Apparatus and method for detecting leakage from a high-temperature metallurgical industrial furnace having a cooling system

Abstract

A device for detecting leakages is provided in a cooling system of a furnace lining and / or of at least one component arranged in the furnace interior and / or of exhaust-gas-carrying components of a metallurgical high-temperature industrial furnace which has at least one coolant duct through which a coolant flows. A section of a wall bounding the coolant channel and facing an interior of the industrial furnace is exposed to a high thermal load and to intense light radiation, the leakage being caused by damage to the wall in the form of at least one hole, crack, gap or fracture. Such a device is to be improved in such a way that the occurrence of the smallest damage leading to leakage can be detected and signalled immediately. At least one sensor is to be arranged inside the coolant channel, adjacent to the wall, with which light radiation entering the interior of the coolant channel via the damage is detectable.

Description

[0001] Apparatus and method for detecting leakage from a high-temperature metallurgical industrial furnace having a cooling system

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a device for detecting leakages of a cooling system of a furnace casing and / or of at least one component arranged in the interior of the furnace and / or of exhaust-gas-conducting components of a metallurgical high-temperature industrial furnace, having at least one coolant duct or coolant space which runs inside the furnace casing and / or the component and at the wall of which at least one coolant flow is guided, a section of the coolant duct or coolant space facing an interior of the industrial furnace and on the wall of which at least one coolant flow is guided, wherein a section of the wall bounding the coolant channel or coolant chamber and facing an interior of the industrial furnace is exposed to a high thermal load and to intense light radiation, wherein the leakage is caused by damage to the wall in the form of at least one hole, crack, gap or break, and wherein a signal is detected by means of at least one sensor and characterizing the damage to the wall enclosing the coolant channel or coolant space is transmittable to a monitoring unit triggering an alarm signal or a control function of the high-temperature industrial furnace.

[0004] Furthermore, the invention relates to a method for monitoring a metallurgical high-tem- perature industrial furnace with a cooling system of a furnace casing and / or of at least one component arranged in the interior of a furnace vessel and / or of exhaust-gas-carry- ing components, wherein at least one coolant duct through which a coolant flows extends within the furnace casing and / or the respective component, which is exposed to a high thermal load and to intense light radiation at a section of a wall bounding the coolant duct facing an interior of the industrial furnace, and a signal which is detected by means of at least one sensor and characterizes damage to the coolant duct with a leakage resulting therefrom being transmitted to a monitoring unit. BACKGROUND OF THE INVENTION

[0005] Metallurgical high-temperature industrial furnaces are designed as alternating current (AC) arc furnaces or direct current (DC) arc furnaces, in which the required heat or melting temperature is provided by means of an arc generated via electric current. In addition, chemical energy can be provided in the form of a gaseous medium, a liquid medium or a solid in order to reduce the expenditure for electrical energy. For this purpose, injectors are provided which are preferably designed as lances. The gaseous medium can be oxygen or a combustible gas. Light oil or kerosene, for example, are used as liquid media, while blown pulverized coal, for example, is suitable as a solid.

[0006] The feed material used is primarily steel scrap, to which sponge iron or crude iron can also be added. For the melting process, graphite electrodes are inserted into the furnace vessel when it is closed. The furnace vessel consists essentially of a bottom vessel, a top vessel and a top lid, which is closed before the start of a melting process, openings in which are used to insert three graphite electrodes in the case of an AC furnace and one graphite electrode in the case of a DC furnace. In the latter, a metal electrode embedded in magnesium oxide is provided at the bottom of the bottom vessel.

[0007] During the melting of the feed material, which takes place with a thermal energy of up to 3,500°C, the entire furnace vessel is exposed to a very high thermal load and to intense radiation from the arc generated by the graphite electrodes or the graphite electrode. For this reason, it is necessary to provide liquid-cooled panels on the upper vessel and on the top lid to prevent damage to these components from the extreme heat of the molten steel and from the radiation of the arc. Other causes of damage can also be the considerable heat fluctuations occurring in the furnace vessel, which result in different thermal expansion of the furnace components, or the mechanical stresses on these components of the furnace vessel occurring during filling of the furnace interior with the charge.

