Tail afterburning system and method for increasing SCR inlet smoke temperature

Abstract

The invention discloses a tail afterburning system and method for increasing SCR inlet smoke temperature, the tail afterburning system comprises a boiler and a combustion chamber for mixed combustion of hydrogen and air, an economizer is arranged on a smoke channel of the boiler, a tail flue of the boiler is connected with a smoke inlet of an SCR denitration device, a smoke outlet of the combustion chamber is connected with the tail flue through a third bypass flue, and the third bypass flue is connected with the tail flue through a fourth bypass flue. The combustion chamber is connected with an outlet flue of an air pre-heater of the boiler through a second bypass flue, an induced draft fan is arranged in the second bypass flue, and the induced draft fan is used for feeding smoke in the outlet flue of the air pre-heater into the combustion chamber. The bypass flue and the oxyhydrogen burner are arranged at the tail, afterburning is conducted through the tail burner, hot flue gas obtained after afterburning enters the tail flue to be mixed with low-temperature flue gas, the SCR inlet temperature is effectively increased, it is ensured that SCR is normally put into operation, carbon emission is reduced, and emission control over pollution gas under the low load of a coal-fired unit is effectively achieved.

Description

Technical Field

[0001] The invention belongs to the field of coal-fired boilers, and in particular relates to a tail-end supplementary combustion system and method for increasing the smoke temperature at an SCR inlet. Background Art

[0002] At present, most coal-fired boilers use ammonia selective catalytic reduction for desulfurization treatment. When the boiler is running at low load, the flue gas temperature at the tail of the boiler discharged through the economizer is too low, resulting in the flue gas temperature entering the SCR desulfurization device being lower than the catalyst activation temperature (310℃-400℃). At the same time, acidic gases such as sulfur dioxide in the flue gas will condense on the metal pipe wall at low temperature, causing low-temperature corrosion. Sulfur dioxide will also be oxidized to sulfur trioxide. When the low-temperature flue gas enters the SCR desulfurization device, ammonium sulfate may be generated and deposited in the air preheater, damaging the air preheater. Therefore, when the boiler is running at low load, it is necessary to increase the flue gas temperature in the SCR area to a suitable temperature that satisfies the catalyst reaction to ensure the normal operation of the SCR desulfurization device.

[0003] Traditional methods of increasing the temperature before SCR include bypass flue, economizer grading, tail heating, hot water circulation, etc. The bypass flue is difficult to control accurately and reduces boiler efficiency; economizer grading does not have the flexibility to adjust; tail heating will increase flue resistance; hot water recirculation is currently less studied and less invested. The mixed combustion of hydrogen and oxygen is an effective way to utilize hydrogen energy. When hydrogen burns in oxygen, it produces water, which contains no pollutants and no carbon emissions. It can be used as a new way of energy conversion. Therefore, exploring a low-carbon method that can effectively increase the flue gas temperature at the tail SCR inlet under low load is of great significance to wide load off-line low-carbon operation, and is in line with the national dual carbon strategy. Summary of the invention

[0004] In order to effectively increase the SCR temperature when the boiler is running at low load, the present invention provides a tail supplementary combustion system and method for increasing the SCR inlet smoke temperature. The present invention can effectively increase the SCR inlet temperature and ensure the normal operation of the SCR.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A tail supplementary combustion system for increasing the inlet smoke temperature of an SCR comprises a boiler and a combustion chamber for burning a mixture of hydrogen and air, an economizer is arranged on the smoke passage of the boiler, the tail flue of the boiler is connected to the smoke inlet of an SCR deoxidation device, the smoke outlet of the combustion chamber is connected to the tail flue through a No. 3 bypass flue, the combustion chamber is connected to the outlet flue of an air preheater of the boiler through a No. 2 bypass flue, an induced draft fan is arranged in the No. 2 bypass flue, and the induced draft fan is used to send the smoke in the outlet flue of the air preheater into the combustion chamber.

