EP0126328A2 - Arc smelt furnace charging process and device for carrying it out - Google Patents

Abstract

In order to protect those wall areas which are especially subjected to radiant heat within the arc smelt furnace, the fluxes are, according to the method, fed into the arc smelt furnace spatially separated from the other charging materials, specifically at the wall areas nearest to the electrodes within the furnace. For this purpose, the charging device is provided internally with at least two chambers, each of which has an upper opening for charging the chamber and a lower closable opening for emptying the chamber. <IMAGE>

Description

The invention relates to a method for charging arc melting furnaces, in which the iron-containing feed material, e.g. Iron ore or pieces of metal in the form of scrap, pellets or the like by means of a loading device together with the usual pourable additives, e.g. Lime to which the melting furnace is fed. The invention further relates to a loading device for performing this method.

The areas in the ring wall part of the interior of arc melting furnaces that are particularly exposed to temperature, primarily in the melting phase, include those areas that are closest to the electrodes on the side and which are accordingly most strongly exposed to the radiation emitted by the electrodes. In the preferred arrangement of three electrodes in practice, these are the three wall areas, the so-called "hot spots", which are distributed inside the furnace at a distance of 120 ° around the circumference of the furnace wall. Since the furnace wall in these areas is subjected to greater wear and tear than in the other areas, the life of the furnace until it is relined largely determined by the condition of these areas.

In order to keep the damage to the "hot spots" as low as possible and thus to increase the service life of the melting furnace, it is already known to protect these wall areas by means of the feed material which is fed to the melting furnace and which goes down there. In this regard, in DE-AS 21 19 692 proposed to install electromagnets in the areas of the "hot spots" on the outer wall of the arc melting furnace which partially and temporarily hold the descending iron-containing and thus magnetic charging material on the inside of the furnace wall. The "hot spots" can be largely protected from damage as a result; the corresponding device, however, is so complex in terms of its construction and mode of operation that there is practically no economic application.

With regard to the protection of the inner wall surface of arc melting furnaces from the high thermal stress due to radiation, a charging device has already been used, with which pourable additives, such as lime, are fed to the furnace wall inside the melting furnace simultaneously with the charging material, but spatially separated from the charging material will. The loading device consists of a cylindrical container, the bottom closure of which consists of conically moving plates or lamellae. This so-called lamella scrap basket is surrounded by an additional annular outer jacket which, together with the outer wall of the container, forms an annular chamber which runs around the outside of the container. While the container is being filled with the iron-containing feed material, the annular chamber receives most of the pourable aggregates. At the lower end of the annular chamber there are a plurality of outwardly leading openings distributed over the circumference, which are released when this charging device is emptied by lifting the outer jacket in the axial direction. In this way, the pourable aggregates are placed in a ring near the wall inside the furnace.

This loading device is also very complex in terms of its structural design and, in particular with regard to the proposed opening and closing mechanism of the annular chamber, is very fragile during its operation. Although the charging device is usually inserted into the opened melting furnace when charging electric arc furnaces by means of lamella scrap baskets, in many cases such a fitting or retrofitting of a lamellar scrap basket with an annular outer chamber is only possible if the diameter is additional of the scrap basket is chosen to be sufficiently small compared to the diameter of the arc melting furnace.

In particular, however, it is not possible to additionally equip a loading device in which the bottom closure consists of two gripper-shaped pivotable half-shells, a so-called shell scrap basket, with such an outer annular chamber. If arc melting furnaces are not completely emptied after the melting process for metallurgical reasons and accordingly, shell scrap baskets are preferably used to feed these furnaces, it is therefore not possible in these cases to pass the inner wall of the melting furnaces with the aid of the additives before the high thermal stress Protect radiation.

The invention is essentially based on the object of providing a method and a charging device for carrying out the method, which make it possible to protect the wall areas in the interior of an arc melting furnace which are particularly exposed to radiation, and which, in particular, also because of the predetermined mode of operation of the melting furnace With the help of a tray scrap basket.

This task is first of all achieved with the aid of the method mentioned at the outset in that the predominant part of the additives, which is spatially separated from the feed material, is delayed in time and is only supplied to the wall areas closest to the electrodes in the interior of the melting furnace.

As a result, the additives are concentrated according to the invention on the most heavily used wall areas and thus offer the greatest protection. However, this concentration of the additives on only a few wall areas inside the melting furnace means that the method can be carried out with the aid of a very simple charging device in terms of its construction.

