System and method for predicting banking-up duration of circulating fluidized bed boiler

Abstract

The invention discloses a banking-up duration prediction system and method for a circulating fluidized bed boiler. The system comprises a bed material system module, a castable system module, a steam-water system module, a pipe wall system module and a banking-up duration prediction module. Firstly, boiler structure parameters and banking-up operation parameters are obtained; based on boiler structure parameters, a bed material system module, a castable system module, a steam-water system module and a pipe wall system module are constructed; calculating a bed material temperature, a castable temperature, a steam temperature of each pipe wall outlet and a pipe wall temperature based on the banking-up operation parameters; and judging whether banking fire can be continued or not by combining the bed material temperature, the pipe wall outlet steam temperature and the pipe wall temperature. According to the method, the maximum banking-up duration of the boiler can be quickly and accurately predicted, and the safety and economy of banking-up operation are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of circulating fluidized bed boiler shut-off technology, specifically to a system and method for predicting the shut-off time of a circulating fluidized bed boiler. Background Technology

[0002] With the increasing grid connection of renewable energy, traditional coal-fired power generation boilers often need to perform deep peak shaving or even shut-down start-up peak shaving. Circulating fluidized bed boilers have a great advantage in the shut-down process due to their large heat storage capacity. In order to improve the economy and safety of the boiler shut-down start-up peak shaving process, the following four conditions must be met: (1) the temperature of the uppermost bed material is higher than the coal ignition temperature; (2) the feedwater in the water-cooled wall can be completely evaporated; (3) the steam at the outlet of the high-temperature superheater / high-temperature reheater has sufficient superheat; (4) the tube wall temperature cannot exceed the safety threshold.

[0003] However, existing technologies for predicting the duration of heat suppression mainly rely on multivariate degradation models, which require a large amount of historical data for training. Therefore, developing a system and method for predicting the duration of heat suppression solely based on energy conservation and heat transfer equations has significant engineering application value and theoretical significance for rapidly and accurately predicting the duration of heat suppression. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a system and method for predicting the shutdown time of a circulating fluidized bed boiler, so as to at least quickly and accurately predict the maximum shutdown time of the boiler and ensure the safety and economy of shutdown operation.

[0005] To solve the above technical problems, according to one aspect of the present invention, a circulating fluidized bed boiler shut-off time prediction system is provided, comprising: The bed material system module couples bed material temperature, castable temperature, and pipe wall temperature to predict bed material temperature changes. The castable system module couples bed material temperature, castable temperature, and pipe wall temperature to predict the change in castable temperature. The steam-water system module couples the working fluid parameters on the steam-water side with the pipe wall temperature to predict the change in the steam temperature at the pipe wall outlet. The pipe wall system module couples the working fluid parameters on the steam-water side, bed material temperature, castable temperature, and pipe wall temperature to predict the change in pipe wall temperature. The boiler can continue to perform the pressure-down operation based on the bed material temperature, tube wall temperature, and tube wall outlet steam temperature.

[0006] In a preferred embodiment, the temperature change ΔT is obtained from the energy change ΔE within the time interval dt, using the following formula: ; In the formula, m is the mass of the heat exchange component, and c p Specific heat capacity at constant pressure; In the bed material system module, castable refractory system module, steam-water system module, and pipe wall system module, ΔE represents the energy change of the bed material. b Energy change ΔE of castable refractory c Or the energy change ΔE of the pipe wall t ΔT represents the change in bed material temperature, the change in castable temperature, or the change in steam temperature at the pipe wall outlet, respectively. In a preferred embodiment, the bed material system module calculates the energy change ΔE of the bed material. b The formula is: ; Q cd,b-b Q is the heat conduction between adjacent bed layers. cd,b-c Q is the heat conduction between the bed material and the castable. r,b-b For radiative heat transfer between adjacent bed layers, Q r,b-c For radiative heat transfer between the bed material and the castable, Q r,b-t For radiative heat exchange between the bed material and the tube wall.

