A power plant boiler combustion stability identification system based on the measurement of the burner nozzle temperature

Abstract

The present invention discloses a combustion stability identification system for a power station boiler based on the temperature measurement of the burner nozzle. This system obtains the flue gas temperature distribution in the burner nozzle area during the operation of the coal-fired boiler through a high-temperature measurement device, establishes a mathematical function relationship between the burner nozzle temperature and the corresponding coal mill fuel quantity, thereby obtaining the calculated temperature of the burner nozzle under a specific coal mill fuel quantity. By performing mathematical operations on the measured temperature of the burner nozzle and the calculated temperature of the burner nozzle, it is determined whether there is a phenomenon of rapid temperature drop in the burner nozzle area, so as to determine whether the combustion of the boiler burner is in a stable state. When it is determined that the combustion of the boiler burner is unstable, the corresponding boiler combustion support device is immediately started to ensure stable boiler combustion; when it is determined that the combustion of the boiler burner is stable, the current boiler load operation can be maintained or the fuel quantity can be reduced to continue the load reduction operation. This system can solve the problem of unclear stable combustion bottom line during the deep peak shaving process of coal-fired boilers.

Description

Technical Field

[0001] The present invention belongs to the technical field of combustion monitoring of coal-fired power plant boilers, and particularly relates to a combustion stability identification system for power plant boilers based on the measurement of the temperature at the burner nozzles. Background Art

[0002] With the stable and healthy development of the national economy, the power demand in China has been continuously increasing, and the peak-valley difference of the power grid has been increasing year by year. The rapid growth and grid connection of power sources with strong randomness and intermittency such as wind power and photovoltaic power have brought challenges to the safe and stable operation of the power grid. In order to improve the consumption of renewable energy and ensure the safe and stable operation of the power grid, coal-fired generating units, which account for more than 70% of the total national power generation, are urgently required to improve their deep peak shaving capabilities and undertake the task of peak shaving for the power grid.

[0003] For coal-fired generating units to carry out deep peak shaving, the stable combustion of the boiler at low load is a prerequisite. At present, the minimum operating load of boilers in most domestic coal-fired generating units is generally 40% - 50% of the rated load, and there is still a certain gap from the minimum deep peak shaving load required by the power grid, which is 30% - 35% of the rated load. The unclear bottom line of stable combustion at low load of the boiler and the insufficient self-stable combustion ability are the main factors restricting the reduction of the load of coal-fired generating unit boilers in China. For boilers that need to carry out deep peak shaving, the primary task is to determine the minimum non-assistive peak shaving ability of the boiler under the existing coal quality. In this process, the identification of boiler combustion stability is particularly important. The operating parameter indicators reflecting boiler combustion stability mainly include furnace negative pressure, burner flame detection intensity, furnace temperature, pulverized coal ignition distance, etc. Professional test personnel mainly judge the combustion status in the furnace based on the fluctuations of furnace negative pressure and burner flame detection intensity in the DCS system, combined with means such as observing the fire through the furnace viewing hole and manually measuring the furnace temperature, and according to their own personal experience, so as to obtain the minimum non-assistive load of the boiler. However, considering that there are cases of false detection and missed detection in some boiler flame detection equipment, and the differences in professional experience among different professional test personnel, the minimum non-assistive load of some boilers obtained through tests does not truly represent the stable combustion ability of the boilers. Therefore, with more and more coal-fired generating units participating in deep peak shaving, it is urgent to develop monitoring and data mining technologies for key boiler parameters, form a quantitative analysis of boiler combustion stability, and improve the accuracy and intelligence of the identification of coal-fired boiler combustion stability. At present, the main methods for identifying boiler combustion stability mainly include the flame image method and the characteristic state parameter method.

[0004] The invention patent with the application number 201811011018.6 discloses a combustion stability identification method based on the fractal characteristics of furnace flame images. By extracting the fractal characteristic parameters of the flame combustion video and calculating parameters such as the mean value of the fractal dimension and the variance value of the fractal dimension as combustion characteristic values, a stable and unstable fuzzy set for fuzzy pattern discrimination is established, and the stability of the furnace flame combustion is discriminated according to the distance between the combustion characteristic values and the corresponding fuzzy sets.

