Method and system for soot blowing suitable for low temperature economizer

Abstract

The application relates to the technical field of coal-fired power plant equipment, in particular to a soot blowing method and system suitable for a low-temperature economizer. The method comprises the following steps: calculating a fly ash deposition and setting index; calculating a comprehensive blockage index; when the fly ash deposition and setting index is greater than a first critical value, performing a soot blowing operation on the low-temperature economizer; when the comprehensive blockage index is greater than a second critical value, performing a soot blowing operation on the low-temperature economizer; the number of soot blowing operations on the low-temperature economizer in a single day is not more than a first preset value; and the interval time between two adjacent soot blowing operations is not more than a threshold time. According to the method, the best soot blowing time can be determined based on the fly ash deposition and setting index and the comprehensive blockage index, so that the working performance of the low-temperature economizer is ensured and the service life of the low-temperature economizer is prolonged.

Description

Technical Field

[0001] This application relates to the field of coal-fired power plant equipment technology, specifically to a soot blowing method and system suitable for low-temperature economizers. Background Technology

[0002] Low-temperature economizers are waste heat recovery devices designed and developed to meet the needs of deep cooling of flue gas in thermal power plants for efficiency improvement and emission reduction. They recover waste heat from the flue gas of thermal power plants, heat condensate, reduce steam extraction from turbines, increase power generation, and constitute a waste heat recovery condensate reheating system for thermal power plants. Considering the utilization of flue gas waste heat, environmental protection, and the economic and social benefits of thermal power generating units, most large-capacity, high-parameter units have already installed low-temperature economizers.

[0003] Because the operating environment of the low-temperature economizer is harsh, during hot commissioning, the water and flue gas temperatures are prone to falling below design requirements, and the flue gas contains high levels of ash and sulfur. Furthermore, the sulfates and ammonium salts formed from ammonia escape from the denitrification equipment can lead to ash blockage and low-temperature corrosion in the economizer, thus affecting the normal operation of the unit. In addition to developing reasonable operation control and maintenance strategies, an effective ash removal system is crucial for ensuring its safe and economical operation.

[0004] Soot blowing on the heated surfaces can directly solve the problem of ash accumulation. Although most power plant low-temperature economizers are equipped with soot blowing devices, the dense piping in these devices results in highly viscous fly ash under the influence of sulfuric acid vapor and ammonium bisulfate, which can even harden and clump together. The longer the ash remains, the stronger its viscosity and the greater the hardening effect, making conventional soot blowing ineffective in removing the sticky ash. Conventional soot blowing only considers the pressure difference between the inlet and outlet of the heated surfaces, neglecting the gelling effect of sulfuric acid vapor and ammonium bisulfate that leads to scale formation. This results in insufficient soot blowing in the early stages, making it impossible to blow away the ash later. Conventionally arranged soot blowing equipment cannot effectively solve the problems of ash accumulation and scale buildup, thus affecting the normal operation of the unit, increasing the induced draft fan current, and increasing energy consumption. Summary of the Invention

[0005] The purpose of this application is to provide a soot blowing method and system applicable to low-temperature economizers, which relates to the technical field of coal-fired power plant equipment.

[0006] To achieve the above objectives, the first aspect of this application provides a soot blowing method applicable to a low-temperature economizer, wherein the low-temperature economizer is applicable to a coal-fired power plant and is used to absorb heat from the flue gas of the power plant boiler to heat condensate; the method includes: calculating a fly ash deposition caking index; calculating a comprehensive blockage index; performing soot blowing on the low-temperature economizer when the fly ash deposition caking index is greater than a first critical value; performing soot blowing on the low-temperature economizer when the comprehensive blockage index is greater than a second critical value; the number of soot blowing operations on the low-temperature economizer per day does not exceed a first preset value; and the interval between two adjacent soot blowing operations does not exceed a threshold time.

[0007] Based on the first aspect, in some embodiments of this application, the calculation of fly ash deposition caking index includes: calculating the amount of ammonium bisulfate generated and the amount of sulfuric acid condensed within a preset time period; measuring the flue gas temperature of the power plant boiler; measuring the dust concentration at the inlet of the low-temperature economizer; and calculating the fly ash deposition caking index based on the amount of ammonium bisulfate generated, the amount of sulfuric acid condensed, the flue gas temperature, and the dust concentration at the inlet of the low-temperature economizer.

[0008] Based on the first aspect, in some embodiments of this application, a coal-fired power plant is equipped with an SCR denitrification device; calculating the amount of ammonium bisulfate generated within a preset time period includes: measuring the ammonia slip concentration at the outlet of the SCR denitrification device; calculating the amount of ammonia slip within the preset time period based on the ammonia slip concentration; and calculating the amount of ammonium bisulfate generated within the preset time period based on the amount of ammonia slip.

