A method for correcting the flue gas temperature of a parallel system in the boiler tail flue

Abstract

The present invention discloses a method for correcting the flue gas temperature of a parallel system in the tail flue of a boiler. The system includes a high-temperature economizer and a parallel assembly. The parallel assembly includes an air preheater, a low-temperature economizer group, and a gas heater that are arranged in parallel. The correction method includes the following steps: calculating the corrected flue gas temperature at the outlet of the air preheater; calculating the corrected flue gas temperature at the outlet of the low-pressure and low-temperature economizer; calculating the corrected flue gas temperature at the outlet of the gas heater; calculating or measuring the flue gas flow rate at the outlet of the high-temperature economizer; calculating the flue gas flow rate at the outlet of the low-temperature economizer group; calculating the flue gas flow rate at the outlet of the gas heater; calculating the flue gas flow rate at the outlet of the air preheater according to the air leakage rate of the air preheater; calculating the mixed flue gas flow rate; calculating the corrected total flue gas temperature. The correction method covers the correction of the flue gas temperature under the condition that various boundary parameters deviate from the design values, is more accurate and does not require iteration, is simple and practical, and can more accurately evaluate the operation economy index of the boiler.

Description

Technical Field

[0001] The present invention belongs to the technical field of boiler energy conservation and emission reduction, and particularly relates to a method for correcting the flue gas temperature of a parallel system in the tail flue of a boiler. Background Art

[0002] In recent years, with the increasing progress and popularization of blast furnace gas combustion technology, blast furnace gas-fired boilers have been widely used in iron and steel enterprises, and more and more self-provided power plants in steel mills use blast furnace gas as the main fuel for power station boilers. With the gradual increase of the parameters of high-pressure gas boilers, gas boilers have reached supercritical parameters. In the future energy utilization of the tail flue of gas boilers, the application of high- and low-pressure low-temperature economizers (high-pressure low-temperature economizer and low-pressure low-temperature economizer) and high-temperature gas heaters is possible. However, at present, both the GB10184 and ASME PTC 4 standards introduce the method for correcting the flue gas temperature when only the air preheater exists in the tail flue. For the parallel arrangement of the tail flue of gas boilers, especially for the units with high- and low-pressure low-temperature economizers and high-temperature gas heaters in parallel with the air preheater at the tail of gas boilers, the above two standards for the method of correcting the flue gas temperature are no longer applicable.

[0003] The paper "Ye Yalan, etc. Calculation method of thermal efficiency of blast furnace gas-fired boilers. "Thermal Power Generation". 2015, Vol. 44 (No. 3), pp. 21-27." and the invention patent with the authorization announcement number CN 104504290 B, "Method for correcting the flue gas temperature of a blast furnace gas-fired boiler", both provide methods for correcting the flue gas temperature when the gas temperature at the inlet of the gas heater and the flue gas temperature at the inlet of the gas heater deviate from the guaranteed value. However, the disadvantage is that the influence on the flue gas temperature after the feed water temperature and the flue gas temperature at the inlet of the air preheater deviate from the design value or the guaranteed value is not considered, and it can only be applicable to the series arrangement system of the tail flue and is not applicable to the parallel arrangement system of the tail flue.

[0004] The invention patent with the authorization announcement number CN 112664922 B, "Method for correcting the flue gas temperature of a boiler with an air preheater bypass economizer", first assumes the flue gas temperature of the bypass economizer after correction, and then through energy balance iteration, finally calculates the finally corrected flue gas temperature. However, this method does not consider the correction calculation of the flue gas temperature due to the deviation of the feed water temperature at the inlet of the economizer from the design value, and through a complex iteration process, the calculation method is relatively complex.

