An adaptive load sncr injection coverage regulation method

Abstract

The application provides a self-adaptive load SNCR injection coverage regulation method, and belongs to the technical field of coal-fired boiler nitrogen oxide control, and can at least partially solve the problem of low denitration efficiency caused by the fact that the SNCR injection gun cannot be self-adaptively adjusted in coverage range with load variation in the prior art. The application comprises the following steps: performing a cold-state test on the atomization characteristics of a double-fluid atomization injection gun to construct an atomization characteristic database; establishing a numerical model to obtain a furnace multi-field database under different loads; coupling the cold-state database with the hot-state field database to simulate spray evaporation and obtain a coverage uniformity index; constructing a load-parameter mapping database based on the coverage uniformity index; self-learning and correcting parameters through wall temperature monitoring and DCS data; and adjusting injection gun working parameters in real time according to load variation. The application realizes self-adaptive optimization of the coverage range of the reducing agent injection under wide load conditions.

Description

Technical Field

[0001] This invention relates to the field of nitrogen oxide control technology for coal-fired boilers, and specifically to an adaptive load SNCR injection coverage control method. Background Technology

[0002] Selective non-catalytic reduction (SNR) denitrification technology is a low-cost, easy-to-operate and maintain NOx emission control technology for coal-fired boilers. Its principle involves injecting an ammonia-containing reducing agent into a region of the furnace at 850℃ to 1050℃, where the reducing agent decomposes and releases... It reacts with NOx in the flue gas to produce harmless substances. and Compared with selective catalytic reduction (SNCR) denitrification technology, the overall investment and operating costs of SNCR denitrification technology are at least 30% to 40% lower, making it more economically attractive.

[0003] The application of SNCR (Synchronous Non-Combustion Reduction) denitrification technology in large pulverized coal boilers is significantly limited. The furnace cross-section of large pulverized coal boilers is typically between 15 m and 25 m. After being injected from the furnace wall, the reducing agent droplets need to penetrate several meters or even more than ten meters to fully contact and mix with the high-concentration NOx flue gas in the central area of ​​the furnace. However, when the boiler operates under wide load conditions, the temperature field, velocity field, and NOx concentration field within the furnace change significantly with load variations. Under high load conditions, the flue gas velocity is high, requiring a large droplet penetration depth; under low load conditions, the flue gas velocity decreases, and if the original injection parameters are maintained, the droplets may penetrate too deeply, reaching the opposite wall area, causing water-cooled wall corrosion or even tube rupture. Simultaneously, if the droplet penetration depth is insufficient, the reducing agent coverage is limited, making it difficult to improve denitrification efficiency.

[0004] Current SNCR denitrification control methods mainly involve setting up multiple layers of spray guns at different heights in the furnace and determining the operation strategy and parameters of the spray guns based on hot-state tests under different loads. The published patent "A Control Method for an SNCR Denitrification System of a Coal-fired Unit (CN202011248449.1)" constructs a database by acquiring urea solution flow rates and diluted demineralized water pressure values ​​from each metering module under different loads. During actual operation, it searches for corresponding parameters and corrects the injection flow rate based on the outlet NOx value. However, this method only adjusts the overall urea solution flow rate and demineralized water pressure, failing to control the spray coverage of each spray gun from the perspective of coordinated adjustment of atomizing air pressure and liquid flow rate. It cannot achieve fine-grained parameter adjustment at the individual spray gun level, nor can it quantitatively assess the actual effective coverage of the injected reducing agent under various loads.

[0005] Therefore, how to adaptively adjust the atomizing air pressure and liquid flow rate of each spray gun according to the real-time changes in boiler load, so that the reducing agent droplets can achieve effective coverage and matching with the high NOx concentration area under different load conditions, is a technical problem that the current SNCR denitrification technology for large pulverized coal boilers urgently needs to solve. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide an adaptive load SNCR injection coverage control method.

[0007] To achieve the above objectives, the present invention provides an adaptive load SNCR injection coverage control method, comprising: A cold-state test was conducted on the atomization characteristics of the atomizing spray gun under different operating parameters to construct an atomization characteristic database; and a numerical model of the boiler furnace was established to simulate the furnace field distribution data of the boiler under different loads within a preset load range to construct a hot-state field database. Using the atomization characteristic database as boundary conditions, the thermal field database is coupled to simulate the evaporation process of the atomized droplets ejected by the atomizing spray gun under various loads, so as to obtain the spray characteristic parameters under thermal conditions and calculate the coverage evaluation index. Based on the coverage evaluation index meeting the preset conditions, the working parameters of the atomizing spray gun under each load are screened, and a load-parameter mapping database is constructed. During the operation of the boiler, the working parameters in the load-parameter mapping database are self-learned and corrected. Based on the actual load changes of the boiler, the load-parameter mapping database is queried, and the working parameters of each atomizing spray gun are adjusted in real time to make the reducing agent spray coverage adapt to load changes.

[0008] Furthermore, the atomizing spray gun is a dual-fluid atomizing spray gun, and the operating parameters include atomizing air pressure and liquid flow rate.

[0009] Furthermore, the atomization characteristics include atomized particle size distribution, injection angle, and initial injection velocity; The specific method of the cold state test is as follows: The atomized air pressure is gradually varied within a preset pressure step size from a first preset pressure value to a second preset pressure value. The liquid flow rate is gradually varied within a preset flow rate step size within the range of a first preset flow rate value to a second preset flow rate value. Under the combined conditions of the atomizing air pressure and the liquid flow rate, the atomized particle size distribution, spray angle and initial spray velocity of the atomizing spray gun are measured, and the measurement results are stored in the atomization characteristic database.

[0010] Furthermore, the furnace field distribution data includes temperature field distribution, velocity field distribution, and NOx concentration field distribution; The numerical model is established as follows: A three-dimensional CFD numerical calculation model was established based on the actual structure of the boiler. The three-dimensional CFD numerical calculation model is used to simulate the temperature field distribution, velocity field distribution, and NOx concentration field distribution of the boiler furnace under different loads from the preset minimum load to the preset maximum load range; The temperature field distribution, velocity field distribution, and NOx concentration field distribution under each load are stored as the thermal field database.

[0011] Furthermore, the coverage evaluation indicators include coverage area and coverage uniformity index; The coverage area is calculated as follows: ; in, The coverage area of ​​a single atomizing spray gun. For the spray distance, The spray angle; The coverage uniformity index is calculated as follows: ; in, The coverage uniformity index is... This represents the overlap area between the reducing agent-covered region and the high-concentration NOx region. The total area of ​​the high-concentration NOx region; The preset conditions include: The coverage uniformity index is greater than or equal to a preset coverage threshold, and the spraying distance is less than the distance to the opposite wall of the furnace. Wherein, the preset coverage threshold is that the coverage uniformity index is greater than or equal to 80%; When the coverage uniformity index is greater than or equal to 80% and the spraying distance is less than the distance between the front and rear walls of the boiler furnace, the corresponding operating parameters are stored in the load-parameter mapping database.

