Layered secondary air duct flow equalizing device of opposed firing boiler

Abstract

The flow equalizing device comprises a first flow equalizing element, a second flow equalizing element and a porous flow equalizing element, the second flow equalizing element is installed at the position, located at an air inlet, in a layer air box, the first flow equalizing element is installed at the position, close to the second flow equalizing element, in the layer air box, and the porous flow equalizing element is installed at the position, located at the air inlet, in the layer air box. The second flow equalizing element is perpendicular to the first flow equalizing element; the porous flow equalizing element is installed in the layer air box and located on the windward side of the secondary air volume measuring element, and the porous flow equalizing element is adjacent to the first flow equalizing element. According to the layer secondary air channel flow equalizing device, the second flow equalizing element, the first flow equalizing element and the porous flow equalizing element are sequentially arranged at the air inlet and the secondary air volume measuring element in the layer air box, so that secondary air reaching the secondary air volume measuring element flows uniformly, and the air speed distribution uniformity in a layer secondary channel is improved; the error of data measured by the secondary air volume measuring element is small, and actual air volume data are provided for operators.

Description

Technical Field

[0001] The utility model belongs to the technical field of boiler flow balancing, in particular to a secondary air duct flow balancing device for a counter-combustion boiler layer. Background Art

[0002] For opposed-fired boilers, the efficient and stable combustion process relies heavily on precisely controlling the amount of secondary air required by each burner layer. This secondary air not only provides the necessary oxygen for pulverized coal combustion but also promotes mixing within the furnace, helping to optimize combustion efficiency and reduce pollutant emissions.

[0003] In each layer of burner, the secondary air volume enters the layer air duct and layer air box from the distribution wind box. In this process, the connection section from the secondary air duct to the layer air box is relatively short, which makes it difficult for the air to fully diffuse and evenly distribute during the flow. In addition, the secondary air needs to pass through multiple elbows, reducers and other special-shaped parts on the path from the air preheater (air preheater) outlet to the layer air box inlet, which further aggravates the turbulence of the air flow and makes the secondary air appear uneven before entering the layer air duct. At the same time, when the secondary air enters the layer air duct from the distribution wind box, it often needs to be turned horizontally and vertically, which increases the resistance of the air flow. It also makes the secondary air distribution in the layered air duct more difficult to control. Inside the layered secondary air duct, since the straight section is very short, the airflow does not have enough space and time to recover stability, resulting in an extremely disordered flow field distribution. This disordered flow field state continues to the position of the secondary air volume measuring element, which brings great difficulties to online measurement, and thus makes the data measured by the measuring device have large deviations, resulting in the distortion of the secondary air volume in the burner layer and the burnt air layer in the hedge combustion boiler, and the inability to provide actual air volume data to the operating personnel, which worsens the local combustion of coal powder in the hedge combustion boiler and increases the NOx concentration. Utility Model Content

[0004] In order to solve the problem that the cross-sectional flow field distribution provided by the existing air duct structure for the online measurement device is disordered, resulting in large errors in the measurement results, the utility model provides a secondary air duct flow equalization device for the hedging combustion boiler layer.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] The utility model proposes a layer secondary air duct flow balancing device for a counter-combustion boiler, comprising a first flow balancing element, a second flow balancing element and a porous flow balancing element, wherein the second flow balancing element is installed in the layer wind box near the air inlet, the first flow balancing element is installed in the layer wind box near the second flow balancing element, and the second flow balancing element and the first flow balancing element are perpendicular to each other; the porous flow balancing element is installed in the layer wind box on the windward side of the secondary air volume measuring element, and the porous flow balancing element is adjacent to the first flow balancing element.

[0007] Preferably, the porous flow-balancing element includes a connecting plate, which is installed in the layer wind box. A plurality of ventilation holes are provided on the connecting plate. The plurality of ventilation holes are arranged in multiple rows with equal spacing, and the difference in the number of the ventilation holes in two adjacent rows is.

