A Low-Resistance Structure and Control Method for Boiler Primary Air Duct

Abstract

This invention relates to the field of circulating fluidized bed boiler technology, specifically to a low-resistance structure and control method for a boiler primary air duct. It is applied to the air duct between the air preheater outlet and the circulating fluidized bed boiler. The air duct consists of an upper air duct and a lower air duct connected together. A flow sensor is installed inside the upper air duct. Both the upper and lower air ducts include rectangular bends. Inside each rectangular bend, at least one fixed arc-shaped guide plate and multiple movable arc-shaped deflector plates are installed. One end of each arc-shaped guide plate is connected to a rotating shaft. A drive mechanism is installed outside the air duct, and a fine-tuning device is installed at the end of the rotating shaft. Based on the pressure and flow rate obtained from the flow sensor within the air duct, the target spacing of the arc-shaped guide plates is determined. A control command is generated and sent to the drive mechanism to adjust the arc-shaped guide plates to the target spacing. The fine-tuning device then performs small-amplitude reciprocating adjustments to the arc-shaped guide plates, maintaining optimal fluidization and minimal air duct resistance, thus avoiding energy loss due to excessive flow.

Description

Technical Field

[0001] This invention relates to the field of circulating fluidized bed boiler technology, and in particular to a low-resistance structure and control method for a boiler primary air duct. Background Technology

[0002] Currently, many circulating fluidized bed boilers have poor fluidized bed equipment design. The primary hot air duct is split into two at the outlet of the upper air preheater. There are two air inlet methods on the primary air inlet ignition tube: one is 45° air inlet and the other is 90° air inlet. The 90° air inlet has greater resistance, while the 45° air inlet has slightly less resistance. However, the 45° air inlet will cause the air volume at the center of the air distribution plate to be too large, which is not conducive to the uniform fluidization of the circulating fluidized bed and the uneven distribution of fluidized air volume.

[0003] In the prior art, such as the patent with announcement number CN105927973A, a low-resistance primary air system for a circulating fluidized bed boiler is disclosed, including a primary air fan outlet duct PAFD connected to the outlet of the primary air fan PAF, a cold primary air duct CPAD connected to the primary air fan outlet duct PAFD, a hot primary air duct HPAD connected to the cold primary air duct CPAD through an air preheater AH, and a fluidizing duct FAD connected to the hot primary air duct HPAD. The fluidizing duct FAD is connected to the air chamber AD. The primary air fan outlet duct PAFD, cold primary air duct CPAD, turning duct SD, gradual change duct GD, hot primary air duct HPAD, and fluidizing duct FAD are provided with flow dividers and guide plates inside or on their walls.

[0004] The aforementioned air ducts are connected by turning air ducts and gradual air ducts, which reduces the resistance of the primary air duct. However, in actual application, the resistance increases when the airflow enters the bend, making it impossible to maintain the optimal fluidization state and the minimum air duct resistance. Excessive airflow leads to energy loss. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a low-resistance structure and control method for boiler primary air ducts, so as to solve the problems of increased resistance when airflow enters the bend, failure to maintain the optimal fluidization state and minimum duct resistance, and excessive flow causing energy loss.

[0006] Based on the above objectives, the present invention provides a low-resistance structure for a boiler primary air duct, which is applied to the air duct between the air preheater outlet and the circulating fluidized bed boiler. The air duct is composed of an upper air duct and a lower air duct connected together. An electric regulating gate is provided between the upper air duct and the lower air duct. A flow sensor is provided inside the upper air duct. Both the upper air duct and the lower air duct include rectangular elbows. At least one fixed arc-shaped guide plate and multiple movable arc-shaped backflow plates are provided inside the rectangular elbows. One end of the arc-shaped guide plate is connected to a rotating shaft, which is rotatably mounted on the inner wall of the air duct. A drive mechanism is provided outside the air duct, and the drive mechanism is connected to the rotating shaft for continuously adjusting the spacing between multiple arc-shaped guide plates. The end of the rotating shaft is equipped with a fine-tuning device, which is used to continuously adjust the angle of the multiple arc-shaped guide vanes facing the airflow.

