A system for removing impurities from a ceramic raw material

Abstract

The present invention relates to a system for removing impurities from dry powder of ceramic tile raw material produced by dry milling, which is used to sieve the impurities in the coarse powder coming from the grinding system or grinding device, thus obtaining fine powder for use in the granulator for granulation.

Description

TECHNICAL FIELD

[0001] The present application relates to a system for removing impurities in the production of ceramic tile raw materials by dry powdering, and belongs to the field of ceramic tile raw materials, in particular, the field of dry powdering ceramic tile raw materials. BACKGROUND

[0002] Ceramic tiles are thin plate materials made of clay and other raw materials, usually formed by pressing powder. The common powder preparation process in industry includes wet process and dry process.

[0003] In the preparation process of the wet process (also known as wet powdering), the slurry (water content up to 40% by weight) ground by wet process is dried by spray drying to produce the powder needed for subsequent pressing forming. Spray drying requires drying the slurry at high temperature (700℃-900℃) until the water content is reduced to 7% by weight. The amount of water evaporated per ton of powder (dry basis) is about 600kg, and a large amount of energy is consumed in the evaporation process.

[0004] In the preparation process of the dry process (also known as dry powdering), dry powder is first prepared by grinding, and the dry powder is then moistened and agglomerated with water. The amount of water added during the agglomeration process is controlled to be below 12%, and the moisture content of the agglomerated particles is reduced to 7% by a fluidized bed dryer. The amount of water evaporated per ton of powder (dry basis) is about 60kg, which is much less than the amount of water evaporated when preparing the same dry basis by wet powdering. Therefore, the energy consumed, especially the heat energy, in the process of dry powdering is much lower than that in the process of wet powdering, which can reduce carbon emissions by more than 40%.

[0005] The dry powdering process has great advantages in raw materials, water and energy consumption compared to the wet powdering process. Especially in the case of increasingly stringent environmental regulations on high energy consumption and / or high pollution production, the use of corresponding low energy consumption and low pollution alternative processes has become a development trend in various industries.

[0006] However, before granulation, impurities in the dry powder obtained by grinding must be removed, including unground fibrous impurities and ferromagnetic impurities. The moisture content of the dry powder is about 2-4% by weight, the particle size is small (in the case of producing floor tiles, the 58 μm sieve residue needs to be controlled within 2% by weight), the static angle of repose is above 45°, and the flowability is poor; in addition, the dry powder also contains flocculent substances, plastics, organic matter and other impurities. The impurity removal equipment (double-bin flat screen & high square flat screen) of the impurity removal process can still meet the production requirements when the mesh size of the screen is below 50 meshes and the moisture content of the raw dry powder is less than 2.0%, but when the mesh size of the screen is above 60 meshes and the moisture content of the raw dry powder is greater than 2.0%, the traditional impurity removal equipment (double-bin flat screen & high square flat screen) is basically ineffective in removing the clean block under the screen, and cannot effectively remove the flocculent impurities on the screen. The flocculent impurities are bonded with the clay raw materials in the raw dry powder, forming a film-shaped deposition layer on the surface of the screen, causing the screen of the traditional impurity removal equipment (double-bin flat screen & high square flat screen) to be blocked, the screening efficiency to drop sharply, and the operation rate and efficiency of the impurity removal process to be severely affected; further, the powder enters the screening link and blocks the screen or even bonds with the clay raw materials in the coarse powder, causing blockage; thus, the screening efficiency of the impurity removal screen system drops sharply and the driving components such as motors cannot operate normally due to excessive load. In this case, maintenance of the screen and other components such as motors leads to shutdown, thereby reducing the productivity of the dry-process ceramic tile (body) production line; at the same time, frequent repair or replacement of various components of the impurity removal screen system leads to increased use cost.

