Boiler air and smoke internal circulation system

Abstract

The utility model relates to the technical field of boiler flue gas treatment, and discloses a boiler air and flue gas internal circulation system which comprises a boiler, a first air preheater, a first electric precipitator, a first induced draft fan, a desulfurizing tower, a chimney and a first flue gas recirculation bypass. A first branch bin air outlet of the first air preheater is sequentially communicated with a first electric precipitator, a first induced draft fan, a desulfurizing tower and a chimney; a first flue gas recirculation bypass communicated with a third branch bin air inlet of the first air preheater is arranged at a flue inlet of the first induced draft fan, and a first inlet main air flue of the boiler is communicated with a second branch bin outlet and a third branch bin outlet of the first air preheater. According to the boiler air and smoke internal circulation system, the high-temperature smoke discharge amount can be effectively reduced, the load of a smoke desulfurization system is reduced, heat attached to high-temperature smoke is fully absorbed, smoke discharge heat loss is reduced, and boiler coal consumption is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of boiler flue gas treatment, in particular to a boiler air and flue gas internal circulation system. Background Art

[0002] At present, when the tangential circle combustion, opposed firing and W-shaped flame boilers in thermal power plants and heat and power plants of the power system burn, sufficient air intake needs to be ensured to guarantee the combustion efficiency of the boiler. In the existing technologies, an air intake pipe is mostly directly arranged for the boiler to introduce the outside air into the combustion chamber. A large amount of flue gas generated by the boiler is directly discharged into the atmosphere after denitration, dust removal and desulfurization treatments. Since there are a large number of harmful substances such as nitrogen oxides, sulfur dioxide and dust in the flue gas, direct discharge causes air environmental pollution, and the discharged boiler flue gas has a high temperature, forming a large amount of exhaust heat loss, resulting in a certain amount of heat energy loss and leading to a high coal consumption of the boiler. In addition, when the hot flue gas passes through desulfurization, water evaporation will also be caused, increasing the desulfurization water consumption. Thus, it can be seen that there is a general situation in the current thermal power plants and heat and power plants of the power system that the utilization of the high-temperature flue gas generated by the boiler is insufficient. The high-temperature flue gas is not reused but simply treated and then directly discharged, which not only causes environmental pollution, but also leads to an increase in the coal consumption of the boiler and an increase in the desulfurization water consumption during the desulfurization of the high-temperature flue gas, resulting in an increase in the overall production cost. Content of the Utility Model

[0003] To overcome the problems existing in the related technologies, the utility model provides a boiler air and flue gas internal circulation system, which reforms the original boiler air and flue gas system, adds a flue gas recirculation bypass, reuses the high-temperature flue gas generated by the boiler, so as to reduce the boiler flue gas emission and lower the load of the flue gas desulfurization system. This flue gas recirculation bypass can make full use of the heat of the high-temperature flue gas discharged by the boiler, reduce the exhaust heat loss and lower the coal consumption of the boiler.

[0004] The technical solution adopted by the utility model is as follows: a boiler air and flue gas internal circulation system, including a boiler, a first air preheater, a first electrostatic precipitator, a first induced draft fan, a desulfurization tower and a chimney. The boiler is provided with a first main outlet flue and a first main inlet flue. The first bin air inlet of the first air preheater is communicated with the first main outlet flue, and the first bin air outlet of the first air preheater is sequentially communicated with the first electrostatic precipitator, the first induced draft fan, the desulfurization tower and the chimney;

[0005] The second bin air inlet of the first air preheater is communicated with the air outlet of the first forced draft fan;

[0006] A first flue gas recirculation bypass is arranged at the flue gas inlet of the first induced draft fan, and the first flue gas recirculation bypass is communicated with the third bin air inlet of the first air preheater;

[0007] The hot secondary air at the outlet of the second bin of the first air preheater is mixed with the hot flue gas at the outlet of the third bin of the first air preheater, and the mixed hot flue gas enters the boiler through the first inlet main air duct.

[0008] Further, the first flue gas recirculation bypass includes a first flue gas recirculation mixer and a first flue gas recirculation booster fan. The inlet of the first flue gas recirculation mixer is respectively connected to the first oxygen inlet pipeline and the inlet of the first induced draft fan flue.

