A pulverized coal boiler with flue gas fly ash secondary combustion function

Abstract

The application discloses a pulverized coal boiler with flue gas fly ash secondary combustion function, and belongs to the technical field of flue gas fly ash secondary combustion of the pulverized coal boiler. One side of a boiler box of the pulverized coal boiler is fixedly connected with a wall-encased superheater, the lower end of the wall-encased superheater is fixedly connected with a water cooling box, the lower end of the water cooling box is provided with an air preheater, the flue gas outlet of the air preheater is connected with a backflow air bellow, a flow guide mechanism is arranged on the inner side of the backflow air bellow, and flue gas backflow pipes are fixedly connected to the two sides of the backflow air bellow; the two flue gas backflow pipes are connected to the front and rear sides of the boiler box respectively at the ends away from the backflow air bellow; the backflow air bellow and the flue gas backflow pipes make the burned fly ash in the pulverized coal boiler to be secondary circulated; the application makes the unburned fly ash to be burned again, improves the stability of complete combustion of the pulverized coal boiler, and finally solves the problem of low energy utilization efficiency.

Description

Technical Field

[0001] This invention belongs to the field of secondary combustion technology of flue gas and fly ash in pulverized coal boilers, specifically a pulverized coal boiler with secondary combustion function of flue gas and fly ash. Background Technology

[0002] With increasingly stringent environmental protection requirements, the reduction of nitrogen oxides (NOx) x Emissions of pollutants such as NOx have become a key concern; traditional pulverized coal boilers, limited by furnace size and combustion methods, emit flue gas containing NOx. x Problems such as high emissions and high combustible content in fly ash are becoming increasingly prominent for small and medium-sized industrial pulverized coal boilers under increasingly stringent emission standards.

[0003] Meanwhile, in traditional pulverized coal boilers, the fly ash formed after pulverized coal combustion often contains unburned pulverized coal particles and coke particles produced during combustion. These combustibles are the main source of incomplete solid combustion loss in pulverized coal boilers, leading to reduced energy utilization efficiency. For example, the combustible content in the fly ash produced by existing pulverized coal boilers is about 4% to 5%, and the fly ash produced by pulverized coal boilers cannot be re-burned. Therefore, this application designs a pulverized coal boiler with a secondary combustion function for flue gas fly ash to solve the above problems. Summary of the Invention

[0004] This invention overcomes the shortcomings of existing technologies and proposes a pulverized coal boiler with secondary combustion function for flue gas and fly ash; this invention is achieved through the following technical solution:

[0005] A pulverized coal boiler with secondary combustion function of flue gas and fly ash includes a boiler box; multiple sets of heating mechanisms are installed at the upper end of the boiler box; a wall-mounted superheater is fixedly connected to one side of the boiler box; a water-cooled box is fixedly connected to the lower end of the wall-mounted superheater; an air preheater is installed at the lower end of the water-cooled box; the flue gas outlet of the air preheater is connected to a return air box; a flow guiding mechanism is installed inside the return air box; and flue gas return pipes are fixedly connected to both sides of the return air box. The ends of the two flue gas return pipes away from the return air box are respectively connected to the front and rear sides of the boiler box; and a blower is fixedly connected to each of the two flue gas return pipes; through the return... The wind box and flue gas return pipe enable the pulverized fly ash after combustion to undergo secondary circulation in the pulverized coal boiler. The flow guiding mechanism includes cross blades installed at both ends inside the return wind box. The cross blades are rotatably connected to the inner wall of the return wind box via a rotating shaft. Flow guide plates are installed at equal intervals on the rear side of the cross blades. A flow obstruction screen is set on the rear side of the flow guide plates. One side of the flow obstruction screen is hinged to the inner wall of the return wind box. A third servo motor is installed outside the return wind box. The output end of the third servo motor passes through the return wind box and is fixedly connected to an elliptical block. The elliptical block is located at the lower end of one side of the flow obstruction screen and is in contact with the flow obstruction screen.

[0006] Furthermore, an auger is installed at the lower end of the flow-blocking screen plate. The auger is located inside the return air box and below the flue gas return pipe. One end of the auger extends through to the outside of the return air box and is connected to the first servo motor. The end of the auger away from the first servo motor is connected to a collection box.

