A co-firing type biomass gas burner

Abstract

This invention discloses a co-firing biomass gas burner and method, belonging to the technical field of combustion equipment. The burner includes a central duct, an inner secondary duct, and an outer secondary duct, coaxially arranged from the inside out. A pulverized coal concentrator is installed inside the central duct, and its outlet end has a slitted blunt body structure with a central through-hole and an axial slit, used to form a graded pulverized coal gas flow. The biomass gas pipeline is equipped with a mechanical tar reduction structure based on temperature detection and flow rate regulation. Through the cooperation of the pulverized coal concentrator, the slitted blunt body, the secondary air swirl blades, and the guide plate, a series of primary and secondary recirculation zones are formed within the burner, achieving zoned mixing and graded combustion of pulverized coal and biomass gas. This invention solves the technical problems of incomplete co-firing, tar blockage, and low-NOx combustion in existing technologies, improving combustion efficiency, stable combustion performance, and reducing pollutant emissions.

Description

Technical Field

[0001] This invention relates to the field of burner technology, and specifically to a co-firing swirl burner capable of simultaneously burning pulverized coal and biomass gas. Background Technology

[0002] Driven by the strategic goals of "peak carbon emissions and carbon neutrality," the need for transformation and upgrading of coal-fired power is urgent. Biomass energy, as a renewable energy source with low sulfur content and low ash content, is an important pathway to optimizing the energy structure when coupled with coal for power generation. Among these technologies, the co-firing of biomass gasification with pulverized coal offers advantages such as material isolation, accurate metering, and the comprehensive utilization of biomass ash.

[0003] However, existing co-firing technology still faces the following challenges:

[0004] Incomplete combustion and high NOx emissions: If biomass gas and pulverized coal are directly mixed in the furnace, there will be problems of uneven mixing and incomplete combustion, which will easily lead to low combustion efficiency. In addition, the high volatile matter and fuel nitrogen in biomass gas may generate more nitrogen oxides (NOx) at high temperatures, which is not conducive to achieving low-NOx combustion.

[0005] Tar deposition and blockage risk: Biomass gas contains tar components. If the temperature is not properly controlled during pipeline transportation, condensation and deposition can easily occur, leading to blockage of pipelines and burners, and affecting the stable operation of the system.

[0006] Poor low-load stable combustion performance: Conventional burners are prone to flame instability or even flameout when operating under fluctuating or low load conditions.

[0007] In the prior art, patent CN221055002U discloses a biomass gas burner, but does not involve a coal powder co-firing strategy or a tar treatment scheme. Patent CN115405924A discloses a tar treatment structure for biomass gas, but similarly does not propose an effective method for co-firing coal powder and biomass gas.

[0008] Therefore, there is an urgent need for a burner that can achieve efficient, clean, and stable co-firing of pulverized coal and biomass gas, and effectively solve the problem of tar blockage. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a co-firing biomass gas burner. This burner integrates technologies such as pulverized coal concentration separation, zoned reflux combustion, and intelligent tar control to achieve efficient, clean, and stable co-firing of pulverized coal and biomass gas, while effectively preventing tar blockage.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] In the first aspect, a co-firing type biomass gas burner includes a central air duct, an inner secondary air duct, and an outer secondary air duct that are coaxially arranged from the inside to the outside.

[0012] The central duct is used to transport primary air and pulverized coal.

[0013] A coal powder concentrator is installed axially inside the central duct to separate the coal powder airflow into a dense phase coal powder airflow located in the center and a light phase coal powder airflow located in the outer ring.

[0014] The outlet end of the central air duct is provided with a slit blunt body structure, which has a central through hole and several slits along the axial direction.

[0015] The pulverized coal concentrator is located upstream of the slotted blunt body structure;

[0016] It also includes an independently set biomass gas pipeline, which is equipped with a mechanical tar reduction structure and its outlet direction is inclined towards the downstream area of ​​the burner outlet.

[0017] The outlet of the internal secondary air duct is equipped with secondary air swirl blades;

[0018] A baffle plate is provided downstream of the slotted blunt body structure, near the burner outlet;

[0019] Through the cooperation of the pulverized coal thickener, the slotted blunt body structure, the secondary air swirl blades, and the guide plate, a primary recirculation zone and a secondary recirculation zone are formed in the burner along the airflow direction. The primary recirculation zone is located downstream of the slotted blunt body structure, in the annular space between the outer side of the slotted blunt body structure and the inner wall of the burner. It is a recirculation area induced by the secondary air swirl and the light-phase pulverized coal airflow, used for the preliminary premixing of pulverized coal and air and stable combustion. The secondary recirculation zone is located downstream of the primary recirculation zone. It is formed by the combined action of the dense-phase pulverized coal airflow passing through the central through-hole, the inclined injected biomass gas, and the downstream airflow guided by the guide plate, used to enhance the mixing and combustion of pulverized coal and biomass gas.

