Metallurgical melting furnace and method for determining the amount of heteromolecular gases

Abstract

The present invention relates to a metallurgical melting furnace having a furnace vessel, an exhaust gas exhaust device arranged in the furnace vessel for exhausting an exhaust gas flow, and an air inlet opening for supplying air to the exhaust gas flow. The exhaust gas discharge system has a measuring opening arranged downstream of the intake opening and spaced apart from the measuring opening. In this way, the electromagnetic radiation generated inside the exhaust gas discharge system by the hot molecules is detected and statistically evaluated. The invention also relates to a method for determining the amount of hetero-molecular gas and a method for determining the temperature of the gas.

Description

[Technical field]

[0001] The present invention relates to a metallurgical melting furnace having a furnace vessel, an exhaust gas exhaust device for exhausting an exhaust gas flow arranged in the furnace vessel, an air inlet opening for supplying air to the exhaust gas flow, a method for determining the amount of a hetero-molecular gas, and a method for determining the temperature of the gas. [Background technology]

[0002] During the operation of a metallurgical melting furnace, different, often harmful, gases are produced, depending on the processes taking place in the metallurgical melting furnace. In order to optimize the processes taking place in the metallurgical melting furnace and to reduce the proportion of harmful gases, precise knowledge of the produced gases, especially in their ratio to one another, is an important overall condition for efficient control of the individual process parameters. The main obstacle to many possible measurement methods is the extremely high temperatures occurring during the processes, which are in the range of more than 1000°C.

[0003] From the prior art, various approaches are known as to how the proportion of gas molecules in a metallurgical smelting furnace can be determined.

[0004] DE 10 2008 009 923 A1 discloses a method for determining combustible exhaust gas components in an arc furnace by means of optical sensors. To measure the local CO concentration, light guides are arranged in such a way that the light in the area under the individual oxygen injectors is optically detected. The amount of the exhaust gas components is then evaluated and used to regulate the oxygen supply to the arc furnace. The advantage here is that uneven distribution in the arc furnace is detected accordingly and the individual oxygen injectors can be controlled separately. However, light guides in the furnace can cause major problems due to the high temperatures. In particular, spectroscopy using lasers is used here, which makes such measurement structures very complex and therefore expensive.

[0005] EP 1776576 describes a contactless exhaust gas measurement by FTIR spectroscopy in a metallurgical unit. An FTIR spectroscopy is arranged in the vicinity of the converter, the measurement beam of which is directed into the exhaust gas at a suitable opening in the exhaust duct. The spectrum determined by the FTIR spectroscopy is used to calculate the exhaust gas composition without time delay, taking into account the exhaust gas temperature and a mathematical model. The disadvantage is that this method is also very complex and requires a lot of maintenance.

[0006] DE 2 857 795 A1 discloses a radiation detector for a flame detector which comprises a sensor element and, arranged upstream thereof, a spectral filter which is transparent in the range of carbon dioxide resonance radiation.

[0007] DE 19509704 A1 discloses a method and a device for monitoring and regulating a combustion process. In an oil or gas burner, radiation measurements are evaluated and two different spectral regions of the flame are detected by a sensor device. The selectively amplified signals are used by an algorithm for regulating and monitoring the combustion process. Such a process evaluates the radiation emitted by the flame in a controlled combustion process, which is an indicator for the type of reaction taking place. However, this process does not allow a direct measurement of the amount or composition of gas.

[0008] Another option for monitoring the flame is described in US Pat. No. 3,903,014, which is particularly applicable when controlling processes for melting steel, although here too no direct measurement of the amount of gas is carried out.

[0009] US 2009102103 A1 describes a method for detecting radiation in an industrial furnace by means of a spectrometer and an infrared sensor. For this purpose, a spectrometer device is placed in a window opening that also ensures the intake of the exhaust gas. However, the use of a spectrometer is disadvantageously complex and expensive.

