Method for calculating dynamic influence of fuel quantity disturbance on hearth outlet smoke temperature and product

Abstract

The invention discloses a method for calculating dynamic influence of fuel quantity disturbance on hearth outlet smoke temperature and a product, and belongs to the technical field of thermal equipment performance calculation. A mathematical model based on a heat balance method is established, the factors of flue gas heat storage capacity in a hearth, ash deposition on a heating surface and heat storage capacity of a slagging layer and the dynamic influence of fuel quantity disturbance on the boiler hearth outlet flue gas temperature are comprehensively considered, the calculation accuracy is improved, and the actual operation condition of a boiler system is reflected more accurately; the dynamic response of the system under fuel quantity disturbance can be predicted and controlled by calculating the time constants of the flue gas heat storage capacity in the hearth and the heat storage capacity of the ash deposition and slagging layers on the heating surface, the stability of the boiler system can be enhanced, and temperature fluctuation caused by fuel quantity fluctuation is reduced; by drawing a hearth outlet smoke temperature variation curve, the dynamic influence of fuel quantity disturbance on the hearth outlet smoke temperature can be intuitively analyzed, and the operation state of the boiler can be optimized by operators.

Description

Technical Field

[0001] The present invention relates to the technical field of calculating the performance of thermal equipment, and particularly to a calculation method and product for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet. Background Art

[0002] As an important equipment for power production, industrial heating and other energy conversions, the operation efficiency and stability of the boiler system are of great significance for energy utilization efficiency and environmental protection. The flue gas temperature at the furnace outlet of the boiler, as one of the key parameters for boiler operation, directly affects the thermal efficiency of the boiler, the stability of the combustion process, and the control of emissions. In actual operation, the fuel supply of the boiler is disturbed by various factors, such as fluctuations in the calorific value of the fuel, changes in the performance of the combustion equipment, and changes in operating conditions. These factors may cause fluctuations in the flue gas temperature at the furnace outlet of the boiler. To ensure that the boiler can operate in an optimal state, it is necessary to accurately analyze the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet of the boiler.

[0003] Traditional boiler control systems usually rely on manual experience and empirical formulas to adjust fuel supply and air flow to maintain the stable operation of the boiler. However, with the progress of modern combustion technology, traditional empirical methods are difficult to cope with complex combustion processes and external disturbances, especially the influence of fuel quantity fluctuations on the flue gas temperature at the furnace outlet of the boiler. This influence is not only reflected in the short-term temperature fluctuations but may also affect the long-term stability and combustion efficiency of the boiler.

[0004] Therefore, how to accurately calculate the flue gas temperature at the furnace outlet affected by dynamic fuel quantity disturbance has become a technical problem that needs to be solved urgently by those skilled in the art in the current field. Summary of the Invention

[0005] The purpose of the present invention is to provide a calculation method and product for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet to overcome the problem that it is difficult to accurately calculate the flue gas temperature at the furnace outlet affected by dynamic disturbance in the prior art.

[0006] The present invention solves the above technical problems through the following technical solutions: A calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet includes the following steps: Step 1: Based on the heat balance relationship of the furnace combustion products, establish the first heat balance equation; based on the thermodynamic principle of furnace combustion, establish the effective heat release equation of the furnace; based on the Stefan-Boltzmann law, establish the equation for the radiant heat received by the furnace heating surface; substitute the effective heat release equation of the furnace and the equation for the radiant heat received by the furnace heating surface into the first heat balance equation to obtain the first heat balance equation after substitution, and through derivation, obtain the time constant formula for the heat storage capacity of the flue gas in the furnace, the first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of the flue gas in the furnace; differentiate the first heat balance equation after substitution to obtain the first differential equation; Step 2: Based on the heat transfer relationship between the ash layer on the water-cooled wall tube of the furnace and the water-cooled wall tube, establish the heat transfer equation; based on the heat balance relationship of the ash layer on the water-cooled wall tube, establish the second heat balance equation; substitute the heat transfer equation and the equation for the radiant heat received by the furnace heating surface into the second heat balance equation to obtain the second heat balance equation after substitution, and through derivation, obtain the time constant formula for the heat storage capacity of the ash and slag layer on the furnace heating surface and the parameter characterizing the heat storage capacity of the ash and slag layer on the furnace heating surface; differentiate the second heat balance equation after substitution to obtain the second differential equation; Step 3: Based on the first differential equation and the second differential equation, obtain the input-output function of the influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet, and through the inverse Laplace transform, obtain the functional relationship of the change in the flue gas temperature at the furnace outlet; Step 4: Obtain the design data and measured data of the boiler, and combine the time constant formula for the heat storage capacity of the flue gas in the furnace, the first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of the flue gas in the furnace, the time constant formula for the heat storage capacity of the ash and slag layer on the furnace heating surface and the parameter characterizing the heat storage capacity of the ash and slag layer on the furnace heating surface, calculate the specific values, substitute the specific values into the functional relationship of the change in the flue gas temperature at the furnace outlet, draw the curve of the change in the flue gas temperature at the furnace outlet, and analyze the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet.

