An ammonia injection device for denitrification of large gas waste heat boilers

Abstract

The invention discloses an ammonia injection device for denitration of a large gas-fired waste heat boiler, comprising a reactor, a top primary mother pipe, a bottom primary mother pipe, a secondary mother pipe and a branch pipe, wherein the secondary mother pipe comprises an upper secondary mother pipe and a lower secondary mother pipe, wherein the top primary mother pipe is fixedly connected to a plurality of upper secondary mother pipes through a tee, and the bottom primary mother pipe is also fixedly connected to a plurality of lower secondary mother pipes through a tee, and the plurality of upper secondary mother pipes and the lower secondary mother pipes penetrate the interior of the reactor. The invention has a scientific and reasonable structure, is safe and convenient to use, and is suitable for a large horizontal gas-fired waste heat boiler denitration device. Under the conditions of an ultra-short distance and an ultra-large cross-section between the heating surface modules of the horizontal waste heat boiler, the arrangement of the ammonia injection device satisfies the requirement that the NOx emission of flue gas from the gas unit is less than 20 mg / Nm 3 It meets the ultra-low emission requirements of flue gas, the control requirements of ammonia escape concentration below 3ppm, and the 5% concentration deviation requirement of the denitrification standard.

Description

Technical Field

[0001] The invention relates to the technical field of denitration of large-scale horizontal waste heat boilers, and in particular to an ammonia injection device for denitration of large-scale gas-fired waste heat boilers. Background Art

[0002] Ammonia injection device is one of the important components of the denitration system of power plants. The mixing uniformity of ammonia flue gas is directly related to the efficiency of denitration and the control of ammonia escape. Ammonia injection device is usually composed of ammonia injection main pipe, branch pipe, nozzle and load-bearing support part of ammonia injection device. With the continuous improvement of national environmental protection requirements, most domestic gas-steam combined cycle units have put forward new NOx emission requirements. When the original combustion engine NOx emission is less than 50mg / Nm 3 On the basis of the above, the NOx emission is further improved to less than 10-20mg / Nm 3 Ultra-low emission standards, however, the existing denitrification device of this type of gas waste heat boiler is arranged between the heating surface modules of the waste heat boiler, and there is no independent reactor. The space of the denitrification device is small, which makes the flow cross-section of the flue gas extremely large, usually above the area formed by 10m wide and 15m high. At the same time, the mixing distance of ammonia flue gas is very short, usually less than 5m, and it is impossible to install a guide plate. Under this condition, it is difficult to meet the uniformity requirements of ammonia injection, that is, at 0.3m from the catalyst surface, the maximum relative standard deviation of the ammonia nitrogen molar ratio is between ±5%, so as to ensure that the NOx emission and ammonia escape meet the standards in both directions. Therefore, it is extremely important to solve the problem of uniformity of ammonia injection under ultra-short mixing distance in large waste heat boilers. Therefore, people are in urgent need of an ammonia injection device for denitrification of large gas waste heat boilers to solve the above problems. Summary of the invention

[0003] The object of the present invention is to provide an ammonia injection device for denitrification of a large gas waste heat boiler to solve the problems raised in the above background technology.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: an ammonia injection device for denitrification of a large gas waste heat boiler, comprising a reactor, a top primary mother pipe, a bottom primary mother pipe, a secondary mother pipe and a branch pipe, the secondary mother pipe comprising an upper secondary mother pipe and a lower secondary mother pipe, the top primary mother pipe is fixedly connected to a plurality of upper secondary mother pipes through a tee, the bottom primary mother pipe is also fixedly connected to a plurality of lower secondary mother pipes through a tee, a plurality of upper secondary mother pipes and lower secondary mother pipes pass through the reactor, the secondary mother pipe is fixedly connected to the branch pipe through a tee, the top primary mother pipe, the plurality of upper secondary mother pipes and the arrangement mode of the bottom primary mother pipe and the plurality of lower secondary mother pipes are symmetrically arranged up and down, the plurality of secondary mother pipes are symmetrically arranged left and right, a plurality of branch pipes are provided, and a plurality of ammonia injection groups are provided on the branch pipe;

[0005] Furthermore, the top primary mother pipe and the bottom primary mother pipe are both provided with regulating main valves, a plurality of the secondary mother pipes are each provided with a regulating valve, a top plate is provided on the top of the reactor, and a bottom plate is provided on the bottom of the reactor;

