An ammonia nitrogen double control ammonia injection optimization method and device for an SCR system and a storage medium

Abstract

The application discloses an ammonia-nitrogen double-control ammonia injection optimization method and device for an SCR system and a storage medium, and the method comprises the following steps: acquiring actual flue gas data; performing CFD numerical modeling on the SCR system; performing visual analysis on the trajectory and influence area of ammonia injection fluid, defining an ammonia injection flow influence coefficient, and determining the corresponding relationship between different partitions / nozzles of the ammonia injection grid and the upstream cross-section area of the catalyst; performing flow and reaction simulation of ammonia-nitrogen double species, counting the flue gas data at the inlet and outlet of the catalyst, and acquiring a segmented linear fitting formula between the denitration efficiency and the ammonia-nitrogen ratio; coupling the optimization matrix equation of the ammonia injection flow influence coefficient of different partitions / nozzles, and quantitatively solving to obtain the optimized ammonia injection amount corresponding to the ammonia injection grid with the outlet NOx concentration pressure line emission of the SCR system as the target. The application performs visual analysis on the ammonia flow, provides intuitive guidance for actual ammonia injection optimization adjustment tests and operation, and reduces blindness. The application can be widely applied to the field of SCR denitration technology.

Description

Technical Field

[0001] This invention relates to the field of SCR denitrification technology, and in particular to an optimized method, apparatus and storage medium for dual-control ammonia injection for SCR systems. Background Technology

[0002] Adjusting the ammonia injection rate in different zones of the ammonia injection grid in a selective catalytic reduction (SCR) denitrification reactor is crucial for improving the mixing and matching of ammonia and nitrogen concentrations within the flue gas duct. A reasonable ammonia-nitrogen mixing equivalence ratio ensures complete SCR denitrification and improves the uniformity of NOx concentration distribution at the outlet. Therefore, fine-tuning of ammonia injection in different zones of the SCR denitrification system is necessary. Currently, most ammonia injection adjustments in actual engineering rely on manual experience, which is highly unreliable and lacks theoretical guidance. CFD numerical simulation technology can visualize the flue gas flow trajectory and its affected area, providing a theoretical reference for optimizing ammonia injection in the field. In existing research, researchers have used CFD numerical simulation to optimize ammonia injection, and the proposed optimization strategies often focus on solving the problem of uniform ammonia-nitrogen mixture concentration distribution upstream of the first catalyst layer. Adjustments to the ammonia injection rate based on minimizing the relative deviation of the ammonia-nitrogen ratio at the upstream cross-section of the catalyst are performed. However, the results show that the NOx concentration at the SCR outlet cannot achieve the optimal distribution, and even after optimization, there are still issues with NOx concentration at the outlet. Problems include large concentration deviations and significant local ammonia escape. Furthermore, most simulation optimization studies require multiple trial calculations to obtain the optimal ammonia injection strategy for the corresponding ammonia injection grid zone, leading to a degree of blindness in the adjustment process and a long simulation time. Moreover, no researchers have yet analyzed the corresponding influence of ammonia injection rates in different zones of the ammonia injection grid on the NOx concentration distribution at the SCR outlet. Therefore, it is impossible to provide a clear mathematical formula based on the NOx concentration distribution characteristics of the outlet zone to quantitatively calculate the required ammonia injection rates for different zones of the ammonia injection grid, failing to achieve simulation of dual ammonia and nitrogen control. This results in poor accuracy and specificity of existing adjustment strategies, and significant blindness in ammonia injection adjustments. Summary of the Invention

[0003] In order to at least partially solve one of the technical problems existing in the prior art, the purpose of this invention is to provide a method, device and storage medium for optimizing ammonia injection with dual control of ammonia nitrogen in an SCR system.

[0004] The technical solution adopted in this invention is:

[0005] An optimization method for ammonia injection under dual control of ammonia nitrogen in an SCR system includes the following steps:

[0006] Obtain actual flue gas data through on-site performance tests;

[0007] CFD numerical modeling was performed on the SCR denitrification system, and the CFD numerical simulation model was verified using the flue gas data.

[0008] The trajectory and influence area of ​​the ammonia injection fluid were visualized and analyzed based on the CFD numerical simulation model. The ammonia injection flow influence coefficient was defined, and the correspondence between different sections / nozzles of the ammonia injection grid and the upstream cross-sectional area of ​​the catalyst was determined.

[0009] The flow and reaction of ammonia and nitrogen dual species were simulated based on the CFD numerical simulation model. The flue gas data at the catalyst inlet and outlet were statistically analyzed to obtain the piecewise linear fitting formula between the denitrification efficiency and the ammonia-nitrogen ratio.

[0010] The optimization matrix equations of the ammonia injection flow influence coefficients of different zones / nozzles are coupled, and the optimized ammonia injection rate corresponding to the ammonia injection grid with the goal of achieving NOx concentration pressure line emission at the outlet of the SCR system is quantitatively solved.