[0007] A further improvement of the present invention lies in that: The first heat balance equation is specifically:

[0008] In the formula: is the effective heat release of the furnace in the initial state; is the radiant heat received by the furnace heating surface; is the flue gas flow rate at the furnace outlet; is the specific heat capacity of the combustion products in the furnace; is the flue gas temperature at the furnace outlet; is the mass of the combustion products in the furnace; is the time; The flue gas flow rate at the furnace outlet Specifically:

[0009] In the formula: is the designed fuel quantity; is the volume of flue gas generated by the combustion of each kilogram of fuel; is the density of the flue gas generated by combustion; Designed fuel quantity Specifically:

[0010] In the formula: is the actual fuel quantity in the initial state; is the mechanical incomplete combustion loss; The specific equation of the effective calorific value of the furnace is:

[0011] In the formula, is the lower calorific value of the fuel on the applied basis; , are the chemical incomplete combustion and slag discharge heat losses respectively; is the specific heat capacity of air; is the hot air temperature; is the mass flow rate of air; Mass flow rate of air Specifically:

[0012] In the formula, is the air quantity required for burning one kilogram of fuel; is the air density; The specific equation of the radiant heat received by the furnace heating surface is:

[0013] In the formula, is the radiant heat received by the furnace heating surface; is the furnace emissivity; is the heat effective coefficient of the water wall; is the area of the water wall receiving thermal radiation; is the absolute black body radiation coefficient; is the water wall angle factor; is the flue gas temperature at the furnace outlet; is the ash wall temperature of the water wall tube.

[0014] A further improvement of the present invention is that the specific first heat balance equation after substitution is:

[0015] In the formula, The parameters set for convenience of solution have no practical significance; is the flue gas temperature at the furnace outlet under the initial state; is the actual fuel quantity under the initial state; is the volume of combustion products in the furnace; is the temperature of the ash layer on the water wall tubes under the initial state; is the temperature of the ash layer on the water wall tubes; is the effective calorific value of the furnace under the initial state; The specific first differential equation is: + = + +

[0016] In the formula, is the time constant of the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace; is the change in flue gas temperature at the furnace outlet; is the parameter of the influence of hot air temperature change on the heat storage capacity of flue gas in the furnace; is the change in hot air temperature; is the first parameter characterizing the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace; is the change in the temperature of the ash layer on the water wall tubes; is the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace; is the change in actual fuel quantity; The specific formula for the time constant of the heat storage capacity of flue gas in the furnace is: =

[0017] The first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace are respectively: =

[0018] .

[0019] A further improvement of the present invention lies in that: the heat transfer equation is specifically:

[0020] In the formula, is the heat transferred through the ash layer to the water wall tubes; is the reduction coefficient of the ash layer thermal resistance of the water wall tubes; is the temperature of the ash layer on the water wall tube; is the metal wall temperature of the water wall tube; The specific form of the second heat balance equation is:

[0021] In the formula, is the mass of the ash layer on the water wall tube; is the specific heat capacity of the ash layer on the water wall tube.

[0022] A further improvement of the present invention is that the specific form of the second heat balance equation after substitution is:

[0023] The specific formula for the time constant of the heat storage capacity of the fouling and slagging layer on the furnace heating surface is: =

[0024] The parameter characterizing the heat storage capacity of the fouling and slagging layer on the furnace heating surface is specifically: =

[0025] In the formula, is the time constant of the heat storage capacity of the fouling and slagging layer on the furnace heating surface; is the parameter characterizing the heat storage capacity of the fouling and slagging layer on the furnace heating surface; The specific form of the second differential equation is: .

[0026] A further improvement of the present invention is that the input-output function of the influence of fuel quantity disturbance on the furnace outlet flue gas temperature is specifically: = +

[0027] In the formula, is the function representing the change in the furnace outlet flue gas temperature after Laplace transform; is the function representing the fuel quantity disturbance input after Laplace transform; is the function representing the hot air temperature disturbance after Laplace transform; The functional relationship of the change in the furnace outlet flue gas temperature is specifically:

[0028] In the formula, = , is the transfer function after Laplace transform, which characterizes the influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet; is the function of the change in flue gas temperature at the furnace outlet over time after being disturbed by the fuel quantity.

[0029] A further improvement of the present invention lies in that: the design data specifically includes: the absolute black body radiation coefficient , the actual fuel quantity under the initial state , the specific heat capacity of the combustion products in the furnace , the excess air coefficient at the rated load, the area of the water wall subjected to thermal radiation , the specific heat capacity of the ash wall layer of the water wall tube , the density of the flue gas generated by combustion and the reduction coefficient of the thermal resistance of the ash wall layer ; The measured data specifically includes: the flue gas temperature at the furnace outlet under the initial state , the effective calorific value of the furnace under the initial state , the temperature of the ash wall layer of the water wall tube under the initial state , the mass of the ash wall layer of the water wall tube , the emissivity of the furnace , the mass of the combustion products in the furnace , the thermal effective coefficient of the water wall and the volume of the flue gas generated by the combustion of each kilogram of fuel .

[0030] The present invention also provides a computer device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the above calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet are implemented.

[0031] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet are implemented.

[0032] The present invention also provides a computer program product, including a computer program. When the computer program is executed by a processor, the steps of the calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet as described above are implemented.

