Supercritical carbon dioxide boiler furnace thermal analysis method

Abstract

This invention relates to the field of boiler furnace thermal analysis, specifically to a method for thermal analysis of a supercritical carbon dioxide boiler furnace. This method sequentially performs iterative thermal analysis of the maximum heat release zone, the intermediate zone, and the furnace outlet zone. The iterative thermal analysis includes iterative analysis of the average outer wall temperature parameters of the furnace heating surface and the outlet flue gas temperature parameters. This application considers the influence of the average outer wall temperature on radiative heat transfer during the iterative thermal analysis process; simultaneously, it considers the influence of convective heat transfer to calculate the heat transfer between the furnace flue gas and the heating surface. Compared with traditional methods, this invention is applicable to various operating conditions such as air combustion, flue gas recirculation, and oxygen-enriched combustion, and has higher accuracy, providing a reliable basis for selecting suitable steel and ensuring a reasonable furnace structure.

Description

Technical Field

[0001] This invention relates to the field of boiler furnace thermal analysis, and specifically to a method for thermal analysis of supercritical carbon dioxide boiler furnaces. Background Technology

[0002] Accurate boiler thermal calculations can determine the relationship between the boiler's various heating surfaces and the parameters of combustion products and working fluid, which is of great significance for boiler design, production, and operation. Supercritical carbon dioxide boilers are one of the key pieces of equipment in supercritical carbon dioxide power generation technology. Because the working fluid in supercritical carbon dioxide boilers differs from that in traditional water boilers, and changes in the working fluid can lead to significant changes in boiler design, traditional thermal calculation methods for water boilers are not applicable to supercritical carbon dioxide boilers. Currently, there is a lack of thermal calculation methods specifically for supercritical carbon dioxide boilers.

[0003] As described in patents such as ZL202010986243.2, ZL202010377111.X, and ZL201910457553.2, the furnace wall temperature of a supercritical carbon dioxide boiler will rise by approximately 200°C, necessitating the introduction of flue gas recirculation to address the excessively high furnace wall temperature. However, both the increased wall temperature and the introduction of flue gas recirculation lead to a decrease in radiative heat transfer and an increase in convective heat transfer within the furnace. Existing furnace thermal calculation methods only consider radiative heat transfer and ignore the influence of wall temperature. This assumption may introduce significant errors when calculating the furnace of a supercritical carbon dioxide boiler. When there are significant errors in the thermal calculations, reliable data such as heat load and outlet flue gas temperature cannot be obtained, making it difficult to determine the rationality of the furnace structure and select suitable steel. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for thermal analysis of the furnace of a supercritical carbon dioxide boiler, which can accurately analyze the thermal distribution of the supercritical carbon dioxide boiler and provide a reliable basis for selecting suitable steel.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: a method for thermal analysis of the furnace of a supercritical carbon dioxide boiler.

[0006] The supercritical carbon dioxide boiler furnace to be analyzed is divided into multiple zones along the flue gas travel direction. The last zone immediately adjacent to the furnace outlet is designated as the furnace outlet zone, which does not include the screen-type superheater. It is determined whether the supercritical carbon dioxide boiler has an ash hopper. If so, the first zone is designated as the zone where the ash hopper is located, which is called the ash hopper zone. The second zone immediately adjacent to the ash hopper zone is designated as the maximum heat release zone. If not, the maximum heat release zone is the first zone. In addition, the zone located between the maximum heat release zone and the furnace outlet zone is the intermediate zone, and there are zero or one or more intermediate zones between the maximum heat release zone and the furnace outlet zone.

[0007] The supercritical carbon dioxide boiler furnace thermal analysis method includes the following steps.

[0008] S1, set the assumed average outer wall temperature of the furnace heating surface in the maximum heat release zone;

[0009] S2, set the assumed value of the outlet flue gas temperature of the maximum heat release zone;

[0010] S3. Based on the assumed value of the outlet flue gas temperature of the maximum heat release zone, and combined with the effective radiation layer thickness of the furnace and the average thermal efficiency coefficient of the furnace wall in the maximum heat release zone, the furnace emissivity of the maximum heat release zone is calculated.

[0011] S4. Based on the assumed value of the outlet flue gas temperature of the maximum heat release zone, the assumed value of the average outer wall temperature of the furnace heating surface, the average thermal efficiency coefficient of the furnace wall, and the furnace emissivity, and combined with the convective heat transfer coefficient of the flue gas in the maximum heat release zone to the heating surface, the calculated value of the outlet flue gas temperature of the maximum heat release zone is calculated.

[0012] S5, determine whether the difference between the calculated value of the outlet flue gas temperature of the maximum heat release zone and the assumed value of the outlet flue gas temperature is greater than the preset value of the outlet flue gas temperature difference of the maximum heat release zone; if yes, modify the set assumed value of the outlet flue gas temperature of the maximum heat release zone and return to S2 for iterative execution; if no, execute S6.

[0013] S6. After the iterative calculation of the outlet flue gas temperature of the maximum heat release zone is completed, the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated. Based on the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface in the maximum heat release zone is calculated.

[0014] S7: Determine whether the difference between the calculated value of the average outer wall temperature of the furnace heating surface in the maximum heat release zone and the assumed value of the average outer wall temperature of the furnace heating surface is greater than the preset value of the average outer wall temperature difference of the furnace heating surface in the maximum heat release zone; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the maximum heat release zone and return to S1 for iterative execution; if no, the thermal analysis of the maximum heat release zone is completed and S8 is executed.

[0015] S8, determine if there is an ash hopper zone; if yes, calculate the heat absorbed by the heating surface of the ash hopper zone and execute S9; if no, execute S9 directly.

[0016] S9, set the assumed average outer wall temperature of the furnace heating surface in the furnace outlet zone;

[0017] S10, Set the assumed value of the flue gas temperature at the furnace outlet zone;

[0018] S11. Based on the assumed value of the flue gas temperature at the furnace outlet, and combined with the effective radiation layer thickness of the furnace and the average thermal efficiency coefficient of the furnace wall at the furnace outlet, the furnace emissivity at the furnace outlet is calculated.

[0019] S12, determine if an intermediate region exists; if yes, execute S13 to S24 in sequence; if no, execute S21 to S24 in sequence.

[0020] S13. Based on the furnace emissivity of the maximum heat release zone and the furnace emissivity of the furnace outlet zone, the furnace emissivity of each intermediate zone is calculated using the linear difference method.

[0021] S14, Set the assumed average outer wall temperature of the furnace heating surface in the current intermediate zone;

[0022] S15, Set the assumed value of the current outlet flue gas temperature in the intermediate zone;

[0023] S16. Based on the assumed value of the outlet flue gas temperature of the current intermediate zone, the assumed value of the average outer wall temperature of the furnace heating surface, and the furnace emissivity, and combined with the inlet flue gas temperature of the current intermediate zone, the convective heat transfer coefficient of the flue gas to the heating surface, and the average thermal efficiency coefficient of the furnace wall, calculate the calculated value of the outlet flue gas temperature of the current intermediate zone; wherein, the inlet flue gas temperature of the current intermediate zone is the assumed value of the outlet flue gas temperature set in the last iteration calculation of the outlet flue gas temperature in the previous zone of the current intermediate zone or the calculated value of the outlet flue gas temperature obtained.

[0024] S17, determine whether the difference between the calculated value of the outlet flue gas temperature of the current intermediate zone and the assumed value of the outlet flue gas temperature is greater than the preset value of the outlet flue gas temperature difference of the current intermediate zone; if yes, modify the set assumed value of the outlet flue gas temperature of the current intermediate zone and return to S15 for iterative execution; if no, execute S18.

[0025] S18, after the iterative calculation of the outlet flue gas temperature of the current intermediate zone is completed, the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated. Based on the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface of the current intermediate zone is calculated.

[0026] S19: Determine whether the difference between the calculated average outer wall temperature of the furnace heating surface in the current intermediate zone and the assumed average outer wall temperature of the furnace heating surface is greater than the preset value of the average outer wall temperature difference of the furnace heating surface in the current intermediate zone; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the current intermediate zone and return to S14 for iterative execution; if no, the thermal analysis of the current intermediate zone is completed and S20 is executed.

