A device and method for leveling coal powder concentration in coal-fired power plant coal powder pipelines

Abstract

This invention discloses a coal powder concentration leveling device for coal-fired power plant coal powder pipelines. At least one bypass pipe is connected in parallel to each main air-coal pulverizer pipeline (03) on the coal mill, running from the separator (01) upwards to the mixer (02) and then to each main pulverizer pipe (03). Alternatively, two bypass pipes with opposite flow directions can be used to connect the main pulverizer pipes (03) above each mixer (02). The diameter of the bypass pipe is significantly smaller than the diameter of the main pipe. An ejector (04) is installed on each bypass pipe, and the suction action of the ejector (04) is used to balance the powder concentration between the pipelines. A method for leveling coal powder concentration in coal-fired power plant coal powder pipelines is also disclosed. First, a bypass structure is set up; then, an ejector (04) is connected to each bypass pipe, and the suction action of the ejector is used to balance the powder concentration between the pipelines. This invention has the beneficial effect of more efficient and stable coal powder leveling.

Description

Technical Field

[0001] This invention relates to the field of pulverizing system technology, specifically to a device for leveling the coal powder concentration in the pulverizing pipeline of a coal mill in a direct-fired pulverizing system of a coal-fired power plant. Background Technology

[0002] Renewable energy sources, represented by solar and wind power, will become the main power source in the future. However, due to their inherent randomness and intermittency, they cannot provide stable power output. To address this issue, in addition to vigorously developing energy storage, stable and reliable coal-fired power can be used as a peak-shaving power source, playing a crucial role in providing a safety net and serving as an emergency backup power source for the new energy power system. Flexibility retrofitting of coal-fired power plants is a vital means of achieving peak shaving for coal-fired power units. During this process, the stability of boiler combustion plays a decisive role in the lower limit of peak shaving for the unit. As the unit load decreases, the boiler combustion load also needs to decrease. This means that the amount of air and pulverized coal entering the furnace will decrease. The lower the load, the greater the reduction in air and pulverized coal. At this point, the heat generated by combustion may be insufficient to maintain the thermal stability of the entire furnace, leading to furnace flameout and ultimately unit shutdown. Therefore, during load reduction, pulverized coal is key to maintaining combustion, encompassing both the quality of the pulverized coal itself and its distribution throughout the furnace.

[0003] Currently, the pulverizing systems of large coal-fired power boilers are direct-fired pulverizing systems. These systems lack independent pulverized coal distributors; the pulverized coal from the mill enters the furnace directly for combustion through multiple pipes (e.g., four). Generally, inconsistencies in the flow velocity and pulverized coal concentration within the primary air ducts of the same burner layer can cause problems such as combustion deviation, uneven boiler heat load, flame adhesion to the walls, scouring of water-cooled walls, coking, and flameout. To ensure a balance between airflow velocity and pulverized coal concentration in the pipes, the commonly used solution in existing technology is to install adjustable orifices on the pipes to regulate the air velocity and concentration. Because existing direct-fired pulverizing systems in coal-fired power plants generally assume that the pulverized coal concentration will also be balanced once the airflow velocity in each mill's output pipe is balanced, the method for adjusting concentration balance is transformed into adjusting the size of the orifices. However, in practical applications, it has been found that even when the airflow in the pipes is balanced, deviations in pulverized coal quantity are still prevalent; the pulverized coal concentration in different pipes of the same mill can even differ by more than double. Especially during peak load regulation, the pulverized coal quantity deviation in each pipe is significant, and power plants lack the means to achieve a deviation of ±5%. To address this issue, the inventors of this patent application discovered, through searching, that Chinese patent application number 201510264326.X, entitled "Device and Method for Adjusting Pulverized Coal Quantity Deviation in Direct-Blow Pulverizing Systems," discloses a technical solution that uses branch pipes with air-powder separators on the pulverized coal pipes to separate pulverized coal and achieve pulverized coal balance in each pipe. However, the inventors of this patent application found through practice that due to significant ventilation resistance at the valves of the separator and branch pipes, the flow of air and pulverized coal is hindered, resulting in a limited amount of air and pulverized coal entering the branch pipes. Consequently, the actual effect of pulverized coal concentration adjustment does not meet expectations. Similarly, the non-powered branch pipe balancing method based on the above structure cannot achieve pulverized coal leveling. Moreover, the devices and methods under the above structure can only adjust in one direction and cannot achieve reverse adjustment.