[0005] The invention patent with the application number 201810146849.8 discloses an intelligent boiler combustion stability judgment system and method applicable to large power plants. By collecting coal quality component data and boiler operation status data, a dimensionless combustion stability analysis criterion under actual operation conditions is obtained and compared with the set dimensionless combustion stability analysis criterion, so as to obtain a conclusion on whether the boiler combustion is stable.

[0006] Neither the flame image method nor the characteristic state parameter method takes into account the direct influence of the temperature in the burner nozzle area on the boiler combustion stability. When the boiler combustion is stable, as the fuel quantity of the coal mill increases, the pulverized coal concentration at the burner outlet increases, and the temperature of the stable ignition area near the burner nozzle rises; when the boiler has unstable combustion under low load, the pulverized coal ignition is delayed, the mixing of high-temperature flue gas and primary air flow becomes worse, and the temperature in the area near the burner nozzle drops significantly. When the high-temperature flue gas entrained by the burner nozzle is not enough to support the stable ignition of the primary air flow, the boiler will face the risk of extinguishing. Summary of the Invention

[0007] The purpose of the present invention is to provide a power station boiler combustion stability identification system based on the measurement of the burner nozzle temperature in view of the limitations of the combustion stability identification technology in the deep peak shaving process of existing coal-fired boilers. The system obtains the temperature distribution in the burner nozzle area during the operation of the coal-fired boiler through a high-temperature measurement device, establishes a mathematical function relationship between the fuel quantity of the coal mill and the burner nozzle temperature, obtains the calculated temperature of the burner nozzle under a specific fuel quantity of the coal mill during the deep peak shaving process of the boiler through this mathematical function relationship, and at the same time considers the fluctuation of the measured value and sets a deviation threshold. When the measured temperature of the burner nozzle is lower than the calculated temperature of the burner nozzle minus the deviation threshold, it indicates that there is a phenomenon of rapid temperature reduction in the burner nozzle area, and it is determined that the combustion of the boiler burner is unstable, and the corresponding boiler rapid combustion support device is immediately started to ensure stable combustion; when the measured temperature of the burner nozzle is higher than the calculated temperature of the burner nozzle minus the deviation threshold, it is determined that the combustion of the boiler burner is stable, and stable operation can be maintained or the fuel quantity can be continuously reduced for peak shaving operation. The system can solve the problem that the stable combustion bottom line is not clear during the deep peak shaving process of coal-fired boilers, safely explore the peak shaving capacity of coal-fired boilers on the basis of ensuring the boiler combustion stability, and create space for the accommodation of new energy.

[0008] The present invention is implemented by adopting the following technical solutions:

[0009] A power station boiler combustion stability identification system based on the measurement of the burner nozzle temperature includes a plurality of temperature measurement devices, a temperature acquisition device, a boiler DCS system, a data analysis and processing center, a display, and a plurality of boiler combustion support devices; wherein,

[0010] The temperature measurement devices are arranged on the water-cooled wall of the boiler, with one temperature measurement device corresponding to one boiler burner; one boiler combustion assisting device is installed inside or beside the corresponding boiler burner; temperature measurement devices are installed beside the burner nozzles corresponding to 2 - 3 coal mills operating under deep peak shaving and fixed operation. The temperature measurement devices are aligned with the area 1 - 3 meters away from the burner nozzles and measure the temperature thereof. The temperature data of each nozzle of the boiler burner is transmitted to the data analysis and processing center through the temperature acquisition device, and the operating parameters of the boiler load, the fuel quantity of each coal mill, and the evaporation capacity are transmitted to the data analysis and processing center through the boiler DCS system. The data analysis and processing center completes the mathematical function fitting of the temperature of each burner nozzle and the fuel quantity of each coal mill. When the fuel quantity of the coal mill changes, the data analysis and processing center obtains a calculated value of the burner nozzle temperature and a measured value of the burner nozzle temperature transmitted from the temperature acquisition device through mathematical function operations. The calculated value and the measured value of the burner nozzle temperature are displayed on the monitor in real time;

