Pulverizing system exhaust gas transfer device explosion-proof optimization method based on fluid mechanics calculation

Abstract

The invention relates to the technical field of coal pulverizing system explosion prevention, and discloses a coal pulverizing system exhaust gas transfer device explosion-proof optimization method based on fluid mechanics calculation, which comprises the following steps: step a, establishing a three-dimensional geometric model based on an exhaust gas transfer device of a coal pulverizing system to be optimized; b, simulating the three-dimensional geometric model by adopting computational fluid mechanics, and identifying a low-speed region and a local high-temperature region; and c, the bottom molded line of the primary air bellow is adjusted, the optimal bottom molded line is determined, the optimal bottom molded line is used for minimizing the size of the low-speed area, and the minimized low-speed area and the local high-temperature area are not overlapped in space. According to the method, a low-speed area and a local high-temperature area coexisting at the bottom of the primary air bellow are identified through simulation, and the optimization targets of minimizing the volume of the low-speed area and separating the space of the low-speed area and the space of the local high-temperature area are achieved. According to the method, coexistence conditions of pulverized coal deposition and high-temperature ignition can be destroyed, so that the deflagration probability of the exhaust gas transfer device is effectively reduced, and the operation safety is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of explosion prevention of pulverizing system, in particular to an explosion prevention optimization method for a pulverizing system gas transfer device based on fluid mechanics calculation. BACKGROUND

[0002] In the industrial field of coal-fired power generation, the pulverizing system is one of the core equipment. With the change of the coal market, power plants often need to burn different types of coal, especially coal with high volatile matter content, which makes the safe operation of the pulverizing system face higher challenges. In order to adapt to the change of coal and improve the efficiency of the system, many pulverizing systems have been technically reformed, such as the addition of a gas transfer device, the core component of which is a primary air box used to mix the gas containing fine coal powder with hot air. In this process, there will be combustible materials (coal powder), combustion-supporting agents (air) and potential ignition sources (high temperature) in the primary air box, thereby forming a deflagration risk.

[0003] In the prior art, in order to reduce such risks, computational fluid dynamics (CFD) simulation or methods based on engineering experience are often used to analyze and optimize the internal flow field of the primary air box. However, these conventional methods have certain limitations in analysis: The prior art generally ignores the spatial correlation between the coal powder deposition area as the fuel source and the high temperature area as the ignition source, as the coexistence of the two is not considered as the root cause of the deflagration risk, resulting in insufficient and comprehensive diagnosis of the risk.

[0004] And the existing optimization measures are often single-targeted. For example, by adjusting the air flow speed to blow off the accumulated powder, but such adjustment may inadvertently change the flow path of the hot air, thereby causing new and more hidden local high temperature points; on the contrary, the scheme of reducing the overall temperature will affect the coal powder drying efficiency, thereby reducing the operation safety. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides an explosion prevention optimization method for a pulverizing system gas transfer device based on fluid mechanics calculation, which solves the problem of single-targeted explosion prevention optimization and reduced operation safety due to the neglect of the spatial coexistence of the coal powder deposition area and the high temperature area in the prior art.

[0006] To achieve the above purpose, the present application realizes the following technical scheme: an explosion prevention optimization method for a pulverizing system gas transfer device based on fluid mechanics calculation, comprising the following steps: Step a, establishing a three-dimensional geometric model based on the gas transfer device of the pulverizing system to be optimized; the gas transfer device includes a primary air box for mixing the gas containing coal powder with hot air; Step b, simulating the three-dimensional geometric model by using computational fluid dynamics to obtain the flow field and temperature field distribution inside the primary air box, and identifying the low-speed zone for depositing coal powder and the local high-temperature zone for igniting coal powder existing at the bottom of the primary air box at the same time according to the flow field and temperature field distribution; Step c, adjusting the bottom contour line of the primary air box for the low-speed zone and the local high-temperature zone, and determining the optimal bottom contour line by repeatedly simulating step b, which is used to minimize the volume of the low-speed zone and make the minimized low-speed zone not overlap with the local high-temperature zone in space.

[0007] Preferably, the simulation in step b by using computational fluid dynamics method specifically includes: Coupling calculation of gas-solid two-phase flow by using Euler-Lagrange method; Simulating the release process of coal powder volatile by using a two-step competitive reaction rate model.

[0008] Preferably, the adjustment of the bottom contour line of the primary air box in step c is specifically: filling at the bottom of the primary air box to change the tangent angle of the air box bottom .

[0009] Preferably, the step of determining the optimal bottom contour line specifically includes: Simulating a plurality of different tangent angle values, and determining a tangent angle value from them that can both minimize the volume of the low-speed zone and make the minimized low-speed zone not overlap with the local high-temperature zone in space.

[0010] Preferably, the minimum value is 0.15.

[0011] Preferably, the method further includes: Step d, adjusting the primary air inlet speed of the primary air box, and determining the safe operation speed for avoiding the peak value of volatile concentration by repeatedly simulating step b.

[0012] Preferably, the step of determining the safe operation speed in step d specifically includes: Simulating a plurality of different primary air inlet speeds to determine the law of volatile concentration changing with the primary air inlet speed; According to the law, analyzing the risk speed leading to the peak value of volatile concentration; Based on the speed interval of the risk speed, setting the safe operation speed.

[0013] Preferably, the verification step is further included between step b and step c, and the verification step includes: The parameter calculation result obtained by simulation in step b is compared with the actually measured operation data collected from the DCS system of the coal pulverizing system to verify the reliability of the three-dimensional geometric model.

[0014] Preferably, the method is applied to the coal pulverizing system for processing coal powder with volatile content higher than 30%.

[0015] Preferably, step b further comprises spatial position correlation analysis on the identified low-speed area and local high-temperature area to evaluate the risk level of coincidence of the two areas causing deflagration; and step c is based on the risk level for adjustment.

[0016] The present application provides a deflagration prevention optimization method for a coal pulverizing system based on fluid mechanics calculation. 1. The present application can effectively reduce the probability of deflagration of the exhaust gas transfer device and improve the operation safety by establishing a three-dimensional geometric model of the exhaust gas transfer device, identifying the low-speed area and local high-temperature area existing at the bottom of the primary air box at the same time according to the distribution of flow field and temperature field, and taking the minimization of the low-speed area volume and the non-overlapping of the two areas in space as the optimization target, thereby destroying the physical environment in which the two necessary conditions of coal powder deposition and high-temperature ignition for deflagration are met at the same time.

