Boiler flue gas temperature correction method based on external heat transfer of tail flue gas

Abstract

The application relates to a boiler flue gas temperature correction method based on external heat transfer of tail flue gas, and relates to the technical field of power plant boiler energy saving. The application solves the problem that the traditional boiler flue gas temperature correction method cannot be applied to the scene of introducing external heat exchange devices into a boiler system. The method is realized based on heat exchange devices introduced outside the tail flue of the boiler system, each heat exchange device outside the tail flue is arranged in a corresponding branch flue, and the inlet and outlet of each branch flue are communicated with the tail flue of the boiler. According to the collected operation data of the boiler system and the introduced heat exchange devices, the application corrects the inlet air temperature measured value and the feed water temperature measured value to the outlet flue gas temperature of the lower air preheater corresponding to the design value, and further corrects the corrected boiler flue gas temperature under the external heat exchange scene. The application is mainly applied to the correction of the boiler flue gas temperature under external heat transfer.

Description

Technical Field

[0001] This invention relates to the field of energy-saving technology for power plant boilers. Background Technology

[0002] For power plant boilers, boiler fuel efficiency is a crucial means of evaluating the boiler's energy utilization level and energy consumption. The testing process generally requires that characteristic parameters such as inlet air, feedwater, and fuel meet design requirements to facilitate comparison of the same boiler's operating conditions at different times. When some characteristic parameters deviate from design values, within a certain deviation range, boiler fuel efficiency correction is necessary. Among these, the correction of flue gas temperature caused by deviations in measured inlet air and feedwater temperatures from design values ​​is a critical step. This is because when inlet air and feedwater temperatures deviate from design values, it is equivalent to a change in the working fluid inlet temperature of the air preheater and economizer, inevitably affecting the heat exchange effect between the working fluid and flue gas within the air preheater and economizer, ultimately impacting the flue gas temperature. Flue gas temperature is a vital parameter for calculating boiler fuel efficiency. Accurately converting the actual boiler flue gas temperature to the flue gas temperature under design inlet air and feedwater temperatures (i.e., boiler flue gas temperature correction) to obtain the corrected boiler fuel efficiency is crucial for accurately determining whether boiler efficiency has decreased due to equipment aging, developing targeted maintenance and repair plans, and evaluating the actual effectiveness of energy-saving retrofit measures.

[0003] Figure 1 This is the conventional layout of the economizer and air preheater in the tail flue of the boiler in existing technology. Figure 1 Under this layout, the traditional method for correcting boiler flue gas temperature yields the following corrected flue gas temperature:

[0004] ;

[0005] In the formula, The exhaust gas temperature (unit: °C) is the result of correcting both the measured inlet air temperature and the measured water supply temperature to their corresponding design values. Design value for inlet air temperature (unit: °C); The air preheater inlet flue gas temperature (unit: °C). Currently, most air preheaters consist of an upper-stage air preheater and a lower-stage air preheater connected in series (see...). Figure 1 ), so here Specifically, it can be the inlet flue gas temperature of the upper-level air preheater; The air preheater outlet flue gas temperature (unit: °C) can be specifically the outlet flue gas temperature of the next stage air preheater, which is the boiler exhaust temperature. The inlet air temperature is the measured value (unit: °C). The economizer inlet flue gas temperature (unit: °C). Currently, most economizers consist of an upper-stage economizer and a lower-stage economizer connected in series (see...). Figure 1 ), so here Specifically, it can be the inlet flue gas temperature of the upper-level economizer; The economizer outlet flue gas temperature (unit: °C) can be specifically the outlet flue gas temperature of the next stage economizer. The measured value of the water supply temperature (unit: °C); This is the design value for water supply temperature (unit: °C).

[0006] However, some power plant boilers currently extract a portion of the hot flue gas from the tail flue as a heat source for external heat exchange devices (such as low-temperature SCR denitrification devices and activated carbon adsorption devices); the flue gas after heat exchange is usually returned to the tail flue. Traditional boiler exhaust temperature correction methods only apply when all tail flue gas passes through the economizer and air preheater sequentially, meaning all flue gas temperature changes originate from heat exchange with the inlet air and feedwater, and are related to the inlet air and feedwater temperatures. When external heat exchange devices exist and tail flue gas transfers heat to the outside, flue gas temperature changes are also affected by external factors. Therefore, traditional boiler exhaust temperature correction methods are no longer applicable, the calculation results are no longer accurate, and a new derivation is required.

