Low-nitrogen anti-vibration ammonia-doped natural gas burner

Abstract

The application discloses a low-nitrogen anti-vibration natural gas ammonia blending burner, ammonia gas is partially decomposed into nitrogen and hydrogen after being introduced into a central fuel inlet and passing through a plasma pre-decomposition zone, and the ammonia gas is input into a combustion chamber together with a mixture of natural gas and air through a pipeline assembly; a bushing is coaxially arranged in the combustion chamber; a cavity between the bushing and a combustion chamber shell is a back cavity; a back cavity adjusting plate is arranged in the back cavity to adjust the volume of the back cavity; a plurality of secondary air inlets are formed in the combustion chamber shell; an adjustable flared ring which can swing and stretch is arranged at the inlet of the combustion chamber, and one end of the adjustable flared ring is in contact with the bushing; a control screw is arranged outside a variable cross-section flow channel and controls the cross-section size of the variable cross-section flow channel; a NOx sensor is arranged at the outlet of the burner, and a pressure sensor is arranged on the outer wall surface of the downstream; a controller receives data of the two sensors and controls the adjustable flared ring, the back cavity adjusting plate and the control screw. The application ensures the high efficiency, low emission and stability of combustion, and effectively suppresses the thermoacoustic vibration.

Description

Technical Field

[0001] This invention relates to the field of combustion technology, and in particular to a low-NOx, vibration-resistant ammonia-blended natural gas burner. Background Technology

[0002] With the continuous growth of global energy demand and increasing emphasis on environmental protection, the performance requirements for combustion equipment in the industrial sector have become more stringent, especially in terms of efficient and low-pollution combustion technologies. One feasible method to reduce carbon emissions during combustion is to blend a portion of carbon-free ammonia fuel into natural gas. However, this introduces potential problems such as combustion instability, low combustion efficiency, excessive nitrogen oxide (NOx) emissions, and thermoacoustic vibration.

[0003] During combustion, especially under high loads or complex conditions, burners may experience combustion instability, such as unstable flames, localized overheating, or oxygen deficiency. These problems not only reduce combustion efficiency but also increase equipment maintenance costs and operational risks. Common causes of combustion instability include uneven fuel-air mixing, unstable airflow, and burner design flaws.

[0004] NOx (nitrogen oxides) is one of the main pollutants in industrial combustion processes, and its formation is particularly significant under high-temperature and high-pressure combustion conditions. Therefore, reducing NOx emissions has become an important indicator for evaluating the environmental performance of burners.

[0005] Thermoacoustic vibration is a high-frequency sound wave or vibration phenomenon generated during combustion due to the interaction of temperature, airflow, and pressure fluctuations. This vibration not only affects the stability and safety of the burner but can also cause physical damage to the equipment and increase noise pollution. The occurrence of thermoacoustic vibration is usually closely related to factors such as uneven airflow, incomplete combustion, or localized overheating.

[0006] While some existing combustion technologies have improved combustion efficiency and stability to some extent by modifying airflow paths and optimizing air-fuel mixing, they still struggle to simultaneously achieve multiple objectives, including reducing NOx emissions, suppressing thermoacoustic vibrations, and improving combustion efficiency. This is especially true in energy-efficient industrial systems, where current technologies have yet to effectively address these comprehensive challenges. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention proposes a low-NOx, vibration-resistant ammonia-blended natural gas burner, which can reduce carbon emissions during the combustion process and regulate pressure fluctuations during combustion, thereby more intelligently improving combustion stability and efficiency while reducing NOx emissions.

[0008] The specific technical solution is as follows:

[0009] A low-NOx, vibration-damping natural gas ammonia-blended burner includes: a central fuel inlet, a plasma pre-decomposition zone, a piping assembly, a combustion chamber, a variable cross-sectional area flow channel, and a burner outlet arranged coaxially in sequence; as well as a controller, an adjustable flared ring, a deflecting acoustic liner sound-absorbing structure, a control screw, a NOx sensor, a pressure sensor, and a controller. The central fuel inlet is used to introduce ammonia gas, and the plasma pre-decomposition zone is used to decompose part of the ammonia gas into nitrogen and hydrogen gas. The piping assembly has two-stage fuel channels: an inner-stage fuel channel is used to guide the gas output from the plasma pre-decomposition zone to the combustion chamber through a cyclone separator, and an outer-stage fuel channel is used to introduce a mixture of natural gas and air and guide it to the combustion chamber through a reverse cyclone separator. In the gas flow direction, the direction closer to the starting point is designated as upstream, and the direction further away is designated as downstream.

[0010] The plasma pre-decomposition zone includes: a central ground electrode, outer ground electrodes, and high-voltage electrodes; the central ground electrode is arranged in the center, two outer ground electrodes are symmetrically arranged on both sides of the central ground electrode, and two high-voltage electrodes are symmetrically arranged outside the outer ground electrodes with the central ground electrode as the center, and fixed on the outer shell of this zone; a grid structure is set between each level of electrodes, and a catalyst is arranged inside the grid to promote the decomposition of ammonia.