[0017] 2. The present application can provide a clear technical basis for the adjustment of operation parameters by the operator under different working conditions by determining the optimal hardware structure to suppress coal powder deposition and giving the risk speed interval to be avoided in step d, which is helpful to maintain the system in a safe working condition.

[0018] 3. The present application can improve the representation accuracy of the three-dimensional geometric model and the simulation method for the actual operation state of the physical equipment by comparing the simulation result with the actually measured data of the DCS system for verification and correction, thereby improving the reliability of the subsequent optimization calculation result, and providing a reference for actual equipment modification and operation adjustment. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The figure is a flow chart of the method of the present application; Figure 2 The figure is a schematic diagram of the geometric modeling of the exhaust gas transfer system in the application embodiment of the present application; Figure 3 The figure is a TG-DTG curve of coal powder in the application embodiment of the present application; Figure 4 The figure is a schematic diagram of grid division of the exhaust gas transfer system in the application embodiment of the present application; Figure 5 The figure is a schematic diagram of grid independence verification in the application embodiment of the present application; Figure 6This is a schematic diagram of the overall velocity field distribution inside the primary windbox in an application embodiment of the present invention; Figure 7 This is a schematic diagram of the velocity field distribution at different cross sections inside the primary windbox in an application embodiment of the present invention; Figure 8 This is a schematic diagram of the temperature field distribution inside the primary air box in an application embodiment of the present invention; Figure 9 This is a schematic diagram showing the average temperature, average flow rate, and average CO mass fraction of the primary air box area under different hot air velocities in an application embodiment of the present invention. Figure 10 This is a schematic diagram showing the CO distribution inside the air box under different hot air velocities in an application embodiment of the present invention; Figure 11 In an application embodiment of the present invention, the volume of the low-speed zone at the bottom of the primary air box varies with... Schematic diagram of the change curve. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To better understand the present invention, the above content will be described in detail below with reference to specific embodiments.

[0022] Please see the appendix Figure 1 This invention provides an explosion-proof optimization method for a pulverizing system exhaust gas transfer device based on hydrodynamic calculations. The method includes the following steps: Step a: Establish a three-dimensional geometric model based on the exhaust gas transfer device of the pulverizing system to be optimized; the exhaust gas transfer device includes a primary air box for mixing exhaust gas containing pulverized coal with hot air; In this embodiment, this step is used to create a high-fidelity digital geometric carrier for subsequent computational fluid dynamics (CFD) simulation analysis.

[0023] Specifically, the modeling object is the exhaust gas transfer system within the pulverizing system identified as having a potential risk of deflagration. This system is a key subsystem of the power plant boiler pulverizing system. Its core component is the primary air box. Physically, the primary air box is a container with multiple inlets and one or more outlets. Its function is to thoroughly mix the relatively low-temperature exhaust gas carrying fine pulverized coal (also known as desiccant exhaust gas in some systems) with high-temperature hot air from the air preheater. The resulting mixed airflow, i.e., the primary air, must reach the specific temperature and pulverized coal concentration required by the boiler burners before being conveyed to the furnace.

[0024] Alternatively, the construction of the three-dimensional geometric model can begin with the original design drawings of the exhaust gas transfer system, the technical specifications provided by the equipment manufacturer, or the as-built drawings archived by the power plant. These documents typically contain key geometric information such as the main dimensions of the equipment, pipe diameters, and interface locations.

[0025] In one possible implementation, considering potential deformation of the equipment during long-term operation, on-site construction errors, or subsequent modifications not documented in drawings, non-contact measurement techniques can be used to acquire the actual dimensional data of the equipment on-site to ensure the highest fidelity of the model. For example, a 3D laser scanner can be used to perform a global scan of the exhaust gas transfer system, generating high-density point cloud data. Subsequently, the point cloud data is denoised, registered, and feature extracted in specialized point cloud processing software, ultimately reconstructing a 3D surface model reflecting the current true state of the equipment. Alternatively, in situations where 3D scanning is not feasible, traditional manual surveying methods can be used, employing tools such as laser rangefinders and angle meters to accurately measure key components, and then using this measured data to create a 3D model.

[0026] Typically, the creation of this 3D geometric model is completed in a professional computer-aided design (CAD) software environment. In some embodiments, software tools that can be used to perform this modeling step include, but are not limited to, SolidWorks, CATIA, AutoCAD-3D, Unigraphics-NX (UG), or Creo (Pro / E). Using the solid modeling capabilities of these tools, the shell of the primary air box, the exhaust gas inlet pipe, the hot air inlet pipe, the outlet pipe, and all internal geometric structures related to fluid flow and heat transfer, such as baffles and support ribs, can be accurately constructed. The model is built at a 1:1 scale to ensure dimensional accuracy.

[0027] In order for the established three-dimensional geometric model to be recognized and processed by computational fluid dynamics solvers, it must be spatially discretized, i.e., meshed. This process divides the continuous geometric space into a large number of interconnected tiny control volumes or cells, forming a computational mesh.

[0028] Specifically, considering the complexity of the internal geometry of the exhaust gas transfer system, a hybrid mesh generation strategy is recommended. Specifically, for areas with relatively regular and simple geometries, such as exhaust gas pipes and the main body of the primary air box, structured meshes, such as hexahedral meshes, are preferred. This is because the hexahedral mesh has a regular node distribution and good alignment with the flow direction, achieving higher computational accuracy and better convergence with the same number of meshes. For areas with irregular geometries, such as square / round joints and T-junctions at pipe connections, more adaptable unstructured meshes, such as tetrahedral meshes, are used for filling and transition, ensuring seamless mesh coverage of the entire computational domain.

[0029] To improve the computational accuracy of critical flow regions, local mesh refinement is often required for specific areas. For example, at the confluence of multiple fluid streams at the hot air inlet and exhaust gas inlet, intense shearing and mixing result in extremely large gradients in flow field parameters, necessitating the use of smaller mesh cells to capture these variations. Similarly, mesh refinement is required at the bottom, corners, and near the walls of the primary air box, where flow separation, backflow, and coal dust deposition may occur. Mesh refinement near the walls also involves the generation of boundary layer meshes, i.e., arranging multiple layers of thin meshes with gradually varying thicknesses in the direction close to the wall's normal to accurately simulate flow and heat transfer in the near-wall region.