[0008] It is therefore absolutely necessary to provide a cooling system in the walls of the upper vessel and the top lid, and possibly also inside other components. In one embodiment of this cooling system, a coolant, preferably water, circulates through coolant channels, selectively removing heat from specific areas. The wall cladding of the upper vessel may be formed by individual wall segments, also referred to as panels, with the coolant channels running within them, or in coolant tubes extending horizontally or vertically in a serpentine fashion as part of each panel. Other components to be cooled are the cooling boxes of the injectors, usually located on panels of the upper vessel, which are operated with a gas-oxygen mixture or a hydrogen-oxygen mixture. In another embodiment of the cooling system, the coolant channels or a coolant chamber receive the coolant without pressure, and the coolant is applied to the walls of the coolant channels or coolant chambers via spray nozzles to dissipate the heat.

[0009] If the upper vessel, the top lid or the cooling boxes are damaged despite the cooling, the wall parts surrounding the coolant channels or coolant spaces or directly the coolant pipes are mostly affected, whereby damage occurs in the form of a hole, crack or break in the coolant line. The coolant, which is usually cooling water, penetrates from the coolant channels or coolant spaces into the interior of the furnace vessel via leakages. It can also be part of the coolant applied to the wall parts by spray nozzles, which escapes from the coolant channel or space as a fine water mist. The intense heat then leads to boiling of the coolant and a resulting formation of water vapor, with the risk of explosion arising from the impact of this water vapor on the steel bath and the slag.

[0010] The explosion can also be caused by the formation of oxyhydrogen gas when hydrogen is split off from the water molecule due to the high temperature. Situations also occur in which larger quantities of water vapor in the steel bath lead to water confinement, which can result in a large and very violent explosion. It is not uncommon for the explosion to result in serious injuries and deaths, as considerable quantities of molten steel, parts of the unmelted or only partially melted charge and components of the arc furnace are hurled through the steel plant building at high speed, penetrating walls or ceilings.

[0011] Since this poses a considerable risk to the employees working in the steel mill, it is very important to provide metallurgical high-temperature industrial furnaces whose components facing the inside of the furnace vessel are cooled with a monitoring system that reliably detects leaks in the cooling system and immediately triggers a visual and / or audible alarm. A device for detecting leaks in a cooling system of a furnace lining of the type mentioned in the generic term of patent claim 1 is known from US 2009 / 0148800 A1. Herein, the system for detecting leaks in the furnace panel is to comprise several types of redundant mechanisms for detecting leaks in the cooling panel, which continuously and actively monitor and report the condition of the panel itself or the cooling fluid flowing through it. Further, pressure sensors are provided for sensing pressure signals and flow sensors are provided for continuously transmitting flow data signals from the cooling system. One of each of the combinations of temperature, pressure and flow sensors is in communication with a coolant supply conduit, while another is in communication with a coolant return conduit.

[0012] The furnace casing is formed by a plurality of panels in which the temperature sensors are provided for continuous transmission of temperature data signals to a monitoring unit. The temperature sensors continuously monitor the temperature of the coolant entering and leaving the panels. These signals are transmitted to the monitoring unit. If the temperature sensors suddenly detect a significant difference between the water inlet and outlet temperatures, system software transmits an alarm condition to the monitoring unit. Depending on the software and hardware architecture of the system, the alarm condition detected by the temperature sensors can either cause automatic closing of inlet valves and / or outlet valves for the cooling liquid, or allow an operator to manually close these valves. Furthermore, the pressure sensors and the flow sensors can detect a sudden significant difference in flow between the water supply and return lines. If this is the case, which is said to be a sign of leakage, the system software indicates an alarm condition at the monitoring unit.

[0013] Furthermore, EP 312 714 A1 describes a method for detecting leaks in metallurgical vessels which are filled with refractory material and equipped with cooling elements. These can be electric arc furnaces. In this case, the cooling liquid escaping in the event of a leakage is to be collected as vapor and fed to a moisture indicator, which then registers it. For this purpose, perforated vapor collection tubes are arranged underneath cooling elements, the outlets of which are connected to the moisture indicator outside the furnace vessel. EP 2 312 250 A1 describes a metallurgical vessel of a melting furnace with a wall having a hot side facing the interior of the vessel and a cold side facing the exterior of the vessel. Between the hot side and the cold side is a space through which a coolant flows. Sensor elements are arranged on the hot side of the wall, which can be used to measure the temperatures at several points on the wall can be determined. In order to measure the temperature of the wall precisely and quickly, the sensor elements should include optical waveguides that are attached to the hot side of the wall. By means of a detection system, laser light is to be generated which is fed into the optical fiber.

[0014] The data collected by the optical fiber is converted into temperatures by the detection system and assigned to the various measurement locations. The evaluation can be carried out, for example, using the so-called fiber Bragg grating (FBG) method. By inserting optical fibers into the walls of an electric arc furnace, temperatures can be recorded as a profile over the vessel surface. Dynamic changes caused by flows in the melt are also to be recorded. This will make it possible to determine the state of wear, the thermal load on the components over their surface in the respective operating state and an existing flow situation. These measured values are to be fed back to the process control.

