MXPA99008793A - Method to load scrap for electric arc furnace and relative system - Google Patents

Abstract

Method to load scrap for electric arc furnace including at least a roof (13) associated with movable moving means (17) cooperating with second movable moving means (24), the roof (13) including at least a hole (15) to discharge the fumes (16), the scrap (22) being contained in baskets (21), there being included at least a system to process the fumes (32) connected with the chimney, the full basket (21) including at least a first position (21a) to pre-heat the scrap arranged at the side of and in proximity to the furnace (10) and a second position (21b) to unload the scrap arranged in cooperation with the mouth of the furnace (10), the movable moving means (24) of the basket (21) and the movable moving means (17) of the roof (13) being functionally associated at least momentarily, the basket (21) containing the scrap being installed in a removable manner on the second movable moving means (24) and being associated at least temporally with a covering system (29), which can be translated from a closed position to an open position, the fumes (16) leaving the fourth hole (15) of the furnace (10) being sent inside the basket (21) containing the scrap (22) through a discharge duct which connects an inlet aperture (27) included on the covering system (29) with the fourth hole of the furnace (13), the fumes (16) being made to leave the basket (21) through an outlet aperture cooperating with the bottom of the basket (21) and directly connected with a combustion chamber (28), the roof (13) passing from its first closed position (13a) to its second open position (13b) in coordination with the passage of the basket (21) from its first pre-heating position (21a) to its second unloading position (21b).

Description

METHOD FOR LOADING SCRAP FOR AN ELECTRIC ARC OVEN AND RELATIVE SYSTEM FIELD OF THE INVENTION This invention relates to a system for loading scrap through baskets for an electric steel furnace, and also the relative system, as set forth in the respective main claims. The invention is applied in the field of steel production in order to load, through baskets, the electric furnaces with scrap, which is pre-heated through the fumes coming from said electric ovens. The electric arc furnaces to which the invention is applied can be of the type fed by alternating or direct current. The invention makes it possible to reduce the times needed to open the oven vault in order to load the oven, thus limiting the heat losses from the interior of the oven. Furthermore, the invention makes it possible to load the furnace with scrap, which has been heated in the same moving basket used to discharge the scrap in the furnace. Additionally, the invention makes it possible to simplify and automate all the movements necessary to load, to reduce the cycle times, and to minimize the required spaces and the equipment used.

STATE OF THE ART The state of the art includes electric arc furnaces used to produce steel from scrap and regenerated material of various types. In the state of the art, the furnaces can be loaded continuously, for example, through conveying means such as a band, connected to the interior of the furnace and fed continuously with fresh scrap, which gradually replaces the one already loaded in the furnace . In another solution, the ovens are loaded discontinuously through baskets or containers. The baskets, in one or more successive steps, are loaded in the scrap loading area and then transported, by means of lifting and moving means, in correspondence with the mouth of the furnace, which is open. The bottom of the basket is then opened and the material is discharged into the oven. For this purpose, the baskets are equipped at the bottom with movable doors, valves, teeth, sliding grilles or other suitable opening system. The systems that use baskets to load the oven, which are known in the state of the art, have a plurality of disadvantages. * First, it takes a long time to open the oven, which causes a considerable loss of heat from the inside of the oven to the outside, and also the leak to the surrounding environment of fumes containing powders, incandescent particles and other contaminants. A further disadvantage is that if the scrap is charged cold in the furnace, the melt takes longer and this causes problems for the penetration of the electrodes. At present, in some steel plants, the furnaces are loaded with scrap, which is pre-heated by the heat of the fumes discharged from the same furnace through the fourth hole on the vault. WO 92/10594 discloses a method and an installation for producing steel by melting scrap, wherein the scrap is preheated in a basket by the fumes coming from an electric arc furnace having a shell downward as a vault. The fumes leave the furnace through the vault and are conducted through ducts to a combustion chamber before being introduced into the basket by means of its removable vault. The basket is placed in a removable form on a movement mechanism to be moved or rotated from a first preheat position to a second discharge position. The furnace vault can be rotated through a second movement mechanism from a closed position to an open position. The installation described in this document has the disadvantage that the oven vault must be completely open before the basket, which contains the scrap, is moved in its unloading position. This causes the furnace to remain open for a long period, causing a large amount of smoke to leave the furnace and diffuse into the surrounding environment, with considerable contamination and heat loss. The loading systems known in the state of the art, where the scrap is pre-heated, use cargo baskets located in the appropriate rooms where the fumes are transported before they are purified and discharged by the appropriate plants. There are also known solutions in the state of the art, which include a single room containing several cargo baskets, or several rooms connected to each other, each of which contains a single loading basket. These systems cause problems in the structuring of the rooms, the movements of the baskets and also the wear of the baskets. Furthermore, in the case of baskets heated inside the room, the scrap loses some of the heat that it has accumulated, both when it is removed from the room and when it is transported near the mouth of the oven and also when it is discharged to the oven, where, always and in any case, there is a considerable loss of heat. Furthermore, the scrap is not uniformly heated from one basket to another.