[0030] After completing the initial mesh generation, mesh independence verification must be performed to prove that the calculation results are not affected by the mesh density.

[0031] Specifically, multiple schemes with different mesh densities can be designed. For example, by globally adjusting the mesh size or only changing the mesh density in the enriched area, four mesh schemes with total mesh counts of 330,000, 430,000, 530,000, and 630,000 can be generated. Subsequently, simulations are performed on these four mesh schemes under identical physical conditions. By comparing the calculated velocity or temperature at points along one or more characteristic lines selected inside the primary wind tunnel (e.g., along the central axis or within a critical section) under different mesh schemes, the impact of mesh count on the calculation results is determined. If, after increasing the mesh count from 530,000 to 630,000, the relative difference in the calculation results is less than an acceptable threshold (e.g., 1%), then the 530,000 mesh scheme can be considered to have achieved mesh independence, meaning the calculation results have converged to the true solution. Further enriching the mesh has minimal impact on the results but would only increase computational cost. Therefore, the 530,000 mesh scheme is ultimately selected for all subsequent formal simulation calculations.

[0032] Step b: Use computational fluid dynamics to simulate the three-dimensional geometric model to obtain the flow field and temperature field distribution inside the primary air box, and identify the low-speed zone for coal powder deposition and the local high-temperature zone for coal powder ignition at the bottom of the primary air box based on the flow field and temperature field distribution. In this embodiment, after completing the construction of the three-dimensional geometric model of the exhaust gas transfer system and the validated computational mesh generation, step b will be performed. This step is a key link connecting the physical entity and the virtual analysis. Its purpose is to reproduce and reveal the complex gas-solid two-phase flow, heat transfer, and chemical reaction processes inside the primary windbox through numerical calculation, thereby providing quantitative and physically based guidance for subsequent structural optimization and adjustment.

[0033] Specifically, this simulation step is performed on a computing workstation equipped with a computational fluid dynamics (CFD) solver. Based on the three-dimensional geometric model and computational mesh generated and verified in the previous step, the solver obtains detailed distribution information of the gas-solid two-phase flow inside the primary windbox by iteratively solving a series of physical conservation laws in the form of partial differential equations.

[0034] As an alternative, commercial software platforms that can perform this simulation calculation include ANSYS-Fluent, Siemens-STAR-CCM+, or the open-source platform OpenFOAM.

[0035] Specifically, the execution of a simulation first requires setting an accurate physical model and boundary conditions. The data for these boundary conditions comes from the actual operating data of the distributed control system (DCS) of the system to be optimized or the design specifications of the equipment, to ensure the realism of the simulation conditions.

[0036] In one possible implementation, the hot air inlet is set as a velocity inlet, with its airflow velocity, temperature (e.g., 610 K), and gas composition all given according to actual operating parameters. The exhaust gas inlet is also set as a velocity inlet, with its airflow velocity (e.g., 25 m / s), temperature (e.g., 364 K), gas composition, and the particle size distribution, mass flow rate, and initial temperature of the carried pulverized coal particles all specified in detail. The multiple outlet pipes of the primary air box are typically set as pressure outlets, with their outlet gauge pressures defined. All solid walls are set as no-slip walls, and heat exchange between them and the fluid is considered.

[0037] For the complex flow and heat transfer phenomena within a primary windbox, it is necessary to select an appropriate mathematical model for description.

[0038] Generally, the turbulent characteristics in a flow field have a significant impact on momentum and heat transfer. In this embodiment, a k-ε two-equation turbulence model, such as the realizable k-ε model, can be used to simulate the turbulent flow of the gas phase (i.e., the mixture of exhaust gas and hot air).

[0039] To address the characteristics of the gas-solid two-phase flow within the system, this embodiment employs the Euler-Lagrange method for coupled calculations. In this method, the gas phase is converted into a continuous fluid field, and its velocity, pressure, and temperature distribution throughout the computational space are obtained by solving a set of continuum mechanics equations. Simultaneously, the pulverized coal particles are treated as a discrete phase, and the method simulates the behavior of the entire pulverized coal mass by tracing the motion trajectories of a large number of representative individual pulverized coal particles within the computational domain. The trajectory of each particle is determined by calculating the resultant force of various forces acting on it.

[0040] These forces mainly include: the drag force generated by the surrounding gas flow, which is the main force determining the particle's movement following the airflow; the resultant force of the particle's own weight and the buoyancy generated by the gas; and the pressure gradient force generated by the pressure unevenness in the flow field. In this way, a two-way coupling is achieved between the influence of the gas phase flow field on particle motion and the reaction of particle motion on the gas phase flow field.

[0041] For the crucial chemical reaction process of pulverized coal particles releasing volatiles upon heating in a high-temperature environment, this embodiment employs a two-step competing reaction rate model for simulation. In this model, the pyrolysis of pulverized coal is not a single chemical reaction, but rather consists of two parallel and competing reaction pathways.

[0042] One pathway occurs at a relatively low temperature, while the other requires a higher temperature to be effectively activated. Both pathways convert solid coal into coke and gaseous volatiles, but the rates of occurrence and the final proportion of volatiles produced differ. The reaction rate of each pathway is highly dependent on the ambient temperature of the coal particles; the higher the temperature, the faster the reaction. This specific relationship between reaction rate and temperature is determined by the inherent chemical kinetic parameters of the coal type, such as activation energy and pre-exponential factor. These parameters need to be pre-determined using laboratory analytical methods such as thermogravimetric analysis (TGA) for the specific coal type to be optimized. Furthermore, the method of this invention is primarily applied to processing high-volatile coal powder (e.g., volatile content higher than 30%), therefore, accurate simulation of its pyrolysis process is crucial.

[0043] After completing all model settings and parameter inputs, start the simulation and iterate until the calculation results converge. The convergence criterion is typically that the computational residuals of all solved equations decrease to below a preset threshold (e.g., the residual for the energy equation is less than 10). 6 The residuals of other equations are less than 10. 4 Furthermore, the parameter values ​​of some key monitoring points (such as the primary air box outlet temperature and pressure) no longer fluctuate significantly in subsequent iterations.