The loading device from which the invention is based for carrying out the method according to the invention has a cylindrical container which is open at the top and a bottom closure at its opposite end. According to the invention, it is characterized in that at least two axially extending chambers are arranged on the wall of the inside of the cylindrical container on the wall corresponding to the number of electrodes of the arc melting furnace, with an upper opening for filling the chambers with the additives and with one lower closable opening for emptying the chambers. Since these chambers are provided according to the invention only in those areas in the cylindrical container which correspond to the wall areas closest to the electrodes in the interior of the arc melting furnace when charging the arc melting furnace, charging devices known per se can also be equipped with these chambers in a simple manner . This is preferably done by welding the chambers onto the inner wall the loading device. The cross section of the chambers can be, for example, circular, rectangular or preferably a circular section. Part of the wall of each chamber can preferably be formed by the wall of the loading device.

With such a loading device according to the invention, the additives can in particular also emerge from the chambers with a time delay, i.e. if the majority of the arc furnace, i.e. e.g. 2/3 to 3/4 of the feed material is filled. This on the one hand prevents the additives from reaching the furnace floor and, on the other hand, enables the wall areas of the inner furnace wall, which are particularly exposed to heat, to be protected by the additives.

Advantageously, there is no need for a separate opening and closing mechanism at the lower opening for emptying the chambers, for example by means of a flap, which is complicated in terms of equipment and susceptible to faults, in that, according to the invention, the walls forming the chambers extend beyond the lower edge of the cylindrical container of the loading device are extended down to the bottom lock. Furthermore, all chambers are thus advantageously combined with only a single closure, i.e. through the bottom lock of the loading device, opened and closed.

A shell scrap basket according to the invention is additionally characterized in that in at least one of its two half-shells beneath those chambers which are not completely released by the shells when the basket is opened, additional blind openings are provided, which are designed with the shell closed hold back the feed material and the aggregates can fall vertically downwards when the half-shells are open. It is only in this way that it is possible for the particularly hot areas of the wall ("hot spots") inside an arc melting furnace to be protected with a shell scrap basket by means of the additives even when the furnace is being charged.

A charging device according to the invention, which is particularly suitable for charging two arc melting furnaces arranged in mirror image to one another, each with three electrodes, is characterized in that the chambers for the additives in the interior of the cylindrical container of the charging device at a distance of 60 ° on the circumference of the cylindrical container are arranged distributed. In this case, four of these chambers can form two double chambers, which are arranged opposite one another. This arrangement is preferably selected when the walls of the chambers lying towards the inside of the charging device are flat sheets according to the invention.

In addition, it is a further operational and constructive advantage if pouring chutes are provided in the lower part of the chambers, by means of which the wall areas of the arc melting furnace to be protected are protected, in particular with a structurally simple design and arrangement of the chambers within the cylindrical container. e.g. if the cross section of the chambers is a circular section (segment), can be poured more precisely.

In the following, the invention is explained in more detail using exemplary embodiments in the case of shell scrap baskets.

• Fig. 1a eine schematische Draufsicht-Darstellung eines Lichtbogen-Schmelzofens mit drei eingesetzten Elektroden,
• Fig. 1b eine schematische Querschnittsdarstellung einer erfindungsgemäß ausgebildeten Beschickungsvorrichtung,
• Fig. 1c eine Umrißdarstellung der einen Halb-Schale des Bodenverschlusses eines Schalen-Schrottkorbs von unten gesehen mit einem Merkmal der Erfindung,
• Fig. 1d eine schematische Seitenansicht eines Schalen-Schrottkorbs,
• Fig. 1e eine schematische Längsschnittdarstellung des Schalen-Schrottkorbs gemäß Fig. 1d längs der Schnittebene e-e in Fig. 1b mit Merkmalen der Erfindung,
• Fig. 2a eine schematische Draufsicht-Darstellung zweier spiegelsymmetrisch zueinander angeordneter Lichtbogen-Schmelzöfen mit je drei eingesetzten Elektroden,
• Fig. 2b eine schematische Querschnittsdarstellung einer erfindungsgemäß ausgebildeten Beschickungsvorrichtung,
• Fig. 2c eine Schemadarstellung zweier geschlossener Halb- Schalen des Bodenverschlusses mit Merkmalen der Erfindung,
• Fig. 2d eine Längsschnittdarstellung von erfindungsgemäßen Schüttöffnungen in den Halb-Schalen gemäß dem Schnitt f-f in Fig. 2c,
• Fig. 3a eine vergrößerte Längsschnittdarstellung eines erfindungsgemäß ausgebildeten Schalen-Schrottkorbs längs der Schnittebene a-a in Fig. 2b und
• Fig. 3b einen Schnitt gemäß Fig. 3a jedoch entlang der Schnittebene b-b in Fig. 2b.