[0011] Furthermore, the flue gas data includes flue gas temperature, flow rate, NOx content, and ammonia leakage concentration in each zone of the inlet and outlet measurement sections of the SCR system;

[0012] The acquisition of actual flue gas data includes:

[0013] The flow field characteristics at the inlet measurement section of the SCR system were measured using measuring equipment to obtain the velocity field, temperature field, and NOx concentration field at the inlet measurement section, providing inlet parameters for CFD numerical simulation.

[0014] The velocity field, temperature field, and NH3 / NOx concentration field at the SCR system outlet and measurement section are obtained for verification of the CFD numerical simulation model.

[0015] Furthermore, the CFD numerical modeling of the SCR system includes:

[0016] The standard k-ε model was selected as the turbulence model.

[0017] A component transport model was used to simulate the mixing and transport of six gaseous components in flue gas: NO, NH3, H2O, CO2, O2, and N2, without considering the influence of fly ash.

[0018] The standard SCR reaction and ammonia oxidation side reaction were selected to recreate the actual denitrification process and simulate the ammonia-nitrogen dual-species reaction.

[0019] Furthermore, the definition of the ammonia injection flow influence coefficient includes:

[0020] Based on Fluent flow field simulation, the influence of inlet ammonia injection rate on the inlet ammonia concentration of the first catalyst layer was quantitatively analyzed, and the ammonia gas trace flow pattern of ammonia injection in different zones of the ammonia injection grid was analyzed.

[0021] The correspondence between different zones / nozzles of the ammonia injection grid and different regions of the upstream cross-section of the catalyst was determined, and the ammonia injection flow influence coefficient was defined as follows:

[0022]

[0023] In the formula: a i The influence coefficient of different ammonia injection zones / nozzles, m i The effect of ammonia injection in a single zone / nozzle on the ammonia concentration in a certain area upstream of the catalyst is represented by m, where m is the total ammonia concentration injected in a single zone / nozzle.

[0024] Furthermore, the step of obtaining the piecewise linear fitting formula between the denitrification efficiency and the ammonia nitrogen ratio includes:

[0025] By statistically analyzing the NOx concentration, NH3 concentration, ammonia-nitrogen molar ratio, and outlet NOx concentration distribution data of multiple zones at the catalyst inlet section under different ammonia-nitrogen ratios, and calculating the denitrification efficiency of the corresponding zones, the linear variation law of two segments separated by an inflection point was obtained through data fitting.

[0026] Furthermore, the expression for the optimization matrix equation is:

[0027]

[0028] In the formula, a i,j Y represents the influence coefficient of ammonia injection in the i-th section of the ammonia injection grid on a certain j-th region upstream of the catalyst; i Both represent the ammonia concentration requirement in the i-th region upstream of the catalyst; X i This indicates the amount of ammonia injected at the corresponding zone / nozzle of the ammonia injection grid to be determined.

[0029] Furthermore, the quantitative solution for obtaining the optimized ammonia injection rate corresponding to the ammonia injection grid with the target NOx concentration at the outlet of the SCR system as the baseline emission standard includes:

[0030] With the NOx concentration at the outlet of the SCR system as the optimization target, the NH3 concentration distribution at the inlet of the first catalyst layer is determined by using the piecewise linear fitting formula between the denitrification efficiency and the ammonia-nitrogen ratio. Combined with the optimization matrix equation based on the ammonia flow influence coefficient of different zones / nozzles, a quantitative calculation correlation between the ammonia injection rate of different zones of the ammonia injection grid and the NOx concentration distribution characteristics at the outlet is established.

[0031] Furthermore, the quantitative solution for obtaining the optimized ammonia injection rate corresponding to the ammonia injection grid with the target NOx concentration at the outlet of the SCR system as the baseline emission standard includes:

[0032] By analyzing the corresponding influence of ammonia injection rate in different zones of the ammonia injection grid on the NOx concentration distribution in the outlet zone, the optimization matrix equation was solved using the gradient descent method in Matlab. The optimized ammonia injection rate for different zones / nozzles of the ammonia injection grid with NOx concentration just above the emission line and ammonia escape within the limit was obtained, thus achieving the ammonia injection optimization goal of dual control of ammonia and nitrogen.

[0033] Furthermore, the optimized ammonia injection quantity can be considered as a relative value and converted proportionally. Combined with on-site ammonia injection valve commissioning experience, this provides guidance for the scale adjustment of the ammonia injection butterfly valve.

[0034] Another technical solution adopted in this invention is:

[0035] An optimized ammonia injection device for dual control of ammonia nitrogen in an SCR system includes:

[0036] At least one processor;

[0037] At least one memory for storing at least one program;

[0038] When the at least one program is executed by the at least one processor, the at least one processor implements the method described above.

[0039] Another technical solution adopted in this invention is:

[0040] A computer-readable storage medium storing a processor-executable program, which, when executed by a processor, performs the method described above.

