Electric arc furnace with slag level regulation system and method of slag level regulation in an electric arc furnace

Abstract

The present invention relates to an electric arc furnace (1) comprising: a shell (10) for containing a bath of molten metal (M), on which a layer of slag (S) floats in use, which extends in height from the surface of said bath up to an upper level (H) varying over time, said shell (10) being provided with a tapping channel (11) and a slag door (12); a detection apparatus (40) suitable to detect the upper slag level over time. The furnace comprises a slag level regulation system (50) which : includes said detection apparatus (40); is connected to said slag door (12); and is programmed to regulate the upper slag level during the operation of the furnace (1) in accordance with a predefined adjustment strategy based on values of said upper level (H) detected by said detection apparatus (40), performing one or more partial slagging operations by means of controlled opening and closing of said slag door to discharge the excess slag. The invention also relates to a method for regulating the slag level in an electric arc furnace.

Description

ELECTRIC ARC FURNACEWITH SLAG LEVELREGULATION SYSTEM AND METHOD OFSLAG LEVELREGULATION IN AN ELECTRIC ARC FURNACEDESCRIPTIONField of application

[0001] The present invention relates to an electric arc furnace with slag level regulation system and a method for regulating the slag level in an electric arc furnace. Background art

[0002] The direct melting of materials which contain iron, such as scrap, is usually performed in electric arc furnaces (EAFs).

[0003] There are two main operating steps in the operation of an electric arc furnace:

[0004] - scrap melting, in which electrodes and injectorburners are used to melt the scrap; and

[0005] - molten metal refining, in which oxygen injectors are used for decarburization.

[0006] FeO and CO, which leave the melt in the form of bubbles, are generated during decarburization. FeO must then be reduced; in order to maintain a good yield in FeO reduction, carbon is injected into the liquid slag which is at the interface with the molten metal. In turn, FeO reduction generates additional CO in the form of bubbles, increasing the foaming slag level.

[0007] The advantage of the foaming slag formation is the creation of a volume capable of protecting the walls of the EAF and protecting the electric arc. The amount of energy discharged to the molten metal is thus increased, reducing power consumption.

[0008] A step of slagging, which consists in discharging the slag from the furnace, is performed before tapping the molten metal from the furnace. For this purpose, the furnace EAF is provided with a slag door SD. Operatively, the furnace (supported by a tilting system) is inclined so that the slag layer which floats on the molten metal bath flows through the previously opened slag door.

[0009] As shown in figure 1, the tapping channel TD (or tapping door), generally made according to the known EBT (Eccentric Bottom Tap-hole) configuration, is obtained in a position opposite to the slag door, at a lower height with respect to the bottom.

[0010] Sometimes, due to the composition of the loaded scrap, a large amount of foam with the formation of a very high foaming slag layer is obtained from the beginning. If this foam formation is excessive, the foam level will reach the balcony B of the EBT panels. In this case, if there is no free space in the slag door area (due to the probable presence of unmolten scrap), the slag foam will escape from the holes (if any) obtained onthe upper furnace shell or through the slots or openings on the EBT panels or through the vault.

[0011] The uncontrolled escape of slag foam can cause damage on other equipment or people.

[0012] Furnaces are generally provided with slag doors which are not designed to resist long when in contact with the slag. Therefore, if the foam level exceeds the threshold of the slag door, a step of slagging must be performed by opening the door itself. However, such an operation would still be necessary because the traditional slag doors cannot seal the slag opening due to the presence of solidified slag residue. Therefore, if the slag were allowed to rise in level beyond the threshold of the slag door it would come out of the door anyway.

[0013] Due to these possible problems, it is known to provide EAF furnaces with devices suitable to detect the slag foam level.

[0014] In particular, it is known to detect the foam level by means of a radar or ultrasound device capable of resisting high temperatures.

[0015] Generally, as a function of the detected foam levels, action is taken by introducing suitable chemical agents suitable to slow down the formation of foam into the furnace.

[0016] However, such an operating mode is laborious and complex to implement and not always effective.

[0017] Therefore, the need to regulate the foam level in an electric arc furnace in a more effective and efficient manner than currently performed is still completely unmet in the technical field.Presentation of the invention

[0018] Therefore, it is the main object of the present invention to eliminate the drawbacks of the aforementioned prior art either entirely or in part by providing an electric arc furnace with slag level regulation system which allows regulating the slag level in an effective and efficient manner.