[0007] Preferably, the upper air duct further includes a reducer connected to the air preheater outlet, the end of the reducer is connected to a rectangular elbow, the end of the rectangular elbow is connected to a square-round joint, the end of the square-round joint is connected to a circular straight pipe, and the bottom end of the circular straight pipe is connected to an electric regulating door. The downdraft duct also includes a reducing pipe connected to the bottom of the electric regulating valve. The bottom of the reducing pipe is connected to a circular straight pipe, and the end of the circular straight pipe is connected to a rectangular elbow. The end of the rectangular elbow is connected to the circulating fluidized bed boiler.

[0008] Preferably, both sets of circular straight pipes are provided with circular metal compensators on their exteriors, and multiple sets of rectifier grids are provided inside the circular straight pipes. The circular straight pipes in the lower air duct are provided with openings that are connected to the external flue gas recirculation air duct.

[0009] Preferably, the drive mechanism includes a housing fixedly installed inside a rectangular elbow, side flow plates are installed on both sides of the housing, and an inner tube is opened inside the housing, the inner tube being connected to; A secondary rod is fixedly installed at both ends of the rotating shaft, and multiple sets of secondary rods are hinged to each other. A connecting rod is movably connected to the end of one set of secondary rods, and a gear rod is fixedly connected to the end of the connecting rod. A toothed plate meshes with the end of the gear rod. An electric telescopic rod is fixedly installed on the outside of the casing. The output end of the electric telescopic rod is connected to the end of the toothed plate, and the electric telescopic rod is electrically connected to the flow sensor.

[0010] Preferably, the side flow plate sleeve has a triangular cross-section, a slider is fixedly installed at the end of the rotating shaft, and an annular groove corresponding to the slider is opened inside the sleeve.

[0011] Preferably, the fine-tuning device includes an annular opening inside the housing, an annular rack slidably mounted inside the annular opening, and a large gear fixedly mounted at the end of the rotating shaft; The annular rack corresponds to the large gear. A thick plate is fixedly installed on the other side of the annular rack. One end of the thick plate is set with an inclined surface. A top block is slidably installed on one side of the annular opening. A drive cylinder is movably connected to the outside of the housing. The end of the drive cylinder is movably connected to the top block.

[0012] A control method for a low-resistance structure of a boiler primary air duct, applied to the aforementioned low-resistance structure of the boiler primary air duct, includes the following steps: S1. Obtain the real-time operating parameters of the boiler; S2. Based on the real-time operating parameters, determine the target spacing of the arc-shaped guide vanes by obtaining the pressure and flow rate in the air duct from the flow sensor. S3. Generate control commands and send them to the drive mechanism to adjust the arc-shaped guide vane to the target spacing; S4. Under stable boiler operation, after controlling the drive mechanism to drive the arc-shaped guide plate to the current set position, the arc-shaped guide plate is then finely adjusted by the fine-tuning device until the target angle is reached. The change of primary fan current or total system resistance is monitored. If the current or resistance decreases, the position of the arc-shaped guide plate is further optimized along this adjustment direction.

[0013] Preferably, the real-time operating parameters include at least one of the following: boiler load command, primary air fan current, total primary air volume, and pressure of each branch air chamber.