[0033] Compared with the prior art, the positive and progressive effects of the present invention are as follows: The calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet provided by the present invention establishes a mathematical model based on the heat balance method, comprehensively considers factors such as the heat storage capacity of flue gas in the furnace, the heat storage capacity of the ash deposit and slag layer on the heating surface, as well as the dynamic influence of fuel quantity disturbance on the flue gas temperature at the boiler furnace outlet, improves the calculation accuracy, and more accurately reflects the actual operation of the boiler system; by calculating the time constants of the heat storage capacity of flue gas in the furnace and the heat storage capacity of the ash deposit and slag layer on the heating surface, it can predict and control the dynamic response of the system under fuel quantity disturbance, which helps to enhance the stability of the boiler system and reduce the temperature fluctuation caused by fuel quantity fluctuation; by plotting the curve of the change in the flue gas temperature at the furnace outlet, the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet can be intuitively analyzed, which helps the operator to adjust the fuel supply and air flow according to the actual situation, optimize the operation state of the boiler, and improve the thermal efficiency and combustion stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings in the specification are used to provide a further understanding of the present invention, and constitute a part of the present invention. 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.

[0035] Figure 1 It is a schematic flow chart of a calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the accompanying drawings here can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0038] Glossary: Water wall: The water wall is the main heat-absorbing part of the boiler, consisting of several rows of steel pipes distributed around the boiler furnace. The inside of it is flowing water or steam, and it receives the heat of the flame in the boiler furnace from the outside.

[0039] Water-cooled wall tube: The basic component unit of the water-cooled wall, which is a radiant heating surface arranged around the furnace. In industrial boilers, it is generally made of boiler steel pipes with a diameter of 51 - 63.5 mm and is the main heating surface of a water-tube boiler.

[0040] Ash layer on the water-cooled wall tube: The ash deposit layer formed on the outer wall of the water-cooled wall tube, which is mainly formed by the sublimation of fusible basic metal oxides and sulfates in the fuel ash at high temperatures or the condensation after forming fusible eutectics.

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, which is an explanation rather than a limitation of the present invention.

[0042] See Figure 1 , a calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet, including the following steps: Step 1: Based on the heat balance relationship of the furnace combustion products, establish the first heat balance equation; based on the thermodynamic principle of furnace combustion, establish the effective heat release equation of the furnace; based on the Stefan-Boltzmann law, establish the equation for the radiant heat received by the furnace heating surface; substitute the effective heat release equation of the furnace and the equation for the radiant heat received by the furnace heating surface into the first heat balance equation to obtain the first heat balance equation after substitution. Through derivation, obtain the time constant formula for the heat storage capacity of the flue gas in the furnace, the first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of the flue gas in the furnace; differentiate the first heat balance equation after substitution to obtain the first differential equation; Step 2: Based on the heat transfer relationship between the ash layer on the water-cooled wall tube of the furnace and the water-cooled wall tube, establish the heat transfer equation; based on the heat balance relationship of the ash layer on the water-cooled wall tube, establish the second heat balance equation; substitute the heat transfer equation and the equation for the radiant heat received by the furnace heating surface into the second heat balance equation to obtain the second heat balance equation after substitution. Through derivation, obtain the time constant formula for the heat storage capacity of the ash deposit and slag layer on the furnace heating surface and the parameter characterizing the heat storage capacity of the ash deposit and slag layer on the furnace heating surface; differentiate the second heat balance equation after substitution to obtain the second differential equation; Step 3: Based on the first differential equation and the second differential equation, obtain the input-output function of the influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet. Through the inverse Laplace transform, obtain the functional relationship of the change in the flue gas temperature at the furnace outlet; Step 4: Obtain the design data and measured data of the boiler. Combine the time constant formula for the heat storage capacity of the flue gas in the furnace, the first parameter and the second parameter characterizing the influence of the fuel quantity change on the heat storage capacity of the flue gas in the furnace, the time constant formula for the heat storage capacity of the ash fouling and slagging layer on the furnace heating surface, and the parameters characterizing the heat storage capacity of the ash fouling and slagging layer on the furnace heating surface to calculate the value of the time constant. Substitute the value of the time constant into the functional relationship of the change in the flue gas temperature at the furnace outlet, plot the curve of the change in the flue gas temperature at the furnace outlet, and analyze the dynamic influence of the fuel quantity disturbance on the flue gas temperature at the furnace outlet.

[0043] The calculation method for the dynamic influence of the fuel quantity disturbance on the flue gas temperature at the furnace outlet provided by the present invention, by establishing a mathematical model based on the heat balance method, comprehensively considers factors such as the heat storage capacity of the flue gas in the furnace, the heat storage capacity of the ash fouling and slagging layer on the heating surface, and the dynamic influence of the fuel quantity disturbance on the flue gas temperature at the boiler furnace outlet, improves the calculation accuracy, and more accurately reflects the actual operation of the boiler system; by calculating the time constants of the heat storage capacity of the flue gas in the furnace and the heat storage capacity of the ash fouling and slagging layer on the heating surface, it can predict and control the dynamic response of the system under the fuel quantity disturbance, which helps to enhance the stability of the boiler system and reduce the temperature fluctuation caused by the fuel quantity fluctuation; by plotting the curve of the change in the flue gas temperature at the furnace outlet, it can visually analyze the dynamic influence of the fuel quantity disturbance on the flue gas temperature at the furnace outlet, which helps the operator to adjust the fuel supply and air flow according to the actual situation, optimize the operation state of the boiler, and improve the thermal efficiency and combustion stability.

