Electric arc furnace with electrode adjustment system and method for managing electrodes in an electric arc furnace

Abstract

The present invention relates to an electric arc furnace (1) comprising an electrode handling apparatus (30), comprising an electrode holder clamp (31) configured to vertically support said one or more electrodes; a first detection apparatus (40) configured to detect in real time the vertical position of said electrode-holder clamp (31) relative to a predefined reference point; - an image acquisition apparatus (60) configured to acquire images of said one or more electrodes when they are removed from the shell (10) and are positioned relative to the roof (20) in such a way that the tip and optionally also the wear zone are framed; a control unit of the electric arc furnace (70) comprising in turn an electrode adjustment system (700) which is configured to adjust the ignition and positioning of the electrodes inside the shell and is operatively connected to said electrode handling apparatus (30). Said control unit of the electric arc furnace (70) is operatively connected to said first detection apparatus (40) to acquire in real time the vertical position (YF) of said electrode-holder clamp relative to said predefined reference point and to said image acquisition apparatus ( 60 ) to acquire images of said electrodes. Said unit ( 70 ) is configured to process said images in such a way that at each electrode removal and for each electrode it calculates the length of the electrode (L Emin F). Said control unit of the electric arc furnace ( 70 ) is configured to calculate the vertical position (YE ) taken over time by the tip of the electrode relative to said predefined reference point, knowing the vertical position (YE) of said electrode- holder clamp acquired by said first detection apparatus ( 40 ) and the length of the electrode (L). Said control unit of the electric arc furnace ( 70 ) is configured to adj ust, via said electrode adj ustment system ( 700 ), the movements of the electrodes relative to the shell ( 10 ) in terms of vertical position and / or speed and / or the ignition time of the arc, as a function of predefined electrode management programs in different operating steps of the electric arc furnace based on the vertical position taken by the tip of the electrode, and / or is configured to generate an alarm signal in the event that, during one or more steps of the furnace operating cycle the trend of the vertical position taken by the tip of the electrode follows a temporal profile that deviates at least in part from a reference temporal profile within predefined tolerances.

Description

"ELECTRIC ARC FURNACE WITH ELECTRODE ADJUSTMENT SYSTEMAND METHOD FOR MANAGING ELECTRODES IN AN ELECTRIC ARCFURNACE "DESCRIPTIONField of application

[0001] The subject of the present invention is an electric arc furnace with electrode adjustment system and method for managing electrodes in an electric arc furnace .

[0002] The electric arc furnace may be a vertical preheating furnace of the shaft furnace type, or a batch charging furnace, or a continuous charging furnace.Prior art

[0003] Usually, the direct melting of metallic materials, in particular those containing iron, for example scrap, DRI or HBI, is carried out in electric arc furnaces (EAF) .

[0004] In general, an operating cycle of an electric arc furnace comprises five main operating steps:

[0005] - charging of the material to be melted into the furnace;

[0006] melting of the charged material, when electrodes and injector-burners are used to melt the material itself;

[0007] - refining of the molten metal, when oxygeninj ectors are used for decarburisation;

[0008] - slagging of the molten metal bath; and

[0009] - tapping of the molten metal .

[0010] In one and the same operating cycle of a furnace , the charging and melting steps may be repeated several times depending on the si ze of the furnace shell . In fact , in many cases , in order to create a molten metal bath that exploits the capacity of the shell , it may be necessary to fill the shell itsel f multiple times with the material to be melted; each charging must then be followed by a melting step .

[0011] More in detail , in batch furnaces the charging of the material takes place via baskets through the open roof , whereas in shaft furnaces the charging takes place via one or more shafts (vertical wells ) integrated in the roof . In both cases , the charging of the material is always conducted discontinuously . Di f ferently, in continuous charging furnaces , except for the initial shell charging carried out via baskets with the roo f open ( or in cases of mal function / maintenance of the continuous charging system) , the material to be melted is charged via a lateral opening in a continuous manner while keeping the electrodes inside the shell .

[0012] During the step in which the furnace is not supplying electric power (power of f ) , after tapping andbefore charging the furnace again with material to be melted, the electrodes are typically removed from the furnace in order to prevent them from being damaged by the material being charged . Subsequently, once the charging of the material to be melted into the furnace is completed, i . e . before the melting step, the controlled insertion of the electrodes into the furnace is provided, upon completion of which the arc ignition will follow .

[0013] This situation occurs regularly ( one or more times ) in each operating cycle in batch furnaces and shaft-type furnaces . In continuous charging furnaces , on the other hand, this situation occurs only at the time of the first charging ( carried out via baskets with the opening of the roof ) or in the case of mal functions / maintenance of the continuous charging system which require charging via bas kets .

[0014] After the material to be melted has been charged into the furnace , the electrodes must be inserted into the furnace , lowering them until they suf ficiently approach the pile of material to be melted so that the arc may strike . In the case of a batch furnace ( and also in the case of a continuous charging furnace ) , the movement of the electrodes is accompanied by that of the roof which, rotating together with the electrodes , closes the furnace ; in the case of a shaft furnace , the roofremains positioned above the shell and only the electrodes are moved in height to bring them back inside the furnace .

[0015] Currently, with reference to figure 4 , which schematises a batch furnace , in the step of reinserting the electrodes into the furnace , each electrode is lowered from point 1 to point 3 at the same low speed so that there is no risk of coll ision of the electrode with the pile of material and the consequent breakage of the tip . This leads to a waste of time between points 1 and 2 in which it would be possible to proceed at a higher speed .

[0016] In the technical field of re ference , there is therefore still a completely unmet need to make the step of inserting the electrodes into the furnace faster without the risk of collisions between electrodes and the pile of material to be melted .

[0017] As is known, fusion after fusion, the electrode is consumed . During the fusion, the lower part of the electrode is entirely enclosed inside the furnace , and is not visible from the outside . The only way operators have to macroscopically evaluate the progress of the fusion is to observe the movement of the electrode-holder arm .

[0018] This is particularly true during the initial step of the melting, called "perforation" , wherein thepile of freshly charged material to be melted is present inside the furnace and the electrode penetrates the pile , creating a hole . As already highlighted, this occurs at each operating cycle in batch furnaces after each discharge of a basket and in shaft furnaces after each discharge of a shaft , whereas in continuous charging furnaces it occurs only in those situations in which the furnace is charged via basket and not via continuous charging .

[0019] In this step, to estimate the progress of the perforation, the descent of the electrode-holder clamp 31 is observed . The electrode-holder clamp is part of an electrode handling system . As illustrated for example in figure 2 , such system comprises a support base 33 which may be rotating and from which a support column 35 extends in height ( generally equipped with a hydraulic li fting system) . In turn, the column supports an arm 34 at the end of which the clamp 31 is f ixed .

[0020] The descent of the electrode-holder arm, although always comparable in successive heats as regards the "magnitude" ( intended as the di f ference between initial height and final height ) , is of fset downward, one melting after the other, by the length by which the electrode has been shortened . I f there is a measurement of the column height , the resulting diagram ( columnposition as a function of the number of melts / basket ) may therefore be represented as a sawtooth that decreases in trend ( curve of the graph shown in figure 5 ; each peak and subsequent valley corresponds to a descent of the electrodes and their permanence in the shell ) . This makes it di f ficult to make estimates by observing the progress of the perforation step . For example , in the first melting shown in the graph of figure 5 , there was a greater descent of the column than normal , but this is not recognisable immediately .

[0021] In light of the above , based on the observation of the movements of the electrode-holder clamp ( column height ) , an operator is not able to understand whether the perforation is proceeding in a physiological manner or not , and in general how the melting is progressing .

[0022] In the technical field of reference , there therefore also exists the still completely unmet need to monitor the progress of the perforation process to know whether or not it is occurring in a physiological way and to implement countermeasures in subsequent melts , for example by adopting controlled basket strati fication practices or having control over what has been charged .

[0023] During the final step of the operating cycle , called the refining step, it is possible that inside the furnace there are :

[0024] - pieces of scrap (more massive ) that have not been completely melted during the initial steps of the melting and that are immersed; and / or

[0025] -accumulations in the wall ( due to incorrect basket strati fication practice , incorrect use of auxiliary chemical energy on the perimeter of the shell or incorrect management of the arc length during the melting step ) .

