A circulating fluidized bed boiler system with adjustable separator efficiency and a method of operation

Abstract

This invention relates to a circulating fluidized bed boiler system with adjustable separator efficiency and its operation method. The system includes a furnace, a cyclone separator, a baffle, a drive unit, a control unit, and a coal quality analysis device. The cyclone separator is connected to the furnace. One end of the baffle is located outside the cyclone separator, and the other end passes through the outer wall of the cyclone separator and is located at its flue gas inlet. The drive end of the drive unit is connected to the end of the baffle located outside the cyclone separator to control the depth to which the baffle is inserted into the flue gas inlet of the cyclone separator. The coal quality analysis device is located at the coal drop pipe at the coal feeder inlet to analyze the composition of the coal entering the furnace. Both the drive unit and the coal quality analysis device are electrically connected to the control unit. This system can adjust the separator efficiency online according to changes in the quality of the incoming coal and the load, achieving optimal separator efficiency. This effectively improves the boiler's combustion efficiency and enhances the boiler's fuel adaptability and combustion stability.

Description

Technical Field

[0001] This invention relates to the field of circulating fluidized bed technology, and in particular to a circulating fluidized bed boiler system with adjustable separator efficiency and its operation method. Background Technology

[0002] The separation efficiency of the cyclone separator in a circulating fluidized bed boiler is a crucial parameter affecting its operation. Higher separator efficiency results in a larger amount of circulating ash within the furnace, allowing the boiler to establish a good thermal cycle, preventing excessively high bed temperatures, reducing NOx emissions, enhancing fly ash capture capabilities, and increasing the residence time of fuel and limestone in the furnace, thus improving combustion efficiency. However, excessively high efficiency can also lead to excessively low bed temperatures and unstable combustion. Currently, influenced by the coal market, the quality of coal fed into the boiler fluctuates significantly, resulting in corresponding changes in the amount of flue gas produced. This causes the separator efficiency to fluctuate dynamically, making it particularly important to maintain a stable and reasonable separator efficiency.

[0003] Currently, my country's energy structure is undergoing significant adjustments. With the rapid growth of new energy installed capacity, circulating fluidized bed boilers need to participate in deep peak shaving. Under low loads, to maintain stable combustion in the furnace, a higher excess air coefficient is adopted, resulting in a large actual flue gas volume and increased flue gas velocity at the cyclone separator inlet. This keeps the separator efficiency at a high level, leading to a rapid decrease in bed temperature, which is detrimental to stable combustion. To address this issue, some scholars have proposed solutions for maintaining lower separator efficiency in circulating fluidized bed boilers under low load conditions, but there are currently no engineering practice examples.

[0004] Therefore, during operation, it is necessary to select a separator efficiency that matches the boiler system based on changes in the quality of coal entering the boiler and the load, so as to improve the stability and economy of boiler operation. Summary of the Invention

[0005] This invention provides a circulating fluidized bed boiler system with adjustable separator efficiency and its operation method. The separator efficiency is adjusted online according to changes in the quality of the coal fed into the boiler and the load, so that the separator efficiency reaches the optimal level. This can effectively improve the boiler's combustion efficiency and enhance the adaptability and stable combustion of boiler fuel.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A circulating fluidized bed boiler system with adjustable separator efficiency includes a furnace, a cyclone separator, baffles, a drive device, a control device, and a coal quality analysis device, wherein the cyclone separator is connected to the furnace.

[0008] One end of the baffle is located outside the cyclone separator, and the other end passes through the outer wall of the cyclone separator and is located at its flue gas inlet. The driving end of the driving device is connected to the end of the baffle located outside the cyclone separator to control the depth of the baffle inserted into the flue gas inlet of the cyclone separator.

[0009] The aforementioned coal quality analysis device is located at the coal drop pipe at the inlet of the coal feeder and is used to analyze the composition of the coal entering the furnace.

[0010] Both the aforementioned drive device and the aforementioned coal quality analysis device are electrically connected to the aforementioned control device. The aforementioned control device obtains the displacement of the aforementioned baffle based on the composition analysis results of the aforementioned coal quality analysis device, and the aforementioned control device controls the operation of the aforementioned drive device.

[0011] Preferably, the angle between the installation center line of the baffle and the cross-section of the flue is in the range of 30° to 60°.

[0012] Preferably, the baffle is provided with a circulating water channel, and the circulating water channel is connected to a heat exchange pipeline to reduce the temperature of the baffle.

