Method and device for determining primary and secondary air volume of coal-fired boiler based on heat balance

Abstract

The application discloses a coal-fired boiler primary and secondary air volume determination method and device based on heat balance, which comprises the following steps: obtaining the running state information of the coal-fired boiler, wherein the running state information comprises environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, a first temperature measurement value related to the coal mill system and a second temperature measurement value related to the air preheater system; calculating the cold primary air volume and the hot primary air volume of each coal mill and the total hot primary air volume and the total cold primary air volume of all coal mills according to the environmental parameters, the coal quality analysis parameters and the first temperature measurement value; calculating the total secondary air volume according to the environmental parameters, the air preheater inlet flue gas parameters, the coal quality analysis parameters and the second temperature measurement value; and adjusting the opening degree of the cold primary air adjusting baffle at the inlet of each coal mill to the hot primary air adjusting baffle based on the cold primary air volume, the hot primary air volume, the total hot primary air volume, the total cold primary air volume and the total secondary air volume.

Description

Technical Field

[0001] This invention relates to the field of air volume measurement technology for flue gas systems of thermal power units, specifically to a method and apparatus for determining the primary and secondary air volumes of a coal-fired boiler based on thermal balance. Background Technology

[0002] As the main production equipment in thermal power plants, the economic efficiency and safety of coal-fired boilers directly impact the competitiveness and safety of these enterprises. The combustion and flue gas systems in coal-fired boilers are complex control systems with multiple inputs, multiple outputs, strong coupling, multiple interferences, and large time lags. Accurate control of the primary and secondary air volumes is crucial for ensuring the ventilation and drying output of the pulverizing system and for ensuring the rational grading and distribution of secondary air entering the furnace. Therefore, accurately measuring the volume of cold and hot primary air entering the coal mill system and the volume of secondary air entering the boiler is essential for determining the normal output of the pulverizing system under different coal qualities and for guiding the combustion status within the furnace.

[0003] Existing airflow measurement devices for thermal power units are susceptible to interference from fluid media, with issues such as blockage of measuring orifices in Pitot tubes and other airflow measurement devices leading to inaccurate measurements. Furthermore, the flue gas volume in traditional flue gas systems is affected by turbulent flow and flow stratification, resulting in unrepresentative flow measurement points. Patent application CN108405165A proposes a method for determining the primary airflow of a direct-fired coal mill. This method calculates the primary airflow using parameters such as the heat balance equation, ambient atmospheric pressure, the measured outlet airflow velocity of the direct-fired coal mill, and the corresponding desiccant flow rate. However, the outlet airflow velocity and desiccant flow rate are often affected by turbulent flow, making accurate measurement impossible and impacting the precise calculation of the primary airflow. The patent application document CN114909670A proposes a composite heat transfer synergistic control system for adaptable hot air heating to various coal types. By setting two separate air preheaters and using logical judgment to control parameters within a set range, the system still relies on unreliable and inaccurate air volume measurement devices for parameters such as the coal mill inlet air volume. Furthermore, it fails to achieve precise control of the primary and secondary air volumes as well as the coal mill inlet air volume. The set range changes for different coal types and operating conditions, requiring resetting, and is highly subjective, allowing only qualitative analysis. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to accurately calculate the primary and secondary air volumes to precisely guide the adjustment and control of the pulverizing system and the combustion system.

[0005] The present invention solves the above-mentioned technical problems through the following technical means:

[0006] In a first aspect, the present invention proposes a method for determining the primary and secondary air volumes of a coal-fired boiler based on heat balance, the method comprising:

[0007] The operating status information of the coal-fired boiler is obtained, including environmental parameters, flue gas parameters at the air preheater inlet, coal quality analysis parameters, first temperature measurement values ​​related to the coal mill system, and second temperature measurement values ​​related to the air preheater system.

[0008] Based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value, calculate the cold primary air volume and hot primary air volume of each coal mill, as well as the total hot primary air volume and total cold primary air volume of all coal mills.

[0009] Calculate the total secondary air volume based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, and the second temperature measurement value.

[0010] Based on the aforementioned cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume, adjust the opening of the cold primary air regulating damper at the inlet of each coal mill to the opening of the hot primary air regulating damper.

[0011] Furthermore, the first temperature measurement value includes the temperature on the cold primary air main pipe, the temperature on the hot primary air main pipe, the temperature on the cold and hot primary air mixing pipe at the coal mill inlet, the temperature on the pipe from the coal feeder outlet to the coal mill inlet, and the temperature on the primary air pulverized coal pipe at the coal mill outlet.

[0012] The second temperature measurement value includes the temperature on the hot primary air header at the air preheater outlet, the temperature on the primary air fan outlet pipe at the air preheater inlet, the temperature on the secondary air pipe at the air preheater outlet, the temperature on the blower outlet pipe at the air preheater inlet, the temperature on the flue gas pipe at the air preheater inlet, and the temperature on the flue gas pipe at the air preheater outlet.

[0013] Further, the step of calculating the cold primary air volume and hot primary air volume of each coal mill, as well as the total hot primary air volume and total cold primary air volume of all coal mills, based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value, includes:

[0014] Based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value, the cold primary air volume and hot primary air volume of each coal mill are calculated using the heat balance formula.

[0015] Calculate the total hot primary air volume and total cold primary air volume of all coal mills based on the cold primary air volume and hot primary air volume of each coal mill.

