Method and device for detecting a water leak in a metallurgical melting furnace

Abstract

The invention relates to a method for detecting a water leak in a metallurgical melting furnace. The invention also relates to a device for carrying out the method. In the process, a water leak is detected in a cooling tube or a water tube of a furnace vessel in that a time-resolved measurement of an exhaust gas characteristic, such as the water quantity, at the exhaust gas outlet and a controlled pressure fluctuation, i.e. a variation of the pressure, of the cooling circuit are combined and correlated together. In the event of a leak, the variation of the water pressure leads to a variation of the discharge quantity of the water into the furnace vessel, said discharge quantity correlating chronologically to the variation of the pressure of the cooling circuit. By determining the correlation of the signals, an analysis device can ascertain a relationship based on a water leak.

Description

[0001] Method and device for detecting a water leak in a metallurgical melting furnace

[0002] The invention relates to a method for detecting a water leak in a metallurgical melting furnace having a furnace vessel whose walls consist at least partially of water pipe walls through which cooling water flows, as well as to a device suitable for carrying out the method.

[0003] In a metallurgical melting furnace, such as an electric arc furnace, metals are melted and subsequently cast. This process requires particularly high temperatures inside such a metallurgical melting furnace, meaning the materials within the furnace vessel must withstand temperatures of up to 3500 °C. Such temperatures pose a particular challenge for the equipment used.

[0004] The individual components of a metallurgical melting furnace that come into contact with the molten metal and the hot exhaust gases are therefore made either of refractory material or of water-cooled components. Some parts of the metallurgical melting furnace, especially the furnace vessel, consist, at least in sections, of water-tube walls, through which water pipes run, through which cooling water flows during operation. This reduces the risk of damage or destruction to the walls of the furnace vessel by the molten metal and the hot exhaust gases.

[0005] Such a metallurgical melting furnace, which has water tube walls, is described in EP 2 601 469 B1. The water tube walls are designed as fluid-cooled panels and are particularly suitable for applications in metallurgical furnaces, especially in electric arc furnaces for steel production. However, it is a common problem that the strong thermal loads acting on the water tube walls, particularly due to the large temperature differences, lead to leaks in the water tube walls. This results in water inflow into the metallurgical melting furnace.

[0006] In metallurgical melting furnaces, water is also generated by combustion processes within the furnace vessel, for example, through the combustion of added natural gas or hydrogen. Furthermore, at the beginning of the melting cycle, water is introduced by the metallic components inserted into the furnace vessel. A further water component comes from vertically mounted graphite electrodes, along which water flows down into the furnace vessel for cooling. The water present in the furnace vessel evaporates and is removed via the exhaust gas systems. Even in the event of a leak, however, the majority of the water present in the exhaust gas comes from the aforementioned sources.

[0007] The problem with additional water penetrating the furnace vessel via water leaks is that it enters in an undefined and localized manner at one point, meaning that the penetrating water can collect in certain places. This results from the fact that the metallic components to be melted, such as scrap, are generally irregularly constructed and can contain numerous pocket-like cavities in which at least some of the water remains and therefore does not completely evaporate. The water that has accumulated in liquid form in certain places can grow over time into a constantly growing water bubble. If, as the metal scrap continues to heat up during the melting cycle, very hot liquid metal comes into contact with such a water bubble, there is a risk of explosive evaporation.This can result in severe damage to the metallurgical melting furnace or even its destruction. Furthermore, metal masses escaping from the metallurgical melting furnace and possibly splashing around pose a serious hazard to those working in the vicinity.

[0008] There are various approaches to detecting such water leaks, although these approaches have so far been calculated using longer-term furnace balances. DE 10 2009 051 931 A1, for example, describes a method for the early detection of leaks in a cooling device for cooling a technical system, in particular a continuous casting plant. A controllable inlet-side and a controllable outlet-side valve are operated remotely, and deviations from expected pressures are determined. The pressure curve can also be examined for changes over time. However, due to the high process noise, such considerations cannot be used as a reliable indicator, as the dispersive effect of the entire process—in particular the input into the melting furnace, the evaporation during the process, and also the discharge through the exhaust gas duct—is too vague and dependent on a number of factors.Process noise is the influence of stochastic fluctuations and cross-effects on process variables such as flow, pressure, temperature, or water content. It should be noted that in complex engineering processes, the respective variables can never be measured in isolation, as they are usually influenced by other processes occurring. For example, the water input into the exhaust gas is fed by various sources whose timing and location cannot be clearly determined and which overlap in the measured signal. For example, switching a burner on and off, as well as the spontaneous evaporation of water in a scrap batch, regularly leads to a sudden increase or change in the water content in the exhaust gas.