[0007] In a preferred embodiment, the energy change ΔE of the castable refractory is calculated in the castable system module. c The formula is: ; Q cd,c-b Q is the heat conduction between the castable and the bed material. cd,c-c Q represents the heat conduction between adjacent layers of castable refractory. cd,c-t Q is the heat conduction between the castable refractory and the pipe wall. r,c-b For radiative heat transfer between the castable and the bed material, Q r,c-t This is for radiative heat exchange between the castable refractory and the pipe wall.

[0008] In a preferred embodiment, the pipe wall system module is used to solve for the energy change ΔE of the pipe wall. t The formula is: ; Q cv,t-w For convective heat transfer between the working fluid and the tube wall, Q cd,t-c Q is the heat conduction between the pipe wall and the castable refractory. r,t-c For radiative heat transfer between the pipe wall and the castable, Q r,t-b For radiative heat transfer between the tube wall and the bed material, Q r,t-t For radiative heat exchange between pipe walls.

[0009] In a preferred embodiment, the calculation formulas for each type of convective heat transfer, conductive heat transfer, and radiative heat transfer are as follows: ; k is the heat transfer coefficient, A is the heat transfer area, and ΔT c This refers to the temperature difference between components.

[0010] In a preferred embodiment, the energy change ΔE of the working fluid at the water inlet and outlet is calculated in the steam-water system module. w The formula is: , ; Q cv,w-t For convective heat transfer between the tube wall and the working fluid side, m w For water supply mass flow rate, c p For the specific heat capacity at constant pressure, ΔT w This represents the temperature difference between the inlet and outlet of the working fluid in the pipe wall.

[0011] According to another aspect of the present invention, a method for predicting the shutdown time of a circulating fluidized bed boiler is provided, based on the circulating fluidized bed boiler shutdown time prediction system described above, comprising: Step 1: Obtain boiler structural parameters and fire suppression operation parameters; Step 2: Based on the boiler structural parameters, construct the bed material system module, castable refractory system module, steam-water system module, and tube wall system module; Step 3: Based on the pressure firing operation parameters, calculate the bed material temperature, castable temperature, steam temperature at the outlet of each tube wall, and tube wall temperature; Step four: Based on the bed material temperature, tube outlet steam temperature, and tube wall temperature obtained in step three, determine whether the pressure firing can continue. The process for determining whether the suppression of heat can continue includes: (1) Determine whether the bed material temperature is sufficient for coal ignition; (2) Determine whether the feedwater can be completely evaporated in the water-cooled wall; (3) Determine whether the steam has sufficient superheat at the outlet of the high-temperature superheater / high-temperature reheater tube wall; (4) Determine whether the pipe wall temperature has not exceeded the safety threshold; Based on the above judgment results, if all judgment results are "yes", then return to step three to perform the next time step calculation; if any judgment result is "no", then the fire suppression will terminate, and the time at this time is the maximum fire suppression time of the boiler.

[0012] In a preferred embodiment, in step one, the boiler structural parameters include the depth, width, and height of the furnace, the spatial geometric relationship of each component within the furnace, and the dimensions of each pipe.

[0013] In a preferred embodiment, the fire suppression operation parameters in step one include water supply volume, water supply pressure, water supply temperature, and the temperature of each component before fire suppression.

[0014] This invention proposes a prediction system and method for the burn-off time of a circulating fluidized bed boiler. The system considers the boiler's structural parameters (such as boiler size, spatial position of components, tube structural parameters, refractory thickness, refractory material, etc.) and burn-off operation parameters (such as feedwater flow rate, bed material flow rate, tube wall temperature, etc. during burn-off). Through energy conservation and heat transfer equations, it achieves rapid and accurate prediction of the burn-off time of the circulating fluidized bed boiler, preventing problems such as tube wall overheating, failure to start up without oil injection, incomplete evaporation of feedwater, and insufficient steam parameters.

