Maintenance system and method for the tapping channel in an electric arc furnace

Abstract

The present invention relates to a maintenance system for the tapping channel of an electric arc furnace. The maintenance system (1) comprises a platform (10) which is movable at a height lower than the bottom of the furnace vessel between at least one operating position, in which at least one free end (11) of the platform is arranged below the furnace vessel near the tapping channel, and a parking position, in which the free end (11) of the platform is not arranged below the furnace vessel. The system (1) further comprises a linear actuator (30) which is arranged at the free end of said platform (10) and is adapted to axially engage a ferrule with the aid of at least one support body (40) removably associable with the ferrule and a movable head (31) of the actuator. The actuator is axially movable with respect to a walking plane of said platform (10) between a lowered position and at least one lifted position, so as allow both the support in lowering in the extraction step of a worn ferrule from the tapping hole and the support in lifting in the insertion step of a replacement ferrule inside the tapping hole, previously freed from the worn ferrule. In use, said replacement ferrule is positioned on said platform above said axial translation device.

Description

"MAINTENANCE SYSTEM AND METHOD FOR THE TAPPING CHANNEL INAN ELECTRIC ARC FURNACE" DESCRIPTIONField of application

[0001] The present invention relates to a maintenance system and method for the tapping channel in an electric arc furnace .

[0002] Such system is capable of carrying out both cleaning operations and operations for restoring the tapping channel .

[0003] In particular, such system is suitable for operating in furnaces with a tapping channel in both an EBT (Eccentric Bottom Tap-hole ) and OBT ( Of fset Bottom Tap-hole ) configuration .Prior art

[0004] There are di f ferent versions of electric arc furnaces (EAF) that di f fer therebetween in relation to the configuration of the molten steel tapping device .

[0005] Tapping is the process of draining or pouring liquid steel from the melting vessel during steel production and is performed by means of a special device obtained within the melting vessel of the furnace (hereinafter also a vat ) .

[0006] EAFs may have a tapping device in the form of a spout or hole / channel formed at the bottom of the vat ora combination thereof.

[0007] With reference to the configuration with a hole / tapping channel, three versions are possible: with a central hole (CBT; Centric Bottom tapping) , with an offset hole (Offset Bottom Tapping) or with an eccentric hole (EBT, Eccentric Bottom Tapping) . In an EAF with an OBT, the bottom of the furnace is circular and the tapping hole is offset with respect to the center. In the case of an EAF with an EBT, the bottom of the furnace has a radial appendage protruding from the circular crosssection of the bottom and wherein the tapping hole is obtained .

[0008] The different versions of the furnace differ in the way in which they may be used. This leads to various requirements and problems in terms of maintenance.

[0009] As regards, in particular, the tapping hole, there are various needs and problems.

[0010] Steel deposits or slag (skull formation) may form inside the tapping hole and at the inlet (mouth) thereof .

[0011] Fragments of the electrodes or of the refractory coating of the furnace vessel may also be deposited or get stuck inside the tapping hole and at the inlet thereof.

[0012] In both cases, clogging or at least severevariations in the diameter of the tapping hole may occur, which must be eliminated .

[0013] Freeing of the obstruction and / or deposits within the tapping hole by means of combustion with the aid of an oxygen lance which is inserted through an opening in the EAF furnace vessel is known .

[0014] Devices for cleaning the tapping hole are also known to consist of a noz zle pivoted on a movable arm arranged underneath the tapping hole . By means of the arm, the noz zle is inserted into the hole and progressively moved along the longitudinal axis of said hole starting from below . In particular, those deposits that are located at the inlet of the hole ( inner furnace side ) may be removed by means of oxygen or a mixture of oxygen and gas from the burner .

[0015] An example of a device for cleaning the tapping hole is described in US2021 / 0318069 Al . Such a device is provided with a support arm for a lance . The arm is in turn pivotally anchored to the furnace itsel f and follows it in the movements thereof . Such solution has the advantage of being able to clean the channel , theoretically, at any angle of the furnace , net of the liquid steel remaining in the furnace after the tapping .The main limit of such solution is in relation to the installation thereof on board the furnace as it entailsan increased burden upon the tilting platform and may involve operational di f ficulties .

[0016] There is therefore a need for a device for cleaning the tapping channel of an EAF furnace that is operationally ef ficient , allowing for rapid centering, and at the same time that is not installed on board the furnace .

[0017] As is known, the tapping channel is internally delimited by a coating made of refractory material V, referred to in j argon as a " ferrule" . It is a hollow cylindrical body that is si zed in such a way as to be axially inserted and slid into the tapping hole . As shown in Figures 4a, b, c, the ferrule is provided at the bottom with a support flange FV, having a larger diameter than the tapping hole TH in order to anchor itsel f to the bottom of the container and thus hold the ferrule itsel f in position inside the tapping hole .