[0005] In summary, there is an urgent need to construct a method for correcting the flue gas temperature specifically for the parallel system of the boiler tail flue, so as to be able to more accurately evaluate the operation economic index of gas boilers. Summary of the Invention

[0006] To solve the above technical problems, the object of the present invention is to provide a method for correcting the flue gas temperature of a parallel system in the boiler tail flue. This correction method corrects the flue gas temperature for the parallel system in the boiler tail flue, covering the correction of the flue gas temperature under various boundary parameters deviating from the design values; this correction method is more accurate and does not require iteration, is simple and practical, and can more accurately evaluate the operating economy index of the boiler.

[0007] To achieve the above technical objectives and reach the above technical effects, the present invention is realized through the following technical solutions:

[0008] A method for correcting the flue gas temperature of a parallel system in the boiler tail flue, wherein the system includes a high-temperature economizer and a parallel assembly connected to the high-temperature economizer. The parallel assembly includes an air preheater, a low-temperature economizer group, and a gas heater. The air preheater, the low-temperature economizer group, and the gas heater are arranged in parallel. The low-temperature economizer group includes a high-pressure low-temperature economizer and a low-pressure low-temperature economizer; this correction method includes the following steps:

[0009] S1, calculate the corrected flue gas temperature t at the outlet of the air preheater kpyδ ;

[0010] S2, calculate the corrected flue gas temperature t at the outlet of the low-pressure low-temperature economizer dpyδ ;

[0011] S3, calculate the corrected flue gas temperature t at the outlet of the gas heater mpyδ ;

[0012] S4, calculate or measure the flue gas flow rate m at the outlet of the high-temperature economizer g ;

[0013] S5, calculate and obtain the flue gas flow rate m at the outlet of the low-temperature economizer group d ;

[0014] S6, calculate and obtain the flue gas flow rate m at the outlet of the gas heater m ;

[0015] S7, calculate and obtain the flue gas flow rate m at the outlet of the air preheater according to the air preheater leakage rate k ;

[0016] S8, calculate the mixed flue gas flow rate m 混 , and this mixed flue gas flow rate includes the flue gas flow rate at the outlet of the air preheater, the flue gas flow rate at the outlet of the low-temperature economizer group, and the flue gas flow rate at the outlet of the gas heater;

[0017] S9, calculate and obtain the corrected total flue gas temperature t pyδ :

[0018]

[0019] Further, the process of calculating the corrected outlet flue gas temperature of the air preheater in step S1 includes the following steps:

[0020] S11. Considering the deviation between the measured value of the inlet air temperature of the air preheater and the designed value of the inlet air temperature of the air preheater, calculate the corrected outlet flue gas temperature of the air preheater one t kpyδ,1 , and the calculation formula is as follows:

[0021]

[0022] In the formula, t jfd is the designed value of the inlet air temperature of the air preheater, t jf is the measured value of the inlet air temperature of the air preheater, t gpy is the measured outlet flue gas temperature of the high-temperature economizer, t kpy is the measured outlet flue gas temperature of the air preheater;

[0023] S12. Considering the deviation between the measured value of the inlet water temperature of the high-temperature economizer and the designed value of the inlet water temperature of the high-temperature economizer, calculate the corrected outlet flue gas temperature of the air preheater two t kpyδ,2 , and the calculation formula is as follows:

[0024]

[0025] In the formula, t gjy is the measured inlet flue gas temperature of the high-temperature economizer, t gwd is the designed value of the inlet water temperature of the high-temperature economizer, t gw is the measured value of the inlet water temperature of the high-temperature economizer;

[0026] S13. The calculation formula of the corrected outlet flue gas temperature t kpyδ of the air preheater is as follows:

[0027] t kpyδ = t kpyδ,1 + t kpyδ,2 - t kpy .

