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

Abstract

The low-nitrogen vibration-proof natural gas ammonia-doped combustor is characterized in that after being introduced into a central fuel inlet, ammonia is partially decomposed into nitrogen and hydrogen through a plasma pre-decomposition area, and the nitrogen and the hydrogen are input into a combustion chamber together with a mixture of natural gas and air through a pipeline assembly; a lining is coaxially arranged in the combustion chamber, a cavity between the lining and the 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, and a plurality of secondary air inlets are formed in the combustion chamber shell; a swinging and telescopic adjustable flaring ring is arranged at an inlet of the combustion chamber, and one end of the adjustable flaring ring is in contact with the lining; the control screw is arranged outside the variable-sectional-area flow channel and controls the sectional area of the variable-sectional-area flow channel; an NOx sensor is arranged at an outlet of the combustor, and a pressure sensor is arranged on the downstream outer wall surface; the controller receives data of the two sensors and controls the adjustable flaring ring, the back cavity adjusting plate and the control screw. According to the invention, high efficiency, low emission and stability of combustion are ensured, and thermo-acoustic vibration is effectively inhibited at the same time.

Description

Technical Field

[0001] The present invention relates to the field of combustion technology, and particularly to a natural gas-ammonia blended burner with low nitrogen and anti-vibration performance. Background Art

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

[0003] During the combustion process, especially under high load or complex operating conditions, the burner may exhibit unstable combustion phenomena, such as unstable flames, local overheating, or oxygen deficiency. These problems not only lead to a decrease in combustion efficiency but also increase the equipment maintenance cost and operating risk. Common causes of unstable combustion include factors such as uneven fuel-air mixing, unstable airflows, and burner design defects.

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

[0005] Thermoacoustic vibration is a high-frequency sound wave or vibration phenomenon generated during the combustion process due to the interaction of temperature, airflow, and pressure fluctuations. This vibration not only affects the stability and safety of the burner but may 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 airflows, incomplete combustion, or local overheating.

[0006] Although some existing combustion technologies have improved the combustion efficiency and stability to a certain extent by means of improving the airflow path and optimizing the mixing of air and fuel, it is still difficult to simultaneously achieve multiple objectives such as reducing NOx emissions, suppressing thermoacoustic vibrations, and improving combustion efficiency. Especially in high-efficiency and energy-saving industrial systems, the existing technologies have not been able to effectively solve these comprehensive problems. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the present invention proposes a natural gas-ammonia blended burner with low nitrogen and anti-vibration performance, which can reduce carbon emissions during the combustion process, and can regulate the pressure fluctuations during the combustion process, and can more intelligently improve the combustion stability and combustion efficiency while reducing NOx emissions.

[0008] The specific technical solutions are as follows:

[0009] A low-nitrogen anti-vibration natural gas-ammonia blended burner, comprising: a central fuel inlet, a plasma pre-decomposition zone, a pipeline assembly, a combustion chamber, a variable cross-sectional area flow channel, a burner outlet, which are arranged coaxially in sequence, and a controller, an adjustable flare ring, a bias flow acoustic lining sound absorption structure, a control screw, a NOx sensor, a pressure sensor, and a controller; the central fuel inlet is used for introducing ammonia gas, and 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 channels, the inner-stage fuel channel is used for guiding the gas output from the plasma pre-decomposition zone to the combustion chamber through a swirler, and the outer-stage fuel channel is used for introducing a mixture of natural gas and air and guiding it to the combustion chamber through a reverse swirler; in the gas flow direction, the part close to the starting point is denoted as the upstream, and the opposite is the downstream;

[0010] The plasma pre-decomposition zone includes: a central ground electrode, an outer ground electrode, and a high-voltage electrode; 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 area; 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;