[0044] After the simulation is completed, the massive amount of calculation results can be visualized and analyzed in post-processing software. This analysis allows for the acquisition of detailed distribution cloud maps of the flow field (velocity vector field) and temperature field (temperature scalar field) at any cross-section or in three-dimensional space within the entire computational domain. Based on this data, potential deflagration risk areas can be identified.

[0045] In this embodiment, the low-speed zone is defined and identified as a connected space region where the fluid velocity is below a certain preset threshold (e.g., 0.5 m / s). Within this region, the kinetic energy of the airflow is insufficient to re-entrain and carry away the coal dust particles that have settled due to gravity, thus providing the physical conditions for the long-term deposition of coal dust.

[0046] Localized high-temperature zones are defined and identified as spatial regions where the temperature exceeds the critical temperature at which pulverized coal begins to release large amounts of volatiles through thermal decomposition (e.g., 555 K). Within these zones, once pulverized coal is deposited, it will be continuously subjected to high temperatures, leading to the precipitation and accumulation of large amounts of volatiles, forming a flammable and explosive gaseous environment.

[0047] As an extension of this step, step b also includes a spatial correlation analysis of the identified low-speed zone and local high-temperature zone.

[0048] Specifically, this analysis involves overlaying the isosurfaces (or isovolutes) representing the low-velocity region with those representing the local high-temperature region in the same three-dimensional coordinate system within the simulation post-processing software. By observing whether the two overlap or are closely adjacent in space, the risk of deflagration can be intuitively determined.

[0049] To conduct a quantitative assessment, the volume of the spatially overlapping portion of the two risk areas can be precisely calculated. The size of this overlapping volume can serve as a quantitative indicator to assess the risk level of deflagration. A larger overlapping volume means a wider area where both the necessary conditions for deflagration—combustible material (pulverized coal) deposition and an ignition source (high temperature)—are simultaneously met, resulting in a higher deflagration risk level for the system. Therefore, the risk level assessment results will directly serve as the basis for judging and optimizing the scheme in subsequent steps.

[0050] Step c: For the low-speed zone and the local high-temperature zone, adjust the bottom profile of the primary air box, and determine the optimal bottom profile by repeating the simulation of step b. The optimal bottom profile is used to minimize the volume of the low-speed zone and ensure that the minimized low-speed zone does not overlap with the local high-temperature zone in space.

[0051] In this embodiment, after clarifying the deflagration risk levels caused by the low-speed zone, local high-temperature zone, and their spatial overlap in the original design of the primary bellows through simulation analysis and risk assessment in step b, the process proceeds to the optimization stage, namely step c. The goal of this step is to eliminate or significantly reduce the identified risks by iteratively modifying and verifying the geometry of the primary bellows.

[0052] Specifically, this step involves systematically adjusting the geometry of the primary air box based on the risk areas identified and the assessed risk levels from the previous step. Since the low-speed zone is mainly caused by insufficient fluid kinetic energy and flow separation, and mostly occurs at the bottom of the primary air box, the core objective of the adjustment is to change the internal geometric profile of the bottom of the primary air box, i.e., the bottom profile.

[0053] Specifically, adjusting the bottom profile of the primary air box involves geometric filling in a specific area at the bottom of the primary air box. In practice, this filling corresponds to adding a flow-guiding structure made of wear-resistant and high-temperature-resistant materials (such as castable or wear-resistant steel plates) inside the existing air box. Through this filling, the original flat or gently sloping structure can be changed to form a new bottom interface with a specific tilt angle.

[0054] This adjustment process is parameterized by a key geometric variable: the tangential inclination angle at the bottom of the bellows. This angle is defined as the angle between the newly formed bottom slope and the horizontal plane. The magnitude of this angle directly affects the flow field morphology in the bottom region. A small angle may not be sufficient to change the flow separation state, while an excessively large angle may induce new flow problems in other locations.

[0055] Determining the optimal bottom profile is an iterative optimization process, which specifically includes: First, based on the original model, a range and step size for the variation of the tangent inclination angle value are defined. For example, the inclination angle can be set to start from 5 degrees, increasing in increments of 5 degrees to 60 degrees, thus forming a discrete set of schemes containing multiple different tangent inclination angle values.

[0056] Secondly, for each tangent inclination angle value in the scheme set, a complete modeling and simulation process is performed. That is, the bottom filling structure in the 3D geometric model is modified to achieve the corresponding tangent inclination angle. Then, the modified new model is re-meshed, and the computational fluid dynamics simulation with the same boundary conditions and physical model defined in step b is repeated.

[0057] After each simulation of an inclination scheme is completed, the volume of the low-speed region and the volume of the local high-temperature region under the new scheme must be extracted and calculated according to the same method and threshold in step b, and the spatial relationship between the two must be analyzed, especially their overlapping volume.

[0058] Then, the calculation results of all tilt angle schemes are summarized and compared. The comparison is based on a dual optimization objective: The first objective is to minimize the volume of the low-velocity region. By comparing the volume values ​​of the low-velocity region under different tilt angle schemes, one or more tilt angle values ​​can be found that significantly reduce the volume of the low-velocity region.

[0059] The second objective is to eliminate spatial overlap of risk areas. Assuming the first objective is met, these preferred tilt angle schemes are further examined to determine whether the minimized low-speed zone and the local high-temperature zone still spatially overlap. The optimal scheme must satisfy the condition that the spatial overlap volume between the two is zero.

[0060] Through the above iterative simulations and comparative analyses, an optimal tangent inclination angle was finally determined. The bottom profile corresponding to this value can both eliminate or reduce the potential area of ​​coal powder deposition to the greatest extent and ensure that these residual, incompletely eliminated, extremely small low-velocity areas are completely separated in space from the high-temperature areas that may trigger ignition.

[0061] In some embodiments, for pulverizing systems processing pulverized coal with a volatile content higher than 30%, the pyrolysis process is more rapid and the system is more sensitive to high temperatures, making the control of local high-temperature zones particularly critical. During the optimization process, in addition to focusing on the volume of the low-velocity zone and the overlapping volume, the highest temperature point inside the primary wind box is also monitored to ensure that the optimization scheme does not unexpectedly lead to the emergence of new, higher-temperature local hot spots in other locations due to changes in the flow field.

