Flue gas recirculation system for improving performance of household garbage incineration power generation boiler

Abstract

The utility model provides a household garbage incineration power generation boiler performance improvement flue gas recirculation system which comprises an incinerator, and a primary air mechanism is arranged on one side of the incinerator. A waste heat boiler is arranged on one side of the incinerator, a semi-dry method deacidification tower is arranged on one side of the waste heat boiler, a bag-type dust collector is arranged on one side of the semi-dry method deacidification tower, and an induced draft fan is arranged on one side of the bag-type dust collector; smoke recirculation is matched with low-oxygen combustion, so that the boiler efficiency can be improved, and the boiler evaporation capacity is increased. By means of flue gas recirculation low-NOx combustion, the original generation amount of nitric oxide can be reduced by about 30%, the usage amount of denitration agents at the rear end is reduced, and the production cost is reduced; and meanwhile, the pressure of a rear-end denitration system is relieved, and the emission concentration of nitrogen oxide and ammonia escape can be controlled at a lower level. Flue gas generated after biogas combustion is fed into primary air to be mixed and then fed into a drying section of a lower air chamber of the incinerator to dry garbage, the functionality of biogas combustion heat energy is fully exerted, and the steam consumption of a primary air preheater can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of domestic waste incineration power generation, in particular to a flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler. Background Technique

[0002] Domestic waste incineration power generation is currently the most mainstream way of waste reduction and harmless treatment. Compared with other treatment methods such as sanitary landfill and composting, the flue gas emitted from waste incineration power generation contains a large amount of pollutants. The purification of flue gas has always been a difficult point in waste incineration power generation. Among them, the control of the emission concentration of NOx nitrogen oxides and ammonia slip is relatively difficult, which is a relatively prominent problem in the current industry.

[0003] With the increasingly strict national requirements for air quality, local standards for waste incineration flue gas emissions have been gradually introduced in various provinces and cities. The requirements for the reduction of nitrogen oxides are becoming increasingly strict. The NOx emission requirements in some provinces and cities are 120 mg / Nm3, and the ammonia slip is lower than 8 mg / Nm3 at the same time. This poses a higher challenge to the existing flue gas treatment processes. Although SCR can meet the requirements, the operating cost is too high.

[0004] Studying low-NOx combustion technology and controlling the original generation amount of NOx is one of the effective technical measures to reduce the cost of flue gas treatment.

[0005] Some domestic waste incineration power generation enterprises have done a lot of research and practical work in low-NOx combustion and achieved certain research results. However, in the operation of specific projects, there are more or less some problems that affect the long-term stable operation of the system, and the technical means are single. For example, problems such as excessive CO concentration, low furnace temperature when burning low calorific value waste or operating at low load, corrosion of system pipelines, poor operating stability, and failure to achieve the expected design effect. Content of the Utility Model

[0006] In view of the above situation, in order to overcome the defects of the prior art, the purpose of the utility model is to provide a flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler, which effectively solves the problems that there are more or less some problems affecting the long-term stable operation of the system and the technical means are single in the operation of specific projects. For example, problems such as excessive CO concentration, low furnace temperature when burning low calorific value waste or operating at low load, corrosion of system pipelines, poor operating stability, and failure to achieve the expected design effect.

[0007] The technical solution adopted by the utility model is to provide a flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler, including an incinerator, and a primary air mechanism is arranged on one side of the incinerator;

[0008] One side of the incinerator is provided with a waste heat boiler, one side of the waste heat boiler is provided with a semi-dry desulfurization tower, one side of the semi-dry desulfurization tower is provided with a bag filter, and one side of the bag filter is provided with an induced draft fan;

[0009] One side of the induced draft fan is provided with a circulation fan, one side of the circulation fan is provided with a first nozzle and a second nozzle. The first nozzle is inclined downward and arranged on one side of the waste heat boiler, the second nozzle is inclined upward and arranged on one side of the waste heat boiler. One side of the waste heat boiler is provided with a secondary air fan, and the output end of the secondary air fan is provided with a front wall combustion-supporting secondary air damper nozzle and a rear wall combustion-supporting secondary air damper nozzle. The front wall combustion-supporting secondary air damper nozzle is inclined downward and arranged on one side of the waste heat boiler, the rear wall combustion-supporting secondary air damper nozzle is inclined upward and arranged on one side of the waste heat boiler. One side of the waste heat boiler is installed with a detection component;

[0010] A mechanism for burning low calorific value waste is arranged between the circulation fan and the incinerator;

[0011] One side of the incinerator is also provided with a biogas inlet mechanism.

[0012] Preferably, the waste heat boiler, the semi-dry desulfurization tower and the bag filter are sequentially connected to each other through a flue gas path. One side of the bag filter facing away from the semi-dry desulfurization tower is provided with an induced draft fan connection flue, and the other side of the induced draft fan connection flue is arranged on the induced draft fan.

[0013] Preferably, the incinerator includes a garbage inlet, one side of the garbage inlet is provided with an incinerator grate, one side of the incinerator grate is provided with a drying section of the lower air chamber of the incinerator, one side of the drying section of the lower air chamber of the incinerator is provided with a combustion and burnout section of the lower air chamber of the incinerator, and one side of the combustion and burnout section of the lower air chamber of the incinerator is provided with a slag discharge port.

[0014] Preferably, the primary air mechanism includes a primary air fan. The air outlet end of the primary air fan is provided with an air preheating chamber through a pipeline. The air outlet end of the air preheating chamber is connected to a flue gas mixer through a primary air pipeline A. The air outlet end of the flue gas mixer is connected to the drying section of the lower air chamber of the incinerator through a pipeline. An electric regulating damper A is arranged at one end of the primary air pipeline A close to the flue gas mixer. The middle part of the primary air pipeline A is connected to the combustion and burnout section of the lower air chamber of the incinerator through a primary air pipeline B.