[0006] Furthermore, a plurality of ammonia injection groups on the branch pipes in the top row are plugged, and a plurality of ammonia injection groups on the branch pipes in the bottom row are plugged;

[0007] Furthermore, a plurality of the branch pipes are evenly arranged at equal intervals, a plurality of the ammonia spraying groups are evenly arranged at equal intervals, the ammonia spraying group comprises two nozzles, one end of the two nozzles are connected to the same cross-sectional position of the branch pipe, and a smoke sealing plate is provided between the top plate and the bottom plate and the nozzle arrangement area;

[0008] Furthermore, the spacing between the plurality of branch pipes is set to 625 mm, the spacing between the ammonia spraying groups 6 on the branch pipes is set to 253 mm, the angle between the two nozzles is set to 120°, and the angle between the directions of the two nozzles and the direction of the flue gas flow is set to 60°;

[0009] Furthermore, a hanger is provided inside the reactor, one end of the hanger is fixedly connected to the furnace top hanging beam, the other end of the hanger is fixedly connected to the upper secondary mother pipe, the lower secondary mother pipe is fixedly connected to the limit support plate, and one side of the limit support plate is fixedly connected to the bottom plate;

[0010] Furthermore, a plurality of boiler heating surface tubes are provided on one side of the secondary mother tube, and a heating surface tube sheet is provided on the plurality of boiler heating surface tubes. The secondary mother tube is fixedly connected to the boiler heating surface tube through a first clamping plate and a second clamping plate, and the second clamping plate is arranged in a U shape;

[0011] Furthermore, the secondary main pipe is fixedly connected to the branch pipe via a load-bearing plate;

[0012] Furthermore, the connection between the upper secondary mother pipe and the lower secondary mother pipe is fixedly connected by sleeve 1, the branch pipe includes a plurality of branch pipes, and the ends of the plurality of branch pipes are fixedly connected by sleeve 2;

[0013] Furthermore, a gap is provided between the connection ends of the upper secondary mother pipe and the lower secondary mother pipe, and a gap is provided between the connection ends of the plurality of branch pipes;

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0015] 1. It is suitable for large-scale horizontal gas waste heat boiler denitrification device. Under the condition of ultra-short distance and ultra-large cross-section between the heating surface modules of the horizontal waste heat boiler, the layout of the ammonia injection device can meet the requirement of gas unit flue gas NOx emission less than 20mg / Nm 3 It meets the ultra-low emission requirements of flue gas, the control requirements of ammonia escape concentration below 3ppm, the relative standard deviation of ammonia concentration of the unit under different operating load conditions is less than 3%, and the 5% concentration deviation requirement of the denitrification standard is met with a large margin.

[0016] 2. By arranging ammonia spraying groups with uniform spacing on each branch pipe, the ammonia nozzles in the ammonia spraying section are generally uniform and meet the flue gas uniform distribution characteristics on the ammonia spraying section of the gas-fired waste heat boiler. At the same time, in the local flue gas non-uniform flow areas at the top and bottom of the ammonia spraying section, some nozzles are sealed to block them, or the ammonia spraying nozzles are arranged in a local non-uniform manner, so that the final ammonia spraying amount is adapted to the flue gas flow rate, thereby achieving ammonia spraying within the overall ammonia spraying section, so that the concentration deviation meets the ammonia spraying uniformity requirements.

[0017] 3. The secondary main pipe is used as the ammonia delivery pipeline and also as the support system of the branch pipes to support several branch pipes, which effectively solves the problem that the ammonia injection pipe system in the ultra-large ammonia injection section inside the waste heat boiler cannot bear the load, meets the problem of uniform ammonia injection mixing in an ultra-short distance space, and solves the problem of supporting and limiting the ammonia injection device in the ultra-large reactor section.

[0018] 4. Considering the free expansion performance of the pipe system in a high temperature environment, the heating surface tube sheet is used to limit the secondary mother pipe and branch pipe, which effectively prevents the secondary mother pipe and branch pipe from shaking or tipping over under the action of flue gas flow. At the same time, it can also avoid the thermal stress of the pipe caused by the thermal expansion of several secondary mother pipes and branch pipes.

