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

Abstract

Disclosed in the present invention are a partitioned ammonia spraying control method and system based on comprehensive calculation of a velocity field and a concentration field. The partitioned ammonia spraying system comprises a reactor mechanism, a partitioned ammonia spraying device, a measurement mechanism and a control mechanism, wherein the reactor mechanism comprises an inlet flue, an outlet flue and a catalytic reactor, the catalytic reactor being located between the inlet flue and the outlet flue, and the catalytic reactor being divided into a plurality of partitions; the partitioned ammonia spraying device comprises a spraying pipe array and an ammonia flow regulation device, the spraying pipe array being arranged corresponding to each of the partitions, and the ammonia flow regulation device being connected to the spraying pipe array; the measurement mechanism enters the plurality of partitions to measure the flow velocity of flue gas and the concentration of NOx; and the control mechanism is electrically connected to the ammonia flow regulation device and the measurement mechanism. The partitioned ammonia spraying system provided in the present invention has the advantages of accurate measurement of the concentration and flow velocity of flue gas and accurate distribution of ammonia.

Description

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

[0001] The present invention relates to the technical field of flue gas pollutant treatment, and in particular to a partitioned ammonia injection control method and system based on comprehensive calculation of velocity field and concentration field. Background Art

[0002] Coal-fired power plant boilers produce flue gas containing a large amount of pollutants during operation, among which nitrogen oxides (NOx) are significantly harmful to organisms and need to be controlled. In the actual denitrification process of power plants, it is very easy to cause excessive ammonia injection, that is, too much reducing agent NH3 is injected into the reactor, and some remains after reacting with NOx in the flue gas. This excess NH3, on the one hand, causes waste of denitrification materials and increases the cost of the power plant; on the other hand, the unreacted NH3 and the acidic gas in the flue gas easily form inorganic salts at the cold end of the air preheater, greatly increasing the risk of blockage of the air preheater. The main reasons for excessive ammonia injection are: 1. Inaccurate measurement of NOx, and the obtained NOx concentration data cannot represent the situation of the entire cross-section; 2. Inaccurate calculation of the total NOx amount. The influence of the flow rate at the measurement point on the ammonia demand is not considered. It is difficult to accurately obtain relevant data on ammonia demand in related technologies.

[0003] Summary of the Invention

[0004] The present invention aims to address, at least to some extent, one of the technical problems in the related art. To this end, embodiments of the present invention provide a method and system for controlling zoned ammonia injection based on the comprehensive calculation of velocity and concentration fields. This method and system, based on the comprehensive calculation of velocity and concentration fields, offers the advantages of accurate measurement of flue gas concentration and flow rate, and precise ammonia distribution.

[0005] According to an embodiment of the present invention, the partitioned ammonia injection system includes a reactor mechanism, a partitioned ammonia injection device, a measuring mechanism and a control mechanism. The reactor mechanism includes 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 includes a nozzle array and an ammonia flow regulating device. The nozzle array is arranged corresponding to each partition. The ammonia flow regulating device is connected to the nozzle array. The measuring mechanism enters multiple partitions to measure the flue gas flow rate and nitrogen oxide concentration. The control mechanism is electrically connected to the ammonia flow regulating device and the measuring mechanism.

[0006] The zoned ammonia injection system according to an embodiment of the present invention offers the advantages of accurate measurement of flue gas concentration and flow rate, and precise ammonia distribution. This application utilizes a zoned ammonia injection device in conjunction with a measurement mechanism to divide the catalytic reactor into multiple zones, thereby improving the measurement accuracy of flue gas flow rate and flue gas component concentrations. This allows for precise ammonia control in each zone to address excessive ammonia injection.

[0007] In some embodiments, the catalytic reactors are arranged in layers, and there is a preset gap between each layer of catalytic reactors and the adjacent layer of catalytic reactors.

[0008] In some embodiments, the catalytic reactor is divided along the length direction and the width direction to obtain the partitions arranged in a matrix.

[0009] In some embodiments, the measuring mechanism includes an electronic micromanometer and a flue gas analyzer.

