System and method for improving the adaptability of coal species of air preheater anti-blocking of coal-fired unit

Abstract

The present application provides a kind of coal-fired unit air preheater prevents blocking and promotes system and method of coupling coal kind adaptation, including boiler body, boiler body is equipped with bypass flue, bypass flue is connected with high-efficiency flue gas heat exchanger, high-efficiency flue gas heat exchanger is connected with denitration SCR, the outlet of denitration SCR is connected with air preheater, primary air cooling air duct is connected with air preheater, air preheater is connected with coal mill, coal mill is connected with boiler body, secondary air cooling air duct is connected with air preheater, air preheater is connected with boiler body.The present application greatly improves air preheater inlet air temperature, improves the flue gas temperature of air preheater heat storage element, makes the metal wall temperature of air preheater rise, makes the ammonium bisulfate deposited on air preheater completely gasify, solves air preheater blockage problem, when unit burns lignite or Zhundong coal, can make the primary air temperature entering coal mill reach the requirement of coal mill drying output, also makes secondary air temperature as high as possible, optimizes combustion, improves combustion efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air preheaters, in particular to a system and method for preventing air preheater blockage and improving coupled coal adaptability of a coal-fired unit. BACKGROUND

[0002] The primary air and secondary air in a boiler play different roles in the combustion process. The primary air is mainly used to transport heated coal powder and is sent into the furnace through the primary air duct, while providing the oxygen required for the ignition and combustion of volatile matter in the coal powder. The secondary air is hot air sent into the furnace through a separate channel of the burner, mainly providing oxygen for carbon combustion and enhancing the disturbance of the airflow, promoting the backflow of high-temperature flue gas and the mixing of combustible matter and oxygen, and providing conditions for complete combustion.

[0003] An air preheater is a heat exchanger that uses the heat of exhaust gas from a boiler or other device to preheat the air. Its function is to reduce the exhaust gas temperature of the boiler and other equipment, improve thermal efficiency, make the fuel easy to ignite, stabilize combustion, and improve combustion efficiency. However, air preheaters often experience blockage.

[0004] Under certain operating conditions, such as when the air preheater is severely blocked, adjusting the opening and closing states of the air duct and shut-off door can change the flow of primary air and secondary air, allowing the high-efficiency flue gas heat exchanger to heat the primary air and secondary air before the air preheater, thereby solving the problem of air preheater blockage. In addition, when the unit burns lignite or Zhundong coal, resulting in insufficient drying capacity of the coal mill, it is also necessary to adjust the flow of primary air and secondary air to increase the inlet air temperature of the coal mill, thereby increasing the drying capacity and outlet temperature of the coal mill, optimizing combustion, and improving combustion stability. In general, primary air and secondary air play a crucial role in the boiler combustion process, and by reasonably adjusting and controlling their air volume and temperature, the efficient and stable operation of the boiler can be ensured. Therefore, there is an urgent need to develop a system and method for preventing air preheater blockage and improving coupled coal adaptability of a coal-fired unit. SUMMARY

[0005] The present application aims to provide a system and method for preventing air preheater blockage and improving coupled coal adaptability of a coal-fired unit, which solves the problem of air preheater blockage and optimizes coal combustion to improve combustion stability.

[0006] According to one purpose of the present application, the present application provides a system for preventing blocking of an air preheater of a coal-fired unit and improving coupling of coal species, comprising a boiler body, a coal mill, a primary air cooling air duct, a secondary air cooling air duct, an air preheater and a high-efficiency flue gas heat exchanger, the boiler body is provided with a bypass flue, the bypass flue is connected with the high-efficiency flue gas heat exchanger, the high-efficiency flue gas heat exchanger is connected with a denitration SCR, an outlet of the denitration SCR is connected with the air preheater through a third air duct, the primary air cooling air duct is connected with the air preheater, the air preheater is connected with the coal mill, the coal mill is connected with the boiler body, the secondary air cooling air duct is connected with the air preheater, the air preheater is connected with the boiler body, the high-efficiency flue gas heat exchanger is connected with the primary air cooling air duct through a second air duct, a first air duct is connected on the second air duct, the high-efficiency flue gas heat exchanger is connected with the primary air cooling air duct through the second air duct and the first air duct, an outlet of the high-efficiency flue gas heat exchanger is connected with the coal mill through a fourth air duct, a fifth air duct is connected with the fourth air duct, the fifth air duct is connected with the primary air cooling air duct, the high-efficiency flue gas heat exchanger is connected with the air preheater through a seventh air duct, a sixth air duct is connected on the seventh air duct, the sixth air duct is connected with the secondary air cooling air duct, an outlet of the high-efficiency flue gas heat exchanger is connected with the boiler body and the air preheater through an eighth air duct, a ninth air duct is connected with the eighth air duct, the ninth air duct is connected with the secondary air cooling air duct.

