Partitioned ammonia injection control method and system based on comprehensive calculation of velocity field and concentration field

Abstract

The application discloses a partitioned ammonia injection control method and system based on comprehensive calculation of a velocity field and a concentration field, and relates to the technical field of ammonia injection control. The partitioned ammonia injection system comprises a reactor mechanism, a partitioned ammonia injection device, a measuring mechanism and a control mechanism. The reactor mechanism comprises an inlet flue, an outlet flue and a catalytic reactor. The catalytic reactor is located between the inlet flue and the outlet flue. The catalytic reactor is divided into multiple partitions. The partitioned ammonia injection device comprises a nozzle array and an ammonia flow adjusting device. The nozzle array is arranged corresponding to each partition. The ammonia flow adjusting device is connected with the nozzle array. The measuring mechanism measures the flue gas flow rate and the nitrogen oxide concentration in the multiple partitions. The control mechanism is electrically connected with the ammonia flow adjusting device and the measuring mechanism. The partitioned ammonia injection system provided by the application has the advantages of accurate flue gas concentration and flow rate measurement and accurate ammonia distribution.

Description

Technical Field

[0001] This invention relates to the field of flue gas pollutant treatment technology, and in particular to a zoned ammonia injection control method and system based on comprehensive calculation of velocity field and concentration field. Background Technology

[0002] Coal-fired power plant boilers generate flue gas containing a large amount of pollutants during operation. Nitrogen oxides (NOx) in this gas pose a significant hazard to organisms and require control. In actual denitrification processes at power plants, excessive ammonia injection is a common problem, meaning too much NH3 (the reducing agent) is injected into the reactor, leaving some remaining after reacting with NOx in the flue gas. This excess NH3 wastes denitrification materials, increasing power plant costs. Furthermore, unreacted NH3 and acidic gases in the flue gas can easily form inorganic salts at the cold end of the air preheater, significantly increasing the risk of blockage. The main reasons for excessive ammonia injection are: 1. Inaccurate NOx measurement, resulting in NOx concentration data that does not represent the entire cross-section; 2. Inaccurate calculation of total NOx volume, failing to consider the impact of flow velocity at the measurement point on ammonia demand; and 3. Difficulty in accurately obtaining ammonia demand data in related technologies. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a zoned ammonia injection control method and system based on comprehensive calculation of velocity and concentration fields. This zoned ammonia injection control method and system based on comprehensive calculation of velocity and concentration fields has the advantages of accurate measurement of flue gas concentration and flow rate, and precise ammonia distribution.

[0004] According to an embodiment of the present invention, a zoned ammonia injection system includes a reactor structure, a zoned ammonia injection device, a measuring mechanism, and a control mechanism. The reactor structure includes an inlet flue, an outlet flue, and a catalytic reactor. The catalytic reactor is located between the inlet flue and the outlet flue and is divided into multiple zones. The zoned ammonia injection device includes a nozzle array and an ammonia flow regulating device. The nozzle array is arranged corresponding to each zone, and the ammonia flow regulating device is connected to the nozzle array. The measuring mechanism enters multiple zones to measure the flue gas velocity and nitrogen oxide concentration. The control mechanism is electrically connected to the ammonia flow regulating device and the measuring mechanism.

[0005] The zoned ammonia injection system according to embodiments of the present invention has the advantages of accurate measurement of flue gas concentration and flow rate, and precise ammonia distribution. This application improves the measurement accuracy of flue gas flow rate and flue gas component concentration by dividing the catalytic reactor into multiple zones using a zoned ammonia injection device in conjunction with a measuring mechanism, thereby enabling precise ammonia control in each zone to solve the problem of excessive ammonia injection.

[0006] In some embodiments, the catalytic reactors are arranged in layers, with a predetermined interval between each layer of catalytic reactors and the adjacent layer of catalytic reactors.

[0007] In some embodiments, the catalytic reactor is divided into partitions arranged in a matrix along both the length and width directions.

[0008] In some embodiments, the measuring device includes an electronic micromanometer and a flue gas analyzer.

