Accurate ammonia spraying system after urea hydrolysis ammonia preparation

Abstract

The invention relates to the technical field of flue gas denitration, and discloses a precise ammonia spraying system after urea hydrolysis ammonia preparation, the precise ammonia spraying system comprises a conveying unit, the conveying unit comprises an ammonia supply mother pipe, a steam air heater and two ammonia supply branch pipes connected to the ammonia supply mother pipe, the ammonia supply branch pipes are provided with mixers, and the steam air heater is communicated with the mixers; the at least two ammonia spraying units are arranged on the ammonia supply branch pipe; the device has the beneficial effects that through mutual cooperation of the multiple ammonia spraying units, when one ammonia spraying unit is blocked and the like, it is ensured that the multiple ammonia spraying units still can operate cooperatively, smoke in the depth direction of the whole flue is fully mixed, through arrangement of the force application unit, pressurization can be conducted during ammonia spraying, and the ammonia spraying efficiency is improved. Not only can the ammonia gas nozzle be prevented from being blocked, but also a certain turbulent flow effect is generated on the flue gas, and sufficient mixing with the flue gas is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flue gas denitration, and in particular to a precise ammonia injection system after urea hydrolysis ammonia production. BACKGROUND

[0002] With the increasing requirements of the state for environmental protection, more and more attention is paid to the emission of nitrogen oxides of coal-fired units. Due to the importance of safety production, the reduction agent, i.e. liquid ammonia, is gradually replaced by urea, and the urea hydrolysis ammonia production system gradually becomes the mainstream of urea ammonia production system because of its safety, stability, reliability and low operation cost. Urea hydrolysis ammonia production causes a large amount of ammonia escape due to unstable concentration, and also causes side reactions and catalyst poisoning, affecting the service life of the catalyst.

[0003] The existing ammonia injection after urea hydrolysis ammonia production has the following technical problems:

[0004] 1. Too much ammonia gas input causes ammonia escape, and the escaped ammonia gas and water vapor and sulfur trioxide in the flue gas further generate ammonium bisulfate, which is in a molten state in the range of 146-207℃, easily adsorbed on the surface of fly ash, and finally adhered to the surface of the heat storage element of the air preheater, causing air preheater cold end low temperature corrosion and blockage.

[0005] 2. Too much ammonia escape also causes dust collector dusting and blockage, affecting the dust removal efficiency and the service life of the dust collector.

[0006] 3. The escaped ammonia also enters the desulfurization system with the flue gas, dissolves in the slurry, and finally leads to excessive ammonia nitrogen content in the effluent. SUMMARY

[0007] Therefore, the technical problem to be solved by the present application is to solve the phenomenon of ammonia escape in the ammonia injection process and cause blockage of other devices.

[0008] The above technical problems are solved by the following technical scheme: the present application provides a precise ammonia injection system after urea hydrolysis ammonia production, which comprises a conveying unit, the conveying unit comprising an ammonia supply main pipe, a steam air heater, two ammonia supply branch pipes connected to the ammonia supply main pipe, a mixer arranged on the ammonia supply branch pipe, and the steam air heater being in communication with the mixer; an ammonia injection unit, at least two of the ammonia injection units being arranged on the ammonia supply branch pipe, the ammonia injection unit comprising a connecting pipe in communication with the ammonia supply branch pipe, and two first connecting branch pipes and one second connecting branch pipe in communication with the connecting pipe, the two first connecting branch pipes being respectively in communication with a first ammonia injection pipe and a second ammonia injection pipe located in a flue gas pipeline, and the second connecting branch pipe being connected with a third ammonia injection pipe in another group of ammonia injection units.

[0009] In a preferred embodiment of the application, the connecting pipe is provided with a first valve, and the two first connecting branch pipes and the second connecting branch pipe are respectively provided with a second valve and a third valve.

[0010] In a preferred embodiment of the application, the first ammonia injection pipe and the second ammonia injection pipe are located at opposite corners of the flue gas pipeline, and the third ammonia injection pipe is located at the center line of the flue gas pipeline.

[0011] In a preferred embodiment of the application, the ammonia supply branch pipe is provided with a stop valve and an adjusting valve for controlling the on-off and size of the ammonia supply.