These systems are also not very functional, are too expensive, and occupy a large space inside the plant. Other disadvantages of this type of loading system are that it is necessary to limit the use of hoisting cranes for the basket for the step of loading the scrap, that is, to the melting cycles of the furnace; therefore, it is possible to use cranes for other purposes required by the steel plant. A further disadvantage is that the pre-heating rooms are normally located in positions that are not very close to the oven, and, therefore, the times necessary to transport the baskets from this position towards the oven are very long and the losses of heat are very high. There are also other systems known in the state of the art, which load the furnace with stable containers, which can be moved only from a heating position to one where they load the furnace, in which case the containers are loaded with either conveyor belts or with baskets. EP-A-O.225.939 teaches heating the scrap with the fumes coming out of the furnace and then discharging the scrap in the furnace. The scrap is heated from top to bottom in a fixed, vertical container and the fumes also overlap the lower opening means of the container. According to this document, it is necessary to move the furnace, with all the problems of movement and placement that this produces. If, on the one hand, this teaching has the advantage that the scrap is heated in a differentiated manner from the top down, on the other hand, it is complex, annoying, considerably difficult to manipulate, place and center, and presents considerable problems of maintenance and handling; In addition, the system involves the transfer of the scrap from the baskets to the fixed, vertical container, which causes vertical space problems. In addition, this system does not allow the baskets to be used directly for the purpose of pre-heating the scrap, since they are used exclusively to transport and unload the scrap to the fixed, vertical container. This leads to an increase in the number of parts of the plant and, therefore, to higher handling and maintenance costs.

The pre-heating of the scrap from above has the advantage that it allows the aforementioned vertical fixed container to be easily emptied as it reduces the risks of adhesion or clogging, due to the fact that the scrap does not reach excessively high temperatures at the level of the valve bars. In addition, a high temperature in the upper part of the scrap facilitates the penetration of the electrodes during the first melting step inside the furnace. The patent of E.U.A. 4,506,370 teaches enclosing the furnace inside a closed box type structure equipped with two doors, one used to discharge the molten metal contained in the furnace into the ladle, and the other to allow the entry and exit of a container for the pre-heating of the scrap, which moves on rails. A disadvantage of this embodiment is that the mobile preheating container is part of an individual structure with the movement trailer; this means that, in order to load the container outside the box-like structure, suitable loading baskets are used which are moved through bridge cranes or conveyor belts, but the same basket that arrives from the storage area of Scrap can not be used to load the oven. This creates problems regarding the movement, replacement and exchange of the baskets. Another disadvantage is that fumes are released within the box type structure, which escape from the furnace when the container is in the loading position outside the box type structure. As a result, every time the aforementioned doors are opened, large quantities of fumes, dust, incandescent particles and other material can possibly escape from the box-like structure., and consequently cause contamination problems to the environment where the oven is installed. In addition, the box type structure is filled with hot fumes and this makes it difficult for workers to access. In this embodiment, as in EP-A-0 225 939, there is the advantage that the scrap is heated from the top down, even if, in this case, the scrap located in the lower part of the container is not directly overlapped by the fumes. Actually, fumes escape from the container on the sides, and not in the background; therefore, the scrap loaded at the bottom of the basket is heated very little, and in any case not in a uniform manner, compared to the scrap that is higher up in the container. In addition, the inclusion of a side hole for the exit of the smoke causes a consumption, which is not uniform and which can cause zones of different temperatures inside the basket, and consequently the scrap is not pre-heated in a homogeneous way. Additionally, using a box type structure equipped with entry / exit doors and suitable for closing the oven, the cargo container and the smoke conduits, causes extremely high costs and volume. WO 96/32616 teaches heating the scrap in a vertical moving container, which is solid with a moving structure, the scrap being heated from the bottom upwards. This document does not provide the aforementioned advantages over the heating of the scrap from above to the bottom; nor is it possible, with this invention, to use the baskets directly since the scrap must be transferred to the container with the consequent problems of vertical space. There is no possibility of acting directly with autonomous baskets, nor is it easy to carry out maintenance operations. The preheating of the bottom can create problems of overheating in the opening means located on the bottom of the containers, and also the risk of adhesion and clogging in the lower part of the scrap, which, due to the high temperatures, it takes an almost plastic state. In addition, this system also has the disadvantage that it is necessary to load the containers from above through bridge cranes, and this system covers a considerable amount of vertical space, which may not be compatible with the characteristics of the plant where the oven is going to be installed. In addition, the loading system that incorporates containers involves major operational difficulties, safety problems, movement problems, increases in cycle times and a number of other operating disadvantages. A further disadvantage is that there are long downtimes necessary to load the fixed pre-heating structure; These downtimes prevent a greater saving of energy, which can be obtained by exploiting as much as possible the passage of hot fumes through scrap. In this system, moreover, there is no system to derive the ducts connecting the discharge hole, or fourth hole, from the furnace to the vertical container, which could make it possible, at least while the vertical container is being loaded, to transport the fumes that come out of the furnace directly to the plants that purify the fumes and discharge them into the atmosphere. Consequently, every time the vertical container is loaded, fumes, powders, incandescent particles necessarily escape into the environment, where the oven is installed, with the result of contamination problems. Applicants hereby have designed, tested and modalized this invention to overcome the disadvantages of the state of the art and obtain additional advantages.