[0018] Such coating is subj ect to wear and must therefore be periodically replaced, albeit less frequently than the cleaning operations .

[0019] The replacement of the ferrule ( restoration of the tapping channel ) currently takes place operating from above the furnace with the aid of an overhead crane and by inserting from below a support pin, provided at the bottom with a support base , into the tapping channel .Operationally, the support pin is moved from above by means of the overhead crane . In the case of a CBT or OBT configuration, the operation requires the availability of an opening within the canopy of the furnace that is vertically aligned with the tapping hole or, alternatively, the canopy of the furnace may be removed in such a way as to allow access from above to the tapping hole , thereby making it possible to intervene with li fting means .

[0020] Also in the case of an EBT configuration, the ferrule is replaced from above with the aid of an overhead crane but not from the canopy, but rather from the balcony of the EBT through an opening made thereupon . The sequence of Figures 4a, b, c shows the steps for uncoupling the worn ferrule , whilst the sequence of Figure 5a, b, c shows the steps for coupling the new ferrule in the case of a furnace in the EBT configuration .

[0021] As shown in Figures 1 , 2 and 3 , some installations for EAF furnaces are equipped with a movable platform P that allows operators to access the bottom of the furnace in order to perform tapping channel maintenance operations . Such movable platform consists of a walkway which may be moved between a parking position ( see Figure 1 ) wherein the walkway is moved away from thefurnace , and an operating position ( see Figure 2 ) wherein the walkway is arranged below the furnace .

[0022] Also when using the walkway, the ferrule changing operating mode necessarily requires the use of an overhead crane , which is consequently rendered temporarily unusable for other furnace intervention operations . This slows down the maintenance operations , thus lengthening the plant downtime ; it also requires operators , both on the walkway under the tapping channel and above the EBT balcony .

[0023] In the technical sector of reference there is still therefore a completely unsatis fied need to replace the tapping hole ferrule of an EAF furnace in an operationally more ef ficient way than using the current method, without the use of an overhead crane and whilst reducing the number of operators necessary for the operation .

[0024] More generally, there is a need to simpli fy the tapping channel maintenance operations of an EAF furnace , in terms of both the cleaning and the restoration of the refractory coating . Disclosure of the invention

[0025] The main obj ect of the present invention is therefore to eliminate in whole or in part the drawbacks of the aforementioned prior art , by providing amaintenance system for the tapping channel in an electric arc furnace which allows the operations for restoring the refractory coating to be performed without the use of an overhead crane whilst reducing the number of operators necessary for the operation .

[0026] A further obj ect of the present invention is to provide a maintenance system for the tapping channel in an electric arc furnace which allows for both cleaning operations and operations for restoring the refractory coating .

[0027] A further obj ect of the present invention is to provide a maintenance system for the tapping channel in an electric arc furnace that does not require modi fications to the tilting structure of the furnace .

[0028] A further obj ect of the present invention is to provide a maintenance system for the tapping channel in an electric arc furnace that is operationally simple to manage .

[0029] A further obj ect of the present invention is to provide a maintenance system for the tapping channel in an electric arc furnace that is economical to implement . Brief description of the drawings

[0030] The technical features of the invention, according to the aforesaid obj ects , may be clearly seen in the contents of the claims below, and its advantageswill become more readily apparent in the detailed description that follows , made with reference to the accompanying drawings , which represent one or more purely exempli fying and non-limiting embodiments thereof , wherein :

[0031] - Figure 1 shows an orthogonal elevation view of a plant of a known type for an electric arc furnace in an EBT configuration, shown without the closing canopy, the plant being provided with a movable platform that allows operators access to the bottom of the furnace and that is shown in a parking position;

[0032] - Figure 2 shows the plant of Figure 1 shown with the movable platform in an operating position with at least one portion located below the furnace ;

[0033] - Figure 3 shows an orthogonal view from above of the plant of Figure 2 ;

[0034] - Figures 4a, b, c show the steps for releasing the worn ferrule according to a known type ;

[0035] - Figures 5a, b, c show the steps of coupling a new ferrule according to a known type

[0036] - Figure 6 shows an orthogonal elevation view of a plant for an electric arc furnace in an EBT configuration, shown without the closing canopy, the plant being equipped with a tapping channel maintenance system according to a preferred embodiment of theinvention, the maintenance system being shown in an operational refractory replacement position;

[0037] - Figure 7 shows an orthogonal view from above of a detail of the plant in Figure 6 relating to the maintenance system;

[0038] - Figure 8 shows an orthogonal view from above of a detail of the plant in Figure 6 relating to the maintenance system shown in a parking position;

[0039] - Figure 9 shows an orthogonal elevation view of the plant in Figure 6 , the maintenance system being shown in an operational cleaning position;

[0040] - Figure 10 shows an orthogonal view from above of a detail of the plant in Figure 9 relating to the maintenance system;