[0011] The bias flow acoustic lining sound absorption structure is arranged inside the combustion chamber, and includes: a secondary air inlet, a back cavity adjusting plate, a back cavity, and a bushing; the bushing is arranged coaxially along the axial direction of the combustion chamber, and a plurality of non-uniformly inclined holes are axially opened thereon, and the hole diameter and hole spacing increase sequentially from the upstream to the downstream; the cavity between the bushing and the combustion chamber outer shell is the back cavity, and a back cavity adjusting plate is arranged in the back cavity to adjust the volume of the back cavity, and several secondary air inlets are opened in the upstream part of the combustion chamber outer shell;

[0012] An adjustable flare ring with an adjustable swing angle and telescopic function is arranged at the entrance of the combustion chamber, and the movable end of the adjustable flare ring contacts the bushing; the variable cross-sectional area flow channel is communicated with the downstream of the combustion chamber, and its tail is fixedly connected with the burner outlet; the control screw is arranged outside the variable cross-sectional area flow channel to control its cross-sectional area size; 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; 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 flare ring, the opening degree of the back cavity adjusting plate, and the control screw according to the monitoring data.

[0013] Further, the pipeline assembly includes: a central partition structure, an inner-stage fuel channel, a partition wall, an outer-stage fuel channel, an outer shell of the pipeline assembly, which are arranged coaxially from the center to the outside in sequence, and a side fuel inlet, an inner-stage swirler, and an outer-stage swirler;

[0014] The partition wall forms a horn-like structure with one end flared, the inner diameter unchanged in the middle, and one end constricted. The flared end is fixedly connected to the outer shell of the plasma pre-decomposition zone, the constricted end is located at the entrance of the combustion chamber, and a central partition structure is arranged at the axis of the region with the unchanged inner diameter in the middle, so as to form an annular channel inside the partition wall, and 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 swirler is arranged therein.

[0015] The annular channel between the partition wall and the outer shell of the pipeline assembly is the outer-stage fuel channel; a plurality of side fuel inlets are symmetrically arranged along the axis on the outer shell of the pipeline assembly for introducing the premixed gas of natural gas and air. The upstream of the outer-stage fuel channel is connected to the side fuel inlets, and the downstream is connected to the combustion chamber. An outer-stage swirler is arranged at a position close to the downstream in the outer-stage fuel channel; the swirling directions of the inner-stage swirler and the outer-stage swirler are opposite.

[0016] Further, four tangential secondary air inlets are evenly arranged circumferentially on the combustion chamber shell, so that the secondary air enters the combustion chamber tangentially; the gases introduced into the two opposite secondary air inlets are the same, and the flow rate can be adjusted; air is introduced into two of the opposite secondary air inlets, and oxygen is introduced into the other two opposite secondary air inlets.

[0017] Further, the adjustable flared 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 pipeline assembly; the other end of the fixed section is slidably connected to one end of the telescopic section, so that the telescopic section can slide relatively, and the other end of the telescopic section contacts the bushing; the swing angle and the telescopic length of the adjustable flared ring are adjusted, so as to change the contact position between the adjustable flared ring and the bushing.

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

[0019] A low-nitrogen and anti-vibration natural gas ammonia-doping combustion method is realized based on the low-nitrogen and anti-vibration natural gas ammonia-doping burner, and includes the following steps:

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

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

[0022] S3: Feed the mixture of natural gas and air into the pipeline assembly. The swirler in the pipeline assembly deflects the mixture gas flow and the gas output from the plasma pre-decomposition zone into a swirling flow, enhancing the mixing effect of different component gases, and then input it into the combustion chamber;

[0023] S4: Tangentially feed the secondary air into the combustion chamber from the secondary air inlet to provide the secondary air required for combustion. The combustion gas sequentially passes through the variable cross-sectional area flow channel and the burner outlet and discharges from the burner;

[0024] During the process of S2 - S4, the pressure sensor real-time monitors the thermoacoustic vibration frequency in the combustion chamber, and the NOx sensor real-time monitors the NOx emission of the burner, and respectively feeds back the monitored data to the controller. The controller adjusts the swing angle and telescopic length of the adjustable flare ring, the opening degree of the back cavity adjusting plate, and the control screw according to the monitored data, thereby alleviating the thermoacoustic vibration and reducing the NOx emission.

