A separation and cleaning device for coal mine water tanks

Abstract

This invention relates to the field of water sump cleaning technology, and discloses a separation and cleaning device for coal mine water sumps. The device includes a main cleaning machine, a spiral collector, and a scraper conveyor. It also includes a receiving hopper, a discharging hopper, and a multi-stage separation mechanism. The multi-stage separation mechanism comprises several conveying hoppers, each with a distribution bend inside. The distribution bend has an inlet on its exterior, and both ends of the distribution bend are rotatably connected to separation drums. The two separation drums inside each conveying hopper have identical separation apertures, and the apertures of the separation drums decrease progressively along the direction from the receiving hopper to the discharging hopper. This invention allows the water-slag mixture output by the scraper conveyor to undergo progressive dynamic separation through multiple stages of separation drums, enabling precise separation and discharge of solid particles of different sizes. This solves the problem that static, fixed-aperture separation nets are unable to effectively separate solid particles with a large size range.

Description

Technical Field

[0001] This invention relates to the field of water tank cleaning technology, and more specifically, to a separation and cleaning device for coal mine water tanks. Background Technology

[0002] During underground drilling operations, coal mines experience both natural water inflow (formation water seepage) and production water (such as dust suppression at the mining face and equipment cooling water). As this water flows, it carries solid particles from the roadways, including coal slag, rock debris, coal dust, silt, and rock fragments, eventually flowing into the mine's water sump through the drainage system. To alleviate the accumulation problem in coal mine water sumps, cleaning machines (water removal machines) are commonly used to remove water and prevent safety accidents caused by underground water accumulation.

[0003] The existing cleaning machine (cleaning machine) mainly includes a tracked walking system, an explosion-proof electrical control system, a hydraulic drive system, a screw collector, a scraper conveyor, and a hopper. The hopper is equipped with a separation net. The hydraulic drive system is activated by the explosion-proof electrical control system, which moves the tracked walking system to the water tank cleaning area. The screw collector disperses the slag and mud mixture deposited in the coal mine water tank, forming a water-slag mixture with better fluidity. The scraper conveyor then pushes the water-slag mixture into the hopper. The separation net in the hopper separates the slag, and the water-mud mixture that passes through the separation net settles, thus completing the cleaning of the coal mine water tank.

[0004] Although the aforementioned cleaning machine (cleaning machine) can separate water, slag, and mud through a separation net and gravity settling, in actual use, the solid particles in coal mine water tanks have a large particle size range (from micron-sized mud to centimeter-sized slag). A static separation net with a fixed aperture is difficult to handle the separation of solid particles with a large particle size range. If the aperture of the separation net is statically designed for micron-sized mud, centimeter-sized slag will easily clog the separation net. If the aperture of the separation net is statically designed for centimeter-sized slag, the separation net can only trap coarse slag particles, while fine slag particles pass through the separation net and enter the hopper with the cement. In other words, a static separation net with a fixed aperture is difficult to handle the separation of solid particles with a large particle size range, thus affecting the separation of water and slag mixtures and failing to meet the requirements for efficient separation and cleaning operations in coal mine water tanks. Summary of the Invention

[0005] This invention provides a separation and cleaning device for coal mine water tanks, which solves the technical problem in related technologies that static and fixed aperture separation nets are difficult to separate solid particles with large particle size ranges, thus affecting the separation of water slag mixture.

[0006] This invention provides a separation and cleaning device for coal mine water sump, including a cleaning machine body, a screw conveyor, and a scraper conveyor, and further comprising: A receiving hopper is located below the discharge port of the scraper conveyor; The discharge hopper is located on the side away from the discharge port of the scraper conveyor; A multi-stage separation mechanism is installed between the receiving hopper and the discharge hopper to perform step-by-step separation of the water-slag mixture. The multi-stage separation mechanism includes several mutually fixed conveying hoppers. Each conveying hopper has a distribution bend inside, and the distribution bend has an inlet on the outside. Both ends of the distribution bend are rotatably connected to a separation drum located inside the conveying hopper. The two separation drums inside each conveying hopper have the same separation hole diameter. The separation hole diameter of the several separation drums decreases step-by-step along the direction from the receiving hopper to the discharge hopper. That is, the water-slag mixture can pass through multiple separation drums for step-by-step dynamic separation, so that solid particles of different sizes can be accurately separated and discharged.