[0015] It is an object of the present invention to provide a device for detecting leaks in a cooling system of a metallurgical high-temperature industrial furnace, by means of which the occurrence of the smallest damage leading to leaks can be detected and signaled immediately.

[0016] This object is solved on the basis of the generic term of the patent claim with its characterizing features. The patent claims dependent on patent claim 1 contain further embodiments of this solution according to the invention.

[0017] SUMMARY OF THE INVENTION

[0018] According to this, a device for detecting leakages of a cooling system, which is arranged in a furnace casing and / or in at least one component arranged in the furnace interior and / or of exhaust-gas-carrying components of a metallurgical high-temperature industrial furnace, has at least one coolant duct or coolant space. This extends within the furnace lining and / or the component and / or the exhaust gas-carrying component, wherein a section of a wall bounding the coolant channel and facing an interior of the industrial furnace is exposed to a high thermal load and to intense light radiation. The coolant flows along the wall by being conveyed through the coolant channel or coolant space by means of a pump, or it is applied to its surface facing away from the furnace interior for example by means of spray nozzles. In this case, the leakage is caused by damage to the wall, for example in the form of at least one hole, crack, gap or break, wherein a signal detected by means of at least one sensor, which characterizes the damage to the wall of the coolant channel or coolant chamber, can be transmitted to a monitoring unit triggering an alarm signal or a control function of the high-temperature industrial furnace.

[0019] According to the invention, the at least one sensor is to be arranged inside the coolant duct, adjacent to the wall of the coolant duct or coolant chamber, whereby by means of the at least one sensor, light radiation entering the interior of the coolant duct via the damage is detectable. Consequently, the sensor does not detect the leakage of the coolant, which then already enters or has entered the interior of the furnace vessel. According to the invention, the cause underlying the leakage is already detected, for which purpose an optical sensor is provided that detects the damage to the monitored wall section on the basis of the light radiation entering the coolant channel via the hole, crack, gap or break of a component carrying coolant without delay. Thus, an immediate danger signal as well as an early shutdown of the damaged coolant circuit, possibly with a subsequent draining of the cooling system of the affected panels, will be made possible. It is also possible to shut down the industrial furnace. This can prevent or significantly minimize the major risks that otherwise exist.

[0020] In contrast, according to the generic US 2009 / 0148800 A1 , a leak in the cooling plate of the arc furnace is detected by means of pressure sensors and flow sensors a sudden significant difference in flow rate between the cooling water supply lines and cooling water return lines that occurs in the event of a leak. Consequently, this signal is only available when the pressure and flow rate have changed. However, this already leads to the problems described at the beginning, according to which there is a risk of explosion due to water vapor hitting the steel bath and the slag and endangering the employees working at the industrial furnace.

[0021] Even according to EP 312 714 A1 , which is also cited as prior art, in which the cooling liquid escaping from a leak is collected as vapor and fed to a moisture indicator, a relatively long time elapses before a warning function can be triggered.

[0022] In addition, according to EP 2 312 250 A1 , the wear condition, the thermal load of the components over their surface in the respective operating state and an existing flow situation are to be recorded and these determined measured values fed back to the process control. However, the optical fibers provided for this purpose serve to transmit the temperatures recorded by separate sensors.

[0023] In a further embodiment of the invention, the sensor is to be designed as a fiber-optic sensor in whose fiber the light radiation entering the coolant channel via the leakage is coupled and transmitted to the monitoring unit via the fiber serving as an optical waveguide. The light is thus detected by means of the fiber acting as an optical waveguide, which runs inside the coolant channel and is provided with the fiber-optic sensor serving as an optical measuring sensor. According to a first embodiment, the optical sensor measurement can be carried out with fiber Bragg gratings, whereby the sensor areas are implemented in a single optical fiber and different wavelength ranges of each sensor are assigned to different monitoring areas. The ability to fabricate fiber Bragg gratings with different Bragg wavelengths allows effective use of the "wavelength division multiplexing" method, by which multiple sensors with different Bragg wavelengths can be connected in series on a single optical fiber and transmitted over long distances. Within the light spectrum, each of the fiber Bragg sensors connected in series provides the appropriate wavelength range. Consequently, it is possible to detect at which of the sensors, and thus in which section of the coolant channel, damage to its wall has occurred.

