Circulating fluidized bed boiler slagging pipe blockage degree prediction method based on temperature field

Abstract

This invention belongs to the field of circulating fluidized bed technology for thermal power boilers, specifically relating to a method for predicting the degree of ash discharge pipe blockage in circulating fluidized bed boilers based on temperature field. To address the common problem in current circulating fluidized bed boilers where ash discharge pipe blockage cannot be detected in a timely manner, this invention first establishes a basic online prediction model for the degree of ash discharge pipe blockage based on the temperature field distribution characteristics under different blockage levels. Then, the model is corrected for ambient temperature, bed temperature, and boiler load. Finally, the model's boundary conditions are checked. By inputting the temperatures of the upper and lower walls at the ash discharge pipe inlet into the model, the predicted degree of ash discharge pipe blockage can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of circulating fluidized bed technology for thermal power boilers, specifically relating to a method for predicting the degree of blockage in the ash discharge pipe of a circulating fluidized bed boiler based on a temperature field. Background Technology

[0002] Circulating fluidized bed boilers frequently experience ash discharge pipe blockage during operation, preventing ash from being discharged smoothly from the furnace and posing a significant threat to the boiler's stable operation. Currently, there is no effective method to predict the blockage status of the ash discharge pipe. Only after approximately 30 minutes of complete blockage can the temperature difference between the inlet and outlet water temperatures of the ash cooler be used to determine if the pipe is completely blocked. This significant delay in assessment means that the blockage cannot be addressed promptly. During this period, the boiler cannot discharge ash normally, and the working fluid in the ash cooler cannot be heated properly, reducing the thermal efficiency of the system.

[0003] Therefore, developing an online prediction method for the blockage status of the ash discharge pipe in a circulating fluidized bed boiler has very important practical significance. Summary of the Invention

[0004] To address the common problem of delayed detection of ash blockage in circulating fluidized bed boilers, this invention provides an advanced and computationally simple method for predicting the degree of ash blockage in circulating fluidized bed boiler ash pipes based on a temperature field. This invention can detect blockage in its early stages, allowing for timely notification of relevant personnel to address the issue and preventing complete blockage. This ensures continuous and stable boiler operation and sustained normal heating of the working fluid in the ash cooler.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A method for predicting the degree of blockage in the ash discharge pipe of a circulating fluidized bed boiler based on the temperature field includes the following steps:

[0007] Step 1: Based on the temperature field distribution characteristics under different degrees of blockage in the slag discharge pipe, establish a basic online prediction model for the degree of blockage in the slag discharge pipe;

[0008] Step 2: Correct the established basic model for online prediction of slag pipe blockage degree based on ambient temperature, bed temperature and boiler load.

[0009] Step 3: Input the temperatures of the upper and lower walls at the inlet of the slag pipe into the modified online prediction model for the degree of slag pipe blockage to obtain the predicted degree of slag pipe blockage.

[0010] Compared with existing technologies, the beneficial effects of the above solution are as follows:

[0011] 1. This invention features a novel principle. Details are as follows: The basic principle of this invention is: when no ash or slag deposition occurs inside the pipe, such as... Figure 2 As shown, at this time, the heat of the high-temperature flue gas inside the pipe is evenly transferred to the inner wall of the slag discharge pipe through forced convection, and then evenly transferred from the inner wall to the outer wall. At this point, the temperature distribution on the outer wall of the slag discharge pipe is uniform. However, when ash and slag deposits inside the slag discharge pipe, such as... Figure 3 As shown, the deposited ash introduces additional thermal resistance and hinders direct forced convection heat transfer from the high-temperature flue gas to the inner wall of the pipe. Due to the low thermal conductivity of the ash, its deposition significantly increases the thermal resistance between the flue gas and the pipe wall, thus reducing heat transfer in the ash-deposited area. Consequently, the temperature distribution on the outer wall of the pipe is no longer uniform, exhibiting a decrease in wall temperature in the ash-deposited area and a relatively constant wall temperature in the ash-free area. It should be noted that different ash layer thicknesses result in different thermal resistances, leading to varying degrees of unevenness in the pipe wall temperature distribution. Therefore, the thickness of the ash layer can be inferred from the temperature distribution on the outer wall of the pipe, thereby calculating the degree of blockage.