[0010] The partitioned 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:

[0011] The catalytic reactor is divided into a region along the length direction and b regions along the width direction, and each region is numbered F. 00 、F 01 、F 10 …F ij …F ab Among them, F ij Indicates the i-th zone in the length direction and the j-th zone in the width direction. The measuring mechanism enters the center of the zone to obtain the flue gas dynamic pressure at that position. The density of the single-component gas is calculated based on the gas density under standard conditions, the static pressure at the center of the zone, and the atmospheric pressure. The density of the multi-component flue gas is obtained by weighted summation according to the components. The flue gas flow rate at the center of the zone is obtained based on the density of the multi-component flue gas and the flue gas dynamic pressure.

[0012] The flue gas analyzer measures the oxygen content and nitrogen monoxide content in the flue gas at the partition center, and calculates the nitrogen oxide concentration at the partition center;

[0013] Calculate the total demand for ammonia. Calculate the average concentration of nitrogen oxides in the flue gas based on the measurement data of all zones measured by the flue gas analyzer. Calculate the total nitrogen oxide content based on the total flue gas flow rate. Calculate the total demand for ammonia based on the total nitrogen oxide content.

[0014] The ammonia demand of each partition is calculated according to the total ammonia demand to obtain the partition ammonia injection amount, the partition ammonia injection amount is corrected according to the flow rate of each partition, and the ammonia flow regulating device is controlled according to the partition ammonia injection amount to adjust the ammonia injection amount of each partition.

[0015] In some embodiments, according to the flue gas dynamic pressure p 动压The calculation formula for the flue gas flow velocity v is as follows:

[0016] k 修正 is the correction factor of the measuring device, ρ 烟气 is the density of smoke, ρ 标况 is the density of a gas under standard conditions, P 静压 is the static pressure at the center of the partition.

[0017] In some embodiments, the flue gas contains multiple component gases, 烟气 The density of each component needs to be calculated separately and the average value is calculated based on its proportion. The specific formula is as follows: ρ 烟气 =ρ1×b1+ρ2×b2+ ... +ρ i ×b6+...ρ n ×b n

[0018] Among them, ρ i is the density of component i in the flue gas, b i is the mass share of component i in the flue gas, and the density of multi-component flue gas can be obtained by weighted summation of all components. In this way, F ij The flue gas velocity at the center of the partition is recorded as v ij ,

[0019] p 动压ij is the measured value of dynamic pressure at partition Fij.

[0020] In some embodiments, the NOx concentration at a standard oxygen concentration of 6% is calculated based on the measurement of the nitrogen oxide concentration at the center of the partition.

[0021] Among them, NOx is the concentration of nitrogen oxides, O real is the oxygen content measured by the measuring device, NO is the NO volume content measured by the measuring device, the coefficient n is the correction coefficient for converting NOx concentration from volume fraction to mass fraction, the coefficient m is an empirical value, and the percentage of NO in the total NOx content, thus, F can be obtained. ij NOx concentration N in the center of the partition ij .

[0022] In some embodiments, the total demand for ammonia is calculated, and the average of the measurement results of all partitions is calculated to obtain the overall concentration of nitrogen oxides in the flue gas, N 均 :

[0023] The total flue gas flow is L, then the total NOx content in the flue gas is H总 is: H 总 =d 修正 ×F 均 ×L

[0024] Correction coefficient d 修正 Used to correct the flue gas flow, the total ammonia demand N 总 The calculation is as follows:

[0025] Among them, N 总 is the total demand for ammonia, H 总 is the total NOx content in the flue gas, H 出口 is the target control value; M 总 is the total coal consumption of the current unit; A 总 is the total air volume of the current unit, based on which the total ammonia demand N can be obtained 总 .

[0026] In some embodiments, F ij The ammonia demand of the partition is P ij , then:

[0027] Due to the different flue gas flow rates in each zone, the ammonia injection amount of each zone is corrected. The corrected ammonia injection amount of each zone P 修正ij for: BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic structural diagram of a zoned ammonia injection system according to an embodiment of the present invention.

