A staged cyclone low-nitrogen burner and a working method thereof

Abstract

The present application relates to a kind of hierarchical cyclone low-nitrogen burner and its working method, including combustion shell, distribution chamber, conical backflow chamber, conical diffusion chamber and delivery chamber are sequentially arranged in longitudinal direction in combustion shell, distribution chamber includes primary feed channel and multiple primary air channels arranged circumferentially around primary feed channel, primary air channel is tangentially connected with one end of conical backflow chamber, igniter is arranged outside conical backflow chamber, multiple secondary air channels are also arranged in combustion shell, one end of secondary air channel is tangentially connected with one end of conical diffusion chamber, multiple air feed channels are arranged on the circumferential wall outside delivery chamber, air feed channel is tangentially connected with delivery chamber. By air with three different delivery paths respectively tangential cyclone into distribution chamber, conical backflow chamber and conical diffusion chamber, and with direct injection primary fuel and tangential circle secondary fuel fully mixed atomization break, form gas-liquid two-phase fuel, enhance combustion stability, reduce nitrogen oxide emission.

Description

Technical Field

[0001] This invention relates to the field of burner technology, specifically to a staged swirl low-NOx burner and its operating method. Background Technology

[0002] Biomass is an abundant, carbon-neutral, and environmentally friendly renewable energy source. It is diverse, rich in resources, and high in carbon content, making it an excellent raw material for biochar production. Biomass pyrolysis is a common technology for converting biomass into biochar products. This technology involves the thermal decomposition of organic materials such as biomass under anaerobic or anoxic conditions to produce biochar. In addition to biochar, this process also produces byproducts—pyrolysis volatiles, which consist of pyrolysis gas and bio-oil. Directly burning these two components as fuel offers advantages in reducing emissions and lowering costs. However, pyrolysis gas has a low calorific value and is difficult to burn stably, while bio-oil has high water content, poor stability, high tar viscosity, and strong acidity and corrosiveness, requiring complex processing to prepare it into chemicals. Therefore, research on the utilization of pyrolysis volatiles during biomass pyrolysis is crucial.

[0003] The utilization of pyrolysis volatiles mainly involves improving burners to directly combust them, thereby increasing processing efficiency. However, this approach suffers from drawbacks such as difficulty in ignition, tar coking, and unstable combustion due to the low calorific value and high moisture content of the pyrolysis volatiles. To address the low calorific value of the pyrolysis gas, it is generally mixed with other high-calorific-value fuels such as methane, hydrogen, and ethanol for combustion. While this improves efficiency, it can easily lead to localized overheating of the burner, resulting in the production of thermal NO. X Light biofuels mainly use burners with atomizing nozzles, which can effectively break down biofuels into smaller molecules. However, they have high operational requirements and are prone to causing the fuel to fail to ignite or the flame to be unstable. Moreover, high-viscosity substances are prone to coking, corrosion, and clogging when passing through the nozzle, resulting in unstable operating conditions and high maintenance costs.

[0004] Due to the high viscosity, low thermal stability, and high moisture content of pyrolysis volatiles, it is difficult to achieve efficient combustion and low NOx emissions using traditional burners. Therefore, it is necessary to design a novel burner to achieve efficient and low-NOx combustion of pyrolysis volatiles. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the first objective of this invention is to provide a staged swirl low-NOx burner. This burner includes a combustion shell open at both ends, within which a distribution chamber, a conical recirculation chamber, a conical diffusion chamber, and a delivery chamber are sequentially arranged in a longitudinal direction. By tangentially swirling air into the distribution chamber, conical recirculation chamber, and conical diffusion chamber through three different delivery paths, and thoroughly mixing, atomizing, and breaking down the air with direct-injection primary fuel and tangentially circular secondary fuel, a gas-liquid two-phase fuel is formed, enhancing combustion stability and reducing NOx emissions.

