A device for regulating the concentration of coal powder in the outlet air powder pipe of a coal mill

Abstract

This utility model discloses a device for adjusting the pulverized coal concentration in the pulverized coal outlet air-coal pipes of a coal mill, comprising a pulverized coal storage bin and a pulverized coal feeder. The pulverized coal storage bin has an inlet and an outlet, and a pulverized coal storage control valve with a multi-blade structure is installed at the inlet of the pulverized coal storage bin. The pulverized coal feeder is located at the outlet of the pulverized coal storage bin. The above device can effectively adjust the pulverized coal concentration in each air-coal pipe at the outlet of the coal mill, making the pulverized coal concentration in each air-coal pipe tend to be uniform, ensuring uniform pulverized coal supply to the furnace and stable combustion. At the same time, when the output of the coal mill is insufficient and the pulverized coal output is less than the boiler fuel demand, the pulverized coal stored in the pulverized coal storage bin can be transported to the central coal drop pipe of the coal mill, so that it recirculates inside the coal mill and is redistributed to each air-coal pipe at the outlet of the coal mill, realizing rapid and precise dynamic matching between the fuel system and the combustion system in the rapid peak shaving of coal-fired power plant boilers. It is small in size, occupies little space, has a simple structure, is easy to modify and lay out on site, is convenient to control, and is easy to promote.

Description

Technical Field

[0001] This utility model relates to a device for adjusting the coal powder concentration in the outlet air-coal pipe of a coal mill, and belongs to the technical field of coal powder concentration adjustment in the outlet air-coal pipe of a coal mill. Background Technology

[0002] The pulverized coal preparation system in a coal-fired power plant is often simply referred to as the pulverizing system. The pulverizing system refers to the combination of equipment and related connecting pipes required to grind and dry raw coal into pulverized coal with a certain fineness and moisture content, which is then fed into the boiler furnace for combustion. Common pulverizing systems are classified into two types according to their operating characteristics: direct-fired and intermediate-storage.

[0003] In a direct-fired pulverizing system, the pulverized coal produced by the coal mill is directly sent to the boiler furnace for combustion without intermediate stops. Therefore, the normal operation of the boiler depends on the reliability of the pulverizing system. Coal mills with good variable load operating characteristics, such as medium-speed, high-speed, and double-inlet / double-outlet mills, are preferable. Direct-fired pulverizing systems equipped with medium-speed coal mills have a simple structure, fewer equipment, compact layout, low steel consumption, lower investment, and relatively low power consumption, making them commonly used in medium and large-scale coal-fired power plants. A medium-speed coal mill consists of at least three parts: a drive unit, a grinding unit, and a coarse powder separator. The grinding unit typically consists of a grinding disc driven by the drive unit and three fixed (meaning their positions are fixed) and self-rotating grinding rollers that roll along the grinding ring. The coarse powder separator consists of coarse powder separation baffles and a conical shell, located above the grinding disc. Raw coal falls onto the grinding disc through the central coal drop pipe. The centrifugal force of the rotating grinding disc propels the raw coal onto the grinding track, where it is ground by the grinding rollers. The grinding and drying of raw coal are carried out simultaneously. High-temperature primary air enters relatively evenly around the grinding disc through nozzle rings, drying the coal powder mixture tangentially ejected from the grinding disc and conveying it to the coarse powder separator above the grinding disc. Stone coal falls into the stone coal box through the nozzle rings. The coal powder mixture is separated from the coarse powder by the coarse powder separation baffles. Qualified fine powder is carried by the primary air and enters the furnace for combustion through the coal mill outlet air-coal pipe. Coarse powder returns to the grinding disc from the bottom of the cone shell under its own gravity for re-grinding. The aforementioned central coal drop pipe is arranged vertically, with raw coal entering from above the medium-speed coal mill. Four to six air-coal pipes are arranged around the central coal drop pipe, allowing coal powder meeting certain fineness and temperature requirements to enter the furnace under the influence of primary air. Primary air enters from the coal mill inlet pipe, passing through nozzle rings to mix with the coal. To regulate the coal mill temperature, a cold primary air pipe is connected to the coal mill inlet pipe, and its flow rate is controlled.