[0007] Further, a flue gas shut-off door and a flue gas adjusting door are installed on the bypass flue, and a flue gas adjusting baffle is arranged at the outlet of the high-efficiency flue gas heat exchanger.

[0008] Further, the boiler body comprises a furnace and a boiler tail flue, a low-temperature superheater is arranged in the boiler tail flue, and an outlet of the boiler tail flue is connected with the denitration SCR through a flue.

[0009] Further, a primary air fan is arranged on the primary air cooling air duct, and an air supply fan is arranged on the secondary air cooling air duct.

[0010] Further, the first air duct and the second air duct are connected through a tee joint, an electric shut-off door H is arranged on the first air duct, the fourth air duct and the fifth air duct are connected through a tee joint, an electric shut-off door is arranged on the fifth air duct, the sixth air duct and the seventh air duct are connected through a tee joint, and an electric shut-off door C is arranged on the sixth air duct.

[0011] Further, the eighth air duct and the ninth air duct are connected through a tee joint, the ninth air duct is provided with an electric closing door E, the primary air cooling air duct is provided with an electric closing door A, the second air duct is provided with an electric closing door J, the secondary air cooling air duct is provided with an electric closing door G, the seventh air duct is provided with an electric closing door D, and the eighth air duct is provided with an electric closing door F.

[0012] According to another purpose of the present application, the present application provides a use method of the system for preventing blockage and improving coupling of coal species of the air preheater of the coal-fired unit, comprising the following steps:

[0013] S1, when the air preheater is seriously blocked, the unit is operated to full load, the flue gas closing door on the bypass flue is opened, part of the flue gas enters the high-efficiency flue gas heat exchanger through the bypass flue, and flows into the SCR denitration inlet after heat exchange in the high-efficiency flue gas heat exchanger; the flue gas after the high-efficiency flue gas heat exchanger is adjusted by the flue gas adjusting door on the bypass flue, so that the flue gas reaches the SCR inlet at a temperature of 337℃; the temperature of the primary air and the secondary air heated by the high-efficiency flue gas heat exchanger reaches 108℃; and the metal wall temperature of the air preheater is higher than 207℃, so that the ammonium bisulfate deposited on the air preheater is completely gasified, and the problem of air preheater blockage is solved;

[0014] S2, when the outlet temperature of the coal mill is too low and the coal pipe is blocked, the electric closing door A on the primary air cooling air duct is opened, the electric closing door H on the first air duct is closed, the electric closing door J on the second air duct is opened, the electric closing door K on the fourth air duct after the high-efficiency flue gas heat exchanger is opened, and the electric closing door I on the fifth air duct is closed, and the electric closing door L on the air preheater outlet hot primary air duct is also closed;

[0015] S3, when the primary air temperature entering the coal mill meets the drying output requirement of the coal mill, due to the need for unit peak regulation, there is a long-term low load operation or frequent load fluctuation operation, the hot secondary air temperature has a great influence on the flame combustion stability in the furnace in the low load condition or frequent load fluctuation operation, and improving the hot secondary air temperature can improve the stable combustion capability of the boiler; the electric closing door A on the primary air cooling air duct is opened, the electric closing door H on the first air duct is closed, the electric closing door J on the second air duct is closed, the electric closing door K on the fourth air duct after the high-efficiency flue gas heat exchanger is closed, the electric closing door I on the fifth air duct is closed, and the electric closing door L on the air preheater outlet hot primary air duct is opened.

[0016] Further, in S1, the electric closing door A on the primary air cooling air duct is closed, the electric closing door H on the first air duct is opened, and the electric closing door J on the second air duct is closed, the electric closing door K on the fourth air duct after the high-efficiency flue gas heat exchanger is closed, the electric closing door I on the fifth air duct is opened, and the primary air enters the first air duct after passing through the primary air fan.

