Transient calculation method suitable for rapid variable-load combustion of boiler

Abstract

The invention provides a transient calculation method suitable for rapid variable load combustion of a boiler, and belongs to the technical field of combustion loads in the boiler. The method comprises the steps that firstly, a three-dimensional geometric model of the boiler is built, and boundary conditions and initial conditions are set; configuring a gas-solid two-phase flow model; configuring a combustion characteristic model; setting variable load operation conditions; initialization and operation simulation are carried out, and monitoring and adjustment are carried out through a NOx generation model; and finally, performing result analysis and verification. According to the method, a Realizable k-epsilon turbulence model, a DPM random orbit model, a P1 radiation model, a component transport model, UDF code control and other technologies are used for achieving calculation of the rapid negative change and the combustion transient state of the boiler; more efficient and environment-friendly boiler operation is achieved, meanwhile, a more accurate simulation and prediction tool is provided, and a scientific basis is provided for operation and optimization of the boiler.

Description

Technical Field

[0001] The present invention belongs to the technical field of boiler combustion load, and in particular, relates to a transient calculation method for boiler rapid load change combustion. Background Art

[0002] In modern power systems, boilers are key heat energy conversion equipment, and their operating efficiency and environmental performance have received extensive attention. However, the existing technology has some shortcomings and problems in the variable load operation of the entire furnace of the boiler, which are mainly reflected in the following aspects:

[0003] Combustion stability issues: During deep peak load regulation, load fluctuations may lead to combustion instability, affecting the stable operation of the boiler. This is because under low load, the flow uniformity of the boiler furnace decreases, the combustion stability deteriorates, and the furnace temperature decreases, resulting in increased pollutant generation and excessive emissions.

[0004] Pollutant emission control: Existing combustion optimization technologies often focus on steady-state conditions. The model accuracy under rapidly changing load conditions is poor, and there is a lack of engineering application and verification, which makes it difficult to achieve the coordination and unity of low emissions and economic operation in actual operation.

[0005] Limitations of combustion process simulation: Although some studies have numerically simulated the combustion process of boilers, these studies are mostly limited to specific operating conditions or structures, and there is a lack of systematic research on the influence of flow and heat transfer in the furnace under different loads.

[0006] Insufficient intelligent control technology: Industrial boilers face problems such as extensive energy efficiency management, opaque combustion status, high safety risks and large fluctuations in water quality. Existing intelligent control technology has not been able to fully optimize the operation mode of industrial boilers and improve operating efficiency.

[0007] The combustion process in the furnace includes the flow, heat transfer and combustion in the boiler. The flow in the boiler mainly involves turbulent flow, gas-solid two-phase flow and multi-component mixed flow; the heat transfer in the boiler includes three basic heat transfer modes: heat conduction, heat convection and radiation heat transfer; the combustion of pulverized coal particles is divided into volatile thermal desorption, volatile combustion and coke combustion processes. Therefore, the selection of control equations and models that need to be followed in the simulation of the boiler using Fluent is crucial. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention proposes a transient calculation method suitable for boiler rapid load change combustion, which adopts the fusion of multiple models to solve the shortcomings of the prior art in the variable load operation of the boiler's entire furnace and achieve more efficient and environmentally friendly boiler operation.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for calculating transient state of boiler combustion with rapid load change: the method specifically comprises the following steps:

[0011] Step 1: Construct a three-dimensional geometric model of the boiler and mesh the geometric model;

[0012] Step 2: Set boundary conditions and initial conditions;

[0013] Step 3: Configure the gas-solid two-phase flow model;

[0014] The turbulence model Realizable k-ε is used to simulate turbulent flow; the particle motion model is used to simulate the motion of coal powder particles;

[0015] Step 4: Configure the combustion characteristics model;

[0016] The P1 radiation model is used to simulate the radiation heat transfer in the furnace; the component transport model is used to simulate the transport and reaction of different components during the combustion process; the gas phase combustion model is used to simulate the combustion reaction in the gas phase; the volatile analysis model is used to simulate the volatile removal process of coal powder before combustion; the coke combustion model is used to simulate the combustion process of coke after volatile analysis;

[0017] Step 5: Set variable load operation conditions;

[0018] Write code through user defined function (UDF) to control the change of inlet feed rate and air supply rate over time to simulate the variable load operation of the boiler;

[0019] Step 6: Initialize and run the simulation, monitor and adjust the NOx generation model;

[0020] Step 7: Result analysis and verification;

[0021] Analyze simulation results to evaluate boiler combustion efficiency and pollutant emissions under different load conditions;

[0022] Compare the simulation results with experimental data or field operation data to verify the accuracy of the model.

