Digital Twin-Based Boiler Fine Air Distribution Method and Boiler System

Abstract

The present invention discloses a boiler refined air distribution method and a boiler system based on digital twins. The air distribution method comprises: performing three-dimensional modeling and simulation on each secondary air damper corresponding to each secondary air nozzle in the air distribution system of a physical boiler system; embedding a one-dimensional thermal fluid model of each secondary air damper into the one-dimensional thermal fluid model of the air distribution system to form a digital twin model of the air distribution system; determining a target secondary air volume of each secondary air nozzle; performing PID control adjustment on the opening of each secondary air damper in the digital twin model so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume; after the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume, outputting the opening adjustment result of each secondary air nozzle to a DCS distributed control system, and adjusting the opening of each secondary air damper of each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment result.

Description

Technical Field

[0001] The present invention relates to the technical field of boiler combustion air distribution, and particularly relates to a refined air distribution method for boilers based on digital twins and a boiler system. Background Art

[0002] Coal-fired power plants need to frequently adjust the load due to the integration of new energy into the grid and the different peak electricity consumption of users. Coupled with the variability of the coal types burned, the operation of boilers often deviates from the optimal operating conditions, and the problems are more prominent during low-load and rapid load increase and decrease processes. Many common problems of boilers are related to uneven combustion in many cases. The uneven combustion directly affects the distribution of the air flow field and temperature field in the boiler, leading to uneven burning in the furnace, excessive local heat load on the water wall, and further causing problems such as increased coking, high-temperature corrosion of the water wall, thermal deviation of the superheater and reheater, reduced combustion efficiency, and high emissions of nitrogen oxides (NOx). This is common for coal-fired power generation units that often perform peak shaving and is also a problem of great concern in actual production.

[0003] The patent document (application number: 201810700365.3), "A Dynamic Optimization Method for Secondary Air Distribution in a Tangential Coal-Fired Boiler", provides a method for optimizing the air supply dynamics in the furnace based on the traditional optimization of secondary air distribution. The optimal opening degree of the secondary air baffle of the nozzle determined can minimize the pressure drop from the air box to the furnace outlet, and as much as possible reduce the power consumption of the forced draft fan under the condition that the combustion efficiency and nitrogen oxide emissions reach the best. This patent obtains the change curve of the resistance coefficient of the secondary air baffle with the opening degree through cold-state tests.

[0004] The patent document (application number: 201910170428.3), "A Method and Device for Real-Time Adjusting the Secondary Air Volume of a Swirl Burner", takes the relatively common opposed combustion boiler in China as the research object, and adjusts the inlet pressure of each swirl burner in the operating burner layer to real-time adjust the secondary air volume required by each swirl burner.

[0005] At present, the adjustment of boiler combustion air distribution in thermal power plants is mostly based on traditional operation methods related to boiler parameters such as fan speed, air box baffle door opening degree, primary and secondary air pressures, coal feeder speed, furnace oxygen content, and furnace negative pressure. When parameters such as coal quality, load, air-coal ratio of the burner, or air-powder concentration in the primary air duct change, due to the lack of precise control methods, operators cannot comprehensively consider various coupling factors for combustion adjustment based on experience alone, resulting in the boiler operating under unreasonable air distribution, seriously affecting the safety and economy of the unit. Summary of the Invention

[0006] The purpose of the present invention is to provide a more effective and intelligent refined air distribution method for boilers based on digital twins and a boiler system applying this air distribution method.

[0007] The first aspect of the present invention discloses a refined air distribution method for boilers based on digital twins, including:

[0008] Perform three-dimensional modeling and simulation on each secondary air damper corresponding to each secondary air nozzle in the air distribution system of the physical boiler system to obtain the simulation results of the relationship characteristics between the resistance coefficient and the opening degree of each secondary air damper;

[0009] Build a one-dimensional thermal fluid model of the air distribution system based on a one-dimensional thermal fluid platform, establish a one-dimensional thermal fluid model for each secondary air damper according to the above simulation results, and embed the one-dimensional thermal fluid models of the secondary air dampers into the one-dimensional thermal fluid model of the air distribution system to form a digital twin model of the air distribution system;

[0010] Select a combustion air distribution mechanism model, and combine the operating parameters of the physical boiler system read through the DCS distributed control system of the physical boiler system as the boundary conditions of the combustion air distribution mechanism model to determine the target secondary air volume of each secondary air nozzle;

[0011] According to the determined target secondary air volume of each secondary air nozzle, combine the relationship characteristics between the resistance coefficient and the opening degree of each secondary air damper and the operating parameters of the physical boiler system read through the DCS distributed control system, and perform PID control adjustment on the opening degree of each secondary air damper in the digital twin model, so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume;

[0012] After the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume, output the opening degree adjustment results of each secondary air nozzle to the DCS distributed control system, and adjust the opening degree of each secondary air damper of each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment results.

[0013] In some embodiments, the air distribution system includes a forced draft fan, an air preheater, an air box, a plurality of secondary air nozzles, a first pipeline between the fan and the air preheater, a second pipeline between the air preheater and the air box, and a third pipeline between the air box and the plurality of secondary air nozzles. After forming the digital twin model of the air distribution system, perform cold-state tests and / or hot-state tests on the digital twin model to correct the resistance characteristics of the first pipeline, the second pipeline, and the third pipeline of the air distribution system. Among them, during the cold-state tests and / or hot-state tests, the opening degree of each secondary air damper in the digital twin model is adjusted to the maximum opening degree.

[0014] In some embodiments, after adjusting the opening degrees of the secondary air dampers of each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment result, the oxygen content of the flue gas at the outlet of the economizer of the physical boiler system is monitored, and the excess air coefficient in the main combustion zone in the selected combustion air distribution mechanism model is corrected according to the monitoring result.

[0015] In some embodiments, the excess air coefficient in the main combustion zone in the combustion air distribution mechanism model is controlled within 0.7 to 0.92.