[0007] Therefore, traditional boiler flue gas temperature correction methods are only applicable when the tail flue gas only exchanges heat in the economizer and air preheater. Figure 1 In application scenarios where there are external heat exchange devices in the boiler and the tail flue gas transfers heat to the outside, the traditional boiler exhaust temperature correction method cannot be applied to scenarios where the boiler system introduces external heat exchange devices. The above problems urgently need to be solved. Summary of the Invention

[0008] The purpose of this invention is to solve the problem that traditional boiler flue gas temperature correction methods cannot be applied to scenarios where external heat exchange devices are introduced into the boiler system. This invention provides a boiler flue gas temperature correction method based on external heat transfer from the tail flue gas.

[0009] A boiler exhaust gas temperature correction method based on external heat transfer from tail flue gas is implemented using heat exchange devices introduced outside the tail flue of the boiler system. Each heat exchange device is installed in a corresponding branch flue, and the inlet and outlet of each branch flue are connected to the tail flue of the boiler. The layout of each branch flue is determined according to the flue gas temperature requirements of the heat exchange devices in that branch flue, and the flue gas temperature requirements of each heat exchange device are different. An upper economizer, a lower economizer, an upper air preheater, and a lower air preheater are arranged sequentially along the flue gas flow direction in the tail flue. The corresponding positions of the tail flue upstream of the upper economizer, between the upper and lower economizers, between the lower economizer and the upper air preheater, between the upper and lower air preheaters, and downstream of the lower air preheater are all considered as the connection points between the tail flue and the branch flues.

[0010] The method includes:

[0011] S1. Based on the collected operating data of the boiler system and its heat exchange devices, calculate the actual flue gas temperature entering the air preheater system. Actual flue gas temperature leaving the air preheater system When the inlet air temperature is the measured value, the theoretical limit flue gas temperature of the air preheater system is... When the inlet air temperature is at the design value, the theoretical limit flue gas temperature of the air preheater system is... Actual flue gas temperature entering the economizer system Actual flue gas temperature leaving the economizer system When the feedwater temperature is the measured value, the flue gas temperature deviates from the theoretical limit temperature of the economizer system. ;

[0012] S2, according to , and Calculate the flue gas side heat transfer efficiency of the air preheater system. ;

[0013] according to Determine the cold-end temperature difference characteristic coefficient of the air preheater system. ;

[0014] according to , and Calculate the heat transfer efficiency on the flue gas side of the economizer system. ;

[0015] S3, according to , and Constructing conversion factors ;

[0016] S4. Reuse The measured value of the inlet air temperature in the collected operational data and the design value of the air intake temperature For the outlet flue gas temperature of the lower-stage air preheater After correction, the measured inlet air temperature is corrected to its corresponding design value, resulting in the downstream air preheater outlet flue gas temperature. ;

[0017] S5, Utilization , The measured values ​​of feedwater temperature in the collected operational data and water supply temperature design value right After correction, the measured values ​​of the inlet air temperature and feedwater temperature are obtained, both corrected to their corresponding design values, resulting in the downstream air preheater outlet flue gas temperature. ;

[0018] S6. Based on the collected operational data, the percentage of flue gas mass flow rate corresponding to the branch flue located downstream of the lower-level air preheater relative to the total flue gas mass flow rate of the tail flue, and the corresponding outlet flue temperature of the branch flue... After correction, the corrected boiler flue gas temperature for the external heat exchange scenario is obtained. .

[0019] Preferably, the flue gas temperature requirements for each branch flue include the matching requirements between the inlet and outlet flue gas temperatures of the branch flue and the flue gas temperature in the tail flue. Specifically, the inlet flue gas temperature of the branch flue is close to the flue gas temperature at the corresponding connection point of the tail flue, and the outlet flue gas temperature of the branch flue is close to the flue gas temperature at the corresponding connection point of the tail flue.