[0009] The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to an embodiment of the present invention includes the following steps:

[0010] The catalytic reactor is divided into 'a' regions along its length and 'b' regions along its width. Each region is numbered F. 00 F 01 F 10 …F ij …F ab Among them, F ij This represents the i-th partition in the length direction and the j-th partition in the width direction. The measuring mechanism enters the center of the partition to obtain the flue gas dynamic pressure at that location. Based on the gas density under standard conditions, the static pressure at the center of the partition, and the atmospheric pressure, the density of a single component gas is calculated. The density of the multi-component flue gas is obtained by weighted summation of the components. The flue gas velocity at the center of the partition is obtained based on the density of the multi-component flue gas and the flue gas dynamic pressure.

[0011] The flue gas analyzer measures the oxygen and nitric oxide content in the flue gas at the center of the zone, and calculates the nitrogen oxide concentration at the center of the zone.

[0012] The total demand for ammonia is calculated by calculating the average concentration of nitrogen oxides in the flue gas based on the measurement data of all zones measured by the flue gas analyzer, obtaining the total nitrogen oxide content based on the total flue gas flow rate, and then calculating the total demand for ammonia based on the total nitrogen oxide content.

[0013] The ammonia demand for each zone is calculated based on the total ammonia demand, and then the ammonia injection amount for each zone is obtained. The ammonia injection amount for each zone is adjusted according to the flow rate of each zone, and the ammonia flow regulating device is used to adjust the ammonia injection amount for each zone according to the ammonia injection amount for each zone.

[0014] In some embodiments, based on the flue gas dynamic pressure p 动压 The formula for calculating the flue gas velocity v is as follows:

[0015] k 修正 ρ is the correction factor for the measuring device. 烟气 The density of the flue gas, ρ 标况 Let P be the density of a gas under standard conditions.静压 It is the static pressure at the center of the partition.

[0016] In some embodiments, the flue gas contains multiple component gases, ρ 烟气 The density of each component needs to be calculated separately, and the average value should be obtained based on its proportion. The specific formula is as follows:

[0017] ρ 烟气 =ρ1×b1+ρ2×b2+...+ρ i ×b i +...ρ n ×b n

[0018] Where, ρ i Let b be the density of component i in the flue gas. i To determine the mass fraction of component i in the flue gas, the density of the multi-component flue gas can be obtained by weighted summing of all components. From this, F can be obtained. ij The flue gas velocity at the center of the partition is recorded as v. ij ,

[0019] p 动压ij This represents the dynamic pressure measurement value at partition Fij.

[0020] In some embodiments, the measurement of nitrogen oxide concentration at the center of the partition is used to calculate the NOx concentration under standard conditions at a 6% oxygen concentration.

[0021]

[0022] Where NOx is the concentration of nitrogen oxides, and O real Let F be the oxygen content measured by the measuring device, NO be the NO volume content measured by the measuring device, coefficient n be the correction factor for converting NOx concentration from volume fraction to mass fraction, coefficient m be an empirical value, and NO be the percentage of total NOx. From this, F can be derived. ij NOx concentration N in the partition center ij .

[0023] In some embodiments, the total ammonia demand is calculated by averaging the measurements from all zones to obtain the overall nitrogen oxide concentration N in the flue gas. 均 :

[0024]

[0025] If the total flue gas flow rate is L, then the total NOx content in the flue gas is H. 总 for:

[0026] H 总 =d 修正 ×F均 ×L

[0027] Correction coefficient d 修正 Used to correct flue gas flow rate, total ammonia demand N 总 The calculation is as follows:

[0028]

[0029] Where, N 总 For the total demand of ammonia, H 总 The total NOx content in flue gas, H 出口 M is the target control value. 总 A represents the total coal consumption of the current generating unit; 总 Given the current total air volume of the unit, the total ammonia demand N can be calculated from this. 总 .

[0030] In some embodiments, F ij The ammonia demand of the zone is P. ij Then we have:

[0031] Because the flue gas velocity varies in each zone, the ammonia injection rate for each zone is adjusted. The adjusted ammonia injection rate for each zone is P. 修正ij for:

[0032] Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the partitioned ammonia injection system according to an embodiment of the present invention.