[0012] 2. This invention can eliminate ash discharge pipe blockage in its early stages, thus preventing complete blockage. Details are as follows: The temperature difference between the upper and lower walls of the ash discharge pipe is closely related to the degree of blockage; different temperature differences reflect different degrees of blockage. Therefore, by closely monitoring the temperature difference between the upper and lower walls of the ash discharge pipe and using the aforementioned model for calculation, the blockage situation within the ash discharge pipe can be calculated online. This allows for timely detection and treatment of ash blockage in its early stages, ultimately eliminating the blockage in its initial stages and preventing the boiler from being unable to continuously discharge ash due to complete blockage of the ash discharge pipe.

[0013] 3. This invention features high computational accuracy. Details are as follows: This invention not only establishes a basic mathematical model relating the temperature difference between the upper and lower walls of the slag discharge pipe and the degree of blockage, but also corrects the basic model for ambient temperature, bed temperature, and boiler load, encompassing all major factors affecting the temperature difference between the upper and lower walls of the slag discharge pipe. Furthermore, it establishes boundary conditions for the model. Therefore, this invention considers all factors and possesses high computational accuracy.

[0014] Furthermore, step 1 specifically includes:

[0015] The temperature distribution of the slag discharge pipe was simulated when the blockage level was 0%, and the accuracy of the simulation results was verified by using the true values ​​obtained from actual temperature measurement points. If the error of the simulation results was large, the parameter settings of the simulation software model were adjusted until the error of the simulation results was less than 5%.

[0016] After the simulation results for the 0% blockage condition are satisfactory, simulations for other blockage conditions will be performed.

[0017] Based on the temperature field distribution characteristics under different degrees of blockage, the temperature difference between the upper and lower walls of the slag discharge pipe corresponding to different degrees of blockage was calculated, and multiple sets of temperature difference data were obtained.

[0018] Multiple fitting methods were used to fit the obtained temperature difference data, and the fitting results were accurately verified. The fitting method with the highest accuracy was selected, and the following fitting results were finally obtained:

[0019] y≈-0.000003(T1-T2) 2 +0.0034(T1-T2)+0.002;

[0020] Where T1 is the temperature of the upper wall at the inlet of the slag discharge pipe, T2 is the temperature of the lower wall at the inlet of the slag discharge pipe, and y is the degree of blockage of the slag discharge pipe.

[0021] Compared with existing technologies, the beneficial effects of the above solution are as follows:

[0022] 1. The basic model derived in this invention has the advantages of accurate calculation and simple equations. Details are as follows: (1) The model is obtained by fitting multiple sets of data and the accuracy has been confirmed. The maximum deviation is 1.35%, which is within the acceptable range for engineering applications. (2) The model is simple to calculate. For example, assuming T1=830℃ and T2=800℃, substituting into Equation 1, we can calculate y≈48%, which means that the slag pipe is blocked by about 48% under this working condition.

[0023] 2. The data required for fitting the basic model are obtained through simulation under certain premises, as detailed below: ambient temperature T3 = 40℃, boiler dense phase zone bed temperature T4 = 850℃, and boiler load Q = 100%.

[0024] Furthermore, step 2 specifically includes:

[0025] Taking the average degree of blockage as the operating condition, the ambient temperature was changed alone while other parameters remained constant. Temperature distribution cloud maps of the slag discharge pipe corresponding to different ambient temperatures were simulated. The temperature difference between the upper and lower walls of the slag discharge pipe at different ambient temperatures was then calculated, and the ratio of this temperature difference to the baseline operating condition was determined. Multiple sets of data were obtained, and various methods were used to fit these data. The fitting results were then precisely verified, and the fitting method with the highest accuracy was selected. The final fitting results are as follows:

[0026] k1≈0.0003(T3-40) 2 +0.018 (T3-40) +1.0;

[0027] Where T3 is the ambient temperature at the slag discharge pipe;

[0028] Compared with existing technologies, the beneficial effects of the above solution are as follows:

[0029] 1. Explanation of the necessity of ambient temperature correction: The temperature difference between the upper and lower walls of the slag discharge pipe is caused by different heat dissipation conditions. Since ambient temperature has a certain impact on the heat dissipation of the pipe, it is necessary to correct the impact of changes in ambient temperature on the temperature difference between the upper and lower walls of the slag discharge pipe.

[0030] 2. The environmental temperature correction coefficient equation derived in this invention has the advantages of accurate calculation and simple form. It is detailed as follows: (1) The equation is obtained by fitting multiple sets of data and the accuracy has been confirmed. The maximum deviation is 1.33%, which is within the acceptable range for engineering applications. (2) The equation is simple to calculate. For example, if T1=830℃, T2=800℃, and T3=45℃, first substitute T3=45℃ into the equation to calculate the environmental temperature correction coefficient k1≈1.08. Then substitute the T1 value, T2 value and k1 value into the equation to calculate y≈50%, which means that the slag pipe is blocked by about 50% under this working condition.