[0007] Furthermore, fixed blocks are installed at equal intervals on the flue gas return pipe, and semi-circular sealing plates are symmetrically installed at the lower end of the fixed blocks. A torsion spring is provided between the semi-circular sealing plate and the fixed block, and an arc-shaped barrier strip is fixedly connected to the inner wall of the flue gas return pipe. One side of the semi-circular sealing plate abuts against the arc-shaped barrier strip, and the arc-shaped barrier strip and the semi-circular sealing plate are fixed by neodymium iron boron magnets.

[0008] Furthermore, symmetrical inverted L-shaped flue gas pipes are arranged inside the boiler box, and one end of the flue gas return pipe connected to the boiler box is connected to the corresponding inverted L-shaped flue gas pipe; U-shaped support frames are fixedly connected to the front and rear sides of the boiler box, and a second servo motor is installed on the U-shaped support frame. The drive shaft of the second servo motor passes through the U-shaped support frame and is fixedly connected to a drive gear. A driven gear is meshed at the lower end of the drive gear, and a fixed rod is fixedly connected to the middle of the driven gear. The other end of the fixed rod passes through the boiler box and is fixedly connected to one end of a drive bevel gear inside the boiler box. The other end of the drive bevel gear meshes downward with a driven bevel gear. A connecting rod is fixedly connected vertically downward to the driven bevel gear. The connecting rod passes vertically through the inverted L-shaped flue gas pipe and is fixedly connected to the inner surface of the sealing plate; the sealing plate is rotatably connected to the outlet end of the inverted L-shaped flue gas pipe; fan-shaped air outlets are symmetrically opened on the sealing plate, and a base plate is rotatably connected to the bottom of the sealing plate. One side of the base plate is fixedly connected to the inner wall of the boiler box; fan-shaped air outlets are also symmetrically arranged on the base plate.

[0009] Furthermore, a protective box is installed on the outside of the inverted L-shaped flue pipe, and a high-temperature resistant asbestos layer is provided on the inner wall of the protective box; the driving bevel gear, the driven bevel gear and the connecting rod are all located inside the protective box, and the outlet end of the inverted L-shaped flue pipe is located on the outside of the protective box.

[0010] Furthermore, magnetic mesh plates are vertically inserted and installed on both sides above the return air box, and sealing blocks are installed at the connection between the two ends of the return air box and the flue gas return pipe. A telescopic spring is installed between the sealing block and the blower. One end of the telescopic spring is fixedly connected to the cross fixing plate at the blower outlet, and the other end of the telescopic spring is fixedly connected to one side of the sealing block. The sealing block is movably engaged at the blower outlet.

[0011] Furthermore, the multiple heating mechanisms include a roof superheater, a rear screen superheater block, a high-temperature superheater block, a low-temperature superheater block, and an economizer block installed on the top of the boiler box; a full-screen superheater, a rear screen superheater, and a high-temperature superheater are installed inside the boiler box; a low-temperature superheater is installed inside the wall-mounted superheater; the lower end of the roof superheater is connected to the full-screen superheater, the lower end of the rear screen superheater block is fixedly connected to the rear screen superheater, the lower end of the high-temperature superheater block is fixedly connected to the high-temperature superheater, and the lower end of the low-temperature superheater block is fixedly connected to the low-temperature superheater.

[0012] Furthermore, a water-cooling mechanism is installed inside the water-cooled box. The water-cooling mechanism includes a serpentine tube, with a hanging pipe fixedly connected to the upper end of the serpentine tube. The end of the hanging pipe away from the serpentine tube is connected to the lower end of the coal-saving block.

[0013] Furthermore, the bottom of the boiler box is covered with a water-cooled block, and multiple vertically upward cooling pipes are fixedly connected to one side of the water-cooled block at equal intervals. The ends of the cooling pipes away from the water-cooled block are all fixedly connected to the lower end of the steam drum. The steam drum, roof superheater, rear screen superheater, high-temperature superheater, low-temperature superheater, and economizer are interconnected through multiple connecting pipes.

[0014] Furthermore, a feeding hopper is installed at the upper rear side of the boiler box, and burners are installed at equal intervals around the lower side of the boiler box. The burners penetrate the boiler box, and multiple combustion nozzles are vertically and equally spaced at the end of the burners located inside the boiler box.

[0015] The beneficial effects of this invention compared to the prior art are as follows:

[0016] 1. This invention uses multiple sets of heating mechanisms in conjunction with the boiler box to increase the boiler's heat conversion efficiency and improve the efficiency of heat conversion in fly ash; furthermore, the flow guiding mechanism works in conjunction with the flue gas return pipe to allow unburned fly ash to be burned again, improving the stability of complete combustion in pulverized coal boilers and ultimately solving the problem of low energy utilization efficiency.