[0012] In a preferred embodiment of the application, one side of the steam air heater is connected to a drain tank, and the other side of the steam air heater is connected to two air fans for inputting air into the steam air heater.

[0013] In a preferred embodiment of the application, the system further comprises a gas supply unit, the gas supply unit comprises a steam main pipe and two steam branch pipes connected to the steam main pipe, the steam branch pipes are provided with at least two steam sub-pipes, and the steam sub-pipes are provided with steam valves.

[0014] In a preferred embodiment of the application, the steam sub-pipes are connected to two third connecting branch pipes, the two third connecting branch pipes are respectively connected to the two first connecting branch pipes, and one of the steam branch pipes is connected to the steam air heater.

[0015] In a preferred embodiment of the application, the system further comprises a force applying unit, the force applying unit is installed on the first ammonia injection pipe, the second ammonia injection pipe, and the third ammonia injection pipe; the force applying unit comprises an installation cylinder, a first blocking member and a second blocking member arranged at the top and the side of the installation cylinder, respectively, and a force applying member and a moving member arranged in the installation cylinder, and the installation cylinder is connected to the first ammonia injection pipe, the second ammonia injection pipe, and the third ammonia injection pipe.

[0016] In a preferred embodiment of the application, the top inner side of the installation cylinder is fixedly connected to a sealing plate, the first blocking member comprises a first blocking ball arranged on the sealing plate and a first spring arranged below the first blocking ball; the second blocking member comprises a fixed cylinder fixed to the outer side of the installation cylinder, a blocking ring fixed to the inner side of the fixed cylinder, and a second blocking ball and a second spring arranged in the fixed cylinder, and the two ends of the second spring are respectively fixed to one side of the blocking ring and the bottom of the second blocking ball.

[0017] In a preferred embodiment of the urea hydrolysis ammonia production accurate ammonia injection system, the force applying member comprises a rotating rod rotating in the mounting cylinder and a fan fixed to the bottom end of the rotating rod, and the part of the rotating rod inside the mounting cylinder is provided with a sliding groove; the moving member comprises a moving cylinder movably sleeved on the outer circle of the rotating rod, a piston head fixed to the top of the moving cylinder and a sliding block fixed to the inside of the moving cylinder, and the sliding block cooperates with the sliding groove.

[0018] The urea hydrolysis ammonia production accurate ammonia injection system has the advantages that through the cooperation between the multiple groups of ammonia injection units, when one group of ammonia injection units is blocked or the like, the multiple groups of ammonia injection units can still work cooperatively to realize the full mixing of the flue gas in the depth direction of the flue, and through the setting of the force applying unit, the ammonia injection can be pressurized, which not only prevents the ammonia injection port from being blocked, but also produces a certain turbulence effect on the flue gas, ensuring the full mixing with the flue gas. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present application, but not limit the present application. Among them:

[0020] Figure 1 The system diagram of the urea hydrolysis ammonia production accurate ammonia injection system is shown;

[0021] Figure 2 The system schematic diagram of the ammonia injection unit is shown;

[0022] Figure 3 The vertical arrangement diagram of the multiple groups of ammonia injection units in the flue gas pipeline is shown;

[0023] Figure 4 The system schematic diagram of the gas supply unit is shown;

[0024] Figure 5 The structural schematic diagram of the force applying unit is shown;

[0025] Figure 6 The cross-sectional structural schematic diagram of the force applying unit is shown;

[0026] Figure 7 The structural schematic diagram of the force applying member is shown; DETAILED DESCRIPTION

[0027] In order to make the skilled in the art better understand the present application, the present application will be further described in detail below in combination with the specific embodiments and the drawings.

[0028] The terms used in the present application are those general terms currently widely used in the art in consideration of the functions regarding the present application, but the terms can be changed according to the intention of those of ordinary skill in the art, precedents, or new technology in the art. Also, specific terms can be selected by the applicant, and in this case, the detailed meaning thereof will be described in the detailed description of the present application. Therefore, the terms used in the specification should not be understood as simple names, but based on the meaning of the terms and the general description of the present application.