[0027] S20: Based on the direction of flue gas flow, determine whether the current intermediate zone is the last intermediate zone; if not, take the next intermediate zone of the current intermediate zone as the current intermediate zone and return to S14 for iterative execution; if yes, the thermal analysis of the intermediate zone is completed and S21 is executed; where the initial zone of the current intermediate zone is the intermediate zone adjacent to the maximum heat release zone.

[0028] S21. Based on the assumed value of the outlet flue gas temperature in the furnace outlet zone, the assumed value of the average outer wall temperature of the furnace heating surface, the average thermal efficiency coefficient of the furnace wall, and the furnace emissivity, and combined with the inlet flue gas temperature in the furnace outlet zone and the convective heat transfer coefficient of the flue gas to the heating surface, the calculated value of the outlet flue gas temperature in the furnace outlet zone is calculated. Among them, the inlet flue gas temperature in the furnace outlet zone is the assumed value of the outlet flue gas temperature set in the last cycle of the calculation of the outlet flue gas temperature in the previous zone of the furnace outlet zone or the calculated value of the outlet flue gas temperature obtained.

[0029] S22, determine whether the difference between the calculated value of the flue gas temperature at the furnace outlet and the assumed value of the flue gas temperature at the furnace outlet is greater than the preset value of the flue gas temperature difference at the furnace outlet; if yes, modify the set assumed value of the flue gas temperature at the furnace outlet and return to S10 for iterative execution; if no, execute S23.

[0030] S23. After the iterative calculation of the outlet flue gas temperature in the furnace outlet area is completed, the average heat load of the furnace heating surface in the furnace outlet area, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated. Based on the average heat load of the furnace heating surface in the furnace outlet area, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface in the furnace outlet area is calculated.

[0031] S24: Determine whether the difference between the calculated value of the average outer wall temperature of the furnace heating surface in the furnace outlet area and the assumed value of the average outer wall temperature of the furnace heating surface is greater than the preset value of the average outer wall temperature difference of the furnace heating surface in the furnace outlet area; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the furnace outlet area and return to S9 for iterative execution; if no, the thermal analysis of the furnace outlet area is completed and ends, that is, the furnace thermal analysis is completed.

[0032] The beneficial effects of this invention are as follows: In the supercritical carbon dioxide boiler furnace thermal analysis method of this invention, cyclic iterative thermal analysis is performed sequentially in the maximum heat release zone, the ash hopper zone (if an ash hopper exists), the intermediate zone (if an intermediate zone exists), and the furnace outlet zone; wherein, the cyclic iterative thermal analysis includes cyclic iterative analysis of the average outer wall temperature parameter of the furnace heating surface and the outlet flue gas temperature parameter. During the cyclic iterative thermal analysis in the intermediate zone, the assumed value of the outlet flue gas temperature in the furnace outlet zone is used as a condition for the cyclic iterative thermal analysis; therefore, if the calculated value of the outlet flue gas temperature does not meet the condition during the thermal analysis of the furnace outlet zone, the process returns to the intermediate zone to repeat the cyclic iterative thermal analysis until all thermal parameters meet the preset requirements. This application considers the influence of the average outer wall surface temperature on radiative heat transfer during the cyclic iterative thermodynamic analysis; at the same time, it considers the influence of convective heat transfer during the analysis to calculate the heat transfer between the furnace flue gas and the heated surface; compared with traditional methods, this invention is applicable to various operating conditions such as air combustion, flue gas recirculation and oxygen-enriched combustion, and has higher accuracy, providing a reliable basis for selecting suitable steel and ensuring a reasonable furnace structure. Attached Figure Description

[0033] Figure 1 This is a flowchart of a supercritical carbon dioxide boiler furnace thermal analysis method according to the present invention;

[0034] Figure 2 This is a schematic diagram illustrating the thermal analysis principle of the maximum heat release zone in a supercritical carbon dioxide boiler furnace thermal analysis method of the present invention.

[0035] Figure 3 This is a schematic diagram illustrating the thermal analysis principle of the furnace outlet zone in a supercritical carbon dioxide boiler furnace thermal analysis method according to the present invention.

[0036] Figure 4 This is a schematic diagram illustrating the thermal analysis principle of the intermediate zone in a supercritical carbon dioxide boiler furnace thermal analysis method according to the present invention.

[0037] Figure 5 This is a schematic diagram of the partitioning of the furnace in a carbon dioxide boiler in the example. Detailed Implementation

[0038] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0039] A method for thermal analysis of the furnace of a supercritical carbon dioxide boiler involves dividing the furnace of the supercritical carbon dioxide boiler to be analyzed into multiple zones along the flue gas travel direction; designating the last zone immediately adjacent to the furnace outlet as the furnace outlet zone, which does not include a screen-type superheater; determining whether the supercritical carbon dioxide boiler has an ash hopper, and if so, designating the first zone as the zone where the ash hopper is located, which is called the ash hopper zone, and designating the second zone immediately adjacent to the ash hopper zone as the maximum heat release zone; otherwise, the maximum heat release zone is the first zone; additionally, the zone located between the maximum heat release zone and the furnace outlet zone is called the intermediate zone, and there are zero or one or more intermediate zones between the maximum heat release zone and the furnace outlet zone.

[0040] like Figure 1 As shown, the supercritical carbon dioxide boiler furnace thermodynamic analysis method includes the following steps:

[0041] S1, set the assumed average outer wall temperature of the furnace heating surface in the maximum heat release zone;

[0042] S2, set the assumed value of the outlet flue gas temperature of the maximum heat release zone;

[0043] S3. Based on the assumed value of the outlet flue gas temperature of the maximum heat release zone, and combined with the effective radiation layer thickness of the furnace and the average thermal efficiency coefficient of the furnace wall in the maximum heat release zone, the furnace emissivity of the maximum heat release zone is calculated.

[0044] S4. Based on the assumed value of the outlet flue gas temperature of the maximum heat release zone, the assumed value of the average outer wall temperature of the furnace heating surface, the average thermal efficiency coefficient of the furnace wall, and the furnace emissivity, and combined with the convective heat transfer coefficient of the flue gas in the maximum heat release zone to the heating surface, the calculated value of the outlet flue gas temperature of the maximum heat release zone is calculated.

[0045] S5, determine whether the difference between the calculated value of the outlet flue gas temperature of the maximum heat release zone and the assumed value of the outlet flue gas temperature is greater than the preset value of the outlet flue gas temperature difference of the maximum heat release zone; if yes, modify the set assumed value of the outlet flue gas temperature of the maximum heat release zone and return to S2 for iterative execution; if no, execute S6.

[0046] S6. After the iterative calculation of the outlet flue gas temperature of the maximum heat release zone is completed, the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated. Based on the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface in the maximum heat release zone is calculated.

[0047] S7, determine whether the difference between the calculated value of the average outer wall temperature of the furnace heating surface in the maximum heat release zone and the assumed value of the average outer wall temperature of the furnace heating surface is greater than the preset value of the difference of the average outer wall temperature of the furnace heating surface in the maximum heat release zone; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the maximum heat release zone and return to S1 for iterative execution; if no, the thermal analysis of the maximum heat release zone is completed and S8 is executed; wherein, during the iterative calculation of the calculated value of the average outer wall temperature of the furnace heating surface in the maximum heat release zone, the assumed value of the outlet flue gas temperature of the maximum heat release zone is set as follows: the assumed value of the outlet flue gas temperature of the maximum heat release zone is set to the assumed value of the outlet flue gas temperature set in the last iterative calculation of the outlet flue gas temperature in the maximum heat release zone or the calculated value of the outlet flue gas temperature obtained.

[0048] S8, determine if there is an ash hopper zone; if yes, calculate the heat absorbed by the heating surface of the ash hopper zone and execute S9; if no, execute S9 directly.

[0049] S9, set the assumed average outer wall temperature of the furnace heating surface in the furnace outlet zone;

[0050] S10, Set the assumed value of the flue gas temperature at the furnace outlet zone;

[0051] S11. Based on the assumed value of the flue gas temperature at the furnace outlet, and combined with the effective radiation layer thickness of the furnace and the average thermal efficiency coefficient of the furnace wall at the furnace outlet, the furnace emissivity at the furnace outlet is calculated.

[0052] S12, determine if an intermediate region exists; if yes, execute S13 to S24 in sequence; if no, execute S21 to S24 in sequence.

