A method and system for optimizing the aerodynamic field of pulverized coal boiler under low load for stable combustion

Abstract

This invention provides a method and system for optimizing the aerodynamic field of pulverized coal boilers under low-load stable combustion. The key feature is the addition of at least one guide vane in the secondary air chamber supplying secondary air to the furnace, thereby creating multiple parallel air supply channels. Each air supply channel is equipped with a baffle for adjusting airflow and velocity, and the baffle for each air supply channel can be independently rotated. The aerodynamic field optimization method and system for pulverized coal boilers under low-load conditions provided by this invention can ensure the rigidity of the secondary air under low-load conditions, enhance the combustion of pulverized coal in the center of the furnace, and effectively improve the boiler's stable combustion at low loads.

Description

Technical Field

[0001] This invention relates to the field of efficient and clean coal combustion technology, and in particular to a method and system for optimizing the aerodynamic field of pulverized coal boilers under low load for stable combustion. Background Technology

[0002] In pulverized coal boilers at low loads, the pulverizing system must maintain the primary air velocity to prevent pipe blockage. The primary air rigidity decreases only slightly compared to high loads. Secondary air, providing the combustion air required for pulverized coal combustion, enters the furnace through the large air box. As the load decreases, the pressure in the large air box also decreases, especially in boilers that have undergone low-NOx burner modifications, where the pressure drop is particularly severe. Consequently, it is difficult to replenish the combustion air to the center of the furnace, resulting in extremely poor combustion stability. Therefore, improving the combustion stability of pulverized coal boilers under low-load conditions has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0003] In view of this, the present invention provides a method and system for optimizing the aerodynamic field of pulverized coal boiler under low load stable combustion, which can ensure the rigidity of secondary air under low load conditions of pulverized coal boiler, enhance the combustion of pulverized coal in the center of the furnace, and effectively improve the stable combustion of boiler under low load.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for optimizing the aerodynamic field of a pulverized coal boiler under low load and stable combustion involves adding at least one guide plate to the secondary air chamber used to supply secondary air to the furnace, thereby separating multiple parallel extending air supply channels. Each of the air supply channels is equipped with a baffle for adjusting the air volume and air velocity, and the baffle corresponding to each air supply channel can be independently rotated.

[0006] Optionally, the above-mentioned method for optimizing the aerodynamic field of pulverized coal boilers under low-load stable combustion also includes:

[0007] Reinforcing ribs are added inside the nozzle of the secondary air chamber to separate multiple sub-nozzles, and each sub-nozzle corresponds to one of the air supply channels.

[0008] Optionally, the above-mentioned method for optimizing the aerodynamic field of pulverized coal boilers under low load and stable combustion can be applied to tangential pulverized coal boilers.

[0009] Optionally, in the above-mentioned method for optimizing the aerodynamic field of pulverized coal boiler under low load and stable combustion, the baffles are made to perform a flipping action in sequence according to the arrangement order of the air supply channels, and the baffles in the next sequence are flipped open only after the previous sequence of the baffles has flipped to the maximum opening; the baffles in the previous sequence are flipped closed only after the next sequence of the baffles has flipped to the closed state.

[0010] A low-load stable combustion aerodynamic field optimization system for pulverized coal boilers, obtained by the aforementioned low-load stable combustion aerodynamic field optimization method for pulverized coal boilers, includes:

[0011] A secondary air chamber is used to supply secondary air to the furnace, and the secondary air chamber is divided into multiple parallel air supply channels by at least one guide plate.

[0012] A gate device comprising a plurality of baffles located in each of the air supply channels, wherein the baffle corresponding to each air supply channel can be independently rotated.

[0013] Optionally, in the above-mentioned low-load stable combustion aerodynamic field optimization system for pulverized coal boilers, the nozzle of the secondary air chamber is divided into multiple sub-nozzles by reinforcing ribs, and the sub-nozzles correspond one-to-one with the air supply channel.

[0014] Optionally, in the above-mentioned low-load stable combustion aerodynamic field optimization system for pulverized coal boilers, the gate device includes multiple coaxially arranged and layered circular tubes, each circular tube serving as the flipping shaft of the baffle in each air supply channel and connected to its respective drive device.

[0015] Optionally, in the above-mentioned low-load stable combustion aerodynamic field optimization system for pulverized coal boilers, the drive device is an intermittent control mechanism, including a pair of dials and grooved wheels.

