|Title of Invention||
A DIRECT CURRENT FURNACE FOR GENERATIN HIGH SILICON FOUNDRY PIG IRON
|Abstract||The furnace has a centrally arranged electrode, which projects into the furnace vessel and is guided up to the vacuity of the base, and a counter electrode arranged in the base of the furnace vessel. The electrode projecting into the vessel is enclosed by a coaxially guided sleeve whose outer diameter d is in a ratio to the inner diameter "D" of the fumace vessel such that d; D is about 1:4. The sleeve mouth is at a distance "a" from the base of the furnace vessel such that 2xd^aS4xd. [figure 1]|
The invention relates to a process for the production of foundry pig-iron with a high silicon content, and to a direct-current furnace comprising a centrally arranged electrode which projects into the furnace vessel and is directed into the vicinity of the bottom, and a counter-electrode which is arranged in the bottom of the furnace vessel, for carrying out ties process.
Foundry pig-iron with a high silicon content is an alloy of iron, about 3% carbon and up to 20% silicon. It is melted in foundries, for example with a silicon content of about 2.5%, for the production of centriftigally cast pipes mainly for use in water conduits.
Foundry pig-iron is usually melted in a cupola, furnaces and is then adjusted to the corresponding composition by the admixture of ferrosilicon. A drawback of this process is the high cost of Fest.
It is the object of the invention to provide a process and a correspondmg apparatus, by
means of which process and apparatus the final alloy of the foundry pig-iron with a
high silicon content is melted directly, in an economical manner and
using simple means.
According to the invention, this object is met in that the process comprises the following steps:
a) silicon oxides and carbon/iron metals are charged into a shaft furnace,
b) in so doing, the charge is maintained in a strongly reducing atmosphere,
c) a column of material is guided annularly, at least in the vicinity of the bottom of the vessel, and
d) is exposed to radiant heat of a source of heat disposed in a clear space in an outlet region of the column of material above the furnace bottom,
and in that, in the direct-current furnace, the electrode which projects into the vessel is surrounded by a coaxially directed sleeve, the outside diameter (d) of which relates to the inside diameter (D) of the furnace vessel in a ratio of d:D = 1:4, and an outlet of which is spaced from the bottom of the furnace vessel at a spacing of 2xd<.a> According to the invention, it is proposed that silicon oxides and ferriferous charge, such as scrap iron, sponge iron, sponge iron briquettes, etc., and carboniferous charge, for reducing the silicon oxides and for carburizing, be charged into a shaft furnace, that the charge be guided through an annular shaft, while maintaining said charge at a strongly reducing atmosphere, and that said charge be melted by radiant heat, in particular by means of a transferring arc.
As a result of the charge matter being guided in an annular shaft, it is possible to prevent contact between the charged matter and the electrode. If there were to be contact between the electrically readily conductive charged matter, such as scrap iron, sponge iron, sponge iron briquettes and coal/coke, and the electrode, this would result in a short circuit and it vjould not be possible to provide the electrical power required for the process. When an electrode is used, then it will be possible for the material to be kept at a distance from this source of heat. As a result of the clear or free space
provided, the arc is maintained, without any obstruction,' between the graphite electrode and the melt. The charged matter, which is pushed through the inner vessel toward the edge of the furnace, is melted by the radiated energy of the arc, and the energy required for the reduction of the silicon oxide is made available.
In this regard, the melting process, which is carried out using
electrical energy, is independent of the electrical
conductivity of the charged matter as well as its angle of repose. In addition, there are no specific requirements with regard to the dimensions of the charged matter. Thus, it is possible, for example, to use pieces of scrap iron, the dimensions of which are limited only by the inside width of the annular shaft.
In a further development, it is proposed that the silicon oxides be guided directly and separately from the normal column
of material. To this end, material feeder lances or even a hollow electrode are used. As a result hereof, it is possible for accurately metered quantities of silicon oxide, of a sufficiently fine grain, to be melted down in the shortest possible time. This silicon oxide condenses on the relatively cold coal disposed higher up in the shaft. In so doing, it undergoes transformation and is also melted as the charge descends.
When no separate feeder means are used for the silicon oxide, all the charged matter is carefully and thoroughly mixed prior to being charged into the furnace.
For carrying out the process, use is made of a low-shaft furnace, which includes an annular shaft which comprises a combustion chamber which, with regard to the pouring angle of the charged material, is kept clear during the entire process, such that it is possible for radiant heat to be transmitted unhindered to the material.
In an advantageous manner, the inner shaft is designed to be conical, such that it is possTBTre—foj^-trhe- charge to be fed, without any obstruction, in the direction of the furnace bottom. In this regard, the annular shaft has a size such that a reliable melting of the charged matter is_ ensured.
For carrying out the process, use is made of a closed furnace vessel in which a strongly reducing atmosphere is maintained.
As a result hereof, it is possible for the silicon oxide to be reduced in a reliable manner. In this regard, it is possible for the silicon content of the charged matter to be up to 2 0%.