[0026] When the pieces move near the arc or even collapse from the wall toward the centre ( a fact that physiologically occurs in the case of lateral continuous charging) , the electrode adj ustment system would abruptly raise the electrodes themselves , to prevent the material from hitting and damaging them . These sudden li fts , i f repeated over a short period of time , may excessively stress the electrodes , in addition to compromising ( limiting) the power trans fer to the liquid bath .

[0027] In the technical field of reference , there therefore also exists the still completely unmet need to correlate the automatic actions of the electrode adj ustment system to phenomena that occur inside the furnace so as to be able to implement corrective actions in subsequent melts .

[0028] In the refining step of the direct melting EAF furnace , during decarburisation, FeO and CO aregenerated, which leaves the melting in the form of bubbles . FeO must then be reduced; to maintain a good yield and thus reduce FeO, carbon is inj ected into the liquid slag which is located at the interface with the molten metal . In turn, the reduction of FeO generates further CO in the form of bubbles , increasing the level of foaming slag .

[0029] The advantage of the formation of foaming slag is to create a volume capable of protecting the walls of the EAF by shielding them from the electric arc . In thi s way, the amount o f energy trans ferred to the molten metal is increased, reducing electricity consumption and possible damage to the walls .

[0030] Operationally, during the refining step, the arc is , however, struck between electrode and liquid bath without knowing exactly where the level of the foaming slag is located . In the event that the arc is struck above the level of the slag, it would not benefit from the shielding ef fect of the slag itsel f . This would result in increased energy los ses through radiation towards the cooled furnace panels and the roof . This would increase electricity consumption and the Tap-To-Tap time .

[0031] As a further consequence , there would also be a reduction in the li fe of the panels due to the highthermal load .

[0032] Problems similar to the above are found in electric arc refining furnaces , for example the ladle furnace LF in the case of ferrous materials . There are melting processes in which the electric arc furnace is used in processing non- ferrous materials . Two examples are the refining of copper scrap and the production of brass . Electric arc furnaces are also used in the refining of precious materials ( recycling of electronic waste or primary production of precious materials ) .

[0033] In the technical field of reference , there therefore exists the still completely unmet need to control the ignition of the electric arc based on the slag level in order to make the refining step more ef fective and ef ficient than currently performed . Presenta ti on of the inventi on

[0034] Therefore , the main obj ect of the present invention is to eliminate in whole or in part the drawbacks of the prior art mentioned above , by providing an electric arc furnace with electrode adj ustment system that makes it possible to manage the electrodes more ef ficiently in one or more operating steps of an electric arc furnace .

[0035] A particular obj ect of the present invention is to provide an electric arc furnace with electrodeadj ustment system that allows to perform more quickly the step of inserting the electrodes into the furnace without the risk of colli sions between electrodes and the pile of material to be melted .

[0036] A particular obj ect of the present invention is to provide an electric arc furnace with electrode adj ustment system that allows to monitor the progress of the perforation process so that the operator can see whether it is proceeding in a usual way or, on the contrary, whether an anomaly is occurring .A particular obj ect of the present invention is to provide an electric arc furnace with electrode adj ustment system that allows to correlate the automatic actions of the electrode adj ustment system to phenomena that occur inside the furnace so as to be able to implement corrective actions in subsequent melts .A particular obj ect of the present invention is to provide an electric arc furnace with electrode adj ustment system that allows to control the ignition of the electric arc based on the slag level in order to make the refining step more ef fective and ef ficient than currently performed .

[0037] A further obj ect of the present invention is to provide an electric arc furnace with electrode adj ustment system that is operationally reliable and simple tomanage .

[0038] A further obj ect of the present invention is to provide a method for managing the electrodes that makes it possible to manage the electrodes more ef ficiently in one or more operating steps of an electric arc furnace . Bri ef descripti on of the drawings

[0039] The technical characteristics of the invention, according to the above-mentioned obj ects , are clearly identi fiable from the content of the claims below and the advantages thereof will become more apparent in the detailed description that follows , made with reference to the accompanying drawings , which represent one or more purely exemplary and non-limiting embodiments , in which :

[0040] Figures 1 , 2 and 3 respectively show a schematic view of a shaft-type furnace , a batch ( discontinuous ) charging furnace and a continuous charging furnace ;

[0041] - Figure 4 shows a schematic section of a batch furnace after the charging step before the insertion of the electrodes ;

[0042] - Figure 5 shows a graph of the trend of the height of the column of an electrode handling system of an electric arc furnace as a function of the number of melts / basket during one or more charging and melting steps ;

[0043] - Figure 6 shows a schematic view of an electric arc furnace 1 according to a preferred embodiment of the invention;

[0044] - Figure 7 shows a schematic view of an electric arc furnace 1 according to an alternative embodiment of the invention;

[0045] - Figure 8 shows a graph of the time trend of the height of the column of an electrode handling system of an electric arc furnace with reference to the furnace scheme of figure 4 , relating to a management mode in accordance with the invention ( graph a ) ) and in accordance with a known type mode ( graph b ) ) during an electrode insertion step ;

[0046] - Figure 9 shows a graph of the trend of the electrode tip position as a function of time for the succession of melts / baskets that can be processed by an electric arc furnace according to the invention during one or more charging and melting steps ;

[0047] - Figure 10 shows the superimposition of the graphs of figures 5 and 9 ;

[0048] - Figure 11 shows the graph of the trend of the electrode tip position as a function of time for the succession of melts / baskets during one or more charging and melting steps .

[0049] - Figure 12 shows the graph relating to areference time profile for the electrode tip position as a function of time for the succession of melts / baskets during one or more charging and melting steps , processed by an electric arc furnace 1 according to the invention;

[0050] - Figures 13 to 15 show three examples of deviation from the reference time profile of figure 12 by the electrode tip position as a function of time for the succession of melts / baskets in an electric arc furnace during one or more charging and melting steps ; and

[0051] - Figure 16 shows an example of the time trend of the electrode tip position in an electric arc furnace during a refining step .Detail ed descripti on

[0052] The electric arc furnace with electrode level adj ustment system according to the invention is denoted overall by number 1 in the attached Figures .

[0053] The electric arc furnace 1 according to the invention may be :

[0054] - a vertical preheating furnace of the shaft furnace type , as illustrated for example in figure 1 ;

[0055] - a batch charging furnace ( discontinuous ) , as illustrated for example in figure 2 ; or

[0056] - a continuous charging furnace, as illustrated in figure 3 .

[0057] These types of furnace are in themselves wel lknown to a quali fied person in the sector and will therefore not be described in detail .

[0058] According to a general embodiment of the invention, independently of the speci fic type , the electric arc furnace 1 comprises a shell 10 that is intended to be charged with metallic material to generate a molten metal bath M, on which in use a floating slag layer S is formed, which extends in height from the surface of said bath up to a higher level H variable over time . The shell 10 is provided with a tapping spout 11 and a slag door 12 .

[0059] The electric arc furnace 1 furthermore comprises a roof 20 for closing the shell , on which one or more openings 21 are made for the insertion of one or more electrodes .

[0060] The electric arc furnace 1 also comprises :

[0061] one or more electrodes 22 that can be inserted into the shell 10 through said one or more openings made in the roof ; and

[0062] - an electrode handling apparatus 30 .

[0063] The electrode handling apparatus 30 in turn comprises :

[0064] an electrode-holder clamp 31 adapted to vertically support said one or more electrodes ; and

[0065] - a support structure 32 for the electrode-holder clamp 31 .

[0066] More in detail , as illustrated in figure 6 , the support structure 32 of the electrode-holder clamp 31 comprises a support base 33 from which a support column 35 extends in height . The latter in turn supports an arm 34 that supports the clamp 31 .

[0067] The electric arc furnace 1 according to the invention also comprises a first detection apparatus 40 adapted to detect in real time the vertical position of said electrode-holder clamp 31 with respect to a predefined reference point .