[0019] It is a further object of the present invention to provide an electric arc furnace with slag level regulation system which is operatively reliable and simple to manage.

[0020] It is a further object of the present invention to provide a method for regulating the slag level in an electric arc furnace which allows regulating the slag level in an effective and efficient manner and simultaneously in a reliable and simple manner.Brief description of the drawings

[0021] The technical features of the invention according to the aforesaid objects can be clearly found in thecontents of the claims hereinbelow and the advantages thereof will become more apparent from the following detailed description, given with reference to the accompanying drawings which show one or more embodiments merely given by way of non-limiting example, in which:

[0022] - Figure 1 shows an orthogonal section view of an electric arc furnace with EBT of known type, shown limited to the lower shell and upper shell without the closing vault;

[0023] - Figure 2 shows a section view of an electric arc furnace with slag level regulation system according to a preferred embodiment of the invention, provided with EBT, said furnace being shown in a step of slag accumulation;

[0024] - Figure 3 shows the furnace in figure 2 shown in a step of discharging the slag;

[0025] - Figures 4 and 5 show a detail of a furnace according to the invention relating to a slag door with a closing and cleaning pusher, shown in the closed condition with the pusher in the extended and retracted positions, respectively;

[0026] - Figures 6 and 7 show the slag door in figure 4, shown in the open condition with pusher in the extended and retracted positions, respectively;

[0027] - Figure 8 shows the slag door in figure 4, shown in a fully open condition; and

[0028] - Figure 9 diagrammatically shows the possibilities of controlling the tapping step in relation to the contribution of slag into the ladle in a furnace according to the invention.Detailed description

[0029] The electric arc furnace with slag level regulation system according to the invention is indicated as a whole by reference numeral 1 in Figures 2 and 3.

[0030] According to a general embodiment of the invention, the electric arc furnace 1 comprises:

[0031] - a shell 10 for containing a bath of molten metal M, on which a layer of slag S floats in use, which extends in height from the surface of said bath up to an upper level H varying over time.

[0032] - a shell closing vault 30, on which one or more openings 31 are obtained for the insertion of one or more electrodes .

[0033] The shell 10 is provided with a tapping channel 11 and a slag door 12.

[0034] The electric arc furnace 1 further comprises a detection apparatus 40 suitable to detect the upper slag level over time.

[0035] According to the invention, the furnace 1 comprises a slag level regulation system 50 which:

[0036] - includes said detection apparatus 40;

[0037] - is connected to said slag door 12; and

[0038] - is programmed to regulate the upper slag level during the operation of the furnace 1 in accordance with a predefined regulation strategy based on values of said upper level H detected by said detection apparatus 40, performing one or more partial slagging operations by means of controlled openings and closures of said slag door to discharge the excess slag.

[0039] By virtue of the presence of the slag level regulation system, the electric arc furnace 1 allows regulating the slag level in an effective and efficient manner by simply acting on the opening of the slag door, without necessarily having to provide for the introduction of appropriate chemical agents suitable to slow down the formation of foam into the furnace.

[0040] Indeed, the latter operating mode (preferably, but not necessarily, excluded) is laborious and complex to implement and not always effective.

[0041] Advantageously, the slag level regulation operations can thus be fully automated.

[0042] It is also possible to automate the dosing of chemical agents suitable to slow down the formation of foam.

[0043] Preferably, the aforesaid regulation strategy includes maintaining the upper slag level below apredefined maximum value.

[0044] According to the preferred embodiment shown in figures 2 and 3, the shell 10 is divided into a lower shell 10a and an upper shell 10b. The lower shell 10a is provided with a portion protruding from said upper shell 10b so as to create a balcony 10c. The tapping channel 11 is obtained at the bottom of said lower shell 10b at said protruding portion in a position opposite to the slag door, according to the known EBT (Eccentric Bottom Taphole) configuration.

[0045] Preferably, the aforesaid predefined maximum value of the upper slag level is defined as a function of a predefined minimum interdistance D between the upper slag level and the internal ceiling of said balcony 10c.

[0046] Preferably, said detection apparatus 40 is installed at said protruding portion.