[0006] Preferably, an air supply baffle is provided upstream of the induced draft fan in the No. 2 bypass flue.

[0007] Preferably, the No. 3 bypass flue is arranged vertically, and a No. 3 bypass flue ash hopper is provided at the bottom of the No. 3 bypass flue. The connection point between the flue gas outlet of the combustion chamber and the No. 3 bypass flue is located above the No. 3 bypass flue ash hopper. A primary flue baffle is provided at the flue gas outlet of the combustion chamber on the No. 3 bypass flue, and a secondary flue baffle is provided at the top of the No. 3 bypass flue.

[0008] Preferably, a post-burner temperature detection device for detecting the flue gas temperature at the flue gas outlet of the combustion chamber is provided in the No. 3 bypass flue, and a pre-SCR temperature detection device is provided in the tail flue downstream of the connection point between the No. 3 bypass flue and the tail flue.

[0009] Preferably, in the No. 2 bypass flue, a No. 1 guide plate is provided at the connection between the No. 2 bypass flue and the outlet flue of the boiler's air preheater, and the No. 1 guide plate is used to uniformly introduce the flue gas in the outlet flue of the air preheater into the No. 2 bypass flue; in the No. 3 bypass flue, a No. 2 guide plate is provided at the flue gas outlet of the combustion chamber, and the No. 2 guide plate is used to uniformly introduce the flue gas at the flue gas outlet of the combustion chamber into the connection side of the No. 3 bypass flue and the tail flue; in the No. 3 bypass flue, a No. 3 guide plate is provided at the connection between the No. 3 bypass flue and the tail flue, and the No. 3 guide plate is used to uniformly introduce the flue gas in the No. 3 bypass flue into the tail flue, and the No. 1 guide plate, the No. 2 guide plate and the No. 3 guide plate all adopt guide plates.

[0010] Preferably, the combustion chamber is connected to a bypass flue No. 1, one end of which is connected to a hydrogen station, and the combustion chamber is also provided with an oxyhydrogen burner, the other end of which is connected to the oxyhydrogen burner.

[0011] Preferably, the No. 1 bypass flue is provided with a hydrogen inlet isolation valve and a hydrogen inlet regulating valve in sequence along the hydrogen flow direction upstream of the hydrogen-oxygen burner.

[0012] Preferably, the No. 2 bypass flue is arranged vertically, and a concave air preheater rear ash hopper is provided on the outlet flue of the air preheater at a position opposite to the bottom of the No. 2 bypass flue.

[0013] Preferably, the outlet flue of the air preheater is connected to the boiler furnace, and a blower is provided on the outlet flue of the air preheater. The blower is located downstream of the connection point between the No. 2 bypass flue and the air preheater outlet flue of the boiler.

[0014] The present invention also provides a method for improving the smoke temperature at the inlet of the SCR. The method is performed by the system for improving the smoke temperature at the inlet of the SCR as described above, and includes the following process: When the flue gas temperature at the flue gas inlet of the SCR denitrification device is lower than the catalyst reaction temperature, the hot flue gas generated by combustion in the combustion chamber is sent to the tail flue through the No. 3 bypass flue and mixed with the low-temperature flue gas in the tail flue to increase the flue gas temperature in the tail flue, so that the flue gas temperature before the SCR is raised to above the preset value, ensuring the normal operation of the SCR denitrification device.

[0015] The present invention has the following beneficial technical effects: In the tail supplementary combustion system for increasing the inlet flue temperature of SCR of the present invention, the flue gas outlet of the combustion chamber is connected to the tail flue through the No. 3 bypass flue, so that the flue gas pair of hydrogen and air can be sent to the tail flue, and the hot flue gas after supplementary combustion enters the tail flue and mixes with the low-temperature flue gas, effectively increasing the inlet temperature of SCR, ensuring the normal operation of SCR, and reducing carbon emissions, effectively realizing the emission control of pollutant gases under low load of coal-fired units. The combustion chamber is connected to the outlet flue of the air preheater of the boiler through the No. 2 bypass flue, so when the boiler is running at a lower load, the present invention adds a supplementary combustion system in the tail flue, uses hydrogen and air to burn, and the air comes from part of the primary air heated by the air preheater to heat the flue gas temperature of the tail flue.