[0023] Furthermore, in step 2,

[0024] The boundary conditions include: velocity, temperature and pressure of the boiler inlet airflow; temperature and heat flux of the furnace inner wall; and the initial conditions include initial temperature, pressure and component distribution of the boiler.

[0025] Furthermore, in step 3, the turbulence model is specifically:

[0026] The Realizable k-ε model is used to deal with the rotating flow field of a four-corner tangential boiler, and its equation is:

[0027]

[0028]

[0029] Where: Γ k , Γ s —viscosity coefficient, Pa·s;

[0030] G k - turbulent kinetic energy generated by the mean velocity gradient, J;

[0031] C 1s , C 2ε - constants, 1.44 and 1.92 respectively;

[0032] Among them, the viscosity coefficient Γ k and Γ ε The expression is:

[0033]

[0034]

[0035] Where: μ-laminar viscosity coefficient, Pa·s;

[0036] μ t -turbulent viscosity coefficient, Pa·s;

[0037] σ k , σ ε -Turbulent Prandtl number.

[0038] Furthermore, in step 3, the particle motion model is specifically:

[0039] The discrete phase treatment method (DPM) is used to simulate the gas-solid two-phase flow and the interaction between the gas phase and the particle phase, and the random walk model is used to simulate the turbulent motion of particles.

[0040]

[0041] Where: m p - mass of pellets, kg;

[0042] u ip -The velocity component of the particle in a certain direction, m / s;

[0043] C D - drag coefficient;

[0044] A p - Particle surface area, m 2 ;

[0045] -The average velocity of the gas phase in a certain direction, m / s;

[0046] u′ ig -The pulsation velocity of the gas phase in a certain direction, m / s.

[0047] Further, in step 4, the gas phase combustion model is specifically:

[0048] The finite-rate / eddy-dissipation model in the component transport model is used to simulate the mixed combustion of high-quality coal and low-quality coal; the equation of the model is:

[0049]

[0050] Where: Y i - local mass fraction of each substance;

[0051] R i -The net rate at which a chemical reaction occurs;

[0052] S i - The rate generated by addition from the dispersed phase plus any user defined source.

[0053] Furthermore, in step 4, the volatilization analysis model is specifically:

[0054] A two-competing-rates model is used. In this model, the temperature is divided into two intervals, a low temperature zone and a high temperature zone. Different intervals dominate different first-order reactions. The expression is:

[0055]

[0056]

[0057] In the formula, R1 and R2 are the reaction rate coefficients of the two first-order reactions, and the mathematical expression of the total volatile precipitation rate is:

[0058]

[0059] Where: m v (t)-the mass of volatile matter released at time t;

[0060] m p，0 - the mass of the initial particle jet of coal powder;

[0061] α1, α2-generating factors;

[0062] m a-The mass of ash contained in the coal powder.

[0063] Further, in step 4, the coke combustion model is specifically:

[0064] The diffusion-kinetic controlled reaction rate model is adopted to consider the effects of diffusion and reaction kinetics on the particle surface reaction rate.

[0065] Oxygen diffusion rate to the coke surface:

[0066]

[0067] Chemical reaction rate on coke surface:

[0068]

[0069] Where: C1-diffusion rate constant;

[0070] T∞-surrounding medium temperature, K;

[0071] T p - particle temperature, K;

[0072] d p - diameter of the particles, mm;

[0073] The surface reaction combustion rate of coke is obtained by weighting the diffusion rate and the chemical reaction rate:

[0074]

[0075] Where: p ox - partial pressure of the gas-phase oxidant around the particle, Pa;

[0076] R—The kinetic reaction constant of the reaction on the inner surface of coke and its diffusion, 1 / s.

