An air preheater

Abstract

The present application relates to a kind of air preheaters, including convection shaft, the convection shaft includes vertical sleeve shell, the both ends of sleeve shell are respectively sealed with end plate, multiple vertical heat exchange pipes are spaced in sleeve shell, the both ends of each heat exchange pipe are respectively penetrated the end plate of corresponding end, the both ends of sleeve shell are respectively extended with flue gas pipeline, flue gas pipeline is communicated with each heat exchange pipe;Two air ducts are communicated on the side wall of sleeve shell;Steel ball sowing device is equipped above the heat exchange surface;Adopt steel ball to carry out free fall vibration ash removal, after cleaning, steel ball and dust fall into collection bin, the collection bin is connected with pipeline leading to dust ball separation device, dust ball separation device is connected to bottom steel ball bin, again by steel ball circulation drive device again sent into pipe, so complete cycle and realize online self-cleaning, without stopping furnace and cleaning, and due to the special structure of heat exchange pipe, also without auxiliary ash removal device and drying process, process is simple, greatly improve heat transfer efficiency.

Description

Technical Field

[0001] This invention belongs to the technical field of air preheaters with dust removal devices, and specifically relates to an air preheater. Background Technology

[0002] Air preheaters utilize waste heat flue gas to heat air, transferring the heat carried by the flue gas discharged from the boiler's tail flue to the air entering the boiler through heat exchange tubes, preheating the air to a certain temperature. This is a device used to improve the boiler's heat exchange performance and reduce energy consumption. However, the flue gas contains a high amount of dust, which easily adheres to the heat exchange tubes, significantly reducing the heat exchange efficiency of the heat exchange surface and severely affecting the recovery and utilization of waste heat from the flue gas. Currently, the main methods for cleaning air preheaters include mechanical vibration cleaning, mechanical brush cleaning, high-pressure steam cleaning, and explosive cleaning, as addressed in standards such as CN102252336A, CN211725043U, and CN103939925A. CN103939925A, in particular, describes a waste heat boiler cleaning device that provides a cleaning system and apparatus that primarily uses steel ball impact and is supplemented by liquid solution cleaning. However, the problem of low cleaning efficiency of steel ball impact still exists. When ash accumulates in the gaps between heat exchange tubes, the steel balls cannot fall, requiring the boiler to be shut down and the steel ball cleaning device to be stopped for cleaning. The process is cumbersome and cannot guarantee the cleaning efficiency of steel ball mechanical vibration. Even after cleaning with liquid solution, it is necessary to dry before the steel ball cleaning device can be restarted and the boiler can be started again, which affects the boiler's operating efficiency. Summary of the Invention

[0003] In view of the above-mentioned shortcomings of the prior art, the technical problem to be solved by the present invention is to provide an air preheater that avoids the problem of poor heat exchange tube cleaning effect caused by poor internal heat exchange structure arrangement of the air preheater, improves heat transfer efficiency, and avoids complicated additional measures to ensure cleaning efficiency.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] An air preheater includes a convection shaft, which comprises a vertical sleeve shell. Both ends of the sleeve shell are sealed with end plates. Multiple vertical heat exchange tubes are spaced apart inside the sleeve shell, with each heat exchange tube's ends penetrating the corresponding end end of the end plate. Flue gas ducts extend from both ends of the sleeve shell and communicate with each heat exchange tube. Two air ducts are connected to the side wall of the sleeve shell. A steel ball dispersing device is located above the sleeve shell, comprising an inlet end and an outlet end. The outlet end of the steel ball dispersing device is located inside the flue gas duct at the upper end of the sleeve shell, and steel balls exiting from the outlet end of the steel ball dispersing device can move towards the upper end of each heat exchange tube and fall into the tube. A collection chamber is connected to the wall of the flue gas duct at the lower end of the sleeve shell, and the collection chamber is directly opposite the lower end of each heat exchange tube to collect dust and steel balls.

[0006] To further improve the above technical solution, the heat exchange tube is a non-smooth tube structure with protrusions on the inner wall.

[0007] Furthermore, the heat exchange tube is a vortex-reinforced heat exchange tube with multiple spherical protrusions on the inner wall.