[0007] For example, Chinese Patent Publication CN111375481A discloses a ceramic dry-process powder collecting, dust removing and impurity removing integrated device and method, wherein the dust removing and impurity removing mechanism used includes a dust collector, a discharging cone and a high square flat screen (which can be replaced by a double square screen) arranged in sequence from top to bottom. The high square flat screen used in the device can avoid the problem of excessive floor area of the shaking screen or rotary screen commonly used as the impurity removal equipment in the prior art, and ensure sufficient screening area. However, this impurity removal method can still adapt to production when the mesh size of the screen is below 50 meshes and the moisture content of the raw dry powder is less than 2.0%, but when the mesh size of the screen is above 60 meshes and the moisture content of the raw dry powder is greater than 2.0%, this impurity removal system is difficult to meet the requirements; a new impurity removal system needs to be developed to meet higher impurity removal requirements. SUMMARY

[0008] In order to improve the problems existing in the prior art, the present application provides an impurity removal system for producing ceramic tile raw dry powder by dry-process powder production, which can effectively remove impurities from the coarse powder in the grinding system or grinding equipment, thereby obtaining fine powder for granulation in a granulator.

[0009] The inventors found that, in order to meet the requirements of removing fibrous impurities (e.g. plant impurities such as tree bark, tree roots, grass roots and living garbage such as plastic, tarpaulin, etc.) and ferromagnetic impurities from ceramic raw materials, the use of a dedusting system comprising three-stage dedusting equipment can effectively remove impurities and obtain a powder meeting the requirements of subsequent granulation procedures.

[0010] Therefore, the first aspect of the present application relates to a dedusting system comprising at least three-stage dedusting devices, wherein the first-stage dedusting device comprises a closed double-bin flat screen, the second-stage dedusting device comprises a high square flat screen, and the third-stage dedusting device comprises an electromagnetic iron removal device, and wherein, in addition to the first layer of screen grids of the closed double-bin flat screen, a cleaning brush is arranged above at least one screen core, and an elastic ball is arranged in at least one screen core of the closed double-bin flat screen.

[0011] For example, in addition to the first layer of screen grids of the closed double-bin flat screen, a cleaning brush is arranged above each of the other screen grids, and an elastic ball is arranged in each of the screen cores of the closed double-bin flat screen.

[0012] According to the present application, the first-stage dedusting device comprises a closed double-bin flat screen. The closed double-bin flat screen can first remove fibrous impurities to avoid the adhesion of these impurities to other materials, thereby avoiding the clogging of the dedusting device, especially the screen mesh of the dedusting screen; at the same time, the closed double-bin flat screen can also screen the materials to remove fibrous impurities, thereby obtaining a powder required for subsequent processes.

[0013] According to the present application, the closed double-bin flat screen of the present application comprises an external shell and one, two or more screening units installed inside the shell; each screening unit comprises two or more screen grids, wherein each screen grid comprises a screen frame and a screen core as well as corresponding oversize and undersize passages, and the screen core comprises at least two meshes, wherein the upper mesh is a screen mesh and the lower mesh is a support mesh, both of which are installed on the screen frame to form a screening part of the screen core. Preferably, there is a space between the two meshes to accommodate an elastic ball optionally arranged therein, and the support mesh and the screen mesh together with the screen frame keep the elastic ball in the screen core; those skilled in the art can understand that the distance between the screen mesh and the support mesh will be greater than the diameter of the elastic ball, so that the elastic ball can move freely therein. Preferably, there are two or more screening units in the closed double-bin flat screen, and each of the screening units has a feeding port.

[0014] In one embodiment, no cleaning brush is arranged above the first layer of screen decks at the top of the closed double-deck flat screen, especially above the screen core of the screen decks. In this case, the mesh size of the screen mesh in the first screen deck at the top of the closed double-deck flat screen is larger than the mesh size of the screen mesh of the screen core below, for example, a coarse screen mesh is used in the screen mesh at the top. Preferably, the mesh size of the first layer of screen mesh is at least about 10 mesh, i.e. about 2 mm. Here, the first layer of screen deck can be considered as a separate screening unit (first screening unit).

[0015] As described above, the closed double-deck flat screen comprises a housing and a plurality of screen decks mounted in the housing, wherein two or more screen decks can constitute a screening unit. It is understood by those skilled in the art that each screening unit independently comprises one or more screen decks and independently has a feed inlet and an optional discharge outlet. According to one embodiment, a cleaning brush is arranged above at least one screen deck of the closed double-deck flat screen, especially above the screen core of the screen deck, and / or an elastic ball is arranged in the screen core of at least one screen deck of the closed double-deck flat screen.

