A burner and combustion method suitable for multi-coal combustion by changing the backflow area in coordination with the blade angle and air volume

Abstract

The application relates to a burner and a combustion method suitable for multi-coal combustion by changing a backflow area in cooperation with a blade angle and a wind volume, and belongs to the technical field of tangential circle boiler combustion technology. In order to solve the problems that a self-stabilized combustion burner cannot change the cyclone intensity flexibly along with the change of coal quality, the resistance is increased due to the increase of the blade angle, the wind pressure of the secondary air box is insufficient, and the full combustion of the pulverized coal cannot be guaranteed, the stable combustion flame is difficult to form and the like, the application introduces an inner secondary air cyclone assembly and an inner secondary air air supplementing system, so that the working angle of the blade in the inner secondary air pipeline is adjusted to adaptively change the wind volume of the inner secondary air, the cyclone intensity of the inner secondary air is flexibly adjusted along with the change of the coal quality, the purpose of stable combustion is achieved, and the application is mainly used for improving the stable combustion effect of the boiler during work.

Description

Technical Field

[0001] This invention relates to the field of tangential boiler combustion technology, specifically to a burner and combustion method that can be adapted to the combustion of multiple coal types by synergistically changing the recirculation zone through blade angle and air volume. Background Technology

[0002] In recent years, with the comprehensive implementation of the national "dual-carbon" policy, my country has continuously increased its support and promotion of new energy power generation, resulting in a booming new energy power generation industry. However, the traditional thermal power industry, especially coal-fired boiler power generation, faces significant challenges. The utilization hours of thermal power units have been declining year by year, reflecting the transformation trend of the energy structure. Against this backdrop, in order to promote the smooth transformation of the power industry towards a clean and low-carbon direction, the stability of power grid operation urgently needs to be guaranteed. In particular, due to the inherent randomness and instability of new energy power generation, it has a complex and unpredictable impact on the power system. Therefore, improving the deep flexibility and peak-shaving capacity of traditional thermal power units has become crucial to ensuring the stability of the power system and meeting load regulation needs.

[0003] Coal-fired boiler power generation is currently the mainstay of my country's energy structure. The combustion method of coal-fired boilers primarily employs direct-flow burners arranged at the four or eight corners of the boiler furnace. Pulverized coal gas flow and secondary air are injected into the furnace through the direct-flow burner jets, converging in a tangential circular pattern. The side of the pulverized coal gas flow facing the fire is ignited by the direct impact of the high-temperature flame at the upstream adjacent corner. The four (or eight) corner jets support each other, forming a rotating combustion flame. The four-corner (or eight) tangential-circle pulverized coal combustion boiler is the most widely used and mature boiler type in my country's power plants, accounting for approximately 70% or more of the total installed capacity. However, the stable combustion load of domestic coal-fired power units without oil injection can only reach 30%-40%.

[0004] A method and apparatus for co-combustion using direct-flow burners and swirl burners are employed. Four self-contained combustion stabilizers are positioned at the four corners between the direct-flow primary air nozzle and the direct-flow secondary air nozzle of the direct-flow pulverized coal burner. As a key combustion device, the self-contained combustion stabilizers inject pulverized coal gas into the combustion stabilization chamber in a direct-flow manner under high load. This combustion stabilization chamber has a larger heat load compared to the furnace cross-section. The heat released after combustion causes the temperature within the combustion stabilization chamber to rise rapidly and remain at a high temperature, which is beneficial for complete combustion of the pulverized coal. Under low load, the high-concentration pulverized coal forms a central recirculation zone under the action of the combustion stabilization chamber and the secondary air in the swirl burner, serving as a stable ignition heat source to heat the high-concentration pulverized coal. Simultaneously, the flame generated by the self-contained combustion stabilizers ignites the primary air-pulverized coal flame of the direct-flow burner. This achieves stable combustion of coal-fired power units at 20%-30% of rated load solely through pulverized coal combustion without the aid of external flame-assisted combustion technologies such as micro-oil or plasma.

[0005] However, under market economy conditions, fluctuations in coal prices lead to frequent changes in the coal used in boilers, and the variability in coal quality is a significant challenge for pulverized coal boilers. This variability directly affects the ignition and stable combustion characteristics of pulverized coal. The internal secondary air swirl allows high-temperature flue gas from the rear of the burner to flow back to its root, promoting ignition and subsequent stable combustion of the pulverized coal airflow. Deteriorating coal quality necessitates increasing the swirl intensity to promote the entrainment of high-temperature flue gas and ensure pulverized coal ignition and stable combustion; conversely, good coal quality allows for a suitable reduction in swirl intensity to prevent nozzle overheating and burnout. Therefore, under conditions of varying coal quality, adjustable swirl intensity can significantly enhance the burner's coal adaptability, ensuring boiler efficiency and reliability, as well as power plant economics.

[0006] Currently, existing self-regulating combustion burners have certain limitations in practical applications. Their swirl intensity is usually fixed or has a limited adjustment range, making it unable to adapt to the needs of different types of pulverized coal and different combustion conditions (such as different loads, different pulverized coal particle sizes, and different volatile matter contents). To achieve adjustable swirl intensity, it has been proposed to adjust the angle of the inner secondary blades to change the size of the recirculation zone, thereby changing the swirl intensity. However, increasing the blade angle also increases the resistance to airflow. As the unit load decreases, the air pressure in the secondary air box decreases, making it difficult to provide sufficient inner secondary air volume and failing to form a stable central recirculation zone under low loads, resulting in unstable combustion.

[0007] To address the problems of self-stable combustion burners being unable to flexibly adjust swirl intensity according to varying coal quality, and the increased resistance due to increased blade angle, resulting in insufficient air pressure in the secondary air box, which in turn leads to insufficient combustion of pulverized coal and difficulty in forming a stable combustion flame, this invention proposes a burner and combustion method that can be adapted to the combustion of multiple coal types by synergistically changing the recirculation zone through blade angle and air volume. Summary of the Invention

[0008] The present invention aims to solve the problems that self-stable combustion burners cannot flexibly change the swirl intensity according to the changes in coal quality, and that the increased resistance caused by the increase in blade angle and the insufficient air pressure in the secondary air box, which in turn makes it impossible to ensure the full combustion of coal powder and the formation of a stable combustion flame. Therefore, it provides a burner and combustion method that can be used to burn multiple coal types by synergistically changing the recirculation zone through blade angle and air volume.

[0009] A burner suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume is disclosed. The burner includes a primary air duct, an inner secondary air duct, a combustion stabilization chamber, an inner secondary air swirl assembly, and an inner secondary air makeup system. The inner secondary air duct is coaxially sleeved outside the primary air duct, and the outlet ends of both the primary air duct and the inner secondary air duct are connected to the inlet end of the combustion stabilization chamber. The inner secondary air swirl assembly is installed between the primary air duct and the inner secondary air duct, and the drive end of the inner secondary air swirl assembly extends to the outside of the inner secondary air duct. The inner secondary air makeup system is located outside the burner, and the air volume output end of the inner secondary air makeup system is connected to the inlet end of the inner secondary air duct.

[0010] Furthermore, the inner secondary air swirl assembly includes an adjustable blade unit and N drive units, where N is a positive integer. The adjustable blade unit is disposed between the primary air duct and the inner secondary air duct, and is fixedly connected to the inner wall of the inner secondary air duct and slidably connected to the outer wall of the primary air duct. The N drive units are equidistantly arranged around the outer side of the primary air duct in a circumferential direction, with one end of each drive unit connected to the adjustable blade unit and the other end of each drive unit extending to the outside of the inner secondary air duct. The change of the blade angle in the adjustable blade unit is achieved through the synchronous action of the N drive units.

[0011] Furthermore, the value of N ranges from 2 to 4;

[0012] Furthermore, the adjustable blade unit includes an inner secondary air sleeve, an outer secondary air sleeve, and multiple swirl blades. The inner secondary air sleeve is fitted onto the primary air duct and slidably connected to the outer wall of the primary air duct. The outer secondary air sleeve is inserted into the inner secondary air duct and fixedly connected to the inner wall of the inner secondary air duct. Multiple swirl blades are equidistantly arranged circumferentially between the inner secondary air sleeve and the outer secondary air sleeve. One end of each swirl blade is slidably connected to the inner secondary air sleeve via a sliding pin, and the other end of each swirl blade is rotatably connected to the outer secondary air sleeve via a rotating shaft. One end of each drive unit is fixedly connected to the outer wall of the inner secondary air sleeve at the end away from the combustion stabilization chamber.