[0029] Embodiment 1

[0030] Reference Figures 1-4 For the first embodiment of the present application, the embodiment provides a precise ammonia injection system after urea hydrolysis to produce ammonia, which comprises a conveying unit 1, the conveying unit 1 comprises an ammonia supply main pipe 11, a steam air heater 15, two ammonia supply branch pipes 111 connected to the ammonia supply main pipe 11, and a mixer 14 arranged on the ammonia supply branch pipe 111, and the steam air heater 15 is communicated with the mixer 14.

[0031] The ammonia supply main pipe 11 can provide the system with the need of ammonia gas, and is conveyed to the mixer 14 through the ammonia supply branch pipe 111, the main purpose of the steam air heater 15 is to improve the temperature of the cold air entering the air preheater, so as to prevent ammonium bisulfate in the flue gas from condensing and depositing in the low temperature section of the air preheater, and avoid equipment blockage and corrosion, and the mixer 14 provides sufficient mixing for ammonia gas and heated air, ensures that ammonia gas is efficiently and safely diffused into flue gas, and fully plays the reaction.

[0032] Specifically, the ammonia supply branch pipe 111 is provided with a stop valve 12 and an adjusting valve 13 for controlling the on-off and size of the ammonia supply of the ammonia supply branch pipe 111.

[0033] Through the action of the stop valve 12, the on-off of the ammonia gas in the ammonia supply branch pipe 111 is controlled, and through the adjusting valve 13, the flow rate of the ammonia gas can be adjusted when the ammonia gas passes through, to ensure that there is no ammonia escape phenomenon when mixed with flue gas.

[0034] Specifically, one side of the steam air heater 15 is communicated with a drain tank 151, and the other side of the steam air heater 15 is communicated with two air blowers 152 for inputting air into the steam air heater 15.

[0035] The setting of the two air blowers 152 belongs to redundant setting, when the system is operating, usually one air blower 152 is operating, and the other air blower 152 is standby, to prevent the air blower 152 working from failure, causing system failure, thereby delaying the operation of the system.

[0036] The ammonia injection unit 2 is arranged on the ammonia supply branch pipe 111, and includes a connecting pipe 21 connected with the ammonia supply branch pipe 111, two first connecting branch pipes 211 and a second connecting branch pipe 212 connected with the connecting pipe 21. The two first connecting branch pipes 211 are respectively connected with the first ammonia injection pipe 23 and the second ammonia injection pipe 24 in the flue gas pipeline 3, and the second connecting branch pipe 212 is connected with the third ammonia injection pipe 25 in another group of ammonia injection units 2.

[0037] The ammonia injection unit 2 can accurately inject ammonia into the flue gas pipeline 3. The two first connecting branch pipes 211 can respectively supply ammonia to the first ammonia injection pipe 23 and the second ammonia injection pipe 24, and adjust the flue gas concentration at different positions in the flue gas pipeline 3 at the same horizontal plane.

[0038] The multiple groups of ammonia injection units 2 are arranged in multiple regions in the depth direction of the flue gas pipeline 3, which can gradually mix the ammonia and the flue gas in the flue gas pipeline 3, and ensure that the nitrogen oxides in the flue gas can be completely eliminated. The number of ammonia injection units 2 can be determined according to actual conditions, which is not limited here.

[0039] A patrol device is arranged above each group of ammonia injection units 2. Multiple sampling points are arranged at corresponding positions of each group of ammonia injection units 2 to measure the distribution of nitrogen oxides and oxygen in the entire cross section of the flue gas pipeline 3. The measured oxygen concentration value can be used to determine whether the pipeline in the system is blocked, and ensure the stability and reliability of the system. The patrol device is a prior art, which is not described in detail here. The positions of the sampling points of the patrol device can be set according to actual use, which is not limited here.

[0040] The two first connecting branch pipes 211 are respectively connected with the first ammonia injection pipe 23 and the second ammonia injection pipe 24. The ammonia mixed with hot air is input into the first ammonia injection pipe 23 and the second ammonia injection pipe 24 through the connecting pipe 21, and then input into the flue gas pipeline 3 to mix with the flue gas in the flue gas pipeline 3, so as to ensure that the nitrogen oxides in the flue gas at the cross section can be eliminated.