[0016] Therefore, according to the present application, preferably, the closed double-deck flat screen of the present application has at least two screening units, wherein the uppermost screen deck independently constitutes a first screening unit. The powder material screened out by the first screening unit, which is free of large impurities, can enter the plurality of screening units below (which can be sequentially labeled as second screening unit, third screening unit, fourth screening unit, etc.) for finer screening. It is understood by those skilled in the art that the plurality of screening units exist independently, and the powder material from the first screening unit can be fed into the plurality of screening units through different discharge channels.

[0017] As an example, the screen deck arrangement of the closed double-deck flat screen of the present application can be as follows: from top to bottom in the direction of gravity, the first screening unit comprises m screen decks, the second screening unit comprises n screen decks, the third screening unit comprises p screen decks, the fourth screening unit comprises q screen decks, and so on; the screen deck arrangement of the double-deck flat screen can thus be denoted as m-n-p-q. Preferably, the screen deck arrangement of the closed double-deck flat screen of the present application is 1-n-p-q. More preferably, the screen deck arrangement of the closed double-deck flat screen of the present application is 1-n-p. Preferably, n and p are independently integers of 1-7, for example 1, 2, 3, 4, 5, 6 or 7; more preferably, n and p are independently integers of 2, 3, 4 or 5. Most preferably, the closed double-deck flat screen has a screen deck arrangement of 1-4-5.

[0018] It is understood by those skilled in the art that the mesh size of the screen mesh in the screen decks starting from the second screening unit will depend on the corresponding screening requirements. For example, the mesh size can be 0.20-0.40 mm, preferably 0.23-0.35 mm.

[0019] Exemplarily, the screen path of the closed double-bin flat screen is shown in Figure 1 which the top first layer of screen mesh is a coarse screen mesh (e.g. screen mesh size is about 10 mesh) which can remove large impurities (e.g. wear-resistant ceramic coating) brought in during dry grinding and conveying in the upstream process to avoid these large impurities falling into the lower fine screen mesh, causing damage to the fine screen mesh. After screening, the powder material is divided into two paths to enter the upper screen separation unit including 4 screen grids and the lower screen separation unit including 5 screen grids, respectively. In this case, the screen hole diameters of the screen surfaces of the 2nd to 10th screen cores are independently, for example, 0.23 to 0.35 mm. In order to support the weight of the cleaning brush and prolong the service life of the screen mesh, the screen surface needs to use a coarse wire screen mesh (wire diameter: 0.18 to 0.23 mm), and the screen mesh and the lower grid support contact position is treated with thermoplastic polyurethane elastomer rubber (TPU) hot melting and reinforcement, and the reinforcement width should exceed 3 to 5 mm of the grid. The cleaning brush is arranged on the screen surface of the screen core, and the elastic ball is arranged below the screen surface of the screen core. The cleaning brush can clean the fibrous impurities existing on the screen surface to avoid its adhesion on the screen surface, and the elastic ball is helpful for the screening of the material. Preferably, the cleaning brush has a ring-shaped brush body, and bristles (bristles) are planted on the surface of the brush body facing the screen mesh. Preferably, the ring-shaped brush body has an elliptical or circular, especially circular, external contour when viewed from the top, and has a hollow part, thereby forming a ring-like appearance.

[0020] Preferably, the cleaning brush can be placed on the screen mesh in such a way that the ratio of the projected area of the bristles of the cleaning brush on the screen mesh to the area of the screen mesh is in the range of 1 to 5%, preferably 1.5 to 3.5%, more preferably 2% ± 0.5%. Preferably, the cleaning brush can be placed on the screen mesh in such a way that the ratio of the weight of the cleaning brush to the projected area of the cleaning brush on the screen mesh is in the range of 8 to 25 kg / m 2 , preferably 10 to 20 kg / m 2 , more preferably 12 to 17 kg / m 2 , most preferably about 14 kg / m 2 .

[0021] As described above, the brush body of the cleaning brush is a ring structure, preferably a circular ring structure, in which case the ratio of the inner ring diameter to the outer ring diameter or the ratio of the inner circumference to the outer circumference is 0.6 to 0.9, preferably 0.65 to 0.85, more preferably 0.68 to 0.80, most preferably 0.70 to 0.75, especially for example 0.71, 0.72, 0.73, 0.74.