[0012] Furthermore, the evaporation process employs a discrete phase model. The law of evaporation is simulated, and the... The law of evaporation is expressed as: ; in, For the time elapsed The diameter of the droplets after evaporation The initial droplet diameter, It is the evaporation constant; The evaporation constant The calculation formula is: ; in, For the thermal conductivity of gases, For droplet density, Specific heat capacity of gas It is a prime number.

[0013] Furthermore, the atomized particle size of the atomizing spray gun is characterized by the Sauter mean particle size, and the empirical correlation for the Sauter mean particle size is: ; in, The average particle size is the Soter average. For liquid surface tension, For the density of the liquid, The relative velocity between gas and liquid. For the dynamic viscosity of the liquid, and This is an empirical coefficient; The relative velocity of the gas and liquid is changed by adjusting the atomizing air pressure. To control the average particle size of the SOT.

[0014] Furthermore, the self-learning correction includes: A temperature sensor is installed on the boiler furnace wall to monitor the wall temperature in real time. When the wall temperature detected by the temperature sensor exceeds the preset wall temperature threshold, it is determined that the droplets sprayed by the atomizing spray gun in the corresponding area have reached the opposite wall. The working parameters of the atomizing spray gun are adjusted to shorten the spray distance. The adjustment includes reducing the liquid flow rate of the atomizing spray gun or increasing the atomizing air pressure. The operating parameters in the DCS data of the unit are collected. The operating parameters include load data, flue gas velocity data and flue gas temperature data. The operating parameters under each load in the load-parameter mapping database are iteratively corrected using machine learning methods.

[0015] Furthermore, multiple layers of the atomizing spray guns are arranged along the height direction of the boiler furnace, and multiple atomizing spray guns are arranged in each layer along the width direction of the boiler furnace. Each atomizing spray gun is equipped with a flow regulating valve and a pressure regulating valve to enable independent adjustment of the operating parameters of each atomizing spray gun.

[0016] Furthermore, based on the actual load changes of the boiler, the load-parameter mapping database is queried to adjust the operating parameters of each atomizing spray gun in real time, including: Obtain the real-time load value of the boiler; Query the operating parameters corresponding to the real-time load value in the load-parameter mapping database; The operating parameters of each atomizing spray gun are adjusted to the corresponding parameter values ​​in the load-parameter mapping database by means of the regulating valves installed in front of each atomizing spray gun.

[0017] The beneficial effects of this invention are as follows: This invention overcomes the limitations of existing SNCR technology, which relies solely on hot-state tests or empirical values ​​to determine the working parameters of the spray gun, by coupling cold-state atomization characteristic tests with hot-state field numerical simulations. It can quantitatively evaluate the actual coverage range of the reducing agent droplets under different load conditions and realize the construction of a precise mapping relationship between the spray gun working parameters and the boiler load.

[0018] This invention introduces the coverage uniformity index as a quantitative evaluation index of the reducing agent coverage effect. The effectiveness of spray coverage is characterized by the proportion of the overlapping area between the reducing agent coverage area and the high-concentration NOx area. This provides a scientific basis for the optimization of spray gun working parameters and avoids the shortcomings of traditional methods in that the coverage effect cannot be quantified.

[0019] This invention uses real-time monitoring by a wall temperature sensor and a machine learning self-learning mechanism based on DCS data to continuously correct the spray gun operating parameters during operation. This ensures spray safety, prevents water-cooled wall overheating and tube rupture, and allows parameter adjustments to adapt to the dynamic changes in the actual operating state of the boiler.

[0020] This invention enables independent adjustment of fine parameters at the level of each atomizing spray gun. It queries the load-parameter mapping database in real time according to the actual load changes of the boiler and automatically adjusts the liquid flow rate and atomizing air pressure, so that large pulverized coal boilers can obtain a reducing agent coverage range that matches the NOx distribution in each region under wide load conditions, effectively improving SNCR denitrification efficiency and reducing agent utilization. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system architecture of the adaptive load SNCR injection coverage control method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the regulating valve group and flow meter group of the dual-fluid atomizing spray gun according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the spray pattern and measurement of the cold atomization characteristics test according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the adaptive load SNCR injection coverage control method according to an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the specific embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0023] The adaptive load SNCR injection coverage control method of the present invention is based on an SNCR denitrification system. The SNCR denitrification system includes a urea solution supply system, a demineralized water supply system, a compressed air supply system, a metering and dilution module, a distribution module, injection components, a water-cooled wall surface temperature monitoring system, an industrial control computer, and a server.

[0024] The urea solution supply system stores and transports the urea solution, delivering it from the storage tank to the metering and dilution module via pipelines. The demineralized water supply system provides dilution water, which is mixed with the urea solution in the metering and dilution module according to a preset ratio to prepare a reducing agent solution of a preset concentration. The compressed air supply system provides compressed air for atomization of the dual-fluid atomizing spray guns; the compressed air pressure is adjustable from 0.1 MPa to 0.8 MPa. The metering and dilution module meteres and mixes the urea solution and demineralized water. The distribution module distributes the prepared reducing agent solution to each dual-fluid atomizing spray gun. The spray assembly includes multi-layer dual-fluid atomizing spray guns arranged along the height of the boiler furnace. The water-cooled wall surface temperature monitoring system consists of multiple thermocouples installed on the furnace wall for real-time monitoring of the wall surface temperature. The industrial control computer is responsible for data acquisition, data processing, and control command output. The server is responsible for running numerical simulation programs and machine learning algorithms.

[0025] Example 1 This embodiment uses a counter-firing boiler of a 600 MW supercritical coal-fired unit as the application scenario. The boiler has a furnace cross-section of 20 m by 20 m, a furnace height of approximately 55 m, and a distance of 20 m between the front and rear walls of the furnace. It is equipped with 6 medium-speed coal mills and is designed to burn medium-to-high volatile bituminous coal. The initial NOx emissions across the entire load range are between 180 and 300 mg / m³.

[0026] See Figure 1 and Figure 2 The method in this embodiment includes the following steps: Step S1: Arrange the multi-layer dual-fluid atomizing spray gun.

[0027] Three layers of dual-fluid atomizing spray guns are arranged along the height of the boiler furnace. The first layer of spray guns is located approximately 38 m below the flame deflector, with 5 spray guns each along the front and rear walls of the boiler furnace, totaling 10 spray guns. The second layer of spray guns is located approximately 42 m above the flame deflector, with 10 spray guns along the front wall of the boiler furnace. The third layer of spray guns is located approximately 46 m above the flame deflector, with 10 spray guns along the front wall of the boiler furnace. A total of 30 spray guns are arranged across the three layers.

[0028] See Figure 2 An electric liquid flow regulating valve is installed on the inlet liquid line of each dual-fluid atomizing spray gun, allowing independent adjustment of the reducing agent liquid flow rate entering each spray gun, with a flow rate adjustment range of 0 to 500 L / h. An electric atomizing air pressure regulating valve is also installed on the inlet compressed air line of each dual-fluid atomizing spray gun, allowing independent adjustment of the atomizing air pressure of each spray gun, with a pressure adjustment range of 0.1 MPa to 0.8 MPa. An electromagnetic flow meter is also installed on the inlet liquid line of each spray gun for real-time monitoring of the actual flow rate. A pressure transmitter is installed on the inlet compressed air line of each spray gun for real-time monitoring of the actual atomizing air pressure.

