HEATING APPLIANCE AND METHOD FOR OPERATING A HEATING APPLIANCE

Description

[0001] The invention relates to a heating device according to the preamble of claim 5 and a method for operating a heating device according to the preamble of claim 4.

[0002] A heating device and a method of the type mentioned above are generally known.

[0003] For example, EP 4 043 789 A1 discloses a heating device or a method according to the preamble of the independent claims. DE 10 2020 204089 B3 and DE 10 2018 211599 A1 disclose broadband lambda probes for use with hydrogen-powered gas burners.

[0004] In practical terms, such a heating appliance consists of a combustion chamber, a burner for gaseous fuels located within the combustion chamber, a heat exchanger located within the combustion chamber, and a burner control system that interacts with the burner. In procedural terms, this process involves the combustion of gaseous fuel by a burner located within the combustion chamber, with the burner also interacting with a burner control system.

[0005] The invention is based on the objective of improving a heating appliance and a method of the type mentioned above. In particular, a heating appliance and a method are to be created that ensure particularly good combustion hygiene (i.e., the cleanest possible exhaust gas), especially when the gaseous fuel contains not only hydrocarbons but also, at least partially, pure hydrogen.

[0006] This problem is solved, on the one hand, by a heating device of the type mentioned at the outset, by the features listed in the characterizing portion of claim 1. On the other hand, this problem is solved by a method of the type mentioned at the outset, by the features listed in the characterizing portion of claim 4.

[0007] According to the invention, it is therefore provided that in the combustion chamber, a wideband lambda probe, which interacts with the burner control and with hydrogen, is arranged between the burner and the heat exchanger to monitor the hydrogen content in the exhaust gas.

[0008] In procedural terms, the invention provides that a broadband lambda probe, arranged in the combustion chamber between the burner and the heat exchanger and interacting with hydrogen, works together with the burner control to monitor the hydrogen content in the exhaust gas.

[0009] In other words, the solution according to the invention is characterized by the fact that, in addition to the usual combustion control, a wideband lambda sensor (see also https: / / de.wikipedia.org / w / index.php?title=Lambdasonde&oldid= 222721329 and in particular the section "Wideband lambda sensor") is used, which, due to possible interactions of the exhaust gas with the sensor itself, which will be explained in more detail below, makes it possible to detect incomplete combustion even better, especially with hydrogen-containing fuel gas.

[0010] The term "combustion chamber" used above refers to the space in which combustion takes place, i.e., the combustion chamber.

[0011] Other advantageous embodiments of the heating device according to the invention or of the method according to the invention for operating a heating device are set out in the dependent claims.

[0012] The heating device or the method according to the invention will be explained in more detail below with reference to the graphic representation of a preferred embodiment.

[0013] It shows Figure 1 shows a cross-section of the heating device according to the invention with a wideband lambda probe.

[0014] The in Figure 1The illustrated heating appliance initially consists, in a known manner, of a combustion chamber 1, a burner 2 for gaseous fuels (particularly preferably a so-called premix burner) arranged in the combustion chamber 1, and a burner control unit 3 that interacts with the burner 2. It is particularly preferred that the fuel contains at least 20% by volume, preferably more than 50% by volume, and most preferably more than 90% by volume hydrogen. Furthermore, the fuel preferably also consists of gaseous hydrocarbons and components inert for combustion, such as nitrogen or carbon dioxide. As can be seen, a heat exchanger 5 is also arranged in the combustion chamber 1 according to the invention, with which heat from the exhaust gas can be transferred to a heating circuit medium or the like.

[0015] Essential for the heating device according to the invention is that in the combustion chamber 1, a wideband lambda probe 4, which interacts with the burner control 3 and with hydrogen, is arranged between the burner and the heat exchanger to monitor the hydrogen content in the exhaust gas.

[0016] More precisely, the broadband lambda sensor 4 is designed to detect the oxygen content of an exhaust gas located in the combustion chamber 1, or rather, to measure the oxygen content in the exhaust gas using the broadband lambda sensor 4. The broadband lambda sensor preferably has a sensor head with cell membranes made of zirconium dioxide.

[0017] According to the invention, the wideband lambda probe 4 is arranged between the burner 2 and the (above-mentioned) heat exchanger 5, so that the oxygen content in the exhaust gas can be measured with minimal reaction time.

[0018] In procedural terms, gaseous fuel is burned by the burner 2 located in the combustion chamber 1 to operate the heating appliance. The burner 2 interacts with the burner control 3.

