NOx partition sampling and measurement control system based on differential pressure method

Abstract

The invention belongs to the technical field of flue gas denitration, and relates to a NOx partition sampling and measurement control system based on a differential pressure method. Comprising a sampling pipeline system, a flue gas measuring system and a PLC control system, the sampling pipeline system is connected with the flue gas measuring system; the PLC control system is respectively connected with the sampling pipeline system and the flue gas measuring system; the sampling pipeline system comprises a partition sampling mother pipe; one end of the partition sampling mother pipe is communicated with a denitration inlet pipeline, and the other end of the partition sampling mother pipe is communicated with an air pre-heater outlet flue; a plurality of subarea sampling branch pipes are arranged on the subarea sampling mother pipe; the technical problem that downstream equipment ammonium bisulfate ABS is blocked due to uneven distribution of NOx and ammonia escape concentration at an SCR outlet is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas denitrification technology and relates to a NOx zone sampling and measurement control system based on a differential pressure method. Background Art

[0002] With the increasingly improved flexible peak-shaving and capacity pricing mechanisms for coal-fired units, coal-fired power generation units are facing more complex and changeable operational challenges. Since the units need to respond quickly to load regulation commands, their load regulation rate has increased significantly, and the changes in load commands have become more frequent and irregular. This change directly leads to drastic fluctuations in the combustion state in the furnace, which in turn affects the emission level of NOx (nitrogen oxides), causing it to fluctuate significantly.

[0003] The increase in this volatility makes the inlet flue gas conditions of the SCR (selective catalytic reduction) denitrification system extremely harsh. Operators not only need to ensure that NOx emissions meet environmental standards, but also take into account the requirements for refined ammonia injection operation of the denitrification device, which undoubtedly increases the difficulty and complexity of operation. When the flue gas conditions at the SCR inlet fluctuate rapidly, the amount of ammonia injection will fluctuate greatly, resulting in the denitrification device being over-sprayed or under-sprayed as a whole. This will not only cause ammonia waste, but also cause intermittent overall excess of ammonia slip problems.

[0004] In addition, the distribution of the flue gas flow field at the SCR inlet will also change due to load regulation, especially the distribution of the inlet NOx concentration and flue gas flow rate. These changes will pose new challenges to the fixed valve opening of the ammonia injection grid. The traditional fixed valve opening setting is difficult to meet the needs of dynamic ammonia injection operation in each partition, so the ammonia escape problem may exceed the standard in local areas. This local or overall ammonia escape is one of the main reasons for the fouling of ammonium bisulfate (ABS) in downstream equipment such as air preheaters (air preheaters).

[0005] The generation and deposition of ammonium bisulfate will cause the resistance of the air preheater to increase continuously, thus affecting the thermal efficiency and operational stability of the unit. At the same time, the efficiency of the electrostatic precipitator will also decrease due to the increase in the resistance of the air preheater, causing the dust emission concentration to increase, affecting the emission of environmental protection indicators. In severe cases, these problems may even lead to limited unit output, reduced power generation efficiency, and even lead to over-emission of environmental protection indicators, which will have a negative impact on the stable operation and environmental image of the coal-fired unit.

[0006] Therefore, under the background of flexible peak-shaving and capacity electricity price mechanism of coal-fired units, how to effectively deal with the large fluctuations in furnace combustion and NOx emissions, optimize the operation strategy of the SCR denitrification system, and reduce the occurrence of ammonia slip has become an important issue that needs to be urgently solved for coal-fired power generation units. Summary of the invention

[0007] The purpose of the present invention is to avoid the technical problems of increased ammonia consumption and ammonium bisulfate blockage of downstream equipment caused by uneven distribution of NOx and ammonia slip concentrations at the SCR outlet, and to provide a NOx zoning sampling and measurement control system based on the differential pressure method. To achieve the above purpose, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a NOx zoned sampling and measurement control system based on the differential pressure method, including a sampling pipeline system, a flue gas measurement system and a PLC control system; the sampling pipeline system is connected to the flue gas measurement system; the PLC control system is respectively connected to the sampling pipeline system and the flue gas measurement system; the sampling pipeline system includes a zoned sampling main pipe; one end of the zoned sampling main pipe is connected to the denitrification inlet pipe, and the other end is connected to the air preheater outlet flue; a plurality of zoned sampling branches are arranged on the zoned sampling main pipe.

[0008] Preferably, a partition sampling branch pipe pneumatic valve is provided between the partition sampling branch pipe and the partition sampling main pipe.

