Experimental method for measuring particle size distribution of particulate matters and wet screening instrument

Abstract

The invention provides an experimental method for measuring particle size distribution of particulate matter and a wet screening instrument.The wet screening instrument comprises a centrifugal screening barrel and a rotating mechanism, the centrifugal screening barrel comprises a barrel body, a screen assembly and a washing assembly are arranged in the barrel body, the screen assembly comprises a plurality of screen components which are arranged in a nested mode, and the washing assembly is connected with the rotating mechanism. A plurality of screen holes are formed in the side wall of the screen component; the screen mesh apertures of the screen mesh components are sequentially reduced from the middle part of the screen mesh assembly to the outside; an annular channel used for receiving accumulated materials on the screen is formed between every two adjacent screen components. The flushing assembly is located on the outer side of each screen component, and a water spraying opening of the flushing assembly faces the outer side wall of the screen component; the rotating mechanism is connected with the screen assembly and drives the screen assembly to rotate. The rotating mechanism is fixedly connected with the screen assembly, and a water outlet is formed in the bottom of the barrel body. By adopting the technical scheme of the invention, accurate and efficient measurement of particle size distribution of particles is realized, and the experiment precision and the experiment efficiency are improved.

Description

Technical Field

[0001] The invention relates to the technical field of particle classification, and in particular to a method for measuring particle size distribution of particles and a wet sieving instrument. Background Art

[0002] Particle size distribution is an important indicator of particle fineness and classification. The most common and accurate method for testing particle size distribution of materials is wet screening. Wet screening instrument is an experimental instrument for wet particle size distribution testing of particles. It can screen and test various organic and inorganic particles and is widely used in soil, sandstone, mining, medicine, food, agriculture and other fields.

[0003] The sieve used in wet screening has several sieve holes at the bottom. The general steps of wet screening are: select the required sieves from fine to coarse and stack them on the base of the sieving instrument in sequence with the wastewater collection chassis, then weigh a certain amount of sample and pour it into the top sieve, or make the weighed sample into a suspension and pour it from the top; then add flushing water from the top of the test sieve for screening experiments.

[0004] In a traditional wet screening instrument, the experimental mesh surface of the screen assembly is set at the bottom, and the side wall is a stainless steel surface. The screening of particles is achieved by vibration drive and the introduction of flushing water from the top. The hydraulic efficiency of the flushing water in this way is mainly concentrated on the top layer of screen. When the number of screens used in the experiment is greater than 3, the flushing water has almost no hydraulic flushing effect on the particles on the surface of the bottom screen. The bottom screen often has a small aperture, which can easily cause the screen to be blocked. When the particles are more viscous and there are more materials stacked on the screen surface, the ultrafine materials and flushing water can hardly pass through the bottom fine screen, making the experiment impossible to proceed.

[0005] The common way to solve this problem is to perform layered flushing, that is, flush the upper 1-2 layers of screens first, then remove them, and continue to flush the bottom screens one by one; or reduce the amount of material to be measured and increase the vibration driving force to avoid excessive accumulation of material on the screen surface; this often leads to extended experimental progress, increased experimental errors and experimental noise; and cannot meet the requirements of efficient and high-quality experimental measurements in actual production processes. Summary of the invention

[0006] In view of the above technical problems, the present invention discloses an experimental method for determining the particle size distribution of particulate matter and a wet sieving instrument, which effectively improves the experimental accuracy and efficiency and realizes efficient and high-quality determination.

[0007] To this end, the technical solution adopted by the present invention is:

[0008] A wet screening instrument, comprising a centrifugal screening barrel and a rotating mechanism, wherein the centrifugal screening barrel comprises a barrel body, wherein a screen assembly and a flushing assembly connected to a flushing water pipeline are arranged in the barrel body, wherein the screen assembly comprises a plurality of nested screen members, wherein a plurality of screen holes are arranged on the side walls of the screen members; the screen holes of the screen members decrease in sequence from the middle of the screen assembly to the outside; an annular channel for receiving accumulated materials on the screen is formed between adjacent screen members; the flushing assembly is located on the outside of each screen member, and the water spray port of the flushing assembly faces the outer wall of the screen member;

[0009] The rotating mechanism is connected with the screen assembly to drive the screen assembly to rotate; the rotating mechanism is fixedly connected with the screen assembly, and a drainage port is provided at the bottom of the barrel body.