[0068] Preferably, said reference point i s chosen in a portion of the support base 33 of the electrode handling apparatus 30 .

[0069] Advantageously, the first detection apparatus 40 may be of any type provided that it is adapted to detect in real time the vertical position o f said electrode-holder clamp 31 with respect to a predefined reference point .

[0070] Preferably, as illustrated in figure 6 , the first detection apparatus 40 is constituted by a linear position transducer associated with the column 35 of the support structure 32 of the electrode-holder clamp 31 . Alternatively, the first detection apparatus 40 may be constituted by any device adapted to detect the verticalposition of the electrode-holder clamp and / or of the column, for example of the optical type or using radar or laser .

[0071] The electric arc furnace 1 according to the invention also comprises an image acquisition apparatus 60 adapted to acquire images of said one or more electrodes when they are removed from the shell 10 and are positioned with respect to the roof 20 in such a way that even the tip and optionally also the wear zone are framed .

[0072] The term " images of the electrode" is intended to generically refer to "representations of the electrode" which may be directly optical or may be reconstructions obtained from thermal signals ( in the case of thermal cameras ) or from laser or radar signals .

[0073] By "electrode tip" is strictly meant the lower end of the electrode itsel f ( i . e . the lowest point ) , whereas "wear zone" is more extensively meant as a portion of the end that is subj ect to wear / consumption phenomena in each melting and that extends progressively upward from the tip during use .

[0074] In particular, as schematically illustrated in figures 6 and 7 , the aforesaid image acquisition apparatus 60 may comprise one or more image acquisition devices 61 , 62 arranged externally to the shell .

[0075] Preferably, said devices 61 , 62 are cameras and / or thermal cameras and / or 3D scanners using laser or radar .

[0076] Operationally, as will be addressed later in the description, the image acquisition apparatus 60 is intended to acquire images of said one or more electrodes via said one or more devices 61 , 62 which are preferably installed in a fixed and remote position with respect to the shell 10 and the roof 20 in order to obtain certain information on the electrodes .

[0077] The image acquisition is carried out after the electrode ( s ) have been removed from the shell 10 and positioned with respect to the roof 20 in such a way that the tip and the wear zone are also framed .

[0078] More in detail , in the case in which the furnace 1 is of the shaft type ( in which the roof is generally not moved with respect to the shell as it is integrated with the structures ( shaft ) for charging the material to be melted) , the electrodes are completely removed from the shell and positioned with their tips above the upper edge of the roof .

[0079] In the case in which the furnace 1 is a batch charging furnace (of the batch type ) ( in which the roof must be rotated with respect to the shell to allow, at the beginning of each melting step, the material to bemelted to be charged via bas kets ) , the electrodes are completely removed from the shell together with the roof and then rotated laterally; the relative position between roof and electrodes can be varied so as to allow the tips of the electrodes and optionally also their wear zones to be framed, both in a rotated position with respect to the shell and in a vertical pos ition above the shell ( as in the case of continuous charging) .

[0080] In the case in which the furnace 1 is a continuous charging furnace ( in which the roof is generally not moved with respect to the shell since under normal operating conditions the material to be melted is charged laterally and not from the roof ) , the normal operation of the furnace provides that the electrodes may be completely removed from the shell and positioned with their tips above the upper edge of the roof generally only during the first charge and / or in the event of mal functions of the continuous charging system .

[0081] Advantageously, particularly in the case of a continuous charging furnace , it is however possible to provide for the removal of the electrodes with the roof closed at a frequency not strictly related to the operation of the furnace , even solely to allow the acquisition of images of the electrodes and in particular of their tips and optionally also of the wear zones .

[0082] Advantageously, the ( low) speed of the electrode-holder column also allows to acquire the images without having to stop the column of the electrode handling system .

[0083] Operationally, it is preferable that the single image acquisition device is able to simultaneously frame , in the same shot , the tip of the electrode and the clamp of the electrode-holder arm . Alternatively, i f thi s is not possible , two distinct and fixed image acquisition devices may be present ( for example , one frames the tip and optionally the wear zone of the electrodes and the other frames the clamp ) . Alternatively, i f there is a single image acquisition device (but not capable of framing both tip and clamp in the same shot ) , it is possible for it to resort to a zoom operation; subsequently, the image processing software takes care of reconstructing the distance from the tip to the clamp at a given fixed distance ( from the devices ) .

[0084] In this way, since the electrode is integral with the clamp, the clamp itsel f may be taken as a reference ( for example , to calculate the clamp - electrode tip distance ) during subsequent image processing .

[0085] Preferably, the information that can be obtained from the acquired images , by means of subsequentimage processing, may be , for example , the following :

[0086] - shape of the electrode ( reconstruction of the electrode perimeter from the image )

[0087] - length of the electrode ;

[0088] - ( radial ) width of the electrode ;

[0089] - condition of the end portion of the electrode( i . e . presence of cracks or fractures phenomena )

[0090] It is known from practice that the consumption of the electrode does not occur in a "mono-dimensional" manner ( as in the case of electrodes used in welding) , but rather in a "pencil tip" shape . For this reason, it is advantageous that (by means of image processing) the shape of the electrode be reconstructed, understood as a succession of points (Xi , Yi ) .

[0091] The electric arc furnace 1 furthermore comprises a electric arc furnace control unit 70 which in turn comprises an electrode adj ustment system 700 that is adapted to control the ignition and positioning of the electrodes inside the shell and is operatively connected to said electrode handling apparatus 30 .

[0092] In particular, the electrode adj ustment system 700 of the furnace 1 according to the invention is of a known type and will not be described in detail s ince it is known to a qual i fied person in the sector ; for simplicity of description, the characteristics addedaccording to the invention will be described below .

[0093] According to the invention, said electric arc furnace control unit 70 is operatively connected to said first detection apparatus 40 to acquire in real time the vertical position of said electrode-holder clamp with respect to said predefined reference point .

[0094] According to the invention, said electric arc furnace control unit 70 is also operatively connected to said image acquisition apparatus 60 to acquire images of said electrodes and is configured to process said images in such a way that at each removal and for each electrode :

[0095] - it identi fies the vertical position of the lowest point of the electrode tip (Emin)

[0096] - it identi fies the vertical position of the electrode-holder clamp ( F)

[0097] - it calculates the length of the electrode ( L = Emin - F)

[0098] - it stores the data on the position of the electrode tip with respect to the electrode-holder clamp, namely the length of the electrode L .

[0099] The electric arc furnace control unit 70 is configured to calculate the vertical position YE assumed over time by the electrode tip with respect to said predefined reference point , knowing the vertical positionof said electrode-holder clamp acquired by said first detection apparatus 40 and the length of the electrode L : YE = YF - L .

[0100] In other words , according to the invention, the electric arc furnace control unit 70 is capable of reconstructing the real-time position of the electrode tip based on :

[0101] - real-time acquired position of the clamp ;

[0102] - tip - clamp distance calculated at each electrode removal .

[0103] Advantageously, said control unit 70 is programmed to activate said image acquisition apparatus 60 when the electrodes are removed from the shel l 10 and are positioned with respect to the roof 20 in such a way that even the tip and optionally also the wear zone are framed .

[0104] The control unit 70 of the electric arc furnace is configured to adj ust , via said electrode adj ustment system 700 :

[0105] - the movements of the electrodes with respect to the shell 10 in terms of vertical position and / or speed; and / or

[0106] - the ignition time of the electric arc,

[0107] according to predefined electrode management programs in di f ferent operating steps of the electric arcfurnace based on the vertical position assumed by the electrode tip .

[0108] Advantageously, the control unit 70 of the electric arc furnace is configured to also adj ust , via said electrode adj ustment system 700 , the power of the electric arc .

[0109] Preferably, as will be resumed below, the control unit 70 is configured to adj ust the movements of the electrodes and / or the ignition time of the electric arc in the following operating steps of the furnace 1 :

[0110] - insertion of the electrodes into the furnace after its charging; and

[0111] - optionally, refining of the molten metal bath .

