Coal-fired unit air pre-heater anti-blocking lifting coupling coal type adapting system and method

Abstract

The invention provides a coal-fired unit air pre-heater anti-blocking lifting coupling coal type adapting system and method.The system comprises a boiler body, the boiler body is provided with a bypass flue, the bypass flue is connected with an efficient flue gas heat exchanger, the efficient flue gas heat exchanger is connected with a denitration SCR, an outlet of the denitration SCR is connected with an air pre-heater, and an outlet of the denitration SCR is connected with the air pre-heater; the primary air cold 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 cold air duct is connected with the air preheater, and the air preheater is connected with the boiler body. The air temperature of an inlet of the air preheater is greatly increased, the smoke temperature of a heat storage element of the air preheater is increased, the temperature of a metal wall of the air preheater is increased, ammonium hydrogen sulfate deposited on the air preheater is completely gasified, the problem of blockage of the air preheater is solved, and the service life of the air preheater is prolonged. When lignite or Zhundong coal is mixed and combusted in the unit, the temperature of primary air entering the coal mill can meet the requirement for drying output of the coal mill, the temperature of secondary air is increased as much as possible, combustion is optimized, and combustion efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of air preheaters, and in particular to a system and method for preventing and improving the blocking of air preheaters of coal-fired units and coupling coal type adaptation. Background Art

[0002] The primary air and secondary air of the boiler play different roles in the combustion process. The primary air is mainly used to transport the 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 the volatile matter in the coal powder. The secondary air is the hot air sent into the furnace through a separate channel of the burner, mainly providing oxygen for the combustion of carbon, and strengthening the disturbance of the air flow, promoting the reflux of high-temperature flue gas and the mixing of combustibles and oxygen, providing conditions for complete combustion.

[0003] The air preheater is a heat exchanger that uses the exhaust heat from boilers and other devices to preheat. Its function is to reduce the exhaust temperature of boilers and other equipment, improve thermal efficiency, make the fuel easier to ignite, burn more stably and improve combustion efficiency, but air preheaters often become blocked.

[0004] Under certain working conditions, such as when the air preheater is severely blocked, the flow of primary and secondary air can be changed by adjusting the switch status of the air duct and the shut-off door, so that the high-efficiency flue gas heat exchanger heats the primary and secondary air in front of the air preheater to solve the problem of air preheater blockage. In addition, when the unit burns lignite or Zhundong coal, resulting in insufficient drying output of the pulverizer, it is also necessary to adjust the flow of primary and secondary air to increase the pulverizer inlet wind temperature, thereby increasing the pulverizer drying output and outlet temperature, optimizing combustion and improving combustion stability. In general, primary and secondary air play a vital role in the boiler combustion process. By reasonably adjusting and controlling their air volume and temperature, the efficient and stable operation of the boiler can be ensured. Therefore, it is urgent to develop a system and method for preventing blockage of air preheaters in coal-fired units and improving the adaptability of coupled coal types. Summary of the invention

[0005] The purpose of the present invention is to provide a system and method for preventing air preheater blockage in a coal-fired unit and improving the adaptability of coupled coal types, so as to solve the problem of air preheater blockage, optimize coal combustion and improve combustion stability.

[0006] According to one object of the present invention, the present invention provides a system for preventing and improving the blocking of air preheater of a coal-fired unit and coupling coal type adaptation, comprising a boiler body, a coal mill, a primary air cooling duct, a secondary air cooling 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 to the high-efficiency flue gas heat exchanger, the high-efficiency flue gas heat exchanger is connected to a denitration SCR, the outlet of the denitration SCR is connected to the air preheater through a third air duct, the primary air cooling duct is connected to the air preheater, the air preheater is connected to the coal mill, the coal mill is connected to the boiler body, the secondary air cooling duct is connected to the air preheater, the air preheater is connected to the boiler body, the high-efficiency flue gas heat exchanger is connected to the secondary air cooling duct The high-efficiency flue gas heat exchanger is connected to the coal mill through the fourth air duct, the fifth air duct is connected to the fourth air duct, the fifth air duct is connected to the primary air cooling duct, the high-efficiency flue gas heat exchanger is connected to the air preheater through the seventh air duct, the seventh air duct is connected to the sixth air duct, the sixth air duct is connected to the secondary air cooling duct, the outlet of the high-efficiency flue gas heat exchanger is connected to the boiler body and the air preheater through the eighth air duct, the ninth air duct is connected to the eighth air duct, and the ninth air duct is connected to the secondary air cooling duct.