[0016] Further, the step of calculating the cold primary air volume and hot primary air volume of each coal mill using a heat balance formula based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value includes:

[0017] For the mixing of cold and hot primary air in each coal mill, the first heat balance formula is calculated using heat balance theory:

[0018] ;

[0019] For the working fluid leaving the coal mill and entering the boiler furnace, the second heat balance formula is calculated using heat balance theory:

[0020] ;

[0021] Based on the first and second heat balance formulas corresponding to each coal mill, the cold primary air volume and hot primary air volume of each coal mill are calculated as follows:

[0022]

[0023]

[0024] In the formula: The primary air volume of a certain coal mill; T represents the hot primary air volume of a certain coal mill. 1c The temperature of the primary air cooling pipe at the inlet of a certain coal mill; T 1h The temperature of the primary hot air in the inlet header of a certain coal mill; The primary air temperature at the inlet of a certain coal mill; The primary air temperature at the outlet of a certain coal mill; The saturation temperature at the outlet pressure of a certain coal mill; For a certain coal mill, the inlet and outlet are from arrive The average isobaric specific heat of primary air at a given temperature; M represents the amount of coal consumed by a specific coal mill. w,ar The mass fraction of external water in coal; T a The ambient temperature; The outlet temperature of the coal mill The latent heat of vaporization of water; Q f This refers to the air volume for the sealing air of the coal mill. For the coal mill inlet and outlet from T a arrive Average isobaric specific heat of sealed air at temperature; For the coal mill inlet and outlet from T a arrive Average specific heat at constant pressure of coal at the specified temperature; For the coal mill inlet and outlet from T a To T r The average specific heat of water at a given temperature.

[0025] Furthermore, based on the cold primary air volume and hot primary air volume of each coal mill, the total hot primary air volume and total cold primary air volume of all coal mills are calculated, expressed by the following formula:

[0026]

[0027]

[0028] In the formula: Q 1h Q represents the total primary air volume; 1c Q represents the total primary air volume for cooling. i 1h Q is the primary air volume of the i-th coal mill; i 1c Let be the primary air volume of the i-th coal mill; n is the total number of coal mills.

[0029] Further, the calculation of the total secondary air volume based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, and the second temperature measurement value includes:

[0030] For the working fluid entering the air preheater system, the third heat balance formula calculated using heat balance theory is as follows:

[0031]

[0032] Based on the aforementioned third heat balance formula, the total secondary air volume is calculated as follows:

[0033]

[0034] In the formula: Q 1h T represents the total primary air volume; 1kl The primary air temperature at the air preheater outlet; T 1ke The primary air temperature at the air preheater inlet; C 1k For the air preheater inlet and outlet, from T 1ke To T 1kl The average isobaric specific heat of primary air at temperature T; 2kl The secondary air temperature at the air preheater outlet; T 2ke The secondary air temperature at the air preheater inlet; C 2k For the air preheater inlet and outlet, from T 2ke To T 2kl The average isobaric specific heat of secondary wind at temperature; Q y T represents the total flue gas volume at the air preheater inlet. ykl The temperature of the leak-free flue gas at the air preheater outlet; T yke The inlet flue gas temperature of the air preheater; C yk For the air preheater inlet and outlet, from T yke To T yklThe average isobaric specific heat of flue gas at the specified temperature; Q2 is the total secondary air volume.

[0035] Further, based on the aforementioned cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume, adjusting the opening of the cold primary air regulating damper at the inlet of each coal mill to the opening of the hot primary air regulating damper includes:

[0036] Based on the cold primary air volume and hot primary air volume at the inlet of each coal mill, and combined with the coal feeding method of each coal mill, adjust the opening of the cold and hot primary air regulating damper at the inlet of each coal mill to change the cold primary air volume and hot primary air volume at the inlet of each coal mill.

[0037] Based on the total primary hot air volume, total primary cold air volume, and total secondary air volume, combined with the unit load and the quality of the coal fed into the furnace, the opening of the primary cold air regulating damper and the primary hot air regulating damper at the inlet of the coal mill are adjusted as a whole to change the total primary cold air volume, primary hot air volume, and total secondary air volume at the inlet of the coal mill.

[0038] Secondly, the present invention proposes a device for determining the primary and secondary air volumes of a coal-fired boiler based on thermal balance, the device comprising:

[0039] The information acquisition module is used to acquire the operating status information of the coal-fired boiler. The operating status information includes environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, first temperature measurement values ​​related to the coal mill system, and second temperature measurement values ​​related to the air preheater system.

[0040] The first air volume calculation module is used to calculate the cold primary air volume and hot primary air volume of each coal mill, as well as the total hot primary air volume and total cold primary air volume of all coal mills, based on the environmental parameters, coal quality analysis parameters and the first temperature measurement value.

[0041] The second air volume calculation module is used to calculate the total secondary air volume based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, and the second temperature measurement value.

[0042] The adjustment module is used to adjust the opening degree of the cold primary air regulating damper to the hot primary air regulating damper at the inlet of each coal mill based on the cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume and total secondary air volume.

[0043] Thirdly, the present invention proposes a coal-fired boiler system based on thermal balance, including the determining device as described above. The output of the determining device is connected to the cold primary air regulating baffle and the hot primary air regulating baffle via a transmission line. The input of the determining device is connected to a flue gas analyzer and temperature measuring elements arranged in the coal mill system and the air preheater system.

[0044] Furthermore, the temperature measuring element includes a temperature sensor located on the hot primary air header at the air preheater outlet, a temperature sensor located on the primary air fan outlet pipe at the air preheater inlet, a temperature sensor located on the secondary air pipe at the air preheater outlet, a temperature sensor located on the blower outlet pipe at the air preheater inlet, a temperature sensor located on the flue gas pipe at the air preheater inlet, a temperature sensor located on the flue gas pipe at the air preheater outlet, a temperature sensor located on the cold primary air header, a temperature sensor located on the hot primary air header, a temperature sensor located on the cold and hot primary air mixing pipe at the coal mill inlet, a temperature sensor located on the pipe from the coal feeder outlet to the coal mill inlet, and a temperature sensor located on the primary air-coal pulverized coal pipe at the coal mill outlet.

[0045] The advantages of this invention are:

[0046] (1) This invention uses data such as measured temperature, specific heat capacity, environmental parameters, and flue gas parameters of the flue gas system to calculate the cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume of each coal mill inlet. Based on this, the opening of the cold and hot primary air regulating damper at the coal mill inlet is adjusted to achieve precise control of the ratio of cold and hot primary air volume at the inlet of each coal mill, and the ratio of total hot primary air volume, total cold primary air volume, and total secondary air volume of the unit. The results are more accurate and can accurately guide the adjustment and control of the pulverizing system and the combustion system.