[0041] The second connecting branch pipe 212 is connected with the third ammonia injection pipe 25 in the other group of ammonia injection units 2, which can have two use cases: first, during normal operation, the second connecting branch pipe 212 does not perform ammonia injection operation, and the second connecting branch pipe 212 serves as a backup. When the system in one group of ammonia injection units 2 is blocked, the use of this group needs to be suspended and purging is needed. At this time, the second connecting branch pipe 212 in the other group of ammonia injection units 2 can be connected with the third ammonia injection pipe 25 in this group. At this time, ammonia can be transported to the cross section of the flue gas pipeline 3 through the third ammonia injection pipe 25 to achieve mixing with the flue gas and prevent the situation that the nitrogen oxides in the flue gas are not completely eliminated due to the suspension of the use of one group of ammonia injection units 2. Second, during system operation, the first ammonia injection pipe 23, the second ammonia injection pipe 24, and the third ammonia injection pipe 25 work together to fully mix the ammonia with the flue gas in the cross section.

[0042] As shown in Figure 3 Fig. 3, three groups of ammonia injection units 2 are taken as an example. Each group is a view of the cross section of the flue gas pipeline 3, and the three groups of ammonia injection units 2 are placed in sequence, and the specific connection of the third ammonia injection pipe 25 in multiple groups of ammonia injection units 2 is shown.

[0043] Specifically, the connecting pipe 21 is provided with a first valve 22, and the two first connecting branch pipes 211 and the second connecting branch pipe 212 are respectively provided with a second valve 213 and a third valve 214.

[0044] Through the arrangement of the first valve 22, the on-off and flow of ammonia in the entire connecting pipe 21 can be controlled. By measuring multiple points in the flue gas pipeline 3 through a patrol device, the opening degree of the second valve 213 and the third valve 214 can be adjusted so that they can adjust the second valve 213 and the third valve 214 to the appropriate opening degree according to the concentration of different positions, ensuring that the amount of ammonia injection can be fully mixed with the flue gas and that excessive ammonia can not escape.

[0045] Specifically, the first ammonia injection pipe 23 and the second ammonia injection pipe 24 are located at opposite angles in the flue gas pipeline 3, and the third ammonia injection pipe 25 is located at the center line position of the flue gas pipeline 3.

[0046] The first ammonia injection pipe 23 and the second ammonia injection pipe 24 are located at opposite angles in the cross section of the flue gas pipeline 3, which can achieve wide coverage by only opening the first ammonia injection pipe 23 and the second ammonia injection pipe 24, so that the ammonia can fill the position. The first ammonia injection pipe 23, the second ammonia injection pipe 24, and the third ammonia injection pipe 25 can be arranged in parallel or staggered, which can be arranged according to actual conditions.

[0047] In use, ammonia gas enters the ammonia supply branch pipe 111 through the ammonia supply main pipe 11, and the flow of ammonia gas is controlled by the opening degree of the control stop valve 12 and the regulating valve 13, and after the ammonia gas enters the mixer 14, it is mixed with the air heated by the steam air heater 15, and after the mixing, it enters the ammonia injection unit 2, and is injected out through the first ammonia injection pipe 23 and the second ammonia injection pipe 24, and is mixed with the flue gas in the flue gas pipeline 3, so as to achieve the effect of removing nitrogen oxides.

[0048] Embodiment 2

[0049] With reference to Figure 4 For the second embodiment of the application, which is different from the first embodiment, it further comprises a gas supply unit 4, the gas supply unit 4 comprises a steam main pipe 41 and two steam branch pipes 42 connected with the steam main pipe 41, at least two steam sub-pipes 421 are arranged on the steam branch pipe 42, and steam valves 422 are arranged on the steam sub-pipes 421.

[0050] Further, the steam sub-pipes 421 are communicated with two third connection branch pipes 423, and the two third connection branch pipes 423 are respectively communicated with the two first connection branch pipes 211, and one steam branch pipe 42 is communicated with the steam air heater 15.

[0051] Through the arrangement of the gas supply unit 4, cooperation with the steam air heater 15 can be realized to heat the air, and the blocked pipeline in the ammonia injection unit 2 can be purged to ensure the normal operation of the ammonia injection unit 2.

[0052] Through the steam main pipe 41, steam is input into the steam branch pipe 42 and delivered to the two sides of the ammonia injection unit 2, the number of steam sub-pipes 421 is the same as the number of connection pipes 21, which ensures that each group of ammonia injection units 2 can be purged, and through the third connection branch pipe 423, the two first connection branch pipes 211 can be connected respectively, which ensures that each first connection branch pipe 211 can be purged.