[0011] The deflecting sound-absorbing structure is arranged inside the combustion chamber and includes: a secondary air inlet, a back cavity adjustment plate, a back cavity, and a bushing; the bushing is arranged coaxially along the combustion chamber axis, and has multiple non-uniform inclined holes along the axis, with the hole diameter and hole spacing increasing sequentially from upstream to downstream; the cavity between the bushing and the combustion chamber shell is the back cavity, and a back cavity adjustment plate is installed in the back cavity to adjust the back cavity volume; several secondary air inlets are opened in the upstream part of the combustion chamber shell;

[0012] An adjustable flared ring with an adjustable swing angle and retraction is installed at the combustion chamber inlet, with one movable end of the adjustable flared ring contacting the bushing; a variable cross-sectional area flow channel is connected to the downstream of the combustion chamber, and its tail is fixedly connected to the burner outlet; a control screw is arranged outside the variable cross-sectional area flow channel to control its cross-sectional area; a NOx sensor is installed at the burner outlet, and a pressure sensor is arranged on the downstream outer wall of the combustion chamber; the controller is used to receive monitoring data from the NOx sensor and the pressure sensor in real time, and to control the swing angle and retraction adjustment of the adjustable flared ring, the opening of the back cavity adjustment plate, and the control screw according to the monitoring data.

[0013] Furthermore, the pipeline assembly includes: a central partition structure, an inner stage fuel passage, a partition wall, an outer stage fuel passage, an outer shell of the pipeline assembly arranged coaxially from the center outwards, as well as a side fuel inlet, an inner stage cyclone separator, and an outer stage cyclone separator;

[0014] The partition wall is a trumpet-shaped structure with one end flared, the middle inner diameter unchanged, and the other end constricted. The flared end is fixed to the outer shell of the plasma pre-decomposition zone, and the constricted end is located at the entrance of the combustion chamber. A central partition structure is set at the center of the region with the middle inner diameter unchanged, so that an annular channel is formed inside the partition wall. This annular channel is the inner stage fuel channel. The inner stage fuel channel connects the plasma pre-decomposition zone and the combustion chamber, and an inner stage cyclone is arranged inside it.

[0015] The annular channel between the partition wall and the outer shell of the pipeline assembly is the outer fuel channel; several side fuel inlets are symmetrically opened along the axis on the outer shell of the pipeline assembly for introducing premixed gas of natural gas and air. The upstream of the outer fuel channel is connected to the side fuel inlets, and the downstream is connected to the combustion chamber. An outer cyclone separator is arranged near the downstream position in the outer fuel channel; the swirl direction of the inner cyclone separator is opposite to that of the outer cyclone separator.

[0016] Furthermore, the combustion chamber shell is provided with four tangential secondary air inlets evenly distributed around the perimeter, allowing the secondary air to enter the combustion chamber tangentially; the gas introduced into two opposite secondary air inlets is the same, and the flow rate can be adjusted; two opposite secondary air inlets introduce air, and the other two opposite secondary air inlets introduce oxygen.

[0017] Furthermore, the adjustable flare ring includes a fixed section and a telescopic section. One end of the fixed section is rotatably connected to the combustion chamber shell, and this connection is close to the junction of the combustion chamber shell and the outer shell of the pipe assembly. The other end of the fixed section is slidably connected to one end of the telescopic section, allowing the telescopic section to slide relative to each other. The other end of the telescopic section contacts the bushing. Adjusting the swing angle and telescopic length of the adjustable flare ring changes the contact position between the adjustable flare ring and the bushing.

[0018] Furthermore, an inlet pretreatment system is arranged before the central fuel inlet to filter impurities in the ammonia and adjust its flow rate so that the ammonia concentration and flow rate entering the central fuel inlet meet the requirements.

[0019] A low-NOx vibration-damping natural gas ammonia-blended combustion method, based on the aforementioned low-NOx vibration-damping natural gas ammonia-blended burner, includes the following steps:

[0020] S1: Arrange the low-NOx vibration-damping natural gas ammonia-blended burner, and start the controller, pressure sensor, and NOx sensor;

[0021] S2: Ammonia is introduced into the burner from the central fuel inlet. After some of the ammonia is decomposed into hydrogen and nitrogen in the plasma pre-decomposition zone, it flows into the pipeline assembly.

[0022] S3: The mixture of natural gas and air is introduced into the pipeline assembly. The cyclone separator in the pipeline assembly deflects the mixture gas flow and the gas output from the plasma pre-decomposition zone into a rotating gas flow, enhancing the mixing effect of different component gases, before being introduced into the combustion chamber.

[0023] S4: Secondary air is tangentially introduced into the combustion chamber from the secondary air inlet to provide the secondary air required for combustion. The gas after combustion is discharged from the burner through the variable cross-sectional area flow channel and the burner outlet in sequence.

[0024] During the S2-S4 process, the pressure sensor monitors the thermoacoustic vibration frequency in the combustion chamber in real time, and the NOx sensor monitors the NOx emissions of the burner in real time. The monitored data are fed back to the controller. The controller adjusts the swing angle and extension length of the adjustable flare ring, the opening of the back cavity adjustment plate, and the control screw according to the monitored data, thereby mitigating thermoacoustic vibration and reducing NOx emissions.

