Method for regulating a premix gas burner and device for carrying out the method
By controlling the excess air coefficient λ of the hydrogen burner and monitoring it with sensors, the problem of backfire risk in the hydrogen burner was solved, achieving safe and stable burner power regulation, reducing the risk of backfire and maintaining thermal efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ARISTON SPA
- Filing Date
- 2022-04-01
- Publication Date
- 2026-07-10
AI Technical Summary
Hydrogen combustion in premixed gas burners carries a risk of backfire, posing a potential danger of equipment damage. Furthermore, existing technologies struggle to safely adjust burner power over a wide range.
By controlling the ignition of the air-fuel gas mixture Mag with an excess air coefficient λ≥2.5, and gradually adjusting it to the range of 1.3≤λ≤2.5 after the flame stabilizes, combined with sensor monitoring of burner temperature and flame presence, the system achieves safe management and power regulation of the burner.
It effectively reduces the risk of hydrogen combustion backfire, ensures that the burner operates in a safe state, and can adjust the thermal power over a wide range to avoid equipment damage caused by backfire.
Smart Images
Figure CN117242300B_ABST
Abstract
Description
Technical Field
[0001] The following describes the adjustment method for the premixed gas burner.
[0002] A control and regulation device for a premixed gas burner is also described.
[0003] The methods and apparatus described below are suitable for use with adjustable power burners.
[0004] Specifically, the methods and apparatus described below are suitable for the combustion of premixed gases, wherein the fuel gas is hydrogen.
[0005] The methods and apparatus described below are specifically used in hydrogen-powered boilers for producing domestic hot water. Background Technology
[0006] In the production of domestic hot water, gaseous fuels are known to be used, typically light hydrocarbons such as methane (CH4).
[0007] In order to control nitrogen oxides (NOx) x The emissions are known to be achieved by premixing fuel gas with combustion air.
[0008] To achieve complete combustion of fuel gases (and minimize pollutant emissions), it is known to provide an amount of air higher than the stoichiometric air, i.e., to operate with excess air. In this regard, the excess air coefficient λ is defined as a pure number that defines the ratio between the actual air / fuel ratio and the stoichiometric air / fuel ratio of the mixture.
[0009] However, an excess air coefficient λ can lead to a decrease in the efficiency of the heat generator using the burner.
[0010] In the case of light hydrocarbon combustion, a good trade-off is achieved by using an excess air coefficient λ with a value of approximately 1.25–1.35 to minimize pollutant emissions without excessively negatively impacting yield.
[0011] However, the use of light hydrocarbons (such as methane) as fuel still poses significant pollution problems, primarily represented by carbon dioxide emissions.
[0012] Using hydrogen produced from renewable energy sources as fuel appears to be a promising solution for reducing pollutant emissions from gas-fired boilers.
[0013] However, the combustion of hydrogen is very different from the combustion of light hydrocarbons.
[0014] Specifically, hydrogen molecules burn much faster than light hydrocarbon molecules (meaning that the flame propagation speed of hydrogen is about seven times faster than that of methane).
[0015] Compared to the combustion of fuel gases that contain no hydrogen or have a low hydrogen content, the high propagation velocity of gas combustion results in a much greater risk of backfire.
[0016] In the case of hydrogen combustion, backfire can have more serious consequences compared to the combustion of other fuel gases.
[0017] In extreme cases, backfire in a hydrogen-burning burner can cause an explosion, damaging the burner itself and the entire system.
[0018] The inventors observed that the risk of backfire is particularly significant when the air / gas mixture is ignited during the combustion of hydrogen. Summary of the Invention
[0019] The inventor's aim is to propose a solution that can at least partially prevent the problems of the prior art.
[0020] Specifically, the inventors aim to provide a solution for reducing the risk of backfire during combustion of premixed hydrogen when the burner is ignited.
[0021] Another objective of the inventors is to propose a solution that allows for the safe management of premixed hydrogen burners and also enables power adjustment over a wide range.
[0022] These and other objectives are achieved by means of the method for managing a premixed gas burner according to the present invention, and by means of the control and regulation device for the premixed gas burner according to the present invention.
[0023] Further advantages can be obtained through the additional features of the present invention. Attached Figure Description
[0024] The following describes, with reference to the accompanying drawings, a method for regulating a premixed gas burner and possible examples of apparatus for controlling and regulating the premixed gas burner, wherein:
[0025] - Figure 1 It is a chart showing the adjustment of excess air during the burner ignition process;
[0026] - Figure 2 It is a graph showing the relationship between burner temperature, thermal power, and excess air;
[0027] - Figure 3 This is a schematic diagram of the control and regulation device for a premixed burner, wherein the mixing chamber is located downstream of the fan;
[0028] - Figure 4 This is a schematic diagram of a premixed burner control and adjustment device, in which the mixing chamber is located upstream of the fan. Detailed Implementation
[0029] Refer to the attached diagram. Figure 1 The invention illustrates how the premixed burner 4 is regulated during its ignition step.
