidising gases, such as CO
2
and H
2
O-vapour, formed in the burden may so be removed from the burden.
The reason for removing such oxidising gases relates to the fact that if the temperature in the burden reaches a predetermined value, such oxidising gases may react with the metal and carbon containing components of the burden thus resulting in the consumption of the carbon containing compound.
Further according to the invention such oxidising gases may be removed from the burden by means of a elongated open ended conduit which extends longitudinally through said elongated chamber, so that its one or bottom end is located towards the bottom end of the chamber and its other or upper end communicates with a suitable gas withdrawal system, the conduit including over its length at least one gas outlet which is located at a predetermined level in the chamber.
In use, the conduit will accordingly be surrounded by the burden and its said gas outlet located at a predetermined level in the burden.
Further according to the invention said gas outlet of the conduit is located at a level in the chamber where the burden is at that temperature just before which said oxidising gases will start to react with the metal and carbon containing components of the burden.
Such preferred level may, for example, be determined experimentally by, for example, analysing the gas withdrawn from the conduit.
In addition, or alternatively, the temperature at the gas outlet of the conduit may be measured such as, for example, by means of a thermocouple or the like.
In practice, once the preferred level of said gas outlet of the conduit has been determined, its position will remain fixed and the temperature of the burden in said location controlled by, for example, controlling the rate at which the oxidising gases is removed from the conduit, and/or the rate of the preheating, and/or the rate at which the burden is fed through the chamber.
In the case where the metal containing compound comprises iron, and the carbon containing component coal, the aforesaid temperature will be in the order of 600° C.
The oxidising gases which are so removed may, for example, be utilised elsewhere or they may be passed to the said passage(s) utilised for preheating the burden.
Further according to the invention preheated oxygen and/or air are/is introduced to the conduit towards its said bottom end in order to combust any CO present in that part of the burden to CO
2
, which is then also withdrawn through said gas outlet.
In order to ensure that substantially all the CO is converted to CO
2
before the gas reaches the said gas outlet, the wall of the chamber immediately below the gas outlet is maintained at a lower temperature relative to the rest of the chamber.
Such lower temperature may be obtained through suitable heat insulation, and/or by delaying the rate at which t
Ipcor NV
King Roy V.
McGuthry-Banks Tima
Schwegman Lundberg Woessner & Kluth P.A.
LandOfFree
Metal reduction and melting process and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metal reduction and melting process and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metal reduction and melting process and apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2449310