[0025] Furthermore, the controller controls the swing angle and telescopic length of the adjustable flare ring, changes the contact position between the adjustable flare ring and the bushing, and further changes the perforation rate of the bypass acoustic liner sound absorption structure, thereby changing the sound absorption frequency and sound absorption performance of the bypass acoustic liner sound absorption structure, controlling the thermoacoustic vibration at different frequencies, and simultaneously optimizing the air flow distribution entering the combustion chamber; when the contact position between the adjustable flare ring and the bushing is close to the upstream, the perforation rate is lower, which is beneficial to suppressing the low-frequency thermoacoustic vibration; when the contact position is close to the downstream, the perforation rate is higher, which is beneficial to suppressing the high-frequency thermoacoustic vibration.

[0026] Furthermore, the controller controls the opening degree of the back cavity adjusting plate. According to the acoustic principle of the resonance 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 through the back cavity adjusting plate, so that the optimal sound absorption frequency of the bypass acoustic liner sound absorption structure is consistent with the thermoacoustic vibration frequency generated during the operation of the burner, 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 further changing the phase difference between the sound pressure in the combustion chamber and the heat release of the flame;

[0028] When the oscillation pressure amplitude detected by the pressure sensor increases, adjust the control screw to expand the cross-sectional area of the variable cross-sectional area flow channel, reduce the acoustic reflection coefficient, reduce the sound energy accumulation in the combustion chamber, and alleviate the thermoacoustic vibration; otherwise, adjust the control screw to narrow the cross-sectional area of the variable cross-sectional area flow channel.

[0029] The beneficial effects of the present invention are:

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

[0031] (2)Optimize combustion efficiency: The present invention optimizes the air flow distribution entering the combustion chamber through a swirler, an adjustable flare ring, a bushing, and a back cavity adjusting plate, enabling more uniform mixing of fuel and air, reducing local hot spots, and improving combustion efficiency; the design of the adjustable flare ring also optimizes the distribution of the external recirculation zone in the combustion chamber, enhancing combustion performance.

[0032] (3)Reduce NOx emissions: Part of the ammonia is decomposed into nitrogen and hydrogen through the plasma pre-decomposition zone, optimizing the combustion gas composition, and staged combustion is achieved through a pipeline assembly and secondary air, improving combustion stability and effectively reducing the NOx emissions of natural gas blended with ammonia combustion. Description of the Drawings

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

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

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

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

[0037] In the figure, central fuel inlet 1, plasma pre-decomposition zone 2, central ground electrode 2-1, outer ground electrode 2-2, high-voltage electrode 2-3; pipeline assembly 3, inner-stage fuel channel 3-1, inner-stage swirler 3-2, side fuel inlet 3-3, outer-stage fuel channel 3-4, outer-stage swirler 3-5; combustion chamber 4, controller 5, adjustable flare ring 6; bias flow acoustic lining sound absorption structure 7, secondary air inlet 7-1, back cavity adjusting plate 7-2, back cavity 7-3, bushing 7-4; NOx sensor 8, variable cross-sectional area flow channel 9, control screw 10, burner outlet 11, pressure sensor 12. Detailed Embodiments

[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 more apparent. The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] As Figure 1 shown, a low-nitrogen anti-vibration 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 flare ring 6, a bias flow acoustic liner sound absorption 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, the plasma pre-decomposition zone 2, the pipe assembly 3, the combustion chamber 4, the variable cross-sectional area flow channel 9, and the burner outlet 11 are arranged coaxially in sequence, and a housing is uniformly arranged outside. After passing through the inlet pretreatment system, the combustion gas enters the burner from the central fuel inlet 1, and the combustion gas is ammonia. The inlet pretreatment system adopts an existing system to filter impurities in ammonia and adjust its flow rate to ensure that the ammonia concentration and flow rate entering the burner meet the set requirements, so as to ensure the stability of the decomposition reaction in the subsequent plasma pre-decomposition zone 2. In the main flow direction of the combustion gas, the part close to the starting point is recorded as the upstream, and vice versa as the downstream.