[0030] initial( Figure 1 The chart section OA) Fan 2 at a predetermined speed V p The rotational speed is adjusted to generate a gaseous flow F that activates burner 4. a .
[0031] Subsequently, gaseous flow F (section AB) a Add a fuel gas stream F consisting mainly and / or substantially of hydrogen (H2). g To obtain an air and fuel gas mixture M with an excess air coefficient λ ≥ 2.5. ag .
[0032] M can be used for air and fuel gas mixtures ag A sensor for the volume concentration of hydrogen (described better later) is used to ensure that the excess air coefficient λ is as desired.
[0033] It should be noted that the ignition of burner 4 can only occur when the excess air coefficient λ has reached the desired value.
[0034] The air and fuel gas mixture M escapes from multiple orifices of burner 4 ag Ignition is achieved using an ignition device 5, such as a conventional ignition electrode 5.
[0035] After ignition, the air-fuel gas mixture M ag Continue to maintain a value of λ≥2.5, flame stabilization time t s ≥5 seconds (segment BC).
[0036] The inventors have demonstrated that an air-fuel gas mixture M with an excess air coefficient λ ≥ 2.5... ag Ignition and maintaining the excess air coefficient λ for at least 5 seconds allows for a significant reduction in the risk of backfire when burner 4 is ignited.
[0037] After the flame stabilization time has elapsed, the excess air coefficient λ decreases gradually, for example, in a linear manner, until it reaches a value of 1.3 < λ < 2.5. 目标 .
[0038] Preferably, the excess air coefficient λ decreases to a value λ = 1.5 < λ < 2.0. 目标 ( Figure 1 The chart in the diagram is in sections CDE).
[0039] Once the flame stabilization time has passed and the excess air coefficient λ decreases to a value of λ... 目标 Afterwards, the air and fuel gas mixture M agYou can start based on the required thermal power.
[0040] During its normal operating procedures, the temperature T of burner 4 is monitored cyclically at time intervals Δt. b This is to check whether the temperature of burner 4 is maintained within a predetermined range, which corresponds to the maximum temperature value T. 上 (T) sup (Tempering may occur above this temperature), and is at the lowest temperature value T. 下 (T) inf (Below this temperature, there is a risk of flames rising into the air).
[0041] Burner 4 must be maintained at a minimum temperature value T within it. 下 and maximum temperature value T 上 At that time, the excess air coefficient λ and the thermal power of burner 4 during operation were both taken into account.
[0042] More precisely, under the same excess air coefficient λ, as the working heat power increases, the minimum temperature value T... 下 and maximum temperature value T 上 The value decreases monotonically.
[0043] In the absence of operational abnormalities, more precisely, as long as the temperature T of burner 4... b Maintaining within the minimum temperature value T 下 and maximum temperature value T 上 Within a certain range, the thermal power is adjusted using the excess air coefficient.
[0044] In a possible embodiment, the excess air coefficient remains constant; in an alternative embodiment, the excess air coefficient varies according to the thermal power, but always remains within the range of the above-mentioned excess air value, i.e., 1.3 < λ < 2.5, preferably 1.5 < λ < 2.0.
[0045] If the operating temperature T of burner 4 b Exceeding the predetermined maximum temperature value T 上 The excess air coefficient gradually increases to a predetermined value Δλ, for example, intermittently, until the temperature T of burner 4 is reached. b Return to the value T 上 the following.
[0046] On the other hand, when the temperature T of burner 4 b The temperature dropped below the predetermined minimum temperature value T. 下 At this time, the excess air coefficient is gradually reduced to a predetermined value Δλ, for example, intermittently, until the temperature T of burner 4 is reached. b Return to the value T 下 above.
[0047] The time interval Δt for performing temperature checks on burner 4 and possible corrections to the excess air coefficient λ can vary based on the system's time constant, or more precisely, on the thermal inertia of burner 4.
[0048] In a possible implementation, such a time interval Δt = 1 second.
[0049] The temperature T of burner 4 b Regular inspections and any periodic adjustment of the excess air coefficient λ of the combustion mixture allow for maintaining flame stability, and in particular, avoid the risk of backfire when the burner operates at reduced power for extended periods without being excessively detrimental to heat production.
[0050] The above-described control and regulation method can be performed by means of means 1 for controlling and regulating the operation of the premixed gas burner 4, which is suitable for burning fuel gas that is substantially and / or essentially composed of hydrogen (H2).