[0007] Preferably, several of the conveying hoppers are installed below the scraper conveyor via mounting plates. The several conveying hoppers are arranged in a stepped manner along the direction from the receiving hopper to the discharge hopper. The conveying hoppers near the receiving hopper are fixedly connected to the receiving hopper, and the conveying hoppers near the discharge hopper are fixedly connected to the discharge hopper.

[0008] Preferably, the material distribution bend is fixedly connected to the receiving hopper or the conveying hopper, and the material inlet is connected to the receiving hopper or the conveying hopper.

[0009] Preferably, a discharge pipe is fixedly connected to the end of the separating drum away from the material distribution bend, and the discharge pipe extends rotatably to the outside of the conveying hopper.

[0010] Preferably, the discharge pipe is provided with a drive component for driving its rotation. The drive component includes a drive motor installed outside the conveying hopper and a gear ring fixedly sleeved outside the discharge pipe. The output end of the drive motor is fixedly connected to a gear A that meshes with the gear ring.

[0011] Preferably, except for the two separating drums near the discharge hopper, each of the other separating drums is fixedly connected to a spiral speed reducer, and the spiral direction of the spiral speed reducer is adapted to the rotation direction of its corresponding separating drum.

[0012] Preferably, except for the two separating drums near the discharge hopper, each of the other separating drums is fixedly connected with an axial throwing plate at equal intervals inside, and the axial throwing plate passes through the spiral deceleration plate.

[0013] Preferably, a material collection trough is fixedly connected inside the two separating drums near the discharge hopper. A scraper is fixedly connected to one side of the material collection trough along the rotation direction of the corresponding separating drum. The material collection trough extends to the outside of the discharge pipe and has a discharge port.

[0014] Preferably, except for the two separating drums near the discharge hopper, each of the other separating drums is rotatably connected to a rotating rod. The rotating rod is rotatably connected to the outside of its corresponding conveying hopper. Anti-clogging rubber strips are fixedly connected at equal intervals to the outside of the rotating rod. A gear B that meshes with a gear ring is fixedly connected to the end of the rotating rod.

[0015] The beneficial effects of this invention are as follows: This invention employs a combination of a receiving hopper and a multi-stage separation mechanism. The receiving hopper receives the water-slag mixture output from the scraper conveyor, allowing the mixture to sequentially enter several separation drums. Since the aperture of the separation holes in these drums decreases progressively from the receiving hopper to the discharge hopper, solid particles of different sizes can be dynamically separated by the corresponding aperture drums and discharged through the corresponding discharge pipes. In other words, the water-slag mixture undergoes progressive dynamic separation through multiple stages of separation drums, enabling precise separation and discharge of solid particles of different sizes (from centimeter-sized slag to micron-sized mud). This solves the problem that static, fixed-aperture separation nets cannot effectively separate solid particles with a large size range.

[0016] 2. In the process of dynamic separation through several separating drums, the spiral deceleration plate in the separating drum can impede the incoming slag, prolonging the residence time of the slag in the separating drum. At the same time, the axial throwing plate can throw the decelerated slag down step by step, breaking the aggregation state of the slag inside the separating drum, thereby improving the separation efficiency of the slag.

[0017] 3. In the process of dynamic separation through several separating drums, the rotating rods outside the separating drums can drive the anti-clogging rubber strips arranged in a staggered manner to rotate, periodically patting the outer wall of the separating drums to prevent the separating drums from being blocked by slag. At the same time, the scraper can scrape off the mud adhering to the separating drums to prevent the separating drums from being blocked by mud, thereby ensuring the separation efficiency of the separating drums. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the multi-stage separation mechanism in this invention; Figure 2 This is a bottom view schematic diagram of the multi-stage separation mechanism in this invention; Figure 3 This is a schematic diagram of the overall structure of the present invention; Figure 4 This is a schematic diagram of the first part of the multi-stage separation mechanism in this invention; Figure 5 This is a schematic diagram of the second part of the multi-stage separation mechanism in this invention; Figure 6This is a schematic diagram of the structure of the spiral deceleration plate and the axial throwing plate in this invention; Figure 7 This is a schematic diagram of the third part of the multi-stage separation mechanism in this invention; Figure 8 This is a schematic diagram of the fourth part of the multi-stage separation mechanism in this invention; Figure 9 This is a schematic diagram of the structure of the material collection trough and scraper in this invention.