[0024] Furthermore, in such an embodiment of the fiber conducting light and having a measuring sensor, at least one fiber shall extend along the wall section in the direction of flow of the coolant. Alternatively, at least one fiber may extend helically along the wall section.

[0025] In a second embodiment of the device according to the invention, a plurality of light-con- ducting fibers having a measuring sensor system of different lengths are to extend along the wall section in the direction of flow of the coolant and their end sections forming light detection points facing away from the monitoring unit and serving for coupling in any light radiation are arranged in different regions. Each of the optical fibers thus accommodates, at its end facing away from the monitoring unit, a light detection point or region serving as a fiber-optic sensor.

[0026] Furthermore, it is possible to form the at least one fiber as a semi-transparent light guide that can detect light incidence via its section extending within the coolant channel.

[0027] In addition, the at least one fiber can have several sensor areas for detecting an incidence of light, wherein the respective position of the incidence of light can be determined by a difference in propagation time of the respective detected signals or by differences in their signal strength. This also makes it possible to detect at which of the sensors, and thus in which section of the coolant channel, damage to its wall has occurred.

[0028] The fiber is preferably in the form of an optical fiber. However, the fiber can also be a polymer optical fiber (POF). In general, all light-guiding materials are suitable.

[0029] Furthermore, the transmission of the light incidence can be enhanced by the fact that a jacket surface of the at least one coolant channel has a reflective surface. To ensure the functional reliability of the device, it should also be possible to detect an interruption in the signal transmission of the optical fiber as a fault.

[0030] Furthermore, the high-temperature industrial furnace is designed as an arc furnace. Especially in arc furnaces, leakages of the coolant system can lead to catastrophic accidents, as already described at the beginning. If the furnace is an electric arc furnace, the cooling channels monitored by the device should be arranged in an upper vessel of the electric arc furnace. The at least one graphite electrode provides extreme light radiation in the interior of the upper vessel adjacent to the cooling system. This can advantageously be used to detect damage to the wall separating the coolant channels from the interior of the upper vessel.

[0031] In addition, however, it is also possible to provide the device in a high-temperature industrial furnace designed as a ladle furnace. A ladle furnace, which is similar to an electric arc furnace in terms of its operating principle, is installed downstream of the melting process in steel production and is used before continuous casting. Alloying agents can be added to the melt during treatment in the ladle furnace. Compared with a conventional electric arc furnace, the ladle furnace is operated with a much lower connected load, but graphite electrodes also act on the melt and an electric arc is also generated. A lid and a furnace vessel of the ladle furnace are also provided with coolant tubes on which the aforementioned damage and consequently leakage can occur with the risks already described.

[0032] Furthermore, in the case of use of the device in an arc furnace, it is possible to provide the cooling channels in injector cooling blocks which serve to hold one injector in each case, whereby a gas or a solid can be introduced into the interior of the arc furnace via the respective injector. The respective injector cooling block serves to hold an injector with which a gas or a solid is injected into the interior of the furnace vessel of the arc furnace, and is made of a highly thermally conductive material. Coolant channels are adjacent to a hot area of the wall of the injector cooling block, where leakage may occur due to damage.

[0033] In addition, in an electric arc furnace, the at least one cooling channel can be arranged in a pipe jacket of an exhaust gas pipe. The exhaust pipe, which is designed as a pipe bend, conducts the hot exhaust gases into an exhaust system and a filter system and is also exposed to high temperatures and the light radiation generated by the graphite electrodes.

[0034] The task underlying the invention is also solved in the context of a method. According to this, in the method for monitoring a metallurgical high-temperature industrial furnace having a cooling system of a furnace lining and / or of at least one component arranged in the furnace interior and / or of exhaust-gas-carrying components of a high-temperature industrial furnace, at least one coolant duct through which a coolant flows runs within the furnace lining and / or the component, and in this case a section, facing an interior of the industrial furnace, of a wall bounding the coolant duct is exposed to a high thermal load and to intense light radiation. In addition, the surface of the wall facing away from the interior of the furnace vessel can also be cooled by means of the coolant applied to it by spray nozzles. A signal detected by means of at least one sensor, which characterizes damage to the coolant channel, is transmitted to a monitoring unit according to the method.

[0035] The following process steps are provided according to the invention:

[0036] - a light radiation reaching the interior of the coolant channel due to damage to its wall is detected by a sensor,

[0037] - the light radiation or a signal derived therefrom is transmitted to the monitoring unit, and

[0038] - herefrom a disturbance display and / or a warning system are activated by the monitoring unit.