[0006] The second objective of this invention is to provide a method for operating a staged swirl low-NOx burner, including direct injection feeding and tangential air intake, atomization and crushing, conical recirculation, dual-channel swirl, conical expansion and tangential feeding and air intake, thereby effectively improving combustion efficiency and reducing NOx emissions.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A staged swirl low-NOx burner includes a combustion shell open at both ends. Within the combustion shell, a distribution chamber, a conical reflux chamber, a conical diffuser chamber, and a conveying chamber are sequentially arranged in a longitudinal direction. The distribution chamber provides a flow path for primary fuel and primary air. The distribution chamber includes a primary feed channel and multiple primary air intake channels circumferentially arranged around the primary feed channel. The primary air intake channels are tangentially connected to one end of the conical reflux chamber, which is used for the mixed reflux of primary fuel and primary air. The other end of the conical reflux chamber is connected to one end of the conical diffuser chamber. An igniter is located outside the conical reflux chamber. Multiple secondary air intake channels are also provided within the combustion shell. One end of each secondary air intake channel is tangentially connected to one end of the conical diffuser chamber, and the other end extends outward from the combustion shell. The other end of the conical diffuser chamber is connected to the inlet end of the conveying chamber. Multiple air and feed channels are provided on the circumferential wall outside the conveying chamber. These air and feed channels are used to simultaneously convey secondary fuel and tertiary air. The air and feed channels are tangentially connected to the conveying chamber, and flames are ejected from the outlet end of the conveying chamber.

[0009] Furthermore, the primary feed channel is located on the central axis of the distribution chamber, and multiple primary air intake channels are evenly arranged around the primary feed channel.

[0010] Furthermore, the tangential angle between the primary intake passage and the conical recirculation chamber is 30-89°.

[0011] Furthermore, the tangential directions of the multiple primary intake channels connected to the conical recirculation chamber are all the same.

[0012] Furthermore, the cone-shaped reflux chamber and the cone-shaped diffuser have opposite cone-shaped directions.

[0013] Furthermore, the conical expansion chamber is equipped with a dual-channel vortex chamber at the other end near the conical return chamber. The dual-channel vortex chamber has a conical truncated structure and includes an outer cylinder, an inner cylinder fitted inside the outer cylinder, and a cover plate fixed between the outer cylinder and the inner cylinder. An outer vortex channel for conveying secondary air is formed between the outer cylinder and the inner cylinder. The cover plate is provided with multiple through holes, and the secondary air intake channel is tangentially connected to the through holes. The outer vortex channel is in fluid communication with the secondary air intake channel and the conical expansion chamber, respectively. An inner vortex channel for conveying primary fuel and primary air is formed inside the inner cylinder, and the inner vortex channel is in fluid communication with the conical return chamber and the conical expansion chamber, respectively.

[0014] Furthermore, the tangential directions of the multiple secondary air intake channels connected to the through holes are all the same.

[0015] Furthermore, the air intake and feed channels are arranged perpendicular to the longitudinal direction of the combustion shell.

[0016] Furthermore, the tangential angle between the air intake and feed channels and the conveying chamber is 0-45°.

[0017] A method for operating a staged swirl low-NOx burner includes the following steps:

[0018] S1, Direct Injection Feeding and Tangential Jet Jetting: Primary fuel is directly injected through the primary feed channel of the distribution chamber, and primary air is tangentially jetted through the primary air intake channel of the distribution chamber;

[0019] S2, Atomization and Breakup: Primary air atomizes and breaks up primary fuel and delivers it to the conical recirculation chamber;

[0020] S3, Conical Recirculation: The primary fuel and primary air entering the conical recirculation chamber are mixed, recirculated, and ignited, and then transported to the dual-channel vortex chamber;

[0021] S4, Dual-channel swirl: Secondary air enters the outer swirl channel through the secondary intake channel, while primary fuel and primary air enter the inner swirl channel. Primary fuel, primary air and secondary air are jointly transported to the conical diffuser chamber.

[0022] S5, Conical Diffusion: Primary fuel, primary air and secondary air are mixed in the conical diffusion chamber, and the fuel is atomized and broken up again to enhance the mixed combustion;

[0023] S6, Tangential Feeding and Air Intake: Secondary fuel and tertiary air are tangentially fed into the conveying chamber through the air intake and feeding channel. The secondary fuel and tertiary air are mixed and burned with the primary fuel, primary air and secondary air, and finally the flame is ejected from the outlet end of the conveying chamber.