[0009] Based on the first aspect, in some embodiments of this application, calculating the amount of sulfuric acid condensation includes: calculating the acid dew point of the power plant boiler flue gas; measuring the SO2 concentration in the power plant boiler flue gas, estimating the SO3 concentration in the power plant boiler flue gas based on the SO2 concentration; and predicting the amount of sulfuric acid condensation based on the acid dew point and SO3 concentration.

[0010] Based on the first aspect, in some embodiments of this application, the acid dew point The calculation formula is as follows:

[0011] (1)

[0012] In equation (1), It is the partial pressure of water vapor; For SO3 partial pressure, where, , For SO2 partial pressure, This is the conversion factor.

[0013] Based on the first aspect, in some embodiments of this application, the coal-fired power plant is equipped with generator sets, and the formula for calculating the comprehensive congestion index K is as follows:

[0014] (3)

[0015] In equation (3), This indicates the pressure difference between the inlet and outlet flue gas of the low-temperature economizer. This refers to the oxygen content at the outlet of the low-temperature economizer under rated operating conditions of the generator set. The rated power of the generator set. This refers to the oxygen content at the outlet of the low-temperature economizer under actual operating conditions of the generator set. This represents the actual operating power of the generator set. This refers to the temperature difference between the inlet and outlet flue gas of the low-temperature economizer under rated operating conditions of the generator set. This represents the temperature difference between the inlet and outlet flue gas of the low-temperature economizer under actual operating conditions of the generator set.

[0016] Secondly, this application provides a soot blowing system suitable for a low-temperature economizer, wherein the low-temperature economizer is suitable for coal-fired power plants and is used to absorb heat from the flue gas of the power plant boiler to heat condensate; the system includes: a first calculation unit for calculating the fly ash deposition caking index; a second calculation unit for calculating the comprehensive blockage index; and an execution unit for performing soot blowing operations on the low-temperature economizer when the fly ash deposition caking index is greater than a first critical value, and when the comprehensive blockage index is greater than a second critical value; the execution unit also has the following limiting rules during the soot blowing operation: the number of soot blowing operations on the low-temperature economizer in a single day does not exceed a first preset value; and the interval between two adjacent soot blowing operations does not exceed a threshold time.

[0017] Based on the second aspect, in some embodiments of this application, the low-temperature economizer includes: a shell and a primary economizer and a secondary economizer arranged sequentially within the shell along the flue gas flow direction; the execution unit includes: a first soot blowing pipe, a second soot blowing pipe, a third soot blowing pipe, and a compressed air supply pipe; wherein, the first soot blowing pipe is connected to a plurality of first acoustic nozzles built into the shell, all of which are positioned facing the flue gas inlet of the primary economizer; the second soot blowing pipe is connected to a plurality of second acoustic nozzles built into the shell, at least one of which is positioned facing the flue gas outlet of the primary economizer or the flue gas inlet of the secondary economizer; the third soot blowing pipe is connected to a plurality of third acoustic nozzles built into the shell, all of which are positioned facing the flue gas outlet of the secondary economizer; the first soot blowing pipe, the second soot blowing pipe, and the third soot blowing pipe are respectively connected to the same end of the compressed air supply pipe.

[0018] Based on the second aspect, in some embodiments of this application, the second computing unit includes a data acquisition module built into the low-temperature economizer. The data acquisition module includes: a first pressure acquisition device, disposed on the first soot blowing pipe and built into the outer shell, for acquiring the pressure of the inlet flue gas of the primary economizer; a second pressure acquisition device, disposed on the second soot blowing pipe and built into the outer shell, for acquiring the pressure of the outlet flue gas of the primary economizer or the pressure of the inlet flue gas of the secondary economizer; and a third pressure acquisition device, disposed on the third soot blowing pipe and built into the outer shell, for acquiring the pressure of the outlet flue gas of the secondary economizer.

[0019] Based on the second aspect, in some embodiments of this application, the data acquisition module further includes: a first temperature acquisition device, disposed on the first soot blowing pipe and built into the housing, for acquiring the temperature of the inlet flue gas of the primary economizer; a second temperature acquisition device, disposed on the second soot blowing pipe and built into the housing, for acquiring the temperature of the outlet flue gas of the primary economizer or the temperature of the inlet flue gas of the secondary economizer; and a third temperature acquisition device, disposed on the third soot blowing pipe and built into the housing, for acquiring the temperature of the outlet flue gas of the secondary economizer.