[0053] S13, Based on the furnace emissivity of the maximum heat release zone and the furnace emissivity of the furnace outlet zone, the furnace emissivity of each intermediate zone is calculated using the linear difference method; wherein, the furnace emissivity of the maximum heat release zone in this step is specifically calculated based on the assumed value of the outlet flue gas temperature set during the last cycle iteration calculation of the outlet flue gas temperature in the maximum heat release zone or the calculated value of the outlet flue gas temperature obtained.

[0054] S14, Set the assumed average outer wall temperature of the furnace heating surface in the current intermediate zone;

[0055] S15, Set the assumed value of the current outlet flue gas temperature in the intermediate zone;

[0056] S16. Based on the assumed value of the outlet flue gas temperature of the current intermediate zone, the assumed value of the average outer wall temperature of the furnace heating surface, and the furnace emissivity, and combined with the inlet flue gas temperature of the current intermediate zone, the convective heat transfer coefficient of the flue gas to the heating surface, and the average thermal efficiency coefficient of the furnace wall, calculate the calculated value of the outlet flue gas temperature of the current intermediate zone; wherein, the inlet flue gas temperature of the current intermediate zone is the assumed value of the outlet flue gas temperature set in the last cycle iteration of the previous zone of the current intermediate zone or the calculated value of the outlet flue gas temperature obtained from the last cycle iteration.

[0057] S17, determine whether the difference between the calculated value of the outlet flue gas temperature of the current intermediate zone and the assumed value of the outlet flue gas temperature is greater than the preset value of the outlet flue gas temperature difference of the current intermediate zone; if yes, modify the set assumed value of the outlet flue gas temperature of the current intermediate zone and return to S15 for iterative execution; if no, execute S18.

[0058] S18, after the iterative calculation of the outlet flue gas temperature of the current intermediate zone is completed, the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated. Based on the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface of the current intermediate zone is calculated. In the iterative calculation of the average outer wall temperature of the furnace heating surface of the current intermediate zone, the assumed value of the outlet flue gas temperature of the current intermediate zone is set as follows: the assumed value of the outlet flue gas temperature of the current intermediate zone is set to the assumed value of the outlet flue gas temperature set in the last iterative calculation of the outlet flue gas temperature in the current intermediate zone or the calculated value of the outlet flue gas temperature.

[0059] S19: Determine whether the difference between the calculated average outer wall temperature of the furnace heating surface in the current intermediate zone and the assumed average outer wall temperature of the furnace heating surface is greater than the preset value of the average outer wall temperature difference of the furnace heating surface in the current intermediate zone; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the current intermediate zone and return to S14 for iterative execution; if no, the thermal analysis of the current intermediate zone is completed and S20 is executed.

[0060] S20: Based on the direction of flue gas flow, determine whether the current intermediate zone is the last intermediate zone; if not, take the next intermediate zone of the current intermediate zone as the current intermediate zone and return to S14 for iterative execution; if yes, the thermal analysis of the intermediate zone is completed and S21 is executed; where the initial zone of the current intermediate zone is the intermediate zone adjacent to the maximum heat release zone.

[0061] S21. Based on the assumed value of the outlet flue gas temperature in the furnace outlet zone, the assumed value of the average outer wall temperature of the furnace heating surface, the average thermal efficiency coefficient of the furnace wall, and the furnace emissivity, and combined with the inlet flue gas temperature in the furnace outlet zone and the convective heat transfer coefficient of the flue gas to the heating surface, the calculated value of the outlet flue gas temperature in the furnace outlet zone is calculated. Among them, the inlet flue gas temperature in the furnace outlet zone is the assumed value of the outlet flue gas temperature set in the last cycle of the calculation of the outlet flue gas temperature in the previous zone of the furnace outlet zone or the calculated value of the outlet flue gas temperature obtained.

[0062] S22, determine whether the difference between the calculated value of the flue gas temperature at the furnace outlet and the assumed value of the flue gas temperature at the furnace outlet is greater than the preset value of the flue gas temperature difference at the furnace outlet; if yes, modify the set assumed value of the flue gas temperature at the furnace outlet and return to S10 for iterative execution; if no, execute S23.

[0063] S23, after the iterative calculation of the outlet flue gas temperature in the furnace outlet area is completed, the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated in the furnace outlet area. Based on the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface in the furnace outlet area is calculated. In the iterative calculation of the average outer wall temperature of the furnace heating surface in the furnace outlet area, the assumed value of the outlet flue gas temperature in the furnace outlet area is set as follows: the assumed value of the outlet flue gas temperature in the furnace outlet area is set to the assumed value of the outlet flue gas temperature set in the last iterative calculation of the outlet flue gas temperature in the furnace outlet area or the calculated value of the outlet flue gas temperature.

[0064] S24: Determine whether the difference between the calculated value of the average outer wall temperature of the furnace heating surface in the furnace outlet area and the assumed value of the average outer wall temperature of the furnace heating surface is greater than the preset value of the average outer wall temperature difference of the furnace heating surface in the furnace outlet area; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the furnace outlet area and return to S9 for iterative execution; if no, the thermal analysis of the furnace outlet area is completed and ends, that is, the furnace thermal analysis is completed.

[0065] Figure 2 , Figure 3 and Figure 4 These are schematic diagrams illustrating the thermal analysis principles of the maximum heat release zone, the furnace outlet zone, and the intermediate zone in a supercritical carbon dioxide boiler furnace thermal analysis method according to the present invention.

[0066] The following is combined Figure 2 , Figure 3 and Figure 4 Specific explanations are provided for the thermal analysis of each zone.

[0067] In this specific embodiment, the preferred embodiment is:

[0068] like Figure 2 or Figure 3 As shown, let region A be the maximum heat release zone or the furnace outlet zone. The specific calculation process for the furnace emissivity in region A is as follows:

[0069] Based on the effective radiation layer thickness of the furnace and the assumed outlet flue gas temperature of region A, the triatomic gas emissivity of region A is calculated.

[0070] Based on Beer-Lambert law, the gas radiation attenuation coefficient of region A is calculated according to the effective radiation layer thickness of the furnace and the triatomic gas emissivity of region A.

[0071] For gaseous and liquid fuels, the carbon black particle radiation attenuation coefficient for region A is calculated based on the assumed outlet flue gas temperature of region A; for solid fuels, the ash particle radiation attenuation coefficient and coke particle radiation attenuation coefficient for region A are calculated based on the assumed outlet flue gas temperature of region A.

[0072] The flame emissivity of region A is calculated based on the gas radiation attenuation coefficient, carbon black particle radiation attenuation coefficient, ash particle radiation attenuation coefficient, and coke particle radiation attenuation coefficient of region A.

[0073] The furnace emissivity of region A is calculated based on the average thermal efficiency coefficient of the furnace wall and the flame emissivity of region A.

[0074] in:

[0075] The formula for calculating the effective radiation layer thickness of the furnace is as follows:

[0076] The formula for calculating the emissivity of the triatomic gas in region A is as follows: and

[0077] The formula for calculating the gas radiation attenuation coefficient in region A is k. gas = -ln(1-ε3) / P3s;

[0078] Specifically, s is the effective radiation layer thickness, V is the total volume of the furnace, F is the total furnace wall area, including the inlet and outlet cross-sectional areas; ε3 is the triatomic gas emissivity of region A, and k i Let a be the absorption coefficient of the i-th type of ash gas. ε,i (T) is the weighting factor for the i-th type of gray gas, a ε,0 (T) is the weighting factor for transparent gases, I is the number of gray gases, J is the polynomial number, and b ε,i,jP3 is the coefficient of the j-th term of the i-th type of ash gas, P3 is the partial pressure of the triatomic gas, and T is the assumed value of the outlet flue gas temperature; k gas Let be the gas radiation attenuation coefficient for region A.

[0079] In this specific embodiment, the preferred embodiment is:

[0080] like Figure 4 As shown, the formula for calculating the emissivity of the furnace in the middle zone is:

[0081]

[0082] Where a(n) represents the furnace emissivity of the nth zone, specifically, the nth zone is the intermediate zone; a out a represents the furnace emissivity in the furnace outlet area. max The furnace emissivity is defined as the maximum heat release zone, and N is the total number of zones including the maximum heat release zone, the intermediate zone, and the furnace outlet zone. max This is the sequence number of the zone with the greatest heat release.

