Flue gas delivery biomass burner and method of conditioning

Abstract

This invention provides a flue gas conveying biomass burner and its adjustment method, belonging to the field of biomass co-firing technology in coal-fired boilers. It addresses the difficulty in simultaneously ensuring conveying safety, ignition and burnout in the furnace, NOx control, and nozzle protection when using flue gas to convey biomass powder. The burner includes a primary air chamber, a primary air swirl adjustment structure, a pre-furnace oxygen supply structure, a secondary air chamber, a central air chamber, and combustion stabilizing teeth. The biomass powder carried by the flue gas enters the furnace through the primary air channel. The pre-furnace oxygen supply structure introduces oxygen-containing hot air into the primary air channel. The primary and secondary air swirls work together to improve mixing. The central air chamber adjusts the ignition position and nozzle temperature, and the combustion stabilizing teeth form a high-temperature flue gas entrainment zone near the nozzle. This method judges the deviations in conveying, ignition, burnout, and emissions based on operating parameters and coordinates the oxygen supply air volume, swirl intensity, secondary air volume, and central air volume. This invention is beneficial for improving the stability, burnout effect, and operational adaptability of biomass combustion.

Description

Technical Field

[0001] This invention belongs to the field of biomass co-firing technology in coal-fired boilers, specifically relating to a flue gas conveying biomass burner and its regulation method. Background Technology

[0002] Biomass fuels, with their wide availability, low carbon emission intensity, and suitability for co-firing with coal-fired power units, have received widespread attention in recent years for their application in the retrofitting of coal-fired boilers, low-carbon operation of thermal power units, and resource utilization of agricultural and forestry waste. Blending biomass fuels into coal-fired boilers can reduce fossil fuel consumption and improve the comprehensive utilization of low-grade fuels such as agricultural and forestry residues and wood waste without significantly altering the main equipment of the existing power generation system. However, due to the characteristics of biomass fuels, such as high volatile matter, large fluctuations in moisture content, low density, pronounced fibrous structure, uneven particle size distribution, and relatively low net calorific value, their combustion organization differs significantly from conventional pulverized coal combustion. Therefore, burner structures and air distribution methods need to be adapted to the characteristics of biomass fuels.

[0003] When existing coal-fired power units co-fire biomass, some schemes involve feeding biomass powder and pulverized coal together into the raw pulverized coal burner, or adding a biomass feed pipeline upstream of the raw pulverized coal burner so that the biomass enters the furnace along with the pulverized coal or combustion air. Other schemes use independent biomass burners, but their structures often borrow from conventional direct-flow burners or pulverized coal swirl burners, primarily using primary and secondary air and nozzle structures to complete fuel delivery and combustion organization. For biomass powder transported using flue gas drying, the transport medium typically has a low oxygen content, which helps reduce the risk of ignition, backfire, or deflagration during transport. However, once the biomass powder enters the furnace, it requires sufficient oxygen, strong turbulent mixing, and a stable high-temperature ignition environment to ensure timely ignition and burnout. Therefore, there is a certain contradiction between the safety requirements of the flue gas transport stage and the high-efficiency burnout requirements of the combustion stage.

[0004] Existing technologies have at least the following shortcomings: First, conventional pulverized coal burners are typically designed based on air-fed pulverized coal, failing to adequately consider the low oxygen content during flue gas transport of biomass powder and the need for oxygen supplementation in the initial stage of combustion. This makes it difficult to simultaneously ensure both safe transport and rapid ignition and burnout after entering the furnace. Second, some biomass burners only have fixed primary or secondary air distribution structures, lacking coordinated adjustment of primary air swirl intensity, secondary air swirl intensity, secondary air volume, and supplementary oxygen volume. This results in insufficient fuel adaptability to changes in biomass moisture content, particle size, volatile matter, and feed rate. Third, simply increasing the combustion air volume or enhancing swirl can improve mixing and burnout, but it can easily lead to localized high temperatures and oxygen enrichment near the nozzle, thereby increasing NOx generation or exacerbating the risk of coking and slagging. It is difficult to achieve a good balance between burnout, NOx control, and nozzle safety. Fourth, existing burner nozzle areas lack a combustion-stabilizing structure designed for the initial ignition characteristics of biomass. This can lead to problems such as delayed ignition, insufficient flame stability, or incomplete combustion after the biomass powder enters the furnace. Fifth, ash, fibrous particles, and impurities in the biomass powder can easily cause wear, ash accumulation, or coking of internal burner components. Conventional burner maintenance often requires shutdown or extensive disassembly, resulting in insufficient convenience for operation and maintenance.

[0005] Therefore, it is necessary to provide a burner and adjustment method suitable for conveying biomass powder in flue gas drying, so that it can supplement oxygen in an appropriate amount before the biomass powder enters the furnace, and improve the mixing, ignition and burnout process of biomass powder through the synergistic effect of primary air swirl, secondary air swirl, central air and stable combustion structure, while taking into account the needs of nozzle cooling, NOx control, coking and slagging inhibition and online maintenance. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a flue gas conveying biomass burner and its regulation method.

[0007] This invention provides a flue gas conveying biomass burner, comprising: A primary air chamber includes a primary air duct and a primary air nozzle. The primary air duct has an inlet end, an outlet end, and a primary air channel connecting the inlet end and the outlet end. The primary air channel is used for the flow of biomass powder carried by flue gas. The primary air nozzle is connected to the outlet end of the primary air duct, and the outlet of the primary air nozzle is used to connect to the boiler furnace. A primary air swirl regulating structure is disposed within the primary air channel. The primary air swirl regulating structure includes primary air swirl blades and a primary air swirl regulating component connected to the primary air swirl blades. The pre-furnace oxygen replenishment structure includes an oxygen replenishment duct and an oxygen replenishment air regulating damper. The air inlet of the oxygen replenishment duct is connected to an oxygen-containing hot air supply pipe, and the air outlet of the oxygen replenishment duct is connected to the primary air channel. The air outlet of the oxygen replenishment duct is located in the airflow direction of the primary air channel before the primary air nozzle. The oxygen replenishment air regulating damper is installed on the oxygen replenishment duct. The secondary air chamber includes a secondary air box, a secondary air nozzle, a secondary air swirl adjustment structure, and a secondary air volume adjustment gate. The secondary air box is arranged around the outside of the primary air duct and forms a secondary air channel with the primary air duct. The secondary air nozzle is connected to the outlet end of the secondary air channel and is arranged around the outside of the primary air nozzle. The secondary air swirl adjustment structure is arranged inside the secondary air channel. The secondary air volume adjustment gate is arranged on the air inlet path of the secondary air box. A central air chamber includes a central air supply unit, a central air duct, a central air nozzle, and a central air volume regulating structure. The central air duct is at least partially inserted within the primary air duct. The inlet end of the central air duct is connected to the central air supply unit. The central air nozzle is connected to the outlet end of the central air duct and located within the inner region of the primary air nozzle. The central air volume regulating structure is positioned on the central airflow path between the central air supply unit and the central air duct. The flame-stabilizing teeth are connected to the outlet end of the primary air nozzle and are arranged at intervals along the circumference of the primary air nozzle.

[0008] Furthermore, the primary air swirl adjustment structure also includes a support device, a swirl sleeve, a swirl blade connecting rod, a swirl blade tie rod, and a swirl sleeve tie rod. The swirl sleeve is installed inside the primary air duct via the support device. Multiple primary air swirl blades are arranged circumferentially on the swirl sleeve and are linked together via the swirl blade connecting rod. The swirl blade tie rod is drivenly connected to the primary air swirl blades to adjust the installation angle of the primary air swirl blades. The swirl sleeve tie rod is connected to the swirl sleeve to adjust the axial position of the primary air swirl blades relative to the primary air nozzle.

[0009] Specifically, the oxygen-containing hot air supply duct is a hot primary air duct, the inlet end of the primary air duct is connected to an upstream elbow, and the outlet end of the oxygen-supplementing air duct is connected to the upstream elbow; the oxygen-supplementing air duct is inclined relative to the primary air channel, and the outlet direction of the oxygen-supplementing air duct has a velocity component along the airflow direction in the primary air channel; the oxygen-supplementing air regulating damper is a pneumatic regulating damper and is located between the inlet end and the outlet end of the oxygen-supplementing air duct.

[0010] Specifically, the secondary air swirl adjustment structure includes secondary air swirl blades and a secondary air swirl adjustment mechanism; multiple secondary air swirl blades are arranged circumferentially at intervals along the secondary air channel and located radially outside the primary air duct; the secondary air swirl adjustment mechanism includes an external tie rod extending out of the secondary air box, the external tie rod being tractively connected to the secondary air swirl blades to adjust the installation angle of the secondary air swirl blades; the swirl direction formed by the secondary air swirl blades is the same as the swirl direction formed by the primary air swirl blades.