[0024] The present invention has the following advantages:

[0025] 1. This invention addresses the high viscosity, high moisture content, and low thermal stability of bio-oil in biomass pyrolysis volatiles. It involves tangentially injecting primary air in a swirling flow to atomize and break up the primary fuel, which then enters a conical reflux chamber. Unatomized liquid fuel particles decrease in velocity upon entering the conical expansion chamber and advance along the chamber wall under swirling action. Simultaneously, secondary air entering the outer swirling channel through a secondary air intake channel further atomizes and breaks up the fuel. The secondary fuel and tertiary air are tangentially injected into the feed channel near the combustion chamber, undergoing a third atomization, breaking up, and mixing through interaction with the internal fuel and air. This three-stage swirling flow achieves atomization, breaking up, and thorough mixing of the gas-liquid two-phase fuel from biomass pyrolysis volatiles. For low-calorific-value fuels, this results in stable combustion, less flame extinguishing, and complete fuel combustion, significantly improving combustion efficiency. It solves the problems of poor atomization, insufficient mixing, and nozzle clogging in traditional burners. The burner of this application is applicable to power generation, waste incineration, and chemical treatment applications.

[0026] 2. This invention achieves more uniform mixing by tangentially swirling air into the distribution chamber, conical recirculation chamber, and conical expansion chamber through three different delivery paths, and fully mixing, atomizing, and breaking up the direct injection primary fuel and tangential secondary fuel. This avoids localized high temperatures caused by uneven mixing. At the same time, by classifying the fuel and air, the high-temperature zone of the flame is reduced, thus reducing nitrogen oxide emissions.

[0027] 3. The staged swirl low-NOx burner of the present invention has a compact structure, strong adaptability, and good combustion stability. It can efficiently and cleanly burn biomass pyrolysis volatiles with high viscosity, high water content, and complex composition.

[0028] 4. The distribution chamber of this invention forms a vortex by mixing tangential jetting of primary air with direct fuel injection. Immediately after the vortex is formed, the airflow velocity and vortex intensity are increased by a conical recirculation chamber. The increase in axial velocity and intensity of the vortex promotes a strong recirculation in the conical recirculation chamber, so that the temperature of fuel and air can achieve stable combustion of the main flame through recirculation. This prevents unstable combustion and flameout caused by high viscosity, high moisture content and poor thermal stability of biomass pyrolysis volatiles. At the same time, the structure of vortex plus conical recirculation chamber avoids the problem of a significant reduction in axial vortex velocity and intensity after the vortex is formed. Attached Figure Description

[0029] Figure 1 This is a three-dimensional cross-sectional view of the staged swirl low-NOx burner of the present invention.

[0030] Figure 2 This is a schematic diagram of the structure of the staged swirl low-NOx burner of the present invention.

[0031] Figure 3 This is a front view of the distribution chamber of the present invention.

[0032] Figure 4 yes Figure 3 A three-dimensional cross-section along the AA direction.

[0033] Figure 5 This is a schematic diagram of the conical reflux chamber and the dual-channel vortex chamber of the present invention.

[0034] Figure 6 This is a schematic diagram of the dual-channel vortex chamber of the present invention.

[0035] Figure 7 This is a schematic diagram of the conical expansion chamber and delivery chamber of the present invention.

[0036] Figure 8 This is a cross-sectional view of the conveying chamber of the present invention.

[0037] Figure 9 This is a flowchart of the process of the staged swirl low-NOx burner of the present invention.