[0047] (2) This invention overcomes the limitations of unreliable and inaccurate airflow measurement devices. Based on accurately measurable temperature values ​​at various points in the flue gas system, and utilizing the thermal balance of the coal mill and air preheater, it calculates the cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume at the inlet of each coal mill. The measured temperature, specific heat capacity, environmental parameters, and flue gas parameters of the flue gas system are integrated in real-time into the primary and secondary airflow systems. This control module allows for precise control of the ratio of cold and hot primary air volumes at the inlet of each coal mill, as well as the ratio of total hot primary air volume, total cold primary air volume, and total secondary air volume. This is a quantitative analysis method. This invention can achieve precise measurement and control of airflow under different coal types and operating conditions, making it a highly reliable and economical method for determining airflow.

[0048] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating a method for determining the primary and secondary air volumes of a coal-fired boiler based on thermal balance, as proposed in an embodiment of the present invention.

[0050] Figure 2This is a schematic diagram of a device for determining the primary and secondary air volumes of a coal-fired boiler based on thermal balance, as proposed in an embodiment of the present invention.

[0051] Figure 3 This is a schematic diagram of a coal-fired boiler system based on thermal balance proposed in an embodiment of the present invention.

[0052] In the picture:

[0053] 1. Pulverized coal boiler; 2. Boiler burner; 3. Secondary air box; 4. Primary air / pulverized coal pipe at the pulverizer outlet; 5. Control module; 6. Transmission line from control module to control element; 7. Hot primary air main pipe; 8. Hot primary air regulating baffle at the pulverizer inlet; 9. Cold and hot primary air mixing pipe at the pulverizer inlet; 10. Cold primary air regulating baffle at the pulverizer inlet; 11. Cold primary air main pipe; 12. Pipe from coal feeder outlet to pulverizer inlet; 13. Primary air fan outlet pipe; 14. Blower outlet pipe; 15. Flue gas pipe at the air preheater outlet; 16. Temperature measuring element; 17. Transmission line from measuring element to control module; 18. Secondary air pipe at the air preheater outlet; 19. Flue gas pipe at the air preheater inlet; 20. Flue gas analyzer. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0055] like Figure 1 As shown, the first embodiment of the present invention proposes a method for determining the primary and secondary air volumes of a coal-fired boiler based on heat balance. The method includes the following steps:

[0056] S10. Obtain the operating status information of the coal-fired boiler, the operating status information including environmental parameters, flue gas parameters at the air preheater inlet, coal quality analysis parameters, first temperature measurement values ​​related to the coal mill system, and second temperature measurement values ​​related to the air preheater system;

[0057] It should be noted that the flue gas parameters at the air preheater inlet can be obtained by analyzing the flue gas analyzer arranged at the air preheater inlet. The first and second temperature measurements can be obtained by measuring the temperature measuring elements arranged in the coal mill system and the air preheater system.

[0058] S20. Based on the environmental parameters, coal quality analysis parameters and the first temperature measurement value, calculate the cold primary air volume and hot primary air volume of each coal mill, as well as the total hot primary air volume and total cold primary air volume of all coal mills.

[0059] S30. Calculate the total secondary air volume based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, and the second temperature measurement value.

[0060] S40. Based on the cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume, adjust the opening of the cold primary air regulating damper to the hot primary air regulating damper at the inlet of each coal mill.

[0061] This embodiment uses measured data such as temperature, specific heat capacity, environmental parameters, and flue gas parameters of the flue gas system to calculate the cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume at the inlet of each coal mill. The calculated air volume results are more accurate, avoiding the huge measurement errors of conventional power plants that use air volume measuring devices, which leads to the inability of operators to accurately grasp the actual cold and hot primary air volumes. This makes it easier for operators to reasonably allocate the ratio of cold and hot primary air volumes and the ratio between primary and secondary air volumes, further precisely controlling the pulverizing and combustion systems, and improving the unit's economy and safety.

[0062] In one embodiment, the first temperature measurement value includes the temperature on the cold primary air main pipe, the temperature on the hot primary air main pipe, the temperature on the cold and hot primary air mixing pipe at the coal mill inlet, the temperature on the pipe from the coal feeder outlet to the coal mill inlet, and the temperature on the primary air pulverized coal pipe at the coal mill outlet.

[0063] The second temperature measurement value includes the temperature on the hot primary air header at the air preheater outlet, the temperature on the primary air fan outlet pipe at the air preheater inlet, the temperature on the secondary air pipe at the air preheater outlet, the temperature on the blower outlet pipe at the air preheater inlet, the temperature on the flue gas pipe at the air preheater inlet, and the temperature on the flue gas pipe at the air preheater outlet.

[0064] It should be noted that the primary air temperature T at the coal mill inlet... me and the primary air temperature T at the coal mill outlet ml The value varies depending on the type of coal; for anthracite and bituminous coal, T... ml Generally not exceeding 140℃, for lignite T ml Generally, the temperature should not exceed 80℃.

[0065] This embodiment achieves accurate temperature acquisition by obtaining relevant first temperature measurements at various points in the coal mill system and relevant second temperature measurements at various points in the air preheater system, which helps to accurately calculate the air volume results.

[0066] In one embodiment, step S20, which calculates the cold primary air volume and hot primary air volume of each coal mill, as well as the total hot primary air volume and total cold primary air volume of all coal mills, based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value, includes the following steps:

[0067] S21. Based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value, calculate the cold primary air volume and hot primary air volume of each coal mill using the heat balance formula;

[0068] S22. Based on the cold primary air volume and hot primary air volume of each coal mill, calculate the total hot primary air volume and total cold primary air volume of all coal mills.