[0015] The pressure-down time prediction system proposed in this invention provides strong support for the economy and safety of boiler pressure-down process, and is of great significance for promoting the pressure-down start-up and peak shaving of circulating fluidized bed boilers. Attached Figure Description

[0016] Figure 1 This is an overall flowchart of the circulating fluidized bed boiler shutdown time prediction system and method of the present invention; Figure 2 To compare the simulated and actual values ​​of the compression firing process, (a) is the bed material temperature, and (b) is the water-cooled wall outlet tube wall temperature. Detailed Implementation

[0017] The overall concept of this invention is to establish a prediction system based on multi-parameter coupling. This system includes a bed material system module, a castable refractories system module, a steam-water system module, a tube wall system module, and a pressure-down time prediction module. Based on the energy conservation and heat transfer characteristics of the pressure-down process, the bed material system module, castable refractories system module, steam-water system module, and tube wall system module achieve accurate tracking of key parameters during the pressure-down process. Then, the pressure-down time prediction module is used to determine the maximum allowable pressure-down time of the boiler.

[0018] Based on the above ideas, such as Figure 1 As shown, a typical embodiment of the present invention provides a circulating fluidized bed boiler shut-off time prediction system, which is based on a multi-parameter coupled model and utilizes energy conservation and heat transfer equations to achieve rapid and accurate prediction of shut-off time. The system includes a bed material system module, a castable material system module, a steam-water system module, a tube wall system module, and a shut-off time prediction module.

[0019] The bed material system module is used to establish and solve the bed material temperature. This module couples the data of bed material temperature, castable temperature, tube wall temperature and the physical properties of each component, and combines the furnace layout of the bed material, castable, water-cooled walls, superheater and reheater to predict the change in bed material temperature.

[0020] In this module, the calculation of the temperature change of the bed material involves the following formula: (1) (2) (3) In formula (1), ΔE b Q represents the change in energy of the bed material over time dt. A positive value indicates heat absorption and an increase in energy, while a negative value indicates heat release. cd,b-b Q is the heat conduction between adjacent bed layers. cd,b-c Q is the heat conduction between the bed material and the castable. r,b-b For radiative heat transfer between adjacent bed layers, Q r,b-c For radiative heat transfer between the bed material and the castable, Q r,b-t For radiative heat exchange between the bed material and the tube wall.

[0021] Formula (2) is used to calculate the corresponding Q in formula (1) respectively. cd,b-b Q cd,b-c Q r,b-b Q r,b-c and Q r,b-t In formula (2), k is the heat transfer coefficient, W·m -2 ·K -1 A represents the heat exchange area, in meters. 2 ;ΔT c The temperature difference between the components is expressed in °C.

[0022] In the bed material system module, ΔE in formula (3) is equivalent to the energy change ΔE of the bed material. b Formula (3) is used to calculate the energy change ΔE of the bed material. b Solve for the temperature change ΔT of the bed material. m is the mass of the heat exchanger assembly, kg; c p For isobaric specific heat capacity, J·kg -1 ·K -1 .

[0023] For continuously divided bed materials, the average temperature of the bed materials is calculated according to formula (4); (4) In formula (4), T bed , where is the average temperature of the bed material, in °C; m n For the mass of the submodule bed material, kg; T n Temperature of the submodule bed material, in °C; m a The total mass of the bedding material is expressed in kg.

[0024] The castable system module is used to establish and solve for the castable temperature. This module couples data on bed temperature, castable temperature, tube wall temperature, and the physical properties of each component, and combines the spatial geometric relationships of the components within the furnace to predict the change in castable temperature.

[0025] In this module, the calculation of the temperature change of the castable involves the following formula: (5) (2) (3) In formula (5), ΔE c Q represents the change in energy of the castable refractory over time dt. A positive value indicates heat absorption and an increase in energy, while a negative value indicates heat release. cd,c-b Q is the heat conduction between the castable and the bed material. cd,c-c Q represents the heat conduction between adjacent layers of castable refractory. cd,c-t Q is the heat conduction between the castable refractory and the pipe wall. r,c-b For radiative heat transfer between the castable and the bed material, Q r,c-t This is for radiative heat exchange between the castable refractory and the pipe wall.

[0026] Formula (2) is used to calculate the corresponding Q in formula (5) respectively. cd,c-b Q cd,c-c Q cd,c-t Q r,c-b and Q r,c-t .