[0004] While direct-fired pulverized coal systems offer numerous advantages, they are somewhat less effective at responding to boiler load changes. When boiler load changes, the coal feed rate responds accordingly, but due to a 3-5 minute lag time in the pulverized coal grinding process, the pulverized coal output does not perfectly match the boiler's required fuel consumption in real time. This limits the load change rate (i.e., ramp-up rate, including both upward and downward ramp-up rates) of the coal-fired unit, typically reaching only around 1.5% Pe / min. Furthermore, due to their compact structure, medium-speed pulverized coal mills often exhibit significant variations in pulverized coal concentration in the air-coal pipes at the mill outlet, negatively impacting furnace combustion, such as causing overheating of some water-cooled walls. Utility Model Content

[0005] This invention provides a device for adjusting the pulverized coal concentration in the pulverized coal outlet air-coal pipes of a coal mill. This device effectively regulates the pulverized coal concentration in each air-coal pipe at the coal mill outlet, ensuring a more uniform concentration and thus guaranteeing uniform pulverized coal supply to the furnace and stable combustion. Simultaneously, when the coal mill output is insufficient or the pulverized coal output is less than the boiler fuel demand, the pulverized coal stored in the pulverized coal storage bin can be transported to the central coal drop pipe of the coal mill, allowing it to recirculate within the mill and redistribute to the air-coal pipes at the coal mill outlet. This achieves rapid and precise dynamic matching between the fuel system and the combustion system during rapid peak shaving in coal-fired power plant boilers.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0007] A device for adjusting the coal powder concentration in the outlet air-coal pipe of a coal mill includes a coal powder storage bin and a coal feeder; the coal powder storage bin has an inlet and an outlet, and a coal powder control valve with a multi-blade structure is provided on the inlet of the coal powder storage bin; the coal feeder is located at the outlet of the coal powder storage bin.

[0008] When in use, an installation port is reserved on the coal mill outlet air-coal pipe. The inlet of the coal powder storage bin is connected to the installation port. The coal powder storage bin intercepts or extracts coal powder from the coal mill outlet air-coal pipe, thereby regulating the coal powder concentration in the coal mill outlet air-coal pipe.

[0009] To achieve rapid and precise dynamic matching between the fuel system and combustion system in the rapid peak shaving of coal-fired power plant boilers, a pulverized coal return pipe is added. The return pipe has two inlet branches: a pulverized coal inlet and a conveying air inlet, with the conveying air inlet located upstream of the pulverized coal inlet. The inlet of the pulverizer is connected to the outlet of the pulverized coal storage silo, and the outlet of the pulverizer is connected to the pulverized coal inlet of the return pipe. The outlet of the return pipe leads to and connects with the central coal drop pipe of the coal mill. The conveying air inlet of the return pipe is used to introduce conveying air. When the coal mill output is insufficient and the pulverized coal output is less than the boiler fuel demand, the pulverizer is activated, conveying the pulverized coal stored in the pulverized coal storage silo to the return pipe. The conveying air then sends the pulverized coal from the return pipe into the central coal drop pipe of the coal mill, allowing it to recirculate inside the coal mill and redistribute to the various air-powder pipes at the coal mill outlet. This achieves rapid and precise dynamic matching between the fuel system and combustion system in the rapid peak shaving of coal-fired power plant boilers.

[0010] The central coal drop pipe of the aforementioned coal mill is a standard component of medium-speed coal mills and will not be described in detail here.

[0011] The aforementioned powder return pipe has an inlet at one end and an outlet at the other end. The inlet of the powder return pipe has at least two branches, namely at least one powder inlet and one conveying air inlet, while the outlet does not have any branches.

[0012] Preferably, pulverized coal storage bins are installed on each air-coal pipe at the coal mill outlet (the installation method involves reserving an installation port on each air-coal pipe, and then connecting the inlet of each pulverized coal storage bin to the corresponding installation port on the air-coal pipe). The pulverized coal storage bins intercept or extract pulverized coal from their respective air-coal pipes, thereby achieving the effect of regulating the pulverized coal concentration in each air-coal pipe (generally 4-6 pipes) at the coal mill outlet; it also makes the pulverized coal concentration in each air-coal pipe tend to be uniform, ensuring uniform pulverized coal supply to the furnace and stable combustion;

[0013] The return coal pipe has two inlet branches: a conveying air inlet and two or more powder inlets, with the conveying air inlet located upstream of each powder inlet. The number of powder inlets, powder storage bins, and feeders is equal and they correspond one-to-one. The feeder inlet is connected to the outlet of the corresponding powder storage bin, and the feeder outlet is connected to the corresponding powder inlet. In this way, the pulverized coal in each powder storage bin can enter the same return coal pipe and be conveyed to the central coal drop pipe by primary air supplied from the conveying air inlet.

