Boiler hot secondary air duct flow field optimizing and adjusting method

Abstract

The invention discloses a boiler hot secondary air duct flow field optimizing and adjusting method, and relates to the field, the boiler hot secondary air duct flow field optimizing and adjusting method comprises a hot secondary air mother pipe body, a plurality of sets of branch pipes are installed on the outer wall of the hot secondary air mother pipe body, the ends of the branch pipes penetrate into the hot secondary air mother pipe body, and combustor air boxes are arranged in the middles of the branch pipes; a flow guide assembly is arranged at the end of the branch pipe and comprises first flow guide plates and an air volume measuring device, multiple sets of first flow guide plates are fixed to the two sides of the inner wall of the branch pipe, and the air volume measuring device is arranged at the end of the branch pipe. Accurate and online adjustment of the air volume of each branch pipe is achieved, the problem of inherent uneven distribution is solved, the angles of the flow guide plates can be flexibly adjusted according to changes of boiler loads, fire coal varieties and the like, flow field optimization under all working conditions is achieved, the adaptability is far better than that of a fixed flow guide plate, and airflow is smoothed by optimizing the flow fields at the tee joint and the elbow.

Description

Technical Field

[0001] This invention relates to the field of boiler thermal secondary air duct flow field optimization and adjustment method. Background Technology

[0002] The boiler's hot secondary air is an important component of the boiler combustion system. The flow field distribution within its duct has a significant impact on the boiler's combustion efficiency, safety, and economy. During boiler operation, uneven flow field distribution within the hot secondary air duct is quite common, which makes boiler combustion unstable, reducing combustion efficiency and increasing heat loss.

[0003] Due to unreasonable structural design, some boiler secondary air ducts are prone to eddies and uneven flow velocity at corners and bifurcations, leading to unbalanced hot air distribution and affecting the complete combustion of fuel. At the same time, as the boiler operates for a long time, dust and impurities may accumulate on the inner wall of the duct, further aggravating the turbulence of the flow field. Existing adjustment methods mostly rely on manual experience to adjust valves, lacking scientific theoretical basis and precise control methods, making it difficult to achieve effective optimization of the flow field. Traditional solutions mainly involve optimization through CFD simulation during the design phase or installing fixed guide vanes in the pipeline. However, CFD simulations have errors compared to actual conditions, and fixed guide vanes cannot adapt to changes in the flow field caused by boiler load, coal type, etc., lacking flexibility and adaptability. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a method for optimizing and adjusting the flow field of a boiler hot secondary air duct, so as to solve the technical problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a boiler hot secondary air duct flow field optimization structure, comprising a hot secondary air main pipe body, wherein multiple sets of branch pipes are installed on the outer wall of the hot secondary air main pipe body, and the ends of the branch pipes penetrate into the interior of the hot secondary air main pipe body, a burner air box is provided in the middle of the branch pipe, and a flow guiding component is provided at the end of the branch pipe, the flow guiding component including a first flow guiding plate and an air volume measuring device, multiple sets of first flow guiding plates are fixed on both sides of the inner wall of the branch pipe, and an air volume measuring device is provided at the end of the branch pipe.

[0006] By adopting the above technical solution, precise and online adjustment of the air volume of each branch pipe is achieved, solving the inherent problem of uneven distribution. The angle of the guide vane can be flexibly adjusted according to changes in boiler load, coal type, etc., to achieve flow field optimization under all operating conditions. Its adaptability is far superior to that of a fixed guide vane. By optimizing the flow field at tees and elbows, the airflow is smoothed, which can effectively eliminate or significantly reduce the vibration of the air duct caused by eddies and flow separation, ensuring the uniformity of air distribution in the furnace, making combustion more complete and stable, which is conducive to improving boiler efficiency and reducing coal consumption and NOx emissions. The guide vane structure design takes into account the strength and sealing performance under high temperature environment, and the actuator is located outside the air duct, making maintenance convenient and safe.

