Combustor suitable for multi-coal combustion by synergistically changing backflow area through blade angle and air quantity and combustion method

Abstract

The invention discloses a combustor suitable for multi-coal combustion by synergistically changing a backflow area through a blade angle and air volume and a combustion method, belongs to the technical field of tangential boiler combustion, and aims to solve the problems that a self-service stable combustion combustor cannot flexibly change rotational flow intensity along with variation of coal quality, resistance is increased due to increase of the blade angle, and combustion efficiency is low. In order to solve the problems that pulverized coal cannot be fully combusted and stable combustion flames are difficult to form due to insufficient air pressure of a secondary air box, an inner secondary air rotational flow assembly and an inner secondary air supplementing system are introduced, so that the air volume of inner secondary air is adaptively changed by adjusting the working angle of blades in an inner secondary air pipeline, and the combustion efficiency of the pulverized coal is improved. Therefore, the rotational flow intensity of internal secondary air is flexibly adjusted according to different coal types, the purpose of stable combustion is achieved, and the device is mainly used for improving the stable combustion effect of the boiler during working.

Description

Technical Field

[0001] The invention relates to the technical field of tangential boiler combustion, and in particular to a burner and a combustion method which are suitable for burning multiple types of coal by synergistically changing a reflow zone through blade angle and air volume. Background Art

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

[0003] Coal-fired boiler power generation is the main body of my country's current energy structure. The combustion method of coal-fired boilers mainly adopts the arrangement of direct current burners on the four corners or eight corners of the boiler furnace. The coal powder airflow and the secondary air are sprayed into the furnace through the direct current burner jets and merged in the form of a tangential circle. The coal powder airflow is directly hit by the high-temperature flame of the upstream adjacent corner on the side facing the fire and is ignited. The four-corner (or eight-corner) jets support each other to form a rotating combustion flame. The four-corner (or eight-corner) tangential pulverized coal combustion boiler is the most widely used and mature furnace type in my country's power plants, accounting for more than 70% of the total installed capacity, but the domestic coal-fired power units can only reach 30%-40% of the stable combustion load without oil injection.

[0004] By using the coordinated combustion method and device of DC burner and swirl burner, four self-help stable combustion burners are arranged at the four corners between the DC primary air nozzle of the DC pulverized coal burner and the DC secondary air nozzle of the DC pulverized coal burner. As a key combustion equipment, the self-help stable combustion burner sprays the pulverized coal airflow into the stable combustion chamber in the form of DC at high load. The stable combustion chamber has a larger heat load than the furnace cross section. The heat released after combustion makes the temperature in the stable combustion chamber rise rapidly and maintain it at a high temperature, which is conducive to the combustion of pulverized coal. At low load, high-concentration pulverized coal forms a central reflow zone under the action of the secondary air in the stable combustion chamber and the swirl, which serves as a stable ignition heat source to heat the high-concentration pulverized coal. At the same time, the flame formed by the combustion of the self-help stable combustion burner ignites the primary air pulverized flame of the DC burner. Without the help of external flame combustion-supporting technologies such as micro-oil or plasma, the coal-fired power unit can achieve a stable combustion effect at 20%-30% of the rated load by relying solely on pulverized coal combustion.

[0005] However, under market economy conditions, coal price fluctuations have brought frequent changes to the coal used in boilers, and the variable coal quality is an important challenge facing pulverized coal boilers. The variable coal quality directly affects the characteristics of pulverized coal ignition and stable combustion. The internal secondary air swirl causes the high-temperature flue gas at the rear of the burner to flow back to its root, promoting the ignition of the pulverized coal airflow and subsequent stable combustion. If the coal quality deteriorates, the swirl intensity needs to be increased to promote the entrainment of high-temperature flue gas and ensure the ignition and stable combustion of pulverized coal; if the coal quality is good, the swirl intensity can be appropriately reduced to prevent the nozzle from overheating and burning. Therefore, under the condition of variable coal quality, the adjustable swirl intensity can significantly enhance the coal type adaptability of the burner, ensure the efficiency and reliability of the boiler and the economy of the power plant.

[0006] At present, the existing self-service stable combustion burners have certain limitations in practical applications. The swirl intensity is usually fixed or the adjustment range is limited, which cannot adapt to the needs of different types of coal powder and different combustion conditions (such as different loads, different coal powder particle sizes and volatile matter contents, etc.). In order to achieve adjustable swirl intensity, it is proposed to adjust the angle of the inner secondary blade to change the size of the recirculation zone, and then change the swirl intensity. However, as the blade angle increases, the resistance to the airflow also increases. As the load of the unit decreases, the wind pressure of the secondary air box decreases, making it difficult to provide sufficient inner secondary air volume, and it is impossible to form a stable central recirculation zone under low load, resulting in unstable combustion.

[0007] In order to solve the problems that the self-service stabilizing combustion burner cannot flexibly change the swirl intensity as the coal quality changes, and the increase in blade angle leads to increased resistance, while the wind pressure of the secondary wind box is insufficient, which makes it impossible to ensure sufficient combustion of coal powder and difficult to form a stable combustion flame. The present invention proposes a burner and a combustion method that are suitable for 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 the self-help stable combustion burner cannot flexibly change the swirl intensity as the coal quality changes, and the resistance increases due to the increase of the blade angle, and the wind pressure of the secondary wind box is insufficient, which makes it impossible to ensure the full combustion of coal powder and difficult to form a stable combustion flame. A burner and a combustion method suitable for the combustion of multiple coal types are provided by changing the reflow zone by the blade angle and the air volume;

[0009] A burner suitable for burning multiple types of coal by changing the reflow zone in coordination with blade angle and air volume, the burner comprising a primary air duct, an inner secondary air duct, a combustion stabilizing chamber, an inner secondary air swirl assembly and an inner secondary air supply system, the inner secondary air duct is coaxially sleeved on the outside of the primary air duct, and the air outlet ends of the primary air duct and the inner secondary air duct are both connected to the air inlet end of the combustion stabilizing chamber, the inner secondary air swirl assembly is installed between the primary air duct and the inner secondary air duct, and the driving end of the inner secondary air swirl assembly extends to the outside of the inner secondary air duct, the inner secondary air supply system is arranged on the outside of the burner, and the air volume output end of the inner secondary air supply system is connected to the air inlet end of the inner secondary air duct;