It shows:

• 1a is a schematic top view of an arc melting furnace with three electrodes inserted,
• 1b is a schematic cross-sectional view of a loading device designed according to the invention,
• 1c is an outline view of a half-shell of the bottom closure of a shell scrap basket seen from below with a feature of the invention,
• 1d is a schematic side view of a shell scrap basket,
• 1e is a schematic longitudinal sectional view of the shell scrap basket according to FIG. 1d along the sectional plane ee in FIG. 1b with features of the invention,
• 2a shows a schematic top view of two arc melting furnaces arranged with mirror symmetry to one another, each with three electrodes inserted,
• 2b is a schematic cross-sectional representation of a loading device designed according to the invention,
• 2c is a schematic representation of two closed half-shells of the bottom closure with features of the invention,
• 2d is a longitudinal sectional view of pouring openings according to the invention in the half-shells according to the section ff in Fig. 2c,
• Fig. 3a is an enlarged longitudinal sectional view of a shell scrap basket designed according to the invention along the section plane aa in Fig. 2b and
• 3b shows a section according to FIG. 3a but along the section plane bb in FIG. 2b.

An arc melting furnace shown schematically in FIG. 1 a is equipped within its furnace wall 4 with three electrodes 2 a - c, which are connected to a supply unit 3 for electrical energy.

During operation of the arc melting furnace, in particular in the melting phase, the wall regions 5a-c of the furnace wall 4 which are closest to the side of the melting electrodes in the furnace are most exposed to the heat radiation from the electrodes and correspond to the so-called "hot spots" ".

For charging the arc melting furnace 1, the electrodes 2a-c are moved out and pivoted laterally, so that a charging device 6 can be placed in or on the arc melting furnace, which can pivot a cylindrical container 7 and a bottom closure 8, for example in the form of two grippers Has half-shells 15. These half-shells 15 can be folded up sideways as shown in FIG. 1d - as shown in dashed lines, half-shells (15 ') - and open the lower opening 16 of the cylindrical container 7 for emptying the feed material located in the shell scrap basket into the open interior. However, due to the design of the swivel mechanism for the half-shells 15 and (15 '), areas 16 "remain incompletely open on both sides.

In the interior 12 of the charging device 6, three chambers 9, 9 'are arranged at a distance of 120 ° around the circumference on the inside of the cylindrical container 7, which extend in the direction of the longitudinal axis of the container 7 and in Fig. 1b from its top and in Fig. 1e are shown in partial longitudinal section. While the wall of the cylindrical container 7 forms the outer boundary of the chambers 9, 9 ', they are delimited on the inside by walls 14.

These chambers 9, 9 'are filled with flowable or pourable additives such as e.g. Lime, dolomite etc. filled and emptied through the lower opening 11 into the arc melting furnace 1 together with the scrap or iron-containing feed material when the half-shells 15 are swung open. According to the invention, the walls of the chambers 9, 9 'are extended at their lower opening 11 below the lower edge 13 of the cylindrical container 7 up to the half-shells 15 (FIG. 1e). In addition to the advantages already mentioned, the additives are largely separated from the iron-containing feed material.

When the half-shells 15 (FIG. 1d) are swung open, the two chambers 9, but not also the chamber 9 'located in the region 16 "which is not fully released, is completely open. The chamber 9' located in the region 16" is empty The associated half-shell 15 according to FIG. 1c is provided with a pouring opening 17 designed in the manner of a blind, the blind-type guide plates 21 of which are designed in the manner of a blind (Fig. 2d) prevent the feed material from falling through when the bottom closure 8 is closed, but in the open position of the half-shells 15 the contents of the partially covered chambers 9 'flow out vertically downwards.

According to FIG. 1b, the chambers 9, 9 "are distributed at a distance of 120 ° around the circumference of the wall of the cylindrical container 7, ie at the locations in the interior 12 of the cylindrical container 7, which cover the areas 5a-c of the" hot spots "correspond, so that the additives are always introduced into these areas in the melting furnace.

To use a charging device 6 together for two arc melting furnaces 1 'arranged in mirror symmetry and connected to supply units 3' for electrical energy, each with three electrodes 2a '- c' (FIGS. 2a and 2b), there are six in each case inside 12 of cylindrical container 7 Chambers 9, 9 'are provided, preferably by means of flat plates welded to the inside of the cylindrical container 7 as inner walls 14. By additionally welded plates 18, two opposing double chambers are formed by four of these chambers (FIGS. 2b and 3a).