[0008] Preferably, the connecting plate is made of one or more of low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

[0009] Preferably, the first flow balancing element comprises a plurality of first air guide plates, and the plurality of first air guide plates are installed in the layer air box at equal intervals;

[0010] The second flow balancing element includes a plurality of second air guide plates, and the plurality of second air guide plates are installed in the layer air box at equal intervals.

[0011] Preferably, four first air guide plates are provided, and the four first air guide plates are installed in the layer air box at equal intervals, and the four first air guide plates are installed in an inclined manner in the layer air box;

[0012] There are three second air guide plates, which are installed in the layer air box at equal intervals and are installed obliquely in the layer air box;

[0013] Projection lines of the length of the first air guide plate and the length of the second air guide plate on the same plane are perpendicular to each other.

[0014] Preferably, the first air guide plate is made of one or more of low-alloy high-strength structural steel, low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

[0015] Preferably, the second air guide plate is made of one or more of low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

[0016] Preferably, it further comprises an arc-shaped wall element, which is installed at the right-angle connection between the layer air box and the distribution air box.

[0017] Preferably, the arc-shaped wall element is a prismatic plate, and the prismatic plate is provided with an arc-shaped surface at the air inlet of the layer air box and the distribution air box.

[0018] Preferably, the material of the prismatic plate is low-alloy high-strength structural steel.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] The utility model proposes a flow balancing device for the secondary air duct of a counter-combustion boiler. In this flow balancing device for the secondary air duct, a second flow balancing element, a first flow balancing element and a porous flow balancing element are sequentially arranged at the air inlet and the secondary air volume measuring element in the layer wind box, so that the secondary air entering the layer wind box from the air inlet is rectified in sequence. That is, the second flow balancing element is installed at the air inlet position of the layer wind box, which can preliminarily adjust the direction of the airflow entering the wind box, and effectively avoid the eddy current and turbulence caused by the direct impact of the airflow on the inner wall of the layer wind box. The first flow balancing element and the second flow balancing element are installed perpendicular to each other. This cross layout not only enhances the disturbance of the airflow It not only improves the quality of the airflow but also promotes the full mixing of the airflow in the laminar air box, thereby ensuring the uniformity and stability of the airflow. The porous flow-balancing element is installed on the windward side of the secondary air volume measuring element, which can further refine the airflow, reduce the impact of local high-speed airflow on the measuring element, and improve the accuracy and reliability of air volume measurement. It makes the flow of secondary air reaching the secondary air volume measuring element uniform, improves the uniformity of wind speed distribution in the laminar secondary duct, provides a good environment for accurate measurement of the laminar secondary air volume, and thus improves the accuracy of the laminar secondary air volume measurement, makes the data error measured by the secondary air volume measuring element small, and provides actual air volume data for the operating personnel.

[0021] Furthermore, the layout of the connecting plates in the secondary air duct flow balancing device on this layer, in which the ventilation holes are arranged at equal intervals and the difference in the number of ventilation holes in two adjacent rows is 1, greatly enhances the flow balancing effect. It not only enables the airflow to be more evenly distributed when passing through the porous flow balancing element, but also effectively regulates the flow rate and direction of the airflow, avoiding eddies and turbulence caused by local airflow being too fast or too slow.

[0022] Furthermore, in the secondary air duct flow balancing device of this layer, multiple first air guide plates are installed at equal intervals and at an angle in the layer wind box, forming a preliminary flow balancing and guiding effect on the airflow entering the wind box, increasing the contact area between the airflow and the air guide plates, and also through the guiding effect of the air guide plates, making the airflow more evenly distributed in the layer wind box, avoiding the phenomenon of local airflow being too thick or too thin. Multiple second air guide plates are also installed at equal intervals and at an angle. Through the coordinated effect with the first air guide plates, multi-dimensional flow balancing of the airflow in the layer wind box is achieved, and the stability and uniformity of the airflow are improved. The projection lines of the lengths of the first air guide plate and the second air guide plate on the same plane are perpendicular to each other, ensuring the independence and complementarity of the two in the flow balancing process, avoiding mutual interference, and thus improving the efficiency and reliability of the entire flow balancing device.