[0041] The plasma pre-decomposition zone 2 is used to decompose ammonia introduced from the central fuel inlet 1 by using high-energy plasma, pre-decompose part of the ammonia into hydrogen and nitrogen, optimize the combustion gas composition, thereby improving the combustion efficiency, reducing NOx emissions, and effectively controlling the thermoacoustic vibration during the combustion process. The plasma pre-decomposition zone 2 includes: a central ground electrode 2-1, an outer ground electrode 2-2, and a high-voltage electrode 2-3. The central ground electrode 2-1 is arranged at the center of the plasma pre-decomposition zone 2, and two outer ground electrodes 2-2 are symmetrically arranged on both sides of the central ground electrode 2-1; two high-voltage electrodes 2-3 are also symmetrically arranged on both sides of the central ground electrode 2-1 and are located outside the outer ground electrode 2-2 and fixed on the outer housing of this area; a grid structure is arranged between each electrode, and a catalyst is arranged inside the grid to promote ammonia decomposition. The principle of each electrode cooperating to achieve ammonia decomposition is: the central ground electrode 2-1 serves as the core electrode of the reaction zone, responsible for exciting ammonia molecules and generating a preliminary electric field; the outer ground electrode 2-2 is opposite to the central ground electrode 2-1 to form a strong electric field effect. Ammonia molecules are collided by high-energy electrons in this electric field, resulting in ionization and dissociation, generating a large number of free radicals and ions, forming a plasma; the high-voltage electrode 2-3 further accelerates the movement of electrons by providing a high voltage, increases the collision frequency, enhances the ammonia decomposition effect, and improves the reaction rate.

[0042] The nitrogen and ammonia generated by the decomposition of ammonia are guided into the combustion chamber 4 through the pipeline assembly 3. The pipeline assembly 3 includes: an inner-stage fuel channel 3-1, an inner-stage swirler 3-2, a partition wall, a side fuel inlet 3-3, an outer-stage fuel channel 3-4, and an outer-stage swirler 3-5. The partition wall forms a trumpet-shaped structure with one end flared, the inner diameter unchanged in the middle, and one end constricted. The flared end is fixedly connected to the outer shell of the plasma pre-decomposition zone 2, the constricted end is located at the entrance of the combustion chamber 4, and a central partition structure is arranged at the axis of the region with the unchanged 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 swirler 3-2 is arranged therein. The annular channel between the partition wall and the outer shell of the pipeline assembly 3 region is the outer-stage fuel channel 3-4, and the outer-stage swirler 3-5 is arranged at a position close to the downstream in the outer-stage fuel channel 3-4. The swirling directions of the inner-stage swirler 3-2 and the outer-stage swirler 3-5 are opposite. Two side fuel inlets 3-3 are symmetrically arranged along the axis on the outer shell of the pipeline assembly 3 region. The side fuel inlets 3-3 are connected to the upstream of the outer-stage fuel channel 3-4, and the premixed gas of natural gas and air is input into the outer-stage fuel channel 3-4 through the side fuel inlets 3-3 and then introduced into the combustion chamber 4. In the above structure, the central partition structure, the inner-stage fuel channel 3-1, the partition wall, the outer-stage fuel channel 3-4, and the outer shell are coaxially arranged in sequence from the center to the outside. The inner-stage swirler 3-2 and the outer-stage swirler 3-5 can deflect the mixture gas flow into a swirling gas flow. The design of the inner and outer-stage fuel channels of the pipeline assembly 3 optimizes the combustion performance through staged combustion: the inner-stage fuel channel 3-1 converts the pre-decomposed ammonia product (NH 3 / N 2 / H 2 ) into a high-speed swirling gas flow and injects it into the center of the combustion chamber 4, and uses the high reactivity of hydrogen to quickly ignite to stabilize the flame core. At the same time, the undecomposed ammonia inhibits the generation of NOx through the denitrification reaction; the outer-stage fuel channel 3-4 introduces the premixed gas of natural gas and air through the side fuel inlet 3-3, and forms a peripheral reverse swirling gas flow through the outer-stage swirler 3-5. Its design takes into account flame stability (the wall recirculation zone extends the residence time), temperature field uniformity (diluted combustion reduces local hot spots), and fuel flexibility (high calorific value natural gas makes up for the energy shortage of ammonia fuel). The two fuel flows are independently transported under the isolation of the partition wall, and achieve controllable mixing through reverse swirl shear and turbulence at the entrance of the combustion chamber 4. Finally, they synergistically improve the combustion efficiency, reduce pollutant emissions, and ensure the adaptability of the system to multi-fuel conditions; enhance the mixing effect of different component gases, reduce the local hot spots of the flame in the combustion chamber, and at the same time contribute to improving the flame stability.