[0047] In particular, said detection apparatus 40 takes measurements through a hole 41 obtained in the ceiling of said balcony 10c.

[0048] Such a position is preferred over other possible positions, e.g., on the vault 30, because:

[0049] - it is more protected from molten metal splashes;

[0050] - it is further away from the electrodes;

[0051] - it is less used than the vault;

[0052] - it generally already has an opening for sanddosing, which opening can be utilized for a dual purpose.

[0053] The detection apparatus 40 can be of any type adapted for the purpose.

[0054] Preferably, said detection apparatus 40 is a radartype detection apparatus.

[0055] Alternatively (non-preferred embodiment) , said detection apparatus 40 can be an ultrasound-type detection apparatus.

[0056] Advantageously, said furnace 1 is provided with a shell support system 20, which is suitable to support said shell movably so as to incline it towards the slag door 12 or towards the tapping channel 11.

[0057] Preferably, the slag level regulation system 50 is connected to said tapping door 11 and said shell support system 20. The slag level regulation system 50 is configured to regulate the degree of inclination of the shell during tapping as a function of a predefined regulation strategy based on the upper slag level detected by said radar apparatus 40.

[0058] Advantageously, the furnace 1 comprises an electrode regulation system. The slag level regulation system 50 is connected to said electrode regulation system.

[0059] The electrode regulation system is configured to regulate the electrical power discharged by the electrodes and / or the activation time of the electrodesas a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus 40.

[0060] Advantageously, the slag door 12 defines a tunnel opening 120 and comprises one or more cleaning elements 121 movable through said tunnel opening 120 to remove any solidified slag residues present at the bottom and / or on the side walls of the tunnel opening itself.

[0061] Preferably, the slag door 12 is provided with one or more closing elements 122, 123 configured so that they can seal the tunnel opening 120 in the closing position. In particular, one or more of said closing elements can also act as cleaning elements.

[0062] According to an entirely preferred embodiment, shown in the accompanying figures and in particular in figures from 4 to 8, the slag door 12 defines a tunnel opening 120 and comprises a pusher 121 which:

[0063] - is movable through said tunnel opening 120 with an alternating movement in order to remove any solidified slag residues present at the bottom and / or on the side walls of the tunnel opening;

[0064] - comprises a head 122 suitable to resist when in contact with the slag and sized to seal the tunnel opening 120 by cooperating with a closing panel 123 which is integrated in the slag door 12 above said pusher 121.

[0065] In particular, the head 122 is made by a copper body which is internally cooled so that it can resist the aggressive action of the slag. The closing panel 123 (not intended to come into contact with the slag) can be made by a cooling tube structure.

[0066] Operatively, the pusher 121 and the closing panel 123 are also movable in height with respect to the bottom of the tunnel opening in order as to regulate the degree of opening thereof.

[0067] An example of slag door with such features is described in European Patent EP2489971B1 in the name of the same Applicant.

[0068] Preferably, the slag level regulation system 50 is connected to said slag door 12 in order to control the actuation thereof so as to perform controlled openings of the slag door itself, acting on the degree of opening of the tunnel opening 120 as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus 40.

[0069] The use of a slag door as described above is particularly advantageous because, unlike slag doors without a cleaning and closing pusher, such a slag door can be used to regulate the slag level, at least over the entire height of the pusher itself.

[0070] As already mentioned, such a door is in fact capableof resisting when in contact with the slag and effectively sealing the slag opening preventing uncontrolled spillage of slag.

[0071] In other words, the slag door 12 can be used for all intents and purposes as a "slag valve", enhancing the potential of the slag level regulation system 50.

[0072] Advantageously, by virtue of the invention, and in particular of the use of the aforesaid specific slag door ("slag valve"), there is also the advantage of NOx reduction, by virtue of the fact that false air entry is reduced.

[0073] The present invention also relates to a method for regulating the slag level in an electric arc furnace 1.

[0074] The electric arc furnace 1 (which, in particular, is a furnace according to the invention, in particular as described above) comprises:

[0075] - a shell 10 for containing a molten metal bath, on which a slag layer floats in use, which extends in height from the surface of said bath up to an upper level varying over time, the shell 10 being provided with a tapping channel 11 and a slag door 12;

[0076] - a closing vault 30 of the shell, on which one or more openings 31 are obtained for the insertion of one or more electrodes;

[0077] - a detection apparatus 40 for detecting the upperslag level over time.

