Online wall temperature monitoring method for boiler combustion coupling working medium heat transfer calculation

Abstract

The invention provides an online wall temperature monitoring method for boiler combustion coupling working medium heat transfer calculation. According to the method, the working medium side hydrodynamic calculation flow distribution model and the in-furnace combustion side three-dimensional thermal load distribution model are coupled, the real-time and accurate calculation of the wall temperature of the full-screen tube of the water cooling wall is realized according to loop division, a heat transfer deterioration area is identified, and thus the occurrence of tube explosion accidents is reduced. The implementation and development of the method are beneficial to reducing the occurrence of power plant accidents, improving the reliability of four-pipe equipment of the boiler, reducing the non-planned shutdown times, improving the availability rate of unit equipment, and improving the safety and economical efficiency of unit operation at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of online calculation of boiler water-cooled wall metal wall temperature, and in particular to an online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation. Background Art

[0002] In the context of deep peak regulation of boilers, the non-stop unit caused by leakage of the "four pipes" has become the most concerned issue for users. Especially when the boiler is running at low load, the burst of pipes caused by uneven flow of working fluid in the water-cooled wall, which causes overheating of the wall surface, and then leads to corrosion, coking, wear, stress cracking, etc., is the most urgent problem to be solved. The traditional method of monitoring the wall temperature of the boiler is to install the inlet pipe section of the middle mixing header of the water-cooled wall and the inlet pipe section of the water-cooled wall outlet header at a distance of about half a meter from the water-cooled wall. A thermocouple is arranged every few pipes, and the wall temperature of the boiler pipe is calculated based on the measured temperature. The location of the wall temperature measuring point is as follows: Figure 1 and Figure 2 At present, it is impossible to use measurement technology to obtain the wall temperature of the dangerous part of the full-screen tube of the water-cooled wall, and thus it is impossible to predict problems such as boiler four-tube leakage.

[0003] At present, the main problems of boiler wall temperature monitoring are: the wall temperature measurement points are incomplete, and only some pipe outlet measurement points can be alarmed, and full-screen monitoring cannot be performed; the temperature measured outside the furnace cannot replace the wall temperature on the fire side of the heated surface, and the most dangerous wall temperature cannot be directly obtained; the location of the most dangerous pipe section cannot be confirmed, and thus the leakage of the four pipes of the boiler cannot be predicted. When the wall temperature of individual pipe sections is found to be overheated, the operating personnel need to reduce the operating temperature of the boiler to ensure the safe operation of the boiler, sacrificing the economic efficiency of the boiler. Summary of the invention

[0004] The purpose of the present invention is to solve the problems in the prior art and propose an online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation. The current numerical simulation of boilers focuses on the combustion side, which can obtain relatively accurate combustion side flow, temperature, and component fields, but lacks working medium side coupling. The present invention couples the working medium side hydrodynamic calculation flow distribution model with the three-dimensional heat load distribution model on the combustion side of the furnace, and realizes real-time and accurate calculation of the full-screen tube wall temperature of the water-cooled wall according to the circuit division, identifies the heat transfer deterioration area, and thus reduces the occurrence of pipe burst accidents.

[0005] The present invention is implemented by the following technical scheme. The present invention proposes an online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation, and the method comprises the following steps:

[0006] Step 1: Perform CFD numerical simulation on the entire furnace of the boiler to provide three-dimensional heat load distribution data on the wall for working fluid heat transfer calculation;

[0007] Step 2: Heat transfer calculation on the working fluid side: divide the circuit according to the structural characteristics of the boiler and the heat load distribution data; use the nonlinear iterative calculation model based on the flow network system method to establish the nonlinear equation group of the node, and use the quasi-Newton method to solve the nonlinear equation group to obtain the working fluid temperature and pressure parameters;

[0008] Step 3. Calculate the wall temperature by coupling boiler combustion and working fluid heat transfer: Write a user-defined function UDF file. UDF plays the role of intermediate transfer, that is, coupling the working fluid heat transfer calculation program with the boiler combustion numerical simulation, and calibrating each other. The working fluid heat transfer calculation program provides the working fluid temperature as the boundary for the numerical simulation, and the numerical simulation provides the heat load distribution data for the heat transfer calculation as a premise, realizing information interaction and cyclic iteration. The result of the coupling is the holographic display of the working fluid side and the flue gas side after the iteration converges.