[0016] In some embodiments, the physical boiler system adopts a wall-type opposed firing boiler, and the air distribution system includes each air volume adjustment damper provided in front of the inlet of each tangential burner for adjusting the air intake of the corresponding tangential burner. Before forming the digital twin model of the air distribution system, three-dimensional modeling and simulation are performed on each air volume adjustment damper corresponding to each tangential burner in the air distribution system of the physical boiler system to obtain the simulation result of the relationship between the resistance coefficient and the opening degree of each air volume adjustment damper. Based on the one-dimensional thermal fluid platform, a one-dimensional thermal fluid model of the air distribution system is constructed. According to the above simulation result, a one-dimensional thermal fluid model of each air volume adjustment damper is established, and the one-dimensional thermal fluid model of each secondary air damper is embedded into the one-dimensional thermal fluid model of the air distribution system to form a digital twin model of the air distribution system; according to the determined target secondary air volume of each secondary air nozzle, combined with the relationship between the resistance coefficient and the opening degree of each secondary air damper and the operating parameters of the physical boiler system read through the DCS distributed control system, PID control adjustment is performed on the opening degree of each secondary air damper in the digital twin model and PID control adjustment is performed on the opening degree of each air volume adjustment damper so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume.

[0017] In some embodiments, selecting a combustion air distribution mechanism model and determining the target secondary air volume of each secondary air nozzle by combining the operating parameters of the physical boiler system read through the DCS distributed control system of the physical boiler system as the boundary conditions of the combustion air distribution mechanism model includes:

[0018] Reading the unit load of the physical boiler system, the outside atmospheric pressure, the outside atmospheric temperature, the outside atmospheric humidity, the elemental composition of the pulverized coal, the pulverized coal flow rate of the coal mill, the steam temperature of the main reheater, the steam pressure of the main reheater, the flow rate of the main reheater, the secondary air temperature, the secondary air pressure, and the primary air temperature, the primary air pressure, and the primary air flow rate.

[0019] In some embodiments, when making the secondary air volume output by each secondary air nozzle in the digital twin model match the target secondary air volume, the opening degree of each secondary air damper in the digital twin model is limited to 5% to 95%.

[0020] In some embodiments, the combustion air distribution mechanism model includes a demand-based distribution model, a positive pagoda model, an inverted pagoda model, an equalization model, a waist-constricting model, or a waist-bulging model.

[0021] In some embodiments, it further includes setting a visualization module to be signal-connected to the digital twin model and the DCS distributed control system, so that partial simulation data of the digital twin model and partial operating parameters of the retrieved physical boiler system are displayed on the visualization module, and the visualization module further has a human-computer interaction interface, through which the operation of the digital twin model can be controlled.

[0022] A second aspect of the present invention discloses a boiler system, including a physical boiler system and the digital twin model as described above, and the boiler system is configured to operate the above-mentioned digital twin-based boiler refined air distribution method.

[0023] Based on the digital twin-based boiler refined air distribution method provided by the present invention, after three-dimensional modeling and simulation of each secondary air baffle and embedding them into the digital twin model established based on the one-dimensional thermal fluid platform, and after determining the target secondary air volume of each secondary air nozzle in combination with the combustion air distribution mechanism model, the opening degree of each secondary air baffle is adjusted through the PID control of the digital twin model to achieve the matching of the secondary air volume output by each secondary air nozzle with the target secondary air volume. Then, the air distribution system of the physical boiler system can be adjusted according to the digital twin model, so that the secondary air volume output by each secondary air nozzle of the air distribution system of the physical boiler system is as close as possible to the target secondary air volume, thereby enabling intelligent and refined control of the air distribution combustion of the physical boiler system and improving the combustion efficiency of the physical boiler system.

[0024] Through the following detailed description of the exemplary embodiments of the present invention with reference to the accompanying drawings, other features and advantages of the present invention will become clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings described herein are used to provide a further understanding of the present invention, and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0026] Figure 1 It is a schematic structural diagram of the boiler of the physical boiler system according to an embodiment of the present invention;

[0027] Figure 2 It is a schematic structural diagram of the boiler of the physical boiler system according to another embodiment of the present invention;

[0028] Figure 3 It is a flowchart of the digital twin-based boiler refined air distribution method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually illustrative only and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationship. Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0031] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. Without further statement, the above terms have no special meaning and thus cannot be construed as limiting the protection scope of the present invention.

[0032] For the convenience of description, spatial relative terms such as "above...", "on top of...", "on the upper surface of...", "above" can be used here to describe the spatial position relationship between a device or feature shown in the figure and other devices or features. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation shown in the figure of the device. For example, if the device in the figure is inverted, the device described as "above other devices or structures" or "on top of other devices or structures" will then be positioned "below other devices or structures" or "beneath other devices or structures". Thus, the exemplary term "above..." can include both the orientations of "above..." and "below...". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding explanations should be made for the spatial relative descriptions used here.

[0033] Digital twin makes full use of data such as physical models, sensor updates, and operation history, integrates the simulation processes of multiple disciplines, multiple physical quantities, multiple scales, and multiple probabilities, and completes the mapping in the virtual space, so as to reflect the full life cycle process of the corresponding physical equipment. Digital twin is a concept that transcends reality and can be regarded as a digital mapping system of one or more important and interdependent equipment systems.

[0034] As Figure 3 shown, the fine air distribution method for boilers based on digital twin in this embodiment includes:

[0035] Step a, perform three-dimensional modeling and simulation on each secondary air damper corresponding to the air distribution system of the physical boiler system to obtain the simulation results of the relationship characteristics between the resistance coefficient and the opening degree of each secondary air damper. Three-dimensional modeling software includes UG (Unigraphics NX interactive CAD / CAM system), CATIA (Computer Aided Tri-dimensional Application Interface, interactive CAD / CAE / CAM system), etc. After performing three-dimensional modeling according to the structural parameters of each secondary air damper in the air distribution system of the physical boiler system, and then performing simulation calculations through CFD (Computational Fluid Dynamics) software, the relationship characteristics between the resistance coefficient and the opening degree of each secondary air damper can be obtained. For the relevant introduction of the resistance coefficient and the opening degree of the secondary air damper, reference can be made to the Chinese patent application with the publication number CN105160158A.