[0041] - Figure 11 shows an orthogonal top view of the maintenance system according to the invention wherewith the plant of Figure 6 is provided;

[0042] - Figure 12 shows a lateral orthogonal view of the maintenance system according to the invention shown in Figure 11 , according to the arrow IX shown therein;

[0043] - Figure 13 shows a lateral orthogonal view of the maintenance system according to the invention shown in Figure 11 , according to the arrow XI shown therein;

[0044] Figures 14 and 15 show, respectively, a perspective view from below and an orthogonal side view,according to the arrow XI I I shown in Figure 14 , of a detail of the maintenance system of Figure 11 in relation to a cleaning device ;

[0045] Figure 16 shows a perspective view of a detail of the maintenance system of Figure 11 in relation to a ferrule movement device ;

[0046] - Figure 17 shows the view of Figure 16 with some parts removed in order to better highlight others ;

[0047] - Figure 18 shows an orthogonal elevation view of the ferrule movement device of Figure 16 according to the arrow XVI I shown therein with some parts shown transparently in order to highlight others ;

[0048] - Figure 19 shows an orthogonal plan view of the ferrule movement device of Figure 16 according to the arrow XVI I I shown therein with some parts shown transparently in order to highlight others ;

[0049] - Figure 20 is a perspective view of a ferrule holder carriage intended to operate together with the ferrule movement device shown in Figure 16 ; and

[0050] - Figure 21 shows an orthogonal view from above of the ferrule holder carriage of Figure 20 , according to the arrow XX shown therein .Detailed description

[0051] The maintenance system of the tapping channel of an electric arc furnace according to the invention hasbeen indicated as a whole with the reference numeral 1 in the accompanying figures .

[0052] In general , as shown in the accompanying figures , an electric arc furnace F, for which the maintenance system 1 according to the invention is intended, comprises a vessel S of the furnace which in turn includes a lower vessel S I having a tapping hole TH .

[0053] The tapping hole TH may have an eccentric (EBT ) configuration, as shown in the accompanying figures , of fset ( OBT ) or central ( CBT ) , and extends along a first longitudinal axis X .

[0054] The tapping hole TH houses therein a tubular refractory coating V therein in the form of a ferrule that delimits a tapping channel TC and is axially removable along said first longitudinal axis X .

[0055] The electric arc furnace F further comprises a furnace tilting device FI , for example of the cradle or roller type . The tilting device FI (which defines the tilting structure of said furnace ) supports the furnace vessel and is configured to tilt the furnace vessel with respect to a hori zontal direction of a foundation B that supports the electric arc furnace .

[0056] Herein and in the following description and the claims , reference will be made to the container 1 under usage conditions . Any references to a lower or upperposition or to a hori zontal or vertical orientation should therefore be interpreted in such sense .

[0057] According to a general embodiment of the invention, the maintenance system 1 comprises a platform 10 which is intended to be anchored, preferably cantilevered, to the foundation B .

[0058] The platform 10 is provided with movement means 13 suitable to move the platform itsel f at a height lower than the bottom of the furnace vessel .

[0059] By means of the aforesaid movement means 13 , the platform 10 is movable between :

[0060] - at least one operating position, in which at least one free end 11 of the platform is arranged below the furnace vessel near the tapping channel ( see Figures 7 and 10 ) , and

[0061] - a parking position, in which the free end 11 of the platform is not arranged below the furnace vessel ( see Figure 8 ) .

[0062] The maintenance system 1 further comprises a linear actuator 30 which is arranged at the free end of said platform 10 and is adapted to axially engage a ferrule with the aid of at least one support body 40 that is removably associable with the ferrule and a movable head 31 of the actuator 30 .

[0063] The linear actuator 30 is axially movable withrespect to a walking plane PC of said platform 10, between a lowered position (see Figure 19) and at least one lifted position (see Figure 6) , so as to allow:

[0064] both the support in lowering in the extraction step of a worn ferrule from the tapping hole;

[0065] - and the support in lifting in the insertion step of a replacement ferrule inside the tapping hole TH, previously freed from the worn ferrule.

[0066] In use the replacement ferrule is positioned on the platform 10 above said axial translation device.

[0067] Operationally, in other words, the linear actuator 30 allows ferrules to be moved from the bottom of the lower vessel SI of the furnace to the platform 10 and vice versa.

[0068] By virtue of the invention, the maintenance system 1 of the tapping channel in an electric arc furnace allows operations for restoring the refractory coating to be carried out without the use of an overhead crane and reducing the number of operators necessary for the operation.