[0053] Further, several groups of steam sub-pipes 421 can also be arranged, which are connected with the second connection branch pipe 212, when the system is normally running, if the third ammonia injection pipe 25 or the pipeline connected therewith is blocked, in the case that it does not work, it can also be purged to ensure that it will not be blocked.

[0054] One of the steam branch pipes 42 is communicated with the steam air heater 15 to deliver steam to the steam air heater 15 to heat the air.

[0055] Embodiment 3

[0056] With reference to Figures 5-7For the third embodiment of the present application, which is based on the previous two embodiments, the third embodiment further comprises a force applying unit 5, which is installed on the first ammonia injection pipe 23, the second ammonia injection pipe 24 and the third ammonia injection pipe 25;

[0057] The force applying unit 5 comprises an installation cylinder 51, a first blocking piece 52 and a second blocking piece 53 arranged on the top and the side of the installation cylinder 51 respectively, and a force applying piece 54 and a moving piece 55 arranged in the installation cylinder 51, and the installation cylinder 51 is in communication with the first ammonia injection pipe 23, the second ammonia injection pipe 24 and the third ammonia injection pipe 25.

[0058] One force applying unit 5 is installed on the first ammonia injection pipe 23, the second ammonia injection pipe 24 and the third ammonia injection pipe 25 at every interval, which is used to pressurize the ammonia gas, so that the ammonia gas has a large speed when it is sprayed, on the one hand, the large speed of the ammonia gas at the nozzle can produce a certain impact, which can prevent the blockage to a certain extent, on the other hand, the ammonia gas sprayed at a large speed can cover a larger range, so that it can be mixed with the flue gas more fully.

[0059] Specifically, the top inner side of the installation cylinder 51 is fixedly connected with a sealing plate 511, the first blocking piece 52 comprises a first blocking ball 522 arranged on the sealing plate 511 and a first spring 521 arranged below the first blocking ball 522; the second blocking piece 53 comprises a fixed cylinder 531 fixed to the outer side of the installation cylinder 51, a blocking ring 532 fixed to the inside of the fixed cylinder 531, and a second blocking ball 533 and a second spring 534 arranged in the fixed cylinder 531, and the two ends of the second spring 534 are fixed to one side of the blocking ring 532 and the bottom of the second blocking ball 533 respectively.

[0060] The sealing plate 511 provides a basis for the placement of the first blocking ball 522, when the first blocking ball 522 completely falls on the sealing plate 511, the opening of the sealing plate 511 will be blocked at this time, and the fixed cylinder 531 provides a basis for the placement of the second blocking ball 533 and the second spring 534, the inner side of the opening of the fixed cylinder 531 is a structure that is inwardly collected, which can tightly fit with the outer side of the second blocking ball 533, under the condition of no external force, the second blocking ball 533 is pushed against the opening of the fixed cylinder 531 by the action of the second spring 534, so as to block the fixed cylinder 531.

[0061] The first blocking ball 522 is blocked outside the sealing plate 511, while the second blocking ball 533 is blocked inside the fixed cylinder 531, when the installation cylinder 51 is inflated, the second blocking ball 533 is blocked at the fixed cylinder 531, and due to the force, the first blocking ball 522 moves away from the sealing plate 511, at this time, the gas can be sprayed from the sealing plate 511, and when the installation cylinder 51 inhales, the air has a pushing force from the outside to the inside, at this time, the first blocking ball 522 will not move, and the second blocking ball 533 will move away from the fixed cylinder 531, so that the gas enters the installation cylinder 51 from the fixed cylinder 531.

[0062] Specifically, the force applying member 54 includes a rotating rod 541 rotating in the installation cylinder 51 and a fan blade 542 fixed to the bottom end of the rotating rod 541, and the part of the rotating rod 541 inside the installation cylinder 51 is provided with a sliding groove 543; the moving member 55 includes a moving cylinder 551 movably sleeved on the outer circle of the rotating rod 541, a piston head 552 fixed to the top of the moving cylinder 551, and a sliding block 553 fixed to the inside of the moving cylinder 551, and the sliding block 553 is in sliding cooperation with the sliding groove 543.

