Control method for controlling at least one process in an industrial furnace, and industrial furnace

Abstract

The invention relates to a control method for controlling at least one process in an industrial furnace. The temperature within a particle-laden gas is determined by determining the radiation power of the particles at a measuring wavelength and then directly and unambiguously ascertaining the temperature by taking into account two empirical parameters using a formula (I) or formula (II). The empirical parameters are wavelength-dependent and should therefore be determined separately for each wavelength range. The measurement of the temperature in the industrial furnace can advantageously be carried out without contact and it is advantageous to evaluate only a narrow wavelength range. The control method and in particular the ascertainment of the temperature advantageously prove to be robust vis-à-vis cross-influences occurring in the process. Furthermore, the invention relates to an industrial furnace.

Description

[0001] Control method for controlling at least one process in an industrial furnace as well as an industrial furnace

[0002] The invention relates to a control method for controlling at least one process depending on the measurement of the temperature of a particle-laden gas in an industrial furnace, and to an industrial furnace that can carry out this control method automatically.

[0003] For the efficient operation and precise control of industrial furnaces, knowledge of the exact temperature is essential, as the chemical reactions taking place in industrial furnaces are very temperature-sensitive.

[0004] Knowing the exhaust gas temperature in industrial furnaces is crucial for several important reasons. For example, the exhaust gas temperature can provide insights into the furnace's efficiency. A significant temperature increase, for instance, can indicate that the furnace is not operating optimally and is wasting energy. Furthermore, high exhaust gas temperatures can point to overheating or a malfunction in the furnace, which can lead to safety hazards such as fires or explosions. Monitoring helps to identify and address such risks early on. Continuous monitoring of the exhaust gas temperature can even reveal signs of wear or defects in the furnace. Early detection of problems is essential to avoid costly repairs and downtime.

[0005] In summary, knowledge of the exhaust gas temperature is important to optimize the operation of the furnace, minimize safety risks, comply with environmental regulations, and control operating costs.

[0006] However, a disadvantage of industrial furnaces is the production of hot, particle-laden gases due to the necessary processes involved. Measuring the temperature of these gases is technically very complex, as the high temperatures pose a significant challenge for measuring instruments. A further problem is that flowing gases are generally abrasive, while typical materials have an abrasive resistance that decreases with increasing temperature. Therefore, measuring the temperature of hot, particle-laden gases using tactile methods is either very complex or the measuring devices are subject to high wear.

[0007] In industrial furnaces, for example, thermocouples are used in state-of-the-art technology to determine the temperature within the hot exhaust gases. A disadvantage of these thermocouples is that they can only withstand the high temperatures in industrial furnaces for a short time, causing them to wear out quickly. This high wear leads to high costs, and the high material consumption also has a particularly negative impact on the environment.

[0008] A method for determining the temperature of a gas containing a heteromolecular gas is proposed in DE 10 2021 004 593 A1. The presented method allows the temperature to be determined from the emission spectra of a gas, using two photodiodes to simultaneously measure radiation intensities in two wavelength ranges. To determine the temperature, these radiation intensities are then compared with known temperature-dependent characteristic curves. A problem here is that it is generally unclear which molecules contribute to the measured radiation. Furthermore, the emissions from dust particles have a significant influence on the measured values.

[0009] Another method for determining temperature using a pyrometer is presented in EP 1 647 791 A1. This describes a device for non-contact temperature measurement in a melting furnace. A disadvantage of this method is that measurements must be taken in at least two wavelength ranges.

[0010] Typically, in an industrial furnace, especially an electric arc furnace (EAF), where particle-laden gases from a furnace vessel exit into an exhaust duct, the temperature is measured in areas further away from the furnace outlet. These areas further downstream in the exhaust duct have lower temperatures than those directly at and inside the furnace vessel. To determine the temperatures in the areas immediately adjacent to the furnace outlet, estimated values ​​based on process experience were used. Precise measurements are generally not possible in these areas, resulting in detrimental inaccuracies in process control.

[0011] The invention is therefore based on the objective of providing a method and a device that overcomes the disadvantages of the prior art, in particular providing a measuring method that is suitable for reliably determining the temperature in an industrial furnace.

[0012] The problem is solved by a method and a device with the features of the independent claims. Further developments are specified in the dependent claims.