[0036] Step b: Based on the one-dimensional thermal-fluid platform, establish a one-dimensional thermal-fluid model of the air distribution system. According to the above simulation results, establish one-dimensional thermal-fluid models for each secondary air damper, and embed the one-dimensional thermal-fluid models of each secondary air damper into the one-dimensional thermal-fluid model of the air distribution system to form a digital twin model of the air distribution system. The one-dimensional thermal-fluid platform includes various one-dimensional thermal-fluid simulation software, such as Flownex (pipe network system design software) and Flowmaster (thermal-fluid system simulation and analysis software). Based on the physical structure and operating parameters of the air distribution system of the physical boiler system (the operating parameters can be read from the DCS distributed control system of the physical boiler system), establish a one-dimensional thermal-fluid model of the air distribution system. The parameters of components such as the forced draft fan and air preheater in the one-dimensional thermal-fluid model of the air distribution system can be set by inputting relevant parameters according to the component models selected for the physical structure. Embed the one-dimensional thermal-fluid models of each secondary air damper established according to the simulation results into the one-dimensional thermal-fluid model of the air distribution system, so that a one-dimensional thermal-fluid model of the air distribution system including the one-dimensional thermal-fluid models of each secondary air damper can be obtained. The DCS (Distributed Control System) distributed control system of the physical boiler system includes information for controlling the physical boiler system and also includes various operating parameters of the physical boiler system. After establishing a data connection with the DCS distributed control system of the physical boiler system, a digital twin model of the air distribution system can be formed. The process of generating a boiler digital twin system can be referred to in the Chinese patent application with publication number CN113339787A. Using the one-dimensional thermal-fluid platform to establish a digital twin model, compared with the classical CFD simulation, the advantage of the one-dimensional thermal-fluid platform simulation is that the boiler air distribution system is divided into components (such as pumps, elbows, heat exchangers, etc.), and only the flow and heat transfer information at the inlets and outlets of each component are calculated. For a thermal-fluid network with less than ten components, the steady-state calculation time is about dozens to hundreds of milliseconds; for a thermal-fluid network with up to hundreds of components, the steady-state calculation time is about several seconds, which is 4 to 5 orders of magnitude less than the calculation time of CFD simulation, thus enabling ultra-high-speed simulation of the air distribution system.

[0037] Step c: Select a combustion air distribution mechanism model, and determine the target secondary air volume of each secondary air nozzle by using the operating parameters of the physical boiler system read through the DCS (Distributed Control System) of the physical boiler system as the boundary conditions of the combustion air distribution mechanism model. The combustion air distribution mechanism model is the selected pulverized coal combustion air distribution method, including equal air distribution, positive pagoda, inverted pagoda, waist-reducing or waist-bulging air distribution methods. The relevant calculation methods for various combustion air distribution mechanism models can refer to "Translated by the Design Section of Beijing Boiler Factory, Standard Methods for Thermal Calculation of Boiler Units, Beijing: China Machine Press, 1976" and "Standard Methods for Thermal Calculation of Boilers, 1998 Edition, http: / / 98bj.fishsting.cn / ". After selecting a combustion air distribution mechanism model, determine the boundary conditions based on information such as unit load, external atmospheric pressure, external atmospheric temperature, external atmospheric humidity, elemental composition of pulverized coal, steam temperature of the main reheater, steam pressure of the main reheater, flow rate of the main reheater, secondary air temperature, secondary air pressure, primary air temperature, primary air pressure, and primary air flow rate, so as to calculate the target secondary air volume of each secondary air nozzle.

[0038] Step d: According to the determined target secondary air volume of each secondary air nozzle, combined with the relationship characteristics between the resistance coefficient and the opening degree of each secondary air baffle and the operating parameters of the physical boiler system read through the DCS distributed control system, perform PID (Proportional Integral Derivative) control adjustment on the opening degree of each secondary air baffle in the digital twin model, so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume. The characteristic data of the resistance coefficient and the opening degree of each secondary air baffle are embedded in the digital twin model. According to this characteristic data, combined with data such as furnace negative pressure read in the DCS distributed control system, control the opening degree of each secondary air baffle through PID conditions, and finally make the secondary air volume output by each secondary air nozzle corresponding to each secondary air baffle match the target secondary air volume. Matching means that the difference between the secondary air volume and the target secondary air volume is within a set range, and this set range can be defined by means such as work experience.

[0039] Step e: After the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume, output the opening degree adjustment result of each secondary air nozzle to the DCS distributed control system, and adjust the opening degree of each secondary air baffle of each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment result.

[0040] The fine air distribution method for boilers based on digital twins in this embodiment involves three-dimensional modeling and simulation of each secondary air baffle and embedding it into the digital twin model established based on a one-dimensional thermal fluid platform. After determining the target secondary air volume of each secondary air nozzle according to the combustion air distribution mechanism model, the opening degree of each secondary air baffle is adjusted through PID control of the digital twin model to achieve the matching of the secondary air volume output from each secondary air nozzle with the target secondary air volume. Then, the air distribution system of the physical boiler system can be adjusted according to the digital twin model, so that the secondary air volume output from each secondary air nozzle of the air distribution system of the physical boiler system is as close as possible to the target secondary air volume. At the same time, by establishing a digital twin model of the air distribution system, the air distribution system of the digital twin model can transmit data to the physical boiler system through the DCS distributed control system to control the air distribution system in the physical boiler system, and the air distribution system in the digital twin model can also read the data of the physical boiler system through the DCS distributed control system to adjust and calculate the digital twin model. Thus, the air distribution combustion of the physical boiler system can be controlled intelligently and precisely, improving the combustion efficiency of the physical boiler system