[0020] Furthermore, the pulverized coal concentrator is a louvered concentrator, comprising an inner core cylinder and an outer ring guide shroud arranged coaxially, and a plurality of inclined louvered guide vanes disposed on the outer ring guide shroud; the louvered guide vanes are installed at an angle of 20° to 45° relative to the axis of the central air duct, are evenly distributed circumferentially, and form an annular diversion channel between adjacent guide vanes.

[0021] Furthermore, the slit blunt body structure is a blunt-headed frustum-shaped structure, including a front windward surface of the blunt body, an expanded rearward section of the blunt body, and a through central hole; the number of slits is 2 to 8, evenly distributed circumferentially, the width of a single slit is 2 to 10 mm, and the length is (0.3 to 1.2)D, where D is the diameter of the central duct.

[0022] Furthermore, the tail end of the central air duct is provided with adjustable guide vanes, the angle of which is adjustable and / or detachable.

[0023] Furthermore, the mechanical tar-reducing structure includes:

[0024] The temperature detection unit includes a K-type thermocouple installed on the biomass gas pipeline for real-time detection of biomass gas temperature.

[0025] The control unit includes an electrically operated control valve located downstream of the temperature detection unit for regulating the flow rate of the biomass gas stream.

[0026] The tar dispersion unit includes a tar dispersion disk disposed downstream of the execution adjustment unit, used to change the movement trajectory of the tar-containing biomass airflow.

[0027] The control unit is used to receive signals from the temperature detection unit and control the execution adjustment unit to: reduce the valve opening to reduce the flow rate when the detected temperature is lower than the first preset temperature T1; and increase the valve opening when the detected temperature is higher than the second preset temperature T2.

[0028] Furthermore, the mechanical tar reduction structure also includes a swirl enhancement unit, comprising biomass swirl blades disposed in a pipe section upstream or downstream of the tar dispersion disk, wherein the installation angle of the biomass swirl blades is 15° to 25°.

[0029] Furthermore, the tar dispersion disk is a disc or truncated cone structure with guide vanes, and a gap is left between its outer edge and the inner wall of the biomass gas pipeline to form an annular flow channel; the deflection angle of the guide vanes is 90° to 150°.

[0030] Furthermore, it also includes an independently installed combustion air duct, the outlet of which points towards the primary recirculation zone.

[0031] Secondly, a combustion method using the aforementioned co-firing type biomass gas burner includes the following steps:

[0032] Primary air and pulverized coal are introduced into the central air duct, and through the action of the pulverized coal concentrator, a radial concentration distribution is formed with the inner part being more concentrated and the outer part being less concentrated.

[0033] Dense-phase pulverized coal gas flow is directly injected into the secondary reflux zone through the central through-hole of the slotted blunt body structure;

[0034] Under the guidance and obstruction of the slotted blunt body structure, the light phase pulverized coal gas flow mixes with the swirling secondary air from the inner and / or outer secondary air ducts, and undergoes preliminary premixing and ignition in the primary recirculation zone;

[0035] Biomass gas is fed into the secondary reflux zone at an angle after being processed by a mechanical tar reduction structure via an independent biomass gas pipeline.

[0036] The premixed gas flow from the primary reflux zone, the dense-phase pulverized coal gas flow ejected from the center, and the biomass gas are intensely mixed and combusted in the secondary reflux zone.

[0037] By adjusting the independent air volume and swirl intensity of primary air, internal secondary air, external secondary air, biomass gas, and combustion air, load regulation and low-NOx stable combustion can be achieved.

[0038] The advantages of this invention over the prior art are:

[0039] Highly efficient and stable co-combustion of pulverized coal and biomass gas was achieved: through the synergistic effect of the pulverized coal concentrator and the slotted blunt body structure, radial concentration gradation of pulverized coal was realized. The rich and poor phase pulverized coal gas streams entered the primary and secondary recirculation zones arranged in series, respectively, forming a zoned and staged combustion mode. The poor phase pulverized coal achieved stable ignition in the primary recirculation zone, playing a crucial role in stable combustion; the rich phase pulverized coal and pretreated biomass gas were thoroughly mixed and deeply combusted in the secondary recirculation zone, significantly improving the overall combustion efficiency and burnout rate of both fuels. This structural design particularly ensured the flame stability of the burner under low-load conditions, broadening the stable operating range.