[0029] K-type thermocouples are installed on the water-cooled walls of the boiler furnace in the three-layer spray gun arrangement area. Eight thermocouples are installed in the first layer, four evenly distributed on each of the front and rear walls of the furnace. Six thermocouples are installed in the second layer, on the rear and side walls of the furnace. Six thermocouples are installed in the third layer, on the rear and side walls of the furnace. A total of 20 thermocouples are used. The thermocouples are installed approximately 0.5 m to 1 m away from the wall opposite the spray gun to detect whether droplets reach the wall area.

[0030] Specifically, the thermocouple is attached to the heated surface of the opposite wall. The distance of 0.5 m to 1 m refers to the horizontal offset of the thermocouple mounting point relative to the projection of the spray gun's center line onto the opposite wall. This non-centrally offset arrangement effectively avoids the reduced agent droplets directly scouring the thermocouple, thus preventing damage to its lifespan. Furthermore, by monitoring the wall temperature fluctuations around the spray core area, it can sensitively detect whether the droplets penetrate the flue gas field and reach the wall surface.

[0031] Step S2: Cold atomization characteristic test.

[0032] See Figure 3 The dual-fluid atomizing spray gun selected in this embodiment underwent cold-state atomization characteristic tests on a spray test bench. The test bench was equipped with a phase Doppler particle analyzer, a high-speed camera, and a turbine flow meter.

[0033] The atomizing air pressure was varied from 0.1 MPa to 0.8 MPa in increments of 0.1 MPa, resulting in eight pressure levels. The liquid flow rate was varied from 50 L / h to 500 L / h in increments of 50 L / h, resulting in ten flow rate levels. Tests were conducted under all combinations of the eight pressure levels and ten flow rate levels, totaling 80 test conditions.

[0034] Under each set of experimental conditions, the droplet size distribution parameters were measured using a phase Doppler particle analyzer, including... , and Three characteristic particle size values, among which The particle size corresponding to 10% of the cumulative volume. The median particle size corresponding to 50% of the cumulative volume. The particle size corresponds to 90% of the cumulative volume. The spray pattern is captured using a high-speed camera, and the spray cone angle is measured as the jet angle. The initial velocity of the droplets at the nozzle exit is measured using a phase Doppler particle analyzer.

[0035] Taking the operating conditions of atomizing air pressure of 0.2 MPa and liquid flow rate of 400 L / h as an example, the measurements were obtained. μm, μm, μm, the injection angle is 20°, and the initial injection velocity is 80 m / s.

[0036] Taking the operating conditions of atomizing air pressure of 0.3 MPa and liquid flow rate of 200 L / h as an example, the measurements were obtained. μm, μm, μm, the injection angle is 28°, and the initial injection velocity is 110 m / s.

[0037] Taking the operating conditions of atomizing air pressure of 0.5 MPa and liquid flow rate of 300 L / h as an example, the measurements were obtained. μm, μm, μm, the injection angle is 32°, and the initial injection velocity is 130 m / s.

[0038] The variation law of atomized particle size conforms to the description of the empirical correlation of Sauter mean particle size. The empirical correlation of Sauter mean particle size is: ; in, The average particle size is the Soter average. For urea solution, the surface tension of the liquid is... N / m, The density is the liquid density for a 10% urea solution. kg / m³, The relative velocity between gas and liquid. For urea solution, the dynamic viscosity is the viscosity of the liquid. Pa·s, and This is an empirical coefficient. The relative velocity between gas and liquid is increased by increasing the atomizing air pressure. This can reduce the average particle size of the Sauternes. This makes the droplets smaller, thus accelerating evaporation; it also reduces the relative velocity between the gas and liquid by lowering the atomizing air pressure. This can increase the average particle size of the Sotter. This gives the droplet greater inertia, thereby increasing the penetration depth.

[0039] The atomization characteristic parameters of all 80 test conditions were established into an atomization characteristic database indexed by atomizing air pressure and liquid flow rate.

[0040] Step S3: Establish a numerical model of the boiler furnace thermal field.

[0041] A three-dimensional CFD numerical model was established using the actual boiler of this 600 MW supercritical coal-fired unit as a prototype. The CFD model was built using FLUENT software, with a mesh size of approximately 2.8 million. Turbulence model, P1 radiation model, discrete phase model of pulverized coal particles, and NOx formation model.

[0042] A CFD numerical model was used to simulate the temperature, velocity, and NOx concentration distributions in the boiler furnace under different loads ranging from 30% load (180 MW) to 100% load (600 MW). The simulation was divided into 15 load levels with a step size of 30 MW. At each load level, different coal mill operation modes were simulated, including 6 mills, 5 mills, 4 mills, and 3 mills operating. Simultaneously, different combinations of primary and secondary damper openings were simulated.

[0043] Through the aforementioned CFD numerical simulations, the three-dimensional temperature field distribution, velocity field distribution, and NOx concentration field distribution of the boiler furnace from the bottom of the furnace to the furnace outlet were obtained under various operating conditions. The temperature field distribution, velocity field distribution, and NOx concentration field distribution under each load were stored as a thermal field database. The thermal field database contains approximately 1500 sets of data for different operating conditions.

[0044] Taking a 600 MW full-load operating condition as an example, the cross-sectional temperature distribution at an elevation of 38 m where the first-layer spray gun is located exhibits a characteristic of high temperature in the center and low temperature around the perimeter. The temperature in the central region is approximately 1000℃ to 1100℃, while the temperature near the perimeter walls is approximately 800℃ to 900℃. The flue gas velocity distribution in the cross-section shows a characteristic of high velocity in the center and low velocity around the perimeter. The flue gas velocity in the central region is approximately 8 to 10 m / s, while the flue gas velocity near the walls is approximately 2 to 4 m / s. The NOx concentration distribution in the cross-section shows a characteristic of relatively high concentration in the center. The NOx concentration in the central region is approximately 280 to 350 mg / m³, while the NOx concentration near the walls is approximately 150 to 220 mg / m³.

[0045] Taking a 300 MW (50% load) operating condition as an example, at an elevation of 38 m where the first spray gun is located, the temperature in the central region of the cross-sectional temperature distribution drops to approximately 850°C to 950°C, while the temperature near the surrounding walls drops to approximately 700°C to 800°C. The flue gas velocity in the central region of the cross-section drops to approximately 4 to 6 m / s, and the flue gas velocity near the walls drops to approximately 1 to 2 m / s. The NOx concentration in the central region of the cross-section is approximately 200 to 260 mg / m³.

[0046] Step S4: Cold-hot coupled simulation and coverage uniformity index calculation.