[0078] The method comprises the following operating steps:

[0079] a) a detecting the upper slag level over time by means of said detection apparatus 40;

[0080] b) regulating the upper slag level during the operation of the furnace 1 in accordance with a predefined regulation strategy based on the values of said upper level detected by said detection apparatus 40, discharging at least the excess slag by means of one or more partial slagging operations with controlled openings and closures of said slag door.

[0081] Preferably, said regulation strategy includes maintaining the upper slag level below a predefined maximum value.

[0082] According to the preferred embodiment shown in figures 2 and 3, the shell 10 is divided into a lower shell 10a and an upper shell 10b. The lower shell 10a is provided with a portion protruding from said upper shell 10b so as to create a balcony 10c. The tapping channel 11 is obtained at the bottom of said lower shell 10b at said protruding portion in a position opposite to the slag door, according to the known EBT (Eccentric Bottom Taphole) configuration.

[0083] Preferably, the aforesaid predefined maximum value of the upper slag level is defined as a function of apredefined minimum interdistance D between the upper slag level and the internal ceiling of said balcony 10c.

[0084] Preferably, said detection apparatus 40 is installed at said protruding portion.

[0085] In particular, said detection apparatus 40 takes measurements through a hole 41 obtained in the ceiling of said balcony 10c.

[0086] Such a position is preferred over other possible positions, e.g., on the vault 30, because:

[0087] - it is more protected from molten metal splashes;

[0088] - it is further away from the electrodes;

[0089] - it is less used than the vault;

[0090] - it generally already has an opening for sand dosing, which opening can be utilized for a dual purpose.

[0091] The detection apparatus 40 can be of any type adapted for the purpose.

[0092] Preferably, said detection apparatus 40 is a radartype detection apparatus.

[0093] As an alternative (not preferred), said detection apparatus 40 can be an ultrasound-type detection apparatus.

[0094] Advantageously, said furnace 1 is provided with a shell support system 20, which is suitable to support said shell movably so as to incline it towards the slag door 12 or towards the tapping channel 11.

[0095] Preferably, the method can comprise a step c) of regulating the degree of inclination of the shell during tapping as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus 40.

[0096] In particular, as shown in figure 9. The method according to the invention offers the possibility of controlling the step of tapping in relation to the contribution of slag into the ladle in a furnace 1.

[0097] Advantageously, the method can comprise a step d) of regulating the electrical power discharged by the electrodes and / or the activation time of the electrodes as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus 40.

[0098] Advantageously, the slag door 12 defines a tunnel opening 120 and comprises one or more cleaning elements 121 movable through said tunnel opening 120 to remove any solidified slag residues present at the bottom and / or on the side walls of the tunnel opening itself.

[0099] Preferably, the slag door 12 is provided with one or more closing elements 122, 123 configured so that they can seal the tunnel opening 120 in the closing position. In particular, one or more of said closing elements can also act as cleaning elements.

[0100] According to an entirely preferred embodiment, shown in the accompanying figures and in particular in figures from 4 to 8, in which various operating positions of the door itself are shown, the slag door 12 defines a tunnel opening 120 and comprises a pusher 121 which:

[0101] - is movable through said tunnel opening 120 with an alternating movement in order to remove any solidified slag residues present at the bottom and / or on the side walls of the tunnel opening;

[0102] - comprises a head 122 suitable to resist when in contact with the slag and sized to seal the tunnel opening 120 by cooperating with a closing panel 123 which is integrated in the slag door 12 above said pusher 121.

[0103] In particular, the head 122 is made by a copper body which is internally cooled so that it can resist the aggressive action of the slag. The closing panel 123 (not intended to come into contact with the slag) can be made by a cooling tube structure.

[0104] Operatively, the pusher 121 and the closing panel 123 are also movable in height with respect to the bottom of the tunnel opening in order as to regulate the degree of opening thereof.

[0105] As already mentioned, an example of a slag door with such features is described in European Patent EP2489971B1 in the name of the same Applicant.

[0106] Advantageously, the method can comprise a step e) of regulating the degree of opening of the tunnel opening 120, controlling the actuation of the slag door 12 so as to perform controlled openings of the slag door 12 as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus 40.