[0010] Further, the inner secondary air swirl assembly includes an adjustable blade unit and N drive units, N being a positive integer, the adjustable blade unit being arranged between the primary air duct and the inner secondary air duct, and the adjustable blade unit being fixedly connected to the inner wall of the inner secondary air duct, the adjustable blade unit being slidably connected to the outer wall of the primary air duct, the N drive units being equidistantly arranged around the outer side of the primary air duct along the circumferential direction, and one end of each drive unit being connected to the adjustable blade unit, and the other end of each drive unit extending to the outside of the inner secondary air duct, and the change of the blade angle in the adjustable blade unit is realized by the synchronous action of the N drive units;

[0011] Furthermore, the value range of N is 2 to 4;

[0012] Furthermore, the adjustable blade unit comprises an inner secondary air inner sleeve, an outer secondary air outer sleeve and a plurality of swirl blades, the inner secondary air inner sleeve is sleeved on the primary air duct and slidably connected to the outer wall of the primary air duct, the outer secondary air outer sleeve is inserted into the inner secondary air duct and fixedly connected to the inner wall of the inner secondary air duct, the plurality of swirl blades are equidistantly arranged between the inner secondary air inner sleeve and the outer secondary air outer sleeve along the circumferential direction, and one end of each swirl blade is slidably connected to the inner secondary air inner sleeve through a sliding pin, the other end of each swirl blade is rotatably connected to the outer secondary air outer sleeve through a rotating shaft, and one end of each driving unit is fixedly connected to the outer wall of the inner secondary air inner sleeve away from the combustion stabilizing chamber;

[0013] Furthermore, a plurality of rotating shaft mounting holes are processed on the outer wall of the outer secondary air jacket sleeve at equal intervals along the circumferential direction, and each rotating shaft mounting hole is arranged corresponding to a swirl blade, one end of the rotating shaft is fixedly connected to the corresponding swirl blade, 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 sleeve:

[0014] Furthermore, a plurality of arc-shaped guide grooves are processed on the outer wall of the inner secondary air inner sleeve at equal intervals along the circumferential direction, and each arc-shaped guide groove is arranged corresponding to 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 a corresponding arc-shaped guide groove and slidably connected to the inner secondary air inner sleeve;

[0015] Furthermore, the internal secondary air supply system includes a primary 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 fan and the blower are arranged on one side of the air preheater, and the air outlet end of the primary fan and the air outlet end of the blower are both connected to the air inlet end of the air preheater through a pipeline. The No. 1 air outlet end of the air preheater is connected to the air inlet end of the internal secondary air duct through the hot primary air duct, the No. 2 air outlet end of the air preheater is connected to the air inlet end of the secondary air box through the hot secondary air duct, the air outlet end of the secondary air box is connected to the air inlet end 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 air outlet end of the primary 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, and the hot primary air electric regulating valve is located between the connection of the cold primary air duct and the hot primary air duct and the air preheater;

[0018] An inner secondary air electric regulating valve and an air speed measuring device are sequentially connected in series along the flow direction of the secondary air in the inner secondary air duct;

[0019] Furthermore, a video fire detection device is provided on the air inlet end of the stable combustion chamber. The video fire detection device is composed 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 through a cable.

[0020] A combustion method for a burner suitable for burning multiple types of coal by changing the reflow zone by coordinating blade angle and air volume; the method is specifically operated as follows:

[0021] When the boiler is under the condition of more than 50% of the rated load, loosen the limit nut, adjust the position of the sliding pin in the arc-shaped sliding groove by pulling the pull rod, the rotating shaft rotates accordingly, driving the change of the angle of the swirl vane, so that the angle α of the swirl vane is adjusted to 5°-35°. When the pull rod is at the position where the scale reading m1 = 0.82 - 0.99m, tighten the limit nut, fix the pull rod with a positioning pin, and control the hot primary air volume supplementing into the inner secondary air duct by adjusting the opening degree of the hot primary air electric regulating valve to 20%-40% and the opening degree of the cold primary air electric regulating valve to 30%-50%. By adjusting the opening degree 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 cavity. The swirl intensity cannot form a stable recirculation zone in the stable combustion cavity, 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 load, and improve the boiler efficiency;

[0022] When the boiler is under the condition of 20%-50% of the rated load, loosen the limit nut, adjust the position of the sliding pin in the arc-shaped sliding groove by pulling the pull rod, the rotating shaft rotates accordingly, driving the change of the angle of the swirl vane, so that the angle α of the swirl vane is adjusted to 35°-85°, corresponding to the scale reading m1 = 0.09 - 0.82m. While keeping the opening degree 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 degree of the hot primary air electric regulating valve to 40%-80% and close the opening degree 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 cavity. The swirl intensity makes a large-scale recirculation zone formed in the stable combustion cavity, 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 load while avoiding the burning and slagging of the burner nozzle 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. The present invention provides a burner and a combustion method suitable for burning multiple types of coal by changing the recirculation zone in coordination with the blade angle and the air volume. The swirl intensity is adjusted by adjusting the blade angle to adapt to the change of coal types. At the same time, the internal secondary air supply system is coordinated to adjust the opening of the hot primary air electric regulating door, the cold primary air electric regulating door and the internal secondary air electric regulating door to compensate for the increased resistance caused by the change of the blade angle, ensure the required air volume, achieve the desired expected swirl intensity, and monitor in real time through the wind speed measuring device. Then the boiler reaches the best combustion state when burning different types of coal at different loads.

[0025] Based on the invention of the coordinated combustion of the direct current burner and the swirl burner, the area of ​​the secondary air nozzle is fixed, that is, the air supply and powder combustion are carried out by adjusting the regulating door on the internal secondary air duct under the condition that the nozzle area cannot be changed. When the boiler is peaking and reducing the load, the main wind box pressure is guaranteed to remain unchanged and the wind door of the wind box air supply is closed or reduced to achieve the purpose of load reduction operation. Since the wind door is closed or reduced, the air volume after passing through the wind door becomes smaller, and then the secondary wind speed entering the furnace is reduced, which affects the formation of the central reflow zone, affects the pulverized coal combustion, and causes the boiler combustion to be unstable. When the internal secondary wind speed is increased, the greater the resistance, the higher the required wind pressure, and the secondary wind box pressure under low load is not enough to overcome the resistance caused by the increase in wind speed. At the same time, only increasing the blade angle will lead to increased resistance. Under normal circumstances, the resistance coefficient at an angle of 15-30° is 1.0-2.0; the resistance coefficient at an angle of 45-60° is 3.0-13.0; the resistance coefficient at an angle of 70° can be as high as 30 or more. When the resistance becomes larger, the outlet cannot reach the desired air volume, the swirl intensity decreases accordingly, and the expected effect cannot be achieved.