[0011] On the basis of considering the temperature deviation threshold, when the measured value of the burner nozzle temperature is lower than the calculated value of the burner nozzle temperature minus the deviation threshold, the data analysis and processing center sends an alarm message of "unstable combustion" through the monitor; when the measured value of the burner nozzle temperature continuously remains lower than the calculated value of the burner nozzle temperature minus the deviation threshold for a set duration, the data analysis and processing center automatically issues an operation instruction for the corresponding boiler combustion assisting device to be put into operation through the boiler DCS system to ensure stable combustion at low boiler loads; when the measured value of the burner nozzle temperature is higher than the calculated value of its nozzle temperature minus the deviation threshold, it indicates stable boiler combustion. The data analysis and processing center displays a signal of "stable combustion" through the monitor, and the boiler can maintain stable operation or further reduce fuel for deep peak shaving.

[0012] A further improvement of the present invention is that for a tangentially fired boiler, when operating with the lower three coal mills at a load below 50% of the rated load, the temperature measurement device is used to monitor the burner nozzles corresponding to the lower three coal mills.

[0013] A further improvement of the present invention is that for a front and rear wall opposed firing boiler, when operating with the two bottom coal mills and the second coal mill from the bottom up on the front wall at a load below 50% of the rated load, the temperature measurement device is used to monitor the burner nozzles corresponding to the two bottom coal mills and the second coal mill from the bottom up on the front wall.

[0014] A further improvement of the present invention is that the boiler combustion assisting device is a fuel combustion assisting device or a high-power plasma combustion assisting device.

[0015] A further improvement of the present invention is that the temperature measurement device measures the average temperature of a 1m×2m area on the same center line as the burner nozzle within the area 1 - 3 meters away from the burner nozzle.

[0016] A further improvement of the present invention is that for a tangentially fired boiler with corner firing, the source data for fitting the mathematical function relationship between the temperatures of the nozzles of each burner and the fuel quantity of each coal mill is the measurement data when burning common coal quality and operating three coal mills.

[0017] A further improvement of the present invention is that for a boiler with opposed firing of front and rear walls, the source data for fitting the mathematical function relationship between the temperatures of the nozzles of each burner and the fuel quantity of each coal mill is the measurement data when burning common coal quality and operating the two bottom coal mills and the second coal mill from the bottom up on the front wall.

[0018] A further improvement of the present invention is that when the boiler fuel is stable, the mathematical function fitting between the temperatures of the nozzles of each burner and the fuel quantity of the corresponding coal mill is completed during system commissioning and remains unchanged during operation; when the boiler fuel fluctuates greatly, the mathematical function fitting between the temperatures of the nozzles of each burner and the fuel quantity of the corresponding coal mill is completed in real time and online during boiler operation.

[0019] A further improvement of the present invention is that the set threshold value of the temperature deviation has a positive correlation with the fuel quantity of the coal mill, and is calculated as the measured temperature of the burner nozzle × the fuel quantity of the coal mill ÷ the rated fuel quantity of the coal mill × 5%.

[0020] A further improvement of the present invention is that the trigger condition for the boiler combustion support device to be put into operation is that the measured value of the temperature of the burner nozzle continuously remains lower than the calculated value of the temperature of the burner nozzle minus the deviation threshold for 3 s.

[0021] The present invention has at least the following beneficial technical effects:

[0022] 1) The present invention fully considers the influence of the combustion temperature in the burner nozzle area on the combustion stability of the boiler, establishes the mathematical function relationship between the boiler fuel quantity and the temperature of the burner nozzle, and judges the combustion stability during the deep peak shaving process of the boiler in real time by comparing the difference between the measured value and the calculated value of the temperature of the burner nozzle during the deep peak shaving process of the boiler, without the intervention of the operating personnel, with high accuracy and intelligence, solves the problem that the stable combustion bottom line of the coal-fired boiler is unclear, and safely explores the peak shaving capacity of the coal-fired boiler on the basis of ensuring the combustion stability of the boiler, and improves the acceptance capacity of the power grid for new energy power generation.