[0013] A first aspect of the invention relates to a control method for controlling at least one process in an industrial furnace as a function of a temperature of a particle-laden gas measured in the industrial furnace. The temperature measurement comprises the following steps: i. Detection of a radiant power P of the electromagnetic radiation emitted by the gas in a measurement wavelength range with a width of at most 2.0 pm around a measurement wavelength A by means of a photoelectric sensor unit; ii. Determination of the temperature T of the particle-laden gas from the radiant power P using formula (II). where a and b are empirical parameters, preferably determined by adjusting to an independent temperature measurement or which were already known. For these empirical parameters, empirical values ​​from similar systems or similar installation situations in other systems can also be used.

[0014] The problem is solved in particular by a control method for controlling at least one process in an industrial furnace as a function of a temperature of a particle-laden gas measured in the industrial furnace. The temperature measurement comprises the following steps: i. Detection of a radiant power P of the electromagnetic radiation emitted by the gas in a measurement wavelength range with a width of at most 0.5 pm around a measurement wavelength A using a photoelectric sensor unit, wherein the detection is contactless; ii. Determination of the temperature T of the particle-laden gas from the radiant power P using formula (I). where n is a number from 3 to 5, preferably a natural number from 3 to 5, preferably 3, 4 or 5, where a and b are empirical parameters, preferably determined by adaptation to an independent temperature measurement or which were already known. For the empirical parameters, empirical values ​​from similar systems or from similar installation situations in other systems can also be used.

[0015] The measurement wavelength range is between 0.78 pm and 20 pm. In particular, the measurement wavelength should be in the range between 2.0 pm and 5 pm.

[0016] According to a preferred embodiment, the temperature T is determined according to step ii. using formula (II)

[0017] According to one embodiment of the control method, the empirical parameters a and b are determined before step ii. by means of an evaluation of theoretical radiation spectra or by means of energy balance calculations. A theoretical analysis of the thermal radiation of dust-laden gases is used. The core of such energy balance calculations can be seen as the enthalpy supplied to and exiting the industrial furnace.

[0018] Enthalpy is supplied to the furnace via: a. Fuel in a known quantity (natural gas, coal) b. Electrical energy, in a known quantity

[0019] Enthalpy leaves the furnace via c. exhaust gas in a known quantity but unknown temperature d. radiant heat, which can be estimated e. tapping of a known quantity and known temperature (steel, slag)

[0020] In such a simplified accounting approach, the exhaust gas temperature is the only unknown, which can be calculated accordingly from the other known quantities. Thus, in the control method disclosed herein, the parameters a and b can be determined using an accounting approach, and the method can subsequently be used for temperature determination. A reference measurement is not strictly necessary.

[0021] One possible variant of the control procedure involves determining the empirical parameters a and b from known temperatures at specific furnace conditions before step ii. This often works very well because experienced operators of industrial furnaces are sufficiently familiar with the temperatures at certain settings, as an industrial furnace typically behaves the same way depending on the selected loads and settings.

[0022] The following mathematical relationship is preferably used to determine temperature 1: T = ii However, it can also be done with T = 3 ( - a) / b = (^) 3 or T = j(P - a) / b = (^) 5 This can be calculated. If a curve fitting is then carried out as described using this approach, different values ​​for the parameters a and b will be obtained, but the functional relationship T=f(P) will be very similar, and the results obtained for the temperature determination will advantageously also be reliable.

[0023] Empirical parameters a and b are known within the meaning of the invention if they are predetermined for the method. They were determined, for example, from previous measurements, in particular from reference measurements on the industrial furnace on which the method is carried out, or they were determined in previous measurements on other, preferably similar or comparable, systems. Advantageously, the method is so robust that even slight deviations in the conditions and thus changes in parameters a and b have only a minor influence on the temperature determination. Advantageously, it is not necessary to perform regular repetitions of a reference measurement to determine the empirical parameters a and b.

[0024] Typically, only the portion of the emitted electromagnetic radiation that penetrates through a measuring aperture is evaluated.

[0025] Advantageously, this control method and the method it contains for measuring the temperature by means of a measurement in a single, narrow wavelength range allow for a simple realization of a temperature measurement, in particular a non-contact temperature measurement.

[0026] It should be emphasized that a key difficulty in such measurements in industrial furnaces, particularly in broadband radiometric temperature determination, is the highly variable, sometimes very high, and practically always unknown dust load of the carrier gas. Consequently, the emissivity e of the dust is also typically variable and not sufficiently known. State-of-the-art radiometric methods for determining the temperature of an industrial gas stream are therefore always subject to enormous difficulties regarding the accuracy and reliability of the measurement results. Taking the fluctuating dust load into account in such measurements has been difficult and unsatisfactorily implemented in state-of-the-art methods. The inventors have surprisingly discovered that temperature determination can be advantageously carried out using formula (I) or formula (II).With a suitable choice of the empirical parameters a, b, the method for measuring the temperature, as well as the control method that can be implemented as a result, has proven to be extremely robust against influences or disturbances occurring during the operation of industrial furnaces, such as fluctuating particle loading, fluctuating particle size and varying optical properties of the particles, as well as fluctuations in the concentrations of the accompanying IR-active gases.