[0009] Step 4: Online calculation of wall temperature using machine learning: Based on the wall temperature of typical working conditions and the on-site wall temperature measurement point data, a machine learning algorithm is used to obtain a wall temperature database for all working conditions to achieve online monitoring of the wall temperature.

[0010] Furthermore, the method also includes step five, accuracy verification, which performs accuracy verification based on the wall temperature measurement point data.

[0011] Furthermore, in step one, historical data from the site is collected, the operating rules of the boiler are analyzed, a probability density function is established based on the boiler operating load and the pulverizer operating mode, typical operating conditions and boundary conditions are determined, a three-dimensional model for CFD numerical simulation is established, and CFD fluid calculation software is used to simulate the dynamic field in the furnace. The heat load at each position of the water-cooled wall is simulated through convection heat transfer and radiation heat transfer, the water-cooled wall heat load distribution data is derived, and the spatial coordinates and heat load files of each point on the water-cooled wall are obtained.

[0012] Furthermore, in step 2, the pressure balance of the flow circuit and the connecting pipe in the water-cooled wall flow network system and the flow balance of the header pressure node are calculated, and a nonlinear iterative calculation model of the pressure balance equation and the flow balance equation is established.

[0013] Furthermore, the nonlinear equation group is specifically: for the i-th tube, the pressure drop Δp(i) is related to the flow Mi of the tube:

[0014]

[0015] represents the functional relationship between the flow rate and pressure drop of the i-th pipe, then the total flow rate M of the parallel pipeline is:

[0016] and

[0017] Then the equation system: fi(M1,M2,…,Mm ,Δp)=0.

[0018] Furthermore, the principle of circuit division is based on the intensity of the wall heat load, where the heat load changes greatly, the circuit is refined, and where the heat load changes less, the circuit is coarsened.

[0019] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation are implemented.

[0020] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The current numerical simulation of boilers focuses on the combustion side, which can obtain relatively accurate flow, temperature, and component fields on the combustion side, but lacks coupling on the working fluid side. The present invention couples the hydrodynamic calculation flow distribution model on the working fluid side with the three-dimensional heat load distribution model on the combustion side in the furnace, and realizes real-time and accurate calculation of the full-screen tube wall temperature of the water-cooled wall according to the circuit division, identifies the heat transfer deterioration area, and thus reduces the occurrence of tube burst accidents. The implementation of the present invention is conducive to reducing the occurrence of power plant accidents, improving the reliability of boiler four-tube equipment, reducing the number of unplanned shutdowns, and improving the availability of unit equipment, while improving the safety and economy of unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0024] Figure 1 It is a two-dimensional plane diagram and a three-dimensional stereoscopic schematic diagram of the location of the water-cooled wall intermediate header wall temperature measurement point; among them, (a) is a two-dimensional plane diagram, and (b) is a three-dimensional stereoscopic schematic diagram;

[0025] Figure 2 This is a schematic diagram of the location of the water-cooled wall outlet header wall temperature measurement points;

[0026] Figure 3 It is a structural diagram of an online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation;

[0027] Figure 4This is the water-cooled wall circuit division diagram. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Combination Figure 1-Figure 4 The present invention proposes an online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation, the method comprising the following steps:

[0030] Step 1: Perform CFD numerical simulation on the entire furnace of the boiler to provide three-dimensional heat load distribution data on the wall for working fluid heat transfer calculation;

[0031] In step one, historical data from the site is collected, the operating rules of the boiler are analyzed, a probability density function is established based on the boiler operating load and the pulverizer operating mode, typical operating conditions and boundary conditions are determined, a three-dimensional model for CFD numerical simulation is established, and the dynamic field in the furnace is simulated using CFD fluid calculation software. The heat load at each position of the water-cooled wall is simulated through convection heat transfer and radiation heat transfer, the water-cooled wall heat load distribution data is derived, and the spatial coordinates and heat load files of each point on the water-cooled wall are obtained.