[0013] Furthermore, multiple rotating shaft mounting holes are equidistantly machined along the circumferential direction on the outer wall of the outer secondary air jacket, and each rotating shaft mounting hole corresponds to a swirl vane. One end of the rotating shaft is fixedly connected to the corresponding swirl vane, and the other end of the rotating shaft is inserted into a corresponding rotating shaft mounting hole and rotatably connected to the outer secondary air jacket.

[0014] Furthermore, multiple arc-shaped guide grooves are equidistantly machined along the circumferential direction on the outer wall of the inner secondary air sleeve, and each arc-shaped guide groove is correspondingly set with a swirl blade. One end of the sliding pin is fixedly connected to the corresponding swirl blade, and the other end of the sliding pin is inserted into the corresponding arc-shaped guide groove and slidably connected to the inner secondary air sleeve.

[0015] Furthermore, the internal secondary air supply system includes a primary air fan, a cold primary air duct, an air preheater, a hot primary air duct, a blower, a hot secondary air duct, and a secondary air box. The primary air fan and the blower are arranged on one side of the air preheater, and the outlet of the primary air fan and the outlet of the blower are both connected to the inlet of the air preheater through pipes. The first outlet of the air preheater is connected to the inlet of the internal secondary air duct through the hot primary air duct. The second outlet of the air preheater is connected to the inlet of the secondary air box through the hot secondary air duct. The outlet of the secondary air box is connected to the inlet of the internal secondary air duct. The cold primary air duct is connected in parallel to the air preheater. One end of the cold primary air duct is connected to the hot primary air duct, and the other end of the cold primary air duct is connected to the outlet of the primary air fan.

[0016] A cold primary air electric regulating valve is connected in series on the cold primary air duct;

[0017] A hot primary air electric regulating valve is connected in series on the hot primary air duct. The hot primary air electric regulating valve is located between the connection point of the cold primary air duct and the hot primary air duct and the air preheater.

[0018] An internal secondary air duct is connected in series with an internal secondary air electric regulating valve and a wind speed measuring device along the flow direction of the secondary air.

[0019] Furthermore, a video flame detection device is also installed on the air inlet of the combustion stabilization chamber. The video flame detection device consists of a high-temperature probe, a camera system, a cooling and protection device, a thruster, a power control box, an air source filter and pressure control box, and a monitor, and is connected to the DCS system via a cable.

[0020] A combustion method for a burner applicable to the combustion of multiple coal types is achieved by synergistically changing the recirculation zone through blade angle and air volume; the specific operation of the method is as follows:

[0021] When the boiler is operating at a condition above 50% of the rated load, loosen the limit nut, adjust the position of the sliding pin in the arc-shaped guide groove by pulling the pull rod. The rotating shaft rotates accordingly, driving the change of the swirler blade angle, so that the swirler blade angle α is adjusted to 5° - 35°. Tighten the limit nut when the pull rod is at the position where the scale reading m1 = 0.82 - 0.99m, fix the pull rod with a positioning pin, and control the amount of hot primary air supplementing into the inner secondary air duct by adjusting the opening of the hot primary air electric regulating valve to 20% - 40% and the opening of the cold primary air electric regulating valve to 30% - 50%. By adjusting the opening of the inner secondary air electric regulating valve to 30% - 70%, make u = 20 - 65m / s; After the above operations, a weakly swirling secondary air is generated in the stable combustion chamber. The swirling intensity cannot form a stable recirculation zone in the stable combustion chamber, but a relatively large velocity is generated radially, which can make the mixing and momentum exchange of the primary and secondary air intense, promote the early mixing of the primary and secondary air, ensure complete combustion at high loads, and improve the boiler efficiency;

[0022] When the boiler is operating at a condition of 20% - 50% of the rated load, loosen the limit nut, adjust the position of the sliding pin in the arc-shaped guide groove by pulling the pull rod. The rotating shaft rotates accordingly, driving the change of the swirler blade angle, so that the swirler blade angle α is adjusted to 35° - 85°, corresponding to the scale reading m1 = 0.09 - 0.82m. While keeping the opening of the inner secondary air electric regulating valve at 30% - 70% and the inner secondary air velocity u at 20 - 65m / s, increase the opening of the hot primary air electric regulating valve to 40% - 80% and close the opening of the cold primary air electric regulating valve to 10% - 30%. After the above operations, a strongly swirling secondary air is generated in the stable combustion chamber. The swirling intensity makes a large-scale recirculation zone form in the stable combustion chamber, and the size of the recirculation zone is 0.5De < D < 3.5De; 2.0De < L < 5.0De; 0.1De < a < 0.4De; The size of the adjusted recirculation zone is reasonably reduced compared with that of the difficult-to-burn coal type, but the starting position of the recirculation zone is increased from the outlet, ensuring timely ignition and stable combustion of pulverized coal at low loads while avoiding the burner nozzle being damaged by slagging due to the recirculation zone being too close to the nozzle.

[0023] The beneficial effects of this application compared with the prior art:

[0024] 1. This invention provides a burner and combustion method suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and airflow. The swirl intensity is adjusted by regulating the blade angle to adapt to changes in coal type. Simultaneously, the internal secondary air supply system adjusts the opening of the electric regulating dampers for hot primary air, cold primary air, and internal secondary air to compensate for the increased resistance caused by the blade angle change, ensuring the required airflow and achieving the desired swirl intensity. This is monitored in real-time by an airflow measurement device. Ultimately, the boiler achieves optimal combustion under different loads and with different coal types.

[0025] Based on the invention of co-combustion of DC burners and swirl burners, the area of ​​the internal secondary air nozzle is fixed. This means that air distribution and pulverized coal combustion are achieved by adjusting the regulating dampers on the internal secondary air duct while maintaining a constant nozzle area. When the boiler is undergoing peak load reduction, the main air box pressure is kept constant while the air supply dampers are closed or partially closed to achieve the load reduction operation. Closing or partially closing the dampers reduces the airflow after passing through them, thus lowering the secondary air velocity entering the furnace. This affects the formation of the central recirculation zone, impacting pulverized coal combustion and causing boiler combustion instability. Increasing the internal secondary air velocity increases resistance and requires higher air pressure. However, under low load, the secondary air box pressure is insufficient to overcome the resistance caused by the increased air velocity. Furthermore, simply increasing the blade angle leads to increased resistance. Typically, the resistance coefficient for a 15-30° angle is 1.0-2.0; for a 45-60° angle, it is 3.0-13.0; and for a 70° angle, it can reach over 30. When the resistance increases, the outlet cannot reach the desired air volume, and the swirling intensity decreases accordingly, failing to achieve the expected effect.

[0026] This invention adjusts the swirl intensity by regulating the blade angle, thereby adapting to changes in coal type. Simultaneously, it coordinates with the internal secondary air supply system to adjust the openings of the electric regulating dampers for hot primary air, cold primary air, and internal secondary air, compensating for the increased resistance caused by changes in blade angle. This ensures the required airflow and achieves the desired swirl intensity, which is monitored in real-time by an air velocity measuring device. Ultimately, the boiler achieves optimal combustion under different loads and with different coal types. The hot primary air pressure is 7.5-9.5 kPa. When burning the designed coal, air is drawn from the hot primary air duct. Under low load, after changing the swirl vane angle α to 50-65°, the opening of the hot primary air electric regulating valve is adjusted to 40%-80%, and the opening of the cold primary air electric regulating valve is adjusted to 10%-30%. This mixes the high-pressure, high-temperature hot primary air with the secondary air, and the internal secondary air electric regulating valve is opened to 40%-50%, resulting in an internal secondary air velocity of 35-50 m / s. Under high load, the swirl vane angle α is reduced to 15-25°. While maintaining the internal secondary air electric regulating valve 29 at 40%-50% and the internal secondary air velocity u at 35-50 m / s, the opening of the hot primary air electric regulating valve 28 is closed to 20%-40%, and the opening of the cold primary air electric regulating valve 27 is increased to 30%-50%. When burning bituminous coal with a volatile matter (Vdaf) content higher than 25%, under low load, reduce the swirl vane angle α to 35-50°. Without changing the opening of the hot primary air electric regulating valve and the cold primary air electric regulating valve, reduce the opening of the inner secondary air electric regulating valve to 30%-40% and decrease the inner secondary air velocity to 20-35 m / s. Under high load, reduce the swirl vane angle α to 5°-15°, maintain the opening of the inner secondary air electric regulating valve 29 to 30%-40%, and maintain the inner secondary air velocity u at 20-35 m / s. Then, reduce the opening of the hot primary air electric regulating valve 28 to 20%-40% and increase the opening of the cold primary air electric regulating valve 27 to 30%-50%. When burning anthracite with volatile matter (Vdaf) below 10%, under low load, increase the swirl vane angle α to 65-85°. Without changing the opening of the hot primary air electric regulating valve and the cold primary air electric regulating valve, increase the opening of the inner secondary air electric regulating valve to 50%-70%, and increase the inner secondary air velocity to 50-65 m / s. Under high load, decrease the swirl vane angle α to 25-35°, maintain the opening of the inner secondary air electric regulating valve 29 to 50%-70%, and maintain the inner secondary air velocity u at 50-65 m / s. Then, reduce the opening of the hot primary air electric regulating valve 28 to 20%-40%, and increase the opening of the cold primary air electric regulating valve 27 to 30%-50%.Simultaneously, by adjusting the opening of the electric regulating valve for the internal secondary air, combined with real-time monitoring of the internal secondary air by the wind speed measuring device on the internal secondary air duct, and by directly observing the clear image captured by the video flame detector through DSC to check the combustion status of the flame in the combustion chamber, precise control of the internal secondary air volume is achieved. Consequently, the boiler achieves optimal combustion conditions under different loads and with different types of coal.