[0013] Preferably, the heat exchange pipeline includes an inlet pipe, an outlet pipe, a first low-pressure heater, and a second low-pressure heater, wherein the first low-pressure heater and the second low-pressure heater are connected and disposed on a condensate pipeline connected to the boiler.

[0014] The aforementioned inlet pipe is connected to the condensate pipe on the inlet side of the aforementioned first low-pressure heater, the outlet of the aforementioned inlet pipe is connected to the inlet of the aforementioned circulating water channel, and the outlet of the aforementioned circulating water channel is connected to the condensate pipe between the aforementioned first low-pressure heater and the aforementioned second low-pressure heater.

[0015] Preferably, the inlet of the condensate pipe at the inlet of the first low-pressure heater is connected to the outlet of the condenser.

[0016] Preferably, the circulating water channel is configured in a serpentine shape.

[0017] An operation method for a circulating fluidized bed boiler system with adjustable separator efficiency, comprising:

[0018] The aforementioned control device acquires the real-time operating load of the boiler, and determines the efficiency of the aforementioned cyclone separator and the theoretical flue gas velocity at the inlet based on the real-time operating load of the boiler.

[0019] The aforementioned coal quality analysis device analyzes the composition of the coal at the inlet of the coal feeder, and the control device calculates the actual flue gas volume based on the analysis results;

[0020] The control device calculates the theoretical flue width at the inlet of the cyclone separator based on the actual flue gas volume, flue height, and theoretical flue gas velocity. Then, it calculates the displacement of the drive device driving the baffle based on the flue width before the baffle moves and the theoretical flue width.

[0021] The control device controls the drive device to move the baffle a corresponding distance based on the calculated baffle displacement.

[0022] Preferably, it further includes:

[0023] Before operation, the width of the flue under the baffle is the original width of the flue of the cyclone separator. When the system runs for the first time, the control device calculates the theoretical flue width based on the boiler's operating load and the composition of the coal. Then, it calculates the baffle displacement based on the theoretical flue width and the original flue width. Finally, the control device controls the drive device to move the baffle from the initial position to the corresponding position.

[0024] Preferably, it further includes:

[0025] During operation, when either the operating load or the composition of the coal changes, the control device calculates the theoretical flue width based on the changed boiler operating load and coal composition. Then, based on the flue width at the current position of the damper and the theoretical flue width, the damper displacement is obtained, and the drive device controls the damper to move from its current position to the corresponding position.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The coal quality analysis device is used to detect the composition of the coal at the coal feeder's chutes. Then, the control device calculates the actual flue gas volume and determines the corresponding cyclone separator efficiency and the theoretical flue gas velocity at the inlet based on the boiler's operating load. The control device calculates the theoretical flue width at the cyclone separator inlet based on the actual flue gas volume and theoretical flue gas velocity, and then calculates the displacement of the drive device's baffle based on the theoretical flue width. Finally, the drive device can adjust the depth of the cyclone separator's flue gas inlet through the drive baffle, ensuring the flue width at the cyclone separator inlet reaches the theoretical flue width, thus achieving the optimal efficiency of the cyclone separator under the boiler's operating conditions. Through the coordination of the coal quality analysis device, control device, drive device, and baffle, the separator efficiency can be adjusted online according to changes in the quality of the coal entering the boiler and the load, achieving optimal separator efficiency. This effectively improves the boiler's combustion efficiency, fuel adaptability, and combustion stability. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the overall system in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the heat exchange pipeline in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the baffle working in an embodiment of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Furnace; 2. Cyclone separator; 21. Flue inlet; 3. Baffle; 31. Circulating water channel; 4. Drive unit; 5. Control unit; 6. Coal quality analysis unit; 7. Heat exchange pipeline; 71. Water inlet pipe; 72. Water outlet pipe; 73. First low-pressure heater; 74. Second low-pressure heater; 75. Condensate pipeline. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] like Figure 1-3 As shown in the figure, an embodiment of the present invention discloses a circulating fluidized bed boiler system with adjustable separator efficiency, including a furnace 1, a cyclone separator 2, a baffle 3, a drive device 4, a control device 5, and a coal quality analysis device 6. The cyclone separator 2 is connected to the furnace 1. One end of the baffle 3 is located outside the cyclone separator 2, and the other end passes through the outer wall of the cyclone separator 2 and is located at its flue gas inlet. The drive end of the drive device 4 is connected to the end of the baffle 3 located outside the cyclone separator 2, and is used to control the depth of the baffle 3 inserted into the flue gas inlet of the cyclone separator 2. The drive device 4 can be an existing pneumatic drive device 4 used in power plants. The coal quality analysis device 6 is located at the coal drop pipe at the coal inlet of the coal machine, and is used to analyze the composition of the coal entering the furnace 1. The coal quality analysis device 6 includes at least C, S, H, O and other component analysis modules, because these components are the main components of the flue gas. Both the coal quality analysis device 4 and the coal quality analysis device 6 are electrically connected to the control device 5. Specifically, the coal quality analysis device 6 is also an existing device in the power plant, and the control device 5 is the power plant control system. The control device 5 is used to receive external data and calculate the corresponding data, and controls the operation of the drive device 4 based on the calculated data. In this application, the control device 5 itself is connected to the power plant system and can obtain the real-time operating load of the boiler. The control strategy of the control device 5 needs to be determined after the operation adjustment test. The operation adjustment test is the optimal separator efficiency test under different loads and different coal quality conditions. After the test, the control device 5 stores the data of the flue gas velocity and the optimal efficiency of the cyclone separator 2 under different operating loads throughout the boiler's operation process. That is, knowing the boiler operating load, one can know the corresponding flue gas velocity and the optimal efficiency of the cyclone separator 2.

