Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N1/00—Regulating fuel supply
  • F23N1/02—Regulating fuel supply conjointly with air supply
  • F23N1/022—Regulating fuel supply conjointly with air supply using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/02—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
  • F23N5/08—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements
  • F23N5/082—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
  • F23N5/10—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples
  • F23N5/102—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
  • F23N5/242—Preventing development of abnormal or undesired conditions, i.e. safety arrangements using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C2900/00—Special features of, or arrangements for combustion apparatus using fluid fuels or solid fuels suspended in air; Combustion processes therefor
  • F23C2900/9901—Combustion process using hydrogen, hydrogen peroxide water or brown gas as fuel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2225/00—Measuring
  • F23N2225/08—Measuring temperature
  • F23N2225/21—Measuring temperature outlet temperature

Definitions

• the invention relates to a method for operating a heating device, a heating device, and a computer program product.
• the heating device can be operated with hydrogen and/or a hydrogen-containing fuel gas, in particular with a fuel gas containing at least 80 percent hydrogen.
• Hydrogen as a fuel gas or as an additive to fuel gases is becoming increasingly important, and significant efforts are being made to adapt new and existing heating appliances for its operation. This applies not only to large systems but also to wall-mounted units for heating water and, more generally, to heating appliances for building heating and/or hot water supply.
• Burners for use in such heating appliances are widely known.
• Such a burner is often mounted on a burner door, which is installed in a combustion chamber with a surrounding heat exchanger.
• the burner can comprise a burner body with at least one perforated area from which a premixed, combustible fuel gas-air mixture (combustion mixture) can exit.
• the combustion mixture flows through the burner door into the burner and exits through the perforated area into the combustion chamber, where it combusts.
• the burner can be cylindrical, (semi-)spherical, or flat.
• Holes are incorporated into the perforated area, preferably such that the outflow velocity of the fuel gas-air mixture into the
• the combustion chamber is adjusted to the respective flame speed (dependent on the fuel gas). Furthermore, it is important that the flame burns at a certain distance from the surface of the burner body to keep its temperature low. This should be aimed for across the entire modulation range (range of different adjustable power output) of the heating appliance.
• the temperature of the burner body must never reach the ignition temperature of the fuel gas-air mixture to prevent reignition within the burner (flame flashback into an interior space of the burner body).
• Hydrogen differs from previously used fuel gases in several ways during combustion.
• a hydrogen flame is almost invisible to the human eye (but emits radiation in the ultraviolet spectral range), radiates less heat than flames produced with carbon-based fuels, but burns hotter and has a significantly higher flame speed compared to fossil fuel gases.
• WO 2020/ 197 391 A1 describes a method for combustion control of a gas burner that prevents both flame flashbacks and excessively high temperatures.
• the burner body is intended to prevent flame flashback, which could contribute to the occurrence of a flame flashback. It is proposed to determine a target air ratio based on an input variable, which could be related, for example, to the heat demand or the supplied flow rate of fuel or combustion air, and to incorporate this ratio into the control system.
• US 2022/ 0 120 440 A1 describes a similar method for operating a burner with a hydrogen-containing fuel gas, whereby, according to the method, the air ratio can be adjusted, for example, to a detected temperature of the burner.
• the object of the present invention is to at least partially solve the problems described with reference to the prior art and, in particular, to propose a method for operating a heating device powered by hydrogen as fuel gas, a heating device, and a computer program that prevent the occurrence of cracks and fractures in the Effectively prevent burner surface damage.
• the invention is intended not to increase the complexity of a heating appliance, or at least not significantly, and in particular to be usable with heating appliances that have been converted to burn hydrogen.
• Steps a), b), and c) are performed at least once in the specified order during regular operation. Specifically, step a) can be performed only once, while steps b) and c) can be repeated continuously during operation of the heating appliance, particularly during each modulation cycle, i.e., with every change in the operating point or heat output of the heating appliance.
• This procedure serves to extend the service life of a heating appliance burner, especially the burner body, and to prevent cracks and fractures of the burner body.
• the procedure can be fully automated, for example, by a control unit of the heating appliance.
• the heating appliance, the burner, and the burner body can be configured for the combustion of hydrogen or a fuel gas containing hydrogen.
