Device for improving concentration of tailings based on small mechanical disturbance and application method

Abstract

The invention provides a device for improving tailing concentration based on mechanical small disturbance and an application method. The device is fixedly arranged at the bottom of the thickener and consists of a plurality of groups of filter pipes which are radially and circumferentially distributed along the cross section of the bottom of the thickener and axially distributed in multiple layers. According to the invention, the self-integrated structure (the combined structure of the disturbance part, the porous filtration part and the flow guide part) of the filter pipe, the radial arrangement of the filter pipe and the axial arrangement of the filter pipe are combined in different dimensions and different scales, so that the dual technical effects of mechanical disturbance and water drainage and sand conservation are synchronously and efficiently realized. By means of the combined structural design, the tailing thickening and sand protecting effects are improved, and the efficiency and stability of the whole thickening process are improved.

Description

Technical Field

[0001] The invention relates to the technical field of mine filling and tailings slurry dehydration and separation, and in particular to a device for increasing tailings concentration based on small mechanical disturbances and an application method thereof. Background Art

[0002] The waste tailings generated after the original ore is beneficiated are generally discharged into the tailings pond for storage. However, the tailings pond is a man-made debris flow hazard source with high potential energy, and there is a risk of dam breach. In addition, the harmful components in the tailings will cause serious pollution to the environment around the tailings pond. The filling mining method can refill the tailings in the tailings pond into the mine after a series of processes, effectively solving the problem of green and sustainable development of mines. In the field of mine filling, deep cone thickeners and storage thickeners are generally used to treat the solid-liquid separation process of tailings slurry. The thickening mechanism of these two types of thickeners is to produce flocs through the reaction of tailings and chemical agents. The flocs quickly settle downward under the action of gravity, and the separated liquid overflows the thickener, thereby initially obtaining a tailings slurry of a certain concentration.

[0003] In order to meet the mine's requirements for high concentration of filling tailings, the deep cone thickener is equipped with a motor-driven rake frame inside, and a vertical pipe is installed on the rake frame arm to disturb the tailings in the vertical direction, release the liquid stored between the tailings particles, and achieve the effect of increasing the concentration of tailings. The storage thickener increases the height of the silo, increases the pressure of the tailings slurry in the upper cavity of the thickener on the bottom tailings, and presses out the liquid in the bottom tailings floc molecules through the gravity of the tailings slurry in the upper cavity by standing still. However, the method of expelling water by gravity often has a certain hysteresis, and it takes a long time to complete the thickening work. In addition, it has poor adaptability to coarse-grained tailings, and the rake is prone to pressure during the operation of the rake frame. The installed vertical pipe loses its disturbance ability, affecting the continuous production of the mine and failing to meet the high-concentration filling requirements.

[0004] The invention patent with publication number CN114247187A provides a rapid thickener. It includes a tank body and a feed box hoisted at the center of the top of the tank body. The tank body is divided into a separation transition aggregate area, a compression vibration concentration area and a sand release area from top to bottom. The tank wall diameter of the separation transition aggregate area, the tank wall diameter of the compression vibration concentration area and the tank wall diameter of the sand release area are arranged in descending order. A plurality of jet booster nozzles are evenly distributed along the circumference at the bottom of the tank wall of the separation transition aggregate area, and a vibration assembly is arranged in the compression vibration concentration area. The device can quickly increase the thickness of the mud layer, which is conducive to shortening the preparation time for high-concentration bottom flow discharge of the thickener; it is conducive to the rapid rise and escape of seepage water in the tailings slurry; it can control the overflow runoff speed to prevent the material from running muddy; it can avoid the formation of a sand release funnel, eliminate sand settling, and increase the effective storage volume of the tank body; the rake-free design has a simpler structure and no power consumption during the sand settling process; it is convenient for long-term storage and can achieve rapid thickening of low-concentration tailings slurry. However, the structure of the device achieves accelerated density through jet-boosting nozzles and vibration components, but the jet-boosting nozzles cause too much disturbance, and when used, a large vortex will appear inside the sand layer, causing the clarified layer to run and mix. Moreover, the drainage method used by the device still relies on the natural gravity method, where solid particles sink and liquid floats for drainage. Water separated from the particles will not be able to break through the upper sand layer and remain inside the sand layer, and the drainage and density effect cannot be achieved.