[0027] In the castable system module, ΔE in formula (3) is equivalent to the change in castable temperature ΔE. c Formula (3) is used to calculate the temperature change ΔE of the castable refractory. c Solve for the temperature change ΔT of the castable refractory.

[0028] The steam-water system module is used to establish and solve for the steam temperature at the pipe wall outlet. This module couples the working fluid parameters on the steam-water side with the pipe wall temperature to predict the change in the steam temperature at the pipe wall outlet.

[0029] In this module, the calculation of the change in steam temperature at the pipe wall outlet involves the following formula: (6) (7) In formula (6), ΔE w Q represents the energy change of the working fluid at the feedwater inlet and outlet during time dt. A positive value indicates heat absorption and an increase in energy, while a negative value indicates heat release. cv,w-t The convective heat transfer between the pipe wall and the working fluid side can be calculated using formula (2).

[0030] In formula (7), m w The mass flow rate of the water supply is expressed in kg·s. -1 c p For the specific heat capacity at constant pressure, ΔT w Let ΔT be the temperature difference between the inlet and outlet working fluid of the pipe wall, expressed in °C. When the inlet temperature is determined, the outlet temperature can be calculated from ΔT. w Sure.

[0031] The tube wall system module is used to establish and solve for the tube wall temperature. This module couples the working fluid parameters on the steam-water side, the bed material temperature, the castable temperature, the tube wall temperature and their physical properties, and combines the spatial geometric relationships of various components in the furnace to predict the change in tube wall temperature.

[0032] In this module, the calculation of pipe wall temperature change involves the following formulas: (8) (2) (3) In formula (8), ΔE t Q represents the change in energy of the pipe wall during time dt. A positive value indicates heat absorption and an increase in energy, while a negative value indicates heat release. cv,t-w For convective heat transfer between the working fluid and the tube wall, Q cd,t-c Q is the heat conduction between the pipe wall and the castable refractory. r,t-c For radiative heat transfer between the pipe wall and the castable, Q r,t-b For radiative heat transfer between the tube wall and the bed material, Q r,t-t For radiative heat exchange between pipe walls.

[0033] Formula (2) is used to calculate the corresponding Q in formula (8) respectively. cv,t-w Q cd,t-c Q r,t-c Q r,t-b and Q r,t-t .

[0034] In the pipe wall system module, ΔE in formula (3) is equivalent to the pipe wall temperature change ΔE. t Formula (3) is used to calculate the change in pipe wall temperature ΔE. t Solve for the change in pipe wall temperature ΔT.

[0035] The boiler shut-off duration prediction module is used to determine the maximum shut-off duration of the boiler. This module determines whether the boiler can continue to perform shut-off operation based on the bed material temperature, tube wall temperature, and tube wall outlet steam temperature.

[0036] The above-mentioned bed material system module, castable refractory system module, steam-water system module, and tube wall system module are coupled together. The fire suppression duration prediction module is connected to the bed material system module, tube wall system module, and steam-water system module. Based on the output results of the bed material system module, tube wall system module, and steam-water system module, it is determined whether the boiler can continue to perform fire suppression operation.

[0037] Another typical embodiment of the present invention provides a method for predicting the burn-off time of a circulating fluidized bed boiler. This method is implemented based on the circulating fluidized bed boiler burn-off time prediction system described above and includes the following steps one to four.

[0038] Step 1: Obtain boiler structural parameters and fire suppression operation parameters; The boiler structural parameters include the depth, width, and height of the furnace, the spatial geometry of the components within the furnace, and the dimensions of each tube. The fire suppression operation parameters include the feedwater flow rate, feedwater pressure, feedwater temperature, and the temperatures of each component before fire suppression.

[0039] Step 2: Based on the boiler structural parameters, construct the bed material system module, the castable refractory system module, the steam-water system module, and the tube wall system module.

[0040] Step 3: Based on the pressure firing operation parameters, calculate the bed material temperature, castable temperature, steam temperature at the outlet of each tube wall, and tube wall temperature.