[0022] According to the present application, the material of the brush body of the cleaning brush is not particularly limited, and a polymer material is preferably used, in particular polypropylene; and the material of the bristles is also not particularly limited, and a polymer material is preferably used, in particular thermoplastic polyurethane elastomer rubber (TPU).

[0023] Preferably, the elastic ball has a resilience of 50-100%, preferably 60-90%, more preferably 65-80%, most preferably about 70%, and / or a density of about 1.8-2.5 g / cm 3 , preferably 2.0-2.4 g / cm 3 , more preferably 2.1-2.3 g / cm 3 , most preferably 2.2 g / cm 3 , and / or a diameter of 10-30 mm, preferably 15-25 mm, more preferably about 20 mm. The elastic ball can comprise or be made of a polymer material, preferably thermoplastic polyurethane elastomer rubber (TPU).

[0024] According to the present application, in a preferred embodiment, the swing of the closed double-bin flat sieve can be 55-65 mm, in which case the raw material dry powder flows freely in the sieve without the risk of partial blockage of the sieve machine. Preferably, the upper part of the closed double-bin flat sieve can also be equipped with a feeding / feeding device. The feeding device can include a rotary unloader with a variable frequency speed regulation function. The input signal of this variable frequency speed regulation can be the current of the main motor of the sieve machine, and the rotary unloader speed is set to decrease as the current of the main motor of the sieve machine increases, so as to ensure that the load of the motor of the sieve machine is within a reasonable range and prevent sudden shutdown of the sieve machine due to overload; a temperature sensor is installed on the lower bearing of the sieve machine, and the temperature signal can be transmitted to the central control room, and the control program is provided with a high limit alarm to avoid damage to the equipment due to excessive bearing temperature.

[0025] According to the present application, the second-stage impurity removal device includes a high flat sieve for screening out the not finely ground large particles that are not completely removed in the first-stage impurity removal device. The high flat sieve has the same basic structure as described above for the closed double-bin flat sieve, in particular the screening unit, sieve grid, and sieve mesh structure; but can have different, in particular more, numbers of sieve grids or screening units and finer (generally smaller sieve hole diameter) sieve meshes. Preferably, the sieve core screen surface of the top sieve grid of the high flat sieve uses a coarse sieve mesh, and the material after the coarse sieve mesh is divided into two paths and enters the upper sieve frame group and the lower sieve frame group, respectively; and an elastic ball is arranged between the sieve core screen surface and the bottom supporting net.

[0026] An example of the screen path diagram of the second-stage impurity removal device is shown in Figure 4, the first layer of top screen (first screening unit) is a coarse screen (10 mesh) for removing large impurities (such as wear-resistant ceramic coating) brought in during the dry conveying process to avoid damaging the fine screen when falling into the lower fine screen; after the first layer of screen, the material is divided into two paths, respectively entering the upper screening unit (second screening unit) including 11 screen grids and the lower screening unit (third screening unit) including 12 screen grids; the screen mesh diameter in the remaining screening units is 0.18mm-0.25mm except the first layer of screen; the TPU elastic ball is installed on the lower net for assisting the screen to pass through, and the parameters are, for example, resilience: 70%±10%, density: 2.2±0.3t / m 3 , diameter: 15±5mm; the screen machine swing is 55-65mm.

[0027] According to the application, the third-stage impurity removal device comprises an electromagnetic iron removal device, which can adopt an electromagnetic iron removal device with a magnetic field peak of 20000GS±5000GS for removing ferromagnetic impurities, and the electromagnetic iron removal device is installed below the discharge port of the high square flat screen.

[0028] Advantages of the application

[0029] The application utilizes a three-stage impurity removal system to effectively remove fibrous impurities and ferromagnetic impurities that are not finely ground in the grinding system of the ceramic tile body production line. The screen mesh of the first-stage impurity removal device is a coarse wire screen, and the screen surface is cleaned by a cleaning brush and / or an elastic ball contained in the screen core, which makes the first-stage impurity removal device run more smoothly when screening fibrous impurities and is not easy to be blocked, avoiding the problems of the traditional impurity removal screen, such as frequent blockage, excessive load, and the accompanying transmission system failure and maintenance downtime.