[0004] In summary, there has been a lack of effective and stable solutions and corresponding devices for balancing the concentration of pulverized coal in pipelines, and the regulation of pulverized coal concentration is an important and urgent problem to be solved. Summary of the Invention

[0005] The first technical problem to be solved by this invention is to provide an efficient and stable coal powder concentration leveling device for coal-fired power plant coal powder pipelines.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: a coal powder concentration leveling device for coal-fired power plant coal powder pipelines, wherein at least one bypass pipeline is connected in parallel on each main air-coal powder pipeline of the coal mill, which runs from the separator upward to the mixer and then to each main powder pipeline; an ejector is installed on the bypass pipeline, and the powder concentration between each pipeline is balanced by the suction action of the ejector.

[0007] Preferably, the ejector includes an outlet pipe, a diffuser chamber, a mixing chamber, a receiving chamber, a jet nozzle, an inlet pipe, a suction pipe, and a return pipe. The inlet pipe is connected to a compressed air source at its inlet end and to the jet nozzle at its outlet end. The jet nozzle extends into the receiving chamber. The receiving chamber is sequentially connected to the mixing chamber, the diffuser chamber, and the outlet pipe in the jet nozzle's jet direction. The bottom of the receiving chamber is connected to the return pipe. The side of the receiving chamber is connected to the suction pipe. Both the inlet pipe and the suction pipe are equipped with adjustable valves. The return pipe is equipped with an airlock. The suction pipe is used to connect to a separator or mixer. The outlet pipe is used to connect to the main powder pipe. The return pipe is used to connect to the separator or mixer.

[0008] As a further preferred option, the return pipe is inclined downward along the direction of air-powder outflow inside the pipe; the connecting pipe between the outflow pipe and the main powder pipe is inclined upward along the direction of air-powder flow inside the pipe.

[0009] As a further preferred embodiment, the suction tube is connected to the area between the two main powder tubes on the top cover of the mixer, or to the side of the mixer at a distance from the inlet of the main powder tube that is more than one times the diameter of the main powder tube.

[0010] To solve the above-mentioned technical problems, another technical solution provided by the present invention is: a coal powder concentration leveling device for coal-fired power plant coal powder pipelines, which directly connects the main powder pipe above each mixer through two bypass pipes with opposite flow directions; the diameter of the bypass pipe is significantly smaller than the diameter of the main pipe; an ejector is installed on the bypass pipe, and the powder concentration between each pipe is balanced by the suction action of the ejector.

[0011] Preferably, the ejector includes an outlet pipe, a diffuser chamber, a mixing chamber, a receiving chamber, a jet nozzle, an inlet pipe, a suction pipe, and a return pipe. The inlet pipe is connected to a compressed air source at its inlet end and to the jet nozzle at its outlet end. The jet nozzle extends into the receiving chamber. The receiving chamber is sequentially connected to the mixing chamber, the diffuser chamber, and the outlet pipe in the jet nozzle's jet direction. The bottom of the receiving chamber is connected to the return pipe. The side of the receiving chamber is connected to the suction pipe. Each of the inlet pipe, suction pipe, and return pipe is equipped with an adjustable valve. The suction pipe is used to connect to one main powder pipe or a mixer. The outlet pipe is used to connect to another main powder pipe. The return pipe is used to connect to a separator or a mixer.

[0012] As a further preferred option, the return pipe is inclined downward along the direction of air-powder outflow inside the pipe; the connecting pipe between the outflow pipe and the main powder pipe is inclined upward along the direction of air-powder flow inside the pipe.

[0013] As a further preferred embodiment, the suction tube is connected to the area between the two main powder tubes on the top cover of the mixer, or to the side of the mixer at a distance from the inlet of the main powder tube that is more than one times the diameter of the main powder tube.

[0014] Another technical problem to be solved by the present invention is to provide a method for adjusting the pulverized coal concentration in a pulverized coal pipeline of a coal-fired power plant, which is efficient and stable.

[0015] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: a method for balancing the pulverized coal concentration in pulverized coal pipelines of a coal-fired power plant. First, at least one parallel bypass pipeline with a diameter significantly smaller than that of the main pipeline is set in each main air-pulverized coal pipeline of the coal mill; or the main pulverized coal pipeline above each mixer is directly connected through two bypass pipelines with opposite flow directions; then, an ejector is connected to each bypass pipeline, and the pulverized coal concentration in each pipeline is balanced by the suction action of the ejector.

[0016] As a preferred option, the ejector has three suction methods: the first is to suction qualified powder from the separator to compensate for the main powder tube with a low powder content; the second is to suction powder from the main powder tube with a high powder content into the separator body or mixer; and the third is to suction powder from the main powder tube with a high powder content to compensate for the main powder tube with a low powder content.