[0063] The rotating rod 541 is in rotating cooperation with the bottom of the installation cylinder 51, which ensures that the flue gas in the flue gas pipeline 3 can drive the fan blade 542 to rotate when passing through, thereby driving the rotating rod 541 to rotate, the moving cylinder 551 is sleeved on the outer circle of the rotating rod 541, and is in sliding cooperation with the sliding groove 543 through the sliding block 553 inside, which can drive the moving cylinder 551 to move up and down when the rotating rod 541 rotates, and the moving cylinder 551 is provided with a limit to ensure that it can move vertically along the installation cylinder 51 and will not be rotated with the rotating rod 541.

[0064] When the moving cylinder 551 moves up and down, due to the close fit of the piston head 552 and the inner wall of the installation cylinder 51, the process of inhaling and blowing can be realized, when blowing, the opening of the fixed cylinder 531 is closed and the gas is sprayed from the opening of the sealing plate 511, which accelerates the spraying speed of the ammonia gas, and when inhaling, the opening of the sealing plate 511 is closed and the gas is inhaled from the opening of the fixed cylinder 531.

[0065] Further, the air outlet of the sealing plate 511 can be set according to the specific position of the nozzle on the first ammonia spraying pipe 23, the second ammonia spraying pipe 24 and the third ammonia spraying pipe 25, which can be set as rectangular, circular, etc., which can directly act on the nozzle when blowing, to ensure the acceleration effect of the ammonia gas.

[0066] Further, the orthographic projection of the chute 543 is a ring, and when the rotating rod 541 rotates, there are two processes, the first is the process of the moving cylinder 551 rising, marked as the first process, and the second is the process of the moving cylinder 551 falling, marked as the second process, and the ratio of the first process to the second process is set according to actual conditions, which is not specifically limited here.

[0067] When the first process is short, the second process is long, which means that the process time of the moving cylinder 551 falling to inhale is long, and the process time of the moving cylinder 551 rising to blow is short, which can increase the impact force of blowing, and can more effectively perform the blowing.

[0068] When the first process is long, the second process is short, which means that the process time of the moving cylinder 551 falling to inhale is short, and the process time of the moving cylinder 551 rising to blow is long, which can quickly inhale, and blow for a long time, ensuring that the sprayed ammonia gas covers a large area for a long time, and better mixes with the flue gas.

[0069] When the first process and the second process are the same, which means that the process time of the moving cylinder 551 falling to inhale is the same as the process time of the moving cylinder 551 rising to blow, which can more smoothly mix and blow.

[0070] In summary, ammonia gas enters the ammonia supply branch pipe 111 through the ammonia supply main pipe 11, and the flow of ammonia gas is controlled by controlling the opening of the stop valve 12 and the regulating valve 13, and after the ammonia gas enters the mixer 14, it is mixed with the air heated by the steam heater 15, and after the mixing, it enters the ammonia injection unit 2, and is sprayed out through the first ammonia injection pipe 23 and the second ammonia injection pipe 24, and at the time of spraying, the force unit 5 is in operation at all times, and at this time, through the cooperation with the force unit 5, the speed of ammonia injection can be further accelerated, the nozzle can be effectively prevented from being blocked, and the mixing of ammonia gas and flue gas can be more sufficient, when the pipeline in the ammonia injection unit 2 is blocked, the first valve 22 can be closed, and the steam valve 422 connected thereto is opened, and steam is input through the steam branch pipe 421 to perform blowing.

[0071] Finally, it should be pointed out that the methods and devices described in detail above are only embodiments, and those skilled in the art can modify these embodiments in different ways without departing from the scope of the present application.

Claims

1. A precise ammonia injection system after urea hydrolysis to produce ammonia, characterized in that: The utility model relates to a kind of ammonia supply system, including, Transport unit (1), the transport unit (1) includes ammonia supply main pipe (11), steam heater (15), two ammonia supply branch pipes (111) connected to ammonia supply main pipe (11), the mixer (14) is provided on the ammonia supply branch pipe (111), the steam heater (15) is communicated with mixer (14); At least two of the ammonia injection unit (2) is provided on the ammonia supply branch pipe (111), the ammonia injection unit (2) includes the connecting pipe (21) communicated with the ammonia supply branch pipe (111) and two first connecting branch pipes (211) and a second connecting branch pipe (212) communicated with the connecting pipe (21), two first connecting branch pipes (211) are respectively communicated with the first ammonia injection pipe (23) in the flue gas pipeline (3), the second connecting branch pipe (212) is connected with the third ammonia injection pipe (25) in another group of ammonia injection unit (2).