[0015] Preferably, the induced draft fan and the circulation fan are interconnected through a recirculation fan inlet flue. An electric damper A is arranged on one side of the recirculation fan inlet flue. A bypass purge air electric damper is also arranged on one side of the recirculation fan inlet flue through a pipeline. The outlet end of the circulation fan is provided with a circulation fan outlet flue. An electric damper B is arranged on one side of the circulation fan outlet flue. The outlet end of the circulation fan outlet flue is provided with a front wall header and a rear wall header. One end of the front wall header is connected and installed to a first nozzle. One end of the rear wall header is connected and installed to a second nozzle. One side of the secondary air fan is provided with a secondary air fan outlet flue. The outlet end of the secondary air fan outlet flue is provided with an air supply header A and an air supply header B. One side of the air supply header A is installed at the inlet end of the front wall secondary combustion air damper nozzle. The air supply header B is connected and installed to the inlet end of the rear wall secondary combustion air damper nozzle.

[0016] Preferably, the waste heat boiler includes a front wall of the waste heat boiler. The bottom of the front wall of the waste heat boiler is provided with a front arch water wall. The front arch water wall is arranged on one side of the waste feed inlet. A rear arch water wall is arranged on one side of the slag discharge outlet. The top of the rear arch water wall is provided with a rear wall water wall. The top of the front wall of the waste heat boiler is provided with a roof water wall. A furnace cavity is arranged on one side of the roof water wall and the rear wall water wall. A economizer is arranged inside the furnace cavity.

[0017] Preferably, the detection component includes a CO / O2 online laser gas analyzer installed on one side of the front wall of the waste heat boiler. An zirconia online oxygen analyzer is installed at the outlet of the economizer.

[0018] Preferably, the mechanism for burning low calorific value waste includes a recirculation flue gas bypass pipeline A arranged on one side of the circulation fan outlet flue. An electric damper C is arranged on one side of the recirculation flue gas bypass pipeline A. The outlet end of the recirculation flue gas bypass pipeline A is provided with a flue gas preheater. The flue gas preheater is connected to a flue gas mixer through a recirculation flue gas bypass pipeline B. An electric regulating damper B is arranged on one side of the recirculation flue gas bypass pipeline B;

[0019] The recirculation fan inlet flue, the circulation fan outlet flue, the recirculation flue gas bypass pipeline A and the recirculation flue gas bypass pipeline B are all FRP ventilation pipelines.

[0020] Preferably, the biogas inlet furnace mechanism includes a biogas combustion chamber. A biogas auxiliary burner is arranged on one side of the biogas combustion chamber. A biogas pipeline is arranged on one side of the biogas auxiliary burner. A biogas auxiliary combustion fan is arranged on one side of the biogas pipeline. The biogas combustion chamber is interconnected with the flue gas mixer through a biogas flue gas pipeline. An electric damper D is arranged on one side of the biogas flue gas pipeline.

[0021] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0022] 1. Flue gas recirculation combined with low-oxygen combustion can improve the boiler efficiency and increase the boiler evaporation capacity.

[0023] 2. Flue gas recirculation low-NOx combustion can approximately reduce the original NOx generation amount by 30%, save the usage amount of backend denitration agents, and reduce the production cost. At the same time, it reduces the pressure on the backend denitration system and is also conducive to controlling the NOx emission concentration and ammonia slip at a lower level.

[0024] 3. The flue gas after biogas combustion is sent into the primary air for mixing and then into the drying section of the lower air chamber of the incinerator to dry the garbage, which fully exerts the functional heat energy of biogas combustion and can reduce the steam consumption of the primary air preheater.

[0025] 4. The recirculated flue gas is sent into the lower air chamber of the incinerator to dry the garbage, enhancing the adaptability of the flue gas recirculation system to burn low-calorific-value garbage and reducing the steam consumption of the primary air preheater.

[0026] 5. After implementing flue gas recirculation, it can enhance the reducing atmosphere in the furnace, alleviate the high-temperature corrosion of the heating surface in the furnace. At the same time, the local temperature reduction in the furnace caused by flue gas recirculation can also alleviate furnace coking. Description of the Drawings

[0027] Figure 1 is the first perspective structural schematic diagram of the flue gas recirculation system for performance improvement of the domestic waste incineration power generation boiler of the present utility model.

[0028] Figure 2 is the structural schematic diagram of the primary air mechanism, incinerator and waste heat boiler of the present utility model.

[0029] Figure 3 is the structural schematic diagram of the secondary combustion air system of the present utility model.

[0030] Figure 4 is the structural schematic diagram of the mechanism for burning low-calorific-value garbage of the present utility model.

[0031] Figure 5 is the first perspective structural schematic diagram of the nozzle of the present utility model.

[0032] Figure 6 is the second perspective structural schematic diagram of the nozzle of the present utility model.

[0033] Figure 7 is the third perspective structural schematic diagram of the nozzle of the present utility model.

[0034] Figure 8 is the structural schematic diagram of the nozzle and the waste heat boiler of the present utility model.

[0035] Figure 9 This is a schematic structural diagram of the nozzle of the present utility model and the incinerator.