[0027] 2. The present invention provides a burner and combustion method that can be adapted to the combustion of multiple coal types by synergistically changing the recirculation zone through blade angle and air volume. Depending on the coal type, the shape and size of the recirculation zone in the combustion stabilization chamber can be flexibly adjusted by changing the blade angle and coordinating with the internal secondary air supply when the boiler is under low load. This achieves both flexibility and peak shaving requirements, realizes stable combustion under low load, and avoids burner nozzle burnout and slagging caused by changes in coal type, thereby improving the adaptability of coal types under low load.

[0028] An invention based on the coordinated combustion of direct-current burners and swirl burners, that is, relying on the entrainment effect of the direct-current primary air and direct-current secondary air of the direct-current burners, coordinating with the stable combustion cavity and the swirl inner secondary air of the swirl burners to form a central recirculation zone in the center of the swirl burners as a stable ignition heat source to heat the pulverized coal. At the same time, the flame formed by the combustion of the swirl burners ignites the primary air and pulverized coal flame of the direct-current burners, achieving the stable combustion effect of the coal-fired power unit only relying on pulverized coal combustion at 20%-50% of the rated load. Among them, lean coal with volatile matter Vdaf between 10%-25% is used as the design coal type, the designed secondary air velocity value is 35-50 m / s, and the blade angle is 50-65°. The diameter of the recirculation zone is 0.8De < D < 2De; the length of the recirculation zone is 2.5De < L < 4De; and the starting point of the recirculation zone is 0.2De < a < 0.3De at the burner outlet. However, due to the frequent changes in the coal price, the coal used in the boiler changes frequently, and the variability of coal quality is an important challenge faced by pulverized coal boilers. The variability of coal quality has a great impact on stable combustion at low loads, and even causes phenomena such as boiler flameout. The swirl intensity reflects the ratio of the tangential velocity to the axial velocity of the air flow at the outlet of the swirler. The swirl intensity can affect the position and size of the central recirculation zone. In response to poor coal quality (anthracite with volatile matter Vdaf below 10%), it is necessary to increase the swirl intensity to make the air flow rotate strongly, increase the range of the recirculation zone, and increase the entrainment amount of high-temperature flue gas to ensure the ignition and stable combustion of pulverized coal; when the coal quality is good (bituminous coal with volatile matter Vdaf above 25%), if a certain swirl intensity is continued to be maintained, the ignition will be too early; the flame center is close to the burner outlet, which is likely to cause slagging near the burner or burn out the burner, so the swirl intensity can be appropriately reduced to prevent the nozzle from overheating and burning out. Therefore, under the condition of variable coal quality, the adjustable inner secondary air volume and swirl intensity can significantly enhance the coal type adaptability of the burner, ensuring the boiler efficiency, reliability and power plant economy. The prior art adjusts the positions of the inner secondary air duct and the adjustable primary air duct through a pull rod, incorporates the outlet area of the adjustable channel into the outlet area of the inner secondary air channel or the primary air channel, and then adjusts the outlet air velocities of the inner secondary air and the primary air to achieve the purpose of adjusting the shape and size of the recirculation zone at the burner outlet. This technology actually adjusts the inner secondary air volume to affect the swirl intensity, and this effect has a small impact on the change of the recirculation zone shape and still cannot solve the problems brought by variable coal quality.

[0029] The present invention adjusts the swirl intensity by adjusting the blade angle, thereby adapting to the change of coal types. Meanwhile, in coordination with the inner secondary air make-up air system, it adjusts the opening degrees of the hot primary air electric regulating valve, the cold primary air electric regulating valve and the inner secondary air electric regulating valve to compensate for the increased resistance caused by the change of the blade angle, ensure the required air volume, and achieve the desired swirl intensity. When operating at low load (20%-50% of the rated load), for anthracite with volatile content Vdaf lower than 10% (a difficult-to-burn coal type), by pulling the pull rod 10 forward to the scale 9 with the scale value m1 between 0.09 - 0.42 m, the included angle α between the axis of the swirl blade and the axis of the inner sleeve 3 of the inner secondary air is increased to between 65 - 85°. The opening degree of the inner secondary air electric regulating valve 29 is adjusted to increase the inner secondary air velocity u to 50 - 65 m / s, forming a large-range stable and reasonable central recirculation zone at the burner outlet. The length of the recirculation zone is 4.0De < L < 5.0De; the diameter is 2.0De < D < 3.5De. Compared with the recirculation zone size generated by the original lean coal, it is larger, increasing the amount of high-temperature flue gas entrained back at the burner outlet. And the starting point of the recirculation zone is near 0.1De < a < 0.2De at the burner outlet, which is closer to the starting point of the recirculation zone generated by the original lean coal. This enables the pulverized coal to contact the recirculated high-temperature flue gas at the burner outlet, facilitating the timely ignition and stable combustion of the pulverized coal, and further ensuring that the boiler can still stably burn anthracite with volatile content Vdaf lower than 10% at low load, improving the deep peak-shaving capacity.

[0030] For bituminous coal with volatile content Vdaf higher than 25% (an easy-to-burn coal type), by pulling the pull rod 10 forward to the scale 9 with the scale value m1 between 0.64 - 0.82 m, the included angle α between the axis of the swirl blade and the axis of the inner sleeve 3 of the inner secondary air is decreased to between 35 - 50°. The opening degree of the inner secondary air electric regulating valve 29 is adjusted to reduce the inner secondary air velocity u to 20 - 35 m / s, forming a small-range stable and reasonable central recirculation zone at the burner outlet. The length of the recirculation zone is 2.0De < L < 2.5De; the diameter is 0.5De < D < 0.8De. After adjustment, the size of the recirculation zone is reasonably reduced compared with the recirculation zone size generated by the original lean coal, but the distance from the starting point of the recirculation zone to the burner nozzle is reasonably increased (near 0.3De < a < 0.4De). The pulverized coal burns at a position far from the nozzle, ensuring stable combustion while preventing slagging and burning damage of the nozzle.