[0077] According to the mass fraction of the oxidant, and assuming that the particle size remains unchanged and the particle density decreases, the coke surface reaction combustion rate can be obtained as:

[0078]

[0079] A transient calculation system suitable for boiler rapid load change combustion:

[0080] The computing system includes an initialization module, a gas-solid two-phase flow module, a combustion characteristic module, a variable load operation module and a verification module:

[0081] The initialization module is used to construct a three-dimensional geometric model of the boiler, mesh the geometric model, and set boundary conditions and initial conditions;

[0082] The gas-solid two-phase flow module is used to configure the gas-solid two-phase flow model; the turbulence model Realizablek-ε is used to simulate the turbulent flow; and the particle motion model is used to simulate the motion of the coal powder particles;

[0083] The combustion characteristic module is used to configure the combustion characteristic model; use the P1 radiation model to simulate the radiation heat transfer in the furnace; use the component transport model to simulate the transport and reaction of different components in the combustion process; use the gas phase combustion model to simulate the combustion reaction in the gas phase; use the volatile analysis model to simulate the volatile removal process of coal powder before combustion; use the coke combustion model to simulate the combustion process of coke after volatile analysis;

[0084] The variable load operation module is used to set the variable load operation conditions; the code is written through the user defined function (UDF) to control the change of the inlet feed rate and the air supply rate over time to simulate the variable load operation of the boiler;

[0085] The verification module is used to initialize and run the simulation, monitor and adjust the NOx generation model; analyze the simulation results, evaluate the combustion efficiency and pollutant emissions of the boiler under different load conditions; compare the simulation results with experimental data or field operation data to verify the accuracy of the model.

[0086] An electronic device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0087] A computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the steps of the above method are implemented.

[0088] Beneficial effects of the present invention

[0089] The present invention uses technologies such as Realizable k-ε turbulence model, DPM random orbit model, P1 radiation model, component transport model and UDF code control to realize the calculation of boiler rapid load change and combustion transient.

[0090] The Realizable k-ε turbulence model and the DPM random trajectory model are used to accurately simulate gas-solid two-phase flows and improve the prediction accuracy of particle motion during combustion.

[0091] The P1 radiation model is combined with the component transport model to more accurately simulate the radiation heat transfer and combustion reactions in the furnace, thereby optimizing combustion efficiency and reducing pollutant emissions.

[0092] UDF code control technology dynamically adjusts the inlet feed rate and air supply rate to adapt to rapidly changing load demands and improve the boiler's response speed and operational flexibility.

[0093] Through the comprehensive application of these technologies, the present invention can solve the shortcomings of the existing technology in the variable load operation of the boiler in the entire furnace, achieve more efficient and environmentally friendly boiler operation, and at the same time provide more accurate simulation and prediction tools to provide a scientific basis for the operation and optimization of the boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1 It is a schematic diagram of the method flow of the present invention.

[0095] Figure 2 This is the UDF code for the transient simulation of the burner of the present invention. DETAILED DESCRIPTION

[0096] 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.

[0097] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0098] The control equations and models that need to be followed when simulating a boiler using Fluent include the following basic conservation equations:

[0099] Continuity equation:

[0100]

[0101] Where: ρ—fluid density, kg / s;

[0102] —Velocity vector, m / s.

[0103] Momentum equation:

[0104]

[0105] Where: p—pressure, Pa;

[0106] - Stress tensor, N / m 3 ;

[0107] g-gravitational acceleration, m / s 2 .

[0108] Energy equation:

[0109]

[0110] Where: h-energy, J;

[0111] k eff -Effective heat conduction, W / (m·K);

[0112] T-temperature, K;

[0113] Q d -Energy transfer of component diffusion, J;

[0114] Q v -Energy transfer by viscous dissipation, J;

[0115] S h -Energy transfer such as heat of reaction, J.

[0116] The present invention proposes a transient calculation method suitable for boiler rapid load change combustion.

[0117] The method specifically comprises the following steps:

[0118] Step 1: Construct a three-dimensional geometric model of the boiler and mesh the geometric model;

[0119] Step 2: Set boundary conditions and initial conditions;

[0120] The boundary conditions include: the velocity, temperature and pressure of the boiler inlet airflow, the temperature and heat flux of the furnace inner wall, etc. The initial conditions include the initial temperature, pressure and component distribution of the boiler.