[0019] Essential to the solution according to the invention is that a broadband lambda probe 4, which interacts with hydrogen and is arranged in the combustion chamber 1 between the burner and the heat exchanger, works together with the burner control 3 to monitor the hydrogen content in the exhaust gas.

[0020] Looking more closely, the preferred approach is to use the measured oxygen content in the exhaust gas (more precisely: the corresponding measured value) to infer the hydrogen content or presence of hydrogen in the exhaust gas using burner control 3. This utilizes the understanding that a reduction in the amount of gaseous fuel supplied should actually lead to an increase in the oxygen content of the exhaust gas. However, incomplete combustion in the combustion chamber allows unburned hydrogen to enter the measuring cell of the broadband lambda sensor. Due to locally heterogeneous catalyzed hydrogen reactions within the sensor, this leads to the consumption of the oxidizer, which distorts the measured value. From a physical perspective, this results in a reversal of the control direction of the broadband lambda sensor; that is, further leaning out (reducing the amount of fuel) results in the same or even higher oxygen content.This is even accompanied by decreasing measured oxygen levels. The burner control system 3 includes appropriate means for this purpose (i.e., for determining possible hydrogen in the exhaust gas), optionally in the form of software and / or hardware.

[0021] For a better understanding of the solution according to the invention, the following should be noted: In a combustion system operated with pure hydrocarbons (for example, methane), the ignition or explosion limits, i.e., the mixture range in which combustion takes place (see in particular https: / / de.wikipedia.org / w / index.php?title=Explosionsgrenze&oldid=214973830), are relatively narrow, so that with a shift in the air-fuel ratio, the so-called hygiene limit (formation of unburned hydrocarbons and carbon monoxide) and the loss of flame are close together.

[0022] As the hydrogen content in the fuel gas increases, the ignition limit rises, making incomplete, stable, lean combustion with high levels of unburned hydrogen in the exhaust gas possible. The broadband lambda sensor 4 has catalytically active components in its measuring cell, which, at higher hydrogen concentrations (greater than 500 ppm) in the exhaust gas, lead to heterogeneously catalyzed reactions in the measuring cell. Due to the high reaction rate and the reduction in activation energy, the residual hydrogen in the measuring cell is completely oxidized, causing the oxygen content in the measuring cell to decrease. This creates a discrepancy (anomaly) between the actual oxygen content in the exhaust gas and the measured value. This positive feedback behavior can be interpreted as incomplete combustion in lean combustion. Consequently, the combustion system can then be shut down in a controlled manner, for example.

[0023] The inventive features thus lead to hygienic combustion even in lean operation due to the positive feedback behavior. Furthermore, these features enable precise air-fuel ratio control independent of the gas composition. Finally, they also allow for flexible, power-dependent adjustment of the air-fuel ratio, thereby enabling a wider operating and modulation range. Reference symbol list

[0024] 1 Combustion chamber 2 Burner 3 Burner control 4 Wideband lambda probe 5 Heat exchanger

Claims

1. A heating device comprising a combustion chamber (1), a burner (2) for gaseous fuels, which is arranged in the combustion chamber (1), and a burner control (3) which cooperates with the burner (2), wherein a heat exchanger (5) is arranged in the combustion chamber (1), characterized in that a wideband lambda sensor (4), which cooperates with the burner control (3) and interacts with hydrogen, is arranged in the combustion chamber (1) for monitoring a hydrogen content in the waste gas, wherein the wideband lambda sensor (4) is arranged between the burner (2) and the heat exchanger (5).

2. The heating device according to claim 1, characterized in that the wideband lambda sensor (4) is designed for detecting the oxygen content of the waste gas that is located in the combustion chamber (1).

3. The heating device according to claim 1 or 2, characterized in that the fuel contains at least 20 vol% hydrogen.

4. A method for operating a heating device, in which gaseous fuel is combusted using a burner (2) that is arranged in a combustion chamber (1) and in which the burner (2) cooperates with a burner control (3), wherein a heat exchanger (5) is arranged in the combustion chamber (1), characterized in that a wideband lambda sensor (4), which is arranged in the combustion chamber (1) and interacts with hydrogen, cooperates with the burner control (3) for monitoring a hydrogen content in the waste gas, wherein the wideband lambda sensor (4) is arranged between the burner (2) and the heat exchanger (5).

5. The method according to claim 4, characterized in that an oxygen content in the waste gas is measured using the wideband lambda sensor (4).

6. The method according to claim 5, characterized in that a hydrogen content in the waste gas is concluded from the measured oxygen content in the waste gas using the burner control (3).