[0069] In one embodiment, step S21, which involves calculating the cold primary air volume and hot primary air volume of each coal mill using a heat balance formula based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value, includes the following steps:

[0070] For a coal mill system, the working fluid entering the mill includes cold primary air, hot primary air, coal, and sealing air. The cold and hot primary air are mixed in a certain proportion at the mill inlet before entering the mill. The coal consumption is calculated by deducting a small amount of coke and gravel discharged during mill operation, as these coke and gravel do not participate in energy exchange. Taking the No. 1 coal mill as an example, for the mixing of cold and hot primary air in each mill, the first heat balance formula is calculated using heat balance theory:

[0071] ;

[0072] The working fluid leaving the coal mill and entering the boiler furnace includes primary air that cools down after mixing with the coal, partially heated sealing air carried out, hot coal powder formed by thorough grinding and heating by the primary air, and water vapor formed by the evaporation of some moisture in the raw coal. These four parts mix to form a gas-solid two-phase flow at the same temperature. The sealing air volume is relatively small and generally a fixed value, which is represented as a constant here. According to the heat balance, the heat reduction of the hot and cold primary air in the coal mill is equal to the heat absorbed by the coal powder, the carried-out sealing air, and the evaporation of moisture in the coal. Taking coal mill No. 1 as an example, the second heat balance formula table is used to calculate the working fluid leaving the coal mill and entering the boiler furnace:

[0073] ;

[0074] Based on the first and second heat balance formulas corresponding to each coal mill, the cold primary air volume and hot primary air volume of each coal mill are calculated as follows:

[0075]

[0076]

[0077] In the formula: The primary air volume of a certain coal mill is expressed in t / h. The hot primary air volume of a certain coal mill is expressed in t / h; T 1c The temperature of the primary cooling air in the inlet header of a coal mill, in °C; T 1h The temperature of the primary hot air in the inlet header of a certain coal mill; The primary air inlet temperature of a certain coal mill is given in °C. The primary air temperature at the outlet of a certain coal mill, in °C; Let be the saturation temperature at the outlet pressure of a certain coal mill, in °C; For a certain coal mill, the inlet and outlet are from arrive The average isobaric specific heat of primary air at temperature, kJ / (kg℃); The coal consumption of a specific coal mill, minus the amount of gravel, is expressed in t / h; M w,ar The mass fraction of external water in coal, %; T a The ambient temperature is in °C. The outlet temperature of the coal mill The latent heat of vaporization of water, kJ / kg; Q f The volume of sealing air in the coal mill is t / h; For the coal mill inlet and outlet from T a arrive Average isobaric specific heat of sealed air at temperature, kJ / (kg℃); For the coal mill inlet and outlet from T a arrive Average isobaric specific heat of coal at temperature, kJ / (kg℃); For the coal mill inlet and outlet from T a To T r The average specific heat of water at temperature, kJ / (kg℃); T 1h The temperature on the primary hot air main pipe, in °C; T 1c The temperature on the primary air main pipe is ℃.

[0078] It should be noted that, Q is the measured value; f The value varies slightly depending on the model of the coal mill and sealing fan. For a given fixed system, Q... f It is a fixed constant; and T a The measured value is the temperature measurement point. , The specific heat characteristics of commonly used gases at different temperatures can be obtained by referring to the table of specific heat characteristics of commonly used gases at different temperatures, or by calculating the instantaneous specific heat of commonly used gases at different temperatures using the formula (Appendix E of GB / T 10184-2015 Test Procedure for Performance of Power Plant Boilers). The specific heat of coal can be estimated using the formula (Appendix F of GB / T10184-2015 Test Procedure for Performance of Power Plant Boilers); γ can be obtained by referring to the tables of saturated water and saturated water steam thermodynamic properties; M w,ar It was obtained by using industrial analysis values ​​of coal quality and conversion of fuel matrix.

[0079] In one embodiment, step S22: Calculate the total hot primary air volume and total cold primary air volume of all coal mills based on the cold primary air volume and hot primary air volume of each coal mill, expressed by the formula:

[0080] For different operating conditions, n can be 1 to 6.

[0081] For different operating conditions, n can be 1 to 6.

[0082] In the formula: Q 1h Q represents the total primary air volume; 1c Q represents the total primary air volume for cooling. i 1h Q is the primary air volume of the i-th coal mill; i 1c Let be the primary air volume of the i-th coal mill; n is the total number of coal mills.

[0083] In one embodiment, step S30, which involves calculating the total secondary air volume based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, and the second temperature measurement value, includes the following steps:

[0084] For an air preheater system, the working fluid entering the system includes the air preheater inlet flue gas, the air preheater inlet cold primary air, and the air preheater inlet cold secondary air. The working fluid leaving the system includes the air preheater outlet flue gas after heat exchange, the air preheater outlet hot primary air after heat exchange, and the air preheater outlet hot secondary air after heat exchange. Without considering air preheater leakage, i.e., correcting the air preheater outlet flue gas temperature to the temperature of leak-free flue gas using a formula, and ignoring the small amount of primary and secondary air leaking to the flue gas side without heat exchange, it can be seen from the heat balance that the heat released by the flue gas side in the air preheater is equal to the heat absorbed by the primary and secondary air in the air preheater. For the working fluid entering the air preheater system, the third heat balance formula calculated using heat balance theory is:

[0085]

[0086] Based on the aforementioned third heat balance formula, the total secondary air volume is calculated as follows:

[0087]

[0088] In the formula: Q 1h T represents the total primary air volume; 1kl The primary air temperature at the air preheater outlet; T 1ke The primary air temperature at the air preheater inlet; C 1k For the air preheater inlet and outlet, from T 1ke To T 1kl The average isobaric specific heat of primary air at temperature T; 2kl The secondary air temperature at the air preheater outlet; T 2ke The secondary air temperature at the air preheater inlet; C 2k For the air preheater inlet and outlet, from T 2ke To T 2kl The average isobaric specific heat of secondary wind at temperature; Q y T represents the total flue gas volume at the air preheater inlet. ykl The temperature of the leak-free flue gas at the air preheater outlet; T yke The inlet flue gas temperature of the air preheater; C yk For the air preheater inlet and outlet, from T yke To T ykl The average isobaric specific heat of flue gas at the specified temperature; Q2 is the total secondary air volume.