[0011] Preferably, the central air supply unit includes a central air box, which is connected to a hot secondary air duct; the central air volume adjustment structure includes a central air regulating damper disposed on the central air box or the central air flow path; the central air nozzle and the primary air nozzle are disposed flush with or adjacent to the outlet of the primary air nozzle.

[0012] Specifically, the combustion stabilizing tooth includes a plurality of tooth blocks evenly spaced along the circumference of the primary air nozzle; the tooth blocks have a stop portion that extends at least partially into the outlet region of the primary air nozzle; the tooth blocks are detachably connected to the primary air nozzle, and the tooth blocks are wear-resistant and high-temperature resistant components.

[0013] Furthermore, the primary air chamber also includes a primary air duct side screen, and the central air chamber also includes a central air duct side screen; the primary air duct, the primary air nozzle, the primary air swirl adjustment structure, and the combustion stabilizing teeth are connected to form a primary air extraction module, and the primary air duct side screen forms a primary air disassembly port for the primary air extraction module to pass through, through which the primary air extraction module is installed or extracted; the central air duct and the central air nozzle are connected to form a central air extraction module, and the central air duct side screen forms a central air disassembly port for the central air extraction module to pass through, through which the central air extraction module is installed or extracted; the oxygen supplementation duct and the primary air duct, and the central air duct and the central air supply unit, respectively adopt a disassembly-and-assembly connection structure.

[0014] Another aspect of the present invention provides a method for regulating biomass combustion during flue gas transport, comprising the following steps: S1: Obtain the operating parameters of biomass powder during the process of being transported with flue gas to the burner and entering the furnace for combustion; S2: Determine the operational deviations of the biomass powder in terms of conveying safety, ignition stability, burnout degree, and pollutant emissions based on the operating parameters; S3: Generate coordinated adjustment amounts for oxygen supplementation air volume, primary air swirl intensity, secondary air swirl intensity, secondary air volume, and central air volume based on the aforementioned operational deviations; S4: Adjust the oxygen supply air volume, the primary air swirl intensity, the secondary air swirl intensity, and the secondary air volume according to the coordinated adjustment amount, so as to change the mixing state, ignition position, and oxygen supply distribution in the area near the burner outlet; S5: Correct the coordinated adjustment amount based on the adjusted combustion feedback, and use the corrected coordinated adjustment amount in the next adjustment cycle.

[0015] Furthermore, when determining the operational deviation, the deviations caused by the biomass powder moisture content, particle size, or feed rate deviating from the corresponding set range are taken as fuel-side deviations; the deviations caused by the oxygen content, conveying temperature, or conveying pressure of the conveying medium deviating from the corresponding set range are taken as conveying-side deviations; the deviations caused by the flame position, flame fluctuation, or furnace temperature deviating from the corresponding set range are taken as combustion-side deviations; and the deviations caused by the NOx emission, CO emission, or fly ash carbon content deviating from the corresponding set range are taken as emission-side deviations. The coordinated adjustment amount is determined based on at least one of the fuel-side deviation, the conveying-side deviation, the combustion-side deviation, and the emission-side deviation.

[0016] Specifically, when adjusting the coordinated adjustment amount, if the combustion feedback indicates ignition delay or insufficient burnout, then at least one of the following is increased: oxygen supply air volume, primary air swirl intensity, and secondary air swirl intensity; if the combustion feedback indicates increased NOx emissions or increased nozzle temperature, then at least one of the following is decreased: oxygen supply air volume, secondary air volume, and secondary air swirl intensity, or the central air volume is increased; if the combustion feedback indicates that the oxygen content of the conveying medium reaches or exceeds the preset oxygen content warning value, then the increase in oxygen supply air volume is limited.

[0017] The beneficial effects of this invention are as follows: This invention combines flue gas conveying, pre-furnace oxygen supplementation, primary air swirl, secondary air swirl, central air, and combustion stabilizing teeth to ensure high safety of biomass powder during conveying. It also provides supplemental oxygen and swirl mixing before entering the furnace, improving ignition stability and burnout performance. The coordinated regulation of secondary and central air improves oxygen and temperature distribution in the burner outlet area, facilitating burnout improvement, NOx control, and nozzle cooling. The combustion stabilizing teeth create a high-temperature flue gas entrainment zone, enhancing combustion stability near the nozzle. The primary and central air extraction modules improve burner maintenance convenience. Finally, the coordinated regulation method based on operational deviations and combustion feedback enhances the burner's adaptability to different biomass powders and boiler loads. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a flue gas conveying biomass burner according to a specific embodiment of the present invention; Figure 2This is a schematic diagram of the primary air bend section of a flue gas conveying biomass burner according to a specific embodiment of the present invention; Figure 3 This diagram illustrates the steps of a flue gas conveying and biomass combustion regulation method according to a specific embodiment of the present invention.

[0019] Among them, 1 is the primary air nozzle, 2 is the combustion stabilizing tooth, 3 is the primary air duct, 4 is the swirl device, 401 is the swirl blade connecting rod, 402 is the swirl blade tie rod, 403 is the swirl sleeve tie rod, 5 is the primary air elbow, 6 is the secondary air box, 7 is the secondary air swirl blade, 8 is the secondary air nozzle, 9 is the secondary air swirl blade adjusting rod, 10 is the support device, 11 is the central air chamber, 12 is the central air duct, 13 is the central air nozzle, 14 is the oxygen supply duct, 15 is the primary air duct side screen, and 16 is the central air duct side screen. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 , Figure 2 As shown in the figure, a flue gas conveying biomass burner provided by a specific embodiment of the present invention includes: A primary air chamber includes a primary air duct 3 and a primary air nozzle 1. The primary air duct 3 has an inlet end, an outlet end, and a primary air channel connecting the inlet end and the outlet end. The primary air channel is used for the flow of biomass powder carried by flue gas. The primary air nozzle 1 is connected to the outlet end of the primary air duct 3, and the outlet of the primary air nozzle 1 is used to connect to the boiler furnace. A primary air swirl adjustment structure is disposed within the primary air channel. The primary air swirl adjustment structure includes primary air swirl blades and a primary air swirl adjustment assembly connected to the primary air swirl blades. In this embodiment, the swirl device 4 constitutes a specific structure of the primary air swirl adjustment structure. The swirl device 4 is disposed within the primary air duct 3 and located within the primary air channel. The swirl device 4 includes a swirl sleeve, primary air swirl blades, a swirl blade connecting rod 401, a swirl blade pull rod 402, a swirl sleeve pull rod 403, and a support device 10. The primary air swirl blades are installed within the primary air duct 3 via the swirl sleeve and the support device 10. The swirl blade connecting rod 401 is used to cause multiple primary air swirl blades to rotate in tandem. The swirl blade pull rod 402 is used to drive the primary air swirl blades to change their installation angle. The swirl sleeve pull rod 403 is used to drive the swirl sleeve to move axially along the primary air channel. The pre-furnace oxygen replenishment structure includes an oxygen replenishment duct 14 and an oxygen replenishment air regulating damper. The air inlet of the oxygen replenishment duct 14 is connected to an oxygen-containing hot air supply pipe, and the air outlet of the oxygen replenishment duct 14 is connected to the primary air channel. The air outlet of the oxygen replenishment duct 14 is located in the airflow direction of the primary air channel before the primary air nozzle 1. The oxygen replenishment air regulating damper is installed on the oxygen replenishment duct 14. The secondary air chamber includes a secondary air box 6, a secondary air nozzle 8, a secondary air swirl adjustment structure, and a secondary air volume adjustment door. The secondary air box 6 is arranged around the outside of the primary air duct 3 and forms a secondary air channel with the primary air duct 3. The secondary air nozzle 8 is connected to the outlet end of the secondary air channel and is arranged around the outside of the primary air nozzle 1. The secondary air swirl adjustment structure is arranged inside the secondary air channel. The secondary air volume adjustment door is arranged on the air inlet path of the secondary air box 6. The central air chamber 11 includes a central air supply unit, a central air duct 12, a central air nozzle 13, and a central air volume regulating structure. The central air duct 12 is at least partially inserted into the primary air passage. The air inlet end of the central air duct 12 is connected to the central air supply unit. The central air nozzle 13 is connected to the outlet end of the central air duct 12 and is located inside the primary air nozzle section 1. The central air volume regulating structure is disposed on the central air flow path between the central air supply unit and the central air duct 12. The flame-stabilizing tooth 2 is connected to the outlet end of the primary air nozzle 1 and is arranged at intervals along the circumference of the primary air nozzle 1.

