A quick response system for pulverizing of a medium-speed coal mill

Abstract

The present application relates to the technical field of pulverized coal boiler, and especially relates to a quick response system for pulverizing of medium-speed coal mill. The outlet of the medium-speed coal mill is provided with a powder feeding pipeline which is independent of the pulverized coal pipeline; the powder feeding pipeline is sequentially connected with a cyclone separator, an air lock, a finished product bin and a feeder, the outlet of the feeder is connected to the inside of the medium-speed coal mill, and a circulating path from the finished product bin to the coal mill is formed; in the powder storage stage, the powder feeding valve is opened when the unit is stably operated, the pulverized coal enters the cyclone separator through the independent powder feeding pipeline, the separated pulverized coal is stored in the finished product bin, and the exhaust gas is sent into the boiler by the powder exhaust fan for combustion. The powder storage amount is monitored by a material level meter, and the system is closed after reaching the set value. When quick response to load is needed, the nitrogen generator pressurizes the finished product bin, and the pre-stored pulverized coal is injected into the coal mill through the feeder and is rapidly transported to the burner by the primary air. The present application can ensure timely supply of the pulverized coal in the first few minutes of the unit load increase, and significantly improves the load response speed of the unit.

Description

Technical Field

[0001] This invention relates to the field of pulverized coal boiler technology, and in particular to a rapid response system for pulverizing coal in a medium-speed coal mill. Background Technology

[0002] With the large-scale development of new energy sources such as solar and wind power, traditional coal-fired power units have been revolutionized. Coal-fired power units are increasingly taking on the role of peak shaving. When the output is insufficient at night or during windless periods, or when the load is high and the output is rapidly increasing, coal-fired power units need to quickly increase the load to ensure the supply of electricity. This requires coal-fired power units to have a faster load change capability.

[0003] Currently, most coal-fired power units are equipped with positive-pressure direct-fired medium-speed coal mill pulverizing systems. Changes in boiler load commands require adjustments to the coal feed rate before the pulverized coal reaches the boiler burners for combustion, following grinding, drying, and conveying processes in the medium-speed mill. This process typically takes more than 3 minutes, severely limiting the unit's ability to rapidly change load. To address this issue, the industry has attempted to improve the system by using independent small pulverized coal silos to enhance storage and supply. While these systems can increase the load change rate to 3.5% of rated load per minute, they still cannot fully meet the demand. More importantly, these systems suffer from numerous devices, complex interfaces, and difficult piping layouts, increasing both system complexity and investment costs. Furthermore, the complex system structure also increases the difficulty and cost of operation and maintenance. All these factors limit the practical application of existing technologies in improving the unit's rapid response capability. Therefore, optimizing the unit's rapid pulverizing response capability has become a crucial issue. Summary of the Invention

[0004] The purpose of this system is to ensure timely supply of pulverized coal in the first few minutes of the initial load ramp-up of the unit, so as to ensure that the load change rate in the initial load ramp-up of the unit can meet the requirements of the new generation of coal-fired power technology.

[0005] To rapidly improve the unit's ability to quickly change loads, this invention provides a rapid response system for pulverizing coal in a medium-speed coal mill. This invention adds an independent pulverized coal delivery pipeline at the outlet of the medium-speed coal mill, connecting a cyclone separator, a finished product silo, and a feeder to form a closed-loop circulation system. Through a pulverized coal storage and pressurized conveying mechanism, pre-stored pulverized coal is rapidly injected into the coal mill for combustion, achieving rapid load response.

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

[0007] A medium-speed coal mill pulverizing rapid response system includes a medium-speed coal mill, a pulverized coal pipeline connected to its outlet, and a boiler burner;

[0008] The outlet of the medium-speed coal mill is also equipped with a coal powder feeding pipe that is independent of the coal powder pipeline;

[0009] The powder feeding pipeline is connected in sequence to the cyclone separator, the air lock, the finished product bin and the feeder. The feeder outlet is connected to the inside of the medium-speed coal mill, forming a circulation path from the finished product bin to the coal mill.

[0010] The finished product silo is connected to a nitrogen generator and monitors the pressure difference with the medium-speed coal mill via a differential pressure transmitter.