[0034] Attached reference numerals: 1. Zone; 2. Inlet flue; 3. Catalytic reactor; 4. Outlet flue; 5. Measuring mechanism; 6. Zone ammonia injection device. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] According to an embodiment of the present invention, a zoned ammonia injection system, such as Figure 1As shown, the zoned ammonia injection system includes a reactor structure, a zoned ammonia injection device, a measuring mechanism, and a control mechanism. The reactor structure includes an inlet flue, an outlet flue, and a catalytic reactor. The catalytic reactor is located between the inlet and outlet flues and is divided into multiple zones. The zoned ammonia injection device includes a nozzle array and an ammonia flow regulating device. The nozzle array is arranged corresponding to each zone, and the ammonia flow regulating device is connected to the nozzle array. The measuring mechanism enters multiple zones to measure the flue gas velocity and nitrogen oxide concentration. The control mechanism is electrically connected to the ammonia flow regulating device and the measuring mechanism. In the reactor structure, the flue gas containing nitrogen oxides is guided to the SCR catalyst area. After completing the denitrification reaction, the flue gas leaves the catalytic reactor area. The inlet and outlet flues are both rectangular cross-section, enclosed pipes made of metal. The measuring mechanism measures the flue gas velocity and nitrogen oxide concentration in the flue gas. The measuring mechanism extends into the center of each zone to perform measurements, providing a basis for controlling the ammonia injection rate. Each nozzle in the nozzle array corresponds to a zone, and the ammonia flow rate regulating device corresponds to each nozzle to meet the different ammonia flow rate requirements of different zones based on the measurement results.

[0037] The zoned ammonia injection system according to embodiments of the present invention has the advantages of accurate measurement of flue gas concentration and flow rate, and precise ammonia distribution.

[0038] In some embodiments, the catalytic reactors are arranged in layers, with a predetermined interval between each layer of catalytic reactors and the adjacent layer of catalytic reactors.

[0039] Specifically, the layered arrangement of the catalytic reactor can extend the catalytic time for flue gas, and the interval between each layer and the adjacent layer can further extend the flow time of the flue gas.

[0040] In some embodiments, the catalytic reactor is divided into partitions arranged in a matrix along both the length and width directions.

[0041] Specifically, the catalytic reactor is divided into multiple rectangular sections along its length and width. Dividing the catalytic reactor into multiple sections allows for more accurate determination of data such as flue gas concentration and flow rate within the reactor. This adapts to conditions of uneven flue gas velocity field and uneven distribution of nitrogen oxide concentration, enabling more precise determination and control of ammonia injection amount and avoiding excessive ammonia injection.

[0042] In some embodiments, the measuring device includes an electronic micromanometer and a flue gas analyzer.

[0043] Specifically, electronic micromanometers are used to measure the dynamic pressure of flue gas, while flue gas analyzers are used to measure the concentration of different components in the flue gas.

[0044] The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to an embodiment of the present invention includes the following steps:

[0045] The catalytic reactor is divided into 'a' regions along its length and 'b' regions along its width. Each region is numbered F. 00 F 01 F 10 …F ij …F ab Among them, F ij This represents the i-th partition in the length direction and the j-th partition in the width direction. The measuring mechanism enters the center of the partition to obtain the flue gas dynamic pressure at that location. The density of a single component gas is calculated based on the gas density under standard conditions, the static pressure at the center of the partition, and the atmospheric pressure. The density of the multi-component flue gas is obtained by weighted summation according to the components. The flue gas velocity at the center of the partition is obtained based on the density of the multi-component flue gas and the flue gas dynamic pressure. The flue gas velocity of each partition is obtained based on the flue gas pressure and flue gas density of each partition.

[0046] The flue gas analyzer measures the oxygen and nitric oxide content in the flue gas at the center of the zone, and calculates the nitrogen oxide concentration at the center of the zone.

[0047] The total demand for ammonia is calculated by calculating the average concentration of nitrogen oxides in the flue gas based on the measurement data of all zones measured by the flue gas analyzer, obtaining the total nitrogen oxide content based on the total flue gas flow rate, and then calculating the total demand for ammonia based on the total nitrogen oxide content.

[0048] The ammonia demand for each zone is calculated based on the total ammonia demand, thus obtaining the ammonia injection rate for each zone. The ammonia injection rate for each zone is then adjusted based on the flow rate of each zone. Finally, the ammonia injection rate for each zone is controlled by the ammonia flow regulating device to adjust the ammonia injection rate for each zone. The precise ammonia injection rate for each zone is obtained through the zone flow rate and the zone ammonia injection rate, allowing for precise adjustment of the ammonia injection rate for each zone.