[0026] The present invention adjusts the swirl intensity by adjusting the blade angle, thereby adapting to the change of coal types, and at the same time cooperates with the internal secondary air supply system to adjust the opening of the hot primary air electric regulating door, the cold primary air electric regulating door and the internal secondary air electric regulating door to compensate for the increased resistance caused by the change of blade angle, ensure the required air volume, achieve the desired expected swirl intensity, and monitor in real time through the wind speed measuring device. Then the boiler reaches the best combustion state under different loads and different coal types. The hot primary air pressure is 7.5-9.5kpa. By drawing air from the hot primary air duct, when burning the designed coal, under low load, after changing the angle α of the swirl blade 5 to 50-65°, the hot primary air electric regulating door opening is adjusted to 40%-80%, and the cold primary air electric regulating door opening is adjusted to 10%-30%, so that the high-pressure and high-temperature hot primary air is mixed with the secondary air, and the inner secondary air electric regulating door opening is adjusted to 40%-50%, so that the inner secondary air speed is 35-50m / s. Under high load, the swirl blade 5 angle α is reduced to 15-25°. Keep the opening of the inner secondary air electric regulating valve 29 to 40%-50%, keep the inner secondary air speed u to 35-50m / s, close 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 bituminous coal with volatile matter Vdaf higher than 25%, under low load, reduce the angle α of swirl blade 5 to 35-50°. Without changing the opening of hot primary air electric regulating door and cold primary air electric regulating door, reduce the opening of inner secondary air electric regulating door to 30%-40%, and reduce the inner secondary air speed to 20-35m / s. Under high load, reduce the angle α of swirl blade 5 to 5°-15°, keep the opening of inner secondary air electric regulating valve 29 to 30%-40%, keep the inner secondary air speed u to 20-35m / s, close the opening of hot primary air electric regulating valve 28 to 20%-40%, and increase the opening of cold primary air electric regulating valve 27 to 30%-50%. When burning anthracite with volatile matter Vdaf lower than 10%, under low load, increase the angle α of swirl blade 5 to 65-85°, increase the opening of inner secondary air electric regulating door to 50%-70% without changing the opening of hot primary air electric regulating door and cold primary air electric regulating door, and increase the inner secondary air speed to 50-65m / s. Under high load, reduce the angle α of swirl blade 5 to 25-35°, keep the opening of inner secondary air electric regulating valve 29 to 50%-70%, keep the inner secondary air speed u to 50-65m / s, close the opening of hot primary air electric regulating valve 28 to 20%-40%, and increase the opening of cold primary air electric regulating valve 27 to 30%-50%.At the same time, by adjusting the opening of the electric regulating door of the internal secondary air, cooperating with the wind speed measuring device on the internal secondary air duct to monitor the internal secondary air in real time, and directly observing the clear picture captured by the video fire detection device through DSC, the combustion state of the flame in the stable combustion cavity can be checked, and the internal secondary air volume can be accurately controlled. As a result, the boiler has achieved the best combustion state under different loads and different types of coal.

[0027] 2. The present invention provides a burner and a combustion method suitable for burning multiple types of coal by changing the recirculation zone in coordination with the blade angle and the air volume. According to different types of coal, the shape and size of the recirculation zone in the stable combustion chamber can be flexibly adjusted by changing the blade angle when the boiler is at low load in coordination with the internal secondary air supply, so as to meet the requirements of flexible peak regulation, realize low-load stable combustion, and avoid burnout and slagging of the burner nozzle due to the change of coal types, thereby improving the adaptability of coal types under low load;

[0028] An invention based on the coordinated combustion of a direct-current burner and a swirl burner, that is, relying on the entrainment effect of the direct-current primary air and the direct-current secondary air of the direct-current burner, coordinating with the stable combustion chamber and the swirl inner secondary air of the swirl burner to form a central recirculation zone in the center of the swirl burner as a stable ignition heat source to heat the pulverized coal. At the same time, the flame formed by the combustion of the swirl burner ignites the primary air-pulverized coal flame of the direct-current burner, achieving stable combustion of the coal-fired power unit only relying on pulverized coal combustion at 20%-50% of the rated load. Among them, lean coal with a volatile content Vdaf between 10%-25% is used as the design coal type, the designed secondary air velocity value is 35-50 m / s, and the vane 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 a volatile content Vdaf below 10%), the swirl intensity needs to be increased 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 a volatile content 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 internal 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 existing technology adjusts the positions of the internal secondary air duct and the adjustable primary air duct through a pull rod, incorporates the outlet area of the adjustable channel into the internal secondary air channel or the outlet area of the primary air channel, and then adjusts the outlet air velocities of the internal 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 internal 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 make up 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 matter Vdaf less than 10% (difficult-to-burn coal type), by pulling the pull rod 10 forward to a position where the scale 9 is at m1 = 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° and 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 matter Vdaf less than 10% at low load, improving the deep peak shaving ability.

[0030] For bituminous coal with volatile matter Vdaf higher than 25% (easy-to-burn coal type), by pulling the pull rod 10 forward to a position where the scale 9 is at m1 = 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° and 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 without causing slagging and burning damage to the nozzle.

[0031] 3. A burner and combustion method provided by the present application that adapt to multi-coal combustion by synergistically changing the recirculation zone through blade angle and air volume. For the boiler burning different coal types at high load, flexibly adjusting the blade angle of the inner secondary air and the inner secondary air volume 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 the coordinated combustion of the direct current burner and the swirl burner, when the boiler is operating at a load higher than 50% of the rated load, by closing the regulating valve in the internal secondary air channel, there is no rotating secondary air inside the self-service stable combustion burner, and only direct current primary air is introduced, wherein the direct current primary air rate in the stable combustion chamber is maintained at 20-30%. Affected by the stable combustion chamber, the direct current primary and secondary air in the furnace cannot replenish the oxygen required for combustion in the stable combustion chamber in time, resulting in incomplete combustion. In order to achieve complete combustion of pulverized coal, in addition to ensuring a sufficiently high furnace temperature, sufficient and appropriate air must be supplied, and the pulverized coal and air must be fully disturbed and mixed, and the air must be delivered to the combustion surface of the pulverized coal in time, so that the pulverized coal and air can contact and react to occur. To achieve this, it is required that the primary and secondary air cooperate well, and there is a good air dynamic field in the furnace, so that the pulverized coal and air are fully mixed. However, after the pulverized coal is ignited, the temperature rises, the volume of the flue gas expands, the viscosity increases, and the mixing of the secondary air and the primary air is much more difficult than before ignition. Uneven mixing will lead to poor burnout effect. At the same time, under the condition of variable coal quality, at the same primary air rate, different types of coal with different volatile content require different secondary air rates. Coal with high volatile content ignites quickly, and volatiles are quickly separated and burned in the early stage of combustion. The primary air has provided some oxygen in the process of conveying coal powder, meeting the initial combustion requirements of volatiles. As the combustion proceeds, although secondary air is still needed to supplement oxygen, the amount of additional oxygen required is relatively small because the volatiles burn more fully, so the secondary air rate is low. On the contrary, for coal with low volatile content, ignition is difficult and the combustion speed is slow. The primary air is mainly used to convey coal powder and meet the combustion of a small amount of volatiles. Most combustion requires secondary air to provide sufficient oxygen to maintain and promote complete combustion, so the secondary air rate is relatively high.