[0089] It should be noted that Q y The parameters were calculated based on coal elemental analysis parameters, fly ash and slag combustible analysis parameters, environmental parameters, and measured values ​​of flue gas parameters at the air preheater inlet. See GB / T 10184-2015 "Performance Test Procedure for Power Plant Boilers" for details. 1kl T 1ke T 2kl T 2ke T yke The measured value is the temperature at the measuring point; T ykl Calculated based on the actual air leakage rate of the air preheater, and the measured temperatures of the flue gas at the air preheater inlet and outlet, primary air, and secondary air; see GB / T 10184-2015 Performance Test Procedure for Power Plant Boilers for details; C 1k C 2k C yk The specific heat characteristics of commonly used gases at different temperatures can be obtained by referring to the table of specific heat characteristics of commonly used gases at different temperatures or by calculating the instantaneous specific heat of commonly used gases at different temperatures using the formula (Appendix E of GB / T 10184-2015 Test Procedure for Performance of Power Plant Boilers).

[0090] In one embodiment, step S40, which involves adjusting the opening of the cold primary air regulating damper to the hot primary air regulating damper at the inlet of each coal mill based on the cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume, includes the following steps:

[0091] Based on the cold primary air volume and hot primary air volume at the inlet of each coal mill, and combined with the coal feeding method of each coal mill, adjust the opening of the cold and hot primary air regulating damper at the inlet of each coal mill to change the cold primary air volume and hot primary air volume at the inlet of each coal mill.

[0092] Based on the total primary hot air volume, total primary cold air volume, and total secondary air volume, combined with the unit load and the quality of the coal fed into the furnace, the opening of the primary cold air regulating damper and the primary hot air regulating damper at the inlet of the coal mill are adjusted as a whole to change the total primary cold air volume, primary hot air volume, and total secondary air volume at the inlet of the coal mill.

[0093] Specifically, this embodiment adjusts the opening of the cold and hot primary air regulating dampers at the inlet of each coal mill based on the cold and hot primary air volume at each mill inlet, combined with the different coal feeding methods of each mill. This changes the cold and hot primary air volume at the inlet of each mill, controls the ratio of cold and hot primary air volume, and ensures that the primary air temperature T at the inlet of each mill is maintained. me and the primary air temperature T at the coal mill outlet ml Within a reasonable range.

[0094] Based on the calculated total hot primary air volume, total cold primary air volume, and total secondary air volume, and combined with different unit loads and different coal qualities fed into the furnace, the opening of the cold and hot primary air regulating dampers at the coal mill inlet is adjusted as a whole. Under the premise of ensuring the ventilation and drying output of the coal mill under the current operating conditions, the total cold and hot primary air volume and the total secondary air volume at the coal mill inlet are changed to ensure that the ratio of primary and secondary air volume of the unit is at the optimal ratio under the current conditions, and that the safety and combustion efficiency of the unit are in the optimal range.

[0095] In addition, such as Figure 2 As shown, the second embodiment of the present invention proposes a device for determining the primary and secondary air volumes of a coal-fired boiler based on thermal balance. The device includes:

[0096] The information acquisition module 10 is used to acquire the operating status information of the coal-fired boiler. The operating status information includes environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, first temperature measurement values ​​related to the coal mill system, and second temperature measurement values ​​related to the air preheater system.

[0097] The first air volume calculation module 20 is used to calculate the cold primary air volume and hot primary air volume of each coal mill, as well as the total hot primary air volume and total cold primary air volume of all coal mills, based on the environmental parameters, coal quality analysis parameters and the first temperature measurement value.

[0098] The second air volume calculation module 30 is used to calculate the total secondary air volume based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters and the second temperature measurement value.

[0099] The adjustment module 40 is used to adjust the opening degree of the cold primary air regulating baffle to the hot primary air regulating baffle at the inlet of each coal mill based on the cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume and total secondary air volume.

[0100] In one embodiment, the first temperature measurement value includes the temperature on the cold primary air main pipe, the temperature on the hot primary air main pipe, the temperature on the cold and hot primary air mixing pipe at the coal mill inlet, the temperature on the pipe from the coal feeder outlet to the coal mill inlet, and the temperature on the primary air pulverized coal pipe at the coal mill outlet.

[0101] The second temperature measurement value includes the temperature on the hot primary air header at the air preheater outlet, the temperature on the primary air fan outlet pipe at the air preheater inlet, the temperature on the secondary air pipe at the air preheater outlet, the temperature on the blower outlet pipe at the air preheater inlet, the temperature on the flue gas pipe at the air preheater inlet, and the temperature on the flue gas pipe at the air preheater outlet.

[0102] In one embodiment, the first air volume calculation module 20 includes:

[0103] The first air volume calculation unit is used to calculate the cold primary air volume and hot primary air volume of each coal mill based on the environmental parameters, coal quality analysis parameters and the first temperature measurement value using the heat balance formula.

[0104] The second air volume calculation unit is used to calculate the total hot primary air volume and total cold primary air volume of all coal mills based on the cold primary air volume and hot primary air volume of each coal mill.