• Hydrogen as a fuel is advantageous due to the possibility of sustainable production.
• the hydrogen content in the fuel gas can be at least 80 percent [%], at least 90%, in particular at least 95% or even 98% to 100%.
• the heating appliance has a conveying device that can draw in a mass flow of combustion air.
• a mass flow of fuel gas corresponding to a predetermined combustion air ratio, is added to the combustion air via a gas valve.
• the resulting combustion mixture is fed to the burner located in the combustion chamber of the heating appliance, exits through a burner body, and combusts.
• the combustion mixture can be ignited by an ignition device when the heating appliance is started.
• the heating appliance may include a flame sensor that provides a flame signal, which is used by the combustion control system of the heating appliance.
• At least one heat exchanger can be used around or on the combustion chamber to transfer the heat generated during combustion to a heat transfer medium, such as heating water.
• the heating appliance may be a condensing boiler, which cools the combustion products below the dew point of water, thus utilizing the condensation heat of the combustion exhaust gases.
• the flame sensor can be a temperature sensor for detecting flame temperature, a UV sensor for detecting ultraviolet radiation emitted by the flame, or an ionization sensor (ionization electrode) for detecting the flame's ionization current.
• a hydrogen-powered heating device the disadvantage is that only a few charge carriers are released, making a reliable ionization current measurement as a flame signal unreliable. Therefore, when using hydrogen as the fuel gas, other methods are not suitable. UV sensors or temperature sensors are frequently used in powered heating devices for flame monitoring.
• the heating appliance can form a pneumatic or electronic gas-air mixture.
• a pneumatic gas-air mixture a mass flow of fuel gas is added, corresponding to a control pressure in a throttle point (Venturi) of the combustion air supply.
• An electronic gas-air mixture detects the supplied mass flow of fuel gas directly or indirectly, for example via the rotational speed of the conveying device, and controls the mass flow of fuel gas to be added.
• the heating appliances have a gas valve that can meter a mass flow of fuel gas.
• the heating appliance can operate at various points within a modulation or output range, thus operating at different power levels.
• modern heating appliances often feature a wide modulation range, for example, from a minimum heat output Q min of 2.5 kilowatts [kW] to a maximum heat output Q max of 21 kW, or a modulation ratio (ratio of maximum to minimum output) of 1:5.
• a wide modulation range places high demands on the burner due to the highly variable flame characteristics and properties.
• An operating point or modulation point can also be understood as the heat output Q of the heating appliance.
• the burner can be made from any suitable material.
• Stainless steel alloys are frequently used due to their good temperature and corrosion resistance, as well as their availability. These can be ferritic or austenitic stainless steel alloys. Austenitic alloys, in particular, have proven effective. Stainless steel alloys with a higher aluminum content have proven to be advantageous compared to ferritic stainless steel alloys.
• the geometric shape of the burner can be any form.
• cylindrical or flat burners are known.
• a burner cavity can be connected to the mixture channel of the heating device, and incoming fuel gas can be directed from the burner cavity into the combustion chamber via outlet openings arranged in a combustion zone, where it is combusted.
• a cylindrical burner can be attached to a The burner door is positioned to form the burner cavity inside.
• a flat burner can be connected to a burner hood, and the burner cavity can be defined by the burner and the hood.
• the combustion zone can have a largely flat (planar) or a three-dimensional shape.
• a three-dimensional shape can consist of a raised or recessed area relative to the burner body, or another form such as a bulge.
• the combustion zone and the burner body can have the same material thickness and be within a known range. However, especially if the combustion zone is detachably connected to the burner body, different material thicknesses for the combustion zone and the burner body are also conceivable.
• the combustion zone can comprise several exhaust gas outlets, in which the exhaust ports are arranged.
• the exhaust ports can have any shape, in particular circular, rectangular, square, or oblong shapes. It is also possible to combine different shapes within a single exhaust gas outlet.
• the arrangement of the exhaust openings within an exhaust region is also arbitrary.
• the geometric shape of the exhaust region, as the outer contour of all exhaust openings within the exhaust region, can be, for example, rectangular, square, nearly circular, oval, or even rhombus- or polygonal.
• the orientation of non-rotationally symmetrical intake areas relative to the orientation of the combustion zone can also be varied.
