Fire coal screening device for power plant

Abstract

The invention relates to the technical field of fire coal screening, in particular to a fire coal screening device for a power plant, which comprises a belt conveyor and a feed hopper arranged on the belt conveyor, the fire coal screening device further comprises a first screening drum and a second screening drum, the axial direction of the first screening drum is consistent with the conveying path of the belt conveyor, and the first screening drum is located at a discharging port of the feeding hopper. The conditions of the fire coal input speed and input quantity are correspondingly adjusted through the two working conditions of the first screen drum and the second screen drum, and the first screen drum and the second screen drum are in an overlapped state under the condition that the fire coal input speed is low or the fire coal input quantity is small; according to the fire coal screening device, small fire coal sequentially passes through the screening holes of the second screening drum and the screening holes of the first screening drum to fall onto a belt of the belt conveyor, under the condition that the input speed of the fire coal is high or the input amount of the fire coal is large, the second screening drum stretches out of the first screening drum, and the screening speed of the fire coal is matched through the screening process of extending the stroke.

Description

Technical Field

[0001] The invention relates to the technical field of coal screening, and in particular to a coal screening device used in a power plant. Background Art

[0002] The main reasons why power plants screen coal include: Improve combustion efficiency: Screening can separate coal of different particle sizes to ensure that coal particles suitable for combustion enter the boiler, thereby improving combustion efficiency and thermal energy utilization.

[0003] Reduce pollutant emissions: By screening and removing larger impurities or incombustibles, pollutants generated during the combustion process can be reduced and environmental impact can be reduced.

[0004] Extend equipment service life: After screening, the wear of large coal and impurities on boilers and other equipment is reduced, thereby extending the service life of the equipment.

[0005] Chinese patent: CN201120170860.1 discloses a drum screen for fly ash brick making. A conveyor belt conveys the crushed fly ash material into the drum of the drum screen through a feed port and is rotated by a first motor. The fly ash screened by the sieve falls through a discharge box and passes through a conveyor belt into the next process.

[0006] According to the above patent and in combination with the prior art, it can be known that the screen drum used for coal screening is usually of fixed size, and the length of the drum has a direct impact on the screening effect; the screening speed of the fixed-size screen drum will remain consistent during the process of screening coal with different input rates, and the appropriate length can ensure the smooth flow of materials in the drum, reduce friction and resistance, and thus increase the transmission speed; if the screen drum is too long, the material may be accumulated in certain areas, causing blockage and increasing the burden on the drive device. Summary of the invention

[0007] In view of this, the purpose of the present invention is to propose a coal screening device for a power plant to solve the technical problem that the screen drum cannot control the length of the screen drum according to the coal input rate and input amount in the existing coal screening process.

[0008] Based on the above purpose, the present invention provides a coal screening device for a power plant, comprising a belt conveyor and a feed hopper arranged on the belt conveyor, wherein the conveying path of the belt conveyor is inclined, and the discharge port of the feed hopper faces the lower end of the conveying path of the belt conveyor; The coal screening device also includes a first screen drum and a second screen drum, the axial direction of the first screen drum is consistent with the conveying path of the belt conveyor, and the first screen drum is located at the discharge port of the feed hopper; The second sieve drum is arranged coaxially with the first sieve drum, and the second sieve drum is telescopically arranged inside the first sieve drum. Sieve holes are distributed on the first sieve drum and the second sieve drum. When the second sieve drum is inside the first sieve drum, the sieve holes on the first sieve drum correspond one to one with the sieve holes on the second sieve drum.

[0009] Preferably, a first retaining frame is provided on the first screen drum, the first retaining frame is annularly sleeved on the outer wall of the first screen drum, the first retaining frame is rotatably connected to the outer wall of the first screen drum through a bearing, and the first retaining frame is fixedly connected to the frame of the belt conveyor; The coal screening device also includes a rotary driver, which includes a gear ring sleeved on the outer wall of the first screen drum, and the gear ring is fixedly connected to the first screen drum. The rotary driver also includes a servo motor arranged on the belt conveyor and fixedly connected thereto, and the output shaft of the servo motor is provided with a gear, and the gear is meshed with the gear ring.