[0016] Furthermore, the switch and opening of the damper door and the opening of the hydrogen inlet isolation valve and the regulating valve are controlled by the temperature sensors in the tail flue and the bypass flue, and the combustion of the burner is controlled according to the temperature sensor before the SCR. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a tail post-combustion system for increasing the smoke temperature at the SCR inlet in an embodiment of the present invention; Figure 2 Schematic diagram of guide plates in a bypass flue and a tail flue in an embodiment of the present invention; Figure 3 It is a schematic diagram of the logical structure (PID) in the bypass flue and the tail flue in the embodiment of the present invention.

[0018] Among them: 1 is the boiler furnace, 2 is the economizer, 3 is the SCR deoxidation device, 4 is the air preheater, 5 is the dust collector, 6 is the blower, 7 is the hydrogen station, 8 is the hydrogen-oxygen burner, 9 is the induced draft fan, 10 is the combustion chamber, 11 is the flue gas primary baffle, 12 is the flue gas secondary baffle, 13 is the third bypass flue ash hopper, 14 is the flue gas air supply baffle, 15 is the tail flue, 16 is the burner inlet hot air, 17 is the air The ash hopper after the preheater, 18 is the temperature detection device before SCR, 19 is the temperature detection device after the burner, 20 is the hydrogen inlet isolation valve, 21 is the hydrogen inlet regulating valve, 22 is the bypass flue No. 1, 23 is the bypass flue No. 2, 24 is the bypass flue No. 3, 110 is the guide plate No. 1, 120 is the guide plate No. 2, 130 is the guide plate No. 3, 140 is the guide plate No. 4, and 150 is the guide plate No. 5. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0020] See also Figure 1-Figure 3 The tail supplementary combustion system for improving the inlet flue gas temperature of SCR in this embodiment includes a boiler and a combustion chamber 10 for burning hydrogen and air. An economizer 2 is provided on the flue gas channel of the boiler. The tail flue 15 of the boiler is connected to the flue gas inlet of the SCR deoxidation device 3. The flue gas outlet of the combustion chamber 10 is connected to the tail flue 15 through the No. 3 bypass flue 24. The combustion chamber 10 is connected to the outlet flue of the air preheater 4 of the boiler through the No. 2 bypass flue 23. An induced draft fan 9 is provided in the No. 2 bypass flue 23. The induced draft fan 9 is used to send the flue gas in the outlet flue of the air preheater 4 into the combustion chamber 10. When the tail supplementary combustion system for increasing the flue gas temperature at the SCR inlet of the present embodiment is working, when the flue gas temperature at the flue gas inlet of the SCR deactivation device is lower than the catalyst reaction temperature, the hot flue gas generated by the combustion in the combustion chamber 10 is sent to the tail flue 15 through the No. 3 bypass flue 24, and is mixed with the low-temperature flue gas in the tail flue 15, thereby increasing the flue gas temperature in the tail flue 15, so that the flue gas temperature before the SCR is increased to above the preset value, thereby ensuring the normal operation of the SCR deactivation device 3.

[0021] As a preferred embodiment of the present invention, in this embodiment, an air supply damper 14 is provided upstream of the induced draft fan 9 in the second bypass flue 23. The air supply damper 14 is used to isolate the induced draft fan from the flue air after the air preheater. The induced draft fan is used to introduce part of the primary air heated by the air preheater into the combustion chamber for mixed combustion with hydrogen. The ash hopper is used to prevent ash accumulation on the damper door and the induced draft fan.

