Patrol type SCR precise ammonia spraying measurement and control system and method

Abstract

The invention discloses a patrol type SCR precise ammonia spraying measurement and control system and method. The system comprises a plurality of probes; a probe is arranged under each SCR ammonia spraying area, one probe serves as a standard probe, the tail end of the standard probe is connected with a first CEMS analysis cabinet, the other probes serve as patrol probes, and the tail ends of all the patrol probes are jointly connected with a second CEMS analysis cabinet. And the problems of serious lagging and poor representativeness existing in the conventional patrol measurement type NOx measurement technology can be effectively solved.

Description

Technical Field

[0001] The present invention belongs to the field of SCR denitration, and relates to a patrol-type SCR precise ammonia injection measurement and control system and method. Background Art

[0002] With the increasing requirements for environmental protection, SCR denitrification precision ammonia injection technology has been widely used in coal-fired units. Conventional precision ammonia injection modification technology can be divided into two types according to different NOx measurement technologies: patrol type and simultaneous measurement type. The simultaneous measurement type generally sets a set of CEMS analyzers at the inlet and outlet flues of the denitrification reactor, and controls the amount of ammonia injection according to the deviation between the CEMS test results at the denitrification outlet and the set value, so as to realize automatic control of NOx emissions.

[0003] Due to the large size of the SCR denitrification flue, the poor representativeness of the CEMS measurement points, and the different ammonia requirements in different areas under different working conditions, it is easy to cause uneven ammonia injection, resulting in excessive ammonia escape, and thus causing blockage and corrosion problems in downstream equipment such as air preheaters. For this reason, different forms of precision ammonia injection technology have been widely used. Its main principle is to divide the denitrification flue into smaller partitions and coordinate and automatically control the ammonia injection amount of each partition to improve the impact of the above problems. Due to the high cost of CEMS equipment, most of the current precision ammonia injection renovation projects use a patrol-type CEMS measurement and control system. The patrol-type uses an analyzer to patrol and measure the NOx concentration in different partitions, while the simultaneous measurement type uses an analyzer that matches the number of partitions to simultaneously measure the NOx concentration in each partition. The patrol-type technology is relatively more economical in investment and has many application cases. The latest patrol technology often uses flue gas sampling probes that are consistent with the number of partitions and are arranged at the outlet flue of each partition. The NOx concentration at each point is tested by the same flue gas analyzer. The amount of ammonia sprayed in each partition is adjusted according to the deviation between the NOx test results of the partition and the average of the NOx test results of each partition, so as to achieve a precise ammonia spray effect. When the patrol method is used, the total amount of SCR ammonia spray control is realized by using the original denitrification inlet and outlet NOx measurement system, and the leveling between partitions is controlled according to the deviation between the NOx test results of each point of the newly added partition patrol system and the average of the NOx test results of each partition. The total amount of ammonia spray control and the partition leveling control are independent of each other.

[0004] The above technology has the following problems: Affected by factors such as boiler combustion conditions and fluctuations in the total amount of ammonia injection, the NOx concentration at the denitrification outlet section fluctuates at different amplitudes. Therefore, the control given value (average NOx value of each partition) used by the patrol technology is actually the average value of the NOx concentration of each partition at different times, which itself has serious hysteresis. In addition, when the NOx at the denitrification outlet section fluctuates violently in a short period of time, it cannot effectively reflect the actual situation of the average NOx value at the denitrification outlet section, which is easy to cause misadjustment. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a patrol-type SCR precise ammonia injection measurement and control system and method, which can effectively improve the serious lag and poor representativeness of the current patrol-type NOx measurement technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A patrol-type SCR precise ammonia injection measurement and control system, comprising a plurality of probes; A probe is arranged directly below each SCR ammonia injection area. One of the probes is used as a standard probe, and the end of the standard probe is connected to the first CEMS analysis cabinet. The remaining probes are used as patrol probes, and the ends of all patrol probes are connected to a second CEMS analysis cabinet.