[0062] As a concrete example, when optimizing a primary bellows with a flat bottom, a low-velocity zone with a volume of 0.15 cubic meters might be found at the bottom, completely overlapping with a localized high-temperature zone. Simulations at various tangent angles (e.g., 10°, 20°, 30°, 40°, 45°, 50°) might reveal the following trend: as the angle increases, the volume of the low-velocity zone first decreases and then increases. At 45 degrees, the volume of the low-velocity zone reaches its minimum, for example, 0.02 cubic meters. Furthermore, spatial analysis shows that at a 45-degree angle, this smallest low-velocity zone is located in a corner of the primary bellows, while the localized high-temperature zone, due to changes in the mainstream field morphology, has moved to the center of the bellows, and the two no longer have any spatial contact. Therefore, 45 degrees is determined to be the optimal tangent angle for this operating condition.

[0063] In an extended embodiment, after determining the optimal bottom geometry of the primary windbox through step c, thereby maximizing the suppression of coal powder deposition and eliminating the spatial overlap between the low-speed and high-temperature zones at the physical structure level, the focus shifts to optimizing the system operating parameters. The aim is to actively control the chemical reaction environment inside the system by regulating fluid dynamics conditions, thereby establishing another layer of safety assurance.

[0064] Specifically, this includes step d, which involves adjusting the primary air inlet velocity of the primary air box and determining a safe operating speed to avoid the volatile concentration from reaching its peak by repeatedly performing the simulation of step b.

[0065] In this embodiment, this step is performed based on the geometric model of the already obtained optimal bottom profile. The purpose is to study and determine one or a set of safe operating velocity parameters to ensure that, in actual operation, the volatile matter concentration in any local area within the primary air box will not reach a peak that could trigger deflagration. The inlet velocity of the primary air is a key adjustable parameter affecting the flow field morphology, mixing intensity, and residence time of pulverized coal particles within the box.

[0066] The steps for determining a safe operating speed specifically include: First, by simulating multiple different primary air inlet velocities, the law governing the variation of volatile matter concentration with primary air inlet velocity was determined.

[0067] Alternatively, a speed range can be set to cover the normal operating range and possible fluctuation range of the equipment. For example, the primary air inlet speed can be set to the range of 15 m / s to 35 m / s. Subsequently, a series of discrete speed values ​​are selected within this range for simulation tests. For example, with a step size of 2 m / s, the speed can be set to 15, 17, 19... up to 35 m / s, forming a simulation case set containing multiple independent operating conditions.

[0068] For each set velocity value, a complete computational fluid dynamics simulation, as described in detail in step b, must be repeated based on the optimal geometric model determined in step c. In these simulations, all boundary conditions, such as hot air inlet velocity and temperature, exhaust gas inlet temperature, pulverized coal characteristics and flow rate, remain constant, except for the primary air inlet velocity, which varies across cases. This ensures that differences in simulation results are caused only by variations in the primary air inlet velocity.

[0069] After each simulation, the key analysis object is the concentration distribution of volatiles within the computational domain. It is necessary to extract and record the maximum volatile concentration value occurring within the primary windbox at that operating speed from the full-field three-dimensional data. This maximum value represents the most dangerous chemical environment state at that operating speed.

[0070] Secondly, based on the patterns, analyze the risk rate that leads to the peak concentration of volatile components.

[0071] After completing the simulations for all velocity conditions, the obtained data will be organized and analyzed. A relationship curve can be plotted, with the horizontal axis representing the primary air inlet velocity and the vertical axis representing the corresponding maximum volatile matter concentration value that occurred in the simulation.

[0072] Analyzing this curve reveals the pattern of maximum volatile concentration variation with inlet velocity. Generally, this relationship is not a simple linear increase or decrease. There may be one or more velocity points where the volatile concentration exhibits a significant peak. This peak typically occurs because, at that specific velocity, the flow field structure, mixing effect, and particle residence time reach a particular unfavorable combination, causing the volatiles to form at a rate much higher than their rate of dilution and carryover by the mainstream flow, resulting in high enrichment.

[0073] Finally, a safe operating speed is set based on the speed range of the risk speed.

[0074] Once the risk speed range is determined, a safe operating parameter window can be defined accordingly. The principle for setting the safe operating speed is to proactively avoid the identified risk range.

[0075] In one possible implementation, the safe operating speed is set as one or more consecutive intervals that do not include risk speeds. For example, if the analysis finds that the risk speed is between 21 m / s and 23 m / s, the recommended safe operating speed range could be below 20 m / s or above 24 m / s.

[0076] As a further option, a safe threshold for volatile matter concentration can be set, for example, to 50% or less of the observed peak concentration. Then, on the rate-concentration curve, all rate ranges that result in the maximum volatile matter concentration below this safe threshold can be identified, and these ranges can be defined as the recommended safe operating rate range.

[0077] In another embodiment, after completing the initial simulation analysis in step b and before proceeding to the structural optimization in step c, a verification step can be performed. This step aims to confirm the accuracy of the simulation model by comparing it with actual data from the physical world, ensuring that subsequent optimization work is based on a reliable digital model.

[0078] The specific verification steps include: In this embodiment, the verification step specifically involves: comparing the predicted values ​​of key parameters obtained from the simulation calculation in step b with the actual operating data collected from the power plant's distributed control system (DCS) under the corresponding operating conditions.

[0079] Alternatively, the key parameter for comparison can be the outlet temperature of the primary air box, as it comprehensively reflects the complex mixing and heat transfer processes within the box. The accuracy of the model is evaluated by calculating the relative error between the simulation-predicted outlet temperature and the DCS-measured outlet temperature.

[0080] If the relative error is lower than a preset reliability threshold (e.g., 5%), it proves that the established three-dimensional geometric model and the simulation method used can accurately reflect the physical reality. The model is then confirmed as reliable and can be used for optimization analysis in subsequent step c.

[0081] Conversely, if the relative error exceeds this threshold, it indicates that the model has a bias. In this case, it is necessary to return to step a or step b to check and correct the 3D geometric model, boundary condition settings, or the selected physical model, and re-execute the simulation and verification until the reliability of the model is confirmed. This verification step ensures the effectiveness of the entire optimization method and the engineering applicability of the final result.