[0017] 2. This invention utilizes a wall-mounted superheater in conjunction with the boiler to achieve more complete combustion of fly ash. The fly ash fed into the hopper is burned through a burner and combustion nozzles, with the combustion zone reaching temperatures as high as 1200℃, providing a high-temperature environment for complete combustion. Furthermore, the unburned fly ash is returned to the boiler via a return air box and flue gas return pipe, achieving secondary combustion, thus improving the utilization rate of pulverized coal and reducing energy waste.

[0018] 3. The present invention comprises multiple sets of heating mechanisms (roof superheater, rear screen superheater block, high-temperature superheater block, low-temperature superheater block, and economizer block, etc.) interconnected, and each heating block is equipped with a superheater and other equipment. The high-temperature superheater block and the high-temperature superheater further enhance heat conversion, which facilitates the improvement of energy utilization efficiency of fly ash. The water cooling mechanism uses a serpentine tube in conjunction with the economizer block to absorb heat with water. The steam drum is connected to each heating mechanism through connecting pipes and is equipped with a vertical cyclone separator and a louvered separator inside to facilitate steam-water separation and storage of boiler water, ensuring stable system operation and improving energy conversion efficiency.

[0019] 4. This invention utilizes the cross-shaped blades and guide plates in the flow guiding mechanism to reduce the velocity of high-speed flue gas, facilitating its entry into the flue gas return pipe. The obstruction screen plate screens and collects excess fly ash. The third servo motor and the elliptical block work together to vibrate the obstruction screen plate, causing the deposited fly ash to float again for re-combustion. Simultaneously, the first servo motor drives the auger to collect the fly ash, reducing fly ash emissions and improving environmental performance. The neodymium iron boron magnets between the arc-shaped barrier strip and the semi-arc-shaped sealing plate, along with the cooperation between the fixing block and the semi-arc-shaped sealing plate, effectively prevent flue gas from flowing back into the flue gas return pipe, ensuring the flue gas flows along the designed path and improving the stability of the combustion system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall three-dimensional first-view structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the overall three-dimensional second-view structure of the present invention;

[0022] Figure 3 This is a schematic diagram of the overall three-dimensional third-view structure of the present invention;

[0023] Figure 4 This is a side cross-sectional view of the present invention.

[0024] Figure 5 For the present invention Figure 2 Enlarged schematic diagram of the structure at part A in the middle;

[0025] Figure 6 This is a three-dimensional structural diagram of the semi-circular enclosed plate of the present invention;

[0026] Figure 7 This is a schematic diagram of the side cross-sectional structure of the pot box of the present invention;

[0027] Figure 8 For the present invention Figure 7 Enlarged schematic diagram of the structure of part B in the middle;

[0028] Figure 9 This is a top view cross-sectional structural diagram of the return air box of the present invention;

[0029] Figure 10 This is a schematic diagram of the bottom cross-sectional structure of the boiler box of the present invention;

[0030] Figure 11 This is a top view cross-sectional structural diagram of the flue gas return pipe of the present invention;

[0031] Figure 12 For the present invention Figure 11 Enlarged schematic diagram of the structure at part C;

[0032] Figure 13 For the present invention Figure 4 Enlarged schematic diagram of the structure in part D.

[0033] The components in the diagram are numbered as follows: 1. Support plate; 2. Support block; 3. Boiler box; 4. Burner; 5. Water-cooled block; 6. Steam drum; 7. Connecting pipe; 8. Roof superheater; 9. Rear screen superheater; 10. High-temperature superheater; 11. Low-temperature superheater; 12. Economizer block; 13. Wall-mounted superheater; 14. Water-cooled box; 15. Air preheater; 16. Return air box; 17. Blower; 18. First servo motor; 19. Flue gas return pipe; 20. Fixing block; 21. Second servo motor; 22. Feed hopper; 23. Full-screen superheater; 24. Rear screen superheater. 25. High-temperature superheater; 26. Low-temperature superheater; 27. Serpentine tube; 28. Combustion nozzle; 29. ​​Protective box; 30. Screwdriver; 31. Semi-arc-shaped sealing plate; 32. Arc-shaped barrier strip; 33. U-shaped support frame; 34. Driving gear; 35. Driven gear; 36. Driving bevel gear; 37. Guide plate; 38. Flow-blocking screen plate; 39. Cross blade; 40. Third servo motor; 41. Sealing plate; 42. Magnetic mesh plate; 43. Sealing block; 44. Telescopic spring; 45. Inverted L-shaped flue pipe; 46. Connecting rod; 47. Elliptical block. Detailed Implementation