[0014] The upstream-to-downstream direction of this application is consistent with the material flow direction.

[0015] For ease of installation and control, the mounting port on the air-powder duct is located at the bottom of the horizontal section of the air-powder duct. That is, the powder storage bin is located on the horizontal section of the air-powder duct and below the air-powder duct.

[0016] The preferred method for the conveying air inlet of the aforementioned return pulverizer pipe is to connect to the primary cold air, that is, to send the pulverized coal from the return pulverizer pipe into the central coal drop pipe of the coal mill via the primary cold air.

[0017] For ease of installation and control, the powder storage control valve is composed of two or more adjusting blades spliced ​​together; each adjusting blade is equipped with a rotating shaft; each rotating shaft is driven to rotate by a motor or pneumatic actuator, which in turn drives the adjusting blade to rotate, thereby controlling the opening degree of the powder storage control valve.

[0018] To improve the efficiency and effectiveness of pulverized coal regulation, each regulating blade is rectangular, and each rotating axis is parallel to the others. The direction perpendicular to the axis of rotation of the regulating blade is considered the width direction, and the direction parallel to the axis of rotation of the regulating blade is considered the length direction. Each regulating blade has a different width. In use, the axis of rotation of the regulating blade is perpendicular to the direction of air-pulverized coal flow in the air-pulverized coal pipe (i.e., from upstream to downstream). The width of each regulating blade increases sequentially along the direction of air-pulverized coal flow. This facilitates rapid response in pulverized coal regulation and makes control convenient.

[0019] The length and width are two adjacent sides of the rectangle. The width direction of the aforementioned adjusting blade is also the direction in which the width is located, and the length direction is the direction in which the length is located. For ease of description, this application defines the length and width directions based on the axis of rotation, rather than the actual length of the rectangle's sides. Therefore, in this application, it is not limited to the width of the adjusting blade being less than its length.

[0020] For ease of adjustment and control, the rotation axis of each adjusting blade is located at the downstream end of the blade in the width direction, and / or at the middle position in the width direction of the blade; each rotating axis is synchronously driven by a motor through a crank-connecting rod mechanism. One end of the adjusting blade in the width direction is the upstream end, and the other end is the downstream end, with the direction from the upstream end to the downstream end consistent with the air-powder flow direction in the air-powder pipe.

[0021] To further improve the powder storage speed, each regulating blade is equipped with a baffle plate at a 60-150° angle to its front surface. The angle between the regulating blade and the baffle plate refers to the angle between the front surface of the regulating blade and the baffle plate. The front surface of the regulating blade is the side that is flushed by the powder in the powder duct when the powder storage control valve is open. The baffle plate can be located either above or below the rotating shaft. "Above" and "below" refer to the positions of the baffle plate relative to the rotating shaft when the regulating blade is at a 90° opening. The baffle plate is installed away from the rotating shaft, ensuring that its placement does not affect the rotation of the regulating blade.

[0022] When in use, the horizontal position of each adjusting blade is zero (corresponding to 0°). When all adjusting blades are in the horizontal position, the inlet of the powder storage bin is closed. Each adjusting blade is adjustable within a range of at least 0-45°.

[0023] Further optimization revealed that each adjusting blade is adjustable within the range of 0-90°. When all adjusting blades are at 90°, the opening of the powder storage bin inlet is at its maximum, resulting in the fastest powder storage speed.

[0024] When the inlet of the pulverized coal storage silo is closed, the inlet is completely covered and blocked by the pulverized coal storage control valve. The pulverized coal storage control valve can be closed when it is not necessary to adjust the pulverized coal concentration in the air-coal duct.

[0025] For ease of installation and control, the powder storage control valve is located at the inlet end face of the powder storage silo.

[0026] The inlet of the aforementioned pulverized coal storage silo is located at its top, and its outlet is located at its bottom. The silo has a tapering structure from inlet to outlet. That is, the top of the silo is the larger end, serving as the inlet, and the bottom is the smaller end, serving as the outlet. This facilitates the control of pulverized coal entry and exit.

[0027] To prevent pulverized coal stored in the shrinkage silo from caking, a heating device is installed on the silo, with a heating temperature of 60-100℃.