[0030] The second-stage impurity removal device of the three-stage impurity removal system of the application comprises a high square flat screen for removing impurities larger than 0.212mm (70 mesh) and larger than 0.16mm (90 mesh) in the case of higher requirements; since the fibrous impurities that are not finely ground in the screened material (powder) have been removed by the first-stage impurity removal device, the screening efficiency of the second-stage impurity removal device can be further improved; at the same time, it can also remove a small part of fibrous impurities that enter the dry powder for granulation in the next step due to the leakage of the first-stage impurity removal device, which can help improve the reliability of the impurity removal system.

[0031] The third stage of the three-stage impurity removing system comprises an electromagnetic iron removing device, which can remove ferromagnetic impurities mixed in the powder, so as to improve the whiteness of the granulated dry powder and meet the production requirements of high-quality ceramic tiles with high whiteness requirements. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A screen path diagram of the first stage of the impurity removing device according to Embodiment 1 of the present application;

[0033] Figure 2 A screen grid structure diagram of the first stage of the impurity removing device according to Embodiment 1 of the present application;

[0034] Figure 3 A screen core structure diagram of the first stage of the impurity removing device according to Embodiment 1 of the present application;

[0035] Figure 4 A screen path diagram of the second stage of the impurity removing device according to Embodiment 1 of the present application;

[0036] Figure 5 A layout / flow diagram of the impurity removing system according to Embodiment 1 of the present application;

[0037] Figure 6 A plan view and a sectional view of the layout of the first stage of the impurity removing device according to Embodiment 1 of the present application;

[0038] Figure 7 A plan view and a sectional view of the layout of the second and third stages of the impurity removing device according to Embodiment 1 of the present application.

[0039] LIST OF REFERENCE NUMBERS:

[0040] 1 - screen core, 2 - cleaning brush, 3 - base plate, 4 - undersize passage, 5 - oversize passage, 6 - feeding area, 7 - fence, 8 - screen surface, 9 - supporting net, 10 - elastic ball, 11 - screen frame, 12 - impurity-containing dry powder storage bin, 13 - closed double-bin flat screen, 14 - first air conveying chute, 15 - first bucket elevator, 16 - second air conveying chute, 17 - primary impurity-removed dry powder storage bin, 18 - high square flat screen, 19 - electromagnetic iron removing device, 20 - second bucket elevator, 21 - third air conveying chute. DETAILED DESCRIPTION

[0041] The present application will be further described in conjunction with specific examples. It should be understood that the following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0042] Embodiment 1

[0043] ReferenceFigures 5-7 The three-stage impurity removal system of the present invention is part of the ceramic tile body production line, specifically located between the grinding system (vertical roller mill system, not shown) and the granulation system (not shown). During the operation of the impurity removal system, the impurity-containing dry powder from the vertical roller mill system first enters the impurity-containing dry powder storage bin 12, and then enters the closed double-bin flat screen 13 of the first-stage impurity removal device to remove some impurities. The obtained powder is conveyed to the bucket elevator 15 via the first air conveying chute 14 and then lifted to the second air conveying chute 16, and then enters the primary impurity-removed dry powder storage bin 17. The powder exiting the primary impurity-removed dry powder storage bin 17 enters the high-square flat screen 18, where it continues to be screened to obtain dry powder that meets the particle size requirements of the powder granulation system. This dry powder is further passed through the electromagnetic iron removal device 19 to remove ferromagnetic impurities, and then conveyed to the second bucket elevator 20 via the third air conveying chute 21 below, thereby being lifted to the powder granulation system for use in the next process.

[0044] like Figure 2 The sieve grid shown and / or Figure 3 The screen core 1 shown is horizontally installed in the closed double-compartment flat screen 13 of the first-stage impurity removal device. A circular cleaning brush 2 can be installed above the screen mesh (above the screen surface 8) of the screen core 1 of the closed double-compartment flat screen 13 to clean impurities that reach the screen surface 8 during the screening process. In this embodiment, the cleaning brush 2 has a brush body made of polypropylene and bristles made of thermoplastic polyurethane elastomer rubber. The cleaning brush 2 has the following parameters: inner ring diameter to outer ring diameter ratio: 0.73; bristle projection area on the screen mesh to the screen mesh area: 2%; cleaning brush weight to cleaning brush projection area on the screen mesh: 14 kg / m². 2 .

[0045] In each sieve core 2, multiple thermoplastic polyurethane elastomer rubber elastic balls are installed between the sieve mesh and the support mesh, with a resilience of 70% and a density of 2.2 g / cm³. 3 The diameter is approximately 10–20 mm.