[0014] The beneficial effects of this invention are: Based on the pressure and flow rate obtained from the flow sensor within the air duct, the target spacing of the arc-shaped guide vanes is determined. Control commands are generated and sent to the drive mechanism to adjust the arc-shaped guide vanes to the target spacing. Simultaneously, under stable boiler operation conditions, after the drive mechanism drives the arc-shaped guide vanes to the currently set position, the fine-tuning device performs micro-adjustments on the arc-shaped guide vanes to maintain optimal fluidization and minimal air duct resistance, thus avoiding energy loss due to excessive flow. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this 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 for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a three-dimensional structural diagram of the entire invention; Figure 2 This is a schematic diagram of the overall planar structure of the present invention; Figure 3 This is a schematic diagram of the overall internal structure of the present invention; Figure 4 This is a schematic diagram of the planar structure of the driving structure and fine-tuning device of the present invention; Figure 5 This is a schematic diagram of the assembly structure connecting the air duct, air preheater, and circulating fluidized bed boiler of the present invention. Figure 6 This is a side view of the annular rack and annular opening of the present invention.

[0017] The following are labeled in the diagram: 1. Upper air duct; 2. Lower air duct; 3. Reducer; 4. Rectangular elbow; 5. Square-round joint; 6. Circular metal compensator; 7. Electric regulating gate; 8. Reducer; 9. Opening; 10. Circular straight pipe; 11. Arc-shaped guide plate; 12. Flow rectifier; 13. Drive mechanism; 131. Housing; 132. Side flow plate sleeve; 133. Secondary rod; 134. Connecting rod; 135. Slider; 136. Annular groove; 137. Inner pipe; 138. Gear rod; 139. Gear plate; 141. Electric telescopic rod; 14. Rotating shaft; 15. Fine adjustment device; 151. Annular opening; 152. Annular rack; 153. Thick plate; 154. Top block; 155. Drive cylinder; 156. Large gear; 16. Flow sensor; Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0019] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, a low-resistance structure for a boiler primary air duct is applied to the air duct between the air preheater outlet and the circulating fluidized bed boiler. The air duct is composed of an upper air duct 1 and a lower air duct 2 connected together. The structure is characterized by an electric regulating door 7 being provided between the upper air duct 1 and the lower air duct 2, a flow sensor 16 being provided inside the upper air duct 1, and both the upper air duct 1 and the lower air duct 2 including a rectangular elbow 4. The rectangular elbow 4 is provided with at least one fixed arc-shaped guide plate 11 and multiple movable arc-shaped backflow plates 12. One end of the arc-shaped guide plate 11 is connected to a rotating shaft 14, which is rotatably mounted on the inner wall of the air duct. A drive mechanism 13 is provided outside the air duct. The drive mechanism 13 is connected to the rotating shaft 14 for continuously adjusting the spacing between multiple arc-shaped guide plates 11. A fine-tuning device 15 is provided at the end of the rotating shaft 14. The fine-tuning device 15 is used to continuously adjust the angle of the multiple arc-shaped guide vanes 11 facing the airflow.

[0020] In this embodiment, the real-time operating parameters of the boiler are first obtained. Based on the real-time operating parameters, the pressure and flow rate in the air duct are obtained by the flow sensor 16. The target spacing of the arc-shaped guide plate 11 is determined, a control command is generated and sent to the drive mechanism 13 to adjust the arc-shaped guide plate 11 to the target spacing. At the same time, under the stable operating condition of the boiler, the drive mechanism 13 is controlled to drive the arc-shaped guide plate to the current set position. Then, the arc-shaped guide plate 13 is finely reciprocated by the fine-tuning device 15 until the target angle is reached. The change of the primary fan current or the total system resistance is monitored. If the current or resistance decreases, the position of the arc-shaped guide plate 13 is further optimized along this adjustment direction.

[0021] As one implementation method, such as Figure 1 , Figure 2 , Figure 3 As shown, the upper air duct 1 also includes a reducer 3 connected to the air preheater outlet. The end of the reducer 3 is connected to a rectangular elbow 4. The end of the rectangular elbow 4 is connected to a square-round joint 5. The end of the square-round joint 5 is connected to a circular straight pipe 10. The bottom end of the circular straight pipe 10 is connected to an electric regulating door 7. The downdraft duct 2 also includes a reducing pipe 8 connected to the bottom of the electric regulating valve 7. The bottom of the reducing pipe 8 is connected to a circular straight pipe 10. The end of the circular straight pipe 10 is connected to a rectangular elbow 4. The end of the rectangular elbow 4 is connected to the circulating fluidized bed boiler.