[0069] In fact, using the system 1 according to the invention, all of the operations associated with restoring the refractory coating (ferrule) , i.e., removing the worn ferrule and arranging the replacement ferrule, may be performed:

[0070] operating solely from the bottom of the furnace vessel ;

[0071] - without the aid of an overhead crane ;

[0072] - without the need for interventions from the inside of the furnace itsel f ;

[0073] engaging only the opening comprising the tapping hole ;

[0074] In this way invasive operations on the furnace are minimi zed, both in terms of time and in terms of the parts of the furnace that are involved .

[0075] The operations for restoring the refractory coating that delimits the tapping channel TC ( ferrule ) therefore interfere much less with any other maintenance operations , with the benefit of reducing plant downtime .

[0076] A further advantage of the invention derives from the fact that the maintenance system 1 does not require modi fications to the structure of the furnace .

[0077] The maintenance system 1 according to the invention is also operationally simple to manage , as well as being cost-ef fective to implement .

[0078] Preferably, the linear actuator 30 is axially movable with respect to the walking plane PC of said platform 10 , along an operating direction XL incident to said walking plane . In particular, such operating direction XL is orthogonal to the walking plane PC of theplatform 10 .

[0079] Advantageously, from an operational point of view, the replacement of a worn ferrule by means of the system 1 according to the invention may be performed with the furnace vessel in a substantially hori zontal position, i . e . with the axis of the tapping hole vertically aligned with the walking plane PC of the platform 10 .

[0080] Advantageously, as shown in Figures 7 , 8 , 10 and 12 , the platform 10 defines a transit lane 12 for reaching the free end 11 of the platform itsel f . The linear actuator 30 is arranged at the free end 11 of said platform 10 within the transit lane 12 .

[0081] Advantageously, as shown in Figure 19 , said linear actuator 30 comprises actuation means 32 which are adapted to move said movable head 31 axially and are arranged substantially below the walking plane PC of said platform 10 .

[0082] Preferably, said linear actuator 30 consists of a pneumatic or hydraulic ferrule with a telescopic rod .

[0083] Operationally, the telescopic structure of the linear actuator 30 allows elevated heights to be reached at the maximum extension ( in such a way as to cover the distance between the walking plane of the platform and the inside of the furnace , whilst having the possibilityof reducing the overall dimensions when not in use . In this way, the installation of the linear actuator 30 on the platform 10 adapts to the reduced spaces available between the platform and the bottom of the furnace without requiring structural modi fications to the furnace itsel f .

[0084] Preferably, as shown in Figure 18 , in said lowered position the movable head 31 of said linear actuator 30 is positioned substantially at the level of the walking plane of said platform 10 , in such a way as not to protrude or to protrude a little with respect thereto . In this way, as will be clari fied below, it is possible to arrange a carriage for transporting ferrules above the movable head 31 .

[0085] Preferably, the maintenance system 1 comprises at least one support carriage 50 for moving a ferrule V (previously associated with said support body 40 ) along said transit lane 12 .

[0086] More speci fically, as shown in Figures 20 and 21 , said support carriage 50 is provided with a resting floor 51 below which an engagement seat 52 is obtained for the movable head 31 of the linear actuator 30 .

[0087] In use said support carriage 50 follows the ferrule in the axial li fting and lowering movements generated by said linear actuator 30 and being used tomove the ferrules along said transit lane to reach or leave the free end 11 of the platform 10 .

[0088] Operationally, as mentioned above , the ferrule is loaded onto the carriage 50 which is already associated with the aforesaid support body 40 , as shown in Figures 20 and 21 .

[0089] The support body 40 is preferably comprises :

[0090] - a base 41 intended to abuttingly engage the bottom FV of the ferrule V (preferably consisting of a flange for fastening to the bottom of the furnace vessel ) and

[0091] - a pin 42 extending from said base 41 and is intended to be inserted axially inside the ferrule .

[0092] Advantageously, the pin 42 may be provided at the free end thereof with a ring to allow for engagement on the part of li fting means .

[0093] In use , said base 41 may be engaged directly by the movable head 31 of said actuator 30 or indirectly by means of said support carriage 50 , as shown in Figure 21 . The latter method is entirely preferred, allowing for easier handling of the ferrules .

[0094] Advantageously, the aforementioned platform 10 consists of a movable walkway .

[0095] Preferably, said movable walkway is translatable along a second longitudinal axis Y1 betweensaid at least one operating position and said parking position .

[0096] According to a preferred embodiment shown in the accompanying figures , said movable walkway comprises a telescopic retractable portion 15 .

[0097] Advantageously, as shown in Figure 8 , the aforesaid walkway 30 extends longitudinally along said second longitudinal axis Y1 . The linear actuator 30 is positioned in an appendage 14 of said walkway 10 of fset with respect to said second longitudinal axis Y1 .

[0098] According to a fully preferred embodiment of the invention, the maintenance system 1 further comprises a cleaning device 20 for cleaning the tapping channel TC delimited internally by the refractory coating ( ferrule V) .

[0099] More speci fically, said cleaning device 20 is supported by said platform 10 outside the transit lane 12 .