[0005] In view of this, it is necessary to design an improved device and application method for increasing tailings concentration based on small mechanical disturbances to solve the above problems. Summary of the invention

[0006] The object of the present invention is to provide a device and an application method for increasing tailings concentration based on small mechanical disturbances.

[0007] To achieve the above-mentioned purpose, the present invention provides a device for increasing tailings concentration based on small mechanical disturbance, which is fixedly arranged at the bottom of the thickener and not more than 1 / 2 of the axial height of the thickener, and is composed of a plurality of groups of filter tubes radially arranged circumferentially along the cross section of the bottom of the thickener and arranged in multiple layers in the axial direction;

[0008] The tail end of the filter tube is connected to the bottom side wall of the thickener and is used to guide water to the outside of the thickener;

[0009] The head ends of the filter tubes are all oriented toward the center of the cross section of the bottom of the thickener, and are used for low-rate mechanical disturbance;

[0010] A porous filter portion is provided at the middle end of the filter tube, which is used to filter the water in the tailings slurry while blocking the tailings from being discharged.

[0011] As a further improvement of the present invention, the multi-layered filter tube structure includes a filter tube combination system of n layers of filter tubes arranged parallel to each other in the axial direction, wherein n≥2.

[0012] As a further improvement of the present invention, each layer of the filter tube combination system includes m groups of filter tubes which are radially arranged circumferentially and whose head ends face the center of the circle, wherein m≥6.

[0013] As a further improvement of the present invention, the filter tube includes a disturbance portion arranged at the head end, a porous filter portion arranged at the middle end, and a flow guide portion arranged at the tail end;

[0014] The length of the filter tube is no more than 1 / 2 of the radial radius length of the cross section at the bottom of the thickener.

[0015] As a further improvement of the present invention, the porous filter portion comprises a mesh stainless steel layer, a PP filter cotton layer and a porous tube front end arranged in sequence from the outside to the inside; a porous structure with a predetermined pore size is arranged on the tube wall of the porous tube front end;

[0016] The filtration pore size of the PP filter cotton layer is smaller than the tailings particle size;

[0017] The mesh aperture of the mesh stainless steel layer is larger than the filter aperture of the PP filter cotton layer.

[0018] As a further improvement of the present invention, the disturbance part is rotatably connected to the porous filtering part, and is composed of a rotating blade and a driving motor; the length of the rotating blade is 1.5 to 2 times the radius of the filtering tube.

[0019] As a further improvement of the present invention, the flow guide portion includes a rear end of a porous tube connected to the front end of the porous tube and an annular iron tube fixedly connected to the bottom side wall of the thickener;

[0020] The rear end of the porous tube passes through the through hole on the bottom side wall of the thickener, one end of the annular iron tube is arranged on the side wall around the through hole, and the other end is connected to the mesh stainless steel layer.

[0021] As a further improvement of the present invention, the mechanical disturbance rate of the disturbance part is 500-1000RPM.

[0022] To achieve the above-mentioned object of the invention, the present invention also provides an application method of the above-mentioned device for increasing tailings concentration based on small mechanical disturbance, which comprises the following steps:

[0023] S1, according to the type and properties of tailings, set the number of layers of the filter tube combination system and the number of groups of filter tubes arranged around the circumference in each layer of the filter tube combination system, and fix the device for increasing the tailings concentration based on mechanical small disturbance on the bottom side wall of the thickener;

[0024] S2, the thickener is fed with sand, and the tailings slurry gradually forms a dense layer at the bottom of the thickener. The moisture of the tailings slurry first passes through the mesh stainless steel layer into the filter tube, then passes through the PP filter cotton layer into the front end of the porous tube, and finally the moisture is discharged from the rear end of the porous tube to the outside of the thickener;

[0025] S3, at the same time, the rotating blades of the disturbance part are turned on to perform low-speed mechanical disturbance on the tailings slurry, so as to promote the flow of the tailings slurry, change the distribution of the water channel in the dense layer, accelerate the water flow velocity between the tailings, promote the flow of water to the front end of the porous pipe, guide water, and achieve a dense effect.

