Boiler system capable of recycling flue gas

Abstract

The invention discloses a boiler system capable of recycling flue gas, and relates to the technical field of thermal power generation, the boiler system comprises a main flue and a flue gas recycling assembly; the main flue is communicated with the hearth and the air preheater, and a heat exchanger and a denitration reactor are sequentially arranged in the main flue in the extending direction of the air preheater; the flue gas recirculation assembly comprises a primary air spraying inlet and a secondary air spraying inlet which are connected with the hearth, the flue gas recirculation assembly is connected to the flue gas extraction opening, and the flue gas extraction opening is formed in the main flue; the flue gas recirculation assembly reuses the flue gas in the main flue before being discharged, and the flue gas passes through the primary air spraying inlet and the secondary air spraying inlet again and is introduced into the hearth, so that the discharge of the flue gas and the loss of heat in the hearth are reduced, and the utilization rate of the flue gas is improved. And the requirement for the smoke flow speed of a convection heat exchange surface area in the hearth is met through the primary air spraying inlet and the secondary air spraying inlet, and the high-temperature environment of a combustion area in the hearth is maintained.

Description

Technical Field

[0001] The invention relates to the technical field of thermal power generation, and in particular to a boiler system capable of flue gas recirculation. Background Art

[0002] With the changes in energy structure and the rapid development of new energy, the positioning of coal-fired thermal power units in the power system will change from basic power and main power to supporting and regulating power. In order to respond to the call and adapt to market changes, a large number of coal-fired units have been transformed to improve flexibility, and the peak load depth of some units has reached less than 20%. Long-term (ultra) low-load operation will become the norm, and (ultra) low-load operation will cause the unit's power generation coal consumption to rise sharply, which is more than 100g / kWh higher than normal.

[0003] When a coal-fired boiler is running at (ultra) low load, the total heat exchange area remains unchanged, the exothermic working medium and the heat absorbing working medium are greatly reduced, and the boiler efficiency should be improved in theory. When running under ultra-low conditions, due to the influence of factors such as combustion organization and high-temperature corrosion, the oxygen content of the flue gas can even be as high as about 10%. Compared with 1-2% under normal high-load operation, the flue gas volume has increased by 70-80% compared with the flue gas volume under normal conditions. The main reason for the increase in flue gas heat loss has changed from high flue gas temperature to large flue gas volume. The flue gas oxygen content of about 10% will cause the boiler flue gas heat loss to increase by 2-3%, and at the same time increase the auxiliary power consumption, which is the main reason for the reduction of boiler efficiency when running at (ultra) low load.

[0004] Therefore, how to reduce the amount of flue gas emitted by the boiler and the heat loss of the flue gas is a technical problem that technical personnel in this field currently need to solve. Summary of the invention

[0005] The object of the present invention is to provide a boiler system capable of flue gas recirculation, which can reduce the amount of flue gas discharged by the boiler and the heat loss of the flue gas.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A boiler system capable of flue gas recirculation, comprising:

[0008] The main flue is connected to the furnace and the air preheater, and a heat exchanger and a denitration reactor are sequentially arranged in the main flue in a direction extending toward the air preheater;

[0009] The flue gas recirculation component comprises a primary air injection inlet and a secondary air injection inlet connected to the furnace. The flue gas recirculation component is connected to a flue gas extraction port, and the flue gas extraction port is arranged on the main flue.

[0010] Preferably, the heat exchanger comprises: a platen superheater, a high temperature reheater, a low temperature reheater, a low temperature superheater and an economizer which are arranged in sequence and at intervals;

[0011] A side flue is arranged on the main flue, both ends of the side flue are connected to the main flue, and the side flue is connected to the inlet of the low-temperature reheater and the denitrification reactor.

[0012] Preferably, when the flue gas temperature at the economizer is higher than a preset temperature, the flue gas extraction port is arranged on the main flue between the low-temperature reheater and the economizer, and the side flue is closed.

[0013] Preferably, when the flue gas temperature at the economizer is lower than a preset temperature, the flue gas extraction port is arranged at the inlet of the denitrification reactor or at the outlet of the denitrification reactor, and the side flue is opened.

[0014] Preferably, the flue gas recirculation component comprises:

[0015] A primary dust removal device is connected to the smoke extraction port and is used to filter dust in the passing smoke;

[0016] A primary booster fan, one end of which is connected to the primary dust removal device, and the other end of which is connected to the secondary air injection inlet;

[0017] Coal mill, the inlet of the coal mill is connected with the first-stage booster fan, and the outlet of the coal mill is connected with the primary air injection inlet.