[0121] Step 3: Configure the gas-solid two-phase flow model of the pulverized coal burner;

[0122] The turbulence model Realizable k-ε is used to simulate turbulent flow;

[0123] The airflow in the furnace of a four-corner tangential coal-fired boiler is in a turbulent flow state, which is composed of large vortices generated by boundary conditions and small vortices generated by viscous forces. At present, turbulent flow is mainly simulated and calculated by direct numerical simulation (DNS) and indirect numerical simulation. Among them, DNS can directly obtain large and small vortex structures without a turbulence model, but the calculation cost is high and it is difficult to use for engineering simulation. In order to reduce the calculation cost and be more in line with the actual situation, the two-equation k-ε model in the Reynolds average method in the indirect numerical simulation is used to simulate the airflow state in the furnace of a four-corner tangential coal-fired boiler. The model is divided into the standard k-ε model, the RNG k-ε model, and the Realizable k-ε model. Using the Realizable k-ε model to process the rotating flow field similar to the four-corner tangential boiler can obtain better results. Its equation is:

[0124]

[0125]

[0126] Where: Γ k , Γ ε -viscosity coefficient, Pa·s;

[0127] G k - turbulent kinetic energy generated by the mean velocity gradient, J;

[0128] C 1ε , C 2ε -constants, 1.44 and 1.92 respectively.

[0129] Among them, the viscosity coefficient Γ k and Γ ε The expression is:

[0130]

[0131]

[0132] Where: μ-laminar viscosity coefficient, Pa·s;

[0133] μ t -turbulent viscosity coefficient, Pa·s;

[0134] σ k , σ ε -Turbulent Prandtl number.

[0135] The discrete phase treatment method (DPM) and random trajectory model are used to simulate the movement of coal powder particles;

[0136] Gas-solid two-phase flow can be described by the Eulerian method or the discrete phase processing method (DPM). Among them, the Eulerian method calculates the particles as the continuous phase, and the motion trajectory of the particles cannot be obtained. It is more suitable for the situation where the number of particles is large and the particle size is small. Therefore, the present invention adopts the discrete phase processing method (DPM) to simulate the gas-solid two-phase flow and the process of interaction between the gas phase and the particle phase, and adopts the random orbit model (Discrete random walk modell) to simulate the turbulent motion of particles.

[0137]

[0138] Where: m p - mass of pellets, kg;

[0139] u ip -The velocity component of the particle in a certain direction, m / s;

[0140] C D - drag coefficient;

[0141] A p - Particle surface area, m 2 ;

[0142] -The average velocity of the gas phase in a certain direction, m / s;

[0143] u′ ig -The pulsation velocity of the gas phase in a certain direction, m / s.

[0144] Step 4: Configure the combustion characteristic model of the pulverized coal burner and boiler;

[0145] Step 4: Configure the combustion characteristics model;

[0146] Use the P1 radiation model to simulate the radiation heat transfer in the furnace;

[0147] The main form of heat transfer in the furnace is radiation heat transfer, so it is necessary to select a suitable radiation model to describe the heat exchange. The radiation heat transfer models of coal-fired boilers are mainly based on P1 and DO. The P1 model is relatively simple and requires less computing resources, but the calculation accuracy decreases when the optical thickness does not meet the requirements or the geometric shape is complex. The DO model is applicable to any optical thickness. In a pulverized coal furnace, due to the huge geometric space in the furnace and the presence of a certain concentration of pulverized coal particles, the optical thickness in the furnace is large, and the P1 model will have a large error when solving this type of model. For this reason, this paper uses the DO model to calculate the radiation heat transfer in the furnace and considers the radiation characteristics of the pulverized coal particles.

[0148] Use component transport models to simulate the transport and reactions of different components during combustion;

[0149] Use the gas phase combustion model to simulate combustion reactions in the gas phase;

[0150] Traditional numerical simulation studies of coal-fired boilers mostly use the mixture fraction-probability density function (PDF) model, which solves the turbulent combustion problem by pre-setting the PDF table function to determine the time-averaged values ​​of all scalars in the reaction process. However, the limitation of this model is that it can only solve the reaction of a particle flow fuel and a gaseous / liquid flow fuel with an oxidant flow at most, and cannot realize the chemical reaction of two or more particle flow fuels. Therefore, the present invention adopts the finite-rate / eddy-dissipation model in the component transport model to realize the simulation of the mixed combustion of high-quality coal and low-quality coal. The equation of this model is:

[0151]

[0152] Where: Y i - local mass fraction of each substance;

[0153] R i -The net rate at which a chemical reaction occurs;

[0154] S i - The rate generated by addition from the dispersed phase plus any user defined source.