[0007] Furthermore, a smoke shutoff door and a smoke regulating door are installed on the bypass flue, and a smoke regulating baffle is provided at the outlet of the high-efficiency smoke heat exchanger.

[0008] Furthermore, the boiler body includes 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 to the denitration SCR through the flue.

[0009] Furthermore, a primary fan is provided on the primary air cooling duct, and a blower is provided on the secondary air cooling duct.

[0010] Furthermore, the first air duct and the second air duct are connected via a tee, an electric shutoff door H is provided on the first air duct, the fourth air duct and the fifth air duct are connected via a tee, an electric shutoff door is provided on the fifth air duct, the sixth air duct and the seventh air duct are connected via a tee, and an electric shutoff door C is provided on the sixth air duct.

[0011] Furthermore, the eighth air duct and the ninth air duct are connected by a tee, the ninth air duct is provided with an electric shut-off door E, the primary air cooling duct is provided with an electric shut-off door A, the second air duct is provided with an electric shut-off door J, the secondary air cooling duct is provided with an electric shut-off door G, the seventh air duct is provided with an electric shut-off door D, and the eighth air duct is provided with an electric shut-off door F.

[0012] According to another object of the present invention, the present invention provides a method for using the above-mentioned system for preventing and improving the blocking of air preheater of a coal-fired unit and coupling coal type adaptation, comprising the following steps:

[0013] S1, when the air preheater is seriously blocked, when the unit is running at full load, open the flue gas shut-off door on the bypass flue, and part of the flue gas enters the high-efficiency flue gas heat exchanger through the bypass flue, and flows into the SCR denitrification inlet after heat exchange in the high-efficiency flue gas heat exchanger; by adjusting the flue gas regulating door on the bypass flue, the flue gas temperature after passing through the high-efficiency flue gas heat exchanger is reduced to 337℃ when it reaches the SCR inlet; the primary and secondary air temperatures after heating by the high-efficiency flue gas heat exchanger reach 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;

[0014] S2, when the outlet temperature of the coal mill is too low and the pulverized coal pipe is blocked, open the electric shut-off door A on the cold primary air cooling duct, close the electric shut-off door H on the first air duct, open the electric shut-off door J on the second air duct, open the electric shut-off door K on the fourth air duct after the high-efficiency flue gas heat exchanger, and close the electric shut-off door I on the fifth air duct, and at the same time close the electric shut-off door L on the hot primary air cooling duct at the outlet of the original air preheater;

[0015] S3, when the temperature of the primary air entering the coal mill meets the requirements of the coal mill drying output, due to the need for peak load regulation of the unit, there is a long-term low-load operation or frequent load increase and decrease operation. Under low-load conditions or frequent load increase and decrease operation, the hot secondary air temperature has a greater impact on the flame combustion stability in the furnace. Increasing the hot secondary air temperature can improve the boiler's stable combustion capability; open the electric shut-off door A on the cold primary air cooling duct, close the electric shut-off door H on the first duct, close the electric shut-off door J on the second duct, close the electric shut-off door K on the fourth duct after the high-efficiency flue gas heat exchanger, and at the same time close the electric shut-off door I on the fifth duct, and open the electric shut-off door L on the hot primary air cooling duct at the outlet of the original air preheater.

[0016] Furthermore, in S1, the electric shutoff door A on the primary air cooling duct is closed at the same time, the electric shutoff door H on the first duct is opened, and the electric shutoff door J on the second duct is closed, and the electric shutoff door K on the fourth duct after the high-efficiency flue gas heat exchanger is closed at the same time, and the electric shutoff door I on the fifth duct is opened, so that the primary air passes through the primary fan and enters the first duct;

[0017] At the same time, close the electric shut-off door G on the secondary air cooling duct, open the electric shut-off door C on the sixth duct, close the electric shut-off door D on the seventh duct, close the electric shut-off door F on the eighth duct at the outlet of the high-efficiency flue gas heat exchanger, and open the electric shut-off door E on the ninth duct.

