AU2008314187A1

AU2008314187A1 - Electric furnace with electrode bores for delivering and melting metal powder

Info

Publication number: AU2008314187A1
Application number: AU2008314187A
Authority: AU
Inventors: Rolf Degel; Karl-Heinz Kummer; Juergen Kunze; Detlef Strieder
Original assignee: SMS Siemag AG
Current assignee: SMS Siemag AG
Priority date: 2007-10-12
Filing date: 2008-10-02
Publication date: 2009-04-23
Anticipated expiration: 2028-10-02
Also published as: KR20100046054A; ZA201001099B; DE102007048962A1; CN101861404A; WO2009049777A1; RU2010119037A; EP2203572A1; AU2008314187B2; TW200925285A

Description

44 083.go.nw ELECTRIC FURNACE The invention relates to an electric furnace comprising a receiving chamber for molten material, wherein at least one electrode projects into the receiving chamber and wherein means for introducing dust into the receiving chamber are available. Dust, which partly encompasses components containing potential recyclables, accumulates in response to the production of steel so that the recycling thereof is desired. The dust is produced during the course of the process due to the respective oxidation or other process steps, which are to be carried out. In particular when the dust is a so-called secondary metallurgical dust, the dust can thereby encompass a relatively high portion of connections of high-grade elements, such as chromium and nickel, for example. The release of such dust represents a considerable environmental pollution. On the other hand, the high grade components are of interest for economical reasons because of their value. It is thus known to refeed the dust to a furnace so as to recover the valuable components. Corresponding solutions are described, for example, in EP 0 275 863 B1, wherein the dust is refed to the process in the form of briquettes or pellets. Similar solutions are known from EP 0 467 874 Al, from WO 99/20801 and from DE 26 07 650 Al. The dust, which accumulates in particular in response to the FeNi production, therefore represents a plant-specific problem. The transport and the storage of the dust require a high effort with regard to staff and technology. The effective processing of the dust in the revolving cylindrical furnace succeeds rarely, because the production of mechanically and thermally durable pellets is difficult and extensive. The contamination of the entire plant (roads, buildings, air) is considerable. It is known from EP 1 184 469 B1 to refeed the dust to the furnace in dusty, non-pelletized state. For this purpose, provision is made for conveying troughs for a mixture, which consists of the dust and hydrocarbon-containing reducing agents. In the alternative, this mixture can also be admixed to the furnace via a supply lance.

-2 It became apparent that now and then it is not yet possible to attain a completely satisfactory process in response to the processing of the dust, in particular in the case of the production of iron nickel (FeNi) when using the previously known measures. The instant invention is thus based on the object of proposing an electric furnace, by means of which improved procedural conditions can be attained. The solution of this object by means of the invention is characterized in that the means for introducing dust into the receiving chamber of the furnace comprise a hole, which runs at least partially in longitudinal direction of the electrode. Preferably, the hole thereby has a circular cross section. It can run concentrically to a longitudinal axis of the electrode, but in the alternative it can also run eccentrically thereto. Furthermore, the hole can be directly or indirectly connected to a conveyor for dust. It can be connected with at least one coupling hole, which intersects the hole. The coupling hole can thereby be embodied as a blind hole, which ends in the interior of the electrode. Preferably, the hole or a coupling hole ends close to a tip of the electrode, so as to be capable of being fed under optimal process conditions. Preferably, the at least one electrode is arranged in an upper region of the furnace. Preferably, the electric furnace is an electric reduction furnace or a rotary hearth furnace. Preferably, investment costs can be saved because the use of a pelletization plant and a device for increasing the mechanical stability of the pellets (so called Lepol grate), which is connected upstream of the electric furnace, is not necessary, because the dust is processed in its dusty state.

-3 In particular, investment costs can also be saved in response to the use of a revolving cylindrical furnace in that the dust is discharged from the process and in that the capacity for the revolving tube can be reduced. The operating costs can be decreased by a reduced use of fuel (oil, gas, etc) as well as reducing agents (coke, carbon, etc.). Improved procedural conditions thus result in the revolving cylindrical furnace. Furthermore, a high dust load does not lead to a negative impact on the reduction process. Overall, the results are savings when investing into the plant due to the omission of the storage for the dust, the dust transport system, the pellet transport system, a Lepol grate in front of the rotary hearth furnace, a shorter construction of the rotary hearth furnace and the transport system for revolving cylindrical furnace products. Overall, the operating costs and personnel costs can thus be lowered and the environmental conditions of the entire production plant can be improved. An exemplary embodiment of the invention is illustrated in the drawing. Fig. 1 shows an electric reduction furnace comprising electrodes arranged in the upper region in a diagrammatic manner and Fig. 2 shows an enlarged illustration of one of the electrodes of the furnace, illustrated in a partially cut view. An electric furnace 1 is outlined in Fig. 1 in the form of an electric reduction furnace, which encompasses a receiving chamber 2 for molten material (molten metal). The heating of the material to be melted takes place in the known manner via an arc, which is electrically generated between the tips 11 (see Fig. 2) of two electrodes 4 and 5. Furthermore, the furnace 1 is provided with means 6, by means of which the introduction of dust S (in dusty form) is possible. The dust is subjected to a treatment in the furnace so as to be able to recover valuable elements from the dust.

