MXPA99001781A - Smelting installation with an electric-arc furnace - Google Patents

Abstract

This invention concerns a smelting installation with an electric-arc furnace in which the roof of the oven vessel is constructed out of two units (7, 8) which are separated by an aperture (38) and can be moved independently of one another relative to the vessel horizontally. One of these units (8) consists of a shaft (9) which serves as pre-heater for the charge. The upper part of the vessel and the shaft (9) has a converging wall sector (42a, 58, 59).

Description

FUSING UNIT THAT HAS AN ARC OVEN. The invention relates to a melting unit having an arc furnace, as set forth in the preamble of claim 1. A melting unit of that kind is known from WO 90/10086. In the known fusion unit, an external segment of the chamber lid is replaced by a loading hopper which is fixed to a holding structure and which has in its upper region a loading opening which can be closed, for the material of feed, and an opening for the passage of gases. The gases of the hot furnace are discharged through the loading hopper and, in a heat exchange relationship, heat the material being loaded which is disposed in the loading hopper. This makes it possible to save a substantial amount of energy. In order to carry out the melting process without having to resort to subsequent loading, it is advantageous that the total amount of filler material for the weight of liquid metal to be extracted fit in the total volume that is composed of the furnace and the loading hopper. For that reason, and taking into account the additional requirement of limiting the height of the loading hopper, the cross section of the loading hopper is preferably rectangular and the furnace chamber seen in plan is in the form of an oval defined on one of its sides by a straight line. This makes it necessary to adopt a new camera shape, including the camera chamber below, in comparison with the widely distributed round camera shapes. In the known fusion unit, the whole of the lid of the chamber is movable with respect to the chamber, either together with the supporting structure supporting the loading hopper or independently of it. The removable attachment of the chamber lid to the support structure has proven to be advantageous so that the chamber lid, including the loading hopper, can be rotated or moved linearly with respect to the oven chamber. In the last mentioned design, it is possible to provide a loading of the feed material directed to specific targets in different regions of the furnace chamber, through the loading hopper. In the case of the known fusion unit, there is also the possibility that the material being loaded is retained in the space in the loading hopper by means of retaining elements which are provided in the lower region of the loading hopper of so that after the melting of a charge, during the refining phase, the hot waste gases can be used to preheat the feed material.

In the WO 95/04910 retention elements of that kind are described in detail. In the present application express reference is made to it. DE-A-4332913 discloses a melting unit with an arc furnace, which has a furnace chamber with a lid having first and second lid portions. In each of these lid portions there is a feed opening for loading raw material into the furnace chamber. Above these openings are containers in the form of hoppers to preheat the material to be loaded in the chamber. These are fixed above the arc furnace * on the platform, so that the total weight of the container filled with the feed material is supported by the platform, independent of the chamber. In an alternative embodiment of the mentioned document, the lid of the oven is distributed in the direction of the arms that support the electrodes, and can be moved in independent wings of the upper part of the chamber. By means of this there is the possibility of opening the upper part of the chamber for special purposes or for inspection. There is no joint movement of the container placed on the oven platform. There is only a single opening of electrodes between the lid halves that move outwards. For this reason, a lateral movement towards the outside of the electrode carrying arm is not possible. This also excludes the loading of feed material into the furnace chamber by means of a scrap cage. The present invention aims at the use of proven and proven technology in existing installations. The existing arc furnaces can be converted with a minimum level of cost in such a way that as many components as possible of the existing installation can still be used, and also the building where the fusion unit is located does not have to be substantially altered With respect to this there is the following particular problem ": in the case of conventional arc furnaces with a round or also oval chamber, in which the electrodes are arranged in the center of the chamber lid, a loading hopper which is used as a preheater of the face material and which is to be arranged next to the electrodes as the external segment of the chamber lid, particularly taking into account the height of the building, it has such restricted space requirements that it is not possible provide sufficient volume in the loading hopper for the load material to be heated.The furnace chamber may be composed of a single part or it may be divided above the slag line in a lower chamber (bottom portion) of the chamber) and an upper chamber (top portion of the chamber) The oven lid is generally of domed configuration and has three pastry media for the electrode (s). or (three-phase furnace) in concentric arrangement or a means of passage (dc furnace) centrally located, such means of passage called opening or openings for electrodes. PRESENTATION OF THE INVENTION The object of the present invention is to design a fusion unit of the type established in the exordium of claim 1, so that as many components as possible of the existing arc furnaces can be used, that is to say that a number Minimum of components must be replaced or modified. In the case of an arc furnace with a lower portion of the chamber where the electrodes are arranged concentrically in the region of the center, the invention seeks to provide that, under the conditions of space limitation due to the configuration of the electrodes and the height of the building, there is a volume in the loading hopper for the material to be heated that is sufficient to be able to carry out the fusion process without having to resort, as far as possible, to an operation of rear loading. The retaining elements provided in the loading hopper to retain the loading material must be adapted to the particular factors involved.