[0010] With this technical solution, the liquid containing particles to be screened is added to the middle of the screen assembly, the rotating mechanism is started, the screen assembly is driven to rotate through the rotating mechanism, water is introduced through the flushing water pipeline, and the water spray port of the flushing assembly faces the outer wall of the screen component, that is, the water outlet direction is opposite to the direction of the rotating centrifugal force, that is, the direction of material movement, so as to form a backwash, so that the material accumulated on the surface of the screen component forms a fluidized state, the material accumulated on the surface of the screen is dispersed again, and the material stuck in the gaps of the screen can be washed away. The coarse screen is in the middle and the fine screen is on the outside. The inner diameter of the screen component gradually increases, that is, its surface area also increases linearly step by step, reducing the material load of the screen; and the larger the inner diameter of the screen component, the greater the centrifugal force on the particle surface of the screen component, which better helps the sticky small particle material and flushing water to pass through the fine screen. In addition, the centrifugal force is used as the main driving force for screening, which is much greater than the vibration driving force of traditional screening, solving the problem that the fine material has high viscosity and is difficult to screen and dehydrate on the fine screen. When encountering high-viscosity fine materials that are difficult to screen, such as peat, fine gasified ash, etc., the screening driving force can be further improved by increasing the rotation speed (increasing the angular velocity). At this time, the driving force will increase exponentially with the rotation speed, and the screening effect achieved is far greater than the existing vibration driving force adjustment method.

[0011] In the present invention, centrifugal force is used as the main driving force for screening, which is much greater than the vibration driving force used in the prior art. The centrifugal force formula is: Fg = ω2Rm, where ω- is the centrifugal acceleration (controlled by the speed);

[0012] R-inner diameter of the screen;

[0013] m-mass of material on the screen;

[0014] According to the above formula, when the rotation speed remains unchanged, as the radius R of the screen increases, the centrifugal force on the material on the screen increases linearly; that is, compared with the coarse screen in the middle, the centrifugal force on the outer fine screen is greater. Since the surface area is also larger and the load per unit area is lower, the problem of fine material having high viscosity and being difficult to screen and dehydrate on the fine screen is well solved.

[0015] Moreover, the flushing component is arranged in the annular channel and is fixed. Due to the rotation of the screen assembly in the barrel, the flushing water can evenly cover the entire screen surface, thereby improving the screening efficiency and screening effect, being more conducive to screening, and reducing the flushing water consumption.

[0016] After the wet screening is completed, the flushing water pipeline is closed. The sieving instrument can also centrifugally dehydrate the material, effectively shortening the subsequent drying time. Compared with the traditional wet screening instrument, the overall experimental process can be shortened by about half of the experimental time.

[0017] As a further improvement of the present invention, the rotating mechanism includes a driving assembly, a rotating shaft, and a turntable. The turntable is located in the barrel body, the driving assembly is connected to one end of the rotating shaft, the other end of the rotating shaft is connected to the turntable, and the turntable is connected to the screen assembly to drive the screen assembly to rotate.

[0018] As a further improvement of the present invention, the turntable is fixedly connected to the outer side of the screen assembly through a fixing assembly; the fixing assembly includes a fixing rod, the lower part of the fixing rod is fixedly connected to the turntable, and the upper part of the fixing rod is connected to the outer side of the screen assembly through a fixing buckle.

[0019] As a further improvement of the present invention, the turntable is provided with a U-shaped groove in the radial direction, the lower part of the fixing rod extends into the U-shaped groove, and the fixing rod and the turntable are connected through fixing parts on the upper side and / or lower side of the U-shaped groove.

[0020] As a further improvement of the present invention, adjacent screen members are fixed by screen fixing members, and the screen fixing members are located at the bottom of the annular channels of adjacent screen members.