[0082] Please see the appendix Figure 2 - Figure 11 The present invention provides an application embodiment: This application example specifically includes the following steps: 1.1 Research Subjects This application example studies the intermediate storage pulverizing system of a 330MW coal-fired power unit in a power plant. The main equipment includes a scraper feeder, a centrifugal pulverizer, a low-speed cylindrical ball mill, a toothed conveyor, a pulverized coal silo, a raw coal silo, a coarse powder separator, and a mother-daughter type fine powder separator. Due to a change in coal supply, the operating coal type has shifted from lean coal to blended bituminous coal. To broaden the unit's adaptability to different coal types, the power plant changed the original hot air pulverizing system to a combined exhaust gas and hot air pulverizing system. The type of the pulverizer and pulverizing system remains unchanged. Its key feature is an exhaust gas transfer system where two exhaust gas streams share a primary air box. During operation, only one exhaust gas stream is transferred into the primary air box to mix with the hot air for pulverizing, while the exhaust gas stream not introduced into the primary air box enters the furnace as tertiary air to assist combustion.

[0083] Analysis of historical deflagration accidents reveals that the primary risk area within the system is the exhaust gas transfer system. Therefore, this paper focuses on analyzing the exhaust gas transfer system, performing numerical simulations of this area, and its geometric model is shown below. Figure 2 As shown.

[0084] Under the operating conditions shown in the figure, part of the exhaust gas from the outlet of fan A enters the coal mill through the recirculation valve to participate in the circulation, and the other part enters the tertiary air duct to enter the furnace for combustion; part of the exhaust gas from the outlet of fan B enters the coal mill for recirculation, and the other part is transferred to the primary air box and mixed with the hot air input from the primary air duct, and then flows out from the eight outlet pipes of the primary air box for coal feeding.

[0085] 1.2 Fuel Properties Based on on-site surveys, coal powder after grinding and separation (after the fine powder separator) was sampled for testing and thermogravimetric analysis. The main parameters are listed in Table 1, and the thermogravimetric analysis results are shown below. Figure 3 .

[0086] Table 1: Main parameters of pulverized coal As shown in Table 1, the coal used in the operation of this unit has a high volatile content, making it easy to ignite and burn. Furthermore, the coal dust contained in the exhaust gas is fine coal dust, which may cause safety accidents.

[0087] Depend on Figure 3 It can be seen that the pulverized coal begins deoxidation and decomposition at 281.79 ℃, enters the combustion stage at 397.54 ℃, and burns out at 519.29 ℃. Its maximum combustion rate occurs at 461.39 ℃, at 5.89% / min. Further processing of the thermogravimetric analysis data reveals that the activation energies of the pulverized coal during thermal decomposition and combustion are 79.54 kJ / mol and 116.31 kJ / mol, respectively, with pre-exponential factors of 155 s⁻¹. -1 1.16 × 10⁵ s -1 And it is used in numerical simulation calculations.

[0088] 1.3 Research Methods and Calculation Conditions In the calculations, the finite volume method was used to solve the Navier-Stokes partial differential equations, the Realizable k-ε model was used to describe the gas phase turbulence, the gas-solid coupling was based on the Euler-Lagrange method, the gas phase was regarded as the continuous phase and the particles as the discrete phase, the particle motion was adopted using a stochastic trajectory model, the volatile matter analysis of pulverized coal adopted a two-step competitive reaction rate model, the multi-step coke reaction simulation adopted a finite rate / eddy dissipation model, and the radiation heat transfer simulation adopted a DO model.

[0089] Based on the actual structure and dimensions, a 1:1 three-dimensional geometric model of the waste gas transfer system was established, and its mesh generation is shown in [Figure / Diagram / Illustration]. Figure 4 As shown in the figure, structured meshes are used in most areas such as the exhaust gas pipe and the primary air box, while unstructured meshes are used in a small number of areas such as the square and round joints used for pipe connections. In addition, considering that multiple fluids flow into and converge at the inlet of the primary air box, the mesh in this area has been densified to a certain extent.

[0090] Based on the DCS operating data, the main operating parameters for the calculated operating conditions were set: the inlet velocity of the two exhaust gas streams was 25 m / s, and the temperature was 364 K; the inlet velocity of the hot air stream was 7 m / s, and the temperature was 610 K. The valve openings of the A and B recirculation air streams differed, being 48.4% and 29.1%, respectively.

[0091] 2. Verification of mesh independence and simulation reliability The number of grid cells significantly impacts computational speed and accuracy. This paper designs four grid schemes with grid numbers of 33w, 43w, 53w, and 63w, primarily differing in the mesh density of the primary bellows and at some angular junctions. Here, a straight line is taken at a certain point inside the primary bellows, with 100 sample points distributed along it. The velocity values ​​at these sample points are recorded, and the results are shown below. Figure 5 As shown in the figure, the internal flow field calculated with different grid numbers has certain differences. The calculation results of 53w and 63w grid numbers are relatively consistent, but there are certain differences compared with the calculation results of 43w and 33w grid numbers. In order to balance the accuracy and calculation speed, 53w grid number was finally used for subsequent calculations.

[0092] According to on-site DCS data, the average velocity at the primary air box outlet is 31.45 m / s. Based on the outlet pipe area, the total volumetric flow rate at the outlet is calculated to be 44.96 m³ / s. 3 The average flow velocity at the outlet pipe, calculated by numerical simulation, is 29.19 m / s, and the total volumetric flow rate is 42.26 m³ / s. 3 The numerical simulation results showed errors of 7% and 6% between the measured values ​​and the DCS operating data. Meanwhile, the DCS measured an average temperature of 418.36 K at the outlet of the primary air box and 408.89 K near the upper wall inside the air box. The corresponding air temperatures obtained from the numerical simulation were 447.25 K and 424.65 K, with errors of 7% and 4%, respectively. This demonstrates that the established numerical model and calculation method have a certain degree of reliability.

[0093] 3. Analysis of the causes of deflagration Numerical simulation studies were conducted on the flow state inside the waste gas transfer system to analyze the influence of its internal flow field and temperature field on combustion inducing factors such as coal powder deposition and heat transfer, providing a basis for operation adjustment and structural optimization.