[0043] A bias flow acoustic lining sound absorption structure 7 is arranged in the combustion chamber 4, which can attenuate the pressure fluctuations in the combustion chamber 4 and further reduce the risk of thermoacoustic vibration. The bias flow acoustic lining sound absorption structure 7 includes: a secondary air inlet 7-1, a back cavity adjusting plate 7-2, a back cavity 7-3, and a bushing 7-4. Among them, the bushing 7-4 is arranged coaxially along the axis, and a plurality of non-uniformly inclined holes are axially formed thereon, and the hole diameter and hole pitch increase sequentially from upstream to downstream, and the perforation rate increases sequentially; according to the acoustic principle, when the perforation rate is low, it is beneficial to absorb low-frequency sound waves, and when the perforation rate is high, it is beneficial to absorb high-frequency sound waves. The cavity between the bushing 7-4 and the housing of the combustion chamber 4 is denoted as the back cavity 7-3, and two layers of back cavity adjusting plates 7-2 parallel to the axis are arranged in the back cavity 7-3; the area inside the bushing 7-4 is the main combustion area. As Figure 2 shown, four secondary air inlets 7-1 are circumferentially and evenly formed on the housing of the combustion chamber 4 and communicate with the upstream of the combustion chamber 4. The secondary air inlets 7-1 adopt tangential inlets and are used to provide the secondary air (air or oxygen) required for combustion to the combustion chamber 4. The gases introduced into the two relatively secondary air inlets 7-1 are the same, that is, two inlets introduce air and two inlets introduce oxygen, and the oxygen concentration in the secondary air can be adjusted by controlling the flow rates of air and oxygen.

[0044] An adjustable flare ring 6 is arranged at the inlet of the combustion chamber 4, and its swing angle is adjustable and telescopic can be realized. Specifically, the adjustable flare ring 6 includes a fixed section and a telescopic section. One end of the fixed section is rotatably connected to the housing of the combustion chamber 4, and the connection is close to the junction of the housing of the combustion chamber 4 and the outer housing of the pipe assembly 3 area; the other end of the fixed section is slidably connected to one end of the telescopic section, so that the telescopic section can perform relative sliding, and the other end of the telescopic section contacts the bushing 7-4. By adjusting the swing angle and telescopic length of the adjustable flare ring 6, the contact position between the adjustable flare ring 6 and the bushing 7-4 can be controlled. When the contact position between the adjustable flare 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 flare ring 6 is in a relatively short state. At this time, the secondary air enters the combustion chamber 4 through the inclined holes formed on the bushing 7-4 with a larger area; when the contact position between the adjustable flare 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 flare ring 6 is in a relatively long state. At this time, the secondary air enters the combustion chamber through the inclined holes formed on the bushing 7-4 with a smaller area. The contact position between the adjustable flare ring 6 and the bushing 7-4 will change the perforation rate of the bias flow acoustic lining sound absorption structure 7. Combining with the acoustic principle, the perforation rate is lower when the contact position is close to the upstream, which is beneficial to suppressing low-frequency thermoacoustic vibration; the perforation rate is higher when the contact position is close to the downstream, which is beneficial to suppressing high-frequency thermoacoustic vibration.