[0023] Furthermore, the curved wall elements in the secondary air duct flow equalization device of this layer make it difficult for the secondary air entering the layer air box from the distribution air box to generate eddies and turbulence at the right-angle connection between the layer air box and the distribution air box, thereby guiding the secondary air to transition smoothly, reducing the collision and impact of the air flow at the right-angle connection, thereby reducing energy loss and improving the stability and uniformity of the air flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the secondary air duct structure of the counter-combustion boiler layer;

[0025] Figure 2 This is a schematic diagram of an installation of a secondary air duct flow equalizing device for a counter-firing boiler in a layer wind box, as proposed by the present invention;

[0026] Figure 3 This is a schematic diagram of the installation structure of the first flow balancing element in the layer wind box of the layer secondary air duct flow balancing device of the counter-fired boiler proposed by the present invention;

[0027] Figure 4 This is a structural diagram of the first installation example of the second flow balancing element in the layer wind box of the layer secondary air duct flow balancing device of the counter-fired boiler proposed by the present invention;

[0028] Figure 5 This is a structural schematic diagram of a second example of installation of a second flow balancing element in a layer wind box in a layer secondary air duct flow balancing device for a counter-fired boiler proposed in the present invention;

[0029] Figure 6 This is a schematic diagram of the structure of a porous flow balancing element in a secondary air duct flow balancing device for a counter-fired boiler layer proposed by the present invention;

[0030] Figure 7 This is a schematic structural diagram of an embodiment of a secondary air duct flow equalizing device for a counter-firing boiler layer proposed by the present invention, which is installed in a counter-firing boiler layer;

[0031] In the accompanying drawings: 1. Laminar air box; 2. First flow balancing element; 3. Second flow balancing element; 4. Multi-porous flow balancing element; 5. Secondary air volume measurement element; 6. Arc wall element. DETAILED DESCRIPTION

[0032] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the present invention.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0035] In this utility model, unless otherwise expressly specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. For those skilled in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0036] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] The utility model proposes a secondary air duct flow equalization device for the counter-combustion boiler layer. The device is installed in the layer wind box 1 in the counter-combustion boiler layer to rectify the secondary air entering the layer wind box, so that the secondary air volume measuring element 5 installed in the layer wind box 1 can measure the secondary air volume with a small error, thereby providing actual air volume data for the operating personnel.

[0039] In this implementation, the secondary air duct structure of the hedging combustion boiler layer, such as Figure 1 As shown, it includes a distribution air box, which is connected to a layer air box 1. Secondary air enters the front and rear distribution air boxes from the main air duct, and then enters the layer air box 1, and is measured by the secondary air volume measuring element 5 installed in the layer air box 1.

[0040] See also Figures 2 to 6 , A counter-combustion boiler layer secondary air duct flow balancing device proposed in this embodiment includes a first flow balancing element 2, a second flow balancing element 3 and a porous flow balancing element 4. The second flow balancing element 3 is installed in the layer wind box 1 near the air inlet, the first flow balancing element 2 is installed in the layer wind box 1 near the second flow balancing element 3, and the second flow balancing element 3 and the first flow balancing element 2 are perpendicular to each other; the porous flow balancing element 4 is installed in the layer wind box 1 on the windward side of the secondary air volume measuring element 5, and the porous flow balancing element 4 is adjacent to the first flow balancing element 2.

[0041] See also Figure 2 and Figure 6The porous flow balancing element 4 includes a connecting plate, which is installed in the laminar air box 1, that is, downstream of the first flow balancing element 2 and the second flow balancing element 3. A plurality of ventilation holes are opened on the connecting plate, and the plurality of ventilation holes are arranged in multiple rows with equal intervals. The difference in the number of ventilation holes between two adjacent rows is 1, and the number of ventilation holes in the two interval rows is the same. The secondary air after being guided by the first flow balancing element 2 is rectified through the multiple ventilation holes, and the flow uniformity of the secondary air on the windward section of the secondary air volume measuring element 5 is improved, so as to realize the flow balancing effect of the secondary air duct in the inner layer of the laminar air box 1, wherein the material of the connecting plate is one or more of low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