[0010] Preferably, a first end ring is provided at the lower end of the first sieve cylinder, and a second end ring is provided at the lower end of the second sieve cylinder. The outer wall of the second sieve cylinder is provided with convex strips distributed around it, and the convex strips are arranged axially along the second sieve cylinder. A guide groove corresponding to the convex strip is opened on the first end ring, and the guide groove is slidably connected to the convex strip. A limit block is provided at the end of the convex strip away from the second end ring.

[0011] Preferably, a second retaining frame is provided on the second sieve drum, the second retaining frame is annularly sleeved on the outer wall of the second sieve drum, and the second retaining frame is rotatably connected to the outer wall of the second sieve drum through a bearing; Guide rods are arranged on both sides of the second retaining frame, and the guide rods are fixedly connected to the frame body of the belt conveyor through fasteners. Convex rings are arranged on both sides of the second retaining frame, and the second retaining frame is slidably connected to the guide rods through the convex rings.

[0012] Preferably, the coal screening device further comprises a single-axis cylinder, the tail of the single-axis cylinder is connected to a hinge seat, and the tail of the single-axis cylinder is connected to the frame of the belt conveyor through the hinge seat; The end of the piston rod of the single-axis cylinder is provided with a hinge joint, and the end of the piston rod of the single-axis cylinder is connected to the second retaining frame through the hinge joint.

[0013] Preferably, the coal screening device further comprises a first guide slide and a second guide slide, wherein the first guide slide and the second guide slide are both arc panels, the first guide slide is fixedly connected to the end face of the second retaining frame, and the second guide slide is fixedly connected to the frame of the belt conveyor; A slide groove is arranged on the outer side surface of the first guide slide, a protrusion is arranged on the inner side surface of one end of the second guide slide, the second guide slide is slidably connected to the slide groove of the first guide slide through the protrusion, and the first guide slide and the second guide slide jointly cover the starting end of the conveying path of the belt conveyor.

[0014] Preferably, an inner boss is formed on the inner wall of the first sieve cylinder, the inner boss corresponds to the sieve hole of the first sieve cylinder, and the inner boss is close to the outer edge surface of the second sieve cylinder, and an opening connected to the sieve hole of the first sieve cylinder is formed on the inner boss.

[0015] Preferably, the coal screening device further comprises an end frame, which is located at the feed port of the first screen drum and is fixedly connected to the first retaining frame; The end frame is provided with a central axis, and the central axis is coaxially arranged with the first screen drum. A limiting frame is provided on the central axis, and the limiting frame is away from the belt of the belt conveyor. A brush frame is provided on the limiting frame, and a brush body is provided on one side of the brush frame, and a limiting rod is provided on the other side of the brush frame. The limiting rod passes through the limiting frame and is slidably connected with the limiting frame. A limiting plate is provided at the end of the limiting rod, and the limiting plate is located between the central axis and the limiting frame. An elastic element corresponding to the limiting rod is provided on the central axis, and the output end of the elastic element is connected with the limiting plate.

[0016] Beneficial effects of the present invention: The present invention makes corresponding adjustments to the coal input rate and input amount through the two working conditions of the first sieve drum and the second sieve drum. When the coal input rate is slow or the input amount is small, the first sieve drum and the second sieve drum are in an overlapping state, and the smaller coal will pass through the sieve holes of the second sieve drum and the sieve holes of the first sieve drum in turn and fall onto the belt of the belt conveyor. When the coal input rate is fast or the input amount is large, the second sieve drum will extend from the first sieve drum, and the screening rate of the coal will be matched by extending the screening process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A front view of the first working state of the present invention; Figure 2 for Figure 1 A magnified image of point A; Figure 3 It is a schematic diagram of the three-dimensional structure state of the first working state of the present invention; Figure 4 for Figure 3 The enlarged view of point B; Figure 5 It is a schematic diagram of the contraction state of the first screen drum and the second screen drum of the present invention; Figure 6It is a schematic diagram of the extended state of the first screen drum and the second screen drum of the present invention; Figure 7 It is a schematic diagram of the exploded structure of the first screen drum and the second screen drum of the present invention; Figure 8 It is a front view of the second working state of the present invention.