[0051] The device 1 includes a first pipe 11 or a combustion air inlet pipe, a second pipe 12 or a fuel gas inlet pipe, a variable speed fan 2 with an inlet 21 connected to the first pipe 11, and a delivery pipe 22.
[0052] The speed of fan 2 can be varied according to the required thermal power.
[0053] Air from the first pipe 11 and fuel gas F from the second pipe 12 g The mixing is carried out through the Venturi tube 3, which can be positioned downstream of the fan. Figure 3 ) or upstream of the same fan ( Figure 4 ).
[0054] The second pipe 12 connects to the narrow section of the venturi pipe 3, thereby drawing in fuel gas F. g A conventional motorized (or more generally regulating) valve 7 is provided for regulating the fuel gas F passing through the second conduit 12. g The flow rate is thus used to regulate the excess air coefficient λ.
[0055] Provide a third conduit 13, or for the air and fuel gas mixture M. ag The outflow pipe is located downstream of the Venturi tube 3 that supplies fuel to the burner 4.
[0056] The burner 4 can be a conventional burner of the perforated surface type inserted into the combustion chamber 41. An ignition device 5 (e.g., a known ignition electrode) is provided to ignite the air-fuel gas mixture M escaping from the venturi tube 3 and reaching the burner 4. ag .
[0057] A standard check valve 14 can be installed upstream of the burner 4.
[0058] The first sensor 61, located inside the first duct 11, allows for the measurement of the physical properties of the airflow.
[0059] In a possible embodiment, the first sensor 61 is an air mass flow sensor that can detect the mass flow rate of the air drawn in by the fan 2.
[0060] The second sensor 62, located in or downstream of the venturi tube 3, allows for the measurement of the generated air and fuel gas mixture M. ag The concentration of hydrogen gas (H2) present in the atmosphere.
[0061] The first sensor 61 and the second sensor 62 allow the air and fuel gas mixture M to be detected. ag Control the air and fuel gas mixture M before it reaches burner 4 ag The excess air coefficient λ.
[0062] The third sensor 63 or temperature sensor can detect the temperature T of burner 4. b .
[0063] The fourth sensor 64 detects the presence of a flame on the surface of the burner 41.
[0064] This fourth sensor 64 can be an optical sensor capable of detecting the presence of hydroxyl radicals (OH).
[0065] Alternatively, the fourth sensor 64 may consist of a low thermal inertia thermocouple suitable for measuring flame temperature.
[0066] In both cases, the fourth sensor 64 is used only to detect the presence of a flame, but does not provide any details about the quality of the combustion at that location.
[0067] A regulator 8 is provided, which receives input signals detected by sensors 61, 62, 63, and 64 and a control signal S indicating the desired thermal power. c .
[0068] The regulator 8 can provide the ignition device 5 with an ignition signal, a fan speed regulation signal 2, and an electric valve opening regulation signal 7.
[0069] In the example shown, a device capable of detecting the fuel gas flow rate F is installed inside the second pipe 12. g The fifth sensor for physical quantities, 65.
[0070] In the example shown, the fifth sensor 65 is fuel gas F g Mass flow sensor.
[0071] In the illustrated apparatus, the value of the excess air coefficient λ is determined by measurements from the air quality sensor 61 and the hydrogen concentration sensor 62, while the temperature sensor 63 is only used to measure the temperature T of the burner 4. b When an outlier occurs, the value of the excess air coefficient λ is corrected.
[0072] If present, fuel gas F g The fifth mass sensor 65 allows for checking the accuracy of the information provided by the first two sensors 61 and 62: in other words, if the fuel gas F g If the fuel gas is composed of pure hydrogen (H2), the signal provided by the fifth mass sensor 65 can be redundant relative to the signals already provided by the first two sensors 61 and 62; conversely, if the fuel gas F... g It consists mainly of a mixture of hydrogen (H2) but contains a certain amount of other gaseous fuels (such as methane (CH4)). In order to correctly define the excess air coefficient λ, it is important to combine the signal provided by the mass sensor 65 to the regulator 8 with the aforementioned sensors 61 and 62.
Claims
1. A method for regulating a premixed gas burner (4), wherein hydrogen (H2) is supplied to the premixed gas burner (4), the method comprising: Step a) Predetermined speed V p Start the fan (2) to generate a gas flow F a , Step b) to the gaseous flow F a Add fuel gas F containing hydrogen (H2) g The flow is thus obtained to obtain an air and fuel gas mixture M with an excess air coefficient λ ≥ 2.