[0038] Specifically, the coal quality analysis device 6 detects components such as C, S, H, and O in the coal and transmits the data to the control device 5. The control device 5 calculates the actual flue gas volume and obtains the corresponding theoretical flue gas velocity and cyclone separator 2 efficiency data based on the current boiler operating load. Then, the control device 5 calculates the theoretical flue width at the inlet of cyclone separator 2 based on the actual flue gas volume and theoretical flue gas velocity. Based on the theoretical flue width, the control device 5 determines the required displacement of the baffle 3 and controls the drive device 4 to move the baffle 3 by the corresponding distance, ensuring that the flue width at the inlet of cyclone separator 2 is the theoretical width. Thus, the efficiency of cyclone separator 2 can reach its optimal level under the current boiler operating load conditions. In summary, this system can adjust the efficiency of cyclone separator 2 online according to changes in the quality of the coal entering the boiler and the load, ensuring that the efficiency of cyclone separator 2 reaches the system's specified efficiency. This effectively improves the boiler's combustion efficiency and enhances the boiler's fuel adaptability and combustion stability.

[0039] Furthermore, to prevent flue gas and circulating ash from directly impacting the baffle 3, causing it to wear out quickly and have a short service life, the angle between the installation center line of the baffle 3 and the flue section is set to 30° to 60°, specifically 45°. On the one hand, the inclination of the baffle 3 is not high, which reduces wear compared to a 30° setting. On the other hand, the length of the baffle 3 is shorter than that of a 60° setting, resulting in better performance.

[0040] Furthermore, since the baffle 3 is installed at the flue gas inlet of the cyclone separator 2, in a temperature environment of 800-900℃, a circulating water channel 31 is provided inside the baffle 3 to extend its service life. The circulating water channel 31 is designed in a serpentine shape for better heat exchange efficiency. The circulating water channel 31 is connected to a heat exchange pipeline 7. Specifically, the heat exchange pipeline 7 includes an inlet pipe 71, an outlet pipe 72, a first low-pressure heater 73, and a second low-pressure heater 74. The first low-pressure heater 73 and the second low-pressure heater 74 are connected and located on the condensate pipe 75. The outlet of the condensate pipe 75 is connected to the boiler to provide hot water to the boiler. The inlet pipe 71 is connected to the condensate pipe 75 on the inlet side of the first low-pressure heater 73. The outlet of the inlet pipe 71 is connected to the inlet of the circulating water channel 31, and the outlet of the circulating water channel 31 is connected to the condensate pipe between the first low-pressure heater 73 and the second low-pressure heater 74. Specifically, a control valve is connected to the inlet pipe 71. When the system is running, the control valve is opened, and a portion of the condensate enters the inlet pipe 71 from the condensate pipe 75, then enters the circulating water channel 31 and exchanges heat with the baffle 3, keeping the baffle 3 at a low temperature, thereby extending its service life. Then, the circulating water after heat exchange enters the outlet pipe 72, and another portion of the water directly enters the first low-pressure heater 73, and then mixes together and enters the second low-pressure heater 74 for reheating, thereby increasing the temperature of the circulating water.