[0031] 3. A burner and combustion method provided by the present application that jointly change the recirculation zone through blade angle and air volume to be applicable to multi-coal combustion. For the boiler burning different coal types at high load, it flexibly adjusts the angle of the inner secondary air blade and the inner secondary air volume, which is beneficial to improving the burnout rate of pulverized coal, meeting the combustion characteristics of different coal types, and improving the adaptability of coal types at high load;

[0032] Based on the invention of co-combustion using a direct-flow burner and a swirl burner, when the boiler is operating at a load higher than 50% of its rated capacity, the regulating valve in the internal secondary air channel is shut off, resulting in no rotating secondary air inside the self-regulating combustion burner, only direct-flow primary air. The direct-flow primary air rate within the combustion chamber is maintained at 20-30%. Due to the influence of the combustion chamber, the direct-flow primary and secondary air in the furnace cannot replenish the oxygen required for combustion in a timely manner, leading to incomplete combustion. For pulverized coal combustion to achieve complete combustion, in addition to ensuring a sufficiently high furnace temperature, a sufficient and suitable air supply is necessary, along with thorough agitation and mixing of pulverized coal and air. Air must be delivered to the combustion surface of the pulverized coal in a timely manner so that a combustion reaction can occur. This requires good coordination between the primary and secondary air, and a good aerodynamic field within the furnace to ensure thorough mixing of pulverized coal and air. However, after the pulverized coal ignites, the temperature rises, the flue gas expands in volume and viscosity increases, making the mixing of secondary and primary air much more difficult than before ignition. Uneven mixing leads to poor combustion efficiency. Meanwhile, under varying coal quality conditions and with the same primary air rate, coals with different volatile matter contents require different secondary air rates. Coal with high volatile matter ignites rapidly, with volatile matter quickly released and burned in the initial stages of combustion. The primary air, having already provided some oxygen during the coal powder transport, satisfies the initial combustion needs of volatile matter. As combustion progresses, although secondary air is still needed to supplement oxygen, the amount of additional oxygen required is relatively small due to the more complete combustion of volatile matter, resulting in a lower secondary air rate. Conversely, for coals with low volatile matter, ignition is difficult and combustion is slow. Primary air is mainly used to transport coal powder and satisfy a small amount of volatile matter combustion; most combustion requires sufficient oxygen from secondary air to maintain and promote complete combustion, thus resulting in a higher secondary air rate.

[0033] This invention, under high load, targets anthracite (difficult-to-burn coal) with volatile matter (Vdaf) below 10%. By pulling the lever 10 forward to a scale 9 with a graduation of m1 = 0.82-0.90m, the angle α between the swirl vane axis and the inner secondary air sleeve 3 axis is 25°-35°. Adjusting the opening of the electric regulating valve 29 controls the inner secondary air velocity u to 50-65m / s. Through this operation, a weakly swirling secondary air is generated within the combustion chamber. While this swirling intensity is insufficient to form a stable recirculation zone within the combustion chamber, the airflow can diffuse and mix in both radial and tangential directions. This results in vigorous mixing and momentum exchange between the primary and secondary air, promoting thorough mixing. Simultaneously, with the direct primary air rate maintained at 20-30% within the combustion chamber, a large amount of secondary air is supplemented, achieving a secondary air rate of 70%-80%. This improves high-load burnout and increases boiler efficiency.

[0034] For the designed coal type (lean coal with volatile matter (Vdaf) between 10% and 25%), while ensuring the designed secondary air velocity is 35-50 m / s, by pulling the lever 10 forward to a scale 9 with a graduation of m1 = 0.90-0.96 m, the angle α between the axis of the swirl vanes and the axis of the inner secondary air sleeve 3 is reduced to 15°-25°. This generates a weakly swirling secondary air in the combustion chamber. While this swirling intensity is insufficient to form a stable recirculation zone within the combustion chamber, the airflow can diffuse and mix in both radial and tangential directions. This results in intense mixing and momentum exchange between the primary and secondary air, promoting thorough mixing. Simultaneously, with the direct primary air rate maintained at 20-30% in the combustion chamber, a large amount of secondary air is added, bringing the secondary air rate to 50-60%. This improves high-load burnout and increases boiler efficiency.

[0035] For bituminous coal (easily combustible coal) with a volatile matter content (Vdaf) higher than 25%, the lever 10 is moved forward to a scale 9 with a graduation of m1 = 0.96-0.99m, and the angle α between the axis of the swirl vanes and the axis of the inner secondary air sleeve 3 is 5°-15°. The opening of the electric regulating valve 29 for the inner secondary air is adjusted to control the inner secondary air velocity u to 20-35m / s. After the above operation, a weak swirling secondary air is generated in the combustion chamber. This swirling intensity is insufficient to form a stable recirculation zone in the combustion chamber, but the airflow can diffuse and mix in the radial and tangential directions, resulting in intense mixing and momentum exchange between the primary and secondary air, promoting thorough mixing of the primary and secondary air. At the same time, with the direct primary air rate in the combustion chamber maintained at 20-30%, a large amount of secondary air is added, reaching a secondary air rate of 30%-40%, which can improve high-load burnout and increase boiler efficiency. For different coal types under high load, it provides the optimal secondary air rate for combustion and generates a certain weak swirling effect to promote thorough mixing of primary and secondary air, ensuring complete combustion under high load and improving the adaptability of coal types under high load. Attached Figure Description

[0036] Figure 1 This is a front view schematic diagram of the arrangement of the burner described in this application;

[0037] Figure 2 This is a top view of the arrangement of the burner described in this application;

[0038] Figure 3 This is a schematic diagram of the adjustable blade unit in the burner described in this application;

[0039] Figure 4 This is a schematic diagram showing the fit between the arc-shaped guide groove and the sliding pin in the burner described in this application;

[0040] Figure 5 This is a schematic diagram of the composition of the burner described in this application;

[0041] Figure 6This is a side view of the burner described in this application;

[0042] Figure 7 This is a system diagram of the internal secondary air makeup system in the burner described in this application;

[0043] Figure 8 This is a schematic diagram showing the shape and size of the burner outlet recirculation zone described in this application;

[0044] Figure 9 This is a schematic diagram of the wind speed measuring device in the burner described in this application;

[0045] Figure 10 This is a schematic diagram of the video flame detection device in the burner described in this application. Detailed Implementation

[0046] Specific implementation method one: Combining Figures 1 to 10 This embodiment describes a burner suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume. It includes a primary air duct 1, an inner secondary air duct 2, a combustion stabilization chamber 7, an inner secondary air swirl assembly, and an inner secondary air makeup system. The inner secondary air duct 2 is coaxially sleeved outside the primary air duct 1, and the air outlets of both the primary air duct 1 and the inner secondary air duct 2 are connected to the air inlet of the combustion stabilization chamber 7. The inner secondary air swirl assembly is installed on the primary air duct 1 and the inner secondary air duct 2, and the drive end of the inner secondary air swirl assembly extends to the outside of the inner secondary air duct 2. The inner secondary air makeup system is located outside the burner, and the air volume output end of the inner secondary air makeup system is connected to the air inlet of the inner secondary air duct 2.

[0047] The inner secondary air swirl assembly includes an adjustable blade unit and N drive units, where N is a positive integer. The adjustable blade unit is located between the primary air duct 1 and the inner secondary air duct 2, and is fixedly connected to the inner wall of the inner secondary air duct 2. The adjustable blade unit is slidably connected to the outer wall of the primary air duct 1. The N drive units are equidistantly arranged around the outside of the primary air duct 1 in a circumferential direction, and one end of each drive unit is connected to the adjustable blade unit, while the other end of each drive unit extends to the outside of the inner secondary air duct 2. The change of the blade angle in the adjustable blade unit is achieved through the synchronous action of the N drive units.

[0048] The value of N ranges from 2 to 4;

[0049] The adjustable blade unit includes an inner secondary air sleeve 3, an outer secondary air sleeve 4, and multiple swirl blades 5. The inner secondary air sleeve 3 is fitted onto the primary air duct 1 and is slidably connected to the outer wall of the primary air duct 1. The outer secondary air sleeve 4 is inserted into the inner secondary air duct 2 and is fixedly connected to the inner wall of the inner secondary air duct 2. Multiple swirl blades 5 are equidistantly arranged circumferentially between the inner secondary air sleeve 3 and the outer secondary air sleeve 4. One end of each swirl blade 5 is slidably connected to the inner secondary air sleeve 3 via a sliding pin 18, and the other end of each swirl blade 5 is rotatably connected to the outer secondary air sleeve 4 via a rotating shaft 17. One end of each drive unit is fixedly connected to the outer wall of the inner secondary air sleeve 3 away from the combustion stabilization chamber 7.

[0050] The number of swirl blades 5 is 10~20;

[0051] Multiple rotating shaft mounting holes 17-1 are machined at equal intervals along the circumference on the outer wall of the outer secondary air jacket 4, and each rotating shaft mounting hole 17-1 is correspondingly set with a swirl blade 5. One end of the rotating shaft 17 is fixedly connected to the corresponding swirl blade 5, and the other end of the rotating shaft 17 is inserted into the corresponding rotating shaft mounting hole 17-1 and rotatably connected to the outer secondary air jacket 4.