[0041] Step four: Based on the bed material temperature, tube outlet steam temperature, and tube wall temperature obtained in step three, determine whether the pressure firing can continue. The process for determining whether the suppression of heat can continue includes: (1) Determine whether the bed material temperature is sufficient for coal ignition; (2) Determine whether the feedwater can be completely evaporated in the water-cooled wall; (3) Determine whether the steam has sufficient superheat at the outlet of the high-temperature superheater / high-temperature reheater tube wall; (4) Determine whether the pipe wall temperature has not exceeded the safety threshold; Based on the above judgment results, if all judgment results are "yes", then return to step three to perform the next time step calculation; if any judgment result is "no", then the fire suppression will terminate, and the time at this time is the maximum fire suppression time of the boiler.

[0042] The technical solution claimed in this invention will be further described clearly and completely below with reference to a relatively specific embodiment.

[0043] Taking a 350MW circulating fluidized bed boiler unit in China as an example, boiler structural parameters, shutdown operation parameters, and material properties were collected. Structural parameters included furnace dimensions, tube wall dimensions, and internal space distribution. Operational parameters included steam-water working fluid parameters, furnace component temperatures, and bed material quantity. Material properties included material density, thermal conductivity, and emissivity.

[0044] The furnace chamber has dimensions of 9810×31020×50000 mm, tube outer diameter of 60 mm, wall thickness of 12.2 mm, and castable thickness of 50 mm. The upper space of the furnace chamber is equipped with 6 medium-temperature secondary superheaters, 6 high-temperature superheaters, 6 high-temperature reheaters, and 5 screen-type water-cooled walls.

[0045] During the fire suppression period, the water supply was 46 t / h, the bed material stacking height was 0.65 m, and the average temperatures of the bed material, castable, water-cooled wall, water-cooled wall (double screen), intermediate temperature secondary superheater, high temperature superheater and high temperature reheater were 876.3, 601.4, 355.4, 346.9, 505.8, 547.6 and 518.6 ℃ respectively.

[0046] The thermal conductivity of the bed material is 0.31 W / (m²). 2 •K), emissivity 0.7, and bulk density selected as 1200 kg / m³. 3 The thermal conductivity of the castable refractory is 3 W / (m). 2 •K), emissivity 0.85; thermal conductivity of the tube wall 29.1 W / (m²). 2 •K), with an emissivity of 0.8.

[0047] Based on the boiler structure information, construct the models of each system according to step two.

[0048] Specifically, in constructing the bed material system module, castable refractory system module, and tube wall system module, the radiation angle coefficient between furnace components is calculated based on the bed material stacking height, castable refractory thickness, and tube wall spatial position to determine the radiative heat transfer between each component. The thermal conductivity of the bed material, castable refractory, and tube wall is then used to determine the conductive heat transfer between furnace components.

[0049] In constructing the steam-water system module, the convective heat transfer coefficients of the pipe wall and the water supply are calculated based on the water flow rate and pipe wall size to determine the convective heat transfer.

[0050] Based on the information from the compression firing operation, determine the bed material temperature, castable temperature, tube outlet steam temperature, and tube wall temperature during the compression firing process according to step three.

[0051] According to step four, determine whether the pressing process can continue.

[0052] Specifically, the method for calculating the temperature of the outer layer bed material and determining whether pressing can be carried out based on steps two to four is as follows: (1) Based on the spatial distribution of the internal components of the furnace, the angle coefficients of the bed material and castable, water-cooled wall, medium-temperature secondary superheater, high-temperature superheater and high-temperature reheater are approximately 0.633, 0.332, 0.011, 0.016 and 0.008.

[0053] (2) The calculation of radiation heat transfer inside the bed material needs to be combined with the specific module division method. In this paper, the bed material is divided into 8 continuous layers from the outer layer to the inner layer. The outermost layer of bed material has a thickness of 10 mm, the second outermost layer has a thickness of 10 mm, and the radiation heat transfer angle coefficient of the above two layers of bed material is 0.5.

[0054] (3) According to the formula: (1) (2); Calculate the total heat exchange between the outer and inner bed materials, the castable, and the pipe wall during the time dt. Then, according to the formula: (3) The temperature of the outer layer of bed material is calculated after time dt. During the calculation, the bed material is divided into multiple components from the outside to the inside. Each ΔEb calculates the temperature change of the layered bed material. Therefore, by combining the heat exchange, the temperature change of a single layer can be calculated, thereby determining the overall temperature of the bed material.