[0008] Furthermore, the collection bin is connected to a dust separation device, which in turn connects to an ash hopper and a bottom steel ball bin. The bottom steel ball bin is connected to a steel ball circulation drive device, which is connected to the inlet of the steel ball spreading device via a steel ball recovery pipe.

[0009] Furthermore, the steel ball dispersing device penetrates the wall of the flue gas duct at the upper end of the sleeve housing, and the inlet end of the steel ball dispersing device is located outside the corresponding flue gas duct. A pressurization pipe is also connected to the wall of the flue gas duct at the upper end of the sleeve housing and is connected to the inlet end of the steel ball dispersing device through the pressurization pipe. A shut-off valve is provided on the steel ball recovery pipe and the pressurization pipe respectively. The shut-off valves are all close to the inlet end of the steel ball dispersing device.

[0010] Furthermore, the ball circulation drive device employs a fan and is located below the bottom ball chamber.

[0011] Furthermore, the outlet end of the steel ball dispersing device is located directly above the sealing plate at the upper end of the sleeve shell, and the upper end of each heat exchange tube is flush with the upper surface of the corresponding sealing plate.

[0012] Furthermore, the sealing plate has through holes corresponding to the number of heat exchange tubes, and the inner diameter of the through holes corresponds to the outer diameter of the heat exchange tubes. The heat exchange tubes pass through the corresponding through holes one-to-one for sealing.

[0013] Furthermore, there are two convection shafts. The flue gas pipes at the lower ends of the two sleeve shells are horizontally connected and form a connecting collection space inside. The bottom wall of the connecting collection space is raised in the middle and has a partition so that the two collection chambers can collect the steel balls falling out of the heat exchange tubes of their respective convection shafts.

[0014] Furthermore, the free ends of the flue gas ducts at the upper ends of the two sleeve shells are respectively formed as flue gas inlets and flue gas outlets; two air ducts on the side walls of the sleeve shells are respectively connected to the upper and lower parts of the side walls; the air ducts at the lower part of the side walls of the two sleeve shells are laterally connected and are provided with air communication covers, and the air ducts at the upper part of the side walls of the two sleeve shells are respectively formed as air inlets and air outlets; the air inlets are close to the flue gas outlets, and the air outlets are close to the flue gas inlets.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The air preheater of the present invention uses steel balls for free-fall vibration cleaning. Combined with the vortex-reinforced heat exchange tubes, after cleaning, the steel balls fall into the collection chamber to complete the dust separation, and then are sent back into the tube by the fan. This completes the cycle and realizes online self-cleaning without the need to stop the furnace for cleaning. Moreover, due to the special structure of the heat exchange tubes, there is no need for auxiliary cleaning devices and drying processes. The process is simple and greatly improves the heat transfer efficiency.

[0017] 2. The air preheater of the present invention uses a vortex-reinforced heat exchange tube (see CN210108115U for details). Because the heat exchange tube has multiple protruding spherical protrusions inside, the steel balls collide with the tube wall with higher intensity and more frequency than ordinary bare tubes during natural falling. No additional measures are required, which further improves the dust removal effect and ensures heat transfer efficiency. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an air preheater according to a specific embodiment;

[0019] The components include: 1. Convection shaft; 2. Heat exchange tube; 3. Sealing plate; 4. Steel ball spreading device; 41. Inlet end; 42. Outlet end; 5. Steel ball; 6. Collection bin; 7. Dust ball separation device; 8. Ash hopper; 9. Bottom steel ball bin; 10. Fan; 11. Steel ball recovery pipe; 12. No. 1 shut-off valve; 13. Pressurization pipe; 14. No. 2 shut-off valve; 15. Flue gas inlet; 16. Flue gas outlet; 17. Air inlet; 18. Air connecting hood; 19. Connecting collection space; 20. Flue gas pipe. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] Please see Figure 1An air preheater according to a specific embodiment includes a convection shaft 1, which includes a vertical sleeve shell. Both ends of the sleeve shell are sealed with sealing plates 3. Multiple vertical heat exchange tubes 2 are spaced apart inside the sleeve shell, with each heat exchange tube 2 having its ends passing through the corresponding sealing plate 3. Flue gas pipes 17 extend from both ends of the sleeve shell and communicate with each heat exchange tube 2. Two air pipes communicate on the side wall of the sleeve shell. A steel ball spreading device 4 is provided above the body. The steel ball spreading device 4 includes an inlet end 41 and an outlet end 42. The outlet end 42 of the steel ball spreading device 4 is located in the flue gas duct 17 at the upper end of the sleeve shell, and the steel balls 5 coming out of the outlet end 42 of the steel ball spreading device 4 can move toward the upper end of each heat exchange tube 2 and fall in. A collection chamber 6 is connected to the pipe wall of the flue gas duct at the lower end of the sleeve shell. The collection chamber 6 is directly opposite the lower end of each heat exchange tube 2 to collect dust and steel balls 5.