-4 It can be seen from Fig. 2 how these means 6 for introducing dust are embodied according to the invention: Generally, the means 6 for introducing dust S into the receiving chamber 2 comprise a hole 7, which runs at least partially in longitudinal direction (L) of the electrodes 4, 5. In the exemplary embodiment according to Fig. 2, the hole 7 is arranged so as to be eccentric to the longitudinal axis 8 of the electrode 4. This embodiment makes it possible to convey the dust S via a suitable conveyor 9 (see Fig. 1) along the hole 7 in the interior of the electrode 4, 5 and to divert the dust S therefrom close to the tip 11 of the electrode 4, 5. According to the invention, the electrode 4, 5 is thus embodied as a hollow electrode, wherein dust can be conveyed into the melt through the cavity (hole) in the interior of the electrode 4, 5. Provision is made in the exemplary embodiment for coupling holes 10, which together with the hole 7 form a pneumatic and fluidic conveying duct, respectively, for the dust S. In so doing it becomes possible to arbitrarily output the dust at the location of the arc between the electrodes 4, 5 and to thus improve the treatment of the dust S. It goes without saying that instead of providing only one hole 7, provision can be made for several holes, which run parallel to one another. According to the invention, the dust S, which for the most part accumulates in the process chain in response to the production of FeNi, is thus preferably fed directly to the electrode tips through at least one opening in the electrodes of the electric furnace. The agglomeration of the dust accumulating in the revolving cylindrical furnace, which is often typical in the state of the art, into pellets and the refeeding of the pellets is no longer necessary with the proposal according to the invention. The agglomeration and the intermediate storage of the dust are no longer necessary in particular in response to the production of FeNi.

-5 This also has the advantage that disadvantages of the pellet processing cannot occur. This is so because additional dust can be produced in addition to the dust, which adheres to the ore, as a function of the mechanical stability of the pellets. This creates a ballast of dust, which increases the input of the revolving cylindrical furnace without improving the output thereof. A plant-specifically high effort for the transport, the storage and the pelletization of the dust can thus be avoided. An overdimensioning of the revolving cylindrical furnace and of the dust removal plant by means of the ballast of dust circulation can consequently also be avoided. A revolving cylindrical furnace constructed so as to be small furthermore requires a small amount of energy so that the energy input can be reduced by means of the proposal according to the invention. The known effect of a bad flow process of the calcined Ni-ore in the electric reduction furnace, which leads to interferences in response to the energy conversion at the electrodes, that is, to fluctuating production conditions with respect to the quality and quantity of the calcined ore, can also be avoided.

-6 List of Reference Numerals: 1 electric furnace 2 receiving chamber 3 molten material 4 electrode 5 electrode 6 means for introducing dust 7 hole 8 longitudinal axis 9 conveyor for dust 10 coupling hole 11 tip L longitudinal direction S dust

Claims

2. The electric furnace according to claim 1, characterized in that the hole (7) encompasses a circular cross section.
3. The electric furnace according to claim 1 or 2, characterized in that the hole (7) runs concentrically to a longitudinal axis (8) of the electrode (4, 5).
4. The electric furnace according to claim 1 or 2, characterized in that the hole (7) runs eccentrically to a longitudinal axis (8) of the electrode (4, 5).
5. The electric furnace according to one of claims 1 to 4, characterized in that the hole (7) is directly or indirectly connected to a conveyor (9) for dust.
6. The electric furnace according to one of claims 1 to 5, characterized in that the hole (7) is connected with at least one coupling hole (10), which intersects said hole. -2
7. The electric furnace according to claim 6, characterized in that the coupling hole (10) is embodied as a blind hole, which ends in the interior of the electrode (4, 5).
8. The electric furnace according to one of claims 1 to 7, characterized in that the hole (7) or a coupling hole (10) ends close to a tip (11) of the electrode (4, 5).
9. The 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. The electric furnace according to one of claims 1 to 9, characterized in that it is an electric reduction furnace.
11. The electric furnace according to one of claims 1 to 9, characterized in that it is a rotary hearth furnace. 44 083.go.nw SUMMARY The invention relates to an electric furnace (1) comprising a receiving chamber (2) for molten material (3), wherein at least one electrode (4, 5) projects into the receiving chamber (2) and wherein means (6) for introducing dust into the receiving chamber (2) are available. To enable an improved feed of the dust in response to a simple processing of said dust, the invention provides for the means (6) for introducing dust into the receiving chamber (2) to comprise a hole (7), which extends at least partially in longitudinal direction (L) of the electrode (4, 5). (Fig. 2)