[0018] Preferably, the flue gas recirculation component comprises:

[0019] A primary dust removal device is connected to the smoke extraction port and is used to filter dust in the passing smoke;

[0020] A primary booster fan, one end of which is connected to the primary dust removal device, and the other end of which is connected to the secondary air injection inlet;

[0021] The coal mill has its outlet connected to the primary air injection inlet and the first-stage booster fan respectively.

[0022] Preferably, a secondary dust removal device and a secondary booster fan are sequentially arranged between the primary booster fan and the inlet of the coal mill.

[0023] Preferably, a secondary dust removal device and a secondary booster fan are sequentially arranged between the primary booster fan and the outlet of the coal mill.

[0024] Preferably, a temperature sensor is provided on the inner wall of the main flue close to the economizer, and the temperature sensor is used to detect the temperature of the flue gas passing therethrough.

[0025] Preferably, the first-stage booster fan and the second-stage booster fan are high-temperature fans that can withstand high temperatures.

[0026] Compared with the above-mentioned background technology, the present invention provides a boiler system with flue gas recirculation, comprising: a main flue and a flue gas recirculation component; the main flue connects the furnace and the air preheater, and a heat exchanger and a denitrification reactor are sequentially arranged in the main flue in the direction extending toward the air preheater; the flue gas recirculation component comprises a primary air injection inlet and a secondary air injection inlet connected to the furnace, and the flue gas recirculation component is connected to a flue gas extraction port, and the flue gas extraction port is arranged on the main flue.

[0027] Specifically, a large amount of flue gas will be generated when the boiler system is running at (ultra) low load, and the flue gas will carry a large amount of heat along the main flue. The flue gas will exchange heat when passing through the heat exchanger, transfer the heat it carries to the heat exchanger, and then continue to pass through the denitrification reactor and finally be discharged through the air preheater. In order to reduce flue gas emissions and reduce heat loss caused by flue gas discharge, a flue gas recirculation component is connected to the main flue. The flue gas recirculation component reuses the flue gas in the main flue before it is discharged, and connects it to the furnace through the primary air inlet and the secondary air inlet again. In this way, not only the flue gas emissions and heat loss in the furnace are reduced, but also the flue gas flow rate in the convection heat exchange surface area in the furnace is met through the primary air inlet and the secondary air inlet, thereby maintaining a high temperature environment in the combustion area in the furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0029] Figure 1 A structural principle diagram of a boiler system when the flue gas temperature at the economizer provided by an embodiment of the present invention is higher than a preset temperature;

[0030] Figure 2 A structural principle diagram of a case where the flue gas temperature at the economizer provided by an embodiment of the present invention is lower than a preset temperature;

[0031] Figure 3 A schematic diagram of the structure of a flue gas recirculation assembly in which a flue gas extraction port is connected to a coal mill inlet provided in an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the structure of a flue gas recirculation component in which a flue gas extraction port is connected to a coal mill outlet provided in an embodiment of the present invention.

[0033] in:

[0034] 100-main flue, 110-furnace, 111-primary air injection inlet, 112-secondary air injection inlet, 120-air preheater, 131-screen superheater, 132-high temperature reheater, 133-low temperature reheater, 134-low temperature superheater, 135-economizer, 140-denitrification reactor;

[0035] 200- flue gas recirculation assembly, 210- flue gas extraction port, 220- primary dust removal device, 230- primary booster fan, 240- coal mill, 241- cold primary air duct, 242- hot primary air duct, 243- coal feeding pipe, 250- secondary dust removal device, 260- secondary booster fan;

[0036] 300-Side flue. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not 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.

[0038] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0039] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the position or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as a limitation of the present invention.

[0040] The object of the present invention is to provide a boiler system capable of flue gas recirculation, which can reduce the amount of flue gas discharged by the boiler and the heat loss of the flue gas.

[0041] To achieve the above object, the present invention provides the following technical solutions:

[0042] See also Figures 1 to 4The present embodiment provides a boiler system capable of flue gas recirculation, comprising: a main flue 100 and a flue gas recirculation component 200; the main flue 100 is connected to the furnace 110 and the air preheater 120, and a heat exchanger and a denitrification reactor 140 are sequentially arranged in the main flue 100 in the direction extending toward the air preheater 120; the flue gas recirculation component 200 comprises a primary air injection inlet 111 and a secondary air injection inlet 112 connected to the furnace 110, and the flue gas recirculation component 200 is connected to a flue gas extraction port 210, and the flue gas extraction port 210 is arranged on the main flue 100.