[0019] 5. The uniform spacing between the ammonia spray groups and the angle design between the nozzles strengthen the convection mixing of ammonia flue gas at the ammonia spray nozzle, ensuring that the maximum relative standard deviation of the ammonia nitrogen molar ratio is less than ±5% at 0.3m from the catalyst surface, thereby improving the uniformity of ammonia at the ammonia spray nozzle.

[0020] 6. According to the structural conditions of the boiler heating surface, in the non-uniform flue gas flow area at the top and bottom of the reactor, some nozzles are blocked or not arranged to perform flue gas adaptive adjustment, which meets the deviation of the ammonia injection concentration field within the ultra-large cross-section.

[0021] 7. Through the arrangement and setting of several regulating valves, secondary main pipes and branch pipes, the regulating valve is used to adjust the ammonia injection flow rate, so as to realize the adjustment and control of regional ammonia injection in a super-large cross-section, increase the adjustability of the ammonia injection device, and adopt a new nozzle to make the ammonia injection speed faster and more stable, enhance the turbulence, and enhance the mixing effect of ammonia flue gas, so as to realize the uniform mixing effect of NOx / NH3 concentration distribution relative standard deviation ≤3% at 0.3m from the catalyst surface (the relative standard deviation of ammonia concentration distribution of conventional coal-fired units for denitrification is ≤5%).

[0022] 8. The ammonia injection device has a simple structure and small equipment investment. It does not require an independent reactor and mixing flue, has a low investment cost, and does not require subsequent equipment maintenance. The ammonia injection device occupies a small space, and the total distance between the upstream heating surface pipe is less than 500m. It also reserves the necessary flue gas measurement point installation space between the ammonia injection section and the heating surface, which effectively improves the mixing time and distance of ammonia flue gas and greatly improves the utilization efficiency of the waste heat boiler denitrification space. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 is a front view of the present invention;

[0025] Figure 2 is a side view of the present invention;

[0026] Figure 3 It is a schematic diagram of the installation structure of the secondary mother pipe of the present invention;

[0027] Figure 4 It is a schematic diagram of the structure of the ammonia spraying adjustment partition of the present invention;

[0028] Figure 5 It is a schematic diagram of the nozzle structure of the present invention;

[0029] Figure 6 is a front view of the hanger of the present invention;

[0030] Figure 7 It is a schematic diagram of the installation structure of the hanger of the present invention;

[0031] Figure 8 It is a structural schematic diagram of a position-limiting support plate of the present invention;

[0032] Fig. 9 It is a structural schematic diagram of the heating surface tube plate of the present invention;

[0033] Fig.10 It is a structural schematic diagram of the heating surface tube of the present invention;

[0034] Fig.11 It is a structural schematic diagram of the first and second cardboards of the present invention;

[0035] Fig.12 It is a structural schematic diagram of the invented load-bearing plate;

[0036] Fig.13 It is a schematic structural diagram of the nozzle of the present invention;

[0037] Fig.14 It is a structural schematic diagram of a sleeve 1 of the present invention;

[0038] Fig.15 It is a structural schematic diagram of the sleeve 2 of the present invention;

[0039] In the figure: 1, reactor; 2, top primary main pipe; 3, bottom primary main pipe; 4, secondary main pipe; 5, branch pipe; 6, ammonia injection group; 7, regulating main valve; 8, regulating valve; 9, boiler heating surface pipe;

[0040] 11. Top plate; 12. Bottom plate; 13. Smoke sealing plate; 14. Hanger; 15. Hanging beam; 40. Upper secondary mother pipe; 41. Lower secondary mother pipe; 42. Sleeve one; 43. Limit support plate; 44. Clamp one; 45. Clamp two; 51. Branch pipe; 52. Sleeve two; 53. Load-bearing plate; 61. Nozzle; 91. Heating surface tube plate. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example: See Figure 1-15 The present invention provides a technical solution: an ammonia injection device for denitrification of a large gas waste heat boiler, comprising a reactor 1, a top primary mother pipe 2, a bottom primary mother pipe 3, a secondary mother pipe 4 and a branch pipe 5, the secondary mother pipe 4 comprising an upper secondary mother pipe 40 and a lower secondary mother pipe 41, the top primary mother pipe 2 is fixedly connected to a plurality of upper secondary mother pipes 40 through a tee, the bottom primary mother pipe 3 is also fixedly connected to a plurality of lower secondary mother pipes 41 through a tee, a plurality of upper secondary mother pipes 40 and a plurality of lower secondary mother pipes 41 run through the reactor 1, the secondary mother pipe 4 is fixedly connected to the branch pipe 5 through a tee, the top primary mother pipe 2, the plurality of upper secondary mother pipes 40, and the arrangement mode of the bottom primary mother pipe 3 and the plurality of lower secondary mother pipes 41 are symmetrically arranged up and down, the plurality of secondary mother pipes 4 are symmetrically arranged left and right, a plurality of branch pipes 5 are provided, and a plurality of ammonia injection groups 6 are provided on the branch pipe 5;