[0041] The beneficial effects of this invention are: Based on numerical simulation, this invention performs visual analysis of ammonia flow, studies the flow law of ammonia traces, finds the regional range of downstream SCR inlet ammonia concentration distribution affected by upstream ammonia injection and the regional range of SCR outlet NOx concentration distribution after reaction, provides intuitive guidance for actual ammonia injection optimization and adjustment tests and operation, and reduces blind spots. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following description is provided with accompanying drawings of the relevant technical solutions in the embodiments of the present invention or the prior art. It should be understood that the accompanying drawings described below are only for the purpose of clearly illustrating some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0043] Figure 1 This is a flowchart of an optimized method for dual-control ammonia injection in an SCR system based on numerical simulation, as described in an embodiment of the present invention.

[0044] Figure 2 This is a three-dimensional overall schematic diagram of the SCR denitrification system in an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram illustrating the segmental fitting relationship between denitrification efficiency and ammonia nitrogen ratio in an embodiment of the present invention;

[0046] Figure 4 This is a statistical chart of NOx concentrations in 18 zones at the outlet of the SCR system in this embodiment of the invention;

[0047] Figure 5 This is a statistical chart of ammonia escape from the 18 zones of the SCR system outlet in this embodiment of the invention.

[0048] Figure 2 The attached diagrams are labeled as follows: 1-SCR denitrification system inlet; 2-baffle plate; 3-inlet measurement section; 4-ammonia injection grid; 5-static mixer; 6-rectifier grid; 7-catalyst layer; 8-outlet measurement section; 9-SCR system outlet. Detailed Implementation

[0049] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The step numbers in the following embodiments are set only for ease of explanation, and there is no limitation on the order between the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0050] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not 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 limiting this invention.

[0051] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0052] In the description of this invention, unless otherwise explicitly defined, terms such as "setting," "installing," and "connecting" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0053] The patent with publication number CN112100933A proposes a method, system, device and storage medium for simulating and optimizing ammonia injection in an SCR system. The simulation work for adjusting ammonia injection in the SCR denitrification system mentioned therein is based on minimizing the relative deviation of the ammonia-nitrogen ratio at the upstream cross section of the catalyst to optimize the ammonia injection amount with an equal ammonia-nitrogen ratio. The results show that the NOx concentration at the SCR outlet cannot meet the requirements of the optimal distribution. Even after optimization, there are still problems such as large deviation of the outlet NOx concentration and large local ammonia escape.

[0054] Patent CN113689917A discloses a visualization method and device for optimizing ammonia injection based on the NOx concentration at the SCR outlet. It obtains a mathematical model of the SCR reaction based on six sets of highly nonlinear coupled differential equations to output the mathematical relationship between the outlet NOx concentration and the inlet influencing factors. However, this model is too complex, difficult to model, and has cumbersome calculation steps. It fails to directly provide a mathematical relationship between the NH3 concentration in the upstream section of the catalyst and the NOx concentration in the SCR outlet section in one step. Therefore, it is difficult to directly establish a quantitative calculation correlation between the ammonia injection amount in different sections / nozzles of the ammonia injection grid and the NOx concentration distribution characteristics of the outlet section.

[0055] Patent CN115346610A discloses an ammonia injection optimization method, device, and medium based on an SCR reaction kinetic model. By solving a simplified SCR main reaction model, it gives a direct relationship between the ammonia injection rate of the ammonia injection grid and the NOx concentration in the outlet zone. The optimization objective is to minimize the relative standard deviation of the NOx concentration in the outlet zone. However, due to the complexity of the equation set, it only considers a single main reaction equation and fails to further consider the comprehensive impact of ammonia oxidation side reactions on the outlet NOx concentration and ammonia escape concentration. Therefore, it fails to simulate the dual control of ammonia and nitrogen, resulting in poor accuracy and specificity of the adjustment strategy.

[0056] like Figure 1 As shown, this embodiment provides an optimization method for dual-control ammonia injection in an SCR system based on numerical simulation, including the following steps:

[0057] S1. Obtain actual flue gas data through on-site performance testing.

[0058] The flue gas data includes flue gas temperature, flow rate, NOx content, and ammonia leakage concentration for each zone at the inlet and outlet sections of the SCR system. Step S1 includes steps S11-S12:

[0059] S11. The flow field characteristics of the inlet measurement section of the SCR system are measured using measuring equipment to obtain the velocity field, temperature field and NOx concentration field of the inlet measurement section, providing inlet parameters for CFD numerical simulation;

[0060] S12. Obtain the velocity field, temperature field, and NH3 / NOx concentration field at the SCR system outlet and measurement section for verification of the CFD numerical simulation model.

[0061] S2. Perform CFD numerical modeling on the SCR denitrification system and verify the CFD numerical simulation model using flue gas data.

[0062] CFD numerical modeling of the SCR denitrification system can be performed. The specific methods can be referred to JB / T 12131 and DL / T 1418. The simulation results are verified by the performance test results of step S1 above.