[0009] In contrast, water ingress from a leak is a gradual, uniform process that results in a comparatively low water ingress. The water ingress through a leak creates a constant background of water vapor in the exhaust gas flowing out of the exhaust outlet, making clear detection of a water leak difficult or even impossible using state-of-the-art methods. This background signal from the water ingress through the leak increases only very slowly, sometimes over weeks. Very precise material and furnace balances are required to reliably detect such a water content. Even the use of neural networks to evaluate the signal curves has proven very difficult to date, as such a network cannot be trained in a real furnace, as this would be too dangerous.

[0010] Even balancing the cooling water circuits, which examines the amount of water entering and leaving the water cooling system per unit of time, does not produce reliable results. A water leakage through which, for example, 3 m 3 Water per hour escapes into the furnace vessel is too low to be able to cope with a total flow of approx. 900 m 3 per hour. Furthermore, water leaks can also occur at numerous other locations outside the furnace. The invention is therefore based on the object of providing a simple and cost-effective method for reliably detecting water leaks in a metallurgical melting furnace despite high process noise.

[0011] The problem is solved by a method and a device having the features according to independent patent claims 1 and 8. Further developments are specified in the dependent claims.

[0012] The object is achieved in particular by a method for detecting a water leak in a metallurgical melting furnace. The method according to the invention is carried out by means of a metallurgical melting furnace, an exhaust gas measuring device for measuring at least one exhaust gas parameter, a pressure regulator, and an evaluation device.

[0013] The metallurgical melting furnace comprises a furnace vessel, the walls of which consist at least partially of water pipe walls through which cooling water flows, a lid and an exhaust gas outlet.

[0014] The flue gas measuring device is arranged downstream of the flue gas outlet in the direction of flue gas flow and is connected to the evaluation device via data transmission. Depending on the exact arrangement of the flue gas measuring device, detected leaks are assigned to different areas. According to an advantageous variant, the flue gas measuring device is arranged close downstream of the flue gas outlet, which advantageously prevents additional water sources from contributing. A further advantage of this arrangement is that leaks that only occur downstream of the furnace vessel, i.e. in the flue gas pipe, do not contribute. Since a leak in the water pipe walls of the furnace vessel has a particularly high hazard potential, it is advantageous to be clear whether the leak is actually in the furnace vessel. A leak in the flue gas duct, on the other hand, is harmless in terms of its hazard potential.

[0015] Furthermore, the evaluation device is also connected to the pressure regulator for data transmission. The pressure regulator can adjust and regulate the pressure of the cooling water in the water pipe walls. The method comprises the following steps: a) applying a pressure fluctuation to the cooling water using the pressure regulator, whereby a pressure fluctuation is a result of temporary pressure deviations from an average pressure; b) measuring the course of an exhaust gas parameter, i.e. determining the measured values ​​over time, using the exhaust gas measuring device; c) determining the correlation between the course of the pressure fluctuation of the cooling water and the course of the exhaust gas parameter using the evaluation device. A correlation function is used for this purpose; d) outputting the correlation by the evaluation device.

[0016] The result of the correlation can be processed within the evaluation device after each evaluation cycle, so that a signal is only output when certain conditions are met, or the correlation is output after each evaluation cycle.

[0017] For the purposes of the invention, cooling water refers to a fluid suitable for use in a cooling device for cooling a technical system. In particular, this fluid can be water. The method according to the invention can also be carried out with other fluids, in particular with other cooling liquids.

[0018] Preferably, the evaluation device provides an output signal, for example a warning signal, when predetermined criteria are met.

[0019] To determine the correlation according to step c), the pressure fluctuation profile is preferably forwarded to the evaluation device or input into the evaluation device. Furthermore, the result of the measurement according to step b) is forwarded to the evaluation device.

[0020] In the context of the invention, the course of a parameter is a series of values ​​of this parameter determined one after the other. Thus, the temporal development of this parameter is represented.

[0021] Subjecting the cooling water to a pressure fluctuation within the meaning of the invention involves generating a pressure fluctuation, in particular generating a sequence of predetermined, time-limited pressure deviations, i.e., a sequence of predetermined, time-limited increases and / or decreases in the pressure, in particular the nominal pressure, of the cooling water, whereby the pressure can deviate upwards and / or downwards from a mean pressure. The pressure is the pressure of the cooling water or the cooling liquid in the cooling water pipes of the water pipe walls.

[0022] In the context of the invention, a pressure fluctuation refers to a sequence of temporary pressure deviations from a mean pressure. Several consecutive pressure deviations follow a certain predetermined pattern.

[0023] Such a pressure deviation has a certain duration and a certain deviation value, i.e., an amplitude and a deviation direction. In this sense, the deviation value describes the magnitude of the deviation from a mean pressure, whereby a deviation value can be either positive or negative. Furthermore, the pressure deviations can also be separated by a certain time interval.