[0041] In some embodiments, the air distribution system includes a forced draft fan, an air preheater, an air box, a plurality of secondary air nozzles, a first pipe located between the fan and the air preheater, a second pipe located between the air preheater and the air box, and a third pipe located between the air box and the plurality of secondary air nozzles. After forming the digital twin model of the air distribution system, cold-state tests and / or hot-state tests are carried out on the digital twin model to correct the resistance characteristics of the first pipe, the second pipe, and the third pipe of the air distribution system. During the cold-state tests and / or hot-state tests, the opening degrees of the secondary air dampers of the digital twin model are adjusted to the maximum opening degrees. During the commissioning phase of the thermal power generating unit or after the overhaul is completed, the furnace aerodynamic field test is often carried out. Under cold-state conditions, the hot-state operation conditions in the furnace are simulated to understand the air flow characteristics and check whether the installation angles of the burners are correct. The cold-state test in this embodiment refers to using the digital twin model to conduct an air distribution simulation test, and correspondingly, non-coal combustion is carried out in the boiler furnace of the physical boiler system. The air distribution system of the physical boiler system conducts an air distribution work test. Then, by measuring the air velocities of the secondary air nozzles in the air distribution system of the physical boiler system, as well as the pressure difference and temperature between the secondary air box and the furnace in the air distribution system, the resistance characteristics of the pipes in the air distribution system of the physical boiler system are obtained, and the resistance characteristics of the first pipe, the second pipe, and the third pipe are corrected according to the calculation results. The hot-state test in this embodiment refers to using the digital twin model to conduct an air distribution simulation test, and correspondingly, coal combustion is carried out in the boiler furnace of the physical boiler system. The air distribution system of the physical boiler system conducts an air distribution work test. Then, by measuring the air velocity, pressure difference, temperature, etc. between the air distribution system of the physical boiler system and the furnace, the resistance characteristics of the pipes in the air distribution system of the physical boiler system are obtained, and the resistance characteristics of the first pipe, the second pipe, and the third pipe are corrected according to the calculation results. During this process, the opening degrees of the secondary air dampers are adjusted to 100% opening degrees. At this time, the opening degrees of the secondary air dampers are the largest, eliminating the resistance influence caused by the non-maximum opening degrees of the secondary air dampers.

[0042] In some embodiments, after adjusting the opening degrees of the secondary air dampers of each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment result, the oxygen content of the flue gas at the outlet of the economizer of the physical boiler system is monitored, and the excess air coefficient in the main combustion zone of the selected combustion air distribution mechanism model is corrected according to the monitoring result. The excess air coefficient in the combustion air distribution mechanism model is usually within a certain range. According to experience, it is more appropriate to control the excess air coefficient in the main combustion zone at 0.7 to 0.92, and the specific value selection can fluctuate according to experience or needs. For different excess air coefficients, the target secondary air volume results calculated according to the same selected combustion air distribution mechanism model are different. If the oxygen content of the flue gas at the outlet of the economizer of the boiler is too high, the boiler combustion efficiency will decrease, and the wear of equipment such as the heating surface tubes of the boiler and the blades of the induced draft fan will increase, and the service life of the equipment will decrease. If the oxygen content of the flue gas at the outlet of the economizer of the boiler is too low, the fuel combustion will be incomplete and the boiler combustion efficiency will be low. In this embodiment, after using the digital twin model to control the air distribution of the physical boiler system, the excess air coefficient in the main combustion zone of the combustion air distribution mechanism model can be corrected according to the oxygen content of the flue gas at the outlet of the economizer.

[0043] In some embodiments, the physical boiler system adopts a wall-type opposed firing boiler. The air distribution system includes each air volume adjustment damper provided in front of the inlet of each tangential burner for adjusting the air intake volume of the corresponding tangential burner. Before forming the digital twin model of the air distribution system, three-dimensional modeling and simulation are performed on each air volume adjustment damper corresponding to each tangential burner in the air distribution system of the physical boiler system to obtain the simulation result of the relationship between the resistance coefficient and the opening degree of each air volume adjustment damper. Based on the one-dimensional thermal fluid platform, a one-dimensional thermal fluid model of the air distribution system is constructed. According to the above simulation result, a one-dimensional thermal fluid model of each air volume adjustment damper is established, and the one-dimensional thermal fluid model of each secondary air damper is embedded into the one-dimensional thermal fluid model of the air distribution system to form a digital twin model of the air distribution system; according to the determined target secondary air volume of each secondary air nozzle, combined with the relationship between the resistance coefficient and the opening degree of each secondary air damper and the operating parameters of the physical boiler system read through the DCS distributed control system, PID control adjustment is performed on the opening degrees of each secondary air damper in the digital twin model and PID control adjustment is performed on the opening degrees of each air volume adjustment damper so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume. In the wall-type opposed firing boiler of this embodiment, the air distribution system is provided with air boxes on the front wall and the rear wall of the boiler respectively. Each side air box is connected to multiple air chambers, and each layer of air chamber is connected to multiple tangential burners. There is an air volume adjustment damper between each air chamber and the tangential burner. The air volume adjustment damper can adjust the secondary air volume of each tangential burner. In this embodiment, three-dimensional modeling and simulation are performed on the air volume adjustment damper, which can make the digital twin model of the wall-type opposed firing boiler more accurate and effective.

[0044] In some embodiments, a combustion air distribution mechanism model is selected, and the operating parameters of the physical boiler system are read through the DCS distributed control system of the physical boiler system as the boundary conditions of the combustion air distribution mechanism model to determine the target secondary air volume of each secondary air nozzle, including:

[0045] Read the unit load of the physical boiler system, the external atmospheric pressure, the external atmospheric temperature, the external atmospheric humidity, the elemental composition of the pulverized coal, the pulverized coal flow rate of the coal mill, the steam temperature of the main reheater, the steam pressure of the main reheater, the flow rate of the main reheater, the secondary air temperature, the secondary air pressure, and the primary air temperature, primary air pressure, and primary air flow rate.

[0046] In some embodiments, for safety assurance, a certain margin is left for the opening of the secondary air damper. When matching the secondary air volume output by each secondary air nozzle in the digital twin model with the target secondary air volume, the opening of each secondary air damper in the digital twin model is limited to 5% - 95%.

[0047] In some embodiments, the combustion air distribution mechanism model includes an as-needed distribution model, a positive pagoda model, an inverted pagoda model, an equal model, a waist - shrinking model, or a waist - bulging model.

[0048] In some embodiments, it further includes setting a visualization module to be signal - connected to the digital twin model and the DCS distributed control system, enabling some simulation data of the digital twin model and some operating parameters of the retrieved physical boiler system to be displayed on the visualization module. Moreover, the visualization module also has a human - machine interaction interface, through which the operation of the digital twin model can be controlled. The visualization module may include a display screen, which displays model data such as the opening of each secondary air damper, the air volume and air speed of the secondary air nozzles of the digital twin model, as well as data such as the furnace negative pressure and economizer flue gas temperature read from the DCS distributed control system.

[0049] In some embodiments, a boiler system is also disclosed. The boiler system includes a physical boiler system and a digital twin model, and the boiler system is configured to be operable with the above - mentioned digital - twin - based refined air distribution method for boilers.

[0050] The following uses two specific embodiments to illustrate the present application.

