Coal pulverizing system applied to rapid load response of peak regulation unit and control method of coal pulverizing system

Abstract

The invention provides a coal pulverizing system applied to rapid load response of a peak shaving unit and a control method thereof.The system comprises a boiler, a first coal mill, a second coal mill, a first pulverized coal pipeline, a second pulverized coal pipeline and an air feeder, and the coal outlet end of the first coal mill is connected with one end of the first pulverized coal pipeline; the other end of the first pulverized coal pipeline is communicated with a boiler hearth through a first combustor, the coal outlet end of the second coal mill is connected with one end of a second pulverized coal pipeline, the other end of the second pulverized coal pipeline is communicated with the boiler hearth through a second combustor, a communicating pipe is connected between the two pulverized coal pipelines, and a pipeline valve is arranged on the communicating pipe. The air outlet end of the air feeder is connected with a primary air pipeline and a secondary air pipeline, the end, away from the air feeder, of the primary air pipeline is connected with the two coal mills, and the end, away from the air feeder, of the secondary air pipeline is connected with the two combustors. The inertia of a high-capacity unit when a traditional direct-fired pulverizing system is adopted can be reduced, the delay time is short, and the load response rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of direct-blowing pulverizing systems, and specifically to a pulverizing system and a control method thereof for rapid load response of a peak-shaving unit. Background Art

[0002] At present, the peak-to-valley difference of the load on the user side of the power grid is becoming larger and larger, and the load change rate is increasing. In addition, the huge fluctuations brought by the consumption of new energy sources have made the peak-shaving task of thermal power units increasingly heavier, which requires the combustion side of the power station boiler to respond quickly and flexibly. At present, large-capacity units generally use direct-blowing pulverizing systems with simple structure and convenient maintenance. However, the deep coupling between the pulverizer and the boiler of the direct-blowing pulverizing system has become an important factor restricting the increase in the variable load rate of coal-fired units. The direct-blowing pulverizing system has large delays and large inertia in the warm grinding, coal transportation, and coal grinding processes, and its ability to track the boiler load response is insufficient, which restricts the higher rate of variable load operation of the unit.

[0003] At the same time, when the unit changes load over a large range, the coal mill needs to be started and stopped multiple times due to the output limitation of the coal mill itself. When the load change rate is very high (such as 5% / min), the time required for the unit load change process is very short, but the time required for the normal start and stop of the coal mill is necessary. This causes the direct-blowing pulverizing system to be seriously affected by the large-range and high-load rate operation of the unit due to the start and stop operations of the grinding group.

[0004] Currently, the small powder silo technology has improved the hysteresis problem of the powder making system, but it has many disadvantages. It occupies a large space on site and is difficult to arrange in certain furnace types. The small powder silo containing a large amount of flammable coal powder is close to the high-temperature furnace, which poses fire, deflagration and explosion hazards, has high safety management costs, huge total investment, and a long cost recovery period.

[0005] Therefore, there is a need for a pulverizing system and a control method thereof that can improve the load response rate, occupy a small space, and is easy to arrange and manage. Summary of the invention

[0006] To solve the problem in the background technology, the present invention proposes a pulverizing system for rapid load response of a peak load regulating unit, comprising a boiler, a first coal mill, a second coal mill, a first pulverized coal pipeline, a second pulverized coal pipeline and a blower, wherein the coal outlet end of the first coal mill is connected to one end of the first pulverized coal pipeline, and the other end of the first pulverized coal pipeline is connected to the boiler furnace through a first burner, the coal outlet end of the second coal mill is connected to one end of the second pulverized coal pipeline, and the other end of the second pulverized coal pipeline is connected to the boiler furnace through a second burner, a connecting pipe is connected between the first pulverized coal pipeline and the second pulverized coal pipeline, and a pipeline valve is provided on the connecting pipe, when the pipeline valve is opened, the first pulverized coal pipeline and the second pulverized coal pipeline are connected to each other, and when the pipeline valve is closed, the first pulverized coal pipeline and the second pulverized coal pipeline are independent of each other; The air outlet end of the blower is connected to a primary air duct and a secondary air duct through a main air duct, one end of the primary air duct away from the blower is connected to the first coal mill and the second coal mill, and one end of the secondary air duct away from the blower is connected to two burners. Preferably, there are two pipeline valves, which are a first pipeline valve and a second pipeline valve. The first pipeline valve is located at one end of the connecting pipe close to the first pulverized coal pipeline, and the second pipeline valve is located at one end of the connecting pipe close to the second pulverized coal pipeline.