[0009] The outlet of the first flue gas recirculation mixer is connected to the inlet of the first flue gas recirculation booster fan, and the outlet of the first flue gas recirculation booster fan is connected to the inlet of the third bin of the first air preheater.

[0010] Further, a first air supply fan to recirculation flue gas slide gate is provided between the outlet of the first air supply fan and the outlet of the first flue gas recirculation booster fan.

[0011] Further, an oxygen production device is also included. The oxygen outlet of the oxygen production device is connected to the first oxygen inlet pipeline, and the first oxygen inlet pipeline is successively provided with an electric valve for the first mixer oxygen inlet pipeline and a regulating valve for the first mixer oxygen inlet pipeline.

[0012] Further, a bypass of the first mixer oxygen inlet pipeline is also provided between the oxygen outlet of the oxygen production device and the inlet of the first flue gas recirculation mixer.

[0013] Further, a first dry desulfurization subsystem is also provided on the first main flue at the outlet of the boiler. Most of the sulfur content is removed by the first dry desulfurization subsystem before the flue gas enters the first air preheater.

[0014] Further, the first flue gas recirculation mixer includes a plurality of nozzles that are evenly distributed along the vertical section of the first flue gas recirculation mixer and cross vertically and horizontally. The nozzles are connected to the oxygen pipeline inside the first flue gas recirculation mixer, and the oxygen pipeline is connected to the oxygen inlet pipeline.

[0015] Further, the inlet of the fourth bin of the first air preheater is connected to the outlet of the primary air fan, and the outlet of the fourth bin of the first air preheater is connected to the inlet of the coal mill. The primary air blown out by the primary air fan enters the coal mill after being heated by the first air preheater, and the pulverized coal is transported into the boiler.

[0016] Further, the boiler air and flue gas internal circulation system includes a second air preheater, a second electrostatic precipitator, a second induced draft fan, and a second flue gas recirculation bypass. The boiler is provided with a second outlet main flue and a second inlet main flue. The second outlet main flue is communicated with the first bin air inlet of the second air preheater. The first bin air outlet of the second air preheater is successively communicated with the second electrostatic precipitator, the second induced draft fan, the desulfurization tower, and the chimney;

[0017] The second bin air inlet of the second air preheater is communicated with the air outlet of the second forced draft fan;

[0018] The second flue gas recirculation bypass is arranged at the inlet of the second induced draft fan flue. The second flue gas recirculation bypass is communicated with the third bin air inlet of the second air preheater; the second inlet main flue is respectively communicated with the second bin air outlet and the third bin air outlet of the second air preheater.

[0019] Further, the second flue gas recirculation bypass includes a second flue gas recirculation mixer and a second flue gas recirculation booster fan. The air inlets of the second flue gas recirculation mixer are respectively communicated with the second oxygen inlet pipeline and the inlet of the second induced draft fan flue;

[0020] The air outlet of the second flue gas recirculation mixer is communicated with the air inlet of the second flue gas recirculation booster fan. The air outlet of the second flue gas recirculation booster fan is communicated with the third bin air inlet of the second air preheater;

[0021] A second forced draft fan to recirculation flue gas slide gate is arranged between the air outlet of the second forced draft fan and the air outlet of the second flue gas recirculation booster fan;

[0022] The second oxygen inlet pipeline is communicated with the oxygen outlet of the oxygen production device. The second oxygen inlet pipeline of the mixer is successively provided with an electric valve for the second oxygen inlet pipeline of the mixer and a regulating valve for the second oxygen inlet pipeline of the mixer;

[0023] A bypass of the second oxygen inlet pipeline of the mixer is further arranged between the oxygen outlet of the oxygen production device and the air inlet of the second flue gas recirculation mixer;

[0024] A second dry desulfurization subsystem is further arranged on the second outlet main flue of the boiler.