[0007] The invention is further configured such that a second guide plate can be installed on both sides of the inner wall of the branch pipe, and the second guide plate is arc-shaped.

[0008] Preferably, the arc-shaped second guide plate can better guide the airflow.

[0009] The present invention is further configured such that the first guide plate is inclined.

[0010] Preferably, the inclined first guide plate can guide the wind and reduce wind resistance.

[0011] The present invention is further configured such that the airflow measuring device is either an airfoil-type or a multi-point array type flow measuring device.

[0012] The present invention is further configured such that both the first guide plate and the second guide plate are made of high-temperature resistant alloy steel.

[0013] Preferably, the first and second guide plates made of high-temperature resistant alloy steel have a longer service life and are less prone to damage.

[0014] A method for adjusting the flow field in a boiler hot secondary air duct includes the following steps: S1: System initialization and baseline establishment. Under stable boiler operating conditions, measure and record the initial air volume value Q_i of each branch pipe, and calculate the average air volume Q_avg and the relative deviation Δ_i of the air volume of each branch pipe.

[0015] S2: Set the air volume distribution target and identify branches where the air volume deviates from the target.

[0016] S3: Adjustment strategy execution: For branch pipes with excessive air volume, adjust the adjustable multi-stage flow guide device at its inlet to deflect the flow guide plate in the direction that increases the flow resistance of the branch pipe; for branch pipes with insufficient air volume, adjust the adjustable multi-stage flow guide device at its inlet to deflect the flow guide plate in the direction that reduces the flow resistance of the branch pipe.

[0017] S4: Iterative adjustment: After the adjustment is performed, the system runs stably and the air volume is remeasured. The new relative deviation of the air volume is calculated. If the target is not reached, the system returns to step S3 for fine-tuning. If the target is reached, the current guide vane angle is recorded.

[0018] S5: Load Adaptability Adjustment: Establish a database of optimal guide vane angles under different boiler loads. When the load changes, the control system automatically calls up the corresponding preset value and adjusts the guide vane to the appropriate position.

[0019] The present invention is further configured such that, in step S3, the adjustment strategy also includes adjusting the adjustable multi-stage flow guiding device after the downstream bend of the branch pipe with insufficient air volume, so as to optimize the internal flow field and reduce resistance loss.

[0020] The present invention is further configured such that, in steps S1 and S4, the formula for calculating the relative deviation of air volume Δ_i is: Δ_i = (Q_i - Q_avg) / Q_avg × 100%.

[0021] The present invention is further configured such that, in step S2, the air volume distribution target is to control the absolute value of the relative deviation Δ_i of the air volume of all branch pipes within ±5%.

[0022] The present invention is further configured such that, in step S5, the different boiler loads include at least the rated load, 75% load, and 50% load.

[0023] In summary, the present invention has the following main beneficial effects: This invention achieves precise, online adjustment of airflow in each branch pipe through real-time airflow feedback, solving the inherent problem of uneven distribution. The angle of the guide vane can be flexibly adjusted according to changes in boiler load, coal type, etc., to achieve flow field optimization under all operating conditions. Its adaptability is far superior to that of a fixed guide vane. By optimizing the flow field at tees and elbows, the airflow is smoothed, which can effectively eliminate or significantly reduce duct vibration caused by eddies and flow separation, ensuring the uniformity of furnace air distribution, making combustion more complete and stable, which is conducive to improving boiler efficiency and reducing coal consumption and NOx emissions. The guide vane structure design takes into account strength and sealing under high-temperature environments, and the actuator is located outside the duct, making maintenance convenient and safe. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a cross-sectional view of the branch pipe of the present invention; Figure 3 This is a schematic diagram of the installation of the second guide plate of the present invention; Figure 4 This is a flowchart of the adjustment method of the present invention.