[0020] Preferably, the number of heat exchange devices introduced outside the tail flue is 10, wherein,

[0021] The inlets of the branch flues where heat exchangers 1, 2, 3 and 7 are located are all upstream of the upper economizer;

[0022] The outlet of the branch flue where heat exchanger No. 1 is located, and the inlet of the branch flue where heat exchangers No. 4, 5 and 8 are located between the upper economizer and the lower economizer.

[0023] The outlets of the branch flues where heat exchangers No. 2 and No. 5 are located, and the inlets of the branch flues where heat exchangers No. 6 and No. 9 are located between the lower economizer and the upper air preheater.

[0024] The outlets of the branch flues where heat exchangers 3, 4 and 6 are located, and the inlet of the branch flue where heat exchanger 10 is located, are all located between the upper-stage air preheater and the lower-stage air preheater.

[0025] The outlets of the branch flues where heat exchangers 7 to 10 are located are all downstream of the lower-level air preheater.

[0026] Preferably, in step S1, the actual flue gas temperature entering the air preheater system is calculated. Actual flue gas temperature leaving the air preheater system When the inlet air temperature is the measured value, the theoretical limit flue gas temperature of the air preheater system is... When the inlet air temperature is at the design value, the theoretical limit flue gas temperature of the air preheater system is... Actual flue gas temperature entering the economizer system Actual flue gas temperature leaving the economizer system When the feedwater temperature is the measured value, the flue gas temperature deviates from the theoretical limit temperature of the economizer system. The implementation method is as follows:

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] ;

[0032] ;

[0033] ;

[0034] in, to These represent the percentage of the flue gas mass flow rate of the branch flues where heat exchangers 1 to 10 are located, relative to the total flue gas mass flow rate of the tail flue. These are the outlet flue gas temperatures collected from heat exchangers 1, 3, 4, and 6, respectively. The collected flue gas temperature at the inlet of the upper-level air preheater. The collected flue gas temperature at the inlet of the upper-level economizer. These are the collected flue gas temperatures at the inlet and outlet of the lower-level economizer, respectively. These are the flue gas temperatures collected at the inlet and outlet of the lower-level air preheater, respectively.

[0035] Preferably, in step S2,

[0036] ;

[0037] ;

[0038] .

[0039] Preferably, .

[0040] Preferably, .

[0041] Preferably, .

[0042] Preferably,

[0043] ;

[0044] in, The values ​​represent the outlet flue gas temperatures of heat exchangers 7, 8, 9, and 10, respectively.

[0045] The beneficial effects of this invention are:

[0046] This invention addresses the problem that traditional boiler flue gas temperature correction methods are only applicable to a single scenario where the tail gas passes through the economizer and air preheater sequentially without external heat transfer during power plant boiler fuel efficiency testing and evaluation. In complex operating conditions involving external boiler heat exchange devices and external heat transfer of the tail gas, the traditional correction method yields inaccurate results. By re-deriving the correction method, this invention offers the core advantages of wider applicability, more accurate calculation results, and compatibility with existing boiler fuel efficiency testing systems. The development process prioritized adaptability to complex real-world conditions and the rigor of the calculation process, ultimately achieving a significant reduction in boiler fuel efficiency testing errors under complex conditions and providing reliable data support for power plant boiler users to contribute to energy conservation and emission reduction goals. Attached Figure Description

[0047] Figure 1 This is a conventional layout diagram of the economizer system and air preheater system in the tail flue of a boiler in existing technology;

[0048] Figure 2 This is a layout diagram of the 10 heat exchange devices in Specific Implementation Method 1 relative to the economizer system and air preheater system in the tail flue.

[0049] Figure 3 This is a flowchart of the boiler flue gas temperature correction method based on external heat transfer from tail flue gas, as described in this invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0052] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0053] Detailed Implementation Method 1, see [link / reference] Figure 3 This embodiment describes a boiler exhaust temperature correction method based on external heat transfer from tail flue gas. This method is implemented using heat exchange devices introduced outside the tail flue of the boiler system. Each heat exchange device outside the tail flue is installed in a corresponding branch flue. The inlet and outlet of each branch flue are connected to the tail flue of the boiler. The layout of each branch flue is determined according to the flue temperature requirement of the heat exchange device in that branch flue, and the flue temperature requirements of each heat exchange device are different.