[0020] This application has at least the following beneficial effects:

[0021] 1. Placing the soot blower inside the low-temperature economizer can achieve better soot blowing results. Similarly, the built-in pressure and temperature acquisition devices can obtain more accurate and reliable data. Based on the inlet and outlet temperatures and pressures of the low-temperature economizer, the blockage status of the economizer can be directly reflected.

[0022] 2. This application starts from the mechanism of ash caking and blockage in low-temperature economizers, and fully considers the phenomenon of long-term hardening of sticky ash. By calculating the fly ash deposition caking index and the comprehensive blockage index, it can more accurately reflect the ash accumulation state of the low-temperature economizer, and determine the best time for soot blowing based on this, so as to ensure the working performance of the low-temperature economizer and extend its service life.

[0023] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. In the drawings:

[0025] Figure 1 A schematic diagram illustrating the model input parameters of an embodiment of this application is shown.

[0026] Figure 2A schematic diagram illustrating the soot blowing logic of an embodiment of this application is shown.

[0027] Figure 3 This illustration schematically shows a soot blowing process diagram according to an embodiment of this application;

[0028] Figure 4 The schematic diagram illustrates the structure of the first and third soot blowing pipes according to embodiments of this application;

[0029] Figure 5 The schematic diagram illustrates the structure of the second soot blowing pipe according to an embodiment of this application;

[0030] Figure 6 A schematic diagram illustrating the arrangement of the acoustic nozzles according to an embodiment of this application is shown.

[0031] Figure 7 This illustration shows a schematic diagram of the arrangement of the temperature acquisition device according to an embodiment of the present application;

[0032] Figure 8 A schematic diagram illustrating the arrangement of the pressure acquisition device according to an embodiment of this application is shown. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the embodiments of this application and are not intended to limit the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0034] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0035] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0036] Example 1

[0037] This embodiment provides a soot blowing method suitable for a low-temperature economizer, wherein the low-temperature economizer is suitable for coal-fired power plants and is used to absorb heat from the flue gas of the power plant boiler to heat condensate; characterized in that the method includes:

[0038] S1. Calculate the fly ash deposition and compaction index;

[0039] The degree of ash accumulation and blockage in the low-temperature economizer can be directly reflected by the pressure difference and temperature of the flue gas at the inlet and outlet of the economizer. The pressure difference is mainly affected by the unit load, coal and flue gas parameters, the concentration of pollutants in the tail flue, and the economizer parameters. Factors affecting the differential pressure of the low-temperature economizer include boiler operating parameters, acid dew point, ammonium bisulfate formation, and economizer parameters. Boiler operating parameters affect the formation rate of pollutants such as NOx, SO3, and dust concentration, which in turn affects the amount of sulfuric acid condensation and ammonium bisulfate formation, causing low-temperature corrosion and ammonium bisulfate blockage, affecting ash adhesion, and thus causing blockage of the low-temperature economizer.

[0040] The fly ash deposition and caking index I(t) of the low-temperature economizer is a function of the unit's operating parameters, particularly the amount of ammonium bisulfate generated and the amount of sulfuric acid condensed. These operating parameters include the flue gas temperature of the power plant boiler and the dust concentration at the inlet of the low-temperature economizer. These operating parameters can be directly measured by instruments; specific measurement methods can be employed using existing technologies and will not be elaborated upon here.

[0041] Regarding the determination of ammonium bisulfate formation: The blockage phenomenon in the low-temperature economizer is mainly caused by ammonium bisulfate adsorbing fly ash from the flue gas and then adhering to the heated wall surface. The underlying reason is that, under the background of flexible power generation, frequent deep peak shaving by the unit leads to increased ammonia slip from the SCR denitrification system. The slipped ammonia reacts chemically with SO3 in the flue gas to form ammonium bisulfate. Within the temperature range of the low-temperature economizer region, ammonium bisulfate exists in solid form. Due to its strong hygroscopic and adhesive properties, a large amount of fly ash adheres to the heat exchange surface of the low-temperature economizer, causing fly ash caking. Over time, the caking strength increases, making it difficult to clean. The amount of ammonium bisulfate formed can be calculated based on the ammonia slip.

[0042] Regarding the determination of sulfuric acid condensation: Low-temperature economizers often experience ash accumulation and blockage, accompanied by low-temperature corrosion; therefore, the impact of sulfuric acid condensation in the flue gas must be considered. The total amount of sulfuric acid condensation can be predicted using acid dew point and SO3 concentration. The dew point temperature of the flue gas is mainly affected by the SO3 and water vapor content. This patent, based on the actual conditions of the flue gas measuring points, uses the AGOkkes formula to calculate the acid dew point:

[0043] (1)

[0044] (1-1)

[0045] In formula (1): The partial pressure of water vapor is Pa; The partial pressure of SO3 is Pa.