[0042] See also Figures 2 to 5 , the first flow balancing element 2 includes a plurality of first air guide plates, and the plurality of first air guide plates are installed at equal intervals in the layer air box 1; there are four first air guide plates, which are installed at equal intervals in the layer air box 1 and arranged along the width direction of the layer air box 1, and the four first air guide plates are installed at an angle in the layer air box 1, with the inclination angle facing the inside of the corner, so as to guide the secondary air in the width direction after being laterally turned, thereby improving the flow uniformity of the secondary air in the width direction of the layer air duct in the layer air box 1;

[0043] The second flow equalizing element 3 includes a plurality of second air guide plates, and the plurality of second air guide plates are installed at equal intervals in the layer air box 1 and arranged along the height direction of the layer air box 1. There are three second air guide plates, and the three second air guide plates are installed at equal intervals in the layer air box 1, and the three second air guide plates are installed at an angle in the layer air box 1, with the angle of inclination facing the inside of the corner, which plays a role in guiding the secondary air in the height direction after the longitudinal turning, thereby improving the flow uniformity of the secondary air in the height direction of the layer air duct in the layer air box 1; the projection lines of the length of the first air guide plate and the length of the second air guide plate on the same plane are perpendicular to each other. Among them, the material of the first air guide plate and the material of the second air guide plate are one or more of low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

[0044] See also Figure 2 The secondary air duct flow equalization device also includes a curved wall element 6, which is installed at the right-angle connection between the layer air box 1 and the distribution air box. The curved wall element 6 is a prismatic plate. The prismatic plate is provided with a curved surface at the air inlet of the layer air box 1 and the distribution air box. This curved surface optimizes the right-angle connection between the layer air box and the distribution air box to an arc connection, reducing the vortex zone formed at the inner corner after the secondary air turns at a right angle at the connection. The prismatic plate is made of one or more of low-alloy high-strength structural steel, high-strength low-alloy steel, and stainless steel.

[0045] The following is a further explanation of the secondary air duct flow equalization device for a counter-fired boiler layer proposed by the present invention in conjunction with an embodiment;

[0046] A 660MW coal-fired unit, an opposed-firing boiler, was equipped with an air flow measurement element in its secondary air duct. Based on the design parameters, CFD numerical simulation was used to calculate the flow field of the secondary air system. The measured cross-sectional flow field distribution revealed that after the secondary air is deflected laterally and longitudinally by the distribution bellows, the distribution uniformity at the secondary air flow measurement section is very poor, with the air flow concentrated in a specific area. The relative standard deviation of the velocity distribution at the online air flow measurement section ranged from 41.3% to 124%, indicating extremely uneven distribution. Air flow calibration test results showed that the ratio of the measured air flow to the online air flow measurement value at each layer ranged from 0.622 to 2.878, and the deviation between different air flow coefficients reached 13.7%. When the dial flow rate increased from 72.9 t / h to 81.0 t / h, the actual air flow decreased from 117.4 t / h to 96.6 t / h, indicating a reversal in the dial flow rate. Currently, the dial air flow meter cannot accurately display the actual air flow through coefficient correction. The accuracy of the secondary air volume measurement values ​​in actual operation is very poor and cannot provide a reference for operating personnel.

[0047] In order to improve the uniformity of the flow field in the layered secondary air duct, a layered secondary air duct flow equalization device is set in the secondary air system, such as Figure 7 As shown in the figure, various installation methods of the flow equalizing device in the secondary air system are shown. After the flow equalizing device is installed, the flow field of the secondary air system is calculated using CFD numerical simulation. The calculation shows that after the secondary air passes through the arc wall element, the first flow equalizing element, the second flow equalizing element and the porous flow equalizing element, the secondary air is well filled in the layer air box, the flow field distribution uniformity is significantly improved, and the relative standard deviation of the velocity distribution at the air volume online measurement section is reduced to within 30%, which is a good effect. According to the results of the modified air volume calibration test, the maximum deviation of the burner layer air box flow coefficient is -4.90%; the maximum deviation of the burnout air layer air box flow coefficient is 4.98%, and the coefficient deviation is within 5%. Correcting the dial online air volume value according to the measured flow coefficient can ensure that the online measurement air volume deviation is within 5%, greatly improving the accuracy.