[0036] Explanation of the reference numerals in the schematic diagram:

[0037] 1. Induced draft fan; 2. Induced draft fan connecting flue; 3. Electric damper A; 4. Bypass purge air electric damper; 5. Recirculation fan inlet flue; 6. Circulation fan; 7. Secondary air fan; 8. Primary air fan; 9. Circulation fan outlet flue;

[0038] 10. Secondary air fan outlet flue; 11. Air supply header A; 12. Air supply header B; 13. Front wall header; 14. Rear wall header; 15. Electric damper B; 16. Electric damper C; 17. Recirculated flue gas bypass pipe A; 18. Flue gas preheater; 19. Recirculated flue gas bypass pipe B;

[0039] 20. Electric regulating damper B; 21. Flue gas mixer; 22. Primary air duct A; 23. Air preheating chamber; 24. Primary air duct B; 25. Combustion burnout section in the lower air chamber of the incinerator; 26. Front wall of the waste heat boiler; 27. Rear wall water-cooled wall; 28. Roof water-cooled wall; 29. Front arch water-cooled wall;

[0040] 30. Rear arch water-cooled wall; 31. Semi-dry desulfurization tower; 32. Bag filter; 33. CO / O2 online laser gas analyzer; 34. Front wall secondary air damper nozzle for combustion support; 35. First nozzle; 36. Rear wall secondary air damper nozzle for combustion support; 37. Second nozzle; 38. Electric damper D; 39. Biogas flue gas pipe;

[0041] 40. Biogas combustion chamber; 41. Biogas combustion support burner; 42. Biogas pipe; 43. Biogas combustion support fan; 44. Incinerator grate; 45. Drying section in the lower air chamber of the incinerator; 46. Electric regulating damper A; 47. Zirconia online oxygen analyzer;

[0042] 50. Incinerator; 51. Waste feed inlet; 52. Slag discharge outlet; 60. Waste heat boiler; 70. Economizer. Specific embodiments

[0043] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0044] By Figures 1 to 2Provided, the present utility model provides a flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler, which includes an incinerator 50, a primary air mechanism, a waste heat boiler 60, a semi-dry desulfurization tower 31, a bag filter 32, an induced draft fan 1, a circulation fan 6, a first nozzle 35, a second nozzle 37, a secondary air fan 7, a front wall combustion-supporting secondary air damper nozzle 34, a rear wall combustion-supporting secondary air damper nozzle 36, a detection component, a mechanism for burning low calorific value waste, and a biogas feeding mechanism into the furnace.

[0045] Specifically, the incinerator 50 includes a waste feeding port 51, an incinerator grate 44, a drying section 45 of the lower air chamber of the incinerator, a combustion and burnout section 25 of the lower air chamber of the incinerator, and a slag discharge port 52. More specifically, the incinerator grate 44 is arranged at the lower right of the waste feeding port 51. The drying section 45 of the lower air chamber of the incinerator and the combustion and burnout section 25 of the lower air chamber of the incinerator are both arranged below the incinerator grate 44. The slag discharge port 52 is arranged on the right side of the incinerator grate 44. Even more specifically, domestic waste enters above the incinerator grate 44 from the waste feeding port 51 for combustion, and the slag after combustion is discharged from the slag discharge port 52 out of the incinerator 50.

[0046] Given Figures 2 to 3 Provided, the waste heat boiler 60 is arranged above the incinerator 50, and the waste heat boiler 60 is interconnected with the incinerator grate 44. The waste heat boiler 60 includes a front wall 26 of the waste heat boiler, a front arch water-cooled wall 29, a rear arch water-cooled wall 30, a rear wall water-cooled wall 27, a roof water-cooled wall 28, and a economizer 70.

[0047] Specifically, the front arch water-cooled wall 29 is arranged at the bottom of the front wall 26 of the waste heat boiler. The bottom of the front arch water-cooled wall 29 is arranged on the groove wall on one side of the waste feeding port 51. The rear arch water-cooled wall 30 is arranged on the groove wall on one side of the slag discharge port 52. The rear wall water-cooled wall 27 is arranged on the top of the rear arch water-cooled wall 30. The roof water-cooled wall 28 is arranged on the tops of the front wall 26 of the waste heat boiler and the rear wall water-cooled wall 27. There is a furnace cavity arranged on the right side of the roof water-cooled wall 28 and the rear wall water-cooled wall 27. The economizer 70 is arranged inside the furnace cavity. More specifically, the flue gas generated by the combustion of waste on the incinerator grate 44 enters the inside of the waste heat boiler 60.

[0048] Given Figures 2 to 3Given that, in addition, the semi-dry desulfurization tower 31 is arranged on the right side of the economizer 70, the bag filter 32 is arranged on the right side of the semi-dry desulfurization tower 31, and the economizer 70, the semi-dry desulfurization tower 31, and the bag filter 32 are sequentially interconnected through pipelines. On the side of the bag filter 32 facing away from the semi-dry desulfurization tower 31, there is an induced draft fan connecting flue 2. The input end of the induced draft fan 1 is connected and arranged on one side of the induced draft fan connecting flue 2, and the output end of the induced draft fan 1 is connected to the chimney. Specifically, the induced draft fan 1 generates suction to draw out the flue gas in the waste heat boiler 60. The flue gas enters the semi-dry desulfurization tower 31 and the bag filter 32 sequentially through pipelines, and then is sent to the chimney through the induced draft fan 1.

[0049] Given by Figures 1 to 2 Given that, in addition, the primary air mechanism is arranged on the tank wall below the drying section 45 of the lower wind chamber of the incinerator and the burnout section 25 of the lower wind chamber of the incinerator. Specifically, the primary air mechanism includes a primary air fan 8, an air preheating chamber 23, a primary air duct A22, a flue gas mixer 21, an electric regulating damper A46, and a primary air duct B24.

[0050] More specifically, the air preheating chamber 23 is arranged on one side of the primary air fan 8, and the air preheating chamber 23 is interconnected with the primary air fan 8 through a pipeline. The primary air duct A22 is arranged on the other side of the air preheating chamber 23. The flue gas mixer 21 is installed on the other side of the primary air duct A22. The flue gas mixer 21 is connected and arranged in the drying section 45 of the lower wind chamber of the incinerator through a pipeline. The electric regulating damper A46 is arranged at one end of the primary air duct A22 close to the flue gas mixer 21. One end of the primary air duct A22 close to the flue gas mixer 21 is connected to the burnout section 25 of the lower wind chamber of the incinerator through the primary air duct B24. More specifically, the air provided by the primary air fan 8 is sent to the drying section 45 of the lower wind chamber of the incinerator and the burnout section 25 of the lower wind chamber of the incinerator after being heated by the air preheating chamber 23 and the flue gas mixer 21. The heat source required for heating the air preheating chamber 23 comes from the boiler steam drum and the first extraction of the steam turbine.