DESCRIPTION OF THE INVENTION The invention is set forth and characterized in the respective main claims, while the dependent claims describe variants of the idea of the main mode. The purpose of the invention is to obtain a method for loading pre-heated scrap for electric arc furnaces, and also the relative system, which will provide a plurality of operating and handling advantages in the melting cycle of an electric arc furnace . A first advantage of the invention is that it reduces the times and spaces required, both in height and in the horizontal plane, for loading the oven through the baskets. A second advantage is that it efficiently loads the pre-heated scrap in the furnace, thus reducing the time needed to melt it, obtaining great energy savings and reducing the problems related to the penetration of the electrodes, particularly during the initial steps of the melting cycle . Another advantage is that it reduces to a minimum the time during which the oven remains open, and in this way reduces the heat loss from it. furnace to the external environment and also the gas emissions through the open vault. Yet another advantage with this invention is that, although it does not use fixed containers placed above the baskets, but always the same removable and interchangeable baskets, both to load the scrap in the storage of scrap metal, and to load scrap directly into the storage station. pre-heating and also to discharge towards the furnace, it is not necessary to raise the monorails of the bridge cranes to excessive levels. This means that a much smaller vertical space is occupied, movements and equipment are simplified and the costs of installation and civil engineering are reduced. In addition, it is easier to carry out maintenance and replacement operations on the baskets. A further advantage is that there is a reduction in the equipment required to move the baskets and the furnace vault, which makes it possible to use the cranes or auxiliary devices when they are out of other work within the plant. The use of cranes or other devices is not restricted by the melting cycle of the furnace. Yet another advantage of the invention is that the scrap is heated from the top down, and this facilitates the start of the melting process and the penetration of the electrodes. Another advantage of the invention is that as the fumes come from the bottom of the basket, they uniformly heat all the scrap contained therein, and are furthermore taken in a uniform and homogeneous manner. It is another advantage of the invention that a reduced number of baskets can be used. Another advantage is that there is an increase in the pre-heating time of the scrap, with a consequently greater reuse of energy. In addition, the invention makes it possible to reduce pollution problems in the environment where the furnace is installed by reducing the dispersion of fumes, powders and incandescent particles during loading operations. The invention also ensures that the entire process is extremely flexible, very reliable, and that it is possible to derive the baskets and, therefore, the pre-heating cycle must exist at any particular requirement for the loading of the scrap or for the process.