[0019] The numbers in the figure are: 1-belt conveyor; 2-feed hopper; 3-first screen drum; 31-first retaining frame; 32-first end ring; 321-guide groove; 33-inner boss; 4-second screen drum; 41-second end ring; 42-convex strip; 421-limiting block; 43-second retaining frame; 44-guide rod; 5-rotation drive; 51-gear ring; 52-servo motor; 53-gear; 61-single-axis cylinder; 62-articulated seat; 63-articulated head; 7-first guide slide; 71-second guide slide; 8-end frame; 81-middle shaft; 82-limiting frame; 83-brush frame; 831-brush body; 832-limiting rod; 833-limiting plate; 84-elastic element. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0021] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] In a first aspect of the present invention, a coal screening device for a power plant is provided, such as Figure 1 and Figure 8 As shown, it includes a belt conveyor 1 and a feed hopper 2 arranged on the belt conveyor 1, the conveying path of the belt conveyor 1 is inclined, and the discharge port of the feed hopper 2 faces the lower end of the conveying path of the belt conveyor 1; The coal screening device further includes a first screen drum 3 and a second screen drum 4, wherein the axial direction of the first screen drum 3 is consistent with the conveying path of the belt conveyor 1, and the first screen drum 3 is located at the discharge port of the feed hopper 2; The second sieve drum 4 is coaxially arranged with the first sieve drum 3, and the second sieve drum 4 is telescopically arranged inside the first sieve drum 3. Sieve holes are distributed on the first sieve drum 3 and the second sieve drum 4. When the second sieve drum 4 is inside the first sieve drum 3, the sieve holes on the first sieve drum 3 and the sieve holes on the second sieve drum 4 correspond one to one.

[0023] In this embodiment, the staff pours the coal into the feed hopper 2 of the coal screening device through a conveyor or a truck hopper, and the coal entering the hopper is guided by the feed hopper 2 into the interior of the first screen drum 3. At this time, the first screen drum 3 and the second screen drum 4 are in an overlapping state, and the purpose is to control the relative state of the first screen drum 3 and the second screen drum 4 according to the feeding speed of the coal; When the coal input rate is slow or the input amount is small, the first screen drum 3 and the second screen drum 4 are in an overlapping state, and the smaller coal will pass through the screen holes of the second screen drum 4 and the screen holes of the first screen drum 3 in sequence and fall onto the belt of the belt conveyor 1. The screening process of a shorter stroke increases the screening rate of the coal, and the larger pieces of coal that have been screened will fall into the external conveyor and move to the next process; When the coal input rate is fast or the input amount is large, the second screen drum 4 will extend from the first screen drum 3, and the screening rate of the coal will be matched by extending the screening process. Smaller coal will pass through the sieve holes of the first screen drum 3 and the second screen drum 4 and fall onto the belt of the belt conveyor 1, and larger pieces of coal will fall into the external conveyor and move to the next process.

[0024] As an implementation method, Figures 2 to 7 As shown, further: The first screen drum 3 is provided with a first retaining frame 31, which is annularly sleeved on the outer wall of the first screen drum 3, and the first retaining frame 31 is rotatably connected to the outer wall of the first screen drum 3 through a bearing, and the first retaining frame 31 is fixedly connected to the frame of the belt conveyor 1; The coal screening device also includes a rotary driver 5, which includes a gear ring 51 sleeved on the outer wall of the first screen drum 3, and the gear ring 51 is fixedly connected to the first screen drum 3. The rotary driver 5 also includes a servo motor 52 arranged on the belt conveyor 1 and fixedly connected thereto, and the output shaft of the servo motor 52 is provided with a gear 53, and the gear 53 is meshed with the gear ring 51.

[0025] A first end ring 32 is provided at the lower end of the first sieve drum 3, and a second end ring 41 is provided at the lower end of the second sieve drum 4. Raised strips 42 are distributed around the outer wall of the second sieve drum 4, and the raised strips 42 are arranged axially along the second sieve drum 4. A guide groove 321 corresponding to the raised strip 42 is opened on the first end ring 32, and the guide groove 321 is slidably connected to the raised strip 42. A limit block 421 is provided at the end of the raised strip 42 away from the second end ring 41.