[0112] In addition or alternatively to the fact that the control unit 70 is configured to adj ust the movements of the electrodes and / or the ignition time of the electric arc, the control unit 70 of the electric arc furnace is configured to generate an alarm signal in the event that during one or more steps of the operating cycle of the furnace , the trend of the vertical position assumed by the electrode tip follows a time profile that deviates at least in part from a reference time profile within predefined tolerances .

[0113] Thanks to the invention, the electric arcfurnace with electrode adj ustment system makes it possible to manage the electrodes more ef ficiently in one or more operating steps of an electric arc furnace, since it is possible to implement electrode control modes knowing in real time the position of the tips of the electrodes themselves even inside the shel l .

[0114] According to a preferred embodiment of the invention, the electrode adj ustment system 700 may be configured to adj ust the insertion of the electrodes into the shell - after a step of charging the material to be melted - by imposing on the electrodes :

[0115] - a first insertion speed until the electrode tip is outside the shell and / or the roof ; and

[0116] - a second speed, lower than the first one , when the electrode tip is inside the shell and / or the roof .

[0117] The second speed is chosen so as to minimise the risk of electrode breakage upon impact with the material to be melted . At the same time , the possibility of carrying out the insertion of the electrodes at a higher speed outs ide the shell and / or the roof ( i . e . in a safe zone ) allows the electrode insertion step into the furnace to be carried out more quickly without the risk of collisions between electrodes and the pile of material to be melted .

[0118] The above-mentioned operational configuration of the electrode adj ustment system 700 is functional - as already mentioned - during the step in which the furnace is not supplying electric power (power off ) , after tapping and before charging the furnace again with new material to be melted . In this operational situation of the furnace , the electrodes are typically removed from the furnace ( in particular from the shell in batch furnaces ; and al so from the roof in shaft furnaces ) to avoid being damaged by the material being charged . Subsequently, once the charging of the material to be melted into the furnace is completed, that is , before the melting step, the controlled insertion of the electrode into the furnace is provided, after which the arc ignition will follow . This situation occurs regularly in each operating cycle in batch furnaces and shaft-type furnaces . In continuous charging furnaces , this situation occurs only at the time of the f irst charge ( carried out via baskets with the opening of the roof ) or in the event of mal functions / maintenance of the continuous charging system that require charging via baskets .

[0119] After the material to be melted has been charged into the furnace , the electrodes must be inserted into the furnace by lowering them until they suf ficiently approach the pile of material to be melted so that thearc may strike .

[0120] In the case of a batch furnace ( and also in the case of a continuous charging furnace ) , the movement of the electrodes is accompanied by that of the roof , which rotating together with the electrodes closes the furnace ; in the case of a shaft furnace , the roof remains positioned above the shell of the furnace and only the electrodes are moved vertically to bring them back into the furnace .

[0121] Thanks to the invention, that is , thanks to the fact of knowing in real time the position of the electrode tips , during the insertion step it is possible to di f ferentiate the descent speed of the electrodes according to the position they are progressively as suming with respect to the shell and / or the roof .

[0122] In figure 8 , two di f ferent speed profiles in the insertion of the electrodes are shown : a first profile in accordance with the invention (profile a ) and a second profile in accordance with a traditional method (profile b ) . It can be seen how, by adopting profile a ) , the ignition of the electric arc is temporally anticipated by a time period indicated as AT . The time saving in one day can also be estimated at 10-15 minutes .

[0123] According to an alternative embodiment of the invention, the electrode adj ustment system 700 may beconfigured to adj ust the insertion of the electrodes into the shell - after a step of charging the material to be melted - by imposing on the electrodes :

[0124] - a first insertion speed until the electrode tip reaches a predefined safety distance from the material pile , even inside the shell and / or the roof ; and

[0125] - a second speed, lower than the first one , when the distance between the electrode tip and the pile is less than said safety distance .

[0126] Advantageously, said electrode adj ustment system 700 is programmed to command the ignition of the electric arc after the electrode tip has got close to the material to be melted . In particular, this can be achieved by means of control over the electrical parameters of the electrode , according to methods that are well known to a quali fied person in the sector and will therefore not be described herein .

[0127] Preferably, the electric arc furnace 1 according to the invention also comprises a second detection apparatus 50 adapted to detect the upper slag level over time .

[0128] Advantageously, the second detection apparatus 50 may be of any type provided that it is adapted to detect the upper slag level over time . In particular, it may be a radar or ultrasonic device .

[0129] Operationally, the upper slag level is detected as the distance between the second detection apparatus 50 (preferably associated with the shell ) and the slag surface . Taking into account the fact that during the refining step the shell 10 is typically kept hori zontal , once the height position of the second detection apparatus 50 is known, the upper slag level H can be expressed in relation to the predefined reference point 0.

[0130] Advantageously, said electric arc furnace control unit 70 may also be operatively connected to said second detection apparatus 50 to acquire in real time the upper slag level .

[0131] According to a preferred embodiment of the invention, the electrode adj ustment system 700 may be programmed to adj ust the movement of the electrodes inside the shell - during a ref ining step of the metal bath - by causing the electrodes to descend until the electrode tip has passed the upper slag level .

[0132] This is possible since , according to the invention, the control unit 70 i s operatively connected to the second detection apparatus 50 adapted to detect the upper slag level over time and can therefore use the readings of said second apparatus 50 . Moreover, since the position of the electrode tip is indirectly detectable inreal time (net o f the delays introduced by the control unit ' s data processing system) , the control unit 70 - via the electrode adj ustment system 700 - is capable of adj usting the electrode handling in relation to the upper slag level .

[0133] Operationally, the electrode can be lowered until it is determined that the electrode tip is located below the slag surface and, only then, the arc can be struck . In this way, the arc strikes below the slag and radiation toward the side panel s and roof is limited, increasing the ef ficiency of energy trans fer to the bath .

[0134] Thanks to the invention, the electric arc furnace 1 with electrode adj ustment system makes it possible to control the ignition of the electric arc based on the slag level so as to make the refining step more ef fective and ef ficient than currently performed .

[0135] Advantageously, said electrode adj ustment system 700 may be programmed to command the ignition of the electric arc after the electrode tip has passed the upper slag level .

[0136] As already highlighted, according to the invention, the control unit 70 of the electric arc furnace is configured to generate an alarm signal in the event that during one or more steps of the furnace operating cycle the trend of the vertical positionassumed by the electrode tip follows a time profile that deviates at least in part from a reference time profile within predefined tolerances .

[0137] Thanks to this , the electric arc furnace 1 with electrode adj ustment system makes it possible , in particular, to monitor the progress of the perforation process so that the operator can see whether it is proceeding normally or, on the contrary, whether an anomaly is occurring .

[0138] Preferably, the furnace 1 comprises a control panel connected to the control unit 70 . The aforesaid alarm signal is displayed on said control panel .

[0139] A preferred method for defining a descriptive time profile of the trend of the vertical position assumed by the tip of an electrode during a perforation / melting step is described below .

[0140] As is known, one melting after the other the electrode is consumed . During the melting, the lower part of the electrode is entirely enclosed inside the melted material , resulting not visible from the outside .

[0141] In absence of information about the status of the electrodes inside the furnace , it is possible to macroscopically assess the progress of the melting by observing the movement of the electrode-holder clamp .

[0142] This is particularly true during the initialstep of the melting, called "perforation", wherein the pile of freshly charged material to be melted is present inside the furnace and the electrode penetrates the pile , creating a hole .

[0143] In this step, to estimate the progress of the perforation, the descent of the electrode-holder clamp can be observed .

[0144] The descent of the electrode-holder clamp, although always comparable in successive melts as regards the "magnitude" ( intended as the di f ference between initial height and final height ) , is shi fted downward, one melting after the other, by the length by which the electrode has been shortened .

[0145] By measuring the height of the electrode-holder column ( or of the clamp ) , it is possible to plot a diagram expressing the position of the column ( or clamp ) as a function of the number of melts / baskets and / or electrode removals . Therefore , this diagram can be represented as a sawtooth profile decreasing in trend, as illustrated in the graph curve shown in figure 5 .