[0049] In some embodiments, based on the flue gas dynamic pressure p 动压 The formula for calculating the flue gas velocity v is as follows:

[0050] k 修正 ρ is the correction factor for the measuring device. 烟气 The density of the flue gas, ρ 标况 Let P be the density of a gas under standard conditions. 静压 It represents the static pressure at the center of the partition. ρ 标况 Density data can be obtained by looking up a table. Static pressure refers to the pressure exerted by gas on the surface of an object parallel to the airflow, while dynamic pressure refers to the pressure that drives the gas forward.

[0051] In some embodiments, the flue gas contains multiple component gases, ρ 烟气 The density of each component needs to be calculated separately, and the average value should be obtained based on its proportion. The specific formula is as follows:

[0052] ρ 烟气 =ρ1×b1+ρ2×b2+...+ρ i ×b i +...ρ n ×b n

[0053] Where, ρ i Let b be the density of component i in the flue gas. i To determine the mass fraction of component i in the flue gas, the density of the multi-component flue gas can be obtained by weighted summing of all components. From this, F can be obtained. ij The flue gas velocity at the center of the partition is recorded as v. ij ,

[0054] p 动压ij This represents the dynamic pressure measurement value at partition Fij.

[0055] The composition of flue gas from coal combustion is quite complex, mainly including carbon dioxide, carbon monoxide, nitrogen oxides, sulfur oxides, oxygen, and water vapor. Therefore, the density ρ of flue gas needs to be calculated separately for each component, and the average value needs to be obtained based on their proportions.

[0056] In some embodiments, the measurement of nitrogen oxide concentration at the center of the partition is used to calculate the NOx concentration under standard conditions at a 6% oxygen concentration.

[0057]

[0058] Where NOx is the concentration of nitrogen oxides, and O real Let F be the oxygen content measured by the measuring device, NO be the NO volume content measured by the measuring device, coefficient n be the correction factor for converting NOx concentration from volume fraction to mass fraction, coefficient m be an empirical value, and NO be the percentage of total NOx. From this, F can be derived. ij NOx concentration N in the partition center ij .

[0059] The flue gas analyzer extracts a certain amount of flue gas from the center of the zone and uses sensors to measure the oxygen content and monoxide content. The coefficient n is 2.05 and the coefficient m is a specific value between 0.9 and 1.0.

[0060] In some embodiments, the total ammonia demand is calculated by averaging the measurements from all zones to obtain the overall nitrogen oxide concentration N in the flue gas. 均 :

[0061]

[0062] If the total flue gas flow rate is L, then the total NOx content in the flue gas is H. 总 for:

[0063] H 总 =d 修正 ×F 均 ×L

[0064] Correction coefficient d 修正 Used to correct flue gas flow rate, total ammonia demand N 总 The calculation is as follows:

[0065]

[0066] Where, N 总 For the total demand of ammonia, H 总 The total NOx content in flue gas, H 出口 M is the target control value. 总 A represents the total coal consumption of the current generating unit; 总 Given the current total air volume of the unit, the total ammonia demand N can be calculated from this. 总 .

[0067] Specifically, 2.68 is an empirical coefficient, H 出口 It is a specific value less than 50.

[0068] In some embodiments, F ij The ammonia demand of the zone is P. ij Then we have:

[0069] Because the flue gas velocity varies in each zone, the ammonia injection rate for each zone is adjusted. The adjusted ammonia injection rate for each zone is P. 修正ij for:

[0070] Based on the calculation structure of this formula, the flow control valves of each zone are adjusted to control the amount of ammonia obtained by each zone, thereby achieving high-precision zone ammonia injection control and avoiding excessive ammonia injection.