[0046] in The partial pressure of SO3 is calculated from the partial pressure of SO2. The partial pressure of SO3 is obtained by multiplying the partial pressure of SO2 in the flue gas by the conversion coefficient k. The value of the conversion coefficient k is in the range of 0.5%-2%, and is determined by the specific characteristics of the coal type, boiler type, and experiments.

[0047] The SO3 concentration is also obtained by multiplying the SO2 concentration by the conversion coefficient. The SO2 concentration in the flue gas is multiplied by the conversion coefficient k to obtain the SO3 concentration. The value of the conversion coefficient k is in the range of 0.5%-2%, and is determined based on the specific characteristics of the coal type, boiler type, and experiments.

[0048] Based on the SO3 concentration, the amount of SO3 involved in the formation of ammonium bisulfate can be subtracted to determine the amount of SO3 present in the form of sulfuric acid, thus yielding the amount of sulfuric acid condensed.

[0049] In summary, the fly ash deposition and compaction index I(t) can be expressed by the following expression:

[0050] (2)

[0051] In equation (2), This indicates the ammonia slip concentration at the outlet of the SCR denitrification equipment; This indicates the SO3 concentration in the flue gas from the power plant boiler; This indicates the dust concentration at the outlet of the electrostatic precipitator (which is also the dust concentration at the inlet of the low-temperature economizer). ，j d1 represents the dust concentration at the outlet of the electrostatic precipitator under design operating conditions; d2 represents the ammonium salt formation rate; d3 represents the sulfate formation rate; m(t) represents the time function of fly ash bonding strength under the action of ammonium salt, determined experimentally; n(t) represents the time function of fly ash bonding strength under the action of sulfate, determined experimentally; h represents the molar ratio of alkali metals to alkaline earth metals in fly ash and the molar ratio of alkali metals to alkaline earth metals in the design coal type, as shown below:

[0052] (2-1)

[0053] Since the fly ash deposition caking index calculated by formula (2) requires the determination of numerous parameters, and the fly ash bonding strength involved also needs to be determined through experiments, a surrogate model was later constructed based on Transformer to explore the correlation between the fly ash deposition caking index I(t) and important operating parameters of the unit and the low-temperature economizer (see Example 2).

[0054] S2. Calculate the overall congestion index;

[0055] Specifically, the formula for calculating the overall congestion index K is as follows:

[0056] (3)

[0057] In equation (3), This indicates the pressure difference between the inlet and outlet flue gas of the low-temperature economizer. This refers to the oxygen content at the outlet of the low-temperature economizer under rated operating conditions of the generator set. The rated power of the generator set. This refers to the oxygen content at the outlet of the low-temperature economizer under actual operating conditions of the generator set. This represents the actual operating power of the generator set. This refers to the temperature difference between the inlet and outlet flue gas of the low-temperature economizer under rated operating conditions of the generator set. This represents the temperature difference between the inlet and outlet flue gas of the low-temperature economizer under actual operating conditions of the generator set.

[0058] S3. When the fly ash deposition and caking index is greater than the first critical value, perform soot blowing operation on the low-temperature economizer.

[0059] S4. When the comprehensive blockage index is greater than the second critical value, perform soot blowing operation on the low-temperature economizer;

[0060] In addition, a timed soot blowing strategy can be used to limit the number of soot blowing operations and the interval between soot blowing operations. For example, the number of soot blowing operations for the low-temperature economizer should not exceed the first preset value in a single day; to prevent frequent soot blowing operations, it is advisable to set the number of soot blowing operations to no more than 6 to 8 times per day.

[0061] The interval between two consecutive soot blowing operations does not exceed the threshold time. Considering the complexity of unit operation under deep peak shaving, a soot blowing strategy combining intelligent soot blowing (the soot blowing logic in steps S3 and S4) and timed soot blowing can be adopted. Because the unit operates at low load for extended periods, there is less ash accumulation in the low-temperature economizer, resulting in a pressure differential growth rate consistently below the set critical value. To prevent ash from caking and hardening into scale, based on intelligent soot blowing, if no soot blowing occurs within 8 hours, soot blowing will be forcibly initiated once.

[0062] By combining physical mechanism-driven and mathematical model-driven approaches in the soot blowing control method, the optimal timing for soot blowing is grasped, thereby achieving timeliness, thoroughness, economy, and safety of the unit's soot blowing system.

[0063] Example 2

[0064] In this embodiment, an intelligent soot blowing model is constructed based on Embodiment 1. This model mainly consists of two parts: one is the prediction of the fly ash deposition caking index, and the other is the prediction of the comprehensive blockage index. During the model training and application phases, the model's input parameters can refer to... Figure 1 After inputting the parameters into the model, the model's processing flow for the parameter data and the soot blowing control logic can be found in [reference needed]. Figure 2 .