[0063] The CFD model establishment process mainly includes the following steps: The standard k-ε model is selected as the turbulence model; a component transport model is used to simulate the mixing and transport of six gaseous components in the flue gas: NO, NH3, H2O, CO2, O2, and N2, without considering the influence of fly ash; the standard SCR reaction and ammonia oxidation side reaction are selected to recreate the actual denitrification reaction process, simulating the ammonia-nitrogen dual-species process. After verifying the CFD model with the field measurement data from step S1, it can realistically reflect the actual flue gas flow and denitrification reaction of the SCR system.

[0064] As an optional implementation method, the overall structural model of the constructed SCR system includes structures such as inlet and outlet flues, ammonia injection grid, guide vanes, static mixer, rectifier grid, and catalyst layer.

[0065] S3. Based on the CFD numerical simulation model, perform a visual analysis of the trajectory and influence area of ​​the ammonia injection fluid, define the ammonia injection flow influence coefficient, and determine the correspondence between different zones / nozzles of the ammonia injection grid and the upstream cross-sectional area of ​​the catalyst.

[0066] The ammonia injection flow influence coefficient is quantitatively analyzed using Fluent flow field simulation to determine the impact of the inlet ammonia injection rate on the ammonia concentration at the inlet of the first-layer catalyst, and to analyze the ammonia gas trajectory flow pattern of ammonia injection in different zones of the ammonia injection grid. To determine the correspondence between different zones / nozzles of the ammonia injection grid and different regions of the upstream cross-section of the catalyst, the following definition of the ammonia injection flow influence coefficient is given:

[0067]

[0068] In the formula: a i The influence coefficient of different ammonia injection zones / nozzles, m iThe effect of ammonia injection in a single zone / nozzle on the ammonia concentration in a certain area upstream of the catalyst is represented by m, where m is the total ammonia concentration injected in a single zone / nozzle.

[0069] S4. Based on the CFD numerical simulation model, the flow and reaction of ammonia nitrogen (NH3, NO) dual species were simulated. The flue gas data at the catalyst inlet and outlet were statistically analyzed to obtain the piecewise linear fitting formula between the denitrification efficiency and the ammonia nitrogen ratio.

[0070] The piecewise linear fitting formula is obtained by statistically analyzing the NOx concentration, NH3 concentration, ammonia-nitrogen molar ratio, and outlet NOx concentration distribution data of 18 zones at the catalyst inlet section under different ammonia-nitrogen ratios, and calculating the denitrification efficiency of the corresponding zones. The linear variation law of two segments separated by an inflection point is obtained through data fitting.

[0071] S5. The optimization matrix equations of the ammonia injection flow influence coefficients of different zones / nozzles are coupled to quantitatively solve for the optimized ammonia injection rate corresponding to the ammonia injection grid with the goal of achieving NOx concentration pressure line emission at the outlet of the SCR system.

[0072] With the NOx concentration at the SCR outlet as the baseline emission standard (generally based on environmental protection requirements and a certain safety margin as a reference standard) as the optimization target, the piecewise linear fitting formula between the denitrification efficiency and the ammonia-nitrogen ratio obtained in step S4 is used to determine the NH3 concentration distribution at the inlet of the first-layer catalyst. At the same time, combined with the optimization matrix equation based on the ammonia flow influence coefficient of different zones / nozzles obtained in step S5, a quantitative calculation correlation between the ammonia injection rate of different zones of the ammonia injection grid and the NOx concentration distribution characteristics at the outlet can be established.

[0073] By analyzing the corresponding influence of ammonia injection rates in different zones of the ammonia injection grid on the NOx concentration distribution in the outlet zones, the optimization matrix equation described in step S5 was solved using the gradient descent method in Matlab. This yielded the optimized ammonia injection rates for different zones / nozzles of the ammonia injection grid, ensuring NOx concentrations were within acceptable limits and ammonia slip did not exceed the emission standards. This achieved the goal of optimizing ammonia injection for dual ammonia and nitrogen control. The optimized ammonia injection rates can be considered as relative values ​​and proportionally converted. Combined with on-site ammonia valve commissioning experience, this provides guidance for adjusting the scale of the ammonia injection butterfly valve.

[0074] As an optional implementation, the optimization matrix equation is defined as follows:

[0075]

[0076] In the formula: a i,j Y represents the influence coefficient of ammonia injection in the i-th section of the ammonia injection grid on a certain j-th region upstream of the catalyst; i Both represent the ammonia concentration requirement in the i-th region upstream of the catalyst; X i This indicates the amount of ammonia injected at the corresponding zone / nozzle of the ammonia injection grid to be determined.

[0077] The above method will be explained in detail below with reference to the accompanying drawings and specific embodiments.