[0031] Taking the average degree of blockage as the operating condition, the bed temperature was changed alone while other parameters remained constant. Temperature distribution cloud maps of the slag discharge pipe corresponding to different bed temperatures were simulated. The temperature difference between the upper and lower walls of the slag discharge pipe at different bed temperatures was then calculated, and the ratio of this temperature difference to the baseline operating condition was determined. Multiple data points were obtained, and various methods were used to fit these data. The fitting results were then precisely verified, and the fitting method with the highest accuracy was selected. The following fitting results were finally obtained:

[0032] k2≈-0.000025(T4-850) 2 +0.0012 (T4-850) +1.002;

[0033] Among them, T4 is the bed temperature in the dense phase zone of the boiler;

[0034] Compared with existing technologies, the beneficial effects of the above solution are as follows:

[0035] 1. Explanation of the necessity of correcting the bed temperature in the dense phase zone of the boiler: Ash and slag flow from the dense phase zone of the boiler into the slag discharge pipe. Therefore, the temperature of the dense phase zone will inevitably affect the temperature of the ash and slag, and the change in the temperature of the ash and slag will inevitably affect the wall temperature of the slag discharge pipe. Therefore, it is necessary to correct the influence of the bed temperature in the dense phase zone on the temperature difference of the slag discharge pipe wall.

[0036] 2. The bed temperature correction coefficient equation derived in this invention has the advantages of accurate calculation and simple form. It is detailed as follows: (1) The equation is obtained by fitting multiple sets of data and the accuracy has been confirmed. The maximum deviation is 0.8%, which is within the acceptable range for engineering applications. (2) The equation is simple to calculate. For example, assuming T1=830℃, T2=800℃, T3=45℃, T4=880℃, firstly, T3=45℃ is substituted into the equation to calculate the ambient temperature correction coefficient k1≈1.08. Then, T4=880℃ is substituted into the equation to calculate the bed temperature correction coefficient k2=1.07. Finally, the values ​​of T1, T2, k1 and k2 are substituted into the equation to calculate y≈51%, which means that the slag pipe is blocked by about 51% at this time.

[0037] Taking the average degree of blockage as the operating condition, the boiler load was changed alone while other parameters remained constant. Temperature distribution cloud maps of the ash discharge pipe corresponding to different boiler loads were simulated, and the temperature difference between the upper and lower walls of the ash discharge pipe corresponding to different boiler loads was calculated. The ratio of this temperature difference to the temperature difference between the upper and lower walls of the ash discharge pipe under the baseline operating condition was obtained. Multiple sets of data were obtained, and various methods were used to fit these data. The fitting results were then accurately verified, and the fitting method with the highest accuracy was selected. The final fitting results are as follows:

[0038] k3≈-0.45(Q-1) 2 -1.15(Q-1)+1.0;

[0039] Where Q represents the boiler load percentage;

[0040] Compared with existing technologies, the beneficial effects of the above solution are as follows:

[0041] 1. Necessity of Boiler Load Correction: When the boiler load changes, the coal feed rate changes synchronously, resulting in a corresponding change in the amount of ash and slag generated from coal combustion. Consequently, the amount of ash and slag flowing into the ash discharge pipe also changes with the boiler load. This change in the mass flow rate of the ash and slag leads to a change in the total heat carried by the ash and slag. The total heat of the ash and slag inevitably affects the wall temperature of the ash discharge pipe, therefore, it is necessary to correct for the impact of boiler load on the temperature difference of the ash discharge pipe wall.

[0042] 2. The boiler load correction coefficient equation derived in this invention has the advantages of accurate calculation and simple form. It is detailed as follows: (1) The equation is obtained by fitting multiple sets of data and the accuracy has been confirmed. The maximum deviation is 1%, which is within the acceptable range for engineering applications. (2) The equation is simple to calculate. For example, as follows: Assuming T1=830℃, T2=800℃, T3=45℃, T4=880℃, and Q=80%, firstly, T3=45℃ is substituted into the equation to calculate the ambient temperature correction coefficient k1≈1.08. Then, T4=880℃ is substituted into the equation to calculate the bed temperature correction coefficient k2=1.07. Next, Q=80% is substituted into the equation to calculate the boiler load correction coefficient k3=1.2. Finally, the values ​​of T1, T2, k1, k2 and k3 are substituted into the equation to calculate y≈55%, which means that the slag pipe is blocked by about 55% at this time.