[0009] Preferably, a first purge pipeline manual valve and a second purge pipeline manual valve are provided between the partition sampling main pipe and the denitrification inlet pipe.

[0010] Preferably, a purge line pneumatic valve is provided between the first purge line manual valve and the second purge line manual valve.

[0011] Preferably, the partitioned sampling main pipe is provided with a partitioned sampling main pipe pneumatic valve; and the partitioned sampling branch pipe is arranged upstream of the partitioned sampling main pipe pneumatic valve.

[0012] Preferably, a smoke sampling pool is provided on the partition sampling main pipe; the smoke sampling pool is arranged downstream of the pneumatic valve of the partition sampling main pipe.

[0013] Preferably, a remote thermometer is provided on the partition sampling main pipe, and the remote thermometer is arranged downstream of the flue gas sampling pool.

[0014] Preferably, the air preheater outlet flue is provided with a CEMS cabin; the flue gas measurement system includes a partitioned flue gas analyzer and an analyzer sampling probe connected thereto; a partitioned flue gas analyzer is installed in the CEMS cabin; the analyzer sampling probe is arranged in the flue gas sampling pool 8 Preferably, the PLC control system is arranged in the CEMS room; the zoned sampling branch pipe pneumatic valve, the pneumatic valve of the purge pipeline, the zoned sampling main pipe pneumatic valve and the zoned flue gas analyzer are all connected to the PLC control system.

[0015] In a second aspect, the present invention provides a method for using a NOx zone sampling and measurement control system based on a differential pressure method, which specifically comprises the following steps: Close all pneumatic valves. After detecting that the pneumatic valve of the purge pipeline is fully closed, the PLC control system opens the pneumatic valve of the partition sampling main pipe and the pneumatic valve of the first partition sampling branch pipe at the same time. After the set time, the pneumatic valve of the next partition sampling branch pipe opens. After the pneumatic valve of the next partition sampling branch pipe opens in place, the pneumatic valve of the previous partition sampling branch pipe will be closed until the pneumatic valve of the last partition sampling branch pipe opens in place; the pneumatic valves of the partition sampling branch pipes perform patrol measurements in turn according to the set time until they receive the PLC purge command and enter the sequential purge mode; after the sequential purge mode is put into use, the partition sampling branches of each route are purged first; the pneumatic valves of the partition sampling main pipe are closed. Close. After the pneumatic valve of the partition sampling main pipe is closed, open the pneumatic valve of the purge pipeline and the pneumatic valve of the first partition sampling branch pipe first, and then open the pneumatic valves of the subsequent partition sampling branches one by one. The pneumatic valve of the previous partition sampling branch pipe is closed according to the opening state of the subsequent one. When all the partition sampling branches are purged, purge the partition sampling main pipe. Open the pneumatic valve of the partition sampling main pipe first, and close the pneumatic valve of the last partition sampling branch pipe for purging. After the purging is completed, the PLC control system automatically performs patrol sampling, and displays the measured NOx concentration values ​​of each partition at the SCR outlet on the screen, providing a basis for the dynamic adjustment of the opening of the automatic valve of the subsequent inlet ammonia spray grid partition.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The system of the present invention can realize accurate sampling of NOx concentrations in different areas of the denitrification system by setting up a partition sampling main pipe and multiple partition sampling branches, which is helpful to capture the distribution characteristics of NOx in different areas and provide more accurate data support for subsequent measurement and control. By measuring the NOx concentration at the outlet of each partition, the opening of the automatic regulating valve corresponding to each partition of the inlet ammonia spray grid is dynamically adjusted to achieve dynamic matching of NOx concentration and ammonia flow rate in each partition, so as to achieve the purpose of real-time optimization of the uniformity of the ammonia nitrogen molar ratio distribution at the catalyst inlet. The real-time monitoring of NOx concentration is realized through the PLC system, and the operating parameters of the denitrification system can be automatically adjusted according to the measurement results, so as to realize efficient control and management of NOx emissions, and avoid the increase of ammonia consumption and the blockage of ammonia bisulfate in downstream equipment due to the uneven distribution of NOx and ammonia escape concentrations at the SCR outlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 It is a structural schematic diagram of the sampling pipeline system of the present invention.