[0007] Preferably, the pipeline valve is a pipeline plug-in door.

[0008] Preferably, it also includes a first raw coal bin, a second raw coal bin, a first coal feeder and a second coal feeder, the output end of the first raw coal bin is connected to the coal inlet end of the first coal mill through the first coal feeder, and the output end of the second raw coal bin is connected to the coal inlet end of the second coal mill through the second coal feeder.

[0009] Preferably, the primary air duct comprises a first primary air duct and a second primary air duct, one end of the first primary air duct is connected to the first coal mill, and the other end of the first primary air duct is communicated with the main air duct, one end of the second primary air duct is connected to the second coal mill, and the other end of the second primary air duct is communicated with the main air duct, and the first primary air duct and the second primary air duct are both provided with a primary air control valve; The secondary air duct includes a first secondary air duct and a second secondary air duct, one end of the first secondary air duct is connected to the first burner, and the other end of the first secondary air duct is connected to the main air duct, one end of the second secondary air duct is connected to the second burner, and the other end of the second secondary air duct is connected to the main air duct, and the first secondary air duct and the second secondary air duct are both provided with secondary air control valves.

[0010] Preferably, the first secondary air duct and the second secondary air duct are both provided with secondary air boxes.

[0011] Preferably, the first pulverized coal pipeline is located at an upper position of the boiler, and the second pulverized coal pipeline is located at a lower position of the boiler.

[0012] A control method for a pulverizing system for rapid load response of a peak load regulating unit comprises the following steps: S1. Under normal operation, the second coal mill is started to make coal, and the pulverized coal is sent into the boiler furnace through the second pulverized coal pipeline to participate in combustion; When the unit receives the AGC load increase command, it opens the first pipeline valve and the second pipeline valve, and increases the output of the second coal mill at the same time. At this time, the first pulverized coal pipeline and the second pulverized coal pipeline are connected, and the pulverized coal in the second pulverized coal pipeline enters the first pulverized coal pipeline under the action of the primary air, and enters the boiler furnace through the first pulverized coal pipeline to participate in combustion. At the same time, the blower inputs secondary air to the first burner through the secondary air pipeline, and the primary air and secondary air at the first pulverized coal pipeline enter the boiler furnace for mixed combustion, quickly releasing heat, so that the boiler load reaches the AGC command level; S2. When performing step S1, the first coal mill is not started. When the unit receives an instruction from the AGC to continuously increase the load or the load remains unchanged, and the coal-making capacity of the second coal mill is unable to meet the boiler combustion demand, the first coal mill is started to participate in the coal feeding; S3. When the first coal mill fully enters the self-powered state, the first pipeline valve is closed first, and then the second pipeline valve is closed after a certain period of time; S4. While ensuring that the total coal supply of the unit remains unchanged, reduce the output of the second coal mill and increase the output of the first coal mill.

[0013] Preferably, the output of the second coal mill is 20%-30% greater than the output of the first coal mill.

[0014] The beneficial effects of the present invention are: The present invention is provided with a connecting pipe, which can realize the connection or independence of the first pulverized coal pipeline and the second pulverized coal pipeline by opening and closing the pipeline valve. When the unit needs to increase the load, the first pulverized coal pipeline and the second pulverized coal pipeline can be connected through the connecting pipe, and the pulverized coal pipeline is first introduced into the two pulverized coal pipelines by the second coal mill, thereby reducing the need for the first coal mill located on the upper layer to first pass hot air to warm the mill, thereby reducing the hysteresis time.