[0043] The revised basic model for online prediction of slag discharge pipe blockage is as follows:

[0044] y≈-0.000003[(T1-T2) k1 k2 k3] 2 +0.0034(T1-T2)+0.002.

[0045] Where k1 is the ambient temperature correction coefficient, k2 is the bed temperature correction coefficient, and k3 is the boiler load correction coefficient.

[0046] Furthermore, the method also includes: verifying the boundary conditions of the modified basic model for online prediction of the degree of blockage of the slag pipe based on the temperature of the dense phase region and the temperature of the upper wall surface of the slag pipe;

[0047] When the degree of blockage in the slag discharge pipe is y=0, the temperature of the dense phase region and the temperature of the upper wall surface of the slag discharge pipe are measured, and the reference value ΔT is calculated. y=0 ;

[0048] Under arbitrary operating conditions of the slag discharge pipe, the real-time temperature of the dense phase region and the temperature of the upper wall surface of the slag discharge pipe were measured, and ΔT was calculated. 实时 ;

[0049] Based on the temperature fluctuation at the measuring point, a correction coefficient k is set. If ΔT 实时 ≥ΔT y=0 +k indicates that the slag discharge pipe is 100% completely blocked.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] The purpose of setting the boundary conditions is to prevent calculation errors in the model: the model calculates the degree of blockage based on the temperature difference between the upper and lower walls of the slag discharge pipe; that is, the greater the temperature difference, the higher the calculated degree of blockage. However, when the slag discharge pipe is completely blocked, since no hot slag flows through, the temperature of all surfaces of the slag discharge pipe will decrease, leading to a gradual decrease in the temperature difference between the upper and lower walls until they are completely identical. During this process, the model will calculate a decreasing degree of blockage, which is completely opposite to the actual situation. Therefore, appropriate boundary conditions must be set for correction. This method uses the temperature difference between the dense phase zone temperature T4 and the upper wall temperature T1 of the slag discharge pipe for constraint correction. The basic idea is: when the slag discharge pipe is operating normally (i.e., under the condition of blockage degree y=0), the dense phase zone temperature T4 and the upper wall temperature T1 of the slag discharge pipe are measured, and ΔT is calculated. y=0 =T4-T1; However, when the slag discharge pipe is completely blocked, the temperature T4 in the dense phase region remains unchanged, while the temperature T1 on the upper wall of the slag discharge pipe gradually decreases due to the lack of hot slag flow. Therefore, ΔT y=1 >ΔT y=0 Therefore, theoretically, as long as ΔT occurs... 实时 >ΔT y=0 The critical state can be used to determine that the slag pipe is 100% blocked. However, in practice, to prevent misjudgment, a correction constant k is added, that is, when ΔT 实时 ≥ΔT y=0 When k is greater than 1, it can be determined that y = 100%. Attached Figure Description

[0052] Figure 1 This is a flowchart of the present invention;

[0053] Figure 2 This is a schematic diagram of the normal operation of the slag discharge pipe of the present invention (without ash deposition).

[0054] Figure 3 This is a schematic diagram of ash deposition inside the slag discharge pipe of the present invention;

[0055] Figure 4 This is a numerical simulation temperature field distribution cloud map of the slag discharge pipe of the present invention (blockage area 0%).

[0056] Figure 5 This is a numerical simulation temperature field distribution cloud map of the slag discharge pipe of the present invention (blockage area 20%).

[0057] Figure 6 This is a numerical simulation temperature field distribution cloud map of the slag discharge pipe of the present invention (blockage area 40%).

[0058] Figure 7 This is a numerical simulation temperature field distribution cloud map of the slag discharge pipe of the present invention (blockage area 60%).

[0059] Figure 8This is a numerical simulation temperature field distribution cloud map of the slag discharge pipe of the present invention (blockage area 80%). Detailed Implementation

[0060] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0061] like Figure 1 As shown in this embodiment, the method for predicting the degree of blockage in the ash discharge pipe of a circulating fluidized bed boiler based on the temperature field includes the following steps:

[0062] Step 1: Based on the temperature field distribution characteristics under different degrees of blockage in the slag discharge pipe, establish a basic online prediction model for the degree of blockage in the slag discharge pipe.

[0063] Step 2: Correct the established basic model for online prediction of slag pipe blockage degree by ambient temperature.

[0064] Step 3: Perform bed temperature correction on the basic online prediction model for the degree of blockage in the slag discharge pipe, which is based on ambient temperature correction.