[0021] As a further improvement of the present invention, the screen fixing member is a U-shaped fixing member or an adjustable V-shaped fixing member. Further, the V-shaped fixing member includes two support rods, one end of the two support rods is connected by a rotating shaft, a fixed support member and an elastic element are provided at the connection of the two support rods, and the other ends of the two support rods are provided with a fixed connection member for connecting with the corresponding screen member.

[0022] As a further improvement of the present invention, a hollow shaft is erected in the middle of the screen component, the hollow shaft is fixedly connected to the bottom of the screen component and penetrates the bottom of the screen component, the hollow shafts of several screen components are stacked in sequence, the rotating shaft extends into the stacked hollow shafts, and is fixedly connected to the hollow shafts through a fixing assembly. With this technical solution, a hollow shaft is provided at the bottom of each screen component, and the inner diameter of the hollow shaft increases in sequence from the outside to the inside of the screen component, that is, the inner diameter of the hollow shaft of the outer screen component is small, and the inner diameter of the hollow shaft of the inner screen component is large, and they are stacked together, easy to assemble, and can be fixed together.

[0023] As a further improvement of the present invention, the fixing assembly includes a pin and a bolt, and the hollow shaft and the rotating shaft are provided with through holes in the radial direction. The pin is inserted into the through holes of the hollow shaft and the rotating shaft and fixed by bolts, thereby realizing the connection between the hollow shaft and the rotating shaft, and further realizing the fixation of the screen on the rotating shaft.

[0024] As a further improvement of the present invention, the barrel body and the rotating shaft are provided with sealing rings to prevent water leakage.

[0025] As a further improvement of the present invention, the top of the screen member is provided with a hanging lug. Furthermore, the number of the hanging lugs is two or more.

[0026] As a further improvement of the present invention, the ratio of the height to the inner diameter of the screen member Hn / Dn≥1, and the ratio of the gap between adjacent screen members to the inner diameter of the screen member with the larger aperture satisfies bn / Dn=0.1-0.5. Among them, the spacing bn between adjacent screens is designed to meet the space for accommodating materials and the installation space for flushing water pipelines, bn≥5cm.

[0027] Taking the bottom diameter of a conventional standard test sieve of 20cm or 30cm as an example, it can be known from the converted screen area that if the inner diameter of the first screen in the middle of this screening instrument is D1 ≥ 10cm, H ≥ 10cm, its surface area can be greater than that of the traditional screen. The surface area of ​​the screen component in this screening instrument Sn = πDH = π(dn-1 + 2bn)H. From this formula, it can be seen that the screen component increases linearly from the middle to the outside. However, all the screens of the traditional screen have the same surface area, and the fine screen is located at the bottom layer, the screen hole surface load is the highest, and the flushing hydraulic intensity is the lowest, which is very unfavorable for fine material screening and detection.

[0028] In traditional vibrating wet sieving instruments, the inner diameter of each level of the sieve is the same; the sieve is set on the bottom surface, and the upper and lower levels are stacked in sequence, that is, the surface area of ​​each sieve is the same. Under the condition of the same bottom inner diameter, the sieve is set on the side wall in this scheme. The surface area of ​​the test sieve is πDH, which is 1 / 4πD of the surface area of ​​the traditional test sieve. 2Compared with the conventional method, the specific surface area is increased by 4 times (with the prerequisite H>D); that is, under the same size, this scheme can allow more experimental materials, and the unit area load of the material passing through the screen surface is lower; thus improving the experimental accuracy and efficiency.

[0029] As a further improvement of the present invention, the flushing assembly includes a vertically arranged flushing water branch pipe, and a plurality of flushing nozzles are arranged on the flushing water branch pipe, wherein the flushing nozzle at the uppermost end of the flushing water branch pipe is obliquely downwardly directed toward the outer side of the screen member, and the flushing nozzle at the lowermost end of the flushing water branch pipe is obliquely upwardly directed toward the outer side of the screen member. Furthermore, the flushing nozzle located in the middle of the flushing water branch pipe is horizontally directed toward the outer side of the screen member.