[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 to adjust 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 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, 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 bypass acoustic liner absorption structure 7, and then changing the absorption frequency and absorption performance of the bypass acoustic liner absorption structure 7 to control the thermoacoustic vibration at different frequencies. At the same time, the airflow distribution entering the combustion chamber 4 and the distribution of the external recirculation zone in the combustion chamber 4 are optimized. 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 the low-frequency thermoacoustic vibration; when the contact position is close to the downstream, the perforation rate is high, which is beneficial to suppressing the 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 resonance 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 bypass 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 3The state A shown; when the pressure sensor 12 feeds back an oscillating pressure of 100 - 1000 Hz, the controller 5 adjusts the back cavity adjusting plate 7-2 to state B; when the pressure sensor 12 feeds back an oscillating pressure greater than 1000 Hz, the controller 5 adjusts the back cavity adjusting 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 acoustic pressure and the flame heat release in the combustion chamber 4. When the amplitude of the oscillating 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, and the accumulation of acoustic energy in the combustion chamber 4 is reduced, thereby alleviating the thermoacoustic vibration. When the burner causes thermoacoustic vibration by changing the fuel composition or the air distribution method, etc., the control screw 10 quickly responds to the changes during the combustion process according to the feedback signal measured by the pressure sensor 12, and optimizes the acoustic reflection coefficient downstream of the combustion chamber 4 by dynamically adjusting the cross-sectional area of the variable cross-sectional area flow channel 9, thereby alleviating the risk of thermoacoustic vibration during operation under conditions such as variable fuel and variable load. As an embodiment, if the initial state of the variable cross-sectional area flow channel 9 is as Figure 4 shown in state 1, when the pressure amplitude fed back by the 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-nitrogen anti-vibration natural gas ammonia-blended burner proposed by the present invention ensures the high efficiency, low emissions and stability of combustion through close cooperation and coordination, while effectively suppressing thermoacoustic vibration and optimizing the overall performance of the combustion process.

[0051] Based on the above low-nitrogen anti-vibration natural gas ammonia-blended burner, this embodiment also proposes a low-nitrogen anti-vibration natural gas ammonia-blended combustion method, including the following steps:

[0052] S1: Arrange the low-nitrogen anti-vibration natural gas ammonia-blended burner as required above, and start the controller 5, the pressure sensor 12, and the NOx sensor 8.

[0053] S2: Feed the pretreated ammonia gas into the burner from the central fuel inlet 1. After part of the ammonia gas is decomposed into hydrogen and nitrogen in the plasma pre-decomposition zone 2, it enters the inner-stage fuel channel 3-1, and then flows through the inner-stage swirler 3-2 into the combustion chamber 4; the plasma pre-decomposition operation can effectively adjust the combustion gas composition, reduce the direct contact between ammonia and air, and effectively reduce the generation of NOx.

[0054] S3: Introduce the premixed gas of natural gas and air into the outer-stage 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-stage swirler 3-5 and enters the combustion chamber 4. The inner-stage swirler 3-2 and the outer-stage swirler 3-5 can deflect the mixture gas flow into a swirling flow, enhance the mixing effect of different component gases, reduce the local hot spots of the flame in the combustion chamber 4, and at the same time contribute to improving the flame stability.

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

[0056] During the process of S2-S4, the pressure sensor 12 monitors the thermoacoustic vibration frequency in the combustion chamber 4 in real time, the NOx sensor 8 monitors the NOx emission of the burner in real time, and respectively feeds the monitored data back to the controller 5. The controller 5 intelligently adjusts the swing angle and telescopic length of the adjustable flare ring 6, the opening degree of the back cavity adjusting plate 7-2, and the control screw 10 in real time according to the input signal, so as to achieve the purpose of alleviating thermoacoustic vibration and reducing NOx emission.