[0040] This invention effectively reduces nitrogen oxide (NOx) emissions by combining fuel staging with spatial zoning to achieve low-NOx combustion. In the primary recirculation zone, the pulverized coal concentration is low, resulting in an oxygen-rich, under-fuel state. In the secondary recirculation zone, the fuel (concentrated pulverized coal and biomass gas) is relatively concentrated, but through mixing with the already ignited gas stream and its own staging, the formation of localized high-temperature zones is avoided. This staged and zoned combustion organization effectively suppresses the formation of thermal NOx, achieving clean combustion.

[0041] This innovative solution addresses the problem of tar blockage in biomass gas: Addressing the condensable nature of tar in biomass gas, an intelligent mechanical tar reduction structure was designed, integrating temperature detection, flow rate regulation, swirling centrifugation, and mechanical impact dispersion. This system can adjust the pipeline flow rate in real time based on the incoming gas temperature, optimizing tar separation conditions. Through the physical action of swirling blades and a dispersion disc, it effectively promotes the capture, aggregation, and separation of tar droplets, significantly reducing the risk of tar deposition and blockage inside the pipelines and burners, ensuring the long-term reliable operation of the system.

[0042] It boasts high operational flexibility and adaptability to a wide range of operating conditions: all gas supply channels (primary air, internal / external secondary air, combustion air, and biomass gas) are independently set up and their flow rates can be independently adjusted. Furthermore, key parameters such as the secondary air swirl intensity and the adjustable guide vane angle downstream of the pulverized coal thickener are also adjustable. This allows the burner to flexibly adapt to different coal characteristics, biomass gas composition, and boiler load variations, achieving precise adjustment and optimization of combustion conditions.

[0043] Compact structure and high degree of functional integration: The present invention adopts a multi-layer coaxial sleeve-type main structure, which highly integrates multiple functions such as coal powder concentration separation, reflux zone organization, cyclone enhancement, and tar pretreatment into one unit. The layout is reasonable and the space utilization rate is high, which is conducive to the transformation or application in existing boiler systems. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic axial cross-sectional view of the co-firing biomass gas burner provided by the present invention.

[0046] Figure 2 The schematic diagram of the working principle of the co-firing biomass gas burner provided by the present invention shows the airflow path and recirculation zone.

[0047] Figure 3 This is a schematic diagram of the pre-installation component (mechanical tar reduction structure) for the biomass gas pipeline provided by the present invention.

[0048] Figure 4 This is a cross-sectional view of the slotted blunt body structure provided by the present invention.

[0049] In the diagram: 1. Central duct; 2. Inner secondary duct; 3. Outer secondary duct; 4a. Guide vane; 4b. Biomass gas cyclone vane; 4c. Secondary air cyclone vane; 5. Guide blunt body; 6. Guide plate; 7. Combustion air duct; 8. Pulverized coal concentrator; 9. Adjustable guide vane; 10. Slit blunt body structure; 11. Biomass gas duct; 12. K-type thermocouple; 13. Electric regulating valve; 14. Tar dispersion disc. Detailed Implementation

[0050] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limiting purposes, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details.

[0051] See Figures 1 to 3 A co-firing biomass gas burner is disclosed. The burner of this invention mainly comprises a multi-layer coaxial sleeve structure. From the inside out, it consists of: a central air duct 1, an inner secondary air duct 2, and an outer secondary air duct 3. The central air duct 1 is used to transport primary air and pulverized coal, and a pulverized coal concentrator 8 is installed axially inside it. In this invention, the pulverized coal concentrator 8 is preferably a louvered type, comprising an inner core cylinder arranged axially along the central air duct, an outer ring guide shroud coaxially mounted with the inner core cylinder, and several inclined louvered guide vanes mounted on the outer ring guide shroud. The installation angle of the guide vanes relative to the axis of the central air duct 1 is 20° to 45°, and they are evenly distributed circumferentially, forming several annular diversion channels between adjacent guide vanes. The pulverized coal concentrator is installed upstream of the outlet of the central air duct 1, with the installation distance measured by the inner diameter D of the central air duct, preferably (1.0 to 2.5)D. After the primary air carrying the coal powder enters the concentrator, under the action of the louvered guide vanes, part of the coal powder-carrying airflow is forced to deflect in the outer diameter direction to form an outer ring of dilute phase flow; while the coal powder particles with larger particle size and stronger inertia are difficult to deflect sharply with the airflow, tend to maintain axial movement and converge near the inner core cylinder, thus forming a "dense phase core" with a higher coal powder volume fraction in the inner core area, and a "light phase outer ring" in the outer ring area, achieving a radial distribution of "dense inside and light outside".