[0038] Wherein, C is the combustion shell, 1 is the distribution chamber, 101 is the primary feed channel, 102 is the primary air intake channel, 102a is the air inlet, 102b is the air outlet, 103 is the distribution chamber body, 2 is the conical reflux chamber, 201 is the conical reflux cylinder, 202 is the igniter, 203 is the partition, 203a is the connecting hole, 3 is the conical diffuser chamber, 301 is the secondary air intake channel, 302 is the conical diffuser cylinder, 4 is the conveying chamber, 401 is the air and feed channel, 402 is the conveying cylinder, 402a is the inlet, 5 is the dual-channel vortex chamber, 501 is the outer cylinder, 502 is the inner cylinder, 503 is the cover plate, 503a is the through hole, 504 is the outer vortex channel, and 505 is the inner vortex channel. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1-2As shown, X represents the longitudinal direction of the combustion shell, and Y represents the transverse direction of the combustion shell. A staged swirl low-NOx burner includes a combustion shell open at both ends. Within the combustion shell, a distribution chamber, a conical recirculation chamber, a conical diffuser chamber, and a conveying chamber are sequentially arranged in the longitudinal direction. One end of the combustion shell mates with the inlet end of the distribution chamber. The distribution chamber provides a flow path for primary fuel and primary air. The distribution chamber includes a primary feed channel and multiple primary air intake channels circumferentially arranged around the primary feed channel. The primary air intake channels are tangentially connected to one end of the conical recirculation chamber, allowing primary air to enter tangentially and form a swirl. The conical recirculation chamber is used for the mixing and recirculation of primary fuel and primary air. The other end of the conical recirculation chamber is connected to one end of the conical diffuser chamber. An igniter is externally located, and the combustion chamber contains multiple secondary air intake channels. One end of each secondary air intake channel is tangentially connected to one end of a conical diffuser, allowing secondary air to enter tangentially and form a swirling flow. The other end of the secondary air intake channel extends outward from the combustion chamber, and the other end of the conical diffuser connects to the inlet of a conveying chamber. Multiple air intake and feeding channels are located on the circumferential wall outside the conveying chamber, simultaneously conveying secondary fuel and tertiary air. These channels are tangentially connected to the conveying chamber, allowing both secondary fuel and tertiary air to enter tangentially and form a swirling flow. A flame is ejected from the outlet of the conveying chamber, which mates with the other end of the combustion chamber. In this embodiment, one end of the combustion chamber has an inlet, and the other end has an outlet. The inlet of the distribution chamber is flush with the inlet of the combustion chamber, and the outlet of the conveying chamber is flush with the outlet of the combustion chamber. The other end of the secondary air intake channel extends towards and is flush with the inlet of the combustion chamber. The combustion shell has a cylindrical structure. The distribution chamber, conical reflux chamber, conical diffuser chamber, and conveying chamber can all be detachably installed inside the combustion shell, facilitating component replacement and parameter adjustment. Primary fuel and secondary fuel refer to the pyrolysis volatiles generated during the biomass pyrolysis charcoal production process. The main components of pyrolysis volatiles are pyrolysis gas and bio-oil. Primary air, secondary air, and tertiary air can be gases at a certain temperature or gases with added chemical components.

[0041] like Figure 1-4As shown, the primary feed channel is located on the central axis of the distribution chamber, and multiple primary air intake channels are evenly arranged around it. The number of primary air intake channels is 3-10, and can be configured according to actual needs. The diameter of the primary air intake channels is determined based on parameters such as structural space, primary air flow rate, and velocity. In this embodiment, the distribution chamber also includes a distribution chamber body, which is a cylindrical structure. The primary feed channel is located on the central axis of the distribution chamber body and is used for direct injection of primary fuel into the conical return chamber. There are six primary air intake channels, which are evenly distributed circumferentially around the primary feed channel. Each of the six primary air intake channels is tangentially connected to one end of the conical return chamber, allowing primary air to enter the conical return chamber tangentially. The primary air intake channels penetrate the distribution chamber body and are inclined in one direction. That is, the inlet and outlet of the primary air intake channel are not on the same axis. Primary air enters the conical return chamber tangentially through the inclined primary air intake channels in the distribution chamber body, achieving primary air swirl.