[0055] When dt = 0.2s, ΔE b It is 9.96×10 5 J, that is, when the pressing time is 0.2s, the temperature of the outer bed material is 875.7℃.

[0056] (4) Set the minimum temperature of the outer bed based on the coal ignition temperature during boiler startup. In this calculation, the coal ignition temperature is selected as 450 ℃.

[0057] When t=0.2 s, the temperature of the outer bed material is greater than 450℃, which is sufficient for coal feeding and ignition, and the fire can continue to be suppressed.

[0058] Similarly, the temperatures of the castable refractory, the water-cooled wall outlet steam, the double-screen water-cooled wall outlet steam, the high-temperature superheater outlet steam, the high-temperature reheater outlet steam, the average water-cooled wall temperature, and the double-screen water-cooled wall temperature at t=0.2 s can also be calculated using the above method. Their values ​​are 601.3, 388.1, 368.15, 564.9, 536.1, 355.5, and 346.9 ℃, respectively.

[0059] The minimum outlet steam temperature of the high-temperature superheater / high-temperature reheater is set at 368.08 ℃, and the safe threshold for the water-cooled wall temperature is set at 500 ℃. It was determined that within 0.2 seconds, the feedwater at the water-cooled wall can completely evaporate, the steam at the outlet of the high-temperature superheater / high-temperature reheater has sufficient superheat, and the water-cooled wall temperature does not exceed the safe threshold.

[0060] Therefore, the pressing process can continue. Then, through continuous iterative solutions, the bed material temperature, castable temperature, steam temperature at each tube outlet, and tube wall temperature at time t can be determined.

[0061] When t=98.6 min, the bed material temperature, water-cooled wall outlet steam temperature, double-screen water-cooled wall outlet steam temperature, high-temperature superheater outlet steam temperature, high-temperature reheater outlet steam temperature, average water-cooled wall temperature, and average double-screen water-cooled wall temperature are 450.1, 318.08, 376, 417.2, 406.2, 319.7, and 340.8 ℃, respectively. The water-cooled walls can no longer maintain complete feedwater evaporation; therefore, the maximum boiler shut-off time is 98.6 min. During the shut-off process, the boiler bed material temperature and water-cooled wall outlet tube wall temperature are shown in the attached figure. Figure 2 As shown, the comparison between simulated and actual values ​​indicates that the model has high accuracy in predicting fire suppression.

[0062] Finally, it should be noted that the above description is only for illustrating the technical solution of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for predicting the burn-off time of a circulating fluidized bed boiler, characterized in that, include: The bed material system module couples bed material temperature, castable temperature, and pipe wall temperature to predict bed material temperature changes. The castable system module couples bed material temperature, castable temperature, and pipe wall temperature to predict the change in castable temperature. The steam-water system module couples the working fluid parameters on the steam-water side with the pipe wall temperature to predict the change in the steam temperature at the pipe wall outlet. The pipe wall system module couples the working fluid parameters on the steam-water side, bed material temperature, castable temperature, and pipe wall temperature to predict the change in pipe wall temperature. The boiler can continue to perform the pressure-down operation based on the bed material temperature, tube wall temperature, and tube wall outlet steam temperature.

2. The circulating fluidized bed boiler shutdown time prediction system according to claim 1, characterized in that, During the time interval dt, the temperature change ΔT is obtained by solving for the energy change ΔE, using the following formula: ； In the formula, m is the mass of the heat exchange component, and c p Specific heat capacity at constant pressure; In the bed material system module, castable refractory system module, steam-water system module, and pipe wall system module, ΔE represents the energy change of the bed material. b Energy change ΔE of castable refractory c Or the energy change ΔE of the pipe wall t ΔT represents the change in bed material temperature, the change in castable temperature, or the change in steam temperature at the pipe wall outlet, respectively.