[0047] Using the atomization characteristic database obtained in step S2 as the boundary conditions for the discrete phase, the atomized particle size distribution, injection angle, and initial injection velocity corresponding to each group of atomized air pressure and liquid flow rate are input into the CFD model as the initial conditions for the droplets. The temperature field distribution, velocity field distribution, and NOx concentration field distribution under each load in the thermal field database obtained in step S3 are used as the background flow field conditions for the continuous phase.

[0048] Under various load conditions, the motion and evaporation process of atomized droplets from each dual-fluid atomizing nozzle, sprayed under different operating parameters, are simulated upon entering the furnace. The evaporation process of the droplets within the furnace is represented by a discrete phase model. The law of evaporation is used for simulation. The law of evaporation is expressed as: ; in, For the time elapsed The diameter of the droplets after evaporation The initial droplet diameter, The evaporation constant is For time.

[0049] Evaporation constant The calculation formula is: ; in, The thermal conductivity of the gas is approximately [value missing] at a furnace temperature of 900℃. W / (m·K), The droplet density is approximately [value missing] for a 10% urea solution. kg / m³, The specific heat capacity of the gas is approximately [value missing] at the furnace temperature. J / (kg·K), This is the mass transfer number, which is approximately 0.78 for water vapor.

[0050] The actual trajectory of the droplets under various operating conditions in a hot state was obtained through simulation. The droplets gradually decelerate under the drag force of the flue gas while continuously evaporating in the high-temperature flue gas environment. The endpoint of the droplet's trajectory is determined by either the point where the droplet completely evaporates or the point where it reaches the wall. The injection angle under hot conditions is determined by the envelope of the droplet's trajectory. The injection distance under hot conditions is determined by the horizontal distance from the point where the droplet completely evaporates to the nozzle outlet.

[0051] Based on the spray angle and spray distance under hot operating conditions, the coverage area of ​​each dual-fluid atomizing spray gun is calculated. The calculation method for the coverage area is as follows: ; in, The coverage area of ​​a single dual-fluid atomizing spray gun. For the spray distance, This refers to the spray angle.

[0052] Simultaneously calculate the coverage evenness index. The calculation method for the coverage evenness index is as follows: ; in, To cover the uniformity index, This represents the overlap area between the reducing agent-covered region and the high-concentration NOx region. This represents the total area of ​​the high-concentration NOx region. The high-concentration NOx region is defined as the area where the NOx concentration is greater than 200 mg / m³. The reducing agent coverage area is determined by the union of the coverage areas of each spray gun. This represents the intersection area between the reducing agent-covered region and the high-concentration NOx region.

[0053] Taking a 600 MW full-load operating condition as an example, when the atomizing air pressure is set to 0.2 MPa and the liquid flow rate is set to 400 L / h, the spraying distance of the third spray gun on the first-layer front wall under hot conditions is 8.5 m, the spraying angle is 15°, and the coverage area is [missing information - likely a specific area or region]. The total coverage area of ​​all 10 spray guns in the first layer is 22.4 m², which is equal to the cross-sectional area of ​​the first layer, which is 20 m². The ratio of 20 m = 400 m² is 5.6%. Through comprehensive coverage using all three layers and 30 spray guns, the ratio of the sum of the coverage areas of each layer to the total cross-sectional area reaches over 65%, satisfying the condition that the cross-sectional coverage area ratio is greater than or equal to 60%. Simultaneously, the coverage uniformity index is calculated. ,satisfy The preset coverage threshold was set. The spray distance of each spray gun was less than 20m between the front and rear walls of the furnace, meeting the safety requirements. The liquid flow rate of 400 L / h and the atomizing air pressure of 0.2 MPa under this condition were stored in the load-parameter mapping database.

[0054] Taking a 300 MW (50% load) operating condition as an example, the flue gas velocity in the furnace decreases by approximately 40% to 50%. If the operating parameters of a liquid flow rate of 400 L / h and an atomizing air pressure of 0.2 MPa are maintained, simulation results show that the droplet penetration depth increases to approximately 14 m, and the spray distance of some nozzles exceeds 18 m, approaching the opposite wall. The droplet coverage density on the wall area increases, posing a risk of droplets reaching the wall. By traversing various operating parameters in the atomization characteristic database, simulations show that under operating parameters of a liquid flow rate of 200 to 260 L / h and an atomizing air pressure of 0.3 MPa, the spray distance is shortened to 6 to 8 m, and the coverage uniformity index... ,satisfy The preset coverage threshold is set, and the spraying distance is less than 20 m between the front and rear walls of the furnace. The operating parameters under this condition are stored in the load-parameter mapping database.

[0055] Following the above method, cold-hot coupled simulations and coverage uniformity index calculations were performed for each of the 15 load levels within the 180 MW to 600 MW range to screen for those that meet the requirements. Furthermore, the operating parameters, such as the injection distance being less than the distance between the front and rear walls of the furnace, are used to construct a complete load-parameter mapping database.

[0056] Step S5: Wall temperature monitoring and DCS data self-learning correction.

[0057] During boiler operation, the industrial control computer collects wall temperature data from 20 thermocouples in real time, with a sampling period of 5 seconds.

[0058] The normal range of wall temperature is determined based on operating experience and design parameters. Without the injection of reducing agent, the water-cooled wall temperature is typically between 350℃ and 420℃. When reducing agent droplets reach the wall area, the droplets evaporate and absorb heat, causing a localized decrease in wall temperature. However, under this abnormal operating condition, due to the high-temperature environment of the furnace, the wall temperature may abnormally rise instead of decrease. The specific reasons are: On the one hand, when a droplet impacts a wall surface with a temperature much higher than the boiling point of water, the Leiden-Frost effect occurs, forming an insulating vapor film between the wall surface and the droplet. This vapor film has extremely high thermal resistance, which hinders the normal transfer of heat from the pipe wall to the working fluid inside the pipe, leading to deterioration of heat transfer and accumulation of heat on the wall surface. On the other hand, after the solution droplets containing reducing agents evaporate, they easily leave solid deposits (such as slag and ash) on the tube wall surface. This also contaminates the tube wall and increases thermal resistance, leading to a sharp decrease in the heat exchange efficiency of the water-cooled wall. Therefore, the preset wall temperature threshold is set to the normal operating temperature of the wall surface plus a deviation of 30°C. When the wall temperature monitored by the thermocouple exceeds the preset wall temperature threshold, the system determines that the droplets sprayed by the dual-fluid atomizing spray gun in the corresponding area have reached the opposite wall surface.

[0059] At this point, the system performs parameter correction. The liquid flow rate of the corresponding dual-fluid atomizing spray gun is reduced by 10% of the current flow rate each time. Simultaneously, the atomizing air pressure is increased by 0.05 MPa each time. By reducing the liquid flow rate to decrease droplet inertia and by increasing the atomizing air pressure to decrease droplet size, both methods shorten the droplet penetration depth, thus preventing the droplets from reaching the opposite wall surface.