The invention uses containment baskets, which are equipped at the bottom with movable means, which can be opened momentarily to discharge the scrap from the bottom. According to the invention, the basket at a time, already loaded with scrap as it arrives loaded with scrap storage or loaded directly when it is already in the pre-heating station, is placed in a removable manner in cooperation with the means of moving bodies placed near the furnace and cooperating with the plane on which the mouth of the furnace lies. The mobile movement means allow the loaded basket to take a first position, arranged on the side and very close to the oven, where the scrap is pre-heated; a second position, which cooperates with the mouth of the furnace, where the scrap is discharged; and a third position, which advantageously coincides with the pre-heating position, where the basket is replaced.

With the system according to the invention, therefore, the same basket loaded with the scrap is directly used to pre-heat the scrap; this makes it possible to reduce the amount of equipment in the plant and thus reduce costs. According to a variant of the invention, the movable movement means comprise a first element associated with the basket and a second element associated with the vault of the oven, the two elements being able to be temporarily connected mechanically, electrically or magnetically. This solution makes it possible to associate the movements of the basket towards / away from the oven in a functional way; and the opening / closing movements of the furnace mouth according to the steps of the scrap loading cycle. The two elements of the mobile movement means can be independent of each other, so that it is possible to perform the maintenance, replacement of parts, special works or for traditional processes of loading of scrap metal. Each basket, at least in its pre-heating position, cooperates temporarily with a moving cover system, which has a first closed position cooperating with the mouth of the basket and a second opening position, where it is released from the mouth of the basket. The second opening position is taken by the cover system at least during operations to replace or load the basket. According to a variant, the side walls and the bottom of the basket cooperate with cooling systems associated with the basket. According to the invention, the basket cooperates at least in its first preheating position with means for transporting the fumes from the fourth hole of the oven towards the interior of the basket. The fumes are transported inside the basket in order to overlap the scrap contained therein from top to bottom.

The fumes in this way overlap the scrap in the upper part of the basket and then gradually extend to overlap the scrap below. In this way, the scrap which is then discharged forms a stack in the furnace, where the temperature in the upper part is higher. This facilitates the penetration of the electrodes towards the scrap, and also the formation and extension of the electric arc; this causes a reduction in the melting times and also of the electrical disturbances in the supply line. In one embodiment of the invention, the inlet opening for the fumes towards the basket is made in the mobile cover system. According to a variant, the inlet opening for the fumes is made in the side wall of the basket, advantageously in the upper part. In a first embodiment of the invention, the outlet opening for the fumes from the basket, through which the fumes, after passing through the basket, are sent to the treatment systems and the chimney, is obtained through of at least one annular duct made on the perimeter at the bottom of the basket, substantially in cooperation with the bottom. The annular duct is connected to the interior of the basket through a plurality of holes, or slots, in the side wall of the basket. According to a variant, the basket does not have any specific opening for the exit of the fumes; the fumes, after overlapping the scrap from the top down, are brought from the inside of the basket by means of a discharge duct disposed below the basket, which can be temporarily associated with the bottom of the basket when the basket is in its first preheat position. According to a variant, the discharge duct is cooled or made of a refractory material. This variant guarantees that all the scrap contained in the basket is heated in a homogeneous way, and that the fumes are carried and discharged in a homogeneous way, too. According to a variant, the ducts for introducing the fumes into the basket and unloading them from the basket consist of one or more mobile elements, flexible or telescopic, which can be extended, contracted or placed by themselves when the basket is placed and moved towards and away from the oven. The ducts for introducing / discharging the fumes to and away from the basket also include interception means, which can be activated momentarily in order to interrupt the flow, for example, during movement, replacement or loading of the basket, and invert the fumes towards the processing systems and the chimney. The unloading cycle of the scrap to the kiln includes the movement of the whole basket containing the pre-heated scrap through the mobile moving means and the coordinated translation of the oven vault in order to open the oven's mouth.

The entire basket immediately covers the mouth of the oven, avoiding both heat losses from the inside of the oven as well as environmental pollution caused by the escape of smoke, dust, incandescent particles and others. Then, the media at the bottom of the basket is opened to discharge the scrap; Subsequently, with a reverse translation movement of the moving movement means, the empty basket is brought back to its original position and the oven vault is brought back to close the oven. In this position, the empty basket can be replaced, through a crane, by a new full basket that arrives from the scrap loading area. The baskets can then be loaded directly into the storage of scrap and subsequently transported and placed near the furnace in a desired resting zone. The operations of replacing the baskets are, therefore, extremely fast but, above all, the loading of the baskets does not constitute a restriction for the furnace work cycles. According to a variant, when the empty basket is in the first position, it is loaded with new scrap, for example, through a scrap carrier, which has its outlet end cooperating with the mouth of the basket. According to a variant, the scrap carrier has at its end means for distributing the discharged scrap, of the magnetic or mechanical type.