[0022] As a preferred embodiment of the present invention, in this embodiment, the No. 3 bypass flue 24 is arranged vertically, the No. 3 bypass flue ash hopper 13 is provided at the bottom of the No. 3 bypass flue 24, the connection point between the flue gas outlet of the combustion chamber 10 and the No. 3 bypass flue 24 is located above the No. 3 bypass flue ash hopper 13, the No. 3 bypass flue 24 is provided with a flue primary baffle 11 at the flue gas outlet of the combustion chamber 10, and the No. 3 bypass flue 24 is provided with a flue secondary baffle 12 at the top of the No. 3 bypass flue 24. The flue primary baffle is used to control the flow of the No. 3 bypass flue, and the flue secondary baffle is used to isolate the No. 3 bypass flue from the tail flue.

[0023] As a preferred embodiment of the present invention, in this embodiment, a post-burner temperature detection device 19 for detecting the flue gas temperature at the flue gas outlet of the combustion chamber 10 is provided in the No. 3 bypass flue 24, and a pre-SCR temperature detection device 18 is provided in the tail flue 15 downstream of the connection point between the No. 3 bypass flue 24 and the tail flue 15.

[0024] As a preferred embodiment of the present invention, in this embodiment, a first guide plate 110 is provided at the connection between the second bypass flue 23 and the outlet flue of the air preheater 4 of the boiler in the second bypass flue 23, and the first guide plate 110 is used to uniformly introduce the flue gas in the outlet flue of the air preheater 4 into the second bypass flue 23; a second guide plate 120 is provided at the flue gas outlet of the combustion chamber 10 in the third bypass flue 24, and the second guide plate 120 is used to uniformly introduce the flue gas in the outlet flue of the air preheater 4 into the second bypass flue 23; The flue gas at the flue gas outlet of the combustion chamber 10 is uniformly introduced into the connection side of the No. 3 bypass flue 24 and the tail flue 15; the No. 3 bypass flue 24 is provided with a No. 3 guide plate 130 at the connection between the No. 3 bypass flue 24 and the tail flue 15, and the No. 3 guide plate 130 is used to uniformly introduce the flue gas in the No. 3 bypass flue 24 into the tail flue 15, and the No. 1 guide plate 110, the No. 2 guide plate 120, and the No. 3 guide plate 130 are all guide plates. By properly arranging the guide plates, the direction of the flue gas flow is guided, the resistance of the flue gas flow is reduced, and the flow field stability is increased.

[0025] As a preferred embodiment of the present invention, in this embodiment, the combustion chamber 10 is connected to a bypass flue 22 No. 1, one end of which is connected to a hydrogen station 7, and the combustion chamber 10 is also provided with an oxyhydrogen burner 8, the other end of which is connected to the oxyhydrogen burner 8. The use of hydrogen and air mixed combustion and hydrogen energy can meet the low-carbon demand, and at the same time can provide hot flue gas to the tail flue to increase the flue temperature. Furthermore, the bypass flue 22 No. 1 is provided with a hydrogen inlet isolation valve 20 and a hydrogen inlet regulating valve 21 in sequence upstream of the oxyhydrogen burner 8 along the flow direction of hydrogen. The hydrogen inlet isolation valve 20 is used to isolate the hydrogen input, and the hydrogen inlet regulating valve 21 is used to adjust the amount of hydrogen and control the combustion rate of the burner, thereby achieving the purpose of controlling combustion. In this embodiment, a bypass flue and an oxyhydrogen burner are arranged at the tail, and supplementary combustion is performed through the tail burner. The hot flue gas after supplementary combustion enters the tail flue and mixes with the low-temperature flue gas, thereby effectively increasing the SCR inlet temperature, ensuring the normal operation of the SCR, and reducing carbon emissions, effectively realizing the emission control of pollutant gases under low load of the coal-fired unit.

[0026] As a preferred implementation scheme of the present invention, in this embodiment, the No. 2 bypass flue 23 is arranged vertically, and a concave air preheater rear ash hopper 17 is provided on the outlet flue of the air preheater 4 at a position opposite to the bottom of the No. 2 bypass flue 23. The air preheater rear ash hopper 17 is used to prevent ash accumulation on the baffle door.