The invention further seeks to ensure that the solution according to the invention can prevent the emission of gases from the furnace in the region of the lid. In order to provide a suitable volume for the loading material to be preheated in the loading hopper disposed laterally next to the electrodes in the chamber lid, the selected cross section for the loading hopper is of such a dimension that in a plan view the internal contour of the wall of the loading hopper which is the rear wall of the loading hopper as viewed from the openings for the electrodes, at least of the upper portion of the loading hopper, it is outside the internal contour of the upper edge of the lower portion of the chamber. Preferably, the transverse profile of the loading hopper in that portion is rectangular in shape or is of a configuration that follows a trapezoidal line. The configuration according to the invention of the sector of the upper portion of the chamber in the area below the loading hopper, namely the design configuration of the upper portion of the chamber with a wall sector converging from its upper edge up to its lower edge, it forms a transition from the walls of the loading hopper located outside the internal contour of the lower portion of the chamber to the internal contour of the upper edge of the lower portion of the chamber, i.e. the hearth of the furnace; said transition guides without any hindrance the loading material from the external regions of the loading hopper to the lower portion of the chamber. The transition from a shape of the loading hopper which is rectangular in profile to a round or oval oven chamber can be produced in various ways, for example by means of cross-sections rectangular-oval-round or rectangular-polygonal-round. The converging wall sector, as well as the other sectors of the upper portion of the chamber, is usually formed by wall panels which, when the feed material is loaded through the loading hopper, lead it to the lower portion of the wall. the chamber (furnace hearth) which is of round or oval cross section. The transition from the internal contour of the walls of the loading hopper, which seen in plan is located outside the internal contour of the upper edge of the lower portion of the chamber, to the upper edge of the lower round or oval portion of the chamber. chamber, can be started already above the upper edge of the upper portion of the chamber, ie above the edge of the chamber, considering that here the walls of the loading hopper that are distant from the electrode openings are guided in an inclined manner and inward toward the center of the chamber (camera axis) or the upper edge of the upper portion of the chamber. Such a configuration can be provided in the lower portion of the loading hopper either by means of an oval-shaped converging wall portion or by means of planar elements forming the transition for the wall of the loading hopper which is distant from the electrodes, from a profile that is linear in a horizontal section and up to a polygonal profile, preferably a profile that follows a trapezoidal line. Preferably the lower edge of the walls of the loading hopper that are distant from the electrodes has approximately the same internal contour as the internal contour of the upper edge of the chamber. This contour then also corresponds to the contour of the second portion of the lid, on which the loading hopper is arranged. In the melting unit according to the invention, the entire furnace substructure, including the lower portion of the chamber and the arrangement for raising and turning the electrodes, can still be used in the case of a conversion. If the convergent transition from a rectangular cross section to the round cross section of the chamber starts already in an upper portion of the loading hopper, for example just below the upper opening of the loading hopper, then, as seen from the electrodes, the front wall of the loading hopper must be arranged so that it extends parallel to the rear wall of the hopper of load, so that the internal cross section of the loading hopper does not decrease in the downward direction. If, therefore, the linear cross-sectional profile of the rear wall of a loading hopper which is rectangular in its upper portion is converted into a polygonal profile, preferably in a profile that follows a trapezoidal line, then in a parallel manner, which also it is necessary to pair the front wall of the loading hopper, the linear profile of the front wall of the loading hopper will be converted into the polygonal profile in question, in a configuration that converges towards the center of the chamber, of the same way. The transversal profile in the lower portion of the loading hopper is then formed by two parallel trapezoidal or polygonal lines which are connected by the profiles of the side walls. If in the lower portion of the loading hopper the rear wall of the loading hopper and the adjacent side walls of the loading hopper are formed by a wall sector converging towards the upper edge of a round or oval chamber, then in a conversion operation is even possible to continue