[0042] like Figure 3 and Figure 4 As shown, the tangential angle α between the primary air intake channel and the conical recirculation chamber is 30-89°, with a preferred angle of 45°. By detachably replacing different models of distribution chambers, and by configuring primary air intake channels with different tangential angles and numbers, optimal combustion performance can be achieved. The tangential directions connecting multiple primary air intake channels to the conical recirculation chamber are all the same; that is, multiple primary air intake channels are all inclined in the same direction within the distribution chamber, allowing primary air to enter the conical recirculation chamber tangentially in the same direction, resulting in better air swirl. Regarding the selection of the distribution chamber, firstly, based on parameters such as the proportion, composition ratio, viscosity, moisture content, and thermal stability of liquid phase products in biomass pyrolysis volatiles, a primary air intake channel with a specific tangential angle is selected, and a corresponding distribution chamber is chosen and installed in the combustion shell. Secondly, based on the mixing and combustion of fuel and air, the proportions and rates of primary fuel, secondary fuel, primary air, secondary air, and tertiary air are fine-tuned to achieve more precise combustion control. The distribution chamber uses a fixed-angle channel instead of an adjustable-angle channel to prevent the bio-oil in the pyrolysis volatiles from becoming too viscous and sticking to the adjustable components, thus clogging the distribution chamber's channels.

[0043] like Figure 5 As shown, the conical reflux chamber includes a conical reflux cylinder. One end of the conical reflux cylinder has a baffle plate with multiple connection holes. The connection holes correspond to the air outlet of the primary air intake channel. The other end of the conical reflux cylinder is in fluid communication with one end of the conical expansion chamber. An igniter is also provided on the outside of the conical reflux cylinder.

[0044] like Figure 1As shown, the conical recirculation chamber and the conical expansion chamber have opposite conical directions. The conical recirculation chamber has a conical structure, divided into a dispersion region and a concentration region. Primary air and primary fuel first pass through the dispersion region and then flow through the concentration region. The flow velocity of primary air increases in the concentration region, causing the slower gas in the dispersion region to be carried to form a recirculation, thereby enhancing the mixing effect. The conical expansion chamber, on the other hand, has a conical structure, divided into a diffusion region and a concentration region. Primary air and primary fuel first pass through the concentration region and then flow through the diffusion region. That is, the process of primary air and primary fuel passing through the conical recirculation chamber and the conical expansion chamber sequentially is dispersion-concentration-concentration-diffusion; therefore, the conical recirculation chamber and the conical expansion chamber have opposite conical directions.

[0045] like Figure 1 , 5 As shown in Figure 6, the conical expansion chamber is further provided with a dual-channel vortex chamber at the other end near the conical return chamber. The dual-channel vortex chamber is detachably installed between the conical expansion chamber and the conical return chamber. The dual-channel vortex chamber is in fluid communication with both the conical expansion chamber and the conical return chamber. The dual-channel vortex chamber has a conical truncated structure and includes an outer cylinder, an inner cylinder fitted inside the outer cylinder, and a cover plate fixed between the outer cylinder and the inner cylinder. An outer vortex channel for conveying secondary air is formed between the outer cylinder and the inner cylinder. The cover plate is provided with multiple through holes. The secondary air intake channel is tangentially connected to the through holes. The outer vortex channel is in fluid communication with both the secondary air intake channel and the conical expansion chamber. The secondary air enters the outer vortex channel tangentially to form a vortex, and then enters the conical expansion chamber to continue swirling. An inner vortex channel for conveying primary fuel and primary air is formed inside the inner cylinder. The inner vortex channel is in fluid communication with both the conical return chamber and the conical expansion chamber. The tangential directions of the multiple secondary air intake channels connected to the through holes are all the same. The length of the dual-channel swirl chamber is 30-160mm, determined by the swirl intensity and velocity of the secondary air. In this embodiment, there are four secondary air intake channels, with four corresponding through holes on the cover plate. The four secondary air intake channels are evenly distributed on the cover plate, and each secondary air intake channel has a straight section and an inclined section. The straight section is parallel to the distribution chamber, and the inclined section is parallel to the conical return chamber. One end of the straight section is flush with the inlet of the combustion shell, and the other end of the straight section is connected to one end of the inclined section. The other end of the inclined section is tangentially connected to the through hole. In other words, the flow path of the secondary air intake channel corresponds to the shape of the distribution chamber and the conical return chamber. By setting up the dual-channel swirl chamber, uniform and stable combustion of the flame can be achieved, ensuring that the flame does not deviate and remains in the central area of ​​the burner, preventing overheating damage to the burner.