[0017] At the same time, the electric closing door G on the secondary air cooling air duct is closed, the electric closing door C on the sixth air duct is opened, the electric closing door D on the seventh air duct is closed, and the electric closing door F on the high-efficiency flue gas heat exchanger outlet eighth air duct is closed, and the electric closing door E on the ninth air duct is opened.

[0018] Further, in S2, the electric closing door G on the secondary air cooling air duct is opened, the electric closing door C on the sixth air duct and the electric closing door E on the ninth air duct are closed, to ensure that the cold secondary air first enters the air preheater for heating, at the same time, the electric closing door D on the air preheater outlet seventh air duct is opened, and the electric closing door F on the high-efficiency flue gas heat exchanger outlet eighth air duct is opened, and the electric closing door B on the original hot secondary air duct is closed.

[0019] Further, in S3, the electric closing door G on the secondary air cooling air duct is opened, the electric closing door C on the sixth air duct and the electric closing door E on the ninth air duct are closed, to ensure that the cold secondary air first enters the air preheater for heating, at the same time, the electric closing door D on the air preheater outlet seventh air duct is opened, and the electric closing door F on the high-efficiency flue gas heat exchanger outlet eighth air duct is opened, and the electric closing door B on the original hot secondary air duct is closed; at this time, the high-efficiency flue gas heat exchanger only heats the secondary air after the air preheater, the flue gas adjusting door opening degree on the bypass flue is adjusted, at the same time, the flue gas baffle door on the high-efficiency flue gas heat exchanger after the primary air side is closed, and the flue gas baffle door on the secondary air side is fully opened. In this way, the primary air temperature after the air preheater is kept unchanged, and the secondary air temperature after the air preheater is increased to above 430℃.

[0020] The technical scheme of the present application can greatly improve the air preheater inlet air temperature, improve the flue gas temperature of the air preheater heat storage element, increase the air preheater metal wall temperature, and completely gasify the deposited ammonium bisulfate on the air preheater, to solve the problem of air preheater blockage. At the same time, when the unit burns lignite or Zhundong coal, the present application can make the primary air temperature entering the coal mill meet the drying output requirement of the coal mill, and also make the secondary air temperature as high as possible, to optimize the combustion and improve the combustion efficiency. In addition, when the unit is in low load condition or frequent load operation, the hot secondary air temperature has a great influence on the flame combustion stability in the furnace 1, and increasing the hot secondary air temperature can improve the stable combustion capacity of the boiler, and also improve the flexibility of the unit operation. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the present application or the technical scheme in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0022] Figure 1 Structure diagram of the embodiment of the present application;

[0023] In the figure, 1, furnace; 2, boiler tail flue; 3, low-temperature superheater; 4, bypass flue; 5, flue gas shut-off door; 6, flue gas regulating door; 7, high-efficiency flue gas heat exchanger; 8, denitration SCR; 9, air preheater; 10, primary air cooling flue; 11, primary air fan; 12, coal mill; 13, secondary air cooling flue; 14, air supply fan; 15, first air flue; 16, second air flue; 17, third air flue; 18, fourth air flue; 19, fifth air flue; 20, sixth air flue; 21, seventh air flue; 22, eighth air flue; 23, ninth air flue. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0026] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited. In addition, the terms "mounting", "connecting", "connection" should be broadly understood, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between the two elements inside. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0027] Embodiment 1

[0028] As Figure 1 shown,

[0029] The system for preventing blockage of a coal-fired unit air preheater and improving coupling of coal species includes a boiler body, a coal mill 12, a primary air cooling air duct 10, a secondary air cooling air duct 13, an air preheater 9, and a high-efficiency flue gas heat exchanger 7.

[0030] The high-efficiency flue gas heat exchanger 7 is provided with a flue gas adjusting baffle, and the high-efficiency flue gas heat exchanger 7 and the flue gas adjusting baffle are an integral structure.