[0083] In this specific embodiment, the preferred embodiment is:

[0084] like Figure 2 As shown, the specific process for calculating the outlet flue gas temperature of the maximum heat release zone is as follows:

[0085] Based on the furnace emissivity of the maximum heat release zone, the average thermal efficiency coefficient of the furnace wall, the assumed value of the outlet flue gas temperature, and the assumed value of the average outer wall temperature of the furnace heating surface, the radiative heat transfer of the flue gas from the maximum heat release zone to the furnace wall, the radiative heat transfer of the flue gas to the next zone, and the radiative heat transfer of the flue gas to the ash hopper are calculated.

[0086] Based on the combustion mode correction coefficient, the convective heat transfer coefficient of the flue gas to the heating surface in the maximum heat release zone is calculated.

[0087] Based on the convective heat transfer coefficient of the flue gas in the maximum heat release zone to the heating surface, the assumed value of the outlet flue gas temperature, and the assumed value of the average outer wall temperature of the furnace heating surface, the convective heat transfer of the flue gas in the maximum heat release zone to the heating surface is calculated.

[0088] Based on the energy balance equation, the calculated value of the outlet flue gas temperature of the maximum heat release zone is calculated according to the convective heat transfer of the flue gas to the heating surface, the radiative heat transfer of the flue gas to the furnace wall, the radiative heat transfer of the flue gas to the next zone, and the radiative heat transfer of the flue gas to the ash hopper.

[0089] If there is no ash hopper zone, the radiative heat transfer of the flue gas from the maximum heat release zone to the ash hopper zone is zero.

[0090] The formula for calculating the outlet flue gas temperature of the maximum heat release zone is as follows:

[0091]

[0092] Specifically, in the region of maximum heat release: Here, c″ represents the calculated outlet flue gas temperature, and Q represents the flue gas heat capacity under the calculated outlet flue gas temperature. fuel Q is the heat brought in by the fuel. air The heat brought in by the air, Q fg Q5 represents the heat introduced by the recirculated flue gas, Q6 represents the heat loss due to heat dissipation, and Q7 represents the ash loss. rad Q represents the radiative heat transfer of flue gas to the furnace wall. hop Q represents the radiative heat transfer of flue gas to the ash hopper area. next Q represents the radiative heat transfer of flue gas to the next zone. con This refers to the convective heat transfer of flue gas to the heated surface.

[0093] Further optimization:

[0094] The formula for calculating the radiative heat transfer of flue gas to the furnace wall in the maximum heat release zone is as follows:

[0095]

[0096] The formula for calculating the radiative heat transfer from the flue gas in the maximum heat release zone to the ash hopper zone is as follows:

[0097]

[0098] The formula for calculating the radiative heat transfer from the flue gas in the maximum heat-generating zone to the next zone is as follows:

[0099]

[0100] The formula for calculating the convective heat transfer of flue gas to the heating surface in the maximum heat release zone is as follows:

[0101]

[0102] In the region of maximum heat release: a max For furnace emissivity, B p To calculate the fuel consumption of the boiler, T″ is the assumed value of the outlet flue gas temperature. w F is the assumed average outer wall temperature of the heated surface. cr F' is the furnace wall area, F″ is the inlet cross-sectional area, F″ is the outlet cross-sectional area, and ψ cp ψ' is the average thermal efficiency coefficient of the furnace wall, ψ″ is the thermal efficiency coefficient of the inlet section, and ψ″ is the thermal efficiency coefficient of the outlet section. f F is the convective heat transfer coefficient of flue gas to the heated surface. cw The area of ​​the heated surface;

[0103] The formula for calculating the convective heat transfer coefficient of the flue gas to the heating surface in the maximum heat release zone is as follows:

[0104]

[0105] Where, λ f Let be the thermal conductivity of the flue gas, d be the equivalent diameter, Nu(Re,Pr,...) be the forced convection heat transfer correlation inside the pipe, and c be the thermal conductivity of the flue gas. cb This is a correction factor for the combustion method, and c cb The value range is 1 to 10.

[0106] In this specific embodiment, the preferred embodiment is:

[0107] like Figure 3 As shown in Figure 4, if we define region B as the intermediate zone or the furnace outlet zone, then the specific process for calculating the outlet flue gas temperature of region B is as follows:

[0108] Based on the furnace emissivity, average thermal efficiency coefficient of the furnace wall, assumed values ​​of inlet flue gas temperature, outlet flue gas temperature, and assumed value of average outer wall temperature of the furnace heating surface in region B, the radiative heat transfer of flue gas in region B to the furnace wall and the difference between the radiative heat transfer of flue gas in the previous region to region B and the radiative heat transfer of flue gas in region B to the next region are calculated.

[0109] Based on the combustion mode correction factor, the convective heat transfer coefficient of flue gas to the heating surface in region B is calculated.

[0110] Based on the convective heat transfer coefficient of flue gas to the heating surface in region B, the assumed values ​​of inlet flue gas temperature, outlet flue gas temperature, and the assumed value of average outer wall temperature of the furnace heating surface, the convective heat transfer of flue gas to the heating surface in region B is calculated.

[0111] Based on the energy balance equation, the calculated value of the outlet flue gas temperature of region B is calculated according to the convective heat transfer of flue gas to the heating surface in region B, the radiative heat transfer of flue gas to the furnace wall, and the difference between the radiative heat transfer of flue gas from the previous region to region B and the radiative heat transfer of flue gas from region B to the next region.

[0112] The formula for calculating the outlet flue gas temperature of region B is as follows:

[0113]

[0114] Specifically, in region B: This is the calculated value for the outlet flue gas temperature. Here, c is the inlet flue gas temperature, c″ is the flue gas heat capacity at the calculated outlet flue gas temperature, and c' is the flue gas heat capacity at the inlet flue gas temperature. Q fuel Q is the heat brought in by the fuel. air The heat brought in by the air, Qfg Q5 represents the heat introduced by the recirculated flue gas, Q6 represents the heat loss due to heat dissipation, and Q7 represents the ash loss. rad Q represents the radiative heat transfer of flue gas to the furnace wall. con Q represents the convective heat transfer from the flue gas to the heated surface. next Q represents the radiative heat transfer of flue gas to the next zone. last Let Q be the radiative heat transfer from the flue gas in the previous zone to zone B. next -Q last This is the difference between the radiative heat transfer of flue gas from the previous zone to zone B and the radiative heat transfer of flue gas to the next zone.

[0115] Additionally, when zone B is the furnace outlet zone, the next zone after zone B is the screen-type superheater; therefore, Q next The radiative heat exchange between the flue gas in area B and the screen-type superheater area.

[0116] Further optimization:

[0117] The formula for calculating the radiative heat transfer of flue gas to the furnace wall in area B is as follows:

[0118]

[0119] The formula for calculating the difference between the radiative heat transfer from the flue gas in the previous zone to zone B and the radiative heat transfer from the flue gas in zone B to the next zone is as follows:

[0120]

[0121] The formula for calculating the convective heat transfer of flue gas to the heating surface in region B is as follows:

[0122]

[0123] In region B: when region B is the intermediate zone, 'a' represents the furnace emissivity of the intermediate zone; when region B is the furnace outlet zone, 'a' represents the furnace emissivity of the furnace outlet zone. p To calculate the fuel consumption of the boiler, T″ is the assumed outlet flue gas temperature, T' is the inlet flue gas temperature, and T... w F is the assumed average outer wall temperature of the heated surface. cr F' is the furnace wall area, F″ is the inlet cross-sectional area, F″ is the outlet cross-sectional area, and ψ cp ψ' is the average thermal efficiency coefficient of the furnace wall, ψ″ is the thermal efficiency coefficient of the inlet section, and ψ″ is the thermal efficiency coefficient of the outlet section. f F is the convective heat transfer coefficient of flue gas to the heated surface. cw The area of ​​the heated surface;

[0124] The formula for calculating the convective heat transfer coefficient of the flue gas to the heated surface in region B is as follows:

[0125]

[0126] In region B: λ f Let d be the thermal conductivity of the flue gas, d be the equivalent diameter, Nu(Re,Pr,...) be the forced convection heat transfer correlation in the pipe, Re represent the Reynolds number, Pr represent the Prandtl number, and c be the thermal conductivity of the flue gas. cb This is a correction factor for the combustion method, and c cb The value range is 1 to 10.