[0022] In one embodiment, the biomass powder carried by the flue gas refers to the air-powder mixture formed by conveying the biomass powder with low-oxygen flue gas or a mixture of flue gas and hot air before it enters the burner. When the flue gas is used as the conveying medium, its oxygen content is lower than that of conventional air conveying medium, so as to reduce the risk of premature ignition, backfire, or abnormal combustion of the biomass powder during the conveying process. The oxygen supplementation structure before entering the furnace is set at an upstream position near the primary air nozzle 1, so that the biomass powder receives supplemental oxygen at the end of the conveying process and mixes with oxygen-containing hot air before entering the furnace. The nozzle cross-sectional range defined by the primary air nozzle refers to the range enclosed by the outlet profile of the primary air nozzle on a cross-section perpendicular to the airflow direction. The central air nozzle is located within the nozzle cross-sectional range, so that the central air enters the furnace from the inside of the primary air nozzle along with the primary air-powder mixture.

[0023] Specifically, the primary air duct, the secondary air duct, and the central airflow path together form the burner's staged air supply structure. The primary air duct is responsible for conveying the biomass powder carried by the flue gas. The pre-furnace oxygen supplementation structure supplies oxygen-containing hot air into the primary air duct. The primary air swirl regulation structure swirls and disturbs the flue gas, biomass powder, and oxygen-containing hot air. The secondary air chamber supplies secondary air to the outside of the primary air nozzle 1, and the central air chamber 11 supplies central air to the inner region of the primary air nozzle 1. The combustion stabilizing teeth 2 are located at the outlet end of the primary air nozzle 1 to form a local turbulence structure near the nozzle.

[0024] Furthermore, the term "inlet end" refers to the end of the primary air duct 3 that receives the biomass powder carried by the flue gas, and the term "outlet end" refers to the end of the primary air duct 3 that is close to the primary air nozzle 1 and faces the boiler furnace; the term "airflow direction" refers to the direction in which the flue gas carrying the biomass powder flows from the inlet end through the primary air channel to the primary air nozzle 1. The air outlet of the oxygen supplement duct 14 is located before the primary air nozzle 1 in the airflow direction within the primary air channel, meaning that the oxygen supplement air enters the primary air channel before the biomass powder enters the furnace, rather than being mixed with the biomass powder again within the furnace.

[0025] Based on the above basic implementation, the primary air swirl adjustment structure further includes a support device 10, a swirl sleeve, a swirl blade connecting rod 401, a swirl blade tie rod 402, and a swirl sleeve tie rod 403. The swirl sleeve is installed inside the primary air duct 3 via the support device 10. Multiple primary air swirl blades are arranged circumferentially on the swirl sleeve and are linked together by the swirl blade connecting rod 401. The swirl blade tie rod 402 is drivenly connected to the primary air swirl blades to adjust the installation angle of the primary air swirl blades. The swirl sleeve tie rod 403 is connected to the swirl sleeve to adjust the axial position of the primary air swirl blades relative to the primary air nozzle 1.

[0026] Furthermore, when the installation angle of the primary air swirl blades changes, the biomass powder carried by the flue gas in the primary air duct forms swirling flows of varying intensities. When the intensity of the primary air swirl is low, the axial transport resistance of the biomass powder along the primary air duct is low; when the intensity of the primary air swirl increases, the radial disturbance between the flue gas, biomass powder, and oxygen-containing hot air is enhanced, which is beneficial for improving the mixing degree before entering the furnace. Thus, the primary air swirl adjustment structure is used both to improve the mixing of biomass powder and supplementary oxygen air, and to adjust the fuel diffusion state in the outlet region of the primary air nozzle 1.

[0027] Furthermore, by adjusting the axial position of the primary air swirl blades relative to the primary air nozzle 1, the swirl sleeve tie rod 403 can change the distance between the swirl action point and the primary air nozzle 1. When the primary air swirl blades are arranged close to the primary air nozzle 1, the swirl disturbance remains strong near the nozzle outlet; when the primary air swirl blades are arranged far from the primary air nozzle 1, the flue gas, biomass powder, and oxygen-containing hot air have a longer mixing distance before entering the nozzle. By adjusting the installation angle and axial position of the primary air swirl blades, it is possible to adapt to biomass powder with different moisture contents, particle sizes, and feed rates.

[0028] In one specific embodiment, the oxygen-containing hot air supply pipeline is a hot primary air pipeline, and the inlet end of the primary air duct 3 is connected to an upstream elbow. The outlet end of the oxygen supplementation duct 14 is connected to the upstream elbow. The oxygen supplementation duct 14 is inclined relative to the primary air channel, and the outlet direction of the oxygen supplementation duct 14 has a velocity component along the airflow direction within the primary air channel. The oxygen supplementation air regulating valve is a pneumatic regulating valve and is located between the inlet and outlet ends of the oxygen supplementation duct 14. In this embodiment, the primary air elbow 5 is an upstream elbow connected to the inlet end of the primary air duct 3. One end of the primary air elbow 5 is connected to the biomass powder conveying pipeline, and the other end is connected to the inlet end of the primary air duct 3 to guide the biomass powder carried by the flue gas into the primary air channel. The outlet end of the oxygen supply duct 14 is connected to the primary air elbow 5, so that the oxygen supply air enters the primary air channel before the biomass powder enters the primary air nozzle 1, and flows together with the biomass powder carried by the flue gas to the swirl device 4.

[0029] In this embodiment, the oxygen-containing hot air is hot air from the primary air duct. The outlet end of the oxygen supplementation duct 14 is connected to the upstream elbow, so that the oxygen supplementation position is close to the burner inlet and located before the primary air nozzle 1. This arrangement ensures that the biomass powder remains in a relatively low-oxygen environment during the long-distance flue gas transportation stage, and receives supplemental oxygen before entering the burner and approaching the furnace, thus balancing transportation safety and the needs of combustion in the furnace.

[0030] Furthermore, the oxygen supplementation duct 14 is inclined relative to the primary air channel, and the outlet direction of the oxygen supplementation duct 14 has a velocity component along the airflow direction within the primary air channel. This structure can reduce the impact of the oxygen supplementation air on the mainstream direction of the biomass powder carried by the flue gas, reduce the risk of local backflow or deposition, and allow the oxygen supplementation air to enter the area where the primary air swirl regulation structure is located along with the mainstream. The oxygen supplementation air regulating gate is used to change the oxygen supplementation air volume entering the primary air channel. When the biomass powder has a high moisture content, large particle size, or insufficient combustion, the oxygen supplementation air volume is appropriately increased; when the oxygen content of the conveying medium is close to the preset conveying oxygen content warning value or NOx emissions increase, the oxygen supplementation air volume is limited or reduced.

[0031] In another specific embodiment, the secondary air swirl adjustment structure includes secondary air swirl blades 7 and a secondary air swirl adjustment mechanism; multiple secondary air swirl blades 7 are arranged circumferentially at intervals along the secondary air channel and located radially outside the primary air duct 3; the secondary air swirl adjustment mechanism includes an external pull rod extending out of the secondary air box 6, the external pull rod being operatively connected to the secondary air swirl blades 7 to adjust the installation angle of the secondary air swirl blades 7; the swirl direction formed by the secondary air swirl blades 7 is the same as the swirl direction formed by the primary air swirl blades; in this embodiment, a secondary air swirl blade adjustment rod 9 constitutes a specific structure of the secondary air swirl adjustment mechanism. The secondary air swirl blade adjustment rod 9 extends at least partially out of the secondary air box 6 and is operatively connected to the secondary air swirl blades 7. When the secondary air swirl blade adjustment rod 9 is operated, the multiple secondary air swirl blades 7 synchronously change their installation angles, thereby adjusting the swirl intensity of the secondary air in the secondary air channel. The secondary wind swirl blade adjusting rod 9 and the swirl blade pull rod 402 have different adjustment objects. The secondary wind swirl blade adjusting rod 9 is used to adjust the secondary wind swirl blade 7, while the swirl blade pull rod 402 is used to adjust the primary wind swirl blade.

[0032] In this embodiment, the secondary air box 6 is arranged outside the primary air duct 3. Secondary air flows through the secondary air channel and enters the boiler furnace through the secondary air nozzle 8. The secondary air swirl blades 7 are disposed within the secondary air channel. By changing the installation angle of the secondary air swirl blades 7, the swirl intensity formed by the secondary air outside the primary air nozzle 1 can be changed. The secondary air volume regulating damper is used to change the secondary air volume entering the secondary air channel, making the secondary air volume regulation and the secondary air swirl intensity regulation independent of each other.