[0016] Optionally, in the above-mentioned low-load stable combustion aerodynamic field optimization system for pulverized coal boilers, the dials of each of the driving devices are fixed on the same rotating shaft, and the blocks on different dials are staggered to achieve that the baffles in each of the air supply channels perform a flipping action in sequence according to the arrangement of the air supply channels under the drive of the same power source.

[0017] Optionally, in the above-mentioned low-load stable combustion aerodynamic field optimization system for pulverized coal boilers, the pulverized coal boiler is designed as a four-cornered tangential pulverized coal boiler.

[0018] As can be seen from the above technical solution, in the low-load stable combustion aerodynamic field optimization system for pulverized coal boilers provided by this invention, the secondary air chamber is divided into multiple parallel extending air supply channels by guide plates, that is, the secondary air chamber changes from a traditional single channel to a multi-channel system. Moreover, the baffle corresponding to each air supply channel can be independently rotated. In this way, when the pulverized coal boiler needs to reduce the secondary air volume at low load, the air volume can be reduced by closing one or more of the baffles in one of the air supply channels. At the same time, since the baffles in other air supply channels can remain stationary, the secondary air in these air supply channels can maintain a high wind speed, that is, the rigidity of the secondary air is maintained. Because the secondary air maintains strong rigidity while the air volume is reduced, it can effectively supplement air to the center of the furnace, enhance the combustion intensity of pulverized coal in the center of the furnace, and play a role in stabilizing combustion of pulverized coal boilers under low load. In addition, the strong rigidity of the secondary air under low load conditions also ensures that the primary air does not deviate, which is beneficial to prevent coking on the water-cooled walls of the pulverized coal boiler. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the gate device of the low-load stable combustion aerodynamic field optimization system for pulverized coal boilers provided in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the nozzle of the pulverized coal boiler low-load stable combustion aerodynamic field optimization system provided in an embodiment of the present invention.

[0022] The diagram is marked as follows:

[0023] 11. First circular tube; 12. First driving plate; 13. First driven plate; 21. Second circular tube; 22. Second driving plate; 23. Second driven plate; 31. First grooved wheel; 32. First dial; 41. Second grooved wheel; 42. Second dial; 5. Connecting rod; 61. First transition air duct; 62. Second transition air duct; 7. Nozzle. Detailed Implementation

[0024] The present invention provides a method for optimizing the aerodynamic field of pulverized coal boiler under low load and stable combustion (hereinafter referred to as "optimization method"). The optimization method includes: adding at least one guide plate to the secondary air chamber for supplying secondary air to the furnace to separate multiple parallel air supply channels; setting baffles for adjusting air volume and air velocity in each air supply channel; and allowing the baffles corresponding to each air supply channel to be independently rotated.

[0025] For ease of understanding, the present invention will be further described below with reference to the accompanying drawings.

[0026] This invention provides an optimized aerodynamic field system for low-load stable combustion of pulverized coal boilers (hereinafter referred to as the "optimized system") obtained by the above-described optimization method. This optimization method mainly improves the secondary air supply system of the pulverized coal boiler, specifically including the following aspects:

[0027] First, a baffle plate is added to the secondary air chamber used to supply secondary air to the furnace. The baffle plate divides the secondary air chamber into two parallel air supply channels, namely the first air supply channel and the second air supply channel. In other words, the baffle plate is arranged along the air supply direction of the secondary air chamber. One side of the baffle plate forms the first air supply channel with the inner wall of the secondary air chamber, and the other side of the baffle plate forms the second air supply channel with the inner wall of the secondary air chamber.

[0028] Secondly, baffles for adjusting air volume and velocity are installed in the first and second air supply ducts, see [reference]. Figure 1 The optimization system includes a gate device, which includes baffles located in each air supply channel, and the baffles corresponding to each air supply channel can be independently rotated. Figure 1 Each baffle in the exemplary air supply channel includes an active plate and a passive plate. The first active plate 12 and the first passive plate 13 correspond to the first air supply channel, while the second active plate 22 and the second passive plate 23 correspond to the second air supply channel. The active and passive plates are linked by a connecting rod. Taking the baffle in the first air supply channel as an example, the two ends of the connecting rod 5 are hinged to the first active plate 12 and the first passive plate 13 respectively, so that the rotation direction of the first passive plate 13 is opposite to the rotation direction of the first active plate 12, thereby enabling them to open and close relative to each other.