[0019] In the diagram: 10. Main body of the cleaning machine; 11. Spiral collector; 12. Scraper conveyor; 20. Receiving hopper; 30. Discharge hopper; 40. Multi-stage separation mechanism; 41. Conveying hopper; 42. Distributing bend; 43. Feed inlet; 44. Separating drum; 45. Mounting plate; 46. Discharge pipe; 47. Drive motor; 48. Gear ring; 49. Gear A; 50. Spiral reducer; 51. Axial throwing plate; 52. Collection trough; 53. Scraper; 54. Discharge port; 55. Rotating rod; 56. Anti-clogging rubber strip; 57. Gear B. Detailed Implementation

[0020] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0021] like Figure 1 - Figure 3 As shown, this embodiment provides a separation and cleaning device for coal mine water tanks, including a cleaning machine body 10, a spiral collector 11, and a scraper conveyor 12. The cleaning machine body 10 mainly includes a track walking system, an explosion-proof electrical control system, and a hydraulic drive system. The spiral collector 11 is installed at the front end of the cleaning machine body 10 and is used to disperse the slag and mud mixture deposited in the coal mine water tank to form a water-slag mixture with good fluidity and to collect the material. The discharge end of the spiral collector 11 is connected to the inlet of the scraper conveyor 12. The cleaning machine body 10, the spiral collector 11, and the scraper conveyor 12 are conventional components of existing cleaning machines. Their specific structures and basic principles are common knowledge to those skilled in the art, so they will not be described in detail in this embodiment. It also includes a receiving hopper 20, which is located below the discharge port of the scraper conveyor 12. The receiving hopper 20 is used to receive the water-slag mixture output by the scraper conveyor 12. The discharge hopper 30 is located on the side away from the discharge port of the scraper conveyor 12. The direction from the receiving hopper 20 to the discharge hopper 30 is the approximate separation flow direction of the water-slag mixture. The multi-stage separation mechanism 40 is located between the receiving hopper 20 and the discharge hopper 30 and is used to separate the water-slag mixture step by step, specifically solving the separation problem of solid particles of different sizes and improving the overall separation efficiency and separation effect.

[0022] Among them, specifically such as Figure 4 - Figure 5 and Figure 7 - Figure 8 As shown, the multi-stage separation mechanism 40 includes several mutually fixed conveying hoppers 41. These hoppers 41 are mounted below the scraper conveyor 12 via mounting plates 45. The hoppers 41 are arranged in a stepped manner along the direction from the receiving hopper 20 to the discharge hopper 30. The hoppers 41 closest to the receiving hopper 20 are fixedly connected to it, and the hoppers 41 closest to the discharge hopper 30 are fixedly connected to it. Each hopper 41 has an internal structure... There is a material distribution bend 42, which is fixedly connected to the receiving hopper 20 or the conveying hopper 41. The material distribution bend 42 has an inlet 43 on the outside, which is connected to the receiving hopper 20 or the conveying hopper 41. That is, the water-slag mixture inside the receiving hopper 20 can enter the conveying hopper 41 through the inlet 43, and the water-slag mixture inside the upper conveying hopper 41 can enter the lower conveying hopper 41 through the inlet 43, so as to realize the step-by-step flow of the water-slag mixture. Both ends of the distribution bend 42 are rotatably connected to the separating drums 44 located inside the conveying hopper 41. The water-slag mixture entering the distribution bend 42 can be evenly divided into two paths and enter the corresponding two separating drums 44. The end of the separating drum 44 away from the distribution bend 42 is fixedly connected to the discharge pipe 46. The discharge pipe 46 extends rotatably to the outside of the conveying hopper 41. After separation, the water-slag mixture entering the separating drum 44 can enter the corresponding collection box through the discharge pipe 46. The separation hole diameter of the two separating drums 44 inside each conveying hopper 41 is the same. The separation hole diameter of several separating drums 44 decreases step by step along the direction from the receiving hopper 20 to the discharge hopper 30. After the water-slag mixture enters the rotating separation drum 44, the solid particles in the mixture are subjected to the combined action of centrifugal force, gravity, and fluid thrust. This causes particles with a diameter larger than the separation hole diameter of the separation drum 44 to be retained and gradually conveyed to the discharge pipe 46 and discharged as the separation drum 44 rotates. Particles with a diameter smaller than the separation hole diameter of the separation drum 44 pass through the separation drum 44 with the liquid and enter the conveying hopper 41 to enter the next stage of dynamic separation. That is, solid particles of different sizes can be separated by the separation drum 44 with the corresponding hole diameter and discharged through the corresponding discharge pipe 46. The discharge pipe 46 is provided with a drive component for driving its rotation. The drive component includes a drive motor 47 installed outside the conveying hopper 41 and a gear ring 48 fixedly sleeved outside the discharge pipe 46. The output end of the drive motor 47 is fixedly connected to a gear A49 that meshes with the gear ring 48. By starting the drive motor 47 to make the gear A49 rotate, the gear ring 48 that meshes with the gear A49 can drive the discharge pipe 46 and the separation drum 44 to rotate, so that the separation drum 44 can dynamically separate the water-slag mixture.