[0026] As a further improvement of the present invention, the number of layers of the filter tube combination system is 5≥n≥2; the number of groups of filter tubes arranged circumferentially is 10≥m≥6.

[0027] The beneficial effects of the present invention are:

[0028] 1. The device for increasing tailings concentration based on mechanical small disturbance provided by the present invention adopts an efficient thickening structure, and its core components are the rotating blades of the disturbance part at the head (head end) and the PP filter cotton layer at the middle end. The rotating blades are made of high-strength materials, which can make small disturbances during the tailings sedimentation process, break the static structure of the tailings sedimentation, increase the relative movement between the tailings particles, and prevent the tailings from settling too quickly to form a dense layer. The PP filter cotton layer has both excellent drainage performance and filtering performance, ensuring that the tailings particles are effectively intercepted while draining water, so as to achieve drainage and sand conservation. Inside the bottom tailings slurry, due to the continuous sedimentation of the upper tailings, the lower tailings gradually become dense, and the drainage channels are reduced. However, after the small disturbance of the rotating blades, the gaps between the tailings particles increase, forming more water flow channels. Through the mutual cooperation between the disturbance part, the porous filter part and the guide part, it is beneficial for the gap water in the dense layer to be discharged from the outside of the thickener, reduce the moisture content in the tailings, and increase the bottom flow density. The above-mentioned combined structural design not only improves the thickening and sand retention effects of tailings, but also improves the efficiency and stability of the entire thickening process.

[0029] 2. The device for increasing tailings concentration based on mechanical small disturbance provided by the present invention combines the integrated structure of the filter tube itself (the combined structure of the disturbance part, the porous filter part and the guide part), the radial arrangement of the filter tube, and the axial arrangement of the filter tube in different dimensions and scales to construct a three-dimensional dense structure, thereby synchronously and efficiently realizing the dual technical effects of mechanical disturbance and drainage and sand preservation. The role of its mechanical disturbance technology is: first, the rotating blades at the head (head end) of the filter tube perform low-rate mechanical disturbance on the tailings slurry within the bottom flow range, while ensuring that the overall structure of the tailings slurry is not damaged, increasing the drainage channel, promoting the flow of water between the tailings, and increasing the drainage channel. Second, after the settled tailings flocs are sheared and destroyed by the rotating blades, the large flocs will be divided into small flocs, and the water inside the large flocs will be discharged as the flocs are destroyed. Third, the static and dense tailings at the bottom of the thickener flow under the small disturbance of the rotating blades, effectively preventing the bottom of the sand bin from compacting and improving the stability of the sand bin. The function of its drainage and sand retention technology is: installing a PP filter cotton layer on the filter tube can effectively block the outflow of tailings while filtering water, which is beneficial to increase the concentration of tailings slurry. A mesh stainless steel layer is set on the outer layer of the PP filter cotton layer, which can pre-block most of the tailings, and through the gradient filtration aperture setting of the mesh stainless steel layer and the PP filter cotton layer, the tailings slurry can be double-filtered, thereby significantly enhancing the technical effect of drainage and water diversion and simultaneous sand retention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the radial installation structure of the device for increasing tailings concentration based on small mechanical disturbance provided by the present invention in a thickener.

[0031] Figure 2 A schematic diagram of the axial installation structure of the device for increasing tailings concentration based on small mechanical disturbance provided by the present invention in a thickener.

[0032] Figure 3 A schematic diagram of the structure of a device for increasing tailings concentration based on small mechanical disturbances provided by the present invention.