[0051] Given by Figures 2 to 3Given, secondly, the recirculating flue gas system consists of a circulating fan 6, a first nozzle 35, a second nozzle 37, and a secondary fan 7. Specifically, the circulating fan 6 is interconnected with the induced draft fan 1 through the recirculating fan inlet flue 5. An electric damper A3 is installed on one side of the recirculating fan inlet flue 5, and a bypass purge air electric damper 4 is also provided on one side of the recirculating fan inlet flue 5. The outlet end of the circulating fan 6 is provided with a circulating fan outlet flue 9. On the other side of the circulating fan outlet flue 9, a front wall header 13 and a rear wall header 14 are provided. An electric damper B15 is provided on one side of the circulating fan outlet flue 9. The first nozzle 35 is installed on one side of the front wall header 13. At the same time, the nozzle end of the first nozzle 35 is inclined downward and penetrates through the groove wall on one side of the front arch water-cooled wall 29. The second nozzle 37 is installed on one side of the rear wall header 14. At the same time, the nozzle end of the second nozzle 37 is inclined upward and penetrates through the groove wall on one side of the rear wall water-cooled wall 27.

[0052] More specifically, the recirculating flue gas is taken from the connecting flue 2 between the bag filter 32 and the induced draft fan, and the recirculating fan inlet flue 5 is connected at the opening of the connecting flue 2 between the bag filter 32 and the induced draft fan; when the recirculating system is out of service, the electric damper A3 can be closed, and at the same time, the bypass purge air electric damper 4 is started, and fresh air is sucked in by the negative pressure of the circulating fan 6 to purge the pipeline.

[0053] When the flue gas recirculation system is enabled, the flue gas in the connecting flue 2 between the bag filter 32 and the induced draft fan is sent into the front wall header 13 and the rear wall header 14 by the circulating fan 6, and then sent into the furnace by the first nozzle 35 connected to the front wall header 13 and the second nozzle 37 connected to the rear wall header 14 to fully stir the high-temperature flue gas in the furnace.

[0054] The distance between the first nozzle 35 and the second nozzle 37 is usually 300 mm - 500 mm, and the specific value is determined comprehensively according to the recirculating flue gas volume, the number of nozzles, and the furnace width.

[0055] Consisted of Figure 5 、 Figure 8 and Figure 9 Given, more preferably, to improve the effective disturbance of the recirculating flue gas to the high-temperature flue gas in the furnace, the nozzles of the first nozzle 35 and the second nozzle 37 are both designed into an elliptical structure, and the nozzles are in a diffused shape, with a diffusion angle of 17.7°. The aspect ratio of the inner diameter of the elliptical nozzle is 100:30, and the wall thickness of the nozzle is 8 mm. The material is made of 310S material; the elliptical and diffused nozzles can increase the coverage range of the recirculating flue gas when disturbing the high-temperature flue gas in the furnace, ensure the full combustion of the volatile matter in the furnace, and reduce the generation of CO. The angle between the first nozzle 35 inclined downward and the horizontal plane is 25°, and the angle between the second nozzle 37 inclined upward and the horizontal plane is 25°, increasing the disturbance range of the flue gas inside the pulverizing furnace 50.

[0056] Consisted of Figure 1 andFigure 4 Given that, in addition, a secondary air combustion support system is composed of a secondary air blower 7, a front wall secondary air damper nozzle 34 for combustion support, a rear wall secondary air damper nozzle 36 for combustion support, and a detection assembly. Specifically, an outlet air duct 10 of the secondary air blower 7 is installed at the output end of the secondary air blower 7. An air supply header A 11 and an air supply header B 12 are provided at the air outlet end of the outlet air duct 10 of the secondary air blower 7. The air inlet end of the front wall secondary air damper nozzle 34 for combustion support is installed on one side of the air supply header A 11. At the same time, the nozzle end of the front wall secondary air damper nozzle 34 for combustion support is inclined downward and penetrates and is installed in the groove wall of the rear arch water-cooled wall 30. The air inlet end of the rear wall secondary air damper nozzle 36 for combustion support is installed on one side of the air supply header B 12. At the same time, the rear wall secondary air damper nozzle 36 for combustion support is inclined upward and penetrates and is installed in the groove wall of the rear wall water-cooled wall 27. More specifically, the external air is sent into the air supply header A 11 and the air supply header B 12 by the secondary air blower 7, and then sent into the furnace by the front wall secondary air damper nozzle 34 for combustion support and the rear wall secondary air damper nozzle 36 for combustion support.

[0057] More specifically, the front wall secondary air damper nozzle 34 for combustion support and the rear wall secondary air damper nozzle 36 for combustion support are arranged 1000 mm above the first recirculated flue gas nozzle 35 and the second nozzle 37. The nozzles of the front wall secondary air damper nozzle 34 for combustion support and the rear wall secondary air damper nozzle 36 for combustion support are both designed into an elliptical structure, and the nozzles are in a diffused shape, with a diffusion angle of 17.7°. The aspect ratio of the inner diameter of the elliptical nozzle is 100:30, and the wall thickness of the nozzle is 8 mm. The material is made of 310S material. The elliptical and diffused nozzles can increase the coverage range when the recirculated flue gas disturbs the high-temperature flue gas in the furnace, ensure the full combustion of the volatile matter in the furnace, and reduce the generation of CO. The front wall secondary air damper nozzle 34 for combustion support and the rear wall secondary air damper nozzle 36 for combustion support are respectively connected to the air supply header A 11 and the air supply header B 12. The secondary air blower 7 sends fresh air into the air supply header A 11 and the air supply header B 12 through the outlet air duct 10 of the secondary air blower 7.