[0029] It should be noted that, Figure 1 This example only illustrates the case of two air supply channels. In other embodiments, two or more guide vanes can be used to divide the secondary air chamber into more air supply channels. The channel areas of these air supply channels can be the same or different, flexibly set according to the secondary air volume required by different loads. Furthermore, the baffles within the air supply channels can also take other forms. For example, each air supply channel can have only one baffle, as long as the baffles in each air supply channel can rotate independently. Independent rotation means that when a baffle in one air supply channel rotates, it does not affect the baffle in another air supply channel remaining stationary; that is, the rotational movement of the baffles in each air supply channel does not affect each other. In specific applications, the optimization method provided by this invention can be used to optimize various types of pulverized coal boilers. For example, this optimization method can be used for tangential pulverized coal boilers.

[0030] like Figure 1 As shown, in order to achieve independent flipping of the baffles in each air supply channel, the gate device in this embodiment is coaxially arranged with a first circular tube 11 and a second circular tube 21. The first circular tube 11 is fixedly connected to the first active plate 12 to become the flipping shaft of the first active plate 12, and the second circular tube 21 is fixedly connected to the second active plate 22 to become the flipping shaft of the second active plate 22. The first circular tube 11 passes through the second circular tube 21 and is connected to the first grooved wheel 31. When the first grooved wheel 31 rotates, the first active plate 12 rotates accordingly. Similarly, the second circular tube 21 is connected to the second grooved wheel 41. When the second grooved wheel 41 rotates, the second active plate 22 rotates accordingly.

[0031] To further improve the stable combustion effect of pulverized coal boilers at low loads, the optimization method of this invention may include: causing the baffles to sequentially perform a flipping action according to the arrangement order of the air supply channels, with the next baffle only flipping open after the previous baffle has flipped to its maximum opening; and the previous baffle only flipping closed after the next baffle has flipped to its closed state. Figure 1 As shown, the "arrangement order of the air supply channels" refers to the order along the horizontal direction (i.e., perpendicular to the air supply direction) of the air supply channels. Because the baffles rotate sequentially according to the arrangement order of the air supply channels, the baffles in each air supply channel open or close sequentially. Figure 1 For example, when it is necessary to increase the opening of the gate device to increase the air volume, the baffle in the first air supply channel moves first, and the baffle in the second air supply channel moves later. That is, during the process of the first active plate 12 and the first driven plate 13 opening each other, the second active plate 22 and the second driven plate 23 remain closed and stationary. Only after the first active plate 12 and the first driven plate 13 are fully opened will the second active plate 22 and the second driven plate 23 gradually open. When it is necessary to decrease the opening of the gate device to reduce the air volume, the baffle in the second air supply channel moves first, and the baffle in the first air supply channel moves later. That is, during the process of the second active plate 22 and the second driven plate 23 closing each other, the first active plate 12 and the first driven plate 13 remain fully open and stationary. Only after the second active plate 22 and the second driven plate 23 are fully closed (i.e., the second air supply channel is closed) will the first active plate 12 and the first driven plate 13 gradually close. As can be seen from the above working process, the first air supply channel remains at its maximum opening until the second air supply channel is completely closed. During this process, the reduction in air volume is only achieved through the baffles in the second air supply channel. Therefore, the air velocity in the first air supply channel will not decrease due to air volume adjustment, meaning that the air in the first air supply channel maintains strong rigidity. This part of the secondary air, which maintains strong rigidity, can effectively supplement air to the center of the furnace, enhance the combustion intensity of pulverized coal in the center of the furnace, and play a role in stabilizing combustion of pulverized coal boilers under low load. In addition, the strong rigidity of the secondary air under low load conditions also ensures that the primary air does not deviate, which is beneficial to preventing coking on the water-cooled walls of pulverized coal boilers.

[0032] It should be noted that, Figure 1 This example merely illustrates the case where the baffle's drive mechanism is an intermittent control mechanism. In this embodiment, the drive mechanism includes a pair of dials and grooved wheels, specifically, the first dial 32 and the first grooved wheel 31 cooperate with each other, and the second dial 42 and the second grooved wheel 41 cooperate with each other. Of course, in other embodiments, the drive mechanism can also take other forms, such as using a motor with a programmable controller as the drive mechanism.