[0044] Specifically, the first heat balance equation is specifically:

[0045] In the formula: is the effective calorific value of the furnace under the initial state; is the radiant heat received by the furnace heating surface; is the flue gas flow rate at the furnace outlet; is the specific heat capacity of the combustion products in the furnace; is the flue gas temperature at the furnace outlet; is the mass of the combustion products in the furnace; is the time; Flue gas flow rate at the furnace outlet Specifically, it is:

[0046] In the formula: is the designed fuel quantity; is the volume of flue gas generated per kilogram of fuel combustion; is the density of the flue gas generated by combustion; Designed fuel quantity Specifically, it is:

[0047] In the formula: is the actual fuel quantity in the initial state; is the mechanical incomplete combustion loss; The specific equation for the effective calorific value of the furnace is:

[0048] In the formula, is the lower calorific value of the fuel on the as-received basis; , are the chemical incomplete combustion loss and the slag discharge heat loss respectively; is the specific heat capacity of air; is the hot air temperature; is the mass flow rate of air; The mass flow rate of air Specifically:

[0049] In the formula, is the air quantity required for burning one kilogram of fuel; is the air density; The specific equation for the radiant heat received by the furnace heating surface is:

[0050] In the formula, is the radiant heat received by the furnace heating surface; is the furnace emissivity; is the heat effective coefficient of the water wall; is the area of the water wall receiving thermal radiation; is the absolute black body radiation coefficient; is the water wall angle factor; is the flue gas temperature at the furnace outlet; is the ash wall temperature of the water wall tube.

[0051] Specifically, the first heat balance equation after substitution is:

[0052] In the formula, is a parameter set for convenience of solution and has no practical significance; is the flue gas temperature at the furnace outlet in the initial state; is the actual fuel quantity in the initial state; is the volume of combustion products in the furnace; is the ash wall temperature of the water wall tube in the initial state; is the ash wall temperature of the water wall tube; is the effective calorific value of the furnace in the initial state; The first differential equation is specifically as follows: + = + +

[0053] In the formula, is the time constant of the influence of the change in fuel quantity on the heat storage capacity of the flue gas in the furnace; is the change in the flue gas temperature at the furnace outlet; is the parameter of the influence of the change in hot air temperature on the heat storage capacity of the flue gas in the furnace; is the change in hot air temperature; is the first parameter characterizing the influence of the change in fuel quantity on the heat storage capacity of the flue gas in the furnace; is the change in the ash wall layer temperature of the water wall tube; is the second parameter characterizing the influence of the change in fuel quantity on the heat storage capacity of the flue gas in the furnace; is the actual change in fuel quantity; The time constant formula of the heat storage capacity of the flue gas in the furnace is specifically as follows: =

[0054] The first parameter and the second parameter characterizing the influence of the change in fuel quantity on the heat storage capacity of the flue gas in the furnace are respectively: =

[0055] .

[0056] Specifically, the heat transfer equation is specifically as follows:

[0057] In the formula, is the heat transferred through the ash wall layer to the water wall tube; is the reduction coefficient of the ash wall layer thermal resistance of the water wall tube; is the ash wall layer temperature of the water wall tube; is the metal wall temperature of the water wall tube; The second heat balance equation is specifically as follows:

[0058] In the formula, is the mass of the ash wall layer of the water wall tube; is the specific heat capacity of the ash wall layer of the water wall tube.

[0059] Specifically, the second heat balance equation after substitution is as follows:

[0060] The time constant formula for the heat storage capacity of the fouling and slagging layers on the furnace heating surface is specifically: =

[0061] The parameter characterizing the heat storage capacity of the fouling and slagging layers on the furnace heating surface is specifically: =

[0062] In the formula, is the time constant of the heat storage capacity of the fouling and slagging layers on the furnace heating surface; is the parameter characterizing the heat storage capacity of the fouling and slagging layers on the furnace heating surface; The second differential equation is specifically: .

[0063] Specifically, the input-output function of the influence of fuel quantity disturbance on the furnace outlet gas temperature is specifically: = +

[0064] In the formula, is the function representing the change in the furnace outlet gas temperature after Laplace transform; is the function representing the fuel quantity disturbance input after Laplace transform; is the function representing the hot air temperature disturbance after Laplace transform; The functional relationship of the change in the furnace outlet gas temperature is specifically:

[0065] In the formula, = , is the transfer function representing the influence of fuel quantity disturbance on the furnace outlet gas temperature after Laplace transform; is the function of the change in the furnace outlet gas temperature with time after being disturbed by fuel quantity.