[0023] 2) Different from most boiler combustion stability monitoring systems, the present invention is equipped with a combustion support device for a single burner. By associating the identification of the combustion stability of a single burner with the combustion support device, the combustion stability of a local part of the boiler can be accurately improved, and the operation safety of the deep peak shaving boiler is ensured. Description of the Drawings

[0024] Figure 1Taking a tangentially fired boiler as an example, a system schematic diagram of the present invention is given. To simplify the description, only one layer of the three layers of burners equipped with burner nozzle temperature measurement devices is shown for illustration purposes.

[0025] Description of the reference numerals:

[0026] 1 - Boiler water wall, 2 - First boiler burner, 3 - Second boiler burner, 4 - Third boiler burner, 5 - Fourth boiler burner, 6 - First boiler combustion support device, 7 - Second boiler combustion support device, 8 - Third boiler combustion support device, 9 - Fourth boiler combustion support device, 10 - First temperature measurement device, 11 - Second temperature measurement device, 12 - Third temperature measurement device, 13 - Fourth temperature measurement device, 14 - Temperature acquisition device, 15 - Data analysis and processing center, 16 - Display, 17 - Boiler DCS system.

[0027] Figure 2 It is the picture of the boiler combustion stability identification system output on the display. Detailed implementation manners

[0028] The present invention will be further described in detail below with reference to the accompanying drawings.

[0029] As Figure 1 shown, for the power station boiler combustion stability identification system based on burner nozzle temperature measurement provided by the present invention, on the boiler water wall 1, several burners such as the first boiler burner 2, the second boiler burner 3, the third boiler burner 4 and the fourth boiler burner 5 are installed. The first boiler burner 2, the second boiler burner 3, the third boiler burner 4 and the fourth boiler burner 5 are respectively equipped with the first boiler combustion support device 6, the second boiler combustion support device 7, the third boiler combustion support device 8 and the fourth boiler combustion support device 9. On the boiler water wall 1, the first temperature measurement device 10, the second temperature measurement device 11, the third temperature measurement device 12 and the fourth temperature measurement device 13 are installed, which are respectively used to measure the flue gas temperature in the area 1 - 3 meters away from the nozzles of the first boiler burner 2, the second boiler burner 3, the third boiler burner 4 and the fourth boiler burner 5. The first temperature measurement device 10, the second temperature measurement device 11, the third temperature measurement device 12 and the fourth temperature measurement device 13 are connected to the temperature acquisition device 14. The data analysis and processing center 15 is respectively connected to the temperature acquisition device 14, the display 16 and the boiler DCS system 17. The data analysis and processing center 15 can communicate with the boiler DCS system 17.