[0033] Reference numerals

[0034] 1-filter tube; 2-front end of porous tube; 3-mesh stainless steel layer; 4-PP filter cotton layer; 5-rear end of porous tube; 6-annular iron tube; 7-rotating blades; 8-filter tube combination system. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0037] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0038] See also Figures 1 to 3 As shown, the present invention provides a device for increasing tailings concentration based on mechanical small disturbance, which is fixedly arranged at the bottom of the thickener and not more than 1 / 2 of the axial height of the thickener, and consists of a plurality of groups of filter tubes 1 which are radially arranged circumferentially along the cross section of the bottom of the thickener and arranged in multiple layers in the axial direction;

[0039] The tail end of the filter tube 1 is connected to the bottom side wall of the thickener to guide water to the outside of the thickener;

[0040] The head ends of the filter tubes 1 are all oriented toward the center of the cross section at the bottom of the thickener, and are used for low-rate mechanical disturbance;

[0041] The middle end of the filter tube 1 is provided with a porous filter portion for filtering the water in the tailings slurry while blocking the discharge of the tailings.

[0042] See also Figure 2 As shown, the multi-layered filter tube structure includes n layers of filter tube assembly systems 8 arranged parallel to each other in the axial direction, wherein n≥2. The specific number of layers is set according to the specific height of the thickener. Considering that there are large and small outlets such as sand outlets at the bottom of the thickener, too many layers may affect the structural strength of the thickener. Therefore, the number of layers of the filter tube assembly system 8 is 5≥n≥2.

[0043] See also Figure 1 As shown, each layer of filter tube assembly system 8 includes m groups of filter tubes 1 arranged circumferentially in the radial direction and with their head ends facing the center of the circle, wherein m≥6. According to the radius length of the bottom of the thickener and the specific characteristics of the tailings, the number of groups of filter tubes 1 arranged circumferentially is 10≥m≥6.

[0044] See also Figure 3 As shown, the filter tube 1 includes a disturbance portion arranged at the head end, a porous filter portion arranged at the middle end, and a flow guide portion arranged at the tail end.

[0045] The length of the filter tube 1 does not exceed 1 / 2 of the radial length of the cross section at the bottom of the thickener. In specific applications, the number of groups of filter tubes 1 arranged around the circumference is considered to prevent mutual interference between the rotating blades 7. The more groups there are, the shorter the length should be.

[0046] The porous filter part includes a mesh stainless steel layer 3, a PP filter cotton layer 4 and a porous tube front end 2 arranged in sequence from the outside to the inside; a porous structure with a predetermined pore size is arranged on the tube wall of the porous tube front end 2;

[0047] The filtration pore size of the PP filter cotton layer 4 is smaller than the tailings particle size;

[0048] The mesh aperture of the mesh stainless steel layer 3 is larger than the filter aperture of the PP filter cotton layer.

[0049] The disturbance part is rotationally connected to the porous filtering part, and is composed of a rotating blade 7 and a driving motor (not shown in the figure); the length of the rotating blade 7 is 1.5 to 2 times the radius of the filtering tube 1.

[0050] The guide part includes a porous tube rear end 5 connected to the porous tube front end 2 and an annular iron tube 6 fixedly connected to the bottom side wall of the thickener;

[0051] The rear end 5 of the porous tube passes through a through hole (not shown in the figure) on the bottom side wall of the thickener, one end of the annular iron tube 6 is arranged on the side wall around the through hole, and the other end is connected to the mesh stainless steel layer 3.

[0052] Example 1

[0053] Embodiment 1 of the present invention provides a device for increasing tailings concentration based on mechanical small disturbance, the composition and structure of which are as follows: Figures 1 to 3 As shown: the number of layers of the filter tube combination system 8 is n=2; the number of groups of filter tubes 1 arranged around the circumference is m=6.

[0054] The filter tube 1 comprises a porous tube front end 2, a mesh stainless steel layer 3, a PP filter cotton layer 4, a porous tube rear end 5, an annular iron tube 6, and rotating blades 7.

[0055] The present invention also provides an application method of the above-mentioned device for increasing tailings concentration based on small mechanical disturbance, which comprises the following steps:

[0056] S1, according to the type and properties of tailings, the number of layers of the filter tube combination system 8 and the number of groups of filter tubes 1 arranged around the circumference in each layer of the filter tube combination system 8 are set (the number of layers of the filter tube combination system 8 n=2; the number of groups of filter tubes 1 arranged around the circumference m=6), and the device for increasing the tailings concentration based on mechanical small disturbance is fixedly installed on the bottom side wall of the thickener;