[0039] The invention is not limited to the indicated combination of the features of independent patent claim 1 and the claims dependent thereon and the features of process claim 18. In addition, there are further possibilities for combining individual features, in particular when they result from the patent claims, the advantages indicated with respect thereto, are also from following description of the embodiments or directly from the drawing. Furthermore, the reference of the patent claims to the drawing by the use of reference signs is not intended to limit the scope of protection of the patent claims to the illustrated embodiments in any case.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Further features of the invention are incidentally apparent from the following description and from the drawing, in which three embodiments of the invention are shown in simplified form; wherein: Figure 1 is a schematic illustration of a top view of an arc furnace with the top lid removed from it, the position of three graphite electrodes being indicated,

[0042] Figure 2 is a schematic illustration of a longitudinal section through the arc furnace designed according to the figure with an upper furnace casing having cooling water tubes and with a top lid closing this, the graphite electrodes being introduced through holes in the top lid,

[0043] Figure 3 is a perspective view of the top lid provided with a cooling system,

[0044] Figure 4 is as a separate illustration, showing the cooling water pipe provided in accordance with Figure 2 and associated with a wall panel of the furnace lining, a sensor system arranged in the interior of the pipe being connected via a light detection unit, a monitoring unit and an optical and / or acoustic warning device,

[0045] Figure 5 is a side view of a section of the cooling water pipe at which leakage can occur due to a shown damage,

[0046] Figure 5a is a side view of the cooling water pipe of Figure 5 rotated by 90° in a longitudinal section, wherein a glass fiber with a sensor area for detecting an incidence of light is arranged in the pipe interior,

[0047] Figure 6 is a longitudinal section of the cooling water pipe with a first embodiment of a sensor system arranged therein, which consists of a bundle of glass fibers of different lengths,

[0048] Figure 7 is a longitudinal section of the cooling water pipe with a second embodiment of a sensor system arranged therein, wherein sensor areas are implemented in a single glass fiber, Figure 8 is a longitudinal section of the cooling water pipe with a third embodiment of a sensor system arranged therein, wherein a single glass fiber runs helically in the pipe interior and sensor areas are implemented in these, and

[0049] Figure 9 is a partial view of a coolant space of an upper furnace lining in longitudinal section, which is provided between an inner and an outer wall, wherein spray nozzles are arranged within the coolant space.

[0050] DETAILED DISCRIPTION OF THE INVENTION

[0051] In Figure 1 , reference numeral 1 indicates a high-temperature metallurgical industrial furnace designed as an electric arc furnace 2. In the illustration, which shows a top view of an opened furnace vessel 3, its upper vessel 4 is visible, which is preferably formed in a segment-like manner from individual panels 5 of a furnace casing 6. The furnace casing 6 of the upper vessel 4 is provided with a cooling system 7 which is not visible in this representation and which will be explained below with reference to Figure 2.

[0052] Furthermore, three injector cooling blocks 8, 9 and 10 extend from the furnace casing 6, which serve as supports for injectors not shown more, a gas being blown into the interior of the furnace vessel 3 via these injectors, which can operate as burners 8a, 9a and 10a, in order to increase the temperature and save electrical energy. A fourth injector 11 also operating as a burner 11 a, is located in the area of a furnace door 12 provided in the furnace vessel 4. In addition, the position of three graphite electrodes 13, 14 and 15 is illustrated in Figure 1 , which, as shown in Figure 2, are inserted vertically into the interior of the furnace vessel 3 via openings 16, 17 and 18 of a removable top lid 19. This separate top lid 19 also serves as a furnace casing 6.

[0053] Figure 2, which shows the essential parts of the arc furnace 2 in longitudinal section, shows a bottom vessel 21 receiving a molten steel 20, the upper vessel 4 placed thereon and the top lid 19 closing the same. It can be seen that the cooling system 7 of the upper vessel 4 is located facing the interior of the furnace vessel 3 and thus the graphite electrodes 13, 14 and 15 are inserted therein. Two injector cooling blocks 8 and 9, visible in the illustration, are also arranged in the panels 5 of the upper vessel 4. From the removable top lid 19, an exhaust manifold 22 operating as an exhaust-gas- carrying component extends, via which the exhaust gases discharged from the interior of the furnace vessel 3 are fed to an exhaust system not shown in more detail and to a filter system. Both the top lid 19 and the exhaust manifold 22 are provided with a cooling system 23. The two cooling systems 7 and 23 have a plurality of cooling medium channels 24 through which the coolant, preferably cooling water, flows. The cooling medium channels 24 can be provided directly in the components furnace casing 6, injector cooling blocks 8, 9 and 10, top lid 19 and exhaust manifold 22, or there are coolant pipes on these components facing the heat source, which will be explained below in connection with Figures 3, 4, 5, 5a, 6, 7 and 8.