[0032] Step 2, working fluid side heat transfer calculation: loop division is performed according to the water-cooled wall structural characteristics and heat load distribution data of the boiler. The principle of loop division is based on the intensity of the wall heat load. The loop is refined in places where the heat load changes greatly, and the loop is coarsened in areas where the heat load changes little. The present invention no longer uses the average loop division method of 4 or 8 tubes. The main influencing factors of flow distribution are the structure and resistance distribution of the loop and the wall heat load distribution. A nonlinear iterative calculation model based on the flow network system method (equation model about flow and pressure) is used to establish a nonlinear equation group of nodes, and the quasi-Newton method is used to solve the nonlinear equation group to obtain the working fluid temperature and pressure parameters.

[0033] In step 2, the pressure balance of the flow circuit and the connecting pipe in the water-cooled wall flow network system and the flow balance of the header pressure node are calculated, and a nonlinear iterative calculation model of the pressure balance equation and the flow balance equation is established, such as Figure 4 shown.

[0034] The nonlinear equations are as follows: For the i-th tube, the pressure drop Δp(i) is related to the flow Mi of the tube:

[0035]

[0036] represents the functional relationship between the flow rate and pressure drop of the i-th pipe, then the total flow rate M of the parallel pipeline is:

[0037] and

[0038] Then the equation system: fi(M1,M2,…,M m ,Δp)=0.

[0039] Step 3: Calculate the wall temperature by coupling boiler combustion and working fluid heat transfer: Use UDF to write a wall temperature calculation program, which calls the three-dimensional heat load data of CFD numerical simulation on the one hand, and the working fluid temperature obtained by the working fluid heat transfer calculation program on the other hand. Realize information interaction and cyclic iteration. The result of the coupling is a holographic display of the working fluid side and the flue gas side after the iteration converges. The structural diagram of the whole method is as follows Figure 3 As shown. Specifically: write a user-defined function UDF file, UDF plays the role of intermediate transfer, that is, coupling the working fluid heat transfer calculation program with the boiler combustion numerical simulation, and calibrating each other; the working fluid heat transfer calculation program provides the working fluid temperature as the boundary for the numerical simulation, and the numerical simulation provides the heat load distribution data for the heat transfer calculation as a premise, realizing information interaction and cyclic iteration; the result of the coupling is the holographic display of the working fluid side and the flue gas side after the iteration converges;

[0040] Step 4: Online calculation of wall temperature by machine learning: The machine learning algorithm is used in combination with the boiler combustion heat transfer mechanism to realize online calculation of the metal wall temperature on the fire side, and then visualized to predict problems such as overheating and leakage of the four-tube boiler. Specifically: Based on the wall temperature of typical working conditions and the on-site wall temperature measurement point data, the machine learning algorithm is used to obtain a full-condition wall temperature database to realize online monitoring of the wall temperature.

[0041] The method also includes step five, accuracy verification, which performs accuracy verification based on the wall temperature measurement point data.

[0042] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation are implemented.

[0043] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation.

[0044] The memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct RAM bus RAM (DRRAM). It should be noted that the memory of the method described in the present invention is intended to include, but is not limited to, these and any other suitable types of memory.

[0045] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (digital subscriber line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a high-density digital video disc (DVD)), or a semiconductor medium (eg, a solid state disc (SSD)).