[0058] Preferably, the detection assembly includes a CO / O2 online laser gas analyzer 33 and a zirconia online oxygen analyzer 47. Specifically, a channel is provided at the upper end of the front wall 26 of the waste heat boiler. The CO / O2 online laser gas analyzer 33 is installed at the outlet of the channel, and the zirconia online oxygen analyzer 47 is installed at the outlet of the economizer 70. More specifically, the CO / O2 online laser gas analyzer 33 and the zirconia online oxygen analyzer 47 installed at the outlet of the channel can quickly and accurately detect the average concentration of the gas on the laser path, which is beneficial to the real-time monitoring of the change of the combustion condition of the incinerator and can make a timely response through the combustion control system. When the CO concentration in the furnace is on the high side and the oxygen content is on the low side, the secondary air blower 7 can quickly adjust the operating frequency, and the primary air blower 8 can also appropriately increase the frequency to ensure stable combustion and the CO concentration does not exceed the standard.

[0059] byFigure 1 and Figure 4 Given that, the low calorific value waste combustion mechanism is installed on one side of the outlet flue 9 of the circulation fan. The low calorific value waste combustion mechanism includes a recirculated flue gas bypass pipeline A17, an electric damper C16, a flue gas preheater 18, a recirculated flue gas bypass pipeline B19, and an electric regulating damper B20.

[0060] Specifically, the recirculated flue gas bypass pipeline A17 is installed on one side of the outlet flue 9 of the circulation fan. The electric damper C16 is installed on one side of the recirculated flue gas bypass pipeline A17. The flue gas preheater 18 is installed at the outlet end of the recirculated flue gas bypass pipeline A17. The recirculated flue gas bypass pipeline B19 is installed at the output end of the flue gas preheater 18. The electric regulating damper B20 is installed on one side of the recirculated flue gas bypass pipeline B19. The outlet end of the recirculated flue gas bypass pipeline B19 is connected and installed on one side of the flue gas mixer 21.

[0061] More specifically, when burning low calorific value waste, the furnace temperature may be relatively low. At this time, injecting recirculated flue gas may lead to the risk that the furnace temperature cannot reach 850 °C. Therefore, another way of injecting recirculated flue gas into the furnace is designed in this system. Close the electric damper B15, open the electric damper C16 and the electric regulating damper B20. The recirculated flue gas passes through the recirculated flue gas bypass pipeline A17, the flue gas preheater 18, and the flue gas mixer 21 in sequence, and is mixed with the primary air and then sent to the drying section 45 of the lower wind chamber of the incinerator. The flue gas preheater 18 can heat the recirculated flue gas temperature to 220 - 250 °C, which can avoid low-temperature corrosion of the drying section 45 of the lower wind chamber of the incinerator. The heating heat source comes from the steam of the steam drum or the first extraction of the steam turbine.

[0062] Sending the recirculated flue gas into the drying section 45 of the lower wind chamber of the incinerator can replace part of the primary hot air, strengthen the drying of the waste, and at the same time, can save the steam extraction amount for heating the primary air.

[0063] By Figure 1 and Figure 4 Given that, finally, as a supplement to the flue gas recirculation low NOx combustion system, the traditional way of injecting biogas into the furnace is to send the biogas into the garbage pit and enter the furnace with the primary air; or burn it through the biogas burner and then send it into the furnace; although these two ways do not waste energy, they do not fully utilize the functionality of injecting biogas into the furnace.

[0064] The biogas injection mechanism into the furnace is installed on one side of the flue gas mixer 21. The biogas injection mechanism into the furnace includes a biogas combustion-supporting burner 41, a biogas combustion chamber 40, a biogas pipeline 42, a biogas combustion-supporting fan 43, a biogas flue gas pipeline 39, and an electric damper D38.

[0065] Specifically, the biogas pipeline 42 is arranged at the input end on the right side of the biogas booster burner 41. The biogas booster fan 43 is arranged on one side of the biogas pipeline 42. The biogas combustion chamber 40 is arranged at the output end on the left side of the biogas booster burner 41. The biogas flue gas pipeline 39 is arranged at the gas transmission end on the left side of the biogas combustion chamber 40. The electric damper D38 is arranged on one side of the biogas flue gas pipeline 39. One side of the biogas flue gas pipeline 39 is connected and installed to the flue gas mixer 21. More specifically, the biogas from the leachate treatment station is sent to the biogas combustion chamber 40 for combustion. The biogas combustion chamber 40 is equipped with a separate biogas booster fan 43. The flue gas after combustion passes through the biogas flue gas pipeline 39 and is sent into the flue gas mixer 21 to be mixed with the primary air, and then sent into the drying section 45 of the lower wind chamber of the incinerator. When the recirculated flue gas and the biogas combustion flue gas enter the drying section 45 of the lower wind chamber of the incinerator simultaneously, the electric regulating damper A46 can be adjusted to flexibly adjust the amount of primary air entering the drying section 45 of the lower wind chamber of the incinerator.

[0066] The high-temperature biogas flue gas after combustion is sent into the drying section 45 of the lower wind chamber of the incinerator, which can replace part of the primary hot air, strengthen the drying of the garbage, and at the same time, can save the extraction amount of the primary air heating steam.