[0030] Furthermore, the angle between the flushing nozzle located at the uppermost end of the flushing water branch pipe, the flushing nozzle located at the lowermost end of the flushing water branch pipe and the flushing water branch pipe is 30°-90°; a main control valve is provided on the flushing water inlet pipe, and a flushing branch pipe control valve is provided on the flushing water branch pipe; the drain outlet is connected to a drain pipe, and the drain pipe is provided with a drain valve.

[0031] With this technical solution, the rotation of the screen assembly drives the material inside it to perform centrifugal motion. The particulate matter is not evenly distributed on the screen, but is mainly concentrated on the lower part of the outer edge. At this time, the nozzles on the lower layer tilted upward can flush the material to the upper part and disperse it for a second time, which is helpful for the grading and screening of the material. At the same time, the nozzles on the upper layer tilt downward to spray water, which can flush the fine material back to the middle position for fluidization, preventing it from being thrown out from the top during centrifugal motion.

[0032] The present invention also discloses a method for determining the particle size distribution of particulate matter, which is determined using the wet sieving instrument as described above, and includes the following steps: placing material into a screen component at the center, opening a main control valve and a flushing branch control valve at the same time, starting a rotating mechanism to drive the screen component to rotate, and flushing and screening the material in the screen component while it is rotating.

[0033] Alternatively, each layer of the screen component can be washed separately. First, the material is put into the screen component at the center. According to the amount of material, the rotation speed is controlled so that the surface centrifugal force F1 of the innermost screen component is 1.8-2.3 times the acceleration of gravity;

[0034] Open the main control valve and the flushing branch pipe control valve corresponding to the innermost screen component, keep other flushing branch pipe control valves closed, flush for several minutes, and close the flushing branch pipe control valve after the material in the innermost screen component no longer decreases;

[0035] Continue the secondary flushing, adjust the rotation speed of the turntable, control the centrifugal force F2 = (1-1.3) F1 on the surface of the second layer of screen components from the inside to the outside, open the flushing branch pipe control valve corresponding to the second layer of screen components from the inside to the outside, and keep the other flushing branch pipe control valves closed; flush for several minutes, and when the material in the second layer of screen components is no longer reduced, close the flushing branch pipe control valve;

[0036] If there are three layers of screen components, continue to perform three-level flushing, adjust the rotation speed of the turntable, control the centrifugal force F3 = (1.3-1.5) F1 on the surface of the third layer of screen components from the inside to the outside, open the flushing branch pipe control valve corresponding to the third layer of screen components from the inside to the outside, and keep other flushing branch pipe control valves closed; flush for several minutes, and when the material in the third layer of screen components is no longer reduced, close the flushing branch pipe control valve;

[0037] If there are more layers of screen components, and so on, each time a layer of screen components is added, a flushing stage is added, and the rotation speed of the turntable is adjusted accordingly to control the surface centrifugal force of the corresponding screen component to increase by (0.2-0.3) F1 relative to the previous flushing stage, and open the flushing branch pipe control valve corresponding to the screen component, and keep other flushing branch pipe control valves closed; flush for several minutes, and when the material in the layer of screen components is no longer reduced, close the flushing branch pipe control valve;

[0038] Repeat the above steps until the last layer of screen components has completed screening; during the whole process, the surface centrifugal force of the screen components is controlled not to exceed 10 times the acceleration of gravity.

[0039] Preferably, after each layer is washed separately, all the flushing branch pipe control valves are finally opened to flush with the same water pressure and speed until the water discharged from the bottom is almost clear, and the screening is completed. When all the flushing branch pipe control valves are finally opened to perform overall screening and flushing of the screen, all the screens have the same backwashing water pressure and the same screen speed, but due to the different inner diameters of the screens, the equivalent centrifugal force on the surface of the screens is different; the larger the inner diameter of the screen, the greater the equivalent centrifugal force, that is, it is more conducive to the screening of small sticky particles on the outer fine screen.