[0031] The boiler body includes a furnace 1 and a boiler tail flue 2, and the boiler tail flue 2 is provided with a low-temperature superheater 3. A bypass flue 4 is led out through the boiler tail flue 2 from a hole in the back wall of the low-temperature superheater 3 of the boiler tail flue 2, and a flue gas shut-off door 5 and a flue gas adjusting door 6 are installed on the bypass flue 4.

[0032] The bypass flue 4 is connected to the high-efficiency flue gas heat exchanger 7 at the other end. The flue gas from the bypass flue 4 is heated by the high-efficiency flue gas heat exchanger 7 and then enters the denitration SCR 8 inlet through the flue. The outlet of the boiler tail flue 2 is connected to the inlet of the denitration SCR 8 through the flue. The outlet of the denitration SCR 8 is connected to the air preheater 9 through a third air duct 17.

[0033] The primary air cooling air duct 10 is provided with a primary air fan 11, and the primary air cooling air duct 10 is connected to the air preheater 9. The air preheater 9 is connected to the coal mill 12. The primary air passes through the primary air fan 11 and then enters the air preheater 9 through the primary air cooling air duct 10, is heated by the air preheater 9, and then enters the coal mill 12. The coal mill 12 is connected to the boiler body.

[0034] The secondary air cooling air duct 13 is provided with a supply fan 14, and the secondary air cooling air duct 13 is connected to the air preheater 9. The air preheater 9 is connected to the furnace 1 of the boiler body. The secondary air passes through the supply fan 14, enters the air preheater 9 through the secondary air cooling air duct 13, and is then sent into the boiler furnace 1 after being heated.

[0035] In this embodiment, the high-efficiency flue gas heat exchanger 7 is connected with the air preheater 9 through the second air duct 16, and the first air duct 15 is connected with the second air duct 16, and the high-efficiency flue gas heat exchanger 7 is connected with the primary air cooling duct 10 through the second air duct 16 and the first air duct 15. In this system, the primary air cooling duct 10 enters the high-efficiency flue gas heat exchanger 7 through two paths, one path is that the primary air cooling duct 10 enters the air preheater 9, and then the hot primary air outlet of the air preheater 9 outlet enters the high-efficiency flue gas heat exchanger 7 through the second air duct 16; the other path is that the primary air cooling duct 10 enters the high-efficiency flue gas heat exchanger 7 through the first air duct 15 and the second air duct 16. Specifically, the first air duct 15 and the second air duct 16 are connected through a three-way connection, and the electric shut-off door H is arranged on the first air duct 15, and the switching of the first air duct 15 and the second air duct 16 is realized through the electric shut-off door H.

[0036] The outlet of the high-efficiency flue gas heat exchanger 7 is connected with the coal mill 12 through the fourth air duct 18, the fifth air duct 19 is connected with the fourth air duct 18, and the fifth air duct 19 is connected with the primary air cooling duct 10. Specifically, the fourth air duct 18 and the fifth air duct 19 are connected through a three-way connection, and the electric shut-off door I is arranged on the fifth air duct 19, and the switching of the fourth air duct 18 and the fifth air duct 19 is realized through the electric shut-off door I.

[0037] The high-efficiency flue gas heat exchanger 7 is connected with the air preheater 9 through the seventh air duct 21, and the sixth air duct 20 is connected with the seventh air duct 21, and the high-efficiency flue gas heat exchanger 7 is connected with the secondary air cooling duct 13 through the seventh air duct 21 and the sixth air duct 20.

[0038] The secondary air cooling duct 13 enters the high-efficiency flue gas heat exchanger 7 through two paths, one path is that the secondary air cooling duct 13 enters the air preheater 9, and then the hot primary air outlet of the air preheater 9 outlet enters the high-efficiency flue gas heat exchanger 7 through the seventh air duct 21; the other path is that the secondary air cooling duct 13 enters the high-efficiency flue gas heat exchanger 7 through the sixth air duct 20 and the seventh air duct 21. Specifically, the sixth air duct 20 and the seventh air duct 21 are connected through a three-way connection, and the electric shut-off door C is arranged on the sixth air duct 20, and the switching of the sixth air duct 20 and the seventh air duct 21 is realized through the electric shut-off door C.

