WO2009049777A1 - Electric furnace with electrode bores for delivering and melting metal powder - Google Patents

Abstract

The invention relates to an electric furnace (1) with a receiving chamber (2) for molten material (3), wherein at least one electrode (4, 5) protrudes into the receiving chamber (2), and wherein means (6) for introducing dust into the receiving chamber (2) are provided. In order to enable an improved supply of the dust with simple processing thereof, the invention provides that the means (6) for introducing dust into the receiving chamber (2) comprise a bore (7) that runs in the longitudinal direction (L) of the electrode (4, 5) at least in some regions.

Description

 ELECTRO-OVEN WITH ELECTRODE HOLES FOR THE DEMANDING AND MELTING OF METAL POWDER

The invention relates to an electric furnace having a receiving space for molten material, wherein at least one electrode protrudes into the receiving space and wherein means for introducing dust are present in the receiving space.

Dust is produced in steelmaking, some of which contain valuable components, so that their recovery is aimed for. The dust is produced in the course of the process as a result of the respective oxidation or other process steps to be carried out. The dust may, especially if it is a so-called secondary metallurgical dust, have a relatively high proportion of compounds of high-quality elements such as chromium or nickel. The release of such dusts represents a not inconsiderable environmental impact. On the other hand, the high quality components are interesting for economic reasons because of their value. It is therefore known to return the dusts to an oven in order to recover the valuable constituents.

Corresponding solutions are described, for example, in EP 0 275 863 B1, in which case the dust is returned to the process in briquetted or pelletized form. Similar solutions are known from EP 0 467 874 A1, WO 99/20801 and DE 26 07 650 A1.

The dust, which is generated in particular during FeNi production, thus represents a technical problem. The transport and storage of the dust require a high personnel and technical effort. The effective processing of the dust in the rotary kiln rarely succeed, since the production of mechanically and thermally stable pellets is difficult and expensive. The contamination of the entire system (roads, buildings, air) is significant.

From EP 1 184 469 B1 it is known to re-supply the dust to the furnace in the dust-like, non-pelletized state. For this purpose, conveyor channels are provided for a mixture consisting of the dusts and hydrocarbon-containing reducing agents. Alternatively, this mixture can also be added to the furnace via a feed lance.

It has been found that with the previously known measures sometimes not fully satisfactory process in the processing of dusts, especially in the case of the production of iron nickel (FeNi) is achieved.

It is therefore an object of the present invention to propose an electric furnace with which improved process engineering conditions can be achieved.

The solution of this object by the invention is characterized in that the means for introducing dusts into the receiving space of the furnace comprise an at least partially extending in the longitudinal direction of the electrode bore.

The bore preferably has a circular cross section. It may be concentric to a longitudinal axis of the electrode, but alternatively also eccentric to this.

The bore may also be directly or indirectly connected to a dewatering conveyor. It can communicate with at least one bore drilling the bore. The connection bore may be formed as a blind bore, which ends in the interior of the electrode. Preferably, the bore or a bore terminates near a tip of the electrode to be delivered under optimal process conditions.

The at least one electrode is preferably arranged in an upper region of the furnace.

The electric furnace is advantageously an electric reduction furnace or a rotary hearth furnace.

Advantageously, there is a saving in the investment costs, since a pelletizing plant or a device upstream of the electric furnace for increasing the mechanical strength of the pellets (so-called Lepol ridges) can be dispensed with, since the dust is processed in the dust-like state.

Investment costs can also be saved in particular when using a rotary kiln, that the dust is discharged from the process and the capacity for the rotary tube can be reduced.

The operating costs can be lowered by a reduced consumption of fuel (oil, gas, etc.) and reducing agents (coke, coal, etc.).

This results in improved process engineering conditions in the rotary kiln.

Furthermore, there is no negative influence on the reduction process due to a high dust load.

Overall, there are savings in the investment in the plant by eliminating the warehouse for the dust, the dust transport system, the peer bed transport system, a Lepol ridge in front of the rotary hearth, a shorter design of the rotary hearth furnace and the transport system for rotary kiln product.

Overall, therefore, the operating costs and personnel costs can be reduced and the environmental conditions of the entire production facility can be improved.

In the drawing, an embodiment of the invention is shown. Show it:

FIG. 1 schematically shows an electroreduction furnace with electrodes arranged in the upper region and FIG

Fig. 2 is an enlarged view of one of the electrodes of the furnace, shown partially in section.

In Fig. 1, an electric furnace 1 is sketched in the form of an electric reduction furnace, which has a receiving space 2 for molten material (molten metal). The heating of the material to be melted is effected in a known manner by means of an arc, which is generated by electrical means between the tips 11 (see FIG. 2) of two electrodes 4 and 5. The furnace 1 is further provided with means 6, with which the introduction of dusts S (in a dust-like state) is possible. The dusts are subjected to a treatment in the oven in order to recover valuable elements from the dust.