[0010] DE 10 2006 005 823 A1 discloses a method for regulating a burner-fired furnace. A component of a gas stream is detected and at least a part of the radiation emitted by the gas stream is detected. Here, not only one spectral line is evaluated, but the emission of the component is detected over a large part of the spectrum. That is to say, a broadband recording of the emitted spectrum is made. From the emissions detected at different wavelengths, a sum signal is constructed, which is then derived twice after a time lapse. The time course of the signal determined in this way provides a qualitative statement regarding the proportion of the component in the gas stream. In this way, a qualitative statement can be made about the amount of the determined component. Here, a calibration by conventional measurements is disadvantageously necessary in order to be able to make a quantitative statement. With this method, only by calibration can the absolute amount of the component of the gas stream be determined. Furthermore, the setting up of such measurements in the furnace vessel of a metallurgical melting furnace is complicated.

[0011] The emission spectrum of the flame or its exhaust gases is also evaluated in the method described in DE 42 31 777. However, the installation of such sensors in metallurgical melting furnaces is fraught with many problems.

[0012] The main problem with the prior art devices and methods is the very high temperatures that occur in melting furnaces, which is why the installation of measuring instruments in the furnace vessel is very complicated and expensive. Often, very complicated and therefore expensive absorption measurements using lasers are used. Therefore, a less complicated measurement option in metallurgical melting furnaces that provides accurate knowledge of the gas composition evolved during the process is desired. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] DE 102008009923 A1 [Patent Document 2] European Patent No. 1776576 [Patent Document 3] German Patent No. 2857795 [Patent Document 4] DE 19509704 A1 [Patent Document 5] U.S. Pat. No. 3,903,014 [Patent Document 6] US Patent Publication No. 2009102103 [Patent Document 7] DE 102006005823 A1 [Patent Document 8] DE 4231777 A1 Summary of the Invention [Problem to be solved by the invention]

[0014] The problem underlying the present invention is therefore to provide a simple and inexpensive option for determining the absolute concentration of gases generated in a metallurgical melting furnace.

[0015] By absolute concentration is understood in the sense of the present invention the number of heteromolecular gas molecules per unit volume of exhaust gas, for example per cubic centimetre. [Means for solving the problem]

[0016] The problem is solved by the subject matter having the features set forth in the independent claims. Developments are set forth in the dependent claims.

[0017] The problem is solved in particular by a metallurgical melting furnace, which comprises a furnace vessel for melting metals, in which an exhaust gas exhaust device for exhausting the exhaust gas flow is arranged. The exhaust gas exhaust device is formed with an air intake opening for supplying fresh air to the exhaust gas flow. According to the invention, the exhaust gas exhaust device comprises at least one measurement opening downstream of the air intake opening, and a photodiode with at least one spectral filter for separating electromagnetic radiation of a certain wavelength range is arranged and formed outside the exhaust gas exhaust device at a distance from the measurement opening, so that the electromagnetic radiation generated inside the exhaust gas exhaust device and leaking through the measurement opening can be detected at least in part by the photodiode. In this case, it is utilized that molecules have typical energy levels, and the electrons of these molecules emit photons during state transitions. A state transition in the sense of the invention is a change in the energy level of an electron that emits a photon, i.e. electromagnetic radiation, when transitioning from an energetically higher level to an energetically lower level.

[0018] Electromagnetic radiation of a certain wavelength range is, in the sense of the present invention, electromagnetic radiation having a predetermined range of wavelengths, which is usually set by one or more spectral filters. The certain wavelength range corresponds to a characteristic curve of the spectral filter, different wavelengths being transmitted through the spectral filter to different degrees depending on the characteristics of the spectral filter.

[0019] The spectral filter is placed between the photodiode and the measurement aperture and filters the electromagnetic radiation before it strikes the photodiode, allowing only electromagnetic radiation of a particular wavelength range corresponding to the characteristics of the spectral filter to reach the photodiode and be detected.