[0052] A flow guide bluff body 5 is installed at the end of the external secondary air duct 3. An adjustable flow guide vane 9 is installed at the tail of the central air duct 1. The angle of the adjustable flow guide vane 9 is adjustable or detachable, used to adjust the outflow direction of the light-phase pulverized coal airflow, adjust the concentration of the central pulverized coal airflow entering the secondary recirculation zone, and adjust the airflow intensity in the primary recirculation zone. Under the action of the adjustable flow guide vane 9, the internal secondary air and the external secondary air enter the primary recirculation zone in a circumferential swirling flow under the action of the flow guide bluff body 5, together forming the main aerodynamic source of the primary recirculation zone with the light-phase pulverized coal.

[0053] A slotted blunt body structure is arranged on one side of the tail end of the central air duct. The slotted blunt body structure is preferably a blunt-headed frustum-shaped blunt body, comprising a frontal windward surface of the blunt body, a rearward expanding section of the blunt body, and a through-hole in the center; an annular gap is formed between the outer surface of the blunt body and the inner wall of the burner. The "slot" is preferably a small-hole slot arranged axially, with 2 to 8 slots evenly distributed circumferentially; the width of a single slot is preferably 2 to 10 mm, and the length of the slot is preferably (0.3 to 1.2)D (D is the diameter of the central air duct); a preferred parameter ratio is a front-to-rear cross-sectional area ratio of 1:5 and a ratio of the outer diameter of the blunt body's front edge to the diameter of the central through-hole of 5:4. This structure helps to form a stable recirculation zone through a combination of geometric obstruction and airflow venting.

[0054] The slit is preferably oriented in a small-angle spiral (spiral angle ≤ 15°) with respect to the axis to induce a stable shear layer near the tail of the bluff body. The slit bluff body structure forms a zoned recirculation through a coupling of "geometric blocking + slit release": the windward side of the bluff body creates a velocity gradient and pressure difference between the central jet and the outer ring vortex, and the shear layer on the outer side of the bluff body generates recirculation; the slit allows some high-speed gas to be released along the slit and form a small-scale vortex structure behind the slit, enhancing the stability and intensity of the recirculation, thereby forming a primary recirculation zone on the outer side of the bluff body and in the near-wall region; while the central through-hole jet, after passing through the bluff body, superimposes with the downstream vortex / wall-induced flow, forming a stronger recirculation in the near-outlet region, constituting a secondary recirculation zone, thus realizing the physical separation and connection of the primary and secondary recirculation zones.

[0055] The inner secondary air duct 2 is equipped with secondary air swirl blades 4c. The tilt angle of the swirl blades is designed between 30° and 45° to generate strong rotation of the secondary air, creating strong shear with the pulverized coal airflow. In addition, an independently arranged combustion air duct 7 is provided on the burner wall, allowing for flexible adjustment of the combustion air volume and aiding in the primary recirculation zone. The combustion air duct 7 is equipped with guide vanes 4a to adjust the injection angle of the combustion air, ensuring it is more accurately directed towards the primary recirculation zone. The outlet direction of the combustion air duct 7 points towards the annular area formed by the outer side of the slotted blunt body structure 10, enhancing the combustion atmosphere in that area.

[0056] The primary recirculation zone is used to achieve primary premixing, and the arrangement of the combustion air duct 7 helps to achieve primary recirculation. The pulverized coal burner is designed with direct primary air and swirling secondary air, which ensures more stable pulverized coal combustion. The pulverized coal burner achieves adjustable design of biomass gas and pulverized coal through the design of the annular central duct, combustion air duct, and biomass gas duct. The central duct 1 introduces primary air and pulverized coal, and under the concentration separation action of the pulverized coal concentrator 8, it is introduced into the slotted blunt body structure 10, realizing the central concentrated pulverized coal airflow into the secondary recirculation zone. The tail ends of the inner secondary air duct 2 and the outer secondary air duct 3 are respectively equipped with adjustable guide vanes 9 and guide blunt bodies 5, and under the influence of the slotted blunt body structure 10, they are directed to the primary recirculation zone. The biomass gas introduced into the biomass gas duct 11, after passing through the tar separation structure, achieves the secondary recirculation zone under the influence of the guide plate 6. The airflow entering the duct, after passing through the primary and secondary recirculation zones, is directed together to the subsequent furnace area.