[0028] To further prevent pulverized coal stored in the shrinkage silo from caking, a fluidizing air inlet pipe is installed at the bottom of the silo to introduce fluidizing air from the bottom of the silo.

[0029] As one preferred implementation, the fluidizing air inlet pipe is connected to the nitrogen outlet of the nitrogen generator via a pipeline. That is, nitrogen is used as the fluidizing air.

[0030] To prevent the stored pulverized coal from exploding, an explosion-proof gas inlet pipe is installed on the top of the pulverized coal storage silo. Inert gas with an oxygen content of less than 12% is introduced into the silo, and an oxygen measuring point is installed on the top of the silo.

[0031] To improve the reliability of pulverized coal conveying, a silo wall vibrator is installed at the outlet of the pulverized coal storage silo. A level gauge is installed on the silo to monitor the amount of pulverized coal in it.

[0032] For the specific installation of the aforementioned heat tracing devices, oxygen measurement points, silo wall vibrators, level gauges, etc., please refer to the product manual or existing mature technologies.

[0033] Any technologies not mentioned in this utility model are based on existing technologies.

[0034] This utility model relates to a device for adjusting the pulverized coal concentration in the outlet air-coal pipes of a coal mill. It effectively regulates the pulverized coal concentration in each outlet air-coal pipe, ensuring a more uniform concentration and thus guaranteeing even pulverized coal supply to the furnace and stable combustion. Simultaneously, when the coal mill's output is insufficient or the pulverized coal output is less than the boiler's fuel demand, it can transport the pulverized coal stored in the pulverized coal storage bin to the central coal drop pipe of the coal mill, allowing it to recirculate within the mill and redistribute to the outlet air-coal pipes. This achieves rapid and precise dynamic matching between the fuel system and the combustion system during rapid peak shaving in coal-fired power plant boilers. The device is small in size, requires little space, has a simple structure, is easy to modify and install on-site, convenient to control, and easy to promote. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a device for adjusting the coal powder concentration in the outlet air-coal pipe of a coal mill according to the present invention.

[0036] Figure 2 for Figure 1 A three-dimensional image;

[0037] Figure 3 for Figure 1 The left view;

[0038] Figure 4 for Figure 1 Top view;

[0039] Figure 5 This is a schematic diagram of the structure of the powder storage control valve of this utility model;

[0040] Figure 6 for Figure 5 A three-dimensional image;

[0041] Figure 7 for Figure 5 The left view;

[0042] Figure 8 for Figure 5 Top view;

[0043] In the diagram, 1 is the powder storage bin, 2 is the powder feeder, 3 is the powder storage control valve, 31 is the adjusting blade, 32 is the rotating shaft, 33 is the motor, 34 is the crank connecting rod mechanism, 35 is the flow-blocking rib plate, 4 is the bin wall vibrator, and 5 is the material level gauge. Detailed Implementation

[0044] To better understand this utility model, the following embodiments further illustrate the content of this utility model, but the content of this utility model is not limited to the following embodiments.

[0045] The directional terms used in this application, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," are based on the orientation or positional relationship shown in the accompanying drawings or in the usage state, and are only for the convenience of describing this application. They are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this application.

[0046] Example 1

[0047] A device for adjusting the coal powder concentration in the outlet air-coal pipe of a coal mill includes a coal powder storage bin and a coal feeder; the coal powder storage bin has an inlet and an outlet, and a coal powder control valve with a multi-blade structure is provided on the inlet of the coal powder storage bin; the coal feeder is located at the outlet of the coal powder storage bin.

[0048] In use, an installation port is reserved on the coal mill outlet air-coal duct. The inlet of the coal pulverized coal storage bin is connected to the installation port. The coal pulverized coal storage bin intercepts or extracts coal powder from the coal mill outlet air-coal duct, thereby regulating the coal powder concentration in the coal mill outlet air-coal duct. In this example, the installation port is reserved at the bottom of the horizontal section of the air-coal duct, meaning the coal pulverized coal storage bin is located on the horizontal section of the air-coal duct and below it.