[0105] In one embodiment, the first air volume calculation unit is specifically used for:

[0106] For the mixing of cold and hot primary air in each coal mill, the first heat balance formula is calculated using heat balance theory:

[0107] ;

[0108] For the working fluid leaving the coal mill and entering the boiler furnace, the second heat balance formula table is calculated using heat balance theory:

[0109] ;

[0110] Based on the first and second heat balance formulas corresponding to each coal mill, the cold primary air volume and hot primary air volume of each coal mill are calculated as follows:

[0111]

[0112]

[0113] In the formula: The primary air volume of a certain coal mill; T represents the hot primary air volume of a certain coal mill. 1c The temperature of the primary air cooling pipe at the inlet of a certain coal mill; T 1h The temperature of the primary hot air in the inlet header of a certain coal mill; The primary air temperature at the inlet of a certain coal mill; The primary air temperature at the outlet of a certain coal mill; The saturation temperature at the outlet pressure of a certain coal mill; For a certain coal mill, the inlet and outlet are from arrive The average isobaric specific heat of primary air at a given temperature; M represents the amount of coal consumed by a specific coal mill. w,ar The mass fraction of external water in coal; T a The ambient temperature; The outlet temperature of the coal mill The latent heat of vaporization of water; Q f This refers to the air volume for the sealing air of the coal mill. For the coal mill inlet and outlet from T a arrive Average isobaric specific heat of sealed air at temperature; For the coal mill inlet and outlet from T a arrive Average specific heat at constant pressure of coal at the specified temperature; For the coal mill inlet and outlet from T a To T r The average specific heat of water at a given temperature.

[0114] In one embodiment, the second air volume calculation unit is specifically used to calculate the total hot primary air volume and total cold primary air volume of all coal mills based on the cold primary air volume and hot primary air volume of each coal mill, as expressed by the formula:

[0115]

[0116]

[0117] In the formula: Q 1h Q represents the total primary air volume; 1c Q represents the total primary air volume for cooling. i 1h Q is the primary air volume of the i-th coal mill; i 1c Let be the primary air volume of the i-th coal mill; n is the total number of coal mills.

[0118] In one embodiment, the second air volume calculation module 30 is specifically used for:

[0119] For the working fluid entering the air preheater system, the third heat balance formula calculated using heat balance theory is as follows:

[0120]

[0121] Based on the aforementioned third heat balance formula, the total secondary air volume is calculated as follows:

[0122]

[0123] In the formula: Q 1h T represents the total primary air volume; 1kl The primary air temperature at the air preheater outlet; T 1ke The primary air temperature at the air preheater inlet; C 1k For the air preheater inlet and outlet, from T 1ke To T 1kl The average isobaric specific heat of primary air at temperature T; 2kl The secondary air temperature at the air preheater outlet; T 2ke The secondary air temperature at the air preheater inlet; C 2k For the air preheater inlet and outlet, from T 2ke To T 2kl The average isobaric specific heat of secondary wind at temperature; Q y T represents the total flue gas volume at the air preheater inlet. ykl The temperature of the leak-free flue gas at the air preheater outlet; T yke The inlet flue gas temperature of the air preheater; C yk For the air preheater inlet and outlet, from T yke To T ykl The average isobaric specific heat of flue gas at the specified temperature; Q2 is the total secondary air volume.

[0124] In one embodiment, the adjustment module 40 includes:

[0125] The first regulating unit is used to adjust the opening of the cold and hot primary air regulating dampers at the inlet of each coal mill according to the cold primary air volume and hot primary air volume at the inlet of each coal mill, combined with the coal feeding method of each coal mill, so as to change the cold primary air volume and hot primary air volume at the inlet of each coal mill.

[0126] The second regulating unit is used to adjust the opening of the cold primary air regulating damper and the hot primary air regulating damper at the inlet of the coal mill based on the total hot primary air volume, the total cold primary air volume, and the total secondary air volume, combined with the unit load and the quality of the coal fed into the furnace, thereby changing the total cold primary air volume, the hot primary air volume, and the total secondary air volume at the inlet of the coal mill.

[0127] It should be noted that other embodiments or implementation methods of the device for determining the primary and secondary air volumes of a coal-fired boiler based on thermal balance described in this invention can refer to the above-mentioned method embodiments, and will not be repeated here.

[0128] In addition, such as Figure 3 As shown, the third embodiment of the present invention proposes a coal-fired boiler system based on thermal balance, including the determining device as described in the above embodiment. The output of the determining device is connected to the cold primary air regulating baffle and the hot primary air regulating baffle via a transmission line. The input of the determining device is connected to a flue gas analyzer and temperature measuring elements arranged in the coal mill system and the air preheater system.

[0129] In one embodiment, the temperature measuring element includes a temperature sensor T located on the hot primary air header 7 at the air preheater outlet. 1kl Temperature sensor T is located on the primary air fan outlet pipe 13 at the air preheater inlet. 1ke Temperature sensor T located on the secondary air duct 18 at the air preheater outlet 2kl Temperature sensor T is located on the blower outlet pipe 14 at the air preheater inlet. 2ke Temperature sensor T located on flue gas duct 19 at the air preheater inlet yke Temperature sensor T located on flue gas duct 15 at the air preheater outlet ykl Temperature sensor T located on primary air header 11 1c Temperature sensor T located on hot primary air main pipe 7 1h The second temperature sensor is located on the cold and hot primary air mixing pipe 9 at the inlet of the No. 1 coal mill. Temperature sensor T is located on pipe 12 from the coal feeder outlet to the coal mill inlet. a Temperature sensor located on primary air-coal pipe 4 at the outlet of coal mill No. 1 .

[0130] Specifically, coal mills are generally low- or medium-speed coal mills, and their types include direct-fired type and intermediate storage type, but are not limited to steel ball type, bowl type, wheel type, ball ring type, and flat plate type.

[0131] Specifically, primary air enters the coal mill inlet cold and hot primary air mixing pipe 9 through the primary air fan outlet pipe 13, passing through the cold primary air header 11 and the coal mill inlet cold primary air regulating baffle 10. The other part enters the air preheater, is heated by the flue gas, and then passes through the hot primary air header 7 and the coal mill inlet hot primary air regulating baffle 8 before entering the coal mill inlet cold and hot primary air mixing pipe 9. The two parts of cold and hot primary air are fully mixed in the coal mill inlet cold and hot primary air mixing pipe 9 before entering the coal mill. Coal enters the coal mill through the coal feeder and its outlet to the coal mill inlet pipe 12. Cold and hot primary air, coal, and sealing air enter the coal mill simultaneously. In the coal mill, the cold and hot primary air heat the sealing air and coal. Some of the moisture in the coal is evaporated to form water vapor. The cooled primary air, heated sealing air, heated coal, and partially evaporated water vapor form an air-coal mixture, which enters the pulverized coal boiler 1 through the boiler burner 2 via the coal mill outlet primary air-coal pipe 4.