[0024] In the event of a leak, an increase or decrease in the pressure of the cooling water leads to an increase or decrease in the amount of cooling water entering the furnace through the leak, i.e., the leakage amount. This creates an image of the pattern of the predetermined pressure fluctuation imprinted on the cooling water, i.e., the sequence of predetermined pressure deviations, also in the exhaust gas in the form of a change in at least one exhaust gas parameter, such as the water concentration. This change in the exhaust gas parameter occurs in accordance with the predetermined pressure fluctuation. A correlation between the predetermined pressure fluctuation in the cooling water and the fluctuations in the values ​​of the exhaust gas parameter can be used to determine whether a leak exists in the cooling system.

[0025] To obtain a pressure fluctuation, i.e., a sequence of pressure deviations, which can preferably be used well for correlation, at least one pressure deviation parameter, selected from duration, deviation value, and interval, is adjusted from one pressure fluctuation to the next. For a sequence of pressure deviations, i.e., a pressure fluctuation, the duration and / or the deviation value and / or the interval of the pressure deviation are thus varied.

[0026] For a sequence of pressure fluctuations, either just one pressure deviation parameter, for example, just the deviation value or just the duration of the pressure deviations, or at least two of the pressure deviation parameters, for example, the duration and the deviation value, can be varied. This creates a characteristic pattern, which is then sought through a correlation in at least one of the exhaust gas parameters. Since the pipelines also lead to a pressure loss, the duration, also referred to as the temporal duration, is an important criterion for the correlation and evaluation.

[0027] According to an advantageous embodiment, the sequence of pressure deviation parameters is determined using a random generator, also referred to as a random number generator. Using a random generator, an irregular sequence of pressure deviations, i.e., an irregular pressure fluctuation, can be realized. The sequence of pressure deviations is determined by a value generated by the random generator between a minimum and a maximum pressure deviation parameter, for example, a value generated by the random generator between a minimum and a maximum time duration.

[0028] Certain smallest units can also be defined for this purpose, allowing a pressure deviation parameter to be randomly selected from, for example, 3, 5, 8, or 10 values. A deterministic random number generator can be used for this purpose.

[0029] Alternatively, a non-deterministic or hybrid random number generator can be used.

[0030] A coincidence of irregular changes in one of the exhaust gas parameters with other effects, as occurs more frequently with periodic pressure fluctuations, can thus be prevented or the probability can at least be greatly reduced.

[0031] For example, a program can generate a sequence of 1-second pulses with varying deviation values. The number of pulses each with the same deviation value is determined by a randomly generated number between a minimum and maximum duration, while the deviation value itself is determined by a randomly generated number between a minimum and maximum deviation value. An additional variation of the amplitude up to the maximum value is possible.

[0032] According to one possible design, the pressure fluctuation can be generated continuously, whereby leaks can advantageously be detected at any time.

[0033] Optionally, certain time periods, such as 1800 seconds, can be specified, which are then subjected to a correlation. Preferably, the patterns do not repeat after this period; instead, a new pattern is generated, which is then used for further correlation. This advantageously allows a positive result to be verified or refuted in a two-stage process. This improves the reliability of the method.

[0034] An exhaust gas characteristic is a parameter of the exhaust gas, for example, the proportion or quantity of water contained in the exhaust gas, or the pressure of the exhaust gas, or the temperature of the exhaust gas. The characteristic pattern resulting from pressurization can be advantageously read off in different parameters or process variables. Thus, different exhaust gas characteristics can be advantageously used for correlation measurements and serve as a reliable indicator of leakage.

[0035] In the context of the invention, a correlation is understood to be a relationship between two signal sequences, in this case the curve of the exhaust gas parameter and the pressure fluctuation over time. If a connection between the curves can be identified and consequently a relationship exists between the curves, this can be read off from the correlation. If certain values ​​and limits are defined depending on the selected evaluation method and correlation function, a decision can be made based on the result of the correlation as to whether a leak has occurred. Since this is a statistical process, the limits can be selected depending on the desired and necessary probability of correct or incorrect warning signals. One advantage of this method is that a signal can be detected even if other possibilities for water ingress into the furnace vessel occur.A small correlated fluctuation in the amount of water measured at the exhaust outlet due to a leak can be reliably detected even if the fluctuation in the amount of water due to other processes is very large.

[0036] Even if the water quantities introduced into the furnace process by other sources, particularly in conjunction with their temporal uncertainty, result in a very low signal to be detected, the method according to the invention can still be used to successfully evaluate the signal. Advantageously, by correlating the pressure fluctuation of the cooling water in the water tube walls with the measured values ​​of the water quantity in the exhaust gas, reliable detection of leaks in the water tube walls of the furnace vessel is achieved.

[0037] It should be noted that even if some of the water entering the furnace vessel through a leak accumulates in liquid form at one point, some of the water will always evaporate. The method according to the invention is based on the fact that the evaporated portion of the water flowing out through the exhaust gas outlet influences the signal from the exhaust gas measuring device.