[0065] Step 4: Perform boiler load correction on the basic online prediction model for the degree of slag pipe blockage with bed temperature correction.

[0066] Step 5: Based on the temperature of the dense phase zone and the temperature of the upper wall of the slag discharge pipe, perform boundary condition verification on the modified basic model for online prediction of slag discharge pipe blockage degree.

[0067] Finally, the temperatures of the upper and lower walls at the inlet of the slag pipe are input into the modified online prediction model for the degree of slag pipe blockage to obtain the predicted degree of slag pipe blockage.

[0068] (1) The specific implementation of establishing a basic model for online prediction of the degree of blockage in the slag discharge pipe is as follows:

[0069] The heat transfer process and temperature field distribution within the slag discharge pipe were simulated using FLUENT software. Specifically, a 1:1 model was established using the slag discharge pipe of a 300MW circulating fluidized bed as a prototype. ANSYS ICEM was used for mesh generation, employing a combination of structured and unstructured meshes. Local mesh refinement was applied in the airflow turning region to ensure computational accuracy near the wall. The mesh's Orthogonal Quality > 0.6, Skewness < 0.5, and Aspect Ratio < 5. An initial mesh size of approximately 300,000 elements was used, and mesh independence was verified with mesh sizes of 400,000, 500,000, 600,000, 700,000, and 800,000 elements. Finally, considering both computational accuracy and cost, a mesh size of 700,000 elements was selected. A standard turbulence model was used. The SIMPLE algorithm was used for pressure-velocity coupling in the model. The transport of ash and its impact on the flow field were simulated using a discrete phase model (DPM), with radiation using the P1 model and convection using a second-order upwind discretization scheme. Some key boundary conditions were set as follows: ambient temperature at the ash discharge pipe T3 = 40℃, bed temperature in the dense phase zone of the boiler T4 = 850℃, and boiler load Q = 100%.

[0070] First, simulate the temperature distribution of the slag discharge pipe under the condition that there is no blockage (i.e., the degree of blockage is 0%), and use the true value obtained from the actual temperature measurement point to verify the accuracy of the simulation results. If the error of the simulation results is large, continue to adjust the parameter settings of the FLUENT software model until the error of the simulation results is less than 5%.

[0071] After the simulation results for the 0% blockage condition are satisfactory, simulations for other conditions (i.e., blockage levels of 20%, 40%, 60%, and 80%) are completed.

[0072] The final simulation results are as follows Figures 4-8 As shown.

[0073] Based on the temperature field distribution characteristics under different blockage levels (0%, 20%, 40%, 60%, and 80%, respectively), the temperature difference between the upper and lower walls of the slag discharge pipe corresponding to different blockage levels was calculated, and a total of 5 sets of data were obtained (T1-T2=0, y=0), (T1-T2=35, y=0.2), (T1-T2=80, y=0.4), (T1-T2=160, y=0.6); (T1-T2=250, y=0.8).

[0074] The above data were fitted using various mathematical methods (quadratic function fitting, linear fitting, cubic polynomial fitting, exponential function fitting, and logarithmic function fitting), and the fitting results were precisely verified. The fitting method with the highest accuracy was selected, and the following fitting results were finally obtained:

[0075] y≈-0.000003(T1-T2) 2 +0.0034(T1-T2)+0.002 Equation 1.

[0076] Substitute the above 5 sets of data into Equation 1 to verify the fitting accuracy of the equation:

[0077] When T1-T2=0, y=0.002, and the absolute error is 0.002 compared with the true value y=0%.

[0078] When T1-T2=35, y=0.1973, compared with the true value y=20%, the absolute error is 0.0027, and the relative error is 1.35%.

[0079] When T1-T2=80, y=0.3948, compared with the true value y=40%, the absolute error is 0.0052, and the relative error is 1.35%.

[0080] When T1-T2=160, y=0.5992, compared with the true value y=60%, the absolute error is 0.002, and the relative error is 0.13%.

[0081] When T1-T2=250, y=0.7945, compared with the true value y=80%, the absolute error is 0.0055, and the relative error is 0.688%.

[0082] Therefore, the error of Equation 1 is no greater than 1.35%.