[0025] The boiler flue gas internal circulation system of the present utility model has the following technical effects: By transforming the boiler flue gas system, a flue gas recirculation bypass is set at the inlet of the induced draft fan flue. The flue gas recirculation bypass is connected to the oxygen inlet pipeline, which can add oxygen to and mix the recirculated flue gas, solve the problem of insufficient oxygen content in the recirculated flue gas, heat the oxygen-added flue gas through the air preheater and then mix it with the hot secondary air, and then send it into each layer of burners in the boiler again for combustion. In this way, it can effectively reduce the flue gas emission in the boiler, reduce the load of the flue gas desulfurization system, improve the service life of the desulfurization system equipment, and reduce the operation cost of the flue gas treatment system. After the high-temperature flue gas is reused, the attached heat can be absorbed by the boiler, reducing the heat loss of the exhaust gas, reducing the coal consumption of the boiler, and improving the economic benefits of the coal-fired power generation unit.

[0026] Other features and advantages of the present utility model will be described in detail in the subsequent specific implementation section. Brief Description of the Drawings

[0027] The drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. They are used to explain the present disclosure together with the following specific implementation, but do not constitute a limitation to the present disclosure. In the drawings:

[0028] Figure 1 It is a schematic diagram of the overall structure of a boiler flue gas internal circulation system shown according to an exemplary embodiment.

[0029] Figure 2 It is a simplified structural diagram of a vertical cross-section inside a first flue gas recirculation mixer shown according to an exemplary embodiment.

[0030] Figure 3 It is a simplified structural diagram of a horizontal cross-section inside a first flue gas recirculation mixer shown according to an exemplary embodiment.

[0031] Reference numerals: 10, boiler; 11, first outlet main flue; 12, first inlet main air duct; 13, second outlet main flue; 14, second inlet main air duct; 20, first air preheater; 21, second air preheater; 30, primary air blower; 40, first forced draft fan; 41, second forced draft fan; 50, first flue gas recirculation booster fan; 51, second flue gas recirculation booster fan; 60, first flue gas recirculation mixer; 61, second flue gas recirculation mixer; 62, nozzle; 63, oxygen pipeline; 70, first electrostatic precipitator; 71, second electrostatic precipitator; 80, first induced draft fan; 81, second induced draft fan; 90, desulfurization tower; 100, chimney; 110, oxygen production device; 120, electric valve of the oxygen inlet pipeline of the first mixer; 121, electric valve of the oxygen inlet pipeline of the second mixer; 130, regulating valve of the oxygen inlet pipeline of the first mixer; 131, regulating valve of the oxygen inlet pipeline of the second mixer; 140, first dry desulfurization subsystem; 141, second dry desulfurization subsystem; 150, bypass of the oxygen inlet pipeline of the first mixer; 151, bypass of the oxygen inlet pipeline of the second mixer; 160, flap valve from the first forced draft fan to the recirculation flue gas; 161, flap valve from the second forced draft fan to the recirculation flue gas. Detailed implementation manners

[0032] The following will describe in detail the specific implementation manners disclosed by the present utility model with reference to the accompanying drawings. It should be understood that the specific implementation manners described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0033] As Figure 1 shown, it is an exemplary embodiment disclosed by the present utility model. The boiler 10 air and flue gas internal circulation system of the present utility model includes a boiler 10, a first air preheater 20, a first electrostatic precipitator 70, a first induced draft fan 80, a desulfurization tower 90 and a chimney 100. The boiler 10 is provided with a first outlet main flue 11 and a first inlet main air duct 12. The first compartment air inlet of the first air preheater 20 is communicated with the first outlet main flue 11, and the first compartment air outlet of the first air preheater 20 is sequentially communicated with the first electrostatic precipitator 70, the first induced draft fan 80, the desulfurization tower 90 and the chimney 100; the second compartment air inlet of the first air preheater 20 is communicated with the air outlet of the first forced draft fan 40; a first flue gas recirculation bypass is provided at the flue gas inlet of the first induced draft fan 80, and the first flue gas recirculation bypass is communicated with the third compartment air inlet of the first air preheater 20; the hot secondary air at the second compartment outlet of the first air preheater 20 is mixed with the hot flue gas at the third compartment outlet of the first air preheater 20, and the mixed hot flue gas enters the boiler 10 through the first inlet main air duct 12.