[0038] According to an advantageous embodiment of the method, cooling water flows through at least two different sections within the water pipe walls, which are subjected to different pressure fluctuations according to step a), and a correlation is performed for each of the sections according to step c). The pressure fluctuations can be varied, for example, in frequency and / or amplitude and / or deviation value.

[0039] According to an advantageous variant, an auxiliary line is provided for each section which is connected to this section. The different sections preferably form different cooling circuits. With different cooling circuits, different pressure curve patterns can be imposed on each circuit. This can happen in the circuits either staggered in time, i.e. in chronological order, or simultaneously. If the patterns are different, the circuit exhibiting a leak can be detected by the corresponding correlation. Depending on the characteristics of the exhaust gas parameter and the resulting correlation, the correlation corresponds to the characteristics of the pressurization in one or more sections. This can advantageously be used to determine in which section or sections the leak is located.

[0040] According to a possible embodiment, each section of a water pipe wall through which cooling water flows has a separate pressure regulator or a unit assigned to the section, which can apply a pressure fluctuation to the pressure within the respective section.

[0041] According to one possible embodiment, valves are arranged within the water pipe walls between the sections. These enable different pressurization characteristics, even in connected sections or interconnected cooling circuits. The installation of valves divides a cooling circuit into different sections or zones, which can then be monitored separately for leaks. Preferably, the exhaust gas parameter measured in step b) is the gas velocity and / or the water content and / or the water quantity and / or the exhaust gas pressure and / or the exhaust gas temperature and / or carbon monoxide (CO) or carbon dioxide (CO2) or methane (CH4) or sulfur dioxide (SO2). These exhaust gas parameters are influenced by leaking water and are therefore suitable as parameters for a correlation measurement.Preferably, one of the exhaust gas parameters evaluated is the water content and / or the water quantity, as these exhibit a particularly strong correlation with incoming water. This is particularly advantageous for the signal-to-noise ratio.

[0042] However, if other exhaust gas parameters are already being determined for other reasons, it may be appropriate and efficient to also use these exhaust gas parameters as the basis for such a correlation.

[0043] Optionally, several exhaust gas parameters can be measured, in particular their profiles are measured and verified using a correlation. This can further improve the signal-to-noise ratio. This advantageously allows for more precise and reliable results. The following calculation example demonstrates the advantages of the method variant in which the measured exhaust gas parameter is the gas velocity.

[0044] A typical leak begins with approximately 1-2 liters of water entering the furnace vessel per minute. 1 liter of water causes a volume of approximately 7 m under normal pressure. 3 Water vapor. However, if the temperature is above 1000 °C, this results in a volume of approximately 420 m 3 Water vapor. With an outlet diameter of 4 m and a maximum flow velocity of 25 m per second, the maximum volume flow is 314 m 3 of water vapor per second. Depending on the flow profile in the outlet, the actual volume flow is approximately 50% of the maximum value, i.e. approximately 157 m 3 Water vapor per second or 565,000 m 3of water vapor per hour. The volume flow of water vapor introduced by a leak of 1 l of water per minute is therefore only 0.075% of the total volume flow of water vapor. If the Bernoulli equation is valid, the flow of incompressible liquids changes proportionally to the square root of the pressure. Doubling the pressure therefore leads to an increase in the leaked water quantity by a factor of approximately 1.4, which for the example calculation would increase the volume flow of water vapor to approximately 595 m 3 Water vapor per second or 0.105% of the total volume flow of water vapor.

[0045] Due to typical process noise, such a change cannot be reliably detected statistically or in a single measurement. However, using frequently correlated repetition, it becomes clearly apparent and can serve as a reliable measure for leak detection.

[0046] For the variant of the method in which the water content is directly measured by the exhaust gas measuring device, a further increased, i.e. improved, sensitivity of the method can be observed. It is not necessary to measure the change in the overall composition of the exhaust gases, but only the relative change in the water content.

[0047] Other processes that lead to water ingress into the furnace vessel include the gas burner or the water cooling of the electrodes, where water flows past the electrodes into the furnace vessel and immediately evaporates. This leads to a water ingress of approximately 100 l / min. In addition, the burner can evaporate up to 2000 m 3 / h of methane is introduced into the furnace vessel.

[0048] The scrap batch can also cause a significantly larger amount of water to enter the melt in a short period of time, but this quickly disappears again during the melting cycle. However, water ingress from such a scrap batch is irrelevant for the correlation, as this water ingress is unrelated to the pressure fluctuation in the cooling water.