[0017] After adopting the above structure and method, the present invention has the following beneficial effects: Existing direct-fired pulverizing systems in coal-fired power plants generally assume that the pulverized coal concentration reaches equilibrium once the air velocity in each mill's output pipe is balanced. This is typically achieved by adjusting the constriction orifice. However, in practical applications, it has been found that even when the air velocity in the pipes reaches equilibrium, deviations in pulverized coal quantity are still common, especially during peak-shaving and load-changing processes. Power plants lack the means to achieve a pulverized coal quantity deviation target of ±5%. The present invention provides a scheme that adds a parallel bypass and ejector, using the power plant's existing compressed air as a power source. The ejector draws in pulverized coal to compensate for insufficient pulverized coal in the pipes, ultimately achieving a balanced concentration in each pipe. This scheme eliminates the need for baffles or other devices on the main pulverized coal pipe, thus avoiding increased pipe resistance. Relying on the ejector to generate suction force to draw in pulverized coal, the operation is efficient, stable, and reliable. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a coal powder concentration leveling device installed on a coal mill in a coal-fired power plant coal powder pipeline according to an embodiment of the present invention.

[0019] Figure 2 It is attached Figure 1 A schematic diagram of the pulverized coal concentration leveling device in the pulverized coal pipeline of a coal-fired power plant.

[0020] Figure 3 This is a schematic diagram of the coal powder concentration leveling device in the coal powder pipeline of a coal-fired power plant under Embodiment 2 of the present invention.

[0021] Figure 4 This is a schematic diagram of the coal powder concentration leveling device in the coal powder pipeline of a coal-fired power plant according to Embodiment 3 of the present invention.

[0022] As shown in the figure: 01, Separator; 02, Mixer; 03, Main powder pipe; 04, Ejector; 1, Outlet pipe; 2, Diffuser chamber; 3, Mixing chamber; 4, Receiving chamber; 5, Jet nozzle; 6, Inlet pipe; 7, Suction pipe; 8, Return pipe. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings. Specific Implementation Example 1:

[0025] Combined with appendix Figure 1 To the attached Figure 2 A coal powder concentration leveling device for coal-fired power plant coal powder pipelines, wherein at least one bypass pipeline is connected in parallel on each main air-coal pipeline of the coal mill, which runs from the separator 01 upward to the mixer 02 and then to each main coal powder pipeline 03; an ejector 04 is installed on the bypass pipeline, and the powder concentration between the pipelines is balanced by the suction action of the ejector 04.

[0026] Preferably, the ejector 04 includes an outlet pipe 1, a diffuser chamber 2, a mixing chamber 3, a receiving chamber 4, a jet nozzle 5, an inlet pipe 6, a suction pipe 7, and a return pipe 8. The inlet end of the inlet pipe 6 is connected to a compressed air source, and the outlet end is connected to the jet nozzle 5. The jet nozzle 5 extends into the receiving chamber 4. The receiving chamber 4 is sequentially connected to the mixing chamber 3, the diffuser chamber 2, and the outlet pipe 1 in the jet direction of the jet nozzle 5. The bottom of the receiving chamber 4 is connected to the return pipe 8. The side of the receiving chamber 4 is connected to the suction pipe 7. Both the inlet pipe 6 and the suction pipe 7 are equipped with adjustable valves, and the return pipe 8 is equipped with an airlock. The suction pipe 7 is used to connect to the separator 01 or the mixer 02. The outlet pipe 1 is used to connect to the main powder pipe 03. The return pipe 8 is used to connect to the separator 01 or the mixer 02.

[0027] As a further preferred option, the return pipe 8 is inclined downward along the direction of air-powder outflow inside the pipe; the connecting pipe between the outflow pipe 1 and the main powder pipe 03 is inclined upward along the direction of air-powder flow inside the pipe.

[0028] As a further preferred embodiment, the suction tube 7 is connected to the area between the two main powder tubes on the top cover of the mixer 02, or to the side of the mixer 02 at a distance from the inlet of the main powder tube 03 that is more than one times the diameter of the main powder tube. Specific Implementation Example 2:

[0030] Combined with appendix Figure 2 With appendix Figure 3A coal powder concentration leveling device for coal-fired power plant coal powder pipelines directly connects the main powder pipe 03 above each mixer 02 through two bypass pipes with opposite flow directions; the diameter of the bypass pipe is significantly smaller than the diameter of the main pipe; an ejector 04 is installed on the bypass pipe, and the powder concentration between each pipe is balanced by the suction action of the ejector 04.