[0078] See Figure 1 This embodiment provides a method for optimizing ammonia injection under dual control of ammonia nitrogen in an SCR system based on numerical simulation, including the following steps:

[0079] (1) The flue gas flow characteristics at 12×3 grid points at the inlet measurement section of the SCR system under 100% load were measured using measuring equipment to obtain the velocity field, concentration field, and temperature field of the inlet measurement section, providing inlet parameters for CFD numerical simulation. The average inlet velocity of the SCR system was 2.9 m / s, and the ammonia injection flow rate of each nozzle was calculated to be 0.046 kg / s, with an ammonia volume fraction of 2.35%.

[0080] (2) Taking the reactor on side A as an example, the overall structure of the SCR system is geometrically modeled, and the ammonia injection grid is divided into specific zones, such as... Figure 2 As shown. Then, the mesh is generated. Unstructured meshes are used at the ammonia injection grid, guide vanes, and mixer, and the mesh density is increased at the nozzle positions; structured meshes are used in other regular areas.

[0081] (3) The numerical simulation of the entire SCR denitrification system model includes turbulent flow model, component transport and chemical reaction model, etc. Selecting appropriate mathematical models and parameter values ​​in Fluent can ensure reliable simulation results. The standard k-ε model is selected for the turbulence model. The component transport model is used to simulate the mixing and transport of six gas components in the flue gas: NO, NH3, H2O, CO2, O2 and N2, without considering the influence of fly ash. The standard SCR reaction and ammonia oxidation side reaction are selected to restore the actual denitrification reaction process, realistically reflecting the actual flue gas flow and denitrification reaction of the SCR system, and performing ammonia and nitrogen dual control simulation. The three catalyst layers are set as porous media regions, and the drag coefficient is set by the actual pressure drop calculation.

[0082] (4) Among them, the main chemical reactions that occur in the catalytic reactor include the standard SCR denitrification main reaction (1) and the ammonia catalytic oxidation side reaction (2). In the actual simulation process, different chemical reaction kinetic parameters can be selected according to different loads and catalyst activity conditions.

[0083] 4NO + 4NH3 + O2 → 4N2 + 6H2O (1)

[0084] 4NH3 + 3O2 → 2N2 + 6H2O (2)

[0085] (5) Based on the NOx concentration and temperature distribution at the inlet measurement section of the performance test, the NOx concentration and temperature distribution at the simulated inlet section are inferred. Numerical calculations are performed in Fluent. After the calculations are confirmed to be converged, the calculation results are compared with the experimental data to verify the reliability of the CFD model.

[0086] (6) The influence of inlet ammonia injection rate on the ammonia concentration distribution at the inlet of the first-layer catalyst was quantitatively analyzed using Fluent flow field simulation. Taking an actual power plant as an example, the inlet cross-section of the first-layer catalyst was divided into 6×3=18 zones, named C11, C12…C62, C63, corresponding to the 18 zones of NOx grid sampling at the outlet. The flow field of ammonia gas flowing out of 5 different zones of the ammonia injection grid was visualized and analyzed. Due to the limitation of the flow guiding structure in the flue gas duct on the mixing and diffusion of NH3 injected by the branch pipe in the flue gas duct, and the limited mixing distance, the ammonia injection in each zone / nozzle affects the ammonia concentration distribution in the 18 zones at the catalyst inlet within a certain area. Therefore, in order to determine the correspondence between different zones / nozzles of the ammonia injection grid and the upstream cross-sectional area of ​​the catalyst, the following definition of the ammonia injection flow influence coefficient is given:

[0087]

[0088] In the formula: a i The influence coefficient of different ammonia injection zones / nozzles, m i The effect of ammonia injection in a single zone / nozzle on the ammonia concentration in a certain area upstream of the catalyst is represented by m, where m is the total ammonia concentration injected in a single zone / nozzle.

[0089] (7) To achieve the optimization goals of NOx concentration and ammonia slip at the outlet measurement section, it is necessary to further determine the correspondence between NOx concentration in different zones of the outlet section and ammonia concentration distribution in 18 zones upstream of the catalyst. By statistically analyzing the NOx concentration, NH3 concentration, ammonia-nitrogen molar ratio, and outlet NOx concentration distribution data of the 18 zones at the catalyst inlet section under different ammonia-nitrogen ratios, and calculating the denitrification efficiency of the corresponding zones, the relationship between denitrification efficiency and ammonia-nitrogen ratio is plotted using linear fitting, as shown below. Figure 3 As shown. From Figure 3 It can be seen that the relationship between the denitrification efficiency of the SCR denitrification system and the ammonia-nitrogen ratio exhibits a non-linear change pattern, with drastically different trends in different ammonia-nitrogen ratio ranges.

[0090] (8) The specific linear expression of the piecewise function is:

[0091] y1 = 0.85x + 0.012

[0092] y2=0.055x+0.93 (4)

[0093]

[0094] In the formula: y represents the denitrification efficiency; x represents the ammonia-nitrogen ratio.