[0051] Embodiment 1

[0052] The physical boiler system of this embodiment includes a tangentially - fired boiler with four corners. The tangentially - fired boiler with four corners has a large number of burners and a large number of secondary air dampers, with 40 - 65 secondary air dampers. Considering various parameters affecting the secondary air volume of the secondary air nozzles, it leads to a slow calculation speed and a decrease in accuracy of the secondary air volume algorithm, causing great difficulties for subsequent solutions. This embodiment couples the influence of various factors on the secondary air volume distribution, effectively solving the problem of mutual influence when the control parameters of multiple secondary air dampers change.

[0053] In this specific embodiment, a 300MW-class coal-fired boiler is taken as an example. The boiler adopts swing burners, is arranged in a tangential firing pattern at the four corners, has a single furnace, is arranged in an open ∏-type, has a fully steel-frame suspension structure, balanced draft, and solid slag removal. The boiler adopts a positive-pressure direct-fired pulverizing system, equipped with five HP-type medium-speed coal mills, which are arranged in front of the furnace. Four coal mills can carry the MCR load, and one is for standby. The outlet of each coal mill is connected to the burner nozzles of each layer by 4 pulverized coal pipelines, as Figure 1 shown. Each corner burner has 5 primary air nozzles. One layer of secondary air nozzles is arranged adjacent to the upper and lower layers of the primary air nozzles respectively. From top to bottom, they are the first nozzle 21, the second nozzle 22, the third nozzle 23, the fourth nozzle 24, the fifth nozzle 25, and the sixth nozzle 26 in sequence. A burnout air box is arranged above the main air box. The burnout air nozzles are the seventh nozzle 11, the eighth nozzle 12, the ninth nozzle 13, and the tenth nozzle 14 in sequence from top to bottom, as Figure 1 shown. The boiler includes a main combustion zone y and a burnout zone x.

[0054] The method for fine air distribution of the boiler based on digital twin in this embodiment includes:

[0055] Three-dimensional modeling and simulation are carried out on each secondary air damper corresponding to each secondary air nozzle in the air distribution system of the physical boiler system including a tangentially fired boiler at the four corners to obtain the simulation results of the relationship characteristics between the resistance coefficient and the opening degree of each secondary air damper. The relationship characteristics between the resistance coefficient and the opening degree of each secondary air damper can be obtained. The air distribution system of the tangentially fired boiler at the four corners includes a forced draft fan, an air preheater, an air box, elbows, multiple secondary air nozzles, a first pipeline between the fan and the air preheater, a second pipeline between the air preheater and the air box, and a third pipeline between the air box and multiple secondary air nozzles. Based on the characteristic parameters of the equipment in the air distribution system of the tangentially fired boiler at the four corners, a one-dimensional thermal fluid model of the air distribution system is constructed on a one-dimensional thermal fluid platform. According to the above simulation results, a one-dimensional thermal fluid model of each secondary air damper is established, and the one-dimensional thermal fluid model of each secondary air damper is embedded into the one-dimensional thermal fluid model of the air distribution system to form a digital twin model of the air distribution system. A cold-state test is carried out on the digital twin model to measure data such as the pressure difference from the air preheater to the air box and the pressure difference from the air box to the boiler furnace of the tangentially fired boiler at the four corners. According to the measured data, the resistance characteristics of the first pipeline, the second pipeline, and the third pipeline of the air distribution system are corrected.

[0056] Through communication technologies such as Ethernet and Modbus, or hardwired data transmission methods, retrieve the real-time data of unit operation in the DCS distributed control system database, and preprocess the collected operation environment data and operation parameter data of the air distribution system physical equipment. For example, the boiler load parameter range is 0-335MW, read the value from the DCS every 10s and store it in the digital twin database; the main steam pressure is 11-16Mpa, read the value from the DCS every 10s and store it in the digital twin database; the secondary air temperature parameter range at the outlet of the air preheater is 285-320°C, read the value from the DCS every 10s and store it in the digital twin database, and so on. Data preprocessing mainly determines whether the collected data is within a reasonable range, that is, whether it contains null values, 0 values or abnormal values. If it contains, correct the null values, 0 values or abnormal values through historical data query to avoid program calculation errors. The digital twin database can not only store real-time data, but also realize the call of historical data.

[0057] Select a combustion air distribution mechanism model, and combine the operation parameters of the physical boiler system read through the DCS distributed control system of the physical boiler system as the boundary conditions of the combustion air distribution mechanism model to determine the target secondary air volume of each secondary air nozzle. After selecting a combustion air distribution mechanism model, determine the boundary conditions according to information such as unit load, outside atmospheric pressure, outside atmospheric temperature, outside atmospheric humidity, elemental composition of pulverized coal, steam temperature of the main reheater, steam pressure of the main reheater, flow rate of the main reheater, secondary air temperature, secondary air pressure, primary air temperature, primary air pressure and primary air flow rate, etc., so that the target secondary air volume of each secondary air nozzle can be calculated. Among them, the temperature, pressure and flow rate of the primary air in the pulverized coal pipe at the outlet of the coal mill are obtained by installing an on-line primary air volume measuring device in each pulverized coal pipe at the mill outlet, providing a basis for more reasonable distribution of the secondary air volume of each nozzle. Before being put into use, the on-line primary air volume measuring device needs to be subjected to cold and hot state tests, adjust the primary air adjustable choke, correct the primary air pressure deviation, and ensure that the deviation of the primary air volume of the same layer is less than ±5% as qualified. The primary air volume measuring device has a self-cleaning function to prevent the measuring device from being blocked and affecting the measurement result.