[0039] The outlet of the high-efficiency flue gas heat exchanger 7 is connected with the furnace 1 of the boiler body and the air preheater 9 through the eighth air duct 22, the ninth air duct 23 is connected with the eighth air duct 22, and the ninth air duct 23 is connected with the secondary air cooling duct 13. The eighth air duct 22 and the ninth air duct 23 are connected through a three-way connection, and the electric shut-off door E is arranged on the ninth air duct 23, and the switching of the eighth air duct 22 and the ninth air duct 23 is realized through the electric shut-off door E. The sixth air duct 20, the seventh air duct 21, the eighth air duct 22 and the ninth air duct 23 are respectively provided with shut-off doors and regulating doors, flow meters and temperature meters.

[0040] In the embodiment, the electric closing door A is arranged on the primary air cooling air duct 10, and the electric closing door A is arranged between the first air duct 15 and the fifth air duct 19 and the connection position of the primary air cooling air duct 10.

[0041] The electric closing door J is arranged on the second air duct 16, and the electric closing door G is arranged on the secondary air cooling air duct 13, and the electric closing door G is arranged between the sixth air duct 20 and the ninth air duct 23 and the connection position of the primary air cooling air duct 10.

[0042] The electric closing door D is arranged on the seventh air duct 21, and the electric closing door F is arranged on the eighth air duct 22.

[0043] In use, the application comprises the following working conditions:

[0044] (1) When the air preheater 9 is seriously blocked, the unit is running to full load, the flue gas closing door 5 on the bypass flue 4 is opened, part of the flue gas enters the high-efficiency flue gas heat exchanger 7 through the bypass flue 4, and then flows into the SCR denitration inlet after heat exchange in the high-efficiency flue gas heat exchanger 7;

[0045] At the same time, the electric closing door A on the primary air cooling air duct 10 is closed, the electric closing door H on the first air duct 15 is opened, the electric closing door J on the second air duct 16 is closed, the electric closing door K on the fourth air duct 18 of the high-efficiency flue gas heat exchanger 7 is closed, the electric closing door I on the fifth air duct 19 is opened, and the primary air enters the first air duct 15 after passing through the primary air fan 11, so that the primary air flow is: primary air→primary air fan 11→first air duct 15→second air duct 16→high-efficiency flue gas heat exchanger 7→fourth air duct 18→fifth air duct 19→air preheater 9→coal mill 12;

[0046] At the same time, the electric closing door G on the secondary air cooling duct 13 is closed, the electric closing door C on the sixth air duct 20 is opened, the electric closing door D on the seventh air duct 21 is closed, the electric closing door F on the eighth air duct 22 at the outlet of the high-efficiency flue gas heat exchanger 7 is closed, and the electric closing door E on the ninth air duct 23 is opened. In this way, the secondary air flow is: secondary air → secondary air fan → sixth air duct 20 → seventh air duct 21 → high-efficiency flue gas heat exchanger 7 → eighth air duct 22 → ninth air duct 23 → air preheater 9 → furnace 1. This flow makes the high-efficiency flue gas heat exchanger 7 heat the primary air and the secondary air before the air preheater 9. At the same time, the primary air and the secondary air heated after passing through the high-efficiency flue gas heat exchanger 7 enter the air preheater 9 for heat exchange, and then enter the coal mill 12 and the burner secondary air duct box in turn. At this time, by adjusting the flue gas adjusting door 6 on the bypass flue 4, the flue gas after passing through the high-efficiency flue gas heat exchanger 7 reaches the SCR inlet with a temperature of 337°C. The temperature of the primary air and the secondary air heated after passing through the high-efficiency flue gas heat exchanger 7 reaches 108°C. That is, the inlet air temperature of the air preheater 9 reaches 108°C, so that the exhaust gas temperature at the outlet of the air preheater 9 reaches 185°C. The metal wall temperature of the air preheater 9 is higher than 207°C, and the ammonium bisulfate deposited on the air preheater 9 is completely gasified, solving the problem of air preheater 9 blockage.

[0047] (2) When some units burn mixed coal or Zhundong coal, due to the high moisture content of the mixed coal, the drying output of the coal mill 12 is insufficient after mixing, the outlet temperature of the coal mill 12 is too low, and the coal powder pipe is blocked. It is necessary to increase the inlet air temperature of the coal mill 12 to improve the drying output of the coal mill 12, so as to increase the outlet temperature of the coal mill 12.