[0015] The present invention can reduce the inertia of large-capacity units when using traditional direct-blowing pulverizing systems, reduce delay time, improve load response rate, and better cope with the increasingly large load peaks and valleys and larger load change rate differences on the power grid user side, thereby better completing the peak-shaving task. At the same time, the present invention has a simple structure, small on-site space occupation, wide adaptability, easy safety management, small total investment, and a short cost recovery period. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0017] Numbers in the figure: 1. first coal mill; 2. second coal mill; 3. boiler; 4. first pulverized coal pipeline; 5. second pulverized coal pipeline; 6. second pipeline valve; 7. first pipeline valve; 8. connecting pipe; 9. second burner; 10. first burner; 11. air preheater; 12. blower; 13. main air duct; 14. first secondary air duct; 15. second secondary air duct; 16. secondary air box; 17. secondary air control valve; 18. first primary air duct; 19. second primary air duct; 20. primary air control valve; 21. second coal feeder; 22. second raw coal bin; 23. first raw coal bin; 24. first coal feeder. DETAILED DESCRIPTION

[0018] In order to make the present invention clearer and more understandable, the technical solution of the present invention is further described in detail below in combination with the accompanying drawings and embodiments. It should be understood that the given embodiment is only one of the implementation methods and does not represent all embodiments.

[0019] In this article, the terms "upper, lower" and the like are established based on the positional relationship shown in the drawings. Depending on the different drawings, the corresponding positional relationship may also change accordingly. Therefore, they cannot be understood as an absolute limitation on the scope of protection.

[0020] Combined with Figure 1 A pulverizing system for rapid load response of a peak load regulating unit, comprising a boiler 3, a first coal mill 1, a second coal mill 2, a first pulverized coal pipeline 4, a second pulverized coal pipeline 5 and a blower 12, wherein the coal outlet end of the first coal mill 1 is connected to one end of the first pulverized coal pipeline 4, and the other end of the first pulverized coal pipeline 4 is connected to the furnace of the boiler 3 through a first burner 10, the coal outlet end of the second coal mill 2 is connected to one end of the second pulverized coal pipeline 5, and the other end of the second pulverized coal pipeline 5 is connected to the furnace of the boiler 3 through a second burner 9, the first pulverized coal pipeline 4 is located at the upper position of the boiler 3, and the second pulverized coal pipeline 5 is located at the lower position of the boiler 3; A connecting pipe 8 is connected between the first pulverized coal pipeline 4 and the second pulverized coal pipeline 5. The connecting pipe 8 is provided with a pipeline valve. There are two pipeline valves, namely a first pipeline valve 7 and a second pipeline valve 6. The first pipeline valve 7 is located at one end of the connecting pipe 8 close to the first pulverized coal pipeline 4, and the second pipeline valve 6 is located at one end of the connecting pipe 8 close to the second pulverized coal pipeline 5. The pipeline valve is a pipeline plug-in door. When the pipeline valve is opened, the first pulverized coal pipeline 4 and the second pulverized coal pipeline 5 are connected to each other, and when the pipeline valve is closed, the first pulverized coal pipeline 4 and the second pulverized coal pipeline 5 are independent of each other; The air outlet end of the blower 12 is connected to a primary air duct and a secondary air duct through a main air duct 13, one end of the primary air duct away from the blower 12 is connected to the first coal mill 1 and the second coal mill 2, respectively, and one end of the secondary air duct away from the blower 12 is connected to two burners.