[0058] The secondary air in the combustion air distribution mechanism model of the digital twin model includes SOFA air, OFA air, perimeter air and secondary air in the main combustion zone. The determination of the target secondary air volume in the combustion air distribution mechanism model includes the following steps: First, determine the total air volume L required for boiler combustion according to unit load, elemental analysis of the coal fed into the furnace, steam temperature of the main reheater, steam pressure of the main reheater, flow rate of the main reheater, feed water temperature, feed water flow rate, etc. 空气 , unit kg / s, and then determine the primary air volume L of each pulverized coal pipe according to the on-line primary air volume measuring device pri , kg / s, and calculate the primary air ratio: Wpri = L pri / L, thereby determining the proportion W of the secondary air volume in the total air volume sec . Secondly, further refine the distribution of the proportion W of the SOFA air in the secondary air in the total air volume sec-SOFA , the proportion Wsec- of the perimeter air in the total air volume 周界风 and the proportion W of the secondary air in the main combustion zone in the total air volume sec-主燃区 The proportion, among which the more important ones are the air distribution ratios of the SOFA air and the secondary air in the main combustion zone. This value affects whether the upper and lower staged combustion in the furnace is sufficient and reasonable, the NOx emission concentration, and the carbon content in fly ash. The proportion W of the SOFA air in the total secondary air sec-SOFA is controlled between 0.28 and 0.34. In this embodiment, the combustion air distribution mechanism model is verified through experiments and engineering experience. The combustion air distribution mechanism model includes fixed control models such as the on-demand distribution model, the positive pagoda model, the inverted pagoda model, the equal model, the constricted waist model, or the bulging waist model that meet the combustion requirements of different boilers under different loads and different coal qualities, realizing upper and lower staged combustion in the furnace

[0059] Examples of the positive pagoda, inverted pagoda, equal type, constricted waist type, and bulging waist type fixed control models are as follows

[0060]

[0061] In addition, a key parameter is the excess air coefficient in the main combustion zone. This value determines the combustion environment in the main combustion zone and has a very important impact on controlling the generation amount of fuel-type NOx. According to different coal types and combustion methods, the excess air coefficient αmain combustion zone in the main combustion zone is controlled between 0.7 and 0.92 to keep the main combustion zone in a fuel-rich and oxygen-deficient state and reduce the generation amount of fuel-type NOx. Determine the secondary air volume required for combustion in each layer according to the pulverized coal volume, primary air volume, and excess air coefficient value in each layer of nozzles

[0062] According to the determined target secondary air volume of each secondary air nozzle, combined with the relationship characteristics between the resistance coefficient and the opening degree of each secondary air baffle and the operating parameters of the physical boiler system read through the DCS distributed control system, perform PID control adjustment on the opening degree of each secondary air baffle in the digital twin model so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume. The characteristic data of the resistance coefficient and the opening degree of each secondary air baffle are embedded in the digital twin model. According to this characteristic data, combined with data such as the furnace negative pressure read in the DCS distributed control system, control the opening degree of each secondary air baffle through PID control conditions, and finally make the secondary air volume output by each secondary air nozzle corresponding to each secondary air baffle match the target secondary air volume. Matching means that the difference between the secondary air volume and the target secondary air volume is within a set range, and this set range can be defined by means such as work experience

[0063] After the secondary air volume output from each secondary air nozzle in the digital twin model matches the target secondary air volume, it is stored in the digital twin body database, and the opening adjustment results of each secondary air nozzle are output to the DCS distributed control system through communication protocols such as Ethernet and Modbus, or hardwired data transmission methods. The opening of each secondary air baffle of each secondary air nozzle in the air distribution system of the physical boiler system is adjusted according to the adjustment results.

[0064] After adjusting the opening of each secondary air baffle of each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment results, the feedback data of relevant parameters is monitored to determine whether the air distribution meets the combustion requirements. If not, the relevant parameters of the digital twin model are optimized; if so, the task continues to be executed. The oxygen content of the flue gas at the outlet of the economizer is used as the basis for judging the furnace combustion, supplemented by the over-temperature points of the high-temperature heating surface, NOx emissions, carbon content in fly ash and slag, and CO concentration, to control the excess air coefficient of each burner nozzle. In addition, the excess air coefficient of the main combustion zone is corrected according to the changes in the water volume of the first and second-stage desuperheaters and the flue gas temperature compared with the previous moment. The oxygen content of the flue gas at the outlet of the economizer is corrected accordingly according to the load and coal quality changes. For example, when the oxygen content at the outlet of the economizer seriously deviates from the combustion required limit, the outlet oxygen content is corrected according to the historical load operation data.

[0065] Embodiment 2

[0066] The physical boiler system of this embodiment includes a wall-type opposed firing boiler. Taking a 600MW-class coal-fired boiler as an example in this specific embodiment, the boiler is a supercritical parameter variable pressure once-through boiler, with once reheat, single furnace, double flue ducts at the tail, using baffle to adjust the reheat steam temperature, balanced draft, outdoor layout, solid slag removal, all-steel structure, and fully suspended structure Π-type boiler. A medium-speed mill direct injection pulverizing system is adopted, with 6 coal mills per furnace, and 1 is reserved for standby. The front and rear wall opposed firing method is adopted. 24 HT-NR3 burners are arranged in three layers on the front and rear walls of the furnace to make the heat load and flue gas temperature distribution more uniform along the furnace width direction. In the HT-NR3 burner, the combustion air is divided into three streams, which are: direct current primary air, direct current secondary air, and swirl secondary air, as Figure 2 shown.

[0067] A wind box is provided in the burner area. The wind box is divided into multiple wind chambers, with one wind chamber for each layer of burners. The large wind box is symmetrically arranged on the front and rear walls. Secondary air baffles are provided at the inlet of each wind chamber, and all secondary air baffles are equipped with actuators and can be programmed for adjustment. A total of 16 actuators are equipped in the whole furnace. The actuators are equipped with position feedback devices and have the function of fault self-locking and position holding.

[0068] Four burners are arranged in each air chamber, and each burner is equipped with an air volume regulating baffle. The adjusting rod of the air volume regulating baffle passes through the burner panel, and the position of the baffle can be conveniently adjusted outside the burner and the air box. Without this device, it is necessary to add an adjusting baffle and an electric actuator specifically at the secondary air inlet of each tangential burner 31 to ensure the real-time adjustment of the secondary air volume of each burner.

[0069] Restricted by the structure of the secondary air box and the secondary air inlet mode of the wall-type opposed firing boiler, the pressure distribution along the width direction of the secondary air box is usually uneven. Generally, the pressure of the burners in the middle part is higher than that on both sides. And during the actual operation of the furnace, the negative pressure in the middle part of the furnace is significantly higher than that in the areas near the water wall on both sides. Considering these two factors, there are large deviations in the secondary air volume of each burner in the same secondary air box, resulting in many problems such as combustion skewing and high-temperature corrosion of the water wall in this area.