[0033] Under high load, the present invention targets anthracite (difficult-to-burn coal) with a volatile matter Vdaf lower than 10%. By pulling the pull rod 10 forward to the scale m1=0.82-0.90m of the ruler 9, 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 25°-35°. The opening of the inner secondary air electric regulating valve 29 is adjusted to control the inner secondary air speed u to 50-65m / s. After the above operation, weakly swirling secondary air is generated in the stable combustion chamber. The swirl intensity cannot form a stable reflow zone in the stable combustion chamber, but the airflow can diffuse and mix in the radial and tangential directions, which can make the mixing and momentum exchange of the primary and secondary air intense, promote the full mixing of the primary and secondary air, and at the same time, when the direct current primary air rate in the stable combustion chamber is maintained at 20-30%, a large amount of secondary air is supplemented, and the secondary air rate reaches 70%-80%, which can improve the high load burnout and improve the boiler efficiency.

[0034] For the designed coal type (lean coal with volatile matter Vdaf between 10% and 25%), under the condition of ensuring the designed secondary air velocity value of 35-50m / s, by pulling the pull rod 10 forward to the scale m1=0.90-0.96m of the ruler 9, the angle α between the axis of the swirl blade and the axis of the inner secondary air inner sleeve 3 is reduced to 15°-25°. This generates weakly swirling secondary air in the stable combustion chamber. The swirl intensity cannot form a stable recirculation zone in the stable combustion chamber, but the airflow can diffuse and mix in the radial and tangential directions, which can make the primary and secondary air mixing and momentum exchange intense, promote the full mixing of the primary and secondary air, and at the same time, when the direct current primary air rate in the stable combustion chamber is maintained at 20-30%, a large amount of secondary air is supplemented, and the secondary air rate reaches 50-60%, which can improve high-load burnout and improve boiler efficiency.

[0035] For bituminous coal (easy-to-burn coal) with volatile matter Vdaf higher than 25%, by pulling the pull rod 10 forward to the scale 9 between m1=0.96-0.99m, the angle α between the axis of the swirl blade and the axis of the inner secondary air inner sleeve 3 is 5°-15°. Adjust the opening of the inner secondary air electric regulating valve 29 to control the inner secondary air speed u to 20-35m / s. After the above operation, weak swirl secondary air is generated in the stable combustion chamber. The swirl intensity cannot form a stable reflow zone in the stable combustion chamber, but the airflow can diffuse and mix in the radial and tangential directions, which can make the primary and secondary air mixing and momentum exchange intense, promote the full mixing of the primary and secondary air, and at the same time, when the DC primary air rate in the stable combustion chamber is maintained at 20-30%, a large amount of secondary air is added, and the secondary air rate reaches 30%-40%, which can improve high-load burnout and improve boiler efficiency. For different types of coal under high load, it provides the best secondary air rate for combustion and produces a certain weak rotation effect to promote full mixing of primary and secondary air, ensure high-load combustion, and improve the adaptability of coal under high load. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0039] Figure 4 This is a schematic diagram of the cooperation 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 6A schematic side view of the burner described in this application;

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

[0043] Figure 8 A schematic diagram of the shape and size of the recirculation zone at the burner outlet described in this application;

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

[0045] Fig.10 This is a schematic diagram of the video fire detection device in the burner described in this application. DETAILED DESCRIPTION

[0046] Specific implementation method 1: Combination Figures 1 to 10 The present embodiment is described. In the present embodiment, there is provided a burner suitable for burning multiple types of coal by coordinating the blade angle and the air volume to change the reflow zone. The burner comprises a primary air duct 1, an inner secondary air duct 2, a combustion stabilizing chamber 7, an inner secondary air swirl assembly and an inner secondary air supply air system. The inner secondary air duct 2 is coaxially sleeved on the outside of the primary air duct 1, and the air outlet ends of the primary air duct 1 and the inner secondary air duct 2 are both connected to the air inlet end of the combustion stabilizing chamber 7. The inner secondary air swirl assembly is installed in the primary air duct 1 and the inner secondary air duct 2, and the driving end of the inner secondary air swirl assembly extends to the outside of the inner secondary air duct 2. The inner secondary air supply air system is arranged on the outside of the burner, and the air volume output end of the inner secondary air supply air system is connected to the air inlet end of the inner secondary air duct 2.

[0047] The inner secondary air swirl assembly includes an adjustable blade unit and N drive units, N being a positive integer, the adjustable blade unit being arranged between the primary air duct 1 and the inner secondary air duct 2, and the adjustable blade unit being fixedly connected to the inner wall of the inner secondary air duct 2, and the adjustable blade unit being slidably connected to the outer wall of the primary air duct 1, the N drive units being equidistantly arranged around the outer side of the primary air duct 1 along the circumferential direction, and one end of each drive unit being connected to the adjustable blade unit, and the other end of each drive unit extending to the outside of the inner secondary air duct 2, and the change of the blade angle in the adjustable blade unit is realized by the synchronous action of the N drive units;

[0048] The value range of N is 2 to 4;

[0049] The adjustable blade unit includes an inner secondary air inner sleeve 3, an outer secondary air outer sleeve 4 and a plurality of swirl blades 5. The inner secondary air inner sleeve 3 is sleeved on the primary air duct 1 and is slidably connected to the outer wall of the primary air duct 1. The outer secondary air outer 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. The plurality of swirl blades 5 are equidistantly arranged between the inner secondary air inner sleeve 3 and the outer secondary air outer sleeve 4 along the circumferential direction, and one end of each swirl blade 5 is slidably connected to the inner secondary air inner sleeve 3 through a sliding pin 18, and the other end of each swirl blade 5 is rotatably connected to the outer secondary air outer sleeve 4 through a rotating shaft 17. One end of each driving unit is fixedly connected to the outer wall of the inner secondary air inner sleeve 3 away from the stable combustion chamber 7.