[0067] Preferably, the inlet flue 5 of the recirculation fan, the outlet flue 9 of the circulation fan, the recirculated flue gas bypass pipeline A17 and the recirculated flue gas bypass pipeline B19 are all fiberglass ventilation pipelines. The fiberglass ventilation pipeline has a strong ability to resist acid and alkali corrosion, and the service temperature is less than 250 °C, meeting the use requirements of the recirculated flue gas pipeline. At the same time, the fiberglass ventilation pipe is relatively light in weight, convenient for installation. The pipeline is installed obliquely along the direction of the flue gas advance, and the inclination is not less than one-thousandth. A drain valve is set at the lowest point of the pipeline to automatically discharge condensate, air and carbon dioxide gas, and at the same time, prevent the leakage of steam to the maximum extent.

[0068] In summary, Embodiment 1:

[0069] The garbage burns on the incinerator grate 44. The air required for combustion mainly comes from the primary air sent by the primary fan 8. In addition, the air sent into the furnace by the secondary fan 7 serves as the auxiliary air to promote the mixing of the furnace flue gas and the full combustion of the volatile matter. The excess air coefficient of the primary air is controlled at λ = 1.1 - 1.27, and the excess air coefficient of the secondary air is controlled at λ = 0.23 - 0.13, keeping the combustion on the incinerator grate 44 in a relatively oxygen-deficient state to inhibit the formation of fuel-type NOx. At this time, the electric damper C16 is closed, and the recirculated flue gas is only sent into the front wall header 13 and the rear wall header 14, and enters the furnace from the connected first nozzle 35 and second nozzle 37 to fully disturb and mix the flue gas and promote the burnout of the volatile matter.

[0070] The new first nozzle 35 and second nozzle 37 adopted have a diffusing effect, with a wider disturbance coverage range for the furnace flue gas. Compared with traditional nozzles, they have a better disturbance effect on the furnace flue gas. The front wall combustion-supporting secondary air damper nozzle 34 and the rear wall combustion-supporting secondary air damper nozzle 36 also adopt the same nozzles, ensuring that the fresh air for afterburning can be fully mixed with the flue gas. After the recirculated flue gas and the afterburning secondary air are sent into the furnace, the local temperature of the furnace can be reduced, inhibiting the generation of thermal NOx. The on-line laser gas analyzer 33 for CO / O2 installed at the outlet of the first channel of the furnace monitors the changes in the CO and O2 concentrations in the furnace in real time to ensure the stability of the combustion condition.

[0071] This low-NOx combustion method is to achieve the goals of a low excess air ratio and a low NOx generation amount through technical means such as relatively oxygen-deficient combustion + air staging combustion + sufficient mixing and disturbance to reduce the local furnace temperature.

[0072] Some studies in the industry further reduce the primary air excess air coefficient λ to 0.9 - 1 to maintain absolute oxygen-deficient combustion. This scheme is difficult to implement in practice. Different from pulverized coal furnaces, the combustion of garbage on the grate belongs to layered combustion and requires more oxygen. When the primary air excess air coefficient λ is further reduced to the range of 0.9 - 1, it will lead to incomplete combustion, the generation of raw materials, and the risk that the furnace temperature drops below 850 °C. When implementing low-NOx combustion with flue gas recirculation, the stability of the combustion of the incinerator 50, the furnace temperature, and the heat loss rate of the furnace slag are issues that must be considered first.

[0073] Example 2:

[0074] When burning low-calorific value garbage or when a large amount of leachate is sprayed back into the furnace, resulting in a low furnace temperature, the recirculated flue gas will not be directly sent into the furnace but will be sent into the drying section 45 of the lower air chamber of the incinerator to strengthen the drying of the garbage and promote combustion. At this time, the primary air excess air coefficient is controlled at λ = 1.1 - 1.27, and the secondary air excess air coefficient is controlled at λ = 0.23 - 0.13. The on-line laser gas analyzer 33 for CO / O2 installed at the outlet of the first channel of the furnace monitors the CO and O2 concentrations in the furnace in real time. When the O2 is low and the CO concentration deviates from the design value, the input of the primary / secondary air is increased in a timely manner to ensure stable combustion.

[0075] The specific operation method is to close the electric damper B15, open the electric damper C16 and the electric regulating damper B20. The recirculated flue gas passes through the recirculated flue gas bypass pipeline A17, the flue gas preheater 18, and the flue gas mixer 21 in sequence, and is mixed with the primary air and then sent into the drying section 45 of the lower air chamber of the incinerator. The flue gas preheater 18 can heat the temperature of the recirculated flue gas to 220 - 250 °C, which can avoid the low-temperature corrosion of the drying section 45 of the lower air chamber of the incinerator. The heating heat source comes from the steam of the steam drum or the first extraction of the steam turbine.

[0076] The recirculated flue gas is sent to the drying section 45 of the lower air chamber of the incinerator, which can replace part of the primary hot air, strengthen the drying of the garbage, and at the same time, save the extraction amount of steam for heating the primary air.

[0077] Example 3:

[0078] While the flue gas recirculation system is operating, the biogas from the leachate treatment station is sent to the biogas combustion chamber 40 for combustion. The biogas auxiliary burner 41 is equipped with a separate biogas auxiliary combustion fan 43, which is installed in the biogas combustion chamber 40. The flue gas after combustion passes through the biogas flue gas pipeline 39 and is sent to the flue gas mixer 21 to be mixed with the primary air, and then sent to the drying section 45 of the lower air chamber of the incinerator; when the recirculated flue gas and the flue gas from biogas combustion enter the drying section 45 of the lower air chamber of the incinerator simultaneously, the electric regulating damper A46 can be adjusted to flexibly adjust the amount of primary air entering the drying section 45 of the lower air chamber of the incinerator.

[0079] This way of introducing biogas into the furnace gives full play to the functional heat of biogas combustion, strengthens the drying of the garbage, and promotes combustion; at the same time, the high-temperature biogas flue gas after combustion is sent to the drying section 45 of the lower air chamber of the incinerator, which can replace part of the primary hot air and save the extraction amount of steam for heating the primary air.