[0057] Those of ordinary skill in the art can understand that the above are only preferred examples of the invention and are not used to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, for those skilled in the art, they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the invention shall be included within the protection scope of the invention.

Claims

1. A low-nitrogen vibration-proof natural gas ammonia burner, characterized in that: include: A central fuel inlet, a plasma pre-decomposition zone, a pipeline assembly, a combustion chamber, a variable cross-sectional area flow channel, a burner outlet, a controller, an adjustable expansion ring, a bias flow sound liner sound absorption structure, a control screw, a NOx sensor, a pressure sensor, and a controller are coaxially arranged in sequence; the central fuel inlet is used to introduce ammonia, and the plasma pre-decomposition zone is used to decompose part of the ammonia into nitrogen and hydrogen; the pipeline assembly has two-stage fuel channels, the inner fuel channel is used to guide the gas output from the plasma pre-decomposition zone to the combustion chamber through a cyclone, and the outer fuel channel is used to introduce a mixture of natural gas and air and guide it to the combustion chamber through a reverse cyclone; In the flow direction of the gas, the one closer to the starting point is recorded as upstream, and the other closer is recorded as downstream; The plasma pre-decomposition zone comprises: a central ground electrode, an outer ground electrode, and a high-voltage electrode; the central ground electrode is arranged at 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 electrode with the central ground electrode as the center, and are fixed on the outer shell of the zone; a grid structure is arranged between each level of electrodes, and a catalyst is arranged inside the grid to promote the decomposition of ammonia; The deflection sound liner sound absorption 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 coaxially arranged along the axial direction of the combustion chamber, and a plurality of non-uniform inclined holes are opened on it along the axial direction, and the hole diameter and the hole spacing increase 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 arranged in the back cavity to adjust the back cavity volume, and a plurality of secondary air inlets are opened in the upstream part of the combustion chamber shell; An adjustable expanding ring with adjustable swing angle and telescopic function is provided at the inlet of the combustion chamber, and the movable end of the adjustable expanding ring is in contact with the bushing; the 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; the control screw is arranged outside the variable cross-sectional area flow channel for controlling the size of its cross-sectional area; a NOx sensor is provided at the burner outlet, and a pressure sensor is arranged on the outer wall surface downstream of the combustion chamber; the controller is used to receive the monitoring data of the NOx sensor and the pressure sensor in real time, and control the swing angle and telescopic adjustment of the adjustable expanding ring, the opening of the back cavity adjustment plate, and the control screw according to the monitoring data.

2. The low-nitrogen vibration-proof natural gas-ammonia burner according to claim 1 is characterized in that: The pipeline assembly comprises: a central partition structure, an inner fuel channel, a partition wall, an outer fuel channel, an outer shell of the pipeline assembly, a side fuel inlet, an inner swirler, and an outer swirler, which are coaxially arranged from the center to the outside; The partition wall is a trumpet-like structure with a flared end, a constant inner diameter in the middle, and a constricted end. The flared end is fixedly connected 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 arranged at the axis of the middle region with a constant inner diameter, so that an annular channel is formed inside the partition wall, and the annular channel is an inner-stage fuel channel. The inner-stage fuel channel connects the plasma pre-decomposition zone with the combustion chamber, and an inner-stage cyclone is arranged inside the inner-stage fuel channel. The annular channel between the partition wall and the outer shell of the pipeline assembly is an outer fuel channel; a plurality of side fuel inlets are symmetrically provided on the outer shell of the pipeline assembly along the axis for introducing premixed gas of natural gas and air; the upstream of the outer fuel channel is connected with the side fuel inlet, and the downstream is connected with the combustion chamber; an outer swirler is arranged near the downstream in the outer fuel channel; the swirling directions of the inner swirler and the outer swirler are opposite.

3. The low-nitrogen vibration-proof natural gas-ammonia burner according to claim 1 is characterized in that: The combustion chamber shell is evenly provided with four tangential secondary air inlets circumferentially, so that the secondary air enters the combustion chamber tangentially; the gases introduced into the two opposite secondary air inlets are the same, and the flow rates can be adjusted; two of the opposite secondary air inlets are introduced with air, and the other two are introduced with oxygen.