[0060] The industrial control computer collects operating parameters from the unit's DCS data, including boiler load, flue gas velocity, flue gas temperature, damper opening, and coal mill operation mode. It correlates the wall temperature monitoring results and spray nozzle operating parameter adjustment records from actual operation with the DCS operating data. Using a gradient boosting decision tree-based machine learning method, a parameter correction model is trained with DCS operating parameters as input and spray nozzle operating parameters that meet coverage uniformity index requirements and do not trigger wall temperature alarms as output. The training data for the parameter correction model comes from accumulated parameter adjustment records during actual operation, and the model is updated every 500 hours of operation. The iteratively corrected operating parameters replace the original parameters corresponding to the load level in the load-parameter mapping database.

[0061] Step S6: Adjust the working parameters of the spray gun in real time according to the actual load changes of the boiler.

[0062] During boiler operation, the industrial control computer acquires the real-time load value of the boiler in real time, with a sampling period of 1 second.

[0063] When the real-time load value changes, the industrial control computer queries the load-parameter mapping database for the liquid flow rate and atomized air pressure corresponding to the load level closest to the real-time load value. When the real-time load value is between two adjacent load levels, the corresponding operating parameters are calculated using a linear interpolation method.

[0064] The industrial control computer sends flow setpoint commands to the electric liquid flow regulating valves installed in front of each dual-fluid atomizing spray gun via the control bus, and sends pressure setpoint commands to the electric atomizing air pressure regulating valves. The flow and pressure regulating valves automatically adjust their openings according to the received setpoints, ensuring that the liquid flow and atomizing air pressure of each spray gun reach the corresponding parameter values ​​in the load-parameter mapping database.

[0065] Taking the load change process of this 600 MW unit from 100% load to 50% load as an example. When operating at full load (600 MW), according to the load-parameter mapping database, the liquid flow rate of each spray nozzle is set to 400 L / h, and the atomizing air pressure is set to 0.2 MPa. When the boiler load drops to 450 MW (75% load), the industrial control computer queries the load-parameter mapping database to obtain the corresponding operating parameters: liquid flow rate 310 L / h, atomizing air pressure 0.25 MPa. The operating parameters of each spray nozzle are then adjusted to these values. When the boiler load continues to drop to 300 MW (50% load), the industrial control computer queries the database to obtain the corresponding operating parameters: liquid flow rate 230 L / h, atomizing air pressure 0.3 MPa. The operating parameters of each spray nozzle are adjusted again.

[0066] Throughout the load change process, the wall temperature monitoring system continuously monitored thermocouple data. Under a 450 MW load, the thermocouple temperature at the location corresponding to the fourth spray gun on the rear wall of the first floor rose above the preset wall temperature threshold. The system determined that the droplets from that spray gun had reached the wall surface and immediately reduced the liquid flow rate of that spray gun from 310 L / h to 280 L / h, while increasing the atomizing air pressure from 0.25 MPa to 0.30 MPa. After adjustment, the thermocouple temperature returned to the normal range within 30 seconds, and the system recorded this adjustment in the DCS data self-learning sample library.

[0067] Through the aforementioned adaptive adjustments, this embodiment achieves a coverage uniformity index under various load conditions within a wide load range of 600 MW to 300 MW. All levels remained above 80%, and the spraying distance of each spray gun was less than 20 m between the front and rear walls of the furnace. No droplets reached the wall surface and triggered a wall temperature alarm.

[0068] Example 2 This embodiment uses a W-flame boiler in a 350 MW subcritical coal-fired unit as an example. The W-flame boiler has a furnace cross-section of 18 m by 12 m, a furnace height of approximately 50 m, and a distance of 12 m between the front and rear walls of the furnace. It is equipped with four medium-speed coal mills, designed to burn anthracite, and its initial NOx emissions are between 550 and 900 mg / m³ across the entire load range.

[0069] Step S1: Arrange the multi-layer dual-fluid atomizing spray gun.

[0070] Based on the temperature variation patterns of the furnace flue gas under various loads in the 350 MW unit's W-flame boiler, four layers of dual-fluid atomizing spray guns are arranged along the furnace height. The first layer of spray guns is located approximately 32 m below the flame deflector, with four guns along the front wall and four along the rear wall, totaling eight. The second layer is located approximately 36 m above the flame deflector, with eight guns along the front wall of the furnace. The third layer is located approximately 40 m above the flame deflector, with eight guns along the front wall of the furnace. The fourth layer uses multi-nozzle long spray guns, located approximately 44 m above the furnace outlet screen superheater and high-temperature superheater, with one multi-nozzle long spray gun on each side wall, totaling two. A total of 26 spray guns are used across the four layers.

[0071] Each dual-fluid atomizing spray gun is equipped with an electrically operated liquid flow regulating valve on its inlet liquid line, with a flow rate adjustment range of 0 to 400 L / h. Each dual-fluid atomizing spray gun is also equipped with an electrically operated atomizing air pressure regulating valve on its inlet compressed air line, with a pressure adjustment range of 0.1 MPa to 0.8 MPa. An electromagnetic flow meter is also installed on the inlet liquid line of each spray gun, and a pressure transmitter is installed on the inlet compressed air line of each spray gun.

[0072] K-type thermocouples are installed on the water-cooled wall surface of the boiler furnace in the four-layer spray gun arrangement area. Six thermocouples are installed in each layer, for a total of 24 thermocouples across the four layers. The thermocouples are installed approximately 0.3 m to 0.8 m away from the wall opposite the spray guns.

[0073] Step S2: Cold atomization characteristic test.

[0074] The dual-fluid atomizing spray gun selected in this embodiment underwent cold-state atomization characteristic tests on a spray test bench. The atomizing air pressure was varied from 0.1 MPa to 0.6 MPa in increments of 0.1 MPa, for a total of six pressure levels. The liquid flow rate was varied from 50 L / h to 400 L / h in increments of 50 L / h, for a total of eight flow rates. Tests were conducted under all combinations of the six pressure levels and eight flow rates, resulting in a total of 48 test conditions.

[0075] Under each set of experimental conditions, the droplet size distribution parameters were measured using a phase Doppler particle analyzer. , and A high-speed camera was used to capture the spray pattern and measure the spray angle. A phase Doppler particle analyzer was used to measure the initial spray velocity.

[0076] Taking the operating conditions of atomizing air pressure of 0.3 MPa and liquid flow rate of 250 L / h as an example, the measurements were obtained. μm, μm, The atomized air pressure was 0.5 MPa, the liquid flow rate was 150 L / h, and the spray angle was 26°. The initial spray velocity was 105 m / s. The measurements were taken under the following conditions: atomizing air pressure of 0.5 MPa and liquid flow rate of 150 L / h. μm, μm, μm, the injection angle is 34°, and the initial injection velocity is 140 m / s.

[0077] The atomization characteristic parameters of all 48 test conditions were established into an atomization characteristic database indexed by atomizing air pressure and liquid flow rate.

[0078] Step S3: Establish a numerical model of the boiler furnace thermal field.

