Device for improving in-furnace air distribution uniformity of tangential combustion boiler

Abstract

The invention provides a device for improving in-furnace air distribution uniformity of a tangential combustion boiler. The device comprises an inlet secondary air duct, a secondary air large air box, a secondary small air door, a first flow guide plate and a second flow guide plate. The middle of one side of the secondary air large air box is connected with the first end of the inlet secondary air duct, and the two ends of the other side of the secondary air large air box are connected with secondary small air doors correspondingly. The first flow guide plate is arranged in the inlet secondary air duct and located at the bent position in the inlet secondary air duct, and the first flow guide plate is distributed in the vertical direction; the second flow guide plate is arranged at the joint of the inlet secondary air duct and the secondary air large air box, and the first flow guide plate is distributed in the horizontal direction. The device has the technical effects that the design is reasonable, the uniformity of air distribution in the secondary air large air box can be effectively improved, the combustion state in the furnace is relieved, and then the safety and reliability of operation of a thermal power generating unit are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of boiler combustion, and particularly relates to a device for improving the uniformity of air distribution in a tangentially fired boiler furnace. Background Art

[0002] At present, the structural design of the secondary air boxes of boilers in major domestic power plants is poor. There are generally uneven flow fields inside the air boxes, and it is difficult to accurately distribute the secondary air, resulting in problems such as local coking of the boiler, overheating of the boiler tube walls, and corrosion of the water walls. Moreover, the fluid development section from the inlet of the large secondary air box to the small secondary air damper is short, the filling degree of the secondary air inside the air box is poor, the corresponding relationship between the opening degree of the small secondary air dampers of the burners in the height direction of the large air box and the secondary air intake volume is poor, and there is a deviation in the secondary air volume in the height direction, further deteriorating the combustion conditions of the boiler and having an adverse impact on boiler coking, overheating of the water wall, etc. In addition, the pressure field uniformity inside the large air box is poor, and there are negative pressure recirculation areas in some areas. In severe cases, it may cause the pulverized coal at the primary air nozzles to be sucked back into the large air box, posing a safety hazard.

[0003] In view of this, the present invention proposes a device for improving the uniformity of air distribution in a tangentially fired boiler furnace to effectively improve the uniformity of air volume distribution in the secondary air box, relieve the combustion state in the furnace, and further improve the safety and reliability of the operation of thermal power units. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art and provides a new technical solution for a device for improving the uniformity of air distribution in a tangentially fired boiler furnace.

[0005] According to a first aspect of the present invention, there is provided a device for improving the uniformity of air distribution in a tangentially fired boiler furnace, including:

[0006] An inlet secondary air duct, a large secondary air box, and small secondary air dampers. The middle of one side of the large secondary air box is connected to the first end of the inlet secondary air duct, and both ends of the other side of the large secondary air box are respectively connected to small secondary air dampers.

[0007] A first guide vane and a second guide vane. The first guide vane is arranged inside the inlet secondary air duct and at the bent part inside the inlet secondary air duct, and the first guide vane is distributed in the vertical direction; the second guide vane is arranged at the connection between the inlet secondary air duct and the large secondary air box, and the first guide vane is distributed in the horizontal direction.

[0008] Optionally, the device for improving the uniformity of air distribution in a tangentially fired boiler furnace further includes a first air flow deflector;

[0009] A plurality of first air flow deflectors distributed in the vertical direction are arranged inside the large secondary air box;

[0010] A plurality of first air flow baffle plates are respectively located on opposite sides of the first end of the inlet secondary air duct.

[0011] Optionally, the device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler further includes a second air flow baffle plate;

[0012] A plurality of second air flow baffle plates distributed in the horizontal direction are arranged in the secondary air plenum.

[0013] The plurality of second air flow baffle plates are arranged at intervals between the first air flow baffle plate and the secondary air damper.

[0014] Optionally, the device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler further includes an air flow equalizing plate;

[0015] A plurality of air flow equalizing plates distributed in the horizontal direction are arranged on the side of the secondary air damper close to the air plenum, and the plurality of air flow equalizing plates are distributed at intervals in the height direction of the secondary air damper.