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

[0019] Furthermore, in S3, the electric shutoff door G on the cold secondary air duct is opened, and the electric shutoff door C on the sixth air duct and the electric shutoff door E on the ninth air duct are closed to ensure that the cold secondary air enters the air preheater first for heating. At the same time, the electric shutoff door D on the seventh air duct at the outlet of the air preheater is opened, and the electric shutoff door F on the eighth air duct at the outlet of the high-efficiency flue gas heat exchanger is opened, and the electric shutoff door B on the original hot secondary air duct is closed at the same time; at this time, the high-efficiency flue gas heat exchanger only heats the secondary air after the air preheater, adjusts the opening of the flue gas regulating door on the bypass flue, and at the same time closes the flue gas damper door on the primary air side after the high-efficiency flue gas heat exchanger, and fully opens the flue gas damper door on the secondary air side. 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°C.

[0020] The technical solution of the present invention can significantly increase the air temperature at the inlet of the air preheater, increase the smoke temperature of the air preheater heat storage element, increase the metal wall temperature of the air preheater, and completely gasify the ammonium bisulfate deposited on the air preheater, thereby solving the problem of air preheater blockage. At the same time, when the unit is mixed with lignite or Zhundong coal, the present invention can make the primary air temperature entering the coal mill meet the requirements of the coal mill drying output, and also make the secondary air temperature as high as possible, optimize combustion, and improve combustion efficiency. In addition, when the unit is under low load conditions or frequently increases and decreases load, the hot secondary air temperature has a greater impact on the flame combustion stability in the furnace 1. Increasing the hot secondary air temperature can improve the boiler's stable combustion capability, and also improve the unit's flexible operation capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[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. denitrification SCR; 9. air preheater; 10. primary air cooling duct; 11. primary fan; 12. coal mill; 13. secondary air cooling duct; 14. blower; 15. first air duct; 16. second air duct; 17. third air duct; 18. fourth air duct; 19. fifth air duct; 20. sixth air duct; 21. seventh air duct; 22. eighth air duct; 23. ninth air duct. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0026] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] Example 1

[0028] like Figure 1 As shown,

[0029] A system for preventing and improving the blocking of air preheaters of coal-fired units and for coupling coal type adaptability comprises a boiler body, a coal mill 12, a primary air cooling duct 10, a secondary air cooling duct 13, an air preheater 9 and a high-efficiency flue gas heat exchanger 7.

[0030] A flue gas regulating baffle is provided at the outlet of the high-efficiency flue gas heat exchanger 7, and the high-efficiency flue gas heat exchanger 7 and the flue gas regulating baffle are an integral structure.

[0031] The boiler body includes a furnace 1 and a boiler tail flue 2. A low-temperature superheater 3 is arranged in the boiler tail flue 2. A hole is opened in the rear wall of the vertical pipe group of the low-temperature superheater 3 in the boiler tail flue 2, and a bypass flue 4 is led out through the boiler tail flue 2. A flue gas shut-off door 5 and a flue gas regulating door 6 are installed on the bypass flue 4.

[0032] The other end of the bypass flue 4 is connected to the high-efficiency flue gas heat exchanger 7. After the flue gas from the bypass flue 4 is heat exchanged by the high-efficiency flue gas heat exchanger 7, it enters the inlet of the denitration SCR 8 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 the third air duct 17.

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

[0034] A blower 14 is provided on the secondary air cooling duct 13, and the secondary air cooling duct 13 is connected to the air preheater 9, and the air preheater 9 is connected to the furnace 1 of the boiler body. The secondary air passes through the blower 14, enters the air preheater 9 from the secondary air cooling duct 13, and is sent to the boiler furnace 1 after being heated.