[0083] (2) The specific implementation of environmental temperature correction for the established basic model for online prediction of slag pipe blockage is as follows:

[0084] The operating condition where the degree of blockage is taken as the average is... Figure 6 The operating condition shown, with a blockage rate of 40%, is the basic operating condition (ambient temperature T3 = 40℃). The ambient temperature is individually changed to 30℃, 35℃, 45℃, and 50℃, while other parameters remain constant. Temperature distribution cloud maps of the slag discharge pipe corresponding to different ambient temperatures are simulated, and the temperature difference between the upper and lower walls of the slag discharge pipe corresponding to different ambient temperatures is calculated. Then, the comparison with the baseline operating condition (i.e.,...) is obtained. Figure 6 The ratio of the temperature difference between the upper and lower walls of the slag discharge pipe under the working condition shown was used to obtain 5 sets of data (T3-40=-10, k1=0.75), (T3-40=-5, k1=0.90), (T3-40=0, k1=1.00), (T3-40=5, k1=1.08), and (T3-40=10, k1=1.13).

[0085] The above data were fitted using various mathematical methods (quadratic function fitting, linear fitting, cubic polynomial fitting, exponential function fitting, and logarithmic function fitting), and the fitting results were precisely verified. The fitting method with the highest accuracy was selected, and the following fitting results were finally obtained:

[0086] k1≈0.0003(T3-40) 2 +0.018(T3-40)+1.0 Equation 3.

[0087] Substitute the above 5 sets of data into Equation 3 to verify the fitting accuracy of the equation:

[0088] When T3-40=-10, k1=0.74, compared with the true value k1=0.75, the absolute error is 0.01, and the relative error is 1.33%;

[0089] When T3-40=-5, k1=0.895, compared with the true value k1=0.90, the absolute error is 0.005 and the relative error is 0.56%;

[0090] When T3-40=0, k1=1.00, and compared with the true value k1=1.00, the absolute error is 0.00 and the relative error is 0.00%.

[0091] When T3-40=5, k1=1.075, compared with the true value k1=1.08, the absolute error is 0.005, and the relative error is 0.46%;

[0092] When T3-40=10, k1=1.13, compared with the true value k1=1.13, the absolute error is 0.00 and the relative error is 0.00%;

[0093] Therefore, the error of equation 3 is no greater than 1.33%.

[0094] Equation 2 is obtained by correcting Equation 1 for ambient temperature:

[0095] y≈-0.000003[(T1-T2) k1] 2 +0.0034(T1-T2)+0.002 Equation 2.

[0096] (3) The specific implementation of bed temperature correction for the basic model for online prediction of slag pipe blockage degree based on ambient temperature correction is as follows:

[0097] The operating condition where the degree of blockage is taken as the average is... Figure 6 The operating condition shown is a 40% blockage level as the basic operating condition (the dense phase zone bed temperature T4 = 850℃). The bed temperature was individually changed to 790℃, 820℃, 880℃, 910℃, and 940℃, while other parameters remained constant. Temperature distribution cloud maps of the slag discharge pipe corresponding to different bed temperatures were simulated, and the temperature difference between the upper and lower walls of the slag discharge pipe corresponding to different bed temperatures was calculated. Then, the comparison with the baseline operating condition (i.e.,...) was determined. Figure 6 The ratio of the temperature difference between the upper and lower walls of the slag discharge pipe under the working condition shown was used to obtain 6 sets of data (T4-850=-60, k2=1.25), (T4-850=-30, k2=1.10), (T4-850=0, k2=1.00), (T4-850=30, k2=1.07), (T4-850=60, k2=1.12), (T4-850=90, k2=1.15).

[0098] The above data were fitted using various mathematical methods (quadratic function fitting, linear fitting, cubic polynomial fitting, exponential function fitting, and logarithmic function fitting), and the fitting results were precisely verified. The fitting method with the highest accuracy was selected, and the following fitting results were finally obtained:

[0099] k2≈-0.000025(T4-850) 2 +0.0012(T4-850)+1.002 Equation 5.

[0100] Substitute the above 6 sets of data into Equation 5 to verify the fitting accuracy of the equation:

[0101] When T4-850=-60, k2=1.24, compared with the true value k2=1.25, the absolute error is 0.01, and the relative error is 0.8%;

[0102] When T4-850=-30, k2=1.09, compared with the true value k2=1.10, the absolute error is 0.01 and the relative error is 0.59%;

[0103] When T4-850=0, k2=1.002, compared with the true value k2=1.00, the absolute error is 0.002 and the relative error is 0.20%;

[0104] When T4-850=30, k2=1.06, compared with the true value k2=1.07, the absolute error is 0.01 and the relative error is 0.42%;

[0105] When T4-850=60, k2=1.124, compared with the true value k2=1.12, the absolute error is 0.004, and the relative error is 0.36%;

[0106] When T4-850=90, k2=1.147, compared with the true value k2=1.15, the absolute error is 0.003, and the relative error is 0.22%;

[0107] Therefore, the error of Equation 5 is no greater than 0.8%.