[0016] Optionally, the device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler further includes an inlet guide plate;

[0017] An inlet guide plate distributed in the vertical direction is arranged on the side of the secondary air damper far from the secondary air plenum.

[0018] Optionally, the first guide plate is arc-shaped, and the bending direction of the first guide plate is the same as the bending direction of the inlet secondary air duct;

[0019] The two first guide plates are parallel and arranged at intervals.

[0020] Optionally, one of the second guide plates is located above the first end of the inlet secondary air duct and bends upward, and the other second guide plate is located below the first end of the inlet secondary air duct and bends downward.

[0021] Optionally, the first air flow baffle plate is inclined, and the first air flow baffle plates on the same side of the first end of the inlet secondary air duct are parallel to each other.

[0022] Optionally, the second air flow baffle plate is inclined, some of the second air flow baffle plates are close to the first air flow baffle plate, and some of the second air flow baffle plates are close to the secondary air damper.

[0023] Optionally, the air flow equalizing plate is inclined, and the plurality of air flow equalizing plates are parallel to each other.

[0024] One technical effect of the present invention is that:

[0025] In the embodiments of the present application, the device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler can effectively improve the uniformity of air volume distribution in the secondary air plenum, alleviate the combustion state in the furnace, and thus improve the safety and reliability of the operation of thermal power units. It has very important engineering application value, broad market application prospects, and remarkable social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. is a schematic structural diagram of a device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to an embodiment of the present invention;

[0027] Figure 2 FIG. is a perspective view of a device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to an embodiment of the present invention;

[0028] Figure 3 FIG. is a contour map of the internal air flow velocity distribution of the secondary air plenum in the prior art;

[0029] Figure 4 FIG. is a contour map of the wind speed distribution in the height direction of the first cross-section of the secondary air plenum in the prior art;

[0030] Figure 5 FIG. is a contour map of the wind speed distribution in the height direction of the second cross-section of the secondary air plenum in the prior art;

[0031] Figure 6 FIG. is a contour map of the inlet wind speed distribution of the secondary air dampers;

[0032] Figure 7 FIG. is a schematic diagram of the statistical results of the numerical simulation calculation of the internal height direction velocity distribution of the secondary air plenum in the prior art;

[0033] Figure 8 FIG. is a schematic diagram of the statistical results of the numerical simulation calculation of the internal height direction velocity distribution of the secondary air plenum in an embodiment of the present invention.

[0034] In the figure: 1, inlet secondary air duct; 2, secondary air plenum; 3, secondary air dampers; 41, first deflector; 42, second deflector; 51, first air flow baffle; 52, second air flow baffle; 6, air flow equalizing plate; 7, inlet deflector. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Now, various exemplary embodiments of the present application will be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps described in these embodiments do not limit the scope of the present application.

[0036] Embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary only for explaining the present application and should not be construed as limiting the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0037] The terms "first" and "second" in the description and claims of the present application may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more. In addition, "and / or" in the description and claims indicates at least one of the connected objects. The character " / " generally indicates an "or" relationship between the associated objects before and after.

[0038] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying 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 construed as limiting the present application.

[0039] In the description of the present application, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0040] According to a first aspect of the present invention, referring to Figure 1 and Figure 2 , a device for improving the air distribution uniformity in the furnace of a tangentially fired boiler is provided, which can preferably improve the air distribution uniformity in the secondary air plenum 2 and alleviate problems such as furnace coking and overheating of the water wall.

[0041] Specifically, the device for improving the air distribution uniformity in the furnace of a tangentially fired boiler includes:

[0042] The inlet secondary air duct 1, the secondary air large wind box 2 and the secondary air small damper 3, the middle part of one side of the secondary air large wind box 2 is connected to the first end of the inlet secondary air duct 1, and both ends of the other side of the secondary air large wind box 2 are respectively connected with the secondary air small damper 3;

[0043] The first deflector 41 and the second deflector 42, the first deflector 41 is arranged in the inlet secondary air duct 1 and located at the bending part in the inlet secondary air duct 1, and the first deflector 41 is distributed along the vertical direction; the second deflector 42 is arranged at the connection part between the inlet secondary air duct 1 and the secondary air large wind box 2, and the first deflector 41 is distributed along the horizontal direction.

