A kind of low-nitrogen combustion grading air distribution mechanism for coal-fired boiler

Abstract

The utility model relates to a wind distribution mechanism technical field especially, relates to a kind of hierarchical wind distribution mechanism for low-nitrogen combustion of coal-fired boiler.The utility model provides a kind of hierarchical wind distribution mechanism for low-nitrogen combustion of coal-fired boiler, including wind distribution mechanism shell, drive motor, impeller, connecting frame and wind distribution pipe etc., drive motor is connected with the rear side of wind distribution mechanism shell, drive motor output shaft is penetrated to wind distribution mechanism shell inner chamber, and is connected with impeller, impeller and wind distribution mechanism shell inner chamber constitute centrifugal wind distribution mechanism, and connecting frame is connected and communicated with the air outlet of wind distribution mechanism shell right end outlet.Through servo motor drive gear pair drive distribution pipe rotation, make the linear variation of the overlapping area of wind distribution through-hole and connecting pipe, realize the continuous accurate control of single branch air volume from full close to full open, combined with external control system, the air volume gradient required by each combustion layer of boiler can be dynamically matched, solve the traditional air door regulation lag problem, guarantee the combustion stability of lean oxygen / oxygen-rich partition.

Description

Technical Field

[0001] This utility model relates to the technical field of air distribution mechanisms, and in particular to a graded air distribution mechanism for low-NOx combustion in coal-fired boilers. Background Technology

[0002] In the field of low-NOx combustion in coal-fired boilers, vertical zoned air distribution in the furnace is the core means to achieve NOx emission reduction. Traditional staged air distribution mechanisms generally use mechanical damper structures (such as gate valves or butterfly valves) to regulate the air volume of each layer, which has the following technical bottlenecks:

[0003] 1. Low adjustment accuracy: Mechanical dampers rely on manual or stepper motor drive, and their opening degree has a non-linear relationship with air volume (especially in the small opening range). The actual air volume deviation often reaches ±10% or more, making it difficult to accurately match the oxygen-deficient / oxygen-rich conditions required in the combustion zone.

[0004] 2. Poor dynamic response: The damper actuator has no stroke and mechanical lag (response time > 5s), which cannot adapt to the real-time air distribution requirements of the boiler under variable load conditions, resulting in fluctuations in the excess air coefficient (fluctuation range ±0.15), which aggravates NOx generation and incomplete combustion of pulverized coal;

[0005] 3. Lack of gradient control: A single damper can only control the air volume of a single layer and lacks a coordinated adjustment mechanism for the air volume ratio of each layer. A stable low-NOx combustion gradient cannot be formed in the vertical direction of the furnace (e.g., the excess air coefficient in the lower oxygen-deficient zone needs to be 0.8-0.9, and the upper oxygen-enriched zone needs to be 1.1-1.2).

[0006] The aforementioned defects severely restrict the efficiency of low-NOx combustion, and there is an urgent need to develop an air distribution mechanism with high precision, fast response, and multi-stage adjustment capabilities. Utility Model Content

[0007] In order to overcome the shortcomings mentioned in the background art, this utility model provides a graded air distribution mechanism for low-NOx combustion in coal-fired boilers.

[0008] The technical implementation scheme of this utility model is as follows: a graded air distribution mechanism for low-NOx combustion in a coal-fired boiler, comprising an air distribution housing, a drive motor, an impeller, a connecting frame, an air distribution pipe, a distribution pipe, a connecting pipe, and an adjustment component. The drive motor is connected to the rear side of the air distribution housing, and the output shaft of the drive motor passes through the inner cavity of the air distribution housing and is connected to the impeller. The impeller and the inner cavity of the air distribution housing form a centrifugal air distribution mechanism. The air outlet at the right end of the air distribution housing is connected to and communicates with the connecting frame. The end of the connecting frame away from the air distribution housing is connected to and communicates with the air distribution pipe. The distribution pipe is rotatably connected to the inner side of the air distribution pipe. The outer side of the air distribution pipe is connected to and communicates with the connecting pipe at the four positions of upper, lower, front, and rear. The distribution pipe has three air distribution holes spaced apart along half a circumference on the upper and lower sides. The air distribution holes and the ports of the connecting pipes form an adjustable flow structure. An adjustment component is provided on the air distribution pipe. The drive motor is electrically connected to an external PLC control system.