[0155] The volatile analysis model is used to simulate the volatile removal process of coal powder before combustion;

[0156] Before the pulverized coal enters the furnace for combustion, it needs to undergo a process of de-volatile matter. This process is relatively complex and is related to factors such as furnace temperature and coal quality. At present, the pulverized coal de-volatile matter model for simulating coal-fired boilers mainly uses a single equation model and a two-equation model. This paper adopts a two-competing-rates model, in which the temperature is divided into two intervals, a low temperature zone and a high temperature zone, and different intervals dominate different first-order reactions. Its expression is:

[0157]

[0158]

[0159] In the formula, R1 and R2 are the reaction rate coefficients of the two first-order reactions, and the mathematical expression of the total volatile precipitation rate is:

[0160]

[0161] Where: m v (t)-the mass of volatile matter released at time t;

[0162] m p，0 - the mass of the initial particle jet of coal powder;

[0163] α1, α2-generating factors;

[0164] m a -The mass of ash contained in the coal powder.

[0165] Use the coke combustion model to simulate the combustion process of coke after volatile analysis;

[0166] After the coal powder particles are volatilized and analyzed, the remaining coke begins to burn. The combustion of coke is a heterogeneous chemical reaction. According to Langmuir's reaction theory, this process includes a series of processes such as oxygen diffusion, internal diffusion, reactant adsorption, oxidation, and shedding. The present invention uses a diffusion-dynamic controlled reaction rate model, which simultaneously considers the effects of diffusion and reaction kinetics on the particle surface reaction rate.

[0167] Oxygen diffusion rate to the coke surface:

[0168]

[0169] Chemical reaction rate on coke surface:

[0170]

[0171] Where: C1-diffusion rate constant;

[0172] T ∞ -Ambient medium temperature, K;

[0173] T p - particle temperature, K;

[0174] d p - Diameter of the particles, mm.

[0175] The surface reaction combustion rate of coke is obtained by weighting the diffusion rate and the chemical reaction rate:

[0176]

[0177] Where: p ox - partial pressure of the gas-phase oxidant around the particle, Pa;

[0178] R - Kinetic reaction constant of the reaction on the inner surface of coke and its diffusion, 1 / s.

[0179] According to the mass fraction of the oxidant, and assuming that the particle size remains unchanged and the particle density decreases, the coke surface reaction combustion rate can be obtained as:

[0180]

[0181] Step 5: Setting the variable load operation conditions of the pulverized coal burner;

[0182] Write code through user defined function (UDF) to control the change of inlet feed rate and air supply rate over time to simulate the variable load operation of the boiler;

[0183] Step 6: Initialize and run the simulation, monitor and adjust the model;

[0184] Initialize the simulation, including flow field, temperature field and component field;

[0185] Run the simulation until steady state is reached or until the desired simulation time;

[0186] Monitor the convergence and accuracy of the simulation and adjust model parameters or mesh if necessary;

[0187] Record key variables and performance indicators such as temperature, pressure, composition distribution and NOx generation;

[0188] NOx generated by coal powder combustion can be divided into thermal NOx, fuel NOx and rapid NOx according to the source form and generation mechanism of nitrogen. Among them, fuel type NOx accounts for 70% to 80% of the NOx generated by combustion in the furnace, thermal NOx accounts for about 15% to 20%, and rapid NOx accounts for a very small proportion. Therefore, only the other two types of NOx are considered in the simulation of the present invention.

[0189] Step 7: Result analysis and verification;

[0190] Analyze simulation results to evaluate boiler combustion efficiency and pollutant emissions under different load conditions;

[0191] Compare the simulation results with experimental data or field operation data to verify the accuracy of the model.