[0044] In the embodiment of the present application, the device for improving the uniformity of the air distribution in the furnace of the tangentially fired boiler can effectively improve the uniformity of the air volume distribution in the secondary air large wind box 2, relieve the combustion state in the furnace, and further improve the safety and reliability of the operation of the thermal power unit, which has very important engineering application value, broad market application prospects and remarkable social benefits.

[0045] Specifically, the first deflector 41 can effectively reduce the air flow centrifugal effect of the air duct elbow at the inlet of the secondary air large wind box 2 and significantly improve the uniformity of the flow field at the inlet air duct; the second deflector 42 can improve the air flow fullness inside the secondary air large wind box 2 as much as possible in the limited air flow development section, reduce the air flow backflow effect of the right-angle elbow, and improve the air flow fullness in the height direction. Therefore, the device for improving the uniformity of the air distribution in the furnace of the tangentially fired boiler can optimize the internal flow field of the secondary air large wind box 2 and improve the air flow fullness.

[0046] Optionally, the device for improving the uniformity of the air distribution in the furnace of the tangentially fired boiler further includes a first air flow baffle 51;

[0047] A plurality of first air flow baffles 51 distributed along the vertical direction are arranged in the secondary air large wind box 2;

[0048] The plurality of first air flow baffles 51 are respectively located on the opposite sides of the first end of the inlet secondary air duct 1.

[0049] In the above embodiment, the first air flow baffle 51 can preferably eliminate the horizontal air flow separation in the secondary air large wind box 2 and improve the horizontal air flow uniformity.

[0050] Optionally, the device for improving the uniformity of the air distribution in the furnace of the tangentially fired boiler further includes a second air flow baffle 52;

[0051] A plurality of second air flow baffles 52 distributed along the horizontal direction are arranged in the secondary air large wind box 2;

[0052] A plurality of second air flow baffle plates 52 are arranged at intervals between the first air flow baffle plate 51 and the secondary air damper 3.

[0053] In the above embodiment, the second air flow baffle plate 52 can preferably improve the air flow fullness in the vertical direction in the secondary air plenum 2.

[0054] Optionally, the device for improving the air distribution uniformity in the tangentially-fired boiler furnace further includes an air flow equalizing plate 6;

[0055] A plurality of air flow equalizing plates 6 distributed in the horizontal direction are arranged on the side of the secondary air damper 3 close to the plenum, and the plurality of air flow equalizing plates 6 are distributed at intervals in the height direction of the secondary air damper 3.

[0056] In the above embodiment, the air flow equalizing plate 6 rectifies the secondary air entering the secondary air damper 3 from the secondary air plenum 2, smooths the air flow inside the secondary air plenum 2, and improves the correspondence of the adjustment of the secondary air damper.

[0057] Optionally, the device for improving the air distribution uniformity in the tangentially-fired boiler furnace further includes an inlet guide vane 7;

[0058] An inlet guide vane 7 distributed in the vertical direction is arranged on the side of the secondary air damper 3 away from the secondary air plenum 2.

[0059] In the above embodiment, the inlet guide vane 7 can eliminate the centrifugal effect of the elbow at the inlet of the secondary air damper 3 and improve the uniformity of the air flow velocity field at the inlet section of the secondary air damper 3.

[0060] Optionally, the first guide vane 41 is arc-shaped, and the bending direction of the first guide vane 41 is the same as the bending direction of the inlet secondary air duct 1;

[0061] The two first guide vanes 41 are arranged in parallel and at intervals.

[0062] In the above embodiment, it helps to significantly reduce the air flow centrifugal effect of the duct elbow at the inlet of the secondary air plenum 2, and further improve the uniformity of the flow field at the inlet duct.

[0063] Optionally, one second guide vane 42 is located above the first end of the inlet secondary air duct 1 and bends upward, and the other second guide vane 42 is located below the first end of the inlet secondary air duct 1 and bends downward.