• the The arrangement of the outlet openings within an outlet area should be at least approximately uniformly distributed.
• the characteristic curve of the combustion air ratio to be set can be stored in a memory, for example, in the control unit configured for combustion control.
• the characteristic curve can be a known curve for combustion control of a hydrogen-powered heating appliance.
• the characteristic curve thus specifies a combustion air ratio to be set as a function of the heat output Q of the heating appliance.
• the invention makes it possible to avoid modulation ranges during the operation of the heating appliance in which critical temperatures could occur when applying the characteristic curve, and to replace these critical modulation ranges with modulation points according to the limit combustion air ratio ⁇ G (Q).
• a limiting combustion air ratio ⁇ G (Q) which depends on the heat output of the heating appliance, is determined. If the combustion air ratio of the heating appliance falls below the limiting combustion air ratio ⁇ G ( Q ) during operation, the burner temperature can rise above the limit temperature (for example , 450 °C or even 475 °C), thus increasing the risk of cracking. Therefore, operating the heating appliance with a combustion air ratio above the limiting combustion air ratio ⁇ G (Q) can effectively prevent weakening of the burner material and thus the formation of cracks or fractures.
• the limiting combustion air ratio ⁇ G (Q) depends on the heating appliance, and in particular its modulation range, as well as the shape and material of the burner .
• the limiting combustion air ratio ⁇ G (Q) can be determined in advance through laboratory tests on a reference heating appliance. Therefore , step a) can only be performed once or as needed.
• the limiting combustion air ratio ⁇ G (Q) can be stored and retrieved on a memory device, for example, a process control unit.
• step b) the combustion air ratio can be compared with the limit combustion air ratio ⁇ G (Q) defined in step a) according to the stored characteristic curve. This comparison is made in relation to the current or target heat output Q of the heating appliance.
• Step b) can be performed continuously or permanently, or triggered by a modulation process, i.e., a change/adjustment of the heat output Q of the heating appliance.
• the heating appliance can be operated with the limiting combustion air ratio ⁇ G (Q) if, for the current heat output, the combustion air ratio specified according to the characteristic curve is less than the limiting combustion air ratio ⁇ G ( Q).
• the heating appliance can be operated with the combustion air ratio specified according to the characteristic curve if, for the current heat output, the combustion air ratio specified according to the characteristic curve is greater than (or equal to) the limiting combustion air ratio ⁇ G (Q).
• Step c) thus ensures that the heating appliance always operates with a combustion air ratio greater than the specified limiting combustion air ratio ⁇ G ( Q).
• G (Q) is operated, thus ensuring that burner temperatures exceeding the limit temperature are excluded.
• Step c) can be performed continuously or permanently, or triggered by a modulation process, i.e., a change/adjustment of the heating unit's heat output Q.
• the limiting air-fuel ratio ⁇ G (Q) determined in step a) can be a piecewise linear function depending on the heat output Q.
• the limiting air-fuel ratio ⁇ G ( Q) can be defined by several points P x (Q, ⁇ G (Q)).
• the limiting air-fuel ratio ⁇ G (Q) can have fewer than five linear sections, or especially three or fewer linear sections.
• the function of the limiting air-fuel ratio ⁇ G (Q) can have two sections, namely a first section and a second section.
• the first section can be bounded by a first point and a second point, and the second section can be bounded by the second point and a third point.
• the first and second sections thus border each other directly at the second point.
• the first point can be defined by a limiting air-fuel ratio.
• ⁇ G Q A ⁇ B ⁇ Qmin Q max
• the second point can be determined at the (previously known or configured) minimum heat output Qmin of the heating device.
• Parameter A can be in the range 1.9 ⁇ A ⁇ 2.2 and parameter B in the range 1.3 ⁇ B ⁇ 1.7.
• the second point can be determined at a heat output Q in the range of 40% to 80% of the (previously known or configured) maximum heat output Qmax of the heating device.
• the third point can be determined at the (previously known or configured) The maximum heat output Q max of the heating appliance (as configured). Furthermore, it can be provided that in the second section the limiting combustion air ratio ⁇ G (Q) is constant and lies in a range of 1 ⁇ ⁇ G ⁇ 1.2.