[0079] Based on the actual structure of this 350 MW flame-fired boiler, a three-dimensional CFD numerical model was established with approximately 2.4 million mesh elements. The CFD model simulated the temperature, velocity, and NOx concentration distributions in the boiler furnace under different loads ranging from 30% load (105 MW) to 100% load (350 MW), divided into 11 load levels with a step size of 25 MW. Different coal mill operation modes were simulated at each load level, resulting in approximately 800 sets of simulation data, which were stored in a thermal field database.

[0080] Taking a 350 MW full-load operating condition as an example, the temperature in the central region of the cross-sectional temperature distribution at an elevation of 32 m where the first-layer spray gun is located is approximately 1050℃ to 1150℃, while the temperature near the surrounding walls is approximately 850℃ to 950℃. Due to its different combustion method compared to a counter-firing boiler, the W-flame boiler exhibits a temperature distribution characteristic of higher temperatures in the lower part of the furnace. The cross-sectional flue gas velocity distribution shows a predominantly upward airflow with a velocity of approximately 6 to 8 m / s in the central region. The NOx concentration distribution in the central region is approximately 600 to 800 mg / m³, while near the walls it is approximately 350 to 500 mg / m³, indicating a significantly higher NOx concentration level than that of a counter-firing boiler.

[0081] Taking a 175 MW (50% load) operating condition as an example, the temperature in the central area of ​​the first cross section drops to about 900℃ to 1000℃, the flue gas velocity drops to about 3 to 5 m / s, and the NOx concentration drops to about 400 to 550 mg / m³.

[0082] Step S4: Cold-hot coupled simulation and coverage uniformity index calculation.

[0083] Using the atomization characteristic database from step S2 as discrete phase boundary conditions, a cold-to-hot coupled simulation was performed by coupling it with the thermal field database from step S3. Since the distance between the front and rear walls of the W-flame boiler furnace is only 12 m, less than the 20 m in Example 1, controlling the droplet penetration distance is even more crucial.

[0084] The droplet evaporation process also uses Evaporation law simulation. In a W-flame boiler, due to the higher furnace temperature, the evaporation constant... Larger droplets result in faster evaporation rates. For example, at a furnace temperature of 1000℃, the gas thermal conductivity... Approximately 0.085 W / (m·K), substituting this into the formula for calculating the evaporation constant: m² / s; At this evaporation constant, the complete evaporation time for a droplet with an initial particle size of 75 μm is approximately s, which is approximately 20 ms.

[0085] Taking a 350 MW full-load operating condition as an example, cold-hot coupled simulation showed that when the atomizing air pressure was set to 0.25 MPa and the liquid flow rate was set to 280 L / h, the hot-hot spraying distance of each spray gun in the first layer was within the range of 5 to 7 m, and the coverage uniformity index was [missing information]. ,satisfy The preset coverage threshold is set so that the spraying distance is less than 12 m between the front and rear walls of the furnace.

[0086] Taking a 175 MW (50% load) operating condition as an example, the flue gas velocity in the furnace decreases by approximately 45%. After extensive screening, under operating parameters of a liquid flow rate of 150 to 180 L / h and an atomizing air pressure of 0.35 MPa, the hot-state spraying distance of each spray gun in the first layer is within the range of 3 to 5 m, achieving a coverage uniformity index... The spraying distance is less than 12 m. The operating parameters under this condition are stored in the load-parameter mapping database.

[0087] Following the above method, cold-hot coupled simulation and parameter screening were completed for 11 load levels ranging from 105 MW to 350 MW, and a complete load-parameter mapping database was constructed.

[0088] Step S5: Wall temperature monitoring and DCS data self-learning correction.

[0089] The industrial control computer collects wall temperature data from 24 thermocouples in real time, with a sampling period of 5 seconds. Since the distance between the front and rear walls of the W-flame boiler furnace is only 12 m, the preset wall temperature threshold is set to the normal operating wall temperature plus a deviation of 25°C. When a thermocouple detects that the wall temperature exceeds the preset threshold, the liquid flow rate of the corresponding spray gun is reduced or the atomizing air pressure is increased. The parameter adjustment sensitivity of the W-flame boiler is higher than that of the opposed-fired boiler; the liquid flow rate is reduced by 8% of the current flow rate each time, and the atomizing air pressure is increased by 0.03 MPa each time.

[0090] The DCS data self-learning method is the same as in Example 1. It adopts a machine learning method based on gradient boosting decision trees, using DCS operating parameters as input and operating parameters that meet the coverage uniformity index requirements and do not trigger wall temperature alarms as output to train parameters to correct the model. The model is updated once every 500 hours of operation.

[0091] Step S6: Adjust the working parameters of the spray gun in real time according to the actual load changes of the boiler.

[0092] The real-time load value sampling period is 1 second. When the load changes, the load-parameter mapping database is queried, and the corresponding operating parameters are calculated using a linear interpolation method. These parameters are then automatically adjusted via an electric liquid flow regulating valve and an electric atomizing air pressure regulating valve.

[0093] Taking the load change process of this 350 MW unit from 100% load to 50% load as an example. When operating at full load (350 MW), the liquid flow rate of each spray nozzle is set to 280 L / h, and the atomizing air pressure is set to 0.25 MPa. When the load drops to 262.5 MW (75% load), the operating parameters are adjusted to a liquid flow rate of 215 L / h and an atomizing air pressure of 0.30 MPa. When the load drops to 175 MW (50% load), the operating parameters are adjusted to a liquid flow rate of 165 L / h and an atomizing air pressure of 0.35 MPa.

[0094] During the load change process, the thermocouple temperature at the location corresponding to the fifth spray gun on the front wall of the second floor rose above the preset wall temperature threshold under a load of 262.5 MW. The system reduced the liquid flow rate of the spray gun from 215 L / h to 198 L / h and increased the atomizing air pressure from 0.30 MPa to 0.33 MPa. The thermocouple temperature returned to the normal range within 25 seconds.

[0095] After the above adaptive adjustment, this embodiment achieves a coverage uniformity index under various load conditions within a wide load range of 350 MW to 105 MW. All remained above 80%.

[0096] Example 3 This embodiment uses a tower boiler of a 1000 MW ultra-supercritical coal-fired unit as the application scenario. The tower boiler has a furnace cross-section of 25 m by 25 m, a furnace height of approximately 75 m, and a distance of 25 m between the front and rear walls of the furnace. It is equipped with 6 medium-speed coal mills, designed to burn low-volatile bituminous coal, and the original NOx emissions are between 250 and 400 mg / m³ across the entire load range.

[0097] Step S1: Arrange the multi-layer dual-fluid atomizing spray gun.

[0098] Four layers of dual-fluid atomizing spray guns are arranged along the height of the furnace. The first layer of spray guns is located at an elevation of approximately 50 m, with 6 spray guns each along the front and rear walls of the boiler furnace, totaling 12 guns. The second layer of spray guns is located at an elevation of approximately 54 m, with 12 spray guns arranged along the front wall of the boiler furnace. The third layer of spray guns is located at an elevation of approximately 58 m, with 12 spray guns arranged along the front wall of the boiler furnace. The fourth layer of spray guns is located at an elevation of approximately 62 m, with 12 spray guns arranged along the front wall of the boiler furnace. A total of 48 spray guns are arranged across the four layers.