[0054] An upper-stage economizer, a lower-stage economizer, an upper-stage air preheater, and a lower-stage air preheater are sequentially arranged along the flue gas flow direction within the tail flue. The corresponding positions in the tail flue upstream of the upper-stage economizer, between the upper and lower-stage economizers, between the lower-stage economizer and the upper-stage air preheater, between the upper and lower-stage air preheaters, and downstream of the lower-stage air preheater are all considered as connection points between the tail flue and the branch flue. This method includes:

[0055] S1. Based on the collected operating data of the boiler system and its heat exchange devices, calculate the actual flue gas temperature entering the air preheater system. Actual flue gas temperature leaving the air preheater system When the inlet air temperature is the measured value, the theoretical limit flue gas temperature of the air preheater system is... When the inlet air temperature is at the design value, the theoretical limit flue gas temperature of the air preheater system is... Actual flue gas temperature entering the economizer system Actual flue gas temperature leaving the economizer system When the feedwater temperature is the measured value, the flue gas temperature deviates from the theoretical limit temperature of the economizer system. ;

[0056] The collected operational data includes to , , , , , , and ;

[0057] to The figures represent the percentage of the flue gas mass flow rate of the branch flues where heat exchangers 1 to 10 are located, relative to the total flue gas mass flow rate of the tail flue (unit: dimensionless). The figures represent the outlet flue gas temperatures (in °C) of heat exchangers 1, 3, 4, 6, 7, 8, 9, and 10, respectively. The collected flue gas temperature at the inlet of the upper-stage air preheater (unit: °C). The collected flue gas temperature at the inlet of the upper-level economizer (unit: °C). These are the collected flue gas temperatures at the inlet and outlet of the lower-level economizer (unit: °C). These are the collected flue gas temperatures at the inlet and outlet of the lower-level air preheater (unit: °C). The measured value of the inlet air temperature (unit: °C). The measured value of the water supply temperature (unit: °C);

[0058] In practical applications, when , and When the value cannot be obtained directly through measurement, it can be obtained using the following formula:

[0059] Formula 1;

[0060] Formula 2;

[0061] Formula 3;

[0062] in, , The values ​​are the outlet flue gas temperatures (unit: °C) of heat exchangers 2 and 5, respectively. The collected flue gas temperature at the outlet of the upper-level economizer (unit: °C). The collected flue gas temperature at the outlet of the upper-stage air preheater (unit: °C);

[0063] S2, according to , and Calculate the flue gas side heat transfer efficiency of the air preheater system. (Unit: dimensionless)

[0064] according to Determine the cold-end temperature difference characteristic coefficient of the air preheater system. (Unit: dimensionless)

[0065] according to , and Calculate the heat transfer efficiency on the flue gas side of the economizer system. (Unit: dimensionless)

[0066] S3, according to , and Constructing conversion factors (Unit: dimensionless); specifically,

[0067] Formula 4;

[0068] S4. Reuse The measured value of the inlet air temperature in the collected operational data and the design value of the air intake temperature For the outlet flue gas temperature of the lower-stage air preheater After correction, the measured inlet air temperature is corrected to its corresponding design value, resulting in the downstream air preheater outlet flue gas temperature. (Unit: °C); Specifically,

[0069] Formula 5;

[0070] Get During the process, the correction of boiler flue gas temperature caused by correcting the measured value of the inlet air temperature to the design value was taken into account.

[0071] S5, Utilization , The measured values ​​of feedwater temperature in the collected operational data and water supply temperature design value right After correction, the measured values ​​of the inlet air temperature and feedwater temperature are obtained, both corrected to their corresponding design values, resulting in the downstream air preheater outlet flue gas temperature. (Unit: °C); Specifically,

[0072] Formula 6;

[0073] Get During the process, the correction of boiler flue gas temperature caused by correcting the measured value of feedwater temperature to the design value was taken into account.

[0074] S6. Based on the collected operational data, the percentage of flue gas mass flow rate corresponding to the branch flue located downstream of the lower-level air preheater relative to the total flue gas mass flow rate of the tail flue, and the corresponding outlet flue temperature of the branch flue... After correction, the corrected boiler flue gas temperature for the external heat exchange scenario is obtained. (Unit: °C); Specifically,

[0075] Formula 7.