[0019] Among them: 1-partition sampling main pipe; 2-partition sampling branch pipe; 3-partition sampling branch pipe pneumatic valve; 4-first purge pipeline manual valve; 5-purge pipeline pneumatic valve; 6-second purge pipeline manual valve; 7-partition sampling main pipe pneumatic valve; 8-flue gas sampling pool; 9-remote thermometer. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0024] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0025] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings: The first purpose of the present invention is to provide a NOx zoned sampling and measurement control system based on the differential pressure method. The present invention mainly relies on the differential pressure between the air preheater outlet flue and the denitrification outlet flue to achieve automatic induced ejection without the need for additional power. The system specifically includes a sampling pipeline system, a flue gas measurement system and a PLC control system. The sampling pipeline system is connected to the flue gas measurement system. The PLC control system is respectively connected to the sampling pipeline system and the flue gas measurement system. The sampling pipeline system includes a zoned sampling main pipe 1. One end of the zoned sampling main pipe 1 is connected to the denitrification inlet pipe, and the other end is connected to the air preheater outlet flue. A number of zoned sampling branches 2 are arranged on the zoned sampling main pipe 1.

[0027] The system of the present invention can realize accurate sampling of NOx concentration in different areas of the denitrification system by setting up a partition sampling main pipe 1 and multiple partition sampling branch pipes 2, which is helpful to capture the distribution characteristics of NOx in different areas and provide more accurate data support for subsequent measurement and control. At the same time, combined with the high-precision measurement technology of the flue gas measurement system, the accuracy and reliability of the measurement results can be ensured. The introduction of the PLC control system makes the entire sampling and measurement process automated and intelligent. The PLC system can receive data from the sampling pipeline system and the flue gas measurement system in real time, and quickly process and analyze according to the preset algorithm and logic. Not only can the real-time monitoring of NOx concentration be realized, but also the operating parameters of the denitrification system can be automatically adjusted according to the measurement results, so as to realize efficient control and management of NOx emissions. By accurately measuring the NOx concentration in different areas, the system can promptly discover deficiencies and potential problems in the denitrification process. For example, if it is found that the NOx concentration in a certain area is abnormally high, the ammonia injection amount in the area can be adjusted immediately or the denitrification reaction conditions can be optimized to improve the denitrification efficiency and reduce NOx emissions, which helps to optimize the denitrification effect and reduce environmental pollution.

[0028] Secondly, the present invention can determine the number of outlet flue zone sampling branches 2 according to the number of automatic adjustment valves of the inlet ammonia spraying grid of Selective Catalytic Reduction (SCR). Generally, the number of zone sampling branches 2 of units of 300MW and above is not less than 6; the pipe diameter ratio of the zone sampling branch 2 and the zone sampling main pipe 1 is determined according to the CFD numerical simulation results to ensure that the internal flue gas flow deviation of each sampling branch is less than 10%. Each zone sampling branch 2 is arranged with no less than 3 flue gas sampling ports in the depth direction, in order to ensure that the three-point sampling in the zone can represent the mean value of the NOx concentration of the zone cross section after mixing, so as to avoid misadjustment in the subsequent zone ammonia spraying leveling due to the lack of cross-sectional representativeness of the NOx measurement value of the zone. In principle, the zone sampling branch 2 and the flue gas sampling port are arranged according to the equal cross-section grid method.

[0029] like Figure 1 As shown, a partition sampling branch pipe pneumatic valve 3 is provided between the partition sampling branch pipe 2 and the partition sampling main pipe 1. A first purge pipeline manual valve 4 and a second purge pipeline manual valve 6 are provided between the partition sampling main pipe 1 and the denitrification inlet pipe. A purge pipeline pneumatic valve 5 is provided between the first purge pipeline manual valve 4 and the second purge pipeline manual valve 6. The introduction of the partition sampling branch pipe pneumatic valve 3 enables each partition sampling branch pipe 2 to be opened and closed independently. The first purge pipeline manual valve 4 and the second purge pipeline manual valve 6, as well as the purge pipeline pneumatic valve 5 between them, together constitute an efficient purge system. After the sampling is completed, the system can remove the residual flue gas and impurities by injecting a purge medium such as compressed air or nitrogen into the sampling pipeline to prevent pipeline blockage and pollution. At the same time, due to the coordinated use of the pneumatic valve and the manual valve, the system is more convenient during normal operation and maintenance. When the sampling pipeline or measurement system needs to be maintained, the corresponding manual valve can be closed to isolate the fault area to avoid affecting the entire system. In addition, the first purge pipeline manual valve 4 and the second purge pipeline manual valve 6 are normally open valves during normal operation and are only used when the purge pipeline pneumatic valve 5 fails or is under maintenance.