[0107] The advantages resulting from the method according to the invention are the same as those already described in connection with the furnace 1 according to the invention and will not be detailed again for simplicity of disclosure.

[0108] The invention allows achieving several advantages, which have already been partially described.

[0109] The electric arc furnace with slag level regulation system according to the invention allows regulating the slag level in an effective and efficient manner as well as in an automated manner.

[0110] The electric arc furnace with slag level regulation system according to the invention is operatively reliable and simple to manage.

[0111] The method for regulating the slag level in an electric arc furnace according to the invention allows regulating the slag level in an effective and efficient manner and simultaneously in a reliable and simplemanner.

[0112] Therefore, the invention thus devised achieves the preset objects.

[0113] Obviously, in practice, it may also take different shapes and configurations from that disclosed above, without departing from the present scope of protection .

[0114] Moreover, all details may be replaced by technically equivalent elements, and any size, shape, and material may be used as needed.

Claims

CLAIMS1. An electric arc furnace (1) comprising:- a shell (10) for containing a bath of molten metal (M), on which a layer of slag (S) floats in use, which extends in height from the surface of said bath up to an upper level (H) varying over time, said shell (10) being provided with a tapping channel (11) and a slag door (12); a shell closing vault (30) on which one or more openings (31) are obtained for the insertion of one or more electrodes;- a detection apparatus (40) suitable to detect the upper slag level over time; characterized in that it comprises a slag level regulation system (50) which:- includes said detection apparatus (40);- is connected to said slag door (12); and- is programmed to regulate the upper slag level during the operation of the furnace (1) in accordance with a predefined adjustment strategy based on values of said upper level (H) detected by means of said detection apparatus (40), performing one or more partial slagging operations by means of controlled openings and closures of said slag door to discharge excess slag.

2. A furnace according to claim 1, wherein saidregulation strategy includes maintaining the upper slag level below a predefined maximum value.

3. A furnace according to claim 1 or 2, comprising a shell support system (20) which is suitable to support said shell movably so as to be able to incline it towards the slag door (12) or towards the tapping channel (11).

4. A furnace according to claim 2 or 3 when dependent on claim 2, wherein said shell (10) is divided into a lower shell (10a) and an upper shell (10b), said lower shell (10a) being provided with a portion protruding with respect to said upper shell (10b) so as to create a balcony (10c), said tapping channel (11) being obtained on the bottom of said lower shell (10b) at said protruding portion, and wherein said predefined maximum value of the upper slag level is defined as a function of a predefined minimum interdistance (D) between the upper slag level and the internal ceiling of said balcony (10c).

5. A furnace according to claim 4, wherein said detection apparatus (40) is installed at said protruding portion.

6. A furnace according to claim 5, wherein said detection apparatus (40) is installed at said protruding portion and measures through a hole obtained in the ceiling of said balcony.

7. A furnace according to any one of the preceding claims when dependent on claim 3, wherein said slag level regulation system (50) is connected to said tapping channel (11) and said shell support system (20), and wherein said slag level regulation system (50) is configured to regulate the degree of inclination of the shell during the step tapping step as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus (40).

8. A furnace (1) according to any one of the preceding claims, comprising an electrode regulation system, wherein said slag level regulation system (50) is connected to said electrode regulation system, the latter being configured to regulate the electrical power discharged by the electrodes and / or the activation time of the electrodes as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus (40).

9. A furnace (1) according to any one of the preceding claims, wherein said slag door (12) defines a tunnel opening (120) and is provided with one or more closing elements (121, 122, 123) configured so that they can seal the tunnel opening (120) in the closing position.

10. A furnace (1) according to claim 9, wherein the slag door (12) comprises one or more cleaning elements (121)movable through said tunnel opening (120) to remove any solidified slag residues present on the bottom and / or on the side walls of the tunnel opening itself.

11. A furnace (1) according to any one of the preceding claims, wherein said slag door (12) defines a tunnel opening (120) and comprises a pusher (121) which:- is movable through said tunnel opening (120) with an alternating movement in order to remove any solidified slag residues present on the bottom and / or on the side walls of the tunnel opening; comprises a head (122) suitable to resist when in contact with the slag and sized to seal the tunnel opening (120) by cooperating with a closing panel (123) which is integrated in the slag door (12) above said pusher (121), wherein said pusher (121) and said closing panel (123) are also movable in height with respect to the bottom of the tunnel opening in order as to regulate the degree of opening thereof.