[0026] In this embodiment, the first sieve drum 3 and the second sieve drum 4 are rotated to improve the screening rate and effect. The rotary driver 5 starts to work, and the output shaft of the servo motor 52 drives the gear 53 to rotate. Since the gear 53 and the ring gear 51 are meshed, the gear 53 drives the first sieve drum 3 to rotate through the ring gear 51. Since the second sieve drum 4 is slidably connected to the guide groove 321 of the first sieve drum 3 through the convex strip 42, the second sieve drum 4 will be driven to rotate with the first sieve drum 3 during its rotation. The rotational movement of the first sieve drum 3 and the second sieve drum 4 causes the coal therein to continuously roll and move, thereby avoiding the accumulation of materials in the sieve drums and facilitating the rapid separation of particles of different particle sizes.

[0027] As an implementation method, Figures 2 to 4 and Figure 8 As shown, further: The second sieve drum 4 is provided with a second retainer 43, which is annularly sleeved on the outer wall of the second sieve drum 4, and the second retainer 43 is rotatably connected to the outer wall of the second sieve drum 4 through a bearing; Guide rods 44 are provided on both sides of the second retaining frame 43 , and the guide rods 44 are fixedly connected to the frame body of the belt conveyor 1 through fasteners. Convex rings are provided on both sides of the second retaining frame 43 , and the second retaining frame 43 is slidably connected to the guide rods 44 through the convex rings.

[0028] The coal screening device also includes a single-axis cylinder 61, the tail of the single-axis cylinder 61 is connected to a hinge seat 62, and the tail of the single-axis cylinder 61 is connected to the frame of the belt conveyor 1 through the hinge seat 62; The end of the piston rod of the single-axis cylinder 61 is provided with a hinge joint 63 , and the end of the piston rod of the single-axis cylinder 61 is connected to the second retaining frame 43 through the hinge joint 63 .

[0029] In this embodiment, the convex ring can be specifically connected to the guide rod 44 by sliding with a linear sliding bearing or an oil-free bushing, but is not limited thereto; The moving direction of the second retainer 43 is limited by the guide rod 44, thereby improving the stability of the axial movement of the second screen drum 4 and the first screen drum 3, and the second retainer 43 is rotatably connected to the second end ring 41 through the bearing, thereby avoiding the influence on the rotation of the second screen drum 4; The purpose of the hinged seat 62 at the tail end of the single-axis cylinder 61 and the hinged joint 63 at the end of the piston rod is to prevent the single-axis cylinder 61 from being damaged and to improve the stability of the equipment. Since the belt conveyor 1 and its brother mechanism will generate vibrations and slight deviations in various positions to a certain extent during operation, it is necessary to give the single-axis cylinder 61 a flexible motion pair during the output process; The piston rod of the uniaxial cylinder 61 pushes the second retaining frame 43 to move along the moving direction of the guide rod 44 through the hinge joint 63. The second retaining frame 43 drives the second screen drum 4 to extend out of the first screen drum 3 through the second end ring 41, thereby completing the extension action of the second screen drum 4, and then matching the screening rate of the coal through the screening process with an extended stroke.

[0030] As an implementation method, Figure 3 As shown, further: The coal screening device also includes a first guide slide 7 and a second guide slide 71, wherein the first guide slide 7 and the second guide slide 71 are both arc panels, the first guide slide 7 is fixedly connected to the end surface of the second retaining frame 43, and the second guide slide 71 is fixedly connected to the frame of the belt conveyor 1; The outer side surface of the first guide slide 7 is provided with a slide groove, and the inner side surface of one end of the second guide slide 71 is provided with a protrusion. The second guide slide 71 is slidably connected to the slide groove of the first guide slide 7 through the protrusion. The first guide slide 7 and the second guide slide jointly cover the starting end of the conveying path of the belt conveyor 1.

[0031] In this embodiment, due to the telescopic action of the first sieve drum 3 and the second sieve drum 4, the landing points of the coal that has not passed through the sieve holes of the two sieve drums will also be different. In order to avoid the problem of invalid screening caused by the coal that rolls out directly falling on the belt of the belt conveyor 1 when the second sieve drum 4 retracts into the first sieve drum 3, the first guide slide 7 and the second guide slide 71 are set and coordinated to control the landing of the coal that has not passed through the sieve holes to be in a consistent state.