[0052] Multiple arc-shaped guide grooves 19 are machined equidistantly along the circumferential direction on the outer wall of the inner secondary air sleeve 3, and each arc-shaped guide groove 19 is correspondingly set with a swirl blade 5. One end of the sliding pin 18 is fixedly connected to the corresponding swirl blade 5, and the other end of the sliding pin 18 is inserted into the corresponding arc-shaped guide groove 19 and slidably connected to the inner secondary air sleeve 3.

[0053] The drive unit includes a scale 9, a pull rod 10, a bracket 15, and a connecting block 16. The bracket 15 is fixed to the end of the inner secondary air duct 2 away from the combustion chamber 7. A pull rod sleeve 11 is inserted into the bracket 15 and is arranged between the primary air duct 1 and the inner secondary air duct 2. The outer surface of the pull rod sleeve 11 is machined with external threads. The pull rod sleeve 11 is detachably connected to the bracket 15 by two limiting nuts 13. A washer 14 is provided between each limiting nut 13 and the bracket 15. The pull rod 10 is inserted into the pull rod 15. The rod 10 is slidably connected to the tie rod sleeve 11. Both ends of the tie rod 10 extend to the outside of the tie rod sleeve 11. One end of the tie rod 10 is installed on the outer wall of the inner secondary air sleeve 3 through the connecting block 16. The other end of the tie rod 10 serves as the driving end for pulling the tie rod 10 to slide back and forth in the tie rod sleeve 11. The scale 9 is fixed on the bracket 15, and the length extension direction of the scale 9 is the same as the length extension direction of the tie rod 10. The driving end of the tie rod 10 is positioned by the positioning pin 12 and the limiting hole on the scale 9.

[0054] The internal secondary air supply system includes a primary air fan 20, a cold primary air duct 21, an air preheater 22, a hot primary air duct 23, a blower 24, a hot secondary air duct 25, and a secondary air box 26. The primary air fan 20 and the blower 24 are arranged on one side of the air preheater 22, and the outlet ends of the primary air fan 20 and the blower 24 are both connected to the inlet end of the air preheater 22 through pipes. The first outlet end of the air preheater 22 is connected to the hot secondary air box 26. Secondary air duct 23 is connected to the air inlet of the inner secondary air duct 2. The second air outlet of the air preheater 22 is connected to the air inlet of the secondary air box 26 through the hot secondary air duct 25. The air outlet of the secondary air box 26 is connected to the air inlet of the inner secondary air duct 2. The cold primary air duct 21 is connected in parallel to the air preheater 22. One end of the cold primary air duct 21 is connected to the hot primary air duct 23, and the other end of the cold primary air duct 21 is connected to the air outlet of the primary air fan 20.

[0055] A primary air electric regulating valve 27 is connected in series on the primary air duct 21;

[0056] A hot primary air electric regulating valve 28 is connected in series on the hot primary air duct 23. The hot primary air electric regulating valve 28 is located between the connection point of the cold primary air duct 21 and the hot primary air duct 23 and the air preheater 22.

[0057] An internal secondary air duct 2 is connected in series with an internal secondary air electric regulating valve 29 and an air velocity measuring device 30 along the flow direction of the secondary air.

[0058] An air velocity measuring device 30 is installed after the internal secondary air electric regulating valve 29 to monitor the air velocity entering the internal secondary air duct 2 in real time. During operation, the air velocity measuring device 30 is inserted perpendicularly into the internal secondary air duct 2. When the internal secondary air flows, the total pressure is measured on the windward side and the static pressure on the leeward side. The total pressure and static pressure of the airflow in the internal secondary air duct 2 are collected and transmitted to the air velocity sensor. The pressure is then detected by connecting to the positive and negative terminals of a differential pressure transmitter. This allows the device to be connected to a DCS industrial control system to display the air velocity and airflow, thereby controlling the air velocity to achieve the desired effect.

[0059] The combustion stabilization chamber 7 is also equipped with a video flame detection device 6 at its air inlet. This device consists of a high-temperature probe, a camera system, a cooling and protection device, a thruster, a power control box, a gas source filter and pressure control box, and a monitor, all connected to the DCS system via cables. The probe and camera system are horizontally mounted. When recording is required, the thruster is controlled to extend the probe, camera system, and cooling and protection device from the connector into the combustion stabilization chamber. The camera system sends the acquired video signal to the controller, which then sends the received video signal to the DSC (Digital Selector Center) to monitor the flame combustion.

[0060] This embodiment provides a burner that can be used to adapt to the combustion of multiple coal types by coordinating the change of the recirculation zone through the blade angle and air volume. It is mainly used in the self-stable combustion burner part of the co-combustion system of DC burner and swirl burner. The co-combustion system of DC burner and swirl burner includes a four-corner tangential pulverized coal combustion boiler 38, a DC pulverized coal burner 35, and a self-stable combustion burner 31. The DC pulverized coal burner 35 in the four-corner tangential pulverized coal combustion boiler 38 is arranged at the four corners of the furnace. The outlet of the DC pulverized coal burner 35 consists of a set of rectangular nozzles. The primary air and pulverized coal airflow, along with the secondary air required for combustion, are injected into the furnace in the form of direct jets from different nozzles. The direct primary air nozzles 32 and 34 are arranged alternately. The upstream corner flame is ignited at the root of the downstream direct pulverized coal burner 35, forming an actual flame zone 37, and an imaginary tangential circle 36 is formed at the center of the four-corner tangential pulverized coal combustion boiler. Four self-sustaining combustion burners 31 are arranged at the four corners between the direct primary air nozzles 32 and 34 of the direct pulverized coal burner 35. By relying on the ejection effect of the DC primary air and DC secondary air of the DC burner, and in conjunction with the combustion stabilization chamber and swirling secondary air of the self-stable combustion burner, a central recirculation zone is formed in the center of the self-stable combustion burner, which serves as a stable ignition heat source to heat high-concentration pulverized coal. At the same time, the flame 40 formed by the combustion of the self-stable combustion burner ignites the primary air pulverized coal flame 39 of the DC burner. The newly added make-up air system is used to change the internal secondary air volume to overcome the phenomenon of increased resistance and decreased wind speed caused by the change of internal secondary air blades. The swirling intensity is adjusted by changing the blade angle.

[0061] The burner provided in this embodiment, which is suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume, operates as follows:

[0062] The pulverized coal-air mixture enters the combustion chamber 7 through the primary air duct 1. The internal secondary air enters the combustion chamber 7 in a rotating manner after passing through the adjustable swirl vane device in the internal secondary air duct 2. The direct-flow primary air enters the direct-flow primary air nozzle 32 through the direct-flow primary air channel 33 and is injected into the furnace in a direct-flow manner. The direct-flow secondary air enters the direct-flow secondary air nozzle 34 through the direct-flow secondary air channel 34-1 and is injected into the furnace in a direct-flow manner. At low loads, relying on the entrainment effect of the direct-flow primary and secondary air from the direct-flow burner, a large central recirculation zone is formed in the furnace, entraining the high-temperature flue gas in the furnace to heat and ignite the pulverized coal airflow, serving as a stable ignition heat source to heat the high-concentration pulverized coal. Simultaneously, the flame formed by the self-sustaining combustion of the combustion-stabilizing burner ignites the primary air-pulverized coal flame of the direct-flow burner. At high loads, the internal secondary air enters at a certain angle, enhancing its rotational capacity. The rapid mixing speed of the primary and secondary air ensures thorough mixing of the pulverized coal airflow with the circumferentially entering secondary airflow, achieving optimal combustion results. At the same time, it provides sufficient oxygen for the complete combustion of pulverized coal, which is conducive to complete combustion.

[0063] Pulling the lever 10 adjusts the angle α between the axis of the swirl blade 5 and the axis of the inner secondary air sleeve 3, thereby changing the swirl intensity of the inner secondary air. The scale 9 on the support 15 is used to observe the size of the angle α. Tightening the limit nut 13 at the desired position fixes the lever 10 to the support 15. The positioning pin 12 can fix the angle α between the axis of the swirl blade 5 and the axis of the inner secondary air sleeve 3, thus fixing the swirl intensity of the inner secondary air. By controlling the swirl intensity of the inner secondary air, the range, length, diameter, and starting point of the recirculation zone in the combustion stabilization chamber can be adjusted. The larger the angle α between the axis of the swirl blade 5 and the axis of the inner secondary air sleeve 3, the greater the swirl intensity of the inner secondary air, and the larger the recirculation zone formed in the combustion stabilization chamber 7; the smaller the angle α between the axis of the swirl blade 5 and the axis of the inner secondary air sleeve 3, the smaller the swirl intensity of the inner secondary air, and the smaller the recirculation zone formed in the combustion stabilization chamber 7, thereby improving the adaptability to different coal types.