[0028] Further, the process of calculating the corrected outlet flue gas temperature of the low-pressure and low-temperature economizer in step S2 includes the following steps:

[0029] S21. Considering the deviation between the measured value of the inlet water temperature of the low-pressure and low-temperature economizer and the designed value of the inlet water temperature of the low-pressure and low-temperature economizer, calculate the corrected outlet flue gas temperature of the low-pressure and low-temperature economizer one t dpyδ,1 , and the calculation formula is as follows:

[0030]

[0031] In the formula, t′ dwd is the designed value of the inlet water temperature of the low-pressure and low-temperature economizer, t′ dw is the measured value of the inlet water temperature of the low-pressure and low-temperature economizer, tdjy is the measured inlet flue gas temperature of the low-pressure and low-temperature economizer, t dpy is the measured outlet flue gas temperature of the low-pressure and low-temperature economizer;

[0032] S22. Considering the deviation between the measured value and the designed value of the inlet water temperature of the high-pressure and low-temperature economizer, the corrected outlet flue gas temperature of the low-pressure and low-temperature economizer is calculated as t dpyδ,2 , and the calculation formula is as follows:

[0033]

[0034] In the formula, t″ dwd is the designed value of the inlet water temperature of the high-pressure and low-temperature economizer, and t″ dw is the measured value of the inlet water temperature of the high-pressure and low-temperature economizer;

[0035] S23. Considering the deviation between the measured value and the designed value of the inlet water temperature of the high-temperature economizer, the corrected outlet flue gas temperature of the low-pressure and low-temperature economizer is calculated as t dpyδ,3 ;

[0036] First, calculate the corrected inlet flue gas temperature of the low-pressure and low-temperature economizer t djyδ , and the calculation formula is as follows:

[0037]

[0038] Then, calculate the corrected outlet flue gas temperature of the low-pressure and low-temperature economizer t dpyδ,3 , and the calculation formula is as follows:

[0039]

[0040] The calculation formula for the corrected outlet flue gas temperature t of the low-pressure and low-temperature economizer dpyδ is as follows:

[0041] t dpyδ = t dpyδ,1 + t dpyδ,2 + t dpyδ,3 - 2t dpy .

[0042] Further, the process of calculating the corrected outlet flue gas temperature of the gas heater in step S3 includes the following steps:

[0043] S31. Considering the deviation between the measured value and the designed value of the inlet gas temperature of the gas heater, the corrected outlet flue gas temperature of the gas heater is calculated as t mpyδ,1 , and the calculation formula is as follows:

[0044]

[0045] where t mq is the measured value of the inlet gas temperature of the gas heater, and t mqd is the designed value of the inlet gas temperature of the gas heater, and t mpy is the measured flue gas temperature at the outlet of the gas heater;

[0046] S32. Considering the deviation between the measured value and the designed value of the inlet water temperature of the high-temperature economizer, the corrected flue gas temperature at the outlet of the gas heater is calculated as t mpyδ,2 . The calculation formula is as follows:

[0047]

[0048] S33. The calculation formula for the corrected flue gas temperature t mpyδ at the outlet of the gas heater is as follows:

[0049] t mpyδ = t mpyδ,1 + t mpyδ,2 - t mpy .

[0050] Furthermore, in step S5, the flue gas flow rate at the outlet of the low-temperature economizer group is calculated based on the parameters on the flue gas side and the water side of the low-temperature economizer group and based on energy balance.

[0051] Furthermore, in step S6, the flue gas flow rate at the outlet of the gas heater is calculated based on the parameters on the gas side and the flue gas side of the gas heater.

[0052] Furthermore, in step S7, the calculation formula for the flue gas flow rate m k at the outlet of the air preheater is as follows:

[0053] m k = (1 + α) · (m g - m d - m m )

[0054] where α is the measured air preheater air leakage rate.

[0055] The beneficial effects of the present invention are:

[0056] The present invention constructs a correction method specifically for the exhaust gas temperature under the parallel system of the boiler tail flue; this correction method covers the correction of the exhaust gas temperature under the deviation of various boundary parameters from the designed values; this correction method is more accurate and does not require iteration, is simple and practical, can calculate the corrected exhaust gas temperature more accurately, can evaluate the operation economy index of the boiler more accurately, and is of great significance for assessing the boiler exhaust gas temperature and guiding the operation and optimization of new boilers. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1It is a schematic structural diagram of the parallel system of the boiler tail flue in the present invention.