[0108] Equation 4 is obtained by correcting Equation 2 for bed temperature:

[0109] y≈-0.000003[(T1-T2) k1] 2 +0.0034(T1-T2)+0.002 Equation 4.

[0110] (4) The specific implementation of boiler load correction for the basic model of online prediction of slag pipe blockage degree with bed temperature correction is as follows:

[0111] The operating condition where the degree of blockage is taken as the average is... Figure 6The 40% blockage level shown is the basic operating condition (boiler load Q=100%). The boiler load is individually changed to 40%, 60%, and 80%, while other parameters remain constant. Temperature distribution cloud maps of the ash discharge pipe corresponding to different boiler loads are simulated, and the temperature difference between the upper and lower walls of the ash discharge pipe corresponding to different boiler loads is calculated. Then, the temperature difference is compared with the baseline operating condition (i.e.,...). Figure 6 The ratio of the temperature difference between the upper and lower walls of the slag discharge pipe under the working condition shown was used to obtain 6 sets of data (Q-1=-0.6, k3=1.45), (Q-1=-0.4, k3=1.35), (Q-1=0.2, k3=1.20), and (Q-1=0, k3=1.00).

[0112] The above data were fitted using various mathematical methods (quadratic function fitting, linear fitting, cubic polynomial fitting, exponential function fitting, and logarithmic function fitting), and the fitting results were precisely verified. The fitting method with the highest accuracy was selected, and the following fitting results were finally obtained:

[0113] k3≈-0.45(Q-1) 2 -1.15(Q-1)+1.0 Equation 7.

[0114] Substitute the above four sets of data into Equation 7 to verify the fitting accuracy of the equation:

[0115] When Q-1=-0.6, k3=1.448, compared with the true value k3=1.45, the absolute error is 0.002 and the relative error is 0.138%;

[0116] When Q-1=-0.4, k3=1.348, compared with the true value k3=1.35, the absolute error is 0.002 and the relative error is 0.148%;

[0117] When Q-1=-0.2, k3=1.192, compared with the true value k3=1.20, the absolute error is 0.008 and the relative error is 0.667%;

[0118] When Q-1=0, k3=0.99, compared with the true value k3=1.00, the absolute error is 0.01 and the relative error is 1%.

[0119] Therefore, the error of equation 7 is no greater than 1%.

[0120] Equation 6 is obtained by correcting Equation 4 for bed temperature:

[0121] y≈-0.000003[(T1-T2) k1 k2 k3] 2 +0.0034(T1-T2)+0.002 Equation 6.

[0122] (5) The specific implementation of boundary condition verification for the modified basic model for online prediction of slag pipe blockage degree based on the temperature of the dense phase zone and the temperature of the upper wall of the slag pipe is as follows:

[0123] First, when the slag discharge pipe is operating normally (i.e., under the condition of 0% blockage), the temperature T4 in the dense phase region and the temperature T1 on the upper wall of the slag discharge pipe are measured, and the reference value ΔT is calculated. y=0 =T4-T1; Secondly, under any operating condition of the slag discharge pipe, the real-time temperature T4 of the dense phase region and the temperature T1 of the upper wall of the slag discharge pipe are measured, and ΔT is calculated. 实时 =T4-T1; Next, based on the temperature fluctuation at the measuring point, set the correction coefficient k, typically with a value ranging from 5℃ to 10℃; Finally, if ΔT 实时 ≥ΔT y=0 +k indicates that the slag discharge pipe is 100% completely blocked.

[0124] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0125] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for predicting the degree of blockage in the ash discharge pipe of a circulating fluidized bed boiler based on a temperature field, characterized in that, Includes the following steps: Step 1: Based on the temperature field distribution characteristics under different degrees of blockage in the slag discharge pipe, establish a basic online prediction model for the degree of blockage in the slag discharge pipe; Step 2: Correct the established basic model for online prediction of slag pipe blockage degree based on ambient temperature, bed temperature and boiler load. Step 3: Input the temperatures of the upper and lower walls at the inlet of the slag pipe into the modified online prediction model for the degree of slag pipe blockage to obtain the predicted degree of slag pipe blockage.