[0020] Preferably, the spectral filter has molecular specific transmission properties.

[0021] The exhaust gas ejection device can be tubular in design.

[0022] Downstream of the intake opening in the sense of the present invention means that the measurement opening is located downstream of the intake opening in the flow direction of the exhaust gas flow, where downstream of the intake opening in particular means that the measurement opening is located on the side of the intake opening facing away from the furnace vessel.

[0023] Preferably, the air intake opening is formed as an air intake ring.

[0024] Such an arrangement of the measurement aperture and the photodiode downstream of the intake air aperture, spaced apart from the measurement aperture, is remarkable because the incoming air causes a change in the composition of the mixture in the exhaust gas discharge system. Additional CO2 and O2 may enter through the intake air aperture and cause the CO2 or CO, or H2O, CH4, NO2, etc., in the exhaust gas discharge system to change. X , S.O. XThe amount of CO2 or other heteromolecular gases, such as CO2, CO, or O2, is changed by the oxygen in the incoming air, which causes a reaction with the heteromolecules in the hot exhaust gas. Surprisingly, the measuring device for determining the absolute concentration in the exhaust gas discharge system may be arranged downstream of the intake air opening, but other CO2 and O2 enter through the intake air opening and change the amount of CO2 or CO or other heteromolecular gases in the exhaust gas discharge system. This is because, on the one hand, the incoming air has a low temperature such that the number of photons emitted by these molecules is sufficiently low to not affect the measurement, and, on the other hand, the re-burning of CO to CO2 or the reaction with other heteromolecular gases only takes place in the course of mixing the incoming air with the exhaust gas flow. The further reaction of CO to react to form CO2, as well as other reaction processes that are still taking place, takes place essentially in a further course, i.e. only downstream of the measuring opening in the flow direction of the exhaust gas flow. The hot gas flow can thus be measured through the incoming cold air. The incoming cold air is positioned around the hot gas or exhaust gas in the form of a gas curtain, and the state transition of the hot gas or exhaust gas, which exceeds the detection threshold due to the high temperature, can be determined. This advantageously allows the gas composition of the hot exhaust gas to be determined at a location that is not exposed to too high temperatures due to the distance from the furnace vessel and the incoming air. In particular, in the case of the preferred design of the inlet air opening in the form of a ring, the interruption of the exhaust gas exhaust system results in a certain degree of thermal and mechanical decoupling of the exhaust gas exhaust system, which is therefore particularly preferred.

[0025] The measurement opening is, according to a preferred embodiment, closed by a transparent material, preferably in the form of a protective glass.

[0026] An advantageous variant is that at least two measurement openings are arranged in the exhaust gas exhaust system with at least two photodiodes arranged at a distance from the measurement openings. Preferably, three or four measurement openings are arranged in the exhaust gas exhaust system with at least three or four photodiodes. Alternatively, more than two photodiodes can also be arranged at a distance from the measurement openings. What is important is that all measurement openings are arranged downstream of the intake opening with the photodiodes arranged at a distance from the measurement openings. Preferably, each photodiode is equipped with a different spectral filter, so that different wavelength ranges can be detected by the individual photodiodes.

[0027] Each photodiode is positioned within the line of sight of the electromagnetic radiation passing through the measurement aperture.

[0028] Preferably, a measurement channel extends from the measurement opening to the photodiode, the measurement channel is not formed transparent, thereby protecting the measurement from negative external influences, such as, for example, disturbing radiation, i.e. the measurement channel is formed between the measurement opening and the photodiode.

[0029] An advantageous configuration of the metallurgical melting furnace provides that the melting furnace comprises a heating device for melting the metal in the molten pool, preferably arranged with a number of electrically operated electrodes for generating an electric arc, such a metallurgical melting furnace also being called an electric arc furnace.