using the existing round or oval upper portion of the chamber. That solution is of particular significance in relation to an arc furnace with a domed lid and a loading hopper with retaining elements. According to another aspect of the present invention, the first portion of the lid having the electrode opening and the second portion of the lid having the loading hopper are presented in the form of units which are divided among themselves by means of a separation in the lid and that can move horizontally with respect to the camera independently of each other. In this case, there are parts of the old lid that can still be used if the conversion occurs. If necessary, the separation that occurs in the lid by virtue of division into two reciprocally independent units that can rotate or move horizontally with respect to the chamber can be sealed in a simple manner so that there is no risk of environmental contamination due to the Exhaust gas from the oven, compared to a lid composed of a single unit. That transition zone from a rectangular contour to a round contour is taken into account, by virtue of a particular configuration and arrangement of the retaining elements. BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in greater detail by means of four embodiments with reference to ten schematic drawing figures in which: Figure 1 is a side view of a fusing unit according to the invention, with the lid of the chamber closed, Figure 2 shows the unit of Figure 1 where the second portion of the lid including the loading hopper has Figure 3 is a plan view of the fusing unit with section III-III of the loading hopper, as shown in Figure 2, and with the first portion of the lid in the outwardly turned position, with an oval-shaped transition form going from a rectangular cross-section of the loading hopper to a lower round portion of the chamber, Figure 4 shows section IV-IV of Figure 3 with the lid of the chamber closed, that is, with the first portion of the cover turned inward, including the electrodes, and the second portion of the cover moved inwardly, Figure 5 shows in enlarged scale a part of the view shown in Figure 4, the Figure 6 is a view corresponding to Figure 3, of a second embodiment in which the transition from the rectangular cross section of the loading hopper to a round chamber of the furnace starts at the lower portion of the loading hopper below the retaining elements and has a configuration polygonal, Figure 7 is a view corresponding to Figure 6, of a third embodiment in which the transition from the rectangular cross section of the loading hopper to a round chamber of the furnace begins already in the upper portion of the hopper of loading above the retaining elements, Figure 8 is a view of this embodiment, corresponding to Figure 4, Figure 9 shows the substantial part of section IX-IX of Figure 8, and Figure 10 is a view, corresponding to Figure 8, of a modification of the third embodiment with a round upper portion of the chamber that does not have a converging wall sector. WAYS OF IMPLEMENTING THE INVENTION The melting unit illustrated in Figures 1 to 5 as the first embodiment includes an arc furnace 1 comprising a furnace chamber, 3, mounted on a furnace base, 2, and a furnace lid. the domed chamber-like chamber 4 covering the upper edge of the furnace chamber, 3. The furnace chamber, 3, comprises a lower portion 5 of the chamber forming the hearth of the furnace to receive the molten material, and a portion upper 6 of the chamber that is usually formed by water-cooled elements. As can be seen in particular in Figures 3 to 5, the lid 4 of the chamber comprises a first portion 7 of the lid shown in Figure 3 in its outwardly rotated position, and a second portion 8 of the lid that is formed substantially by the lower end portion of a loading hopper 9 or by a frame 10 accommodating the lower portion of the loading hopper 9 (Figures 1 and 2). In Figure 1 the lid of two parts of the chamber is closed, in Figure 2 the second portion of the lid including the loading hopper 9 is extended. As shown in particular in Figures 3 to 5, the part shown in the drawings to the right of the center of the oven chamber corresponds to a conventional arc furnace with a round oven chamber and electrodes 12 which can be moved towards inside the oven chamber concentrically to the center 11 of the chamber (central axis of the chamber, see figures 3 and 4). Only the region illustrated in the drawings to the left of the electrodes 12 is modified above the lower portion of the chamber, compared to the usual configuration of an arc furnace with a round-shaped chamber. The first portion 7 of the lid is of domed configuration and has a portion 13 called the heart or core of the cover with electrode openings 14 (Figure 5) for three arc electrodes 12 to be introduced into the chamber, in the arrangement triangular pattern of a three-phase arc furnace. The electrodes 12 are mounted on electrode carrying arms 15 and can be raised / lowered and turned sideways by means of an arrangement for raising and turning electrodes 16. The first portion 7 of the cover can be