[0094] 3.1 Velocity field inside the primary air box The calculated velocity cloud diagram of the overall flow field inside the primary wind box is shown in the figure. Figure 6In this diagram, the Y=0 m plane is the central axis of the primary air box, the Y=0.5 m plane is the plane corresponding to exhaust gas inlet A, and the Y=-0.5 m plane is the plane corresponding to exhaust gas inlet B; the Z=0 m plane is the bottom surface of the primary air box, the Z=0.3 m plane based on this is the plane close to the bottom of the primary air box, the Z=0.5 m plane is the lower plane corresponding to the junction of the primary air box and the exhaust gas pipe, and the Z=1 m plane is the plane corresponding to the hot air bypass and exhaust gas transfer pipe entering the primary air box; the X=0 m plane is the central axis of the hot air inlet. As can be seen from this diagram, the flow velocity in the area where exhaust gas and hot air converge inside the air box is higher than the flow velocity in the air box outlet area, with the high-speed region mainly concentrated at the exhaust gas inlet and inside the outlet pipe.

[0095] Further analysis of the flow field reveals the velocity field distribution at different cross-sections within the primary wind box. Figure 7 .Depend on Figure 6 and 6 In summary, the velocity distribution varies across different cross-sections. The fluid velocity inside the B exhaust gas pipe at the Y=-0.5 m plane is relatively high. After entering the primary air box, the high-speed airflow shifts towards the Y=0 m plane, where the velocity decreases due to the rapid expansion of the volume within the air box. At the Y=0.5 m plane, the overall velocity is low because the A exhaust gas does not enter the air box. Simultaneously, a low-velocity zone exists near the interface between the exhaust gas pipe and the primary air box. Based on the flow characteristics of fine particles, this low-velocity zone can serve as a key area for coal powder deposition and heat accumulation, potentially leading to deflagration.

[0096] 3.2 Temperature field inside the primary air box Temperature cloud diagram inside the primary air box Figure 8 .Depend on Figure 8 It can be seen that the high-temperature zone inside the primary air box is mainly concentrated at the hot air inlet. However, there is also a certain high-temperature zone at the bottom of the primary air box, with its height ranging from approximately 0.2 to 0.7 m from the bottom. The highest temperature of 596.4 K is located at 0.3 m. The temperature fields at Z=0.3 m and Z=0.5 m are shown in the figure. Figure 8(b) and (c), the highest temperature on the Z=0.3 m plane reaches 601.3 K, with temperatures at the locations corresponding to the exhaust gas inlets A and B being 600.2 K and 593.6 K, respectively; the highest temperature on the Z=0.5 m plane reaches 601.7 K, with temperatures at the locations corresponding to the exhaust gas inlets A and B being 600.1 K and 542.7 K, respectively. This shows that the high-temperature region near the exhaust gas inlet A is larger. This is because when the exhaust gas transfer pipe on side A is closed, the hot air rushing in first impacts the wall, then flows downwards along the wall to the vicinity of the interface between the exhaust gas pipe A and the primary air box, where there is no cold airflow to mix with it, causing the temperature at that point to rise. Combining the simulation results of the velocity field and the properties of the pulverized coal itself, it can be seen that at the bottom of the exhaust gas and hot air mixing area in the primary air box, there is a low-velocity zone where particles are more easily deposited, and the temperature is also relatively high, exceeding the thermal decomposition temperature of the pulverized coal at its highest point. The accumulation of pulverized coal at this point easily leads to the further precipitation of volatiles, and the presence of volatiles affects the explosive limit range of the pulverized coal, making deflagration more likely.

[0097] 4. Adjustment of operating parameters and optimization of structure Based on the simulation results of the flow field and temperature field inside the wind box, the effect of hot air velocity on the volatile matter precipitation and enrichment was analyzed, a safe wind speed range suitable for the primary wind box was proposed, and structural optimization was carried out to reduce coal powder deposition.

[0098] 4.1 Effect of hot air velocity on CO generation and enrichment The effects of different hot air velocities on the flow patterns and CO enrichment within the primary air box region were simulated, and the results are shown in the figure. Figure 9 Analysis revealed that as the hot air velocity decreased, both the average flow rate and average temperature in the bellows area decreased. The average CO mass fraction increased slightly when the hot air velocity decreased from 7 m / s to 3 m / s, but the rate of increase accelerated significantly when the velocity decreased to 2 m / s. This is because hot air is the primary source of heat and oxygen inside the bellows. When the hot air velocity decreases, the heat carried by the hot air and the airflow inside the bellows decrease, leading to lower temperature and flow rate. Temperature and flow rate respectively influence the generation and accumulation of volatiles inside the bellows: increased temperature results in more volatiles being released, while increased flow rate makes it easier for volatiles to be carried out of the bellows by the airflow, preventing accumulation. Therefore, when the hot air velocity is 3 to 7 m / s, the generation and enrichment of volatiles are in a relatively balanced stage. At this time, the volatiles can be quickly carried out of the bellows after they are released. However, when the hot air velocity is reduced to below 2 m / s, the amount of volatiles released decreases, but the lower gas flow rate in the bellows is more conducive to the enrichment of volatiles, and the CO mass fraction increases.

[0099] Based on the distribution characteristics of CO, hot air velocities of 7 m / s, 5 m / s, 3 m / s, and 1 m / s were selected as representative operating conditions for analysis. The CO distribution is shown in the figure.Figure 10 As shown in the figure, the CO mass fraction is low at hot air velocities of 7 m / s and 5 m / s, while it significantly increases at a hot air velocity of 1 m / s. Specifically, at a hot air velocity of 7 m / s, CO is mainly distributed at the two outlets at the end of the primary air box process; at 5 m / s, CO gradually diffuses to other outlet locations; at 3 m / s, a certain amount of CO is also present at all outlets and the bottom of the primary air box; at 1 m / s, the CO distribution further spreads to the hot air inlet at the beginning of the primary air box process. The main reason for this distribution is that when the air velocity is high, the airflow can carry the released CO effectively, until most of the airflow has flowed out from other outlets at the end, where the CO mass fraction is high. As the hot air velocity gradually decreases, the airflow velocity inside the air box decreases, the airflow's ability to carry CO weakens, and the CO distribution range gradually expands.