[0076] Figure 1 Under normal circumstances, the outlet flue gas temperature of the lower-stage air preheater is the same as the boiler exhaust temperature. However, when an external heat exchange device is introduced into the boiler system, the temperature is... Figure 2 For example, the flue gas from the branch flues corresponding to heat exchangers 7 to 10 returns to the boiler tail flue. At this time, the boiler exhaust temperature is not equal to the outlet flue gas temperature of the lower-level air preheater, but is determined by the outlet flue gas temperature of the lower-level air preheater and the outlet flue gas temperatures of heat exchangers 7 to 10.

[0077] Furthermore, the flue gas temperature requirements for each branch flue include the matching requirements between the inlet and outlet flue gas temperatures of the branch flue and the flue gas temperature in the tail flue. Specifically, the inlet flue gas temperature of the branch flue should be close to the flue gas temperature at the corresponding connection point of the tail flue, and the outlet flue gas temperature of the branch flue should be close to the flue gas temperature at the corresponding connection point of the tail flue.

[0078] In practical applications, Figure 1 The heat exchange devices introduced outside the tail flue of the boiler system can have up to 10 different layout options. For details, please refer to [link / reference needed]. Figure 2 The number of heat exchange devices introduced outside the tail flue is 10, of which,

[0079] The inlets of the branch flues where heat exchangers 1, 2, 3 and 7 are located are all upstream of the upper economizer;

[0080] The outlet of the branch flue where heat exchanger No. 1 is located, and the inlet of the branch flue where heat exchangers No. 4, 5 and 8 are located between the upper economizer and the lower economizer.

[0081] The outlets of the branch flues where heat exchangers No. 2 and No. 5 are located, and the inlets of the branch flues where heat exchangers No. 6 and No. 9 are located between the lower economizer and the upper air preheater.

[0082] The outlets of the branch flues where heat exchangers 3, 4 and 6 are located, and the inlet of the branch flue where heat exchanger 10 is located, are all located between the upper-stage air preheater and the lower-stage air preheater.

[0083] The outlets of the branch flues where heat exchangers 7 to 10 are located are all downstream of the lower-level air preheater.

[0084] Furthermore, in step S1, the actual flue gas temperature entering the air preheater system is calculated. Actual flue gas temperature leaving the air preheater system When the inlet air temperature is the measured value, the theoretical limit flue gas temperature of the air preheater system is... When the inlet air temperature is at the design value, the theoretical limit flue gas temperature of the air preheater system is... Actual flue gas temperature entering the economizer system Actual flue gas temperature leaving the economizer system When the feedwater temperature is the measured value, the flue gas temperature deviates from the theoretical limit temperature of the economizer system. The implementation method is as follows:

[0085] Formula 8;

[0086] Formula 9;

[0087] Formula 10;

[0088] Formula 11;

[0089] Formula 12;

[0090] Formula 13;

[0091] Formula 14;

[0092] In this preferred embodiment, it is assumed that no flue gas leakage occurs and changes in the specific heat capacity of the flue gas are ignored. It can characterize the heat carried by the flue gas actually entering the air preheater system. This can characterize the heat carried by the flue gas actually leaving the air preheater system. It can characterize the theoretical minimum heat carried by the flue gas leaving the air preheater system when the inlet air temperature is the measured value. It can characterize the theoretical minimum heat carried by the flue gas leaving the air preheater system when the inlet air temperature is at the design value. It can characterize the heat carried by the flue gas actually entering the economizer system. This can characterize the heat carried by the flue gas actually leaving the economizer system. This can characterize the theoretical minimum heat carried by the flue gas leaving the economizer system when the feedwater temperature is the measured value. This expression simplifies the heat carried by the flue gas when entering and leaving the air preheater and economizer system into a function of flue gas temperature, while ensuring calculation accuracy.

[0093] Furthermore, in step S2,

[0094] Formula 15;

[0095] Formula 16;

[0096] Formula 17.

[0097] In this preferred embodiment, the heat exchange efficiency of the air preheater system on the flue gas side The construction process considers the heat release capacity of the flue gas side of the air preheater system, the ultimate potential of the system's heat exchange, and the effectiveness of heat transfer. It characterizes the actual heat released by the flue gas to the working medium (air) in the air preheater system, and is related to the temperature of the flue gas from its initial temperature ( ) decreased to the actual intake air temperature ( The ratio of the theoretically maximum heat that can be released is used to measure the actual utilization of the heat transfer capacity of the flue gas side of the air preheater system.