[0058] Figure 2 It is a flowchart of the method for correcting the flue gas temperature of the parallel system of the boiler tail flue according to the present invention.

[0059] In the figure, 1 - high-temperature economizer, 2 - air preheater, 3 - high-pressure low-temperature economizer, 4 - low-pressure low-temperature economizer, 5 - gas heater. Specific embodiments

[0060] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0061] As Figure 1 shown in the parallel system of the boiler tail flue, the system includes a high-temperature economizer 1 provided on the boiler tail flue and a parallel component connected to the high-temperature economizer 1. The parallel component includes an air preheater 2, a low-temperature economizer group, and a gas heater 5 that are sequentially provided on the boiler tail flue. The air preheater 2, the low-temperature economizer group, and the gas heater 5 are arranged in parallel. The low-temperature economizer group includes a high-pressure low-temperature economizer 3 and a low-pressure low-temperature economizer 4.

[0062] The method for correcting the flue gas temperature of this system includes the following steps:

[0063] S1, calculate the corrected flue gas temperature t at the outlet of the air preheater kpyδ ;

[0064] The process of calculating the corrected flue gas temperature at the outlet of the air preheater in step S1 specifically includes the following steps:

[0065] S11, considering the deviation between the measured value of the air temperature at the inlet of the air preheater and the designed value of the air temperature at the inlet of the air preheater, calculate the corrected flue gas temperature t at the outlet of the air preheater kpyδ,1 , and the calculation formula is as follows:

[0066]

[0067] In the formula, t jfd is the designed value of the air temperature at the inlet of the air preheater, t jf is the measured value of the air temperature at the inlet of the air preheater, t gpy is the measured flue gas temperature at the outlet of the high-temperature economizer, t kpy is the measured flue gas temperature at the outlet of the air preheater;

[0068] S12. Consider the deviation between the measured water temperature at the inlet of the high-temperature economizer and the designed value of the water temperature at the inlet of the high-temperature economizer, and calculate the corrected flue gas temperature at the outlet of the air preheater, t kpyδ,2 , and the calculation formula is as follows:

[0069]

[0070] In the formula, t gjy is the measured flue gas temperature at the inlet of the high-temperature economizer, t gwd is the designed value of the water temperature at the inlet of the high-temperature economizer, t gw is the measured value of the water temperature at the inlet of the high-temperature economizer;

[0071] S13. The calculation formula for the corrected flue gas temperature t at the outlet of the air preheater kpyδ is as follows:

[0072] t kpyδ = t kpyδ,1 + t kpyδ,2 - t kpy .

[0073] S2. Calculate the corrected flue gas temperature t at the outlet of the low-pressure and low-temperature economizer dpyδ ;

[0074] The process of calculating the corrected flue gas temperature at the outlet of the low-pressure and low-temperature economizer in this step S2 specifically includes the following steps:

[0075] S21. Consider the deviation between the measured water temperature at the inlet of the low-pressure and low-temperature economizer and the designed value of the water temperature at the inlet of the low-pressure and low-temperature economizer, and calculate the corrected flue gas temperature t at the outlet of the low-pressure and low-temperature economizer dpyδ,1 , and the calculation formula is as follows:

[0076]

[0077] In the formula, t′ dwd is the designed value of the water temperature at the inlet of the low-pressure and low-temperature economizer, t′ dw is the measured value of the water temperature at the inlet of the low-pressure and low-temperature economizer, t djy is the measured flue gas temperature at the inlet of the low-pressure and low-temperature economizer, t dpy is the measured flue gas temperature at the outlet of the low-pressure and low-temperature economizer;

[0078] S22. Consider the deviation between the measured water temperature at the inlet of the high-pressure and low-temperature economizer and the designed value of the water temperature at the inlet of the high-pressure and low-temperature economizer, and calculate the corrected flue gas temperature t at the outlet of the low-pressure and low-temperature economizer dpyδ,2 , and the calculation formula is as follows:

[0079]

[0080] In the formula, t″ dwd is the designed value of the water temperature at the inlet of the high-pressure and low-temperature economizer, t″dw is the measured value of the inlet water temperature of the high-pressure and low-temperature economizer;

[0081] S23. Considering the deviation between the measured value of the inlet water temperature of the high-temperature economizer and the designed value of the inlet water temperature of the high-temperature economizer, the corrected outlet flue gas temperature of the low-pressure and low-temperature economizer, t, is calculated. dpyδ,3 ;

[0082] First, calculate the corrected inlet flue gas temperature of the low-pressure and low-temperature economizer, t djyδ , and the calculation formula is as follows:

[0083]

[0084] Then, calculate the corrected outlet flue gas temperature of the low-pressure and low-temperature economizer, t dpyδ,3 , and the calculation formula is as follows:

[0085]

[0086] The calculation formula for the corrected outlet flue gas temperature of the low-pressure and low-temperature economizer, t dpyδ , is as follows:

[0087] t dpyδ = t dpyδ,1 + t dpyδ,2 + t dpyδ,3 - 2t dpy .

[0088] S3. Calculate the corrected outlet flue gas temperature of the gas heater, t mpyδ ;

[0089] The process of calculating the corrected outlet flue gas temperature of the gas heater in this step S3 specifically includes the following steps:

[0090] S31. Considering the deviation between the measured value of the inlet gas temperature of the gas heater and the designed value of the inlet gas temperature of the gas heater, calculate the corrected outlet flue gas temperature of the gas heater, t mpyδ,1 , and the calculation formula is as follows:

[0091]

[0092] In the formula, t mq is the measured value of the inlet gas temperature of the gas heater, t mqd is the designed value of the inlet gas temperature of the gas heater, and t mpy is the measured outlet flue gas temperature of the gas heater;

[0093] S32. Considering the deviation between the measured value of the inlet water temperature of the high-temperature economizer and the designed value of the inlet water temperature of the high-temperature economizer, calculate the corrected outlet flue gas temperature of the gas heater, t mpyδ,2 , and the calculation formula is as follows:

[0094]

[0095] S33, the flue gas temperature t at the outlet of the corrected gas heater mpyδ The calculation formula is as follows:

[0096] t mpyδ = t mpyδ,1 + t mpyδ,2 - t mpy .

[0097] S4, calculate or measure the flue gas flow rate m at the outlet of the high-temperature economizer g , and the specific method refers to the GB or ASME method.

[0098] S5, calculate the flue gas flow rate m at the outlet of the low-temperature economizer group d ;

[0099] In this step, the flue gas flow rate at the outlet of the low-temperature economizer group is calculated based on the flue gas side and water side parameters at the outlet of the low-temperature economizer group and based on energy balance. Among them, the flue gas flow rate at the outlet of the low-pressure low-temperature economizer is equal to the flue gas flow rate at the outlet of the high-pressure low-temperature economizer, and the flue gas flow rate at the outlet of the low-temperature economizer group can take one of them. For the high-pressure low-temperature economizer, the parameters required include the flue gas temperature at the inlet and outlet of the high-pressure low-temperature economizer, the water side flow rate, pressure and temperature at the inlet and outlet of the high-pressure low-temperature economizer; for the low-pressure low-low-temperature economizer, the parameters required include the flue gas temperature at the inlet and outlet of the low-pressure low-temperature economizer, the water side flow rate, pressure and temperature at the inlet and outlet of the low-pressure low-temperature economizer.

[0100] S6, calculate the flue gas flow rate m at the outlet of the gas heater m ;

[0101] The flue gas flow rate at the outlet of the gas heater is calculated according to the gas side parameters of the gas heater (gas flow rate, gas temperature at the inlet and outlet) and the flue gas side parameters (flue gas temperature at the inlet and outlet of the gas heater).