[0034] In the flue gas internal circulation system of the boiler 10 of the present utility model, a first flue gas recirculation bypass is provided at the flue gas inlet of the first induced draft fan 80, and the high-temperature flue gas discharged from the first outlet main flue 11 is recycled. On the one hand, the pollutant emissions of the boiler 10 are reduced, and the environmental protection and emission reduction capacity of the boiler 10 is improved. On the other hand, the high-temperature flue gas is re-introduced into the boiler 10 through the first flue gas recirculation bypass, effectively utilizing the heat of the flue gas, reducing the heat loss of the exhaust gas, reducing the coal consumption of the boiler 10, and improving the efficiency of the boiler 10. At the same time, this also reduces the amount of flue gas for desulfurization treatment, reduces the power consumption and water consumption of desulfurization, etc., and improves the economic benefits of coal-fired power generation units.

[0035] Specifically, the first flue gas recirculation bypass includes a first flue gas recirculation mixer 60 and a first flue gas recirculation booster fan 50. The air inlets of the first flue gas recirculation mixer 60 are respectively connected to the first oxygen inlet pipe and the flue gas inlet of the first induced draft fan 80; the air outlet of the first flue gas recirculation mixer 60 is connected to the air inlet of the first flue gas recirculation booster fan 50, and the air outlet of the first flue gas recirculation booster fan 50 is connected to the third bin air inlet of the first air preheater 20.

[0036] A first flue gas recirculation mixer 60 is provided on the first flue gas recirculation bypass. The air inlets of the mixer include an oxygen inlet and a flue gas inlet. One end of the oxygen inlet is connected to the first oxygen inlet pipe, and the other end is connected to the oxygen pipe 63 in the mixer. The flue gas inlet is connected to the flue gas inlet of the first induced draft fan 80. The high-temperature flue gas flows out from the flue gas inlet of the first induced draft fan 80 and enters the mixer through the flue gas inlet, and is mixed with oxygen in the mixer. By adding oxygen to the flue gas for mixing, the problem of insufficient oxygen content in the flue gas is solved, and the oxygen content in the flue gas is increased to about 20%, and then it is sent into the first air preheater 20 for heating through the first flue gas recirculation booster fan 50.

[0037] Exemplarily, in the exemplary embodiment disclosed by the present utility model, the flue gas internal circulation system of the boiler 10 further includes an oxygen production device 110. The oxygen outlet of the oxygen production device 110 is connected to the first oxygen inlet pipe. The first oxygen inlet pipe is sequentially provided with an electric valve 120 for the oxygen inlet pipe of the first mixer and a regulating valve 130 for the oxygen inlet pipe of the first mixer. A bypass 150 for the oxygen inlet pipe of the first mixer is further provided between the oxygen outlet of the oxygen production device 110 and the air inlet of the first flue gas recirculation mixer 60. Further, a flap gate 160 from the first forced draft fan to the recirculation flue gas is provided between the air outlet of the first forced draft fan 40 and the air outlet of the first flue gas recirculation booster fan 50.

[0038] An electric valve and a regulating valve are sequentially arranged on the first oxygen inlet pipeline. Corresponding flow meters are arranged at the flue gas inlet and outlet of the first flue gas recirculation mixture. The regulating valve calculates the required oxygen amount based on the flue gas flow rate at the flue gas inlet and the oxygen content in the flue gas at the outlet of the first flue gas recirculation mixer 60 and adjusts it accordingly. If the oxygen content in the flue gas at the outlet of the first flue gas recirculation mixer 60 is relatively high, the regulating valve 130 of the oxygen inlet pipeline of the first mixer is closed. If the oxygen content in the flue gas at the outlet of the first flue gas recirculation mixer 60 is relatively low, the regulating valve 130 of the oxygen inlet pipeline of the first mixer is opened. When the oxygen content in the flue gas at the outlet of the first flue gas recirculation mixer 60 is relatively low and the regulating valve 130 of the oxygen inlet pipeline of the first mixer is fully open, at this time, the air volume of the flue gas entering the first flue gas recirculation mixer 60 is reduced, and the bypass 150 of the oxygen inlet pipeline of the first mixer is opened if necessary. An electric slide gate is arranged between the outlet of the first flue gas recirculation booster fan 50 and the outlet of the first forced draft fan 40. When the first flue gas recirculation booster fan 50 fails, the electric slide gate can be opened to supply air to the boiler 10 through the forced draft fan to ensure the air supply volume of the boiler 10.