[0066] Specifically, the design data specifically includes: the absolute blackbody radiation coefficient , the actual fuel quantity under the initial state, and the specific heat capacity of the combustion products in the furnace, rated load excess air coefficient, area of the water wall exposed to thermal radiation , specific heat capacity of the ash layer on the water wall tubes , density of the flue gas generated by combustion and reduction coefficient of the thermal resistance of the ash layer ; The measured data specifically includes: flue gas temperature at the furnace outlet under the initial condition , effective calorific value of the furnace under the initial condition , temperature of the ash layer on the water wall tubes under the initial condition , mass of the ash layer on the water wall tubes , furnace emissivity , mass of the combustion products in the furnace , thermal effectiveness coefficient of the water wall and volume of the flue gas generated per kilogram of fuel combustion .

[0067] Example 1 There is an existing 600MW boiler for producing superheated steam. The measured data and design data are collected as shown in Table 1. Now, a diagnostic case description of the influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet is given.

[0068] Table 1 Boiler collected data

[0069] Step 1: Calculation link for the time constant of the heat storage capacity of the flue gas in the furnace: The definition formula of the heat balance equation of the combustion products in the furnace (the first heat balance equation) is: (1) Where: is the effective calorific value of the furnace, kJ / s; is the radiant heat received by the furnace heating surface, kJ / s; is the flue gas flow rate at the furnace outlet, kg / s; is the specific heat capacity of the combustion products in the furnace, kJ / (kg·°C); is the flue gas temperature at the furnace outlet, °C; is the mass of the combustion products in the furnace, kg; is time, s; Among them, the calculation formula for the flue gas flow rate flowing out of the furnace outlet is: (2) Where: is the designed fuel quantity; is the volume of the flue gas generated per kilogram of fuel combustion, / kg; is the density of the combustion products, kg / ; The calculation formula for the designed fuel quantity is: The calculation formula for the designed fuel quantity is as follows: (3) In the formula: is the actual fuel quantity, kg / s; is the mechanical incomplete combustion loss (when is very small, it can be approximately considered that ≈ ); The effective heat release in the furnace is composed of the heat released by fuel combustion and the heat carried by hot air, and can be expressed as: (4) In the formula: is the lower calorific value of the fuel as-received basis; , are the chemical incomplete combustion loss and slag discharge heat loss respectively; is the specific heat capacity of air; is the hot air temperature, °C, is the mass flow rate of air; Among them, the calculation formula for the mass flow rate of air is: (5) In the formula: is the air quantity required to burn one kilogram of fuel, / kg; is the air density, kg / ; The radiant heat received by the furnace heating surface can be determined by the Stefan-Boltzmann equation: (6) In the formula; is the radiant heat received by the furnace heating surface; is the furnace emissivity; is the water wall angle factor; is the area of the water wall receiving thermal radiation, ; is the absolute black body radiation coefficient, ; is the water wall angle factor, generally considered that ≈ 1; is the flue gas temperature at the furnace outlet, K; is the ash wall layer temperature of the water wall tube, K; Substitute equations (4) and (6) into equation (1) to eliminate the variables and , since in the initial state, , , All are neglected. Assume that among them , we can obtain: (7) In the formula, is a parameter set for convenience of solution and has no practical significance; is the flue gas temperature at the furnace outlet in the initial state; is the actual fuel quantity in the initial state; is the volume of combustion products in the furnace; is the ash wall layer temperature of the water wall tubes in the initial state; is the ash wall layer temperature of the water wall tubes; is the effective calorific value of the furnace in the initial state; After simplifying and differentiating Equation (7), the first differential equation is obtained: + = + + (8) In the formula, is the time constant of the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace; is the change in flue gas temperature at the furnace outlet; is the parameter of the influence of hot air temperature change on the heat storage capacity of flue gas in the furnace; is the change in hot air temperature; is the first parameter characterizing the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace; is the change in the ash wall layer temperature of the water wall tubes; is the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace; is the change in actual fuel quantity; The specific formula for the time constant of the heat storage capacity of flue gas in the furnace can be obtained as: = (9) The first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace are respectively: = (10) (11) Step 2: Calculation link for the time constant of the heat storage capacity of the ash and slag layers on the heating surface: The heat transfer equation between the ash wall layer and the water wall tubes is: (12) In the formula: is the heat transferred to the water-cooled wall tube through the ash layer, kJ / s; is the reduction coefficient of the ash layer thermal resistance of the water-cooled wall tube, m 2 / (kW·K); is the ash layer temperature of the water-cooled wall tube, °C; is the metal wall temperature of the water-cooled wall tube, °C; The heat balance equation (the second heat balance equation) of the ash layer of the water-cooled wall tube is: (13) In the formula: is the mass of the ash layer of the water-cooled wall tube, kg; is the specific heat capacity of the ash layer of the water-cooled wall tube, ; Therefore, substituting equations (6) and (12) into equation (13), we can get: (14) The time constant formula for the heat storage capacity of the fouling and slagging layer on the furnace heating surface can be derived as follows: = (15) In the formula, is the time constant of the heat storage capacity of the fouling and slagging layer on the furnace heating surface; The parameters characterizing the heat storage capacity of the fouling and slagging layer on the furnace heating surface are specifically: = (16) In the formula, is the parameter characterizing the heat storage capacity of the fouling and slagging layer on the furnace heating surface; After differentiation, the second differential equation is obtained: (17) Step 3: Calculate the magnitude of the transfer function describing the dynamic disturbance: By eliminating the variable from equations (8) and (17), and since << , so let = We can get: + ( + ) + (1 - )