3. The circulating fluidized bed boiler shutdown time prediction system according to claim 2, characterized in that: In the bed material system module, the energy change ΔE of the bed material is calculated. b The formula is: ； Q cd,b-b Q is the heat conduction between adjacent bed layers. cd,b-c Q is the heat conduction between the bed material and the castable. r,b-b For radiative heat transfer between adjacent bed layers, Q r,b-c For radiative heat transfer between the bed material and the castable, Q r,b-t For radiative heat exchange between the bed material and the tube wall.

4. The circulating fluidized bed boiler shutdown time prediction system according to claim 2, characterized in that: In the refractory system module, the energy change ΔE of the refractory is calculated. c The formula is: ； Q cd,c-b Q is the heat conduction between the castable and the bed material. cd,c-c Q represents the heat conduction between adjacent layers of castable refractory. cd,c-t Q is the heat conduction between the castable refractory and the pipe wall. r,c-b For radiative heat transfer between the castable and the bed material, Q r,c-t This is for radiative heat exchange between the castable refractory and the pipe wall.

5. The circulating fluidized bed boiler shutdown time prediction system according to claim 2, characterized in that: In the pipe wall system module, solve for the energy change ΔE of the pipe wall. t The formula is: ； Q cv,t-w For convective heat transfer between the working fluid and the tube wall, Q cd,t-c Q is the heat conduction between the pipe wall and the castable refractory. r,t-c For radiative heat transfer between the pipe wall and the castable, Q r,t-b For radiative heat transfer between the tube wall and the bed material, Q r,t-t For radiative heat exchange between the pipe walls.

6. The circulating fluidized bed boiler shut-off time prediction system according to claim 3, 4 or 5, characterized in that: The calculation formulas for each type of convective heat transfer, conductive heat transfer, and radiative heat transfer are as follows: ； k is the heat transfer coefficient, A is the heat transfer area, and ΔT c This refers to the temperature difference between components.

7. The circulating fluidized bed boiler shutdown time prediction system according to claim 2, characterized in that: In the steam-water system module, solve for the energy change ΔE of the working fluid at the feedwater inlet and outlet. w The formula is: 、 ； Q cv,w-t For convective heat transfer between the tube wall and the working fluid side, m w For water supply mass flow rate, c p For the specific heat capacity at constant pressure, ΔT w This represents the temperature difference between the working fluid at the pipe wall outlet and inlet.

8. A method for predicting the shutdown time of a circulating fluidized bed boiler, characterized in that: The circulating fluidized bed boiler shut-off time prediction system according to any one of claims 1-7 includes: Step 1: Obtain boiler structural parameters and fire suppression operation parameters; Step 2: Based on the boiler structural parameters, construct the bed material system module, castable refractory system module, steam-water system module, and tube wall system module; Step 3: Based on the pressure firing operation parameters, calculate the bed material temperature, castable temperature, steam temperature at the outlet of each tube wall, and tube wall temperature; Step four: Based on the bed material temperature, tube outlet steam temperature, and tube wall temperature obtained in step three, determine whether the pressure firing can continue. The process for determining whether the suppression of heat can continue includes: (1) Determine whether the bed material temperature is sufficient for coal ignition; (2) Determine whether the feedwater can be completely evaporated in the water-cooled wall; (3) Determine whether the steam has sufficient superheat at the outlet of the high-temperature superheater / high-temperature reheater tube wall; (4) Determine whether the pipe wall temperature has not exceeded the safety threshold; Based on the above judgment results, if all judgment results are "yes", then return to step three to perform the next time step calculation; if any judgment result is "no", then the fire suppression will terminate, and the time at this time is the maximum fire suppression time of the boiler.

9. The method for predicting the shutdown time of a circulating fluidized bed boiler according to claim 8, characterized in that: In step one, the boiler structural parameters include the depth, width, and height of the furnace, the spatial geometric relationship of each component within the furnace, and the dimensions of each pipe.

10. The method for predicting the shutdown time of a circulating fluidized bed boiler according to claim 8 or 9, characterized in that: In step one, the parameters for fire suppression operation include water supply volume, water supply pressure, water supply temperature, and the temperature of each component before fire suppression.

Images