[0043] The top primary mother pipe 2 and the bottom primary mother pipe 3 are used to transport ammonia, the secondary mother pipe 4 is used as a pipeline for transporting ammonia, the upper secondary mother pipe 40 and the lower secondary mother pipe 41 are separate and independent pipelines, and the secondary mother pipe 4 is used to transport ammonia in different areas, and it is also convenient for the subsequent control of the regulating valve 8. Figure 3 , reference numeral 10 in the figure is a three-way valve, and the control valve 8 on the far right controls the three branch pipes 5 in the box, thereby realizing the zoning control of the regulating valve 8 in turn.

[0044] A regulating main valve 7 is provided on the top primary main pipe 2 and the bottom primary main pipe 3, and a regulating valve 8 is provided on a plurality of secondary main pipes 4. A top plate 11 is provided on the top of the reactor 1, and a bottom plate 12 is provided on the bottom of the reactor 1.

[0045] Each regulating valve 8 corresponds only to the three branch pipes connected to the secondary main pipe 4, and there are about 60 nozzles 61 with a total ammonia injection amount. The ammonia injection device is provided with 48 ammonia injection control partitions, such as Figure 4 , the entire ammonia injection section is divided into 48 adjustment zones for control. Figure 4 In the rectangular frame of the middle number 16, there is a secondary mother pipe 4 connected to the branch pipe 5. The number 17 in the figure is the interface between the secondary mother pipe 4 and the branch pipe 5 through the tee. The top primary mother pipe 2 is connected to the secondary mother pipe 4, and only a small section of the secondary mother pipe 4 is connected to the branch pipe 51. The part not connected to the branch pipe 51 plays the role of transmitting ammonia. The reactor 1 is combined according to a certain rule and can be divided into 4 horizontal grouping areas and upper and lower grouping areas. The 4 horizontal grouping areas are symmetrically distributed about the center line of the cross section, and the upper and lower grouping areas are symmetrically distributed about the center line of the interface. From the two sides of the reactor 1 to the middle position of the reactor 1, the length of the secondary mother pipe 4 is getting shorter and shorter. Each horizontal row has four branch pipes 5, which correspond to the four rectangular frames in the horizontal row respectively. Through the arrangement and setting between a plurality of regulating valves 8, the secondary mother pipe 4 and the branch pipe 5, the regulating valve 8 is used to adjust the ammonia injection flow rate, so as to realize the regional ammonia injection regulation and control within the super-large cross-section, and increase the adjustability of the ammonia injection device.

[0046] A plurality of ammonia spraying groups 6 on the top row of branch pipes 5 are plugged, and a plurality of ammonia spraying groups 6 on the bottom row of branch pipes 5 are plugged;

[0047] The ammonia spraying section of a large gas waste heat boiler is very large. In the ammonia spraying area of ​​11m wide and 21m high, in most of the cross-sectional positions in the middle part, the flue gas flows in uniformly after passing through the front heating surface. However, in the local positions at the top and bottom of the ammonia spraying section, based on the structural conditions of the boiler heating surface, the flue gas is in an uneven state, that is, the flue gas non-uniform flow area. At this time, the method of sealing (blocking) the upper and lower rows of nozzles 61 of the cross section is adopted to adapt to the local non-uniform flue gas area, so as to ensure that the flue gas volume in the area matches the ammonia spraying volume. Alternatively, the method of not arranging the upper and lower rows of nozzles 61 of the cross section can be adopted to adapt to the local non-uniform flue gas area, such as Figure 5 , reference numeral 18 in the figure denotes the non-uniform ammonia injection in the low velocity zone.