[0022] In this embodiment, after exiting the air preheater, a reducer 3 is connected to a rectangular elbow 4, which is then directly connected downwards to a circular straight pipe 10 until it reaches the elevation of the ignition tube. The rectangular elbow 4 is then connected to the ignition tube, which is on the same axis as the ignition tube. The primary air is evenly delivered into the furnace through the flared opening on the rear wall of the water-cooled air chamber. During operation, the boiler reduces the current by 5A under the same operating conditions and load, while also reducing the fluidization dead zone, thus improving the safe operation performance of the boiler.

[0023] As one implementation method, such as Figure 1 , Figure 2 , Figure 3 As shown, both sets of circular straight pipes 10 are equipped with circular metal compensators 6 on their exteriors, and multiple sets of rectifier grids 12 are installed inside the circular straight pipes 10. The circular straight pipes 10 in the lower air duct 2 are provided with openings 9, which are connected to the external flue gas recirculation air duct.

[0024] In this embodiment, when the airflow passes through the straight section of the duct, it passes through the rectifier grid 12 inside the circular straight pipe 10, which eliminates airflow rotation and improves the uniformity of flow velocity distribution.

[0025] As one implementation method, such as Figure 3 , Figure 4As shown, the drive mechanism 13 includes a housing 131 fixedly installed inside the rectangular elbow 4. Side flow plate sleeves 132 are installed on both sides of the housing 131. An inner tube 137 is opened inside the housing 131. The inner tube 137 is connected to the inner flow plate sleeve 132. A secondary rod 133 is fixedly installed at both ends of the rotating shaft 14. Multiple sets of secondary rods 133 are hinged to each other. One set of secondary rods 133 is movably connected to a connecting rod 134 at its end. A gear rod 138 is fixedly connected to the end of the connecting rod 134. A toothed plate 139 meshes with the end of the gear rod 138. An electric telescopic rod 141 is fixedly installed on the outside of the housing 131. The output end of the electric telescopic rod is connected to the end of the toothed plate 139. The electric telescopic rod 141 is electrically connected to the flow sensor 16.

[0026] In this embodiment, a high-temperature bearing and a dynamic sealing structure are provided at the position where the gear rod 138 passes through the air duct wall. The dynamic sealing structure is a stuffing box seal. The auxiliary rod 133 and the connecting rod 134 have the same length, and both the auxiliary rod 133 and the connecting rod 134 are installed at an angle. After passing through the reducer 3, the airflow enters the rectangular bend 4. The side flow plate sleeve 132 guides the airflow to turn and enter the arc-shaped backflow plate 11 in the inner pipe 137. The electric telescopic rod 141 pushes the toothed plate 139 to move. The toothed plate 139 moves and meshes with the gear rod 138, thereby driving the gear rod 138 to rotate. This causes the connecting rod 134 to drive the auxiliary rods 133 at both ends of multiple sets of rotating shafts 14 to connect and pull the spacing between the arc-shaped guide plates 11 on the rotating shafts 14 to adjust the distance between them. This ensures that the primary air duct system maintains the optimal flow state throughout the entire operating range. The pressure and flow rate inside the duct are monitored by the flow sensor 16 to maintain the optimal fluidization state and the minimum duct resistance. The spacing of the guide vanes needs to be adjusted according to the new air volume target. Generally, the time interval is reduced when the air volume increases to suppress airflow separation, and the time interval is increased when the air volume decreases to avoid excessive airflow and energy loss.

[0027] As one implementation method, such as Figure 2 , Figure 3 and Figure 4 As shown, the side flow plate sleeve 132 has a triangular cross-section, and a slider 135 is fixedly installed at the end of the rotating shaft 14. The sleeve 131 has an annular groove 136 corresponding to the slider 135 inside.