[0070] = ( + )+ ( + )(18) After Laplace transform, it can be obtained that: + = ( + ) + ( + )(19) Therefore, the input-output function of the influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet is: = + (20) In the formula, is the function representing the change in the flue gas temperature at the furnace outlet after Laplace transform; is the function representing the fuel quantity disturbance input after Laplace transform; is the function representing the hot air temperature disturbance after Laplace transform; Among them, let = , which is the transfer function describing the dynamic characteristics of the fuel quantity disturbance on the flue gas temperature at the furnace outlet. When the excess air coefficient is a fixed value, the dynamic characteristics of the change in the flue gas temperature at the furnace outlet can be described and calculated.

[0071] Step 4: Calculation link of the change in the flue gas temperature at the furnace outlet: When the input quantity is set as a fuel quantity disturbance in a certain functional form (generally a step disturbance of 10% of the fuel quantity), the functional relationship of the change in the flue gas temperature at the furnace outlet can be obtained as: (21) In the formula, is the function of the change in the flue gas temperature at the furnace outlet varying with time after being disturbed by the fuel quantity; is the transfer function representing the influence of the fuel quantity disturbance on the flue gas temperature at the furnace outlet after Laplace transform.

[0072] The obtained function curve is an exponential function, which will stabilize at a certain value after a period of time, that is, the stable value of the change at the furnace outlet. By analyzing the influence of fuel quantity disturbance on flue gas temperature, it can guide the optimization of boiler combustion, improve fuel utilization efficiency, and reduce combustion deviation. Combining the calculation results, the mathematical relationship between fuel quantity and flue gas temperature change can be established to achieve the adaptive adjustment of combustion parameters, reduce temperature fluctuations, and improve system stability.

[0073] Based on Step 1, the calculation step of the time constant of the heat storage capacity of flue gas in the furnace, first obtain:

[0074] It can be obtained that the time constant of the heat storage capacity of flue gas in the furnace, the first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of flue gas in the furnace are respectively:

[0075]

[0076]

[0077] Based on Step 2, the calculation step of the time constant of the heat storage capacity of the ash and slag layer on the heating surface, it can be obtained that the time constant formula of the heat storage capacity of the ash and slag layer on the furnace heating surface and the parameters characterizing the heat storage capacity of the ash and slag layer on the furnace heating surface are respectively:

[0078]

[0079] Based on Step 3, the calculation step of the transfer function describing the dynamic disturbance, the time τ can be obtained:

[0080] Then the fuel quantity disturbance on the flue gas temperature at the furnace outlet of the dynamic characteristics of the transfer function is: =

[0081] Since the actual fuel quantity is 69.5 kg / s, it is assumed that the input is a 10% step disturbance, that is, it changes by 6.95 kg per second, and we get:

[0082] Then, the change curve of the flue gas temperature at the furnace outlet at this time is:

[0083]

[0084] The curve is an exponential function. By observing the changing curve, we can see that the function curve stabilizes at about 16.7 degrees Celsius after 4 seconds. Therefore, when the rated load excess air coefficient is 1.2, the change in the flue gas temperature at the furnace outlet after about 4 seconds is Stable at 16.7 degrees Celsius.

[0085] The present invention is a method for calculating the dynamic influence of fuel quantity disturbance on the flue gas temperature at the boiler furnace outlet, and is characterized in that it includes steps such as the time constant calculation link of the flue gas heat storage capacity in the furnace, the time constant calculation link of the heat storage capacity of the ash and slag layer on the heating surface, and the transfer function calculation link describing the dynamic disturbance. The present invention is based on the heat balance method, on which the time constant of the flue gas heat storage capacity in the furnace is obtained by integrating the radiation heat received by the furnace heating surface with the disturbance of the fuel quantity, and then the heat exchange between the water-cooled wall and the ash wall layer is analyzed, and the time constant of the heat storage capacity of the ash and slag layer on the heating surface is comprehensively given by combining the heat balance equation of the ash wall layer and the water-cooled wall, and finally the differential equations are combined for Laplace transformation to obtain the transfer function describing the dynamic disturbance, so as to achieve the purpose of calculating the dynamic influence of the fuel quantity disturbance on the flue gas temperature at the boiler furnace outlet, and solve the technical problem that the dynamic influence of the fuel quantity disturbance on the flue gas temperature at the boiler furnace outlet cannot be accurately calculated.

[0086] Based on the same inventive concept, an embodiment of the present application provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for calculating the dynamic influence of the fuel quantity disturbance on the flue gas temperature at the furnace outlet are implemented. The memory may include a memory, such as a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk memory, etc. The processor, the network interface, and the memory are interconnected through an internal bus, which may be an industrial standard architecture bus, a peripheral component interconnection standard bus, an extended industrial standard structure bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. The memory is used to store programs. Specifically, the program may include a program code, and the program code includes computer operation instructions. The memory may include a memory and a non-volatile memory, and provide instructions and data to the processor.