• the burner can have a flame arrestor. This can be arranged between the burner surface and the mixture channel and can be made of a known material. A flame arrestor can significantly reduce the risk of a flashback, as it prevents the flame from passing into the mixture channel.
• the heating appliance includes a conveying system for pumping a mass flow. Combustion air, a gas valve for metering the fuel gas to be added, a combustion chamber and a burner arranged in the combustion chamber, as well as a control unit configured to adjust the combustion air ratio of the heating appliance.
• the heating appliance may include a control unit configured to carry out a method proposed herein.
• the control unit may have a processor capable of executing instructions from a computer program that effect the execution of a method presented herein.
• the control unit may also have a memory in which a computer program product that executes a method proposed herein and in which method-related parameters, such as a characteristic curve or a limiting combustion air ratio ⁇ G (Q), are stored.
• This document proposes a method for operating a heating device, a heating device itself, and a computer program that at least partially solve the problems described with reference to the state of the art.
• the method, the heating device, and the computer program enable robust operation of the heating device and, in particular, significantly increase the service life of the burner or burner body.
• the invention can be implemented particularly easily, for example in the form of a software update as part of a conversion of a heating appliance from the use of fossil/natural fuel gases to the use of hydrogen-containing fuel gases with a hydrogen content of at least 80%.
• the combustion products can be fed from the combustion chamber 8 to an exhaust pipe (exhaust system) 10 via an exhaust pipe 9.
• a flame monitoring device 12 for example a UV sensor, can also be arranged on the burner door 6.
• the UV sensor can be located outside the combustion chamber 8, protected from the high temperatures of the burner 3.
• the heating unit 1 can also have a control unit 7.
• the heating unit 1 can be specifically designed for the combustion of hydrogen as fuel.
• the burner 3 can have a burner body 14 suitable for hydrogen combustion with a combustion zone 15.
• the control and regulating device is configured to execute a procedure proposed here, i.e., blocks 110, 120 and 130, and may include a memory on which a computer program product 16 proposed here is stored.
• Fig. 3 This shows exemplary parameter profiles that can occur when carrying out a procedure proposed here.
• a diagram is shown depicting the combustion air ratio ⁇ , expressed in kilowatts, as a function of the heat output Q of the heating appliance.
• the heating appliance 1 has a minimum heat output Q ⁇ sub> min ⁇ /sub> 23 of 5 kW and a maximum heat output Q ⁇ sub>max ⁇ /sub> 23 of 35 kW, and thus a modulation ratio of 1:7.
• the characteristic curve 25 of the combustion control of the heating device 1 is shown, which can be stored on a memory of the control and regulating unit 7.
• a limiting combustion air ratio ⁇ G (Q)17 can be determined according to step a).
• the limiting combustion air ratio ⁇ G (Q)17 can be set section by section . be linear and comprise a first section 18 and a second section 19.
• the first section 18 can be defined by a first point 20 and a second point 21.
• the first point 20 and the second point 21 thus define the first section 18 of the limiting combustion air ratio ⁇ G (Q) 17.
• the characteristic curve 25 of the combustion control can be compared with the limit combustion air ratio ⁇ G (Q) 17.
• the heating appliance can be operated with the limiting combustion air ratio ⁇ G (Q) as the combustion air ratio to be set by the combustion control, if the combustion air ratio specified according to the characteristic curve is smaller than the limiting combustion air ratio ⁇ G ( Q ) for the current heat output. If the combustion air ratio specified according to the characteristic curve is larger than the limiting combustion air ratio ⁇ G ( Q) for the current heat output, the heating appliance is operated with a combustion air ratio according to characteristic curve 25, if the current Heat output is increased when the combustion air ratio specified according to characteristic curve 25 is greater than the limiting combustion air ratio ⁇ G (Q). As in Fig. 3 To be recognized, the heating device 1 in the present example is operated in a range of approximately 5.25 kW ⁇ Q ⁇ 17 kW with the limiting combustion air ratio ⁇ G (Q).
• step c) Block 130

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Regulation And Control Of Combustion (AREA)

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• 2024
  • 2024-07-05 DE DE102024119191.0A patent/DE102024119191A1/de active Pending
• 2025
  • 2025-07-01 EP EP25186506.9A patent/EP4675169A1/fr active Pending

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