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

[0051] A plurality of rotating shaft mounting holes 17-1 are processed on the outer wall of the outer secondary air jacket sleeve 4 at equal intervals along the circumferential direction, and each rotating shaft mounting hole 17-1 is arranged corresponding to 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 a corresponding rotating shaft mounting hole 17-1 and is rotatably connected to the outer secondary air jacket sleeve 4;

[0052] A plurality of arc guide grooves 19 are processed on the outer wall of the inner secondary air inner sleeve 3 at equal intervals along the circumferential direction, and each arc guide groove 19 is arranged corresponding to 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 a corresponding arc guide groove 19 and slidably connected to the inner secondary air inner sleeve 3;

[0053] The driving unit includes a scale 9, a tie 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 stabilization chamber 7. A tie rod sleeve 11 is inserted in the bracket 15, and the tie rod sleeve 11 is arranged between the primary air duct 1 and the inner secondary air duct 2. An external thread is processed on the outer circumferential surface of the tie rod sleeve 11. The tie rod sleeve 11 is detachably connected to the bracket 15 through two limit nuts 13. A gasket 14 is provided between each limit nut 13 and the bracket 15. The tie rod 10 is inserted in The pull rod sleeve 11 is in sliding connection with the pull rod sleeve 11, both ends of the pull rod 10 extend to the outside of the pull rod sleeve 11, and one end of the pull rod 10 is installed on the outer wall of the inner secondary air inner sleeve 3 through the connecting block 16, and the other end of the pull rod 10 is used as a driving end to pull the pull rod 10 to slide back and forth in the pull 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 pull rod 10, and the driving end of the pull rod 10 is positioned by the positioning pin 12 and the limit 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 air outlet end of the primary air fan 20 and the air outlet end of the blower 24 are connected to the air inlet end of the air preheater 23 through a pipeline. The No. 1 air outlet end of the air preheater 23 is connected to the air inlet end of the air preheater 23 through a hot air outlet end. The secondary air duct 23 is connected to the air inlet end of the inner secondary air duct 2, the second air outlet end of the air preheater 23 is connected to the air inlet end of the secondary air box 26 through the hot secondary air duct 25, the air outlet end of the secondary air box 26 is connected to the air inlet end 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 end of the primary fan 20;

[0055] A cold primary air electric regulating valve 27 is connected in series to the cold primary air duct 24;

[0056] A hot primary air electric regulating valve 28 is connected in series to the hot primary air duct 23, and 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;

[0057] An inner secondary air electric regulating valve 29 and an air speed measuring device 30 are sequentially connected in series along the flow direction of the secondary air on the inner secondary air duct 2;

[0058] The wind speed measuring device 30 is arranged behind the electric regulating valve 29 of the inner secondary air, and the wind speed entering the inner secondary air duct 2 is monitored in real time. When the wind speed measuring device 30 is working, the wind speed measuring device is inserted into the inner secondary air duct 2 perpendicularly to the pipe wall. When the inner secondary air flows, the total pressure is measured on the windward side, and the static pressure is measured on the leeward side. The total pressure and static pressure of the airflow in the inner secondary air duct 2 are collected and transmitted to the wind speed sensor, and the pressure is detected at the +- end connected to the micro differential pressure transmitter. It is connected to the DCS industrial control system to display the wind speed and air volume, so as to control the wind speed to achieve the expected purpose;

[0059] A video fire detection device 6 is also provided on the air inlet end of the stable combustion chamber 7. The video fire detection device 6 is composed of a high temperature probe, a camera system, a cooling protection device, a propeller, a power control box, an air source filter and pressure control box, and a monitor. The probe and the camera system are connected to the DCS system through a cable. The probe and the camera system are installed horizontally. When it is necessary to shoot a picture, the propeller is controlled to extend the probe, the camera system and the cooling protection device from the connector into the stable combustion chamber. The camera system sends the obtained video signal to the controller, and the controller sends the received video signal to the DSC, and the flame combustion condition is monitored through the DSC.

[0060] The burner provided in this embodiment is suitable for the combustion of multiple types of coal by coordinating the blade angle and the air volume to change the recirculation zone. It is mainly used in the self-help stabilizing combustion burner part of the coordinated combustion system of the DC burner and the swirl burner. The coordinated combustion system of the DC burner and the swirl burner includes a four-corner cut coal powder combustion boiler 38, a DC coal powder burner 35, and a self-help stabilizing combustion burner 31. The DC coal powder burner 35 in the four-corner cut coal powder combustion boiler 38 is arranged at the four corners of the furnace, and the outlet of the DC coal powder burner 35 is composed of a group of rectangular nozzles. The primary pulverized coal airflow and the secondary air required for combustion are sprayed into the furnace in the form of direct current jets from different nozzles. The direct current primary air nozzles 32 and the direct current secondary air nozzles 34 are arranged alternately. The upstream adjacent corner flame is ignited at the root of the downstream direct current pulverized coal burner 35 to form an actual flame zone 37, and an imaginary tangential circle 36 is formed at the center of the four-corner tangential circle pulverized coal combustion boiler. Four self-help stable combustion burners 31 are arranged at the four corners between the direct current primary air nozzles 32 of the direct current pulverized coal burner 35 and the direct current secondary air nozzles 34 of the direct current pulverized coal burner 35. Relying on the induced effect of the DC primary air and DC secondary air of the DC burner, the stable combustion chamber of the self-help stable combustion burner and the secondary air in the swirl are coordinated to form a central reflow zone in the center of the self-help stable combustion burner as a stable ignition heat source to heat the high-concentration coal powder. At the same time, the flame 40 formed by the combustion of the self-help stable combustion burner ignites the primary air powder flame 39 of the DC burner. The newly added air supply system is used to change the internal secondary air volume to overcome the phenomenon that the resistance increases and the wind speed decreases due to the change of the internal secondary air blades, and the swirl intensity is adjusted by changing the blade angle;

[0061] The burner provided in this embodiment is suitable for burning multiple types of coal by changing the reflow zone in coordination with the blade angle and the air volume, and its working process is as follows:

[0062] The pulverized coal-air mixture passes through the primary air duct 1 and enters the stable combustion chamber 7. The internal secondary air passes through the adjustable swirl blade device in the internal secondary air duct 2 and enters the stable combustion chamber 7 in a rotating form. The DC primary air enters the DC primary air nozzle 32 from the DC primary air channel 33 and is injected into the furnace in a DC form. The DC secondary air enters the DC secondary air nozzle 34 from the DC secondary air channel 34-1 and is injected into the furnace in a DC form. At low load, relying on the injection effect of the DC primary air and DC secondary air of the DC burner, a large-scale central reflow zone is formed in the furnace, and the high-temperature flue gas in the entrained furnace is heated and ignited by the pulverized coal airflow, which serves as a stable ignition heat source to heat the high-concentration pulverized coal. At the same time, the flame formed by the combustion of the self-stable combustion burner ignites the primary air pulverized flame of the DC burner. At high load, the internal secondary air is injected at a certain angle, which enhances the rotation ability of the internal secondary air, and the mixing speed of the primary and secondary air is fast, so that the pulverized coal airflow and the secondary airflow entering the circumference are fully mixed to achieve the best combustion effect. At the same time, it provides sufficient oxygen for the complete combustion of coal powder, which is conducive to burnout.