[0030] The partition sampling main pipe 1 is provided with a partition sampling main pipe pneumatic valve 7; the partition sampling branch pipe 2 is arranged upstream of the partition sampling main pipe pneumatic valve 7. The partition sampling main pipe 1 is provided with a flue gas sampling pool 8; the flue gas sampling pool 8 is arranged downstream of the partition sampling main pipe pneumatic valve 7. The partition sampling main pipe 1 is provided with a remote thermometer 9, and the remote thermometer 9 is arranged downstream of the flue gas sampling pool 8. The remote thermometer 9 can monitor the blockage of the upstream pipeline of the partition flue gas analyzer. If the monitored temperature is low, it means that there is a risk of fly ash blockage in the pipeline.

[0031] The air preheater outlet flue is provided with a CEMS room; the flue gas measurement system includes a zoned flue gas analyzer and an analyzer sampling probe connected thereto; a zoned flue gas analyzer is installed in the CEMS room; the analyzer sampling probe is arranged in a flue gas sampling pool 8. The flue gas enters through the analyzer sampling probe, is extracted by the built-in pump of the flue gas analyzer, and is then discharged to the air preheater outlet flue after dust removal, water removal and cooling by the flue gas analyzer. The flue gas analyzer is connected to the PLC control program to realize continuous monitoring of the flue gas (NO / O2) in the zoned sampling main pipe 1, and the continuous monitoring data is processed to obtain the NO / O2 measurement value of each zoned branch outlet.

[0032] The PLC control system is arranged in the CEMS room; the partition sampling branch pipe pneumatic valve 3, the purge pipeline pneumatic valve 5, the partition sampling main pipe pneumatic valve 7 and the partition flue gas analyzer are all connected to the PLC control cabinet through hard wiring. The PLC control system can control the switch of each partition sampling branch pipe pneumatic valve 3, the partition sampling main pipe pneumatic valve 7 and the purge pipeline pneumatic valve 5, and realize the automatic sampling, automatic purge and NO / O2 partition data measurement and display of the partition sampling system.

[0033] The second object of the present invention is to provide a method for using a NOx zone sampling and measurement control system based on a differential pressure method, which specifically comprises the following steps: Close all pneumatic valves. After detecting that the pneumatic valve 5 of the purge pipeline is closed in place, the PLC control system opens the partition sampling main pipe pneumatic valve 7 and the first partition sampling branch pipe pneumatic valve 3 at the same time. After the set time, the next partition sampling branch pipe pneumatic valve 3 opens. After the next partition sampling branch pipe pneumatic valve 3 opens in place, the previous partition sampling branch pipe pneumatic valve 3 will be closed until the last partition sampling branch pipe pneumatic valve 3 opens in place; the partition sampling branch pipe pneumatic valve 3 performs patrol measurement according to the set time in turn until it receives the PLC purge command and enters the sequential purge mode; after the sequential purge mode is put into use, the partition sampling branch pipes 2 of each route are purged first; the partition sampling main pipe pneumatic valve 7 is closed, After the partition sampling main pipe pneumatic valve 7 is closed, first open the pneumatic valve 5 of the purge pipeline and the pneumatic valve 3 of the first partition sampling branch pipe, and then open the pneumatic valves 3 of the subsequent partition sampling branch pipes one by one, and the pneumatic valve 3 of the previous partition sampling branch pipe is controlled to close according to the opening state of the subsequent one; when all the partition sampling branches 2 are purged, purge the partition sampling main pipe 1; first open the pneumatic valve 7 of the partition sampling main pipe, and close the pneumatic valve 3 of the last partition sampling branch pipe for purge; purge; after the purge is completed, the PLC control system automatically performs patrol sampling, and displays the measured NOx concentration values ​​of each partition at the SCR outlet on the screen, providing a basis for the subsequent dynamic adjustment of the automatic valve opening of the inlet ammonia spray grid partition.

[0034] Among them, the PLC control system function design is as follows: Take the example of 6 partition sampling branches 2. After the mode is put into operation, all pneumatic valves are closed. After detecting that the pneumatic valve 5 of the purge pipeline is closed, the PLC control system simultaneously opens the partition sampling main pipe pneumatic valve 7 and the first partition sampling branch pipe pneumatic valve 3. After the set pre-pumping time T1 (default 20 seconds) plus the sampling analysis time T2 (default 5 seconds), the next partition sampling branch pipe pneumatic valve 3 is opened. After the pneumatic valve 3 of the next partition sampling branch pipe is opened, the pneumatic valve 3 of the previous partition sampling branch pipe will be closed. The pneumatic valve 7 of the partition sampling main pipe is always in the open state, and the pneumatic valve of the purge pipeline is always in the closed state. The pneumatic valve 3 of the partition sampling branch pipe performs patrol measurement in the order of 1-6 according to the set pre-pumping time T1 and sampling analysis time T2 until it enters the sequential purge mode after receiving the PLC purge command.