[0049] The direct detection of the water quantity at the exhaust outlet improves the possibilities for leak detection compared to measuring the flow rate of the entire exhaust gas quantity at the exhaust outlet due to the improved signal-to-noise ratio. This reduces the required pressure fluctuation, which minimizes the mechanical stress on the components. The cooling water is typically fed into the cooling water circuit at approximately 25 - 35 °C and thus experiences a temperature increase of approximately 15 °C at a nominal flow rate. Since an increase in pressure places greater stress on the components in the long term, while a decrease in pressure leads to an increase in the water outlet temperature, a small fluctuation around a suitable water pressure is desirable. Since a fluctuation of only 10 % in pressure is only expected to result in a change in the water outlet of just under 5 %, optimized evaluation is necessary.

[0050] According to an advantageous variant, the pressure fluctuation is irregular, i.e., the pressure fluctuation applied according to step a) follows a predetermined, irregular pattern. The cooling water is subjected to a predetermined, irregular sequence of pressure deviations according to step a). This advantageously creates a temporally distinct signal at the exhaust outlet that exhibits no periodicity and exhibits a strong signal entropy over a longer period.

[0051] A non-periodic pressure fluctuation also repeats after a certain time unit. The time unit after which such a pressure fluctuation is repeated is preferably greater than half an hour. The measurement cycles do not necessarily have to be particularly short in order to reduce the hazard. It should be noted that an accident due to explosive evaporation processes within the furnace vessel does not necessarily occur with every melting cycle. A water leak can remain undetected for a long time and grow, causing the amount of water entering the furnace vessel to rise. However, if a corresponding scrap arrangement or other batch-related changing geometries in the furnace vessel can cause water to accumulate in the lower region of the furnace vessel, this can lead to a spontaneous explosion.

[0052] The time constants must be selected so that the relative slope of the actual water flow change can still be reliably detected using a correlation. The signals indicating the change in water pressure can range in time from several tens of seconds to several minutes. Several signal sequences from various melting processes can thus be combined into a single, correlable signal sequence.

[0053] An advantageous variant of the method provides for filtering in the frequency spectrum to adapt to the pressure fluctuation in the water pressure according to step a), thereby adjusting the signal from the exhaust gas measuring device. This advantageously improves the signal-to-noise ratio.

[0054] The cooling water is preferably passed through the cooling pipes at a pressure of 6 bar. A pressure fluctuation by means of the pressure regulator according to step a) preferably involves a variation of the pressure by +2 bar upwards and -2 bar downwards. A suitable pressure fluctuation is preferably in a range of 10% to 50% of the pressure by which the fluctuation occurs, i.e., generally the mean value.

[0055] By varying the water pressure in this way, in the event of a leak, the amount of water escaping per unit of time would be slightly changed in a controlled manner with the water pressure.

[0056] The application of a pressure fluctuation or preferably an irregular sequence of pressure deviations to the cooling water is implemented by means of a pressure regulator described herein, which is also referred to as a pressure control device.

[0057] One possible embodiment of the method provides for the correlation according to step c) to be a cross-correlation. If a clear maximum of the cross-correlation is obtained, it can be assumed that a water leak is present. The cross-correlation has then detected the temporal pattern of the water pressure change in the exhaust gas signal, i.e., in the signal from the exhaust gas measuring device.

[0058] The advantage of using cross-correlation is that it allows a useful signal to be extracted even from a highly disturbed or noisy signal. The key factor here is using a sufficiently long signal duration to retain sufficient statistical information.

[0059] The reliable formation of a maximum cross-correlation enables reliable detection of a water leak. Interference signals from other water inputs, which are subject to different temporal dynamics, are suppressed so strongly by cross-correlation that even small water leaks can be detected. Small water leaks, within the meaning of the invention, are leaks with a water discharge of 1 to 10 liters per minute, or 1 to 5 liters per minute, or 1 to 2 liters per minute. Preferably, the method according to the invention can detect a leak that is at least 3 liters per minute, preferably 1 liter per minute.

[0060] According to an advantageous embodiment of the method, the measurement according to step b) is carried out using spectroscopy. Spectroscopy, as defined by the invention, is a measurement method that utilizes optical principles while observing the individual wavelengths of the evaluated signal. A laser-based emission measurement or a laser-based absorption measurement is preferably used.

[0061] By using optical measurement systems that operate using spectroscopy, the exhaust gas composition can be determined by measuring emission or absorption spectra in specific wavelength ranges. Such an optical measurement system is preferably located in or on the exhaust pipe. Online systems or extractive systems that extract a partial flow of the exhaust gas through a water-cooled lance can be used. Optical measurement systems are advantageously suited to enable time-resolved analysis of the exhaust gas composition. Advantageously, the amount of water at the exhaust outlet can thus be measured directly.

[0062] An advantageous embodiment of the method provides that the metallurgical melting furnace is designed as an arc furnace with electrodes as heating device.