[0064] An inner sleeve roller 3-1 is provided on the inner ring wall of the inner secondary air sleeve 3, and an outer sleeve roller 4-1 is provided on the outer ring wall of the outer secondary air sleeve 4. The inner sleeve roller 3-1 and the outer sleeve roller 4-1 reduce the friction between the adjustable blade unit and the primary air duct 1 and the inner secondary air duct 2, which is beneficial to the smooth operation of the adjustable blade unit. At the same time, a limiter 8 is provided on the inner wall of the inner secondary air duct 2. The limiter 8 is used to limit the movement limit position of the adjustable blade unit, so as to avoid the situation where the adjustable blade unit collides with the combustion chamber due to excessive adjustment range, which is beneficial to improving the working safety of the adjustable blade unit.

[0065] The internal secondary air supply system operates as follows: Hot primary air is pressurized by the primary air fan 20 and then splits into two paths: one path passes through the cold primary air duct 21 and then through the cold primary air electric regulating damper 27, where it mixes with the other path, which passes through the air preheater 22 and then through the hot primary air electric regulating damper 28. After thorough mixing, the mixture flows into the internal secondary air duct 2. Secondary air is pressurized by the supply fan 24 and then enters the air preheater 22 for heating. It then enters the secondary air box 26 through the hot secondary air duct 25. The secondary air mixes with the high-temperature, high-pressure hot primary air to form high-temperature, high-pressure internal secondary air. The internal secondary air volume is controlled by the internal secondary air electric regulating damper 29, and then passes through the swirl vanes 5, finally entering the self-regulating burner 31 in a rotating manner.

[0066] Specific Implementation Method Two: Combining Figures 1 to 10This embodiment describes a combustion method for burners adaptable to multiple coal types by coordinating blade angle and airflow to change the recirculation zone. The method adjusts the swirl intensity by regulating the blade angle to adapt to changes in coal type. Simultaneously, it coordinates with the internal secondary air supply system to adjust the openings of the electric regulating dampers for hot primary air, cold primary air, and internal secondary air, compensating for the increased resistance caused by the blade angle change, ensuring the required airflow, and achieving the desired swirl intensity. At high loads (above 50% of rated load), a weak swirling secondary airflow is generated to rationally organize the flow field within the combustion chamber, ensuring complete combustion at high loads. At low loads (20%-50% of rated load), a strong swirling secondary airflow is generated to adjust the shape and size of the recirculation zone within the combustion chamber of the self-regulating burner, ensuring stable combustion at low loads while preventing nozzle burnout and slagging due to changes in coal type. Real-time monitoring of the flame condition within the combustion chamber can be achieved using signals transmitted from a video flame detector. This is specifically achieved through the following steps:

[0067] 1. The flammability of coal is judged based on the volatile matter (Vdaf%) content. Anthracite with a Vdaf content below 10% has an ignition temperature above 800℃ and is considered a difficult-to-burn coal. Bituminous coal with a Vdaf content above 25% has an ignition temperature below 700℃ and is considered a easily combustible coal. Lean coal with a Vdaf content between 10% and 25% has an ignition temperature between 700 and 800℃ and is considered a moderately combustible coal.

[0068] 2. For anthracite (difficult-to-burn coal) with volatile matter (Vdaf) below 10%, the flue gas temperature in the combustion chamber is high under high load (above 50% of rated load). Therefore, it is necessary to rationally organize the flow field within the combustion chamber to promote thorough mixing of primary and secondary air and supplement the air required for complete fuel combustion to ensure complete combustion under high load. The specific operation is as follows: Loosen the limit nut 13, and pull the pull rod 10 to move the sliding pin 18 to the position within the arc-shaped guide groove 19. The rotating shaft 17 will then rotate, causing the swirl vane 5 to adjust its angle α to 25-35°. When the pull rod is at the scale reading m1 = 0.82-0.90m, tighten the limit nut 13 and fix the pull rod with the positioning pin 12. By adjusting the opening of the hot primary air electric regulating valve 28 to 20%-40% and the cold primary air electric regulating valve 27 to 30%-50%, the amount of hot primary air supplemented into the inner secondary air duct 2 is controlled. By adjusting the opening of the inner secondary air electric regulating valve 29 to 50%-70%, u=50-65m / s is achieved. After the above operations, a weakly swirling secondary air is generated in the combustion stabilization chamber. The intensity of this swirling flow is insufficient to form a stable recirculation zone in the combustion stabilization chamber, but it generates a large radial velocity, which can cause intense mixing and momentum exchange between the primary and secondary air, promote the early mixing of the primary and secondary air, ensure high-load burnout, and improve boiler efficiency.

[0069] At low loads (20 - 50% of the rated load), the flue gas temperature in the main combustion zone is much lower than that at high loads. It is necessary to form a large - scale central recirculation zone in the stable combustion cavity to entrain more high - temperature flue gas, enabling the pulverized coal to burn in a timely manner. Meanwhile, the flame formed by the self - supporting stable combustion burner ignites the primary air - pulverized coal flame of the direct - flow burner to ensure stable combustion at low loads. The specific operation is as follows: increase the angle α of the swirl vane 5 to 65 - 85°, the corresponding scale reading is m1 = 0.09 - 0.42m, keep the opening of the inner secondary air electric regulating valve 29 at 50% - 70%, and keep the inner secondary air velocity u at 50 - 65m / s. Then, increase the opening of the hot primary air electric regulating valve 28 to 40% - 80% and close the cold primary air electric regulating valve 27 to 10% - 30%. After the above operations, a strongly swirling secondary air is generated in the stable combustion cavity. This swirl intensity forms a large - scale recirculation zone in the stable combustion cavity, and the size of the recirculation zone is 2.0De < D < 3.5De; 4.0De < L < 5.0De; 0.1De < a < 0.2De. The size of the adjusted recirculation zone is reasonably reduced compared to that of the difficult - to - burn coal type, but the starting position of the recirculation zone is increased from the outlet, ensuring timely ignition and stable combustion of pulverized coal at low loads while avoiding damage and slagging of the burner nozzle due to the recirculation zone being too close to the nozzle.

[0070] 3. For lean coal with volatile matter Vdaf between 10% - 25% (moderate - combustion coal type), at high loads (above 50% of the rated load), the flue gas temperature in the stable combustion cavity is high. It is necessary to reasonably organize the flow field in the stable combustion cavity to promote the full mixing of primary and secondary air and supplement the air required for complete combustion of the fuel to ensure complete combustion at high loads. The specific operation is as follows: loosen the limit nut 13, pull the position of the sliding pin 18 in the arc - shaped guide groove 19 by pulling the pull rod 10, and the angle of the swirl vane 5 is adjusted by the rotation of the rotating shaft 17, making the angle α of the swirl vane 5 adjusted to 15° - 25°. Tighten the limit nut 13 when the pull rod is at the scale reading m1 = 0.90 - 0.96m and fix the pull rod with the positioning pin 12. Control the amount of hot primary air supplementing into the inner secondary air duct 2 by adjusting the opening of the hot primary air electric regulating valve 28 to 20% - 40% and the opening of the cold primary air electric regulating valve 27 to 30% - 50%. Adjust the opening of the inner secondary air electric regulating valve 29 to 40% - 50% to make u = 35 - 50m / s. After the above operations, a weakly swirling secondary air is generated in the stable combustion cavity. This swirl intensity cannot form a stable recirculation zone in the stable combustion cavity, but a relatively large radial velocity is generated, which can make the mixing and momentum exchange of primary and secondary air intense, promote the early mixing of primary and secondary air, ensure complete combustion at high loads, and improve the boiler efficiency.