[0009] As a further preferred option, both the air distribution duct and the distribution pipe are made of 310S high-temperature resistant stainless steel, and their inner walls are coated with a ceramic wear-resistant coating.

[0010] As a further preferred option, the adjustment component includes a servo motor, a drive gear, and a gear ring. The servo motor is installed on the rear side of the air distribution duct, and the drive gear is connected to the output shaft of the servo motor. The gear ring is connected to the outer side of the right end of the distribution duct. The gear ring and the drive gear form a meshing transmission pair. The servo motor is connected to the signal of the external PLC control system.

[0011] As a further preferred option, a filter screen is also included, with the filter screen connected to the air inlet on the front side of the fan housing.

[0012] As a further preferred option, a quick-release flange is installed at the interface between the connecting pipe and the air distribution pipe.

[0013] As a further preferred embodiment, it also includes a rotating tube, fan blades, and turbulence-disrupting blades. The rotating tube is rotatably connected to the inside of the distribution tube, and the fan blades are connected inside the rotating tube. The outer periphery of the left end of the rotating tube is provided with a circular arc transition guide surface, and the right end is an open structure. Several turbulence-disrupting blades are evenly distributed along the circumferential direction on the outer wall of the rotating tube.

[0014] The beneficial effects of this utility model are: 1. By using a servo motor to drive a gear pair to rotate the distribution pipe (0°-360° stepless adjustment), the overlapping area of ​​the air distribution hole and the connecting pipe changes linearly, achieving continuous and precise control of the air volume of a single branch from fully closed to fully open. Combined with an external control system, it can dynamically match the required air volume gradient of each combustion layer of the boiler, solving the problem of lag in traditional damper adjustment and ensuring the combustion stability of oxygen-deficient / oxygen-rich zones.

[0015] 2. Built-in rotating airflow acceleration unit (combination of rotating pipe, fan blade, and turbulence blades) utilizes the split gas to drive rotation and generate centrifugal pressurization effect, increasing the jet pressure of the air distribution orifice by 15%-20%. This design enhances the airflow penetration depth, improves the turbulent mixing efficiency of pulverized coal and air, and reduces the risk of localized oxygen-deficient combustion. Attached Figure Description

[0016] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0017] Figure 2 This is a three-dimensional structural diagram of the components of this utility model, including the fan housing, drive motor, and impeller.

[0018] Figure 3 This is a three-dimensional structural diagram of the components of this utility model, including the distribution pipe, connecting pipe, and air distribution vent.

[0019] Figure 4This is a three-dimensional structural diagram of the connecting pipe, air vent, and servo motor of this utility model.

[0020] Figure 5 This is a three-dimensional structural diagram of the rotating tube, fan blades, and turbulence blades of this utility model.

[0021] Figure 6 This is a three-dimensional structural diagram of the connecting pipe, air distribution hole, and gear ring component of this utility model.

[0022] Wherein: 1: fan housing, 2: drive motor, 3: impeller, 4: filter screen, 5: connecting frame, 6: air distribution duct, 7: distribution pipe, 8: connecting pipe, 9: air distribution through hole, 10: servo motor, 11: drive gear, 12: gear ring, 13: rotating pipe, 14: fan blade, 15: turbulence blade. Detailed Implementation