[0022] After the sealing plates 3, which are sealed to both ends of the sleeve shell, are penetrated by both ends of each heat exchange tube 2, a heat exchange space is formed inside the sleeve shell. Steel balls 5 are continuously supplied from the inlet end 41 of the steel ball dispensing device 4. Since the outlet end 42 of the steel ball dispensing device 4 is located in the flue gas pipe 17 at the upper end of the sleeve shell, the steel balls 5 can fall randomly into each heat exchange tube 2. During the free fall, the steel balls 5 collide with the tube wall, realizing mechanical collision-type dust removal. The steel balls 5 and the dust fall into the collection chamber 6 together, completing the dust removal operation of the flue gas dust attached to the inner wall of each heat exchange tube 2.

[0023] In implementation, the steel ball dispersing device 4 can be a simple single-tube structure. To make the probability of the steel balls 5 falling into each heat exchange tube 2 more uniform, the steel ball dispersing device 4 can also be an inlet end 41, which extends through a main pipe to connect to multiple subsequent branch pipes. The ends of the multiple branch pipes form multiple outlet ends 42, all of which are located in the flue gas duct 17 at the upper end of the sleeve shell. The outlet end 42 can be located directly above the upper end of each heat exchange tube 2, that is, after the steel balls 5 come out along the outlet end 42, they move towards the upper end of each heat exchange tube 2 by gravity and fall in. Alternatively, the flue gas duct 17 at the upper end of the sleeve shell can be structured so that the free end gradually decreases towards the connection end connected to the upper end of the sleeve shell. In this case, the outlet end 42 of the steel ball dispersing device 4 can be located at any position in the flue gas duct 17, and the steel balls 5 coming out of the outlet end 42 can always move towards the upper end of each heat exchange tube 2 and fall in along the gradually decreasing flue gas duct 17.

[0024] The specific correspondence (i.e. flow direction) between the air inlet / outlet and the flue gas inlet / outlet and the two air ducts and two flue gas ducts 17 is not limited. Since the upper and lower flue gas ducts need to be connected to the steel ball spreading device 4 and the collection chamber 6 respectively, occupying the position in the upper and lower positive directions, the flue gas inlet / outlet is preferably located in the side direction.

[0025] The dust and steel balls 5 collected in the collection bin 6 can be manually separated by sieving, with the steel balls 5 collected for recycling and the dust discharged; or they can be automatically sieved, and the steel balls 5 collected by the sieve can be transported to the inlet end 41 of the steel ball spreading device 4 by the circulation drive device, thereby realizing automatic circulation and reducing manpower.

[0026] Furthermore, the heat exchange tube 2 is a non-smooth tube structure with protrusions on the inner wall, preferably a vortex-reinforced heat exchange tube with multiple spherical protrusions on the inner wall.

[0027] In this way, since the inner wall of the vortex-reinforced heat exchange tube is provided with spherical protrusions (please refer to CN210108115U for details), the steel ball 5 will collide with the tube wall with higher intensity and more frequency than ordinary bare tubes during the natural fall process, which further improves the heat transfer efficiency and dust removal effect, and no additional dust removal measures are required.