[0030] Preferably, a measurement amplifier is arranged on the photodiode for amplifying the electrical signal generated by the photodiode. According to an advantageous embodiment, the spectral filter as well as the photodiode and the measurement amplifier are arranged in one housing.

[0031] Preferably, either the photodiode or the measurement amplifier is connected to an evaluation unit for processing the generated electrical signal, so that, based on the electromagnetic radiation detected by the photodiode, the evaluation unit can determine the amounts of the individual gas components.

[0032] In order to be able to determine the absolute concentration, i.e. the proportion, of a heteromolecular gas in a hot gas, it is utilized that a hot gas having a given temperature T and a given pressure within the normal pressure range, i.e. with a deviation of ±10%, contains thermally excited heteromolecules that emit photons. The required temperature is T>400K so that the number of emitted photons reaches a level at which the photodiode can detect them.

[0033] Preferably, the calculation of the density and molecular distances in a gas mixture at a given temperature is carried out via the ideal gas equation, and in conjunction with information about the geometric shape of the components, i.e. in this case in particular the geometric shape of the exhaust gas discharge device and the installation conditions of the measurement aperture and the photodiode, the number of excited molecules can be determined.

[0034] The photodiode is preferably made of, for example, InAsSb for detection in the infrared range. Selective materials are InSb, InAs, PbS or PbSe. The exact characteristic curve of the photodiode, in particular its temperature-dependent behavior, as well as the physical and electrotechnical properties of the photodiode and the exact area of ​​the photodiode are utilized during the evaluation.

[0035] For a finely divided detection of gas components, according to a possible variation, one spectral filter or alternatively a combination of several spectral filters with defined spectral ranges is used for each desired molecule.

[0036] Such a filter or a combination of such filters is called a molecule-specific filter. These molecule-specific spectral filters are used to be able to determine the selection of photons from the infrared band, also called IR band, of the desired heteromolecule. IR bands are, in the sense of the present invention, typical spectral curves of emitted electromagnetic radiation with identical maxima, which can be expressed differently molecule-specifically. From the IR bands it is possible to determine the wavelengths of the molecule-specific maxima as well as their typical intensity ratios. An accurate knowledge of the characteristic curves of the spectral filters is necessary as a basis for quantum-mechanical and statistical evaluations, so that from the characteristic curves it is possible to determine which IR transitions contribute to the measurement and to what extent. The appropriate molecule-specific part from the total IR band is analyzed.

[0037] The object of the present invention is to provide a method for determining hetero-molecular gases occurring in a melting furnace by means of a melting furnace according to the invention having an evaluation unit, a) directing a gas having a proportion of hetero-molecular gas through an exhaust gas ejection device; b) supplying cool air to the exhaust gas flow; c) detecting electromagnetic radiation of a particular wavelength emitted by the gas with a photodiode having a spectral filter; d) determining the proportion of the hetero-molecular gas by the evaluation unit The problem is solved by a method comprising the steps of:

[0038] The transition rate, i.e. the number of photons emitted per molecule, results in a characteristic emission spectrum for each molecule, if the temperature is known. From this, taking into account the geometry of the metallurgical smelting furnace according to the invention, it is possible to create concentration characteristic curves for different molecular concentrations, taking into account the characteristic curves of the spectral filter and the photodiode as well as the characteristics of the measurement amplifier. Different concentration characteristic curves can preferably be stored in the evaluation unit, so that the output current of the measurement amplifier provides information on the concentration of the gas for a given configuration of the metallurgical smelting furnace. From this, if the temperature is known, the amount of emitting molecules, i.e. the absolute concentration of the molecules, can be determined directly.