[0099] Each dual-fluid atomizing spray gun is equipped with an electric liquid flow regulating valve and an electric atomizing air pressure regulating valve, with a flow rate regulation range of 0 to 600 L / h and a pressure regulation range of 0.1 MPa to 0.8 MPa.

[0100] K-type thermocouples are installed on the water-cooled wall surface of the boiler furnace in the four-layer spray gun arrangement area. Eight thermocouples are installed in each layer, for a total of 32 thermocouples across the four layers.

[0101] Step S2: Cold atomization characteristic test.

[0102] The dual-fluid atomizing spray gun selected in this embodiment underwent cold-state atomization characteristic tests on a spray test bench. Due to the large cross-sectional size of the tower boiler furnace, the droplets need to penetrate a greater distance, necessitating a spray gun model with stronger spraying capability. The atomizing air pressure was varied from 0.1 MPa to 0.8 MPa in 0.1 MPa increments, for a total of 8 pressure levels. The liquid flow rate was varied from 100 L / h to 600 L / h in 50 L / h increments, for a total of 11 flow rate levels. A total of 88 combined operating conditions were tested.

[0103] Under each set of experimental conditions, the atomized particle size distribution, injection angle, and initial injection velocity were measured using a phase Doppler particle analyzer and a high-speed camera. Taking the condition of atomizing air pressure of 0.2 MPa and liquid flow rate of 500 L / h as an example, the measurements were obtained... The atomized air pressure was 0.4 MPa, the liquid flow rate was 300 L / h, and the spray angle was 18° with an initial velocity of 75 m / s. Taking the operating conditions of 0.4 MPa atomizing air pressure and 300 L / h liquid flow rate as an example, the measured values ​​were... μm, the injection angle is 30°, and the initial injection velocity is 125 m / s.

[0104] The atomization characteristic parameters of all 88 test conditions were established as an atomization characteristic database.

[0105] Step S3: Establish a numerical model of the boiler furnace thermal field.

[0106] Using the actual structure of this 1000 MW ultra-supercritical tower boiler as a prototype, a three-dimensional CFD numerical model was established with approximately 3.8 million grid cells. The model simulated the temperature, velocity, and NOx concentration distributions in the boiler furnace under different loads ranging from 300 MW (30% load) to 1000 MW (1000 MW), divided into 15 load levels with a step size of 50 MW. Approximately 1800 sets of simulation data were collected and stored in a thermal field database.

[0107] Taking a 1000 MW full-load operating condition as an example, the temperature in the central region of the cross-sectional temperature distribution at an elevation of 50 m where the first layer of spray guns is located is approximately 950℃ to 1080℃, the flue gas velocity in the central region is approximately 9 to 12 m / s, and the NOx concentration in the central region is approximately 300 to 380 mg / m³. Since the cross-sectional area of ​​the tower boiler furnace is 25 m²... 25 m = 625 m², which is much larger than in Examples 1 and 2, indicating that the uniformity of the reducing agent coverage has a more significant impact on the denitrification efficiency.

[0108] Taking a 500 MW (50% load) operating condition as an example, the central area of ​​the cross-sectional temperature drops to about 800℃ to 920℃, the central area of ​​flue gas velocity drops to about 4 to 6 m / s, and the central area of ​​NOx concentration drops to about 180 to 260 mg / m³.

[0109] Step S4: Cold-hot coupled simulation and coverage uniformity index calculation.

[0110] A cold-to-hot coupled simulation was performed using a fogging characteristic database as discrete phase boundary conditions and coupled with a thermal field database. The droplet evaporation process was simulated using... Simulation of the law of evaporation.

[0111] Taking a 1000 MW full-load operating condition as an example, through cold-hot coupled simulation, when the atomizing air pressure is set to 0.2 MPa and the liquid flow rate is set to 500 L / h, the hot-hot spraying distance of each spray gun in the first layer is within the range of 10 to 13 m, and the coverage uniformity index is [missing information]. ,satisfy The preset coverage threshold is set so that the spray distance is less than 25 m between the front and rear walls of the furnace.

[0112] Taking a 500 MW (50% load) operating condition as an example, after extensive screening, under operating parameters of liquid flow rate of 250 to 320 L / h and atomizing air pressure of 0.35 MPa, the hot spray distance of each spray gun is within the range of 6 to 9 m, and the coverage uniformity index is [not specified]. The spraying distance is less than 25 m.

[0113] Following the above method, cold-hot coupled simulation and parameter screening were completed for 15 load levels in the range of 300 MW to 1000 MW, and a complete load-parameter mapping database was constructed.

[0114] Step S5: Wall temperature monitoring and DCS data self-learning correction.

[0115] The industrial control computer collects wall temperature data from 32 thermocouples in real time, with a sampling period of 5 seconds. The preset wall temperature threshold is set to the normal operating wall temperature plus a deviation of 35°C. After a wall temperature alarm, the liquid flow rate decreases by 10% of the current flow rate each time, and the atomized air pressure increases by 0.05 MPa each time. The DCS data self-learning method is the same as in Example 1.

[0116] Step S6: Adjust the working parameters of the spray gun in real time according to the actual load changes of the boiler.

[0117] Taking the load change process of this 1000 MW unit from 100% load to 50% load as an example. When operating at full load of 1000 MW, the liquid flow rate of each spray nozzle is set to 500 L / h, and the atomizing air pressure is set to 0.2 MPa. When the load drops to 750 MW (75% load), the operating parameters are adjusted to a liquid flow rate of 380 L / h and an atomizing air pressure of 0.28 MPa. When the load drops to 500 MW (50% load), the operating parameters are adjusted to a liquid flow rate of 285 L / h and an atomizing air pressure of 0.35 MPa.

[0118] During the load change process, the wall temperature monitoring system continued to operate. The second spray gun on the rear wall of the first floor triggered a wall temperature alarm under a load of 750 MW. The system reduced the liquid flow rate of the spray gun from 380 L / h to 342 L / h and increased the atomizing air pressure from 0.28 MPa to 0.33 MPa. The thermocouple temperature returned to the normal range within 35 seconds.

[0119] After the above adaptive adjustment, this embodiment achieves a coverage uniformity index under various load conditions within a wide load range of 1000 MW to 300 MW. All levels remained above 80%, and no droplets reached the wall surface, causing damage to the water-cooled wall.

[0120] In summary, the embodiments of the present invention have at least the following technical effects: This invention overcomes the limitations of existing SNCR technology, which relies solely on hot-state tests or empirical values ​​to determine the working parameters of the spray gun, by coupling cold-state atomization characteristic tests with hot-state field numerical simulations. It can quantitatively evaluate the actual coverage range of the reducing agent droplets under different load conditions and realize the construction of a precise mapping relationship between the spray gun working parameters and the boiler load.