[0127] In this specific embodiment, the preferred embodiment is:

[0128] The formula for calculating the average outer wall temperature of the furnace heating surface in the maximum heat release zone, intermediate zone, or furnace outlet zone is as follows:

[0129]

[0130] in,

[0131] Specifically, in the maximum heat release zone, intermediate zone, or furnace outlet zone: t w This is the calculated value of the average outer wall temperature of the furnace heating surface. The correlation for calculating the average outer wall temperature of the furnace heating surface under the condition that the outer wall of the tube is free of contamination, Δt slag h CO2 The supercritical carbon dioxide convective heat transfer coefficient inside the tube. λ represents the average temperature of supercritical carbon dioxide inside the tube. M D is the thermal conductivity of the metal. out Where D is the outer diameter of the pipe, δ is the wall thickness of the pipe, and D is the outer diameter of the pipe. in λ is the inner diameter of the pipe. CO2 Let q be the thermal conductivity of supercritical carbon dioxide inside the tube, Nu(Re,Pr,...) be the correlation for forced convection heat transfer inside the tube, and q be the thermal conductivity of supercritical carbon dioxide inside the tube. cw B represents the average heat load on the furnace heating surface. p To calculate the fuel consumption of the boiler, F cw Q is the area of ​​the heated surface. rad Q represents the radiative heat transfer of flue gas to the furnace wall. con This refers to the convective heat transfer of flue gas to the heated surface.

[0132] In this specific embodiment, the preferred embodiment is:

[0133] After the furnace thermal analysis is completed, based on the known furnace structure and working fluid parameters and the results of the furnace thermal analysis, the design manual is consulted to select steel that meets the strength requirements for the supercritical carbon dioxide boiler. If no suitable steel is available, the furnace structure and working fluid parameters are readjusted, and the furnace thermal analysis is repeated until steel that meets the strength requirements is obtained.

[0134] For example, based on the obtained flue gas temperature at the furnace outlet, compare it with the design manual to determine whether the temperature is reasonable. If it does not meet the requirements for safe and economical boiler operation, then readjust the furnace structure and working fluid parameters.

[0135] The following analysis uses a specific example to examine the furnace thermodynamic parameters of a supercritical carbon dioxide boiler:

[0136] The furnace has a rectangular cross-section, measuring 0.5m x 0.5m, and is 2m long. It is horizontally arranged, with a single diesel burner, no ash hopper, and no flue gas recirculation. A screen-type superheater is located after the furnace outlet. The outer diameter of the furnace heating surface tubes is 22mm, and the wall thickness is 5mm; it uses membrane walls. The furnace is divided into zones as follows... Figure 5 As shown.

[0137] The relevant initial data is as follows:

[0138] Area F of furnace wall in Zone 1 cr,1 =2m 2 Area 2 furnace wall area F cr,2 =1m 2 Area F of furnace wall in Zone 3 cr,3 =1.25m 2 ;

[0139] Zone 1 heating surface area F cw,1 =1m 2 Area F of heated surface in zone 2 cw,2 =1m 2 ; Area F of heated surface in zone 3 cw,3 =1m 2 ;

[0140] The total volume of the furnace is V = 0.5 m³. 3 ;

[0141] The cross-sectional area of ​​the exit of Zone 1 is F1″ = 0.25m². 2 The cross-sectional area of ​​the exit of zone 2 is F2″ = 0.25m². 2 The cross-sectional area of ​​the exit of zone 3 is F3″ = 0.25m². 2 The cross-sectional area of ​​the entrance to Zone 2 is F2' = 0.25m². 2 The cross-sectional area of ​​the entrance to Zone 3 is F3' = 0.25m². 2 ;

[0142] Heat Q brought in by fuel in Zone 1 fuel,1= 40470 kJ / kg; Heat Q brought in by fuel in Zone 2 fuel,2 =1278kJ / kg; Heat Q brought in by fuel in Zone 3 fuel,3 =852kJ / kg;

[0143] Heat Q brought in by the air in zone 1 air,1 =1510kJ / kg; Heat Q brought in by air in zone 2 air,2 =0 kJ / kg; Heat Q brought in by air in zone 3 air,3 =0 kJ / kg;

[0144] The heat Q brought in by the recirculated flue gas in Zone 1 fg,1 =0 kJ / kg; Heat Q carried in by the recirculated flue gas in Zone 2 fg,2 =0 kJ / kg; Heat Q carried in by the recirculated flue gas in Zone 3 fg,3 =0 kJ / kg;

[0145] Heat loss Q in zone 1 5,1 = 8000 kJ / kg; Heat loss in zone 2 Q 5,2 = 800kJ / kg; Heat loss in zone 3 Q 5,3 =800kJ / kg;

[0146] Area 1 Ash and Slag Loss Q 6,1 =0 kJ / kg; Ash loss in Zone 2 Q 6,2 =0 kJ / kg; Ash loss in Zone 3 Q 6,3 =0 kJ / kg;

[0147] The average thermal efficiency coefficient ψ of the furnace wall in Zone 1 cp,1 =0.3575; Average thermal efficiency coefficient ψ of furnace wall in Zone 2 cp,2 =0.65; Average thermal efficiency coefficient ψ of furnace wall in Zone 3 cp,3 =0.5733;

[0148] The effective thermal coefficient of the outlet section in Zone 1 is ψ1″=0.4; the difference in effective thermal coefficient between the inlet and outlet sections in Zone 2 is ψ″2-ψ'2=-0.2; the difference in effective thermal coefficient between the inlet and outlet sections in Zone 3 is ψ″2-ψ'2=-0.1;

[0149] P3s = 0.007 MPa*m in region 1; P3s = 0.007 MPa*m in region 3;

[0150] Boiler fuel consumption calculation B p =13.35 kg / h;

[0151] Combustion mode correction factor c for Zone 1 cb,1 =4; Combustion mode correction factor c for zone 2 cb,2 =3.5; Combustion mode correction factor c for Zone 3cb,3 =3;

[0152] The average temperature of supercritical carbon dioxide inside the tube in Zone 1 The average temperature of supercritical carbon dioxide inside the tube in zone 2 The average temperature of supercritical carbon dioxide inside the tube in zone 3

[0153] The calculation process is as follows:

[0154] (1) Zone 1 (maximum heat release zone)

[0155] Effective radiant layer thickness of the furnace

[0156] Assume the average outer wall temperature t of the furnace heating surface in zone 1 w =296℃, assuming an allowable deviation of 3℃;

[0157] Assuming the outlet flue gas temperature of zone 1 Assume the allowable deviation is 3℃;

[0158] triatomic gas emissivity of region 1

[0159]

[0160] Gas radiation attenuation coefficient in zone 1

[0161] k gas =-ln(1-ε3) / P3s=-ln(1-0.1465) / 0.007=22.495m -1 *MPa -1 ;

[0162] Radiation attenuation coefficient of carbon black particles in Zone 1

[0163] k cb =f(θ″,α,...)=0.93m -1 *MPa -1 ;

[0164] Flame darkness in Zone 1

[0165] The average thermal efficiency coefficient ψ of the furnace wall in Zone 1 cp,1 =0.3575;

[0166] The furnace blackness of Zone 1

[0167] The radiative heat transfer of flue gas to the furnace wall in Zone 1

[0168]

[0169] Radiative heat exchange between zone 1 and zone 2

[0170]

[0171] The convective heat transfer coefficient of flue gas to the heating surface in Zone 1

[0172]

[0173] Convective heat transfer of flue gas to the heating surface in Zone 1

[0174]

[0175] Calculated outlet flue gas temperature of zone 1

[0176]

[0177] 860.3-859=1.3<3℃, therefore the iterative calculation of the outlet flue gas temperature is complete.

[0178] Average heat load of the heating surface in zone 1

[0179]

[0180] The average temperature of supercritical carbon dioxide inside the tube in Zone 1

[0181] The supercritical carbon dioxide convective heat transfer coefficient inside the tube in Zone 1

[0182]

[0183] Average outer wall surface temperature of the heating surface in Zone 1

[0184]

[0185] 297.0-296=1.0<3℃, therefore the iterative calculation of the average outer wall temperature is complete, and the thermal calculation of zone 1 is complete.