raised by means of a provision for raising and turning the lid 17 and can be raised from the position shown in Figures 4 and 5 in which said portion is at the edge of the chamber, and can be turned to the side to the position shown in Figure 3 to open the oven chamber, for example to load baskets from above. A suitable arrangement for raising and turning the lid is described, for example, in EP-O 203 339. In the illustrated embodiment, not only the furnace chamber 3 but also the arrangement for raising and turning the lid 17 and the The arrangement for raising and turning the electrodes 16 are mounted on the base of the oven 2, so that the oven chamber can be tilted together with the electrodes. In order that the arrangement of the electrodes does not have to be modified in a conversion operation, the design according to the first embodiment provides the first portion of the oval-shaped lid 19 which is defined by a string 18 and includes the usual configuration of the electrodes. When the first portion of the lid is mounted on the oven chamber, the string 18 must be located in the direction of the inclination, ie perpendicular to the plane of the paper in the view shown in Figure 2. In this way the camera of the furnace can be inclined for the emptying operation or for the removal operation of the slag, with the portion 7 of the lid in closed position and without displacement of the portion 8 of the lid. In this situation the loading hopper 9 only has to be lifted slightly. In this way the heat losses due to radiation are reduced or the hot gases from the furnace pass mostly to the loading hopper for preheating. Possibly, the separation that occurs when the loading hopper 9 is lifted between the lower edge of the loading hopper or the second portion 8 of the lid and the edge of the chamber (39 in Figure 5) can be sealed by of a socket or other means that are mounted in the loading hopper or on the edge of the chamber. The loading hopper 9 is fixed to a reinforced structure 20 which can enclose the loading hopper 9 in the form of a cage; the frame 10 illustrated in Figures 1 and 2, of the second portion 8 of the lid, represents a part of the reinforced structure. The reinforced structure 20 which is illustrated only schematically in the Figures as a support for the loading hopper 9, is mounted on a supporting structure 21 in such a way that the reinforced structure 20 can be lifted and lowered together with the loading hopper by means of of a lifting device 22. To this end, in the transverse beam elements 23 of the reinforced structure, coupling places have been provided for the lifting devices 22 which are supported on the supporting structure 21, so that the beam element 2 and with it the reinforced structure 20 that supports the loading hopper can be lifted and removed from the lower position shown in Figure 2. In this situation, the required guiding effect is provided by the guide bars 25. holding structure 21 with loading hopper 9 can be moved horizontally. For this purpose, rails 27 are implemented on a support structure 26, and the support structure 21 is provided with wheels 28 that allow the movement of the support structure 21 in the horizontal direction. The loading hopper 9 is closed on its upper part by means of a lid of the loading hopper 29 which, in the illustrated embodiment, can be moved horizontally on the rails 30, in order to open the upper opening of the loading hopper for load, by means of a crane 31 (Figure 4). On the side which is the rear side in Figure 1, the lid of the loading hopper 29, whose configuration is of the cap or hemispherical type, has an opening for the passage of gases 32 connected to a waste gas conduit. 33 when the loading hopper 9 and with it the frame 10 are in the position shown in Figure 1. Figure 3 shows that the cross section of the loading hopper 9 is of transverse configuration. Preferably, the loading hopper is rectangular in its lower region when the assembly has retaining elements for retaining the feeding material, as described in greater detail below. Accordingly, the loading hopper 9 has walls which are configured with a rectangular shape at least in its lower region, with a front wall of the loading hopper 34 which is adjacent to the rope 18 of the first portion 7 of the lid when the lid of the chamber is closed (Figure 1, Figure 4 and Figure 5), a rear wall of the loading hopper 35 which is distant from the rope 18, and two side walls of the loading hopper, 36 and 37, which connect those walls. In this arrangement, the front wall 34 of the loading hopper has approximately the same length as the rope 18, that is to say that the wall 34 of the loading hopper is adjacent to the rope 18, with a narrow gap 38 in the lid. The separation of the lid is shown in enlarged scale in Figure 5. It should be noted at this point that, in the case of a dome-shaped chamber lid, as shown in Figures 4 and 5, the string seen in FIG. The plan is only a straight line, but a line that follows the profile section of the dome, and thus the lower edge of the front wall 34 of the loading hopper also has the same shape.