[0007] Preferably, in each SCR ammonia injection area, a partition pipe is branched downward from the SCR ammonia injection main pipe, a plurality of ammonia injection branch pipes are connected to the bottom of the partition pipe, and a nozzle is connected to the end of each ammonia injection branch pipe.

[0008] Furthermore, each partition pipeline is provided with a partition regulating valve.

[0009] Preferably, a denitrification inlet probe is also provided in the denitrification flue, the denitrification inlet probe is located above the SCR ammonia injection main pipeline, and the denitrification inlet probe is connected to a third CEMS analysis cabinet.

[0010] Preferably, a sampling pump is provided between the probe and the CEMS analysis cabinet.

[0011] An ammonia injection measurement and control method includes the following process: The standard probe collects gas from the corresponding SCR ammonia injection area, and the first CEMS analysis cabinet performs analysis to obtain the ammonia injection amount of the SCR ammonia injection area; Each patrol probe collects gas corresponding to the SCR ammonia injection area in turn according to the set period, and the second CEMS analysis cabinet receives the gas collected by each patrol probe in turn, and analyzes them one by one to obtain the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe; Take the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe as the standard value, calculate the difference between the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe and the standard value, and adjust the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe according to the difference, so that the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe is consistent with the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe.

[0012] Preferably, when the opening of the partition regulating valve corresponding to the SCR ammonia injection area of ​​a certain patrol probe exceeds the limit, the opening of the partition regulating valve corresponding to the SCR ammonia injection area of ​​the standard probe is increased.

[0013] Preferably, the amount of ammonia injected in the ammonia injection area of ​​the SCR is adjusted by adjusting the opening of the zone regulating valve of the corresponding zone pipeline.

[0014] Preferably, the collection setting period of the patrol probe is 30-120s.

[0015] Preferably, according to the total number of areas, the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe is multiplied by the total number of areas to calculate the total ammonia injection amount of the denitrification outlet flue.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention connects the end of the standard probe to a first CEMS analysis cabinet separately, and the ends of the remaining patrol probes are commonly connected to a second CEMS analysis cabinet, so that the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe can be used as a reference object for the ammonia injection amount of the SCR ammonia injection area corresponding to the remaining patrol probes. The ammonia injection amount of the SCR ammonia injection area corresponding to the remaining patrol probes is adjusted according to the difference with the standard value. The standard probe does not participate in the patrol process, and always collects the gas in the corresponding SCR ammonia injection area without delay, and the patrol cycle of the patrol probe is reduced, thereby avoiding the serious lag and poor representativeness of the conventional patrol-type NOx measurement technology, and effectively combining the zone leveling control system and the total ammonia injection control system to make the adjustment more stable; and the system can replace one of the original patrol CEMS probes with the original denitrification outlet CEMS probe, and directly improve the original patrol-type SCR ammonia injection measurement and control system without adding new probes and equipment, thereby reducing equipment investment to a certain extent.

[0017] Furthermore, the amount of ammonia injected in a single SCR ammonia injection area can be directly adjusted through the zone regulating valve, which is flexible and convenient.

[0018] Furthermore, through the denitrification inlet probe and the third CEMS analysis cabinet, nitrogen oxides, oxygen and ammonia at the denitrification flue inlet can be detected, thereby improving the monitoring of the SCR denitrification process.

[0019] Furthermore, the sampling pump can suck the gas at the probe into the CEMS analysis cabinet, and blow air outward in the opposite direction after the sampling is completed to clean the probe and prevent smoke from entering and accumulating in the probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the precise ammonia injection measurement and control of the patrol-type SCR of the present invention.

[0021] Among them: 1-standard probe; 2-patrol probe; 3-denitrification inlet probe; 4-first CEMS analysis cabinet; 5-second CEMS analysis cabinet; 6-third CEMS analysis cabinet; 7-SCR ammonia injection main pipeline; 8-partition pipeline; 9-partition regulating valve. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs. The terms "installed", "connected", and "connected" 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, an electrical connection, or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" used in this article includes any and all combinations of one or more related listed items. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0025] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0026] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0027] Example 1 like Figure 1 As shown, a patrol-type SCR precise ammonia injection measurement and control system according to the present invention includes multiple groups of probes.