[0057] The primary recirculation zone is located in the annular space between the outer side of the slotted blunt body structure 10 and the inner wall of the burner. The light-phase pulverized coal gas flow separated by the pulverized coal thickener 8, under the adjustment of the adjustable guide vanes 9 and the guiding and blocking effect of the slotted blunt body structure 10, mixes with the strongly swirling secondary air from the inner and outer secondary air ducts in this zone, inducing a stable high-temperature flue gas recirculation. This zone is mainly used for the initial premixing and stable ignition of pulverized coal and air, and is crucial for achieving stable combustion at low loads and rich-lean staged combustion. The secondary recirculation zone is located downstream of the primary recirculation zone, near the burner outlet. The dense-phase pulverized coal gas flow ejected from the central air duct 1 and passing through the central through-hole of the slotted blunt body structure 10, mixes intensely with the ignited high-temperature premixed gas flow from the primary recirculation zone, and with the biomass gas treated by the mechanical tar reduction structure and injected at an angle, under the guidance of the guide plate 6, forming a larger-scale secondary recirculation. This zone is the main reaction zone for deep mixing and complete combustion of pulverized coal and biomass gas.

[0058] The flow path after concentration-lean separation is as follows: The dense-phase core pulverized coal airflow formed by the pulverized coal thickener moves axially along the central duct. Under the guidance of the central through-hole of the slotted blunt body structure, it basically maintains its axial momentum and directly enters the secondary recirculation zone after passing through the leading edge of the blunt body. The light-phase outer ring pulverized coal airflow formed by the pulverized coal thickener is located in the near-wall region of the central duct. Due to the deflection of the adjustable guide vanes and the obstruction and guidance of the blunt body shape, it is deflected radially outward and axially backward, and introduced into the annular space between the outer side of the blunt body and the inner wall of the burner. Here, it forms strong shear with the inner and outer secondary air and induces recirculation, thus entering the primary recirculation zone to achieve premixing. At the same time, the inner and outer secondary airflows enter the above-mentioned annular space in a circumferential swirling motion under the action of the tail guide structure, and together with the light-phase pulverized coal, they constitute the main aerodynamic source of the primary recirculation zone.

[0059] Meanwhile, the burner also includes an independently installed biomass gas pipeline 11. The upstream section of this pipeline integrates a mechanical tar reduction structure. The mechanical tar reduction structure includes a K-type thermocouple, a mechanical device, a tar dispersion disk, and a swirl blade structure. The K-type thermocouple is connected to the mechanical device, and the flow rate of the biomass gas is controlled through the mechanical device and the thermocouple, thereby achieving tar settling in the biomass gas and controlling the flow rate of the biomass gas.

[0060] The mechanical tar reduction structure mainly includes: a temperature detection unit, consisting of a K-type thermocouple 12 installed on the pipeline, used to detect the temperature of the biomass gas inlet in real time. The K-type thermocouple is preferably installed in a straight section of the biomass gas inlet pipeline or close to the pipe wall, preferably at a position (0.5–2.0) Dg upstream of the mechanical regulating unit (Dg is the inner diameter of the biomass gas pipeline), used to measure the inlet gas temperature in real time and output a temperature signal; and an actuation regulating unit, an electric regulating valve 13 (such as an electric butterfly valve, electric baffle, or electric needle valve) located downstream of the temperature detection unit. The valve opening can be continuously adjusted to regulate the biomass gas in the pipeline. The flow rate and residence time are controlled by the following logic: When the detected temperature is lower than the preset temperature T1, the control unit reduces the opening to decrease the flow rate and increase the residence time, making it easier for tar droplets to separate under gravity settling and wall capture; when the detected temperature is higher than the preset temperature T2, and T2>T1, the control unit increases the opening to reduce resistance and avoid excessive throttling; the swirl enhancement unit is equipped with swirl blades located in the pipe section upstream or downstream of the tar dispersion disk. The number of swirl blades is preferably 4 to 12, and the blade installation angle is preferably 15° to 25°. The tar droplets are migrated to the near wall and the separation is enhanced through centrifugal force. Tar dispersion unit: The tar dispersion disk is installed downstream of the control unit at (0.2~1.5)Dg. The dispersion disk can be a disc or a truncated cone structure with guide vanes. The outer edge of the disk has a gap with the pipe wall to form an annular flow channel. The deflection angle of the guide vanes of the dispersion disk is preferably 90°~150°, so that the tar-containing airflow will be impacted, atomized and deflected, thereby changing the tar movement trajectory and making the tar easier to settle / disperse.