[0039] Exemplarily, such as Figure 2 、 Figure 3 As shown, in the exemplary embodiment disclosed by the present utility model, the first flue gas recirculation mixer 60 includes a plurality of nozzles 62 that are uniformly distributed along the vertical section of the first flue gas recirculation mixer 60 and cross vertically and horizontally. The nozzles 62 are communicated with the oxygen pipeline 63 inside the first flue gas recirculation mixer 60, and the oxygen pipeline 63 is communicated with the oxygen inlet pipeline.

[0040] Inside the first flue gas recirculation mixer 60, a plurality of nozzles 62 that are uniformly distributed along the vertical section of the mixer and cross vertically and horizontally spray oxygen towards the flue gas airflow inside the mixer from all directions to ensure the full mixing of the flue gas and oxygen. The oxygen pipeline 63 and the nozzles 62 inside the mixer are made of stainless steel to prevent corrosion and improve safety.

[0041] Exemplarily, such as Figure 1 As shown, the air and flue gas internal circulation system of the boiler 10 of the present utility model further includes a first dry desulfurization subsystem 140 on the main flue 11 at the first outlet of the boiler 10. Most of the sulfur content is removed by the first dry desulfurization subsystem 140 before the flue gas enters the first air preheater 20.

[0042] In the air and flue gas internal circulation system of the boiler 10 of the present utility model, the amount of flue gas recirculation depends on the oxygen production capacity of the oxygen production device 110. When the boiler 10 is at low load, the oxygen content in the recirculated flue gas can exceed 21% to achieve oxygen-enriched combustion, so as to improve the combustion efficiency of the boiler 10 and enhance the economy. When the boiler 10 is at high load, the oxygen content in the recirculated flue gas is about 20%. If the oxygen production capacity can meet the requirement, the recirculated flue gas volume can reach more than 50% of the total flue gas volume. If the recirculated flue gas volume is increased to about 90% of the total flue gas volume, the first dry desulfurization subsystem 140 needs to be put into use. The flue gas needs to pass through the first dry desulfurization subsystem 140 first to remove most of the sulfur in the flue gas, ensuring that the sulfur content of the flue gas entering the flue gas recirculation bypass is not too high, and the flue gas discharged into the desulfurization tower 90 undergoes wet desulfurization to meet the environmental protection ultra-low emission requirements. In this way, the amount of pollutants discharged into the atmosphere will be greatly reduced, achieving the effect of environmental protection and energy conservation.

[0043] Exemplarily, the air inlet of the fourth bin of the first air preheater 20 in the air and flue gas internal circulation system of the boiler 10 of the present utility model is communicated with the air outlet of the primary air fan 30, and the air outlet of the fourth bin of the first air preheater 20 is communicated with the air inlet of the coal mill. The primary air blown out by the primary air fan 30 enters the coal mill after being heated by the first air preheater 20, and conveys pulverized coal into the boiler 10.

[0044] The first air preheater 20 in the air and flue gas internal circulation system of the boiler 10 of the present utility model is a four-bin rotary air preheater. The air inlet of the fourth bin of this air preheater is communicated with the air outlet of the primary air fan 30, which is used to heat the primary air blown out by the primary air fan 30. The air outlet of the fourth bin is communicated with the air inlet of the coal mill. The primary hot air blown out from the fourth bin is used to convey pulverized coal into the boiler 10, ensuring the combustion efficiency of the pulverized coal after it enters the boiler 10.

[0045] Exemplarily, as Figure 1 shown, in the exemplary embodiment disclosed by the present utility model, the air and flue gas internal circulation system of the boiler 10 includes a second air preheater 21, a second electrostatic precipitator 71, a second induced draft fan 81, and a second flue gas recirculation bypass. The boiler 10 is provided with a second outlet main flue 13 and a second inlet main flue 14. The second outlet main flue 13 is communicated with the air inlet of the first bin of the second air preheater 21. The air outlet of the first bin of the second air preheater 21 is successively communicated with the second electrostatic precipitator 71, the second induced draft fan 81, the desulfurization tower 90, and the chimney 100. The air inlet of the second bin of the second air preheater 21 is communicated with the air outlet of the second forced draft fan 41. A second flue gas recirculation bypass is provided at the flue gas inlet of the second induced draft fan 81, and the second flue gas recirculation bypass is communicated with the air inlet of the third bin of the second air preheater 21. The second inlet main flue 14 is respectively communicated with the air outlets of the second bin and the third bin of the second air preheater 21.