[0132] Secondary air enters the air preheater through the blower outlet pipe 14, is heated by the flue gas, and then enters the secondary air box 3 through the secondary air outlet pipe 18. The hot flue gas generated by the combustion of pulverized coal boiler 1 passes through the heating surfaces of each stage of the boiler, is sampled by the flue gas analyzer 20 at the air preheater inlet, and then enters the air preheater through the air preheater inlet flue gas pipe 19. After being cooled by the primary and secondary air, it enters the tail flue through the air preheater outlet flue gas pipe 15.

[0133] Furthermore, the temperature measuring elements 16 arranged on each flue gas duct are used to measure temperature data, data collected by the flue gas analyzer 20, coal quality analysis results of the coal entering the furnace, environmental parameters, and calculation results of the specific heat of flue gas and raw coal. All these parameters are integrated in real time into the primary and secondary air volume determining device 5. The primary and secondary air volume determining device 5 calculates the ratio of cold and hot primary air and the ratio of primary air to secondary air, and adjusts the cold primary air regulating baffle 10 and the hot primary air regulating baffle 8 at the inlet of the coal mill through the control module to the control element transmission line 6, thereby adjusting the cold primary air volume, hot primary air volume, and secondary air volume. The measurement data of the temperature measuring elements 16 and the data collected by the flue gas analyzer 20 are transmitted to the primary and secondary air volume determining device 5 through the measurement element to control module transmission line 17.

[0134] T 1c T 1h , , and T a Isotemperature measurement value, Q f Equal flow measurement value, , , γ, M w,arAll coal quality parameters, including those for viewing or calculation, are transmitted in real time and integrated into the primary and secondary air volume determination device to calculate the primary cold air volume at the inlet of each mill. primary air volume for heating Then, based on the actual operation of the coal mills in the unit, the total primary hot air volume Q is obtained by summing. 1h Total primary air volume Q 1c T 1kl T 1ke T 2kl T 2ke T yke Isotemperature measurement value, C 1k C 2k C yk Q y T ykl The system can access or calculate values ​​such as air preheater leakage rate, as well as parameters for coal element analysis, fly ash and slag combustible analysis, environmental parameters, air preheater inlet flue gas parameters, air preheater inlet and outlet flue gas, primary air, and secondary air temperature measurements. All of these are transmitted in real time and integrated into the primary and secondary air volume determination device to calculate the total secondary air volume Q2.

[0135] This embodiment, based on accurately measurable temperature values ​​at various points in the flue gas system, utilizes the thermal balance of the coal mill and the air preheater to calculate the cold primary air volume, hot primary air volume, and total hot primary air volume, total cold primary air volume, and total secondary air volume at the inlet of each coal mill. Real-time data such as measured temperature, specific heat capacity, environmental parameters, and flue gas parameters of the flue gas system are integrated into the primary and secondary air volume determination device. Through adjustment by this control module, precise control is achieved over the ratio of cold and hot primary air volumes at the inlet of each coal mill, as well as the ratio of total hot primary air volume, total cold primary air volume, and total secondary air volume of the unit.

[0136] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0137] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0138] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for determining the primary and secondary air volumes of a coal-fired boiler based on heat balance, characterized in that, The method includes: The operating status information of the coal-fired boiler is obtained, including environmental parameters, flue gas parameters at the air preheater inlet, coal quality analysis parameters, first temperature measurement values ​​related to the coal mill system, and second temperature measurement values ​​related to the air preheater system. Based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value, calculate the cold primary air volume and hot primary air volume of each coal mill, as well as the total hot primary air volume and total cold primary air volume of all coal mills. Based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, and the second temperature measurement value, the total secondary air volume is calculated, including calculating the cold primary air volume and hot primary air volume of each coal mill using the heat balance formula based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value; and calculating the total hot primary air volume and total cold primary air volume of all coal mills based on the cold primary air volume and hot primary air volume of each coal mill. Based on the aforementioned cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume, adjust the opening of the cold primary air regulating damper and the hot primary air regulating damper at the inlet of each coal mill. The calculation of the cold primary air volume and hot primary air volume of each coal mill using a heat balance formula, based on the environmental parameters, coal quality analysis parameters, and the first temperature measurement value, includes: For the mixing of cold and hot primary air in each coal mill, the first heat balance formula is calculated using heat balance theory: ； For the working fluid leaving the coal mill and entering the boiler furnace, the second heat balance formula table is calculated using heat balance theory: ； Based on the first and second heat balance formulas corresponding to each coal mill, the cold primary air volume and hot primary air volume of each coal mill are calculated as follows: In the formula: The primary air volume of a certain coal mill; T represents the hot primary air volume of a certain coal mill. 1c The temperature of the primary air cooling pipe at the inlet of a certain coal mill; T 1h The temperature of the primary hot air in the inlet header of a certain coal mill; The primary air temperature at the inlet of a certain coal mill; The primary air temperature at the outlet of a certain coal mill; The saturation temperature at the outlet pressure of a certain coal mill; For a certain coal mill, the inlet and outlet are from arrive The average isobaric specific heat of primary air at a given temperature; M represents the amount of coal consumed by a specific coal mill. w,ar The mass fraction of external water in coal; T a The ambient temperature; The outlet temperature of the coal mill The latent heat of vaporization of water; Q f This refers to the air volume for the sealing air of the coal mill. For the coal mill inlet and outlet from T a arrive Average isobaric specific heat of sealed air at temperature; For the coal mill inlet and outlet from T a arrive Average specific heat at constant pressure of coal at the specified temperature; For the coal mill inlet and outlet from T a To T r The average specific heat of water at a given temperature.