[0095] (9) The matrix equation defined by the ammonia injection influence coefficient is as follows:

[0096]

[0097] This embodiment performs optimization in two ways: partitioning and nozzle optimization. Therefore, in Equation 2: 1) If 5 partitions are optimized, then a i,j (i = 1:5, j = 1:18) represents the influence coefficient of ammonia injection in the i-th section of the ammonia injection grid on a certain j-th region among the 18 regions upstream of the catalyst; 2) If optimization is performed with 42 nozzles, then a i,j (i = 1:42, j = 1:18) represents the influence coefficient of the i-th nozzle of the ammonia injection grid on a certain j-th region among the 18 regions upstream of the catalyst; in both cases, Y i Both represent the ammonia concentration requirement in the i-th region among the 18 regions upstream of the catalyst; X i This indicates the amount of ammonia injected at the corresponding zone / nozzle of the ammonia injection grid to be determined.

[0098] (10) Taking the NOx concentration at the outlet as the optimization target, the mathematical relationship between the NH3 concentration at the upstream section of the catalyst and the NOx concentration at the outlet is determined based on the piecewise linear formula obtained from data fitting. At the same time, combined with the optimization matrix equation based on the flow influence coefficient of ammonia injection in different zones / nozzles, a quantitative calculation correlation between the ammonia injection amount in different zones of the ammonia injection grid and the NOx concentration distribution characteristics of the outlet zone can be established. This optimization method is simple and easy to model to obtain the mathematical relationship for quantitatively solving the ammonia injection amount. It can realize the dual control of ammonia and nitrogen injection optimization in the SCR system, improve the accuracy and pertinence of ammonia injection adjustment, reduce the blindness of adjustment work, and improve calculation efficiency.

[0099] (11) By analyzing the corresponding influence of ammonia injection rate in different zones of the ammonia injection grid on the NOx concentration distribution of the outlet zone, and keeping the NOx concentration at the outlet section at the line, it is assumed that the target NOx concentration at the outlet of each zone is 40 mg / Nm³ (the cross-sectional average). 3 The denitrification efficiency of the corresponding zones was calculated. Using the theoretically calculated denitrification efficiencies of different zones, the y1 segmented formula was used to calculate the ammonia-nitrogen ratio corresponding to the catalyst inlet zone. After calculating the ammonia-nitrogen ratio distribution for each zone, the required ammonia concentration for each zone was determined based on the inlet NOx concentration distribution. Combining the ammonia injection flow influence coefficient of the ammonia injection grid zone (nozzle) and the ammonia concentration requirements of the 18 zones upstream of the catalyst, the ammonia injection optimization matrix equation was calculated using Matlab to obtain the ammonia injection rate for each zone (or nozzle) at the ammonia injection grid. The optimized ammonia injection rates for different zones were then substituted into Fluent for simulation calculations. Specific simulation results are shown below. Figure 4 and Figure 5 As shown.

[0100] (12) After optimizing ammonia injection using this method, the average outlet ammonia slip concentration decreased from 2.7 ppm to 2.0 ppm, and the average NOx and ammonia slip cross-sections were 40 mg / Nm³. 3 At 2.0 ppm, the NOx concentration meets the requirements for strict emission control, ensuring that NOx concentration and ammonia slip do not exceed emission standards. The relative standard deviation of NOx concentration in the outlet zone decreased from 70% before optimization to 9%, and the relative standard deviation of ammonia slip in different zones also decreased from 38% to 4%, demonstrating a significant improvement in optimization effectiveness. There are no risks of low NOx concentration, excessive ammonia injection, or ammonia slip exceeding emission standards. This approach achieves both strict emission control of NOx and ammonia slip to meet environmental requirements and avoids areas with excessively high or low denitrification efficiency, thus improving the uniformity of NOx and NH3 concentration distribution at the outlet.

[0101] (13) Assuming the initial valve opening is 90° under uniform ammonia injection conditions before adjustment, and the valve opening range is 0-100°. The optimized ammonia injection volume of 42 nozzles under this simulated condition is compared with that under uniform ammonia injection conditions to obtain the relative values ​​of the optimized ammonia injection valve opening adjustment, as shown in Table 1. Compared with the opening size of the 42 valves before adjustment, valve A4-3 needs to reduce its opening by 28.6°, that is, the valve has a minimum opening of 61.4°, and valve A14-1 needs to increase its opening by 9.8°, that is, the valve has a maximum opening of 99.8°. After obtaining the optimized opening of the 42 ammonia injection valves, the ammonia injection valves are adjusted based on the on-site ammonia injection valve commissioning experience and the gridded measurement results of the outlet NOx concentration to achieve optimized ammonia injection in the SCR denitrification system, so as to achieve the goal of improving the uniformity of outlet NOx concentration distribution and reducing ammonia escape, and to provide a theoretical reference for the optimized commissioning of ammonia injection in actual power plants.