[0041] Preferably, the inlet of the condensate pipe 75 at the inlet of the first low-pressure heater 73 is connected to the outlet of the condenser. This is because the condensate from the condenser is at its lowest temperature at this time. When it enters the circulating water channel 31 inside the baffle 3, the temperature of the baffle 3 can be reduced to the maximum extent. Moreover, the temperature of this part of the condensate after heating is increased, which indirectly utilizes the heat of the flue gas. Furthermore, this part of the condensate does not pass through the first low-pressure heater 73 and does not utilize the heat of the steam inside the first low-pressure heater 73, thus saving this part of energy. To a certain extent, this can improve the circulation efficiency of the thermal system and improve the economic operation of the unit.

[0042] This invention also provides an operation method for a circulating fluidized bed boiler system with adjustable cyclone separator efficiency, comprising:

[0043] Before the system is running, the baffle 3 is in the initial position. At this time, the width of the flue at the inlet of the cyclone separator 2 is the original width. The baffle 3 does not block the inlet flue of the cyclone separator 2, which facilitates maintenance when the baffle 3 is not running.

[0044] When the system is running for the first time, the control device 5 obtains the real-time boiler operating load from the power plant system and determines the efficiency of the cyclone separator 2 and the theoretical flue gas velocity at the inlet based on the real-time boiler operating load.

[0045] The coal quality analysis device 6 analyzes the C, S, H and O components in the coal at the coal inlet of the coal machine. The control device 5 calculates the theoretical flue gas volume based on the analysis results, and then calculates the actual flue gas volume based on the theoretical flue gas volume.

[0046] The control device 5 calculates the theoretical flue width at the inlet of the cyclone separator 2 based on the actual flue gas volume, flue height, and theoretical flue gas velocity. Then, it calculates the displacement of the baffle 3 based on the theoretical flue width and the original flue width. The control device 5 controls the drive device 4 to drive the baffle 3 to move from the initial position to the corresponding position, so that the flue width at the inlet of the cyclone separator 2 reaches the theoretical flue width.

[0047] During system operation, when either the operating load or the coal composition changes, the control device 5 calculates the corresponding actual flue gas volume and theoretical flue gas velocity based on the changed boiler operating load and coal composition. Then, it calculates the corresponding theoretical flue width and determines the displacement of the baffle 3. The control device 5 then controls the drive device 4 to move the baffle 3 from its current position (before the change in operating load and coal composition) to the corresponding position (after the change in operating load and coal composition), ensuring that the flue width at the inlet of the cyclone separator 2 reaches the theoretical flue width. During system operation, the displacement of the baffle and the flue width of the cyclone separator 2 after any change in operating load or coal composition are recorded by the control device 5 and can be directly retrieved when needed. Because the calculated theoretical flue width changes with any change in operating load or coal composition, the relevant data needs to be recalculated. Specifically, when the operating load changes, the corresponding flue gas velocity and the efficiency of the cyclone separator 2 will change; when the coal composition changes, the corresponding actual flue gas volume will also change.

[0048] In the above method, the online coal quality analysis device must at least include a module for analyzing the C, S, H, and O components in the fuel, used to calculate the theoretical flue gas volume. The formula for calculating the theoretical flue gas volume is as follows:

[0049] V 0 =0.0889(C ar +0.375S ar )+0.265H ar -0.3330 ar (1)

[0050] Among them, V 0 Theoretical flue gas volume, unit: Nm³ 3 / kg; Car, Sar, Har, and Oar represent the measured carbon, sulfur, hydrogen, and oxygen content.

[0051] Then, based on the excess air coefficient α, the actual flue gas volume is calculated:

[0052] V = V 0 (1+α)m (2)

[0053] Where V0 is the theoretical flue gas volume, in Nm³. 3 / kg; V is the actual flue gas volume, in Nm³. 3 m represents the coal feed rate, in kg / s.

[0054] During system operation, the formula for calculating the width of the inlet flue of the pre-cyclone separator is as follows:

[0055] L1=V / (h·v1) (3)

[0056] Where h is the height of the cyclone separator inlet flue, in meters; L1 is the width of the cyclone separator inlet flue before adjustment, in meters. Figure 3 Indicated; v1 is the flue gas velocity at the inlet of the cyclone separator before adjustment, in m / s.

[0057] The formula for calculating the width of the inlet flue of the cyclone separator after adjustment is as follows:

[0058] L2=V(h·v2) (4)

[0059] Where h is the height of the cyclone separator inlet flue, in meters; L2 is the width of the cyclone separator inlet flue before adjustment, in meters. Figure 3 As shown; v2 is the flue gas velocity at the inlet of the cyclone separator after adjustment, in m / s.