[0064] In the above embodiment, it can preferably improve the air flow fullness inside the secondary air plenum 2 and significantly reduce the air flow backflow effect of the right-angle elbow.

[0065] Optionally, the first air flow baffle 51 is inclined, and the first air flow baffles 51 on the same side of the first end of the inlet secondary air duct 1 are parallel to each other.

[0066] In the above embodiment, it helps to further eliminate the horizontal air flow separation in the secondary air plenum 2, thereby improving the horizontal air flow uniformity.

[0067] Optionally, the second air flow baffle 52 is inclined, and some of the second air flow baffles 52 are close to the first air flow baffle 51, and some of the second air flow baffles 52 are close to the secondary air damper 3.

[0068] In the above embodiment, it can effectively improve the air flow fullness in the vertical direction in the secondary air plenum 2.

[0069] Optionally, the air flow equalizing plate 6 is inclined, and a plurality of the air flow equalizing plates 6 are parallel to each other. This can better rectify the secondary air entering the secondary air damper 3, thereby effectively improving the correspondence of the adjustment of the secondary air damper.

[0070] In a specific embodiment, first, three-dimensional modeling can be carried out according to the layout diagram of the secondary air plenum 2, and through three-dimensional diagnostic analysis, the key reasons for the existing vertical air volume deviation problem inside the current secondary air plenum 2 are diagnosed; then, targeted measures are taken for the problems existing in the internal flow field of the secondary air plenum 2, so as to optimize the internal flow field of the secondary air plenum 2, and further improve the air flow fullness. The positions, lengths, angles, arcs, etc. of the first guide plate 41, the second guide plate 42, the first air flow baffle 51, the second air flow baffle 52, the air flow equalizing plate 6, the inlet guide plate 7, etc. are all determined according to the results of numerical simulation.

[0071] Exemplarily, taking the secondary air plenum flow field of a certain power plant as an example, the existing problems in the current secondary air plenum flow field are quantitatively analyzed, and a CFD numerical simulation study is carried out on the inlet air duct of the secondary air plenum to the secondary air plenum flow field. The boundary conditions of the simulation calculation are shown in Table 1.

[0072] Table 1 Boundary Conditions of Secondary Air Duct (BMCR Condition)

[0073] Hot secondary air flow rate, t / h Hot secondary air temperature, °C Secondary air pressure at the outlet of air preheater, Pa 1795 343 1500

[0074] From Figure 3It can be clearly seen that in the prior art, due to the very short development section at the connection of the inlet secondary air duct and the secondary air plenum, the air filling degree inside the secondary air plenum is poor, the secondary air volume is overly concentrated in the middle area of the cross-section, and the air diffusion effect is poor, which is not conducive to the uniform distribution of the air volume inside the plenum. Moreover, there are obvious high- and low-flow velocity regions inside the secondary air plenum, which will inevitably cause low pressure in some areas, forming an air flow recirculation zone, deteriorating the air distribution organization inside the plenum, and making the air distribution uniformity of the burner extremely poor.

[0075] Furthermore, from Figure 4 and Figure 5 it can be seen that in the prior art, the air volume inside the secondary air plenum is overly concentrated in the middle area, with relatively small air volumes in the upper and lower parts. At the same time, there are also obvious air volume deviations in the horizontal direction of the cross-section, further indicating that the air flow field distribution filling degree inside the secondary air plenum is low, which is not conducive to accurate air distribution in the vertical direction.

[0076] Even further, from Figure 6 it can be seen that in the prior art, the velocity field uniformity at the inlet of the secondary air damper is very poor. The non-uniform velocity field will inevitably lead to obvious deviations in the air intake of each layer of the secondary air damper, bringing great difficulties to the uniform air distribution of the boiler.

[0077] From Figure 7 the statistical results show that the velocities at the upper and lower parts of the secondary air plenum are low, the air velocity in the middle area inside the secondary air plenum is about 2 - 3 times that of the upper and lower areas, and the air filling degree of the secondary air inside the secondary air plenum is very poor, which will lead to a poor correspondence between the opening of the secondary air damper of the burner in the height direction of the secondary air plenum and the secondary air intake volume, and there are deviations in the secondary air volume in the height direction, further deteriorating the combustion condition of the boiler and bringing adverse effects to boiler slagging, overheating of the water wall, etc.