[0011] Furthermore, the exhaust gas outlet of the cyclone separator is connected to the boiler burner via an exhaust gas pipeline, and the exhaust gas pipeline is equipped with a pulverizing fan and an exhaust gas valve.

[0012] Furthermore, the finished product silo is equipped with a level gauge to monitor the amount of powder stored.

[0013] Furthermore, a nitrogen valve is provided between the nitrogen generator and the finished product silo to control inerting and pressurization.

[0014] Furthermore, a powder feeding valve is provided on the powder feeding pipeline, and a cyclone valve is provided between the cyclone separator and the finished product silo.

[0015] Furthermore, the rapid response method includes the following steps:

[0016] Powder storage stage:

[0017] When the medium-speed coal mill is running, the coal feeding valve, cyclone valve, exhaust gas valve and exhaust fan are opened; the coal powder at the coal mill outlet is sent to the cyclone separator through the coal feeding pipeline, and the separated coal powder is stored in the finished product silo, and the exhaust gas is sent to the boiler for combustion.

[0018] After the level gauge triggers a high-level alarm, the powder feeding valve, cyclone valve, exhaust gas valve, and powder discharge fan are closed; the nitrogen valve is opened, and the nitrogen generator is started to pressurize until the differential pressure transmitter shows that the finished product silo pressure is greater than the coal mill pressure;

[0019] Powder supply stage:

[0020] Upon receiving the load increase command, the feeder is started to input the finished coal powder from the silo into the medium-speed coal mill; the coal powder is carried by the primary air in the medium-speed coal mill to the coal powder pipeline and then transported to the boiler burner; when the coal supply of the coal mill meets the load demand, the feeder is stopped.

[0021] Furthermore, the coal storage stage operates during the unit's steady state or when the load is reduced, while the coal supply stage operates when the load increase command is triggered.

[0022] Furthermore, during pressurization, the pressure in the finished product silo is controlled to be higher than the internal pressure of the medium-speed coal mill by a differential pressure transmitter, thus forming positive pressure coal conveying.

[0023] Furthermore, during the coal feeding stage, the medium-speed coal mill simultaneously increases the coal feed rate, working in tandem with the feeder to enhance fuel supply.

[0024] Furthermore, the system is recommended to be equipped with at least three medium-speed coal mills, with a unit load change rate ≥ 10% of rated load / minute.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] This invention relates to a rapid response system for medium-speed coal mill pulverization. The system utilizes a separate pulverized coal feeding pipeline at the outlet of the medium-speed coal mill. The pulverized coal fed through this pipeline passes through a cyclone separator and is stored in a finished product bin. Upon receiving a load increase command, the system feeds fine pulverized coal into the coal mill via a feeder. The pulverized coal is then carried by the primary air within the mill to the pulverized coal pipeline and rapidly transported to the boiler burner for combustion. This system significantly improves the unit's load response speed. The system can be configured with three or more medium-speed coal mills, and the maximum load change rate of the configured unit can reach over 10% of the rated load per minute.

[0027] This system optimizes the operation of medium-speed coal mills, reduces unnecessary start-ups and load changes, can serve as a transitional fuel, mitigates boiler heat load fluctuations, enhances operational flexibility and stability, improves low-load combustion stability, and reduces the need for oil-assisted combustion. The outlet of the medium-speed coal mill is equipped with a pulverized coal feeding pipe. The pulverized coal pipeline and the pulverized coal feeding pipe are independent of each other. This independent pulverized coal feeding pipe reduces disturbances to the airflow and pulverized coal quantity during the system's pulverized coal storage process, thus minimizing the impact on stable boiler combustion.

[0028] The powder feeding pipeline sequentially connects to a cyclone separator, airlock, finished product silo, feeder, and medium-speed coal mill. All equipment in the system is configured as a single unit, resulting in a simple structure, system stability, ease of operation, and simple coupling with the unit's control system. A differential pressure transmitter is installed between the finished product silo and the medium-speed coal mill, enabling better control of the silo's pressure, facilitating powder feeding into the mill, and further enhancing system stability.