[0121] This invention introduces the coverage uniformity index as a quantitative evaluation index of the reducing agent coverage effect. The effectiveness of spray coverage is characterized by the proportion of the overlapping area between the reducing agent coverage area and the high-concentration NOx area. This provides a scientific basis for the optimization of spray gun working parameters and avoids the shortcomings of traditional methods in that the coverage effect cannot be quantified.

[0122] This invention uses real-time monitoring by a wall temperature sensor and a machine learning self-learning mechanism based on DCS data to continuously correct the spray gun operating parameters during operation. This ensures spray safety, prevents water-cooled wall overheating and tube rupture, and allows parameter adjustments to adapt to the dynamic changes in the actual operating state of the boiler.

[0123] This invention enables independent adjustment of fine parameters at the level of each dual-fluid atomizing spray gun. It queries the load-parameter mapping database in real time according to the actual load changes of the boiler and automatically adjusts the liquid flow rate and atomizing air pressure, so that large pulverized coal boilers can obtain a reducing agent coverage range that matches the NOx distribution in each region under wide load conditions, effectively improving SNCR denitrification efficiency and reducing agent utilization.

[0124] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An adaptive load SNCR injection coverage control method, characterized in that, include: Cold-state tests were conducted on the atomization characteristics of the atomizing spray gun under different operating parameters, and an atomization characteristic database was constructed. In addition, a numerical model of the boiler furnace is established to simulate the furnace field distribution data of the boiler under different loads within a preset load range, and a thermal field database is constructed. Using the atomization characteristic database as boundary conditions, the thermal field database is coupled to simulate the evaporation process of the atomized droplets ejected by the atomizing spray gun under various loads, so as to obtain the spray characteristic parameters under thermal conditions and calculate the coverage evaluation index. Based on the coverage evaluation index meeting the preset conditions, the working parameters of the atomizing spray gun under each load are screened, and a load-parameter mapping database is constructed. Based on the actual load changes of the boiler, the load-parameter mapping database is queried, and the working parameters of each atomizing spray gun are adjusted in real time to make the reducing agent spray coverage adapt to load changes.

2. The adaptive load SNCR injection coverage control method according to claim 1, characterized in that, The atomizing spray gun is a dual-fluid atomizing spray gun, and the operating parameters include atomizing air pressure and liquid flow rate.

3. The adaptive load SNCR injection coverage control method according to claim 1, characterized in that, The atomization characteristics include atomized particle size distribution, injection angle, and initial injection velocity; The specific method of the cold state test is as follows: The atomized air pressure is gradually varied within a preset pressure step size from a first preset pressure value to a second preset pressure value. The liquid flow rate is gradually varied within a preset flow rate step size within the range of a first preset flow rate value to a second preset flow rate value. Under the combined conditions of the atomizing air pressure and the liquid flow rate, the atomized particle size distribution, spray angle and initial spray velocity of the atomizing spray gun are measured, and the measurement results are stored in the atomization characteristic database.

4. The adaptive load SNCR injection coverage control method according to claim 1, characterized in that, The furnace field distribution data includes temperature field distribution, velocity field distribution, and NOx concentration field distribution; The numerical model is established as follows: A three-dimensional CFD numerical calculation model was established based on the actual structure of the boiler. The three-dimensional CFD numerical calculation model is used to simulate the temperature field distribution, velocity field distribution, and NOx concentration field distribution of the boiler furnace under different loads from the preset minimum load to the preset maximum load range; The temperature field distribution, velocity field distribution, and NOx concentration field distribution under each load are stored as the thermal field database.

5. The adaptive load SNCR injection coverage control method according to claim 1, characterized in that, The coverage evaluation indicators include coverage area and coverage uniformity index; The coverage area is calculated as follows: ； in, The coverage area of ​​a single atomizing spray gun. For the spray distance, The spray angle; The coverage uniformity index is calculated as follows: ; in, The coverage uniformity index is... This represents the overlap area between the reducing agent-covered region and the high-concentration NOx region. The total area of ​​the high-concentration NOx region; The preset conditions include: The coverage uniformity index is greater than or equal to a preset coverage threshold, and the spraying distance is less than the distance to the opposite wall of the furnace. Wherein, the preset coverage threshold is that the coverage uniformity index is greater than or equal to 80%; When the coverage uniformity index is greater than or equal to 80% and the spraying distance is less than the distance between the front and rear walls of the boiler furnace, the corresponding operating parameters are stored in the load-parameter mapping database.

6. The adaptive load SNCR injection coverage control method according to claim 1, characterized in that, The evaporation process employs a discrete phase model. The law of evaporation is simulated, and the... The law of evaporation is expressed as: ； in, For the time elapsed The diameter of the droplets after evaporation The initial droplet diameter, It is the evaporation constant; The evaporation constant The calculation formula is: ； in, For the thermal conductivity of gases, For droplet density, Specific heat capacity of gas It is a prime number.

7. The adaptive load SNCR injection coverage control method according to claim 1, characterized in that, The atomized particle size of the atomizing spray gun is characterized by the Sauter mean particle size, and the empirical correlation for the Sauter mean particle size is: ； in, The average particle size is the Soter average. For liquid surface tension, For the density of the liquid, The relative velocity between gas and liquid. For the dynamic viscosity of the liquid, and This is an empirical coefficient; The relative velocity of the gas and liquid is changed by adjusting the atomizing air pressure. To control the average particle size of the SOT.

8. The adaptive load SNCR injection coverage control method according to claim 1, characterized in that, It also includes self-learning correction of the operating parameters in the load-parameter mapping database during the boiler operation, the self-learning correction including: A temperature sensor is installed on the boiler furnace wall to monitor the wall temperature in real time. When the wall temperature detected by the temperature sensor exceeds the preset wall temperature threshold, it is determined that the droplets sprayed by the atomizing spray gun in the corresponding area have reached the opposite wall. The working parameters of the atomizing spray gun are adjusted to shorten the spray distance. The adjustment includes reducing the liquid flow rate of the atomizing spray gun or increasing the atomizing air pressure. The operating parameters in the DCS data of the unit are collected. The operating parameters include load data, flue gas velocity data and flue gas temperature data. The operating parameters under each load in the load-parameter mapping database are iteratively corrected using machine learning methods.

9. The adaptive load SNCR injection coverage control method according to claim 1, characterized in that, Multiple layers of atomizing spray guns are arranged along the height direction of the boiler furnace, and multiple atomizing spray guns are arranged in each layer along the width direction of the boiler furnace. Each atomizing spray gun is equipped with a flow regulating valve and a pressure regulating valve to enable independent adjustment of the operating parameters of each atomizing spray gun.

10. The adaptive load SNCR injection coverage control method according to any one of claims 1 to 9, characterized in that, Based on the actual load changes of the boiler, the load-parameter mapping database is queried to adjust the operating parameters of each atomizing spray gun in real time, including: Obtain the real-time load value of the boiler; Query the operating parameters corresponding to the real-time load value in the load-parameter mapping database; The operating parameters of each atomizing spray gun are adjusted to the corresponding parameter values ​​in the load-parameter mapping database by means of the regulating valves installed in front of each atomizing spray gun.

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