[0078] Figure 8 FIG. is a schematic diagram of the statistical results of the numerical simulation calculation of the velocity distribution in the height direction inside the secondary air plenum in an embodiment of the present invention. From Figure 8 it can be known that in the embodiment of the present application, the velocity deviation in the height direction of the burner inside the secondary air plenum is significantly reduced. The range of change in the air flow velocity in the height direction of the secondary air plenum is significantly reduced, the velocity deviation in the height direction of the secondary air plenum is significantly reduced, the air filling degree of the secondary air inside the secondary air plenum is significantly improved, the correspondence between the opening of the secondary air damper of the burner in the height direction of the secondary air plenum and the secondary air intake volume is improved, and the secondary air distribution uniformity in the height direction is significantly improved, creating conditions for the good organization of the boiler combustion condition. At the same time, the resistance of the secondary air plenum increases by about 16 Pa, and the resistance increase rate is about 4%. The increase in resistance is limited and will not affect the system.

[0079] It is understandable that the above embodiments are merely exemplary embodiments adopted to illustrate the principles of the present invention. However, the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims

1. An apparatus for improving the uniformity of air distribution in the furnace of a tangentially fired boiler, characterized in that, Including: An inlet secondary air duct, a secondary air large wind box and secondary air small dampers. The middle part of one side of the secondary air large wind box is connected to the first end of the inlet secondary air duct, and both ends of the other side of the secondary air large wind box are respectively connected with secondary air small dampers; A first deflector plate and a second deflector plate. The first deflector plate is arranged in the inlet secondary air duct and located at the bending part in the inlet secondary air duct, and the first deflector plate is distributed along the vertical direction; the second deflector plate is arranged at the connection part between the inlet secondary air duct and the secondary air large wind box, and the first deflector plate is distributed along the horizontal direction.

2. The device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to claim 1, characterized in that, It further includes a first air flow baffle plate; A plurality of first air flow baffle plates distributed along the vertical direction are arranged in the secondary air large wind box; The plurality of first air flow baffle plates are respectively located on the relative two sides of the first end of the inlet secondary air duct.

3. The device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to claim 2, wherein It further includes a second air flow baffle plate; A plurality of second air flow baffle plates distributed along the horizontal direction are arranged in the secondary air large wind box; The plurality of second air flow baffle plates are arranged at intervals between the first air flow baffle plates and the secondary air small dampers.

4. The device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to claim 3, characterized in that, It further includes an air flow equalizing plate; A plurality of air flow equalizing plates distributed along the horizontal direction are arranged on the side of the secondary air small damper close to the large wind box, and the plurality of air flow equalizing plates are distributed at intervals along the height direction of the secondary air small damper.

5. The device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to claim 4, wherein It further includes an inlet deflector plate; An inlet deflector plate distributed along the vertical direction is arranged on the side of the secondary air small damper far from the secondary air large wind box.

6. The device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to claim 5, characterized in that, The first deflector plate is arc-shaped, and the bending direction of the first deflector plate is the same as the bending direction of the inlet secondary air duct; The two first deflector plates are parallel and arranged at intervals.

7. The device for improving the air distribution uniformity in the furnace of a tangentially fired boiler according to claim 6, characterized in that, One second deflector plate is located at the upper part of the first end of the inlet secondary air duct and bends upward, and the other second deflector plate is located at the lower part of the first end of the inlet secondary air duct and bends downward.

8. The device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to claim 7, characterized in that, The first air flow baffle plate is inclined, and the first air flow baffle plates on the same side of the first end of the inlet secondary air duct are parallel to each other.

9. The device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to claim 8, characterized in that, The second air flow baffle plate is inclined, some of the second air flow baffle plates are close to the first air flow baffle plate, and some of the second air flow baffle plates are close to the secondary air small damper.

10. The device for improving the uniformity of air distribution in the furnace of a tangentially fired boiler according to claim 9, wherein The air flow equalizing plate is inclined, and the plurality of air flow equalizing plates are parallel to each other.

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