12. A furnace (1) according to claim 11, wherein said slag level regulation system (50) is connected to said slag door (12) in order as to control the actuation thereof so as to perform controlled openings of the slag door (12), acting on the degree of opening of the tunnel opening (120) as a function of a predefined regulationstrategy based on the upper slag level detected by said detection apparatus (40).

13. A furnace according to any one of the preceding claims, wherein said detection apparatus (40) is a radartype detection apparatus.

14. A method for regulating the slag level in an electric arc furnace (1) comprising:- a shell (10) for containing a molten metal bath, on which a slag layer floats in use, which extends in height from the surface of said bath up to an upper level varying over time, said shell (10) being provided with a tapping channel (11) and a slag door (12); a shell closing vault (30) on which one or more openings (31) are obtained for the insertion of one or more electrodes;- a detection apparatus (40) for detecting the upper slag level over time; said method comprising the following operating steps: a) detecting the upper slag level over time by means of said detection apparatus (40); b) regulating the upper slag level during the operation of the furnace (1) in accordance with a predefined regulation strategy based on the values of said upper level detected by means of said detection apparatus (40), discharging at least the excess slag by means of one ormore partial slagging operations with controlled openings and closures of said slag door.

15. A method according to claim 14, wherein said regulation strategy includes maintaining the upper slag level below a predefined maximum value.

16. A method according to claim 14 or 15, wherein said furnace (1) is provided with a shell support system (20) which is suitable to support said shell movably so as to be able to incline it towards the slag door (12) or towards the tapping door (11).

17. A method according to claim 15 or 16, wherein said shell (10) is divided into a lower shell (10a) and an upper shell (10b), said lower shell (10a) being provided with a portion protruding with respect to said upper shell (10b) so as to create a balcony, said tapping channel (11) being obtained on the bottom of said lower shell (10b) at said protruding portion, and wherein said predefined maximum value of the upper slag level is defined as a function of a predefined minimum interdistance between the upper slag level and the internal ceiling of said balcony.

18. A method according to claim 17, wherein said detection apparatus (40) is installed at said protruding portion.

19. A method according to claim 18, wherein saiddetection apparatus (40) is installed at said protruding portion and measures through a hole obtained in the ceiling of said balcony.

20. A method according to any one of claims 14 to 19 when dependent on claim 16, comprising the step c) of regulating the degree of inclination of the shell during the tapping step as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus (40).

21. A method according to any one of claims 14 to 20, comprising the step d) of regulating the electrical power discharged by the electrodes and / or the activation time of the electrodes as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus (40).

22. A method according to any one of claims 14 to 21, wherein said slag door (12) defines a tunnel opening (120) and is provided with one or more closing elements (121, 122, 123) configured so that they can seal the tunnel opening (120) in the closing position.

23. A method according to claim 22, wherein the slag door (12) comprises one or more cleaning elements (121) movable through said tunnel opening (120) to remove any solidified slag residues present on the bottom and / or on the side walls of the tunnel opening itself.

24. A method according to any one of claims 14 to 23, wherein said slag door (12) defines a tunnel opening (120) and comprises a pusher (121) which:- is movable through said tunnel opening (120) with an alternating movement in order to remove any solidified slag residues present on the bottom and / or on the side walls of the tunnel opening; comprises a head (122) suitable to resist when in contact with the slag and sized to seal the tunnel opening (120) by cooperating with a closing panel (123) which is integrated in the slag door (12) above said pusher (121), wherein said pusher (121) and said closing panel (123) are also movable in height with respect to the bottom of the tunnel opening in order as to regulate the degree of opening thereof.

25. A method (1) according to claim 24, comprising a step e) of regulating the degree of opening of the tunnel opening (120), controlling the actuation of the slag door (12) so as to perform controlled openings of the slag door (12) as a function of a predefined regulation strategy based on the upper slag level detected by said detection apparatus (40).

26. A method according to any one of claims 14 to 25, wherein said detection apparatus (40) is a radar-typedetection apparatus.

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