5. ag , Step c) The air and fuel gas mixture M ag Ignition is performed. Step d) Maintain the air and fuel gas mixture M ag Combustion stability time t s ≥5 seconds Step e) Gradually decrease the excess air coefficient λ until it reaches a value of 1.3 < λ < 2.
5. 目标 .
2. The method as described in claim 1, characterized in that, include: Step f) Check how much heat power is required. Step g) Adjust the air and fuel gas mixture M according to the required thermal power. ag The flow rate, thereby maintaining the value λ. 目标 .
3. The method as described in claim 2, characterized in that, include: Step h) Periodically check the temperature T of the premixed gas burner (4) at each time interval Δt. b : If the temperature T of the premixed gas burner b Exceeding the predetermined maximum temperature value T 上 Then the value λ 目标 Increase the predetermined value Δλ; And if the temperature T of the premixed gas burner b Below the predetermined minimum temperature value T 下 Then the value λ 目标 Decrease the predetermined value Δλ, Step i) periodically returns to step h).
4. The method as described in claim 1, characterized in that, In step e), the excess air coefficient λ is gradually reduced to the value λ = 1.5 < λ < 2.
5. 目标 .
5. The method as described in claim 3, characterized in that, In step h), the time interval Δt is equal to 1 second.
6. The method as described in claim 2, characterized in that, In step g), the value λ 目标 Keep it constant.
7. The method as described in claim 2, characterized in that, In step g), the value λ 目标 It varies depending on the thermal power, but always remains at the stated value λ. 目标 Within the range.
8. An apparatus (1) for performing the adjustment method as described in any one of claims 1 to 7, the apparatus (1) comprising: a) At least one premixed gas burner (4) containing fuel gas F containing hydrogen (H2). g The flow is supplied to the premixed gas burner (4), and the premixed gas burner (4) is inserted into the combustion chamber (41). b) First pipe (11), c) Second pipe (12), d) A variable speed fan (2) having an inlet (21) connected to the first pipe (11) and a delivery pipe (22). e) Electric valve (7), said electric valve being used to regulate the fuel gas F passing through the second pipe (12) g Traffic, f) Venturi tube (3), the Venturi tube being used to combine air from the first conduit (11) with fuel gas F from the second conduit (12). g mix, g) Air and fuel gas mixture M ag The third conduit (13) is located downstream of the Venturi tube (3), wherein the premixed gas burner (4) is connected to the third conduit (13). h) Ignition device (5), said ignition device being used to ignite the air and fuel gas mixture M escaping from the premixed gas burner (4). ag , i) A first sensor (61), which is located inside the first pipe (11), j) A second sensor (62), which is located inside or downstream of the Venturi tube (3), k) A fourth sensor (64), the fourth sensor being used to detect the presence of a flame within the combustion chamber (41), l) A regulator (8) adapted to receive the following input: - Signal S indicating the required thermal power c , -Indicative air mass flow rate F provided by the first sensor (61) a The signal - The air and fuel gas mixture M is indicated by the second sensor (62). ag The signal of hydrogen (H2) concentration in the gas. -A signal indicating the presence of flame provided by the fourth sensor (64), And provide the following output: - An ignition signal is sent to the ignition device (5). -A signal for adjusting the speed of the fan (2), and -A signal used to regulate the opening of the electric valve (7).
9. The apparatus (1) as claimed in claim 8, characterized in that, The first pipe (11) is a combustion air inlet pipe. The second pipe (12) is a fuel gas inflow pipe.
10. The apparatus (1) as claimed in claim 8, characterized in that, The first sensor (61) is an air mass flow sensor and is located inside the first pipe (11). The second sensor (62) is a hydrogen concentration sensor H2, and is located inside or downstream of the Venturi tube (3).
11. The apparatus (1) as claimed in claim 8, characterized in that, The premixed gas burner (4) is a perforated surface type burner.
12. The apparatus (1) as claimed in claim 8, characterized in that, It also includes a third sensor (63) or a temperature sensor, which is capable of detecting the temperature T of the premixed gas burner (4). b , Furthermore, the regulator (8) includes components adapted to further receive an indication of the temperature T of the premixed gas burner (4). b The input of the signal, And provide the following output: -A signal used to adjust the speed of the fan (2), -A signal for regulating the opening of the electric valve (7), and - A signal used to regulate thermal power.
13. The apparatus (1) as claimed in any one of claims 8 to 10, characterized in that, It also includes a fifth sensor (65) or fuel gas F located inside the second pipe (12). g mass flow sensor, Furthermore, the regulator (8) includes components adapted to further receive indicator fuel gas F. g The input of the mass flow rate signal.
14. The apparatus (1) as claimed in claim 8. Its features are, The fourth sensor (64) is an optical sensor or a low-thermal-inertia thermocouple.