[0027] It is unexpected and surprising for the person skilled in the art that the method disclosed herein, i.e., by means of a narrowband measurement at only one measurement wavelength and an evaluation via a dependence on T, 4 , good and reliable measurement results can be achieved.

[0028] A further advantage is that this measuring method does not require any measuring instrument to come into contact with the hot, particle-laden gases. This eliminates the need to bring, for example, a measuring instrument such as a thermocouple into contact with the hot, particle-laden gases. Advantageously, the method disclosed here, i.e., the method for measuring the temperature necessary for the control method according to the invention, can be carried out without contact. This significantly reduces wear and tear, thereby lowering both costs and the potential for errors.

[0029] Surprisingly, a complex theoretical analysis of dust and gas radiation, taking into account the superposition of Mie and Rayleigh scattering, is not necessarily required. Given the complexity of dust radiation theory and the significant influence of unknown and variable dust concentrations and dust emissivity, such a simple relationship is surprising. Another factor influencing the measurement method is the presence of cooler upstream zones, which, surprisingly, nevertheless allow for this advantageous and straightforward procedure.

[0030] It is therefore surprising and an expression of inventive achievement that the method according to the invention leads to such good results.

[0031] The detection according to step i. is preferably carried out without contact. This advantageously means that the photoelectric sensor unit does not need to be in contact with the hot, particle-laden gases. Surprisingly, it is sufficient to detect the radiation entering through a measuring aperture in a narrow wavelength range and to evaluate it according to formula (I) or formula (II).

[0032] Surprisingly, a simple correlation was discovered between the radiative power of the particles and the temperature of these particles, and thus also of the gas. This is based on the fact that the particles contained in the gas emit thermal radiation.

[0033] Furthermore, the particle-laden gas is preferably conveyed in a pipeline. Depending on the specific particles involved, the precise composition of the gas, and other parameters such as temperature, the particles carried by the gas have different emissivity coefficients, for example, in the range of E = 0.6 to 0.9. The exact value varies and cannot be precisely determined. Therefore, known thermodynamic relationships can only be applied imprecisely.

[0034] Advantageously, the control method according to the invention allows the temperature to be reliably determined by only a single measurement of the radiation power in the measurement wavelength range, thus making the control method more precise and efficient.

[0035] According to one possible implementation of the control method, the measurement wavelength range has a width of at most 1.0 pm, preferably at most 0.5 pm. The measurement wavelength range is the wavelength range in which the photoelectric sensor unit is sensitive and in which the measurement wavelength lies. Advantageously, the temperature can be reliably determined by only one measurement in a single, narrow wavelength range. The control method becomes more efficient due to the reliable and precise temperature measurement. The temperature is advantageously determined by measurement in a single, narrow, and contiguous wavelength range.

[0036] The measurement wavelength range can be chosen to be very narrow. Preferably, the measurement wavelength range has a width of at most 0.2 pm, more preferably at most 0.1 pm. According to a particularly advantageous embodiment of the control method, the width of the wavelength range lies in a range between 0.05 pm and 0.5 pm, particularly preferably in a range between 0.08 pm and 0.15 pm. According to a possible embodiment, the width of the wavelength range is 0.1 pm.

[0037] This allows for the advantageous evaluation of a narrow range where the influencing factors of the different gases are low and the temperature measurements are therefore very accurate.

[0038] Before step ii. of determining the temperature T of the gas from the radiant power P using formula (I) or formula (II), the empirical parameters a and b are preferably determined by means of a reference measurement using an alternative temperature measurement.

[0039] In an advantageous implementation of the control method, the empirical parameters a and b are determined by performing at least one reference measurement using an alternative temperature determination method. A mathematical procedure for least-squares adjustment, such as the method of least squares, is used.

[0040] The reference measurement, which is an alternative method for determining temperature, can be carried out, for example, using a thermocouple. Preferably, the temperature measurement using the thermocouple is performed for at least two, preferably at least three, and preferably at least ten different temperatures. The reference measurement is preferably carried out on a typical production cycle of the industrial furnace, so that all practically occurring temperatures are recorded. The number of measurement points is, for example, between five and twenty. These temperatures are preferably spaced at least 30 K apart.Simultaneously with determining the temperature using an alternative measurement method, such as temperature measurement using a thermocouple, the radiant power of the electromagnetic radiation emitted by the gas is detected within a measurement wavelength range around a measurement wavelength A using a photoelectric sensor unit. Thus, the radiant power of the gas is determined using the photodiode.