[0192] A transient calculation system suitable for boiler rapid load change combustion:

[0193] The computing system includes an initialization module, a gas-solid two-phase flow module, a combustion characteristic module, a variable load operation module and a verification module:

[0194] The initialization module is used to construct a three-dimensional geometric model of the boiler, mesh the geometric model, and set boundary conditions and initial conditions;

[0195] The gas-solid two-phase flow module is used to configure the gas-solid two-phase flow model; the turbulence model Realizablek-ε is used to simulate the turbulent flow; and the particle motion model is used to simulate the motion of the coal powder particles;

[0196] The combustion characteristic module is used to configure the combustion characteristic model; use the P1 radiation model to simulate the radiation heat transfer in the furnace; use the component transport model to simulate the transport and reaction of different components in the combustion process; use the gas phase combustion model to simulate the combustion reaction in the gas phase; use the volatile analysis model to simulate the volatile removal process of coal powder before combustion; use the coke combustion model to simulate the combustion process of coke after volatile analysis;

[0197] The variable load operation module is used to set the variable load operation conditions; the code is written through the user defined function (UDF) to control the change of the inlet feed rate and the air supply rate over time to simulate the variable load operation of the boiler;

[0198] The verification module is used to initialize and run the simulation, monitor and adjust the NOx generation model; analyze the simulation results, evaluate the combustion efficiency and pollutant emissions of the boiler under different load conditions; compare the simulation results with experimental data or field operation data to verify the accuracy of the model.

[0199] An electronic device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0200] A computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the steps of the above method are implemented.

[0201] 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 but not limitation, many forms of RAM are available, such as static random access memory static RAM, SRAM, dynamic random access memory dynamic RAM, DRAM, synchronous dynamic random access memory synchronous DRAM, SDRAM, double data rate synchronous dynamic random access memory double data rate SDRAM, DDR SDRAM, enhanced synchronous dynamic random access memory enhanced SDRAM, ESDRAM, synchronous link dynamic random access memory synchlink DRAM, SLDRAM, and direct memory bus random access memory direct rambus RAM, DR RAM. It should be noted that memory of the methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0202] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented by 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 can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can 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 can be transmitted from a website site, computer, server or data center through a wired method such as coaxial cable, optical fiber, digital subscriber line digital subscriber line, DSL or wireless such as infrared, wireless, microwave, etc. to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more available media integrated. The available medium can be a magnetic medium such as a floppy disk, a hard disk, a tape, an optical medium such as a high-density digital video disc digital video disc, DVD, or a semiconductor medium such as a solid state hard disk solid state disc, SSD, etc.

[0203] 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.

[0204] 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 to perform. 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.

[0205] The above is a detailed introduction to the transient calculation method for boiler rapid load change combustion proposed in the present invention, and the principles and implementation methods of the present invention are explained. 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 the 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. A transient calculation method for boiler rapid load change combustion, characterized in that: The method specifically comprises the following steps: Step 1: Construct a three-dimensional geometric model of the boiler and mesh the geometric model; Step 2: Set boundary conditions and initial conditions; Step 3: Configure the gas-solid two-phase flow model; The turbulence model Realizable k-ε is used to simulate turbulent flow; the particle motion model is used to simulate the motion of coal powder particles; Step 4: Configure the combustion characteristics model; The P1 radiation model is used to simulate the radiation heat transfer in the furnace; the component transport model is used to simulate the transport and reaction of different components during the combustion process; the gas phase combustion model is used to simulate the combustion reaction in the gas phase; the volatile analysis model is used to simulate the volatile removal process of coal powder before combustion; the coke combustion model is used to simulate the combustion process of coke after volatile analysis; Step 5: Set variable load operation conditions; Write code through user defined function (UDF) to control the change of inlet feed rate and air supply rate over time to simulate the variable load operation of the boiler; Step 6: Initialize and run the simulation, monitor and adjust the NOx generation model; Step 7: Result analysis and verification; Analyze simulation results to evaluate boiler combustion efficiency and pollutant emissions under different load conditions; Compare the simulation results with experimental data or field operation data to verify the accuracy of the model.

2. The calculation method according to claim 1, characterized in that: In step 2, The boundary conditions include: velocity, temperature and pressure of the boiler inlet airflow; temperature and heat flux of the furnace inner wall; and the initial conditions include initial temperature, pressure and component distribution of the boiler.

3. The calculation method according to claim 2, characterized in that: In step 3, the turbulence model is specifically: The Realizable k-ε model is used to deal with the rotating flow field of a four-corner tangential boiler, and its equation is: Where: k , Γ s —viscosity coefficient, Pa·s; G k - turbulent kinetic energy generated by the mean velocity gradient, J; C 15 , C 2s - constants, 1.44 and 1.92 respectively; Among them, the viscosity coefficient Γ k and Γ ε The expression is: Where: μ-laminar viscosity coefficient, Pa·s; μ t -turbulent viscosity coefficient, Pa·s; σ k , σ ε -Turbulent Prandtl number.