[0043] Specifically, a large amount of flue gas will be generated when the boiler system is running at (ultra) low load, and the flue gas will move along the main flue 100 with a large amount of heat. The flue gas will exchange heat when passing through the heat exchanger, transfer the heat it carries to the heat exchanger, and then continue to move through the denitrification reactor 140 and finally be discharged through the air preheater 120. In order to reduce the emission of flue gas and reduce the heat loss caused by the exhaust of flue gas, a flue gas recirculation component 200 is connected to the main flue 100. The flue gas recirculation component 200 reuses the flue gas in the main flue 100 before it is discharged, and connects it to the inside of the furnace 110 again through the primary air inlet 111 and the secondary air inlet 112. In this way, not only the emission of flue gas and the heat loss in the furnace 110 are reduced, but also the flue gas flow rate in the convection heat exchange surface area in the furnace 110 is met through the primary air inlet 111 and the secondary air inlet 112, and the high temperature environment of the combustion area in the furnace 110 is maintained.

[0044] Among them, in order to ensure the combustion stability of the boiler during flue gas recirculation, the recirculated flue gas should, on the one hand, be higher than the temperature of the original hot primary and secondary air leading to the furnace 110, but not too high, and cannot exceed the temperature resistance of the remaining equipment in the boiler system. If the flue gas temperature exceeds 500°C, it will have an adverse effect on the supporting equipment; at the same time, the flue gas after the air preheater 120 cannot be used as the circulating flue gas, because the low temperature is not conducive to organizing combustion in the furnace 110; therefore, in this embodiment, a flue gas recirculation component 200 is connected to the main flue 100, and the flue gas in the main flue 100 is reused before being discharged, and connected to the primary air injection inlet 111 and the secondary air injection inlet 112; of course, the position of the flue gas extraction port 210 needs to be selected according to the actual situation, and it is necessary to ensure that the temperature of the flue gas entering the flue gas recirculation component 200 is appropriate.

[0045] With such arrangement, part of the primary and secondary air originally injected into the furnace 110 can be replaced by the recycled and reused flue gas, so as to ensure low-oxygen combustion under the premise of stable combustion in the furnace 110, reduce the oxygen content of the flue gas and the total flue gas volume; at the same time, the flue gas flow rate in the convection heat exchange surface area is increased through the primary air injection inlet 111 and the secondary air injection inlet 112, so as to prevent the problem of low or large deviation of the main steam temperature and the reheat steam temperature of the boiler, solve the problem of a sharp decrease in boiler efficiency caused by a large amount of flue gas emissions when the boiler is running at (ultra) low load, and reduce its energy consumption.

[0046] Preferably, the heat exchanger includes: a screen superheater 131, a high-temperature reheater 132, a low-temperature reheater 133, a low-temperature superheater 134 and an economizer 135 which are arranged in sequence and at intervals; a side flue 300 is arranged on the main flue 100, both ends of the side flue 300 are connected to the main flue 100, and the side flue 300 is connected to the inlet of the low-temperature reheater 133 and the denitrification reactor 140.

[0047] like Figure 1 and Figure 2 As shown, in the passage along the main flue 100 from the furnace 110 to the air preheater 120, a screen superheater 131, a high-temperature reheater 132, a low-temperature reheater 133, a low-temperature superheater 134 and an economizer 135 are arranged in sequence and at intervals. These heat exchangers are filled with water to absorb the heat generated by the combustion in the furnace 110.

[0048] In this embodiment, a side branch pipe connecting the low-temperature reheater 133 and the inlet of the denitrification reactor 140 is also provided on the main flue 100. In this way, the side branch pipe can connect the flue gas in the main flue 100 that has not passed through all the heat exchangers to the inlet of the denitrification reactor 140 from the side flue 300 in advance.

[0049] Preferably, when the flue gas temperature at the economizer 135 is higher than a preset temperature, the flue gas extraction port 210 is provided on the main flue 100 between the low-temperature reheater 133 and the economizer 135, and the side flue 300 is closed.

[0050] It is understandable that since it is necessary to ensure that the temperature of the flue gas entering the flue gas recirculation component 200 is not too low, it is necessary to make appropriate choices for the position of the flue gas extraction port 210 and the opening of the side flue 300; when the flue gas temperature at the economizer 135 is higher than the preset temperature, that is, when the temperature of the flue gas in the main flue 100 reaching the inlet of the denitrification reactor 140 after passing through the heat exchanger is not too low, the side flue 300 can be closed, and the flue gas extraction port 210 can be selected at the last economizer 135 in the heat exchanger.