[0025] Furthermore, the controller controls the swing angle and extension length of the adjustable flared ring, changing the contact position between the adjustable flared ring and the bushing, thereby changing the perforation rate of the deflector sound-absorbing structure, thus changing the sound absorption frequency and sound absorption performance of the deflector sound-absorbing structure, controlling thermoacoustic vibrations at different frequencies, and optimizing the airflow distribution entering the combustion chamber; when the contact position between the adjustable flared ring and the bushing is closer to the upstream, the perforation rate is lower, which is beneficial for suppressing low-frequency thermoacoustic vibrations; when the contact position is closer to the downstream, the perforation rate is higher, which is beneficial for suppressing high-frequency thermoacoustic vibrations.

[0026] Furthermore, the controller controls the opening of the back cavity adjustment plate. According to the acoustic principle of the resonant sound absorption structure, the volume of the back cavity is inversely proportional to the sound absorption frequency. When the thermoacoustic vibration frequency changes, the volume of the back cavity is adjusted by the back cavity adjustment plate so that the optimal sound absorption frequency of the deflection sound liner sound absorption structure is consistent with the thermoacoustic vibration frequency generated by the burner operation, thereby controlling the thermoacoustic vibration.

[0027] Furthermore, the controller adjusts the control screw to change the cross-sectional area of ​​the variable cross-sectional area flow channel, thereby changing the acoustic reflection coefficient downstream of the combustion chamber, and thus changing the phase difference between the sound pressure and the heat release of the flame inside the combustion chamber.

[0028] When the amplitude of the oscillating pressure detected by the pressure sensor increases, the control screw is adjusted to expand the cross-sectional area of ​​the variable cross-sectional area flow channel, reduce the acoustic reflection coefficient, reduce the accumulation of acoustic energy in the combustion chamber, and alleviate thermoacoustic vibration; conversely, the control screw is adjusted to reduce the cross-sectional area of ​​the variable cross-sectional area flow channel.

[0029] The beneficial effects of this invention are:

[0030] (1) Improve combustion stability: The present invention effectively improves combustion stability through plasma pre-decomposition zone, swirler and adjustable flaring ring, back cavity adjustment plate and variable cross-sectional area flow channel, avoiding thermoacoustic vibration and other adverse phenomena caused by unstable combustion; and further mitigates the risk of thermoacoustic vibration through the structural linkage of adjustable flaring ring and bushing, and the design of variable cross-sectional area flow channel.

[0031] (2) Optimize combustion efficiency: The present invention optimizes the airflow distribution entering the combustion chamber through a swirler, adjustable flaring ring, bushing and back cavity adjustment plate, so that the fuel and air are mixed more evenly, reducing local hot spots and improving combustion efficiency; the design of the adjustable flaring ring also optimizes the distribution of the external recirculation zone of the combustion chamber and improves combustion performance.

[0032] (3) Reduce NOx emissions: A portion of ammonia is decomposed into nitrogen and hydrogen through the plasma pre-decomposition zone, optimizing the composition of combustion gases. Staged combustion is achieved through pipeline components and secondary air, improving combustion stability and effectively reducing NOx emissions from ammonia-blended natural gas combustion. Attached Figure Description

[0033] Figure 1 This is a structural diagram of a low-NOx vibration-damping natural gas ammonia-blended burner in an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of the secondary air inlet arranged around the combustion chamber in an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of the opening degree of the back cavity adjustment plate in an embodiment of the present invention, wherein (a) is the opening degree of the back cavity adjustment plate in state A, (b) is the opening degree of the back cavity adjustment plate in state B, and (c) is the opening degree of the back cavity adjustment plate in state C.

[0036] Figure 4 This is a diagram showing the expansion and contraction of the control screw and the variable cross-sectional area flow channel under two burner outlet states in an embodiment of the present invention.

[0037] In the diagram, 1 is the central fuel inlet, 2 is the plasma pre-decomposition zone, 2-1 is the central ground electrode, 2-2 is the external ground electrode, and 2-3 is the high-voltage electrode; 3 is the pipeline assembly, 3-1 is the inner stage fuel channel, 3-2 is the inner stage cyclone separator, 3-3 is the side fuel inlet, 3-4 is the outer stage fuel channel, and 3-5 is the outer stage cyclone separator; 4 is the combustion chamber, 5 is the controller, and 6 is the adjustable flare ring; 7 is the deflecting sound liner sound absorption structure, 7-1 is the secondary air inlet, 7-2 is the back cavity adjustment plate, 7-3 is the back cavity, and 7-4 is the bushing; 8 is the NOx sensor, 9 is the variable cross-sectional area flow channel, 10 is the control screw, 11 is the burner outlet, and 12 is the pressure sensor. Detailed Implementation

[0038] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The objectives and effects of the present invention will become clearer as a result. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0039] like Figure 1 As shown, a low-NOx, vibration-damping natural gas ammonia-blended burner includes: a central fuel inlet 1, a plasma pre-decomposition zone 2, a pipe assembly 3, a combustion chamber 4, a controller 5, an adjustable flared ring 6, a deflecting acoustic liner sound-absorbing structure 7, a NOx sensor 8, a variable cross-sectional area flow channel 9, a control screw 10, a burner outlet 11, and a pressure sensor 12.