[0146] The decreasing sawtooth profile makes it di f ficult to make estimates by observing the progress of the perforation step .

[0147] Thanks to the invention, however, it is possible to know the position of the electrode tip ( inparticular one melting after the other, therefore taking into account the shortening that has occurred) , in order to be able to compare in each melting the traj ectory actually made by the electrode tip .

[0148] More in detail , in the furnace 1 , before loading each bas ket ( i . e . before each melting i f it is a batch or shaft charging furnace or a continuous charging furnace fed by baskets ) or at the end of each operating cycle ( i f it is a continuous charging furnace ) , and generally at each electrode removal , it is possible to measure the distance between the clamp (point integral with the electrode-holder arm) and the tip of the electrode itsel f .

[0149] Knowing how much the electrode has been shortened, together with the measurement of the height of the electrode-holder column, it is possible to generate a graph ( electrode tip position as a function of time for the succession of baskets / melts or generally of electrode removals ) that is represented by a sawtooth profile as illustrated in the graph of figure 9 . This graph has a constant trend .

[0150] From the comparison of the two graphs ( figure 5 and figure 9 ) shown visually in figure 10 , it is noted that the position of the electrode tip always remains within a certain range , whereas the position of thecolumn, although it has a constant amplitude ( initial position minus f inal position for each melt / basket ) , is progressively translated downward .

[0151] The measurement of the electrode tip position being available , it is possible to generate a graph by superimposing the sawteeth of successive melts . An example of such a graph is illustrated in figure 11 .

[0152] Then, by selecting a group of "representative" melts for a given charging condition and furnace practice , for which the sawtooth shape is considered "physiological" , it is possible to define a fingerprint of the system, as illustrated in figure 12 . This fingerprint represents a reference time profile with predefined tolerances .

[0153] Advantageously, said control unit 70 is programmed to generate a di f ferent alarm signal depending on predefined types of deviation from said reference time profile .

[0154] A first type of deviation is defined in the case in which the electrode tip position follows a time profile that deviates from the reference time profile with a segment of invariance of the height position .

[0155] An example of such a situation is illustrated in the graph of figure 13 , wherein the analysed time profile is graph c ) and the segment of invariance(horizontal) of the height position with respect to the reference time profile is indicated by h. This example is related to the presence of partially conductive (or partially insulating) material in the charge.

[0156] More in detail, in the case in which a piece of partially insulating material is present in the charge, the arc current is lower (e.g. 30 kA) than what should be delivered (e.g. 60 kA) and, consequently, the melting of that piece takes longer (see the horizontal segment h of curve c, which means that the electrode is not descending) . This causes an increase in Power On Time (and consequently in Tap to Tap Time) , since the arc has operated for a certain period of time melting with lower current .

[0157] The presence of partially conductive material is due to a defect in operational practice and is substantially attributable to lime and how it is supplied in the process (it may be caused by malfunction of the crane or the hopper or by how it has been loaded into the basket) , or, more rarely, to the presence of very low- quality scrap.

[0158] Preferably, curve c) (which deviates from the fingerprint in the manner illustrated above, i.e. with a horizontal segment h in which the electrode is stationary and then starts descending again) may, after N melts inwhich this occurs , generate an alarm for the operator, noti fying him / her of the anomaly .

[0159] A second type of deviation is defined in the case in which the electrode tip position follows a time profile that deviates downward from the reference time profile by a di f ference less than a predefined threshold value .

[0160] An example of such a situation is illustrated in the graph of figure 14 , wherein the analysed time profile is graph d) ; the predefined threshold value is represented by the dashed line tv, while the segment of the graph where the trend deviates downward from the reference time profile is indicated by vl . This example is related to the partial breakage of the electrode .

[0161] In the case of breakage of a piece of the electrode af fecting only part of the electrode crosssection, a faster descent of the electrode will be observed (not as fast as the breakage of the entire section, but still faster than the electrode under "physiological" conditions ) , since it will be as i f an electrode of smaller diameter was being used, which will therefore undergo wear more quickly, soon leading to the same deviation as in the case of breakage of an electrode across its entire section .

[0162] A third type of deviation is defined in thecase in which the electrode tip position follows a time profile that deviates downward from the reference time profile by a di f ference greater than said predefined threshold value .

[0163] An example of such a situation is illustrated in the graph of figure 15 , wherein the analysed time profile is graph e ) ; the predefined threshold value is represented by the dashed line tv, while the segment of the graph wherein the trend deviates downward from the reference time profile is indicated with v2 . This example is related to the breakage of the entire section of the electrode .

[0164] In the case of breakage of a piece of the electrode af fecting the entire cross-section of the electrode , a rapid descent of the tip position will be observed .

[0165] Advantageously, said control unit may be programmed to generate a di f ferent alarm signal depending on predefined types of deviation from a re ference time profile also relating to a refining step .

[0166] Preferably, a type of deviation is defined in the case in which - during a refining step of the metal bath - the electrode tip position follows a time profile that deviates upward from the reference time pro file in the refining step, drawing one or more peaks .

[0167] Preferably, the reference time profile in the refining step is defined by a fluctuation band of the electrode tip centred on an ideal average position variable as a function of the upper height of the slag .

[0168] An example of such a situation is illustrated in the graph of figure 16 , wherein the analysed time profile is graph f ) and the peaks are indicated by pl and p2 . This example is related to the presence ins ide the furnace during the refining step of the molten metal bath of :

[0169] - pieces of scrap (more massive ) that have not been completely melted during the initial steps of the melting and that are present in the bath; and / or

[0170] - accumulations o f material to be melted on the wall ( due to incorrect bas ket strati fication practice , incorrect use of auxiliary chemical energy on the perimeter of the shell or incorrect management of arc length in the melting step ) .

[0171] When the pieces move near the arc or even collapse from the wall towards the centre , the electrode adj ustment system automatically causes the electrode to rise abruptly, risking excessive stress on the electrode and impairing (by limiting) the power trans fer to the liquid bath .

[0172] Operationally, i f during refining there isfrequent presence of unmelted or collapsed massive pieces requiring the electrode to be raised, the measurement of the electrode tip position can give the operator indications of problems in the charging steps ( e . g . charging of massive pieces that are too large and cannot be melted in the perforation and melting steps ) or of the need to modi fy the melting profile to allow complete melting before the refining step ( for example increasing the energy suppl ied by the burners or operating in the final part of the melting step with a long arc, in order to suf ficiently irradiate the walls and ensure melting of any pieces stuck to the walls ) . The graph of figure 16 describes a situation which, in the case of basket- charged or shaft furnaces ( or continuous charging furnaces charged by baskets ) , is symptomatic of a problem that occurred in the initial steps of melting, whereas in the case of continuous charging furnaces it is a physiological situation .

[0173] According to a preferred embodiment , said control unit 70 is operatively connected to said image acquisition apparatus 60 to acquire images of said electrodes and is configured to process said images in such a way that for each basket / melt / removal and for each electrode it may :

[0174] - detect the electrode profile ;

[0175] compare prof iles of images captured at di f ferent moments , to determine the missing area due to electrode consumption and thus estimate the volume loss and preferably, knowing the density, also estimate the weight loss ;

[0176] - store the weight loss data and compare it with subsequent electrode consumption data .

[0177] Advantageously, said control unit 70 is configured to generate an alarm signal i f the electrode consumption data deviates from a reference time profile of electrode consumption within prede fined tolerances .

[0178] According to a preferred embodiment , said control unit 70 is operatively connected to said image acquisition apparatus 60 to acquire images of said electrodes and is configured to process said images in such a way that for each removal / basket / melting and for each electrode it may store the image of the electrode tip and optionally of the wear zone .

[0179] Advantageously, said control unit 70 comprises a library of images of electrode damage phenomena and is configured to compare the acquired images with said image library to recognise possible damage phenomena so as to generate an alarm signal .

[0180] Advantageously, said control unit 70 is configured to generate an alarm signal i f the acquiredimages are comparable with one or more images in said image library .

[0181] It may happen that , in order to maximise production, a plant attempts to continue producing without proceeding with the electrode extension ( slipping) or even the addition of a stub, operations which are time consuming and slow down production .