[0035] In this embodiment, the high-efficiency flue gas heat exchanger 7 is connected to the air preheater 9 through the second air duct 16, the first air duct 15 is connected to the second air duct 16, and the high-efficiency flue gas heat exchanger 7 is connected to 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 routes, one route is to enter the air preheater 9 through the primary air cooling duct 10, and then enter the high-efficiency flue gas heat exchanger 7 through the second air duct 16 from the outlet of the original air preheater 9; the other route is to enter the high-efficiency flue gas heat exchanger 7 through the first air duct 15 and the second air duct 16 from the primary air cooling duct 10. Specifically, the first air duct 15 and the second air duct 16 are connected through a three-way connection, and an electric shutoff door H is provided on the first air duct 15, and the switching between the first air duct 15 and the second air duct 16 is realized by the electric shutoff door H.

[0036] The outlet of the high-efficiency flue gas heat exchanger 7 is connected to the coal mill 12 through the fourth air duct 18, the fifth air duct 19 is connected to the fourth air duct 18, and the fifth air duct 19 is connected to 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 an electric shutoff door I is provided on the fifth air duct 19, and the switching between the fourth air duct 18 and the fifth air duct 19 is realized by the electric shutoff door I.

[0037] The high-efficiency flue gas heat exchanger 7 is connected to the air preheater 9 via the seventh air duct 21 , the sixth air duct 20 is connected to the seventh air duct 21 , and the high-efficiency flue gas heat exchanger 7 is connected to the secondary air cooling duct 13 via 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 routes. One route is to enter the air preheater 9 through the secondary air cooling duct 13, and then enter the high-efficiency flue gas heat exchanger 7 through the seventh air duct 21 from the outlet of the original air preheater 9. The other route is to enter the high-efficiency flue gas heat exchanger 7 through the sixth air duct 20 and the seventh air duct 21 from the secondary air cooling duct 13. Specifically, the sixth air duct 20 and the seventh air duct 21 are connected through a three-way connection, and an electric shutoff door C is provided on the sixth air duct 20, and the switching between the sixth air duct 20 and the seventh air duct 21 is realized through the electric shutoff door C.

[0039] The outlet of the high-efficiency flue gas heat exchanger 7 is connected to 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 to the eighth air duct 22, and the ninth air duct 23 is connected to the secondary air cooling air duct 13. The eighth air duct 22 and the ninth air duct 23 are connected through a three-way connection, and the ninth air duct 23 is provided with an electric shutoff door E, and the switching between the eighth air duct 22 and the ninth air duct 23 is realized through the electric shutoff 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 a shutoff door and an adjustment door, a flow meter and a temperature meter.

[0040] In this embodiment, an electric shutoff door A is provided on the primary air cooling duct 10 , and the electric shutoff door A is arranged between the connection between the first air duct 15 and the fifth air duct 19 and the primary air cooling duct 10 .

[0041] The second air duct 16 is provided with an electric shutoff door J, the secondary air cooling duct 13 is provided with an electric shutoff door G, and the electric shutoff door G is arranged between the connection between the sixth air duct 20 and the ninth air duct 23 and the primary air cooling duct 10 .

[0042] The seventh air duct 21 is provided with an electric shutoff door D, and the eighth air duct 22 is provided with an electric shutoff door F.

[0043] When the present invention is used, it includes the following working conditions:

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

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

[0046] At the same time, close the electric shutoff door G on the secondary air cooling duct 13, open the electric shutoff door C on the sixth duct 20, close the electric shutoff door D on the seventh duct 21, close the electric shutoff door F on the eighth duct 22 at the outlet of the high-efficiency flue gas heat exchanger 7, and open the electric shutoff door E on the ninth duct 23. In this way, the secondary air flow is: secondary air → secondary fan → sixth duct 20 → seventh duct 21 → high-efficiency flue gas heat exchanger 7 → eighth duct 22 → ninth duct 23 → air preheater 9 → furnace 1. This process enables the high-efficiency flue gas heat exchanger 7 to heat the primary air and secondary air before the air preheater 9. At the same time, the primary and secondary air heated by 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 regulating door 6 on the bypass flue 4, the flue gas temperature is reduced to 337°C when the flue gas after passing through the high-efficiency flue gas heat exchanger 7 reaches the SCR inlet. The primary and secondary air temperatures after being heated by the high-efficiency flue gas heat exchanger 7 reach 108°C. That is, the air temperature at the inlet 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 blockage problem of the air preheater 9.