[0071] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0072] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0073] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0074] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0075] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0076] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field, characterized in that, The ammonia injection control system for implementing the method includes: The reactor structure includes an inlet flue, an outlet flue, and a catalytic reactor, wherein the catalytic reactor is located between the inlet flue and the outlet flue, and the catalytic reactor is divided into multiple zones. A zoned ammonia injection device, comprising a nozzle array and an ammonia flow regulating device, wherein the nozzle array is arranged corresponding to each zone, and the ammonia flow regulating device is connected to the nozzle array. The measuring mechanism enters multiple zones to measure flue gas velocity and nitrogen oxide concentration; A control mechanism, which is electrically connected to the ammonia flow regulating device and the measuring mechanism; The method includes the following steps: The catalytic reactor is divided into 'a' regions along its length and 'b' regions along its width. Each region is numbered F. 00 F 01 F 10 …F ij …F ab Among them, F ij This represents the i-th partition in the length direction and the j-th partition in the width direction. The measuring mechanism enters the center of the partition to obtain the flue gas dynamic pressure at that location. Based on the gas density under standard conditions, the static pressure at the center of the partition, and the atmospheric pressure, the density of a single component gas is calculated. The density of the multi-component flue gas is obtained by weighted summation of the components. The flue gas velocity at the center of the partition is obtained based on the density of the multi-component flue gas and the flue gas dynamic pressure. The flue gas analyzer measures the oxygen and nitric oxide content in the flue gas at the center of the zone, and calculates the nitrogen oxide concentration at the center of the zone. The total demand for ammonia is calculated by calculating the average concentration of nitrogen oxides in the flue gas based on the measurement data of all zones measured by the flue gas analyzer, obtaining the total nitrogen oxide content based on the total flue gas flow rate, and then calculating the total demand for ammonia based on the total nitrogen oxide content. The ammonia demand for each zone is calculated based on the total ammonia demand, and then the ammonia injection rate for each zone is obtained. The ammonia injection rate for each zone is adjusted according to the flow rate of each zone, and the ammonia injection rate for each zone is adjusted by the ammonia flow regulating device based on the ammonia injection rate for each zone.

2. The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to claim 1, characterized in that, The catalytic reactors are arranged in layers, with a predetermined interval between each layer of catalytic reactors and the adjacent layer.

3. The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to claim 1, characterized in that, The catalytic reactor is divided into matrix-arranged sections along its length and width.

4. The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to claim 1, characterized in that, The measuring mechanism includes an electronic micromanometer and a flue gas analyzer.

5. The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to claim 1, characterized in that, According to flue gas dynamic pressure p 动压 The formula for calculating the flue gas velocity v is as follows: , k 修正 The correction factor for the measuring device. ρ 烟气 The density of the flue gas, , ρ 标况 The density of a gas under standard conditions. Ρ 静压 It is the static pressure at the center of the partition.

6. The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to claim 5, characterized in that, Flue gas contains a variety of component gases. ρ 烟气 The density of each component needs to be calculated separately, and the average value should be obtained based on its proportion. The specific formula is as follows: in, ρ i Let i be the density of component i in the flue gas. b i To determine the mass fraction of component i in the flue gas, the density of the multi-component flue gas can be obtained by weighted summing of all components; from this, F can be obtained. ij The flue gas velocity at the center of the partition is recorded as v. ij , p 动压ij This represents the dynamic pressure measurement value at partition Fij.

7. The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to claim 1, characterized in that, The concentration of nitrogen oxides at the center of the partition was measured, and the NOx concentration under standard conditions with 6% oxygen was calculated. ， in, NOx The concentration of nitrogen oxides, O real The oxygen content measured by the measuring device. NO Measured by the measuring device NO Volume content, coefficient n for NOx The correction factor for converting concentration from volume fraction to mass fraction, the factor m Based on experience points. NO occupy NOx The percentage of the total amount, from which F can be derived. ij NOx concentration N in the partition center ij .

8. The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to claim 7, characterized in that, The total ammonia demand is calculated by averaging the measurement results from all zones, and the overall nitrogen oxide concentration N in the flue gas is obtained. 均 : If the total flue gas flow rate is L, then the total NOx content in the flue gas is H. 总 for: Correction coefficient d 修正 Used to correct flue gas flow rate, total ammonia demand N 总 The calculation is as follows: Where, N 总 For the total demand of ammonia, H 总 The total NOx content in flue gas, H 出口 M is the target control value. 总 A represents the total coal consumption of the current generating unit; 总 Given the current total air volume of the unit, the total ammonia demand N can be calculated from this. 总 .

9. The zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field according to claim 8, characterized in that, F ij The ammonia demand of the zone is P. ij Then: Because the flue gas velocity varies in different zones, the ammonia injection rate for each zone is adjusted. The adjusted ammonia injection rate P for each zone is as follows. 修正ij for: 。

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