4. The low-nitrogen vibration-proof natural gas-ammonia burner according to claim 1 is characterized in that: The adjustable flaring ring includes a fixed section and a telescopic section, one end of the fixed section is rotatably connected to the combustion chamber outer shell, and the connection is close to the junction of the combustion chamber outer shell and the outer shell of the pipeline assembly; the other end of the fixed section is slidably connected to one end of the telescopic section, so that the telescopic section can slide relatively, and the other end of the telescopic section is in contact with the bushing; the swing angle and telescopic length of the adjustable flaring ring are adjusted to change the contact position of the adjustable flaring ring and the bushing.

5. The low-nitrogen vibration-proof natural gas-ammonia burner according to claim 1 is characterized in that: 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 concentration and flow rate of the ammonia entering the central fuel inlet meet the requirements.

6. A low-nitrogen vibration-proof natural gas ammonia combustion method, which is implemented based on the low-nitrogen vibration-proof natural gas ammonia burner according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Arrange the low-nitrogen vibration-proof natural gas-ammonia burner, and start the controller, pressure sensor, and NOx sensor; S2: Ammonia is introduced into the burner from the central fuel inlet, and part of the ammonia is decomposed into hydrogen and nitrogen in the plasma pre-decomposition zone and then flows into the pipeline assembly; S3: A mixture of natural gas and air is introduced into a pipeline assembly, and a cyclone in the pipeline assembly deflects the mixed gas flow and the gas output from the plasma pre-decomposition zone into a rotating gas flow, thereby enhancing the mixing effect of different component gases, and then inputs the mixed gas flow into the combustion chamber; S4: The secondary air is introduced into the combustion chamber tangentially from the secondary air inlet to provide the secondary air required for combustion, and the combusted gas is discharged from the burner through the variable cross-sectional area flow channel and the burner outlet in sequence; During the process of S2-S4, 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, and feeds back the monitored data to the controller respectively. The controller adjusts the swing angle and telescopic length of the adjustable expansion ring, the opening of the back cavity adjustment plate, and the control screw according to the monitored data, thereby alleviating thermoacoustic vibration and reducing NOx emissions.

7. The low-nitrogen vibration-proof natural gas ammonia combustion method according to claim 6, characterized in that: The controller controls the swing angle and telescopic length of the adjustable flaring ring, changes the contact position between the adjustable flaring ring and the bushing, and then changes the perforation rate of the bias flow sound liner sound absorption structure, thereby changing the sound absorption frequency and sound absorption performance of the bias flow sound liner sound absorption structure, controlling the thermoacoustic vibration at different frequencies, and optimizing the airflow distribution entering the combustion chamber; when the contact position between the adjustable flaring ring and the bushing is close to the upstream, the perforation rate is low, which is conducive to suppressing low-frequency thermoacoustic vibration; When the contact position is close to the downstream, the perforation rate is higher, which is beneficial to suppress high-frequency thermoacoustic vibrations.

8. The low-nitrogen vibration-proof natural gas ammonia combustion method according to claim 6, characterized in that: The controller controls the opening of the back cavity adjustment plate. According to the acoustic principle of the resonant sound-absorbing structure, the volume of the back cavity is inversely proportional to the sound absorption frequency. When the thermoacoustic vibration frequency changes, the back cavity volume is adjusted by the back cavity adjustment plate so that the optimal sound absorption frequency of the bias flow sound liner sound-absorbing structure is consistent with the thermoacoustic vibration frequency generated during the operation of the burner, thereby controlling the thermoacoustic vibration.

9. The low-nitrogen vibration-proof natural gas ammonia combustion method according to claim 6, characterized in that: 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 oscillation 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 alleviate thermal acoustic vibration; otherwise, the control screw is adjusted to reduce the cross-sectional area of ​​the variable cross-sectional area flow channel.

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