[0033] Specifically, the swirl direction formed by the secondary air swirl blades 7 is the same as that formed by the primary air swirl blades, causing the primary air-coal mixture and secondary air to form a co-directional swirl mixture near the burner outlet. When using co-directional swirl, the secondary air can enhance the entrainment and diffusion of the primary air-coal mixture at its periphery, while reducing the strong disturbance of the flow field at the burner outlet caused by the reverse swirl. This helps to maintain a relatively stable flame shape while enhancing mixing, and reduces the risk of NOx increases due to excessive local mixing or localized high temperature and oxygen enrichment.

[0034] In another specific embodiment, the central air supply unit includes a central air box, which is connected to a hot secondary air duct; the central air volume adjustment structure includes a central air regulating damper disposed on the central air box or the central air flow path; the central air nozzle 13 and the primary air nozzle 1 are disposed flush with or adjacent to the outlet of the primary air nozzle 1.

[0035] Furthermore, the central air duct 12 is at least partially inserted within the primary air channel, and supplies central air to the inner region of the primary air nozzle 1 through the central air nozzle 13. The central air is not simply combustion air; its main functions include cooling the primary air nozzle 1 and its surrounding structures, adjusting the ignition position near the burner outlet, and coordinating with secondary air and oxygen supplementation air to improve NOx formation. If the central air volume is too small, the temperature near the nozzle will be high, easily increasing the risk of nozzle burn-out or coking; if the central air volume is too large, the flame ignition position may shift backward, which is not conducive to timely ignition of biomass powder.

[0036] Specifically, the central air nozzle 13 and the primary air nozzle section 1 are arranged flush with or adjacent to the outlet of the primary air nozzle section 1. This means that the outlet position of the central air nozzle 13 is located in the vicinity of the outlet of the primary air nozzle section 1, so that the central air is ejected in the central region of the primary air-coal mixture. The central air volume regulating structure is arranged on the central air flow path, and changes the central airflow velocity and local temperature distribution near the burner outlet by adjusting the central air volume. The central air volume regulating structure is used in conjunction with the secondary air volume regulating damper, the secondary air swirl regulating structure, and the oxygen supplementation air regulating damper to balance nozzle cooling, ignition stability, and pollutant emission control.

[0037] In another specific embodiment, the flame stabilizing tooth 2 includes a plurality of tooth blocks evenly spaced along the circumference of the primary air nozzle 1; the tooth blocks have a stop portion that at least partially extends into the outlet region of the primary air nozzle 1; the tooth blocks are detachably connected to the primary air nozzle 1, and the tooth blocks are wear-resistant and high-temperature resistant components.

[0038] Furthermore, the teeth of the combustion-stabilizing tooth 2 extend at least partially into the outlet region of the primary air nozzle 1. When the flue gas carrying biomass powder is ejected from the primary air nozzle 1, the teeth generate local disturbances to the outlet airflow. The baffle portion creates a local low-speed zone and a recirculation entrainment zone near the outlet of the primary air nozzle 1. High-temperature flue gas in the furnace is entrained and retained in this zone, thereby forming a stable high-temperature combustion zone near the primary air nozzle 1. This stable high-temperature combustion zone helps improve the initial ignition stability of the biomass powder and reduces the possibility of the flame detaching from the nozzle.

[0039] Specifically, the toothed blocks are evenly spaced around the circumference of the primary air nozzle 1, creating multiple local turbulence points around the outlet of the primary air nozzle 1. The toothed blocks are detachably connected to the primary air nozzle 1, facilitating replacement after wear, ablation, or ash accumulation. The wear-resistant and high-temperature-resistant components include silicon carbide castings, refractory ceramic parts, or other components resistant to the high temperatures of the boiler furnace and the erosion of biomass powder. The number, size, and specific shape of the combustion-stabilizing teeth 2 are determined based on the size of the primary air nozzle 1, the particle size of the biomass powder, and the burner output.

[0040] In another specific embodiment, the primary air chamber further includes a primary air duct side screen 15, and the central air chamber 11 further includes a central air duct side screen 16; the primary air duct 3, the primary air nozzle 1, the primary air swirl adjustment structure, and the combustion stabilizing tooth 2 are connected to form a primary air extraction module, and the primary air duct side screen 15 forms a primary air disassembly port for the primary air extraction module to pass through, through which the primary air extraction module is installed or extracted; the central air duct 12 and the central air nozzle 13 are connected to form a central air extraction module, and the central air duct side screen 16 forms a central air disassembly port for the central air extraction module to pass through, through which the central air extraction module is installed or extracted; the oxygen supplementation duct 14 and the primary air duct 3, and the central air duct 12 and the central air supply unit, respectively adopt a disassembly-and-assembly connection structure.

[0041] Furthermore, the primary air duct side panel 15 and the central air duct side panel 16 respectively form disassembly and maintenance channels. When overhauling the primary air extraction module, first close or isolate the airflow paths related to the primary air duct and the oxygen supply duct 14, then disassemble the disassembly-type connection structure between the oxygen supply duct 14 and the primary air duct 3, open the primary air duct side panel 15, and allow the primary air duct 3, the primary air nozzle 1, the primary air swirl adjustment structure, and the combustion stabilizing teeth 2 to be extracted as a whole through the primary air disassembly port. After maintenance, the primary air extraction module is reinstalled through the primary air disassembly port, and the corresponding connections are restored.

[0042] Specifically, when overhauling the central air extraction module, the central air flow path is closed or isolated, the detachable connection structure between the central air duct 12 and the central air supply unit is disassembled, and the central air duct side screen 16 is opened, allowing the central air duct 12 and the central air nozzle 13 to be extracted through the central air disassembly port. The detachable connection structure includes flange connections, clamp connections, plug-in sealing connections, or other connection structures that meet the requirements for airflow sealing and repeated disassembly / reassembly. Through this structure, easily worn, easily ash-accumulated, or maintenance-required components in the burner can be disassembled and reassembled in modules, reducing the impact of large-scale disassembly on boiler operation and maintenance.

[0043] In one specific implementation, such as Figure 3 As shown, a method for regulating biomass combustion during flue gas transport is provided, comprising the following steps: S1: Obtain the operating parameters of biomass powder during the process of being transported with flue gas to the burner and entering the furnace for combustion; S2: Determine the operational deviations of the biomass powder in terms of conveying safety, ignition stability, burnout degree, and pollutant emissions based on the operating parameters; S3: Generate coordinated adjustment amounts for oxygen supplementation air volume, primary air swirl intensity, secondary air swirl intensity, secondary air volume, and central air volume based on the aforementioned operational deviations; S4: Adjust the oxygen supply air volume, the primary air swirl intensity, the secondary air swirl intensity, and the secondary air volume according to the coordinated adjustment amount, so as to change the mixing state, ignition position, and oxygen supply distribution in the area near the burner outlet; S5: Correct the coordinated adjustment amount based on the adjusted combustion feedback, and use the corrected coordinated adjustment amount in the next adjustment cycle.

[0044] In this embodiment, the coordinated adjustment amount refers to the combined adjustment result of oxygen supplementation air volume, primary air swirl intensity, secondary air swirl intensity, secondary air volume, and central air volume, including the adjustment direction and adjustment range; combustion feedback refers to feedback information reflecting changes in combustion state after adjustment, including at least one of flame position, flame fluctuation, nozzle temperature, NOx, CO, fly ash carbon content, and oxygen content of the conveying medium; the operating parameters include fuel parameters, conveying parameters, boiler load parameters, combustion parameters, and emission parameters. The fuel parameters include at least one of biomass powder moisture content, particle size, volatile matter, and feed rate; the conveying parameters include at least one of conveying medium oxygen content, conveying temperature, conveying pressure, and conveying velocity; the boiler load parameters include unit load, furnace heat load, or burner operating output; the combustion parameters include at least one of flame position, flame fluctuation, furnace temperature, nozzle temperature, and coking / slagging trend; the emission parameters include at least one of NOx emission, CO emission, flue gas oxygen content, and fly ash carbon content.

[0045] Specifically, the coordinated adjustment amount is not the adjustment amount of a single air volume, but the combined adjustment result of oxygen supplementation air volume, primary air swirl intensity, secondary air swirl intensity, secondary air volume, and central air volume. The oxygen supplementation air volume mainly affects the oxygen replenishment before biomass powder enters the furnace; the primary air swirl intensity mainly affects the mixing degree of flue gas, biomass powder, and oxygen supplementation air in the primary air channel; the secondary air swirl intensity mainly affects the entrainment and diffusion in the outer peripheral area of ​​the burner outlet; the secondary air volume mainly affects the oxygen supply distribution in the furnace; and the central air volume mainly affects nozzle cooling, ignition position, and temperature distribution in the central area.