[0040] The central fuel inlet 1, plasma pre-decomposition zone 2, piping assembly 3, combustion chamber 4, variable cross-sectional area flow channel 9, and burner outlet 11 are arranged coaxially in sequence and are uniformly enclosed by a shell. The combustion gas, ammonia, enters the burner through the central fuel inlet 1 after passing through the inlet pretreatment system. The inlet pretreatment system uses an existing system to filter impurities in the ammonia and regulate its flow rate, ensuring that the ammonia concentration and flow rate entering the burner meet the set requirements to guarantee the stability of the subsequent decomposition reaction in the plasma pre-decomposition zone 2. In the main flow direction of the combustion gas, the direction closer to the starting point is designated as upstream, and vice versa.

[0041] The plasma pre-decomposition zone 2 utilizes high-energy plasma to decompose ammonia gas introduced from the central fuel inlet 1, pre-decomposing some of the ammonia into hydrogen and nitrogen gas, optimizing the composition of the combustion gases, thereby improving combustion efficiency, reducing NOx emissions, and effectively controlling thermoacoustic vibrations during combustion. The plasma pre-decomposition zone 2 includes: a central ground electrode 2-1, outer ground electrodes 2-2, and high-voltage electrodes 2-3. The central ground electrode 2-1 is located at the center of the plasma pre-decomposition zone 2, with two outer ground electrodes 2-2 symmetrically arranged on either side of the central ground electrode 2-1; two high-voltage electrodes 2-3 are also symmetrically arranged on either side of the central ground electrode 2-1, located outside the outer ground electrodes 2-2, and fixed to the outer shell of this zone; a grid structure is installed between each level of electrode, with a catalyst arranged inside the grid to promote ammonia decomposition. The principle of ammonia decomposition achieved by the interaction of the electrodes is as follows: the central electrode 2-1, as the core electrode of the reaction zone, is responsible for exciting ammonia molecules and generating a preliminary electric field; the outer electrode 2-2 is opposite to the central electrode 2-1, forming a strong electric field. Ammonia molecules are subjected to collisions with high-energy electrons in this electric field, resulting in ionization and dissociation, generating a large number of free radicals and ions, forming plasma; the high-voltage electrode 2-3 further accelerates the movement of electrons by providing high voltage, increases the collision frequency, enhances the decomposition effect of ammonia, and increases the reaction rate.

[0042] Nitrogen and ammonia generated from the decomposition of ammonia are guided into the combustion chamber 4 through the piping assembly 3. The piping assembly 3 includes: an inner-stage fuel channel 3-1, an inner-stage cyclone separator 3-2, a partition wall, a side fuel inlet 3-3, an outer-stage fuel channel 3-4, and an outer-stage cyclone separator 3-5. The partition wall has a trumpet-shaped structure with one flared end, a constant inner diameter in the middle, and a constricted end. The flared end is fixed to the outer shell of the plasma pre-decomposition zone 2, and the constricted end is located at the entrance of the combustion chamber 4. A central partition structure is set at the axis of the region with a constant inner diameter in the middle, so that an annular channel is formed inside the partition wall, which is the inner-stage fuel channel 3-1. The inner-stage fuel channel 3-1 connects the plasma pre-decomposition zone 2 and the combustion chamber 4, and the inner-stage cyclone separator 3-2 is arranged inside it. The annular channel between the partition wall and the outer shell of the pipeline assembly 3 area is the outer fuel channel 3-4. An outer cyclone separator 3-5 is arranged near the downstream end of the outer fuel channel 3-4. The inner cyclone separator 3-2 has an axial swirl direction opposite to that of the outer cyclone separator 3-5. Two side fuel inlets 3-3 are symmetrically formed along the axial direction on the outer shell of the pipeline assembly 3 area. The side fuel inlets 3-3 are connected to the upstream of the outer fuel channel 3-4. The premixed gas of natural gas and air enters the outer fuel channel 3-4 through the side fuel inlets 3-3 and then flows into the combustion chamber 4. In the above structure, the central partition structure, inner fuel channel 3-1, partition wall, outer fuel channel 3-4, and outer shell are arranged coaxially from the center outwards. The inner cyclone separator 3-2 and the outer cyclone separator 3-5 can deflect the mixed airflow into a rotating airflow. The inner and outer fuel channels of the pipeline assembly 3 are designed to optimize combustion performance through staged combustion: the inner fuel channel 3-1 converts the pre-decomposed ammonia products (NH3 / N2 / H2) into a high-speed rotating airflow through the inner cyclone separator 3-2 and injects it into the center of the combustion chamber 4. The high reactivity of hydrogen is used to quickly ignite the gas and stabilize the flame core. At the same time, the undecomposed ammonia gas inhibits the formation of NOx through the denitrification reaction. The outer fuel channel 3-4 introduces a premixed gas of natural gas and air through the side fuel inlet 3-3. The outer cyclone separator 3-5 forms a rotating airflow in the opposite direction on the periphery. Its design takes into account flame stability (extending the residence time in the wall recirculation zone), temperature field homogenization (diluting combustion to reduce local hot spots), and fuel flexibility (high-calorific-value natural gas to compensate for the insufficient energy of ammonia fuel). The two fuel streams are transported independently under the separation of the partition wall. At the inlet of the combustion chamber 4, they are controlled to mix through reverse swirling shear and turbulence. This results in a synergistic improvement in combustion efficiency, a reduction in pollutant emissions, and an assurance of the system's adaptability to multi-fuel conditions. It also enhances the mixing effect of different gas components, reduces local hot spots in the combustion chamber, and helps improve flame stability.