[0080] Method for using the flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler: Garbage enters above the incinerator grate 44 from the garbage feed inlet 51 for combustion. The flue gas of the incinerator, starting from the outlet of the waste heat boiler, enters the semi-dry desulfurization tower 31, the bag filter 32, the flue connecting the induced draft fan 2 and the induced draft fan 1 in sequence under the suction of the induced draft fan 1 and is sent to the chimney;

[0081] Primary air: The air provided by the primary air fan 8 is sent to the drying section 45 of the lower air chamber of the incinerator and the burnout section 25 of the lower air chamber of the incinerator after being heated in the air preheating chamber 23 and passing through the flue gas mixer 21. The heat source required for heating the air preheating chamber 23 comes from the boiler steam drum and the first extraction of the steam turbine;

[0082] Recirculated flue gas: Close the electric damper C16. The recirculated flue gas is sent to the front wall header 13 and the rear wall header 14 of the furnace through the circulation fan 6, and then sent into the furnace through the first nozzle 35 and the second nozzle 37 to fully stir the high-temperature flue gas in the furnace. When the recirculation system is shut down, close the electric damper A3, and at the same time start the bypass purge air electric damper 4, and use the negative pressure of the circulation fan 6 to suck in fresh air to purge the pipeline;

[0083] Combustion-supporting secondary air: The secondary air blower 7 transports air to the air inlet header A11 and the air inlet header B12 through the secondary air blower outlet air duct 10, and then sends it into the furnace through the front wall combustion-supporting secondary air damper nozzle 34 and the rear wall combustion-supporting secondary air damper nozzle 36. The CO\O2 online laser gas analyzer 33 and the zirconia online oxygen analyzer 47 detect the average gas concentration. When the CO concentration in the furnace is on the high side and the oxygen content is on the low side, the secondary air blower 7 quickly adjusts the operating frequency, and the primary air blower 8 appropriately increases the frequency to ensure stable combustion and that the CO concentration does not exceed the standard;

[0084] Combustion of low calorific value waste: Close the electric damper B15, open the electric damper C16 and the electric regulating damper B20. The recirculating flue gas sequentially passes through the recirculating flue gas bypass pipeline A17, the flue gas preheater 18 and the flue gas mixer 21, mixes with the primary air and is sent to the drying section 45 of the lower wind chamber of the incinerator, and then the flue gas preheater 18 heats the temperature of the recirculating flue gas to 220 - 250 °C, and the heating heat source comes from the steam of the steam drum or the first extraction of the steam turbine;

[0085] Biogas into the furnace: The biogas is sent to the biogas combustion chamber 40 for combustion. The biogas combustion-supporting burner 41 is equipped with a separate biogas combustion-supporting blower 43. The flue gas after combustion passes through the biogas flue gas pipeline 39 and is sent into the flue gas mixer 21 to mix with the primary air, and finally sent to the drying section 45 of the lower wind chamber of the incinerator; When the recirculating flue gas and the biogas combustion flue gas enter the drying section 45 of the lower wind chamber of the incinerator at the same time, adjust the electric regulating damper A46 to control the primary air volume entering the drying section 45 of the lower wind chamber of the incinerator.

[0086] Beneficial effects obtained from the incinerator 50, the primary air mechanism, the waste heat boiler 60, the semi-dry desulfurization tower 31, the bag filter 32, the induced draft fan 1, the circulation fan 6, the first nozzle 35, the second nozzle 37, the secondary air blower 7, the front wall combustion-supporting secondary air damper nozzle 34, the rear wall combustion-supporting secondary air damper nozzle 36, the detection component, the low calorific value waste combustion mechanism and the biogas into the furnace mechanism: Flue gas recirculation combined with low oxygen combustion can improve the boiler efficiency and increase the boiler evaporation capacity. Flue gas recirculation low NOx combustion can approximately reduce the original nitrogen oxide generation amount by 30%, save the usage amount of the backend denitration agent, and reduce the production cost; At the same time, it reduces the pressure on the backend denitration system and is also beneficial to controlling the nitrogen oxide emission concentration and ammonia slip at a lower level. The flue gas after biogas combustion is sent into the primary air for mixing and then sent to the drying section of the lower wind chamber of the incinerator to dry the waste, giving full play to the functional heat energy of biogas combustion and reducing the steam consumption of the primary air preheater. The recirculating flue gas is sent into the lower wind chamber of the incinerator to dry the waste, enhancing the adaptability of the flue gas recirculation system to the combustion of low calorific value waste and reducing the steam consumption of the primary air preheater. After implementing flue gas recirculation, the reducing atmosphere in the furnace can be enhanced, mitigating the high-temperature corrosion of the heating surface in the furnace. At the same time, the local temperature reduction in the furnace brought about by flue gas recirculation can also mitigate furnace fouling.

[0087] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler, characterized in that, It comprises an incinerator (50), wherein a primary air mechanism is provided on one side of the incinerator (50); A waste heat boiler (60) is disposed on one side of the incinerator (50), a semi-dry deacidification tower (31) is disposed on one side of the waste heat boiler (60), a bag filter (32) is disposed on one side of the semi-dry deacidification tower (31), and an induced draft fan (1) is disposed on one side of the bag filter (32); A circulation fan (6) is arranged on one side of the induced draft fan (1), and a first nozzle (35) and a second nozzle (37) are arranged on one side of the circulation fan (6), the first nozzle (35) being arranged obliquely downward on one side of the waste heat boiler (60), and the second nozzle (37) being arranged obliquely upward on one side of the waste heat boiler (60), a secondary fan (7) is arranged on one side of the waste heat boiler (60), and a front wall combustion-supporting secondary air gate nozzle (34) and a rear wall combustion-supporting secondary air gate nozzle (36) are arranged at the output end of the secondary fan (7), the front wall combustion-supporting secondary air gate nozzle (34) being arranged obliquely downward on one side of the waste heat boiler (60), and the rear wall combustion-supporting secondary air gate nozzle (36) being arranged obliquely upward on one side of the waste heat boiler (60), and a detection component is installed on one side of the waste heat boiler (60); A low calorific value garbage burning mechanism is provided between the circulating fan (6) and the incinerator (50); A biogas inlet mechanism is also provided on one side of the incinerator (50).