When the basket has been replaced or loaded, the mobile cover system is replaced and the fumes are again transported inside the basket to preheat the scrap to the next loading step of the oven. In accordance with the invention, all operations to move the basket, such as loading, replacement, scrap discharge into the furnace, etc., are automatically handled by a data processing unit.

ILLUSTRATION OF THE DRAWINGS The attached drawings are presented as a non-restrictive example and show some preferred embodiments of the invention as follows: Figures 1a, 1b and 1c show in diagram form three steps of operation of the method according to the invention in a first embodiment; Figure 2 shows a subsequent operation step of the invention according to the embodiment of Figures 1a, 1b and 1c; Figure 3 shows a top view of the electric oven system adopting the method according to the invention; Figure 4 shows a view in part of Figure 3 during the operation step when the basket is in the position to preheat the scrap; Figure 5 shows a side view of Figure 4; Figure 6 shows a variant of Figure 5; Figure 7 shows a view in part of Figure 3 during the operation step when the basket is in a position to discharge the scrap; Figure 8 shows a side view of Figure 7; Figure 9 shows a view in part of Figure 3 during the operation step when the basket has returned to the pre-heating position and the oven vault remains laterally offset with respect to the oven; and Figure 10 shows a side view of Figure 9.

DESCRIPTION OF THE DRAWINGS The electric arc furnace 10, shown diagrammatically in the figures, is fed by direct current and has an individual electrode 11; The following description, however, is also valid for electric furnaces operating with alternating current. The furnace 10 comprises a shell 12, closed at the top through a dome 13, which has a central hole 14 for housing the electrode 11 and a hole 15 arranged on the side, or fourth hole, for discharging the fumes 16 A dome 13 is associated with its own mobile movement means 17, in this case of the type that includes a trailer equipped with wheels 18, which can be moved on a monorail 19. The dome 13 can have at least two positions a along the monorail 19, respectively a first position 13a for closing the oven 10 and a second open position 13b. In this case, the monorail 19 consists of guides 34 arranged substantially in cooperation with the plane on which the mouth of the furnace 10 lies. In the monorail 19 there are also second movable movement means 24 with which the basket 21 containing the scrap 22 that will be discharged to the oven 10 is momentarily associated and in a removable manner. When the second moving moving means 24 are activated, the loaded basket 21 is able to take at least two positions; a first position 21a near the furnace 10 in order to preheat the scrap, and a second position 21b disposed above the mouth of the furnace 10 for the purpose of discharging the scrap. In the first pre-heating position 21a, the basket 21 cooperates in the upper part with an air-tight cover system 29, which can be temporarily associated with the mouth of the basket 21. In the first position 21a, the scrap 22 it is pre-heated before being discharged to the oven; when the entire discharge cycle has been completed, after moving the cover system 29 to a non-contact position 29a, with a rotational movement about a vertical axis and also, possibly, with a vertical movement, from the position 21a, the empty basket 21 is replaced by a new full basket 121 which arrives from the scrap loading zone, or the same basket remains in the pre-heating position and is loaded with new scrap. In this case, the first and second moving means of movement, 17 and 124, can be associated with each other through connection means 23, which momentarily restrict them is their "translation movements along the monorail 19 and coordinate the movements of the basket 21 towards and away from the furnace 10 and the displacement of the dome 13 towards / from its open / closed position In this case, the connecting means 23 are of the mechanical type.

Since these movements are coordinated, the translation of the first mobile movement means 17, since they take the vault 13 from its first position 13a towards its second open position 13b, causes the coordinated translation of the second moving means of movement 24 to carry the basket 21 from its first pre-heating position 21a to its second position 21b, where the scrap is discharged to the furnace. Once the scrap has been discharged, to replace the vault 13 in its closed position 13b, it is necessary to replace the empty basket in position 21a in order to replace it with a full basket 121. According to a variant, in this position 21a, the empty basket is loaded with new scrap.