[0100] All the above results indicate that maintaining a high airflow velocity inside the wind box plays an important role in mitigating the enrichment of volatiles and reducing the risk of deflagration inside the wind box. When the hot air temperature does not exceed the ignition point of pulverized coal, maintaining the hot air velocity at 3 to 7 m / s is more conducive to the safe operation of the pulverizing system.

[0101] 4.2 Optimization of the primary air box flow field Analysis revealed a potential coal dust deposition area at the bottom of the primary air box. Therefore, flow field optimization was performed in this area by filling the bottom of the air box with material to alter its angle. The simulated 11 optimization scenarios and the resulting low-velocity zone volumes are listed in Table 2. The table shows that as the height of the filler in the Z-direction increases, the volume of the low-velocity zone at the bottom of the air box continuously decreases; conversely, as the width of the filler in the X-direction continuously decreases, the volume of the low-velocity zone at the bottom of the air box increases.

[0102] Table 2: Optimized operating conditions and calculation results of the primary air box flow field Geometric dimensions in both directions In summary, The effect on the volume of the low-speed region is shown in Figure 11 As shown in the figure, with As the velocity increases, the volume of the low-velocity region first decreases and then increases, with a minimum point in the volume of the low-velocity region. The value is 0.15, corresponding to a low-velocity zone volume of 0.132 m³. This is because when the height in the Z direction is small, the slope formed by the filling material is insufficient to effectively eliminate interference in the low-velocity zone at the bottom of the primary air box, and low-velocity backflow still exists. However, when the width in the X direction is small, although the low-velocity zone closest to the left wall is less likely to form, The supplementary angle is relatively small, and there is still an angle between it and the main direction of the airflow entering the bellows, causing the low-speed zone to shift in the positive direction of the X-axis, but it is not completely eliminated.

[0103] 5. Conclusion There is a low-speed zone at the bottom of the primary air box, where there is a high possibility of coal powder particles accumulating inside the air box. Furthermore, due to the unobstructed downward flow of hot air along the wall during the mixing process, a local high-temperature area is formed, and the temperature at the bottom of the air box can reach up to 601.7 K, which exceeds the pyrolysis temperature of coal powder. Coal powder accumulating here may further oxidize, and there is a certain risk of deflagration in the corner area at the bottom of the air box.

[0104] The average CO mass fraction inside the wind box increases slightly when the hot air velocity decreases from 7 m / s to 3 m / s. When the hot air velocity decreases to 2 m / s, the CO concentration inside the wind box increases significantly. Maintaining the hot air velocity between 3 and 7 m / s is beneficial to the safe operation of the pulverizing system, provided that the hot air temperature does not significantly exceed the ignition point of the pulverized coal.

[0105] The flow field at the bottom of the primary air box was optimized by changing the bottom angle. ,along with As the velocity increases, the volume of the low-velocity region first decreases and then increases, with a minimum point in the volume of the low-velocity region. The value is 0.15, corresponding to a low-speed region volume of 0.132 m³. 3 This provides a theoretical basis for optimizing the shape of the bellows.

[0106] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An explosion-proof optimization method for exhaust gas transfer devices in pulverizing systems based on fluid dynamics calculations, characterized in that, Includes the following steps: Step a: Establish a three-dimensional geometric model based on the exhaust gas transfer device of the pulverizing system to be optimized; the exhaust gas transfer device includes a primary air box for mixing exhaust gas containing pulverized coal with hot air; Step b: Use computational fluid dynamics to simulate the three-dimensional geometric model to obtain the flow field and temperature field distribution inside the primary air box, and identify the low-speed zone for coal powder deposition and the local high-temperature zone for igniting coal powder that exist simultaneously at the bottom of the primary air box based on the flow field and temperature field distribution. Step c: Adjust the bottom profile of the primary air box for the low-speed zone and the local high-temperature zone, and determine the optimal bottom profile by repeating the simulation of step b. The optimal bottom profile is used to minimize the volume of the low-speed zone and ensure that the minimized low-speed zone does not overlap with the local high-temperature zone in space.

2. The explosion-proof optimization method for the waste gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 1, characterized in that, Step b employs computational fluid dynamics (CFD) methods for simulation, specifically including: The Euler-Lagrange method was used to perform coupled calculations on gas-solid two-phase flow. A two-step competitive reaction rate model was used to simulate the precipitation process of volatiles from pulverized coal.

3. The explosion-proof optimization method for the waste gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 1, characterized in that, In step c, adjusting the bottom profile of the primary air box specifically involves: filling the bottom of the primary air box to change the tangent angle at the bottom of the air box. .

4. The explosion-proof optimization method for the exhaust gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 3, characterized in that, The steps for determining the optimal bottom profile specifically include: Simulations were performed on multiple different tangent inclination angle values, and a tangent inclination angle value was determined that minimizes the volume of the low-speed region while preventing spatial overlap between the minimized low-speed region and the local high-temperature region.

5. The explosion-proof optimization method for the waste gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 4, characterized in that, The smallest The value is 0.

15.

6. The explosion-proof optimization method for the waste gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 1, characterized in that, The method further includes: Step d: Adjust the primary air inlet velocity of the primary air box, and determine the safe operating speed to avoid the volatile concentration from reaching its peak by repeatedly performing the simulation of step b.

7. The explosion-proof optimization method for the waste gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 6, characterized in that, The step of determining the safe operating speed in step d specifically includes: The variation of volatile matter concentration with primary air inlet velocity was determined by simulating multiple different primary air inlet velocities. Based on the aforementioned pattern, analyze the risk rate that leads to the peak concentration of volatile components; A safe operating speed is set based on the speed range of the risk speed.

8. The explosion-proof optimization method for the exhaust gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 1, characterized in that, A verification step is also included between step b and step c, and the verification step includes: The simulation results obtained in step b are compared with the measured operating data collected from the DCS system of the pulverizing system to verify the reliability of the three-dimensional geometric model.

9. The explosion-proof optimization method for the waste gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 1, characterized in that, The method is applied to a pulverizing system that processes pulverized coal with a volatile content higher than 30%.

10. The explosion-proof optimization method for the exhaust gas transfer device of a pulverizing system based on fluid dynamics calculations according to claim 1, characterized in that, Step b also includes performing a spatial correlation analysis on the identified low-speed zone and local high-temperature zone to assess the risk level of their overlap leading to deflagration; and step c makes adjustments based on the risk level.

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