[0021] Specifically, it also includes a first raw coal bin 23, a second raw coal bin 22, a first coal feeder 24 and a second coal feeder 21. The output end of the first raw coal bin 23 is connected to the coal inlet end of the first coal mill 1 through the first coal feeder 24, and the output end of the second raw coal bin 22 is connected to the coal inlet end of the second coal mill 2 through the second coal feeder 21. The first and second raw coal bins 22 are used to store lump raw coal that has not been ground into powder, and the first and second coal feeders 21 are used to transport the raw coal in the corresponding raw coal bins to the corresponding coal mills.

[0022] Specifically, the primary air duct includes a first primary air duct 18 and a second primary air duct 19, one end of the first primary air duct 18 is connected to the first coal mill 1, and the other end of the first primary air duct 18 is communicated with the main air duct 13, one end of the second primary air duct 19 is connected to the second coal mill 2, and the other end of the second primary air duct 19 is communicated with the main air duct 13, and the first primary air duct 18 and the second primary air duct 19 are both provided with a primary air control valve 20; The secondary air duct includes a first secondary air duct 14 and a second secondary air duct 15, wherein one end of the first secondary air duct 14 is connected to the first burner 10, and the other end of the first secondary air duct 14 is connected to the main air duct 13, one end of the second secondary air duct 15 is connected to the second burner 9, and the other end of the second secondary air duct 15 is connected to the main air duct 13, and the first secondary air duct 14 and the second secondary air duct 15 are both provided with secondary air control valves 17.

[0023] By selecting the opening and closing of the secondary air control valve 17 and the primary air control valve 20, the air supply path of the blower 12 can be selected.

[0024] Specifically, the first secondary air duct 14 and the second secondary air duct 15 are both provided with a secondary air box 16, which can be used to adjust and control the flow rate and direction of the secondary air to ensure the stability and efficiency of the pulverized coal combustion process.

[0025] Specifically, the output end of the air blower 12 is connected to the main air duct 13 through the air preheater 11, and the cold air can be heated into hot air through the air preheater 11.

[0026] The action and effect of the pulverizing system are not limited by the types of the first coal mill 1 and the second coal mill 2, and the coal mill may be an existing type such as a medium-speed coal mill and a steel ball coal mill.

[0027] A control method for a pulverizing system for rapid load response of a peak load regulating unit comprises the following steps: S1. In the normal operation state, the second coal mill 2 is started to make coal, and the pulverized coal is sent to the furnace of the boiler 3 through the second pulverized coal pipeline 5 to participate in combustion; When the unit receives the load increase command from the AGC (automatic generation control system), the first pipeline valve 7 and the second pipeline valve 6 are opened, and the output of the second coal mill 2 is increased at the same time. At this time, the first coal powder pipeline 4 and the second coal powder pipeline 5 are connected, and the coal powder in the second coal powder pipeline 5 enters the first coal powder pipeline 4 under the action of the primary air, and enters the furnace of the boiler 3 through the first coal powder pipeline 4 to participate in combustion. At the same time, the blower 12 inputs secondary air to the first burner 10 through the secondary air pipeline, and the primary air and secondary air at the first coal powder pipeline 4 enter the furnace of the boiler 3 for mixed combustion, and quickly release heat, so that the load of the boiler 3 reaches the AGC command level; if the first coal powder pipeline 4 and the second coal powder pipeline 5 are not connected, and the first coal mill 1 is started directly, the coal mill needs to be warmed by hot air first, and then coal is added. After the coal is pulverized, it is blown into the furnace to participate in combustion. The response load is slow and the hysteresis time is long; And if the first coal mill 1 and the second coal mill 2 are not connected, during the AGC load increase process, simply increasing the output of the second coal mill 2 to increase the heat entering the furnace will cause a large amount of coal powder to be concentrated in the same area, and the heat load of the combustion area cross section will exceed the design value, which can easily cause the flame to brush the wall, leading to coking and high-temperature corrosion problems, which is not good for the safety of the unit.