The close proximity of the first preheating position 21a of the basket 21 to the oven 10 means that the opening times of the mouth of the oven 10 are kept to a minimum since, when the dome 13 is brought to the open position 13b, the basket 21 immediately occupies the position previously occupied by the vault 13 and thus is the basket 21 that closes the mouth of the furnace 10. The heat loss from the interior of the furnace 10 during the discharge of the scrap, and also the environmental pollution caused Because of the fumes and dust, they are reduced to a minimum. In the case shown in Figures 1a-1c and 2, each basket 21 has a first opening 27 for the fumes to enter to transport the fumes leaving the oven 10 inside the basket 21 from above to the bottom of the basket 21. In the solutions shown here, the opening 27 through which the fumes enter, is placed in correspondence with the cover system 29. According to a variant, which is not shown here, the opening 27 is placed in correspondence with the wall side of the basket 21 in its upper part. In this case, the inlet opening 27 for the fumes is connected to the fourth hole 15 of the furnace 10 through a first cooled pipe 30a equipped with its own interception means.

The exit opening for the fumes is located in correspondence with the bottom of the basket 21, and is connected to a cooled or refractory pipe 30c, equipped with interception means 33c, through which the pre-heating fumes 16 are transported to a combustion chamber 28 and thence to the treatment systems 32 and the chimney through a pipe 31. The combustion chamber is equipped, at least in its upper part, with burners 41. The combustion chamber 28 can to be directly connected to the fourth hole 15 of the oven, during those steps when the scrap is not pre-heated, through a cooled or refractory duct 30b equipped with interception means 33b. The duct 30b is connected to the fourth hole 15 through fast attachment / separation means 35. With the basket 21 in the pre-heating position 21a (Figures 1a and 3), the interception means 33a are opened and the fumes 16 leaving the oven 10 are transported inside the basket 21 from above through the inlet opening 27 for the fumes, which is placed on the cover system 29. The fumes 16 overlap the scrap 22 from above to the bottom, causing a maximum pre-heating temperature in correspondence with the upper part of the scrap 22; this temperature gradually decreases towards the bottom of the basket 21.

In this way, when the scrap 22 is discharged into the furnace , the stack that is formed is hotter and facilitates the penetration of the electrode 11 and the generation of the electric arc; consequently, the beginning of the fusion process is facilitated and the distortions in the feeding line are reduced. The fumes 16 exit the basket 21 through the bottom and, according to a variant, this can be achieved through a smoke inlet ring 30d, which includes the smoke flow 16 to submerge a substantially cyclonic development within the basket 21 before the fumes are discharged to the combustion chamber 28. This makes the consumption of smoke uniform and prevents the formation of zones with different temperatures inside the basket. According to the variant shown in Figure 6, after the fumes have passed through the basket 21, these are discharged through a discharge duct 130c, cooled or made of refractory material, from the basket 21 and can be associated at least momentarily with their bottom 25. according to this variant, the discharge duct 130c cooperates with a connecting ring 38 associated with the movement means 20 to temporarily secure, when the basket 21 is in the pre-heating position 21a, the air tight connection between the bottom 25 of the basket 21 and the discharge duct 130c. In this case, the part of the duct 130a associated with the bottom 25 of the basket 21 is equipped with its own cooling system, which allows the temperature of the fumes to be further reduced before they reach the purification plants and are expelled. to the atmosphere. The part of the duct 130c associated with the bottom 25 of the basket 21 is furthermore equipped at the top with an inspection door 230c, which allows any precipitate of particles or slag contained in the fumes to be discharged. This mode allows fumes to pass in the basket to overlap the scrap located very low; this gives a more homogeneous distribution of temperatures in the scrap and, therefore, a greater operation in the part of the furnace. When the scrap 22 is discharged to the furnace, the dome 13 and the basket 21 together, with their respective moving means 17 and 24 constrained by the connecting means 32, moves in the direction 36 in order to bring the basket 21 through above the mouth of the oven 10 (Figures 1b, 7 and 8). At least the discharge duct 31 is of a flexible or telescopic type and extends (Figure 7) to assist the translation movement of the basket 21-vault 13. When the discharge is complete, through the opening of the movable valves 26, which constitute the bottom of the basket 21, a reverse translation is made in the direction 37 to bring the dome 13 back to the closed position 13a and the empty basket 21 to the replacement position 21a (Figures 1c, 9 and 10) During this step, the intercepting means 33a and the interception means 33c are closed and the interception means 33b are opened, in order to transport the fumes 16 from the fourth hole .15 directly to the combustion chamber 28, the discharge duct 31 and to the processing system 32 through the duct 30b. During the melting cycle inside oven 10, the empty basket 21 is removed by means of movement 24. The empty basket 21 is arranged on a first handling trailer 39 and is replaced by a full basket 121, arranged on a second handling trailer 40 arriving from the filling zone. When the filled basket 121 has replaced the empty basket 21, the cover system 29 is again brought to the closed position, thus allowing the preheating cycle to start again.