[0060] The formula for calculating the displacement of the baffle is as follows:

[0061] S=(L1-L2) / cos a (5)

[0062] Where S is the baffle displacement in meters (m); L2 is the width of the inlet flue of the cyclone separator before adjustment in meters (m); and L1 is the width of the inlet flue of the cyclone separator before adjustment in meters (m).

[0063] In summary, this system can adjust the separator efficiency online according to changes in the quality of the coal fed into the furnace and the load, so that the separator efficiency reaches the system's optimal efficiency, which can effectively improve the boiler's combustion efficiency and enhance the boiler's fuel adaptability and combustion stability.

[0064] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for operating a circulating fluidized bed boiler system with adjustable separator efficiency, characterized in that, The application relates to a boiler with a cyclone separator and a baffle. The control device obtains the real-time operation load of the boiler, and determines the efficiency of the cyclone separator and the theoretical flue gas flow rate at the inlet according to the real-time operation load of the boiler; The coal quality analysis device analyzes the composition of the coal at the inlet of the coal feeder, and the control device calculates the actual flue gas volume according to the analysis result; The control device calculates the theoretical flue width at the inlet of the cyclone separator according to the actual flue gas volume, the flue height and the theoretical flue gas flow rate, and then calculates the displacement of the driving device according to the flue width before the baffle moves and the theoretical flue width; The control device controls the driving device to drive the baffle to move a corresponding distance according to the calculated displacement of the baffle; Before operation, the flue width under the baffle is the original width of the cyclone separator flue, when the system is operated for the first time, the control device calculates the theoretical flue width according to the operation load of the boiler and the composition of the coal, and then calculates the displacement of the baffle according to the theoretical flue width and the original flue width, and then the control device controls the driving device to drive the baffle to move from the initial position to the corresponding position; During operation, when the operation load or the composition of the coal changes, the control device calculates the theoretical flue width according to the changed operation load of the boiler and the composition of the coal, and then calculates the displacement of the baffle according to the flue width at the present position of the baffle and the theoretical flue width, and the driving device controls the baffle to move from the present position to the corresponding position.

2. A circulating fluidized bed boiler system with adjustable separator efficiency for operating the method of operating a circulating fluidized bed boiler system as claimed in claim 1, characterized by The application relates to a boiler with a cyclone separator and a baffle. One end of the baffle is located outside the cyclone separator, the other end penetrates through the outer wall of the cyclone separator and is located at the flue gas inlet of the cyclone separator, the driving end of the driving device is connected with the end of the baffle located outside the cyclone separator, and the driving device is used for controlling the depth of the baffle inserted into the flue gas inlet of the cyclone separator; The coal quality analysis device is arranged at the coal falling pipe at the inlet of the coal feeder and is used for analyzing the composition of the coal entering the furnace; The driving device and the coal quality analysis device are electrically connected with the control device, the control device obtains the displacement of the baffle according to the composition analysis result of the coal quality analysis device, and the control device controls the driving device to work so that the baffle moves by the corresponding displacement.

3. The separator-efficiency-adjustable circulating fluidized bed boiler system according to claim 2, characterized by The included angle between the mounting center line of the baffle and the flue cross section ranges from 30 DEG to 60 DEG.

4. The separator efficiency adjustable circulating fluidized bed boiler system according to claim 2, characterized in that, A circulating water channel is arranged in the baffle, and a heat exchange pipeline is connected with the circulating water channel and is used for reducing the temperature of the baffle.

5. The separator-efficiency-adjustable circulating fluidized bed boiler system according to claim 4, characterized by The heat exchange pipeline comprises a water inlet pipe, a water outlet pipe, a first low-pressure heater and a second low-pressure heater, the first low-pressure heater and the second low-pressure heater are communicated and are arranged on a condensate water pipeline communicated with the boiler; The water inlet pipe is communicated with the condensate water pipeline at the water inlet side of the first low-pressure heater, the water outlet of the water inlet pipe is communicated with the inlet of the circulating water channel, and the outlet of the circulating water channel is communicated with the condensate water pipeline between the first low-pressure heater and the second low-pressure heater.

6. The separator-efficiency-adjustable circulating fluidized bed boiler system according to claim 5, characterized by The water inlet of the condensate water pipeline at the water inlet of the first low-pressure heater is communicated with the water outlet of the condenser.

7. The separator-efficiency-adjustable circulating fluidized bed boiler system according to claim 5, characterized by The circulating water channel is arranged in a serpentine shape.

Images