In this chamber arrangement, the chambers 9, 9 'or the lower openings 11 of these chambers are distributed over the circumference of the cylindrical container 7 at 60 ° intervals. Depending on which of the two arc melting furnaces 1 'is to be charged, however, only those three chambers are filled which are each assigned to the areas 5a-c., Ie the "hot spots" of the respective melting furnace. A correspondingly symmetrical emptying option To ensure that the partially concealed areas 16 ″ of the charging device 6 are provided with a pouring opening 17 in each of the half-shells 15. The chambers 9 have outward-pointing pouring chutes 19 in the region of their lower opening 11, while the chambers 9 ¹ with are directed towards the center of the chute 20.

When charging the arc melting furnace 1 'on the left in FIG. 2a, those three chambers 9, 9' are each filled with additives (in FIG. 2b, the chutes 19, 20 of these chambers are shown hatched) which correspond to the electrode arrangement of this arc melting furnace correspond. When charging the right-hand arc melting furnace 1 'in FIG. 2a, the three other chambers 9, 9' shown in FIG. 2b are filled with additives.

The time required for this use of the charging device 6 in the half-shells 15 _'louvre-like design pouring opening 17 is corresp. Fig. 2c twice, that is provided in each half-shell 15. As a result of the blind-like grating of these pouring openings 17, passage of the iron-containing feed material in the closed state of the trays is prevented according to FIG. 2d.

The enlarged sectional views Fig. 3a and 3b show the arrangement of the chambers 9, 9 'and in particular their chutes 19 and 20 of a shell scrap basket that can be set up on a standing ring profile 22, the extensions extending to the bottom closure 8 of the shell scrap basket 23 of the chamber walls are illustrated.

Claims (10)

1. A method for charging electric arc furnaces, in which the iron-containing feed material is fed by means of a feed device together with the usual pourable additives / the melting furnace, characterized in that the predominant part of the additives separated from the feed material delays in time and specifically only the inside the melting furnace is supplied to the electrodes closest to the wall areas. 2. Feeding device for performing the method according to claim 1, which consists of an open-topped cylindrical container (7) and at its opposite end (16) from a bottom closure (8), characterized in that inside (12) of the cylindrical container the wall of which, according to the number of electrodes of the arc melting furnace (1), has at least two chambers (9, 9 ') distributed around the circumference, with an upper opening (10) for filling the chambers with the additives and with a lower closable opening (11) for emptying the chambers. 3. Feeding device according to claim 2, characterized in that the chambers (9, 9 ') in the interior (12) of the cylindrical container (7) are arranged in those areas which when charging the arc The melting furnace (1) corresponds to the wall regions (5a, b, c) closest to the electrodes (2a, b, c or 2a ', b ^l , c') in the interior of the melting furnace (1). 4. Feeding device according to claim 1 or 2, characterized in that the chambers (9, 9 ¹ ) forming walls over the lower edge (13) of the cylindrical container (7) also vertically downwards to the bottom closure (8) of the loading device are extended. 5. Feeding device according to one of claims 2 to 4, wherein the bottom closure consists of two gripper-shaped pivotable shells halves (15) which incompletely release the lower opening of the cylindrical container (7) in the open state, characterized in that in at least one the half-shells (15) underneath each chamber (9 ¹ ), which are not fully released by the half-shells, there are also blind openings (17) designed to hold the loading material when the half-shells are closed and through the opened ones Half-shells the aggregates fall down vertically. 6. Feeding device according to one of claims 2 to 5, characterized in that for an arc melting furnace (1) with three electrodes (2a - c or 2a '- c') the chambers (9, 9 ') inside the cylindrical Container (7) are arranged at a distance of 120 ° distributed over its circumference. 7. Feeding device according to one of claims 2 to 5, characterized in that for two mirror-symmetrical arranged arc melting furnaces (1 '), each with three electrodes (2a' - c '), the chambers (9, 9 ^1st ) inside the cylindrical container (7) are arranged at a distance of 60 ° around its circumference. 8. Loading device according to one of claims 2 to 7, characterized in that the inside (12) of the cylindrical container (7) lying walls (14) of the chambers (9, 9 ¹ ) are flat sheets. 9. Feeding device according to claim 8, characterized in that in the lower part of the chambers (9, 9 ') pouring chutes (19, 20) are provided. 10. Feeding device according to one of claims 2 to 9, characterized in that the upper opening (10) of the chambers (9, 9 ') is covered with a grating which prevents the entry of the iron-containing feed material into the chambers.

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