[0048] At this time, the electric closing door A on the primary air cooling duct 10 is opened, the electric closing door H on the first air duct 15 is closed, the electric closing door J on the second air duct 16 is opened, the electric closing door K on the fourth air duct 18 behind the high-efficiency flue gas heat exchanger 7 is opened, and the electric closing door I on the fifth air duct 19 is closed. At the same time, the electric closing door L on the hot primary air duct at the outlet of the air preheater 9 is closed. At this time, the primary air flow is: primary air → primary air fan 11 → air preheater 9 → second air duct 16 → high-efficiency flue gas heat exchanger 7 → fourth air duct 18 → original hot primary air duct → coal mill 12.

[0049] In addition, the electric closing door G on the secondary air cooling air duct needs to be opened, the electric closing door C on the sixth air duct 20 and the electric closing door E on the ninth air duct 23 need to be closed, the electric closing door D on the seventh air duct 21 at the outlet of the air preheater 9 needs to be opened, the electric closing door F on the eighth air duct 22 at the outlet of the high-efficiency flue gas heat exchanger 7 needs to be opened, and the electric closing door B on the original hot secondary air duct needs to be closed. At this time, the secondary air flow is: secondary air → secondary air fan → air preheater 9 → seventh air duct 21 → high-efficiency flue gas heat exchanger 7 → eighth air duct 22 → original hot secondary air duct → furnace 1. At this time, the high-efficiency flue gas heat exchanger 7 switches to heat the primary air and secondary air after the air preheater 9, and the flue gas adjusting door 6 of the bypass flue 4 is adjusted to keep the SCR inlet flue gas temperature at 337℃. At the same time, the flue gas adjusting baffle after the high-efficiency flue gas heat exchanger 7 is adjusted, so that the primary air temperature entering the coal mill 12 reaches the requirement of the drying output of the coal mill 12. Similarly, the secondary air temperature is as high as possible. Thus, the combustion is optimized, and the combustion stability is improved.

[0050] (3) When the unit does not burn lignite or Zhundong coal, the primary air temperature entering the coal mill 12 meets the drying output requirement of the coal mill 12. Due to the need for unit peak shaving, there is a long-term low load operation or frequent load operation. In the low load condition or frequent load operation, the hot secondary air temperature has a great influence on the flame combustion stability in the furnace 1. Increasing the hot secondary air temperature can improve the stable combustion capability of the boiler. The following system and method can be used. The electrically operated closing door A on the primary air cooling air duct 10 needs to be opened, the electrically operated closing door H on the first air duct 15 needs to be closed, the electrically operated closing door J on the second air duct 16 needs to be closed, the electrically operated closing door K on the fourth air duct 18 behind the high-efficiency flue gas heat exchanger 7 needs to be closed, and the electrically operated closing door I on the fifth air duct 19 needs to be closed, and the electrically operated closing door L on the air preheater 9 outlet hot primary air duct needs to be opened. In this way, the primary air flow is: primary air→primary air fan 11→air preheater 9→original hot primary air duct→coal mill 12. In addition, the electrically operated closing door G on the secondary air cooling air duct needs to be opened, the electrically operated closing door C on the sixth air duct 20 and the electrically operated closing door E on the ninth air duct 23 need to be closed, to ensure that the cold secondary air enters the air preheater 9 for heating first, and the electrically operated closing door D on the seventh air duct 21 at the outlet of the air preheater 9 is opened, and the electrically operated closing door F on the eighth air duct 22 at the outlet of the high-efficiency flue gas heat exchanger 7 is opened, and the electrically operated closing door B on the original hot secondary air duct is closed. At this time, the secondary air flow is: secondary air→secondary air fan→air preheater 9→seventh air duct 21→high-efficiency flue gas heat exchanger 7→eighth air duct 22→original hot secondary air duct→furnace 1. At this time, the high-efficiency flue gas heat exchanger 7 only heats the secondary air after the air preheater 9, the opening degree of the flue gas adjusting door 6 on the bypass flue 4 is adjusted, and at the same time, the flue gas baffle door on the primary air side of the high-efficiency flue gas heat exchanger 7 is closed and the flue gas baffle door on the secondary air side is fully opened. In this way, the primary air temperature after the air preheater 9 is kept unchanged, and the secondary air temperature after the air preheater 9 is increased to above 430°C.