[0063] A further aspect of the invention relates to a device for carrying out the method according to the invention, comprising a metallurgical melting furnace, which is preferably designed as an arc furnace, an exhaust gas measuring device for measuring at least one exhaust gas parameter according to step b), a pressure regulator for subjecting the pressure of the cooling water to a pressure fluctuation according to step a) and an evaluation device connected to the pressure regulator for data transmission for carrying out the correlation according to step c).

[0064] The metallurgical melting furnace comprises a furnace vessel, the walls of which consist at least partially of water pipe walls through which cooling water flows, and an exhaust gas outlet. The exhaust gas measuring device is arranged downstream of the exhaust gas outlet in the direction of exhaust gas flow and is connected to the evaluation device for data transmission.

[0065] Preferably, the metallurgical melting furnace is designed as an arc furnace with electrodes as heating device.

[0066] The metallurgical melting furnace preferably has a lid, particularly preferably a pivotable lid.

[0067] The application of a pressure fluctuation, or preferably an irregular sequence of pressure deviations, to the cooling water is implemented by means of a pressure regulator. In the context of the invention, a pressure regulator is a device that can control and / or regulate the pressure of the cooling medium through the water pipe walls.

[0068] On a main line, a pressure regulator usually has a controllable and / or adjustable main pump for conveying the cooling water through the water pipes of the water pipe walls. According to one possible variant, a change in pressure can be achieved by controlling and / or regulating the main pump. The main pump is preferably designed and arranged such that controlling the pump directly leads to a change in the pressure of the coolant and thus directly to the cooling water being subjected to a pressure fluctuation. A pattern of pressure fluctuation is thus achieved by changing or adjusting the delivery rate of the main pump. This is a simple variant for implementing the application of a pressure fluctuation, for which no additional components need to be installed.

[0069] An advantageous embodiment of a pressure regulator provides that the pressure regulator is designed as a pressure regulating device which, in addition to a main pump on a main cooling water line, has an auxiliary line connected to the cooling circuit, in particular to the water pipe walls, for the flow of a portion of the cooling water in the manner of a bypass. At least one, optionally several controllable and / or regulatable valves are provided on the auxiliary line, which vary the flow through the auxiliary line and thus also the flow through the main line. This influences the pressure in the main cooling line and can thus generate a pressure fluctuation in the cooling water. Generating the pressure fluctuation by varying a volume flow in an auxiliary line advantageously results in the main pump having to realize pressure changes less frequently and less severely. This advantageously protects the main pump from premature wear.

[0070] One possible design of a pressure regulator provides for the pressure regulator to be designed as a pressure control device, with a change in the volume in the cooling water circuit generating the pressure fluctuation. For this purpose, a piston, similar to a plunger, is preferably arranged movably on a volume-changing region of the water pipe walls such that a movement of the piston varies the volume and thus the pressure within the water pipe walls. Advantageously, this also eliminates the need for the main pump to generate the pressure fluctuation, thus protecting it from wear.

[0071] According to an advantageous embodiment, the pressure regulator has an auxiliary pump in addition to a main pump for generating a cooling water flow. The auxiliary pump is designed to be controllable and / or adjustable in such a way that an additional volume flow is generated, thus allowing the pressure fluctuation to be generated by the auxiliary pump. The auxiliary pump is preferably smaller than the main pump. The auxiliary pump preferably has a pumping capacity of 5% to 20% of the main pump. Advantageously, a smaller auxiliary pump can be controlled more quickly and precisely, which improves the efficiency of the process.

[0072] The pressure regulator is preferably designed as a pressure regulating device which, in addition to a main pump on a main cooling water line, has an auxiliary line connected to the cooling circuit for the flow of a portion of the cooling water in the manner of a bypass, at which auxiliary pump controls and / or regulates the cooling water flow through the auxiliary line. Generating the pressure fluctuation by an auxiliary pump advantageously leads to greater steepness of the pressure deviations compared to pressure deviations that can be generated by the main pump, and also means that the generally larger main pump has to implement less frequent and less severe pressure changes for the larger portion of the cooling water flow. This advantageously protects the main pump from premature wear. The auxiliary line is preferably dimensioned such that a flow of 5% to 20% of the cooling water is generated through this bypass.

[0073] According to an alternative design, an auxiliary pump is arranged directly on the main cooling water line so that an additional volume flow is generated by the auxiliary pump and the main pump can be protected from wear caused by frequent pressure changes.

[0074] Particularly preferably, the water pipe walls through which cooling water flows consist of at least two sections, which can be subjected to different pressure fluctuations by means of several pressure regulators. Valves can be arranged between the sections.