[0033] like Figure 2 As shown, the first dial 32 and the second dial 42 can be fixed on the same rotating shaft. By staggering the paddles on the two dials (i.e., the parts of the dials that can slide into the grooved wheel), the first active plate 12 and the second active plate 22 can be opened or closed sequentially under the control of one actuator. The angle at which the paddles on the two dials are staggered determines the time interval between sequential opening or closing. This can save the number of actuators (or power sources). For example, a power source (e.g., a motor) can be set to drive the rotating shaft where the first dial 32 and the second dial 42 are located. When this rotating shaft rotates, because the paddles on the two dials are staggered, the first active plate 12 controlled by the first dial 32 and the second active plate 22 controlled by the second dial 42 open or close sequentially. Assuming that the angle at which the paddles on the two dials are staggered is 120°, and the rotating shaft takes 30 seconds to rotate one revolution at a constant speed, then the opening or closing time of the first active plate 12 and the second active plate 22 will differ by 10 seconds. Because the secondary air chamber has been changed from a traditional single-channel to a multi-channel design, with each channel having its own baffle, it ensures that while reducing the airflow by decreasing the baffle opening, some secondary air maintains a higher velocity. This solves problems such as insufficient secondary air rigidity, uneven air-coal mixing, delayed combustion, and poor stable combustion performance in pulverized coal boilers at low loads. Furthermore, to achieve better aerodynamic field effects, the pulverized coal boiler is preferably designed as a tangentially circular design. In this design, the optimized system also prevents the primary airflow from diverging at the end under low load conditions, thus preventing scouring of the water-cooled walls and causing coking and wear. This helps reduce the minimum non-oil-injection stable combustion load of the pulverized coal boiler.

[0034] like Figure 2 As shown, to better ensure the rigidity of the secondary air, in this embodiment, the nozzle 7 is divided into two sub-nozzles by reinforcing ribs. One sub-nozzle is connected to the aforementioned first air supply channel via a first transition air duct 61, and the other sub-nozzle is connected to the aforementioned second air supply channel via a second transition air duct 62. That is, the sub-nozzles and air supply channels are arranged in a one-to-one correspondence. Figure 2 It is evident that the sub-nozzle can be further layered using reinforcing ribs.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-load stable combustion aerodynamic field optimization system for pulverized coal boilers, characterized in that, include: A secondary air chamber is used to supply secondary air to the furnace, and the secondary air chamber is divided into multiple parallel air supply channels by at least one guide plate. A gate device, the gate device comprising a plurality of baffles respectively located in each of the air supply channels, and the baffles corresponding to each air supply channel being independently flipped; The gate device includes multiple coaxially arranged and nested in layers, and each of the round tubes serves as the flipping shaft of the baffle in each of the air supply channels and is connected to its respective drive device. The drive device is an intermittent control mechanism, including a pair of dials and grooved wheels; Each of the drive devices has a dial fixed to the same rotating shaft, and the paddles on different dials are staggered to enable the baffles in each air supply channel to perform a flipping action in sequence according to the arrangement of the air supply channels under the drive of the same power source.

2. The aerodynamic field optimization system for low-load stable combustion of pulverized coal boilers according to claim 1, characterized in that, The nozzle of the secondary air chamber is divided into multiple sub-nozzles by reinforcing ribs, and each sub-nozzle corresponds to one of the air supply channels.

3. The low-load stable combustion aerodynamic field optimization system for pulverized coal boilers according to claim 1, characterized in that, The pulverized coal boiler is designed as a four-cornered pulverized coal boiler.

4. A method for optimizing the aerodynamic field of a pulverized coal boiler under low load for stable combustion, comprising the aerodynamic field optimization system for a pulverized coal boiler under low load for stable combustion as described in any one of claims 1-3, characterized in that, At least one guide plate is added to the secondary air chamber used to supply secondary air to the furnace to separate multiple parallel air supply channels. Baffles for adjusting air volume and air speed are respectively set in each of the air supply channels, and the baffles corresponding to each air supply channel can be independently rotated. Each of the baffles in the air supply channels includes an active plate and a driven plate. The active plate and the driven plate are linked together by a connecting rod. The two ends of the connecting rod are respectively hinged to the active plate and the driven plate, so that the rotation direction of the driven plate is opposite to the rotation direction of the active plate. The baffles are rotated sequentially according to the arrangement of the air supply channels. The baffles in the previous sequence are rotated to the maximum opening before the baffles in the next sequence are rotated to open. The baffles in the previous sequence are rotated to the closed state before the baffles in the next sequence are rotated to close.

5. The method for optimizing the aerodynamic field of a pulverized coal boiler under low load for stable combustion according to claim 4, characterized in that, Also includes: Reinforcing ribs are added inside the nozzle of the secondary air chamber to separate multiple sub-nozzles, and each sub-nozzle corresponds to one of the air supply channels.

6. The method for optimizing the aerodynamic field of a pulverized coal boiler under low load for stable combustion according to claim 4, characterized in that, The method for optimizing the aerodynamic field of pulverized coal boilers under low load and stable combustion is applied to pulverized coal boilers with tangential corners.

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