[0046] Exemplarily, the second flue gas recirculation bypass includes a second flue gas recirculation mixer 61 and a second flue gas recirculation booster fan 51. The inlet of the second flue gas recirculation mixer 61 is respectively communicated with the second oxygen content inlet pipeline and the flue inlet of the second induced draft fan 81; the outlet of the second flue gas recirculation mixer 61 is communicated with the inlet of the second flue gas recirculation booster fan 51, and the outlet of the second flue gas recirculation booster fan 51 is communicated with the air inlet of the third bin of the second air preheater 21; a second air supply fan to recirculation flue gas slide gate 161 is provided between the outlet of the second air supply fan 41 and the outlet of the second flue gas recirculation booster fan 51; the second oxygen content inlet pipeline is communicated with the oxygen outlet of the oxygen production device 110, and the second oxygen content inlet pipeline of the mixer is successively provided with an electric valve 121 and a regulating valve 131 for the second oxygen content inlet pipeline of the mixer; a bypass 151 of the second oxygen content inlet pipeline of the mixer is further provided between the oxygen outlet of the oxygen production device 110 and the inlet of the second flue gas recirculation mixer 61; a second dry desulfurization subsystem 141 is further provided on the second main flue 13 at the second outlet of the boiler 10.

[0047] The air and flue gas internal circulation system of the boiler 10 of the present utility model includes main and standby flue gas exhaust pipelines such as a first air preheater 20, a first electrostatic precipitator 70, a first induced draft fan 80, a first flue gas recirculation bypass, a second air preheater 21, a second electrostatic precipitator 71, a second induced draft fan 81 and a second flue gas recirculation bypass, and main and standby flue gas recirculation bypasses. It can ensure that when a failure occurs in one of the flue gas exhaust pipelines or flue gas recirculation bypasses, the other flue gas exhaust pipeline and flue gas recirculation bypass can continue to operate, ensuring that the boiler 10 will not stop production due to a failure in one of them. The main and standby flue gas exhaust pipelines and main and standby flue gas recirculation bypasses of the air and flue gas internal circulation system of the boiler 10 of the present utility model can be put into production simultaneously, improving the flue gas exhaust efficiency and flue gas recirculation efficiency of the air and flue gas internal circulation system of the boiler 10, thereby improving the combustion efficiency of the boiler 10.

[0048] The preferred embodiments of the present disclosure have been described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0049] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination manners.

[0050] In addition, any combination can be made between various different embodiments of the present disclosure as long as it does not violate the idea of the present disclosure, and it should also be regarded as the content disclosed by the present disclosure.

Claims

1. A boiler air and smoke internal circulation system, characterized in that The boiler air and smoke internal circulation system comprises: a boiler, a first air preheater, a first electrostatic precipitator, a first induced draft fan, a desulfurization tower and a chimney. The boiler is provided with a first outlet main flue and a first inlet main flue. The first compartment air inlet of the first air preheater is connected to the first outlet main flue. The first compartment air outlet of the first air preheater is connected to the first electrostatic precipitator, the first induced draft fan, the desulfurization tower and the chimney in sequence. The second compartment air inlet of the first air preheater is connected to the air outlet of the first blower; A first flue gas recirculation bypass is provided at the inlet of the first induced draft fan flue, and the first flue gas recirculation bypass is connected to the third compartment air inlet of the first air preheater; The hot secondary air at the second compartment outlet of the first air preheater is mixed with the hot flue gas at the third compartment outlet of the first air preheater, and the mixed hot flue gas enters the boiler through the first inlet main air duct.