[0034] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0035] See Figures 1 to 13This embodiment proposes a pulverized coal boiler with secondary combustion function of flue gas and fly ash, including a support plate 1 and a support block 2 located on the upper end of the support plate 1. A boiler box 3 is installed vertically on the upper end of the support block 2. The boiler box 3 is composed entirely of water-cooled walls, and multiple sets of heating mechanisms are installed on the upper end of the boiler box 3. A wall-mounted superheater 13 is fixedly connected to one side of the boiler box 3, and a water-cooled box 14 is fixedly connected to the lower end of the wall-mounted superheater 13. The connection between the boiler box 3 and the wall-mounted superheater 13 facilitates complete combustion of fly ash. A water-cooling mechanism is installed inside the water-cooled box 14, and two air preheaters 15 are installed at the lower end of the water-cooled box 14. The flue gas inlet of the air preheater 15 is connected to the water... The cold box 14 is connected, and the air inlet of the air preheater 15 is connected to a fan; the air outlet of the air preheater 15 is connected to the boiler box 3 to provide air to the boiler box 3, and the flue gas outlet of the air preheater 15 is connected to the return air box 16. A flow guiding mechanism is installed inside the return air box 16, and flue gas return pipes 19 are fixedly connected to both sides of the return air box 16. The ends of the two flue gas return pipes 19 away from the return air box 16 are respectively connected to the front and rear sides of the boiler box 3, and blowers 17 are fixedly connected to both flue gas return pipes 19. Through the return air box 16 and the flue gas return pipes 19, the pulverized fly ash after combustion can be circulated in the pulverized coal boiler.

[0036] A feeding hopper 22 is installed at the upper rear side of the boiler box 3. Burners 4 are installed at equal intervals around the lower perimeter of the boiler box 3. The burners 4 penetrate the boiler box 3, and multiple combustion nozzles 28 are vertically and equally spaced at the end of the burners 4 located inside the boiler box 3. The combustion of pulverized coal added from the feeding hopper 22 is facilitated by the burners 4 and the combustion nozzles 28. A water-cooled block 5 covers the outer bottom of the boiler box 3. Multiple vertically upward cooling pipes are fixedly connected to one side of the water-cooled block 5 at equal intervals. The ends of the cooling pipes away from the water-cooled block 5 are all fixedly connected to the lower end of the steam drum 6.

[0037] The steam drum 6 is connected to multiple sets of heating mechanisms. In this invention, the multiple sets of heating mechanisms include a roof superheater 8, a rear screen superheater block 9, a high-temperature superheater block 10, a low-temperature superheater block 11, and an economizer block 12 installed on the top of the boiler box 3. The steam drum 6, the roof superheater 8, the rear screen superheater block 9, the high-temperature superheater block 10, the low-temperature superheater block 11, and the economizer block 12 are interconnected through multiple connecting pipes 7. The steam drum 6 is equipped with a vertical cyclone separator and a louvered separator, which facilitates steam-water separation and boiler water storage. The multiple sets of heating mechanisms facilitate the improvement of the energy utilization efficiency of fly ash.

[0038] The boiler box 3 is equipped with a full-screen superheater 23, a rear-screen superheater 24, and a high-temperature superheater 25; the wall-mounted superheater 13 is equipped with a low-temperature superheater 26; the lower end of the ceiling superheater 8 is connected to the full-screen superheater 23, the lower end of the rear-screen superheater block 9 is fixedly connected to the rear-screen superheater 24, the lower end of the high-temperature superheater block 10 is fixedly connected to the high-temperature superheater 25, and the lower end of the low-temperature superheater block 11 is fixedly connected to the low-temperature superheater 26; the water-cooling mechanism includes a serpentine tube 27, with a hanging pipe fixedly connected to the upper end of the serpentine tube 27, and the end of the hanging pipe away from the serpentine tube 27 is connected to the lower end of the economizer block 12. Through multiple sets of heating mechanisms and the full-screen superheater 23, rear-screen superheater 24, high-temperature superheater 25, low-temperature superheater 26, and serpentine tube 27 connected to the multiple sets of heating mechanisms, heat is easily absorbed by water.