When the lid of the chamber is closed, that is to say in the condition shown in figures 1, 4 and 5, the external contour of the lid of the chamber is formed by the lower edge of the rear wall of the loading hopper 35, the lower edge of the two adjacent side walls of the loading hopper, 36 and 37, and the oval part 19, adjacent thereto, of the first portion 7 of the lid. The upper edge of the chamber 39, that is to say the upper edge of the upper portion 6 of the chamber, is adapted to that contour. The outline of the upper edge 39 of the chamber then corresponds in this embodiment to an oval defined by a straight line or a low arch 40, and with rounded edges 41. The transition from the sector of the edge of the chamber defined by the line straight 40 and the adjacent portions of the oval, up to the respective sector of the round cross section of the lower portion of the chamber, is formed by a converging wall sector 42 of the upper portion 6 of the chamber (see Figure 3). As already mentioned and shown in Figure 5, the first portion 7 of the lid is divided from the second portion 8 of the lid by a partition 38 extending parallel to the rope 18 so that the oven chamber can be inclined in this direction that is determined by the base of the furnace, in which a drain hole 43 and a working opening 44 are arranged, as seen from the center 11 of the chamber, without this being prevented by the adjacent front wall 34 of the loading hopper 9. When the second portion 8 of the lid, and with it the loading hopper 9, is fixed to a support structure supported on the support structure 26, ie not on the base of the furnace, that part of the lid can not also perform the tilting movement. However, it is sufficient that the lower edge of the loading hopper is slightly raised and separated from the upper edge 39 of the chamber to allow slight tilting movements of the oven chamber with the first portion of the lid located thereon and with the electrodes retracted. In order to prevent furnace gases from escaping through the gap 38 between the two lid portions, in accordance with an innovation of the invention means are provided for sealing the lid on at least one of the mutually adjacent edges. and 46 of the first and second portions of the lid, respectively. Such sealing means are described below. One of these means causes a sealing gas 47 to be blown into the separation 38. For this purpose, a conduit 48 with an opening has been implemented along the edge 46, ie in the front wall 34 of the loading hopper. Slot-like nozzle type pointing towards the separation of the cover 38, or a row of holes. In the illustrated embodiment, the duct is formed by a hollow bar element 49 which is fixed to the front wall 34 of the loading hopper. The nozzle-like opening is arranged on the underside of the hollow bar element and is identified by the reference number 50. Another means that can be additionally used is that provided on the edge 45 of the first portion of the lid, an arrangement of tape type 51 which is formed by cooling tubes and which, when the lid is closed, engages play with a groove 52. In the present case, the groove 52 is formed by the bottom side of the hollow bar element 49, together with an oblique tape-type obturator element 53 provided in the hollow bar element 49. Preferably, the loading hopper 9 is provided with retention elements 54 (fingers) for the loading material). The retaining elements described in WO 95/04910 are particularly suitable for that purpose. However depending on the respective contour of the upper edge of the chamber 39, 40 and 41 and the configuration of the convergent wall sector 42, these retaining elements need to have a special configuration and arrangement.

In the first embodiment with a transition from a rectangular cross-section of the loading hopper to the round section of the lower portion of the chamber by means of an oval, the converging wall sector 42 of the upper portion of the chamber means that they present other requirements with respect to guiding the loading material with a pivoting movement of the fingers towards the opening position. The angle of rotation of the external fingers is limited. As an adaptation to the shape of the wall sector 42 of the upper portion 6 of the chamber, the configuration has, in addition to the pivoting fingers 54, fingers 55 which serve as deflectors. The pivoting fingers 54 are arranged parallel to each other and spaced apart from one another (see Figure 3) and are mounted on supports 56 disposed in the reinforced structure 20 on the rear wall of the loading hopper 35. The pivoting fingers 54 can to be pivoted down from the closed position, which is shown in full line in Figure 5 and in which the internal portions of the fingers project into the internal space of the loading hopper and prevent the loading material from passing through it, to an opening position shown in dotted line in the Fugra 5 and in which the inner portions of the fingers point downwards and allow the loading material to pass through the loading hopper. The pivoting fingers 54 are also inclined downwards at an angle of approximately 20 * with respect to the