[0102] S7, calculate the flue gas flow rate m at the outlet of the air preheater according to the air preheater leakage rate k ;

[0103] The flue gas flow rate m at the outlet of the air preheater k The calculation formula is as follows:

[0104] m k = (1 + α) · (m g - m d - m m )

[0105] Among them, α is the measured air preheater leakage rate.

[0106] S8, calculate the mixed flue gas flow rate m 混, the mixed flue gas flow rate includes the flue gas flow rate at the outlet of the air preheater, the flue gas flow rate at the outlet of the low-temperature economizer group, and the flue gas flow rate at the outlet of the gas heater;

[0107] m 混 = m d + m k + m m

[0108] S9, the corrected total exhaust gas temperature t is calculated based on the following formula pyδ :

[0109]

[0110] Table 1 is a calculation table for correcting the boiler exhaust gas temperature for the specific example data of the system for Figure 1 .

[0111] Table 1 Calculation Table for Correcting the Exhaust Gas Temperature of the Parallel System in the Boiler Tail Flue

[0112]

[0113]

[0114]

[0115] For those of ordinary skill in the art, the specific examples only exemplarily describe the present invention. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantial improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for correcting the flue gas temperature of a parallel system in the boiler tail flue. The system includes a high-temperature economizer and a parallel assembly connected to the high-temperature economizer. The parallel assembly includes an air preheater, a low-temperature economizer group, and a gas heater. The air preheater, the low-temperature economizer group, and the gas heater are arranged in parallel. The low-temperature economizer group includes a high-pressure low-temperature economizer and a low-pressure low-temperature economizer; it is characterized in that, The correction method includes the following steps: S1. Calculate the corrected flue gas temperature t at the outlet of the air preheater kpyδ ; S2, calculate the flue gas temperature t at the outlet of the modified low-pressure and low-temperature economizer dpyδ ; S3, calculate the flue gas temperature t at the outlet of the corrected gas heater mpyδ ; S4, calculate or measure the flue gas flow rate m at the outlet of the high-temperature economizer g ; S5, calculate the flue gas flow rate m at the outlet of the low-temperature economizer group d ; S6, calculate the flue gas flow rate m at the outlet of the gas heater m ; S7. Calculate the flue gas flow rate m at the outlet of the air preheater based on the air leakage rate of the air preheater k ; S8, calculate the mixed flue gas flow rate m 混 , which includes the flue gas flow rate at the outlet of the air preheater, the flue gas flow rate at the outlet of the low-temperature economizer group, and the flue gas flow rate at the outlet of the gas heater; S9, the corrected total exhaust gas temperature t is calculated based on the following formula pyδ :[[]]END]] Among them, the process of calculating the corrected flue gas temperature at the outlet of the air preheater in step S1 includes the following steps: S11. Considering the deviation between the measured value of the air temperature at the inlet of the air preheater and the designed value of the air temperature at the inlet of the air preheater, the corrected flue gas temperature at the outlet of the air preheater - t is calculated. kpyδ,1 The calculation formula is as follows: where, t jfd is the designed value of the air inlet temperature of the air preheater, and t jf is the measured value of the air inlet temperature of the air preheater, t gpy is the measured flue gas temperature at the outlet of the high-temperature economizer, and t kpy is the measured flue gas temperature at the outlet of the air preheater; S12. Considering the deviation between the measured value of the inlet water temperature of the high-temperature economizer and the designed value of the inlet water temperature of the high-temperature economizer, the corrected outlet flue gas temperature of the air preheater, i.e., t, is calculated. kpyδ,2 The calculation formula is as follows: where t gjy is the measured flue gas temperature at the inlet of the actual high-temperature economizer, t gwd is the designed value of the water temperature at the inlet of the high-temperature economizer, t gw is the measured value of the water temperature at the inlet of the high-temperature economizer; S13, the corrected flue gas temperature t at the outlet of the air preheater kpyδ The calculation formula is as follows: t kpyδ = t kpyδ,1 + t kpyδ,2 - t kpy ; The process of calculating the corrected flue gas