2. The accurate ammonia injection system after urea hydrolysis to produce ammonia according to claim 1, characterized in that: First valve (22) is provided on the connecting pipe (21), and second valve (213) and third valve (214) are respectively installed on two first connecting branch pipes (211) and second connecting branch pipe (212).

3. The accurate ammonia injection system after urea hydrolysis to produce ammonia according to claim 2, characterized in that: The first ammonia injection pipe (23) and the second ammonia injection pipe (24) are located at the diagonal position in the flue gas pipeline (3), and the third ammonia injection pipe (25) is located at the center line position of the flue gas pipeline (3).

4. The accurate ammonia injection system after urea hydrolysis to produce ammonia according to claim 1, characterized in that: The ammonia supply branch pipe (111) is provided with a stop valve (12) and an adjusting valve (13) for controlling the on-off and size of the ammonia supply of the ammonia supply branch pipe (111).

5. The accurate ammonia injection system after urea hydrolysis to produce ammonia according to any one of claims 2-4, characterized in that: The steam heater (15) is communicated with a drain tank (151) on one side, and two fans (152) are communicated with the steam heater (15) on the other side for inputting air into the steam heater (15).

6. The accurate ammonia injection system after urea hydrolysis to produce ammonia of claim 1, wherein: It also includes a gas supply unit (4), which includes a steam main pipe (41) and two steam branch pipes (42) communicated with the steam main pipe (41), at least two steam sub-pipes (421) are provided on the steam branch pipe (42), and steam valves (422) are provided on the steam sub-pipes (421).

7. The precise ammonia injection system after urea hydrolysis to ammonia production according to claim 6, characterized in that: The steam sub-pipe (421) is communicated with two third connecting branch pipes (423), and two first connecting branch pipes (211) are respectively communicated with two third connecting branch pipes (423), wherein one of the steam branch pipes (42) is communicated with the steam heater (15).

8. The accurate ammonia injection system after urea hydrolysis to produce ammonia of claim 1, wherein: It also includes a force applying unit (5) installed on the first ammonia injection pipe (23), the second ammonia injection pipe (24) and the third ammonia injection pipe (25); The force applying unit (5) includes a mounting cylinder (51), a first sealing member (52) and a second sealing member (53) provided on the top and side of the mounting cylinder (51) respectively, and a force applying member (54) and a moving member (55) provided in the mounting cylinder (51), and the mounting cylinder (51) is communicated with the first ammonia injection pipe (23), the second ammonia injection pipe (24) and the third ammonia injection pipe (25).

9. The system for accurate ammonia injection after urea hydrolysis according to claim 8, characterized in that: The top inner side of the mounting cylinder (51) is fixedly connected with an enclosing plate (511), the first plugging member (52) comprises a first plugging ball (522) arranged on the enclosing plate (511) and a first spring (521) arranged below the first plugging ball (522); The second plugging member (53) comprises a fixing cylinder (531) fixed to the outer side of the mounting cylinder (51), a stop ring (532) fixed to the inner part of the fixing cylinder (531), a second plugging ball (533) and a second spring (534) arranged in the inner part of the fixing cylinder (531), and both ends of the second spring (534) are fixed to one side of the stop ring (532) and the bottom of the second plugging ball (533) respectively.

10. The precise ammonia injection system after urea hydrolysis to ammonia production according to claim 9, characterized in that: The force applying member (54) comprises a rotating rod (541) rotating in the mounting cylinder (51) and a fan blade (542) fixed to the bottom end of the rotating rod (541), and the part of the rotating rod (541) located in the inner part of the mounting cylinder (51) is provided with a sliding groove (543); The moving member (55) comprises a moving cylinder (551) movably sleeved on the outer circle of the rotating rod (541), a piston head (552) fixed to the top of the moving cylinder (551) and a sliding block (553) fixed to the inner part of the moving cylinder (551), and the sliding block (553) is matched with the sliding rod of the sliding groove (543).

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