[0028] In this embodiment, when the connecting rod 134 drives the auxiliary rods 133 at both ends of multiple sets of rotating shafts 14 to connect and pull the spacing between the arc-shaped guide plates 11 on the rotating shaft 14 for adjustment, the slider 135 at the end of the rotating shaft moves on the annular groove 136, thereby keeping the arc-shaped guide plates 11 rotating along the inner tube 137 for adjustment, avoiding movement during the adjustment process and causing uneven distribution of the arc-shaped guide plates 11.

[0029] As one implementation method, such as Figure 3 , Figure 4 and Figure 6 As shown, the fine-tuning device 15 includes an annular opening 151 inside the housing 131, an annular rack 152 is slidably installed inside the annular opening 151, and a large gear 156 is fixedly installed at the end of the rotating shaft 14. The annular rack 152 corresponds to the large gear 156. A thick plate 153 is fixedly installed on the other side of the annular rack 152. One end of the thick plate 153 is set with an inclined surface. A top block 154 is slidably installed on one side of the annular opening 151. A drive cylinder 155 is movably connected to the outside of the housing 131. The end of the drive cylinder 155 is movably connected to the top block 154.

[0030] In this embodiment, the top block 154 is moved upward by the drive cylinder 155. After the top block 154 contacts the thick plate 153, due to the inclined surface of the thick plate 153, the top block 154 drives the annular rack 152 to move towards the large gear 156. After the annular rack 152 meshes with the large gear 156, the drive cylinder 155 continues to push the top block 154, thereby causing the annular rack 152 to rotate, which in turn drives the rotating shaft 14 on the large gear 156 to rotate, thereby making the angle of the arc-shaped guide plate 11 slightly adjusted to adapt to the airflow.

[0031] This specification also provides an embodiment of a control method for a low-resistance structure of a boiler primary air duct, comprising the following steps: S1. Obtain the real-time operating parameters of the boiler; S2. Based on real-time operating parameters, the target spacing of the arc-shaped guide vane 11 is determined by obtaining the pressure and flow rate in the air duct from the flow sensor 16. S3. Generate control commands and send them to the drive mechanism 13 to adjust the arc-shaped guide vane 11 to the target spacing; S4. Under stable boiler operation conditions, after the control drive mechanism 13 drives the arc-shaped guide plate to the current set position, the fine adjustment device 15 makes a small reciprocating adjustment of the arc-shaped guide plate 13 until the target angle is reached, and monitors the change of primary fan current or total system resistance. If the current or resistance decreases, the position of the arc-shaped guide plate 13 is further optimized along this adjustment direction.

[0032] The real-time operating parameters include at least one of the following: boiler load command, primary air fan current, total primary air volume, and pressure of each branch air chamber.

[0033] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in the details for the sake of brevity.

[0034] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A low-resistance structure for a boiler primary air duct, applied to the air duct between the air preheater outlet and the circulating fluidized bed boiler, the air duct being composed of an upper air duct (1) and a lower air duct (2) connected together, characterized in that, An electric regulating door (7) is provided between the upper air duct (1) and the lower air duct (2). A flow sensor (16) is provided inside the upper air duct (1). Both the upper air duct (1) and the lower air duct (2) include a rectangular elbow (4). At least one fixed arc-shaped guide plate (11) and multiple movable arc-shaped backflow plates (12) are provided inside the rectangular elbow (4). One end of the arc-shaped guide plate (11) is connected to a rotating shaft (14), which is rotatably installed on the inner wall of the air duct. A drive mechanism (13) is provided outside the air duct. The drive mechanism (13) is connected to the rotating shaft (14) for continuously adjusting the spacing between multiple arc-shaped guide plates (11). The end of the rotating shaft (14) is provided with a fine-tuning device (15), which is used to continuously adjust the angle of the multiple arc-shaped guide vanes (11) facing the airflow.