[0041] According to one possible approach, the radiant power of the gas is measured at the measurement wavelength A by using a narrowband filter to determine the emitted radiation in a narrowband region around the measurement wavelength A. From at least two, preferably at least three, measurements of the radiant power at different temperatures, as well as the temperature using the alternative temperature measurement method, the empirical parameters a and b for the measurement wavelength A can then be determined.

[0042] One possible embodiment of the control method provides that the measurement wavelength range lies in the band between 0.78 pm and 20 pm, preferably in the band between 2 pm and 5 pm. This wavelength range is advantageously in the region of infrared electromagnetic radiation.

[0043] According to one possible implementation of the control method, the gas, i.e. the particle-laden gas in the industrial furnace, has first infrared-active molecules and the measurement wavelength A is preferably selected in a radiation minimum of the first infrared-active molecules before detection according to step i.

[0044] For the purposes of the invention, infrared-active molecules are those molecules that absorb and emit electromagnetic radiation in the infrared range, particularly between 780 nm and 20 pm. The gas molecules do not interact with electromagnetic radiation of every wavelength in this range; rather, each type of infrared-active gas possesses a characteristic spectrum. Examples of such molecules are carbon dioxide (CO2) and water vapor (H2O). The spectra and emission spectra of these molecules are known to those skilled in the art.

[0045] The first infrared-active molecules selected are preferably those molecules from among the various options whose radiation intensity is highest, which often applies to CO2.

[0046] The gas can contain various types of infrared-active molecules, such as heteronuclear molecules. A heteronuclear molecule is a molecule containing at least two different chemical elements. The first infrared-active molecules, whose spectra are used to determine the measurement wavelength A, are preferentially selected from those present in particularly high concentrations in the gas.

[0047] According to one possible approach, the first infrared-active molecules could also be those exhibiting particularly high radiative power, especially in the range between 2 pm and 5 pm. Optionally, the radiation from a heteronuclear molecule, such as CO2, could be used. However, the radiation from homonuclear molecules could also be used, provided these molecules are infrared-active.

[0048] The control procedure then includes a step i'. Determination of the measurement wavelength A using a spectrum of an infrared-active molecule of the gas. Step i' is performed before step i.

[0049] Preferably, a wavelength is used as the measurement wavelength at which the influence of the gases' radiation is low. This reduces interference with emission spectra of the gases, so that the evaluated radiation powers originate almost exclusively from the dust particles.

[0050] Surprisingly, it was also shown that the control method and the temperature measurement method are so robust that they can be carried out with reliable results at various wavelengths, including those with a significant contribution from infrared-active molecules. Therefore, step i* can advantageously be omitted. The empirical parameters are preferably determined separately for each measurement wavelength.

[0051] Prior to detection according to step i., the particle-laden gas is first passed through an exhaust gas discharge device, according to one possible implementation of the control method. Preferably, cool air is then introduced into the exhaust gas stream.

[0052] The control procedure then includes a step i" before step i., which introduces cool air into the exhaust gas stream. At this point, i.e., in the exhaust gas direction after the opening for the cold air supply, the exhaust pipe advantageously has a lower temperature, so that the measuring components installed in this area are exposed to less high temperatures and can therefore be used for a longer period. Surprisingly, it was shown that the temperature measurement can be implemented accurately even after the introduction of the cool air. The emission of infrared radiation from the dust particles penetrates the cool air and can therefore also be detected after the air supply gap.

[0053] Preferably, the particle-laden gas is first passed through an exhaust gas discharge device before cold air is introduced.

[0054] The control method is used to control one or more of the following processes:

[0055] • Control of the supply of fuel, such as natural gas, hydrogen and blast furnace coal, and / or

[0056] • Controlling the supply of an oxidizing agent, such as air and / or oxygen, and / or

[0057] • Controlling the afterburning process,

[0058] • Optimization of the energy balance of the process.

[0059] The energy balance of such a process can be improved by a favorable fuel-to-oxidizer ratio. An excess of fuel leads to fuel being wasted and lost, for example, as soot. Furthermore, this can result in an increased production of environmentally harmful carbon monoxide. Conversely, an excess of air, including oxygen, can lead to increased heat loss, as the excess air enters the furnace cold and exits hot.