[0046] In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in a processor or an instruction in the form of software. The steps of the method disclosed in conjunction with the embodiment of the present application can be directly embodied as a hardware processor for execution, or a combination of hardware and software modules in a processor for execution. The software module can be located in a storage medium mature in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor reads the information in the memory and completes the steps of the above method in conjunction with its hardware. To avoid repetition, it is not described in detail here.

[0047] It should be noted that the processor in the embodiment of the present application can be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method embodiment can be completed by an integrated logic circuit of hardware in the processor or an instruction in the form of software. The above processor can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the embodiment of the present application can be directly embodied as a hardware decoding processor to perform, or the hardware and software modules in the decoding processor can be combined and performed. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

[0048] The above is a detailed introduction to the online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation proposed in the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An online wall temperature monitoring method for boiler combustion coupled working medium heat transfer calculation, characterized in that: The method comprises the following steps: Step 1: Perform CFD numerical simulation on the entire furnace of the boiler to provide three-dimensional heat load distribution data on the wall for working fluid heat transfer calculation; Step 2: Heat transfer calculation on the working fluid side: divide the circuit according to the structural characteristics of the boiler and the heat load distribution data; use the nonlinear iterative calculation model based on the flow network system method to establish the nonlinear equation group of the node, and use the quasi-Newton method to solve the nonlinear equation group to obtain the working fluid temperature and pressure parameters; Step 3. Calculate the wall temperature by coupling boiler combustion and working fluid heat transfer: Write a user-defined function UDF file. UDF plays the role of intermediate transfer, that is, coupling the working fluid heat transfer calculation program with the boiler combustion numerical simulation, and calibrating each other. The working fluid heat transfer calculation program provides the working fluid temperature as the boundary for the numerical simulation, and the numerical simulation provides the heat load distribution data for the heat transfer calculation as a premise, realizing information interaction and cyclic iteration. The result of the coupling is the holographic display of the working fluid side and the flue gas side after the iteration converges. Step 4: Online calculation of wall temperature using machine learning: Based on the wall temperature of typical working conditions and the on-site wall temperature measurement point data, a machine learning algorithm is used to obtain a wall temperature database for all working conditions to achieve online monitoring of the wall temperature.

2. The online wall temperature monitoring method according to claim 1, characterized in that: The method also includes step five, accuracy verification, which performs accuracy verification based on the wall temperature measurement point data.

3. The online wall temperature monitoring method according to claim 2, characterized in that: In step one, historical data from the site is collected, the operating rules of the boiler are analyzed, a probability density function is established based on the boiler operating load and the pulverizer operating mode, typical operating conditions and boundary conditions are determined, a three-dimensional model for CFD numerical simulation is established, and the dynamic field in the furnace is simulated using CFD fluid calculation software. The heat load at each position of the water-cooled wall is simulated through convection heat transfer and radiation heat transfer, the water-cooled wall heat load distribution data is derived, and the spatial coordinates and heat load files of each point on the water-cooled wall are obtained.

4. The online wall temperature monitoring method according to claim 3, characterized in that: In step 2, the pressure balance of the flow circuit and the connecting pipe in the water-cooled wall flow network system and the flow balance of the header pressure node are calculated, and a nonlinear iterative calculation model of the pressure balance equation and the flow balance equation is established.

5. The online wall temperature monitoring method according to claim 4, characterized in that: The nonlinear equations are as follows: For the i-th tube, the pressure drop Δp(i) is related to the flow Mi of the tube: represents the functional relationship between the flow rate and pressure drop of the i-th pipe, then the total flow rate M of the parallel pipeline is: and Then the equation system: fi(M1,M2,…,M m ,Δp)=0.

6. The online wall temperature monitoring method according to claim 1, characterized in that: The principle of circuit division is based on the intensity of the wall heat load. The circuit is refined in areas with large changes in heat load, and coarsened in areas with small changes in heat load.

7. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

8. A computer-readable storage medium for storing computer instructions, characterized in that: When the computer instructions are executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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