[0065] In the data cleaning and preprocessing stage, the 3σ method (also known as the Laida criterion) is used to remove data with large errors. The standard deviation is calculated according to the Bessel formula. Let the sample data be... The average value is ,deviation The sample standard deviation σ can be calculated using the following formula:

[0066] (4)

[0067] For a normally distributed array, the following must be satisfied:

[0068] (4-1)

[0069] If the dataset perfectly conforms to a normal distribution, then within the confidence interval The probability within is 99.7%.

[0070] The variation ranges of different influencing factors are inconsistent. To ensure that all input parameters are on the same order of magnitude for ease of calculation, normalization is performed using the min-max method.

[0071] For the sequence to be processed The scaling method is as follows:

[0072] (5)

[0073] in, and These represent the maximum and minimum values ​​in the sequence to be processed, respectively. and These represent the maximum and minimum values ​​of the scaling interval, respectively. The scaling interval for the data sequence is typically chosen to be [0, 1].

[0074] After being cleaned and normalized, the relevant historical data is formed into standardized numerical matrices, which will serve as the input to the Transformer prediction model.

[0075] 2) The Transformer module predicts the fly ash deposition and caking index. The Transformer model is a deep learning model based entirely on a self-attention mechanism, suitable for parallel computation. A black-box model is constructed based on the Transformer, with inputs consisting of various operating parameters affecting the low-temperature economizer (such as...). Figure 2 The output is the fly ash deposition and caking index I(t) of the low-temperature economizer.

[0076] This black-box model mainly consists of two parts: an Encoder and a Decoder. An encoder-decoder network is constructed to solve the mapping relationship between influencing factors and the differential pressure of the cryogenic economizer. Relevant parameters are input into the Encoder module, transforming the input into a low-dimensional context vector. This context vector is then input into the Decoder module to generate predicted values. Each Encoder module consists of a self-attention mechanism and a feedforward neural network. The self-attention mechanism does not require reference to any external conditions and is used to learn the relationships between relevant influencing factors. By decomposing the task through the self-attention mechanism, different network structures are designed to focus on different sub-tasks, reallocating the network's learning capacity, thereby reducing the difficulty of the original task and making the network easier to train. In this model, the self-attention mechanism is used to learn the relationships between different influencing factors. The input parameters are distributed to multi-level networks for learning based on the correlation between different unit parameters and cryogenic economizer parameters, transforming the initial numerical matrix into a low-dimensional vector matrix.

[0077] Similarly, the Decoder module uses the same structure, first calculating the self-attention score on the input. The difference lies in that after the self-attention mechanism, the output of the self-attention is then compared with the output of the Decoder module to calculate the attention score again (i.e., the model prediction). This attention layer refers to encoder-decoder attention, used to learn the relationship between influencing factors and the fly ash deposition and caking characteristics on the low-temperature economizer. Afterward, it enters the feedforward neural network module. The input to the Decoder module is the low-dimensional vector matrix obtained from the decomposition of the Encoder module. Based on the module's output, i.e., the fly ash deposition and caking index I(t) of the low-temperature economizer, the mapping relationship between the low-dimensional vector matrix and the fly ash deposition and caking index of the low-temperature economizer is learned.

[0078] Example 3

[0079] This application provides a soot blowing system suitable for a low-temperature economizer, wherein the low-temperature economizer is applicable to a coal-fired power plant and is used to absorb heat from the flue gas of the power plant boiler to heat condensate; characterized in that the system includes: a first calculation unit for calculating the fly ash deposition caking index; a second calculation unit for calculating the comprehensive blockage index; and an execution unit for performing soot blowing operations on the low-temperature economizer when the fly ash deposition caking index is greater than a first critical value, and when the comprehensive blockage index is greater than a second critical value; the execution unit also has the following limiting rules during the soot blowing operation: the number of soot blowing operations on the low-temperature economizer in a single day does not exceed a first preset value; and the interval between two adjacent soot blowing operations does not exceed a threshold time.

[0080] Specifically, the low-temperature economizer of a large boiler is generally arranged in two stages with a certain distance between them. In this embodiment, the execution unit can be an acoustic soot blower, and the second calculation unit calculates the comprehensive blockage index, requiring the collection of data such as the inlet and outlet temperatures and pressures of the low-temperature economizer. Therefore, the second calculation unit also includes a temperature acquisition device and a pressure acquisition device. For example, in this embodiment, the acoustic soot blower (acoustic nozzle), flue gas temperature acquisition device (temperature acquisition device), and flue gas pressure acquisition device (pressure acquisition device) are all integrated into the front, rear, and middle sections of the low-temperature economizer (the front section is near the inlet of the first-stage economizer, the middle section is between the first-stage and second-stage economizers, and the rear section is near the outlet of the second-stage economizer) to ensure that the flue gas temperature and pressure measurements in different areas of the low-temperature economizer accurately reflect the blockage status of the economizer.