[0040] Further preferably, after completing the flushing and screening, close all flushing valves, continue to control the rotation speed to perform in-situ centrifugal dehydration on the material in the screen; after no free water flows out, the mechanical dehydration is deemed to be completed; open the screen fixings; take out all the screens together with the materials one by one for the next drying experiment.

[0041] As a further improvement of the present invention, when the main control valve and the flushing branch control valve corresponding to the innermost screen component are opened, the flushing water pressure P1 is controlled to be 2-3 bar; when performing the second flushing, the flushing water pressure P2 is controlled to be (1-1.3) P1; when performing the third flushing, the flushing water pressure P3 is controlled to be (1.3-1.5) P1. If there are more layers of screen components, and so on, for each additional layer, the flushing water pressure is controlled to increase by (0.2-0.3) P1 relative to the previous flushing. Until each layer of the screen components is flushed and screened separately, the maximum flushing water pressure does not exceed 12 bar during the entire process.

[0042] Further, if there are many layers of screen components, the flushing water pressure of the last stage of flushing is Pn=(4-6)P1.

[0043] As a further improvement of the present invention, the rotating mechanism adopts frequency conversion control to continuously rotate clockwise, continuously rotate counterclockwise, rotate intermittently, or rotate clockwise and counterclockwise alternately, and controls the equivalent centrifugal force in the screen member within the range of 2-10 times gravity. More preferably, it is controlled within the range of 3-5 times gravity.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] According to the technical solution of the present invention, the screen components are stacked and arranged in the barrel body, and the mesh surface of the screen components is set on the side wall. By driving the screening component to rotate, the flushing component sprays water on the outside of the screen component at the same time. The centrifugal force and the high-pressure backwashing water evenly distributed on the screen can realize the accurate and efficient determination of the particle size distribution of the particles, and the qualitative analysis can be carried out quickly. Compared with the traditional test sieve with the mesh surface set at the bottom and stacked up and down, the screening device with the same bottom area has a larger screening specific surface area, can screen more experimental materials, and the unit area load of the material passing through the screen surface is lower, which improves the experimental accuracy and experimental efficiency. Under the condition of lower washing water consumption, the experimental time is effectively shortened. The screening instrument has a more compact structure, is lighter and more practical, has high hydraulic efficiency, low washing water consumption, and less experimental waste liquid. Moreover, one device has dual functions, which can be used for both screening and centrifugal dehydration. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of a rotary wet sieving apparatus according to Example 1 of the present invention.

[0047] Figure 2 It is a schematic diagram of the structure of the fixing assembly of Example 1 of the present invention.

[0048] Figure 3 It is a schematic diagram of the structure of the turntable of Example 1 of the present invention.

[0049] Figure 4It is a schematic diagram of the distribution of nozzles on the flushing water branch pipe of Example 1 of the present invention.

[0050] Figure 5 It is a schematic diagram of the cross-sectional structure of the screen assembly of Example 1 of the present invention.

[0051] Figure 6 It is a schematic diagram of the three-dimensional structure of the screen assembly of Example 1 of the present invention.

[0052] Figure 7 It is a schematic diagram of the structure of the screen assembly of Example 2 of the present invention.

[0053] Figure 8 It is a schematic diagram of the structure of the screen fixing member of Example 2 of the present invention.

[0054] Fig. 9 It is a schematic diagram of the structure of the wet sieving instrument of Example 3 of the present invention.

[0055] Fig.10 It is a schematic structural diagram of the screen component of Example 3 of the present invention.

[0056] Fig.11 It is a schematic diagram of the structure of the fixing assembly of Example 3 of the present invention.

[0057] Fig.12 It is a schematic diagram of the state of particles in the screen component with and without flushing water in an embodiment of the present invention.

[0058] Fig.13 This is a flow chart of an experimental method for determining particle size distribution in Example 4 of the present invention.