[0043] A deflector acoustic liner sound-absorbing structure 7 is arranged inside the combustion chamber 4 to attenuate pressure fluctuations within the combustion chamber 4, further reducing the risk of thermoacoustic vibration. The deflector acoustic liner sound-absorbing structure 7 includes: a secondary air inlet 7-1, a back cavity adjustment plate 7-2, a back cavity 7-3, and a bushing 7-4. The bushing 7-4 is coaxially arranged along the axial direction and has multiple non-uniform inclined holes along its axial direction. The hole diameter and hole spacing increase sequentially from upstream to downstream, and the perforation rate also increases sequentially. According to acoustic principles, a lower perforation rate is beneficial for absorbing low-frequency sound waves, while a higher perforation rate is beneficial for absorbing high-frequency sound waves. The cavity between the bushing 7-4 and the shell of the combustion chamber 4 is designated as the back cavity 7-3. Two layers of back cavity adjustment plates 7-2, both parallel to the axial direction, are installed within the back cavity 7-3. The area within the bushing 7-4 is the main combustion zone. Figure 2 As shown, the combustion chamber 4 has four secondary air inlets 7-1 evenly distributed around its shell and connected to the upstream of the combustion chamber 4. The secondary air inlets 7-1 are tangential inlets used to supply the combustion chamber 4 with the secondary air (air or oxygen) required for combustion. The gas introduced into two opposite secondary air inlets 7-1 is the same, that is, two are air and two are oxygen. The oxygen concentration in the secondary air can be adjusted by controlling the flow rate of air and oxygen.

[0044] An adjustable flaring ring 6 is provided at the inlet of the combustion chamber 4. Its swing angle is adjustable and it can extend and retract. Specifically, the adjustable flaring ring 6 includes a fixed section and an extension section. One end of the fixed section is rotatably connected to the shell of the combustion chamber 4, and this connection is close to the junction of the shell of the combustion chamber 4 and the outer shell of the pipe assembly 3 area. The other end of the fixed section is slidably connected to one end of the extension section, so that the extension section can slide relative to each other. The other end of the extension section contacts the bushing 7-4. By adjusting the swing angle and extension length of the adjustable flaring ring 6, the contact position between the adjustable flaring ring 6 and the bushing 7-4 can be controlled. When the contact position between the adjustable flared ring 6 and the bushing 7-4 is close to the inlet of the combustion chamber 4 (i.e., close to the upstream), the adjustable flared ring 6 is in a relatively short state. At this time, secondary air enters the combustion chamber 4 through the inclined holes opened on the larger area of ​​the bushing 7-4. When the contact position between the adjustable flared ring 6 and the bushing 7-4 is close to the outlet of the combustion chamber 4 (i.e., close to the downstream), the adjustable flared ring 6 is in a relatively long state. At this time, secondary air enters the combustion chamber through the inclined holes opened on the smaller area of ​​the bushing 7-4. The contact position between the adjustable flared ring 6 and the bushing 7-4 will change the perforation rate of the deflector acoustic liner sound-absorbing structure 7. Based on acoustic principles, a lower perforation rate when the contact position is closer to the upstream is beneficial for suppressing low-frequency thermoacoustic vibrations; a higher perforation rate when the contact position is closer to the downstream is beneficial for suppressing high-frequency thermoacoustic vibrations.

[0045] At the tail of the combustion chamber 4, a variable cross-sectional area flow channel 9 is fixedly connected, serving as the outlet flow channel of the combustion chamber 4. At the tail of the variable cross-sectional area flow channel 9, a burner outlet 11 is fixedly connected, and an NOx sensor 8 is arranged on its outer periphery for monitoring NOx. A control screw 10 is arranged outside the variable cross-sectional area flow channel 9 for adjusting the cross-sectional area of the outlet flow channel of the combustion chamber 4, thereby changing the acoustic reflection coefficient downstream of the combustion chamber 4. When the fuel composition in the burner changes, the acoustic reflection performance downstream of the combustion chamber 4 can be adjusted by adjusting the control screw 10, thereby alleviating the risk of thermoacoustic vibration. A pressure sensor 12 is arranged on the outer wall surface downstream of the combustion chamber 4 for monitoring the pressure at different positions.