[0046] Inside the housing, the top first layer of screen is set as a coarse screen (e.g., 10 mesh) to remove large impurities (such as wear-resistant ceramic coatings) brought in during the dry conveying process, so as to prevent them from falling into the lower fine screen and thus protect the fine screen from damage.

[0047] A rotary unloader with variable frequency speed control can also be installed on the upper part of the screening machine. The input signal for this variable frequency speed control is the main motor current of the drive device of the impurity removal screening system, thereby causing the rotary unloader speed to decrease as the main motor current of the screening machine increases. In this case, it can be ensured that the motor load of the drive device is controlled within a reasonable range, preventing the system from suddenly shutting down due to overload.

[0048] The temperature sensor installed on the bearing under the shell transmits the temperature signal obtained by the temperature sensor to the central control room. The computer control program of the central control room has a temperature overrun alarm function, which stops the motor of the transmission mechanism when the temperature exceeds the threshold, thereby avoiding damage to the equipment caused by excessive bearing temperature.

[0049] During the operation of the impurity removal and screening system with the above structure, the transmission drives the shell to rotate, thereby causing the respective screens (screening units) fixed in the shell to move correspondingly. The shell swing is set to 55-65 mm, the coarse powder from the powder grinding equipment is introduced into the shell from the coarse powder inlet at the top of the shell, and then is screened in sequence. In this process, the cleaning brush 2 continuously brushes off the flocculent impurities and large impurities from the surface of the accumulated powder, and the bristles keep the screen surface 8 smooth at all times. At the same time, the elastic balls continuously move between the first and second screens, making the powder flow better in the screen core 2.

[0050] Through experiments, the output of the impurity removal and screening system with the above structure is calculated to be about 50 t / h, and after running for 300 hours, active shutdown inspection is performed, and no blockage of the internal screens is found.

[0051] Comparative Example 1

[0052] The annular cleaning brush 2 above the screen surface of the screen core 2 of the first-stage impurity removal device of Example 1 is removed during shutdown, and the first-stage impurity removal device is reconnected to the ceramic tile body production line for testing. After 12 hours of feeding and operation, it is observed that the powder discharge outside the discharge port of the closed double-bin flat screen begins to increase, and after 36 hours, a large amount of slag is discharged from the discharge port. At this time, active shutdown inspection is performed, and the calculation result shows that the output of the impurity removal and screening system is about 20 t / h, and serious blockage occurs in each layer of the screens of the first-stage impurity removal device, and a film-like barrier layer is accumulated on the screen surface 8 of the screen core 2.

[0053] Comparative Example 2

[0054] The elastic balls 10 in the screen core 2 of the first-stage impurity removal device of Example 1 are removed during shutdown, and then the screen core without elastic balls is reinstalled into the first-stage impurity removal device, and the first-stage impurity removal device is reconnected to the ceramic tile body production line for testing. After 12 hours of feeding and operation, it is observed that the powder discharge outside the discharge port of the closed double-bin flat screen begins to increase, and after 36 hours, a large amount of slag is discharged from the discharge port. At this time, active shutdown inspection is performed, and the calculation result shows that the output of the impurity removal and screening system is about 20 t / h, and serious blockage occurs in each layer of the screens of the first-stage impurity removal device, and a film-like barrier layer is accumulated on the screen surface 8 of the screen core 2.