[0048] The trunk branch pipes 5 are evenly arranged at equal intervals, and a plurality of ammonia spraying groups 6 are evenly arranged at equal intervals. The ammonia spraying group 6 includes two nozzles 61. One end of the two nozzles 61 is connected to the same cross-sectional position of the branch pipe 5. A flue gas sealing plate 13 is provided between the top plate 11 and the bottom plate 12 and the nozzle 61 arrangement area.

[0049] By arranging ammonia spraying groups 6 with uniform spacing on each branch pipe 5, the ammonia nozzles 61 in the ammonia spraying section are generally uniform and meet the flue gas uniform distribution characteristics on the ammonia spraying section of the gas-fired waste heat boiler. The top plate 11, the bottom plate 12 and the side boundary of the reactor 1 are composed of the furnace wall of the boiler. The flue gas sealing plate 13 is a boiler header flue gas partition, which is used to prevent the flue gas from flowing from the nozzle-free area (non-ammonia spraying area).

[0050] The spacing between the plurality of branch pipes 5 is set to 625 mm, the spacing between the ammonia spraying groups 6 on the branch pipes 5 is set to 253 mm, the angle between the two nozzles 61 is set to 120°, and the angle between the directions of the two nozzles 61 and the direction of the flue gas flow is set to 60°;

[0051] This arrangement can make the nozzles 61 in the ammonia injection section generally evenly distributed, which is consistent with the uniform characteristics of the flue gas on the ammonia injection section of the gas-fired waste heat boiler. The angle of 120° between the two nozzles 61 is an optimal injection angle calculated based on the arrangement spacing of the nozzles 61 and the flow rate of the nozzle holes, combined with CFD flow field numerical simulation technology. The nozzle holes are at the ends of the nozzles 61. The uniform spacing between the ammonia injection groups 6 and the angle design between the nozzles 61 strengthen the convection mixing of ammonia flue gas at the ammonia injection nozzle, ensuring that the maximum relative standard deviation of the ammonia-nitrogen molar ratio is less than ±5% at 0.3m from the catalyst surface, thereby improving the uniformity of ammonia at the ammonia injection nozzle.

[0052] A hanger 14 is provided inside the reactor 1, one end of the hanger 14 is fixedly connected to the furnace top hanging beam 15, the other end of the hanger is fixedly connected to the upper secondary mother pipe 40, the lower secondary mother pipe 41 is fixedly connected to the limit support plate 43, and one side of the limit support plate 43 is fixedly connected to the bottom plate;

[0053] The ammonia injection device is arranged in the section between the boiler heating surface modules, and the upper secondary mother pipe 40 and the connected horizontal branch pipe 5 are gravity supported by the hanger group 14. The top of each vertical secondary mother pipe 4 is hung on the hanging beam 15 at the top of the furnace by the hanger 14 to bear the weight of the upper secondary mother pipe 40 and the connected branch pipe 5. The lower secondary mother pipe 41 and the connected horizontal branch pipe 5 are gravity supported by the limiting support plate 43 arranged at the bottom plate 12 of the reactor 1.

[0054] A plurality of boiler heating surface tubes 9 are provided on one side of the secondary mother tube 4, and a heating surface tube sheet 91 is provided on the plurality of boiler heating surface tubes 9. The secondary mother tube is fixedly connected to the boiler heating surface tube 9 through a clamping plate 1 44 and a clamping plate 2 45, and the clamping plate 2 45 is arranged in a U shape;

[0055] The heating surface tube sheet 91 is used to fix the horizontal spacing between several heating surface tubes 9. In actual use, the heating surface tube sheet 91 can be set at the appropriate position of the heating surface tube 9 to limit it. At the same time, the secondary mother pipe 4 also needs to be limited. In addition to the load-bearing of the upper hanger 14 and the limiting of the lower limiting support plate 43, it is necessary to stop the shaking of the secondary mother pipe 4 at the appropriate position. The secondary mother pipe 4 is limited by several clamping plates 1 44 and clamping plates 2 45 and the heating surface tube 9 of the boiler. At the same time, the use of sleeve 1 42 and sleeve 2 52 is used to solve the problem of unstable structure of the ammonia injection device caused by the continuous shaking of the lower end of the secondary mother pipe 4 due to the blowing of the flue gas flow.

