Metallurgical apparatus – Process – Tuyere operation
Reexamination Certificate
1999-05-11
2001-02-13
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Process
Tuyere operation
C266S268000
Reexamination Certificate
active
06187258
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for operating a blast furnace, in particular a cupola furnace, to which metallic charge materials, alloy elements and energycarriers, such as coke, are fed in the upper part of the shaft, and an oxidizing agent, such as air, is fed in the lower part of the shaft, filler materials, namely alloy elements, metal chips or dusts, being supplied to the melting zone.
The introduction of such filler materials into the melting zone separately from one another is standard in the prior art.
For instance, it is known to inject alloy elements, such as carburizing compounds, silicon carbide or ferrosilicon, into the melting zone of cupola furnaces with the aim of correcting the iron analysis (EP 0 336 121 B1)
In recent times, dusts occurring in the foundry and in the operation of cupola furnaces have been injected in the tuyere zone for the furnace wind of the cupola furnace (EP 0 504 700 A1). Such dusts are, for example, filter dusts from cupola furnace dedusting, used foundry sands which can no longer be reconditioned, dusts from the cleaning department and grinding floor, etc. These dusts contain, inter alia, SiO
2
which can be used as slag-forming constituents for the cupola furnace melting process, as well as combustible organic constituents whose calorific value can be used for the melting process. Some of these dusts are considered to be special waste which is expensive to dispose of.
In the case of injection into the melting zone of the cupola furnace, the calorific value of the combustible constituents of the dusts is used as melting energy and the SiO
2
is used as a slag-forming constituent.
Problematic constituents of the dusts, such as heavy metals, are integrated into the slag, e.g. vitrified, in an environmentally friendly manner.
All these filler materials which are introduced into the melting zone of the cupola furnace have to be injected under different and, in some cases, contradictory conditions. Whereas for the alloy elements a deoxidizing atmosphere is required at the point of injection, for dusts which have a high calorific value, there must be an oxidizing operation. In the case of dusts which have a low calorific value, it is expedient to introduce an energy carrier as well, so that the slagging of the SiO
2
proportion of these dusts does not take place at the cost of the coke rate.
In general, the introduction, in particular of dusts, lowers the melting temperature.
To counteract this incompatibility, it was proposed in EP 0 618 419 A1 to provide a burner with supply of fuel and oxygen, and introduce the dusts into the flame of the said burner. In this case, NO
x
may form which is harmful to the environment. Moreover, valuable constituents of the filler materials may oxidize, i.e. burn.
SUMMMARY OF THE INVENTION
The invention is based on the object of specifying a method and an apparatus, with which the different requirements described for the use of the said filler materials can be satisfied, undesirable lowering of the melting temperature can be avoided and the occurrence of pollutants, in particular NO
x
, to an unacceptable extent can be prevented.
When applying a method and an apparatus according to the invention, the conditions of introducing the filler materials, the fuel and the additionally introduced oxygen can be adapted in such a way, in particular the speeds can be set so high, that no flame is formed. The occurrence of NO
x
compounds which are harmful to the environment and the burning of valuable constituents, such as alloy elements, can thus be avoided.
The method according to the invention is equally suitable for all common types of cupola furnace, i.e. furnaces operated with hot wind, warm wind, cold wind and secondary wind, lined and unlined types of furnaces, long-duration furnaces, changing furnaces, shuttle furnaces, etc.
The charge material of such furnaces may comprise
as a metallic charge:
steel scrap, returns (casting waste), scrap castings, pig iron, ferro manganese, FeSi
as a non-metallic charge:
carbon (e.g. coke), silicon carbide, ferromanganese, lime, gravel, basalt.
As is known, air (“wind”) is fed as oxidizing agent to the furnace via one or more rows of tuyeres, said air either being pre-heated (hot wind, warm wind) or having an ambient temperature (cold wind). Said air may be enriched with oxygen.
The method according to the invention is suitable for all sizes of furnace.
In an apparatus according to the invention, one or more of the loaded combination lances described below are installed in the melting zone of the cupola furnace to introduce the filler materials.
With an apparatus according to the invention, three different materials can be introduced into a cupola furnace simultaneously or successively in any desired order. The first material may be an alloy element, such as a carburizing compound (FeSi, SiC or the like) or dust (e.g. cupola furnace dust, used sand, cleaning dust, etc.) or iron chips or a mixture of the abovementioned materials.
The second material serves to establish the oxidizing or deoxidising conditions which are necessary for the respective use of the first material. Consequently, these materials may be gaseous, liquid and solid materials containing a calorific value, primarily materials containing carbon or hydrocarbons.
The third material compensates for the lowering of the melting temperature which occurs due to the introduction of the first two materials. It is thus oxygen which emerges from the device primarily at supersonic speed.
The three material flows can be controlled separately from one another within a range of 0%-100%. The optimum setting depends on the type, quantity and composition of material
1
and the respective requirements of the melting operation.
The conditions of introduction via the or each combination lance are adapted in such a way, in particular the speeds of introduction are selected in such a way, that the occurrence of a flame directly in front of the lance is prevented under all possible operating parameters. It is advantageous to arrange introduction through the combination lance of the oxygen in the second jet at supersonic speed, preferably within the range from 1.5 to 2.5 mach, and of the filler materials and fuels in the first jet at the speed of sound as a maximum. This ensures optimum effectiveness of the method and prevents any increase in the NO. values. In addition to the oxygen which is fed to the cupola furnace via the combination lances, oxygen may also be fed to the cupola furnace via separate oxygen lances, primarily at supersonic speed.
The combination lances according to the invention and the oxygen injection lances for the additional introduction of oxygen are preferably installed in the existing air-blast tuyeres (water-cooled copper tuyeres or uncooled, pounded tuyeres). However, it is also possible to install these devices and the additional oxygen injection lances in separate feed lines in the melting zone of the cupola furnace.
In particular, the following advantageous effects are achieved by a method and an apparatus according to the invention:
a) The supply of carburizing compounds in a deoxidizing atmosphere and additional oxygen permits lowering of the coke rate and, associated with the latter, a higher melting rate, less harm to the environment and the possibility of rapid analysis correction.
b) The supply of FeSi or SiC in a deoxidizing atmosphere and additional oxygen permits a reduction in the introduction of SiC formed bodies via the charge make up and a rapid analysis correction (cost saving as a result of less Si burn-off).
c) The supply of chips in conjunction with oxygen permits optimum return of the chips into the furnace, less or no discharge and an optimum yield. Furthermore, the iron analysis can be controlled by the introduction of casting or steel chips, and the iron temperature can be lowered, if necessary.
d) The supply of dusts in possible conjunction with additional fuel and oxygen permits the slag practice to be controlled instantaneously and problematic materia
Hamberger Ralf
Schmidt Juergen
von Hoesslin Gerhard
Connolly Bove Lodged Hutz LLP
Kastler Scott
Messer Griesheim GmbH
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