[0025] Explanation of reference numerals in the attached figures: 1. Main body of secondary hot air duct; 2. Branch pipe; 3. Burner air box; 4. Flow guide assembly; 41. First flow guide plate; 42. Air volume measuring device; 43. Second flow guide plate. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] The embodiments of the present invention will now be described.

[0028] Please see Figures 1-3 The system includes a main body 1 for hot secondary air, with multiple sets of branch pipes 2 installed on the outer wall of the main body 1. The ends of the branch pipes 2 penetrate into the interior of the main body 1. A burner air box 3 is installed in the middle of the branch pipe 2, and a flow guiding component 4 is installed at the end of the branch pipe 2. The flow guiding component 4 includes a first guide plate 41 and an air volume measuring device 42. The air volume measuring device 42 is either an airfoil-shaped or a multi-point array flow measuring device. Multiple sets of first guide plates 41 are fixed on both sides of the inner wall of the branch pipe 2, and the air volume measuring device 42 is installed at the end of the branch pipe 2. During operation, air enters from the air inlet of the main body 1 for hot secondary air, and then enters the branch pipe 2. The burner air box 3 operates, and then the air is guided by the first guide plate 41 and measured by the air volume measuring device 42.

[0029] For details regarding the above embodiments, please refer to [link / reference]. Figure 3 A second guide plate 43 can also be installed on both sides of the inner wall of the branch pipe 2. The second guide plate 43 is arc-shaped, and the arc-shaped second guide plate 43 can better guide the air.

[0030] For details regarding the above embodiments, please refer to [link / reference]. Figure 2 The first guide plate 41 is inclined, and the inclined first guide plate 41 can guide the wind and reduce wind resistance.

[0031] For details regarding the above embodiments, please refer to [link / reference]. Figure 2 and Figure 3 The first guide plate 41 and the second guide plate 43 are both made of high-temperature resistant alloy steel. The first guide plate 41 and the second guide plate 43 made of high-temperature resistant alloy steel have a longer service life and are not easily damaged.

[0032] A method for adjusting the flow field in a boiler hot secondary air duct includes the following steps: S1: System initialization and baseline establishment. Under stable boiler operating conditions, measure and record the initial air volume value Q_i of each branch pipe 2, and calculate the average air volume Q_avg and the relative deviation Δ_i of the air volume of each branch pipe.

[0033] S2: Set the air volume distribution target and identify branches where the air volume deviates from the target.

[0034] S3: Adjustment strategy execution: For branch pipes with excessive air volume, adjust the adjustable multi-stage flow guide device 4 at its inlet to deflect the flow guide plate 41 in the direction that increases the flow resistance of the branch pipe; for branch pipes with insufficient air volume, adjust the adjustable multi-stage flow guide device 4 at its inlet to deflect the flow guide plate 41 in the direction that reduces the flow resistance of the branch pipe.

[0035] S4: Iterative adjustment: After the adjustment is performed, the system runs stably and the air volume is remeasured. The new relative deviation of the air volume is calculated. If the target is not reached, the system returns to step S3 for fine-tuning. If the target is reached, the current guide vane angle is recorded.

[0036] S5: Load Adaptability Adjustment: Establish a database of optimal guide vane angles under different boiler loads. When the load changes, the control system automatically calls up the corresponding preset value and adjusts the guide vane to the appropriate position.

[0037] In step S3, the adjustment strategy also includes adjusting the adjustable multi-stage flow guide device 4 after the downstream bend of the branch pipe with insufficient air volume to optimize the internal flow field and reduce resistance loss.

[0038] In steps S1 and S4, the formula for calculating the relative deviation of air volume Δ_i is: Δ_i = (Q_i - Q_avg) / Q_avg × 100%.

[0039] In step S2, the air volume distribution target is to control the absolute value of the relative deviation Δ_i of the air volume of all branches within ±5%.

[0040] In step S5, the different boiler loads include at least the rated load, 75% load, and 50% load.