[0035] The pre-pumping time T1 is used to exhaust the residual flue gas in the partition sampling main pipe 1. This data can be assigned in combination with the on-site commissioning test; the sampling analysis time T2 is the NO / O2 analysis and measurement time of the partition sampling branch pipe 2 of this road. The average value of the NO / O2 data measured by the flue gas analyzer within the T2 time is used as the NO / O2 measurement value of the partition branch pipe of this road. T1 and T2 data can be manually modified on the PLC control system.

[0036] (2) Sequential purge mode Sequential purging is to purge all partition sampling branch pipes 2 and the main pipe one by one in sequence.

[0037] After the purge mode is put into use, purge the 6-way partition sampling branch pipe 2 first. The partition sampling main pipe pneumatic valve 7 is closed. After the partition sampling main pipe pneumatic valve 7 is closed, open the purge pipeline pneumatic valve 5 and the first partition sampling branch pipe pneumatic valve 3 first, and purge according to the branch pipe purge time T3 (default 20 seconds) and the main pipe purge time T4 (default 30s) set by the PLC control system. The branch pipe valves behind are opened one by one, and the previous branch pipe valve is closed according to the opening state of the next one. When the 6-way partition sampling branch pipe 2 is purged, purge the partition sampling main pipe 1. First open the partition sampling main pipe pneumatic valve 7, close the 6th partition sampling branch pipe pneumatic valve 3, and purge. After the 6 sampling branch pipes + 1 sampling main pipe are purged, this round of sequential purge is completed. T3 and T4 data can be manually modified on the PLC control system.

[0038] (3) Exit inspection sampling mode In the outlet patrol sampling mode, the system will automatically perform regular purges based on multiples of the purge time intervals of the denitrification outlet partition CEMS analyzer's own probe and sampling pipeline.

[0039] If the automatic purge time interval is 3 times (settable), that is, every time the CEMS analyzer probe and sampling pipeline are purged 3 times, the outlet partition patrol sampling system will automatically purge once. This setting scheme can ensure the automatic purge of the outlet partition patrol sampling system and the synchronous purge of the denitrification outlet partition CEMS analyzer, avoiding the error of NOx data measured by the CEMS analyzer due to the automatic purge of the outlet partition patrol sampling system, which in turn affects the automatic control of the denitrification ammonia injection amount.

[0040] (4) Remote and local switching operation The PLC control system can exchange data with the DCS system through communication, measure the NOx concentration value of each partition at the SCR outlet, and display the NOx concentration value on the DCS screen, providing a basis for the subsequent dynamic adjustment of the automatic valve opening of the inlet ammonia injection grid partition.

[0041] Before DCS remote operation, the button on the local PLC cabinet touch screen needs to be set to "remote" to operate, otherwise it can only monitor data remotely; after remote operation, the DCS host computer interface can achieve the same functions as the on-site PLC cabinet touch screen. On the contrary, if the on-site PLC cabinet touch screen operation is required, the mode needs to be switched to "local".

[0042] The NOx zoning sampling and measurement control system based on the differential pressure method proposed in the present invention can realize the automatic injection of the sampled flue gas in each zone based on the differential pressure method without external power; through the NOx inspection, the number of flue gas analyzers supporting the system can be guaranteed to be the minimum, reducing the initial investment, operation and maintenance costs; the NOx data of each zone obtained by the inspection can be used to guide the automatic adjustment of the pneumatic regulating valve of the inlet ammonia grid zone. It ensures the accurate and timely measurement of the NOx concentration in each zone of the SCR outlet, and avoids the blockage of the downstream equipment ammonia bisulfate ABS due to the uneven distribution of NOx and ammonia escape concentration at the SCR outlet.