horizontal, in the closed position. The other fingers 55 which are in the form of fixed fingers are elastically mounted in the reinforced structure adjacent to the side walls of the loading hopper, 36 and 37, and project through the side walls of the loading hopper, 36. and 37, towards the interior of the loading hopper, those fingers being also arranged with a spacing between one and the other. The ends 56 of the fixed fingers are adjacent to the two external pivoting fingers 54 when the latter are in the closed position (full line in Figure 5). In this way, in the lower region of the loading hopper, a retaining element is formed for the loading material, which extends over the entire cross section of the loading hopper and which allows the hot gases from the oven to pass through. the column of charge material retained in the loading hopper, so as to heat the column of loading material. When the pivoting fingers 54 are pivoted together downwardly from the closed position shown in full line in Figure 5, to the open position illustrated by the dotted line, the material falling downwards is guided by both the pivoting fingers 54. as by the fixed fingers 55 towards the center, that is towards the lower round portion of the chamber, so that the wall sector 43 of the upper portion of the chamber is protected from an excessively large load. In the second embodiment illustrated in Figure 6, the transition from a rectangular cross section of the loading hopper 9 to the round cross section of the lower portion 5 of the chamber is formed by means of a polygonal cross section which follows in this example a trapezoidal line. In addition, the transition is already begun above the upper edge 39 of the upper portion of the chamber, since in the lower portion of the loading hopper below the retaining elements 54 the corners between the walls 35 and 36 and 35 and 37 of the loading hopper are of such a configuration that they converge towards the center of the chamber. The converging wall sections of the loading hopper are identified by references 58 and 59. They are flat surfaces that convert the cross section into a transverse profile of the walls 36, 35 and 37, profile that follows a trapezoidal line and which is then reflected in the profile of the upper edge 39 of the chamber by straight portions 40a and 41a. The other transition, from the outline of the upper edge 39 of the upper portion of the chamber to the round cross-section d the lower portion of the chamber, a transition following a trapezoidal line in the region below the loading hopper 9, is formed by of a convergent wall sector 42a. With the transition shape shown in Figure 6, it is possible to omit the fingers 55 of the first embodiment, which serve as deflectors. However, the fingers 5 which are disposed above the sectors 58 and 59 of the wall of the loading hopper can not be pivoted downwards as far as the central fingers do. In Figure 6 the open position of the fingers 54 is illustrated in full lines and the closed position in dotted lines. It will be seen that in the example in question, three fingers that are respectively adjacent to each of the walls 36 and 37 of the loading hopper and for which the maximum open position is illustrated, can not be pivoted down as far as they do. the middle fingers. This presupposes the individual activation of the pivoting movement of those fingers, while the central fingers can be pivoted together. In the second embodiment, the transition from the rectangular cross section to the round cross section has already begun in the lower portion of the loading hopper below the retaining elements, although the wall 34 adjacent to the electrode openings has not changed in comparison with the first embodiment. However, the direct passage cross section of the loading hopper in the lower region of the loading hopper does not undergo any reduction, at least appreciable, if the chamber lid is domed and the lower edge of the wall 34 of the loading hopper follows the contour of that vaulted form. In the embodiment illustrated in Figures 7 to 9, the transition from a rectangular cross section to the round cross section occurs already in an upper portion of the loading hopper - as shown in Figure 8, immediately below the upper opening of the loading hopper - although also in this case, as in the second embodiment, the wall 35 of the loading hopper, which is the rear wall as seen from the electrodes, is converted into a contour following a trapezoidal line. So that the cross section of the loading hopper is not reduced in the downward direction - it should rather be increased in its dimensions in order to allow unimpeded emptying - the third embodiment also makes it possible for the wall 34 of the hopper of The load, which is the front wall as viewed from the electrode openings, is of such a configuration that it converges towards the center of the chamber, more specifically parallel to the rear wall 35 of the loading hopper. The convergent portions of the rear wall of the loading hopper are indicated by means of references 60 and 61 and those of the front wall of the loading hopper are indicated by references 62 and 63.