[0028] Please continue reading Figure 1 In specific implementation, the collection bin 6 is connected to the dust separation device 7, and the dust separation device 7 is connected to the ash hopper 8 and the bottom steel ball bin 9 respectively. The bottom steel ball bin 9 is connected to a steel ball circulation drive device, which is connected to the inlet end 41 of the steel ball spreading device 4 through the steel ball recovery pipe 11. The steel ball circulation drive device uses a fan 10 and is located below the bottom steel ball bin 9. The steel ball spreading device 4 penetrates the pipe wall of the flue gas pipe 17 at the upper end of the sleeve shell. The inlet end 41 of the steel ball spreading device 4 is located outside the corresponding flue gas pipe 17. The pipe wall of the flue gas pipe 17 at the upper end of the sleeve shell is also connected to a pressure supply pipe 13, which is connected to the inlet end 41 of the steel ball spreading device 4. The steel ball recovery pipe 11 and the pressure supply pipe 13 are respectively equipped with shut-off valves. The shut-off valves are all close to the inlet end 41 of the steel ball spreading device 4.

[0029] This achieves automatic circulation and reduces manpower. After the steel ball 5 falls into the collection bin 6, it is automatically screened by the dust separation device 7. The dust enters the ash hopper 8, while the steel ball 5 falls into the bottom steel ball bin 9. Under the action of the steel ball circulation drive device, namely the fan 10, the steel ball 5 is sent into the steel ball recovery pipe 11. The steel ball 5 returns to the upper end of the steel ball spreading device 4 along the steel ball recovery pipe 11, completing the circulation of the steel ball 5. This allows for continuous ash removal and realizes online self-ash removal without the need to shut down the furnace for cleaning.

[0030] Meanwhile, during daily operation, the invention opens the No. 1 shut-off valve 12 on the steel ball recovery pipe 11, while the No. 2 shut-off valve 14 on the pressure supply pipe 13 remains closed, thus achieving the cleaning, separation, and recovery of the steel balls 5. After prolonged use, if the steel ball channel inside the steel ball dispensing device 4 becomes blocked, the No. 1 shut-off valve 12 on the steel ball recovery pipe 11 is closed, and the No. 2 shut-off valve 14 on the pressure supply pipe 13 is opened. Some flue gas enters the steel ball dispensing device 4 through the pressure supply pipe 13, applying gas pressure to the inside of the steel ball dispensing device 4. This achieves a certain cleaning and unblocking effect on the steel ball channel inside the steel ball dispensing device 4, maintaining the smooth dispensing effect of the steel balls 5.

[0031] During implementation, the outlet end 42 of the steel ball dispensing device 4 is located directly above the sealing plate 3 at the upper end of the sleeve shell, and the upper end of each heat exchange tube 2 is flush with the upper surface of the corresponding sealing plate 3. The sealing plate 3 has through holes corresponding to the number of heat exchange tubes 2, and the inner diameter of the through holes corresponds to the outer diameter of the heat exchange tubes 2. The heat exchange tubes 2 pass through the corresponding through holes in a one-to-one sealing manner.

[0032] This ensures that after the steel balls 5 come out of the outlet end 42 of the steel ball dispensing device 4, they fall randomly and smoothly into each heat exchange tube 2.

[0033] In specific implementation, there are two convection shafts 1. The flue gas pipes at the lower ends of the two sleeve shells are horizontally connected and form a connecting collection space 16 inside. The bottom wall of the connecting collection space 16 has a partition protruding in the middle to facilitate the collection of steel balls 5 falling from the heat exchange tubes 2 of their respective corresponding convection shafts 1 by the two collection chambers 6. Further, the free ends of the flue gas pipes 17 at the upper ends of the two sleeve shells are respectively formed as flue gas inlet A and flue gas outlet B; two air pipes on the side walls of the sleeve shells are respectively connected to the upper and lower parts of the side walls; the air pipes at the lower part of the side walls of the two sleeve shells are horizontally connected and are provided with an air connecting hood 15; the air pipes at the upper part of the side walls of the two sleeve shells are respectively formed as air inlet C and air outlet D; the air inlet C is close to the flue gas outlet B, and the air outlet D is close to the flue gas inlet A.