[0046] The controller 5 is fixed outside the housing of the combustion chamber 4 and is electrically connected to the adjustable flare ring 6, the back cavity adjusting plate 7-2, and the control screw 10 for linkage control. The pressure pulsation (corresponding to the thermoacoustic vibration frequency) in the combustion chamber 4 and the NOx emissions monitored in real time by the NOx sensor 8, which are monitored in real time by the pressure sensor 12, are used as the input signals of the controller 5. The controller 5 intelligently adjusts the adjustable flare ring 6, the back cavity adjusting plate 7-2, and the control screw 10 in real time according to the input signals, specifically as follows:

[0047] (1) The controller 5 changes the contact position between the adjustable flare ring 6 and the bushing 7-4 by controlling the swing angle and telescopic length of the adjustable flare ring 6, thereby changing the perforation rate of the offset flow acoustic liner absorption structure 7, and thus changing the absorption frequency and absorption performance of the offset flow acoustic liner absorption structure 7, controlling the thermoacoustic vibration at different frequencies, and at the same time optimizing the airflow distribution entering the combustion chamber 4 and the distribution of the external recirculation zone in the combustion chamber 4. Combining with the acoustic principle, when the contact position between the adjustable flare ring 6 and the bushing 7-4 is close to the upstream, the perforation rate is low, which is beneficial to suppressing low-frequency thermoacoustic vibration; when the contact position is close to the downstream, the perforation rate is high, which is beneficial to suppressing high-frequency thermoacoustic vibration.

[0048] (2) The controller 5 adjusts the opening degree of the back cavity adjusting plate 7-2 to adjust the structural parameters of the back cavity 7-3; according to the acoustic principle of the resonant absorption structure, the volume of the back cavity 7-3 is inversely proportional to the absorption frequency. Increasing the volume of the back cavity 7-3 will reduce the elastic stiffness of the air, resulting in a decrease in the absorption frequency, and vice versa, a decrease in volume will increase the absorption frequency; therefore, when the thermoacoustic vibration frequency changes, the volume of the back cavity can be adjusted by the back cavity adjusting plate 7-2, so that the optimal absorption frequency of the offset flow acoustic liner absorption structure 7 is consistent with the thermoacoustic vibration frequency generated during the operation of the burner, thereby controlling the thermoacoustic vibration to the greatest extent. As an embodiment, when the pressure sensor 12 feeds back an oscillating pressure below 100 Hz, the controller 5 adjusts the back cavity adjusting plate 7-2 to Figure 3State A is shown; when the pressure sensor 12 reports an oscillating pressure of 100-1000Hz, the controller 5 adjusts the back cavity adjustment plate 7-2 to state B; when the pressure sensor 12 reports an oscillating pressure greater than 1000Hz, the controller 5 adjusts the back cavity adjustment plate 7-2 to state C.

[0049] (3) The controller 5 changes the cross-sectional area of ​​the variable cross-sectional area flow channel 9 by adjusting the control screw 10, thereby changing the acoustic reflection coefficient downstream of the combustion chamber 4. The adjustment of the acoustic reflection coefficient changes the phase difference between the sound pressure and the heat release of the flame in the combustion chamber 4. When the amplitude of the oscillation pressure detected by the pressure sensor 12 increases, the acoustic reflection coefficient is reduced by expanding the outlet flow channel area of ​​the combustion chamber 4, thereby reducing the accumulation of sound energy in the combustion chamber 4 and alleviating thermoacoustic vibration. When the burner causes thermoacoustic vibration due to changes in fuel composition or air distribution, the control screw 10 responds quickly to changes in the combustion process based on the feedback signal measured by the pressure sensor 12. By dynamically adjusting the cross-sectional area of ​​the variable cross-sectional area flow channel 9, the acoustic reflection coefficient downstream of the combustion chamber 4 is optimized, thereby alleviating the risk of thermoacoustic vibration during operation under conditions such as changing fuel and changing load. As an example, if the initial state of the variable cross-sectional area flow channel 9 is as follows: Figure 4 As shown in state 1, when the pressure amplitude fed back by pressure sensor 12 increases, the control screw 10 can be adjusted to change the variable cross-sectional area flow channel 9 to state 2, thereby controlling the thermoacoustic vibration.

[0050] The low-NOx, vibration-damping natural gas ammonia-blended burner proposed in this invention ensures high combustion efficiency, low emissions, and stability through close cooperation and synergy, while effectively suppressing thermoacoustic vibration and optimizing the overall performance of the combustion process.

[0051] Based on the aforementioned low-NOx vibration-damping ammonia-blended natural gas burner, this embodiment also proposes a low-NOx vibration-damping ammonia-blended natural gas combustion method, comprising the following steps:

[0052] S1: Arrange the low-NOx, vibration-damping natural gas ammonia-blended burner according to the above requirements, and start the controller 5, pressure sensor 12, and NOx sensor 8.

[0053] S2: Pretreated ammonia is introduced into the burner from the central fuel inlet 1. Part of the ammonia is decomposed into hydrogen and nitrogen in the plasma pre-decomposition zone 2 and then enters the inner stage fuel channel 3-1. It then flows through the inner stage cyclone separator 3-2 and enters the combustion chamber 4. The plasma pre-decomposition operation can effectively regulate the composition of the combustion gas, reduce the direct contact between ammonia and air, and effectively reduce the formation of NOx.