[0030] During operation, the boiler load is below 50% of the rated load, and the lower three layers of coal mills are put into operation. The first boiler burner 2, the second boiler burner 3, the third boiler burner 4, and the fourth boiler burner 5 correspond to any one of the lower three layers of coal mills. The temperature acquisition device 14 respectively transmits the flue gas temperatures measured by the first temperature measurement device 10, the second temperature measurement device 11, the third temperature measurement device 12, and the fourth temperature measurement device 13 in the area 1 - 3 meters away from the nozzles of the first boiler burner 2, the second boiler burner 3, the third boiler burner 4, and the fourth boiler burner 5 to the data analysis and processing center 15. The data analysis and processing center 15 extracts real - time operation parameters such as boiler load, coal feeder fuel quantity, and boiler evaporation from the boiler DCS system. The data analysis and processing center 15 completes the mathematical function fitting of the nozzle temperatures of the first boiler burner 2, the second boiler burner 3, the third boiler burner 4, and the fourth boiler burner 5 and the corresponding coal mill fuel quantities through data processing and calculation. When the coal mill fuel quantity changes, the data analysis and processing center 15 obtains the calculated values of the nozzle temperatures of the first boiler burner 2, the second boiler burner 3, the third boiler burner 4, and the fourth boiler burner 5 through mathematical function operations, and at the same time, the calculated values of the nozzle temperatures of the first boiler burner 2, the second boiler burner 3, the third boiler burner 4, and the fourth boiler burner 5 and the measured values of the nozzle temperatures of the first boiler burner 2, the second boiler burner 3, the third boiler burner 4, and the fourth boiler burner 5 transmitted from the temperature acquisition device 14 are displayed on the display 16 in real - time (as Figure 2 shown). Considering the temperature measurement deviation, a temperature deviation threshold is set. When the measured values of the nozzle temperatures of the first boiler burner 2, the second boiler burner 3, the third boiler burner 4, and the fourth boiler burner 5 are lower than the calculated values of their nozzle temperatures minus the deviation threshold, the data analysis and processing center 15 displays an alarm signal of "unstable combustion" through the display 16. When the measured nozzle temperature continuously remains lower than the calculated value of its nozzle temperature minus the deviation threshold for a certain period of time, the data analysis and processing center 15 immediately triggers the boiler combustion support device corresponding to this burner through the boiler DCS system 17 to ensure stable boiler combustion. For example, when the coal mill fuel quantity decreases and the measured value of the nozzle temperature of the first boiler burner 2 continuously remains lower than the calculated value of its nozzle temperature minus the deviation threshold for a certain period of time, the data analysis and processing center 15 issues an alarm of "unstable combustion" on the display 16 and at the same time immediately triggers the operation instruction of the corresponding boiler combustion support device 6 through the boiler DCS system 17. When the measured values of the nozzle temperatures of the first boiler burner 2, the second boiler burner 3, the third boiler burner 4, and the fourth boiler burner 5 are higher than the calculated values of their nozzle temperatures minus the deviation threshold, it indicates that the boiler combustion is stable. The data analysis and processing center 15 displays a signal of "stable combustion" through the display 16, and the boiler can maintain stable operation or further reduce the fuel for deep peak shaving.

[0031] Further, when the boiler fuel is stable, the mathematical function fitting between the temperature of each burner nozzle and the fuel quantity of the corresponding coal mill can be completed during system commissioning and maintained unchanged during operation; when the boiler fuel fluctuates greatly, the mathematical function fitting between the temperature of each burner nozzle and the fuel quantity of the corresponding coal mill can be completed in real time online during boiler operation.

[0032] Further, the set threshold of the temperature deviation is positively correlated with the fuel quantity of the coal mill, and is calculated as the temperature of the burner nozzle × the fuel quantity of the coal mill ÷ the rated fuel quantity of the coal mill × 5%.

[0033] Further, the trigger condition for the boiler combustion-supporting device to be put into operation is that the measured value of the burner nozzle temperature continuously remains lower than the calculated value of the burner nozzle temperature minus the deviation threshold for 3 s.

[0034] Further, the power station boiler combustion stability identification system has two working modes: input and cut-off. As Figure 2 shown, when put into operation, the system has the function of identifying the boiler combustion stability; when cut off, only the measured temperature of the burner nozzle is displayed, the calculated temperature and threshold of the burner nozzle are not displayed, and the boiler combustion stability is not identified.

[0035] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited thereto. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the patent protection scope determined by the claims submitted for the present invention.