[0070] The existing tangential burners of wall-type opposed firing boilers generally adjust the air volume of the tangential burners by changing the angles of the inner secondary air and outer secondary air swirl vanes. However, adjusting the swirl vanes will affect the shape, size, and position of the recirculation zone, and it is impossible to achieve real-time adjustment with the load. The secondary air volume of each tangential burner cannot accurately match the required target secondary air volume.

[0071] Therefore, on the premise of maintaining the swirl intensity of the secondary air at the outlet of the tangential burner unchanged, adjusting the opening degrees of the secondary air baffles on both sides of each layer of secondary air box and the opening degrees of the air volume regulating baffles at the inlets of each tangential burner is of great significance for optimizing combustion uniformity and reducing the generation amount of nitrogen oxides.

[0072] The method for fine air distribution of boilers based on digital twin in this embodiment includes:

[0073] Three-dimensional modeling and simulation are carried out on the secondary air dampers corresponding to each secondary air nozzle and the air volume regulating dampers corresponding to each tangential burner in the air distribution system of a solid boiler system including a wall-type opposed firing boiler, so as to obtain the simulation results of the relationship characteristics between the resistance coefficients and the opening degrees of the secondary air dampers and the air volume regulating dampers. The air distribution system of the wall-type opposed firing boiler includes a forced draft fan, an air preheater, an air box, an elbow, a plurality of secondary air nozzles, a first pipeline between the fan and the air preheater, a second pipeline between the air preheater and the air box, and a third pipeline between the air box and the plurality of secondary air nozzles. The CFD software is used to conduct three-dimensional numerical simulation on the detailed structure of the tangential burner to obtain the resistance coefficient of the tangential burner when participating in air distribution, and the ROM model is used for order reduction processing. The three-dimensional results are exported as Functional Mockup Unit (FMU), and co-simulation is realized through FMU, taking into account both system-level simulation and component-level simulation, which not only meets the overall resistance analysis and evaluation of the air distribution system, but also fully considers the influence of the complex structure of the tangential burner and the difference in the swirl structure of the inner secondary air and the outer secondary air on the flow resistance.

[0074] Based on the characteristic parameters of the equipment in the air distribution system of the wall-type opposed firing boiler, a one-dimensional thermal fluid model of the air distribution system is constructed on a one-dimensional thermal fluid platform. According to the above simulation results, a one-dimensional thermal fluid model of each secondary air damper is established, and the one-dimensional thermal fluid model of each secondary air damper is embedded into the one-dimensional thermal fluid model of the air distribution system to form a digital twin model of the air distribution system. A cold state test is carried out on the digital twin model to measure data such as the pressure difference from the air preheater to the air box and the pressure difference from the air box to the boiler furnace of the wall-type opposed firing boiler, and the resistance characteristics of the first pipeline, the second pipeline and the third pipeline of the air distribution system are corrected according to the measured data.

[0075] Through communication technologies such as Ethernet and Modbus, or hardwired data transmission methods, the real-time data of the unit operation in the DCS distributed control system database is retrieved, and the collected operation environment data and operation parameter data of the physical equipment of the air distribution system are preprocessed. For example, the boiler load parameter range is 0 - 335 MW, and the value is read from the DCS every 10 s and stored in the digital twin database; the main steam pressure is 11 - 16 Mpa, and the value is read from the DCS every 10 s and stored in the digital twin database; the secondary air temperature parameter at the outlet of the air preheater ranges from 285 to 320 °C, and the value is read from the DCS every 10 s and stored in the digital twin database, etc. The data preprocessing mainly determines whether the collected data is within a reasonable range, that is, whether it contains null values, 0 values or abnormal values. If it contains, the null values, 0 values or abnormal values are corrected through historical data query to avoid program calculation errors. The digital twin database can not only store real-time data, but also realize the call of historical data.

[0076] Select a combustion air distribution mechanism model, and determine the target secondary air volume of each secondary air nozzle by combining the operating parameters of the physical boiler system read through the DCS distributed control system of the physical boiler system as the boundary conditions of the combustion air distribution mechanism model. After selecting a combustion air distribution mechanism model, determine the boundary conditions based on information such as unit load, external atmospheric pressure, external atmospheric temperature, external atmospheric humidity, elemental composition of pulverized coal, steam temperature of the main reheater, steam pressure of the main reheater, flow rate of the main reheater, secondary air temperature, secondary air pressure, primary air temperature, primary air pressure, and primary air flow rate, so that the target secondary air volume of each secondary air nozzle can be calculated. Among them, the temperature, pressure, and flow rate of the primary air in the pulverized coal pipe at the outlet of the coal mill are obtained by installing an on-line primary air volume measuring device in each pulverized coal pipe at the mill outlet, providing a basis for more reasonable distribution of the secondary air volume of each nozzle. Before being put into use, the on-line primary air volume measuring device needs to undergo cold and hot state tests, adjust the adjustable primary air orifice, correct the primary air pressure deviation, and ensure that the deviation of the primary air volume of the same layer is less than ±5% as qualified. The primary air volume measuring device has a self-cleaning function to prevent the measuring device from being blocked and affecting the measurement results.

[0077] According to the determined target secondary air volume of each secondary air nozzle, combined with the relationship characteristics between the resistance coefficient and the opening degree of each secondary air baffle and the operating parameters of the physical boiler system read through the DCS distributed control system, perform PID control adjustment on the opening degree of each secondary air baffle in the digital twin model and perform PID control adjustment on the opening degree of each air volume adjustment baffle so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume.

[0078] After the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume, store it in the digital twin body database, and output the opening degree adjustment results of each secondary air nozzle to the DCS distributed control system through communication protocols such as Ethernet and Modbus, or hardwired data transmission methods, and adjust the opening degrees of each secondary air baffle and the air volume adjustment baffle of each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment results.

[0079] After adjusting the opening degrees of the secondary air dampers of each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment result, monitor the feedback data of relevant parameters to determine whether the air distribution meets the combustion requirements. If it does not meet the requirements, optimize the relevant parameters of the digital twin model. If it meets the requirements, continue to execute the task. Use the oxygen content in the flue gas at the economizer outlet as the basis for judging furnace combustion, supplemented by the over-temperature points of high-temperature heating surfaces, NOx emissions, carbon content in fly ash and slag, and CO concentration, and control the excess air coefficient of each burner nozzle. In addition, correct the excess air coefficient in the main combustion zone according to the changes in the water flow rates of the first and second-stage desuperheaters and the flue gas temperature compared with the previous moment. The oxygen content in the flue gas at the economizer outlet is corrected according to the load and coal quality changes. For example, when the oxygen content at the economizer outlet seriously deviates from the combustion required limit, the outlet oxygen content is corrected according to the historical load operation data.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or perform equivalent replacements for some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered by the scope of the technical solutions claimed in the present invention.