[0027] As a preferred embodiment of the present invention, in this embodiment, the outlet flue of the air preheater 4 is connected to the boiler furnace 1, and a blower 6 is provided on the outlet flue of the air preheater 4, and the blower 6 is located downstream of the connection point between the second bypass flue 23 and the outlet flue of the boiler air preheater 4. The blower 6 can send the hot air or flue gas of the outlet flue of the air preheater 4 into the boiler furnace 1.

[0028] Example refer to Figure 1 This embodiment is a combination of the above embodiments. The tail-end supplementary combustion system and method for increasing the inlet flue gas temperature of SCR in this embodiment are suitable for coal-fired units that require deep peak regulation, and can effectively increase the inlet flue gas temperature of SCR under low boiler load. The tail-end supplementary combustion system for increasing the inlet flue gas temperature of SCR includes a boiler furnace 1, an economizer 2, an SCR degassing device 3, an air preheater 4, a dust collector 5 and a blower 6. Flue gas comes out of the furnace and passes through the economizer 2. The economizer 2 exchanges heat with the flue gas through boiler feed water, reduces the flue gas temperature, recovers the waste heat, enters the SCR degassing device to remove nitrogen oxides, and finally enters the air preheater 4 and reaches the dust collector 5.

[0029] During the specific implementation process, when the boiler is peak-shaving, the load is generally less than 25% of the full load. When the boiler is at 25% load, the flue gas temperature after the economizer and before the SCR is about 270℃~280℃, which is lower than the catalyst activity temperature of the SCR degassing device. The SCR degassing device cannot be put into operation normally, resulting in the risk of over-emission accidents.

[0030] refer to Figure 1 In this embodiment, a supplementary combustion burner system is added to the tail flue, and a bypass flue No. 1 22, a bypass flue No. 23, and a bypass flue No. 3 24 are provided. The inlet of the bypass flue No. 1 22 is connected to the hydrogen station 7, and the outlet of the bypass flue No. 1 22 is connected to the hydrogen-oxygen burner 8 of the combustion chamber 10; the inlet flue of the bypass flue No. 2 23 is connected to the outlet flue of the air preheater 4 of the boiler, and the outlet flue of the bypass flue No. 2 23 is connected to the combustion chamber 10; in the bypass flue No. 2 23, the induced draft fan 9 is located upstream of the combustion chamber 10, and the air supply baffle 14 is located upstream of the induced draft fan 9; the inlet flue of the bypass flue No. 3 24 is connected to the outlet flue of the air preheater 4 of the boiler, and the outlet flue of the bypass flue No. 2 23 is connected to the combustion chamber 10; in the bypass flue No. 2 23, the induced draft fan 9 is located upstream of the combustion chamber 10, and the air supply baffle 14 is located upstream of the induced draft fan 9; The duct is connected to the combustion chamber 10, and the exhaust flue of the No. 3 bypass flue 24 is connected to the tail flue 15 of the boiler; the No. 1 bypass flue 22 is a burner system, and the No. 2 bypass flue 23 is an air supply system. The air heated by the air preheater 4 is sent into the combustion chamber 10 through the induced draft fan 9 to be mixed with hydrogen for combustion. The No. 3 bypass flue 24 controls the flue gas flow rate of the hot flue gas after combustion entering the tail flue 15 through the flue gas primary baffle 11 and the flue gas secondary baffle 12.