[0046] In one specific embodiment, when determining the operational deviation, the deviation of the biomass powder moisture content, particle size, or feed rate from the corresponding set range is taken as the fuel-side deviation; the deviation of the conveying medium oxygen content, conveying temperature, or conveying pressure from the corresponding set range is taken as the conveying-side deviation; the deviation of the flame position, flame fluctuation, or furnace temperature from the corresponding set range is taken as the combustion-side deviation; and the deviation of NOx emission, CO emission, or fly ash carbon content from the corresponding set range is taken as the emission-side deviation. The coordinated adjustment amount is determined based on at least one of the fuel-side deviation, the conveying-side deviation, the combustion-side deviation, and the emission-side deviation.

[0047] Furthermore, when judging the operational deviation, it is not only necessary to determine whether a single parameter deviates from its corresponding set range, but also to judge the combined state of multiple parameters. For example, when the moisture content of biomass powder increases and CO emissions increase, it is judged that there is insufficient ignition or burnout; when the oxygen content of the conveying medium increases and the oxygen supply air volume is at a large opening, it is judged that the conveying safety margin has decreased; when NOx emissions increase and the nozzle temperature increases, it is judged that there is a local high-temperature oxygen enrichment trend near the nozzle; when the flame position shifts backward and the flame fluctuation increases, it is judged that the ignition stability has decreased.

[0048] Furthermore, the corresponding setting range is determined based on the boiler load, biomass powder type, burner design output, and safety requirements of the conveying medium. The setting range includes a target range, an allowable fluctuation range, and a warning range. When the operating parameters are within the target range, the current adjustment state is maintained; when the operating parameters exceed the allowable fluctuation range, a corresponding coordinated adjustment is generated; when the operating parameters reach the warning range, priority is given to meeting conveying safety and equipment safety requirements, followed by burnout and emission optimization.

[0049] In one specific implementation, when correcting the coordinated adjustment amount, if the combustion feedback indicates ignition delay or insufficient burnout, then at least one of the following is increased: oxygen supply air volume, primary air swirl intensity, and secondary air swirl intensity; if the combustion feedback indicates increased NOx emissions or increased nozzle temperature, then at least one of the following is decreased: oxygen supply air volume, secondary air volume, and secondary air swirl intensity, or the central air volume is increased; if the combustion feedback indicates that the oxygen content of the conveying medium reaches or exceeds a preset oxygen content warning value, then the increase in oxygen supply air volume is limited.

[0050] Specifically, the preset oxygen content warning value refers to an oxygen content warning threshold set according to the type of conveying medium, the properties of biomass powder, and conveying safety requirements, used to limit the continued increase of the supplemental oxygen air volume. If the combustion feedback indicates delayed ignition or insufficient burnout, at least one of the supplemental oxygen air volume, primary air swirl intensity, and secondary air swirl intensity is increased to enhance oxygen supplementation before entering the furnace and mixing near the burner outlet. If the oxygen content of the conveying medium approaches the preset oxygen content warning value after increasing the supplemental oxygen air volume, the increase of the supplemental oxygen air volume is stopped, and mixing is improved primarily by increasing the primary air swirl intensity or the secondary air swirl intensity. If the combustion feedback indicates increased NOx emissions or increased nozzle temperature, at least one of the supplemental oxygen air volume, secondary air volume, or secondary air swirl intensity is reduced, and the temperature near the nozzle is reduced or the local strong combustion zone is delayed by increasing the central air volume.

[0051] Furthermore, if the combustion feedback simultaneously indicates incomplete burnout and increased NOx emissions, it is first determined whether the oxygen content of the conveying medium meets the safety margin. If the safety margin is met, the oxygen supply air volume or primary air swirl intensity is slightly increased, while the secondary air volume is simultaneously reduced or the central air volume is adjusted to avoid localized high-temperature oxygen enrichment near the nozzle. If the safety margin is not met, the oxygen supply air volume is no longer increased, but the mixing and ignition position are improved by adjusting the primary air swirl intensity, secondary air swirl intensity, and central air volume. Thus, the synergistic adjustment method forms a closed-loop adjustment process with conveying safety as a constraint, ignition stability and burnout improvement as objectives, and pollutant emission control as feedback. The flue gas conveying refers to the process by which biomass powder is carried into the burner by flue gas or a mixture of flue gas and hot air. The oxygen content of the conveying medium refers to the oxygen content in the flue gas conveying medium before entering the burner or the primary air duct. Pre-furnace oxygen supplementation refers to the injection of oxygen-containing hot air into the primary air duct through the oxygen supplementation duct 14 before the biomass powder enters the boiler furnace through the primary air nozzle 1. The primary air swirl intensity and secondary air swirl intensity respectively represent the degree to which the primary air swirl blades and secondary air swirl blades 7 generate rotational flow in the corresponding airflow, and are adjusted by the blade installation angle, blade position, or duct airflow. The stable combustion high-temperature zone refers to the high-temperature area formed when the stable combustion teeth 2 create local turbulence near the outlet of the primary air nozzle 1, causing the high-temperature flue gas in the furnace to be entrained and remain near the nozzle. The coking and slagging trend refers to the risk of ash melting and deposition judged based on changes in nozzle temperature, furnace temperature, flame position, heating surface temperature, or operational observations.

[0052] In one specific embodiment, the flue gas conveying biomass burner of the present invention is applied to a biomass direct combustion coupled co-firing system in a 350MW supercritical coal-fired boiler. The boiler employs a front and rear wall opposed combustion method, with the biomass burners arranged in a single layer, each layer containing four flue gas conveying biomass burners. The biomass fuel is powder or granular powder formed from forestry and wood processing residues, including at least one of bark, wood shavings, tree stumps, and wood tails. After crushing, screening, and drying, the biomass fuel is carried into each flue gas conveying biomass burner by the flue gas conveying medium. In this embodiment, the biomass co-firing rate is designed at 33.4 t / h, and the four flue gas conveying biomass burners distribute the biomass powder. The conveying medium is a mixture of hot flue gas, cold flue gas, and hot air. The hot flue gas is taken from the cold ash hopper area at the bottom of the boiler, the cold flue gas is taken from the induced draft fan outlet area, and the hot air is taken from the primary hot air header. By using the above-mentioned mixed conveying medium to dry and convey biomass powder, the temperature of the conveying medium before entering the burner is reduced to a suitable range for conveying, and the oxygen content of the conveying medium is kept below the upper limit of the safe conveying limit, thereby reducing the risk of premature ignition of biomass powder in the conveying pipeline.

[0053] In this embodiment, each flue gas conveying biomass burner includes a primary air chamber, a primary air swirl regulating structure, a pre-furnace oxygen supply structure, a secondary air chamber, a central air chamber 11, and a combustion stabilizing tooth 2. The primary air chamber includes a primary air duct 3 and a primary air nozzle 1. The inlet end of the primary air duct 3 is connected to the biomass powder conveying pipeline, and the outlet end of the primary air duct 3 is connected to the primary air nozzle 1. The outlet of the primary air nozzle 1 is connected to the boiler furnace. The biomass powder carried by the flue gas enters the primary air channel from the inlet end of the primary air duct 3 and is injected into the furnace through the primary air nozzle 1.

[0054] The primary air swirl adjustment structure is installed within the primary air duct and positioned in the middle-front section of the primary air casing 3. The primary air swirl adjustment structure includes a swirl sleeve, a support device 10, multiple primary air swirl blades, a swirl blade connecting rod 401, a swirl blade tie rod 402, and a swirl sleeve tie rod 403. The swirl sleeve is installed within the primary air casing 3 via the support device 10. Multiple primary air swirl blades are spaced circumferentially on the swirl sleeve along the primary air duct and are linked together via the swirl blade connecting rod 401. The swirl blade tie rod 402 extends beyond the outer side of the primary air casing 3 and is connected to the primary air swirl blades via a transmission mechanism. Pushing or pulling the swirl blade tie rod 402 changes the installation angle of the primary air swirl blades. The swirl sleeve tie rod 403 is connected to the swirl sleeve, and pushing or pulling the swirl sleeve tie rod 403 changes the axial position of the primary air swirl blades relative to the primary air nozzle 1.

[0055] During operation, when the biomass powder has a high moisture content, large particle size, or insufficient combustion, the installation angle of the primary air swirl blades should be increased to create a stronger swirling mixture of flue gas, biomass powder, and supplemental oxygen in the primary air duct. When the resistance of the primary air duct is too high or the flame is too close to the nozzle, the installation angle of the primary air swirl blades should be decreased, or the swirl sleeve should be adjusted to a position away from the primary air nozzle 1 to reduce excessive disturbance near the nozzle. By adjusting the angle and axial position of the primary air swirl blades, the mixing distance before entering the furnace and the swirl retention strength at the nozzle outlet can be changed.