[0028] Specifically, in the normal operation state, the primary air control valve 20 on the first primary air supply duct and the secondary air control valve 17 on the first secondary air supply duct are closed, the primary air control valve 20 on the second primary air supply duct and the secondary air control valve 17 on the second secondary air supply duct are opened, and the blower 12 supplies primary air to the second coal mill 2 and supplies secondary air to the second burner 9; When the first pulverized coal pipeline 4 and the second pulverized coal pipeline 5 are connected and the pulverized coal produced by the second coal mill 2 is introduced into the first pulverized coal pipeline 4 , the secondary air control valve 17 on the first secondary air pipeline 14 is opened, and the blower 12 introduces secondary air into the first burner 10 .

[0029] S2. When performing step S1, the first coal mill 1 is not started. When the unit receives the AGC's instruction to continuously increase the load or the load remains unchanged, and the coal making capacity of the second coal mill 2 is unable to meet the combustion demand of the boiler 3, the first coal mill 1 is started to allow the first coal mill 1 to participate in coal feeding. The process of starting the first coal mill 1 and switching to the coal feeding state and becoming self-powered can be carried out according to the coal mill start-up and warm-up operation procedures. This process is a routine operation and will not be elaborated here. During the start-up and warm-up process of the first coal mill 1, its corresponding first burner 10 has participated in combustion, and the load response speed of the unit is improved.

[0030] S3. When the first coal mill 1 is warmed up and the first coal feeder 24 has an output of 30%-50% of its maximum output capacity, it can be considered that the first coal mill 1 has completely entered the self-output state. When the first coal mill 1 has completely entered the self-output state, the first pipeline valve 7 is closed first, and the second pipeline valve 6 is closed after a certain period of time. Specifically, at this time, the primary air control valve 20 on the first primary air supply pipeline can be opened, and the two coal mills receive independent air supply.

[0031] S4. While ensuring that the total coal supply of the unit remains unchanged, reduce the output of the second coal mill 2 and increase the output of the first coal mill 1. At this time, the connecting pipe 8 exits the working state.

[0032] The output of the second coal mill 2 is preferably increased to 20%-30% greater than the output of the first coal mill 1 , and the margin output meets the requirement of rapid response during load increase, and the margin output is the margin output of the second coal mill 2 .

[0033] While embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pulverizing system for rapid load response of a peak load regulating unit, characterized in that: The invention comprises a boiler (3), a first coal mill (1), a second coal mill (2), a first pulverized coal pipeline (4), a second pulverized coal pipeline (5) and a blower (12); the coal outlet end of the first coal mill (1) is connected to one end of the first pulverized coal pipeline (4); the other end of the first pulverized coal pipeline (4) is connected to the furnace of the boiler (3) through a first burner (10); the coal outlet end of the second coal mill (2) is connected to one end of the second pulverized coal pipeline (5); the other end of the second pulverized coal pipeline (5) is connected to the furnace of the boiler (3) through a second burner (9); a connecting pipe (8) is connected between the first pulverized coal pipeline (4) and the second pulverized coal pipeline (5); a pipeline valve is provided on the connecting pipe (8); when the pipeline valve is opened, the first pulverized coal pipeline (4) and the second pulverized coal pipeline (5) are connected to each other; when the pipeline valve is closed, the first pulverized coal pipeline (4) and the second pulverized coal pipeline (5) are independent of each other; The air outlet end of the blower (12) is respectively connected to a primary air duct and a secondary air duct via a main air duct (13); one end of the primary air duct away from the blower (12) is respectively connected to the first coal mill (1) and the second coal mill (2); and one end of the secondary air duct away from the blower (12) is respectively connected to two burners.

2. A pulverizing system for rapid load response of a peak load regulating unit according to claim 1, characterized in that: There are two pipeline valves, namely a first pipeline valve (7) and a second pipeline valve (6); the first pipeline valve (7) is located at one end of the connecting pipe (8) close to the first pulverized coal pipeline (4); and the second pipeline valve (6) is located at one end of the connecting pipe (8) close to the second pulverized coal pipeline (5).