[0061] The outlet of the biomass gas pipeline 11 is inclined towards the downstream area of ​​the burner outlet. The biomass gas pipeline 11 has independent ventilation, and the biomass gas is inclined into the burner. The air volume of the biomass gas introduced into the burner can be flexibly adjusted, and it helps to realize the secondary recirculation zone.

[0062] Downstream of the slotted blunt body structure 10, near the burner outlet, a baffle plate 6 is also installed to guide the downstream airflow. The overall recirculation zone is symmetrically arranged and helps to stabilize the shape of the recirculation zone.

[0063] Through the cooperation of the pulverized coal concentrator 8, the slotted blunt body structure 10, the secondary air swirl blade 4c and the guide plate 6, a primary recirculation zone and a secondary recirculation zone are formed in series along the airflow direction in the burner.

[0064] The combustion method using the co-firing type biomass gas burner described in this invention is as follows:

[0065] Coal powder concentration separation and airflow conveying: The mixed airflow of primary air and coal powder is introduced into the central air duct 1. Inside the central air duct 1, the mixed airflow flows through the coal powder concentrator 8. Under the action of the louvered guide vanes, the coal powder airflow achieves "concentrated inside and dilute outside" concentration classification in the radial direction, forming a concentrated coal powder airflow in the center and a dilute coal powder airflow in the outer ring.

[0066] Construction of the recirculation zone and initial fuel diversion: The air supply system is activated, and secondary air is introduced into the inner secondary air duct 2 and the outer secondary air duct 3 respectively. The secondary air forms a strong rotating airflow through the action of the secondary air swirl blades 4c. The dense-phase pulverized coal airflow maintains its axial momentum and directly passes through the central through-hole of the slotted blunt body structure 10, entering the downstream region of the burner. The light-phase pulverized coal airflow flows in the near-wall region of the central air duct 1. After being adjusted by the angle of the adjustable guide blades 9, it is deflected into the annular space between the outer side of the slotted blunt body structure 10 and the inner wall of the burner under the guidance and obstruction of the slotted blunt body structure 10, and strongly mixes with the rotating secondary air. Here, the swirl and the blunt body together induce the formation of a stable high-temperature flue gas primary recirculation zone. In this zone, the light-phase pulverized coal undergoes preliminary premixing, heating, and stable ignition with the high-temperature flue gas and the air supplied from the combustion air duct 7.

[0067] Biomass gas pretreatment and supply: Biomass gas is introduced into a separate biomass gas pipeline 11. The biomass gas first flows through the mechanical tar-reducing structure: the gas temperature is monitored in real time by a K-type thermocouple 12. When the temperature is lower than the preset value T1, the electric regulating valve 13 is controlled to reduce the opening to decrease the flow rate and promote tar settling. At the same time, the gas flow passes sequentially through the biomass gas swirl vanes 4b and the tar dispersion disk 14, where centrifugal force and impact are used to separate or disperse the tar. The treated clean biomass gas is ejected from the pipeline outlet at an inclined angle, pointing downstream of the burner outlet.

[0068] Secondary fuel mixing and deep combustion: The pre-mixed, ignited gas stream from the primary recirculation zone, the high-temperature dense-phase pulverized coal stream ejected from the central through-hole, and the clean biomass gas injected obliquely from the side—these three streams undergo intense entrainment and mixing under the guidance of the guide plate 6 located downstream of the slotted blunt body structure 10. This mixing process, combined with the downstream wall effect, forms a secondary recirculation zone with even higher turbulence intensity near the burner outlet. Within this zone, the pulverized coal and biomass gas undergo deep mixing and complete combustion.

[0069] Operational adjustment and optimization: During combustion, the following parameters are independently adjusted to achieve load adaptation and low-NOx stable combustion: adjusting the flow ratio of primary air, internal secondary air, external secondary air, biomass gas, and combustion air; adjusting the swirl intensity of the secondary air swirl blade 4c and the biomass gas swirl blade 4b; adjusting the angle of the adjustable guide blade 9 according to changes in coal type and load; and adaptively adjusting the airflow speed and tar separation effect through the control unit of the mechanical tar reduction structure according to the temperature and quality of biomass gas.

[0070] Through the above steps, the staged and zoned mixed combustion of pulverized coal and biomass gas in terms of physical space and combustion time is realized. While ensuring stable combustion performance under low load, the combustion efficiency and burnout rate are improved, and the generation of nitrogen oxides is effectively suppressed.

[0071] Example 1:

[0072] This embodiment provides a specific configuration of structural parameters for a co-firing type biomass gas burner to illustrate the implementation of the present invention in detail.