[0063] Pull the pull rod 10 to adjust the angle between the axis of the swirl blade 5 and the axis of the inner sleeve 3 of the inner secondary air to α, thereby changing the swirl intensity of the inner secondary air. The scale 9 on the bracket 15 is used to observe the size of the angle α. Tighten the limit nut 13 at the required position to fix the pull rod 10 on the bracket 15. The angle α between the axis of the swirl blade 5 and the axis of the inner sleeve 3 of the inner secondary air can be fixed by the positioning pin 12, thereby 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 reflux zone in the stable combustion chamber are adjusted. The larger the angle α between the axis of the swirl blade 5 and the axis of the inner sleeve 3 of the inner secondary air, the greater the swirl intensity of the inner secondary air, and the larger the reflux zone formed in the stable combustion chamber 7; the smaller the angle α between the axis of the swirl blade 5 and the axis of the inner sleeve 3 of the inner secondary air, the smaller the swirl intensity of the inner secondary air, and the smaller the reflux zone formed in the stable combustion chamber 7, thereby improving the adaptability of coal types.

[0064] An inner sleeve roller 3-1 is arranged on the inner ring wall of the inner secondary air inner sleeve 3, and an outer sleeve roller 4-1 is arranged on the outer ring wall of the outer secondary air outer sleeve 4. The inner sleeve roller 3-1 and the outer sleeve roller 4-1 are used to 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 smoothness of the adjustable blade unit during operation. 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 to avoid the situation where the adjustable blade unit has an excessive adjustment range and collides with the stable combustion chamber, which is beneficial to improving the working safety of the adjustable blade unit.

[0065] Working process of the internal secondary air supply system: After the hot primary air is pressurized by the primary fan 20, the outlet is divided into two routes: one route passes through the cold primary air duct 21 and passes through the cold primary air electric regulating door 27, and then mixes with the cold and hot primary air of the other route after passing through the air preheater 22 and the hot primary air electric regulating door 28, and then merges into the internal secondary air duct 2 after being fully mixed. After the secondary air is pressurized by the blower 24, it enters the air preheater 22 for temperature increase, and enters the secondary air box 26 through the hot secondary air duct 25. The secondary air is mixed with the high-temperature and high-pressure hot primary air to form a high-temperature and high-pressure internal secondary air, which is regulated by the internal secondary air electric regulating door 29 to control the range of the internal secondary air volume, and then passes through the swirl blades 5, and finally enters the self-help stable combustion burner 31 in a rotating form.

[0066] Specific implementation method 2: Combination Figures 1 to 10This embodiment is described. In this embodiment, a combustion method is provided for a burner that is suitable for burning multiple types of coal by changing the recirculation zone in coordination with the blade angle and the air volume. The method adjusts the swirl intensity by adjusting the blade angle, thereby adapting to changes in the type of coal. At the same time, the internal secondary air supply system is coordinated to adjust the opening of the hot primary air electric regulating door, the cold primary air electric regulating door and the internal secondary air electric regulating door to compensate for the increased resistance caused by the change in the blade angle, ensure the required air volume, and achieve the desired expected swirl intensity. At high loads (higher than 50% of the rated load), weak swirl secondary air is generated to reasonably organize the flow field in the stable combustion chamber to ensure high-load burnout. At low loads (20%-50% of the rated load), strong swirl secondary air is generated to adjust the shape and size of the recirculation zone in the stable combustion chamber of the self-service stable combustion burner, so as to ensure low-load stable combustion while avoiding nozzle burning and slagging due to the change in coal types. And the flame condition in the stable combustion chamber can be monitored in real time according to the signal transmitted by the video fire detection. It is specifically achieved through the following steps:

[0067] 1. Whether a coal is flammable is determined by the volatile matter Vdaf% content. Anthracite with a volatile matter Vdaf lower than 10% has an ignition temperature greater than 800°C, which is a difficult-to-burn coal; bituminous coal with a volatile matter Vdaf higher than 25% has an ignition temperature less than 700°C, which is an easy-to-burn coal; lean coal with a volatile matter Vdaf between 10% and 25% has an ignition temperature between 700 and 800°C, which is a moderately flammable coal;

[0068] 2. For anthracite (difficult-to-burn coal) with a volatile matter Vdaf lower than 10%, at high load (higher than 50% rated load), the flue gas temperature in the stable combustion chamber is high. It is necessary to reasonably organize the flow field in the stable combustion chamber to promote full mixing of the primary and secondary air, and to supplement the air required for complete combustion of the fuel to ensure high-load burnout. The specific operation is: loosen the limit nut 13, pull the sliding pin 18 in the arc-shaped sliding groove 19 by pulling the pull rod 10, and the rotating shaft 17 rotates accordingly to drive the angle of the swirl blade 5, so that the angle α of the swirl blade 5 is adjusted to 25-35°. Tighten the limit nut 13 when the pull rod is at the scale reading m1=0.82-0.90m, 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 opening of the cold primary air electric regulating valve 27 to 30%-50%, the amount of hot primary air supplemented into the internal secondary air duct 30 is controlled, and by adjusting the opening of the internal secondary air electric regulating valve 29 to 50%-70%, u=50-65m / s; after the above operation, weakly swirling secondary air is generated in the stable combustion chamber. The swirl intensity cannot form a stable reflux zone in the stable combustion chamber, but a larger radial speed is generated, which can make the primary and secondary air mixing and momentum exchange intense, 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 - stabilizing combustion burner ignites the primary air - pulverized coal flame of the tangential firing burner, ensuring stable combustion at low loads. The specific operation is as follows: increase the angle α of the swirler vane 5 to 65 - 85°, and the corresponding scale reading is m1 = 0.09 - 0.42 m. Keep the opening of the inner secondary air electric control valve 29 at 50% - 70%. When the inner secondary air velocity u is 50 - 65 m / s, increase the opening of the hot primary air electric control valve 28 to 40% - 80%, and reduce the opening of the cold primary air electric control valve 27 to 10% - 30%. After the above operations, strongly swirling secondary air is generated in the stable combustion cavity. This swirl intensity causes a large - scale recirculation zone to form 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 farther 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 a volatile content 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 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 sliding groove 19 by pulling the pull rod 10, and the angle of the swirler vane 5 is adjusted by the rotation of the rotating shaft 17, so that the angle α of the swirler vane 5 is adjusted to 15° - 25°. Tighten the limit nut 13 when the pull rod is at the scale reading m1 = 0.90 - 0.96 m, and fix the pull rod with the positioning pin 12. Control the amount of hot primary air entering the inner secondary air duct 30 by adjusting the opening of the hot primary air electric control valve 28 to 20% - 40% and the opening of the cold primary air electric control valve 27 to 30% - 50%. By adjusting the opening of the inner secondary air electric control valve 29 to 40% - 50%, make u = 35 - 50 m / s. After the above operations, weakly swirling secondary air is generated in the stable combustion cavity. This swirl intensity cannot cause a stable recirculation zone to form in the stable combustion cavity, but a relatively large radial velocity is generated, which can cause intense mixing and momentum exchange between the primary and secondary air, promoting the early mixing of the primary and secondary air, ensuring complete combustion at high loads, and improving the boiler efficiency.