Claims

1. A power station boiler combustion stability identification system based on burner nozzle temperature measurement, characterized in that, It includes several temperature measurement devices, a temperature acquisition device (14), a boiler DCS system (17), a data analysis and processing center (15), a display (16), and several boiler combustion assisting devices; among them, the temperature measurement devices are arranged on the boiler water wall (1), and one temperature measurement device corresponds to one boiler burner; one boiler combustion assisting device is installed inside or beside the corresponding boiler burner; temperature measurement devices are installed beside the burner nozzles corresponding to 2 to 3 coal mills operating in deep peak shaving and fixed operation, and the temperature measurement devices are aimed at the area 1 to 3 meters away from the burner nozzles and measure the temperature thereof. The temperature data of each nozzle of the boiler burner is transmitted to the data analysis and processing center (15) through the temperature acquisition device (14), and the boiler load, the fuel quantity of each coal mill, and the evaporation operation parameters are transmitted to the data analysis and processing center (15) through the boiler DCS system (17). The data analysis and processing center (15) completes the mathematical function fitting of the temperature of each burner nozzle and the fuel quantity of each coal mill. When the fuel quantity of the coal mill changes, the data analysis and processing center (15) obtains a calculated value of the burner nozzle temperature and an actual measured value of the burner nozzle temperature transmitted from the temperature acquisition device (14) through mathematical function operations, and the calculated value and the actual measured value of the burner nozzle temperature are displayed on the display (16) in real time; On the basis of considering the temperature deviation threshold, when the actual measured value of the burner nozzle temperature is lower than the calculated value of the burner nozzle temperature minus the deviation threshold, the data analysis and processing center (15) sends an alarm message of "unstable combustion" through the display (16); when the actual measured value of the burner nozzle temperature continuously is lower than the calculated value of the burner nozzle temperature minus the deviation threshold for the set duration, the data analysis and processing center (15) automatically issues an operation instruction for the corresponding boiler combustion assisting device to be put into operation through the boiler DCS system (17) to ensure stable combustion at low load of the boiler; when the actual measured value of the burner nozzle temperature is higher than the calculated value of its nozzle temperature minus the deviation threshold, it indicates that the boiler combustion is stable. The data analysis and processing center (15) displays a signal of "stable combustion" through the display (16), and the boiler can maintain stable operation or further reduce the fuel for deep peak shaving; The boiler combustion assisting device is a fuel combustion assisting device or a high-power plasma combustion assisting device; when the boiler fuel is stable, the mathematical function fitting of the temperature of each burner nozzle and the corresponding fuel quantity of the coal mill is completed during system commissioning and remains unchanged during operation; when the boiler fuel fluctuates greatly, the mathematical function fitting of the temperature of each burner nozzle and the corresponding fuel quantity of the coal mill is completed in real time and online during the operation of the boiler.

2. The power plant boiler combustion stability identification system based on burner nozzle temperature measurement according to claim 1, wherein For a tangentially fired boiler, when operating with the lower three coal mills below 50% of the rated load of the boiler, the temperature measurement device is used to monitor the burner nozzles corresponding to the lower three coal mills.

3. The power station boiler combustion stability identification system based on burner nozzle temperature measurement according to claim 1, wherein For a boiler with front and rear wall opposed firing, when operating with the two bottom coal mills and the second coal mill from the bottom up on the front wall below 50% of the rated load of the boiler, the temperature measurement device is used to monitor the burner nozzles corresponding to the two bottom coal mills and the second coal mill from the bottom up on the front wall.

4. The power plant boiler combustion stability identification system based on burner nozzle temperature measurement according to claim 1, characterized in that, The temperature measurement device measures the average temperature of a 1m×2m area on the same center line as the burner nozzle in the area 1-3 meters away from the burner nozzle.

5. The combustion stability identification system for a power station boiler based on the measurement of the burner nozzle temperature according to claim 1, characterized in that, For tangentially fired boilers, the source data for fitting the mathematical function relationship between the temperature of each burner nozzle and the fuel quantity of each coal mill comes from the measurement data when burning common coal quality and operating three coal mills.

6. The power station boiler combustion stability identification system based on burner nozzle temperature measurement according to claim 1, characterized in that For opposed fired boilers with front and rear walls, the source data for fitting the mathematical function relationship between the temperature of each burner nozzle and the fuel quantity of each coal mill comes from the measurement data when burning common coal quality and operating the two bottom coal mills and the second coal mill from the bottom up on the front wall.

7. The power station boiler combustion stability identification system based on burner nozzle temperature measurement according to claim 1, characterized in that The set threshold of temperature deviation has a positive correlation with the fuel quantity of the coal mill, and is calculated as the measured temperature of the burner nozzle × the fuel quantity of the coal mill ÷ the rated fuel quantity of the coal mill × 5%.

8. The combustion stability identification system of a power station boiler based on the temperature measurement of the burner nozzle according to claim 1, wherein, The trigger condition for the boiler combustion support device to be put into operation is that the measured value of the burner nozzle temperature continuously remains lower than the calculated value of the burner nozzle temperature minus the deviation threshold for 3s.

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