[0023] Through the above structure, solid particles of different sizes can be dynamically separated by the corresponding aperture of the separation drum 44 and discharged through the corresponding discharge pipe 46. That is, the water-slag mixture can be dynamically separated step by step through multiple stages of separation drum 44, so that solid particles of different sizes (from centimeter-sized slag to micron-sized mud) can be accurately separated and discharged, thereby solving the problem that static and fixed aperture separation meshes cannot take into account the separation of solid particles with a large size range.

[0024] In addition, specifically as follows Figure 6 As shown, except for the two separating drums 44 near the discharge hopper 30, each of the other separating drums 44 is fixedly connected to a spiral speed reducer 50. The spiral direction of the spiral speed reducer 50 is matched with the rotation direction of the corresponding separating drum 44. When the separating drum 44 rotates, the spiral speed reducer 50 can impede the slag entering the separating drum 44, thereby prolonging the residence time of the slag in the separating drum 44 and improving the separation efficiency of the slag.

[0025] Except for the two separating drums 44 near the discharge hopper 30, each of the other separating drums 44 is fixedly connected with an axial throwing plate 51 at equal intervals. The axial throwing plate 51 passes through the spiral deceleration plate 50. During the rotation of the separating drum 44, the axial throwing plate 51 can throw the slag material that has been decelerated by the spiral deceleration plate 50 down step by step, thereby breaking the aggregation state of the slag material inside the separating drum 44 and improving the separation efficiency of the slag material.

[0026] Through the above structure, the spiral deceleration plate 50 in the corresponding separation drum 44 can impede the incoming slag, prolonging the residence time of the slag in the separation drum 44. At the same time, the axial throwing plate 51 can throw the decelerated slag down step by step, breaking the aggregation state of the slag inside the separation drum 44, thereby improving the separation efficiency of the slag.

[0027] In addition, specifically as follows Figure 9 As shown, both of the two separating drums 44 near the discharge hopper 30 are fixedly connected to a collection trough 52. One end of the collection trough 52 is fixed inside the corresponding distribution bend 42 by an installation rod, and the other end of the collection trough 52 is fixed outside the corresponding installation plate 45 by an installation rod. A scraper 53 is fixedly connected to one side of the collection trough 52 along the rotation direction of the corresponding separating drum 44. The collection trough 52 extends to the outside of the discharge pipe 46 and has a discharge port 54. During the rotation of the separating drum 44, the scraper 53 can scrape off the mud adhering to the separating drum 44, so that the scraped mud falls into the collection trough 52, so as to prevent the separating drum 44 from being blocked and affecting the separation of liquid.