[0071] At low load (20%-50% rated load), the flue gas temperature in the main combustion zone is much lower than that at high load. 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-stabilizing combustion burner ignites the primary air and pulverized coal flame of the tangential combustion burner, ensuring stable combustion at low load. 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 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 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 recirculation zone within an appropriate range in the stable combustion cavity, and the size of the recirculation zone is 0.8De < D < 2De; 2.5De < L < 4De; 0.2De < a < 0.3De. 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 timely ignition and stable combustion of the pulverized coal at low load 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 load (higher than 50% 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 load. The specific operation is as follows: loosen the limit nut 13, pull the position of the sliding pin 18 in the arc-shaped sliding 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 driven by the rotation, so that the angle α of the swirl vane 5 is adjusted to 5-15°. Tighten the limit nut 13 when the pull rod is at the scale reading m1 = 0.96-0.99m, and fix the pull rod with the positioning pin 12. Control the amount of hot primary air supplementing into the inner secondary air duct 30 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%. By adjusting the opening 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 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 the primary and secondary air intense, promote the early mixing of the primary and secondary air, ensure complete combustion at high load, 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. It is necessary to form a small central recirculation zone in the stable combustion cavity to entrain high-temperature flue gas, enabling the pulverized coal to burn in a timely manner, while avoiding damage and slagging of the burner nozzles due to the recirculation zone being too close to the nozzles. 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 internal secondary air electric regulating valve 29 at 30%-40%, and keep the internal secondary air velocity u at 20-35 m / s. Then, increase the opening of the hot primary air electric regulating valve 28 to 40%-80%, and reduce the opening 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 causes a small recirculation zone to form in the stable combustion cavity, with the size of the recirculation zone being 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. This ensures timely ignition and stable combustion of the pulverized coal at low loads while avoiding damage and slagging of the burner nozzles due to the recirculation zone being too close to the nozzles.

[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 relevant art can make some modifications or decorations equivalent to equivalent change within the scope of the technical solution of the present invention without departing from the technical solution of the present invention. However, any simple modification, equivalent change, and decoration 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 the tangential firing method. Four self-stabilizing combustion burners are arranged at the four corners between the DC primary air nozzles and the DC secondary air nozzles of the B-layer direct current pulverized coal burner. 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 transformation, 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. 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 damage and slagging of the burner nozzles.

[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, and 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 vane 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 vane 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 vane 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 boiler flameout and other accidents occur, reducing the losses caused by flameout, totaling 3 million yuan. Greatly improving the adaptability of coal types, reducing the fuel cost of the units participating in deep peak shaving by about 2 million yuan. After 2 years, normal shutdown for maintenance is carried out, and there are no problems such as burner nozzle burnout and slagging.

Claims

1. A burner suitable for burning multiple types of coal by changing the reflow zone by synergistically changing the blade angle and the air volume, characterized in that: The burner comprises a primary air duct (1), an inner secondary air duct (2), a combustion stabilizing chamber (7), an inner secondary air swirl assembly and an inner secondary air supply system. The inner secondary air duct (2) is coaxially sleeved on the outside of the primary air duct (1), and the air outlet ends of the primary air duct (1) and the inner secondary air duct (2) are both connected to the air inlet end of the combustion stabilizing 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 driving end of the inner secondary air swirl assembly extends to the outside of the inner secondary air duct (2). The inner secondary air supply system is arranged on the outside of the burner, and the air volume output end of the inner secondary air supply system is connected to the air inlet end of the inner secondary air duct (2).

2. A burner suitable for burning multiple types of coal by changing the reflow zone by synergistically changing the blade angle and the air volume according to claim 1, characterized in that: The inner secondary air swirl assembly comprises an adjustable blade unit and N drive units, N being a positive integer, the adjustable blade unit being arranged between the primary air duct (1) and the inner secondary air duct (2), and the adjustable blade unit being fixedly connected to the inner wall of the inner secondary air duct (2), and the adjustable blade unit being slidably connected to the outer wall of the primary air duct (1), the N drive units being arranged equidistantly around the outer side of the primary air duct (1) along the circumferential direction, and one end of each drive unit being connected to the adjustable blade unit, and the other end of each drive unit extending to the outside of the inner secondary air duct (2), and the change of the blade angle in the adjustable blade unit is achieved through the synchronous action of the N drive units.

3. A burner suitable for burning multiple types of coal by changing the recirculation zone by synergistically changing the blade angle and the air volume according to claim 2, characterized in that: The value range of N is 2 to 4.

4. A burner suitable for burning multiple types of coal by changing the reflow zone by synergistically changing the blade angle and the air volume according to claim 3, characterized in that: The adjustable blade unit comprises an inner secondary air inner sleeve (3), an outer secondary air outer sleeve (4) and a plurality of swirl blades (5); the inner secondary air inner sleeve (3) is sleeved on the primary air duct (1) and is slidably connected to the outer wall of the primary air duct (1); the outer secondary air outer 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); the plurality of swirl blades (5) are equidistantly arranged between the inner secondary air inner sleeve (3) and the outer secondary air outer sleeve (4) along the circumferential direction; one end of each swirl blade (5) is slidably connected to the inner secondary air inner sleeve (3) via a sliding pin (18); the other end of each swirl blade (5) is rotatably connected to the outer secondary air outer sleeve (4) via a rotating shaft (17); and one end of each driving unit is fixedly connected to the outer wall of the inner secondary air inner sleeve (3) at one end away from the combustion stabilization chamber (7).