[0054] Figure 3 shows the top lid 19, which is essentially formed by coolant pipes 25, the coolant flowing into these coolant pipes 25 via coolant inlet lines 26 and being discharged therefrom via coolant outlet lines 27 in a cooling circuit formed by the cooling system 23. The latter are in communication with coolant distribution lines 28 and coolant collection lines 29.

[0055] Figure 4 also shows separately a coolant tube 30 arranged on one of the panels 5, which runs in a serpentine configuration from a coolant inlet connection 31 to a coolant outlet connection 32. At least one optical fiber 33 conducting a light signal is introduced into the interior of the coolant pipe 30, which is connected on the other side to a light detection unit 34. The signals detected by the light detection unit 34, which indicate damage to the coolant pipe 30, are transmitted to a monitoring unit 35, which in this case activates a visual and or acoustic warning device 36. In addition, the monitoring unit 35 can intervene in the control of the arc furnace 2 in such a way that a change in operation is made which, on the one hand, minimizes the risk of accidents to the employees and, on the other hand, minimizes the risk of damage to the arc furnace 2. Further optical fibers 33a and 33b extend from the light detection unit 34 and lead to further coolant pipes, not shown, which are also associated with panels not shown.

[0056] Figure 5 shows a section of coolant pipe 25 or 30 which has a damaged portion 37 through which coolant can leak therefrom. Figure 5 shows a section of coolant pipe 25 or 30 which has a damage 37 through which coolant will leak from it. Further Figure 5a shows this coolant tube 25 or 30 in longitudinal section and rotated by 90°. The damage 37 results from the high thermal stress on a portion of its wall 38 facing the interior of the furnace vessel 3 from the graphite electrodes 13, 14 and 15. The damage 37 is thus located in a position where the radiation generated by the arcs of the graphite electrodes 13, 14 and 15, the burners 8a, 9a, 10a 11 a, the molten steel 20 and the molten material impinges on the wall 38. This schematically shown part of the radiation 39 enters the cooling medium channel 24 via the damaged portion 37, which in the present case appears as a hole, and impinges on a fiber-optic sensor 40, whereby the light radiation entering the cooling medium channel 24 is coupled into the optical fiber 33 and transmitted to the light detection unit 34 as shown in Figure 4.

[0057] Further Figures 6, 7 and 8 show different embodiments of the arrangement of optical fibers and the fiber-optic sensors provided thereon. In the designed example according to Figure 6, which shows a bundle 50 consisting of the optical fiber 33 and further optical fibers 33a, 33b, 33c and 33d in abbreviated form, the fiber-optic sensor 40 and further fiber-optic sensors 40a, 40b, 40c and 40d are arranged at their ends respectively. These are used to monitor different sections of the coolant duct 24 with regard to damages 37 causing leaks, whereby these can also be assigned locally to the corresponding sections of the cooling medium channel 24.

[0058] According to Figure 7, a single optical fiber 41 runs within the cooling medium channel 24, on which fiber-optic sensors 42, 42a and 42b, which are in relation to the detection of damage in different areas of the cooling medium channel 24. These are sensor sections 42, 42a and 42b implemented in a single optical fiber 41 , with different wavelength ranges of each sensor section 42, 42a and 42b being assigned to different monitoring sections. The sensor regions are fabricated with different fiber Bragg wavelengths for this purpose, allowing the use of the Wavelength Division Multiplexing (WDM) method, which provides the appropriate wavelength range within the light spectrum for each sensor region 42, 42a and 42b.

[0059] Furthermore, Figure 8 shows an embodiment in which, again in accordance with the embodiment according to Figure 7, a single optical fiber 41 is also provided with sensor regions 42, 42a 42b and is operated by means of an optical sensor measurement with fiber Bragg gratings, whereby, in contrast to Figure 7, the single optical fiber 41 runs helically within the coolant channel 24. In the arrangement of sensor areas on a single optical fiber provided according to Figures 7 and 8, however, it is also possible to detect the individual monitoring areas by determining the respective position of the light incidence by a difference in transit time of the signals detected in each case or by differences in their signal strength.