[0028] According to the patrol method, the denitrification flue is horizontally divided into multiple areas, and the SCR ammonia injection pipeline is divided into multiple SCR ammonia injection areas according to the partitions, and the same number and structure of nozzles are set in each SCR ammonia injection area.

[0029] The SCR ammonia spraying main pipeline 7 extends into the denitrification flue. In each SCR ammonia spraying area, a partitioning pipeline 8 is branched downwards. A plurality of ammonia spraying branch pipelines are connected to the bottom of the partitioning pipeline 8. A nozzle is connected to the end of each ammonia spraying branch pipeline for spraying a mixed gas of ammonia and air downwards.

[0030] Wherein, each partition pipeline 8 is provided with a partition regulating valve 9, and by controlling the opening of the partition regulating valve 9, the amount of ammonia sprayed in the SCR ammonia spraying area can be adjusted to achieve a precise ammonia spraying effect.

[0031] The number of probes is the same as the number of areas. A probe is set directly under each SCR ammonia spraying area, and the distance between each probe and the SCR ammonia spraying area is 10-20m.

[0032] One of the probes is used as the standard probe 1. The standard probe 1 directly adopts the original denitrification outlet CEMS probe, and the end is connected to the first CEMS analysis cabinet 4. The first CEMS analysis cabinet 4 adopts the original denitrification outlet CEMS analysis cabinet. The original denitrification outlet CEMS analysis cabinet only receives the gas collected by the original denitrification outlet CEMS probe, and analyzes it to obtain the ammonia injection amount of the SCR ammonia injection area; the original denitrification outlet CEMS probe and the original denitrification outlet CEMS analysis cabinet are used to continuously detect the ammonia injection amount of the corresponding area, and according to the total number of areas, the ammonia injection amount of the corresponding area is multiplied by the total number of areas to calculate the total ammonia injection amount of the denitrification outlet flue.

[0033] The remaining probes except the standard probe 1 are used as patrol probes 2. The patrol probes 2 directly adopt the original patrol CEMS probes without adding new probes. The ends of these original patrol CEMS probes are connected to a second CEMS analysis cabinet 5. The second CEMS analysis cabinet 5 adopts the original patrol CEMS analysis cabinet. The original patrol CEMS analysis cabinet receives the gases collected by all the original patrol CEMS probes, and analyzes them one by one to obtain the results; the original patrol CEMS probes are used to collect the gases corresponding to the SCR ammonia injection area according to the set period, and the original patrol CEMS analysis cabinet is used to receive the gases collected by each original patrol CEMS probe in turn, and analyze them one by one to obtain the ammonia injection amount of the SCR ammonia injection area corresponding to each original patrol CEMS probe.

[0034] The above-mentioned patrol-type SCR precise ammonia injection measurement and control system can be directly improved on the original patrol-type SCR ammonia injection measurement and control system by replacing one of the original patrol CEMS probes with the original denitrification outlet CEMS probe. There is no need to add new probes and equipment, and it can also meet the measurement and control of the partitioned ammonia injection amount and the total ammonia injection amount.

[0035] A denitrification inlet probe 3 is also provided in the denitrification flue. The denitrification inlet probe 3 is located above the SCR ammonia injection main pipeline 7 and at the center of the denitrification flue. The denitrification inlet probe 3 is connected to a third CEMS analysis cabinet 6 for denitrification inlet gas analysis.

[0036] Using CEMS analysis cabinet to detect ammonia (NH3) is one of the detection functions of CEMS system. CEMS system can also detect nitrogen oxides (NO x ) and oxygen (O2) are monitored and controlled in real time. This monitoring process is critical to ensure the effective operation of the SCR system, optimize the denitrification efficiency and avoid ammonia slip (i.e. excessive ammonia content in the flue gas).