[0060] Exhaust gas temperature influences the quantity and type of emissions released into the environment. Precise monitoring and control of these processes helps to comply with legal emission limits and minimize pollution.

[0061] Measuring the temperature in the exhaust gas stream can be used to advantageously detect the completion of process phases. This allows these process phases to be controlled precisely, for example, terminated, thus saving time and fuel. For instance, a product can be heated in the furnace until a predetermined temperature is reached in the exhaust gas.

[0062] Exhaust gas temperature can influence the quality of the final product in many production processes, for example in glass or ceramics manufacturing. Therefore, a described control method can improve product quality through precise temperature control.

[0063] Advantageously, by precisely determining the temperature and thereby adapting the combustion process, afterburning can be optimized, resulting in both economic advantages and improved environmental compatibility.

[0064] Another aspect of the invention relates to an industrial furnace for measuring the temperature of a particle-laden gas, comprising

[0065] • an oven dish,

[0066] • a subsequent exhaust gas discharge device,

[0067] • a measuring aperture,

[0068] • a photoelectric sensor unit for detecting the radiant power emitted through the measuring aperture and • an evaluation arrangement which is electrically and / or data-wise connected to the photoelectric sensor unit, and which is designed for automated determination of the temperature according to a method described herein for measuring the temperature according to one of the embodiments presented herein.

[0069] The measurement of the temperature of the particle-laden gas in the industrial furnace comprises at least the following steps: i. Detection of a radiant power P of the electromagnetic radiation emitted by the particle-laden gas in a measurement wavelength range with a width of at most 2.0 pm around a measurement wavelength A using a photoelectric sensor unit; ii. Determination of the temperature T of the particle-laden gas from the radiant power P using formula (I). where n is a number from 3 to 5, where n is preferably a natural number from 3 to 5, preferably 3, 4 or 5, where a and b are empirical parameters.

[0070] Preferably, the temperature T is determined according to step ii. using formula (II)

[0071] The aforementioned advantages also apply in particular to the industrial furnace.

[0072] A measuring opening can be designed as a recess in an area of ​​an outer boundary of the industrial furnace, for example, at the annular gap. A measuring opening can also be designed as an aperture and / or incorporate a lens. The measuring opening can be closed with a transparent material. A transparent material with high transparency in the infrared range is preferred. Those skilled in the art are familiar with suitable materials.

[0073] The measuring port is preferably located on the furnace vessel or in the exhaust gas discharge direction. Multiple measuring ports can also be arranged on the industrial furnace, allowing the temperature to be determined at different points within the furnace using several photoelectric sensor ports.

[0074] The photoelectric sensor unit comprises a photoelectric sensor, which can be designed, for example, as a photodiode, a phototransistor, a phototube, or a photoresistive sensor. The photoelectric sensor is preferably arranged in the line of sight of the electromagnetic radiation passing through the measuring aperture.

[0075] Optionally, the photoelectric sensor unit includes a photoelectric sensor designed to measure in a range between 0.78 pm and 50 pm.

[0076] The photoelectric sensor unit preferably includes a measuring amplifier, which is electrically connected to the photodiode, to amplify the electrical signals generated by the photodiode.

[0077] An industrial furnace, as defined in the invention, is a technical system in which a material is exposed to high temperatures exceeding 100°C within a chamber. The material is preferably heated by the supply of thermal energy, causing chemical reactions to occur within the material or on its surface. These high temperatures can be generated, for example, by the combustion of added fuel such as natural gas, hydrogen, or cinder or blast furnace coal. Optionally, the material is heated using electric current or inductive methods.

[0078] Furthermore, a technical installation is also an industrial furnace within the meaning of this disclosure, in which heat is generated by burning a fuel, such as in a power plant and / or heating plant.

[0079] Industrial furnaces include, for example, metallurgical furnaces or power plants, which are used for energy generation or energy conversion.

[0080] According to the invention, the operation of the industrial furnace produces a particle-laden gas at a high temperature exceeding 100°C. For the purposes of this invention, a particle-laden gas is defined as a gas with a dust content in the range of 1 g / m³. 3 up to 200 g / m² 3 , preferably in a range of 5 g / m³ 3 up to 150 g / m² 3 , particularly preferably in a range of 10 g / m³ 3 up to 80 gl m 3 exhibits. In particular, technical installations that can both expose a material to high temperatures and generate heat, such as waste incineration plants, are also considered industrial furnaces.

[0081] According to one possible design, the industrial furnace is configured as a metallurgical melting furnace, comprising a heating device for melting metal in the molten bath, wherein the heating device may have several electrically operated electrodes for generating an electric arc.