[0059] 1- centrifugal screening barrel, 2- screen assembly, 3- rotating mechanism, 4- fixed assembly, 5- flushing assembly, 6- drainage pipeline;

[0060] 11-barrel body, 12-sealing ring, 13-drainage port;

[0061] 21-screen member, 22-annular channel, 23-hanging ear, 24-U-shaped fixing piece, 25-V-shaped fixing piece; 251-support rod, 252-fixed support rod, 253-elastic element, 254-fixed connecting piece; 26-hollow shaft;

[0062] 31-driving assembly, 32-rotating shaft, 33-turntable, 35-U-shaped groove;

[0063] 41-fixing rod, 42-fixing buckle, 43-bolt; 44-pin;

[0064] 51-flushing water branch pipe, 52-flushing nozzle, 53-flushing branch pipe control valve, 54-flushing water inlet pipe, 55-main control valve;

[0065] 61-drain pipe, 62-drain valve. DETAILED DESCRIPTION

[0066] The preferred embodiments of the present invention are described in further detail below.

[0067] Example 1

[0068] like Figure 1 to Figure 6 As shown, a wet screening instrument includes a centrifugal screening barrel 1 and a rotating mechanism 3, wherein the centrifugal screening barrel 1 includes a barrel body 11, wherein a screen assembly 2 and a flushing assembly 5 connected to a flushing water inlet pipe 54 are arranged in the barrel body 11, wherein the screen assembly 2 includes a plurality of nested screen members 21, wherein the bottom of the screen member 21 is a non-porous contact surface, and the side wall of the screen member 21 is provided with a plurality of screen holes; from the middle of the screen assembly 2 to the outside, the screen aperture of the screen member 21 decreases successively, i.e., the screen aperture of the middle screen member 21 is large, and the screen aperture of the screen member 21 becomes smaller as it moves to the outside. The screen members 21 are stacked at the bottom. An annular channel 22 for receiving the accumulated material on the screen is formed between adjacent screen members 21. The flushing assembly 5 is located on the outside of each screen component 21, and the water spray port of the flushing assembly 5 is facing the outer wall of the screen component 21; the rotating mechanism 3 is connected to the screen assembly 2 to drive the screen assembly 2 to rotate; a drain outlet 13 is provided at the bottom of the barrel body 11, and the drain outlet 13 is connected to the drainage pipe 6, and the separated liquid can be discharged from the drain outlet 13.

[0069] The rotating mechanism 3 includes a driving assembly 31, a rotating shaft 32 and a rotating disk 33. The driving assembly 31 provides a rotating centrifugal driving force. The rotating disk 33 is located in the barrel body 11. The driving assembly 31 is connected to one end of the rotating shaft 32. The other end of the rotating shaft 32 is connected to the rotating disk 33. The rotating disk 33 is connected to the bottom of the screen assembly 2 to drive the screen assembly 2 to rotate. The driving assembly 31 is a motor.

[0070] The rotating mechanism 3 is fixedly connected to the screen assembly 2 through a fixing assembly 4. In this embodiment, the rotating mechanism 3 fixes the screen assembly 2 from the outside. Specifically, the rotating disk 33 is fixedly connected to the screen assembly 2 through the fixing assembly 4. The fixing assembly 4 includes a fixing rod 41, the lower part of the fixing rod 41 is fixedly connected to the rotating disk 33, and the upper part of the fixing rod 41 is connected to the outer side of the screen assembly 2 through a fixing buckle 42, so as to fix the screen assembly 2 in place.

[0071] Further, the rotating disk 33 is provided with a U-shaped groove 34 in the radial direction, and four U-shaped grooves 34 are symmetrically provided in this embodiment. The lower part of the fixing rod 41 extends into the U-shaped groove 34, and the fixing rod 41 is connected to the rotating disk 33 at the upper and lower sides of the U-shaped groove 34 by bolts 43. When in use, the external fixation of the screen assembly 2 can be achieved by moving the position of the fixing rod 41 in the U-shaped groove 34 according to the size of the screen assembly 2. Further, the number of the fixing rods 41 is greater than or equal to 2. Further, a plurality of fixing rods 81 are evenly arranged.