[0081] The sonic sootblower uses compressed air as its air source. The air first passes through a check valve and then a filter to remove impurities. Finally, it passes through a pneumatic butterfly valve and a pressure switch to reach the sonic generator. The generator then emits high-energy sound waves, creating a seamless sound field between the heated surfaces through reflection, diffraction, and direct projection. This continuous movement of dust particles on the heated surfaces causes them to fall off. The sonic sootblower is set as a point source, with a typical frequency range of 20 to 250 Hz and an average sound intensity of 135–145 dB.

[0082] The soot blowing process is as follows Figure 3 As shown, compressed air first passes through a pressure stabilizing tank, then through a check valve to a filter, ensuring the quality of the compressed air. The flow rate of the compressed air is controlled by a pneumatic butterfly valve and a pressure switch. The compressed air is distributed in three lines (first, second, and third soot blowing lines) via switching valves to fixed sonic nozzles (first, second, and third sonic nozzles) located at different positions. The check valve prevents the compressed air from flowing in the opposite direction. The filter uses an F-series medium-efficiency filter, which uses porous filter material to capture dust from the gas-solid two-phase flow and purify the compressed air. The pneumatic butterfly valve receives programmable soot blowing signals and functions as a shut-off and throttling device. The pressure switch monitors the compressed air pressure in the pipes and controls the on / off status of the pipes, achieving the purpose of controlling pipe pressure and protecting the sonic soot blowing system.

[0083] The first soot blowing pipe goes to the front end of the low-temperature economizer (near the inlet of the first-stage economizer) and is responsible for soot blowing in the front end area of ​​the low-temperature economizer; the third soot blowing pipe goes to the rear end of the low-temperature economizer (near the outlet of the second-stage economizer) and is responsible for soot blowing in the rear end area of ​​the low-temperature economizer; the second soot blowing pipe goes to the middle section of the low-temperature economizer (between the first-stage and second-stage economizers) and is responsible for soot blowing in the middle section area of ​​the low-temperature economizer.

[0084] For example, such as Figure 4 The image shows the acoustic nozzles installed on the first and third sootblowing pipes. Each sootblowing pipe is equipped with seven acoustic nozzles, evenly spaced, with a center-to-center distance of L1 (0.8–1.2 m). Figure 5 The image shows the acoustic nozzles installed on the second sootblowing pipeline. Seven nozzles are evenly distributed on both sides of the pipeline, with a center-to-center distance of L1. The compressed air pressure of a single nozzle is 0.4–0.7 MPa, and the flow rate is 1–3 m³ / s. 3 / min.

[0085] like Figure 6The diagram shows a top view of the acoustic nozzles arranged in the low-temperature economizer. There are three sets of sootblowing pipes arranged at the front, middle, and rear ends. The first and third acoustic nozzles are positioned at 1 / 2H height, where H represents the height of the low-temperature economizer. The second acoustic nozzle is positioned between the two stages of the low-temperature economizer, with a front-to-rear spacing of L2 (0.6–0.8 m). The distance between the fixed front and rear acoustic sootblower nozzles and the low-temperature economizer is L3 (1.5–2.2 m), thus achieving uniform sootblowing.

[0086] like Figure 7 and Figure 8 As shown, flue gas temperature and pressure acquisition devices are arranged in the front, middle, and rear sections of the low-temperature economizer, respectively, relying on the first, second, and third soot blowing pipes. The front-end flue gas temperature and pressure acquisition devices are located along the first soot blowing pipe, generally at a height of 1 / 2H, with three sets of measuring points evenly arranged in a grid pattern in the horizontal direction. The rear-end flue gas temperature and pressure acquisition devices are located along the third soot blowing pipe, also generally at a height of 1 / 2H, with three sets of measuring points evenly arranged in a grid pattern in the horizontal direction. The distance between the front and rear flue gas temperature and pressure acquisition devices and the low-temperature economizer is L3 (1.5–2.2 m). The middle-section flue gas temperature and pressure acquisition devices are located in the middle of the low-temperature economizer, relying on the second soot blowing pipe, with a front-to-back spacing of L2 (0.6–0.8 m), and three sets of measuring points evenly arranged in a grid pattern in the horizontal direction.