[0051] Preferably, when the flue gas temperature at the economizer 135 is lower than a preset temperature, the flue gas extraction port 210 is disposed at the inlet of the denitration reactor 140 or at the outlet of the denitration reactor 140, and the side flue 300 is opened.

[0052] When the flue gas temperature at the economizer 135 is lower than the preset temperature, that is, when the temperature of the flue gas in the main flue 100 is too low when reaching the inlet of the denitrification reactor 140 after passing through the heat exchanger, the side flue 300 is opened to allow the flue gas in the main flue 100 that has not passed through all the heat exchangers to directly pass into the inlet of the denitrification reactor 140 and mix with the flue gas with too low temperature in the main flue 100. In this way, the flue gas with increased temperature can enter the flue gas recirculation component 200 through the flue gas extraction port 210; wherein, the denitrification reactor 140 in this embodiment does not reduce the temperature of the passing flue gas. Therefore, at this time, the flue gas extraction port 210 can select the inlet or outlet of the denitrification reactor 140, which is not specifically limited in this article.

[0053] Preferably, the flue gas recirculation component 200 includes: a primary dust removal device 220, a primary booster fan 230 and a coal mill 240; the primary dust removal device 220 is connected to the flue gas extraction port 210, and is used to filter dust passing through the flue gas; one end of the primary booster fan 230 is connected to the primary dust removal device 220, and the other end is connected to the secondary air injection inlet 112; the coal mill 240; the inlet of the coal mill 240 is connected to the primary booster fan 230, and the outlet of the coal mill 240 is connected to the primary air injection inlet 111.

[0054] like Figure 3 As shown, this article provides an embodiment of a flue gas recirculation component 200, and the flue gas recirculation component 200 includes a primary dust removal device 220 and a primary booster fan 230 connected in sequence, and the primary dust removal device 220 is connected to the flue gas extraction port 210; the flue gas coming out of the flue gas extraction port 210 is firstly dusted by the primary dust removal device 220, and then pressurized by the primary booster fan 230 to meet the pressure requirement for entering the secondary air injection inlet 112, and then injected into the furnace 110 from the secondary air injection inlet 112; in addition, this embodiment is suitable for the situation where the drying output of the coal mill 240 is insufficient, and a part of the flue gas after being pressurized by the primary booster fan 230 is mixed with the cold air of the cold primary air duct 241, the hot air of the hot primary air duct 242 and the coal powder in the coal feeding pipe 243, and is passed into the coal feeder, and the outlet of the coal mill 240 is connected to the primary air injection inlet 111.

[0055] Preferably, the flue gas recirculation component 200 includes: a primary dust removal device 220, a primary booster fan 230 and a coal mill 240; the primary dust removal device 220 is connected to the flue gas extraction port 210, and is used to filter dust passing through the flue gas; one end of the primary booster fan 230 is connected to the primary dust removal device 220, and the other end is connected to the secondary air injection inlet 112; the coal mill 240 and the outlet of the coal mill 240 are respectively connected to the primary air injection inlet 111 and the primary booster fan 230.

[0056] like Figure 4 As shown, the present application also provides an embodiment of a flue gas recirculation component 200 suitable for a coal mill 240 with sufficient drying output. In this embodiment, the connection method of the first-stage dust removal device 220 and the first-stage booster fan 230 is the same as the above-mentioned embodiment. The flue gas coming out of the flue gas extraction port 210 is firstly dust-removed by the first-stage dust removal device 220, and then pressurized by the first-stage booster fan 230 to meet the pressure requirement for entering the secondary air injection inlet 112, and then injected into the furnace 110 from the secondary air injection inlet 112; however, a part of the flue gas after being pressurized by the first-stage booster fan 230 is not passed into the inlet of the coal mill 240, but is directly connected to the outlet of the coal mill 240 and connected to the primary air injection inlet 111.

[0057] Preferably, a secondary dust removal device 250 and a secondary booster fan 260 are sequentially arranged between the primary booster fan 230 and the inlet of the coal mill 240 .

[0058] It can be understood that in the above two embodiments of the flue gas recirculation component 200, a dust removal device is provided to filter the dust in the flue gas to prevent the dust from entering the booster fan and reducing its service life. Therefore, in order to further reduce the dust in the flue gas, a secondary dust removal device 250 and a secondary booster fan 260 are successively provided between the inlet of the primary booster fan 230 and the coal mill 240. The secondary dust removal device 250 and the secondary booster fan 260 further filter and pressurize the flue gas to meet the requirements of flue gas recycling.

[0059] Preferably, a temperature sensor is provided on the inner wall of the main flue 100 close to the economizer 135, and the temperature sensor is used to detect the temperature of the flue gas passing therethrough.