[0028] Except for the two separating drums 44 near the discharge hopper 30, each of the other separating drums 44 is rotatably connected to a rotating rod 55. The rotating rod 55 is rotatably connected to the outside of its corresponding conveying hopper 41. Anti-clogging rubber strips 56 are fixedly connected at equal intervals to the outside of the rotating rod 55. The end of the rotating rod 55 is fixedly connected to a gear B57 that meshes with a gear ring 48. When the separating drum 44 rotates, the gear ring 48 on its outside can drive the gear B57 to rotate, so that the rotating rod 55 drives the anti-clogging rubber strips 56 on its outside to rotate. The rotating anti-clogging rubber strips 56 can periodically tap the outer wall of the separating drum 44 to prevent the separating drum 44 from being blocked by slag, thereby ensuring the separation efficiency of the separating drum 44.

[0029] With the above structure, the rotating rod 55 outside the separating drum 44 can drive the anti-clogging rubber strips 56 arranged in a staggered manner to rotate, periodically patting the outer wall of the separating drum 44 to prevent the separating drum 54 from being blocked by slag. At the same time, the scraper plate 53 can scrape off the mud adhering to the separating drum 44 to prevent the separating drum 44 from being blocked by mud, thereby ensuring the separation efficiency of the separating drum 44.

[0030] The specific working principle of this implementation is as follows: First, the main body 10 of the cleaning machine drives the spiral collector 11 and the scraper conveyor 12 to the working area of ​​the coal mine water tank. The spiral collector 11 at the front end disperses the slag and mud mixture deposited in the coal mine water tank, forming a water-slag mixture with good fluidity and completing the collection. Then, the spiral collector 11 transports the water-slag mixture to the scraper conveyor 12, and the scraper conveyor 12 transfers the water-slag mixture to the receiving hopper 20 below its discharge port. The water-slag mixture entering the receiving hopper 20 enters the first distribution bend 42 through the inlet 43. The water-slag mixture entering the distribution bend 42 is then divided into two paths and enters the corresponding two separation drums 44. Since the separating drum 44 is arranged at an angle, and the gear A49 is rotated by starting the drive motor 47, the gear ring 48 meshing with the gear A49 can drive the separating drum 44 to rotate. That is, after the water-slag mixture enters the rotating separating drum 44, the solid particles in the water-slag mixture will be subjected to the combined action of centrifugal force, gravity and fluid thrust, so that particles with a diameter larger than the separation hole diameter of the separating drum 44 are intercepted and gradually conveyed to the discharge pipe 46 and discharged as the separating drum 44 rotates. Particles with a diameter smaller than the separation hole diameter of the separating drum 44 pass through the separating drum 44 with the liquid and enter the first conveying hopper 41 (several conveying hoppers 41 are arranged in a stepped manner, with the height decreasing along the general separation flow direction of the water-slag mixture to ensure the natural flow of the water-slag mixture). In this way, the first-stage dynamic separation of the water-slag mixture can be completed. During the process of dynamic separation through several separation drums 44, the spiral deceleration plate 50 in the separation drum 44 can impede the incoming slag, prolonging the residence time of the slag in the separation drum 44. At the same time, the axial throwing plate 51 can throw the decelerated slag step by step, breaking the aggregation state of the slag inside the separation drum 44. Meanwhile, the gear ring 48 on the outside of the separating drum 44 can drive the gear B57 to rotate, which causes the rotating rod 55 to drive the anti-clogging rubber strips 56 arranged in a staggered manner on its outside to rotate. The rotating anti-clogging rubber strips 56 can periodically beat the outer wall of the separating drum 44 to prevent the separating drum 44 from being blocked by slag. The scraper 53 can scrape off the mud adhering to the corresponding separating drum 44, so that the scraped mud falls into the collection trough 52 to prevent the separating drum 44 from being blocked by mud. Subsequently, the water-slag mixture entering the first conveying hopper 41 enters the next distribution bend 42 through the feed inlet 43. The water-slag mixture entering the distribution bend 42 is also divided into two paths and enters the corresponding two separation drums 44. The corresponding two separation drums 44 rotate to perform the next stage of dynamic separation. The subsequent stepwise dynamic separation works similarly, that is, solid particles of different sizes can be dynamically separated by the corresponding aperture of the separation drum 44 and discharged through the corresponding discharge pipe 46, so that the water-slag mixture can be dynamically separated stepwise through multiple stages of separation drum 44, so that solid particles of different sizes (from centimeter-sized slag to micron-sized mud) can be accurately separated and discharged, and the liquid after separation enters the coal mine water tank through the discharge hopper 30.