According to a variant, which is not shown here, the empty basket 21, in position 21a, is loaded with scrap through a scrap-carrying band, which has the terminal end arranged in cooperation with the mouth of the basket 21 in the position 21a. The basket 21 is then filled with scrap without the need to be moved by the movement means 24. According to another variant, the carrier band has a rotating distributor element, which regulates and makes uniform the distribution of the scrap inside the basket 21. In this case, upon releasing the connecting means 23 and the joining / separating means 35 between the fourth hole 15 and the duct 30b, the movement means 17 and 24 become independent of each other (Figure 2). This allows the dome 13 and the basket 21 to be placed in respective positions 13b and 21a, for example, for maintenance work on the shell 12 or even, if necessary, to load the furnace 10 with conventional systems.

Claims (13)

1. - A method for loading scrap (22) to an electric arc furnace (10) having a shell (12) and an upper vault (13) moving between a first closed position (13a) and a second open position (13b) ), wherein the vault (13) has a hole (15) for the exit of the fumes (16) produced in the furnace (10), where the scrap (22) is contained in a basket (21) equipped with means lower discharge (26) to discharge the scrap (22) from the bottom (25) and with an upper cover system (29), wherein the basket (21) can be moved between a first pre-heating position (21a) ) adjacent to the furnace (10) to pre-heat the scrap (22) and a second position (21b) above the furnace (10) to discharge the scrap (22) to the furnace (10), where first means of movement (17) to selectively move the vault (13) of the furnace (10) between the first closed position (13a) to the second open position (13b) and vice versa, where second movement means (24) are provided to move the basket (21) between the first pre-heating position (21a) to the second position (21b) and vice versa, and where a connecting tube (30a) connects the hole (15) of the vault (13) with the basket (21), the method is characterized in that the first movement means (17) and the second movement means (24) are moved together along common linear guide means (34) in such a way that the linear translation of the dome (13) of the furnace (10) is correlated with the linear translation of the basket (21) containing the scrap (22), so that the basket (21) gradually covers the lower shell (12) of the furnace (10) while the vault (13) of the furnace (10) gradually moves from its first closed position (13a) to its second open position (13b), since said top cover system (29) of the basket (21) moves between a closed position associated with the basket mouth (21) and a in open position to load the scrap into the basket (21) or to replace an empty basket with a full basket coming from a scrap loading area, said connecting pipe (30a) connects the hole (15) to the cover system upper (29) when the latter is in its closed position, the connecting tube (30a) keeps the vault (13) connected to the upper cover system (29) of the basket (21) during the movement of the first and second means of movement (17, 24), and the fumes (16) leave the basket (21) through an outlet opening disposed in the bottom of the basket (21) and directly connected to the combustion chamber (28).

2. The method according to claim 1, wherein the basket (21) is removably mounted on the second movement means (24) and can also be moved from the first pre-heating position (21a) to a third replacement position where a new full basket (121) replaces the unloaded basket (21), and wherein the covering system (29) is temporarily released from the basket (21) during the movement of said basket (21) from its first pre-heating position (21a) towards its third replacement position.

3. The method according to claim 1 or 2, wherein at least during the replacement of an empty basket (21), fumes (16) are intercepted and inverted directly to a smoke processing system (32). through the combustion chamber (28).

4. The method according to claim 2, wherein the basket (21), in its third replacement position, is released from the cover system (29), removed from the second movement means (24) and deposited on a first driving trailer (39) located over the entire length, a full basket (121) on a second handling trailer (40) located along the first driving trailer (39) being placed in a removable shape over the second means of movement (24) to assume the first pre-heating position (21a).

5. The method according to any of claims 1 to 3 inclusive, wherein in its third position, the empty basket (21) is loaded with scrap (22) through a scrap carrier.