[0049] To achieve rapid and precise dynamic matching between the fuel system and combustion system in the rapid peak shaving of coal-fired power plant boilers, a pulverized coal return pipe is added. The return pipe has two inlet branches: a pulverized coal inlet and a conveying air inlet, with the conveying air inlet located upstream of the pulverized coal inlet. The inlet of the pulverizer is connected to the outlet of the pulverized coal storage silo, and the outlet of the pulverizer is connected to the pulverized coal inlet of the return pipe. The outlet of the return pipe leads to and connects with the central coal drop pipe of the coal mill. The conveying air inlet of the return pipe is used to introduce conveying air. When the coal mill output is insufficient and the pulverized coal output is less than the boiler fuel demand, the pulverizer is activated, conveying the pulverized coal stored in the pulverized coal storage silo to the return pipe. The conveying air then sends the pulverized coal from the return pipe into the central coal drop pipe of the coal mill, allowing it to recirculate inside the coal mill and redistribute to the various air-powder pipes at the coal mill outlet. This achieves rapid and precise dynamic matching between the fuel system and combustion system in the rapid peak shaving of coal-fired power plant boilers. In this example, the conveying air is cold primary air, that is, the pulverized coal from the return pulverizer pipe is sent into the central coal drop pipe of the coal mill through the cold primary air.

[0050] Example 2

[0051] Based on Example 1, the following improvements were made: To facilitate installation and control, the powder storage control valve is located at the inlet end face of the powder storage silo. The powder storage control valve is composed of two or more adjusting blades spliced ​​together. Each adjusting blade is equipped with a rotating shaft. Each rotating shaft is driven to rotate by a motor or pneumatic actuator, which in turn drives the adjusting blade to rotate, thereby controlling the opening degree of the powder storage control valve.

[0052] Example 3

[0053] Based on Example 2, the following improvements were made: To improve the adjustment efficiency and effect of pulverized coal, each adjustment blade is rectangular, and each rotation axis is parallel to the others; the direction perpendicular to the rotation axis of the adjustment blade is considered the width direction, that is, the direction parallel to the rotation axis of the adjustment blade is considered the length direction. Each adjustment blade has a different width. In use, the rotation axis of the adjustment blade is perpendicular to the flow direction of the pulverized coal in the air-coal pipe (i.e., from upstream to downstream). The width of each adjustment blade increases sequentially along the flow direction of the pulverized coal, which facilitates rapid response in pulverized coal adjustment and convenient control. For ease of adjustment and control, the rotation axis of each adjustment blade is located at the downstream end of the width direction of the adjustment blade, and / or the rotation axis of each adjustment blade is located at the middle position of the width direction of its respective adjustment blade, such as... Figure 1 As shown, in this example, the downstream rotating shaft is located at the middle position in the width direction of the adjusting blade, and the remaining rotating shafts are located at the downstream end in the width direction of the adjusting blade; each rotating shaft is synchronously driven to rotate by a motor through a crank-connecting rod mechanism.

[0054] During use, the horizontal position of each adjusting blade is zero (corresponding to 0°). When all adjusting blades are in the horizontal position, the inlet of the powder storage chamber is closed. Each adjusting blade is adjustable within the range of 0-90°. When all adjusting blades are at 90°, the opening of the powder storage chamber inlet is at its maximum, and the powder storage speed is the fastest.

[0055] Example 4

[0056] Based on Example 3, the following improvements were made: To further improve the powder storage speed, each adjusting blade's upstream surface is equipped with a flow-blocking rib that forms an angle of 120° with the adjusting blade (experimentally, it could also be 100°, 150°, etc.). For example... Figure 6 As shown, in this example, the flow-blocking rib is located on the upper side near the rotating shaft, that is, when the adjusting blades are all at a 90° opening, the flow-blocking rib is located above the rotating shaft.

[0057] Example 5

[0058] Based on Example 4, the following improvements were made: the inlet of the powder storage bin is at the top and the outlet is at the bottom, and the powder storage bin has a structure that gradually narrows from the inlet to the outlet.

[0059] Example 6

[0060] Based on Example 5, the following improvements were made: In order to prevent the coal powder stored in the shrinkage silo from caking, a heating device was installed on the silo with a heating temperature of 60-100℃.

[0061] Example 7

[0062] Based on Example 6, the following improvements were made: To further prevent pulverized coal stored in the coal storage silo from caking, a fluidizing air inlet pipe was installed at the bottom of the silo to introduce fluidizing air. In this example, the fluidizing air inlet pipe is connected to the nitrogen outlet of the nitrogen generator via a pipeline. That is, nitrogen is used as the fluidizing air.