[0057] S2, the thickener is fed with sand, and the tailings slurry gradually forms a dense layer at the bottom of the thickener. The water content of the tailings slurry first passes through the mesh stainless steel layer 3 into the filter tube, and then passes through the PP filter cotton layer 4 into the front end 2 of the porous tube. Finally, the water content is discharged from the rear end 5 of the porous tube to the outside of the thickener;

[0058] S3, at the same time, the rotating blades 7 of the disturbance part are turned on (the mechanical disturbance rate of the disturbance part is 500-1000RPM), and the tailings slurry is mechanically disturbed at a low rate to promote the flow of the tailings slurry, change the distribution of the water channel of the dense layer, accelerate the water flow speed between the tailings, promote the flow of water to the front end 2 of the porous pipe, conduct water, and achieve a dense effect.

[0059] The working principle of the device for increasing the tailings concentration based on small mechanical disturbances provided in Example 1 of the present invention is that when the thickener is fed with sand, the material continues to sink under the action of gravity, and four layers of dense layer, compression layer, sedimentation layer, and clarification layer are gradually formed from bottom to top. The device for increasing the tailings concentration based on small mechanical disturbances is arranged on the side wall of the bottom (dense layer) of the thickener, and two layers of filter tube combination systems 8 are arranged in parallel with each other and at a predetermined interval. Six filter tubes 1 are evenly distributed on each layer, and the filter tubes 1 in each layer are arranged radially and circumferentially along the cross-section of the bottom of the thickener, and the head ends of the filter tubes 1 are arranged toward the center of the circle. The tail end is connected to the side wall of the bottom of the thickener for guiding water to the outside of the thickener. Thus, the integrated structure of the filter tube 1 itself (the combined structure of the disturbance part, the porous filter part and the guide part), the radial arrangement of the filter tube 1, and the axial arrangement of the filter tube 1 are combined in three different dimensions and scales.

[0060] After installation, the device for increasing tailings concentration based on mechanical small disturbances drains water in the thickener biological thickening layer (lower layer) and exports it to the outside of the thickener. The water between the tailings will first enter through the mesh stainless steel layer 3, and after the first filtration (used to block most of the tailings), it will enter the front end 2 of the porous tube under the double filtration of the PP filter cotton 4, and flow to the rear end 5 of the porous tube connected to the front end 2 of the porous tube, and finally, export it to the outside of the thickener. At the same time, the rotating blades 7 at the head of the filter tube 1 are turned on to make small disturbances to the tailings within the thickening layer, so as to promote the flow of tailings slurry, change the distribution of the lower waterway, accelerate the water flow speed between the tailings, and improve the thickening effect.

[0061] Those skilled in the art know that in other embodiments, according to the type and properties of the tailings, the number of layers of the filter tube combination system can be set to 5≥n≥2; the number of groups of the filter tubes arranged circumferentially can be set to other settings within the range of 10≥m≥6, thereby setting the radial arrangement of the filter tubes and the axial arrangement of the filter tubes, which can achieve the technical effect of improving the thickening and sand retention effects of the tailings and enhancing the efficiency and stability of the entire thickening process.

[0062] In summary, the present invention provides a device and application method for increasing the concentration of tailings based on small mechanical disturbances. The device is fixedly arranged at the bottom of the thickener, and is composed of a plurality of groups of filter tubes 1 arranged radially and circumferentially along the cross section of the bottom of the thickener and arranged in multiple layers axially; the tail end of the filter tube 1 is connected to the side wall of the bottom of the thickener, and is used to guide water to the outside of the thickener; the head end of the filter tube 1 is facing the center of the cross section of the bottom of the thickener, and is used for low-rate mechanical disturbance; the middle end of the filter tube 1 is provided with a porous filter part, which is used to filter the water in the tailings slurry while blocking the outlet of the tailings. The integrated structure of the filter tube itself (the combined structure of the disturbance part, the porous filter part and the guide part), the radial arrangement of the filter tube, and the axial arrangement of the filter tube are combined in different dimensions and scales, thereby synchronously and efficiently realizing the dual technical effects of mechanical disturbance and drainage and sand retention. The above-mentioned combined structural design not only improves the thickening and sand retention effects of the tailings, but also improves the efficiency and stability of the entire thickening process.