[0182] When it happens that the electrode is so short that the electrode-holder column has reached the lower end stop and can no longer descend, the electrode cannot operate according to what is required by the electrode adj ustment device , in particular it will operate by supplying lower power, resulting in an increase in Power On Time .

[0183] By measuring the length of the electrode one melting after the other, a consumption trend can be removed, so that the operator can predict with good accuracy when it will be necessary to proceed with the electrode extension or the addition o f a stub .

[0184] This has an important impact since EAF downtimes ( for example due to electrode extension) af fect downstream production ( e . g . at least LF and continuous casting) , and the possibility of scheduling when these downtimes will occur provides the advantage of managing production optimally .

[0185] * * *

[0186] The subj ect of the present invention is also a method for managing the electrodes of an electric arc furnace 1 according to the invention and in particular as described above .

[0187] For simplicity of discuss ion, the electrode management method will be described with reference to the preceding part of the description in which the furnace 1 according to the invention has already been described .

[0188] According to a general implementation form of the invention, the method for managing the electrodes of an electric arc furnace 1 comprises the following operational steps :

[0189] a ) at each electrode power-of f , removing said one or more electrodes from the shell 10 , positioning them with respect to the roof 20 in such a way that also the tip and optionally also the wear zone can be framed by said image acquisition apparatus 60 ;

[0190] b ) acquiring images of said one or more electrodes after step a ) via said image acquisition apparatus 60 .

[0191] The electrode power-of f may occur at the beginning, during and / or at the end of each operating cycle of the electric arc furnace ; in particular, it may occur at the end of each melting ( in the case ofcontinuous charging furnace ) or before charging ( for batch or shaft furnaces or continuous charging furnaces exceptionally charged by baskets ) , or according to the need to detect the electrode condition in the continuous charging furnace .

[0192] The electrode management method comprises the operational step c ) of processing said images via the control unit 70 in such a way that at each electrode removal and for each electrode :

[0193] - the vertical position of the lowest point of the electrode tip (Emin) is identi fied

[0194] - the vertical position of the electrode-holder clamp ( F) is identi fied

[0195] - the length of the electrode is calculated ( L= Emin - F)

[0196] - the data on the position of the electrode tip with respect to the electrode-holder clamp, namely the electrode length L is stored .

[0197] The electrode management method according to the invention also comprises the operational steps :

[0198] d) at the end of each electrode power-of f , reinserting said one or more electrodes into said shell ;

[0199] e ) detecting in real time the vertical position YE of said electrode-holder clamp via said first detection apparatus 40 ;

[0200] g) calculating the vertical position YE assumed over time by the electrode tip with respect to said predefined reference point , knowing the vertical position YE of said electrode-holder clamp and the electrode length L : YE = YE - L .

[0201] Preferably, said reference point i s chosen in a portion of the support base 33 of the electrode handling apparatus 30 .

[0202] Step b ) of image acquisition is carried out between step a ) of electrode removal and step d) of electrode reinsertion .

[0203] In particular, step b ) of acquiring images is conducted after said step a ) in which the electrodes have been removed from the shell 10 and positioned with respect to the roof 20 in such a way that also the tip and optionally the wear zone can be framed .

[0204] Preferably, step c ) of image processing is carried out before step d) of electrode reinsertion .

[0205] Step e ) of detecting in real time the vertical position YE of said electrode-holder clamp is carried out in conj unction with step g) of calculating the vertical position assumed over time by the electrode tip with respect to said predefined reference point , knowing the vertical position of said electrode-holder clamp .

[0206] The two steps e ) and g) make it possible totrace a time profile of the trend of the vertical position YE assumed by the electrode tip . In particular, the time profile refers to the trend of the tip position during a single melt .

[0207] The electrode management method according to the invention al so comprises the operational step h) of adj usting, by means of said electrode adj ustment system 700 :

[0208] - the movements of the electrodes with respect to the shell 10 in terms of vertical position and / or speed; and / or

[0209] - the ignition time of the arc,

[0210] depending on predefined electrode management programs in di f ferent operating steps of the electric arc furnace based on the vertical position assumed by the electrode tip as calculated in step g ) .

[0211] Preferably, said adj ustment step h) is carried out during the following operating steps of the furnace 1 :

[0212] - insertion of the electrodes into the furnace after its charging; and

[0213] - optionally, refining of the molten metal bath .

[0214] In addition or as an alternative to the adj ustment step h) , the electrode management methodaccording to the invention comprises the operational step i ) of generating an alarm signal i f during one or more steps of the furnace operating cycle the trend of the vertical position assumed by the electrode tip follows a time profile that deviates at least in part from a reference time profile within predefined tolerances .

[0215] According to a preferred embodiment of the invention, during said insertion step d) of said one or more electrodes into said shell is adj usted by imposing on the electrodes :

[0216] - a first insertion speed until the electrode tip is outside the shell and / or the roof ; and

[0217] - a second speed, lower than the first one , when the electrode tip is inside the shell and / or the roof .

[0218] The second speed is chosen so as to minimise the risk of electrode breakage upon impact with the material to be melted .

[0219] Advantageously, during said step d) of inserting said one or more electrodes into said shell , via said electrode adj ustment system 700 , the ignition of the electric arc is commanded after the electrode tip has reached the proximity to the material to be melted .

[0220] Advantageously, the method may comprise a step f ) of detecting in real time the upper slag level viasaid second detection apparatus 50 during a refining step of the molten metal bath .

[0221] In such case , the adj ustment step h) is carried out , during a ref ining step of the metal bath, also based on the upper slag level .

[0222] According to a preferred embodiment of the invention, during a refining step of the metal bath the movement of the electrodes inside the shell is adj usted via said electrode adj ustment system 700 by causing the electrodes to lower until the tip of the electrodes has passed the upper slag level .

[0223] Advantageously, during said refining step of the metal bath, via said electrode adj ustment system 700 , the ignition of the electric arc is commanded after the electrode tip has passed the upper slag level .

[0224] Preferably, during each operating cycle every deviation from a reference time profile in the melting / perf oration step, within predefined tolerances , by the trend of the vertical position assumed by the electrode tip, is classi fied according to predefined types of deviation, each of which is associated with a di f ferent alarm signal .

[0225] Referring to what has already been described in relation to the furnace 1 , three possible types of deviation are listed .

[0226] A first type of deviation is defined in the case in which the position of the electrode tip fol lows a time profile that deviates from the reference time profile with a segment of invariance in height position . An example of such a situation is illustrated in the graph of figure 13 .

[0227] A second type of deviation is defined in the case in which the position of the electrode tip fol lows a time profile that deviates downward from the reference time profile by a di f ference less than a predefined threshold value . An example of such a situation is illustrated in the graph of figure 14 .

[0228] A third type of deviation is defined in the case in which the position of the electrode tip fol lows a time profile that deviates downward from the reference time profile by a di f ference greater than said predefined threshold value . An example of such a situation is illustrated in the graph of figure 15 .

[0229] Advantageously, during each operating cycle of the furnace , each deviation from a reference time profile relating to a refining step, within predefined tolerances , by the trend of the vertical position assumed by the electrode tip, may be classi fied according to predefined types of deviation, each of which is associated with a di f ferent alarm signal .

[0230] Preferably, a type of deviation is defined in the case in which - during the refining step of the molten metal bath - the position of the electrode tip follows a time profile that deviates upward from the reference time profile drawing one or more peaks . An example of such a situation is illustrated in the graph of figure 16 .

[0231] According to a preferred implementation form of the invention, via said control unit 70 in said processing step c ) , the images acquired in said step b ) are processed in such a way that at each electrode removal ( in particular at each basket / charge , for batch or shaft furnaces or continuous charging furnaces charged by baskets , or at each operating cycle for continuous charging furnaces ) and for each electrode :

[0232] - the profile of the electrode is detected;

[0233] - profiles of images captured at di f ferent times are compared, to determine the missing area due to electrode consumption and thus estimate the volume loss and preferably, knowing the density, also estimate the weight loss ;

[0234] the weight loss data is stored and then compared with subsequent electrode consumption data .