[0047] (2) When some units burn lignite or Zhundong coal, the moisture content of such coal is high, which results in insufficient drying output of the coal mill 12, too low outlet temperature of the coal mill 12, and blockage of the pulverized coal pipe. It is necessary to increase the inlet air temperature of the coal mill 12 to increase the drying output of the coal mill 12, thereby increasing the outlet temperature of the coal mill 12.

[0048] At this time, it is necessary to open the electric shutoff door A on the cold primary air cooling duct 10, close the electric shutoff door H on the first air duct 15, open the electric shutoff door J on the second air duct 16, open the electric shutoff door K on the fourth air duct 18 after the high-efficiency flue gas heat exchanger 7, and close the electric shutoff door I on the fifth air duct 19, and at the same time close the electric shutoff door L on the hot primary air cooling duct 10 at the outlet of the original air preheater 9. At this time, the primary air flow is: primary air → primary 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, it is necessary to open the electric shut-off door G on the cold secondary air duct, close the electric shut-off door C on the sixth air duct 20 and the electric shut-off door E on the ninth air duct 23, ensure that the cold secondary air enters the air preheater 9 for heating first, and at the same time open the electric shut-off door D on the seventh air duct 21 at the outlet of the air preheater 9, open the electric shut-off door F on the eighth air duct 22 at the outlet of the high-efficiency flue gas heat exchanger 7, and at the same time close the electric shut-off door B on the original hot secondary air duct. At this time, the secondary air flow is: secondary air → secondary 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 the primary air and secondary air after heating the air preheater 9, and at the same time adjusts the flue gas regulating door 6 of the bypass flue 4 to keep the SCR inlet flue gas temperature at 337°C. At the same time, the flue gas regulating damper after the high-efficiency flue gas heat exchanger 7 is adjusted to make the primary air temperature entering the coal mill 12 meet the drying output requirements of the coal mill 12. Similarly, the secondary air temperature is increased as much as possible, thereby optimizing combustion and improving combustion stability.

[0050] (3) When the unit does not burn lignite or Zhundong coal, the temperature of the primary air entering the pulverizer 12 meets the drying output requirements of the pulverizer 12. Due to the need for peak load regulation of the unit, there are long-term low-load operation or frequent load increase and decrease operation. Under low-load conditions or frequent load increase and decrease operation, the hot secondary air temperature has a greater impact on the flame combustion stability in the furnace 1. Increasing the hot secondary air temperature can improve the boiler's stable combustion capability. In this case, the following system and method can be used. It is necessary to open the electric shut-off door A on the cold primary air cooling duct 10, close the electric shut-off door H on the first air duct 15, close the electric shut-off door J on the second air duct 16, close the electric shut-off door K on the fourth air duct 18 after the high-efficiency flue gas heat exchanger 7, and at the same time close the electric shut-off door I on the fifth air duct 19, and open the electric shut-off door L on the hot primary air cooling duct 10 at the outlet of the original air preheater 9. In this way, the primary air flow is: primary air → primary fan 11 → air preheater 9 → original hot primary air cooling duct 10 → coal mill 12. In addition, it is necessary to open the electric shut-off door G on the cold secondary air duct, close the electric shut-off door C on the sixth air duct 20 and the electric shut-off door E on the ninth air duct 23, ensure that the cold secondary air enters the air preheater 9 for heating first, and open the electric shut-off door D on the seventh air duct 21 at the outlet of the air preheater 9 at the same time, open the electric shut-off door F on the eighth air duct 22 at the outlet of the high-efficiency flue gas heat exchanger 7, and close the electric shut-off door B on the original hot secondary air duct at the same time. At this time, the secondary air flow is: secondary air → secondary 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 heats only the secondary air after the air preheater 9, and adjusts the opening of the flue gas regulating door 6 on the bypass flue 4. At the same time, the flue gas damper door on the primary air side after the high-efficiency flue gas heat exchanger 7 is closed, and the flue gas damper 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 is increased to above 430℃.