[0071] At low loads (20% - 50% of the rated load), the flue gas temperature in the main combustion zone is much lower than that at high loads. It is necessary to form a large - scale central recirculation zone in the stable combustion cavity to entrain more high - temperature flue gas, enabling the pulverized coal to burn in time. At the same time, the flame formed by the self - stabilizing combustion burner ignites the primary air - pulverized coal flame of the direct - flow burner, ensuring stable combustion at low loads. The specific operation is as follows: increase the angle α of the swirl vane 5 to 50 - 65°, and the corresponding scale reading is m1 = 0.42 - 0.64m. Keep the opening degree of the inner secondary air electric regulating valve 29 at 40% - 50%. When the inner secondary air velocity u is 35 - 50m / s, increase the opening degree of the hot primary air electric regulating valve 28 to 40% - 80%, and reduce the opening degree of the cold primary air electric regulating valve 27 to 10% - 30%. After the above operations, a strongly swirling secondary air is generated in the stable combustion cavity. This swirl intensity makes an appropriate - sized recirculation zone form in the stable combustion cavity, where the size of the recirculation zone is 0.8De < D < 2De; 2.5De < L < 4De; 0.2De < a < 0.3De. The size of the adjusted recirculation zone is reasonably reduced compared to that of the difficult - to - burn coal type, but the starting position of the recirculation zone is farther from the outlet, ensuring that the pulverized coal ignites and burns stably in time at low loads while avoiding damage and slagging of the burner nozzle due to the recirculation zone being too close to the nozzle.

[0072] 4. For bituminous coal with Vdaf higher than 25% (easily combustible coal type), at high loads (higher than 50% of the rated load), the flue gas temperature in the stable combustion cavity is high. It is necessary to reasonably organize the flow field in the stable combustion cavity to promote the full mixing of the primary and secondary air and supplement the air required for complete fuel combustion to ensure complete combustion at high loads. The specific operation is as follows: loosen the limit nut 13, pull the position of the sliding pin 18 in the arc - shaped guide groove 19 by pulling the pull rod 10. The rotating shaft 17 rotates accordingly to带动 the angle of the swirl vane 5, so that the angle α of the swirl vane 5 is adjusted to 5 - 15°. When the pull rod is at the scale reading m1 = 0.96 - 0.99m, tighten the limit nut 13 and fix the pull rod with the positioning pin 12. By adjusting the opening degree of the hot primary air electric regulating valve 28 to 20% - 40% and the opening degree of the cold primary air electric regulating valve 27 to 30% - 50%, control the amount of hot primary air supplementing into the inner secondary air duct 2. By adjusting the opening degree of the inner secondary air electric regulating valve 29 to 30% - 40%, make u = 20 - 35m / s. After the above operations, a weakly swirling secondary air is generated in the stable combustion cavity. This swirl intensity cannot make a stable recirculation zone form in the stable combustion cavity, but a relatively large radial velocity is generated, which can make the mixing and momentum exchange of the primary and secondary air intense, promote the early mixing of the primary and secondary air, ensure complete combustion at high loads, and improve the boiler efficiency.

[0073] At low loads (20% - 50% of the rated load), the flue gas temperature in the main combustion zone is much lower than that at high loads. A small central recirculation zone needs to be formed in the stable combustion cavity to entrain high-temperature flue gas, enabling the pulverized coal to burn in a timely manner, while avoiding the burner nozzle from being damaged by burning and slagging due to the recirculation zone being too close to the nozzle. The specific operation is as follows: increase the angle α of the swirl vane 5 to 35 - 50°, and the corresponding scale reading is m1 = 0.64 - 0.82 m. Keep the opening of the inner secondary air electric regulating valve 29 at 30% - 40%. When keeping the inner secondary air velocity u at 20 - 35 m / s, increase the opening of the hot primary air electric regulating valve 28 to 40% - 80%, and close the cold primary air electric regulating valve 27 to 10% - 30%. After the above operations, a strongly swirling secondary air is generated in the stable combustion cavity. This swirl intensity causes a small recirculation zone to form in the stable combustion cavity, and the size of the recirculation zone is 0.5De < D < 0.8De; 2.0De < L < 2.5De; 0.3De < a < 0.4De. The size of the recirculation zone after adjustment is reasonably reduced compared to that of the difficult-to-burn coal type, but the starting position of the recirculation zone is increased from the outlet, ensuring the timely ignition and stable combustion of pulverized coal at low loads while avoiding the burner nozzle from being damaged by burning and slagging due to the recirculation zone being too close to the nozzle.

[0074] The present invention has been disclosed above with preferred embodiments. However, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, can make some changes or modifications to the above-disclosed structure and technical content to form equivalent embodiments of equivalent changes. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

[0075] Example:

[0076] This technology has been applied to a 600 MW subcritical pressure drum boiler, which adopts a tangential firing method. Four self-stabilizing combustion burners are arranged at the four corners between the direct current primary air nozzles and the direct current secondary air nozzles of the B-layer direct current pulverized coal burners. Powder is taken from the branch pipeline of the B-layer coal pulverizing system, and air is taken from the secondary air box. After the retrofit, the minimum oil-free stable combustion load of the boiler burning high-volatile bituminous coal is 20%, the carbon content in fly ash is 6%, and the boiler efficiency is 92.9%. Due to the fluctuation of coal prices, the coal used in this power station is frequently changed. When burning lean coal, there are potential problems such as flame detector flickering and even boiler extinguishing, and the carbon content in fly ash increases to 8%. Especially when burning anthracite with a volatile content Vdaf lower than 10%, it is difficult to form a stable combustion flame, and the boiler has 3 - 4 extinguishing accidents within one year, seriously affecting the safe operation of the unit, with a loss cost of about more than 3 million yuan. After one year of operation, the boiler is shut down for maintenance, and it is found that there are problems of burner nozzle burning damage and slagging.

[0077] According to the method described in this patent, a method for synergistically changing the recirculation zone by blade angle and air volume and applicable to multiple coal types is designed. A model of this self-stabilizing combustion burner is established in the laboratory. The size ratio of the model burner to the prototype burner is 1:4. A single-phase cold-state modeling test system is built, and the flow field at the burner outlet is measured. The test results are as follows:

[0078] 1) By changing the angle between the axis of the swirler blade and the axis of the inner secondary air duct to 65 - 85°, the inner secondary air velocity u is adjusted to 50 - 65 m / s. Under this condition, a large-scale central recirculation zone is formed, with the recirculation zone diameter 2.0De < D < 3.5De, the recirculation zone length 4.0De < L < 5.0De, and the distance between the burner outlet and the starting point of the recirculation zone 0.1De < a < 0.2De.

[0079] 2) By changing the angle between the axis of the swirler blade and the axis of the inner secondary air duct to 50 - 65°, the inner secondary air velocity u is adjusted to 35 - 50 m / s. Under this condition, a moderately sized central recirculation zone is formed, with the recirculation zone diameter 0.8De < D < 2De, the recirculation zone length 2.5De < L < 4De, and the distance between the burner outlet and the starting point of the recirculation zone 0.2De < a < 0.3De.

[0080] 3) By changing the angle between the axis of the swirler blade and the axis of the inner secondary air duct to 35° - 50°, the inner secondary air velocity u is adjusted to 20 - 35 m / s. Under this condition, a small-scale central recirculation zone is formed, with the recirculation zone diameter 0.5De < D < 0.8De, the recirculation zone length 2.0De < L < 2.5De, and the distance between the burner outlet and the starting point of the recirculation zone 0.3De < a < 0.4De.

[0081] Applying the method and device described in this patent to the above 600MW subcritical pressure drum boiler ensures that the minimum oil-free stable combustion load of the boiler is 20%, the carbon content in fly ash is stable at 4%. When the coal quality fluctuates greatly from anthracite to bituminous coal, no accidents such as boiler flameout occur, reducing the losses caused by flameout, totaling 3 million yuan. It greatly improves the adaptability to coal types and reduces the fuel cost of the units participating in deep peak shaving by about 2 million yuan. After 2 years, during normal shutdown for maintenance, there are no problems with burner nozzle burnout and slagging.