[0102] Table 1. Relative values ​​of opening adjustment for 42 ammonia injection valves

[0103]

[0104] (14) When the boiler load changes, the corresponding relationship between the NOx concentration distribution characteristics of different zones / nozzles of the ammonia injection grid and the outlet section can be determined by establishing flue gas flow and reaction models under different operating conditions and repeating the above calculation steps. This can significantly help and improve the debugging efficiency of the ammonia injection control valve under different operating conditions, and provide theoretical reference for actual ammonia injection optimization adjustment test and operation.

[0105] In summary, this embodiment has at least the following advantages and beneficial effects compared to the prior art:

[0106] 1) By adopting a simulated inlet boundary condition based on experimental measurements and a chemical reaction model of standard SCR reaction and ammonia oxidation side reaction, the overall flue gas flow, ammonia-nitrogen mixing and denitrification reaction process of the SCR system can be more realistically reflected. This provides a stable, reliable and realistic CFD numerical simulation model for the subsequent ammonia-nitrogen dual-control ammonia injection optimization strategy, and improves the accuracy and pertinence of the ammonia injection adjustment strategy.

[0107] (2) Visualize the ammonia flow, study the flow pattern of ammonia traces, find the range of downstream SCR inlet ammonia concentration distribution affected by upstream ammonia injection and the range of SCR outlet NOx concentration distribution after reaction, provide intuitive guidance for actual ammonia injection optimization and adjustment tests and operation, and reduce blind spots.

[0108] (3) Taking the NOx concentration at the outlet as the optimization target and a certain ammonia leakage amount in a certain zone as the constraint value, a quantitative calculation correlation formula is established based on the piecewise linear fitting formula between the ammonia injection amount in different zones of the ammonia injection grid and the outlet NOx concentration distribution characteristics and ammonia leakage amount. This can realize the quantitative solution of the optimized ammonia injection amount corresponding to the ammonia injection grid based on the outlet NH3 / NOx concentration distribution characteristics. This ammonia injection optimization method is simple and easy to implement quantitative calculation, which can improve the calculation efficiency.

[0109] (4) This ammonia injection optimization method can not only control the ammonia injection amount in the ammonia injection grid, but also be applied to the control valve of each nozzle in the ammonia injection grid in a more refined manner. Combined with the on-site debugging experience, the valve opening is proportionally converted to the optimized ammonia injection amount obtained by simulation, which guides the adjustment of the ammonia injection control valve.

[0110] (5) The ammonia injection optimization method based on numerical simulation can be applied to different working conditions and different reaction conditions. By establishing flow and reaction models under different working conditions, repeating the above calculation steps can also determine the correspondence between the NOx concentration distribution characteristics of different zones / nozzles of the ammonia injection grid and the outlet zone, which can significantly help and improve the debugging efficiency of the ammonia injection control valve under different working conditions.

[0111] This embodiment also provides an SCR system ammonia nitrogen dual-control ammonia injection optimization device, including:

[0112] At least one processor;

[0113] At least one memory for storing at least one program;

[0114] When the at least one program is executed by the at least one processor, the at least one processor performs the following: Figure 1 The method shown.

[0115] This embodiment of the SCR system ammonia nitrogen dual control ammonia injection optimization device can execute the SCR system ammonia nitrogen dual control ammonia injection optimization method provided in the method embodiment of the present invention, and can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.

[0116] This application also discloses a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium and execute the computer instructions, causing the computer device to perform... Figure 1 The method shown.

[0117] This embodiment also provides a storage medium storing instructions or programs that can execute the SCR system ammonia nitrogen dual control ammonia injection optimization method provided in the method embodiment of the present invention. When the instructions or programs are run, any combination of implementation steps of the method embodiment can be executed, and the method has the corresponding functions and beneficial effects.

[0118] In some alternative embodiments, the functions / operations mentioned in the block diagrams may not occur in the order shown in the operation diagrams. For example, depending on the functions / operations involved, two consecutively shown blocks may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order. Furthermore, the embodiments presented and described in the flowcharts of this invention are provided by way of example to provide a more comprehensive understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is altered and sub-operations described as part of a larger operation are executed independently.

[0119] Furthermore, although the invention has been described in the context of functional modules, it should be understood that, unless otherwise stated, one or more of the described functions and / or features may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in a separate physical device or software module. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the invention. Rather, given the properties, functions, and internal relationships of the various functional modules in the apparatus disclosed herein, the actual implementation of the module will be understood within the scope of conventional skill of an engineer. Therefore, those skilled in the art can implement the invention as set forth in the claims using ordinary techniques without excessive experimentation. It is also understood that the specific concepts disclosed are merely illustrative and not intended to limit the scope of the invention, which is determined by the full scope of the appended claims and their equivalents.

[0120] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0121] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0122] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0123] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0124] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," or "some embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, 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.