2. The method for predicting the degree of blockage in the ash discharge pipe of a circulating fluidized bed boiler based on a temperature field, as described in claim 1, is characterized in that... Step 1 specifically involves: The temperature distribution of the slag discharge pipe was simulated when the blockage level was 0%, and the accuracy of the simulation results was verified by using the true values ​​obtained from actual temperature measurement points. If the error of the simulation results was large, the parameter settings of the simulation software model were adjusted until the error of the simulation results was less than 5%. After the simulation results for the 0% blockage condition are satisfactory, simulations for other blockage conditions will be performed. Based on the temperature field distribution characteristics under different degrees of blockage, the temperature difference between the upper and lower walls of the slag discharge pipe corresponding to different degrees of blockage was calculated, and multiple sets of temperature difference data were obtained. Multiple fitting methods were used to fit the obtained temperature difference data, and the fitting results were accurately verified. The fitting method with the highest accuracy was selected, and the following fitting results were finally obtained: y ~ -0.000003(T1-T2) 2 +0.0034(T1-T2)+0.002; Where T1 is the temperature of the upper wall at the inlet of the slag discharge pipe, T2 is the temperature of the lower wall at the inlet of the slag discharge pipe, and y is the degree of blockage of the slag discharge pipe.

3. The method for predicting the degree of blockage in the ash discharge pipe of a circulating fluidized bed boiler based on a temperature field, as described in claim 2, is characterized in that... Step 2 specifically involves: Taking the average degree of blockage as the operating condition, the ambient temperature was changed alone while other parameters remained constant. Temperature distribution cloud maps of the slag discharge pipe corresponding to different ambient temperatures were simulated. The temperature difference between the upper and lower walls of the slag discharge pipe at different ambient temperatures was then calculated, and the ratio of this temperature difference to the baseline operating condition was determined. Multiple sets of data were obtained, and various methods were used to fit these data. The fitting results were then precisely verified, and the fitting method with the highest accuracy was selected. The final fitting results are as follows: k1= 0.0003 (T3-40) 2 +0.018 (T3-40) + 1.0; Where T3 is the ambient temperature at the slag discharge pipe; Taking the average degree of blockage as the operating condition, the bed temperature was changed alone while other parameters remained constant. Temperature distribution cloud maps of the slag discharge pipe corresponding to different bed temperatures were simulated. The temperature difference between the upper and lower walls of the slag discharge pipe at different bed temperatures was then calculated, and the ratio of this temperature difference to the baseline operating condition was determined. Multiple data points were obtained, and various methods were used to fit these data. The fitting results were then precisely verified, and the fitting method with the highest accuracy was selected. The following fitting results were finally obtained: k2= -0.000025 (T4-850) 2 +0.0012 (T4-850) + 1.002; Among them, T4 is the bed temperature in the dense phase zone of the boiler; Taking the average degree of blockage as the operating condition, the boiler load was changed alone while other parameters remained constant. Temperature distribution cloud maps of the ash discharge pipe corresponding to different boiler loads were simulated, and the temperature difference between the upper and lower walls of the ash discharge pipe corresponding to different boiler loads was calculated. The ratio of this temperature difference to the temperature difference between the upper and lower walls of the ash discharge pipe under the baseline operating condition was obtained. Multiple sets of data were obtained, and various methods were used to fit these data. The fitting results were then accurately verified, and the fitting method with the highest accuracy was selected. The final fitting results are as follows: k3≈-0.45(Q-1) 2 -1.15(Q-1)+1.0; Where Q represents the boiler load percentage; The revised basic model for online prediction of slag discharge pipe blockage is as follows: y≈-0.000003[(T1-T2) k1 k2 k3] 2 +0.0034(T1-T2)+0.002; Where k1 is the ambient temperature correction coefficient, k2 is the bed temperature correction coefficient, and k3 is the boiler load correction coefficient.

4. The method for predicting the degree of blockage in the ash discharge pipe of a circulating fluidized bed boiler based on a temperature field, as described in claim 3, is characterized in that... The method further includes: verifying the boundary conditions of the modified basic model for online prediction of the degree of blockage of the slag pipe based on the temperature of the dense phase zone and the temperature of the upper wall of the slag pipe; When the degree of blockage in the slag discharge pipe is y=0, the temperature of the dense phase region and the temperature of the upper wall surface of the slag discharge pipe are measured, and the reference value ΔT is calculated. y=0 ; Under arbitrary operating conditions of the slag discharge pipe, the real-time temperature of the dense phase region and the temperature of the upper wall surface of the slag discharge pipe were measured, and ΔT was calculated. 实时 ; Based on the temperature fluctuation at the measuring point, a correction coefficient k is set. If ΔT 实时 ≥ΔT y=0 +k indicates that the slag discharge pipe is 100% completely blocked.

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