[0055] The above describes the embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, and the like made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A system for impurity removal comprising at least three stages of impurity removal devices, wherein, The first-stage impurity removal device comprises a closed double-bin flat sieve, the second-stage impurity removal device comprises a high square flat sieve, and the third-stage impurity removal device comprises an electromagnetic iron removal device, characterized in that The closed double-bin flat sieve comprises an external shell and one, two or more screening units installed inside the shell; each screening unit comprises two or more sieve frames, wherein each sieve frame comprises a sieve frame and a sieve core and corresponding oversize and undersize passages, the sieve core comprises at least two meshes, wherein the upper mesh is a sieve mesh and the lower mesh is a supporting mesh, both are installed on the sieve frame to form a screening part of the sieve core, the distance between the sieve mesh and the supporting mesh is greater than the diameter of the elastic ball, and the elastic ball is freely movable therein; the top sieve mesh of the closed double-bin flat sieve is a coarse sieve mesh, the sieve core screen surface of the top sieve frame of the high square flat sieve adopts a coarse sieve mesh, and the material after passing through the coarse sieve mesh is divided into two paths and enters the upper and lower screening units respectively; wherein elastic balls are arranged between the sieve core screen surface and the bottom supporting mesh; The closed double-bin flat sieve is provided with cleaning brushes above all the sieve frames except the first layer of sieve frames, and the closed double-bin flat sieve is provided with elastic balls in the sieve core. The ratio of the projected area of the bristles of the cleaning brush on the first screen to the area of the screen is 1-5%, and the ratio of the weight of the cleaning brush to the projected area of the cleaning brush on the screen is 8-25 kg / m 2 ; The brush body of the cleaning brush is in a circular ring structure, and the ratio of the inner ring diameter to the outer ring diameter or the ratio of the inner circumference length to the outer circumference length is 0.6-0.

9.

2. The impurity removal system of claim 1, wherein The magnetic field strength of the electromagnetic iron removal device is 20000 GS±5000 GS, and the electromagnetic iron removal device has two independently controlled electromagnetic iron removal cavities, and the two cavities alternately realize feeding and iron removal.

3. The impurity removal system of claim 1, wherein, The ratio of the projected area of the bristles of the cleaning brush on the first screen to the area of the screen is 1.5-3.5%; and / or, the ratio of the weight of the cleaning brush to the projected area of the cleaning brush on the screen is 10-20 kg / m 2 .

4. The impurity removal system of claim 1, wherein The ratio of the projected area of the bristles of the cleaning brush on the first screen to the area of the screen is 2% ± 0.5%; and / or, the ratio of the weight of the cleaning brush to the projected area of the cleaning brush on the screen is 12 to 17 kg / m 2 .

5. The impurity removal system of claim 1, wherein, The ratio of the inner ring diameter to the outer ring diameter or the ratio of the inner circumference length to the outer circumference length of the cleaning brush is 0.65-0.

85.

6. The impurity removal system of claim 1, wherein, The ratio of the inner ring diameter to the outer ring diameter or the ratio of the inner circumference length to the outer circumference length of the cleaning brush is 0.68-0.

80.

7. The impurity removal system of claim 1, wherein, The ratio of the inner ring diameter to the outer ring diameter or the ratio of the inner circumference length to the outer circumference length of the cleaning brush is 0.70-0.

75.

8. The impurity removal system of claim 1, wherein, The brush body of the cleaning brush comprises or is made of thermoplastic polyurethane elastomer rubber TPU.

9. The impurity removal system of claim 1, wherein, The elastic ball has a rebound rate of 50-100%, and / or a density of 1.8-2.5 g / cm 3 , and / or a diameter of 10-30 mm.

10. The impurity removal system of claim 1, wherein, The elastic ball has a rebound rate of 60-90%, and / or a density of 2.0-2.4 g / cm 3 , and / or a diameter of 15-25 mm.

11. The impurity removal system of claim 1, wherein, The elastic ball has a rebound rate of 65-80%, and / or a density of 2.0-2.4 g / cm 3 , and / or a diameter of 15-25 mm.

12. The impurity removal system of claim 1, wherein, The elastic ball comprises or is made of thermoplastic polyurethane elastomer rubber TPU.

13. The impurity removal system of claim 1, wherein, There are two or more screening units in the closed double-bin flat sieve, and the screening units are respectively provided with feeding ports.

14. The impurity removal system of claim 1, wherein, The top of the closed double-bin flat sieve is not provided with a cleaning brush above the first layer of sieve frames; in this case, the sieve mesh of the top sieve frame of the closed double-bin flat sieve has a larger sieve mesh diameter than the sieve mesh of the sieve core below.

15. The impurity removal system of claim 1 or 14, wherein, The sieve mesh diameter of the first layer of sieve meshes is at least 10 meshes.

16. The impurity removal system of claim 1, wherein, The swing range of the closed double-bin flat sieve is 55-65 mm. 17.A ceramic tile body production line comprising the impurity removal system according to any one of claims 1 to 16. 18.A ceramic tile production line comprising the impurity removal system according to any one of claims 1 to 16.

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