3. A pulverizing system and control method for rapid load response of a peak load regulating unit according to claim 2, characterized in that: The pipeline valve is a pipeline plug-in door.

4. The pulverizing system for rapid load response of a peak load regulating unit according to claim 1, characterized in that: It also comprises a first raw coal bin (23), a second raw coal bin (22), a first coal feeder (24) and a second coal feeder (21), wherein the output end of the first raw coal bin (23) is connected to the coal inlet end of the first coal mill (1) via the first coal feeder (24), and the output end of the second raw coal bin (22) is connected to the coal inlet end of the second coal mill (2) via the second coal feeder (21).

5. The pulverizing system for rapid load response of peak load regulating units according to claim 1, characterized in that: The primary air duct comprises a first primary air duct (18) and a second primary air duct (19); one end of the first primary air duct (18) is connected to the first coal mill (1), and the other end of the first primary air duct (18) is communicated with the main air duct (13); one end of the second primary air duct (19) is connected to the second coal mill (2), and the other end of the second primary air duct (19) is communicated with the main air duct (13); and primary air control valves (20) are provided on both the first primary air duct (18) and the second primary air duct (19); The secondary air duct comprises a first secondary air duct (14) and a second secondary air duct (15); one end of the first secondary air duct (14) is connected to the first burner (10), and the other end of the first secondary air duct (14) is communicated with the main air duct (13); one end of the second secondary air duct (15) is connected to the second burner (9), and the other end of the second secondary air duct (15) is communicated with the main air duct (13); and the first secondary air duct (14) and the second secondary air duct (15) are both provided with secondary air control valves (17).

6. A pulverizing system for rapid load response of a peak load regulating unit according to claim 5, characterized in that: The first secondary air duct (14) and the second secondary air duct (15) are both provided with a secondary air box (16).

7. The pulverizing system for rapid load response of peak load regulating units according to claim 1, characterized in that: The first pulverized coal pipeline (4) is located at an upper position of the boiler (3), and the second pulverized coal pipeline (5) is located at a lower position of the boiler (3).

8. A control method for a pulverizing system for rapid load response of a peak load regulating unit, characterized in that: The following steps are involved: S1. In a normal operation state, the second coal mill (2) is started to produce coal, and the pulverized coal is sent to the furnace of the boiler (3) through the second pulverized coal pipeline (5) to participate in combustion; When the unit receives the AGC load increase instruction, the first pipeline valve (7) and the second pipeline valve (6) are opened, and the output of the second coal mill (2) is increased at the same time. At this time, the first pulverized coal pipeline (4) and the second pulverized coal pipeline (5) are connected, and the pulverized coal in the second pulverized coal pipeline (5) enters the first pulverized coal pipeline (4) under the action of the primary air, and enters the furnace of the boiler (3) through the first pulverized coal pipeline (4) to participate in combustion. At the same time, the blower (12) inputs secondary air to the first burner (10) through the secondary air pipeline, and the primary air and secondary air at the first pulverized coal pipeline (4) enter the furnace of the boiler (3) for mixed combustion, and quickly release heat, so that the load of the boiler (3) reaches the AGC instruction level; S2, when performing step S1, the first coal mill (1) is not started, and when the unit receives an AGC instruction to continuously increase the load or the load remains unchanged, and the coal making capacity of the second coal mill (2) is unable to meet the combustion demand of the boiler (3), the first coal mill (1) is selected to be started, so that the first coal mill (1) participates in the coal feeding; S3. When the first coal mill (1) completely enters the self-powered state, the first pipeline valve (7) is closed first, and then the second pipeline valve (6) is closed after a certain period of time; S4. While ensuring that the total coal feed rate of the unit remains unchanged, reduce the output of the second coal mill (2) and increase the output of the first coal mill (1).

9. A control method for a pulverizing system for rapid load response of a peak load regulating unit according to claim 8, characterized in that: The output of the second coal mill (2) is 20%-30% greater than the output of the first coal mill (1).

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