[0100] The cleaning device 20 comprises a movable cleaning head 21 which is arranged near the free end 11 of said platform 10 and is movable by means of an extension 22 so as to be axially inserted inside the tapping channel along the entire axial extension thereof .

[0101] The aforesaid cleaning head 21 is adapted to remove any deposits of steel and / or slag at the entrance( intended as an outlet inside the furnace ) and inside the tapping channel TC .

[0102] The cleaning device 20 is preferably a striker device of which said cleaning head 21 is the striking portion .

[0103] The cleaning device 20 may also be a rotary perforating device or a perforating device with a combined action of rotation and striking, wherein said cleaning head 21 is the perforating tip .

[0104] The cleaning device 20 is preferably electrically operated, whilst the cleaning head 21 is pneumatically cooled . In Figure 15 , the compressed air supply duct is indicated with the numeral 25 .

[0105] Advantageously, as shown in particular in Figure 13 , the cleaning head 21 is supported by a linear guide 23 which extends substantially orthogonally with respect to the walking plane PC of said platform 10 .

[0106] Advantageously, the aforesaid linear guide 23 extends in height substantially from the level of the walking plane PC to the mouth of the tapping channel TC .

[0107] Operationally, the movable head 21 , once inserted into the tapping channel , is guided by said channel . Advantageously, the extension 22 adapted to move the movable head 21 may not be rigid .

[0108] Preferably, the extension 22 is articulated andis slidably inserted inside a sliding duct 29 which extends parallel to the second longitudinal direction Y1 with a first hori zontal section and connects to the linear guide 23 using a curved section . In this way, the articulated extension 22 may extend suf ficiently in length in order to allow the movable head 21 to be inserted inside the tapping channel TC, without however requiring excessive vertical space .

[0109] Advantageously, in order to prevent the articulated extension 22 from bending along the sliding path, the device is equipped with a tensioning chain 25 that extends along the extension 22 .

[0110] Advantageously, the extension 22 is connected to elastic means ( for example a spring pack) arranged at the end of the extension 22 opposite the end connecting the movable head 21 . In this way, a certain degree of elasticity is conferred upon the extension 22 .

[0111] In particular, the articulated extension 22 is moved along the sliding duct by movement means 26 , 27 and 28 adapted to impart an alternating thrust and traction movement to the extension 22 .

[0112] In particular, as shown in Figure 15 , the aforementioned movement means may consist of a pinionrack system 27 , 28 which is driven by a gearmotor 26 and which kinematically engages the extension by means of askid 220 that is constrained at one end of the extension .Alternatively, the aforesaid movement means may consist of a linear actuator (pneumatic or hydraulic cylinder ) acting directly upon the extension 22 .

[0113] Advantageously, as shown in Figures 14 and 15 , the sliding duct 29 and the linear guide 23 (by means of the support rod 230 ) are connected to a support structure in such a way as to tilt about an axis of rotation R (parallel to the axis Yl ) . In this way it is possible to vary the tilting of the linear guide 23 , adapting it to the tilting of the tapping channel TC . Such operation is performed during the installation of the device with the possibility of subsequent adj ustments .

[0114] The aforesaid platform 10 is preferably movable by said movement means 13 with translation movements along said second longitudinal axis Yl between :

[0115] - said parking position ( see Figure 8 ) ,

[0116] a first operating position, in which the movable head 31 of the linear actuator 30 is axially aligned with the first longitudinal axis X of the tapping channel ( see Figure 7 ) ; and

[0117] a second operating position, in which the movable cleaning head 21 of the cleaning device 20 is axially aligned with the first longitudinal axis X of the tapping channel ( see Figure 10 ) .

[0118] Advantageously, as shown in Figures 7 and 10 , the cleaning head 21 is aligned with the movable head 31 of the linear actuator 30 along an operational positioning direction Y2 parallel to said second longitudinal axis Y1 . Operationally, the transition between the two operating pos itions may therefore take place using a simple translation parallel to the axis Y1 . This simpli fies the centering operations within the tapping channel .

[0119] The present invention also relates to a steel plant 100 comprising an electric arc furnace .

[0120] The electric arc furnace F comprises a vessel S of the furnace which in turn includes a lower vessel S I of the furnace having a tapping hole TH . The tapping hole TH may have an eccentric (EBT ) , of fset ( OBT ) or central ( CBT ) configuration and extends along a first longitudinal axis X . The tapping hole TH receives a tubular refractory coating V therein in the form of a ferrule that delimits a tapping channel TC and is axially removable along said first longitudinal axis X .

[0121] The electric arc furnace F further comprises a cradle or roller type furnace tilting device FI . The tilting device FI supports the furnace vessel and is configured to tilt the furnace vessel with respect to ahori zontal direction of a foundation B supporting the electric arc furnace .