[0056] The pre-furnace oxygen replenishment structure includes an oxygen replenishment duct 14 and an oxygen replenishment air regulating damper. The inlet end of the oxygen replenishment duct 14 is connected to the hot primary air duct, which provides oxygen-containing hot air. The outlet end of the oxygen replenishment duct 14 is connected to the upstream bend of the inlet end of the primary air duct 3 and is located before the primary air nozzle 1. The oxygen replenishment duct 14 is inclined relative to the primary air channel, and the outlet direction of the oxygen replenishment duct 14 has a velocity component along the airflow direction within the primary air channel, allowing the oxygen replenishment air to enter the primary air channel in a co-current manner. The oxygen replenishment air regulating damper is a pneumatic regulating damper and is located between the inlet and outlet ends of the oxygen replenishment duct 14.

[0057] In this embodiment, the supplemental oxygen air is taken from the hot primary air after the air preheater outlet. The preferred temperature of the supplemental oxygen air is 250℃~350℃, and the preferred pressure is 8kPa~12kPa. The angle between the supplemental oxygen air duct 14 and the center direction of the burner is preferably about 30°. The supplemental oxygen air is not located at the front end of the long-distance conveying pipeline, but at the upstream bend near the burner inlet. This allows the biomass powder to maintain a low oxygen content during the front-end conveying stage, while obtaining supplemental oxygen before entering the furnace. After entering the primary air channel, the supplemental oxygen air mixes with the flue gas and biomass powder under the action of the primary air swirl regulating structure, thereby improving the ignition conditions of the biomass powder in the initial stage of entering the furnace.

[0058] The secondary air chamber includes a secondary air box 6, a secondary air nozzle 8, a secondary air swirl adjustment structure, and a secondary air volume regulating gate. The secondary air box 6 surrounds the outside of the primary air duct 3, forming an annular or near-annular secondary air channel with the primary air duct 3. The secondary air nozzle 8 is connected to the outlet end of the secondary air channel and surrounds the outside of the primary air nozzle 1. The secondary air swirl adjustment structure includes multiple secondary air swirl blades 7 and a secondary air swirl adjustment mechanism. The multiple secondary air swirl blades 7 are spaced circumferentially along the secondary air channel and located radially outside the primary air duct 3. The secondary air swirl adjustment mechanism includes an external tie rod extending from the secondary air box 6, which is connected to the secondary air swirl blades 7 for adjusting their installation angle. The secondary air volume regulating gate is located on the air inlet path of the secondary air box 6.

[0059] In this embodiment, 16 secondary air swirl blades 7 are preferably evenly arranged circumferentially. The installation angle of the secondary air swirl blades 7 is preferably adjustable within the range of 0° to 79°, and the secondary air volume is preferably adjusted within the range of 30% to 100% of the rated secondary air volume. The swirl direction formed by the secondary air swirl blades 7 is the same as the swirl direction formed by the primary air swirl blades. After adopting co-directional swirl, the primary air-coal mixture and the secondary air form a co-directional swirl mixture near the burner outlet, which can enhance the entrainment and diffusion of the secondary air on the periphery of the primary air-coal mixture, and avoid excessive disturbance to the airflow organization in the furnace caused by reverse swirl.

[0060] The central air chamber 11 includes a central air supply unit, a central air duct 12, a central air nozzle 13, and a central air volume regulating structure. The central air supply unit includes a central air box connected to a hot secondary air duct. The central air duct 12 is at least partially inserted into the primary air duct, with its inlet end connected to the central air box. The central air nozzle 13 is connected to the outlet end of the central air duct 12 and located inside the primary air nozzle section 1. The central air volume regulating structure includes a central air regulating damper installed in the central air box or along the central air flow path. The central air nozzle 13 is flush with or adjacent to the outlet of the primary air nozzle section 1.

[0061] In this embodiment, the central air is taken from the hot secondary air, and the central air volume is preferably adjusted within the range of 30% to 100% of the rated central air volume. The central air is mainly used to cool the primary air nozzle 1 and its surrounding structure, while also adjusting the ignition position and local temperature distribution near the burner outlet. When the central air volume is large, the airflow velocity in the central region increases, which can reduce the local temperature near the nozzle and appropriately shift the ignition position backward; when the central air volume is small, the ignition effect of the high-temperature flue gas near the nozzle on the biomass powder is enhanced, but the nozzle cooling capacity is reduced. Therefore, the central air volume needs to be adjusted in conjunction with the oxygen supply air volume, the primary air swirl intensity, the secondary air swirl intensity, and the secondary air volume.

[0062] The stabilizing teeth 2 are connected to the outlet end of the primary air nozzle 1 and are arranged at intervals along the circumference of the primary air nozzle 1. The stabilizing teeth 2 include multiple tooth blocks, each tooth block having a stop portion that at least partially extends into the outlet area of ​​the primary air nozzle 1. The tooth blocks are detachably connected to the primary air nozzle 1, and the tooth blocks are made of wear-resistant and high-temperature-resistant components. Preferably, eight stabilizing teeth 2 are evenly arranged along the circumference of the primary air nozzle 1, and the tooth blocks are square tooth blocks with a height of 40mm, a width of 60mm, and a thickness of 10mm, made of silicon carbide casting. These specific dimensions and materials are preferred embodiments of this example and do not constitute a limitation on the structure of the stabilizing teeth 2.

[0063] When the flue gas carrying biomass powder is ejected from the primary air nozzle 1, the baffle portion of the combustion stabilizing tooth 2 creates a local disturbance to the airflow at the nozzle outlet, forming a local low-velocity zone and a high-temperature flue gas entrainment zone near the outlet of the primary air nozzle 1. The high-temperature flue gas inside the furnace is entrained and remains in this zone, thus forming a stable high-temperature combustion zone near the primary air nozzle 1. This stable high-temperature combustion zone enhances the heating and ignition conditions of the biomass powder in the initial stage of entering the furnace, reducing the possibility of the flame detaching from the nozzle or the ignition position shifting excessively backward.

[0064] This embodiment also includes an online maintenance structure. The primary air chamber includes a primary air duct side panel 15, and the central air chamber 11 includes a central air duct side panel 16. The primary air duct 3, primary air nozzle 1, primary air swirl adjustment structure, and combustion stabilizing teeth 2 are connected to form a primary air extraction module. The primary air duct side panel 15 forms a primary air disassembly / removal port for the primary air extraction module to pass through, through which the module is installed or removed. The central air duct 12 and central air nozzle 13 are connected to form a central air extraction module. The central air duct side panel 16 forms a central air disassembly / removal port for the module to pass through, through which it is installed or removed. The oxygen supply duct 14 and the primary air duct 3, and the central air duct 12 and the central air supply unit are respectively connected by flanges, clamps, or plug-in sealing connections.

[0065] Specifically, when overhauling the primary air extraction module, first close the oxygen supply air regulating damper, isolate the primary air passage and oxygen supply duct 14, disassemble the detachable connection structure between the oxygen supply duct 14 and the primary air duct 3, and then open the primary air duct side screen 15 to extract the primary air duct 3, primary air nozzle 1, primary air swirl regulating structure, and combustion stabilizing tooth 2 as a whole. When overhauling the central air extraction module, close the central air regulating damper and isolate the central airflow path, disassemble the detachable connection structure between the central air duct 12 and the central air supply section, and then open the central air duct side screen 16 to extract the central air duct 12 and central air nozzle 13 as a whole. This structure facilitates maintenance of easily worn or dust-accumulating components such as the primary air swirl blades, combustion stabilizing tooth 2, and central air nozzle 13.

[0066] During the operation of the aforementioned flue gas conveying biomass burner, the biomass powder is first fed into the primary air duct 3 through the flue gas conveying medium. Subsequently, hot primary air enters the primary air duct through the oxygen supply duct 14 and mixes with the biomass powder carried by the flue gas under the action of the primary air swirl regulating structure. Afterward, the mixed flue gas, biomass powder, and oxygen supply air are injected into the boiler furnace through the primary air nozzle 1. Secondary air enters the outer periphery of the primary air nozzle 1 through the secondary air box 6, secondary air duct, secondary air swirl blades 7, and secondary air nozzle 8, and continues to mix with the primary air-powder mixture. Central air enters the inner region of the primary air nozzle 1 through the central air box, central air duct 12, and central air nozzle 13. The stabilizing teeth 2 entrain the high-temperature flue gas in the furnace near the outlet of the primary air nozzle 1, so that the biomass powder obtains a relatively stable high-temperature ignition environment near the burner outlet.