[0082] In an advantageous embodiment, an air supply device is arranged on the exhaust gas discharge device, and the measuring opening can, in an advantageous embodiment, be arranged downstream of the air supply device on the exhaust gas discharge device in the exhaust gas flow direction (R). Advantageously, this area is exposed to less high temperatures due to the supplied cold air.

[0083] Optionally, a spectral filter is arranged between the photoelectric sensor and the measuring aperture. The spectral filter preferably has a maximum bandwidth of 0.2 pm.

[0084] The spectral filter can be integrated into the photoelectric sensor unit or arranged between the photoelectric sensor unit and the measuring arrangement.

[0085] Conceptually, at least one temperature-dependent process in an industrial furnace is controlled by a control method in which the temperature within a particle-laden gas is determined by measuring the radiative power of the particles at a specific wavelength and then, taking into account two empirical parameters, the temperature is determined directly and unambiguously using formula (I) or formula (II). The empirical parameters are wavelength-dependent and should therefore be determined separately for each wavelength range. Temperature measurement in the industrial furnace can advantageously be performed without contact, and it is sufficient to evaluate only a narrow wavelength range. The control method, and in particular the temperature determination, proved to be advantageously robust against cross-influences occurring during the process.

[0086] 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. These show:

[0087] Fig. 1: an industrial furnace,

[0088] Fig. 2: an industrial furnace with regulator,

[0089] Fig. 3a: a measuring aperture designed as a pinhole aperture,

[0090] Fig. 3b: a measuring aperture designed as an infrared lens,

[0091] Fig. 3c: a measuring aperture designed as a fiber collimator,

[0092] Fig. 4: two temperature profiles, a first being determined by the method for measuring temperature described herein and a second being determined by a thermocouple,

[0093] Fig. 5: Temperature profile and radiation power profile for determining the empirical parameters and

[0094] Fig. 6 shows a representation of the mathematical relationship for determining the temperature from the radiant power.

[0095] Figure 1 shows an industrial furnace 1, such as a metallurgical melting furnace for melting metal. The industrial furnace 1 has a furnace vessel 2 containing a material for thermal treatment 3, such as molten metal. The furnace vessel 2 also has a furnace vessel cover 4 and a furnace vessel wall 5.

[0096] A burner 6 and an exhaust gas discharge device 7 are arranged on the furnace vessel 2. The gas generated in the furnace vessel 2 can be discharged from the industrial furnace 1 as a gas stream 8 through this exhaust gas discharge device 7. An annular gap 9 is arranged on the exhaust gas discharge device 7. This annular gap 9 is preferably a ring-shaped opening on the exhaust gas discharge device 7 through which air is supplied to the gas stream 8 from the outside. This introduction of cool air through the annular gap 9 cools the gas stream 8, thus advantageously protecting the components of the exhaust gas discharge device 7 from excessive thermal stress. Furthermore, the supplied air, and in particular the oxygen it contains, can support the afterburning of carbon monoxide (CO) to carbon dioxide (CO2).

[0097] To optimize the processes taking place in the furnace vessel, it is crucial to be able to determine the temperature in order to adjust individual parameters, such as the air supply. Possible positions for such temperature measurement are shown in Fig. 1 as temperature measuring devices 10.1, 10.2, 10.3 and 10.4. The temperature measuring device on the furnace vessel 10.1 is arranged directly on the furnace vessel wall 5. Since this area is exposed to high thermal stress, additional measures are usually required to protect the measuring device.

[0098] Another possibility is a temperature measuring device on the exhaust gas discharge device 10.2, which is arranged in Fig. 1 in the area close to the furnace vessel 2. Here, too, the thermal load is high.

[0099] Another possibility is shown by the temperature measuring device at the annular gap 10.3, where the temperature measuring device is located directly at the opening of the exhaust gas discharge device 7. Cold air flows in at this point.

[0100] Furthermore, the temperature measuring device is arranged at the exhaust gas discharge outlet 10.4 at the end of the exhaust gas discharge device 7 facing away from the furnace vessel 2. Cold air is already supplied here. Nevertheless, the measuring method according to the invention can still deliver satisfactory measurement results here.

[0101] Preferably, a temperature measuring device is arranged in the exhaust gas discharge direction R after the annular gap 9.