[0051] (4) When the boiler starts, according to the unit operation regulation, when the ambient temperature is lower than -5°C, the warm air heater must be started to heat the air temperature, and when the secondary air temperature reaches 177°C, the pulverizing system needs to be started. Due to the start of the boiler, the bypass of the steam turbine is started, and the flue gas temperature at the outlet of the furnace 1 is controlled to be not more than 538°C. At present, when the boiler starts, most of the auxiliary steam from the adjacent boiler is used to heat the air temperature, which consumes a large amount of energy. By repeating the system steps of the first case, this system uses the bypass flue gas from the boiler to heat the primary air and the secondary air during startup, saving the auxiliary steam from the adjacent boiler.

[0052] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A system for improving the adaptability of coal species for preventing blockage of an air preheater of a coal-fired unit, characterized in that, The application relates to a boiler system, which comprises a boiler body, a coal mill, a primary air cooling air duct, a secondary air cooling air duct, an air preheater and a high-efficiency flue gas heat exchanger, wherein the boiler body is provided with a bypass flue, the bypass flue is connected with the high-efficiency flue gas heat exchanger, the high-efficiency flue gas heat exchanger is connected with a denitration SCR, the outlet of the denitration SCR is connected with the air preheater through a third air duct, the primary air cooling air duct is connected with the air preheater, the air preheater is connected with the coal mill, the coal mill is connected with the boiler body, the secondary air cooling air duct is connected with the air preheater, the air preheater is connected with the boiler body, the high-efficiency flue gas heat exchanger is connected with the air preheater through a second air duct, a first air duct is connected with the second air duct, the high-efficiency flue gas heat exchanger is connected with the primary air cooling air duct through the second air duct and the first air duct, the outlet of the high-efficiency flue gas heat exchanger is connected with the coal mill through a fourth air duct, a fifth air duct is connected with the fourth air duct, the fifth air duct is connected with the primary air cooling air duct, the high-efficiency flue gas heat exchanger is connected with the air preheater through a seventh air duct, a sixth air duct is connected with the seventh air duct, the sixth air duct is connected with the secondary air cooling air duct, the outlet of the high-efficiency flue gas heat exchanger is connected with the boiler body and the air preheater through an eighth air duct, a ninth air duct is connected with the eighth air duct, and the ninth air duct is connected with the secondary air cooling air duct.

2. The system for anti-clogging and enhanced coupling of coal rank adaptation of air preheaters of coal-fired units according to claim 1, characterized in that, A flue gas shutoff door and a flue gas adjusting door are arranged on the bypass flue, and the outlet of the high-efficiency flue gas heat exchanger is provided with a flue gas adjusting baffle.

3. The system for anti-clogging and enhanced coupling of coal rank adaptation of air preheaters of coal-fired units according to claim 1, characterized in that, The boiler body comprises a furnace and a boiler tail flue, a low-temperature superheater is arranged in the boiler tail flue, and the outlet of the boiler tail flue is connected with the denitration SCR through a flue.

4. The system for anti-jamming and enhanced coupling coal kind adaptation of air preheaters of coal-fired units according to claim 1, characterized in that, A primary air fan is arranged on the primary air cooling air duct, and a secondary air fan is arranged on the secondary air cooling air duct.

5. The system for anti-clogging and enhanced coupling of coal rank adaptation of air preheaters of coal-fired units of claim 1, wherein, The first air duct and the second air duct are connected through a tee joint, an electric shutoff door H is arranged on the first air duct, the fourth air duct and the fifth air duct are connected through a tee joint, an electric shutoff door is arranged on the fifth air duct, the sixth air duct and the seventh air duct are connected through a tee joint, and an electric shutoff door C is arranged on the sixth air duct.

6. The system for anti-clogging and enhanced coupling of coal rank adaptation for air preheaters of coal-fired units of claim 1, wherein, The eighth air duct and the ninth air duct are connected through a tee joint, an electric shutoff door E is arranged on the ninth air duct, an electric shutoff door A is arranged on the primary air cooling air duct, an electric shutoff door J is arranged on the second air duct, an electric shutoff door G is arranged on the secondary air cooling air duct, an electric shutoff door D is arranged on the seventh air duct, and an electric shutoff door F is arranged on the eighth air duct.