[0072] Adjacent screen members 21 are fixed by screen fixing members, which are U-shaped fixing members 24 . The U-shaped fixing members 24 are located at the bottom of the annular channels of adjacent screen members 21 and are connected to two adjacent screen members 21 , respectively.

[0073] The flushing assembly 5 includes a vertically arranged flushing water branch pipe 51, on which a plurality of flushing nozzles 52 are arranged. The flushing nozzle 52 at the uppermost end of the flushing water branch pipe 51 is obliquely downwardly directed toward the outer side of the screen member 21, and the flushing nozzle 52 at the lowermost end of the flushing water branch pipe 51 is obliquely upwardly directed toward the outer side of the screen member 21. Specifically, the flushing nozzle 52 at the uppermost end of the flushing water branch pipe 51 and the flushing nozzle 52 at the lowermost end of the flushing water branch pipe 51 have an angle of 30°-90° with the flushing water branch pipe 51. The flushing nozzle 52 at the middle of the flushing water branch pipe 51 is horizontally directed toward the outer side of the screen member 21.

[0074] Furthermore, the flushing water branch pipe 51 is of quick-connect type, which is convenient for disassembly and assembly; after the flushing water enters the screening cylinder, it is evenly distributed into several branch pipes and arranged on the back of the screen, and the nozzles evenly distributed on the branch pipes make the screen form a backwashing effect. The flushing water inlet pipe 54 is provided with a main control valve 55, and the flushing water branch pipe 51 is provided with a flushing branch pipe control valve 53; the drain port 13 is connected to the drain pipe 61, and the drain pipe 61 is provided with a drain valve 62, and the discharge of waste liquid and ultrafine materials is controlled by the drain valve 62.

[0075] Furthermore, a sealing ring 12 is provided at the connection between the barrel body 11 and the rotating shaft 32 to prevent water leakage.

[0076] Furthermore, a hanging ear 23 is provided on the top of the screen member 21, which can be used for fixing and conveniently taking the screen member 21. Furthermore, the number of the hanging ears 23 is greater than or equal to 2.

[0077] Further, the ratio of the height to the inner diameter of the mesh member 21 satisfies Hn / Dn≥1.

[0078] Furthermore, the ratio of the gap between adjacent screen components 21 to the inner diameter of the screen component 21 with the larger aperture satisfies bn / Dn=0.1-0.5 (the spacing bn between adjacent screens is designed to satisfy the accommodating material space and the installation space of the flushing water branch pipe, bn≥5cm).

[0079] When in use, the screen components 21 with different screen apertures are nested and placed on the turntable 33; the positions of the screen components 21 are adjusted so that their centers are located at the center of the turntable 33, and the outermost screen components 21 are connected to the upper part of the fixing rod 41 through the fixing buckle 42. Adjacent screen components 21 are fixed by screen fixing parts. Then, the material is introduced into the innermost screen component 21 in the middle from the top of the screen component 2, the drive component 31 is turned on, the main control valve 55 of the flushing water inlet pipe 54 and the flushing branch pipe control valve 53 are opened, and the flushing nozzle 52 sprays water toward the screening component. The drive component 31 drives the turntable 33, and then drives the screening component to rotate, generating centrifugal force, so that the material passes through the screening components with different screening apertures from the middle in turn, and the classification is realized. The liquid is stored in the barrel and discharged through the drain port 13.

[0080] Example 2

[0081] like Figure 7-Figure 8 As shown, based on Example 1, the difference of this embodiment is that the screen fixing member is a V-shaped fixing member 25, that is, the adjacent screen members 21 are fixed by an adjustable V-shaped fixing member 25, and the adjustable V-shaped fixing member 25 is located at the bottom of the annular channel of the adjacent screen members 21 and is respectively connected to the two adjacent screen members 21. This is suitable for the situation where the spacing between adjacent screen members is different, and can be adjusted according to the actual situation.

[0082] like Figure 8 As shown, the V-shaped fixing member 25 includes two support rods 251, one end of the two support rods 251 is connected by a rotating shaft, a fixed support rod 252 and an elastic element 253 are provided at the connection of the two support rods 251, and the other ends of the two support rods 251 are each provided with a fixed connecting member 254 for fixed connection with the screen member 21. The fixed connecting member 254 is an elastic annular clamp. The elastic element 253 is a spring.