[0102] Figure 2 shows an example of a control loop for controlling the temperature in an industrial furnace 1. Analogous to the illustration in Figure 1, material for thermal treatment 3 is arranged in a furnace vessel 2, and a burner 6 is arranged on the furnace vessel wall 5 through which heat is supplied. An annular gap 9 is also arranged on the exhaust gas discharge device 7 located above the furnace vessel 2. Air is supplied to the gas flow 8, which is an exhaust gas flow, through this annular gap 9. A temperature measuring device 10.3 is also arranged on this annular gap 9. The measured temperature value can be transmitted to a controller 11. This controller 11 can be designed to function according to a conventional method known to those skilled in the art. The controller is designed such that it sends a signal to a valve 13 by comparing the temperature with a setpoint temperature 12.The valve 13 is preferably suitable for controlling a fuel supply 14. In this embodiment, the fuel supply 14 is thus regulated as a function of the temperature.

[0103] Figures 3a-3c illustrate different designs of measuring apertures for detecting electromagnetic radiation emitted from a gas sub-region 15. Figure 3a shows a measuring aperture designed as a pinhole 16 and a window made of an infrared-transparent material 17. The electromagnetic radiation is detected by means of a photoelectric sensor 18. Figure 3b shows a measuring aperture designed as an infrared lens 19, i.e., a lens transparent to infrared electromagnetic radiation. A measuring aperture shown in Figure 3c is designed as a fiber collimator with an infrared lens 20. An optical fiber 21 is used to guide the electromagnetic radiation to the photoelectric sensor 18.

[0104] Figure 4 shows an example of temperature determination in the exhaust gas stream of an electric arc furnace. The temperatures fluctuate between 900°C and 1250°C, depending on the process phase. A first temperature profile 22 was determined using a thermocouple, and a second temperature profile 23 was obtained by applying the method disclosed herein for measuring the temperature using the relationship of formula (I) or formula (II). The radiant power was measured at a wavelength of 2.2 pm.

[0105] The measurement via the thermocouple is inherently slower than the optical method presented here. As a result, the first temperature profile 22 shows fewer fluctuations and appears delayed by 5 to 10 seconds compared to the second temperature profile 23.

[0106] It can be clearly seen that the agreement between the temperature profiles is very good. Thus, for this wavelength, a very good agreement can be shown between the first temperature profile 22 (dashed line) and the second temperature profile 23 (solid line).

[0107] Figure 5 shows a further diagram illustrating the temperature profile. It depicts the time course of a reference measurement in the form of a reference temperature profile 24 and a radiant power profile 25. The reference temperature profile 24 shows the results of the measurement according to an independent method, preferably using a thermocouple, and the radiant power profile 25 shows a measured radiant power P in a wavelength range around a measurement wavelength in arbitrary units.

[0108] The radiated power P has the physical unit [W / (area * wavelength interval * solid angle)] and can be calculated exactly for a blackbody radiator. However, what is measured here is a voltage at the output of the measuring amplifier in mV. This measurement incorporates device-specific factors such as viewing angle, gain, photodiode sensitivity, etc. The unit can also be omitted from the calculation, as the specific parameters a and b can be chosen accordingly. Therefore, "arbitrary units" are used in this example.

[0109] The measurement wavelength is 2.211 pm. The measurement wavelength range is 0.07 pm. The reference measurement can be performed using a type K thermocouple.

[0110] The vertical dash-dot lines mark eight measurement points 26, i.e., times for which a corresponding evaluation of the reference measurement and the determined radiated power was carried out. The measurement can be performed with a filter with the following parameters: The center wavelength can be CWL = 2.220 pm and the bandwidth or full width at half maximum (FWHM) 0.0629 pm.

[0111] Measurement values ​​[P, RT] were recorded at the 8 marked times (columns 1-3). Column 4 shows the temperature T determined according to the claimed method.

[0112] The content of Table 1 was determined at the eight measurement points 26.

[0113] Table 1

[0114] Table 1 shows the radiant power P in arbitrary units (au) in the second column and the results of the reference measurement RT in °C in the third column. The temperature T determined according to the inventive method is shown in the fourth column.

[0115] By fitting the curve in the free parameters a and b, the formula T=^ / (P - a) / b is adjusted so that the sum of the squared errors

[0116] E = £(T — RT) 2 The curve fitting is minimized. In the example shown, this curve fitting results in a = -16.38 and b = 0.809*10'. 9 .