[0122] The steel plant 100 comprises a maintenance system for the tapping channel of said electric arc furnace .

[0123] According to the invention, the aforesaid tapping channel maintenance system is a tapping channel maintenance system 1 according to the present invention and in particular as described above .

[0124] One obj ect of the present invention is also a maintenance method for the tapping channel of an electric arc furnace .

[0125] The electric arc furnace F comprises a vessel S of the furnace which in turn includes a lower vessel S I of the furnace having a tapping hole TH . The tapping hole TH may have an eccentric (EBT ) , of fset ( OBT ) or central ( CBT ) configuration and extends along a first longitudinal axis X . The tapping hole TH receives a tubular refractory coating V therein in the form of a ferrule that delimits a tapping channel TC and is axially removable along said first longitudinal axis X .

[0126] The electric arc furnace F further comprises a cradle or roller type furnace tilting device FI . The tilting device FI supports the furnace vessel and isconfigured to tilt the furnace vessel with respect to a hori zontal direction of a foundation B supporting the electric arc furnace .

[0127] According to the invention, the maintenance method comprises the further operational steps of :

[0128] - a ) providing a tapping channel maintenance system 1 according to the present invention and in particular as described above ;

[0129] b ) replacing a worn ferrule with a replacement ferrule by following the sub-steps described below .

[0130] The first sub-step bl ) requires bringing the platform 10 in said operating position, axially aligning the movable head 31 of the linear actuator 30 with the first longitudinal axis X of the tapping channel .

[0131] After sub-step bl ) the subsequent sub-steps follow :

[0132] - b2 ) bringing the movable head 31 into the li fted position and associating the movable head 31 with the worn ferrule by means of said support body 40 ;

[0133] - b3 ) releasing the worn ferrule from the lower vessel S I ;

[0134] - b4 ) accompanying the extraction of the worn ferrule from the tapping hole by means of said linear actuator 30 , progress ively bringing the movable supporthead 31 from the lifted position to the lowered position;

[0135] - b5) freeing the linear actuator 30 from the worn ferrule;

[0136] - b6) associating a replacement ferrule with the linear actuator 30 by means of said support body 40;

[0137] - b7) inserting the replacement ferrule inside the tapping hole, axially lifting it with the linear actuator 30, progressively bringing the movable support head 31 from the lowered position to the lifted position;

[0138] - b8) anchoring the replacement ferrule to the lower vessel of the furnace;

[0139] - b9) returning the movable support head 31 from the lifted position to the lowered position;

[0140] - blO) bringing the platform 10 to said parking position .

[0141] Advantageously, the aforesaid step b) of replacing a worn ferrule is performed with the furnace vessel in a substantially horizontal position.

[0142] The maintenance method preferably further comprises the operating step c) of performing a cleaning of the tapping channel using said maintenance system 1.

[0143] Step c) of cleaning the tapping channel is performed as an alternative to step b) and comprises the following sub-steps:

[0144] cl) bringing the platform 10 in said operatingposition, axially aligning the movable cleaning head 21 with the first longitudinal axis X of the tapping channel TC ;

[0145] c2 ) inserting the cleaning head inside the tapping channel until it reaches the inside of the furnace ;

[0146] c3 ) extracting the cleaning head from the tapping channel ;

[0147] c4 ) bringing the platform 10 in said parking position .

[0148] Advantageously, said step b ) of cleaning the tapping channel is performed with the furnace vessel tilted by a predetermined angle .

[0149] The advantages in relation to the maintenance method according to the invention are the same as those described in relation to the maintenance system 1 according to the invention . For brevity of description, they will not be presented again .

[0150] The invention allows numerous advantages to be obtained, which have already been described in part .

[0151] The maintenance system 1 of the tapping channel in an electric arc furnace according to the invention allows the operations for restoring the refractory coating to be performed without the use of an overhead crane whilst reducing the number of operators necessaryfor the operation .

[0152] By using the system 1 according to the invention, all of the operations relating to the restoration of the refractory coating that delimits the tapping channel TC, i . e . , the removal of the worn ferrule and the positioning of the replacement ferrule , may be performed :

[0153] operating solely from the bottom of the furnace vessel ,

[0154] - without the aid of an overhead crane

[0155] - without the need for interventions from the inside of the furnace itsel f

[0156] engaging only the opening comprising the tapping hole

[0157] minimi zing invasive operations on the furnace , both in terms of time and in terms of the parts of the furnace that are involved .

[0158] In this way, operations for restoring the refractory coating that delimits the tapping channel TC interfere much less with any other maintenance operations , with the benefit of reducing plant downtime .

[0159] By virtue of the fact that

[0160] The maintenance system 1 of the tapping channel in an electric arc furnace according to the invention allows for both cleaning operations and operations forrestoring the refractory coating .