[0087] Based on the same inventive concept, embodiments of the present application provide a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps of the calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet are implemented. Specifically, the computer-readable storage medium includes, but is not limited to, for example, volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache, etc. The non-volatile memory may include ROM (Read-Only Memory), hard disk, flash memory, optical disc, magnetic disk, etc.

[0088] Based on the same inventive concept, embodiments of the present application provide a computer program product, which includes a computer program stored on a computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer device, the computer device is caused to execute the steps of the above-mentioned calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet.

[0089] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM (Compact Disc Read-Only Memory), optical memory, etc.) containing computer-usable program code.

[0090] Finally, it should be noted that the above-listed embodiments exist only as one or more specific forms of the technical solution of the present invention. Their purpose is to clearly elaborate the concept, principle, and application method of the present invention through specific examples, rather than intending to limit the protection scope of the present invention to these specific embodiments. In fact, the real value of the present invention lies in the proposed technical idea and innovation point, rather than its form of expression or implementation means.

[0091] For those of ordinary skill in the art, after thoroughly reading and understanding the technical solution of the present invention, they are fully capable of making various forms of changes, modifications or equivalent replacements to the specific implementation manners of the invention based on their own professional knowledge and skills. These changes may include, but are not limited to: adjusting the value range of technical parameters, optimizing the algorithm process to improve efficiency, replacing some technical components to achieve better compatibility or reduce costs, etc. As long as the technical solutions after these changes still substantially maintain the technical features required to be protected by the original invention, that is, still can achieve the core functions and effects of the present invention, then these changes should be regarded as falling within the protection scope of the pending claims of the present invention.

[0092] In addition, with the continuous progress and development of technology, new technical means and methods are emerging continuously, which also provides a broad space for the further improvement and perfection of the present invention. Therefore, the protection scope of the present invention should also include those reasonably foreseeable improvements and expansions based on the existing technology. As long as these improvements and expansions do not deviate from the basic principles and core concepts of the present invention, they should be regarded as equivalents of the present invention and are equally protected by the patent right.

Claims

1. A calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet, characterized in that It includes the following steps: Step 1: Based on the heat balance relationship of the furnace combustion products, establish the first heat balance equation; based on the thermodynamic principle of furnace combustion, establish the furnace effective heat release equation; based on the Stefan-Boltzmann law, establish the equation for the radiant heat received by the furnace heating surface; substitute the furnace effective heat release equation and the equation for the radiant heat received by the furnace heating surface into the first heat balance equation to obtain the first heat balance equation after substitution. Through derivation, obtain the time constant formula for the heat storage capacity of the flue gas in the furnace, the first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of the flue gas in the furnace; differentiate the first heat balance equation after substitution to obtain the first differential equation; Step 2: Based on the heat transfer relationship between the ash layer on the water-cooled wall tubes of the furnace and the water-cooled wall tubes, establish the heat transfer equation; based on the heat balance relationship of the ash layer on the water-cooled wall tubes, establish the second heat balance equation; substitute the heat transfer equation and the equation for the radiant heat received by the furnace heating surface into the second heat balance equation to obtain the second heat balance equation after substitution. Through derivation, obtain the time constant formula for the heat storage capacity of the ash fouling and slagging layer on the furnace heating surface and the parameter characterizing the heat storage capacity of the ash fouling and slagging layer on the furnace heating surface; Differentiate the second heat balance equation after substitution to obtain the second differential equation; Step 3: Based on the first differential equation and the second differential equation, obtain the input-output function of the influence of fuel quantity disturbance on the furnace outlet flue gas temperature. Through the inverse Laplace transform, obtain the functional relationship of the change in the furnace outlet flue gas temperature; Step 4: Obtain the design data and measured data of the boiler. Combine the time constant formula for the heat storage capacity of the flue gas in the furnace, the first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of the flue gas in the furnace, the time constant formula for the heat storage capacity of the ash fouling and slagging layer on the furnace heating surface and the parameter characterizing the heat storage capacity of the ash fouling and slagging layer on the furnace heating surface to calculate the specific values. Substitute the specific values into the functional relationship of the change in the furnace outlet flue gas temperature, draw the curve of the change in the furnace outlet flue gas temperature, and analyze the dynamic influence of fuel quantity disturbance on the furnace outlet flue gas temperature.

2. The calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet according to claim 1, characterized in that The first heat balance equation is specifically: In the formula: is the effective calorific value of the furnace under the initial state; is the radiant heat received by the furnace heating surface; is the flue gas flow rate at the furnace outlet; is the specific heat capacity of the combustion products in the furnace; is the flue gas temperature at the furnace outlet; is the mass of the combustion products in the furnace; is time; Flue gas flow rate at the furnace outlet Specifically: Wherein: is the designed fuel quantity; is the volume of flue gas generated by the combustion of each kilogram of fuel; is the density of the flue gas generated by the combustion; Designed fuel quantity Specifically: Where: is the actual fuel quantity in the initial state; is the loss due to incomplete combustion of the machinery; The furnace effective heat release equation is specifically: In the formula, is the lower calorific value of the fuel as received; , are the heat losses due to incomplete chemical combustion and slag discharge respectively; is the specific heat capacity of air; is the temperature of hot air; is the mass flow rate of air; Mass flow rate of air Specifically: In the formula, is the amount of air required to burn one kilogram of fuel; is the air density; The equation for the radiant heat received by the furnace heating surface is specifically: In the formula, is the radiant heat received by the furnace heating surface; is the emissivity of the furnace; is the thermal efficiency factor of the water wall; is the area of the water wall receiving thermal radiation; is the radiation coefficient of a perfect black body; is the angle factor of the water wall; is the flue gas temperature at the furnace outlet; is the temperature of the ash layer on the water wall tube.