6. A system for loading scrap (22) to an electric arc furnace (10) having a lower shell (12) and an upper vault (13) that can move between a first closed position (13a) and a second open position (13b), wherein the vault (13) has a hole (15) for the exit of the fumes (16) produced in the oven (10), where the scrap (22) is contained in a basket (21). ) equipped with lower discharge means (26) to discharge the scrap (22) from the bottom (25), wherein the basket (21) can be moved between a first pre-heating position (21a) adjacent to said oven (10) to pre-heat the scrap (22) and a second position (21b) above the furnace (10) to discharge the scrap (22) to the furnace (10), wherein the first moving means (17) are provided to selectively move the vault (13) of the oven (10) from the first closed position (13a) to the second open position (13b) and vice versa, wherein the second means of movement (24) are provided to move the basket (21) from the first pre-heating position (21a) to the second position (21b) and vice versa, and wherein a connecting tube (30a) connects the hole ( 15) of the vault (13) with the basket (21), wherein the connecting means (23) connect the first movement means (17) to the second movement means (24), where guiding means are provided linear (34) to guide both the first movement means (17) and the second movement means (24) along a common rectilinear monorail (19), such that the linear translation of the vault (13) ) of the furnace (10) is correlated with the linear translation of the basket (21) containing the scrap (22), so that the basket (21) is able to gradually cover the lower shell (12) of the furnace (10), while that the vault (13) of the furnace (10) gradually moves from its first closed position (13a) to its second open position (13b), an upper cover system (29) of the basket (21) is associated with the mouth of the basket (21) and can be moved between a closed position and an open position to load the scrap to the basket (21) or to replace an empty basket with a full basket arriving from a scrap loading zone, said connecting tube (30a) connects said hole (15) to the upper cover system (29) when the latter is in the closed position, the connecting tube (30a) ) is able to be maintained connected to the vault (13) and the upper cover system (29) of the basket (21) during the movement of the first and second movement means (17, 24), and the basket (21) it comprises at least one flue opening opening connected to a combustion chamber (28) communicating, through a discharge duct (31), with the system for treating the fumes (32) and with the chimney.

7. The system according to claim 6, wherein the connection means between the first means (17) and the second movement means (24) are mechanical connection means (23).

8. The system according to claim 6, wherein the means of connection between the first means (17) and the second means (24) of movement are electrical or magnetic means.

9. The system according to claim 6, wherein the basket (21) is associated with a rotating and / or vertically movable cover system.

10. The system according to claim 6, which includes a first duct (30a), equipped with first interception means (33a), between the opening (27) for the entry of fumes into the basket (21) and the hole (15) for the exit of the fumes from the oven (10).

11. The system according to claim 6, which includes a second duct (30c), cooled or made of refractory material, equipped with second intercepting means (33c), arranged between the bottom outlet opening of the basket ( 21) and the discharge duct (31).

12. The system according to claim 6, which includes a third duct (30b), cooled or made of refractory material, equipped with interception means (33b), arranged between the discharge duct (31) and the hole (15) for the exit of the fumes from the oven (10)

13. The system according to claim 6, wherein at least the discharge duct (31) is of the type that can be extended or contracted.SUMMARY A method for loading scrap for an electric arc furnace including at least one dome (13) associated with mobile moving means (17) cooperating with second moving means of movement (24), the dome (13) including at least one hole (15) to discharge the fumes (16), the scrap (22) being contained in the baskets (21), there is included at least one system for processing the fumes (32) connected to the chimney, the full basket (21) including at least a first position (21a) for pre-heating the scrap disposed on the side of and near the furnace (10) and a second position (21b) for unloading the scrap disposed in cooperation with the mouth of the furnace (10), the mobile movement means (24) of the basket (21) and the mobile movement means (17) of the dome (13) being functionally associated at least momentarily, the basket (21) containing the scrap which is installed in a removable way over the second half movable movement devices (24) and being associated at least temporarily with a cover system (29), which can be moved from a closed position to an open position, the fumes (16) leave the fourth hole (15) of the oven (10) and are sent inside the basket (21) containing the scrap (22) through a discharge duct, which connects an entrance opening (27) included in the cover system (29) with the fourth hole of the oven (10), the fumes (16) are released from the basket (21) through an outlet opening cooperating with the bottom of the basket (21) and directly connected to a combustion chamber (28), the vault (13). ) moving from its first closed position (13a) to its second open position (13b) in coordination with the passage of the basket (21) from its first pre-heating position (21a) to its second unloading position (21b).