[0039] Fixed blocks 20 are equidistantly installed on the flue gas return pipe 19. Semi-circular sealing plates 31 are symmetrically installed at the lower end of the fixed blocks 20. A torsion spring is provided between the semi-circular sealing plate 31 and the fixed blocks 20. An arc-shaped barrier strip 32 is fixedly connected to the inner wall of the flue gas return pipe 19. One side of the semi-circular sealing plate 31 abuts against the arc-shaped barrier strip 32, and the arc-shaped barrier strip 32 and the semi-circular sealing plate 31 are fixed together by a neodymium iron boron magnet. When flue gas enters the flue gas return pipe 19, the pressure generated by the flue gas will push the semi-circular sealing plate 31 to rotate and open. When the flue gas volume decreases, the semi-circular sealing plate 31 abuts against the arc-shaped barrier strip 32 under the attraction of the torsion spring and the neodymium iron boron magnet, effectively preventing flue gas backflow.

[0040] The inner side of the boiler box 3 is symmetrically provided with inverted L-shaped flue gas pipes 45. One end of the flue gas return pipe 19 connected to the boiler box 3 is connected to the corresponding inverted L-shaped flue gas pipe 45. U-shaped support frames 33 are fixedly connected to the front and rear sides of the outer wall of the boiler box 3. A second servo motor 21 is installed on the U-shaped support frame 33. The drive shaft of the second servo motor 21 passes through the U-shaped support frame 33 and is fixedly connected to a drive gear 34. A driven gear 35 is meshed at the lower end of the drive gear 34. A fixed rod is fixedly connected to the middle of the driven gear 35. The end of the fixed rod away from the driven gear 35 passes through the boiler box 3 and is connected to one end of the drive bevel gear 36 inside the boiler box 3. A fixed connection is made, with the other end of the driving bevel gear 36 meshing downwards with a driven bevel gear. The driven bevel gear is vertically and fixedly connected to a connecting rod 46, which vertically passes through the inverted L-shaped flue gas pipe 45 and is fixedly connected to the inner surface of the sealing plate 41. The sealing plate 41 is rotatably connected to the outlet end of the inverted L-shaped flue gas pipe 45. The sealing plate 41 has symmetrically opened fan-shaped air outlets, and the bottom of the sealing plate 41 is rotatably connected to a base plate. One side of the base plate is fixedly connected to the inner wall of the boiler box 3. The base plate also has symmetrically arranged fan-shaped air outlets. A protective box 29 is installed on the outside of the inverted L-shaped flue gas pipe 45, and the inner wall of the protective box 29 is provided with a high-temperature resistant asbestos layer. The active bevel gear 36, the driven bevel gear, and the connecting rod 46 are all located inside the protective box 29, while the outlet end of the inverted L-shaped flue gas pipe 45 is located outside the protective box 29. When it is necessary to discharge flue gas from the flue gas return pipe 19 into the boiler 3, the second servo motor 21 is turned on and drives the sealing plate 41 to rotate until the fan-shaped air outlet on the sealing plate 41 corresponds to the fan-shaped air outlet on the bottom plate. At this time, the second servo motor 21 is turned off, and the flue gas can smoothly enter the boiler 3 through the fan-shaped air outlet. When it is not necessary to supply flue gas to the boiler 3, the second servo motor 21 is started, and the fan-shaped air outlet on the sealing plate 41 is rotated to be offset from the fan-shaped air outlet on the bottom plate, which can prevent the flue gas from flowing back through the inverted L-shaped flue gas pipe 45.

[0041] The flow guiding mechanism includes cross blades 39 installed at both ends inside the return air box 16. The cross blades 39 are rotatably connected to the inner wall of the return air box 16 via a rotating shaft. Flow guide plates 37 are installed equidistantly on the rear side of the cross blades 39. The cross blades 39 and the flow guide plates 37 facilitate the reduction of the moving speed of the high-speed flue gas. A flow obstruction screen plate 38 is provided on the rear side of the flow guide plate 37. One side of the flow obstruction screen plate 38 is hinged to the inner wall of the return air box 16. A third servo motor 40 is installed outside the return air box 16. The output end of the third servo motor 40 passes through the return air box 16 and is fixedly connected to an elliptical block 47. The elliptical block 47 is located at the lower end of one side of the flow obstruction screen plate 38 and is in contact with the flow obstruction screen plate 38. The third servo motor 40 drives the elliptical block 47 to rotate, thereby causing the flow obstruction screen plate 38 to vibrate. This allows the fly ash deposited on the flow obstruction screen plate 38 to float again. The floated fly ash can be carried back into the boiler 3 by the flue gas for combustion.