[0063] Example 8

[0064] Based on Example 7, the following improvements were made: To prevent the stored pulverized coal from exploding, an explosion-proof gas inlet pipe was installed at the top of the pulverized coal storage silo. An inert gas with an oxygen content of less than 12% was introduced into the silo, and an oxygen measurement point was installed at the top inside the silo. In this example, […]. Figure 1-3 The pipe connecting the top of the powder storage silo to the air-powder pipe shown is considered part of the air-powder pipe. The explosion-proof gas inlet pipe is located on the air-powder pipe at the top of the powder storage silo. The explosion-proof gas is also nitrogen. The nitrogen generator has two outlet branches: the first outlet and the second outlet. The first outlet is connected to the fluidizing air inlet pipe through the first pipe, which is equipped with a fluidizing air control valve. The second outlet is connected to the explosion-proof gas inlet pipe through the second pipe, which is equipped with an explosion-proof gas interface control valve.

[0065] Example 9

[0066] Based on Example 8, the following improvements were made: To improve the reliability of pulverized coal conveying, a silo wall vibrator was installed at the outlet of the pulverized coal storage silo. To monitor the amount of pulverized coal in the silo, a level gauge was installed on the silo.

[0067] Pulverized coal storage bins are installed on each air-coal pipe at the coal mill outlet (the installation method involves reserving an installation port on each air-coal pipe and then connecting the inlet of each pulverized coal storage bin to the corresponding installation port on the air-coal pipe). The pulverized coal storage bins intercept or extract pulverized coal from their respective air-coal pipes, thereby achieving the effect of regulating the pulverized coal concentration in each air-coal pipe at the coal mill outlet. The pulverized coal concentration in each air-coal pipe at the coal mill outlet can also be monitored in real time, and the opening of the corresponding pulverized coal storage control valve can be adjusted in real time according to the real-time monitored pulverized coal concentration in each air-coal pipe, so that the pulverized coal concentration in each air-coal pipe tends to be uniform, ensuring uniform pulverized coal supply to the furnace and stable combustion.

[0068] The return coal pipe has two or more inlet branches: a conveying air inlet and two or more powder inlets, with the conveying air inlet located upstream of each powder inlet. The number of powder inlets, powder storage bins, and feeders is equal and they correspond one-to-one. The feeder inlet is connected to the outlet of the corresponding powder storage bin, and the feeder outlet is connected to the corresponding powder inlet. In this way, the pulverized coal in each powder storage bin can enter the same return coal pipe and be conveyed to the central coal drop pipe by primary air supplied from the conveying air inlet.

[0069] When the coal mill output is excessive and the amount of coal powder produced is greater than the boiler fuel demand, the opening of the coal powder storage control valve is adjusted to store the excess coal powder in the coal powder storage bin. The coal powder pipe with a higher coal powder concentration corresponds to the coal powder storage bin with more coal powder, and the coal powder pipe with a lower coal powder concentration corresponds to the coal powder storage bin with less coal powder, so that the coal powder concentration in each coal powder pipe tends to be uniform.

[0070] When the coal mill output is insufficient and the pulverized coal output is less than the boiler fuel demand, the pulverizer is turned on. The pulverizer adds the pulverized coal from the storage bin to the return pulverizer pipe, and then the pulverized coal in the return pulverizer pipe is transported to the central coal drop pipe of the coal mill by the cold primary air. It then enters the coal mill for recirculation and is redistributed to the air-pulverizer pipes at the coal mill outlet, realizing rapid and precise dynamic matching between the fuel system and the combustion system in the rapid peak shaving of the coal-fired power plant boiler.

[0071] In this example, each powder storage control valve is composed of 6 adjusting blades spliced ​​together. The length of each adjusting blade is 800mm, and the width of each adjusting blade along the powder flow direction is 100mm, 150mm, 200mm, 250mm, 300mm, and 700mm respectively.

[0072] The above scheme was applied to a 1000MW coal-fired power generating unit, which was equipped with 6 medium-speed coal mills, five in operation and one on standby. Two of the coal mills (mill B and mill E) were equipped with a flexible adjustment system for the output of the medium-speed coal mill in the direct-fired pulverizing system. The total coal storage capacity was not less than 5 tons. Through flexible adjustment, the unit's ramp-up rate exceeded 4% Pe / min in the 50%-100% load range. During this period, the temperature and pressure fluctuations of the main steam and reheat steam of the coal-fired boiler were within the allowable range of the operating procedures, and there were no local overheating problems in the water-cooled walls.