[0043] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. 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. A NOx zone sampling and measurement control system based on differential pressure method, characterized in that: The invention comprises a sampling pipeline system, a flue gas measurement system and a PLC control system; the sampling pipeline system is connected to the flue gas measurement system; the PLC control system is respectively connected to the sampling pipeline system and the flue gas measurement system; the sampling pipeline system comprises a partition sampling main pipe (1); one end of the partition sampling main pipe (1) is connected to the denitrification inlet pipe, and the other end is connected to the air preheater outlet flue; a plurality of partition sampling branch pipes (2) are arranged on the partition sampling main pipe (1).

2. A NOx zone sampling and measurement control system based on differential pressure method according to claim 1, characterized in that: A partition sampling branch pipe pneumatic valve (3) is provided between the partition sampling branch pipe (2) and the partition sampling main pipe (1).

3. A NOx zone sampling and measurement control system based on differential pressure method according to claim 2, characterized in that: A first purge pipeline manual valve (4) and a second purge pipeline manual valve (6) are provided between the partition sampling main pipe (1) and the denitration inlet pipe.

4. A NOx zone sampling and measurement control system based on differential pressure method according to claim 3, characterized in that: A purge pipeline pneumatic valve (5) is provided between the first purge pipeline manual valve (4) and the second purge pipeline manual valve (6).

5. A NOx zone sampling and measurement control system based on differential pressure method according to claim 4, characterized in that: The partitioned sampling main pipe (1) is provided with a partitioned sampling main pipe pneumatic valve (7); the partitioned sampling branch pipe (2) is arranged upstream of the partitioned sampling main pipe pneumatic valve (7).

6. A NOx zone sampling and measurement control system based on differential pressure method according to claim 5, characterized in that: The partitioned sampling main pipe (1) is provided with a smoke sampling pool (8); the smoke sampling pool (8) is arranged downstream of the partitioned sampling main pipe pneumatic valve (7).

7. A NOx zone sampling and measurement control system based on differential pressure method according to claim 6, characterized in that: The partition sampling main pipe (1) is provided with a remote thermometer (9), and the remote thermometer (9) is arranged downstream of the flue gas sampling pool (8).

8. A NOx zone sampling and measurement control system based on differential pressure method according to claim 6, characterized in that: The air preheater outlet flue is provided with a CEMS cabin; the flue gas measurement system comprises a partitioned flue gas analyzer and an analyzer sampling probe connected thereto; the partitioned flue gas analyzer is installed in the CEMS cabin; the analyzer sampling probe is arranged in a flue gas sampling pool (8).

9. A NOx zone sampling and measurement control system based on differential pressure method according to claim 8, characterized in that: The PLC control system is arranged in the CEMS room; the zoned sampling branch pipe pneumatic valve (3), the purge pipeline pneumatic valve (5), the zoned sampling main pipe pneumatic valve (7) and the zoned flue gas analyzer are all connected to the PLC control system.

10. A method for using a NOx zone sampling and measurement control system based on a differential pressure method, characterized in that: The specific steps include: All pneumatic valves are closed. After detecting that the pneumatic valve (5) of the purge pipeline is closed, the PLC control system simultaneously opens the partition sampling main pipe pneumatic valve (7) and the first partition sampling branch pipe pneumatic valve (3). After the set time, the next partition sampling branch pipe pneumatic valve (3) is opened. After the next partition sampling branch pipe pneumatic valve (3) is opened, the previous partition sampling branch pipe pneumatic valve (3) is closed until the last partition sampling branch pipe pneumatic valve (3) is opened. The partition sampling branch pipe pneumatic valve (3) performs patrol measurement in turn according to the set time until it receives the PLC purge command and enters the sequential purge mode. After the sequential purge mode is put into use, the partition sampling branch pipes (2) of each route are purged first; the partition sampling main pipe pneumatic valve (7) After the partition sampling main pipe pneumatic valve (7) is closed, the purge pipeline pneumatic valve (5) and the first partition sampling branch pipe pneumatic valve (3) are opened first, and the subsequent partition sampling branch pipe pneumatic valves (3) are opened one by one, and the previous partition sampling branch pipe pneumatic valve (3) is controlled to close according to the opening state of the subsequent one; when all the partition sampling branch pipes (2) are purged, the partition sampling main pipe (1) is purged; the partition sampling main pipe pneumatic valve (7) is opened first, and the last partition sampling branch pipe pneumatic valve (3) is closed to carry out purging; after the purging is completed, the PLC control system automatically performs patrol sampling, and displays the measured NOx concentration values ​​of each partition at the SCR outlet on the screen, providing a basis for the subsequent dynamic adjustment of the opening degree of the automatic valve of the inlet ammonia spray grid partition.

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