2. The flue gas recirculation system for improving the performance of the domestic waste incineration power generation boiler according to claim 1, wherein The waste heat boiler (60), the semi-dry deacidification tower (31) and the bag filter (32) are interconnected via a smoke path in sequence; an induced draft fan connected to a smoke duct (2) is provided on the side of the bag filter (32) facing away from the semi-dry deacidification tower (31); and an induced draft fan (1) is provided on the other side of the induced draft fan connected to the smoke duct (2).

3. The flue gas recirculation system for improving the performance of the domestic waste incineration power generation boiler according to claim 2, wherein, The incinerator (50) comprises a garbage feed port (51), an incinerator grate (44) is arranged on one side of the garbage feed port (51), an incinerator downwind chamber drying section (45) is arranged on one side of the incinerator grate (44), an incinerator downwind chamber combustion and burnout section (25) is arranged on one side of the incinerator downwind chamber combustion and burnout section (25), and a slag discharge port (52) is arranged on one side of the incinerator downwind chamber combustion and burnout section (25).

4. The flue gas recirculation system for improving the performance of the domestic waste incineration power generation boiler according to claim 3, characterized in that, The primary air mechanism comprises a primary air fan (8), an air preheating chamber (23) is arranged at the air outlet end of the primary air fan (8) through a pipeline, a flue gas mixer (21) is arranged at the air outlet end of the air preheating chamber (23) through a primary air duct A (22), the air outlet end of the flue gas mixer (21) is connected to a drying section (45) of a lower air chamber of the incinerator through a pipeline, an electric regulating damper A (46) is arranged at one end of the primary air duct A (22) close to the flue gas mixer (21), and a middle part of the primary air duct A (22) is connected to a combustion and burnout section (25) of a lower air chamber of the incinerator through a primary air duct B (24).

5. The flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler according to claim 4, wherein, The induced draft fan (1) and the recycle fan (6) are interconnected through the recycle fan inlet flue (5). An electric damper A (3) is arranged on one side of the recycle fan inlet flue (5). A bypass purge air electric damper (4) is also arranged on one side of the recycle fan inlet flue (5) through a pipeline. The outlet end of the recycle fan (6) is provided with a recycle fan outlet flue (9). An electric damper B (15) is arranged on one side of the recycle fan outlet flue (9). The outlet end of the recycle fan outlet flue (9) is provided with a front wall header (13) and a rear wall header (14). One end of the front wall header (13) is connected and installed with a first nozzle (35). One end of the rear wall header (14) is connected and installed with a second nozzle (37). One side of the secondary air fan (7) is provided with a secondary air fan outlet duct (10). The outlet end of the secondary air fan outlet duct (10) is provided with an air supply header A (11) and an air supply header B (12). One side of the air supply header A (11) is installed at the inlet end of the front wall secondary combustion air damper nozzle (34). The air supply header B (12) is connected and installed at the inlet end of the rear wall secondary combustion air damper nozzle (36).

6. The flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler according to claim 5, wherein The waste heat boiler (60) includes a front wall of the waste heat boiler (26). A front arch water-cooled wall (29) is arranged at the bottom of the front wall of the waste heat boiler (26). The front arch water-cooled wall (29) is arranged on one side of the waste feed inlet (51). A rear arch water-cooled wall (30) is arranged on one side of the slag discharge outlet (52). A rear wall water-cooled wall (27) is arranged at the top of the rear arch water-cooled wall (30). A roof water-cooled wall (28) is arranged at the top of the front wall of the waste heat boiler (26). A furnace cavity is arranged on one side of the roof water-cooled wall (28) and the rear wall water-cooled wall (27). A economizer (70) is arranged inside the furnace cavity.

7. The flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler according to claim 6, wherein, The detection component includes a CO / O2 online laser gas analyzer (33) installed on one side of the front wall of the waste heat boiler (26). A zirconia online oxygen analyzer (47) is installed at the outlet of the economizer (70).

8. The flue gas recirculation system for improving the performance of the domestic waste incineration power generation boiler according to claim 5, wherein, The mechanism for burning low calorific value waste includes a recycle flue gas bypass pipeline A (17) arranged on one side of the recycle fan outlet flue (9). An electric damper C (16) is arranged on one side of the recycle flue gas bypass pipeline A (17). The outlet end of the recycle flue gas bypass pipeline A (17) is provided with a flue gas preheater (18). The flue gas preheater (18) is connected to a flue gas mixer (21) through a recycle flue gas bypass pipeline B (19). An electric regulating damper B (20) is arranged on one side of the recycle flue gas bypass pipeline B (19); The recycle fan inlet flue (5), the recycle fan outlet flue (9), the recycle flue gas bypass pipeline A (17) and the recycle flue gas bypass pipeline B (19) are all FRP ventilation pipelines.

9. The flue gas recirculation system for improving the performance of a domestic waste incineration power generation boiler according to claim 6, wherein, The biogas feeding-in mechanism includes a biogas combustion chamber (40). A biogas auxiliary burner (41) is arranged on one side of the biogas combustion chamber (40). A biogas pipeline (42) is arranged on one side of the biogas auxiliary burner (41). A biogas auxiliary combustion blower (43) is arranged on one side of the biogas pipeline (42). The biogas combustion chamber (40) is interconnected with the flue gas mixer (21) through a biogas flue gas pipeline (39). An electric damper D (38) is arranged on one side of the biogas flue gas pipeline (39).

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