[0031] Preferably, the ejector 04 includes an outlet pipe 1, a diffuser chamber 2, a mixing chamber 3, a receiving chamber 4, a jet nozzle 5, an inlet pipe 6, a suction pipe 7, and a return pipe 8. The inlet end of the inlet pipe 6 is connected to a compressed air source, and the outlet end is connected to the jet nozzle 5. The jet nozzle 5 extends into the receiving chamber 4. The receiving chamber 4 is sequentially connected to the mixing chamber 3, the diffuser chamber 2, and the outlet pipe 1 in the jet direction of the jet nozzle 5. The bottom of the receiving chamber 4 is connected to the return pipe 8. The side of the receiving chamber 4 is connected to the suction pipe 7. The inlet pipe 6, the suction pipe 7, and the return pipe 8 are all equipped with valves with adjustable opening and closing degrees. The suction pipe 7 is used to connect to one main powder pipe 03 or a mixer 02. The outlet pipe 1 is used to connect to another main powder pipe 03. The return pipe 8 is used to connect to the separator 01 or to the mixer 02.

[0032] As a further preferred option, the return pipe 8 is inclined downward along the direction of air-powder outflow inside the pipe; the connecting pipe between the outflow pipe 1 and the main powder pipe 03 is inclined upward along the direction of air-powder flow inside the pipe.

[0033] As a further preferred embodiment, the suction tube 7 is connected to the area between the two main powder tubes on the top cover of the mixer 02, or to the side of the mixer 02 at a distance from the inlet of the main powder tube 03 that is more than one times the diameter of the main powder tube.

[0034] This invention patent also provides a method for balancing the pulverized coal concentration in pulverized coal pipelines of a coal-fired power plant. First, at least one parallel bypass pipeline with a diameter significantly smaller than that of the main pipeline is set in each air-pulverized coal main pipeline of the coal mill; or the main pulverized coal pipeline 03 above each mixer 02 is directly connected through two bypass pipelines with opposite flow directions; then, an ejector 04 is connected to each bypass pipeline, and the pulverized coal concentration in each pipeline is balanced by the suction action of the ejector.

[0035] As a preferred option, the ejector 04 has three suction methods: the first is to suction qualified powder from the separator to compensate for the insufficient powder content in the main powder tube; the second is to suction powder from the main powder tube with a high powder content into the separator body or mixer, and the corresponding structural diagram for this method is attached. Figure 4 The first type involves suction from the main powder tube to the separator or mixer; the second type involves suctioning powder from the main powder tube with a high powder content to compensate for the powder in the main powder tube with a low powder content.

[0036] In practice, a bypass is installed at the outlet of the coal mill separator, through which an ejector is connected. The basic structure of the ejector consists of an inlet pipe, a receiving chamber, a mixing chamber, a diffuser chamber, a nozzle, a suction pipe, an outlet pipe, and a return pipe. The ejector's suction pipe is connected to the coal mill separator outlet, the jet nozzle is connected to compressed air, and the outlet section is connected to the pulverized coal pipe. After the compressed air enters the ejector and is ejected from the nozzle, a negative pressure is generated in the receiving chamber. This causes the air and pulverized coal at the separator outlet to be drawn into the receiving chamber by the ejector through the suction pipe and mixed with the compressed air before entering the pulverized coal pipe through the outlet section.

[0037] The coal pulverizer's air and pulverized coal enter each air-pulverized coal pipeline. Simultaneously, a bypass pipeline, significantly smaller in diameter than the air-pulverized coal pipeline, is installed at the separator outlet. This bypass pipeline connects to the ejector's suction pipe, which is inclined upwards along the flow direction. A valve on the suction pipe controls the amount of air and pulverized coal entering. A valve on the compressed air pipeline also controls the compressed air volume, thus controlling the suction force of the suction pipe. Additionally, a return pipe is installed at the ejector's tail end, inclined downwards along the outflow direction, and equipped with an airlock. The ejector's outlet section connects to the air-pulverized coal pipeline, which is also inclined upwards along the flow direction.

[0038] The specific working principle is as follows: Each main coal pulverizer pipe is equipped with the aforementioned ejector structure. If a low coal pulverizer concentration is detected in a certain pipe, the compressed air valve and suction pipe valve of the ejector are opened. The size of the compressed air valve and suction pipe valve is adjusted according to the concentration difference between the air and coal pulverizer pipes to adjust the ejector suction. The coal pulverizer in the separator will enter the receiving chamber under the action of the ejector suction, mix with the compressed air, and then enter the air and coal pulverizer pipe from the outflow section. The concentration of coal pulverizer in the pipe with a low concentration will increase after receiving the coal pulverizer from the ejector, reducing the concentration deviation between pipes and realizing the regulation of coal pulverizer concentration. The coal pulverizer concentration can be quantitatively measured by installing a concentration sensor on the coal pulverizer pipe, or qualitatively determined by the combustion deviation in the furnace.