[0060] It can be understood that in order to accurately determine whether the flue gas extracted by the flue gas extraction port 210 meets the requirements, a temperature sensor can be installed on the inner wall of the main flue 100 near the economizer 135. The temperature sensor is used to detect the temperature of the passing flue gas. In this way, the staff can select the position of the flue gas extraction port 210 more accurately.

[0061] Preferably, the first-stage boost fan 230 and the second-stage boost fan 260 are high-temperature fans that can withstand high temperatures.

[0062] It can be understood that in order to prevent the first-stage booster fan 230 and the second-stage booster fan 260 from being damaged due to the high temperature of the flue gas during use, in the above two embodiments of the flue gas recirculation component 200, the first-stage booster fan 230 and the second-stage booster fan 260 are preferably high-temperature fans that can withstand high temperatures.

[0063] It should be noted that, in this specification, relational terms such as first and second are merely used to distinguish one entity from other entities, but do not necessarily require or imply any actual relationship or order between these entities.

[0064] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0065] The embodiments provided by the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A boiler system capable of flue gas recirculation, characterized in that: include: A main flue (100) is connected to the furnace (110) and the air preheater (120); a heat exchanger and a denitration reactor (140) are sequentially arranged in the main flue (100) in a direction extending toward the air preheater (120); A flue gas recirculation component (200) comprises a primary air injection inlet (111) and a secondary air injection inlet (112) connected to the furnace (110); the flue gas recirculation component (200) is connected to a flue gas extraction port (210); and the flue gas extraction port (210) is arranged on the main flue (100).

2. The boiler system with flue gas recirculation according to claim 1, characterized in that: The heat exchanger comprises: a screen superheater (131), a high-temperature reheater (132), a low-temperature reheater (133), a low-temperature superheater (134), and an economizer (135) which are arranged in sequence and at intervals; The main flue (100) is provided with a side flue (300), both ends of the side flue (300) are connected to the main flue (100), and the side flue (300) is connected to the low-temperature reheater and the inlet of the denitration reactor (140).

3. The boiler system with flue gas recirculation according to claim 2, characterized in that: When the flue gas temperature at the economizer (135) is higher than a preset temperature, the flue gas extraction port (210) is arranged on the main flue (100) between the low-temperature reheater and the economizer (135), and the side flue (300) is closed.

4. The boiler system with flue gas recirculation according to claim 2, characterized in that: When the flue gas temperature at the economizer (135) is lower than a preset temperature, the flue gas extraction port (210) is arranged at the inlet of the denitration reactor (140) or at the outlet of the denitration reactor (140), and the side flue (300) is opened.

5. The boiler system with flue gas recirculation according to claim 3 or 4, characterized in that: The flue gas recirculation component (200) comprises: A primary dust removal device (220), connected to the smoke extraction port (210), and used for filtering dust in the smoke; A primary booster fan (230), one end of which is connected to the primary dust removal device (220), and the other end of which is connected to the secondary air injection inlet (112); A coal mill (240), wherein the inlet of the coal mill (240) is connected to the primary booster fan (230), and the outlet of the coal mill (240) is connected to the primary air injection inlet (111).

6. The boiler system with flue gas recirculation according to claim 3 or 4, characterized in that: The flue gas recirculation component (200) comprises: A primary dust removal device (220), connected to the smoke extraction port (210), and used for filtering dust in the passing smoke; A primary booster fan (230), one end of which is connected to the primary dust removal device (220), and the other end of which is connected to the secondary air injection inlet (112); A coal mill (240), wherein an outlet of the coal mill (240) is respectively connected to the primary air injection inlet (111) and the primary booster fan (230).

7. The boiler system with flue gas recirculation according to claim 5, characterized in that: A secondary dust removal device (250) and a secondary booster fan (260) are sequentially arranged between the primary booster fan (230) and the inlet of the coal mill (240).

8. The boiler system capable of flue gas recirculation according to claim 6, characterized in that: A secondary dust removal device (250) and a secondary booster fan (260) are sequentially arranged between the primary booster fan (230) and the outlet of the coal mill (240).

9. The boiler system with flue gas recirculation according to claim 3, characterized in that: A temperature sensor is provided on the inner wall of the main flue (100) close to the economizer (135), and the temperature sensor is used to detect the temperature of the flue gas passing through.

10. The boiler system capable of flue gas recirculation according to claim 7, characterized in that: The first-stage booster fan (230) and the second-stage booster fan (260) are specifically high-temperature fans that can withstand high temperatures.

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