80% shredder metal, 10% turnings, 5% tin cans and 5% iron turnings are used as iron carriers.
In an additional step, it is possible for the iron carriers to be replaced by iron ore or sponge iron.
An example of the invention is illustrated in the attached drawing, in which;
Figure 1 is a diagrammatic illustration of a furnace which is equipped with a central electrode and comprises an annular conically tapering annular inner shaft.
Figure 2 is a diagrammatic illustration of a shaft furnace comprising an electrode, which is surrounded by an annular sleeve, and a material feeder lance which is directed parallel to the sleeve.
Figure 3 shows a material feeder sleeve which jackets the protective sleeve for the central electrode.
Each of Figures 1 to 3 illustrates a furnace vessel 11 which comprises a furnace bottom. 12 in which a bottom opening 13 is provided. In addition, the furnace vessels illustrated in the Figures are provided with a gas vent 19.
The outside diameter of the sleeve is designated by reference cypher d and the inside diameter of the furnace vessel 11 with the reference cypher D.
A sleeve 14 which jackets an electrode 21 projects into the furnace vessel. The electrode 21 corresponds to a counter-electrode 22 which is provided in the bottom 13.
The sleeve surrounding the electrode is, in each case, sealed by means of a top cover 15.
In Figure 1, the sleeve is designed to be conical, tapering in the direction of the furnace bottom at an angle c/. Feeder means 31 are provided in the top region of the furnace, in the present instance on the conveyor belt 33 which is designed to be charged via a charging valve 32.
In Figure 2, the sleeve 14 is vertically displaceable by means of displacement means 41, In addition, a lance 34, at the leading end of which a transfer wheel 35 is arranged, is provided as a material feeder means 31 in Figure 2. In addition, the lance 34 is connected to a pump 36, by means of which the supplied material is designed to be conveyed pneumatically.
In Figure 3, the sleeve 14 is jacketed by a twin sleeve 17. The clearance between the sleeves 14 and 17 is used as feeder means for the material, and the charge is supplied thereto via
feeder means 31, in the present instance being a conveyor belt 33, and is designed to be conveyed via a charging valve 32 on to the belt 33. In addition, a pump 36 is connected to the feeder means.
LIST OF REFERENCE NUMBERS
11 furnace vessel
12 furnace bottom
13 bottom opening
15 Cop cover
17 twin sleeve
19 gas vent
31 feeder means
32 charging valve
33 conveyor belt
35 transfer wheel
41 displacing member
d outside diameter of the sleeve
D inside diameter of the furnace vessel
1. A direct current furnace for generating high silicon foundry pig iron, the
fumace having a centrally disposed electrode (21) projecting into the fumace vessel
(11) and extending as far as into titer vicinity of the bottom and a counter-electrode
(22) arranged in the bottom (13) of the fumace vessel (11) for performing the process
according to claim 1, having a lock (32) for supplying the feedstock characterized in
thai the electrode (21) projecting into the vessel is surrounded by a coaxially disposed
sleeve (14), the ratio of the outer diameter (d) of which to the internal diameter (D) of
the furnace vessel is d:D = 1:4
and the mouth of which is spaced from the furnace vessel bottom (13) at the distance (a) as per 2 X d 2. The furnace as claimed in claim 1 wherein the sleeve(14) is conical and narrows in the direction of the fumace base at a cone angle "a" of 4'to 6°.
3. The fumace as claimed in claim 1, wherein the sleeve is vertically displaceable by displacement mean (41) with respect to the base of the fumace vessel(13).
4. The furnace as claimed in claim 1 comprising a feeding device (21) which projects moth the vessel optionally up to the mouth of the sleeve (14).
5. The fumace as claimed in claim 4 wherein the feeding device (31) is a material lance (34) connected to a conveying device.
6. The fumace as claimed in claim 4 wherein the feeding device (31) comprises a
tubular casing (17) which encloses the sleeve.
7. The fumace as claimed in claim 1 wherein the electrode (21) projecting into the
vessel is a hollow electrode.
8. The furnace as claimed in claim 1, wherein the heat source is a transmitting arc.
9. The furnace as claimed in claim 1 wherein the charged material comprises iron carriers comprising 80% shredder, 10% turnings, 5% tin cans, and 5% in-plant scrap.
10. The furnace as claimed in claim 1 wherein the charged material comprises iron arc.
11. The fumace as claimed m claim 1 wherein the charged material comprises sponge iron.
12. The furnace as claimed in claim 1 wherein the silicon oxides are transported directly into the free space and exposed to the radiation heat.
|Indian Patent Application Number||1736/MAS/1997|
|PG Journal Number||05/2007|
|Date of Filing||01-Aug-1997|
|Name of Patentee||MANNESMANN AKTIENGESELLSCHAFT|
|Applicant Address||MANNESMANNUFER 2, D-40213 DUSSELDORE,|
|PCT International Classification Number||C21C01/08|
|PCT International Application Number||N/A|
|PCT International Filing date|