[0051] (4) When the boiler is started, according to the unit operation procedures, when the ambient temperature is lower than -5℃, the air heater must be used to heat the air temperature. At the same time, when the secondary air temperature reaches 177℃, the pulverizing system needs to be put into operation. Due to the operation of the turbine bypass when the boiler is started, the flue gas temperature at the furnace 1 outlet is controlled not to exceed 538℃. At present, when the boiler is started, most of the auxiliary steam from the adjacent boiler is used to heat the air temperature, which consumes a lot of energy. Using this system, the system steps of the first case are repeated. This system uses the bypass flue gas from the boiler to heat the primary and secondary air at startup, saving the auxiliary steam from the adjacent boiler.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for preventing blockage and improving coupling coal type adaptation of air preheater of coal-fired unit, characterized in that: The invention comprises a boiler body, a coal mill, a primary air cooling duct, a secondary air cooling 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 to the high-efficiency flue gas heat exchanger, the high-efficiency flue gas heat exchanger is connected to the denitration SCR, the outlet of the denitration SCR is connected to the air preheater through a third air duct, the primary air cooling duct is connected to the air preheater, the air preheater is connected to the coal mill, the coal mill is connected to the boiler body, the secondary air cooling duct is connected to the air preheater, the air preheater is connected to the boiler body, the high-efficiency flue gas heat exchanger is connected to the air preheater through a second air duct, and the third The second air duct is connected to the first air duct, the high-efficiency flue gas heat exchanger is connected to the primary air cooling duct through the second air duct and the first air duct, the outlet of the high-efficiency flue gas heat exchanger is connected to the coal mill through the fourth air duct, the fifth air duct is connected to the fourth air duct, the fifth air duct is connected to the primary air cooling duct, the high-efficiency flue gas heat exchanger is connected to the air preheater through the seventh air duct, the seventh air duct is connected to the sixth air duct, the sixth air duct is connected to the secondary air cooling duct, the outlet of the high-efficiency flue gas heat exchanger is connected to the boiler body and the air preheater through the eighth air duct, the ninth air duct is connected to the eighth air duct, and the ninth air duct is connected to the secondary air cooling duct.

2. The system for preventing and improving the air preheater of a coal-fired unit from blocking and coupling coal type adaptation according to claim 1 is characterized in that: The bypass flue is provided with a smoke shutoff door and a smoke regulating door, and the outlet of the high-efficiency smoke heat exchanger is provided with a smoke regulating baffle.

3. The system for preventing and improving the blocking of air preheater of coal-fired unit and coupling coal type adaptation according to claim 1 is 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 an outlet of the boiler tail flue is connected to the denitration SCR through the flue.

4. The system for preventing and improving the blocking of air preheater of coal-fired unit and coupling coal type adaptation according to claim 1 is characterized in that: The primary air cooling duct is provided with a primary fan, and the secondary air cooling duct is provided with an air supply fan.

5. The system for preventing and improving the blocking of air preheater of coal-fired unit and coupling coal type adaptation according to claim 1 is characterized in that: The first air duct and the second air duct are connected through a tee, and an electric shutoff door H is provided on the first air duct. The fourth air duct and the fifth air duct are connected through a tee, and an electric shutoff door is provided on the fifth air duct. The sixth air duct and the seventh air duct are connected through a tee, and an electric shutoff door C is provided on the sixth air duct.

6. The system for preventing and improving the blocking of air preheater of coal-fired unit and coupling coal type adaptation according to claim 1 is characterized in that: The eighth air duct and the ninth air duct are connected by a tee, the ninth air duct is provided with an electric shut-off door E, the primary air cooling duct is provided with an electric shut-off door A, the second air duct is provided with an electric shut-off door J, the secondary air cooling duct is provided with an electric shut-off door G, the seventh air duct is provided with an electric shut-off door D, and the eighth air duct is provided with an electric shut-off door F.