5. A burner suitable for burning multiple types of coal by changing the reflow zone by synergistically changing the blade angle and the air volume according to claim 4, characterized in that: A plurality of rotating shaft mounting holes (17-1) are machined on the outer wall of the outer secondary air jacket sleeve (4) at equal intervals in the circumferential direction, and each rotating shaft mounting hole (17-1) is arranged corresponding to 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 a corresponding rotating shaft mounting hole (17-1) and is rotatably connected to the outer secondary air jacket sleeve (4).

6. A burner suitable for burning multiple types of coal by changing the recirculation zone by synergistically changing the blade angle and the air volume according to claim 5, characterized in that: A plurality of arc-shaped guide grooves (19) are processed at equal intervals along the circumferential direction on the outer wall of the inner secondary air inner sleeve (3), and each arc-shaped guide groove (19) is arranged corresponding to 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 a corresponding arc-shaped guide groove (19) and is slidably connected to the inner secondary air inner sleeve (3).

7. A burner suitable for burning multiple types of coal by changing the recirculation zone by synergistically changing the blade angle and the air volume according to claim 6, characterized in that: The driving unit comprises a scale (9), a pull rod (10), a bracket (15) and a connecting block (16); the bracket (15) is fixed to one end of the inner secondary air duct (2) away from the combustion stabilization chamber (7); a pull rod sleeve (11) is inserted in the bracket (15), and the pull rod sleeve (11) is arranged between the primary air duct (1) and the inner secondary air duct (2); an external thread is processed on the outer circumferential surface of the pull rod sleeve (11); the pull rod sleeve (11) is detachably connected to the bracket (15) through two limit nuts (13); a gasket (14) is provided between each limit nut (13) and the bracket (15); the pull rod (10 ) is inserted into the tie rod sleeve (11) and 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), and one end of the tie rod (10) is installed on the outer wall of the inner secondary air inner sleeve (3) through a connecting block (16), and the other end of the tie rod (10) is used as a driving end to pull 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), and the driving end of the tie rod (10) is positioned by the positioning pin (12) and the limit hole on the scale (9).

8. A burner suitable for burning multiple types of coal by changing the recirculation zone by synergistically changing the blade angle and the air volume according to claim 7, characterized in that: The internal secondary air supply system comprises 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 air outlet end of the primary air fan (20) and the air outlet end of the blower (24) are both connected to the air inlet end of the air preheater (23) through a pipeline. The first air outlet end of the air preheater (23) is connected to the air inlet end of the air preheater (23) through a hot The primary air duct (23) is connected to the air inlet end of the inner secondary air duct (2); the second air outlet end of the air preheater (23) is connected to the air inlet end of the secondary air box (26) through the hot secondary air duct (25); the air outlet end of the secondary air box (26) is connected to the air inlet end 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 end of the primary fan (20); A cold primary air electric regulating valve (27) is connected in series to the cold primary air duct (24); A hot primary air electric regulating valve (28) is connected in series to the hot primary air duct (23), and the hot primary air electric regulating valve (28) is located between the connection point between the cold primary air duct (21) and the hot primary air duct (23) and the air preheater (22); An inner secondary air electric regulating valve (29) and an air speed measuring device (30) are sequentially connected in series on the inner secondary air duct (2) along the flow direction of the secondary air.

9. A burner suitable for burning multiple types of coal by changing the recirculation zone by synergistically changing the blade angle and the air volume according to claim 8, characterized in that: A video fire detection device (6) is also provided on the air inlet end of the combustion stabilization chamber (7). The video fire detection device (6) is composed of a high temperature probe, a camera system, a cooling protection device, a thruster, a power supply control box, an air source filter and pressure control box, and a monitor, and is connected to the DCS system through a cable.

10. A combustion method using a burner suitable for burning multiple types of coal by changing the recirculation zone by synergistically changing the blade angle and the air volume according to any one of claims 1 to 9, characterized in that: The method is specifically operated as follows: When the boiler is in a condition where the load is higher than 50% of the rated load, the limit nut (13) is loosened, and the position of the sliding pin (18) in the arc-shaped sliding groove (19) is adjusted by pulling the pull rod (10), and the rotating shaft (17) rotates accordingly, driving the angle of the swirl blade (5) to change, so that the angle α of the swirl blade (5) is adjusted to 5° to 35°. When the pull rod is located at the position where the scale reading m1=0.82-0.99m, the limit nut (13) is tightened, and the pull rod (10) is fixed with the positioning pin (12). By adjusting the opening of the hot primary air electric regulating valve (28) to 20%-4 0%, the cold primary air electric regulating door (27) is opened to 30%-50% to control the amount of hot primary air added to the inner secondary air duct (30), and the opening of the inner secondary air electric regulating valve (29) is adjusted to 30%-70% to make u = 20-65m / s; after the above operation, weakly swirling secondary air is generated in the stable combustion chamber, and the swirl intensity cannot form a stable reflow zone in the stable combustion chamber, but a large radial speed is generated, which can make the primary and secondary air mixing and momentum exchange intense, promote the early mixing of the primary and secondary air, ensure high load burnout, and improve boiler efficiency; When the boiler is in the working condition of 20%-50% rated load, loosen the limit nut (13), adjust the position of the sliding pin (18) in the arc-shaped sliding groove (19) by pulling the pull rod (10), and the rotating shaft (17) rotates accordingly, driving the angle of the swirl blade (5) to change, so that the angle α of the swirl blade (5) is adjusted to 35°~85°, and the corresponding scale reading is m1=0.09-0.82m. Keep the opening of the internal secondary air electric regulating valve (29) to 30%-70%, keep the internal secondary air speed u to 20-65m / s, increase the opening of the hot primary air electric regulating valve (28) to 40%-80%, and close the opening of the cold primary air electric regulating valve (27) to 10%-30%. After the above operation, a strong swirling secondary air is generated in the stable combustion chamber. The swirl intensity forms a large-scale reflux zone in the stable combustion chamber, and the size of the reflux zone is 0.5De <D<3.5De; 2.0De <L<5.0De; 0.1De<a<0.4De; after adjustment, the size of the recirculation zone is reasonably reduced compared with the recirculation zone size of the difficult-to-burn coal, but the starting point of the recirculation zone is increased from the outlet, ensuring that the coal powder is ignited in time and burns stably under low load, while avoiding burning and slagging of the burner nozzle due to the recirculation zone being too close to the nozzle.

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