[0048] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and range of equivalents of the claims are included in the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0049] In addition, it should be understood that although this specification describes the embodiments, not every embodiment contains only one independent technical solution. This description is for clarity only. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for the purpose of illustrating the technical concept of the present utility model and cannot be used to limit the scope of protection of the present utility model. Any changes made based on the technical solution in accordance with the technical concept proposed by the present utility model shall fall within the scope of protection of the claims of the present utility model.

Claims

1. A secondary air duct flow equalization device for a counter-combustion boiler layer, characterized in that: The invention comprises a first flow balancing element (2), a second flow balancing element (3) and a porous flow balancing element (4), wherein the second flow balancing element (3) is installed in a laminar wind box (1) at a position close to the air inlet, and the first flow balancing element (2) is installed in the laminar wind box (1) at a position close to the second flow balancing element (3), and the second flow balancing element (3) and the first flow balancing element (2) are perpendicular to each other; the porous flow balancing element (4) is installed in the laminar wind box (1) on the windward side of the secondary air volume measuring element (5), and the porous flow balancing element (4) is adjacent to the first flow balancing element (2).

2. The secondary air duct flow equalization device for a counter-fired boiler layer according to claim 1 is characterized in that: The porous flow-balancing element (4) comprises a connecting plate, which is installed in the layer wind box (1). A plurality of ventilation holes are provided on the connecting plate. The plurality of ventilation holes are arranged in multiple rows at equal intervals, and the difference in the number of ventilation holes in two adjacent rows is 1.

3. The secondary air duct flow equalization device for a counter-fired boiler layer according to claim 2, characterized in that: The connecting plate is made of one or more of low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

4. The secondary air duct flow equalization device for a counter-fired boiler layer according to claim 1, characterized in that: The first flow balancing element (2) comprises a plurality of first air guide plates, and the plurality of first air guide plates are installed at equal intervals in the layer air box (1); The second flow balancing element (3) comprises a plurality of second air guide plates, and the plurality of second air guide plates are installed at equal intervals in the layer air box (1).

5. The secondary air duct flow equalizing device for a counter-fired boiler layer according to claim 4, characterized in that: Four first air guide plates are provided, the four first air guide plates are installed at equal intervals in the layer air box (1), and the four first air guide plates are installed obliquely in the layer air box (1); Three second air guide plates are provided, the three second air guide plates are installed at equal intervals in the layer air box (1), and the three second air guide plates are installed obliquely in the layer air box (1); Projection lines of the length of the first air guide plate and the length of the second air guide plate on the same plane are perpendicular to each other.

6. The secondary air duct flow equalization device for a counter-fired boiler layer according to claim 4, characterized in that: The first air guide plate is made of one or more of low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

7. The secondary air duct flow equalization device for a counter-fired boiler layer according to claim 4, characterized in that: The second air guide plate is made of one or more of low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

8. The secondary air duct flow equalization device for a counter-fired boiler layer according to claim 1, characterized in that: It also includes an arc-shaped wall element (6), which is installed at the right-angle connection between the layer wind box (1) and the distribution wind box.

9. The secondary air duct flow equalizing device for a counter-fired boiler layer according to claim 8, characterized in that: The arc-shaped wall element (6) is a prism-shaped plate, and the prism-shaped plate is provided with an arc-shaped surface at the air inlet of the layer wind box (1) and the distribution wind box.

10. The secondary air duct flow equalizing device for a counter-fired boiler layer according to claim 9, characterized in that: The material of the prismatic plate is one or more of low-alloy high-strength structural steel, high-strength low-alloy steel and stainless steel.

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