[0046] like Figure 1 , 7As shown in Figure 8, the air intake and feeding channel is perpendicular to the longitudinal direction of the combustion shell. The tangential angle β between the air intake and feeding channel and the conveying chamber is 0-45°, preferably 0°. In this embodiment, the conveying chamber is a cylindrical structure, including a conveying cylinder. Multiple inlets are spaced apart on the circumferential wall of the conveying cylinder. One end of the air intake and feeding channel is tangentially connected to an inlet, and the other end extends through the combustion shell to the outside of the combustion shell. The number of inlets is 2-8, and the number of air intake and feeding channels is 2-8, corresponding to the number of inlets. In this embodiment, there are four inlets and four air intake and feeding channels, evenly distributed on the conveying cylinder. A certain distance exists between the inlets and the output port of the combustion shell to prevent secondary fuel and tertiary air from being directly discharged from the output port of the combustion shell when entering the conveying chamber. The distance between the inlets and the output port of the combustion shell is 30-70mm, and the distance between the air intake and feeding channels and the output port of the combustion shell is 30-70mm. Multiple air intake and feed channels are arranged on the same horizontal plane in the transverse direction of the combustion shell, and the tangential directions of the connections between the multiple air intake and feed channels and the inlet are all the same. This allows secondary fuel and tertiary air to enter the conveying chamber tangentially in the same direction and on the same horizontal plane, forming a vortex and fully mixing and burning with the internal fuel and air. The tangential angle of the air intake and feed channels and the position of the inlet can be adjusted according to parameters such as flame length, flame width, combustion heat load, gas-liquid two-phase mixing degree, and vortex intensity.

[0047] like Figure 9 As shown, a method for operating a staged swirl low-NOx burner includes the following steps:

[0048] S1, Direct Injection Feeding and Tangential Jet Jetting: Primary fuel is directly injected through the primary feed channel of the distribution chamber, and primary air is tangentially jetted through the primary air intake channel of the distribution chamber;

[0049] S2, Atomization and Crushing: Primary air atomizes and crushes primary fuel and delivers it to the conical reflux chamber; the primary air is tangentially jetted through the primary air intake channel, and under the action of the conical reflux chamber, the swirling intensity of the primary air increases and the tangential angle of the primary fuel is enhanced, resulting in a strong collision with the primary fuel directly injected into the primary feed channel, thereby atomizing and crushing pyrolysis volatiles;

[0050] S3, Conical Recirculation: The primary fuel and primary air entering the conical recirculation chamber are mixed, recirculated, and ignited, and then transported to the dual-channel vortex chamber; the primary air generates a vortex through the primary intake channel, causing the air to diffuse outward and flow through the conical recirculation chamber. Because the conical recirculation chamber has a conical structure, it is divided into a dispersion area and a concentration area. The primary air first passes through the dispersion area and then flows through the concentration area. Therefore, the flow velocity of the primary air in the concentration area will be accelerated, which will cause the slow gas in the dispersion area to be driven to form a recirculation, thereby enhancing the mixing effect;

[0051] S4, Dual-channel swirl: Secondary air enters the outer swirl channel through the secondary intake channel, while primary fuel and primary air enter the inner swirl channel. Primary fuel, primary air and secondary air are jointly transported to the conical diffuser chamber.

[0052] S5. Conical Diffusion: Primary fuel, primary air, and secondary air are mixed in the conical diffusion chamber, further atomizing and breaking up the fuel to enhance combustion. Due to the reduced inflow velocity of fuel and air caused by the conical diffusion, unburned fuel particles are propelled along the wall of the conical diffusion chamber by the swirling action. At this time, secondary air enters the conical diffusion chamber through the outer swirling channel, forming a swirling flow. On the one hand, the secondary air adheres to the wall to protect the inner surface of the conical diffusion chamber from wear and high-temperature corrosion by bio-oil. On the other hand, the secondary air atomizes and breaks up the unburned fuel particles again, enhancing mixing and combustion.