[0161] The maintenance system 1 of the tapping channel in an electric arc furnace according to the invention does not require changes to the structure of the furnace . Advantageously, such system 1 may therefore be used in pre-existing furnaces without requiring alterations to the furnace itsel f . This is therefore an ideal solution for a furnace retrofitting operation .

[0162] The maintenance system 1 according to the invention is also operationally simple to manage , as well as being cost-ef fective to implement .

[0163] The invention thus conceived therefore achieves its intended obj ectives .

[0164] Obviously, in practice it may also assume di f ferent forms and configurations from the one illustrated above , without thereby departing from the present scope of protection .

[0165] Furthermore , all details may be replaced with technically equivalent elements , and the dimensions , shapes , and materials used may be any according to the needs .

Claims

CLAIMS1. Maintenance system of the tapping channel of an electric arc furnace, said furnace (F) comprising:- a vessel (S) of the furnace which in turn includes a lower vessel (SI) of the furnace having a tapping hole (TH) and extends along a first longitudinal axis (X) , said tapping hole (TH) receiving a tubular refractory coating (V) therein in the form of a ferrule which delimits a tapping channel (TC) and is axially removable along said first longitudinal axis (X) , and a furnace tilting device (FI) , which supports the furnace vessel and is configured to tilt the furnace vessel with respect to a horizontal direction of a foundation (B) supporting the electric arc furnace, the maintenance system (1) of the tapping channel of an electric arc furnace being characterized in that it comprises : a platform (10) which is intended to be anchored, preferably cantilevered, to the foundation (B) and is provided with movement means (13) adapted to move the platform itself at a height lower than the bottom of the furnace vessel between at least one operating position, in which at least one free end (11) of the platform is arranged below the furnace vessel near the tapping channel, and a parking position, in which the free end(11) of the platform is not arranged below the furnace vessel, and- a linear actuator (30) which is arranged at the free end of said platform (10) and is adapted to axially engage a ferrule with the aid of at least one support body (40) removably associable with the ferrule and a movable head (31) of the actuator, said actuator being axially movable with respect to a walking plane of said platform (10) between a lowered position and at least one lifted position, so as to allow both the support in lowering in the extraction step of a worn ferrule from the tapping hole and the support in lifting in the insertion step of a replacement ferrule inside the tapping hole, previously freed from the worn ferrule, in use said replacement ferrule having been positioned on said platform above said axial translation device.

2. Maintenance system (1) according to claim 1, wherein said platform (10) defines a transit lane (12) for reaching the free end (11) and wherein the linear actuator (30) is arranged at the free end of said platform (10) inside the transit lane (12) .

3. Maintenance system (1) according to claim 1 or 2, wherein said linear actuator (30) comprises drive means (32) which are suitable to axially move said movable head (31) and are arranged substantially below the walkingplane of said platform (10) .

4. Maintenance system (1) according to claim 1, 2 or 3, wherein in said lowered position the movable head (31) of said linear actuator (30) is positioned substantially at the level of the walking plane of said platform (10) .

5. Maintenance system (1) according to any one of the preceding claims, wherein said linear actuator (30) consists of a pneumatic or hydraulic cylinder with telescopic rod.

6. Maintenance system (1) according to any one of the preceding claims, when dependent on claim 2, comprising at least one support carriage (50) for moving a ferrule (V) previously associated with said support body (40) along said transit lane (12) , said support carriage (50) being provided with a resting floor (51) below which an engagement seat (52) is obtained for the movable head (31) of the linear actuator (30) , in use said support carriage (50) following the ferrule in the axial lifting and lowering movements generated by said linear actuator (30) and being used to move the ferrules along said transit lane to reach or leave the free end (11) of the platform (10) .

7. Maintenance system (1) according to any one of the preceding claims, wherein the support body (40) comprises :a base (41) intended to abuttingly engage the bottom of the ferrule (V) and- a pin (42) extending from said base (41) and intended to be inserted axially inside the ferrule, in use said base (41) being able to be engaged directly by the movable head (31) of said actuator (30) or indirectly by means of said support carriage (50) .

8. Maintenance system (1) according to any one of the preceding claims, wherein said platform (10) consists of movable walkway.

9. Maintenance system (1) according to claim 8, wherein said movable walkway is translatable along a second longitudinal axis (Y) between said at least one operating position and said parking position, preferably said walkway comprising a telescopic retractable portion.

10. Maintenance system (1) according to claim 9, wherein said walkway (30) extends longitudinally along said second longitudinal axis (Y) and wherein the linear actuator (30) is positioned in an appendage (14) of said walkway (10) which is offset with respect to said second longitudinal axis (Y) .