[0031] The embodiments of the present invention have been described above, but the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the embodiments described above, all of which are within the protection scope of the embodiments described above.

Claims

1. A separation and cleaning device for coal mine water sump, comprising a cleaning machine body (10), a screw conveyor (11), and a scraper conveyor (12), characterized in that, Also includes: The receiving hopper (20) is located below the discharge port of the scraper conveyor (12); The discharge hopper (30) is located on the side away from the discharge port of the scraper conveyor (12); A multi-stage separation mechanism (40) is set between the receiving hopper (20) and the discharge hopper (30) and is used to separate the water-slag mixture step by step. The multi-stage separation mechanism (40) includes several conveying hoppers (41) that are fixed to each other. Each conveying hopper (41) is provided with a distribution bend (42) inside. The distribution bend (42) is provided with an inlet (43) outside. Both ends of the distribution bend (42) are rotatably connected to a separation drum (44) located inside the conveying hopper (41). The two separation drums (44) inside each conveying hopper (41) have the same separation hole diameter. The separation hole diameter of the several separation drums (44) decreases step by step along the direction from the receiving hopper (20) to the discharge hopper (30).

2. The separation and cleaning device for coal mine water tanks according to claim 1, characterized in that, Several conveying hoppers (41) are installed below the scraper conveyor (12) via mounting plates (45). The several conveying hoppers (41) are arranged in a stepped manner along the direction from the receiving hopper (20) to the discharge hopper (30). The conveying hoppers (41) closer to the receiving hopper (20) are fixedly connected to the receiving hopper (20), and the conveying hoppers (41) closer to the discharge hopper (30) are fixedly connected to the discharge hopper (30).

3. The separation and cleaning device for coal mine water tanks according to claim 2, characterized in that, The material distribution bend (42) is fixedly connected to the receiving hopper (20) or the conveying hopper (41), and the inlet (43) is connected to the receiving hopper (20) or the conveying hopper (41).

4. A separation and cleaning device for coal mine water storage according to claim 3, characterized in that, The end of the separating drum (44) away from the material distribution bend (42) is fixedly connected to a discharge pipe (46), which extends rotatably to the outside of the conveying hopper (41).

5. A separation and cleaning device for coal mine water storage according to claim 4, characterized in that, The discharge pipe (46) is provided with a drive component for driving its rotation. The drive component includes a drive motor (47) installed outside the feed hopper (41) and a gear ring (48) fixedly sleeved outside the discharge pipe (46). The output end of the drive motor (47) is fixedly connected to a gear A (49) that meshes with the gear ring (48).

6. A separation and cleaning device for coal mine water storage according to claim 5, characterized in that, Except for the two separating drums (44) near the discharge hopper (30), each of the other separating drums (44) is fixedly connected with a spiral speed reducer (50), and the spiral direction of the spiral speed reducer (50) is adapted to the rotation direction of its corresponding separating drum (44).

7. A separation and cleaning device for coal mine water storage according to claim 6, characterized in that, Except for the two separating drums (44) near the discharge hopper (30), each of the other separating drums (44) is fixedly connected with an axial throwing plate (51) at equal intervals inside, and the axial throwing plate (51) passes through the spiral deceleration plate (50).

8. A separation and cleaning device for coal mine water storage according to claim 7, characterized in that, The two separating drums (44) near the discharge hopper (30) are each fixedly connected to a material collection trough (52). A scraper (53) is fixedly connected to one side of the material collection trough (52) along the rotation direction of the corresponding separating drum (44). The material collection trough (52) extends to the outside of the discharge pipe (46) and has a discharge port (54).

9. A separation and cleaning device for coal mine water storage according to claim 8, characterized in that, Except for the two separating drums (44) near the discharge hopper (30), each of the other separating drums (44) is rotatably connected to a rotating rod (55). The rotating rod (55) is rotatably connected to the outside of its corresponding conveying hopper (41). Anti-clogging rubber strips (56) are fixedly connected at equal intervals to the outside of the rotating rod (55). The end of the rotating rod (55) is fixedly connected to a gear B (57) that meshes with the gear ring (48).

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