[0067] In the adjustment process of this embodiment, at least one of the following parameters is obtained as operating parameters: biomass powder moisture content, particle size, feed rate, oxygen content of the conveying medium, conveying temperature, conveying pressure, flame position, flame fluctuation, furnace temperature, NOx emission, CO emission, and fly ash carbon content. Based on these operating parameters, the operating deviations of the biomass powder in terms of conveying safety, ignition stability, burnout degree, and pollutant emissions are determined, and accordingly, coordinated adjustment amounts for oxygen supplementation air volume, primary air swirl intensity, secondary air swirl intensity, secondary air volume, and central air volume are generated.

[0068] When the moisture content, particle size, CO emissions, or carbon content of fly ash increase in biomass powder, it is determined that the burner is showing signs of flame delay or incomplete combustion. In this case, at least one of the following should be increased: oxygen supply air volume, primary air swirl intensity, and secondary air swirl intensity. This will enhance oxygen replenishment before the furnace enters the furnace and improve mixing near the burner outlet. If, during the process of increasing the oxygen supply air volume, the oxygen content of the conveying medium reaches or exceeds the preset oxygen content warning value, the increase in oxygen supply air volume should be limited, and mixing should be improved primarily by adjusting the primary air swirl intensity and secondary air swirl intensity.

[0069] When NOx emissions increase, nozzle temperature rises, or the tendency for coking and slagging intensifies, it is determined that there is a localized high-temperature oxygen-enriched area or a tendency for excessive heat load near the burner outlet. In this case, at least one of the following should be reduced: oxygen supply air volume, secondary air volume, and secondary air swirl intensity; or the central air volume should be increased to lower the local temperature near the primary air nozzle 1 and adjust the ignition position. When the flame position shifts backward or flame fluctuations increase, the oxygen supply air volume or primary air swirl intensity should be increased, and the central air volume should be appropriately reduced according to the nozzle temperature to move the ignition position back towards the burner outlet.

[0070] After completing one adjustment, the combustion feedback after adjustment is continuously acquired, and the coordinated adjustment amount is corrected based on the combustion feedback. The corrected coordinated adjustment amount is then used in the next adjustment cycle. Thus, this embodiment forms a closed-loop adjustment process with oxygen supply safety as a constraint, ignition stability and improved burnout as objectives, and NOx, CO and fly ash carbon content as feedback. In one verification example, the aforementioned flue gas conveying biomass burner was applied to a biomass direct combustion coupled co-firing system in a 350MW supercritical coal-fired boiler. The boiler employs a front and rear wall opposed combustion method, with the biomass burners arranged in a single layer, four of which are installed on each layer. The biomass fuel is powder formed from forestry and wood processing residues, and the biomass co-firing rate is 33.4 t / h.

[0071] Biomass powder is dried and conveyed using a mixed conveying medium formed by hot furnace flue gas, cold furnace flue gas, and hot air. The hot furnace flue gas is taken from the cold ash hopper area at the bottom of the boiler, the cold furnace flue gas is taken from the induced draft fan outlet area, and the hot air is taken from the primary hot air header. Under 100% rated load, the hot furnace flue gas, cold furnace flue gas, and hot air are mixed in a set proportion to form the conveying medium. The temperature of the conveying medium at the terminal is approximately 75°C, and the oxygen content at the terminal is lower than the upper limit of the safe conveying limit. Therefore, the biomass powder is kept in a relatively low oxygen state during the conveying process, and oxygen-containing hot air is supplemented through oxygen supplementation duct 14 before entering the burner.

[0072] In this verification example, the supplemental oxygen is taken from the hot primary air, with a temperature of 250℃~350℃ and a pressure of 8kPa~12kPa. The supplemental oxygen duct 14 is located at the upstream bend connected to the inlet end of the primary air duct 3 and is inclined and flows in the same direction relative to the primary air channel. After entering the primary air channel, the supplemental oxygen, along with the biomass powder carried by the flue gas, enters the area where the primary air swirl regulating structure is located and is mixed under the action of the primary air swirl. The secondary air enters the furnace after being swirled in the same direction as the primary air swirl by the secondary air swirl blades 7. The central air enters the inner area of ​​the primary air nozzle 1 through the central air nozzle 13, and the combustion stabilizing teeth 2 form a local high-temperature flue gas entrainment zone near the outlet of the primary air nozzle 1.

[0073] Numerical simulations of the above operating conditions were performed, including pure coal and co-firing conditions with different average biomass particle sizes. The furnace temperature field, component field, pollutant emission characteristics, and furnace outlet parameters were compared and analyzed. Simulation results show that after the biomass powder is injected, a high-temperature combustion zone is formed in the main combustion zone, and the fuel particles gradually burn out as the flue gas rises in the furnace. Under different average biomass particle sizes, the biomass particle size affects the combustion rate, fly ash carbon content, and NO generation level. In this embodiment, when the average particle size decreases, the overall combustion rate increases, and the NO mass fraction is generally at a higher level, but the NO concentration under the co-firing biomass condition is still lower than that under the pure coal condition. This result indicates that there is a coupling relationship between biomass particle size, burnout degree, and NOx emissions. Therefore, during combustion regulation, by coordinating the adjustment of oxygen supply air volume, primary air swirl intensity, secondary air swirl intensity, secondary air volume, and central air volume based on the biomass powder particle size, burnout state, and NOx emission feedback, the combustion organization requirements under different fuel conditions can be adapted.

[0074] The above verification examples are only used to illustrate the application of the present invention's flue gas conveying biomass burner and adjustment method in specific boilers and biomass co-firing conditions, and do not limit the present invention to be used only for boilers of this capacity, biomass co-firing amount, or conveying medium ratio. In other embodiments, the biomass co-firing amount, conveying medium ratio, oxygen supplementation air volume, primary air swirl intensity, secondary air swirl intensity, secondary air volume, and central air volume can all be adjusted according to the boiler capacity, biomass powder properties, and burner output; the NO mass fraction in this verification example is used to characterize the NOx formation level.

[0075] In summary, this embodiment has at least the following technical effects: This invention allows biomass powder carried by flue gas to enter the burner through a primary air duct, and oxygen-containing hot air is supplemented by a pre-entry oxygen supply structure before the biomass powder enters the boiler furnace. Therefore, the biomass powder can maintain a relatively low-oxygen transport state during the initial transport process, reducing the risk of premature ignition, backfire, or abnormal combustion; and it can obtain supplemental oxygen near the burner outlet, which is beneficial for improving the ignition and burnout conditions of the biomass powder after entering the furnace. This invention incorporates a primary air swirl adjustment structure within the primary air duct. By altering the primary air swirl intensity through swirl blades and adjustment components, the flue gas, biomass powder, and supplementary oxygen air are mixed in a swirling motion before entering the furnace. Compared to a simple direct current delivery method, this structure enhances the contact between the biomass powder and the oxygen-containing hot air, improving the mixing uniformity before entering the furnace and thus improving the initial ignition conditions of the biomass powder. The primary air swirl intensity, secondary air swirl intensity, secondary air volume, central air volume, and oxygen supplementation air volume of this invention are all adjustable. When the moisture content, particle size, feed rate, or volatile matter of the biomass powder changes, the mixing state, oxygen distribution, and ignition position near the burner outlet can be altered by adjusting the above parameters, thereby improving the burner's adaptability to biomass powders of different sources, particle sizes, and moisture contents. The present invention provides a combustion stabilizing tooth 2 at the outlet end of the primary air nozzle 1. The combustion stabilizing tooth 2 is arranged at intervals around the primary air nozzle 1 and has a baffle portion extending into the outlet area of ​​the primary air nozzle 1. When biomass powder is ejected, the combustion stabilizing tooth 2 can form a local turbulence and high-temperature flue gas entrainment zone near the primary air nozzle 1, so that the high-temperature flue gas in the furnace can stay near the nozzle for a certain period of time. This is beneficial to improving the temperature retention capacity near the nozzle and improving the initial ignition stability and burnout effect of the biomass powder. This invention uses supplementary oxygen air, primary air swirl, secondary air swirl, secondary air volume, and central air volume as synergistic adjustment targets. Supplementary oxygen air and the swirl structure improve mixing and burnout, while secondary air volume and central air volume regulate the oxygen supply and temperature distribution near the burner outlet. Through this synergistic adjustment, it is possible to enhance the combustion of biomass powder while reducing the risk of localized high-temperature oxygen enrichment caused by simply increasing oxygen supply or simply enhancing mixing, thus facilitating a balance between burnout performance and NOx emission control. This invention features a central air chamber 11, through which central air is delivered to the inner region of the primary air nozzle section 1 via a central air duct 12 and a central air nozzle 13. This provides cooling to the primary air nozzle section 1 and its surrounding structures, and adjusts the ignition position and temperature distribution in the burner outlet area. By coordinating and adjusting the central air volume with the oxygen supply air volume, secondary air volume, and swirl intensity, the risk of excessively high nozzle area temperature, localized coking and slagging, or nozzle burn-out can be reduced. This invention features a primary air duct side screen 15 and a central air duct side screen 16, forming a primary air extraction module from the primary air duct 3, primary air nozzle 1, primary air swirl adjustment structure, and combustion stabilizing teeth 2, and a central air extraction module from the central air duct 12 and central air nozzle 13. During maintenance, these modules can be installed or removed through corresponding disassembly ports, facilitating maintenance of easily worn or dust-accumulating components such as the swirl blades, combustion stabilizing teeth 2, and central air nozzle 13, thus reducing the difficulty of burner maintenance and disassembly.