[0186] (2) Furnace emissivity in Zone 3 (furnace outlet zone)

[0187] Assuming the outlet flue gas temperature of zone 3 Assume the allowable deviation is 3℃;

[0188] triatomic gas emissivity of zone 3

[0189]

[0190] Gas radiation attenuation coefficient in zone 3

[0191] k gas=-ln(1-ε3) / P3s=-ln(1-0.1661) / 0.007=25.802m -1 *MPa -1 ;

[0192] Radiation attenuation coefficient of carbon black particles in zone 3

[0193] k cb =f(θ″,α,...)=0.69m -1 *MPa -1 ;

[0194] Flame darkness in Zone 3

[0195]

[0196] The average thermal efficiency coefficient ψ of the furnace wall in Zone 3 cp,3 =0.5733;

[0197] Zone 3 furnace blackness

[0198] (3) Zone 2

[0199] Inlet flue gas temperature in Zone 2

[0200] Assume the average outer wall temperature t of the furnace heating surface in zone 2 w =378℃, assuming an allowable deviation of 3℃;

[0201] Assuming the outlet flue gas temperature of zone 2 Assume the allowable deviation is 3℃;

[0202] Zone 2 furnace blackness

[0203]

[0204] The average thermal efficiency coefficient ψ of the furnace wall in Zone 2 cp,2 =0.65;

[0205] The radiative heat exchange of flue gas in Zone 2 with the furnace wall

[0206]

[0207] The difference between the radiative heat transfer from zone 1 to zone 2 and the radiative heat transfer from zone 2 to zone 3.

[0208]

[0209] The convective heat transfer coefficient of flue gas to the heating surface in Zone 2

[0210]

[0211] Convective heat transfer of flue gas to the heating surface in Zone 2

[0212]

[0213] Calculated outlet flue gas temperature in zone 2

[0214]

[0215] 719.7-720=-0.3<3℃, therefore the iterative calculation of the outlet flue gas temperature is complete.

[0216] Average heat load of the heating surface in zone 2

[0217]

[0218] The average temperature of supercritical carbon dioxide inside the tube in zone 2

[0219] The supercritical carbon dioxide convective heat transfer coefficient inside the tube in zone 2

[0220]

[0221] Average outer wall surface temperature of the heating surface in zone 2

[0222]

[0223] 379.0-378=1.0<3℃, therefore the iterative calculation of the average outer wall temperature is complete, and the thermal calculation of zone 2 is complete.

[0224] (4) Zone 3 (Furnace Outlet Zone)

[0225] Inlet flue gas temperature in Zone 3

[0226] Assume the average outer wall temperature t of the furnace heating surface in zone 3 w =420℃, assuming an allowable deviation of 3℃;

[0227] Assuming the outlet flue gas temperature of zone 3 Assume the allowable deviation is 3℃;

[0228] The furnace emissivity a in zone 3 out =0.264;

[0229] The average thermal efficiency coefficient ψ of the furnace wall in Zone 3 cp ,3=0.5733;

[0230] The radiative heat transfer of flue gas to the furnace wall in Zone 3

[0231]

[0232] The difference between the radiative heat transfer from zone 2 to zone 3 and the radiative heat transfer from zone 3 to the screen.

[0233]

[0234] The convective heat transfer coefficient of flue gas to the heating surface in zone 3

[0235]

[0236] The convective heat transfer of flue gas to the heating surface in Zone 3

[0237]

[0238] Calculated outlet flue gas temperature in zone 3

[0239]

[0240] 641.4-642=-0.6<3℃, therefore the iterative calculation of the outlet flue gas temperature is complete.

[0241] Average heat load of the heating surface in zone 3

[0242]

[0243] (Note: Q here) ra d-value ratio Small, because The outlet flue has been calculated; for detailed calculation formulas, please refer to the 1973 edition of the "Standard Method for Thermal Calculation of Boiler Units".

[0244] The average temperature of supercritical carbon dioxide inside the tube in zone 3

[0245] The supercritical carbon dioxide convective heat transfer coefficient inside the tube in zone 3

[0246]

[0247] Average outer wall surface temperature of the heating surface in Zone 3

[0248]

[0249] 420.5-420=0.5<3℃, therefore the iterative calculation of the average outer wall temperature is complete, and the thermal calculation of zone 3 is complete.

[0250] (5) Compare the calculated flue gas temperature at the furnace outlet with the assumed value used in calculating the opacity, assuming an allowable deviation of 3℃.

[0251] 641.4-642=-0.6<3℃, therefore the thermal calculation of the furnace is complete.

[0252] Notes: 1) To simplify the process, the assumed outer wall temperature and outlet flue gas temperature mentioned above are final calculation results and have not been iterated. 2) When calculating the emissivity of triatomic gases, please refer to the literature "Evaluation of Coefficients for the Weighted Sum of Gray Gases Model" for some unprovided coefficients. 3) Some of the above data are assumed values ​​and need to be adjusted according to the corresponding situation during actual calculation. For calculation formulas not given (such as the radiation attenuation coefficient of carbon black particles, the average thermal efficiency coefficient of the furnace wall, etc.), please refer to the 1973 edition of "Standard Method for Thermal Calculation of Boiler Units". 4) For the forced convection correlation Nu(Re,Pr,...) in the tube, an appropriate correlation can be selected according to the actual situation. In the above embodiment, the correlation of flue gas to the heating surface comes from the literature "New equations for heat and mass transfer in turbulentpipe and channel flows"; the correlation of supercritical carbon dioxide in the tube comes from the literature "Where did the Dittus and Boelter equation come from".

[0253] This application has the following beneficial effects:

[0254] (1) The calculation of radiative heat transfer has been improved, taking into account the influence of the average outer wall surface temperature on radiative heat transfer.

[0255] (2) The influence of convective heat transfer is considered in the energy balance equation. A method based on the combination of combustion mode correction coefficient and forced convection heat transfer correlation in the tube is proposed to calculate the convective heat transfer coefficient of furnace flue gas to the heat transfer surface.

[0256] (3) The weighted gray gas model is used to calculate the gas radiation attenuation coefficient. Compared with the traditional method, it is applicable to various working conditions such as air combustion, flue gas recirculation and oxygen-enriched combustion, and has higher accuracy.