2. The method for determining the primary and secondary air volumes of a coal-fired boiler based on heat balance as described in claim 1, characterized in that, The first temperature measurement values ​​include the temperature on the cold primary air main pipe, the temperature on the hot primary air main pipe, the temperature on the cold and hot primary air mixing pipe at the coal mill inlet, the temperature on the pipe from the coal feeder outlet to the coal mill inlet, and the temperature on the primary air pulverized coal pipe at the coal mill outlet. The second temperature measurement value includes the temperature on the hot primary air header at the air preheater outlet, the temperature on the primary air fan outlet pipe at the air preheater inlet, the temperature on the secondary air pipe at the air preheater outlet, the temperature on the blower outlet pipe at the air preheater inlet, the temperature on the flue gas pipe at the air preheater inlet, and the temperature on the flue gas pipe at the air preheater outlet.

3. The method for determining the primary and secondary air volumes of a coal-fired boiler based on heat balance as described in claim 1, characterized in that, The total hot primary air volume and total cold primary air volume of all coal mills are calculated based on the cold primary air volume and hot primary air volume of each coal mill, expressed by the following formula: In the formula: Q 1h Q represents the total primary air volume; 1c Q represents the total primary air volume for cooling. i 1h Q is the primary air volume of the i-th coal mill; i 1c Let be the primary air volume of the i-th coal mill; n is the total number of coal mills.

4. The method for determining the primary and secondary air volumes of a coal-fired boiler based on heat balance as described in claim 1, characterized in that, The calculation of the total secondary air volume based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, and the second temperature measurement value includes: For the working fluid entering the air preheater system, the third heat balance formula calculated using heat balance theory is as follows: Based on the aforementioned third heat balance formula, the total secondary air volume is calculated as follows: In the formula: Q 1h T represents the total primary air volume; 1kl The primary air temperature at the air preheater outlet; T 1ke The primary air temperature at the air preheater inlet; C 1k For the air preheater inlet and outlet, from T 1ke To T 1kl The average isobaric specific heat of primary air at temperature T; 2kl The secondary air temperature at the air preheater outlet; T 2ke The secondary air temperature at the air preheater inlet; C 2k For the air preheater inlet and outlet, from T 2ke To T 2kl The average isobaric specific heat of secondary wind at temperature; Q y T represents the total flue gas volume at the air preheater inlet. ykl The temperature of the leak-free flue gas at the air preheater outlet; T yke The inlet flue gas temperature of the air preheater; C yk For the air preheater inlet and outlet, from T yke To T ykl The average isobaric specific heat of flue gas at the specified temperature; Q2 is the total secondary air volume.

5. The method for determining the primary and secondary air volumes of a coal-fired boiler based on heat balance as described in claim 1, characterized in that, Based on the aforementioned cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume, and total secondary air volume, the opening degree of the cold primary air regulating damper and hot primary air regulating damper at the inlet of each coal mill is adjusted, including: Based on the cold primary air volume and hot primary air volume at the inlet of each coal mill, and combined with the coal feeding method of each coal mill, adjust the opening of the cold and hot primary air regulating damper at the inlet of each coal mill to change the cold primary air volume and hot primary air volume at the inlet of each coal mill. Based on the total primary hot air volume, total primary cold air volume, and total secondary air volume, combined with the unit load and the quality of the coal fed into the furnace, the opening of the primary cold air regulating damper and the primary hot air regulating damper at the inlet of the coal mill are adjusted as a whole to change the total primary cold air volume, primary hot air volume, and total secondary air volume at the inlet of the coal mill.

6. A device for determining the primary and secondary air volumes of a coal-fired boiler based on heat balance, characterized in that, The apparatus for performing the method as described in any one of claims 1-5, the apparatus comprising: The information acquisition module is used to acquire the operating status information of the coal-fired boiler. The operating status information includes environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, first temperature measurement values ​​related to the coal mill system, and second temperature measurement values ​​related to the air preheater system. The first air volume calculation module is used to calculate the cold primary air volume and hot primary air volume of each coal mill, as well as the total hot primary air volume and total cold primary air volume of all coal mills, based on the environmental parameters, coal quality analysis parameters and the first temperature measurement value. The second air volume calculation module is used to calculate the total secondary air volume based on the environmental parameters, air preheater inlet flue gas parameters, coal quality analysis parameters, and the second temperature measurement value. The adjustment module is used to adjust the opening degree of the cold primary air regulating baffle and the hot primary air regulating baffle at the inlet of each coal mill based on the cold primary air volume, hot primary air volume, total hot primary air volume, total cold primary air volume and total secondary air volume.

7. A coal-fired boiler system based on heat balance, characterized in that, The device includes the determining device as described in claim 6, wherein the output of the determining device is connected to the cold primary air regulating baffle and the hot primary air regulating baffle via a transmission line, and the input of the determining device is connected to the flue gas analyzer and the temperature measuring elements arranged in the coal mill system and the air preheater system.

8. The coal-fired boiler system based on heat balance as described in claim 7, characterized in that, The temperature measuring elements include: temperature sensor 1 located on the hot primary air header at the air preheater outlet; temperature sensor 2 located on the primary air fan outlet pipe at the air preheater inlet; temperature sensor 3 located on the secondary air pipe at the air preheater outlet; temperature sensor 4 located on the blower outlet pipe at the air preheater inlet; temperature sensor 5 located on the flue gas pipe at the air preheater inlet; temperature sensor 6 located on the flue gas pipe at the air preheater outlet; temperature sensor 7 located on the cold primary air header; temperature sensor 8 located on the hot primary air header; temperature sensor 9 located on the cold and hot primary air mixing pipe at the coal mill inlet; temperature sensor 10 located on the pipe from the coal feeder outlet to the coal mill inlet; and temperature sensor 11 located on the primary air-pulverized coal pipe at the coal mill outlet.

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