[0041] Although embodiments of the present invention have been shown and described, these specific embodiments are merely explanations of the invention and are not intended to limit it. The specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions, and variations to the embodiments as needed without departing from the principles and spirit of the invention, but such modifications, substitutions, and variations are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A boiler hot secondary air duct flow field optimization structure, comprising a hot secondary air main pipe body (1), characterized in that: Multiple sets of branch pipes (2) are installed on the outer wall of the main body (1) of the hot secondary air duct, and the ends of the branch pipes (2) penetrate into the interior of the main body (1) of the hot secondary air duct. A burner air box (3) is provided in the middle of the branch pipe (2), and a flow guiding component (4) is provided at the end of the branch pipe (2). The flow guiding component (4) includes a first flow guiding plate (41) and an air volume measuring device (42). Multiple sets of first flow guiding plates (41) are fixed on both sides of the inner wall of the branch pipe (2), and an air volume measuring device (42) is provided at the end of the branch pipe (2).

2. The boiler hot secondary air duct flow field optimization structure according to claim 1, characterized in that: A second guide plate (43) can also be installed on both sides of the inner wall of the branch pipe (2), and the second guide plate (43) is arc-shaped.

3. The boiler hot secondary air duct flow field optimization structure according to claim 1, characterized in that: The first guide plate (41) is inclined.

4. The boiler hot secondary air duct flow field optimization structure according to claim 1, characterized in that: The airflow measuring device (42) is either an airfoil-type or a multi-point array-type flow measuring device.

5. The boiler hot secondary air duct flow field optimization structure according to claim 2, characterized in that: Both the first guide plate (41) and the second guide plate (43) are made of high-temperature resistant alloy steel.

6. A method for adjusting the flow field of a boiler hot secondary air duct according to any one of claims 1-5, comprising the following steps: S1: System initialization and benchmark establishment. Under stable boiler operating conditions, measure and record the initial air volume value Q_i of each branch pipe (2), and calculate the average air volume Q_avg and the relative deviation Δ_i of the air volume of each branch pipe. S2: Set the air volume distribution target and identify branches where the air volume deviates from the target; S3: Adjustment strategy execution: For branch pipes with excessive air volume, adjust the adjustable multi-stage flow guide device (4) at its inlet so that the guide plate (41) deflects in the direction of increasing the flow resistance of the branch pipe; for branch pipes with insufficient air volume, adjust the adjustable multi-stage flow guide device (4) at its inlet so that the guide plate (41) deflects in the direction of reducing the flow resistance of the branch pipe. S4: Iterative adjustment: After the adjustment is performed, the system runs stably and the air volume is remeasured. The new relative deviation of the air volume is calculated. If the target is not reached, the system returns to step S3 for fine-tuning. If the target is reached, the current guide vane angle is recorded. S5: Load Adaptability Adjustment: Establish a database of optimal guide vane angles under different boiler loads. When the load changes, the control system automatically calls up the corresponding preset value and adjusts the guide vane to the appropriate position.

7. The method for adjusting the flow field of a boiler hot secondary air duct according to claim 6, characterized in that: In step S3, the adjustment strategy also includes adjusting the adjustable multi-stage flow guide device (4) after the downstream bend of the branch pipe with insufficient air volume to optimize the internal flow field and reduce resistance loss.

8. The method for adjusting the flow field of a boiler hot secondary air duct according to claim 6, characterized in that: In steps S1 and S4, the formula for calculating the relative deviation of air volume Δ_i is: Δ_i = (Q_i - Q_avg) / Q_avg × 100%.

9. A method for adjusting the flow field of a boiler hot secondary air duct according to claim 6, characterized in that: In step S2, the air volume distribution target is to control the absolute value of the relative deviation Δ_i of the air volume of all branches within ±5%.

10. A method for adjusting the flow field of a boiler hot secondary air duct according to claim 6, characterized in that: In step S5, the different boiler loads include at least the rated load, 75% load, and 50% load.

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