2. The low-resistance structure for a boiler primary air duct according to claim 1, characterized in that, The upper air duct (1) also includes a reducer (3) connected to the air preheater outlet. The end of the reducer (3) is connected to a rectangular elbow (4). The end of the rectangular elbow (4) is connected to a square-round joint (5). The end of the square-round joint (5) is connected to a circular straight pipe (10). The bottom end of the circular straight pipe (10) is connected to an electric regulating door (7). The downdraft duct (2) also includes a reducing pipe (8) connected to the bottom end of the electric regulating valve (7). The bottom end of the reducing pipe (8) is connected to a circular straight pipe (10). The end of the circular straight pipe (10) is connected to a rectangular elbow (4). The end of the rectangular elbow (4) is connected to a circulating fluidized bed boiler.

3. The low-resistance structure for a boiler primary air duct according to claim 2, characterized in that, Both sets of circular straight pipes (10) are provided with circular metal compensators (6) on the outside, and multiple sets of rectifier grids (12) are provided inside the circular straight pipes (10). The circular straight pipes (10) in the downdraft (2) are provided with openings (9), which are connected to the external flue gas recirculation duct.

4. The low-resistance structure for a boiler primary air duct according to claim 1, characterized in that, The drive mechanism (13) includes a housing (131) fixedly installed inside the rectangular elbow (4), side flow plate sleeves (132) are installed on both sides of the housing (131), and an inner tube (137) is opened inside the housing (131). The two ends of the rotating shaft (14) are respectively fixedly installed with auxiliary rods (133), and multiple sets of auxiliary rods (133) are hinged to each other. One set of auxiliary rods (133) is movably connected to a connecting rod (134) at the end, and a gear rod (138) is fixedly connected to the end of the connecting rod (134). The end of the gear rod (138) is meshed with a toothed plate (139). An electric telescopic rod (141) is fixedly installed on the outside of the casing (131). The output end of the electric telescopic rod is connected to the end of the toothed plate (139). The electric telescopic rod (141) is electrically connected to the flow sensor (16).

5. The low-resistance structure for a boiler primary air duct according to claim 4, characterized in that, The side flow plate sleeve (132) has a triangular cross section, and a slider (135) is fixedly installed at the end of the rotating shaft (14). The sleeve (131) has an annular groove (136) corresponding to the slider (135) inside.

6. The low-resistance structure for a boiler primary air duct according to claim 1, characterized in that, The fine-tuning device (15) includes an annular opening (151) inside the housing (131), an annular rack (152) is slidably installed inside the annular opening (151), and a large gear (156) is fixedly installed at the end of the rotating shaft (14). The annular rack (152) corresponds to the large gear (156). A thick plate (153) is fixedly installed on the other side of the annular rack (152). One end of the thick plate (153) is set with an inclined surface. A top block (154) is slidably installed on one side of the annular opening (151). A drive cylinder (155) is movably connected to the outside of the housing (131). The end of the drive cylinder (155) is movably connected to the top block (154).

7. A control method for a low-resistance structure of a boiler primary air duct, applied to the low-resistance structure of the boiler primary air duct as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Obtain the real-time operating parameters of the boiler; S2. Based on the real-time operating parameters, the target spacing of the arc-shaped guide plate (11) is determined by obtaining the pressure and flow rate in the air duct from the flow sensor (16). S3. Generate control commands and send them to the drive mechanism (13) to adjust the arc-shaped guide vane (11) to the target spacing; S4. Under the stable operation of the boiler, after the drive mechanism (13) drives the arc-shaped guide plate to the current set position, the arc-shaped guide plate (13) is then adjusted by the fine-tuning device (15) until the target angle is reached. The change of the primary fan current or the total system resistance is monitored. If the current or resistance decreases, the position of the arc-shaped guide plate (13) is optimized along this adjustment direction.

8. The control method for a low-resistance structure of a boiler primary air duct according to claim 7, characterized in that, The real-time operating parameters include at least one of the following: boiler load command, primary air fan current, total primary air volume, and pressure of each branch air chamber.

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