[0075] According to the concept, a water leak in a cooling pipe or water pipe of a furnace vessel is detected by combining and correlating a time-resolved measurement of an exhaust gas parameter, such as the water quantity, at the exhaust gas outlet, and a controlled pressure fluctuation, i.e., a variation in the pressure, of the cooling circuit. In the event of a leak, the variation in water pressure leads to a variation in the amount of water escaping into the furnace vessel, which is temporally correlated with the variation in the pressure of the cooling circuit. By determining the correlation of these signals, an evaluation device can determine a relationship based on a water leak. An advantageous embodiment provides for various cooling circuits to which different pressure profile patterns can be imposed. This not only detects the leak but also makes it possible to determine in which section, i.e., in which cooling circuit, the leak occurs.This allows the position of the leak to be narrowed down and thus determined more efficiently.

[0076] Further details, features, and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. They show:

[0077] Fig. 1 : a metallurgical melting furnace and

[0078] Fig. 2: a pressure fluctuation with an irregular pattern.

[0079] Fig. 1 shows a metallurgical melting furnace 1 for melting metal, comprising a furnace vessel 2 containing a molten metal 3 and a pivoting lid 4. Water-flowing water pipe walls 5, i.e., walls traversed by water pipes 6, are arranged in the wall area of ​​the furnace vessel 2. The water pipes 6 of the water pipe walls 5 ensure water cooling by virtue of the cooling water 7 flowing through the water pipes 6. This protects the furnace vessel 2 from damage caused by the high temperatures of the molten metal 3.

[0080] A heating device 6, which has three electrodes 7, is arranged on the furnace vessel 2. The electrodes 7 extending into the furnace vessel 2 are preferably designed for three-phase alternating current. The electrodes 7 generate arcs 10, the heat from which is used to melt the metal in the furnace vessel 2. A gas burner 11 and an oxygen supply element 12 designed as an oxygen lance 12 are also arranged on the furnace vessel 2.

[0081] The exhaust gases generated by the combustion and melting processes within the furnace vessel 2 are guided through an exhaust gas outlet 13 into an exhaust pipe 14. An exhaust gas measuring device 15 is also arranged on this exhaust pipe 14, which adjoins the exhaust gas outlet 13, to determine the exhaust gas parameters and monitor the resulting exhaust gases. The exhaust gas flows through the exhaust gas outlet 13, passes through an air supply opening 14, which here is designed as an air supply ring 16, and then flows past at least one exhaust gas measuring device 15.

[0082] Alternatively, the exhaust gas measuring device 15 is arranged upstream of the air supply opening 16 in the exhaust gas flow direction R. However, arranging the exhaust gas measuring devices 15 downstream of the air supply opening 16 has structural advantages, since this area of ​​the exhaust pipe 14 can be thermally separated from the furnace vessel 2. This reduces the thermal loads on the exhaust gas measuring device 15.

[0083] Further downstream of the air supply device on the exhaust pipe 14, a cooler 17 for cooling the exhaust gas flow and a filter 18 for separating solid particles from the exhaust gas are arranged. The exhaust gas is then directed through the induced draft fan 19 and into the chimney 20.

[0084] To detect a leak in the water pipe walls 5, the cooling water 7 flowing into the water pipes 6 of the water pipe walls 5 is subjected to a pressure fluctuation, in particular a sequence of pressure deviations, by means of a pressure regulator 21. The pressure fluctuation of the cooling water 7, i.e. in particular the course of the pressure fluctuation or the pattern of the sequence of pressure deviations of the cooling water 7, is compared with the course of an exhaust gas parameter measured at the exhaust gas measuring device 15. For this purpose, the signal of the exhaust gas parameters is forwarded to an evaluation device 23 via a data cable 22. The course of the pressure fluctuation of the cooling water 7 is also forwarded from the pressure regulator 21 to the evaluation device 23 via a data cable 22.The evaluation device 23 determines the correlation of the pressure fluctuation, i.e. the sequence of predetermined pressure deviations, also referred to as the pressure curve, of the cooling water 7 with the curve of the exhaust gas parameter measured at the exhaust gas measuring device 15, whereby relationships are recognized and reliable leak detection is possible.

[0085] Fig. 2 shows a pressure curve 24 subjected to a pressure fluctuation with an irregular pattern. The pressure fluctuation is formed by several consecutive pressure deviations 25, i.e., deviations from a mean pressure 26. The pressure curve 24 thus takes on a specific pattern.

[0086] Each pressure deviation 25 has a deviation value 25 and a duration 28, also referred to as duration 28. Using a random generator, an irregular sequence can be realized in which a value generated by the random generator between a minimum 29 and a maximum 30, for example, between a minimum and a maximum deviation value and / or a value generated by the random generator between a minimum and a maximum duration, determines the sequence of pressure deviations 25. Certain smallest units can also be defined for this purpose, so that a random selection is made from, for example, 8 or 10 values.

[0087] The pressure deviations 25 shown here are not spaced apart from one another. However, it is also possible to provide intervals between the pressure deviations 25 without changing the mean value, i.e., the mean pressure 26. These intervals can also be varied. According to a simple embodiment of the method, only the intervals between the pressure deviations 25 can be varied.