[0039] The object of the present invention is to provide a method for determining the amount of hetero-molecular gases occurring in a metallurgical melting furnace by means of an apparatus according to the invention having an evaluation unit, the method comprising: a) directing a gas having a proportion of hetero-molecular gas through an exhaust gas ejection device; b) supplying cool air to the exhaust gas flow; c) detecting electromagnetic radiation of a particular wavelength emitted by the gas with a photodiode having a spectral filter; d) determining the temperature and transmitting the temperature to an evaluation unit; d) determining the amount of hetero-molecular gas by the evaluation unit The above problems are also solved by a method comprising the steps of:

[0040] Preferably, the spectral filter that filters the emitted radiation is a molecule specific filter.

[0041] Another aspect of the invention is a method for determining the temperature of a gas at least partially comprising a hetero-molecular gas by means of a device according to the invention having at least two photodiodes and at least two different spectral filters, comprising: a) directing a gas having a proportion of hetero-molecular gas through an exhaust gas ejection device; b) supplying cool air to the exhaust gas flow; b) detecting electromagnetic radiation of at least two specific wavelengths or two IR bands emitted by the gas by a photodiode; c) determining the temperature of the gas by comparison with the temperature-dependent gas release characteristics; The present invention relates to a method for producing a composition comprising the steps of:

[0042] Here, the evaluation principle is based on the fact that for a given molecule, the IR band, i.e. the number and wavelength of emitted photons of a state transition for a specific molecule, depends only on the temperature. Thus, after evaluation of the IR band, i.e. when the molecular composition is known, the number of photons emitted by the molecule at a given temperature can be determined. Now, by comparing the determined IR bands, i.e. the heights of the two photodiode currents with each other, a characteristic curve is obtained which depends only on the gas temperature and which does not depend on the concentration of this molecule, on the geometry of the metallurgical melting furnace and on the arrangement of the measuring aperture and the photodiode. Thus, the determination of the temperature of the gas according to step d) by comparison with the temperature-dependent emission characteristic of the gas preferably first includes a step of determining the proportion of heteromolecular gas by the evaluation unit.

[0043] Two filter-photodiode combinations are used to determine the intensity of electromagnetic radiation in two different wavelength ranges. The geometry of the spectral filters and diodes is only important if they are different from each other. In the case of two identical spectral filter-photodiode combinations, no consideration is necessary, but if this is not the case, it can be considered and corrected mathematically.

[0044] Both spectral filters must cover different spectral ranges, although overlap is possible. It is important that the concentration of the molecule whose spectrum is used is sufficient so that detection is possible. The measurement must be carried out below the saturation range of the temperature characteristic curve. In order to determine the temperature unambiguously, a monotonic characteristic curve is necessary. This should be taken into account when selecting the molecule to be evaluated. Filtering as narrow as possible - i.e. using a filter that transmits only a narrow wavelength range - ensures as low as possible the influence of other molecules on the measurement result. Preferably, the spectral filter has a transmission range, i.e. a range that transmits radiation to at least 50%, preferably at least 70%, particularly preferably at least 85%, which range has a width of at most 10 μm, preferably at most 9 μm, suitably at most 4 nm. An advantageous variation of the method provides that a wavelength or wavelength range that emits substantially one type of molecule, i.e. with a maximum value, is evaluated.

[0045] According to one possible configuration, two spectral ranges are taken into account, which allows mutual correction. In addition, one variation contemplates that the gas temperature determined by the selective method is utilized for control and / or correction.

[0046] Preferably, the spectral filter comprises layers of dielectric materials, in particular selected from the group of oxides, such as titanium dioxide (TiO2), hafnium dioxide (HfO2), tantalum pentoxide (Ta2O5), silicon dioxide (SiO2), yttrium oxide (Y2O3), and / or fluorides, such as magnesium fluoride (MgF2) or barium fluoride (BaF2) or YF3, and / or sulfides, such as zinc sulfide (ZnS), and / or selenides, such as zinc selenide (ZnSe). The layer thicknesses are selected such that predetermined transmission characteristics can be achieved based on constructive and destructive interference.