[0087] With the above arrangement, the flue gas temperature and pressure acquisition devices are placed in different areas of the heating surface of the low-temperature economizer. These temperature and pressure acquisition devices can accurately reflect the ash accumulation on the heating surface of the low-temperature economizer, providing accurate data support for determining whether to perform soot blowing operation in the later stage.

[0088] Based on the arrangement of the temperature and pressure acquisition devices mentioned above, the calculation process for the comprehensive blockage index is as follows:

[0089] First, noise reduction was performed on the collected data. Second, the pressure and temperature data were dimensionless to eliminate the influence of unit load, thus obtaining the distribution trends of the pressure and temperature differences of the cryogenic economizer over time. The comprehensive blockage index of the cryogenic economizer was then calculated. The average value was calculated based on data from multiple measuring points at the front, middle, and rear sections of the cryogenic economizer. Details are as follows:

[0090] At the front end of the low-temperature economizer, the average pressure is p1 and the average temperature is t1.

[0091] In the middle section of the low-temperature economizer, the average pressure p2 and the average temperature t2 are...

[0092] At the front end of the low-temperature economizer, the average pressure p3 and the average temperature t3 are...

[0093] By using the average values ​​of the middle section and the front end, the pressure difference and temperature difference data of the primary heating surface of the low-temperature economizer (primary economizer) can be obtained.

[0094] By using the average values ​​of the middle and rear sections, the pressure difference and temperature difference data of the secondary heating surface of the low-temperature economizer (secondary economizer) can be obtained.

[0095] For different heating surfaces, the comprehensive blockage index K is solved using equation (3). In this way, the comprehensive blockage index of the primary economizer and the secondary economizer can be calculated separately. Combined with the aforementioned on / off valves set on the first, second, and third soot blowing pipes respectively, dust removal can be performed on the primary economizer and the secondary economizer respectively. For example, if the comprehensive blockage index of the primary economizer is greater than the threshold, while the comprehensive blockage index of the secondary economizer is not greater than the threshold, it means that the primary economizer needs dust removal while the secondary economizer does not (not considering the fly ash deposition and caking index). In this case, it is only necessary to open the on / off valves on the first and second soot blowing pipes and close the on / off valve on the third soot blowing pipe to achieve targeted dust removal.

[0096] In this embodiment, better soot blowing effect can be achieved by arranging the sonic nozzles inside the equipment. With the built-in pressure and temperature acquisition devices providing dual monitoring, the blockage status of the low-temperature economizer can be reflected more intuitively.

[0097] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0098] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A soot blowing method suitable for low-temperature economizers, wherein, The low-temperature economizer is suitable for coal-fired power plants. It is used to absorb heat from the flue gas of the power plant boiler to heat condensate. The method is characterized by comprising: The calculation of fly ash deposition compaction index includes: Calculate the amount of ammonium bisulfate generated and sulfuric acid condensed within a preset time period; Measure the flue gas temperature of the power plant boiler; Measure the dust concentration at the inlet of the low-temperature economizer; The fly ash deposition caking index was calculated based on the amount of ammonium bisulfate generated, the amount of sulfuric acid condensed, the flue gas temperature, and the dust concentration at the inlet of the low-temperature economizer. Calculate the overall congestion index; When the fly ash deposition caking index is greater than the first critical value, soot blowing operation is performed on the low-temperature economizer; When the overall blockage index is greater than the second critical value, soot blowing operation is performed on the low-temperature economizer; Within a single day, the number of soot blowing operations for the low-temperature economizer shall not exceed the first preset value; The interval between two consecutive soot blowing operations shall not exceed the threshold time. The coal-fired power plant is equipped with SCR denitrification equipment; the calculation of ammonium bisulfate generation within a preset time period includes: Calculate the amount of ammonia escape within a preset time period based on the ammonia escape concentration; Calculate the amount of ammonium bisulfate generated within a preset time period based on the amount of ammonia escape; The calculation of sulfuric acid condensation within a preset time period includes: Calculate the acid dew point of the flue gas from the power plant boiler; The SO2 concentration in the flue gas of the power plant boiler was measured, and the SO3 concentration in the flue gas was estimated based on the SO2 concentration. Predicting sulfuric acid condensation based on acid dew point and SO3 concentration; The fly ash deposition caking index is calculated based on ammonium bisulfate generation, sulfuric acid condensation, flue gas temperature, and low-temperature economizer inlet dust concentration, including: The Transformer model was used to predict the fly ash deposition and compaction index. The Transformer model is a deep learning model based on the self-attention mechanism. The fly ash deposition and compaction index I(t) can be expressed by the following expression: （2） In equation (2), This indicates the ammonia slip concentration at the outlet of the SCR denitrification equipment; This indicates the SO3 concentration in the flue gas from the power plant boiler; This indicates the dust concentration at the outlet of the electrostatic precipitator, which is also the dust concentration at the inlet of the low-temperature economizer. ，j d1 represents the dust concentration at the outlet of the electrostatic precipitator under design operating conditions; d2 represents the ammonium salt formation rate; d3 represents the sulfate formation rate; m(t) represents the time function of fly ash bonding strength under the action of ammonium salt, determined experimentally; n(t) represents the time function of fly ash bonding strength under the action of sulfate, determined experimentally; h represents the molar ratio of alkali metals to alkaline earth metals in fly ash and the molar ratio of alkali metals to alkaline earth metals in the design coal type, as shown below: （2-1） Based on the Transformer, a proxy model was constructed to explore the correlation between fly ash deposition caking index I(t) and important operating parameters of the unit and the low-temperature economizer; The coal-fired power plant is equipped with generator units. The formula for calculating the comprehensive congestion index K is as follows: （3） In equation (3), This indicates the pressure difference between the inlet and outlet flue gas of the low-temperature economizer. This refers to the oxygen content at the outlet of the low-temperature economizer under rated operating conditions of the generator set. The rated power of the generator set. This refers to the oxygen content at the outlet of the low-temperature economizer under actual operating conditions of the generator set. This represents the actual operating power of the generator set. This refers to the temperature difference between the inlet and outlet flue gas of the low-temperature economizer under rated operating conditions of the generator set. This represents the temperature difference between the inlet and outlet flue gas of the low-temperature economizer under actual operating conditions of the generator set.