[0029] Figure numerals: 1. Partition; 2. Inlet flue; 3. Catalytic reactor; 4. Outlet flue; 5. Measuring mechanism; 6. Partition ammonia injection device. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0031] According to an embodiment of the present invention, the zoned ammonia injection system comprises a reactor mechanism, a zoned 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 and outlet flues and is divided into multiple zones. The zoned ammonia injection device comprises a nozzle array and an ammonia flow control device, each of which is arranged corresponding to a zone and connected to the nozzle array. The measuring mechanism enters each zone to measure the flue gas flow rate and nitrogen oxide concentration. The control mechanism is electrically connected to the ammonia flow control device and the measuring mechanism. The reactor mechanism directs flue gas containing nitrogen oxides to the SCR catalyst area. After the denitrification reaction is completed, the flue gas leaves the catalytic reactor area. The inlet and outlet flue are both enclosed metal pipes with rectangular cross-sections. The measuring mechanism measures the flue gas flow rate 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 amount of ammonia injected. The nozzles of the nozzle array correspond to each partition, and the ammonia flow regulating device corresponds to the nozzle one by one, meeting the different ammonia volume requirements of different partitions according to the measurement results.

[0032] The zoned ammonia injection system according to the embodiment of the present invention has the advantages of accurate measurement of flue gas concentration and flow rate and precise ammonia distribution.

[0033] In some embodiments, the catalytic reactors are arranged in layers, and there is a preset gap between each layer of catalytic reactors and the adjacent layer of catalytic reactors.

[0034] Specifically, the layered arrangement of the catalytic reactors can extend the catalytic time of the flue gas, and the interval between each layer and the adjacent layer can further extend the flow time of the flue gas.

[0035] In some embodiments, the catalytic reactor is divided along the length direction and the width direction to obtain the partitions arranged in a matrix.

[0036] Specifically, the catalytic reactor is divided along the length and width directions to form a plurality of partitions arranged in an array. The shape of the partitions is rectangular. Dividing the catalytic reactor into a plurality of partitions can more accurately judge the flue gas concentration and flow rate and other data in the reactor, adapt to the conditions of uneven flue gas velocity field and uneven nitrogen oxide concentration distribution, and can more accurately determine and control the amount of ammonia injection to avoid excessive ammonia injection.

[0037] In some embodiments, the measuring mechanism includes an electronic micromanometer and a flue gas analyzer.

[0038] Specifically, the electronic micromanometer is used to measure the dynamic pressure of the flue gas, and the flue gas analyzer is used to measure the concentration of different components in the flue gas.

[0039] The partitioned 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:

[0040] The catalytic reactor is divided into a region along the length direction and b regions along the width direction, and each region is numbered F. 00 、F 01 、F 10 …F ij …F ab Among them, F ij It 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 position. 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 flow rate 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 flow rate of each partition is obtained based on the flue gas pressure and flue gas density.

[0041] The flue gas analyzer measures the oxygen content and nitrogen monoxide content in the flue gas at the partition center, and calculates the nitrogen oxide concentration at the partition center;

[0042] Calculate the total demand for ammonia. Calculate the average concentration of nitrogen oxides in the flue gas based on the measurement data of all zones measured by the flue gas analyzer. Calculate the total nitrogen oxide content based on the total flue gas flow rate. Calculate the total demand for ammonia based on the total nitrogen oxide content.

[0043] The ammonia demand for each zone is calculated based on the total ammonia demand, thereby determining the zone ammonia injection amount. The zone ammonia injection amount is then corrected based on the flow rate of each zone. The ammonia flow control device is then controlled based on the zone ammonia injection amount to adjust the ammonia injection amount for each zone. The precise ammonia injection amount for each zone is determined based on the zone flow rate and zone ammonia injection amount, allowing precise control of the ammonia injection amount for each zone.

[0044] In some embodiments, according to the flue gas dynamic pressure p 动压 The calculation formula for the flue gas flow velocity v is as follows:

[0045] k 修正 is the correction factor of the measuring device, ρ 烟气 is the density of smoke, ρ 标况 is the density of a gas under standard conditions, P 静压 is the static pressure at the center of the partition. 标况 Density data can be obtained by looking up the table. Static pressure refers to the pressure exerted by gas on the surface of an object parallel to the airflow, and dynamic pressure refers to the pressure that drives the gas forward.