[0034] Thus, with two convection shafts 1, the internal flow channels of the air preheater of this invention are U-shaped. Flue gas enters the left tube side of the air preheater from the left flue gas inlet A, cools down after passing through the right tube side, and exits from the right flue gas outlet B. Air enters the right shell side from the right air inlet C, heats up after passing through the left shell side, and exits from the left air outlet D, completing the entire heat exchange process. Throughout the heat exchange process, the flowing media (flue gas and air) flow in parallel and opposite directions along the length of the heat exchange tubes, which is a pure counter-current flow. This not only makes the overall resistance less than that of the traditional cross-flow method, but also reduces tube wear and extends service life.

[0035] In practice, there can be multiple convection shafts 1, which can be connected in a serpentine manner in a similar pure counter-current form.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An air preheater, comprising a convection shaft, characterized in that: The convection shaft includes a vertical sleeve shell, with sealing plates sealingly connected to both ends of the sleeve shell. Multiple vertical heat exchange tubes are spaced apart inside the sleeve shell, with each heat exchange tube having its corresponding sealing plate passing through both ends. Flue gas pipes extend from both ends of the sleeve shell and are connected to each heat exchange tube. Two air pipes are connected to the side wall of the sleeve shell. A steel ball spreading device is provided above the sleeve shell. The steel ball spreading device includes an inlet end and an outlet end. The outlet end of the steel ball spreading device is located in the flue gas duct at the upper end of the sleeve shell, and the steel balls coming out from the outlet end of the steel ball spreading device can move toward the upper end of each heat exchange tube and fall in. A collection chamber is connected to the wall of the flue gas duct at the lower end of the sleeve shell. The collection chamber is directly opposite the lower end of each heat exchange tube to collect dust and steel balls. The steel ball dispersing device penetrates the wall of the flue gas duct at the upper end of the sleeve housing. The inlet end of the steel ball dispersing device is located outside the corresponding flue gas duct. A pressurization pipe is also connected to the wall of the flue gas duct at the upper end of the sleeve housing and is connected to the inlet end of the steel ball dispersing device through the pressurization pipe. The steel ball recovery pipe and the pressurization pipe are respectively equipped with shut-off valves. The shut-off valves are all close to the inlet end of the steel ball dispersing device. The outlet end of the steel ball spreading device is located directly above the sealing plate at the upper end of the sleeve shell, and the upper end of each heat exchange tube is flush with the upper surface of the corresponding sealing plate. The number of convection shafts is two. The flue gas pipes at the lower ends of the two sleeve shells are horizontally connected and form a connecting collection space inside. The bottom wall of the connecting collection space is raised in the middle and a partition is provided so that the two collection chambers can collect the steel balls falling out of the heat exchange tubes of their respective corresponding convection shafts. The free ends of the flue gas ducts at the upper ends of the two sleeve shells are respectively formed as flue gas inlet and flue gas outlet; The two air ducts on the side wall of the sleeve housing are connected to the upper and lower parts of the side wall, respectively; The air ducts at the lower part of the side walls of the two sleeve shells are connected laterally and are equipped with air communication covers. The air ducts at the upper part of the side walls of the two sleeve shells are respectively formed as air inlets and air outlets. The air inlet is located near the flue gas outlet, and the air outlet is located near the flue gas inlet.

2. An air preheater according to claim 1, characterized in that: The heat exchange tube is a non-smooth tube structure with protrusions on the inner wall.

3. An air preheater according to claim 2, characterized in that: The heat exchange tube is a vortex-reinforced heat exchange tube with multiple spherical protrusions on the inner wall.

4. An air preheater according to claim 1, characterized in that: The collection bin is connected to the dust separation device, which in turn connects to the ash hopper and the bottom steel ball bin. The bottom steel ball bin is connected to a steel ball circulation drive device, which is connected to the inlet of the steel ball spreading device through a steel ball recovery pipe.

5. An air preheater according to claim 4, characterized in that: The ball circulation drive device uses a fan and is located below the bottom ball chamber.

6. An air preheater according to claim 1, characterized in that: The sealing plate has through holes corresponding to the number of heat exchange tubes. The inner diameter of the through holes corresponds to the outer diameter of the heat exchange tubes, and the heat exchange tubes pass through the corresponding through holes one-to-one for sealing.

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