[0031] When the temperature detection device 18 before the boiler SCR detects that the flue gas temperature is lower than the catalyst reaction temperature, the air and hydrogen can be allowed to enter the tail supplementary combustion system by opening the flue gas primary damper 11 and the flue gas secondary damper 12, and simultaneously opening the flue gas air supply damper 14 and the hydrogen inlet isolation valve 20 and the hydrogen inlet regulating valve 21. The hot flue gas generated by the combustion enters the tail flue and mixes with the low-temperature flue gas. The combustion rate is controlled by the flue gas secondary damper 12 and the hydrogen inlet regulating valve 21, and the flue gas temperature before the SCR is increased to above 310°C, thereby ensuring the normal operation of the SCR denitration device 3 and improving the commissioning rate of the denitration device. When the temperature is normal, first shut down the hydrogen supply in the hydrogen station 7 and the air supply in the oxyhydrogen burner 8, close the hydrogen inlet isolation valve 20 and the hydrogen inlet regulating valve 21, close the air supply damper 14, shut down the induced draft fan 9, shut down the oxyhydrogen burner 8, close the primary flue gas damper 11 and the secondary flue gas damper 12, isolate all bypass flues, and allow the flue gas in the tail flue 15 to enter the SCR denitrification device 3 normally. The flue gas after the air preheater 4 does not enter the No. 2 bypass flue 23.

[0032] refer to Figure 2, in the tail flue and bypass flue, when the flue gas is mixed, it is easy to cause problems such as uneven mixing and unstable flow field. In this embodiment, five groups of guide plates are arranged, namely, guide plate No. 1 110, guide plate No. 2 120, guide plate No. 3 130, guide plate No. 4 140, and guide plate No. 5 150. The five groups of guide plates are all in arc shape, which are used to guide the direction of flue gas. The guide plate No. 1 110 is located in the bypass flue No. 2 23, the guide plate No. 2 120 and the guide plate No. 3 130 are located in the bypass flue No. 3 24, and the guide plate No. 4 140 and the guide plate No. 5 150 are located in the tail flue of the boiler and are connected to the SCR inlet flue. Among them, in the No. 3 bypass flue 24, the No. 2 guide plate 120 is located between the primary flue gas baffle and the secondary flue gas baffle, so that the flue gas can reach the vertical flue smoothly; the No. 3 guide plate 130 is located behind the primary flue gas baffle 11, so that the smoke and the tail flue smoke are mixed sufficiently evenly; the No. 4 guide plate 140 and the No. 5 guide plate 150 are arranged in the tail flue to ensure that the tail flow field is uniform and reduce the smoke resistance.

[0033] refer to Figure 2 , a No. 1 guide plate 110 is set in the bypass flue 2, the inlet of the guide plate is parallel to the flue gas flow direction, the angle is less than 15°, and the outlet is parallel to the vertical flue, the angle is less than 15°. In the No. 3 bypass flue 24, the No. 2 guide plate 120 is located between the primary flue gas baffle 11 and the secondary flue gas baffle 12, so that the flue gas can smoothly reach the vertical flue; the No. 3 guide plate 130 is located behind the secondary flue gas baffle 12, the outlet of the guide plate is opposite to the flue gas flow direction of the tail flue, the angle is less than 15°, and the angle between the inlet and the vertical flue is less than 15°. A No. 4 guide plate 140 and a No. 5 guide plate 150 are set in the tail flue, and the No. 4 guide plate 140 and the No. 5 guide plate 150 are both in the same direction as the flue gas flow direction, and form an obtuse angle with the boiler wall. When the flue gas flows, it changes direction through the guide plate to ensure a uniform tail flow field and reduce flue gas resistance.

[0034] refer to Figure 3 In this embodiment, the damper door and the valve opening are automatically controlled through the signals of the SCR front temperature sensor 18 and the burner rear temperature sensor 19, thereby controlling the input of the supplementary combustion system and the combustion rate.

[0035] In order to realize automatic control, the system of this embodiment also includes a first PLC controller, a second PLC controller, a temperature sensor and related electric heating equipment. The SCR pre-temperature sensor 18 is connected to the signal input end of the first PLC controller, and the flue gas primary damper 11, the flue gas air supply damper 14 and the hydrogen inlet isolation valve 20 are electrically connected to the signal output end of the first PLC controller; the SCR pre-temperature sensor 18 and the burner post-temperature sensor 19 are connected to the signal input end of the second PLC controller, and the flue gas secondary damper 12 and the hydrogen inlet regulating valve 21 are electrically connected to the signal output end of the second PLC controller.