[0039] When the bypass pipeline consists of two sets of pipelines connected to the main powder pipes in opposite directions, taking a common configuration of four main powder pipes as an example, with the four main powder pipes being L1 to L4, the four main powder pipes are connected in pairs via ejectors, and this connection is bidirectional. The ejectors for each main powder pipe are marked Yab, where a and b represent the main powder pipe number. Taking L1 and L2 as an example, the bidirectional connection means that powder in L1 can enter L2 through ejector Y12, and powder in L2 can also enter L1 through ejector Y21. Specifically, the suction pipe of ejector Y12 on L1 connects to L2, and its outlet pipe connects to L1; the suction section of ejector Y21 on L2 connects to L1, and its outlet pipe connects to L2. It should be noted that in this case, the return pipe does not require an airlock.

[0040] Regarding the leveling method, the specific steps for balancing the powder quantity in each main powder tube of the direct-blown pulverizing system can be referred to as follows:

[0041] The first step is to monitor the concentration of powder in each main powder tube. If there are four main powder tubes, namely L1~L4, their powder concentrations are C1, C2, C3, and C4, with the highest concentration being Cmax and the lowest being Cmin.

[0042] The second step is to turn on the compressed air and suction pipe valves of the ejector corresponding to Cmin in the main powder tube, and adjust the ejector inlet pipe valve to control the ejector suction force. At this time, the ejector draws powder from the mixer into the main powder tube, and Cmin increases.

[0043] The third step is to monitor C1 to C4 in real time, so that the size of Cmin is approximately equal to the size of Cmax.

[0044] Fourth step: Repeat steps one through three until the deviation of C1 to C4 is within ±5%.

[0045] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual structure is not limited to this; for example, the ejector can be replaced by a fan or a booster pump with the same function. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for regulating the concentration of coal powder in a coal powder pipeline of a coal-fired power plant, characterized in that: The device includes: at least one bypass pipe connected in parallel on each main air-coal pipeline of the coal mill, from the separator (01) upward to the mixer (02) and then to each main powder pipe (03); an ejector (04) is installed on the bypass pipe, and the powder concentration between the pipelines is balanced by the suction action of the ejector (04); the ejector (04) includes an outlet pipe (1), a diffuser (2), a mixing chamber (3), a receiving chamber (4), a jet nozzle (5), an inlet pipe (6), a suction pipe (7), and a return pipe (8); the inlet end of the inlet pipe (6) is connected to a compressed air source, and the outlet end is connected to the jet nozzle (5), the jet nozzle (5) The nozzle (5) extends into the receiving chamber (4), which is connected in sequence to the mixing chamber (3), the diffuser (2), and the outlet pipe (1) in the jet direction of the jet nozzle (5); the bottom of the receiving chamber (4) is connected to the return pipe (8); the side of the receiving chamber (4) is connected to the suction pipe (7); the inlet pipe (6) and the suction pipe (7) are both equipped with valves with adjustable opening and closing degrees, and the return pipe (8) is equipped with an airlock; the suction pipe (7) is used to connect to the separator (01) or the mixer (02); the outlet pipe (1) is used to connect to the main powder pipe (03); the return pipe (8) is used to connect to the separator (01) or the mixer (02); The return pipe (8) is inclined downward along the direction of air and powder outflow in the pipe; the connecting pipe between the outflow pipe (1) and the main powder pipe (03) is inclined upward along the direction of air and powder flow in the pipe. The suction tube (7) is connected to the area between the two main powder tubes on the top cover of the mixer (02), or to the side of the mixer (02) at a distance from the inlet of the main powder tube (03) that is more than one times the diameter of the main powder tube. The leveling method first involves setting at least one parallel bypass pipe with a diameter significantly smaller than that of the main pipe in each air-coal main pipe of the coal mill; then, an ejector (04) is connected to each bypass pipe, and the powder concentration in each pipe is balanced by the suction action of the ejector. There are two suction methods for ejector (04): the first is to suction qualified powder in mixer (02) to make up for the small amount of powder in the main powder tube; the second is to suction powder in the main powder tube with high powder content into the separator body or mixer.

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