[0046] In some embodiments, the flue gas contains multiple component gases, 烟气 The density of each component needs to be calculated separately and the average value is calculated based on its proportion. The specific formula is as follows: ρ 烟气 =ρ1×b1+ρ2×b2+ ... +ρ i ×b i +...ρ n ×b n

[0047] Among them, ρ i is the density of component i in the flue gas, b i is the mass share of component i in the flue gas, and the density of multi-component flue gas can be obtained by weighted summation of all components. In this way, F ij The flue gas velocity at the center of the partition is recorded as v ij ,

[0048] p 动压ij is the measured value of dynamic pressure at partition Fij.

[0049] The composition of coal-fired flue gas is relatively complex, mainly including carbon dioxide, carbon monoxide, nitrogen oxides, sulfur oxides, oxygen, water vapor, etc. Therefore, the density of each component in flue gas needs to be calculated separately and the average value is calculated based on their proportions.

[0050] In some embodiments, the NOx concentration at a standard oxygen concentration of 6% is calculated based on the measurement of the nitrogen oxide concentration at the center of the partition.

[0051] Among them, NOx is the concentration of nitrogen oxides, O real is the oxygen content measured by the measuring device, NO is the NO volume content measured by the measuring device, the coefficient n is the correction coefficient for converting NOx concentration from volume fraction to mass fraction, the coefficient m is an empirical value, and the percentage of NO in the total NOx content, thus, F can be obtained. ij NOx concentration N in the center of the partition ij .

[0052] The flue gas analyzer extracts a certain amount of flue gas at the center of the partition and uses sensors to measure the oxygen content and oxide content therein. The coefficient n is taken as 2.05, and the coefficient m is taken as an exact value between 0.9-1.0.

[0053] In some embodiments, the total demand for ammonia is calculated, and the average of the measurement results of all partitions is calculated to obtain the overall concentration of nitrogen oxides in the flue gas, N 均 :

[0054] The total flue gas flow is L, then the total NOx content in the flue gas is H 总 is: H 总 =d 修正 ×F 均 ×L

[0055] Correction coefficient d 修正 Used to correct the flue gas flow, the total ammonia demand N 总 The calculation is as follows:

[0056] Among them, N 总 is the total demand for ammonia, H 总 is the total NOx content in the flue gas, H 出口 is the target control value; M 总 is the total coal consumption of the current unit; A 总 is the total air volume of the current unit, based on which the total ammonia demand N can be obtained 总 .

[0057] Specifically, 2.68 is the empirical coefficient, H 出口 A specific value less than 50.

[0058] In some embodiments, F ij The ammonia demand of the partition is P ij , then:

[0059] Due to the different flue gas flow rates in each zone, the ammonia injection amount of each zone is corrected. The corrected ammonia injection amount of each zone P 修正ij for:

[0060] According to the calculation structure of the formula, the flow control valve of each partition is adjusted to control the amount of ammonia obtained by each partition, thereby achieving high-precision partition ammonia injection control to avoid excessive ammonia injection.

[0061] 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", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations 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 should not be understood as limiting the present invention.

[0062] 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0063] In the present invention, unless otherwise specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they may refer to fixed or detachable connections, or integration; mechanical or electrical connections, or communication; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0064] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0065] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0066] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. Any changes, modifications, substitutions and variations of the above embodiments by those skilled in the art are within the scope of protection of the present invention.

Claims

1. A zoned ammonia injection system, characterized in that: include: A reactor mechanism, the reactor mechanism comprising an inlet flue, an outlet flue and a catalytic reactor, the catalytic reactor being located between the inlet flue and the outlet flue, and the catalytic reactor being divided into a plurality of partitions; A partitioned ammonia spraying device, the partitioned ammonia spraying device comprises a nozzle array and an ammonia flow regulating device, the nozzle array is arranged corresponding to each partition, and the ammonia flow regulating device is connected to the nozzle array; A measuring mechanism is provided, wherein the measuring mechanism enters into a plurality of zones to measure the flue gas flow rate and the nitrogen oxide concentration. A control mechanism is electrically connected to the ammonia flow regulating device and the measuring mechanism.

2. The zoned ammonia injection system according to claim 1, characterized in that: The catalytic reactors are arranged in layers, and there is a preset interval between each layer of catalytic reactors and the adjacent layer of catalytic reactors.