[0037] The CEMS analysis cabinet uses a sampling pump to directly extract the flue gas collected by the probe into the analyzer for measurement. In this process, in order to ensure the accuracy of the measurement, the sample gas needs to be pre-treated, including heating the probe and pipeline to prevent the sample gas from condensing, and removing impurities such as particulate matter and moisture in the sample gas. The pre-treated sample gas enters the analyzer, and the concentration of components in the flue gas is analyzed by a specific detection method.

[0038] Main detection components and principles: Nitrogen oxides (NO x ): Detection method: usually non-dispersive infrared absorption (NDIR) or ultraviolet absorption spectroscopy (UV) is used for detection. These technologies can accurately measure the concentration of nitrogen oxides in flue gas and provide basic data for the calculation of denitrification efficiency.

[0039] Function: Monitoring the concentration of nitrogen oxides helps to evaluate the denitrification effect of the SCR system and adjust the amount of ammonia injection according to the actual situation to achieve the expected denitrification target.

[0040] Oxygen (O2): Detection method: Non-dispersive infrared absorption method and other methods can also be used for detection. Monitoring of oxygen concentration is of great significance for understanding the oxygen supply during the combustion process and the environmental conditions of the SCR reaction.

[0041] Function: Changes in oxygen concentration may affect the efficiency of the SCR reaction, so the operating parameters of the SCR system can be further optimized by monitoring the oxygen concentration.

[0042] Ammonia (NH3): Detection method: For the detection of ammonia, chemiluminescence (CLD) or spectrophotometry are often used. These technologies can accurately measure the escape amount of ammonia in the flue gas and ensure that the amount of ammonia sprayed is controlled within a reasonable range.

[0043] Function: Monitoring ammonia escape is crucial to prevent secondary pollution caused by excessive ammonia injection and protect the SCR catalyst from damage. Generally, the ammonia escape at the outlet of the SCR reactor needs to be controlled at a low level (such as 2-3ppm) to ensure the economy and environmental protection of the system.

[0044] Key elements of CEMS system: Sampling system: The flue gas in the flue is safely and accurately extracted into the analyzer through the probe. The sampling system needs to have the ability to operate stably in harsh environments such as high temperature and high dust.

[0045] Pretreatment system: perform pretreatment operations such as dehumidification and dust removal on the sample gas to ensure the measurement accuracy of the analyzer.

[0046] Analyzer: Uses high-precision detection technology and algorithms to perform real-time analysis of components in the sample gas.

[0047] Data processing and control system: Process and analyze the measurement data of the analyzer, and adjust the operating parameters such as the amount of ammonia injection according to the preset control logic.

[0048] Example 2 The process of measuring and controlling ammonia injection by using the patrol-type SCR precise ammonia injection measurement and control system described in Example 1 is as follows: The standard probe 1 collects gas from the SCR ammonia injection area corresponding thereto, and the first CEMS analysis cabinet 4 performs analysis to obtain the ammonia injection amount of the SCR ammonia injection area.

[0049] Each patrol probe 2 collects gas corresponding to the SCR ammonia injection area in sequence according to a set period, and the second CEMS analysis cabinet 5 receives the gas collected by each patrol probe 2 in sequence, and analyzes one by one to obtain the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe 2.

[0050] The setting period is generally 30-120s. In this embodiment, the setting period is 60s.

[0051] Take the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe 1 as the standard value, calculate the difference between the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe 2 and the standard value, and adjust the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe 2 according to the difference, so that the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe 2 is consistent with the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe 1.

[0052] The ammonia injection amount of each patrol probe 2 corresponding to the SCR ammonia injection area is regulated by adjusting the opening of the partition regulating valve 9 of the corresponding partition pipeline 8, thereby regulating the ammonia injection amount in the SCR ammonia injection area.

[0053] According to the total number of areas, multiply the ammonia injection amount of the SCR ammonia injection area corresponding to standard probe 1 by the total number of areas to calculate the total ammonia injection amount of the denitrification outlet flue.