[0029] The system has a simple structure, small equipment selection, small space occupation, and convenient layout. It does not affect the relevant space layout design of existing units and facilitates corresponding modifications to existing units. The finished product silo can be located near the medium-speed coal mill. The coal feeding pipeline from the medium-speed coal mill to the finished product silo is short, and the finished product silo and related conveying, metering, and control equipment are few, resulting in good economic efficiency. Attached Figure Description

[0030] Figure 1 This is a structural schematic diagram of a specific embodiment of the present invention;

[0031] Figure 2 This is a usage state diagram of a specific embodiment of the present invention.

[0032] Numbers in the diagram:

[0033] 1-Boiler burner, 2-Pulverized coal pipeline, 3-Medium-speed coal mill, 4-Feeder, 5-Finished product silo, 6-Differential pressure transmitter, 7-Nitrogen valve, 8-Nitrogen generator, 9-Level gauge, 10-Cyclone valve, 11-Pulverized coal conveying pipeline, 12-Air lock, 13-Pulverized coal conveying valve, 14-Cyclone separator, 15-Exhaust gas pipeline, 16-Pulverized coal exhaust fan, 17-Exhaust gas valve. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] Please see Figure 1 This invention provides a rapid response system for pulverizing coal in a medium-speed coal mill, comprising a medium-speed coal mill 3, a pulverized coal pipeline 2 connected to its outlet, and a boiler burner 1. The outlet of the medium-speed coal mill 3 is provided with the pulverized coal pipeline 2, which directly leads to the boiler burner 1. In addition, the outlet of the medium-speed coal mill 3 also has a pulverized coal feeding pipeline 11, independent of the pulverized coal pipeline 2. The pulverized coal feeding pipeline 11 sequentially connects to a cyclone separator 14, an airlock 12, a finished product silo 5, and a feeder 4. The outlet of the feeder 4 is connected to the interior of the medium-speed coal mill 3, forming a circulation path from the finished product silo to the coal mill. Furthermore, the finished product silo 5 is connected to a nitrogen generator 8, and a differential pressure transmitter 6 monitors the pressure difference between the silo 5 and the medium-speed coal mill 3. The exhaust gas outlet of the cyclone separator 14 is connected to the boiler burner 1 through an exhaust gas pipeline 15, which is equipped with a pulverized coal exhaust fan 16 and an exhaust gas valve 17. The finished product silo 5 is equipped with a level gauge 9 for monitoring the amount of pulverized coal stored. A nitrogen valve 7 is installed between the nitrogen generator 8 and the finished product silo 5 to control inerting and pressurization. A pulverized coal feeding valve 13 is installed on the pulverized coal feeding pipeline 11, and a cyclone valve 10 is installed between the cyclone separator 14 and the finished product silo 5. This system achieves the storage and rapid supply of pulverized coal through independent pulverized coal feeding pipelines and related equipment.

[0037] In this embodiment, the level gauge 9 can provide timely feedback on the powder storage status of the finished product silo 5, allowing operators to store and deliver powder according to the actual situation, further improving the system's operability and flexibility.

[0038] In this embodiment, the nitrogen generator 8 has two functions: one is to perform explosion-proof inerting treatment on the finished product silo 5, and the other is to pressurize the finished product silo 5 to facilitate the feeding of powder from the finished product silo into the coal mill.

[0039] In this embodiment, a pulverized coal exhaust fan 16 is provided between the cyclone separator 14 and the boiler burner 1. The pulverized coal exhaust fan 16 can extract the exhaust gas from the cyclone separator 14 in a timely manner and send it to the boiler burner 5, so that the pulverized coal in the exhaust gas can participate in combustion and improve combustion efficiency.

[0040] In this embodiment, the feeder 4 is a screw feeder. The amount of powder fed can be controlled relatively accurately by adjusting the speed of the screw feeder through a variable frequency motor.

[0041] This invention performs coal storage operation during stable load operation or reduced load operation of the unit. The specific operation process is as follows:

[0042] First, the medium-speed coal mill 3 operates normally, preparing pulverized coal and outputting it from the outlet. At this time, the nitrogen generator 8 stops operating, and the nitrogen valve 7 is closed to prevent nitrogen from interfering with the pulverized coal storage process.