[0036] Instructions for use: The flue gas temperature in the tail flue 15 is detected by the pre-SCR temperature detection device 18. When the flue gas temperature is detected to be higher than 315°C, the first PLC controller controls the flue gas primary damper 11, the air supply damper 14 and the hydrogen inlet isolation valve 20 to be in a closed state, and the second PLC controller controls the flue gas secondary damper 12 to be in a closed state, and the hydrogen inlet regulating valve 21 is in a closed state. When the flue gas temperature is detected to be lower than 305°C, the first PLC controller controls the flue gas primary damper 11 and the flue gas air supply damper 14 to be opened, the air supply system is put into operation, the hydrogen inlet isolation valve is in an open state, and the combustion system is put into operation; the second PLC controller automatically controls the opening of the flue gas secondary damper 12 and the opening of the hydrogen inlet regulating valve 21 according to the pre-SCR temperature and the post-burner temperature to keep the temperature of the tail flue 15 higher than 310°C.

[0037] When the temperature signal is high, the flue gas primary damper 11 and the flue gas secondary damper 12 are closed, the air supply damper 14 is closed, the hydrogen inlet isolation valve 20 is closed, and the supplementary combustion system is exited. When the temperature signal is low, the flue gas primary damper 11 and the flue gas secondary damper 12 are opened, the hydrogen inlet isolation valve 20 is opened, the hydrogen inlet regulating valve 21 is opened, and the supplementary combustion system is put into operation.

[0038] According to the above analysis, the present invention sets a supplementary hydrogen-oxygen burner at the tail, introduces part of the primary air heated by the air preheater into the combustion chamber, heats the flue gas through the combustion of hydrogen and oxygen, and mixes the hot flue gas with the low-temperature flue gas in the tail flue to increase the temperature before the SCR. The present invention introduces high-temperature flue gas from the outside, avoiding the traditional method of adding a heater in the tail flue, which increases the flue gas resistance; the use of hydrogen-oxygen burners to heat the flue gas is also in line with the national dual-carbon strategy, using hydrogen energy to reduce carbon emissions; guide plates in different directions are set to stabilize the flue gas flow field in the original flue and mix evenly. Through logical control and signal feedback, the damper door and the hydrogen inlet regulating valve are controlled to be at a suitable opening, thereby controlling the hydrogen combustion rate and the tail flue temperature, and controlling the temperature to be higher than the SCR denitration catalyst reaction temperature, so that the commissioning rate of the SCR denitration device is improved and the NOx at the boiler outlet is effectively controlled.

[0039] 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 above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A tail afterburning system for increasing the smoke temperature at the SCR inlet, characterized in that: The invention comprises a boiler and a combustion chamber (10) for burning a mixture of hydrogen and air. An economizer (2) is provided on the flue gas passage of the boiler. The tail flue (15) of the boiler is connected to the flue gas inlet of an SCR deoxidation device (3). The flue gas outlet of the combustion chamber (10) is connected to the tail flue (15) via a No. 3 bypass flue (24). The combustion chamber (10) is connected to the outlet flue of an air preheater (4) of the boiler via a No. 2 bypass flue (23). An induced draft fan (9) is provided in the No. 2 bypass flue (23). The induced draft fan (9) is used to send the flue gas in the outlet flue of the air preheater (4) into the combustion chamber (10).

2. A tail-end supplementary combustion system for increasing the SCR inlet smoke temperature according to claim 1, characterized in that: An air supply damper (14) is provided upstream of the induced draft fan (9) in the No. 2 bypass flue (23).