[0047] According to a possible embodiment, the spectral filter or filters are formed as semiconductor filters, which act in particular as absorption filters for electromagnetic radiation below a certain wavelength, which is considered as the absorption edge. Due to the band gap, electromagnetic radiation can be transmitted to a high extent above the absorption edge.

[0048] Semiconductor filters consist of coated, optically polished semiconductor disks with long-wave transmission properties, often mounted in a holder for protection. Due to their very high absorption in the stop band, semiconductor filters are particularly useful for rejecting higher orders of the spectrum in IR grating monochromators, i.e., spectral filters for transmission within a narrow range of infrared light. The use of semiconductor filters is particularly advantageous when high-temperature sources are used, since the higher orders, i.e., shorter wavelengths and higher energy, of the spectrum are particularly problematic.

[0049] According to one advantageous embodiment, the spectral filter, in particular a spectral filter made of a dielectric material or a semiconductor filter, is provided with an anti-reflection coating on one side, preferably on the radiation input side, which is arranged towards the irradiated electromagnetic radiation, or on the radiation input side and on the radiation output side, which is arranged towards the photodiode. This increases the transmission of the electromagnetic radiation passing through the spectral filter. Advantageously, an improvement of up to 60% can be achieved compared to a spectral filter without such an anti-reflection coating. That is, if the spectral filter is arranged in front of the photodiode, up to 60% more radiation of the relevant wavelength reaches the photodiode and can thus be detected by the photodiode.

[0050] The spectral filter is preferably at least partially transmissive in at least one subrange of the infrared spectrum. Preferably, the anti-reflection coating of such a spectral filter has a transmission of at least 20%, preferably at least 30%, particularly preferably at least 50%, for the wavelength range from 3 to 12 μm, preferably from 3 to 5 μm or from 5 to 8 μm or from 8 to 12 μm.

[0051] Preferably, the anti-reflective coating is formed as a single-layer or multi-layer coating. A single-layer has the advantage that it can be easily and cheaply produced.

[0052] Multi-layer coatings can also be advantageously optimized and adapted for multiple angles of incidence and multiple wavelength ranges. A preferred substrate material for multi-layer coatings is germanium. Advantageously, a transmission of more than 95% can be achieved within each wavelength range.

[0053] Preferred substrate materials for anti-reflective layers composed of a single layer are germanium, silicon, sapphire, zinc selenide or gallium arsenide.

[0054] Preferably, the spectral filter is formed as a narrow band pass filter. Thus, only a narrow range of wavelengths is transmitted, with a maximum of 6%, preferably a maximum of 5%, of the peak value, at which the transmission is greatest. Outside the transmission range, the attenuation values ​​are high, so that the transmission of radiation outside the range is a maximum of 10%, preferably a maximum of 1%, particularly preferably a maximum of 0.1%.

[0055] According to one possible configuration, two spectral ranges are taken into account, which allows mutual correction. In addition, one variation contemplates that the gas temperature determined by the selective method is utilized for control and / or correction.

[0056] Preferably, the geometry of the metallurgical melting furnace is not important, since all transition levels within the spectral range set by the filter, which give rise to the temperature characteristic curve, are taken into account. A particularly preferred variation of the method first performs a determination of the temperature and then performs a determination of the concentration taking the temperature into account.

[0057] The stored characteristic curves can advantageously be determined theoretically, so that no calibration or recalibration or measurement is required.

[0058] Further details, features and advantages of embodiments of the invention emerge from the following description of examples with reference to the associated drawings. [Brief description of the drawings]

[0059] [Figure 1] Electric arc furnace [Diagram 2] Principle diagram of the measurement technology setup [Diagram 3] Principle diagram of a measuring device with a photodiode DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] In Fig. 1, a metallurgical melting furnace 1 for melting metal is shown in the form of an electric arc furnace 1a. A molten metal pool 2 is arranged in a furnace vessel 3. Into the furnace vessel 3, a heating device 4 projects, which comprises three electrodes 5 designed for supplying a three-phase alternating current. The heat generated by the electrical energy of the arc 6 is utilized for melting the metal in the molten metal pool 2. Furthermore, a gas burner 7 and an oxygen supply element 8 designed as an oxygen lance 8a are arranged in the furnace vessel 3.