Claims

1. A refined air distribution method for boilers based on digital twin, characterized in that, it includes: Performing three-dimensional modeling and simulation on each secondary air baffle corresponding to each secondary air nozzle in the air distribution system of the physical boiler system to obtain the simulation results of the relationship characteristics between the resistance coefficient and the opening degree of each secondary air baffle; Constructing a one-dimensional thermal fluid model of the air distribution system based on a one-dimensional thermal fluid platform, establishing a one-dimensional thermal fluid model for each secondary air baffle according to the above simulation results, and embedding the one-dimensional thermal fluid models of the secondary air baffles into the one-dimensional thermal fluid model of the air distribution system to form a digital twin model of the air distribution system; Selecting a combustion air distribution mechanism model, and determining the target secondary air volume of each secondary air nozzle by combining the operating parameters of the physical boiler system read through the DCS distributed control system of the physical boiler system as the boundary conditions of the combustion air distribution mechanism model; According to the determined target secondary air volume of each secondary air nozzle, combining the relationship characteristics between the resistance coefficient and the opening degree of each secondary air baffle and the operating parameters of the physical boiler system read through the DCS distributed control system, performing PID control adjustment on the opening degree of each secondary air baffle in the digital twin model, so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume. When making the secondary air volume output by each secondary air nozzle in the digital twin model match the target secondary air volume, the opening degree of each secondary air baffle in the digital twin model is limited to 5% - 95%; After the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume, output the opening degree adjustment results of each secondary air nozzle to the DCS distributed control system, and adjust the opening degree of each secondary air baffle corresponding to each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment results.

2. The refined air distribution method for boilers based on digital twin according to claim 1, wherein the air distribution system includes a forced draft fan, an air preheater, an air box, a plurality of secondary air nozzles, a first pipeline between the fan and the air preheater, a second pipeline between the air preheater and the air box, and a third pipeline between the air box and the plurality of secondary air nozzles, characterized in that, After forming the digital twin model of the air distribution system, performing cold state tests and / or hot state tests on the digital twin model to correct the resistance characteristics of the first pipeline, the second pipeline, and the third pipeline of the air distribution system. During the cold state tests and / or hot state tests, the opening degree of each secondary air baffle in the digital twin model is adjusted to the maximum opening degree.

3. The refined air distribution method for boilers based on digital twin according to claim 1, characterized in that, After adjusting the opening degree of each secondary air baffle corresponding to each secondary air nozzle in the air distribution system of the physical boiler system according to the adjustment results, monitoring the oxygen content of the flue gas at the outlet of the economizer of the physical boiler system, and correcting the excess air coefficient in the main combustion zone of the selected combustion air distribution mechanism model according to the monitoring results.

4. The method for refined air distribution of a boiler based on digital twin as described in claim 3, characterized in that, the excess air coefficient in the main combustion zone of the combustion air distribution mechanism model is controlled within 0.7 to 0.

92.

5. The method for refined air distribution of a boiler based on digital twin as described in claim 1, wherein the physical boiler system adopts a wall-type opposed firing boiler, and the air distribution system includes air volume adjustment baffles provided on the front side of the inlet of each tangential burner for adjusting the air volume entering the corresponding tangential burner, characterized in that, before forming the digital twin model of the air distribution system, three-dimensional modeling and simulation are performed on each air volume adjustment baffle corresponding to each tangential burner in the air distribution system of the physical boiler system to obtain the simulation result of the relationship between the resistance coefficient and the opening degree of each air volume adjustment baffle, a one-dimensional thermal fluid model of the air distribution system is constructed based on a one-dimensional thermal fluid platform, a one-dimensional thermal fluid model of each air volume adjustment baffle is established according to the above simulation result, and the one-dimensional thermal fluid models of the secondary air baffles are embedded into the one-dimensional thermal fluid model of the air distribution system to form the digital twin model of the air distribution system; according to the determined target secondary air volume of each secondary air nozzle, combining the relationship between the resistance coefficient and the opening degree of each secondary air baffle and the operating parameters of the physical boiler system read through the DCS distributed control system, PID control adjustment is performed on the opening degree of each secondary air baffle in the digital twin model and PID control adjustment is performed on the opening degree of each air volume adjustment baffle so that the secondary air volume output by each secondary air nozzle in the digital twin model matches the target secondary air volume.

6. The method for refined air distribution of a boiler based on digital twin as described in claim 1, characterized in that, selecting a combustion air distribution mechanism model, and combining the operating parameters of the physical boiler system read through the DCS distributed control system of the physical boiler system as the boundary conditions of the combustion air distribution mechanism model to determine the target secondary air volume of each secondary air nozzle includes: reading the unit load, external atmospheric pressure, external atmospheric temperature, external atmospheric humidity, elemental composition of pulverized coal, pulverized coal flow rate of the coal mill, steam temperature of the main reheater, steam pressure of the main reheater, flow rate of the main reheater, secondary air temperature, secondary air pressure, primary air temperature, primary air pressure, and primary air flow rate of the physical boiler system.

7. The method for refined air distribution of a boiler based on digital twin as described in claim 1, characterized in that, the combustion air distribution mechanism model includes a demand distribution model, a positive pagoda model, an inverted pagoda model, an equal model, a waist shrinking model, or a waist swelling model.

8. The method for refined air distribution of a boiler based on digital twin as described in claim 1, characterized in that, it further includes setting a visualization module to be signal-connected to the digital twin model and the DCS distributed control system, enabling partial simulation data of the digital twin model and partial operating parameters of the retrieved physical boiler system to be displayed on the visualization module, and the visualization module further has a man-machine interaction interface, and the operation of the digital twin model can be controlled through the man-machine interaction interface.

9. A boiler system, characterized in that, Comprising a physical boiler system and the digital twin model as described in claim 1, the boiler system being configured to operate the digital twin-based refined air distribution method for boilers as described in any one of claims 1 to 8.

Images