[0117] Fig. 6 shows, for the eight measurement times from Fig. 5, the radiant power on the abscissa and the determined temperature T(P) according to the claimed method on the ordinate. The mathematical relationship of the formula with the parameters a = -16.38 and b = 0.809*10' 9 is represented by the solid line. List of reference symbols

[0118] 1 industrial furnace

[0119] 2 Oven vessel

[0120] 3. Good for thermal treatment

[0121] 4 Oven pot cover

[0122] 5 Oven vessel wall

[0123] 6 burners

[0124] 7 Exhaust gas discharge device

[0125] 8 Gas flow

[0126] 9 annular gap

[0127] 10.1 Temperature measuring device in the furnace vessel

[0128] 10.2 Temperature measuring device on the exhaust gas discharge system

[0129] 10.3 Temperature measuring device at the annular gap

[0130] 10.4 Temperature measuring device at the exhaust gas discharge outlet

[0131] 11 regulators

[0132] 12 Target temperature setting

[0133] 13 valve

[0134] 14 Fuel supply

[0135] 15 Gas section

[0136] 16-hole aperture

[0137] 17 Infrared-transparent material 18 Photoelectric sensor

[0138] 19 Infrared lens

[0139] 20 Fiber collimator with infrared lens

[0140] 21 Optical fiber

[0141] 22 First temperature profile

[0142] 23 Second temperature profile

[0143] 24 Reference temperature profile

[0144] 25 Radiation power curve

[0145] 26 Measurement time

[0146] R Exhaust direction

Claims

Patent claims 1. Control method for controlling at least one process in an industrial furnace as a function of a temperature of a particle-laden gas measured in the industrial furnace, characterized in that the measurement of the temperature of the particle-laden gas comprises the following steps: i. Detection of a radiant power P of the electromagnetic radiation emitted by the particle-laden gas in a measurement wavelength range with a width of at most 0.5 pm around a measurement wavelength A by means of a photoelectric sensor unit, wherein the detection is carried out without contact, ii. Determination of the temperature T of the particle-laden gas from the radiant power P by means of formula (I) where n is selected from a number of 3 to 5, where a and b are empirical parameters, and where the measurement wavelength range is between 0.78 pm and 20 pm.

2. Control method according to claim 1, wherein the determination of the temperature T according to step ii. is carried out using formula (II) This has been done.

3. Control method according to claim 1 or 2, wherein prior to step ii. the empirical parameters a and b are determined by means of a reference measurement using an alternative temperature measurement or wherein the empirical parameters a and b are known.

4. Control method according to claim 1 or 2, wherein, prior to step ii., the empirical parameters a and b are determined by means of an evaluation of theoretical radiation spectra or determined by means of balancing considerations.

5. Control method according to one of claims 1 to 3, wherein, prior to step ii., the empirical parameters a and b are determined via known temperatures at certain states of the furnace.

6. Control method according to any one of claims 1 to 5, wherein the measuring wavelength range has a maximum width of 0.2 pm.

7. Control method according to one of claims 1 to 6, wherein the detection according to step i. is performed only about one measuring wavelength.

8. Control method according to one of claims 1 to 7, wherein the gas has first infrared-active molecules and wherein, prior to detection according to step i., the measurement wavelength A is determined in a radiation minimum of the first infrared-active molecules.

9. Control method according to one of claims 1 to 8, wherein prior to detection according to step ii. the particle-laden gas is guided through an exhaust gas discharge device and cool air is subsequently supplied to the exhaust gas stream.

10. Control method according to any one of claims 1 to 9, wherein the process which depends on the temperature of the particle-laden gas is the supply of fuel and / or the supply of an oxidizing agent.

11. Industrial furnace comprising a furnace vessel, an adjoining exhaust gas discharge device, a measuring opening, a photoelectric sensor unit for detecting the radiant power emitted through the measuring opening, and an evaluation arrangement which is electrically and / or data-technically connected to the photoelectric sensor unit, and which is designed for automated determination of the temperature according to one of claims 1 to 10.

12. Industrial furnace according to claim 11, wherein an air supply device is arranged on the exhaust gas discharge device and the measuring opening is arranged on the exhaust gas discharge device downstream of the air supply device in the direction of exhaust gas flow (R).

13. Industrial furnace according to claim 11 or 12, wherein the photoelectric sensor unit comprises a photoelectric sensor, wherein the photoelectric sensor is configured to measure in a range between 0.78 pm and 20 pm.

14. Industrial furnace according to one of claims 11 to 13, wherein a spectral filter is arranged between the photoelectric sensor and the measuring aperture, wherein the spectral filter has a maximum transmission width of 0.2 pm.

15. Industrial furnace according to one of claims 11 to 14, wherein the industrial furnace is designed as a metallurgical melting furnace, comprising a heating device for melting metal in the molten bath, wherein the heating device comprises several electrically operated electrodes for generating an electric arc.

Images