[0043] Next, the cyclone valve 10, exhaust gas valve 17, and pulverized coal feeding valve 13 are opened, and the exhaust fan 16 is started simultaneously. The pulverized coal from the outlet of the medium-speed coal mill 3 is transported to the cyclone separator 14 through the pulverized coal feeding pipe 11. In the cyclone separator 14, the pulverized coal is separated and falls into the finished product bin 5 for storage through the air lock 12, while the separated exhaust gas is extracted by the exhaust gas pipe 15 by the exhaust fan 16 and sent to the boiler burner 1 for combustion.

[0044] When the coal powder in the finished product silo 5 accumulates to a certain amount, the level gauge 9 triggers a high-level alarm, indicating that the coal powder storage process is complete.

[0045] Subsequently, the coal powder conveying valve 13, cyclone valve 10, and exhaust gas valve 17 are closed, and the coal powder discharge fan 16 is stopped to end the coal powder conveying process.

[0046] Next, the nitrogen valve 7 is opened, the nitrogen generator 8 is started, and nitrogen is injected into the finished product silo 5 to pressurize it until the differential pressure transmitter 6 shows that the pressure in the finished product silo 5 is greater than the internal pressure of the medium-speed coal mill 3. The above stages achieve efficient storage of pulverized coal through the effective cooperation of the cyclone separator 14 and the finished product silo 5, and prepare for subsequent pulverized coal supply by pressurizing it with the nitrogen generator 8.

[0047] This invention initiates the coal supply phase upon receiving a load increase command from the generating unit. The specific operation process is as follows:

[0048] When the unit needs to rapidly increase its load, the medium-speed coal mill 3 increases its coal feed rate and operates normally according to instructions to gradually improve its pulverized coal preparation capacity. Simultaneously, the feeder 4 is started, feeding the pre-stored fine pulverized coal from the finished product bin 5 into the medium-speed coal mill 3. This fine pulverized coal is carried by the primary air within the mill 3 and rapidly transported to the boiler burner 1 through the pulverized coal pipeline 2 for combustion, thereby rapidly increasing the fuel supply and achieving a rapid increase in the unit load.

[0049] When the coal supply of the medium-speed coal mill 3 can stably meet the load demand, the feeder 4 stops operating, ending the coal feeding process. During this process, the pulverized coal in the finished product bin 5 is rapidly replenished to the coal mill 3 via positive pressure conveying, ensuring timely fuel supply. The coal storage stage and the coal feeding stage are automatically switched through commands from the control system, ensuring the system's high efficiency and responsiveness. The system is configured with at least three medium-speed coal mills, enabling the unit load change rate to reach more than 10% of rated load per minute, meeting the requirements for rapid response.

[0050] As shown in Table 1, during the use of the above systems, the unit load change rate can be increased to over 10% of rated load / min, overcoming the inherent delay of direct-fired systems. Optimizing coal mill operation reduces unnecessary start-up and load-changing operations; it can also serve as a transitional fuel, mitigating boiler heat load fluctuations and enhancing operational flexibility and stability. Furthermore, it improves low-load combustion stability and reduces the need for oil-assisted combustion.

[0051] Furthermore, each coal mill only requires a cyclone separator 14, a finished product bin 5, and a screw feeder as its main equipment. The equipment configuration is small, the system is simple, and the equipment selection is small, occupying little space and easy to arrange. It does not affect the relevant space layout design of the existing units and facilitates the corresponding modification of the existing units.

[0052] In this embodiment, the system uses three commonly used coal mills 3 with their own finished product bins 5, two for regular use and one as a backup. During steady-state operation, the coal mills 3 prepare fine coal powder, which is then stored in their respective finished product bins 5. When the unit increases its load, the airflow of the coal mills 3 is increased, and simultaneously, a screw feeder feeds the fine coal powder from the two finished product bins 5 into the two coal mills 3, rapidly increasing the fuel supply and achieving a rapid load increase. The finished product bins 5 are located near the coal mills 3, occupying little space; the path from the coal mills 3 to the finished product bins 5 is short; and the finished product bins 5 and related conveying, metering, and control equipment are minimal, resulting in low investment costs.