[0076] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A flue gas conveying biomass burner, characterized in that, include: A primary air chamber includes a primary air duct and a primary air nozzle. The primary air duct has a primary air channel connecting an inlet end and an outlet end, and the primary air nozzle is connected to the outlet end of the primary air duct. A primary air swirl regulating structure is disposed within the primary air channel. The primary air swirl regulating structure includes primary air swirl blades and a primary air swirl regulating component connected to the primary air swirl blades. The pre-furnace oxygen replenishment structure includes an oxygen replenishment duct and an oxygen replenishment air regulating damper. The air inlet of the oxygen replenishment duct is connected to the oxygen-containing hot air supply pipeline, and the air outlet is connected to the primary air channel. The connection position of the air outlet of the oxygen replenishment duct is located in the airflow direction of the primary air channel before the primary air nozzle. The oxygen replenishment air regulating damper is set on the oxygen replenishment duct. A secondary air chamber includes a secondary air box, a secondary air nozzle, a secondary air swirl adjustment structure, and a secondary air volume adjustment gate. The secondary air box has an inner cavity that accommodates the primary air duct. The inner wall of the secondary air box and the outer wall of the primary air duct form a secondary air channel. The secondary air nozzle is connected to the outlet end of the secondary air channel and is located outside the primary air nozzle. The secondary air swirl adjustment structure is disposed within the secondary air channel. The secondary air volume adjustment gate is disposed on the air inlet path of the secondary air box. A central air chamber includes a central air supply unit, a central air duct, a central air nozzle, and a central air volume regulating structure. The central air duct is at least partially inserted within the primary air duct. The inlet end of the central air duct is connected to the central air supply unit. The central air nozzle is connected to the outlet end of the central air duct and located within the nozzle cross-sectional area defined by the primary air nozzle. The central air volume regulating structure is positioned on the central air flow path between the central air supply unit and the central air duct. The flame-stabilizing teeth are connected to the outlet end of the primary air nozzle and are arranged at intervals along the circumference of the primary air nozzle.

2. The flue gas conveying biomass burner according to claim 1, characterized in that, The primary air swirl adjustment structure further includes a support device, a swirl sleeve, a swirl blade connecting rod, a swirl blade tie rod, and a swirl sleeve tie rod. The swirl sleeve is installed inside the primary air duct via the support device. Multiple primary air swirl blades are arranged circumferentially on the swirl sleeve and are linked together via the swirl blade connecting rod. The swirl blade tie rod is drivenly connected to the primary air swirl blades to adjust the installation angle of the primary air swirl blades. The swirl sleeve tie rod is connected to the swirl sleeve to adjust the axial position of the primary air swirl blades relative to the primary air nozzle.

3. The flue gas conveying biomass burner according to claim 1, characterized in that, The oxygen-containing hot air supply duct is a hot primary air duct. The inlet end of the primary air duct is connected to an upstream elbow, and the outlet end of the oxygen-supplementing air duct is connected to the upstream elbow. The oxygen-supplementing air duct is inclined relative to the primary air channel, and the outlet direction of the oxygen-supplementing air duct has a velocity component along the airflow direction in the primary air channel. The oxygen-supplementing air regulating valve is a pneumatic regulating valve and is located between the inlet end and the outlet end of the oxygen-supplementing air duct.

4. The flue gas conveying biomass burner according to claim 1, characterized in that, The secondary air swirl adjustment structure includes secondary air swirl blades and a secondary air swirl adjustment mechanism; multiple secondary air swirl blades are arranged circumferentially at intervals along the secondary air channel and located radially outside the primary air duct; the secondary air swirl adjustment mechanism includes an external tie rod extending out of the secondary air box, the external tie rod being tractively connected to the secondary air swirl blades for adjusting the installation angle of the secondary air swirl blades; the swirl direction formed by the secondary air swirl blades is the same as the swirl direction formed by the primary air swirl blades.

5. The flue gas conveying biomass burner according to claim 1, characterized in that, The central air supply unit includes a central air box, which is connected to a hot secondary air duct; the central air volume adjustment structure includes a central air regulating damper disposed on the central air box or the central air flow path; the central air nozzle and the primary air nozzle are disposed flush with or adjacent to the outlet of the primary air nozzle.

6. The flue gas conveying biomass burner according to claim 1, characterized in that, The stabilizing tooth includes a plurality of tooth blocks arranged circumferentially along the primary air nozzle; each tooth block has a stop portion that extends at least partially into the outlet region of the primary air nozzle; the tooth block is detachably connected to the primary air nozzle, and the tooth block is a wear-resistant and high-temperature resistant component.

7. The flue gas conveying biomass burner according to any one of claims 1 to 6, characterized in that, The primary air chamber also includes a primary air duct side screen, and the central air chamber also includes a central air duct side screen; the primary air duct, the primary air nozzle, the primary air swirl adjustment structure, and the combustion stabilizing teeth are connected to form a primary air extraction module, and the primary air duct side screen constitutes a primary air disassembly and assembly port for the primary air extraction module to pass through; the central air duct and the central air nozzle are connected to form a central air extraction module, and the central air duct side screen constitutes a central air disassembly and assembly port for the central air extraction module to pass through; the oxygen supplementation duct and the primary air duct, and the central air duct and the central air supply unit respectively adopt a disassembly and assembly connection structure.

8. A method for regulating flue gas transport and biomass combustion, characterized in that, The steps include the following: S1: Obtain the operating parameters of biomass powder during the process of being transported with flue gas to the burner and entering the furnace for combustion; S2: Determine the operational deviations of the biomass powder in terms of conveying safety, ignition stability, burnout degree, and pollutant emissions based on the operating parameters; S3: Generate coordinated adjustment amounts for oxygen supplementation air volume, primary air swirl intensity, secondary air swirl intensity, secondary air volume, and central air volume based on the aforementioned operational deviations; S4: Adjust the oxygen supply air volume, the primary air swirl intensity, the secondary air swirl intensity, and the secondary air volume according to the coordinated adjustment amount, so as to change the mixing state, ignition position, and oxygen supply distribution in the area near the burner outlet; S5: Correct the coordinated adjustment amount based on the adjusted combustion feedback, and use the corrected coordinated adjustment amount in the next adjustment cycle.

9. The method for regulating flue gas transport and biomass combustion according to claim 8, characterized in that, When determining the operational deviation, the deviation of the biomass powder moisture content, particle size, or feed rate from the corresponding preset range is taken as the fuel-side deviation; the deviation of the conveying medium oxygen content, conveying temperature, or conveying pressure from the corresponding set range is taken as the conveying-side deviation; the deviation of the flame position, flame fluctuation, or furnace temperature from the corresponding preset range is taken as the combustion-side deviation; and the deviation of NOx emission, CO emission, or fly ash carbon content from the corresponding preset range is taken as the emission-side deviation. The coordinated adjustment amount is determined based on at least one of the fuel-side deviation, the conveying-side deviation, the combustion-side deviation, and the emission-side deviation.

10. The flue gas conveying and biomass combustion regulation method according to claim 8, characterized in that, When adjusting the coordinated adjustment amount, if the combustion feedback indicates ignition delay or insufficient burnout, then at least one of the oxygen supply air volume, the primary air swirl intensity, and the secondary air swirl intensity is increased; if the combustion feedback indicates increased NOx emissions or increased nozzle temperature, then at least one of the oxygen supply air volume, the secondary air volume, and the secondary air swirl intensity is decreased, or the central air volume is increased; if the combustion feedback indicates that the oxygen content of the conveying medium reaches or exceeds a preset oxygen content warning value, then the increase in the oxygen supply air volume is limited.

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