[0257] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for thermal analysis of the furnace of a supercritical carbon dioxide boiler, characterized in that: The supercritical carbon dioxide boiler furnace to be analyzed is divided into multiple zones along the flue gas travel direction. The last zone immediately adjacent to the furnace outlet is designated as the furnace outlet zone, which does not include the screen-type superheater. It is determined whether the supercritical carbon dioxide boiler has an ash hopper. If so, the first zone is designated as the zone where the ash hopper is located, which is called the ash hopper zone. The second zone immediately adjacent to the ash hopper zone is designated as the maximum heat release zone. If not, the maximum heat release zone is the first zone. In addition, the zone located between the maximum heat release zone and the furnace outlet zone is the intermediate zone, and there are zero or one or more intermediate zones between the maximum heat release zone and the furnace outlet zone. The supercritical carbon dioxide boiler furnace thermal analysis method includes the following steps. S1, set the assumed average outer wall temperature of the furnace heating surface in the maximum heat release zone; S2, set the assumed value of the outlet flue gas temperature of the maximum heat release zone; S3. Based on the assumed value of the outlet flue gas temperature of the maximum heat release zone, and combined with the effective radiation layer thickness of the furnace and the average thermal efficiency coefficient of the furnace wall in the maximum heat release zone, the furnace emissivity of the maximum heat release zone is calculated. S4. Based on the assumed value of the outlet flue gas temperature of the maximum heat release zone, the assumed value of the average outer wall temperature of the furnace heating surface, the average thermal efficiency coefficient of the furnace wall, and the furnace emissivity, and combined with the convective heat transfer coefficient of the flue gas in the maximum heat release zone to the heating surface, the calculated value of the outlet flue gas temperature of the maximum heat release zone is calculated. S5, determine whether the difference between the calculated value of the outlet flue gas temperature of the maximum heat release zone and the assumed value of the outlet flue gas temperature is greater than the preset value of the outlet flue gas temperature difference of the maximum heat release zone; if yes, modify the set assumed value of the outlet flue gas temperature of the maximum heat release zone and return to S2 for iterative execution; if no, execute S6. S6. After the iterative calculation of the outlet flue gas temperature of the maximum heat release zone is completed, the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated. Based on the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface in the maximum heat release zone is calculated. S7: Determine whether the difference between the calculated value of the average outer wall temperature of the furnace heating surface in the maximum heat release zone and the assumed value of the average outer wall temperature of the furnace heating surface is greater than the preset value of the average outer wall temperature difference of the furnace heating surface in the maximum heat release zone; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the maximum heat release zone and return to S1 for iterative execution; if no, the thermal analysis of the maximum heat release zone is completed and S8 is executed. S8, determine if there is an ash hopper zone; if yes, calculate the heat absorbed by the heating surface of the ash hopper zone and execute S9; if no, execute S9 directly. S9, set the assumed average outer wall temperature of the furnace heating surface in the furnace outlet zone; S10, Set the assumed value of the flue gas temperature at the furnace outlet zone; S11. Based on the assumed value of the flue gas temperature at the furnace outlet, and combined with the effective radiation layer thickness of the furnace and the average thermal efficiency coefficient of the furnace wall at the furnace outlet, the furnace emissivity at the furnace outlet is calculated. S12, determine if an intermediate region exists; if yes, execute S13 to S24 in sequence; if no, execute S21 to S24 in sequence. S13. Based on the furnace emissivity of the maximum heat release zone and the furnace emissivity of the furnace outlet zone, the furnace emissivity of each intermediate zone is calculated using the linear difference method. S14, Set the assumed average outer wall temperature of the furnace heating surface in the current intermediate zone; S15, Set the assumed value of the current outlet flue gas temperature in the intermediate zone; S16. Based on the assumed value of the outlet flue gas temperature of the current intermediate zone, the assumed value of the average outer wall temperature of the furnace heating surface, and the furnace emissivity, and combined with the inlet flue gas temperature of the current intermediate zone, the convective heat transfer coefficient of the flue gas to the heating surface, and the average thermal efficiency coefficient of the furnace wall, calculate the calculated value of the outlet flue gas temperature of the current intermediate zone; wherein, the inlet flue gas temperature of the current intermediate zone is the assumed value of the outlet flue gas temperature set in the last iteration calculation of the outlet flue gas temperature in the previous zone of the current intermediate zone or the calculated value of the outlet flue gas temperature obtained. S17, determine whether the difference between the calculated value of the outlet flue gas temperature of the current intermediate zone and the assumed value of the outlet flue gas temperature is greater than the preset value of the outlet flue gas temperature difference of the current intermediate zone; if yes, modify the set assumed value of the outlet flue gas temperature of the current intermediate zone and return to S15 for iterative execution; if no, execute S18. S18, after the iterative calculation of the outlet flue gas temperature of the current intermediate zone is completed, the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated. Based on the average heat load of the furnace heating surface, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface of the current intermediate zone is calculated. S19: Determine whether the difference between the calculated average outer wall temperature of the furnace heating surface in the current intermediate zone and the assumed average outer wall temperature of the furnace heating surface is greater than the preset value of the average outer wall temperature difference of the furnace heating surface in the current intermediate zone; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the current intermediate zone and return to S14 for iterative execution; if no, the thermal analysis of the current intermediate zone is completed and S20 is executed. S20: Based on the direction of flue gas flow, determine whether the current intermediate zone is the last intermediate zone; if not, take the next intermediate zone of the current intermediate zone as the current intermediate zone and return to S14 for iterative execution; if yes, the thermal analysis of the intermediate zone is completed and S21 is executed; where the initial zone of the current intermediate zone is the intermediate zone adjacent to the maximum heat release zone. S21. Based on the assumed value of the outlet flue gas temperature in the furnace outlet zone, the assumed value of the average outer wall temperature of the furnace heating surface, the average thermal efficiency coefficient of the furnace wall, and the furnace emissivity, and combined with the inlet flue gas temperature in the furnace outlet zone and the convective heat transfer coefficient of the flue gas to the heating surface, the calculated value of the outlet flue gas temperature in the furnace outlet zone is calculated. Among them, the inlet flue gas temperature in the furnace outlet zone is the assumed value of the outlet flue gas temperature set in the last cycle of the calculation of the outlet flue gas temperature in the previous zone of the furnace outlet zone or the calculated value of the outlet flue gas temperature obtained. S22, determine whether the difference between the calculated value of the flue gas temperature at the furnace outlet and the assumed value of the flue gas temperature at the furnace outlet is greater than the preset value of the flue gas temperature difference at the furnace outlet; if yes, modify the set assumed value of the flue gas temperature at the furnace outlet and return to S10 for iterative execution; if no, execute S23. S23. After the iterative calculation of the outlet flue gas temperature in the furnace outlet area is completed, the average heat load of the furnace heating surface in the furnace outlet area, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube are calculated. Based on the average heat load of the furnace heating surface in the furnace outlet area, the average temperature of supercritical carbon dioxide in the tube, and the convective heat transfer coefficient of supercritical carbon dioxide in the tube, the average outer wall temperature of the furnace heating surface in the furnace outlet area is calculated. S24: Determine whether the difference between the calculated value of the average outer wall temperature of the furnace heating surface in the furnace outlet area and the assumed value of the average outer wall temperature of the furnace heating surface is greater than the preset value of the average outer wall temperature difference of the furnace heating surface in the furnace outlet area; if yes, modify the set assumed value of the average outer wall temperature of the furnace heating surface in the furnace outlet area and return to S9 for iterative execution; if no, the thermal analysis of the furnace outlet area is completed and ends, that is, the furnace thermal analysis is completed.

2. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to claim 1, characterized in that: Let region A be the maximum heat release zone or the furnace outlet zone. The specific calculation process for the furnace emissivity in region A is as follows: Based on the effective radiation layer thickness of the furnace and the assumed outlet flue gas temperature of region A, the triatomic gas emissivity of region A is calculated. Based on Beer-Lambert law, the gas radiation attenuation coefficient of region A is calculated according to the effective radiation layer thickness of the furnace and the triatomic gas emissivity of region A. For gaseous and liquid fuels, the carbon black particle radiation attenuation coefficient for region A is calculated based on the assumed outlet flue gas temperature of region A; for solid fuels, the ash particle radiation attenuation coefficient and coke particle radiation attenuation coefficient for region A are calculated based on the assumed outlet flue gas temperature of region A. The flame emissivity of region A is calculated based on the gas radiation attenuation coefficient, carbon black particle radiation attenuation coefficient, ash particle radiation attenuation coefficient, and coke particle radiation attenuation coefficient of region A. The furnace emissivity of region A is calculated based on the average thermal efficiency coefficient of the furnace wall and the flame emissivity of region A.

3. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to claim 2, characterized in that: The formula for calculating the effective radiation layer thickness of the furnace is as follows: ; The formula for calculating the triatomic gas emissivity in region A is as follows: ,and ; The formula for calculating the gas radiation attenuation coefficient in region A is as follows: ; Specifically, For the effective radiation layer thickness, The total volume of the furnace. This represents the total furnace wall area. The emissivity of the triatomic gas in region A. For the first The absorption coefficient of the ash gas. For the first Weighting factor for ash gas, For transparent gases, the weighting factor is... The number of gray gases, It is a polynomial number. For the first The first type of ash gas The coefficient of the term, The partial pressure of a triatomic gas. This is an assumed value for the outlet flue gas temperature; Let be the gas radiation attenuation coefficient for region A.

4. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to claim 1, characterized in that: The formula for calculating the emissivity of the furnace in the intermediate zone is as follows: ； in, For the first The area's furnace blackness, specifically, the first The area is the middle area; The furnace emissivity in the furnace outlet area, The emissivity of the furnace in the maximum heat release zone. This refers to the total number of the maximum heat release zone, the intermediate zone, and the furnace outlet zone. This is the sequence number of the zone with the greatest heat release.

5. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to claim 1, characterized in that: The specific process for calculating the outlet flue gas temperature of the maximum heat release zone is as follows: Based on the furnace emissivity of the maximum heat release zone, the average thermal efficiency coefficient of the furnace wall, the assumed value of the outlet flue gas temperature, and the assumed value of the average outer wall temperature of the furnace heating surface, the radiative heat transfer of the flue gas from the maximum heat release zone to the furnace wall, the radiative heat transfer of the flue gas to the next zone, and the radiative heat transfer of the flue gas to the ash hopper are calculated. Based on the combustion mode correction coefficient, the convective heat transfer coefficient of the flue gas to the heating surface in the maximum heat release zone is calculated. Based on the convective heat transfer coefficient of the flue gas in the maximum heat release zone to the heating surface, the assumed value of the outlet flue gas temperature, and the assumed value of the average outer wall temperature of the furnace heating surface, the convective heat transfer of the flue gas in the maximum heat release zone to the heating surface is calculated. Based on the energy balance equation, the calculated value of the outlet flue gas temperature of the maximum heat release zone is calculated according to the convective heat transfer of the flue gas to the heating surface, the radiative heat transfer of the flue gas to the furnace wall, the radiative heat transfer of the flue gas to the next zone, and the radiative heat transfer of the flue gas to the ash hopper. If there is no ash hopper zone, the radiative heat transfer of the flue gas from the maximum heat release zone to the ash hopper zone is zero. The formula for calculating the outlet flue gas temperature of the maximum heat release zone is as follows: ； Specifically, in the maximum heat release zone: This is the calculated value for the outlet flue gas temperature. This refers to the heat capacity of the flue gas under the calculated value of the outlet flue gas temperature. The heat brought in by the fuel, Heat brought in by the air The heat brought in by the recirculated flue gas, For heat dissipation loss, For ash and slag loss, This refers to the radiative heat exchange between the flue gas and the furnace walls. This refers to the radiative heat exchange between the flue gas and the ash hopper area. This refers to the radiative heat exchange of flue gas with the next zone. This refers to the convective heat transfer of flue gas to the heated surface.

6. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to claim 5, characterized in that: The formula for calculating the radiative heat transfer of flue gas to the furnace wall in the maximum heat release zone is as follows: ； The formula for calculating the radiative heat transfer from the flue gas in the maximum heat release zone to the ash hopper zone is as follows: ； The formula for calculating the radiative heat transfer from the flue gas in the maximum heat-generating zone to the next zone is as follows: ； The formula for calculating the convective heat transfer of flue gas to the heating surface in the maximum heat release zone is as follows: ； In the region of maximum heat release: For the blackness of the furnace, Calculate fuel consumption for the boiler. This is an assumed value for the outlet flue gas temperature. This is an assumed value for the average outer wall temperature of the heated surface. For the area of ​​the furnace wall, The inlet cross-sectional area is... The cross-sectional area of ​​the outlet is... The average thermal efficiency coefficient of the furnace wall. The effective thermal coefficient of the inlet section. The effective thermal coefficient of the outlet section. The convective heat transfer coefficient of flue gas to the heating surface is denoted as . This represents the area of ​​the heated surface. The formula for calculating the convective heat transfer coefficient of the flue gas to the heating surface in the maximum heat release zone is as follows: ； in, The thermal conductivity of the flue gas is... Equivalent diameter For forced convection heat transfer within the pipe, Represents the Reynolds number. Representing Prandtl numbers, This is a correction factor for the combustion method, and The value range is 1 to 10.

7. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to claim 1, characterized in that: Let region B be the intermediate zone or the furnace outlet zone. The specific process for calculating the outlet flue gas temperature of region B is as follows: Based on the furnace emissivity, average thermal efficiency coefficient of the furnace wall, assumed values ​​of inlet flue gas temperature, outlet flue gas temperature, and assumed value of average outer wall temperature of the furnace heating surface in region B, the radiative heat transfer of flue gas in region B to the furnace wall and the difference between the radiative heat transfer of flue gas in the previous region to region B and the radiative heat transfer of flue gas in region B to the next region are calculated. Based on the combustion mode correction factor, the convective heat transfer coefficient of flue gas to the heating surface in region B is calculated. Based on the convective heat transfer coefficient of flue gas to the heating surface in region B, the assumed values ​​of inlet flue gas temperature, outlet flue gas temperature, and the assumed value of average outer wall temperature of the furnace heating surface, the convective heat transfer of flue gas to the heating surface in region B is calculated. Based on the energy balance equation, the calculated value of the outlet flue gas temperature of region B is calculated according to the convective heat transfer of flue gas to the heating surface in region B, the radiative heat transfer of flue gas to the furnace wall, and the difference between the radiative heat transfer of flue gas from the previous region to region B and the radiative heat transfer of flue gas from region B to the next region. The formula for calculating the outlet flue gas temperature of region B is as follows: ； Specifically, in region B: This is the calculated value for the outlet flue gas temperature. The temperature of the inlet flue gas. This refers to the heat capacity of the flue gas under the calculated value of the outlet flue gas temperature. The heat capacity of the flue gas at the inlet flue gas temperature. The heat brought in by the fuel, Heat brought in by the air The heat brought in by the recirculated flue gas, For heat dissipation loss, For ash and slag loss, This refers to the radiative heat exchange between the flue gas and the furnace walls. This refers to the convective heat transfer of flue gas to the heating surface. This refers to the radiative heat exchange of flue gas with the next zone. This represents the radiative heat transfer from the flue gas in the previous zone to zone B, and This is the difference between the radiative heat transfer of flue gas from the previous zone to zone B and the radiative heat transfer of flue gas to the next zone. Furthermore, when zone B is the furnace outlet zone, the next zone after zone B is the screen-type superheater; therefore, The radiative heat exchange between the flue gas in area B and the screen-type superheater area.

8. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to claim 7, characterized in that: The formula for calculating the radiative heat transfer of flue gas to the furnace wall in area B is as follows: ； The formula for calculating the difference between the radiative heat transfer from the flue gas in the previous zone to zone B and the radiative heat transfer from the flue gas in zone B to the next zone is as follows: ； The formula for calculating the convective heat transfer of flue gas to the heating surface in region B is as follows: ； In region B: when region B is the intermediate region, The furnace emissivity is measured in the intermediate zone; when zone B is the furnace outlet zone... The furnace emissivity in the furnace outlet area; Calculate fuel consumption for the boiler. This is an assumed value for the outlet flue gas temperature. The temperature of the inlet flue gas. This is an assumed value for the average outer wall temperature of the heated surface. For the area of ​​the furnace wall, The inlet cross-sectional area is... The cross-sectional area of ​​the outlet is... The average thermal efficiency coefficient of the furnace wall. The effective thermal coefficient of the inlet section. The effective thermal coefficient of the outlet section. The convective heat transfer coefficient of flue gas to the heating surface is denoted as . This represents the area of ​​the heated surface. The formula for calculating the convective heat transfer coefficient of the flue gas to the heated surface in region B is as follows: ； In region B: The thermal conductivity of the flue gas is... Equivalent diameter For forced convection heat transfer within the pipe, Represents the Reynolds number. Representing Prandtl numbers, This is a correction factor for the combustion method, and The value range is 1 to 10.

9. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to claim 1, characterized in that: The formula for calculating the average outer wall temperature of the furnace heating surface in the maximum heat release zone, intermediate zone, or furnace outlet zone is as follows: ； in, , ; Specifically, in the maximum heat release zone, the intermediate zone, or the furnace outlet zone: This is the calculated value of the average outer wall temperature of the furnace heating surface. The correlation formula is used to calculate the average outer wall temperature of the furnace heating surface under the condition that the outer wall of the tube is free of contamination. The temperature rise on the outer wall due to contamination The supercritical carbon dioxide convective heat transfer coefficient inside the tube. This represents the average temperature of supercritical carbon dioxide inside the tube. The thermal conductivity of the metal is... The outer diameter of the pipe. For thick pipe walls, The inner diameter of the pipe. The thermal conductivity of supercritical carbon dioxide inside the tube. For forced convection heat transfer within the pipe, Represents the Reynolds number. Representing Prandtl numbers, The average heat load of the furnace heating surface. Calculate fuel consumption for the boiler. The area of ​​the heated surface. This refers to the radiative heat exchange between the flue gas and the furnace walls. This refers to the convective heat transfer of flue gas to the heated surface.

10. The method for thermal analysis of the furnace of a supercritical carbon dioxide boiler according to any one of claims 1 to 9, characterized in that: After the furnace thermal analysis is completed, based on the known furnace structure and working fluid parameters and the results of the furnace thermal analysis, steel that meets the strength requirements is selected for the supercritical carbon dioxide boiler in the design manual. If the design manual does not contain steel that meets the strength requirements, the furnace structure and working fluid parameters should be adjusted, and the furnace thermodynamic analysis should be performed again until steel that meets the strength requirements is obtained.

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