[0042] An auger 30 is installed at the lower end of the flow-blocking screen plate 38. The auger 30 is located inside the return air box 16 and below the flue gas return pipe 19. One end of the auger 30 extends to the outside of the return air box 16 and is connected to the first servo motor 18. The end of the auger 30 away from the first servo motor 18 is connected to a collection box. The fly ash deposited at the bottom of the return air box 16 can be collected into the collection box through the auger 30 and the first servo motor 18.

[0043] Magnetic mesh plates 42 are vertically inserted and installed on both sides of the upper part of the return air box 16, and sealing blocks 43 are installed at the connection between the two ends of the return air box 16 and the flue gas return pipe 19. A telescopic spring 44 is installed between the sealing block 43 and the blower 17. One end of the telescopic spring 44 is fixedly connected to the cross fixing plate at the air outlet of the blower 17, and the other end of the telescopic spring 44 is fixedly connected to one side of the sealing block 43. The sealing block 43 is movably locked at the air outlet of the blower 17. Through the telescopic spring 44 and the sealing block 43, the flue gas and dust can be prevented from entering the interior of the blower 17.

[0044] The working principle of a pulverized coal boiler with secondary combustion function of flue gas and fly ash described in this embodiment is as follows:

[0045] First, pulverized coal to be burned is added to the boiler 3 through the feeding hopper 22. Then, the burner 4 is started, and the combustion flame is ejected from the combustion nozzle 28 to burn the added pulverized coal. The temperature in the combustion zone is as high as 1200℃. Then, through heat flow, the heat is gradually absorbed through the water-cooled wall of the boiler 3, the full-screen superheater 23, the rear screen superheater 24, the high-temperature superheater 25, the low-temperature superheater 26 and the serpentine tube 27, so that the flue gas temperature is reduced. As a result, when the flue gas reaches the air preheater 15, the temperature drops to below 120℃.

[0046] The heat absorbed by the large-screen superheater 23, rear-screen superheater 24, high-temperature superheater 25, low-temperature superheater 26, and serpentine tube 27 is transferred to multiple sets of heating mechanisms. Steam flows within the roof superheater 8, rear-screen superheater block 9, high-temperature superheater block 10, low-temperature superheater block 11, and economizer block 12. The roof superheater 8 absorbs the radiant heat from the high-temperature flue gas inside the boiler 3, further heating the saturated steam into superheated steam, thus improving the steam temperature and energy quality. The rear-screen superheater block 9 absorbs heat from the flue gas through a combination of convective and radiative heat transfer. The steam continues to be heated, increasing the superheated steam temperature and balancing the flue gas temperature at the boiler box 3 outlet, reducing thermal deviation of the heating surfaces. The function of the high-temperature superheating block 10 is to utilize the convective heat of the high-temperature flue gas to heat the steam to the maximum design temperature, meeting the power requirements of equipment such as the steam turbine. The function of the low-temperature superheating block 11 is to utilize the residual heat in the flue gas to heat the steam, avoiding heat waste. The function of the coal-saving block 12 is to absorb the waste heat of the flue gas to heat the boiler feedwater, increase the feedwater temperature, reduce the heat consumption of the boiler evaporation section, thereby reducing fuel consumption and achieving a "coal-saving" effect. Multiple sets of heating mechanisms are connected in series or parallel through the connecting pipe 7 to form a complete steam / feedwater circulation path, ensuring that the working fluid (such as water and steam) passes through each heating surface sequentially according to the design process, achieving continuous heating.

[0047] The superheated steam absorbed by the roof superheater 8, rear screen superheater 9, high-temperature superheater 10, low-temperature superheater 11, and economizer 12 enters the steam drum 6. After passing through the cyclone separator and louver separator inside the steam drum 6, the steam and water are separated. The steam drum 6 is connected to the external gas-using equipment. The hot steam enters the gas-using equipment for utilization, and the condensate enters the water-cooled block 5 to cool the outer wall of the boiler 3.

[0048] When the flue gas passes through the air preheater 15, it further absorbs heat from the flue gas through the heat storage element inside the air preheater 15, storing the heat in the heat storage element. This heat is then used to heat the air from the blower, and the heated air is then transported to the boiler 3 through a pipeline to replenish the air in the boiler 3 for combustion. The flue gas enters the return air box 16, which discharges unburned flue gas fly ash back into the boiler 3 through the flue gas return pipe 19, achieving secondary combustion.