[0054] S3: The premixed gas of natural gas and air is introduced into the outer fuel flow channel 3-4 through the side fuel inlet 3-3, and then the premixed gas of natural gas and air flows through the outer cyclone separator 3-5 into the combustion chamber 4. The inner cyclone separator 3-2 and the outer cyclone separator 3-5 can deflect the mixed gas flow into a rotating gas flow, enhance the mixing effect of different component gases, reduce local hot spots of the flame in the combustion chamber 4, and at the same time help improve the stability of the flame.

[0055] S4: Secondary air is tangentially introduced into combustion chamber 4 from secondary air inlet 7-1 to provide the secondary air required for combustion. The gas after combustion is discharged from the burner through variable cross-sectional area flow channel 9 and burner outlet 11 in sequence.

[0056] During the S2-S4 process, the pressure sensor 12 monitors the thermoacoustic vibration frequency in the combustion chamber 4 in real time, and the NOx sensor 8 monitors the NOx emission of the burner in real time. The monitored data are fed back to the controller 5. The controller 5 intelligently adjusts the swing angle and extension length of the adjustable flare ring 6, the opening of the back cavity adjustment plate 7-2, and the control screw 10 in real time according to the input signal, thereby achieving the purpose of mitigating thermoacoustic vibration and reducing NOx emissions.

[0057] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A low-nitrogen anti-vibration ammonia-doped natural gas combustor, characterized by, It comprises: a central fuel inlet, a plasma pre-decomposition zone, a pipeline assembly, a combustion chamber, a variable cross-section flow channel, a burner outlet, and a controller, an adjustable flared ring, a bias flow acoustic lining sound absorption structure, a control screw, a NOx sensor, and a pressure sensor, which are arranged coaxially in sequence; the central fuel inlet is used for feeding ammonia gas, the plasma pre-decomposition zone is used for decomposing part of the ammonia gas into nitrogen and hydrogen, the pipeline assembly has two-stage fuel passages, an inner-stage fuel passage is used for guiding the gas output by the plasma pre-decomposition zone to the combustion chamber through a cyclone, and an outer-stage fuel passage is used for introducing a mixture of natural gas and air and guiding the mixture to the combustion chamber through a reverse cyclone; In the flow direction of the gas, the point close to the starting point is recorded as upstream, and vice versa as downstream; The plasma pre-decomposition zone comprises a central electrode, two outer electrodes, and two high-voltage electrodes; the central electrode is arranged at the center, the two outer electrodes are symmetrically arranged on the two sides of the central electrode, and the two high-voltage electrodes are symmetrically arranged outside the outer electrodes with the central electrode as the center and are fixed on the outer shell of the region; a grid structure is arranged between each stage of electrodes, and a catalyst is arranged inside the grid to promote the decomposition of ammonia gas; The bias flow acoustic lining sound absorption structure is arranged inside the combustion chamber and comprises a secondary air inlet, a back cavity adjusting plate, a back cavity, and a lining; the lining is arranged coaxially along the axial direction of the combustion chamber, a plurality of non-uniform inclined holes are formed on the lining along the axial direction, and the hole diameter and the hole spacing increase from upstream to downstream; the cavity between the lining and the combustion chamber shell is the back cavity, a back cavity adjusting plate is arranged in the back cavity to adjust the volume of the back cavity, and a plurality of secondary air inlets are formed on the upstream part of the combustion chamber shell; An adjustable flared ring with adjustable swing angle and telescopic function is arranged at the inlet of the combustion chamber, and the movable end of the adjustable flared ring is in contact with the lining; a variable cross-section flow channel is in communication with the downstream of the combustion chamber, and the tail of the variable cross-section flow channel is fixedly connected with a burner outlet; a control screw is arranged outside the variable cross-section flow channel to control the cross-sectional area of the variable cross-section flow channel; a NOx sensor is arranged at the burner outlet, and a pressure sensor is arranged on the outer wall surface of the downstream of the combustion chamber; and the controller is used for receiving the monitoring data of the NOx sensor and the pressure sensor in real time and controlling the swing angle and telescopic adjustment of the adjustable flared ring, the opening of the back cavity adjusting plate, and the control screw according to the monitoring data.

2. The low NO ammonia-doped natural gas burner of claim 1, wherein, The pipeline assembly comprises a central separation structure, an inner-stage fuel passage, a separation wall, an outer-stage fuel passage, and a pipeline assembly outer shell, which are arranged coaxially from the center outward in sequence, and a side fuel inlet, an inner-stage cyclone, and an outer-stage cyclone; The separation wall forms a trumpet-like structure with a flared end, a constant inner diameter in the middle, and a tapered end, the flared end of the separation wall is fixedly connected with the outer shell of the plasma pre-decomposition zone, the tapered end is located at the inlet of the combustion chamber, and the central separation structure is arranged at the center of the constant inner diameter region to form an annular passage in the separation wall, and the annular passage is the inner-stage fuel passage; the inner-stage fuel passage is in communication with the plasma pre-decomposition zone and the combustion chamber, and the inner-stage cyclone is arranged in the inner-stage fuel passage. The annular passage between the partition wall and the pipeline assembly outer shell is an outer stage fuel passage; a plurality of side fuel inlets are symmetrically formed on the pipeline assembly outer shell along the axis for introducing premixed gas of natural gas and air, the upstream of the outer stage fuel passage is communicated with the side fuel inlets, the downstream of the outer stage fuel passage is communicated with the combustion chamber, and the outer stage fuel passage is arranged with an outer stage swirler at a position close to the downstream.