2. The boiler air and smoke internal circulation system according to claim 1 is characterized in that The first flue gas recirculation bypass includes a first flue gas recirculation mixer and a first flue gas recirculation booster fan, and the air inlet of the first flue gas recirculation mixer is respectively connected to the first oxygen inlet duct and the first induced draft fan flue inlet; The air outlet of the first flue gas recirculation mixer is communicated with the air inlet of the first flue gas recirculation booster fan, and the air outlet of the first flue gas recirculation booster fan is communicated with the air inlet of the third compartment of the first air preheater.

3. The boiler air and smoke internal circulation system according to claim 2 is characterized in that A first blower to recirculating flue gas plug-in door is provided between the first blower outlet and the first flue gas recirculation booster blower outlet.

4. The boiler air and smoke internal circulation system according to claim 2 is characterized in that , also includes an oxygen production device, the oxygen outlet of the oxygen production device is connected to the first oxygen inlet pipeline, and the first oxygen inlet pipeline is sequentially provided with a first mixer oxygen inlet pipeline electric door and a first mixer oxygen inlet pipeline regulating door.

5. The boiler air and smoke internal circulation system according to claim 4 is characterized in that A first mixer oxygen inlet pipeline bypass is also provided between the oxygen outlet of the oxygen production device and the air inlet of the first flue gas recirculation mixer.

6. The boiler air and smoke internal circulation system according to claim 1 is characterized in that A first dry desulfurization subsystem is also provided on the main flue of the first outlet of the boiler, and most of the sulfur in the flue gas is removed by the first dry desulfurization subsystem before entering the first air preheater.

7. The boiler air and smoke internal circulation system according to claim 2 is characterized in that The first flue gas recirculation mixer includes a plurality of nozzles evenly distributed along the vertical section of the first flue gas recirculation mixer and crossed horizontally and vertically. The nozzles are connected to the oxygen pipe in the first flue gas recirculation mixer, and the oxygen pipe is connected to the oxygen inlet pipe.

8. The boiler air and smoke internal circulation system according to claim 1 is characterized in that The fourth compartment air inlet of the first air preheater is connected to the air outlet of the primary air fan, and the fourth compartment air outlet of the first air preheater is connected to the air inlet of the coal mill. The primary air blown out by the primary fan is heated by the first air preheater and then enters the coal mill to transport the coal powder into the boiler.

9. The boiler air and smoke internal circulation system according to claim 4 is characterized in that The boiler air and smoke internal circulation system includes a second air preheater, a second electrostatic precipitator, a second induced draft fan and a second flue gas recirculation bypass. The boiler is provided with a second outlet main flue and a second inlet main flue. The second outlet main flue is connected to the first compartment air inlet of the second air preheater, and the first compartment air outlet of the second air preheater is connected to the second electrostatic precipitator, the second induced draft fan, the desulfurization tower and the chimney in sequence; The second compartment air inlet of the second air preheater is connected to the air outlet of the second air blower; The second flue gas recirculation bypass is arranged at the inlet of the second induced draft fan flue, and the second flue gas recirculation bypass is connected to the third compartment air inlet of the second air preheater; the second inlet main air duct is respectively connected to the second compartment air outlet and the third compartment air outlet of the second air preheater.

10. The boiler air and smoke internal circulation system according to claim 9, characterized in that The second flue gas recirculation bypass includes a second flue gas recirculation mixer and a second flue gas recirculation booster fan, and the air inlet of the second flue gas recirculation mixer is respectively connected to the second oxygen inlet duct and the second induced draft fan flue inlet; The air outlet of the second flue gas recirculation mixer is communicated with the air inlet of the second flue gas recirculation booster fan, and the air outlet of the second flue gas recirculation booster fan is communicated with the air inlet of the third compartment of the second air preheater; A second blower to recirculating flue gas plug-in door is provided between the second blower outlet and the second flue gas recirculating booster blower outlet; The second oxygen inlet pipeline is in communication with the oxygen outlet of the oxygen production device, and the second oxygen inlet pipeline is provided with a second mixer oxygen inlet pipeline electric door and a second mixer oxygen inlet pipeline regulating door in sequence; A second mixer oxygen inlet pipeline bypass is also provided between the oxygen outlet of the oxygen production device and the air inlet of the second flue gas recirculation mixer; A second dry desulfurization subsystem is also provided on the second outlet main flue of the boiler.

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