[0053]

[0054] Table 1

[0055] This invention forms a closed-loop circulation system by adding an independent coal powder feeding pipeline 11, a finished product silo 5, and a feeder 4 to the traditional medium-speed coal mill system. During the coal powder storage phase, which operates under steady-state conditions or reduced load, coal powder is stored using a cyclone separator 14 and the finished product silo 5. During the coal powder supply phase, when the load increases, the feeder 4 rapidly delivers the pre-stored coal powder to the medium-speed coal mill 3, improving the load variation capability. The entire operation is precisely controlled by a differential pressure transmitter 6 and a level gauge 9, ensuring system stability and ease of operation. Furthermore, the system has a simple structure, occupies little space, and is easy to retrofit existing units, exhibiting good economic efficiency and practicality.

[0056] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A rapid response method using a medium-speed coal mill pulverizing rapid response system, the rapid response system comprising a medium-speed coal mill (3), a pulverized coal pipeline (2) connected to its outlet, and a boiler burner (1), characterized in that: The outlet of the medium-speed coal mill (3) is also provided with a coal powder feeding pipe (11) independent of the coal powder pipe (2); the coal powder feeding pipe (11) is provided with a coal powder feeding valve (13), and a cyclone valve (10) is provided between the cyclone separator (14) and the finished product bin (5). The pulverized coal feeding pipe (11) is connected in sequence to the cyclone separator (14), the air lock (12), the finished product bin (5) and the feeder (4). The outlet of the feeder (4) is connected to the interior of the medium-speed coal mill (3) to form a circulation path from the finished product bin to the coal mill. The exhaust gas outlet of the cyclone separator (14) is connected to the boiler burner (1) through the exhaust gas pipe (15), and the exhaust gas pipe (15) is equipped with a pulverized coal exhaust fan (16) and an exhaust gas valve (17). The finished product silo (5) is connected to the nitrogen generator (8), and the pressure difference with the medium-speed coal mill (3) is monitored by the differential pressure transmitter (6); a nitrogen valve (7) is provided between the nitrogen generator (8) and the finished product silo (5) to control inerting and pressurization; The rapid response method includes the following steps: Powder storage stage: The medium-speed coal mill (3) is running, and the powder feeding valve (13), cyclone valve (10), exhaust gas valve (17) and exhaust fan (16) are turned on. The pulverized coal from the coal mill outlet is fed into the cyclone separator (14) via the pulverized coal feeding pipe (11). After separation, the pulverized coal is stored in the finished product silo (5), and the exhaust gas is sent to the boiler for combustion. After the level gauge (9) triggers a high-level alarm, the powder feeding valve (13), cyclone valve (10), exhaust valve (17) and powder discharge fan (16) are closed. Open the nitrogen valve (7), start the nitrogen generator (8) and pressurize until the differential pressure transmitter (6) shows that the pressure in the finished product silo (5) is greater than the pressure in the coal mill; Powder supply stage: After receiving the load increase command, start the feeder (4) and input the coal powder from the finished product bin (5) into the medium-speed coal mill (3). The pulverized coal is carried by the primary air inside the medium-speed coal mill (3) to the pulverized coal pipeline (2) and then transported to the boiler burner (1). When the coal mill's coal supply meets the load demand, the feeder is stopped (4); The powder storage stage operates when the unit is in steady state or under reduced load, and the powder supply stage operates when the load increase command is triggered; in the powder supply stage, the medium-speed coal mill (3) increases the coal feed rate synchronously, and works in coordination with the feeder (4) to improve fuel supply.

2. The rapid response method using a medium-speed coal mill pulverizing rapid response system according to claim 1, characterized in that, The finished product silo (5) is equipped with a level gauge (9) for monitoring the amount of powder stored.

3. The rapid response method using a medium-speed coal mill pulverizing rapid response system according to claim 1, characterized in that, When pressurized, the pressure of the finished product silo (5) is controlled by the differential pressure transmitter (6) to be higher than the internal pressure of the medium-speed coal mill (3), forming positive pressure powder conveying.

4. The rapid response method using a medium-speed coal mill pulverizing rapid response system according to claim 1, characterized in that, The system is configured with at least three medium-speed coal mills, and the unit load change rate is ≥10% of rated load / minute.

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