[0056] The secondary main pipe 4 is fixedly connected to the branch pipe 5 through a bearing plate 53;

[0057] The load-bearing plate 53 is used to bear the branch pipe 5. After the secondary mother pipe 4 is fixed by the hanger 14, the limit support plate 43, the clamping plate 1 44 and the clamping plate 2 45, the load-bearing of the branch pipe 5 utilizes the force transmission of the secondary mother pipe 4 and is realized by the load-bearing plate 53. The load-bearing plate 53 is welded to the outer wall of the secondary mother pipe 4. The branch pipe 5 is gravity-supported by several load-bearing plates 53 welded on the secondary mother pipe 4. A 20° bevel on one side of the load-bearing plate 53 is set upward to prevent the branch pipe 5 from falling during the installation process.

[0058] The secondary mother pipe 4 is used as the ammonia delivery pipeline and also as the support system of the branch pipe 5 to support a plurality of branch pipes 5, thereby effectively solving the problem that the ammonia injection pipe system in the ultra-large ammonia injection section inside the waste heat boiler cannot bear the load, meeting the problem of uniform ammonia injection mixing in an ultra-short distance space, and solving the problem of supporting and limiting the ammonia injection device in the ultra-large reactor section.

[0059] The connection between the upper secondary mother pipe 40 and the lower secondary mother pipe 4 is limited by a sleeve 1 42, and the branch pipe 5 includes a plurality of branch pipes 51, and the ends of the plurality of branch pipes 51 are limited by a sleeve 2 52;

[0060] The sleeve 1 42 is used for interconnecting the upper secondary mother pipe 40 and the lower secondary mother pipe 41, so as to limit the end of the secondary mother pipe 4, which can effectively prevent the end of the secondary mother pipe 4 from shaking under the action of airflow. A plurality of branch pipes 51 are connected to form a long-distance branch pipe 5. The sleeve 2 52 is used for interconnecting the branch pipes 51, so as to limit the end of the branch pipes 51, which can effectively prevent the end of the branch pipes 51 from shaking under the action of airflow. At the same time, it can also ensure that the secondary mother pipe 4 and the branch pipe 5 will not have the problem of excessive local bending deflection in the high-temperature flue gas environment. The sleeve 1 42 is used for interconnecting the upper secondary mother pipe 40 and the lower secondary mother pipe 41, so as to limit the end of the branch pipes 51, which can effectively prevent the end of the branch pipes 51 from shaking under the action of airflow. At the same time, it can also ensure that the secondary mother pipe 4 and the branch pipe 5 will not have excessive local bending deflection in the high-temperature flue gas environment. 2 is welded to the secondary mother pipe 4, and the other end of the sleeve 1 42 is in contact with the secondary mother pipe branch 4 (welding is prohibited), which can ensure the free expansion of the upper and lower pipe groups under heat, and at the same time play a limiting role. One end of the sleeve 2 52 is welded to the branch pipe 51, and the other end of the sleeve 2 52 is in contact with the branch pipe 51 (welding is prohibited), which can ensure the free expansion of the horizontal pipe groups under heat, and at the same time play a limiting role. Each branch pipe 51 is not connected. Each branch pipe 51 cooperates with the nozzle 61 to be used only for the ammonia injection area of ​​one area. The four horizontal grouping areas of the reactor 1 are the first group to the fourth group from left to right. Fig.14 In the first and second groups, the upper and lower secondary mother tubes 4 on the far left are connected by a sleeve 42, and the upper and lower secondary mother tubes 4 on the far right of the third and fourth groups are also connected by a sleeve 42. The ends of the rest of the secondary mother tubes 4 are sealed.

[0061] A gap is provided between the connecting ends of the upper secondary mother pipe 40 and the lower secondary mother pipe 41, and a gap is provided between the connecting ends of the plurality of branch pipes 51; a gap is provided between the connecting ends of the secondary mother pipe 4, and a gap is provided between the connecting ends of the branch pipes 51, to compensate for the expansion between the ends of the secondary mother pipe 4 and the expansion between the ends of the branch pipes 51, and to perform expansion pretreatment so that the secondary mother pipe 4 and the branch pipe 5 can expand freely under heating, that is, expansion of the pipeline will occur at the end where welding is prohibited.