[0053] S6. Tangential Feeding and Air Intake: Secondary fuel and tertiary air are tangentially fed into the conveying chamber through the feed inlet channel. The secondary fuel and tertiary air mix and burn with the primary fuel, primary air, and secondary air, finally exiting as flames from the outlet of the conveying chamber. At the other end near the combustion chamber, the secondary fuel and tertiary air enter the main flame through the feed inlet channel, interacting with the main airflow to enhance atomization, fragmentation, and mixing. This also increases the radial velocity of the main flame, improves swirling intensity, strengthens recirculation, stabilizes the flame, enhances the cross-sectional heat load of the main flame, and shortens the flame length.

[0054] The burner of this invention supplies air and fuel for combustion in stages. Air is introduced proportionally from the primary air intake channel, secondary air from the outer swirl channel, and tertiary air from the air intake and feed channel. Fuel is directly injected into the primary feed channel and tangentially injected into the secondary feed channel in proportion to the primary fuel injection. The staged air intake and feed process is simultaneous and continuous; that is, primary and secondary fuels are fed simultaneously, and primary, secondary, and tertiary airs are introduced simultaneously.

[0055] In summary, this invention addresses the high viscosity, high moisture content, and low thermal stability of bio-oil in biomass pyrolysis volatiles. It achieves this by tangentially injecting primary air in a swirling flow to atomize and break up the primary fuel, which then enters a conical reflux chamber. Unatomized liquid fuel particles decrease in velocity upon entering the conical expansion chamber and advance along the chamber wall under swirling action. Simultaneously, secondary air entering the outer swirling channel through a secondary air intake channel further atomizes and breaks up the fuel. The secondary fuel and tertiary air are tangentially injected into the feed channel near the combustion chamber, undergoing a third atomization, breaking up, and mixing process through interaction with the internal fuel and air. This three-stage swirling flow achieves atomization, breaking up, and thorough mixing of the gas-liquid two-phase fuel from biomass pyrolysis volatiles, resulting in stable combustion, less flame extinguishing, and complete fuel combustion, significantly improving combustion efficiency, and solving the problems of poor atomization, insufficient mixing, and nozzle clogging in traditional burners. The burner of this application is applicable to power generation, waste incineration, and chemical treatment applications. This invention achieves more uniform mixing by introducing air into the distribution chamber, conical recirculation chamber, and conical expansion chamber via three different delivery paths, allowing for thorough mixing, atomization, and fragmentation with direct-injection primary fuel and tangentially circular secondary fuel. This avoids localized high temperatures caused by uneven mixing. Simultaneously, the staged mixing of fuel and air reduces the high-temperature zone of the flame, thereby decreasing nitrogen oxide emissions. The staged swirl low-NOx burner of this invention features a compact structure, strong adaptability, and good combustion stability, enabling efficient and clean combustion of biomass pyrolysis volatiles with high viscosity, high water content, and complex composition. The distribution chamber of this invention forms a vortex by mixing tangential jetting of primary air with direct fuel injection. Immediately after the vortex is formed, the airflow velocity and vortex intensity are increased by a conical recirculation chamber. The increase in axial velocity and intensity of the vortex promotes a strong recirculation within the conical recirculation chamber, allowing the fuel and air temperature to achieve stable combustion of the main flame through the recirculation. This prevents unstable combustion and flameout caused by the high viscosity, high moisture content, and poor thermal stability of biomass pyrolysis volatiles. At the same time, the structure of the vortex plus the conical recirculation chamber avoids the problem of a significant reduction in axial vortex velocity and intensity after the vortex is formed.