[0073] Secondary air system: The installation angle of both the inner secondary air swirl blade 4c and the outer secondary air swirl blade 4c is set to 37°.

[0074] Biomass gas treatment system: The swirl vanes 4b inside the biomass gas pipeline 11 are installed at an angle of 20°, with a total of 8 vanes. The deflection angle (i.e., dispersion angle) of the guide vanes of the tar dispersion disc 14 is set to 120°, and its installation position is located 0.8Dg downstream of the actuator (electric regulating valve 13), where Dg is the inner diameter of the biomass gas pipeline 11. The control temperature thresholds of the actuator are set as follows: first preset temperature T1 = 180℃, second preset temperature T2 = 240℃.

[0075] Coal powder thickening system: The coal powder thickener 8 adopts a louvered structure, and the installation angle of its louvered guide vanes relative to the axis of the central air duct 1 is 30°. The coal powder thickener 8 is installed at a position 1.5D upstream of the outlet of the central air duct 1, where D is the inner diameter of the central air duct 1.

[0076] Blunt body structure: The slit blunt body structure 10 has 4 axial slits, each slit width is 5mm. The ratio of the front and rear cross-sectional areas of this blunt body is 1:5, and the ratio of the outer diameter of the leading edge of the blunt body to the diameter of the central through hole is 5:4.

[0077] Simulation and experimental runs were conducted under these parameter configurations. The results show that this embodiment can form stable and clearly defined primary and secondary reflux zones, significantly improving the mixing uniformity of biomass gas and pulverized coal in the combustion chamber. During continuous operation, the tendency for tar deposition in the biomass gas pipeline and burner head was significantly reduced. Performance tests show that compared with the simple co-firing method of directly introducing biomass gas into the furnace, the fuel burnout rate increased from approximately 94.2% to approximately 95% after using this burner; compared with the baseline condition of simply burning pulverized coal, under the same heat load conditions, the nitrogen oxide (NOx) emission concentration was reduced by approximately 26.9%, and the overall furnace efficiency was also improved to a certain extent.

[0078] Example 2:

[0079] This embodiment maintains the overall structure and other parameters of Embodiment 1 unchanged, but adjusts only two key dimensions of the slotted blunt body structure 10 to explore the effect of structural parameter changes on combustion performance and to demonstrate the adjustability of the present invention.

[0080] The specific adjustments are as follows:

[0081] The ratio of the outer diameter of the blunt body leading edge to the diameter of the central through hole in the slit blunt body structure 10 is adjusted from 5:4 to 6:5.

[0082] The width of the single seam of the axially opened seam was reduced from 5 mm to 3 mm.

[0083] The aforementioned dimensional adjustments altered the flow field structure in the outlet region of the central duct 1: these adjustments changed the central jet flow distribution and near-wall shear layer strength, consequently altering the recirculation intensity and stability of the primary recirculation zone, thus affecting the formation location and premixing degree of the secondary recirculation zone. Compared to Example 1, the overall ignition and premixing positions shifted downstream, resulting in poorer low-load combustion stability and an increased likelihood of unburned CO. However, simultaneously, the overall downstream mixing was enhanced, leading to a slight improvement in the overall burnout rate, but the overall combustion stability deteriorated.

[0084] This embodiment illustrates that by adjusting the key dimension ratio of the slotted blunt body, the characteristics of the primary and secondary recirculation zones can be specifically adjusted, thereby adapting and optimizing the burner according to the different emphases on low-load stable combustion performance and high-load burnout efficiency in actual applications.

[0085] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0086] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A co-firing type biomass gas burner, characterized in that, It includes a central air duct (1), an inner secondary air duct (2), and an outer secondary air duct (3) that are coaxially arranged from the inside to the outside. The central duct (1) is used to transport primary air and pulverized coal; The central duct (1) is provided with a coal powder concentrator (8) along the axial direction, which is used to separate the coal powder airflow into a dense phase coal powder airflow located in the center and a light phase coal powder airflow located in the outer ring. The outlet end of the central air duct (1) is provided with a slit blunt body structure (10), which has a central through hole and several slits along the axial direction. The coal pulverizer (8) is located upstream of the slotted blunt body structure (10); It also includes an independently set biomass gas pipeline (11), which is equipped with a mechanical tar reduction structure and its outlet direction is inclined to the downstream area of ​​the burner outlet; The outlet of the inner secondary air duct (2) is provided with a secondary air swirl blade (4c). A baffle plate (6) is provided downstream of the slotted blunt body structure (10) and near the burner outlet. Through the cooperation of the coal pulverizer (8), the slotted blunt body structure (10), the secondary air swirl blade (4c), and the guide plate (6), a primary recirculation zone and a secondary recirculation zone are formed in the burner along the airflow direction. The primary recirculation zone is located downstream of the slotted blunt body structure (10) in the annular space between the outer side of the slotted blunt body structure (10) and the inner wall of the burner. It is a recirculation area induced by the secondary air swirl and the light-phase coal pulverized gas flow, used for the preliminary premixing of coal pulverized gas and air and stable combustion. The secondary recirculation zone is located downstream of the primary recirculation zone. It is formed by the combined action of the dense-phase coal pulverized gas flow passing through the central through hole, the inclined injected biomass gas, and the downstream airflow guided by the guide plate (6). It is used to enhance the mixing and combustion of coal pulverized gas and biomass gas.