temperature at the outlet of the low-pressure and low-temperature economizer in step S2 includes the following steps: S21. Considering the deviation between the measured value of the inlet water temperature of the low-pressure and low-temperature economizer and the designed value of the inlet water temperature of the low-pressure and low-temperature economizer, the corrected outlet flue gas temperature - t of the low-pressure and low-temperature economizer is calculated as follows: dpyδ,1 , and the calculation formula is as follows: where t' dwd is the designed inlet water temperature of the low-pressure and low-temperature economizer, and t' dw is the measured inlet water temperature of the low-pressure and low-temperature economizer, t djy is the measured inlet flue gas temperature of the low-pressure and low-temperature economizer, and t dpy is the measured outlet flue gas temperature of the low-pressure and low-temperature economizer; S22. Considering the deviation between the measured value of the inlet water temperature of the high-pressure low-temperature economizer and the designed value of the inlet water temperature of the high-pressure low-temperature economizer, the corrected outlet flue gas temperature of the low-pressure low-temperature economizer, i.e., θ, is calculated as follows: dpyδ,2 , and the calculation formula is as follows: where, t” dwd is the designed value of the water temperature at the inlet of the high-pressure and low-temperature economizer, and t” dw is the measured value of the water temperature at the inlet of the high-pressure and low-temperature economizer; S23. Considering the deviation between the measured value of the inlet water temperature of the high-temperature economizer and the designed value of the inlet water temperature of the high-temperature economizer, the corrected outlet flue gas temperature θt of the low-pressure and low-temperature economizer is calculated. dpyδ,3 ; First, calculate the corrected inlet flue gas temperature t of the low-pressure and low-temperature economizer djyδ , and the calculation formula is as follows: Then, calculate the corrected outlet flue gas temperature θt of the low-pressure and low-temperature economizer dpyδ,3 , and the calculation formula is as follows: Revised outlet flue gas temperature t of the low-pressure and low-temperature economizer dpyδ The calculation formula is as follows: t dpyδ = t dpyδ,1 + t dpyδ,2 + t dpyδ,3 - 2t dpy ; The process of calculating the corrected flue gas temperature at the outlet of the gas heater in step S3 includes the following steps: S31. Considering the deviation between the measured value of the inlet gas temperature of the gas heater and the designed value of the inlet gas temperature of the gas heater, the corrected flue gas temperature at the outlet of the gas heater - t is calculated. mpyδ,1 The calculation formula is as follows: where t mq is the measured value of the inlet gas temperature of the gas heater, and t mqd is the designed value of the inlet gas temperature of the gas heater, and t mpy is the measured outlet flue gas temperature of the gas heater; S32. Considering the deviation between the measured value of the water temperature at the inlet of the high-temperature economizer and the designed value of the water temperature at the inlet of the high-temperature economizer, the corrected flue gas temperature t at the outlet of the gas heater is calculated. mpyδ,2 The calculation formula is as follows: S33, the flue gas temperature t at the outlet of the corrected gas heater mpyδ The calculation formula is as follows: t mpyδ = t mpyδ,1 + t mpyδ,2 - t mpy 。 2. A method for correcting the flue gas temperature of a parallel system for the boiler tail flue gas according to claim 1, characterized in that, In step S5, the flue gas flow rate at the outlet of the low-temperature economizer group is calculated based on the flue gas side and water side parameters at the outlet of the low-temperature economizer group and based on energy balance.

3. A method for correcting the flue gas temperature of a parallel system for the boiler tail flue, as claimed in claim 1, wherein In step S6, the flue gas flow rate at the outlet of the gas heater is calculated according to the gas side and flue gas side parameters of the gas heater.

4. A method for correcting the flue gas temperature of a parallel system for the boiler tail flue, according to claim 1, characterized in that In step S7, the flue gas flow rate m at the outlet of the air preheater k is calculated as follows: m k = (1 + α)·(m g - m d - m m ) Among them, α is the measured air preheater air leakage rate.

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