[0061] The exhaust gases generated in the furnace vessel 3 are led through an exhaust opening to the exhaust gas discharge device 9. Between the furnace vessel 3 and the exhaust gas discharge device 9 an exhaust manifold 10 and an air supply opening 11 formed as an air supply ring 11a are arranged. Via the air supply opening 11, cold air flows into the exhaust gas discharge device 9. The air supply opening 11 is arranged between the furnace vessel 3 and the exhaust gas discharge device 9. In the exhaust gas discharge device 9, recombustion takes place, in particular reactions with the incoming oxygen.

[0062] In the exhaust gas exhaust device 9, furthermore, two photodiodes 12 are arranged downstream of the intake air opening 11 in the exhaust gas flow direction R and at a distance from the exhaust gas exhaust device 9. In order to be able to detect electromagnetic radiation from inside the exhaust gas exhaust device 9, there are two measurement openings 13 in the exhaust gas exhaust device 9, via which the electromagnetic radiation can reach a measurement channel 14 and then the photodiodes 12. The measurement openings 13 can be closed by a material that is transparent to the relevant electromagnetic radiation. This prevents the exhaust gas flowing in the exhaust gas exhaust device 9 from escaping.

[0063] In the further process, downstream of the air intake opening 11, a cooler 15 for cooling the exhaust gas flow and a filter 16 for separating solid particles from the exhaust gas are arranged in the exhaust gas discharge system 9. The exhaust gas is then led via an induced draft 17 into a chimney 18.

[0064] 2 shows a principle diagram of a measurement technology setup for use in an exhaust gas exhaust system 9 of a metallurgical melting furnace 1, in particular an electric arc furnace 1a. Electromagnetic radiation of all wavelengths 19 strikes a spectral filter 20, so that downstream of the spectral filter 20 only electromagnetic radiation in a specific wavelength range 21 is forwarded to a photodiode 12. The electrical signal generated by the photodiode 12 is then amplified by a measurement amplifier 22 and processed by an evaluation unit 23. The values ​​output by a measurement value output 24 can then be used to optimize the control of the electric arc furnace, not shown here.

[0065] A principle diagram of the measuring device with at least one photodiode 12 and one measurement channel 14 is shown in Figure 3. The measuring device is fixed to the outside of the exhaust gas discharge system (not shown here) by means of a mounting flange 25. The photodiode 12 together with the spectral filter 20 is arranged directly adjacent to the measurement channel 14.

[0066] Between the measurement channel 14 and the interior of the exhaust gas exhaust system 9, a measurement opening (not shown separately) is formed in the wall of the exhaust gas exhaust system 9 in order to allow electromagnetic radiation from the interior of the exhaust gas exhaust system 9 to pass through the measurement channel 14 in the direction of the photodiode 12. A transparent protective glass 26 is arranged at the end 8 of the measurement channel 14, which end faces towards the exhaust gas exhaust system in the installed state. This protective glass 26, also called protective window 26, allows the electromagnetic radiation generated inside the exhaust gas exhaust system to reach the measurement channel 14 while at the same time preventing exhaust gases from entering the measurement channel 14. [Explanation of symbols]

[0067] 1 Metallurgical melting furnace 1a Arc furnace 2 Molten metal pool, molten metal pool 3 Furnace vessel 4 Heating device 5 Electrodes, heating device 6. Arc 7 Gas Burner 8. Oxygen Supply Elements 8a Oxygen Lance 9 Exhaust gas exhaust system 10 Exhaust manifold 11 Air supply opening 11a Air supply ring 12 Photodiode 13 Measurement aperture 14 measuring channels, sleeve tube 15 Cooler 16 Filters 17 Incentive Draft 18 Chimney 19 Electromagnetic radiation of all wavelengths 20 Spectral Filters 21 Electromagnetic radiation of a specific wavelength range 22 Measuring amplifier 23 Evaluation Units 24 Measurement value output 25 Mounting flange 26 Protective glass, protective windows R Exhaust gas flow direction