How dese means 6 for introducing dusts are formed according to the invention, it is apparent from Fig. 2:

In general, the means 6 for introducing dusts S into the receiving space 2 comprise a bore 7 running at least partially in the longitudinal direction L of the electrode 4, 5. The bore 7 is arranged eccentrically to the longitudinal axis 8 of the electrode 4 in the exemplary embodiment according to FIG. With this Ausges- By means of a suitable conveying device 9 (see Fig. 1), it is possible to convey the dust S along the bore 7 in the interior of the electrode 4, 5 and to discharge it out of the electrode 11 near the tip 11.

The electrode 4, 5 is therefore designed according to the invention as a hollow electrode, wherein dust can be passed through the cavity (bore) in the interior of the electrode 4, 5 in the melt.

In the exemplary embodiment connecting bores 10 are provided, which together with the bore 7 form a pneumatic or fluidic conveying channel for the dust S. This makes it possible to apply the dust as close as possible to the location of the arc between the electrodes 4, 5 and thus to improve the processing of the dust S.

Of course, instead of just one bore 7, a plurality of bores can be provided running parallel to one another.

The dusts S, which are generally produced in the process chain during the production of FeNi, are thus preferably fed directly to the electrode tips by at least one opening in the electrodes of the electric furnace.

The often customary in the prior art agglomeration of the dust that is produced in the rotary kiln, pellets and the reintroduction of the pellets is eliminated with the proposal of the invention. Especially in the production of FeNi, the agglomeration and intermediate storage of the dust are eliminated.

This also has the advantage that disadvantages of pellet processing can not occur. Namely, depending on the mechanical strength of the pellets, additional dust may be generated to the dust adhering to the ore. This creates a ballast of dust, which increases the amount of use of the rotary tube, without improving the application of the same. An equipment-technically high cost of transport, storage and pelletizing of the dust can therefore be avoided. An oversizing of the rotary kiln and dedusting by the ballast to dust circulation can therefore also be avoided. A small rotary kiln still requires less energy, so that the energy input can be reduced with the proposal according to the invention.

It is also possible to avoid the previously known effect of a poor flow of the calcined Ni ore in the electroreduction furnace, which leads to disturbances in the energy conversion at the electrodes, ie to fluctuating production conditions with regard to the quality and quantity of the calcined ore.

LIST OF REFERENCE NUMBERS

1 electric oven

2 recording room

3 molten material

4 electrode

5 electrode

6 Means for introducing dusts

7 hole

8 longitudinal axis

9 conveyor for dusts

10 connection hole

11 tip

L longitudinal direction

S dust

Claims

claims: Electric furnace (1) having a receiving space (2) for molten material (3), wherein at least one electrode (4, 5) protrudes into the receiving space (2) and wherein means (6) for introducing dusts into the receiving space (2) are present, characterized, in that the means (6) for introducing dusts into the receiving space (2) comprise at least one bore (7) extending at least partially in the longitudinal direction (L) of the electrode (4, 5). 2. Electric furnace according to claim 1, dad u rch gekennze ichnet that the bore (7) has a circular cross-section. 3. Electric furnace according to claim 1 or 2, dad u rch geken nzeich net, that the bore (7) concentric to a longitudinal axis (8) of the electrode (4, 5). 4. Electric furnace according to claim 1 or 2, dad u rch geken nzeich net that the bore (7) eccentrically to a longitudinal axis (8) of the electrode (4, 5). 5. Electric furnace according to one of claims 1 to 4, d ad urch geken nzeich net that the bore (7) is directly or indirectly connected to a conveyor (9) for dusts. 6. Electric furnace according to one of claims 1 to 5, dad u rch ge indicates that the bore (7) with at least one of these cutting port bore (10) is in communication. 7. Electric furnace according to claim 6, dad u rch geken nzeich net, that the connection bore (10) is formed as a blind bore, which ends in the interior of the electrode (4, 5). 8. Electric furnace according to one of claims 1 to 7, dad u rch geken Nzeichnet that the bore (7) or a connection bore (10) near a tip (11) of the electrode (4, 5) ends. Electric furnace according to one of claims 1 to 8, characterized in that the at least one electrode (4, 5) is arranged in an upper region of the furnace. 10. Electric furnace according to one of claims 1 to 9, dad u rch characterized that he is an electroreduction furnace. 11. An electric furnace according to any one of claims 1 to 9, d ad u rch nge sign that it is a rotary hearth furnace.