2. A soot blowing system suitable for a low-temperature economizer, applied to the soot blowing method for a low-temperature economizer as described in claim 1, wherein, The low-temperature economizer is suitable for coal-fired power plants. It is used to absorb heat from the flue gas of the power plant boiler to heat condensate. The system is characterized by comprising: The first calculation unit is used to calculate the fly ash deposition and compaction index. The second calculation unit is used to calculate the overall congestion index; The execution unit is used to perform soot blowing operations on the low-temperature economizer when the fly ash deposition caking index is greater than the first critical value, and when the comprehensive blockage index is greater than the second critical value; the execution unit is also subject to the following limiting rules during the soot blowing operation: Within a single day, the number of soot blowing operations for the low-temperature economizer shall not exceed the first preset value; The interval between two consecutive soot blowing operations shall not exceed the threshold time.

3. The soot blowing system for a low-temperature economizer according to claim 2, characterized in that, The low-temperature economizer includes: an outer shell and a primary economizer and a secondary economizer arranged sequentially inside the outer shell along the flue gas flow direction; The execution unit includes: a first soot blowing pipe, a second soot blowing pipe, a third soot blowing pipe, and a compressed air supply pipe; wherein, The first soot blowing pipe is connected to multiple first acoustic nozzles built into the outer shell, and all the first acoustic nozzles are set facing the flue gas inlet of the first-stage economizer. The second soot blowing pipe is connected to multiple second acoustic nozzles built into the outer casing, and at least one second acoustic nozzle is set to face the flue gas outlet of the first-stage economizer or the flue gas inlet of the second-stage economizer. The third soot blowing pipe is connected to multiple third acoustic nozzles built into the outer shell, and all the third acoustic nozzles are set facing the flue gas outlet of the secondary economizer. The first, second, and third soot blowing pipes are each connected to the same end of the compressed air supply pipe.

4. The soot blowing system for a low-temperature economizer according to claim 3, characterized in that, The second computing unit includes a data acquisition module built into the low-temperature economizer, the data acquisition module comprising: The first pressure acquisition device is located on the first soot blowing pipe and built into the outer casing, and is used to acquire the pressure of the inlet flue gas of the first-stage economizer. The second pressure acquisition device is located on the second soot blowing pipe and built into the outer casing. It is used to acquire the pressure of the flue gas at the outlet of the first-stage economizer or the pressure of the flue gas at the inlet of the second-stage economizer. The third pressure acquisition device is located on the third soot blowing pipeline and is built into the outer casing. It is used to collect the pressure of the flue gas at the outlet of the secondary economizer.

5. The soot blowing system for a low-temperature economizer according to claim 4, characterized in that, The data acquisition module also includes: The first temperature acquisition device is located on the first soot blowing pipe and built into the outer casing, and is used to acquire the temperature of the inlet flue gas of the first-stage economizer. The second temperature acquisition device is located on the second soot blowing pipe and built into the outer casing. It is used to acquire the temperature of the flue gas at the outlet of the first-stage economizer or the temperature of the flue gas at the inlet of the second-stage economizer. The third temperature acquisition device is located on the third soot blowing pipe and is built into the outer casing. It is used to collect the temperature of the flue gas at the outlet of the secondary economizer.

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