[0023] Example: A staged air distribution mechanism for low-NOx combustion in a coal-fired boiler, such as... Figures 1-3 and Figure 6 As shown, the system includes a fan housing 1, a drive motor 2, an impeller 3, a filter screen 4, a connecting frame 5, a distribution duct 6, a distribution pipe 7, a connecting pipe 8, and an adjusting assembly. The fan housing 1 adopts a volute structure, with the drive motor 2 connected to its rear flange. The output shaft of the drive motor 2 passes through the inner cavity of the fan housing 1 and is connected to the impeller 3 via a coupling. The impeller 3 and the inner cavity of the fan housing 1 form a centrifugal air distribution mechanism. A filter screen 4 is connected to the air inlet on the front side of the fan housing 1 to intercept dust and solid impurities in the air, preventing them from entering the furnace and affecting combustion efficiency and low-NOx emission performance. The right end of the fan housing 1 is connected to and connected to the connecting frame 5. The end of the connecting frame 5 away from the fan housing 1 is connected to and connected to the distribution duct 6. The right end of the distribution duct 6 is used to connect to the flange of the boiler's main air duct. The inner side of the distribution duct 6 rotates... The distribution pipe 7 is dynamically connected to the air distribution pipe 6. Both the distribution pipe 7 and the air distribution pipe 6 are made of 310S high-temperature resistant stainless steel. The inner wall of the distribution pipe 6 is coated with a ceramic wear-resistant coating, which can withstand the furnace radiation temperature of over 800℃, reduce high-temperature oxidation and airflow erosion wear, and extend the service life of the equipment. The air distribution pipe 6 is connected to the connecting pipe 8 at the top, bottom, front and back four positions. Each connecting pipe 8 is used to connect to the air pipe of different combustion layers of the boiler. The interface between the connecting pipe 8 and the air distribution pipe 6 is equipped with a quick-release flange, so that the air distribution pipe 6 does not need to be disassembled when maintaining the connecting pipe 8, thus improving efficiency. The distribution pipe 7 has three air distribution holes 9 spaced apart along half a circumference on the top and bottom sides. The air distribution holes 9 and the ports of the connecting pipe 8 form an adjustable flow structure. The air distribution pipe 6 is equipped with an adjustment component. The drive motor 2 is electrically connected to the external PLC control system.

[0024] like Figures 2-4 and Figure 6As shown, the adjustment assembly includes a servo motor 10, a drive gear 11, and a gear ring 12. The servo motor 10 is bolted to the rear side of the air distribution duct 6. The drive gear 11 is connected to the output shaft of the servo motor 10. The gear ring 12 is connected to the outer side of the right end of the distribution pipe 7. The gear ring 12 and the drive gear 11 form a meshing transmission pair. The servo motor 10 is connected to the signal of the external PLC control system, which can realize the rotation angle control with an accuracy of 0.1°.

[0025] Based on the differences in oxygen demand in different combustion zones at different heights of the boiler furnace, connecting pipes 8 are connected to the corresponding air ducts of the combustion layers. The right end of the air distribution pipe 6 is connected to the main air duct of the furnace. During air distribution operation, an external PLC control system sends a start signal to the drive motor 2, which drives the impeller 3 to rotate at high speed, drawing outside air into the air distribution fan housing 1 through the air inlet. The airflow enters the connecting frame 5 and the air distribution pipe 6 sequentially through the air outlet. The mainstream air directly enters the main air duct of the furnace, while the tributary air is distributed to each connecting pipe 8 through the air distribution throughlet 9 to achieve stratified air supply. When it is necessary to adjust the airflow of a certain layer, the control system can be activated. When the servo motor 10 is started, the output shaft of the servo motor 10 rotates, which drives the distribution pipe 7 to rotate through the transmission of the drive gear 11 and the gear ring 12. The air distribution hole 9 on it rotates synchronously. The distribution pipe 7 can rotate within 0°-360°. The flow overlap area between the air distribution hole 9 and the interface of the connecting pipe 8 will change continuously with the rotation. The air intake volume of each connecting pipe 8 can be linearly adjusted between fully closed (zero overlap) and fully open (maximum flow area) to meet the differentiated air volume requirements of each combustion zone. After the adjustment is completed, the servo motor 10 will lock itself in position. When the air distribution is stopped, the power supply of the drive motor 2 can be cut off through the control system.