Claims

1. A metallurgical melting furnace (1) comprising a furnace vessel (3) for melting metal, in which an exhaust gas discharge device (9) for discharging an exhaust gas stream is arranged, wherein the exhaust gas discharge device (9) has an air supply opening (11) for supplying fresh air to the exhaust gas stream formed therein. In the metallurgical melting furnace (1), the exhaust gas discharge device (9) comprises at least one measurement opening (13) downstream of the air supply opening (11) in the flow direction (R) of the exhaust gas stream, and an electromagnetic radiation (19) generated inside the exhaust gas discharge device (9) leaking through the measurement opening (13) is at least partially detectable by a photodiode (12), and a photodiode (12) having a spectral filter (20) for separating electromagnetic radiation in a specific wavelength range (21) is arranged and formed outside the exhaust gas discharge device (9) at a distance from the measurement opening (13). The metallurgical melting furnace (1) is characterized by this.

2. The metallurgical melting furnace (1) according to claim 1, characterized in that the melting furnace comprises a heating device (5) for melting the metal in the molten metal pool (2).

3. The metallurgical melting furnace (1) according to claim 2, characterized in that the melting furnace comprises a heating device (5) having a plurality of electrically operated electrodes (5) for generating an arc.

4. The metallurgical melting furnace (1) according to claim 1, characterized in that the measurement opening (13) is closed by a transparent material.

5. The metallurgical melting furnace (1) according to claim 4, characterized in that the photodiode (12) is arranged within the visual axis of the electromagnetic radiation passing through the measurement opening (13).

6. The metallurgical melting furnace (1) according to claim 5, characterized in that a measurement amplifier (22) is arranged on the photodiode (12) to amplify the electrical signal generated by the photodiode (12).

7. The metallurgical melting furnace (1) according to claim 3, characterized in that a measurement amplifier (22) is arranged on the photodiode (12) to amplify the electrical signal generated by the photodiode (12).

8. The metallurgical melting furnace (1) according to claim 1, characterized in that at least two measurement openings (13) are arranged in the exhaust gas discharge device (9) together with at least two photodiodes (12) arranged at a distance from the measurement openings.

9. The metallurgical melting furnace (1) according to any one of claims 1 to 8, characterized in that a photodiode (12) or a measuring amplifier (22) is connected to an evaluation unit (23) for processing the generated electrical signal.

10. A method for determining a hetero-molecular gas generated in a metallurgical melting furnace (1) by the metallurgical melting furnace (1) according to claim 9, comprising: a) guiding a gas comprising a certain proportion of hetero-molecular gas through an exhaust gas discharge device (9); b) supplying cold air to the exhaust gas stream; c) detecting electromagnetic radiation in a specific wavelength range (21) emitted by the gas by means of a photodiode (12); d) determining the proportion of hetero-molecular gas by means of an evaluation unit (23). The method is characterized by having the above steps.

11. A method for determining the temperature of a gas containing hetero-molecular gas by the metallurgical melting furnace (1) according to claim 9, comprising at least two photodiodes (12) and at least two different spectral filters (20), comprising: a) guiding a gas comprising a certain proportion of hetero-molecular gas through an exhaust gas discharge device (9); b) supplying cold air to the exhaust gas stream; c) detecting electromagnetic radiation in at least two specific wavelength ranges (21) emitted by the gas by means of a photodiodes (12); d) determining the temperature of the gas by comparison with the emission characteristics of the gas depending on temperature. The method is characterized by having the above steps.

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