[0088] List of reference symbols

[0089] I Metallurgical melting furnace, arc furnace2 furnace vessel

[0090] 3 Metal melt

[0091] 4 lids

[0092] 5 Water pipe wall

[0093] 6 water pipe

[0094] 7 Cooling water

[0095] 8 Heating device

[0096] 9 Electrode

[0097] 10 arc

[0098] II Gas burner

[0099] 12 Oxygen supply element, oxygen lance

[0100] 13 Exhaust outlet

[0101] 14 Exhaust pipe

[0102] 15 Exhaust gas measuring device

[0103] 16 Air supply opening, air supply ring

[0104] 17 coolers

[0105] 18 filters

[0106] 19 induced draft

[0107] 20 Chimney

[0108] 21 Print Control

[0109] 22 data cables

[0110] 23 Evaluation device

[0111] 24 print

[0112] 25 pressure deviation

[0113] 26 medium pressure

[0114] 27 Deviation value

[0115] 28 duration

[0116] 29 minimum

[0117] 30 maximum

[0118] R Exhaust gas flow direction

Claims

Patent claims 1. Method for detecting a water leak in a metallurgical melting furnace (1) by means of • a metallurgical melting furnace (1), comprising a furnace vessel (2) whose walls consist at least partially of water pipe walls (5) through which cooling water (7) flows, and an exhaust gas outlet (13), • an exhaust gas measuring device (15) arranged in the direction of exhaust gas flow (R) downstream of the exhaust gas outlet (13) for measuring at least one exhaust gas characteristic parameter, • a pressure regulator (21) for adjusting the pressure of the cooling water (7) in the water pipe walls (5) as well as • an evaluation unit (23) connected to the exhaust gas measuring device (15) and the pressure regulator (21) via data transmission, comprising the following steps: a) subjecting the cooling water (7) to a pressure fluctuation, wherein a pressure fluctuation is a sequence of time-limited pressure deviations from a mean pressure, by means of the pressure regulator (21), b) measuring the course of an exhaust gas parameter by means of the exhaust gas measuring device (15), c) determining the correlation of the course of the pressure fluctuation of the cooling water (7) with the course of the exhaust gas parameter by the evaluation unit (23), d) outputting the correlation by the evaluation unit (23).

2. Method according to claim 1, characterized in that the pressure fluctuation applied according to step a) follows a predetermined, irregular pattern.

3. Method according to claim 2, characterized in that a random number generator is used to create an irregular sequence of pressure deviations (25). A method according to any one of claims 1 to 3, characterized in that at least two different sections within the water pipe walls (5) are traversed by cooling water (7), which are subjected to different pressure fluctuations according to step a), and wherein a correlation according to step c) is performed for each of the sections. A method according to claim 4, characterized in that valves are arranged within the water pipe walls (5) between the sections. A method according to any one of claims 1 to 5, characterized in that the exhaust gas parameter measured in step b) is the gas velocity and / or the water content and / or the amount of water. A method according to any one of claims 1 to 6, characterized in that the pressure fluctuation in step a) is not periodic. A method according to any one of the preceding claims, characterized in that the correlation according to step c) is a cross-correlation.A method according to any one of the preceding claims, characterized in that the measurement according to step b) is carried out by means of spectroscopy. A method according to claim 9, characterized in that the measurement is a laser-based emission measurement or a laser-based absorption measurement. A method according to any one of the preceding claims, characterized in that the metallurgical melting furnace (1) is designed as an electric arc furnace (1) with electrodes (9) as a heating device (8). Device for carrying out the method according to one of the preceding claims, comprising • a metallurgical melting furnace (1) with a furnace vessel (2) whose walls consist at least partially of water pipe walls (5) through which cooling water (7) flows, and an exhaust gas outlet (13) as well as • an exhaust gas measuring device (15) arranged in the direction of exhaust gas flow (R) downstream of the exhaust gas outlet (13) for measuring at least one exhaust gas characteristic according to step b), • a pressure regulator (21) for applying a pressure fluctuation to the pressure of the cooling water (7) according to step a) and • An evaluation unit (23) connected to the pressure regulator (21) and the exhaust gas measuring device (15) for performing the correlation according to step c). Device according to claim 12, characterized in that the pressure regulator has a main pump and an auxiliary pump, wherein the auxiliary pump is designed to be controllable and / or regulated such that an additional volume flow generated by the auxiliary pump produces the pressure fluctuation. Device according to claim 12 or 13, characterized in that the pressure regulator (21) has an auxiliary line in contact with the water pipe walls, wherein a valve is designed and arranged on the auxiliary line such that the flow through this auxiliary line can be controlled and / or regulated by the valve.Device according to claim 14, characterized in that the pressure regulator (21) has a volume change area in which a piston is designed and arranged such that a volume change generated by the movement of the piston influences the pressure in the water pipe walls.

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