As in this embodiment the transition is started already above the fingers 54, the fingers are arranged in a plane in which the contour of the rear wall 35 of the loading hopper as well as the outline of the front wall 34 of the hopper of load follow a trapezoidal line. To correspond to that cross-section, the horizontal frame element of the reinforced structure 20, which is adjacent to the rear wall 35 of the loading hopper and in which the rotating supports 56 of the pivoting fingers 54 are arranged, is also arranged parallel to the trapezoidal line contour of the rear wall 35 of the loading hopper. In comparison with the second embodiment, all fingers can be opened in equal measure, as in the first embodiment. The open position of the fingers 54 is shown in Figures 7 and 9 in full lines, while the closed position is illustrated respectively with dotted lines. As to avoid a narrowing in the cross-section of direct passage the front wall of the loading hopper is also of convergent configuration downwards, so that in a plan view the contour of the lower edge of the front wall 34 of the hopper of load follows a trapezoidal line, the adjacent edge (rope 18a) of the first portion 7 of the lid has the same contour. In this way, with the two portions 7 and 8 of the lid in the rotated and retracted position towards "in as shown in figure 9, the separation between those two portions of the lid is throughout its length as narrow as in the previous embodiments Figure 10 represents a modification of the third embodiment In this case, with the conversion it is possible to even continue to use the existing round or oval upper portion of the chamber In the embodiment shown in Figure 10 the rear wall 35 of the loading hopper converges below the fingers 54 to the round transverse profile of the upper edge of the upper portion 6 of the chamber of a round or oval oven chamber.In other respects, the embodiment of Figure 10 corresponds to The third embodiment The desirable configurations are a domed lid which prevents the internal cross section of the loading hopper from being reduced in the lower region, and the fingers pivots 54 which, when rotated downward, guide the loading material towards the center of the chamber and protect the upper edge of the chamber from the feeding material falling downwards.

Claims (24)

1. CLAIMS 1.- A melting unit having an arc furnace which includes: a furnace chamber comprising a lower portion of the chamber and an upper portion of the chamber and a chamber lid comprising a first and second portions of which the first portion of the lid includes at least one opening for electrodes, the second portion of the lid includes a loading hopper fixed in a holding structure with a lockable loading opening and an opening for the passage of gases in the upper region of the loading hopper, for preheating the feed material to be loaded in the furnace chamber; in addition, the holding structure and the chamber can move horizontally with respect to one another characterized in that, in a hopper, in which part of the internal contour of the upper edge of the lower part of the chamber, a vertical projection remains, because the upper part of the chamber presents in the area below the hopper and / or the electrode openings, seen from the rear wall of the hopper a wall sector converging to the center of the chamber; characterized in that, in a hopper, in which a part of the internal contour of the upper edge of the lower part of the chamber, remains in a vertical projection, because the upper part of the chamber presents in the area below the hopper and / or from the electrode openings, seen from the rear wall of the hopper, a wall section that converges to the center of the chamber.
2. 2. Fusion unit according to claim 1, characterized in that the first and second portions of the lid are presented in the form of units that are divided one from the other by a separation of the lid and that can be moved horizontally with respect to the chamber. independently of one another.
3. 3. A fusion unit according to claim 1 or the re-identification 2, characterized in that the first portion of the lid can be lifted / lowered and rotated outward and to the side by means of an arrangement for lifting and turning the top.
4. 4. A fusion unit according to claim 3, characterized in that an arrangement for the elevation and rotation of the electrodes can be rotated outwards together with the arrangement for lifting and turning the lid.
5. 5. A fusion unit according to any of claims 1 to 4, characterized in that the second portion of the lid can be lifted / lowered together with the loading hopper in the support structure and the support structure can be moved horizontally.
6. 6. A fusion unit according to any of claims 1 to 5, characterized in that the support structure can move perpendicularly to the separation of the lid.
7. 7. - A unit of fusion according to any of claims 1 to 6, characterized in that means are provided for sealing the separation of the lid on at least one of the two mutually adjacent edges of the first and second portions of the lid .
8. 8. A melting unit according to claim 7, characterized in that on one of the two mutually adjacent edges of the first and second portions of the lid a groove extending along the edge is provided; and on the other of the edges there is provided a tape element extending along the edge and engaging with play to the groove when the cover is closed.
9. 9. A melting unit according to claim 7 or claim 8, characterized in that at least one of the two mutually adjacent edges of the first and second portions of the lid is a duct extending along the length of the edge, with at least one nozzle-like opening pointing towards the separation of the lid and through which a gas can be insufflated in the separation of the lid.
10. 10. A fusion unit according to claim 9, characterized in that a nozzle-like opening is provided which extends along the edge.
11. 11. A fusion unit conformed to claim 9, characterized in that a row of holes extending along the edge is provided as the nozzle-like opening.