3. The zoned ammonia injection system according to claim 1, characterized in that: The catalytic reactor is divided along the length direction and the width direction to obtain the partitions arranged in a matrix.

4. The zoned ammonia injection system according to claim 1, characterized in that: The measuring mechanism comprises an electronic micromanometer and a flue gas analyzer.

5. A zoned ammonia injection control method based on comprehensive calculation of velocity field and concentration field, characterized in that The following steps are involved: The catalytic reactor is divided into a regions along the length direction and b regions along the width direction, and each region is numbered F. 00 、F 01 、F 10 …F ij …F ab Among them, F ij It 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 position. The single-component gas density is calculated according to the gas density under standard conditions, the static pressure at the center of the partition and the atmospheric pressure. The density of multi-component flue gas is obtained by weighted summation according to the components. The aerodynamic pressure is used to obtain the flue gas flow rate at the center of the partition; The flue gas analyzer measures the oxygen content and nitrogen monoxide content in the flue gas at the center of the partition, and calculates the nitrogen oxide concentration at the center of the partition; Calculate the total demand for ammonia, calculate the average concentration of nitrogen oxides in the flue gas based on the measurement data of all partitions measured by the flue gas analyzer, obtain the total content of nitrogen oxides based on the total flue gas flow, and calculate the total demand for ammonia based on the total content of nitrogen oxides; The ammonia demand of each partition is calculated according to the total ammonia demand to obtain the partition ammonia injection amount, the partition ammonia injection amount is corrected according to the flow rate of each partition, and the ammonia flow regulating device is controlled according to the partition ammonia injection amount to adjust the ammonia injection amount of each partition.

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

7. The method for controlling the partitioned ammonia injection based on the comprehensive calculation of the velocity field and the concentration field according to claim 6 is characterized in that: Flue gas contains multiple components of gas, ρ 烟气 The density of each component needs to be calculated separately and the average value is calculated based on its proportion. The specific formula is as follows: ρ 烟气 =ρ1×b1+ρ2×b2+...+ρ i ×b i +...ρ n ×b n Among them, ρ i is the density of component i in the flue gas, b i is the mass share of component i in the flue gas. The density of multi-component flue gas can be obtained by weighted summing of all components. In this way, F ij The flue gas velocity at the center of the partition is recorded as v ij , p 动压ij is the measured value of dynamic pressure at partition Fij.

8. The method for controlling the partitioned ammonia injection based on the comprehensive calculation of the velocity field and the concentration field according to claim 5 is characterized in that: The NOx concentration at the center of the partition is measured and the NOx concentration at 6% oxygen concentration under standard conditions is calculated. Where NOx is the concentration of nitrogen oxides, O real is the oxygen content measured by the measuring device, NO is the NO volume content measured by the measuring device, coefficient n is the correction coefficient for converting NOx concentration from volume fraction to mass fraction, coefficient m is an empirical value, and is the percentage of NO in the total NOx content. Thus, F ij NOx concentration N in the center of the zone ij .

9. The method for controlling the partitioned ammonia injection based on the comprehensive calculation of the velocity field and the concentration field according to claim 8 is characterized in that: Calculate the total demand for ammonia and average the measurement results of all partitions to obtain the overall concentration of nitrogen oxides in the flue gas N 均 : The total flue gas flow is L, then the total NOx content in the flue gas is H 总 for: H 总 =d 修正 ×F 均 ×L Correction factor d 修正 Used to correct flue gas flow, total ammonia demand N 总 The calculation is as follows: Among them, N 总 is the total demand for ammonia, H 总 is the total NOx content in the flue gas, H 出口 is the target control value; M 总 is the total coal consumption of the current unit; A 总 is the total air volume of the current unit, based on which the total ammonia demand N can be obtained 总 .

10. The method for controlling the partitioned ammonia injection based on the comprehensive calculation of the velocity field and the concentration field according to claim 9, characterized in that: F ij The ammonia demand of the partition is P ij When , we have: Due to the different flue gas flow rates in each zone, the ammonia injection amount of each zone is corrected. The corrected ammonia injection amount of each zone P 修正ij for:

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