[0056] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A staged swirl low-NOx burner, characterized in that: The combustion chamber includes a combustion shell open at both ends. Within the combustion shell, a distribution chamber, a conical reflux chamber, a conical expansion chamber, and a conveying chamber are arranged sequentially along the longitudinal direction. The distribution chamber provides a flow path for primary fuel and primary air. The distribution chamber includes a primary feed channel and multiple primary air intake channels arranged circumferentially around the primary feed channel. One end of the primary air intake channel is tangentially connected to the conical reflux chamber, which is used for the mixed reflux of primary fuel and primary air. The other end of the conical reflux chamber is connected to one end of the conical expansion chamber. An igniter is located outside the conical reflux chamber. The combustion shell also includes multiple secondary air intake channels. One end of each secondary air intake channel is tangentially connected to one end of the conical expansion chamber, and the other end extends outward from the combustion shell. The other end of the conical expansion chamber is connected to the inlet end of the conveying chamber. Multiple air and feed channels are provided on the circumferential wall outside the conveying chamber. These air and feed channels are used to simultaneously convey secondary fuel and tertiary air. The air and feed channels are tangentially connected to the conveying chamber, and flames are ejected from the outlet end of the conveying chamber. The cone-shaped reflux chamber and the cone-shaped diffuser chamber have opposite cone-shaped directions; At the other end of the conical expansion chamber, near the conical return chamber, there is also a dual-channel vortex chamber. The dual-channel vortex chamber has a conical truncated structure and includes an outer cylinder, an inner cylinder fitted inside the outer cylinder, and a cover plate fixed between the outer cylinder and the inner cylinder. An outer vortex channel for conveying secondary air is formed between the outer cylinder and the inner cylinder. The cover plate has multiple through holes, and the secondary air intake channel is tangentially connected to the through holes. The outer vortex channel is in fluid communication with the secondary air intake channel and the conical expansion chamber, respectively. An inner vortex channel for conveying primary fuel and primary air is formed inside the inner cylinder. The inner vortex channel is in fluid communication with the conical return chamber and the conical expansion chamber, respectively.

2. The staged swirl low-NOx burner according to claim 1, characterized in that: The primary feed channel is located on the central axis of the distribution chamber, and multiple primary air intake channels are evenly arranged around the primary feed channel.

3. A staged swirl low-NOx burner according to claim 1 or 2, characterized in that: The tangential angle between the primary intake passage and the conical recirculation chamber is 30-89°.

4. A staged swirl low-NOx burner according to claim 1 or 2, characterized in that: The tangential directions of the multiple primary air intake channels connected to the conical recirculation chamber are all the same.

5. A staged swirl low-NOx burner according to claim 1, characterized in that: The tangential directions of the multiple secondary air intake channels and through holes are all the same.

6. A staged swirl low-NOx burner according to claim 1, characterized in that: The air intake and feed channels are set perpendicular to the longitudinal direction of the combustion shell.

7. A staged swirl low-NOx burner according to claim 1, characterized in that: The tangential angle between the air intake and feed channel and the conveying chamber is 0-45°.

8. A method of operating a staged swirl low-NOx burner according to any one of claims 1 to 7, characterized in that: Includes the following steps: S1, Direct Injection Feeding and Tangential Jet Jetting: Primary fuel is directly injected through the primary feed channel of the distribution chamber, and primary air is tangentially jetted through the primary air intake channel of the distribution chamber; S2, Atomization and Breakup: Primary air atomizes and breaks up primary fuel and delivers it to the conical recirculation chamber; S3, Conical Recirculation: The primary fuel and primary air entering the conical recirculation chamber are mixed, recirculated, and ignited, and then transported to the dual-channel vortex chamber; S4, Dual-channel swirl: Secondary air enters the outer swirl channel through the secondary intake channel, while primary fuel and primary air enter the inner swirl channel. Primary fuel, primary air and secondary air are jointly transported to the conical diffuser chamber. S5, Conical Diffusion: Primary fuel, primary air and secondary air are mixed in the conical diffusion chamber, and the fuel is atomized and broken up again to enhance the mixed combustion; S6, Tangential Feeding and Air Intake: Secondary fuel and tertiary air are tangentially fed into the conveying chamber through the air intake and feeding channel. The secondary fuel and tertiary air are mixed and burned with the primary fuel, primary air and secondary air, and finally the flame is ejected from the outlet end of the conveying chamber.

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