[0063] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A device for increasing tailings concentration based on small mechanical disturbances, characterized in that: The device is fixedly arranged at the bottom of the thickener and not more than 1 / 2 of the axial height of the thickener, and is composed of a plurality of groups of filter tubes which are radially arranged circumferentially along the cross section of the bottom of the thickener and arranged in multiple layers in the axial direction; The tail end of the filter tube is connected to the bottom side wall of the thickener to guide water to the outside of the thickener; The head ends of the filter tubes are all oriented toward the center of the cross section of the bottom of the thickener, and are used for low-rate mechanical disturbance; A porous filter portion is provided at the middle end of the filter tube, which is used to filter the water in the tailings slurry while blocking the tailings from being discharged.

2. The device for increasing tailings concentration based on small mechanical disturbance according to claim 1, characterized in that: The multi-layered filter tube structure comprises a filter tube combination system of n layers arranged parallel to each other in the axial direction, wherein n≥2.

3. The device for increasing tailings concentration based on small mechanical disturbance according to claim 2, characterized in that: Each layer of the filter tube combination system includes m groups of filter tubes which are radially arranged circumferentially and whose head ends face the center of the circle, wherein m≥6.

4. The device for increasing tailings concentration based on small mechanical disturbance according to claim 1, characterized in that: The filter tube includes a disturbance portion arranged at the head end, a porous filter portion arranged at the middle end, and a flow guide portion arranged at the tail end; The length of the filter tube does not exceed 1 / 2 of the radial radius length of the cross section at the bottom of the thickener.

5. The device for increasing tailings concentration based on small mechanical disturbance according to claim 4, characterized in that: The porous filter part comprises a mesh stainless steel layer, a PP filter cotton layer and a porous tube front end which are arranged in sequence from the outside to the inside; a porous structure with a predetermined pore size is arranged on the tube wall of the porous tube front end.

6. The device for increasing tailings concentration based on small mechanical disturbance according to claim 4, characterized in that: The disturbance part is rotatably connected to the porous filtering part, and is composed of a rotating blade and a driving motor; the length of the rotating blade is 1.5 to 2 times the radius of the filtering tube.

7. The device for increasing tailings concentration based on small mechanical disturbance according to claim 5, characterized in that: The flow guide portion includes a porous tube rear end connected to the porous tube front end and an annular iron tube fixedly connected to the bottom side wall of the thickener; The rear end of the porous tube passes through the through hole on the bottom side wall of the thickener, one end of the annular iron tube is arranged on the side wall around the through hole, and the other end is connected to the mesh stainless steel layer.

8. The device for increasing tailings concentration based on small mechanical disturbance according to claim 1, characterized in that: The mechanical disturbance rate of the disturbance part is 500-1000RPM.

9. The application method of the device for increasing tailings concentration based on small mechanical disturbance according to any one of claims 1 to 8, characterized in that: The steps include: S1, according to the type and properties of tailings, set the number of layers of the filter tube combination system and the number of groups of filter tubes arranged around the circumference in each layer of the filter tube combination system, and fix the device for increasing the tailings concentration based on mechanical small disturbance on the bottom side wall of the thickener; S2, the thickener is fed with sand, and the tailings slurry gradually forms a dense layer at the bottom of the thickener. The moisture of the tailings slurry first passes through the mesh stainless steel layer into the filter tube, then passes through the PP filter cotton layer into the front end of the porous tube, and finally the moisture is discharged from the rear end of the porous tube to the outside of the thickener; S3, at the same time, the rotating blades of the disturbance part are turned on to perform low-speed mechanical disturbance on the tailings slurry, so as to promote the flow of the tailings slurry, change the distribution of the water channel in the dense layer, accelerate the water flow velocity between the tailings, promote the flow of water to the front end of the porous pipe, guide water, and achieve a dense effect.

10. The application method of the device for increasing tailings concentration based on small mechanical disturbance according to claim 9 is characterized in that: The number of layers of the filter tube combination system is 5≥n≥2; the number of groups of filter tubes arranged around the circumference is 10≥m≥6.

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