[0054] Under normal circumstances, the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe 1 remains unchanged, and the partition regulating valve 9 of the corresponding partition pipeline 8 is not adjusted. However, when the opening of the partition regulating valve 9 of the remaining SCR ammonia injection areas exceeds the limit, the opening of the partition regulating valve 9 of the SCR ammonia injection area corresponding to the standard probe 1 is increased.

[0055] 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.

[0056] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this patent should not be determined with reference to the above description, but rather with reference to the preceding claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a waiver of such subject matter, nor should it be considered that the applicant has not considered such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A patrol-type SCR precise ammonia injection measurement and control system, characterized in that: Includes multiple probes; A probe is arranged directly below each SCR ammonia injection area, one of the probes is used as a standard probe (1), the end of the standard probe (1) is connected to a first CEMS analysis cabinet (4), and the remaining probes are used as patrol probes (2), and the ends of all the patrol probes (2) are commonly connected to a second CEMS analysis cabinet (5).

2. The patrol-type SCR precise ammonia injection measurement and control system according to claim 1 is characterized in that: In each SCR ammonia spraying area, the SCR ammonia spraying main pipeline (7) branches out a partition pipeline (8) downwards, and a plurality of ammonia spraying branch pipelines are connected to the bottom of the partition pipeline (8), and a nozzle is connected to the end of each ammonia spraying branch pipeline.

3. The patrol-type SCR precise ammonia injection measurement and control system according to claim 2 is characterized in that: Each partition pipeline (8) is provided with a partition regulating valve (9).

4. The patrol-type SCR precise ammonia injection measurement and control system according to claim 1 is characterized in that: A denitrification inlet probe (3) is also provided in the denitrification flue. The denitrification inlet probe (3) is located above the SCR ammonia injection main pipeline (7). The denitrification inlet probe (3) is connected to a third CEMS analysis cabinet (6).

5. The patrol-type SCR precise ammonia injection measurement and control system according to claim 1 is characterized in that: A sampling pump is provided between the probe and the CEMS analysis cabinet.

6. A method for measuring and controlling ammonia injection based on the system according to any one of claims 1 to 5, characterized in that: The process includes: The standard probe (1) collects gas from the SCR ammonia spraying area corresponding thereto, and the first CEMS analysis cabinet (4) performs analysis to obtain the ammonia spraying amount of the SCR ammonia spraying area; Each patrol probe (2) collects gas corresponding to the SCR ammonia injection area in sequence according to a set period, and the second CEMS analysis cabinet (5) receives the gas collected by each patrol probe (2) in sequence, and analyzes the gas one by one to obtain the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe (2); The ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe (1) is taken as the standard value, the difference between the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe (2) and the standard value is calculated, and the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe (2) is adjusted according to the difference, so that the ammonia injection amount of the SCR ammonia injection area corresponding to each patrol probe (2) is consistent with the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe (1).

7. The patrol-type SCR precise ammonia injection measurement and control method according to claim 6 is characterized in that: When the opening degree of the partition regulating valve (9) corresponding to the SCR ammonia injection area of ​​a certain patrol probe (2) exceeds the limit, the opening degree of the partition regulating valve (9) corresponding to the SCR ammonia injection area of ​​the standard probe (1) is increased.

8. The patrol-type SCR precise ammonia injection measurement and control method according to claim 6 is characterized in that: The amount of ammonia sprayed in the ammonia spraying area of ​​the SCR is adjusted by adjusting the opening of the zone regulating valve (9) of the corresponding zone pipeline (8).

9. The patrol-type SCR precise ammonia injection measurement and control method according to claim 6 is characterized in that: The collection period of the patrol probe (2) is set to 30-120 seconds.

10. The patrol-type SCR precise ammonia injection measurement and control method according to claim 6 is characterized in that: According to the total number of zones, the ammonia injection amount of the SCR ammonia injection area corresponding to the standard probe (1) is multiplied by the total number of zones to calculate the total ammonia injection amount of the denitrification outlet flue.

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