7. The method of claim 1, wherein the system is used for coal-fired units. The application further relates to a boiler system operation method, which comprises the following steps: S1, when the air preheater is blocked seriously, the unit is running to full load, the flue gas shut-off door on the bypass flue is opened, part of the flue gas enters the high-efficiency flue gas heat exchanger through the bypass flue, and after heat exchange through the high-efficiency flue gas heat exchanger, it flows into the SCR denitration inlet; By adjusting the flue gas regulating door on the bypass flue, the flue gas after the high-efficiency flue gas heat exchanger reaches the SCR inlet, the flue gas temperature is reduced to 337℃; The temperature of the primary and secondary air heated by the high-efficiency flue gas heat exchanger reaches 108℃; The metal wall temperature of the air preheater is higher than 207℃, and the ammonium bisulfate deposited on the air preheater is completely gasified, solving the problem of air preheater blockage; S2, when the outlet temperature of the coal mill is too low and the coal pipe is blocked, the electric shut-off door A on the primary air cooling flue is opened, the electric shut-off door H on the first flue is closed, the electric shut-off door J on the second flue is opened, the electric shut-off door K on the fourth flue behind the high-efficiency flue gas heat exchanger is opened, and the electric shut-off door I on the fifth flue is closed, and the electric shut-off door L on the air preheater outlet hot primary air flue is closed; S3, when the primary air temperature entering the coal mill meets the requirement of the coal mill drying output, due to the need for unit peak shaving, there is a long-term low load operation or frequent load operation, in low load condition or frequent load operation, the hot secondary air temperature has a great influence on the flame combustion stability in the furnace, and improving the hot secondary air temperature can improve the stable combustion capability of the boiler; Open the electric shut-off door A on the primary air cooling flue, close the electric shut-off door H on the first flue, close the electric shut-off door J on the second flue, close the electric shut-off door K on the fourth flue behind the high-efficiency flue gas heat exchanger, and close the electric shut-off door I on the fifth flue at the same time, and open the electric shut-off door L on the air preheater outlet hot primary air flue.

8. The method of claim 7, wherein, In S1, the electric shut-off door A on the primary air cooling flue is closed, the electric shut-off door H on the first flue is opened, and the electric shut-off door J on the second flue is closed, the electric shut-off door K on the fourth flue behind the high-efficiency flue gas heat exchanger is closed, and the electric shut-off door I on the fifth flue is opened, so that the primary air enters the first flue after passing through the primary air fan; Close the electric shut-off door G on the secondary air cooling flue, open the electric shut-off door C on the sixth flue, close the electric shut-off door D on the seventh flue, and close the electric shut-off door F on the eighth flue behind the high-efficiency flue gas heat exchanger, and open the electric shut-off door E on the ninth flue.

9. The method of claim 7, wherein, In S2, the electric shut-off door G on the secondary air cooling flue is opened, the electric shut-off door C on the sixth flue and the electric shut-off door E on the ninth flue are closed, to ensure that the cold secondary air enters the air preheater for heating first, the electric shut-off door D on the seventh flue behind the air preheater outlet is opened, the electric shut-off door F on the eighth flue behind the high-efficiency flue gas heat exchanger outlet is opened, and the electric shut-off door B on the original hot secondary air flue is closed.

10. The method of claim 7, wherein, In S3, the electric closing door G on the secondary air cooling air duct is opened, the electric closing door C on the sixth air duct and the electric closing door E on the ninth air duct are closed, the cold secondary air is ensured to enter the air preheater first for heating, the electric closing door D on the seventh air duct at the outlet of the air preheater is opened, the electric closing door F on the eighth air duct at the outlet of the high-efficiency flue gas heat exchanger is opened, and the electric closing door B on the original hot secondary air duct is closed; at this time, the high-efficiency flue gas heat exchanger only heats the secondary air after the air preheater, the opening degree of the flue gas adjusting door on the bypass flue is adjusted, the flue gas baffle door on the primary air side after the high-efficiency flue gas heat exchanger is closed, the flue gas baffle door on the secondary air side is fully opened, the primary air temperature after the air preheater is kept unchanged, and the secondary air temperature after the air preheater is increased to above 430 ℃.

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