[0235] Preferably, the method comprises step 1 ) of generating, via said control unit 70 , an alarm signal inthe event that the electrode consumption data deviates from a reference time profile of electrode consumption within predefined tolerances .

[0236] Preferably, via said control unit 70 in said processing step c ) , the images acquired in said step b ) are processed in such a way that after each electrode removal ( in particular at each basket / charge , for batch or shaft furnaces or continuous charging furnaces charged by baskets , or at each operating cycle for continuous charging furnaces ) and for each electrode the image of the electrode tip and also of the wear zone is stored .

[0237] Advantageously, the method may comprise step m) of comparing via said control unit 70 the images acquired with a library of images of electrode damage phenomena to recognise possible damage phenomena and thus generate an alarm signal .

[0238] Preferably, the method comprises step n) of generating, via said control unit 70 , an alarm signal in the event that the images acquired are comparable with one or more images of said image library .

[0239] The advantages deriving from the method according to the invention are the same as those already described in relation to the furnace 1 according to the invention and will not be presented again for simplicity of description .

[0240] The invention makes it possible to achieve numerous advantages , some of which have already been described .

[0241] The electric arc furnace with electrode adj ustment system according to the invention makes it possible to manage the electrodes more ef ficiently in one or more operating steps of an electric arc furnace .

[0242] The electric arc furnace with electrode adj ustment system according to the invention allows the electrode insertion step into the furnace to be carried out more quickly without the risk of collisions between the electrodes and the pile of material to be melted .

[0243] The electric arc furnace with electrode adj ustment system according to the invention makes it possible to monitor the progress of the perforation process so that the operator can see whether it is proceeding normally or, on the contrary, whether an anomaly is occurring .The electric arc furnace with electrode adj ustment system according to the invention makes it possible to correlate the automatic interventions of the electrode adj ustment system with phenomena occurring inside the furnace , thereby enabling corrective actions to be implemented in subsequent melts .The electric arc furnace with electrode adj ustment systemaccording to the invention makes it possible to control the ignition of the electric arc based on the slag level in order to make the refining step more ef fective and ef ficient compared to current practice .

[0244] The electric arc furnace with electrode adj ustment system according to the invention is operationally reliable and simple to manage .

[0245] The method of electrode management according to the invention enables more ef ficient management of the electrodes in one or more operating steps of an electric arc furnace .

[0246] The invention thus conceived achieves the intended obj ectives .

[0247] Obviously, it may take , in its practical implementation, also di f ferent forms and configurations from the one illustrated above , without thereby departing from the present scope of protection .

[0248] Furthermore , all details may be replaced by technically equivalent elements , and the dimensions , shapes and materials used may be any, according to requirements .

Claims

CLAIMS1. An electric arc furnace (1) comprising: a shell (10) intended to be loaded with a metal material to generate a molten metal bath (M) , on which a floating slag layer (S) is formed in use, extending in height from the surface of said bath to a higher level (H) varying over time, said shell (10) being provided with a tapping channel (11) and a slagging door (12) ;- a shell closing roof (20) on which one or more openings (21) are made for inserting one or more electrodes;- one or more electrodes (22) insertable into the shell(10) through said one or more openings; an electrode handling apparatus (30) , comprising an electrode-holder clamp (31) suitable to vertically support said one or more electrodes,- a first detection apparatus (40) suitable to detect the vertical position of said electrode-holder clamp (31) in real time with respect to a predefined reference point;- image acquisition apparatus (60) suitable to acquire images of said one or more electrodes when they are removed from the shell (10) and positioned with respect to the roof (20) so that the tip and possibly the wearzone can also be framed;- an electric arc furnace control unit (70) comprising, in turn, an electrode adjustment system (700) which is suitable to adjust the ignition and positioning of the electrodes inside the shell and which is operatively connected to said electrode handling apparatus (30) characterized in that said electric arc furnace control unit (70) is operatively connected to said first detection apparatus (40) to acquire the vertical position YE) of said electrode-holder clamp in real time with respect to said predefined reference point; and in that said electric arc furnace control unit (70) is operatively connected to said image acquisition apparatus (60) to acquire images of said electrodes and is configured to process said images so that, upon each electrode removal and for each electrode:- it identifies the vertical position of the lowest point of the electrode tip (Emin)- it identifies the vertical position of the electrodeholder clamp (F) it calculates the electrode length (L = Emin - F)- it stores the data on the position of the electrode tip with respect to the electrode-holder clamp, i.e., the electrode length L, wherein said electric arc furnace control unit (70) is configured to calculate the vertical position (YE) taken over time by the electrode tip with respect to said predefined reference point, knowing the vertical position (YE) of said electrode-holder clamp acquired by said first detection apparatus (40) and the electrode length (L) , and wherein said electric arc furnace control unit (70) is configured to adjust, by means of said electrode adjustment system (700) :- the movements of the electrodes with respect to the shell (10) in terms of vertical position and / or speed; and / or- the arc ignition time as a function of predefined electrode management programs at different steps of operation of the electric arc furnace based on the vertical position taken by the electrode tip, and / or is configured to generate an alarm signal if,during one or more steps of the furnace operating cycle, the trend of the vertical position taken by the electrode tip follows a time profile which deviates at least partially from a reference time profile within predefined tolerances .

2. An electric arc furnace (1) according to claim 1, wherein said electrode adjustment system (700) is configured to adjust the insertion of the electrodes into the shell - after a step of loading the material to be melted - setting a first speed for the electrodes until the tip of the electrodes is outside the shell and a second speed, lower than the first speed, when the tip of the electrodes is inside the shell, wherein said second speed is selected so as to minimize the risk of the electrodes breaking upon impact with the material to be melted .

3. An electric arc furnace (1) according to claim 2, wherein said electrode adjustment system (700) is programmed to command the ignition of the electric arc after the tip of the electrodes has come close to the material to be melted.

4. An electric arc furnace (1) according to claim 1, 2 or 3, comprising a second detection apparatus (50) suitable to detect the higher slag level over time, wherein said electric arc furnace control unit (70) isoperatively connected to said second detection apparatus(50) to acquire the higher slag level in real time and wherein said electric arc furnace control unit (70) is configured to adjust, by means of said electrode adjustment system (700) :- the movements of the electrodes with respect to the shell (10) in terms of vertical position and / or speed; and / or- the arc ignition time as a function of predefined electrode management programs during an operation step of the electric arc furnace related to the refining of the molten metal bath, based on the vertical position taken by the electrode tip and also based on the higher slag level, wherein preferably said electrode adjustment system (700) is programmed to adjust the movement of the electrodes inside the shell - during said metal bath refining step - causing the electrodes to lower until the tip of the electrodes has exceeded the higher slag level.

5. An electric arc furnace (1) according to claim 4, wherein said electrode adjustment system (700) is programmed to command the ignition of the electric arc after the tip of the electrodes has exceeded the higherslag level.

6. An electric arc furnace (1) according to any one of the preceding claims, comprising a control panel and wherein said alarm signal is displayed on said control panel .

7. An electric arc furnace (1) according to any one of the preceding claims, wherein said control unit is programmed to generate a different alarm signal depending on predefined types of deviation from a reference time profile related to a melting step.

8. An electric arc furnace (1) according to claim 7, wherein a first type of deviation is defined if the position of the electrode tip follows a time profile which deviates from the reference time profile in the melting step with a segment of position invariance in height .

9. An electric arc furnace (1) according to claim 7 or 8, wherein a second type of deviation is defined if the position of the electrode tip follows a time profile, which deviates downwards from the reference time profile in the melting step by a difference of less than a predefined threshold value.

10. An electric arc furnace (1) according to claim 7, 8 or 9, wherein a third type of deviation is defined if the position of the electrode tip follows a time profilewhich deviates downwards from the reference time profile in the melting step by a difference above said predefined threshold value.

11. An electric arc furnace (1) according to any one of the preceding claims, wherein said control unit is programmed to generate a different alarm signal depending on predefined types of deviation from a reference time profile related to a refining step and wherein preferably a type of deviation is defined if - during the metal bath refining step - the position of the electrode tip follows a time profile which deviates upwards from the reference time profile in the melting step drawing one or more peaks .