[0049] The cross-shaped blades 39 and the guide plate 37 facilitate the reduction of the exhaust gas velocity, allowing the gas to effectively enter the flue gas return pipe 19. The magnetic mesh plates 42 on both sides of the return air box 16 absorb and filter the magnetic substances in the fly ash. The blower 17 blows out the sealing block 43, causing the air to blow out from one side of the flue gas return pipe 19. A certain air pressure is formed between the flue gas return pipe 19 and the return air box 16, allowing the fly ash to pass through the flue gas return pipe 19 stably. At this time, under the airflow pressure, the semi-arc sealing plate 31 rotates and opens. When the blower 17 is not working, the semi-arc sealing plate 31 closes under the action of the torsion spring and neodymium iron boron magnet, thus preventing the flue gas from flowing back through the flue gas return pipe 19.

[0050] The second servo motor 21 drives the active gear 34 to rotate via the U-shaped support frame 33, which in turn drives the driven gear 35 to rotate. This causes the active bevel gear 36 and the driven bevel gear in the protective box 29 of the pot box 3 to rotate in coordination, which in turn drives the sealing plate 41 to rotate, thereby realizing the opening and closing of the fan-shaped air outlet.

[0051] Excess fly ash is screened and collected by the choke screen 38. Then, the choke screen 38 is vibrated by the third servo motor 40 and the elliptical block 47, which causes the settled flue gas fly ash to float again and be burned again. The fly ash that falls into the return air box 16 is finally collected into the collection box by the first servo motor 18 and the screw conveyor 30.

[0052] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the present invention, and all of these should be considered to fall within the scope of patent protection determined by the submitted claims.

Claims

1. A pulverized coal boiler with secondary combustion function of flue gas and fly ash, comprising a boiler box (3); multiple sets of heating mechanisms are installed on the upper end of the boiler box (3), a wall-mounted superheater (13) is fixedly connected to one side of the boiler box (3), a water-cooled box (14) is fixedly connected to the lower end of the wall-mounted superheater (13), and an air preheater (15) is installed at the lower end of the water-cooled box (14), characterized in that, The flue gas outlet of the air preheater (15) is connected to a return air box (16). A flow guiding mechanism is installed inside the return air box (16), and flue gas return pipes (19) are fixedly connected to both sides of the return air box (16). The ends of the two flue gas return pipes (19) away from the return air box (16) are respectively connected to the front and rear sides of the boiler box (3). Blowers (17) are fixedly connected to both flue gas return pipes (19). Through the return air box (16) and the flue gas return pipes (19), the pulverized fly ash after combustion is circulated twice in the pulverized coal boiler. The flow guiding mechanism includes crosses installed at both ends inside the return air box (16). The blades (39) and cross blades (39) are rotatably connected to the inner wall of the return air box (16) via a rotating shaft; guide plates (37) are installed at equal intervals on the rear side of the cross blades (39), and a flow-blocking screen plate (38) is provided on the rear side of the guide plate (37). One side of the flow-blocking screen plate (38) is hinged to the inner wall of the return air box (16). A third servo motor (40) is installed on the outside of the return air box (16). The output end of the third servo motor (40) passes through the return air box (16) and is fixedly connected to an elliptical block (47). The elliptical block (47) is located at the lower end of one side of the flow-blocking screen plate (38) and is in contact with the flow-blocking screen plate (38).

2. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 1, characterized in that, An auger (30) is installed at the lower end of the flow-blocking screen plate (38). The auger (30) is located inside the return air box (16) and below the flue gas return pipe (19). One end of the auger (30) extends through to the outside of the return air box (16) and is connected to the first servo motor (18). The end of the auger (30) away from the first servo motor (18) is connected to a collection box.

3. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 1, characterized in that, Fixed blocks (20) are installed at equal intervals on the flue gas return pipe (19). A semi-arc-shaped sealing plate (31) is symmetrically installed at the lower end of the fixed block (20). A torsion spring is provided between the semi-arc-shaped sealing plate (31) and the fixed block (20). An arc-shaped barrier strip (32) is fixedly connected to the inner wall of the flue gas return pipe (19). One side of the semi-arc-shaped sealing plate (31) abuts against the arc-shaped barrier strip (32). The arc-shaped barrier strip (32) and the semi-arc-shaped sealing plate (31) are fixed by neodymium iron boron magnets.

4. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 1, characterized in that, The inner side of the boiler box (3) is symmetrically provided with inverted L-shaped flue gas pipes (45). One end of the flue gas return pipe (19) connected to the boiler box (3) is connected to the corresponding inverted L-shaped flue gas pipe (45). The front and rear sides of the outer wall of the boiler box (3) are fixedly connected with U-shaped support frames (33). A second servo motor (21) is installed on the U-shaped support frame (33). The drive shaft of the second servo motor (21) passes through the U-shaped support frame (33) and is fixedly connected with a drive gear (34). A driven gear (35) is meshed at the lower end of the drive gear (34). A fixed rod is fixedly connected in the middle of the driven gear (35). The other end of the fixed rod passes through the boiler box (3). It is fixedly connected to one end of the active bevel gear (36) inside the boiler box (3), and the other end of the active bevel gear (36) meshes downward with a driven bevel gear. The driven bevel gear is fixedly connected vertically downward with a connecting rod (46). The connecting rod (46) passes vertically through the inverted L-shaped flue gas pipe (45) and is fixedly connected to the inner surface of the sealing plate (41). The sealing plate (41) is rotatably connected to the outlet end of the inverted L-shaped flue gas pipe (45). The sealing plate (41) is symmetrically provided with fan-shaped air outlets. The bottom of the sealing plate (41) is rotatably connected with a base plate. One side of the base plate is fixedly connected to the inner wall of the boiler box (3). The base plate is also symmetrically provided with fan-shaped air outlets.

5. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 4, characterized in that, A protective box (29) is installed on the outside of the inverted L-shaped flue pipe (45), and a high-temperature resistant asbestos layer is provided on the inner wall of the protective box (29); the driving bevel gear (36), the driven bevel gear and the connecting rod (46) are all located inside the protective box (29), and the outlet end of the inverted L-shaped flue pipe (45) is located outside the protective box (29).

6. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 1, characterized in that, A magnetic mesh plate (42) is vertically inserted on both sides above the return air box (16), and a sealing block (43) is installed at the connection between the two ends of the return air box (16) and the flue gas return pipe (19). A telescopic spring (44) is installed between the sealing block (43) and the blower (17). One end of the telescopic spring (44) is fixedly connected to the cross fixing plate at the air outlet of the blower (17), and the other end of the telescopic spring (44) is fixedly connected to one side of the sealing block (43). The sealing block (43) is movably locked at the air outlet of the blower (17).

7. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 1, characterized in that, The multiple heating mechanisms include a roof superheater (8), a rear screen superheater (9), a high-temperature superheater (10), a low-temperature superheater (11), and an economizer (12) installed on the top of the boiler box (3); a full-screen superheater (23), a rear screen superheater (24), and a high-temperature superheater (25) are installed inside the boiler box (3); a low-temperature superheater (26) is installed inside the wall superheater (13); the lower end of the roof superheater (8) is connected to the full-screen superheater (23), the lower end of the rear screen superheater (9) is fixedly connected to the rear screen superheater (24), the lower end of the high-temperature superheater (10) is fixedly connected to the high-temperature superheater (25), and the lower end of the low-temperature superheater (11) is fixedly connected to the low-temperature superheater (26).

8. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 7, characterized in that, A water-cooling mechanism is installed inside the water-cooled box (14). The water-cooling mechanism includes a serpentine tube (27). A hanging pipe is fixedly connected to the upper end of the serpentine tube (27). The end of the hanging pipe away from the serpentine tube (27) is connected to the lower end of the coal-saving block (12).

9. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 8, characterized in that, The bottom outer side of the boiler box (3) is covered with a water-cooled block (5). Multiple vertical cooling pipes are fixedly connected at equal intervals on one side of the water-cooled block (5). The end of the cooling pipe away from the water-cooled block (5) is fixedly connected to the lower end of the steam drum (6). The steam drum (6), the roof superheater (8), the rear screen superheater (9), the high temperature superheater (10), the low temperature superheater (11), and the coal-saving block (12) are interconnected through multiple connecting pipes (7).

10. A pulverized coal boiler with secondary combustion function of flue gas and fly ash according to claim 1, characterized in that, A feeding hopper (22) is installed at the upper rear side of the boiler box (3), and burners (4) are installed at equal intervals around the lower side of the boiler box (3). The burners (4) penetrate the boiler box (3), and multiple combustion nozzles (28) are vertically and equally spaced at the end of the burners (4) located inside the boiler box (3).

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