[0060] Finally, according to Figure 9, between an inner wall 43, which according to Figure 2 is intended to face the interior of the furnace vessel 3, and an outer wall 44, a coolant space 45 is arranged, which is intended to form the exterior of the upper vessel 4 of the arc furnace 2 within the panels 5. Within this coolant space 45 are arranged mutually spaced coolant lines with a plurality of spray nozzles, of which the partial view according to Figure 9 shows a coolant line 46 with spray nozzles 47 and 48. The coolant emerging from the spray nozzles 47 and 48 is directed from the coolant chamber 45 along a circumferential surface 49 of the inner wall 43 facing away from the interior of the furnace vessel 3 and consequently cools the latter. In the process, any damage to the inner wall 43 is to be detected. For this purpose, the optical fiber 41 with sensor areas 42 and 42a runs inside the coolant space 46.

[0061] List of reference signs

[0062] 1 high-temperature metallurgical industrial furnace

[0063] 2 electric arc furnace

[0064] 3 furnace vessel of 2

[0065] 4 top vessel of 3

[0066] 5 panels

[0067] 6 furnace casing of 4 and 19

[0068] 7 cooling system of 6

[0069] 8 injector block

[0070] 8a burner from 8

[0071] 9 injector block

[0072] 9a burner from 9

[0073] 10 injector block

[0074] 10a burner from 10

[0075] 11 injector

[0076] 11a burner from 11

[0077] 12 furnace door

[0078] 13 graphite electrode

[0079] 14 graphite electrode

[0080] 15 graphite electrode

[0081] 16 opening in 19

[0082] 17 opening in 19

[0083] 18 opening in 19

[0084] 19 top lid of 2

[0085] 20 molten steel

[0086] 21 bottom vessel of 2

[0087] 22 exhaust manifold

[0088] 23 cooling system of 19 and 22

[0089] 24 cooling medium channels of 7 and 23

[0090] 25 coolant pipes from 19 and 22

[0091] 26 coolant inlet line 27 coolant outlet line

[0092] 28 coolant distribution line

[0093] 29 coolant manifold line

[0094] 30 coolant pipe from 5

[0095] 31 coolant inlet connector from 30

[0096] 32 coolant outlet connector from 30

[0097] 33 optical fiber

[0098] 33a optical fiber

[0099] 33b optical fiber

[0100] 33c optical fiber

[0101] 33d optical fiber

[0102] 34 light detection unit

[0103] 35 monitoring unit

[0104] 36 acoustic warning device

[0105] 37 damaged portion

[0106] 38 wall of 25

[0107] 39 light radiation

[0108] 40 fiber optic sensor

[0109] 40a fiber optic sensor

[0110] 40b fiber optic sensor

[0111] 40c fiber optic sensor

[0112] 40d fiber optic sensor

[0113] 41 single optical fiber

[0114] 42 fiber optic sensor

[0115] 42a fiber optic sensor

[0116] 42b fiber optic sensor

[0117] 43 inner wall of 5

[0118] 44 outer wall of 5

[0119] 45 coolant space

[0120] 46 coolant line

[0121] 47 spray nozzle

[0122] 48 spray nozzle

[0123] 49 circumferential surface of 43 50 bundle of optical fibers

Claims

What we claim is:

1. A device for detecting leakages of a cooling system (23) of a furnace casing (6) and / or of at least one component (8, 9, 10) arranged in the interior of the furnace and / or of exhaust-gas-conducting components (22) of a metallurgical high-tempera- ture industrial furnace (1 ), having at least one coolant duct (24) or coolant space (46) which runs inside the furnace casing (6) and / or the component (8, 9, 10) and at the wall (38, 44) of which at least one coolant flow is guided, a section of the coolant duct (24) or coolant space (46) facing an interior of the industrial furnace (1 ), 10) and on the wall (38, 44) of which at least one coolant flow is guided, wherein a section of the wall (38, 44) bounding the coolant channel (24) or coolant chamber (46) and facing an interior of the industrial furnace (1 ) is exposed to a high thermal load and to intense light radiation, wherein the leakage is caused by damage (37) to the wall (38, 44) in the form of at least one hole, crack, gap or break, and wherein a signal is detected by means of at least one sensor (40, 40a, 40b, 40c, 40d, 42, 42a, 42a) and characterizing the damage to the wall (38, 44) enclosing the coolant channel (24) or coolant space (46) is transmittable to a monitoring unit (35) triggering an alarm signal or a control function of the high-temperature industrial furnace (1 ), characterized in that the at least one sensor (40, 40a, 40b, 40c, 40d, 42, 42a, 42a) is arranged inside the coolant duct (24) or the coolant space (46), adjacent to the wall (38, 44), and in that, by means of the at least one sensor (40, 40a, 40b, 40c, 40d, 42, 42a, 42a) a light radiation (39) entering the interior of the coolant channel (24) or the coolant chamber (46) via the damage (37) is detectable.