11. Maintenance system (1) according to any one of the preceding claims, when dependent on claim 2, further comprising a cleaning device (20) for cleaning the tapping channel (TC) , which cleaning device (20) issupported by said platform outside the transit lane (12) and comprises a movable cleaning head (21) which is arranged near the free end (11) of said platform (10) and is movable by means of an extension (22) so as to be axially inserted inside the tapping channel along the entire axial extension thereof, said cleaning head (21) being adapted to remove any deposits of steel and / or slag at the entrance and inside the tapping channel (TC) .

12. Maintenance system (1) according to claim 11, wherein said cleaning device (20) is a striker device of which said cleaning head (21) is the striking portion.

13. Maintenance system (1) according to claim 11 or 12, wherein said cleaning head (21) is supported by a linear guide (23) extending substantially orthogonally with respect to the walking plane of said platform (10) .

14. Maintenance system (1) according to claim 13, when dependent on claim 10, wherein said cleaning head (21) is aligned with the movable head (31) of the linear actuator (30) along an operating positioning direction (Y2) which is parallel to said second longitudinal axis (Y) .

15. Maintenance system (1) according to claim 14, wherein said platform (10) is movable by said movement means (13) with translation movements along said second longitudinal axis (Y) between: said parking position,- a first operating position, in which the movable head (31) of the linear actuator (30) is axially aligned with the first longitudinal axis (X) of the tapping channel; and a second operating position, in which the movable cleaning head (21) of the cleaning device (20) is axially aligned with the first longitudinal axis (X) of the tapping channel.

16. Steel plant (100) comprising an electric arc furnace which comprises:- a vessel (S) of the furnace which in turn includes a lower vessel (SI) of the furnace having a tapping hole (TH) which has an eccentric (EBT) or offset (OBT) configuration and extends along a first longitudinal axis (X) , said tapping hole (TH) receiving a tubular refractory coating (V) therein in the form of a ferrule which delimits a tapping channel (TC) and is axially removable along said first longitudinal axis (X) , and a furnace tilting device (FI) comprising a cradle, which supports the furnace vessel and is configured to tilt the furnace vessel with respect to a horizontal direction of a foundation (B) supporting the electric arc furnace, and- a maintenance system of the tapping channel of said electric arc furnace,said steel plant being characterized in that said tapping channel maintenance system is a tapping channel maintenance system (1) according to any one of the preceding claims.

17. Maintenance method of the tapping channel of an electric arc furnace, said furnace comprising:- a vessel (S) of the furnace which in turn includes a lower vessel (SI) of the furnace having a tapping hole (TH) which has an eccentric (EBT) or offset (OBT) configuration and extends along a first longitudinal axis (X) , said tapping hole (TH) receiving a tubular refractory coating (V) therein in the form of a ferrule which delimits a tapping channel (TC) and is axially removable along said first longitudinal axis (X) , and a furnace tilting device (FI) comprising a cradle, which supports the furnace vessel and is configured to tilt the furnace vessel with respect to a horizontal direction of a foundation (B) supporting the electric arc furnace, said method comprising the following operating steps:- a) providing a tapping channel maintenance system (1) according to any one of claims 1 to 15;- b) replacing a worn ferrule with a replacement ferrule following the following sub-steps: bl) bringing the platform (10) in said operatingposition, axially aligning the movable head (31) of the linear actuator (30) with the first longitudinal axis (X) of the tapping channel; b2) bringing the movable head (31) into the lifted position and associating the movable head (31) with the worn ferrule by means of said support body (40) ; b3) releasing the worn ferrule from the lower vessel (SI) ; b4) accompanying the extraction of the worn ferrule from the tapping hole by means of said linear actuator(30) , progressively bringing the movable support head(31) from the lifted position to the lowered position; b5) freeing the linear actuator (30) from the worn ferrule ; b6) associating a replacement ferrule with the linear actuator (30) by means of said support body (40) ; b7) inserting the replacement ferrule inside the tapping hole, axially lifting it with the linear actuator(30) , progressively bringing the movable support head(31) from the lowered position to the lifted position; b8) anchoring the replacement ferrule to the lower vessel of the furnace; b9) returning the movable support head (31) from the lifted position to the lowered position; blO) bringing the platform (10) in said parkingposition .

18. Maintenance method according to claim 17, wherein said step b) of replacing a worn ferrule is performed with the furnace vessel in a substantially horizontal position .

19. Maintenance method according to claim 17 or 18, further comprising the operating step c) of performing a cleaning of the tapping channel using said maintenance system (1) as an alternative to step b) , following the following sub-steps: cl) bringing the platform (10) in said operating position, axially aligning the movable cleaning head (21) with the first longitudinal axis (X) of the tapping channel (TC) ; c2) inserting the cleaning head inside the tapping channel until it reaches the inside of the furnace; c3) extracting the cleaning head from the tapping channel ; c4) bringing the platform (10) in said parking position .

20. Maintenance method according to claim 19, wherein said step b) of performing a cleaning of the tapping channel is performed with the furnace vessel tilted by a predefined angle.

Images