3. The tail afterburning system for increasing the smoke temperature at the SCR inlet according to claim 1 is characterized in that: The No. 3 bypass flue (24) is arranged vertically, and a No. 3 bypass flue ash hopper (13) is provided at the bottom of the No. 3 bypass flue (24). The connection point between the flue gas outlet of the combustion chamber (10) and the No. 3 bypass flue (24) is located above the No. 3 bypass flue ash hopper (13). The No. 3 bypass flue (24) is provided with a primary flue gas baffle (11) at the flue gas outlet of the combustion chamber (10), and a secondary flue gas baffle (12) is provided at the top of the No. 3 bypass flue (24).

4. The tail afterburning system for increasing the smoke temperature at the SCR inlet according to claim 1 is characterized in that: A post-burner temperature detection device (19) for detecting the flue gas temperature at the flue gas outlet of the combustion chamber (10) is provided in the third bypass flue (24), and a pre-SCR temperature detection device (18) is provided in the tail flue (15) downstream of the connection point between the third bypass flue (24) and the tail flue (15).

5. The tail-end supplementary combustion system for increasing the smoke temperature at the SCR inlet according to claim 1 is characterized in that: A first guide plate (110) is provided at the connection between the second bypass flue (23) and the outlet flue of the air preheater (4) of the boiler in the second bypass flue (23). The first guide plate (110) is used to uniformly introduce the flue gas in the outlet flue of the air preheater (4) into the second bypass flue (23). A second guide plate (120) is provided at the flue gas outlet of the combustion chamber (10) in the third bypass flue (24). The second guide plate (120) is used to uniformly introduce the flue gas in the outlet flue of the air preheater (4) into the second bypass flue (23). The flue gas is uniformly introduced into the connection side of the No. 3 bypass flue (24) and the tail flue (15); a No. 3 guide plate (130) is provided at the connection between the No. 3 bypass flue (24) and the tail flue (15) in the No. 3 bypass flue (24); the No. 3 guide plate (130) is used to uniformly introduce the flue gas in the No. 3 bypass flue (24) into the tail flue (15); the No. 1 guide plate (110), the No. 2 guide plate (120), and the No. 3 guide plate (130) are all guide plates.

6. The tail post-combustion system for increasing the SCR inlet smoke temperature according to claim 1 is characterized in that: The combustion chamber (10) is connected to a bypass flue (22), one end of which is connected to a hydrogen station (7). The combustion chamber (10) is also provided with an oxyhydrogen burner (8), the other end of which is connected to the oxyhydrogen burner (8).

7. A post-combustion system for increasing the SCR inlet smoke temperature according to claim 6, characterized in that: The first bypass flue (22) is provided with a hydrogen inlet isolation valve (20) and a hydrogen inlet regulating valve (21) in sequence along the hydrogen flow direction upstream of the hydrogen-oxygen burner (8).

8. The tail afterburning system for increasing the smoke temperature at the SCR inlet according to claim 1 is characterized in that: The second bypass flue (23) is arranged vertically, and a concave air preheater rear ash hopper (17) is provided on the outlet flue of the air preheater (4) at a position opposite to the bottom of the second bypass flue (23).

9. The tail afterburning system for increasing the smoke temperature at the SCR inlet according to claim 1 is characterized in that: The outlet flue of the air preheater (4) is connected to the boiler furnace (1), and a blower (6) is provided on the outlet flue of the air preheater (4). The blower (6) is located downstream of the connection point between the second bypass flue (23) and the outlet flue of the air preheater (4) of the boiler.

10. A method for improving the smoke temperature at the SCR inlet, characterized in that: The method is carried out by the tail afterburning system for increasing the SCR inlet smoke temperature according to any one of claims 1 to 9, and comprises the following process: When the flue gas temperature at the flue gas inlet of the SCR denitration device is lower than the catalyst reaction temperature, the hot flue gas generated by combustion in the combustion chamber (10) is sent to the tail flue (15) through the third bypass flue (24) and mixed with the low-temperature flue gas in the tail flue (15), thereby increasing the flue gas temperature in the tail flue (15) and raising the flue gas temperature before the SCR to above a preset value, thereby ensuring the normal operation of the SCR denitration device (3).

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