[0073] The devices described above for adjusting the pulverized coal concentration in the pulverized coal outlet air-coal pipes can effectively regulate the pulverized coal concentration in each air-coal pipe at the pulverized coal outlet, making the pulverized coal concentration in each air-coal pipe more uniform, ensuring uniform pulverized coal supply to the furnace and stable combustion. At the same time, when the pulverized coal output is insufficient and the pulverized coal output is less than the boiler fuel demand, the pulverized coal stored in the pulverized coal storage bin can be transported to the central coal drop pipe of the pulverized coal mill, allowing it to recirculate inside the pulverized coal mill and be redistributed to each air-coal pipe at the pulverized coal outlet. This achieves rapid and precise dynamic matching between the fuel system and the combustion system in the rapid peak shaving of coal-fired power plant boilers. The devices are small in size, occupy little space, have a simple structure, are easy to modify and lay out on site, are easy to control, and are easy to promote.

Claims

1. A device for regulating the concentration of coal dust in the outlet air duct of a coal mill, characterized in that: It includes a powder storage bin and a powder feeder; the powder storage bin has an inlet and an outlet, and the inlet of the powder storage bin is equipped with a powder storage control valve, which has a multi-blade structure; the powder feeder is located at the outlet of the powder storage bin.

2. The device for regulating the concentration of coal powder in the outlet air powder pipe of a coal mill according to claim 1, characterized in that: The powder storage control valve is composed of two or more adjusting blades; each adjusting blade is equipped with a rotating shaft; each rotating shaft is driven to rotate by a motor or pneumatic actuator, which in turn drives the adjusting blade to rotate, thereby controlling the opening degree of the powder storage control valve.

3. The device for regulating the concentration of coal powder in the outlet air powder pipe of a coal mill according to claim 2, characterized in that: Each adjusting blade is rectangular, and each rotating axis is parallel to the others. The direction perpendicular to the axis of rotation of the adjusting blade is considered as the width direction. Each adjusting blade has a different width. In use, the axis of rotation of the adjusting blade is perpendicular to the direction of air and powder flow in the air-powder pipe. The width of each adjusting blade increases sequentially along the direction of air and powder flow.

4. The device for regulating the concentration of coal powder in the outlet air pipe of a coal mill according to claim 3, characterized in that: The rotation axis of each adjusting blade is located at the downstream end of the adjusting blade in the width direction, and / or the rotation axis of each adjusting blade is located at the middle position in the width direction of the adjusting blade; each rotating axis is synchronously driven to rotate by a motor through a crank-connecting rod mechanism.

5. The device for regulating the concentration of coal powder in the outlet air pipe of a coal mill according to claim 3, characterized in that: Each regulating blade has a flow-blocking rib at an angle of 60-150° to its front surface.

6. The device for regulating the concentration of coal dust in the outlet air duct of a coal mill according to any one of claims 2-5, characterized in that: The horizontal position of each adjusting blade is zero. When all adjusting blades are in the horizontal position, the inlet of the powder storage bin is closed. Each adjusting blade is adjustable within a range of at least 0-45°.

7. The device for regulating the concentration of coal dust in the outlet air duct of a coal mill according to any one of claims 1 to 5, characterized in that: The powder storage control valve is located at the inlet end face of the powder storage silo; the inlet of the powder storage silo is at the top and the outlet is at the bottom, and the powder storage silo has a structure that gradually narrows from the inlet to the outlet.

8. The device for regulating the concentration of coal dust in the outlet air duct of a coal mill according to any one of claims 1 to 5, characterized in that: The powder storage silo is equipped with a heating device with a heating temperature of 60-100℃.

9. The device for regulating the concentration of coal dust in the outlet air duct of a coal mill according to any one of claims 1-5, characterized in that: The bottom of the powder storage silo is equipped with a fluidizing air inlet pipe; the fluidizing air inlet pipe is connected to the nitrogen outlet of the nitrogen generator through a pipeline.

10. The device for adjusting the coal powder concentration in the outlet air-coal pipe of a coal mill according to any one of claims 1-5, characterized in that: The powder storage silo is equipped with an explosion-proof gas inlet pipe at the top and an oxygen measuring point is installed at the top inside the silo; and / or the outlet of the powder storage silo is equipped with a silo wall vibrator; and / or the powder storage silo is equipped with a level gauge.

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