Claims

1. A burner suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume, characterized in that: The burner includes a primary air duct (1), an inner secondary air duct (2), a combustion stabilization chamber (7), an inner secondary air swirl assembly, and an inner secondary air makeup system. The inner secondary air duct (2) is coaxially sleeved outside the primary air duct (1), and the air outlets of the primary air duct (1) and the inner secondary air duct (2) are connected to the air inlet of the combustion stabilization chamber (7). The inner secondary air swirl assembly is installed between the primary air duct (1) and the inner secondary air duct (2), and the drive end of the inner secondary air swirl assembly extends to the outside of the inner secondary air duct (2). The inner secondary air makeup system is located outside the burner, and the air volume output end of the inner secondary air makeup system is connected to the air inlet of the inner secondary air duct (2). The internal secondary air supply system includes a primary air fan (20), a cold primary air duct (21), an air preheater (22), a hot primary air duct (23), a blower (24), a hot secondary air duct (25), and a secondary air box (26). The primary air fan (20) and the blower (24) are arranged on one side of the air preheater (22), and the outlet of the primary air fan (20) and the outlet of the blower (24) are both connected to the inlet of the air preheater (22) through pipes. The first outlet of the air preheater (22) is connected to the inlet of the air preheater (22) through a heat exchanger. The primary air duct (23) is connected to the air inlet of the inner secondary air duct (2). The second air outlet of the air preheater (22) is connected to the air inlet of the secondary air box (26) through the hot secondary air duct (25). The air outlet of the secondary air box (26) is connected to the air inlet of the inner secondary air duct (2). The cold primary air duct (21) is connected in parallel to the air preheater (22). One end of the cold primary air duct (21) is connected to the hot primary air duct (23), and the other end of the cold primary air duct (21) is connected to the air outlet of the primary air fan (20). A primary air electric regulating valve (27) is connected in series on the primary air duct (21); A hot primary air electric regulating valve (28) is connected in series on the hot primary air duct (23). The hot primary air electric regulating valve (28) is located between the connection between the cold primary air duct (21) and the hot primary air duct (23) and the air preheater (22). An internal secondary air duct (2) is connected in series with an internal secondary air electric regulating valve (29) and a wind speed measuring device (30) along the flow direction of the secondary air. The inner secondary air vortex assembly includes an adjustable blade unit and N drive units, where N is a positive integer. The adjustable blade unit is located between the primary air duct (1) and the inner secondary air duct (2), and is fixedly connected to the inner wall of the inner secondary air duct (2). The adjustable blade unit is slidably connected to the outer wall of the primary air duct (1). The N drive units are equidistantly arranged around the outside of the primary air duct (1) in the circumferential direction, and one end of each drive unit is connected to the adjustable blade unit. The other end of each drive unit extends to the outside of the inner secondary air duct (2). The change of the blade angle in the adjustable blade unit is achieved through the synchronous action of the N drive units.

2. The burner according to claim 1, which is suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume, is characterized in that: The value of N ranges from 2 to 4.

3. A burner according to claim 2, which is suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume, is characterized in that: The adjustable blade unit includes an inner secondary air sleeve (3), an outer secondary air sleeve (4), and multiple swirl blades (5). The inner secondary air sleeve (3) is fitted onto the primary air duct (1) and is slidably connected to the outer wall of the primary air duct (1). The outer secondary air sleeve (4) is inserted into the inner secondary air duct (2) and is fixedly connected to the inner wall of the inner secondary air duct (2). Multiple swirl blades (5) are equidistantly arranged circumferentially between the inner secondary air sleeve (3) and the outer secondary air sleeve (4). One end of each swirl blade (5) is slidably connected to the inner secondary air sleeve (3) via a sliding pin (18), and the other end of each swirl blade (5) is rotatably connected to the outer secondary air sleeve (4) via a rotating shaft (17). One end of each drive unit is fixedly connected to the outer wall of the inner secondary air sleeve (3) away from the combustion chamber (7).

4. A burner according to claim 3, which is suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume, is characterized in that: Multiple rotating shaft mounting holes (17-1) are machined equidistantly along the circumference on the outer wall of the outer secondary air jacket (4), and each rotating shaft mounting hole (17-1) is correspondingly set with a swirl blade (5). One end of the rotating shaft (17) is fixedly connected to the corresponding swirl blade (5), and the other end of the rotating shaft (17) is inserted into the corresponding rotating shaft mounting hole (17-1) and rotatably connected to the outer secondary air jacket (4).

5. A burner according to claim 4, which is suitable for multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume, characterized in that: Multiple arc-shaped guide grooves (19) are machined equidistantly along the circumference on the outer wall of the inner secondary air sleeve (3), and each arc-shaped guide groove (19) is correspondingly set with a swirl blade (5). One end of the sliding pin (18) is fixedly connected to the corresponding swirl blade (5), and the other end of the sliding pin (18) is inserted into the corresponding arc-shaped guide groove (19) and slidably connected to the inner secondary air sleeve (3).

6. A burner according to claim 5, which is applicable to the combustion of multiple coal types by synergistically changing the recirculation zone through blade angle and air volume, is characterized in that: The drive unit includes a scale (9), a pull rod (10), a bracket (15), and a connecting block (16). The bracket (15) is fixed on the end of the inner secondary air duct (2) away from the combustion chamber (7). A pull rod sleeve (11) is inserted into the bracket (15), and the pull rod sleeve (11) is arranged between the primary air duct (1) and the inner secondary air duct (2). The outer surface of the pull rod sleeve (11) is machined with external threads. The pull rod sleeve (11) is detachably connected to the bracket (15) through two limit nuts (13). A washer (14) is provided between each limit nut (13) and the bracket (15). The pull rod (10) The rod (10) is inserted into the tie rod sleeve (11) and slidably connected to the tie rod sleeve. Both ends of the rod (10) extend to the outside of the tie rod sleeve (11), and one end of the rod (10) is installed on the outer wall of the inner secondary air sleeve (3) through the connecting block (16). The other end of the rod (10) serves as the driving end for pulling the rod (10) to slide back and forth in the tie rod sleeve (11). The scale (9) is fixed on the bracket (15), and the length extension direction of the scale (9) is the same as the length extension direction of the rod (10). The driving end of the rod (10) is positioned by the positioning pin (12) and the limiting hole on the scale (9).

7. A burner according to claim 6, which is applicable to the combustion of multiple coal types by synergistically changing the recirculation zone through blade angle and air volume, characterized in that: The air inlet of the combustion chamber (7) is also equipped with a video fire detection device (6). The video fire detection device (6) consists of a high temperature probe, a camera system, a cooling protection device, a thruster, a power control box, an air source filter and pressure control box, and a monitor, and is connected to the DCS system via a cable.

8. A combustion method using a burner applicable to the combustion of multiple coal types by synergistically changing the recirculation zone through blade angle and air volume according to any one of claims 1 to 7, characterized in that: The specific operation of the method is as follows: When the boiler is operating at a load higher than 50% of its rated load, loosen the limit nut (13), and adjust the position of the sliding pin (18) in the arc-shaped guide groove (19) by pulling the pull rod (10). The rotating shaft (17) will rotate accordingly, causing the angle of the swirl vanes (5) to change, so that the angle α of the swirl vanes (5) is adjusted to 5°~35°. When the pull rod is at the position of the scale reading m1=0.82-0.99m, tighten the limit nut (13), fix the pull rod (10) with the positioning pin (12), and adjust the opening of the hot primary air electric regulating valve (28) to 20%- 40%, the opening of the cold primary air electric regulating valve (27) is set to 30%-50% to control the amount of hot primary air supplemented into the inner secondary air duct (2). The opening of the inner secondary air electric regulating valve (29) is set to 30%-70% to make u=20-65m / s. After the above operation, a weak swirling secondary air is generated in the combustion chamber. The intensity of this swirling flow cannot form a stable recirculation zone in the combustion chamber, but it generates a large radial velocity, which can make the mixing and momentum exchange of primary and secondary air intense, promote the mixing of primary and secondary air in advance, ensure high load burnout, and improve boiler efficiency. When the boiler is operating at 20%-50% of its rated load, loosen the limit nut (13), and adjust the position of the sliding pin (18) in the arc-shaped guide groove (19) by pulling the pull rod (10). The rotating shaft (17) will rotate accordingly, causing the angle of the swirl blades (5) to change, so that the angle α of the swirl blades (5) is adjusted to 35°~85°, corresponding to a scale reading of m1=0.09-0.82m. Keep the opening of the internal secondary air electric regulating valve (29) at 30%-70%, and keep the internal secondary air velocity u at 20-65m / s. Then, increase the opening of the hot primary air electric regulating valve (28) to 40%-80% and decrease the opening of the cold primary air electric regulating valve (27) to 10%-30%. After the above operations, a strong swirling secondary air is generated in the combustion chamber. The intensity of this swirling air causes a large-scale recirculation zone to be formed in the combustion chamber. The size of the recirculation zone is 0.5De. <D<3.5De; 2.0De <L<5.0De; 0.1De < a < 0.4De; The size of the reflux zone after adjustment is reasonably reduced compared to the reflux zone size of difficult-to-burn coal types, but the distance from the starting point of the reflux zone to the outlet is increased. This ensures that the pulverized coal can ignite and burn stably under low load, while avoiding burnout and slagging of the burner nozzle due to the reflux zone being too close to the nozzle.

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