[0125] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0126] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method for optimizing ammonia injection under dual control of ammonia nitrogen in an SCR system, characterized in that, Includes the following steps: Obtain actual flue gas data; CFD numerical modeling of the SCR system was performed, and the CFD numerical simulation model was verified using the flue gas data. The trajectory and influence area of ​​the ammonia injection fluid were visualized and analyzed based on the CFD numerical simulation model. The ammonia injection flow influence coefficient was defined, and the correspondence between different sections or nozzles of the ammonia injection grid and the upstream cross-sectional area of ​​the catalyst was determined. The flow and reaction of ammonia and nitrogen dual species were simulated using a CFD numerical simulation model. Statistical data of the catalyst inlet and outlet flue gas were collected to obtain a piecewise linear fitting formula between the denitrification efficiency and the ammonia-nitrogen ratio. Specifically, by statistically analyzing the NOx concentration, NH3 concentration, ammonia-nitrogen molar ratio, and outlet NOx concentration distribution data of multiple zones at the catalyst inlet section under different ammonia-nitrogen ratios, the denitrification efficiency of the corresponding zones was calculated. The piecewise linear fitting formula, separated by an inflection point, was then obtained through data fitting. In the formula: Represents denitrification efficiency. Represents the ammonia-to-nitrogen ratio; With the goal of achieving NOx concentration near the emission threshold at the SCR system outlet, the NH3 concentration distribution at the inlet of the first-layer catalyst was determined using a piecewise linear fitting formula between the denitrification efficiency and the ammonia-nitrogen ratio. Combined with the obtained optimization matrix equation based on the ammonia flow influence coefficient of different zones / nozzles, a quantitative calculation correlation was established between the ammonia injection rate of different zones of the ammonia injection grid and the NOx concentration distribution characteristics at the outlet. By analyzing the corresponding influence of the ammonia injection rate of different zones of the ammonia injection grid on the NOx concentration distribution of the outlet zone, the optimization matrix equation was solved using the gradient descent method in Matlab. This yielded the optimized ammonia injection rate for different zones / nozzles of the ammonia injection grid where the outlet NOx concentration was near the emission threshold and the ammonia slip did not exceed the standard, thus achieving the ammonia injection optimization goal of dual control of ammonia and nitrogen.

2. The method for optimizing ammonia injection for dual control of ammonia and nitrogen in an SCR system according to claim 1, characterized in that, The flue gas data includes flue gas temperature, flow rate, NOx content, and ammonia leakage concentration in each zone of the inlet and outlet measurement sections of the SCR system; The acquisition of actual flue gas data includes: The flow field characteristics at the inlet measurement section of the SCR system were measured using measuring equipment to obtain the velocity field, temperature field, and NOx concentration field at the inlet measurement section, providing inlet parameters for CFD numerical simulation. The velocity field, temperature field, and NH3 / NOx concentration field at the outlet measurement section of the SCR system are obtained for verification of the CFD numerical simulation model.

3. The method for optimizing ammonia injection for dual control of ammonia and nitrogen in an SCR system according to claim 1, characterized in that, The CFD numerical modeling of the SCR system includes: The standard k-ε model was selected as the turbulence model. A component transport model was used to simulate the mixing and transport of six gaseous components in flue gas: NO, NH3, H2O, CO2, O2, and N2. The standard SCR reaction and ammonia oxidation side reaction were selected to recreate the actual denitrification process and simulate the ammonia-nitrogen dual-species reaction.

4. The method for optimizing ammonia injection under dual control of ammonia and nitrogen in an SCR system according to claim 1, characterized in that, The definition of the ammonia injection flow influence coefficient includes: Based on Fluent flow field simulation, the influence of inlet ammonia injection rate on the inlet ammonia concentration of the first catalyst layer was quantitatively analyzed, and the ammonia gas trace flow pattern of ammonia injection in different zones of the ammonia injection grid was analyzed. Determine the correspondence between different zones or nozzles of the ammonia injection grid and different regions of the upstream cross-section of the catalyst; the definition of the ammonia injection flow influence coefficient is as follows: In the formula: The influence coefficient of different ammonia injection zones / nozzles, The ammonia injection from a single zone / nozzle affects the ammonia concentration in a specific region upstream of the catalyst. The total concentration of ammonia injected into a single zone / nozzle.

5. The method for optimizing ammonia injection under dual control of ammonia and nitrogen in an SCR system according to claim 1, characterized in that, The expression for the optimization matrix equation is: In the formula, It represents the influence coefficient of ammonia injection in the i-th section of the ammonia injection grid on a certain j-th region upstream of the catalyst; Both represent the ammonia concentration requirement in the i-th region upstream of the catalyst; This indicates the amount of ammonia injected at the corresponding zone / nozzle of the ammonia injection grid to be determined.

6. An optimized ammonia injection device for dual control of ammonia and nitrogen in an SCR system, characterized in that, include: At least one processor; At least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the method of any one of claims 1-5.

7. A computer-readable storage medium storing a processor-executable program, characterized in that, The processor-executable program, when executed by the processor, is used to perform the method as described in any one of claims 1-5.

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