4. The calculation method according to claim 3, characterized in that: In step 3, the particle motion model is specifically: The discrete phase treatment method (DPM) is used to simulate the gas-solid two-phase flow and the interaction between the gas phase and the particle phase, and the random walk model is used to simulate the turbulent motion of particles. Where: m p - mass of pellets, kg; u ip -The velocity component of the particle in a certain direction, m / s; C D - drag coefficient; A p - Particle surface area, m 2 ; -The average velocity of the gas phase in a certain direction, m / s; u′ ig -The pulsation velocity of the gas phase in a certain direction, m / s.

5. The calculation method according to claim 4, characterized in that: In step 4, the gas phase combustion model is specifically: The finite-rate / eddy-dissipation model in the component transport model is used to simulate the mixed combustion of high-quality coal and low-quality coal; the equation of the model is: Where: Y i - local mass fraction of each substance; R i -The net rate at which a chemical reaction occurs; S i - The rate generated by addition from the dispersed phase plus any user defined source.

6. The calculation method according to claim 5, characterized in that: In step 4, the volatilization analysis model is specifically: A two-competing-rates model is used. In this model, the temperature is divided into two intervals, a low temperature zone and a high temperature zone. Different intervals dominate different first-order reactions. The expression is: In the formula, R1 and R2 are the reaction rate coefficients of the two first-order reactions, and the mathematical expression of the total volatile precipitation rate is: Where: m v (t)-the mass of volatile matter released at time t; m p，0 - the mass of the initial particle jet of coal powder; α1, α2-generating factors; m a -The mass of ash contained in the coal powder.

7. The calculation method according to claim 6, characterized in that: In step 4, the coke combustion model is specifically: The diffusion-kinetic controlled reaction rate model is adopted to consider the effects of diffusion and reaction kinetics on the particle surface reaction rate. Oxygen diffusion rate to the coke surface: Chemical reaction rate on coke surface: Where: c1-diffusion rate constant; T ∞ -Ambient medium temperature, K; T p - particle temperature, K; d p - diameter of the particles, mm; The surface reaction combustion rate of coke is obtained by weighting the diffusion rate and the chemical reaction rate: Where: p ox -Partial pressure of gas-phase oxidant around the particle, Pa: R - Kinetic reaction constant of the reaction on the inner surface of coke and its diffusion, 1 / s. According to the mass fraction of the oxidant, and assuming that the particle size remains unchanged and the particle density decreases, the coke surface reaction combustion rate can be obtained as:

8. A computing system for executing the transient computing method for boiler rapid load change combustion as claimed in any one of claims 1 to 7, characterized in that: The computing system includes an initialization module, a gas-solid two-phase flow module, a combustion characteristic module, a variable load operation module and a verification module: The initialization module is used to construct a three-dimensional geometric model of the boiler, mesh the geometric model, and set boundary conditions and initial conditions; The gas-solid two-phase flow module is used to configure the gas-solid two-phase flow model; the turbulence model Realizable k-ε is used to simulate the turbulent flow; and the particle motion model is used to simulate the motion of the coal powder particles; The combustion characteristic module is used to configure the combustion characteristic model; use the P1 radiation model to simulate the radiation heat transfer in the furnace; use the component transport model to simulate the transport and reaction of different components in the combustion process; use the gas phase combustion model to simulate the combustion reaction in the gas phase; use the volatile analysis model to simulate the volatile removal process of coal powder before combustion; use the coke combustion model to simulate the combustion process of coke after volatile analysis; The variable load operation module is used to set the variable load operation conditions; the code is written through the user defined function (UDF) to control the change of the inlet feed rate and the air supply rate over time to simulate the variable load operation of the boiler; The verification module is used to initialize and run the simulation, monitor and adjust the NOx generation model; analyze the simulation results, evaluate the combustion efficiency and pollutant emissions of the boiler under different load conditions; compare the simulation results with experimental data or field operation data to verify the accuracy of the model.

9. 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 7 are implemented.

10. 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 7 are implemented.

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