[0032] As an implementation method, Figure 7 As shown, further: An inner boss 33 is formed on the inner wall of the first sieve drum 3 , which corresponds to the sieve holes of the first sieve drum 3 and is close to the outer edge surface of the second sieve drum 4 . An opening connected to the sieve holes of the first sieve drum 3 is formed on the inner boss 33 .

[0033] In this embodiment, since the second sieve drum 4 is slidably connected to the guide groove 321 of the first sieve drum 3 through the convex strip 42, a certain gap will be generated between the inner walls of the second sieve drum 4 and the first sieve drum 3. Such a gap will cause the coal to get stuck when passing through the sieve holes of the second sieve drum 4 and the first sieve drum 3 at one time when the second sieve drum 4 retracts into the first sieve drum 3. The inner boss 33 and the opening corresponding to the first sieve drum 3 can smoothly allow the coal that meets the specifications to pass through without getting stuck between the first sieve drum 3 and the second sieve drum 4.

[0034] As an implementation method, Figure 7 As shown, further: The coal screening device further includes an end frame 8, which is located at the feed port of the first screen drum 3, and the end frame 8 is fixedly connected to the first retaining frame 31; The end frame 8 is provided with a central axis 81, and the central axis 81 is coaxially arranged with the first screen drum 3. A limiting frame 82 is provided on the central axis 81, and the limiting frame 82 is away from the belt of the belt conveyor 1. A brush frame 83 is provided on the limiting frame 82, and a brush body 831 is provided on one side of the brush frame 83, and a limiting rod 832 is provided on the other side of the brush frame 83. The limiting rod 832 penetrates the limiting frame 82 and is slidably connected thereto, and a limiting plate 833 is provided at the end of the limiting rod 832, and the limiting plate 833 is located between the central axis 81 and the limiting frame 82. An elastic element 84 corresponding to the limiting rod 832 is provided on the central axis 81, and the output end of the elastic element 84 is connected to the limiting plate 833.

[0035] In this embodiment, in order to prevent the inner walls of the first sieve drum 3 and the second sieve drum 4 from getting stuck with the burning coal, the following methods can be used to avoid this: The elastic element 84 in this embodiment is preferably a spring, which pushes the limit rod 832 through the elastic element 84, and then pushes the brush body 831 on the brush holder 83 to contact the inner wall of the second sieve cylinder 4, or the inner walls of the first sieve cylinder 3 and the second sieve cylinder 4. In the accompanying drawings, the brush body 831 is shorter, and the length of the brush body 831 can be appropriately extended when the actual equipment is configured.

[0036] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0037] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A coal screening device for a power plant, characterized in that: It comprises a belt conveyor (1) and a feed hopper (2) arranged on the belt conveyor (1), wherein the conveying path of the belt conveyor (1) is arranged in an inclined manner, and the discharge port of the feed hopper (2) faces the lower end of the conveying path of the belt conveyor (1); The coal screening device further comprises a first screen drum (3) and a second screen drum (4); the axial direction of the first screen drum (3) is consistent with the conveying path of the belt conveyor (1), and the first screen drum (3) is located at the discharge port of the feed hopper (2); The second sieve drum (4) is coaxially arranged with the first sieve drum (3), and the second sieve drum (4) is telescopically arranged inside the first sieve drum (3). Sieve holes are distributed on the first sieve drum (3) and the second sieve drum (4). When the second sieve drum (4) is inside the first sieve drum (3), the sieve holes on the first sieve drum (3) correspond to the sieve holes on the second sieve drum (4) one by one.

2. A coal screening device for a power plant according to claim 1, characterized in that: A first retaining frame (31) is provided on the first sieve drum (3); the first retaining frame (31) is annularly sleeved on the outer wall of the first sieve drum (3); the first retaining frame (31) is rotatably connected to the outer wall of the first sieve drum (3) via a bearing; and the first retaining frame (31) is fixedly connected to a frame body of the belt conveyor (1); The coal screening device further comprises a rotary drive (5), the rotary drive (5) comprising a gear ring (51) sleeved on the outer wall of the first screen drum (3), the gear ring (51) being fixedly connected to the first screen drum (3), the rotary drive (5) further comprising a servo motor (52) arranged on the belt conveyor (1) and fixedly connected thereto, the output shaft of the servo motor (52) being provided with a gear (53), the gear (53) being meshed with the gear ring (51).