3. The low NO ammonia-doped natural gas burner of claim 1, wherein, Four tangential secondary air inlets are uniformly formed on the combustion chamber shell in the circumferential direction, so that the secondary air enters the combustion chamber tangentially; the gases introduced through the opposite two secondary air inlets are the same, and the flow rate can be adjusted; air is introduced through two opposite secondary air inlets, and oxygen is introduced through the other two opposite secondary air inlets.

4. The low NO ammonia-doped natural gas burner of claim 1, wherein, The adjustable flared ring includes a fixed section and an expansion section, one end of the fixed section is rotationally connected with the combustion chamber shell, and the connection position is close to the junction of the combustion chamber shell and the pipeline assembly outer shell; the other end of the fixed section is slidingly connected with one end of the expansion section, so that the expansion section can slide relatively, and the other end of the expansion section is in contact with the bushing; the swing angle and the expansion length of the adjustable flared ring are adjusted, so that the contact position of the adjustable flared ring and the bushing is changed.

5. The low NO ammonia-doped natural gas burner of claim 1, wherein, The inlet pretreatment system is arranged in front of the central fuel inlet, which is used for filtering impurities in the ammonia gas and adjusting the flow rate, so that the concentration and flow rate of the ammonia gas entering the central fuel inlet meet the requirements.

6. A low-nitrogen anti-vibration ammonia-doped natural gas combustion method realized based on the low-nitrogen anti-vibration ammonia-doped natural gas burner of any one of claims 1-5, characterized in that, The method comprises the following steps: S1: arranging the low-nitrogen anti-vibration natural gas ammonia-doped burner, starting the controller, the pressure sensor and the NOx sensor; S2: introducing ammonia gas into the burner from the central fuel inlet, part of the ammonia gas is decomposed into hydrogen and nitrogen in the plasma pre-decomposition zone, and then flows into the pipeline assembly; S3: introducing a mixture of natural gas and air into the pipeline assembly, and the swirler in the pipeline assembly deflects the gas flow and the gas output by the plasma pre-decomposition zone into a rotating gas flow, thereby enhancing the mixing effect of different component gases, and then inputting into the combustion chamber; S4: introducing secondary air tangentially into the combustion chamber from the secondary air inlet to provide secondary air required for combustion, and the gas after combustion is discharged from the burner in turn through the variable cross-section flow channel and the burner outlet; In the process of S2-S4, the pressure sensor monitors the thermal-acoustic vibration frequency in the combustion chamber in real time, the NOx sensor monitors the NOx emission of the burner in real time, and the monitored data are fed back to the controller, respectively, the controller adjusts the swing angle and expansion length of the adjustable flared ring, the opening of the back cavity adjusting plate, and the control screw according to the monitored data, so as to relieve the thermal-acoustic vibration and reduce the NOx emission.

7. The low-nitrogen anti-vibration ammonia-doped natural gas combustion method according to claim 6, characterized by, The controller controls the swing angle and expansion length of the adjustable flared ring, changes the contact position of the adjustable flared ring and the bushing, and then changes the perforation rate of the bias flow sound absorption structure, so as to change the sound absorption frequency and sound absorption performance of the bias flow sound absorption structure, control the thermal-acoustic vibration at different frequencies, and optimize the gas flow distribution into the combustion chamber; when the contact position of the adjustable flared ring and the bushing is close to the upstream, the perforation rate is low, which is beneficial to suppress the low-frequency thermal-acoustic vibration; When the contact position is close to the downstream, the perforation rate is high, which is beneficial to suppress the high-frequency thermal-acoustic vibration.

8. The low-nitrogen anti-vibration ammonia-doped natural gas combustion method according to claim 6, characterized by, The controller controls the opening of the back cavity adjusting plate, according to the acoustic principle of the resonant sound absorption structure, the volume of the back cavity is inversely proportional to the sound absorption frequency, when the thermal acoustic vibration frequency changes, the volume of the back cavity is adjusted through the back cavity adjusting plate, so that the optimal sound absorption frequency of the bias flow sound absorption structure is consistent with the thermal acoustic vibration frequency generated by the operation of the burner, thereby controlling the thermal acoustic vibration.

9. The low-nitrogen anti-vibration ammonia-doped natural gas combustion method according to claim 6, characterized by, The controller adjusts the control screw to change the cross-sectional area of the variable cross-sectional area flow channel, thereby changing the acoustic reflection coefficient downstream of the combustion chamber, and further changing the phase difference between the sound pressure in the combustion chamber and the flame heat release; When the oscillating pressure amplitude detected by the pressure sensor increases, the control screw is adjusted to expand the cross-sectional area of the variable cross-sectional area flow channel, reduce the acoustic reflection coefficient, reduce the accumulation of acoustic energy in the combustion chamber, and relieve the thermal acoustic vibration; otherwise, the control screw is adjusted to reduce the cross-sectional area of the variable cross-sectional area flow channel.

Images