[0098] Cold end temperature difference characteristic coefficient of air preheater system The construction process takes into account the driving force of heat exchange at the cold end of the air preheater system and the rationality of the design of the cold end of the air preheater. It is a characteristic parameter that characterizes the actual heat exchange temperature difference at the cold end of the air preheater system (air inlet side and flue gas outlet side) and is used to judge the degree of heat exchange at the cold end and the potential risks of condensation and corrosion.

[0099] Economizer system flue gas side heat exchange efficiency The construction process considers the heat release capacity of the economizer system's flue gas side, the system's ultimate heat exchange potential, and the effectiveness of heat transfer. It characterizes the actual heat released by the flue gas to the working fluid (water) in the economizer system, and is related to the temperature of the flue gas from its initial temperature ( ) dropped to the actual feedwater temperature ( The ratio of the theoretically maximum heat that can be released is used to measure the actual utilization of the heat transfer capacity of the economizer system on the flue gas side.

[0100] Since the arrangement of the 10 heat exchange devices introduced in this invention covers all cases of external heat exchange in the tail flue, the following examples further illustrate this:

[0101] Example 1: When only heat exchanger #4 is working, and the other heat exchangers are shut down, , , , , , , , , Normal data collection ,as well as All were 0, except for the outlet flue gas temperature of heat exchanger No. 4. Apart from this, the outlet flue gas temperature of other heat exchangers does not need to be collected, and the inlet air temperature is the design value. and water supply temperature design value Since all parameters are known, then:

[0102] Formula 18;

[0103] Formula 19;

[0104] Formula 20;

[0105] Formula 21;

[0106] Formula 22;

[0107] Formula 23;

[0108] Formula 24;

[0109] Formula 25;

[0110] Formula 26;

[0111] Formula 27;

[0112] Formula 28;

[0113] Formula 29;

[0114] Formula 30.

[0115] Example 2:

[0116] When only heat exchangers No. 1 and No. 8 are operating, and the other heat exchangers are shut down, then , , , , , , , , , , Normal data collection ,as well as All were 0, except for the outlet flue gas temperature of heat exchangers 1 and 8. and Apart from this, the outlet flue gas temperature of other heat exchangers does not need to be collected, and the inlet air temperature is the design value. and water supply temperature design value Since all parameters are known, then:

[0117] Formula 31;

[0118] Formula 32;

[0119] Formula 33;

[0120] Formula 34;

[0121] Formula 35;

[0122] Formula 36;

[0123] Formula 37;

[0124] Formula 38;

[0125] Formula 39;

[0126] Formula 40;

[0127] Formula 41;

[0128] Formula 42;

[0129] Formula 43.