12. An electric arc furnace (1) according to any one of the preceding claims, wherein said reference point is selected in a portion of a base of the electrode handling apparatus (30) .

13. An electric arc furnace (1) according to any one of the preceding claims, wherein said control unit (70) is operatively connected to said image acquisition apparatus (60) to acquire images of said electrodes and is configured to process said images so that, upon each electrode removal and for each electrode, it can:- detect the profile of the electrode;- compare profiles of images captured at different times, to determine the missing area due to electrode consumption and thus estimate the volume loss and preferably, knowing the density, also estimate the weight loss ; store the weight loss data and compare it with subsequent electrode consumption data.

14. An electric arc furnace (1) according to claim 13, wherein said control unit (70) is configured to generate an alarm signal if the electrode consumption data deviates from a reference time profile of the electrode consumption within predefined tolerances.

15. An electric arc furnace (1) according to any one of the preceding claims, wherein said control unit (70) is operatively connected to said image acquisition apparatus (60) to acquire images of said electrodes and is configured to process said images so that for each electrode removal and for each electrode it can store the image of the electrode tip and the wear zone and wherein said control unit (70) comprises an image library of electrode damage phenomena and is configured to compare the acquired images with said image library to identify any damage phenomena so as to generate an alarm signal.

16. An electric arc furnace (1) according to claim 15,wherein said control unit (70) is configured to generate an alarm signal if the acquired images are comparable with one or more images of said image library.

17. An electric arc furnace (1) according to any one of the preceding claims, wherein said control unit (70) is programmed to activate said image acquisition apparatus (60) when the electrodes are removed from the shell (10) and are positioned with respect to the roof (20) so that the tip and possibly the wear zone can also be framed.

18. An electric arc furnace (1) according to any one of the preceding claims, wherein said image acquisition apparatus (60) comprises one or more image acquisition devices (61, 62) arranged outside the shell, preferably said devices (61, 62) being cameras and / or thermal imaging cameras and / or 3D laser scanners.

19. A method of managing the electrodes of an electric arc furnace (1) according to any one of the preceding claims, comprising the following operating steps: a) upon each switching off of the electrodes - at the beginning, during and / or at the end of each operating cycle of the electric arc furnace (1) - removing said one or more electrodes from the shell (10) positioning them with respect to the roof (20) so that the tip and possibly the wear zone can also be framed by said imageacquisition apparatus (60) ; b) acquiring images of said one or more electrodes after step (a) by means of said image acquisition apparatus (60) ; c) processing said images by means of said control unit (70) so that upon each electrode removal and for each electrode : the vertical position of the lowest point of the electrode tip (Emin) is identified- the vertical position of the electrode-holder clamp (F) is identified- the electrode length (L = Emin - F) is calculated- the electrode position data tip with respect to the electrode-holder clamp, i.e., the electrode length L, is stored, d) at the end of each switching off of the electrodes, re-inserting said one or more electrodes into said shell; e) detecting the vertical position (YE) of said electrode-holder clamp in real time by means of said first detection apparatus (40) ,f ) optionally detecting the higher slag level (H) in real time by means o f said second detection apparatus ( 50 ) during a molten metal bath refining step, g) calculating the vertical position (YE ) taken over time by the electrode tip with respect to said predefined reference point , knowing the vertical position of said electrode-holder clamp (YE) and the electrode length ( L ) , h) adj usting, by means of said electrode adj ustment system ( 700 ) :- the movements of the electrodes with respect to the shell ( 10 ) in terms of vertical position and / or speed; and / or- the arc ignition time and / or arc power as a function of predefined electrode management programs at di f ferent steps of operation of the electric arc furnace based on the vertical position taken by the electrode tip as calculated in step g) and optional ly, in a metal bath refining step, also based on the higher slag level , and / or i ) generating an alarm signal i f , during one or moresteps of the furnace casting cycle / operation, the trend of the vertical position taken by the electrode tip follows a time profile which deviates at least partially from a reference time prof ile within predefined tolerances .20 . A method according to claim 19 , wherein during said step d) the insertion of said one or more electrodes into said shell is adj usted by setting a first speed for the electrodes until the tip of the electrodes is outside the shell and a second speed, less than the first speed, when the tip of the electrodes is inside the shell , wherein said second speed is selected so as to minimi ze the risk of the electrodes breaking upon impact with the material to be melted previously loaded into the shell .21 . A method according to claim 20 , wherein during said step d) of inserting said one or more electrodes into said shell , by means of said electrode adj ustment system ( 700 ) , the electric arc ignition is commanded after the tip of the electrodes has come close to the material to be melted .22 . A method according to claim 19 , 20 or 21 , wherein during a step of refining the metal bath, the movement of the electrodes inside the shell is adj usted by means of said electrode adj ustment system ( 700 ) causing the electrodes to lower until the tip of the electrodes hasexceeded the higher slag level.

23. A method according to claim 22, wherein during said step of refining the metal bath, by means of said electrode adjustment system (700) , the electric arc ignition is commanded after the tip of the electrodes has exceeded the higher slag level.

24. A method according to any one of claims 19 to 23, wherein during each furnace operating cycle, each deviation from a reference time profile related to a melting step, within predefined tolerances, by the trend of the vertical position taken by the electrode tip, is classified according to predefined deviation types, to each of which a different alarm signal is correlated.

25. A method according to claim 24, wherein a first deviation type is defined if the position of the electrode tip follows a time profile which deviates from the reference time profile in the melting step with a segment of position invariance in height.

26. A method according to claim 24 or 25, wherein a second deviation type is defined if the position of the electrode tip follows a time profile which deviates downwards from the reference time profile in the melting step by a difference of less than a predefined threshold value .

27. A method according to claim 24, 25 or 26, wherein athird deviation type is defined i f the position of the electrode tip follows a time profile which deviates downwards from the reference time profile in the melting step by a di f ference above said predefined threshold value .28 . A method according to any one of the preceding claims , wherein during each furnace operating cycle each deviation from a reference time profile related to a refining step, within predefined tolerances , due to the trend of the vertical position taken by the electrode tip, is classi f ied according to predefined deviation types , to each of which a di f ferent alarm signal is correlated and wherein preferably one deviation type is defined i f - during the metal bath refining step - the position of the electrode tip follows a time profile which deviates upwards from the reference time profile drawing one or more peaks .29 . A method according to any one of claims 19 to 28 , wherein said reference point is selected in a portion of the base of the electrode handling apparatus ( 30 ) .30 . A method according to any one of claims 19 to 29 , wherein, by means of said control unit ( 70 ) in said processing step c ) , the images acquired in said step b ) are processed so that , after each electrode removal and for each electrode :- the profile of the electrode is detected;- profiles of images captured at di f ferent times are compared, to determine the missing area due to electrode consumption and thus estimate the volume loss and preferably, knowing the density, also estimate the weight loss- the weight los s data is stored and then compared with subsequent electrode consumption data .31 . A method according to claim 30 , comprising the step 1 ) of generating, by means of said control unit ( 70 ) , an alarm signal i f the electrode consumption data deviates from a reference time profile of the electrode consumption within predefined tolerances .32 . A method according to any one of claims 19 to 31 , wherein, by means of said control unit ( 70 ) in said processing step c ) , the acquired images in said step b ) are processed so that , after each electrode removal and for each electrode , the image of the electrode tip and of the wear zone is also stored and wherein said method comprises the step m) of comparing, by means of said control unit ( 70 ) , the images acquired with an image library of electrode damage phenomena to identi fy potential damage phenomena and thus generate an alarm signal .

33. A method according to claim 32, comprising a step n) of generating, by means of said control unit (70) , an alarm signal if the acquired images are similar to one or more images of said image library.

34. A method according to any one of claims 19 to 33, wherein said step b) of acquiring images is carried out after said step a) wherein the electrodes have been removed from the shell (10) and positioned with respect to the roof (20) so that the tip and possibly the wear zone can also be framed.

Images