3. The calculation method for the dynamic influence of fuel quantity disturbance on the furnace outlet flue gas temperature according to claim 2, wherein The first heat balance equation after substitution is specifically: In the formula, is a parameter set for convenience of solution and has no practical meaning; is the flue gas temperature at the furnace outlet under the initial state; is the actual fuel quantity under the initial state; is the volume of combustion products in the furnace; is the temperature of the ash layer on the water wall tubes under the initial state; is the temperature of the ash layer on the water wall tubes; is the effective calorific value of the furnace under the initial state; The first differential equation is specifically: + = + + Wherein, is the time constant of the influence of the fuel quantity change on the heat storage capacity of the flue gas in the furnace; is the change in the flue gas temperature at the furnace outlet; is the parameter of the influence of the hot air temperature change on the heat storage capacity of the flue gas in the furnace; is the change in the hot air temperature; is the first parameter characterizing the influence of the fuel quantity change on the heat storage capacity of the flue gas in the furnace; is the change in the ash wall layer temperature of the water wall tube; is the second parameter characterizing the influence of the fuel quantity change on the heat storage capacity of the flue gas in the furnace; is the actual fuel quantity change; The time constant formula for the heat storage capacity of the flue gas in the furnace is specifically: = The first parameter and the second parameter characterizing the influence of fuel quantity change on the heat storage capacity of the flue gas in the furnace are respectively: = 。 4. The calculation method for the dynamic influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet according to claim 3, characterized in that, The heat transfer equation is specifically: Wherein, is the heat transferred to the water wall tube through the ash wall layer; is the reduction coefficient of the ash wall layer thermal resistance of the water wall tube; is the ash wall layer temperature of the water wall tube; is the metal wall temperature of the water wall tube; The second heat balance equation is specifically: Wherein, is the mass of the ash layer on the water wall tube; is the specific heat capacity of the ash layer on the water wall tube.

5. The calculation method for the dynamic influence of fuel quantity disturbance on the furnace outlet flue gas temperature according to claim 4, characterized in that, The second heat balance equation after substitution is specifically: The time constant formula for the heat storage capacity of the ash fouling and slagging layer on the furnace heating surface is specifically: = The parameter characterizing the heat storage capacity of the ash fouling and slagging layer on the furnace heating surface is specifically: = In the formula, is the time constant of the heat storage capacity of the fouling and slagging layer on the furnace heating surface; is the parameter characterizing the heat storage capacity of the fouling and slagging layer on the furnace heating surface; The second differential equation is specifically: 。 6. The calculation method for the dynamic influence of fuel quantity disturbance on the furnace outlet flue gas temperature according to claim 5, wherein, The input-output function of the influence of fuel quantity disturbance on the furnace outlet flue gas temperature is specifically: = + In the formula, is the function representing the change in the flue gas temperature at the furnace outlet after Laplace transform; is the function representing the disturbance of the input fuel quantity after Laplace transform; is the function representing the disturbance of the hot air temperature after Laplace transform; The functional relationship of the change in the furnace outlet flue gas temperature is specifically: In the formula, = , is the transfer function representing the influence of fuel quantity disturbance on the flue gas temperature at the furnace outlet after Laplace transform; is the function of the change in flue gas temperature at the furnace outlet with time after being disturbed by fuel quantity.

7. The calculation method for the dynamic influence of fuel quantity disturbance on the furnace outlet flue gas temperature according to claim 1, characterized in that The design data specifically includes: the absolute black body radiation coefficient , the actual fuel quantity under the initial state , the specific heat capacity of the combustion products in the furnace , the excess air coefficient at the rated load, the area of the water wall subjected to thermal radiation , the specific heat capacity of the ash wall layer of the water wall tube , the density of the flue gas generated by combustion and the reduction coefficient of the thermal resistance of the ash wall layer ; The measured data specifically include: the flue gas temperature at the furnace outlet under the initial state , the effective calorific value of the furnace under the initial state , the ash wall temperature of the water wall tubes under the initial state , the mass of the ash wall layer of the water wall tubes , the furnace emissivity , the mass of the combustion products in the furnace , the heat transfer effective coefficient of the water wall and the volume of flue gas generated per kilogram of fuel combustion .

8. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it realizes the steps of the calculation method for the dynamic influence of fuel quantity disturbance on the furnace outlet flue gas temperature described in any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the calculation method for the dynamic influence of fuel quantity disturbance on the furnace outlet flue gas temperature described in any one of claims 1 to 7.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the calculation method for the dynamic influence of fuel quantity disturbance on the furnace outlet flue gas temperature described in any one of claims 1 to 7.

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