[0062] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0063] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ammonia injection device for denitrification of a large gas waste heat boiler, characterized in that: The invention comprises a reactor (1), a top primary mother pipe (2), a bottom primary mother pipe (3), a secondary mother pipe (4) and a branch pipe (5), wherein the secondary mother pipe (4) comprises an upper secondary mother pipe (40) and a lower secondary mother pipe (41), the top primary mother pipe (2) is fixedly connected to a plurality of upper secondary mother pipes (40) through a tee, the bottom primary mother pipe (3) is also fixedly connected to a plurality of lower secondary mother pipes (41) through a tee, and the plurality of upper secondary mother pipes (40) and lower secondary mother pipes (41) penetrate the interior of the reactor (1). The secondary mother pipe (4) is fixedly connected to the branch pipe (5) through a tee, the top primary mother pipe (2) and the plurality of upper secondary mother pipes (40) are arranged symmetrically with the bottom primary mother pipe (3) and the plurality of lower secondary mother pipes (41), the plurality of secondary mother pipes (4) are arranged symmetrically, the branch pipes (5) are provided with a plurality of ammonia injection groups (6), the top of the reactor (1) is provided with a top plate (11), and the bottom of the reactor (1) is provided with a bottom plate (12); A plurality of the branch pipes (5) are evenly arranged at equal intervals, a plurality of the ammonia spraying groups (6) are evenly arranged at equal intervals, the ammonia spraying group (6) comprises two nozzles (61), one end of the two nozzles (61) are connected to the same cross-sectional position of the branch pipe (5), and a smoke sealing plate (13) is provided between the top plate (11) and the bottom plate (12) and the nozzle (61) arrangement area; The spacing between the plurality of branch pipes (5) is set to 625 mm, the spacing between the ammonia spraying groups (6) on the branch pipes (5) is set to 253 mm, the angle between the two nozzles (61) is set to 120°, and the angle between the directions of the two nozzles (61) and the direction of the flue gas flow is set to 60°; The connection between the upper secondary mother pipe (40) and the lower secondary mother pipe (41) is fixedly connected via a first sleeve (42); the branch pipe (5) comprises a plurality of branch pipes (51); and the ends of the plurality of branch pipes (51) are fixedly connected via a second sleeve (52).

2. The ammonia injection device for denitrification of a large gas waste heat boiler according to claim 1, characterized in that: The top primary mother pipe (2) and the bottom primary mother pipe (3) are both provided with a regulating main valve (7), and a plurality of the secondary mother pipes (4) are each provided with a regulating valve (8).

3. The ammonia injection device for denitrification of a large gas waste heat boiler according to claim 2, characterized in that: A plurality of ammonia spraying groups (6) on the branch pipes (5) in the top row are plugged, and a plurality of ammonia spraying groups (6) on the branch pipes (5) in the bottom row are plugged.

4. The ammonia injection device for denitrification of a large gas waste heat boiler according to claim 1, characterized in that: A hanger (14) is provided inside the reactor (1), one end of the hanger (14) is fixedly connected to the furnace top hanger beam (15), the other end of the hanger is fixedly connected to the upper secondary mother pipe (40), the lower secondary mother pipe (41) is fixedly connected to the limit support plate (43), and one side of the limit support plate (43) is fixedly connected to the bottom plate.

5. The ammonia injection device for denitrification of a large gas waste heat boiler according to claim 1, characterized in that: A plurality of boiler heating surface tubes (9) are arranged on one side of the secondary mother tube (4), and a heating surface tube sheet (91) is arranged on the plurality of boiler heating surface tubes (9). The secondary mother tube is fixedly connected to the boiler heating surface tube (9) via a first clamping plate (44) and a second clamping plate (45), and the second clamping plate (45) is arranged in a U shape.

6. The ammonia injection device for denitrification of a large gas waste heat boiler according to claim 1, characterized in that: The secondary main pipe (4) is fixedly connected to the branch pipe (5) via a bearing plate (53).

7. The ammonia injection device for denitrification of a large gas waste heat boiler according to claim 6, characterized in that: A gap is provided between the connection ends of the upper secondary mother pipe (40) and the lower secondary mother pipe (41), and a gap is provided between the connection ends of the plurality of branch pipes (51).

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