2. A device according to patent claim 1 , characterized in that the sensor is designed as a fiber-optic sensor (40, 40a, 40b, 40c, 40d, 42, 42a, 42b), in the fiber (33, 41 ) of which the light radiation (39) entering the coolant channel (24) via the leakage is coupled and transmitted to the monitoring unit (35) via the fiber (33, 41 ) serving as an optical waveguide.

3. A device according to claim 2, characterized in that the optical sensor measurement is performed with fiber Bragg gratings, wherein sensor regions (42, 42a, 42b) are implemented in a single optical fiber (41 ) and different wavelength regions of each sensor (42, 42a, 42b) are assigned to different monitoring regions.

4. A device according to claim 3, characterized in that at least one fiber (33, 41 ) extends along the wall (38) in the direction of flow of the coolant.

5. A device according to claim 3, characterized in that at least one fiber (41 ) extends helically along the wall (38).

6. A device according to claim 2, characterized in that a plurality of fibers (33) of different lengths extend along the wall (38) in the direction of flow of the coolant and their end portions facing away from the monitoring unit form light detection points (40, 40a, 40b, 40c, 40d), which serve to couple any light radiation (39), are arranged in different regions of the wall (38).

7. A device according to patent claim 2, characterized in that the at least one fiber (33, 41 ) is designed as a semi-transparent light guide by which, via its section extending within the coolant channel (24), an incidence of light into the latter resulting from the light radiation (39) is detectable.

8. A device according to patent claim 2, characterized in that the at least one fiber (33, 41 ) has a plurality of sensor regions (42, 42a, 42b) for detecting an incidence of light resulting from the light radiation (39), the respective position of the incidence of light being determinable by a difference in transit time of the respectively detected signals or by differences in their signal strength.

9. A device according to claim 1 , characterized in that a shell surface of the at least one coolant channel (24) has a reflective surface.

10. A device according to claim 2, characterized in that an interruption in the signal transmission of the fiber (33, 41 ) is detectable as a disturbance.

11. A device according to claim 2, characterized in that the fiber is formed as an optical fiber (33, 41 ).

12. A device according to claim 1 , characterized in that the high-temperature industrial furnace (1) is designed as an electric arc furnace (2).

13. A device according to claim 1 , characterized in that the high-temperature industrial furnace (1) is designed as a ladle furnace.

14. A device according to claim 12, characterized in that the at least one coolant channel (24) or coolant space (46) is arranged in an upper vessel (4) of the arc furnace (2).

15. A device according to one of the claims 12 or 13, characterized in that at least one coolant channel (24) or coolant space (46) is arranged in a top cover (19) of the arc furnace (2) or the ladle furnace.

16. A device according to claim 12, characterized in that at least one coolant channel (24) or coolant space (46) is arranged in an injector cooling block (8, 9, 10) for holding a respective injector (8a, 9a, 10a), wherein a gas, a liquid or a solid is in- troducible into the interior of the arc furnace (2) via the respective injector (8a, 9a, 10a).

17. A device according to claim 12, characterized in that the at least one coolant channel (24) or coolant space (46) is arranged in a pipe jacket of an exhaust pipe (22).

18. A method for monitoring a metallurgical high-temperature industrial furnace (1) with a cooling system (7) of a furnace casing (6, 19) and / or of at least one component (8, 9, 10) arranged in the interior of a furnace vessel (3) and / or of exhaust- gas-carrying components (22), wherein at least one coolant duct (24) through which a coolant flows extends within the furnace casing (6) and / or the respectivecomponent (8, 9, 10, 22), which is exposed to a high thermal load and to intense light radiation (39) at a section of a wall (38) bounding the coolant duct (24) and facing an interior of the industrial furnace (1 ), and wherein a signal which is detected by means of at least one sensor and characterizes damage (37) to the coolant duct (24) with a leakage resulting therefrom being transmitted to a monitoring unit (35), characterized by the following method steps:- due to the damage (37) of the wall (38), the light radiation (39) enters the coolant channel (24) and is detected therein by at least one sensor (40, 40a, 40b, 40c, 40d, 42, 42a, 42b),- the light radiation (39) or a signal derived therefrom is transmitted to the monitoring unit (35), and - a disturbance display and / or a warning system are actuated therefrom in a warning device (36) by the monitoring unit (35).

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