12. 12. - A melting unit according to any of claims 2 to 11, characterized in that the wall of the loading hopper, which is the rear wall of the loading hopper as seen from the electrode openings, has a sector of wall that converges towards the upper edge of the lower portion of the chamber.
13. 13. - A fusion unit according to any of claims 1 to 12, characterized in that the first portion of the lid is presented, seen in plan, in the form of an oval delimited by a rope and the contour of the lower edge of the wall of the loading hopper, which is the front wall of the loading hopper as seen from the electrode openings, is adapted to the contour of the rope.
14. 14. A fusion unit according to any of claims 1 to 13, characterized in that the profile the lower edge of the wall of the loading hopper, which is the rear wall of the loading hopper as seen from the openings for electrodes, and the adjacent side walls correspond in the region of the second portion of the lid to the profile of the upper edge of the chamber.
15. 15. A fusion unit according to any of claims 1 to 14, characterized in that the transverse profile is rectangular in the upper portion of the loading hopper and the profile of the wall of the loading hopper, which is the rear wall of the loading hopper as seen from the electrode openings, and the adjacent side walls of the loading hopper, converge downward by means of an oval profile to the round profile of the upper edge of the lower portion of the chamber or of the upper portion of the chamber.
16. 16. A melting unit according to any of claims 1 to 14, characterized in that the transverse profile is rectangular in the upper portion of the loading hopper and the profile of the wall of the loading hopper which is the rear wall of the loading hopper. the loading hopper as seen from the electrode openings and the adjacent side walls of the loading hopper, converge downwards by means of a polygonal profile to the round profile of the upper edge of the lower portion of the chamber or the upper portion of the camera.
17. 17. - A fusion unit according to claim 16, characterized in that the polygonal profile is a profile that follows a trapezoidal line.
18. 18. - A fusion unit according to any of claims 1 to 17, characterized in that the wall of the loading hopper, which is the front wall of the loading hopper as viewed from the electrode openings converges extending in relation to parallel to the rear wall of the loading hopper.
19. 19. - A fusion unit according to any of claims 1 to 18, characterized in that in its lower region the loading hopper has retaining elements for the feed material to be heated, retaining elements that are movable from a closed position in which the passage of the gas through them is possible but is blocked by the loading material, to an open position in which the retaining elements also release the passage of the feed material through the loading hopper.
20. 20. A fusion unit according to claim 19, characterized in that the retaining elements include fingers that are arranged parallel to each other and with a spacing between one and the other and that are mounted on rotating supports and that can be pivoted towards down from a closed position in which the inner portions of the fingers project towards the interior of the loading hopper to block the passage of the loading material therethrough, to an open position in which the portions of the fingers They point downwards and release the loading material so that it passes through the loading hopper.
21. 21. A fusion unit according to claim 20, characterized in that the rotating supports for the pivoting fingers are arranged in the reinforced structure in the rear wall of the loading hopper and the fixed fingers project towards the inside of the loading hopper from the adjacent side walls of the loading hopper, the ends of the fixed fingers being disposed adjacent the two external pivoting fingers when the latter are in the closed position.
22. 22. A fusion unit according to claim 21, characterized in that the internal portions of the pivoting fingers are inclined obliquely downwards in the closed position, and the internal ends of the fixed fingers that are located towards the pivoting fingers. they are approximately at the same inclination of the two external pivoting fingers in the closed position.
23. 23. Fusion unit according to claim 20, characterized in that, by means of an individual control of the pivoting movement of the external fingers adjacent to the side walls of the hopper, these can not be moved as much downwards as the intermediate fingers. who are among them, move together.
24. 24.- Fusing unit according to claim 20, characterized in that, in a hopper, in which the rear wall viewed from the electrode openings, and the side walls to the hopper, converge from top to bottom by means of a line trapezoidal profile from an oval profile to a round profile, which runs on the horizontal beams of the frame of construction limited by the rear walls of the hopper with the pivot supports for the pivoting fingers parallel to the outline of the trapezoidal line of the rear wall of the hopper. SUMMARY In a melting unit having an arc furnace, the lid of the furnace chamber is formed by two units (7, 8) which are divided by a gap (38) of the lid and which can be moved horizontally with respect to the chamber independently of one another, and of which the unit (8) includes a loading hopper (9) that serves as a preheater for the loading material. The upper portion of the chamber and the loading hopper (9) have a converging wall sector (42a, 58, 59). (Figure 6)