7. The method for using the anti-blocking and lifting coupled coal type adaptation system for air preheater of a coal-fired unit according to claim 1 is characterized in that: The steps include: S1, when the air preheater is seriously blocked, when the unit is running at full load, open the flue gas shut-off door on the bypass flue, and part of the flue gas enters the high-efficiency flue gas heat exchanger through the bypass flue, and flows into the SCR denitrification inlet after heat exchange in the high-efficiency flue gas heat exchanger; by adjusting the flue gas regulating door on the bypass flue, the flue gas temperature after passing through the high-efficiency flue gas heat exchanger is reduced to 337℃ when it reaches the SCR inlet; the primary and secondary air temperatures after heating by the high-efficiency flue gas heat exchanger reach 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 pulverized coal pipe is blocked, open the electric shut-off door A on the cold primary air cooling duct, close the electric shut-off door H on the first air duct, open the electric shut-off door J on the second air duct, open the electric shut-off door K on the fourth air duct after the high-efficiency flue gas heat exchanger, and close the electric shut-off door I on the fifth air duct, and at the same time close the electric shut-off door L on the hot primary air cooling duct at the outlet of the original air preheater; S3, when the temperature of the primary air entering the coal mill meets the requirements of the coal mill drying output, due to the need for peak load regulation of the unit, there is a long-term low-load operation or frequent load increase and decrease operation. Under low-load conditions or frequent load increase and decrease operation, the hot secondary air temperature has a greater impact on the flame combustion stability in the furnace. Increasing the hot secondary air temperature can improve the boiler's stable combustion capability; open the electric shut-off door A on the cold primary air cooling duct, close the electric shut-off door H on the first duct, close the electric shut-off door J on the second duct, close the electric shut-off door K on the fourth duct after the high-efficiency flue gas heat exchanger, and at the same time close the electric shut-off door I on the fifth duct, and open the electric shut-off door L on the hot primary air cooling duct at the outlet of the original air preheater.

8. The method according to claim 7, characterized in that In S1, the electric shut-off door A on the primary air cooling duct is closed at the same time, the electric shut-off door H on the first duct is opened, and the electric shut-off door J on the second duct is closed. At the same time, the electric shut-off door K on the fourth duct after the high-efficiency flue gas heat exchanger is closed, and the electric shut-off door I on the fifth duct is opened, so that the primary air passes through the primary fan and enters the first duct; At the same time, close the electric shut-off door G on the secondary air cooling duct, open the electric shut-off door C on the sixth duct, close the electric shut-off door D on the seventh duct, close the electric shut-off door F on the eighth duct at the outlet of the high-efficiency flue gas heat exchanger, and open the electric shut-off door E on the ninth duct.

9. The method according to claim 7, characterized in that: In S2, open the electric shut-off door G on the cold secondary air duct, close the electric shut-off door C on the sixth air duct and the electric shut-off door E on the ninth air duct to ensure that the cold secondary air enters the air preheater for heating first, and at the same time open the electric shut-off door D on the seventh air duct at the outlet of the air preheater, open the electric shut-off door F on the eighth air duct at the outlet of the high-efficiency flue gas heat exchanger, and at the same time close the electric shut-off door B on the original hot secondary air duct.

10. The method according to claim 7, characterized in that In S3, open the electric shut-off door G on the cold secondary air duct, close the electric shut-off door C on the sixth air duct and the electric shut-off door E on the ninth air duct, ensure that the cold secondary air enters the air preheater first for heating, and at the same time open the electric shut-off door D on the seventh air duct at the outlet of the air preheater, open the electric shut-off door F on the eighth air duct at the outlet of the high-efficiency flue gas heat exchanger, and at the same time close the electric shut-off door B on the original hot secondary air duct; at this time, the high-efficiency flue gas heat exchanger only heats the secondary air after the air preheater, adjust the opening of the flue gas regulating door on the bypass flue, and at the same time close the flue gas damper door on the primary air side after the high-efficiency flue gas heat exchanger, and fully open the flue gas damper door on the secondary air side to keep the primary air temperature after the air preheater unchanged, and increase the secondary air temperature after the air preheater to above 430°C.

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