[0026] like Figure 4 and Figure 5 As shown, it also includes a rotating pipe 13, a fan blade 14, and a turbulence-disrupting blade 15. The rotating pipe 13 is rotatably connected to the inside of the distribution pipe 7 via a bearing. The fan blade 14 is fixedly connected inside the rotating pipe 13. The left end of the rotating pipe 13 has a circular arc transition guide surface on its outer periphery, and the right end is an open structure. The outer wall of the rotating pipe 13 is evenly distributed with a number of turbulence-disrupting blades 15 along the circumferential direction. When the airflow passes through the air distribution pipe 6, the airflow is guided by the guide surface of the rotating pipe 13 into the air distribution through hole 9 and comes into contact with the turbulence-disrupting blades 15. Part of the airflow enters the rotating pipe 13 and impacts the fan blade 14. Combined with the thrust of the external airflow on the turbulence-disrupting blades 15, a compound driving force is formed, causing the rotating pipe 13 to rotate. This rotational motion forms a swirling flow field through the turbulence-disrupting blades 15, which enhances the impact force of the airflow on the air distribution through hole 9 and accelerates the airflow replacement speed at the air distribution through hole 9, effectively improving the air distribution efficiency and the uniformity of airflow distribution.

Claims

1. A staged air distribution mechanism for low-NOx combustion in a coal-fired boiler, characterized in that: The device includes a fan housing (1), a drive motor (2), an impeller (3), a connecting frame (5), a distribution duct (6), a distribution pipe (7), a connecting pipe (8), and an adjustment assembly. The drive motor (2) is connected to the rear side of the fan housing (1). The output shaft of the drive motor (2) passes through the inner cavity of the fan housing (1) and is connected to the impeller (3). The impeller (3) and the inner cavity of the fan housing (1) form a centrifugal air distribution mechanism. The air outlet at the right end of the fan housing (1) is connected to and communicates with the connecting frame (5). The connecting frame (5) is far from the fan housing (1). One end of the fan housing (1) is connected to and connected to the air distribution pipe (6). The inner side of the air distribution pipe (6) is rotatably connected to the distribution pipe (7). The upper, lower, front and rear four positions of the outer side of the air distribution pipe (6) are all connected to and connected to the connecting pipe (8). The upper and lower sides of the distribution pipe (7) are provided with three air distribution holes (9) spaced apart along half circumference. The air distribution holes (9) and the port of the connecting pipe (8) form an adjustable flow structure. The air distribution pipe (6) is provided with an adjustment component. The drive motor (2) is electrically connected to the external PLC control system.

2. A staged air distribution mechanism for low-NOx combustion in a coal-fired boiler according to claim 1, characterized in that: Both the air distribution duct (6) and the distribution pipe (7) are made of 310S high temperature resistant stainless steel, and their inner walls are coated with a ceramic wear-resistant coating.

3. A staged air distribution mechanism for low-NOx combustion in a coal-fired boiler according to claim 2, characterized in that: The adjustment assembly includes a servo motor (10), a drive gear (11), and a gear ring (12). The servo motor (10) is installed on the rear side of the air distribution pipe (6). The drive gear (11) is connected to the output shaft of the servo motor (10). The gear ring (12) is connected to the outer side of the right end of the distribution pipe (7). The gear ring (12) and the drive gear (11) form a meshing transmission pair. The servo motor (10) is connected to the signal of the external PLC control system.

4. A staged air distribution mechanism for low-NOx combustion in a coal-fired boiler according to claim 3, characterized in that: It also includes a filter screen (4), and the filter screen (4) is connected to the air inlet on the front side of the fan housing (1).

5. A staged air distribution mechanism for low-NOx combustion in a coal-fired boiler according to claim 4, characterized in that: A quick-release flange is installed at the interface between the connecting pipe (8) and the air distribution pipe (6).

6. A staged air distribution mechanism for low-NOx combustion in a coal-fired boiler according to claim 5, characterized in that: It also includes a rotating tube (13), a fan blade (14) and a turbulence blade (15). The rotating tube (13) is rotatably connected to the inside of the distribution tube (7). The fan blade (14) is connected inside the rotating tube (13). The outer periphery of the left end of the rotating tube (13) is provided with a circular arc transition guide surface, and the right end is an open structure. The outer periphery of the rotating tube (13) is evenly provided with a few turbulence blades (15) along the circumferential direction.

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