2. The co-firing type biomass gas burner according to claim 1, characterized in that, The coal pulverizer (8) is a louvered concentrator, including an inner core cylinder and an outer ring guide shroud arranged coaxially, and several inclined louvered guide vanes arranged on the outer ring guide shroud; the installation angle of the louvered guide vanes relative to the axis of the central air duct (1) is 20° to 45°, they are evenly distributed in the circumferential direction, and form an annular diversion channel between adjacent guide vanes.

3. The co-firing type biomass gas burner according to claim 1 or 2, characterized in that, The slit blunt body structure (10) is a blunt-headed frustum structure, including the front windward surface of the blunt body, the rear expansion section of the blunt body, and the through central hole; the number of slits is 2 to 8, evenly distributed along the circumference, the width of a single slit is 2 to 10 mm, and the length is (0.3 to 1.2)D, where D is the diameter of the central air duct (1).

4. The co-firing type biomass gas burner according to claim 1, characterized in that, The tail end of the central air duct (1) is provided with an adjustable guide vane (9), the angle of which is adjustable and / or detachable.

5. The co-firing type biomass gas burner according to claim 1, characterized in that, The mechanical tar-reducing structure includes: The temperature detection unit includes a K-type thermocouple (12) installed on the biomass gas pipeline (11) for real-time detection of biomass gas temperature; The control unit includes an electric control valve (13) located downstream of the temperature detection unit for regulating the flow rate of the biomass gas stream; The tar dispersion unit includes a tar dispersion disk (14) disposed downstream of the execution adjustment unit, used to change the movement trajectory of the tar-containing biomass airflow; The control unit is used to receive signals from the temperature detection unit and control the execution adjustment unit to: reduce the valve opening to reduce the flow rate when the detected temperature is lower than the first preset temperature T1; and increase the valve opening when the detected temperature is higher than the second preset temperature T2.

6. The co-firing biomass gas burner according to claim 5, characterized in that, The mechanical tar reduction structure also includes a swirl enhancement unit, which includes biomass swirl blades (4b) installed in the pipe section upstream or downstream of the tar dispersion disk (14), and the installation angle of the biomass swirl blades (4b) is 15° to 25°.

7. The co-firing biomass gas burner according to claim 6, characterized in that, The tar dispersion disk (14) is a disc or truncated cone structure with guide vanes. There is a gap between its outer edge and the inner wall of the biomass gas pipeline (11) to form an annular flow channel. The deflection angle of the guide vanes is 90° to 150°.

8. The co-firing biomass gas burner according to claim 1, characterized in that, It also includes an independently set combustion air duct (7), the outlet direction of which points to the primary recirculation zone.

9. A combustion method, employing a co-firing type biomass gas burner as described in any one of claims 1-8, characterized in that, Includes the following steps: Primary air and pulverized coal are introduced into the central air duct (1), and a radial concentration distribution with a high concentration inside and a low concentration outside is formed by the action of the pulverized coal concentrator (8). Dense-phase coal powder gas flow is directly injected into the secondary reflux zone through the central through hole of the slotted blunt body structure (10); The light-phase pulverized coal gas flow is guided and blocked by the slotted blunt body structure (10), and mixed with the swirling secondary air from the inner secondary air duct (2) and / or the outer secondary air duct (3) to carry out preliminary premixing and ignition in the primary recirculation zone; Biomass gas is fed into the secondary reflux zone at an angle after being processed by a mechanical tar reduction structure via an independent biomass gas pipeline (11). The premixed gas flow from the primary reflux zone, the dense-phase pulverized coal gas flow ejected from the center, and the biomass gas are intensely mixed and combusted in the secondary reflux zone. By adjusting the independent air volume and swirl intensity of primary air, internal secondary air, external secondary air, biomass gas, and combustion air, load regulation and low-NOx stable combustion can be achieved.

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