[0130] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for correcting boiler flue gas temperature based on heat transfer from the tail flue gas to the outside. This method is implemented using heat exchange devices introduced outside the tail flue of the boiler system. Each heat exchange device is installed in a corresponding branch flue. The inlet and outlet of each branch flue are connected to the tail flue of the boiler. The layout of each branch flue is determined according to the flue gas temperature requirement of the heat exchange device in that branch flue, and the flue gas temperature requirements of each heat exchange device are different. An upper economizer, a lower economizer, an upper air preheater, and a lower air preheater are sequentially arranged along the flue gas flow direction in the tail flue. The corresponding positions of the tail flue upstream of the upper economizer, between the upper and lower economizers, between the lower economizer and the upper air preheater, between the upper and lower air preheaters, and downstream of the lower air preheater are all considered as the connection points between the tail flue and the branch flues. The method is characterized by... The number of heat exchange devices introduced outside the tail flue is 10, of which, The inlets of the branch flues where heat exchangers 1, 2, 3 and 7 are located are all upstream of the upper economizer; The outlet of the branch flue where heat exchanger No. 1 is located, and the inlet of the branch flue where heat exchangers No. 4, 5 and 8 are located between the upper economizer and the lower economizer. The outlets of the branch flues where heat exchangers No. 2 and No. 5 are located, and the inlets of the branch flues where heat exchangers No. 6 and No. 9 are located between the lower economizer and the upper air preheater. The outlets of the branch flues where heat exchangers 3, 4 and 6 are located, and the inlet of the branch flue where heat exchanger 10 is located, are all located between the upper-stage air preheater and the lower-stage air preheater. The outlets of the branch flues where heat exchangers 7 to 10 are located are all downstream of the lower-level air preheater; The method includes: S1. Based on the collected operating data of the boiler system and its introduced heat exchange devices, calculate the actual flue gas temperature entering the air preheater system. Actual flue gas temperature leaving the air preheater system When the inlet air temperature is the measured value, the theoretical limit flue gas temperature of the air preheater system is... When the inlet air temperature is at the design value, the theoretical limit flue gas temperature of the air preheater system is... Actual flue gas temperature entering the economizer system Actual flue gas temperature leaving the economizer system When the feedwater temperature is the measured value, the flue gas temperature deviates from the theoretical limit temperature of the economizer system. ; S2, according to , and Calculate the flue gas side heat transfer efficiency of the air preheater system. ;in, ; according to Determine the cold-end temperature difference characteristic coefficient of the air preheater system. ;in, ; according to , and Calculate the heat transfer efficiency of the flue gas side of the economizer system. ;in, ; S3, according to , and Constructing conversion factors ; S4. Reuse The measured value of the inlet air temperature in the collected operational data and the design value of the air intake temperature For the outlet flue gas temperature of the lower-stage air preheater After correction, the measured inlet air temperature is corrected to its corresponding design value, resulting in the downstream air preheater outlet flue gas temperature. ; S5, Utilization , The measured values ​​of feedwater temperature in the collected operational data and water supply temperature design value right After correction, the measured values ​​of the inlet air temperature and feedwater temperature are obtained, both corrected to their corresponding design values, resulting in the downstream air preheater outlet flue gas temperature. ; S6. Based on the collected operational data, the percentage of flue gas mass flow rate corresponding to the branch flue located downstream of the lower-level air preheater relative to the total flue gas mass flow rate of the tail flue, and the corresponding outlet flue temperature of the branch flue... After correction, the corrected boiler flue gas temperature for the external heat exchange scenario is obtained. .

2. The boiler flue gas temperature correction method based on external heat transfer from tail flue gas according to claim 1, characterized in that, The flue temperature requirements for each branch flue include the matching requirements between the inlet and outlet flue temperature and the flue temperature in the tail flue. Specifically, the inlet flue temperature of the branch flue should be close to the flue temperature at the corresponding connection point of the tail flue, and the outlet flue temperature of the branch flue should be close to the flue temperature at the corresponding connection point of the tail flue.

3. The boiler flue gas temperature correction method based on external heat transfer from tail flue gas according to claim 1, characterized in that, In step S1, the actual flue gas temperature entering the air preheater system is calculated. Actual flue gas temperature leaving the air preheater system When the inlet air temperature is the measured value, the theoretical limit flue gas temperature of the air preheater system is... When the inlet air temperature is at the design value, the theoretical limit flue gas temperature of the air preheater system is... Actual flue gas temperature entering the economizer system Actual flue gas temperature leaving the economizer system When the feedwater temperature is the measured value, the flue gas temperature deviates from the theoretical limit temperature of the economizer system. The implementation method is as follows: ； ； ； ； ； ； ； in, to These represent the percentage of the flue gas mass flow rate of the branch flues where heat exchangers 1 to 10 are located, relative to the total flue gas mass flow rate of the tail flue. These are the outlet flue gas temperatures collected from heat exchangers 1, 3, 4, and 6, respectively. The collected flue gas temperature at the inlet of the upper-level air preheater. The collected flue gas temperature at the inlet of the upper-level economizer. These are the inlet and outlet flue gas temperatures of the lower-level economizer, respectively. These are the inlet and outlet flue gas temperatures of the lower-level air preheater, respectively.

4. The boiler flue gas temperature correction method based on external heat transfer from tail flue gas according to claim 1, characterized in that, 。 5. The boiler flue gas temperature correction method based on external heat transfer from tail flue gas according to claim 1, characterized in that, 。 6. The boiler flue gas temperature correction method based on external heat transfer from tail flue gas according to claim 1, characterized in that, ； in, The values ​​represent the outlet flue gas temperatures of heat exchangers 7, 8, 9, and 10, respectively.

Images