3. The coal screening device for a power plant according to claim 1, characterized in that: A first end ring (32) is provided at the lower end of the first sieve drum (3), a second end ring (41) is provided at the lower end of the second sieve drum (4), convex strips (42) are provided around the outer wall of the second sieve drum (4), the convex strips (42) are arranged axially along the second sieve drum (4), a guide groove (321) corresponding to the convex strip (42) is provided on the first end ring (32), the guide groove (321) is slidably connected to the convex strip (42), and a stop block (421) is provided at one end of the convex strip (42) away from the second end ring (41).

4. The coal screening device for a power plant according to claim 1, characterized in that: A second retaining frame (43) is provided on the second sieve drum (4); the second retaining frame (43) is annularly sleeved on the outer wall of the second sieve drum (4); the second retaining frame (43) is rotatably connected to the outer wall of the second sieve drum (4) via a bearing; Guide rods (44) are provided on both sides of the second retaining frame (43), and the guide rods (44) are fixedly connected to the frame body of the belt conveyor (1) via fasteners. Convex rings are provided on both sides of the second retaining frame (43), and the second retaining frame (43) is slidably connected to the guide rods (44) via the convex rings.

5. The coal screening device for a power plant according to claim 4, characterized in that: The coal screening device also includes a single-axis cylinder (61), the tail of the single-axis cylinder (61) is connected to a hinge seat (62), and the tail of the single-axis cylinder (61) is connected to the frame of the belt conveyor (1) through the hinge seat (62); The end of the piston rod of the single-axis cylinder (61) is provided with a hinge joint (63), and the end of the piston rod of the single-axis cylinder (61) is connected to the second retaining frame (43) via the hinge joint (63).

6. The coal screening device for a power plant according to claim 4, characterized in that: The coal screening device further comprises a first guide slide (7) and a second guide slide (71), wherein the first guide slide (7) and the second guide slide (71) are both arc-shaped plate bodies, the first guide slide (7) is fixedly connected to the end surface of the second retaining frame (43), and the second guide slide (71) is fixedly connected to the frame of the belt conveyor (1); The outer side surface of the first guide slide (7) is provided with a slide groove, and the inner side surface of one end of the second guide slide (71) is provided with a protrusion. The second guide slide (71) is slidably connected to the slide groove of the first guide slide (7) via the protrusion. The first guide slide (7) and the second guide slide jointly cover the starting end of the conveying path of the belt conveyor (1).

7. The coal screening device for a power plant according to claim 3, characterized in that: An inner boss (33) is formed on the inner wall of the first sieve cylinder (3), the inner boss (33) corresponds to the sieve holes of the first sieve cylinder (3), and the inner boss (33) is close to the outer edge surface of the second sieve cylinder (4), and an opening communicating with the sieve holes of the first sieve cylinder (3) is formed on the inner boss (33).

8. The coal screening device for a power plant according to claim 2, characterized in that: The coal screening device also includes an end frame (8), the end frame (8) is located at the feed port of the first screen drum (3), and the end frame (8) is fixedly connected to the first retaining frame (31); The end frame (8) is provided with a central axis (81), the central axis (81) and the first screen drum (3) being arranged coaxially, a limiting frame (82) being provided on the central axis (81), the limiting frame (82) being away from the belt of the belt conveyor (1), a brush frame (83) being provided on the limiting frame (82), a brush body (831) being provided on one side of the brush frame (83), a limiting rod (832) being provided on the other side of the brush frame (83), the limiting rod (832) penetrating the limiting frame (82) and being slidably connected thereto, a limiting plate (833) being provided at the end of the limiting rod (832), the limiting plate (833) being located between the central axis (81) and the limiting frame (82), an elastic element (84) corresponding to the limiting rod (832) being provided on the central axis (81), the output end of the elastic element (84) being connected to the limiting plate (833).

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