[0083] Example 3

[0084] like Figures 9 to 11As shown, a wet screening instrument includes a centrifugal screening barrel 1 and a rotating mechanism 3, wherein the centrifugal screening barrel 1 includes a barrel body 11, wherein a screen assembly 2 and a flushing assembly 5 connected to a flushing water pipeline are arranged in the barrel body 11, wherein the screen assembly 2 includes a plurality of nested screen members 21, wherein the bottom of the screen member 21 is a non-porous contact surface, and the side wall of the screen member 21 is provided with a plurality of screen holes; from the middle of the screen assembly 2 to the outside, the screen aperture of the screen member 21 decreases successively, i.e., the screen aperture of the middle screen member 21 is large, and the screen aperture of the screen member 21 becomes smaller as it moves to the outside. The screen members 21 are stacked at the bottom. An annular channel 22 for receiving the accumulated material on the screen is formed between adjacent screen members 21. The flushing assembly 5 is located on the outside of each screen component 21, and the water spray port of the flushing assembly 5 faces the outer wall of the screen component 21; the rotating mechanism 3 is connected to the screen assembly 2 to drive the screen assembly 2 to rotate; a drain port 13 is provided at the bottom of the barrel body 11, and the separated liquid can be discharged from the drain port 13.

[0085] The rotating mechanism 3 includes a driving assembly 31, a rotating shaft 32 and a rotating disk 33. The driving assembly 31 provides a rotating centrifugal driving force. The rotating disk 33 is located in the barrel 11. The driving assembly 31 is connected to one end of the rotating shaft 32. The other end of the rotating shaft 32 is connected to the rotating disk 33. The rotating disk 33 is connected to the screen assembly 2 to drive the screen assembly 2 to rotate. The driving assembly 31 is a motor.

[0086] The rotating mechanism 3 is fixedly connected to the middle of the screen assembly 2 via the fixing assembly 5, so as to fix the screen assembly 2 from the inside.

[0087] Specifically, a hollow shaft 26 is erected in the middle of each screen component 21, and the hollow shaft 26 is fixedly connected to the bottom of the screen component 21 and passes through the bottom of the screen component 21. The hollow shafts of several screen components 21 are stacked in sequence, and the rotating shaft 32 extends into the stacked hollow shafts 26 and is fixedly connected to the hollow shaft 26 through the fixing component 4.

[0088] The fixing assembly 4 includes a pin 44 and a bolt 43. The hollow shaft 26 and the rotating shaft 32 are both provided with through holes in the radial direction, and the hollow shaft 26 and the rotating shaft 32 are connected by the pin 44 inserted into the through hole. The connection between the pin 44 and the hollow shaft 26 is fixed by a bolt 43.

[0089] The structure of the flushing component 5 is the same as that of embodiment 1.

[0090] Furthermore, a sealing ring 12 is provided at the connection between the barrel body 11 and the rotating shaft 32 to prevent water leakage.

[0091] Furthermore, a hanging ear 23 is provided on the top of the screen member 21 to facilitate taking the screen member 21. Furthermore, the number of the hanging ears 23 is greater than or equal to 2.

[0092] Further, the ratio of the height to the inner diameter of the mesh member 21 satisfies Hn / Dn≥1.

[0093] Furthermore, the ratio of the gap between adjacent screen components 21 to the inner diameter of the screen component 21 with the larger aperture satisfies bn / Dn=0.1-0.5 (the spacing bn between adjacent screens is designed to meet the accommodating material space and the installation space of the flushing water pipeline, bn≥5cm).

[0094] When in use, the screen components 21 with different screen apertures are nested and placed on the turntable 33; the position of the screen component 21 is adjusted so that its center is located at the center of the turntable 33, the rotating shaft 32 passes through the center of the turntable 33 and extends into the hollow shaft 26, the pin 44 is inserted into the through holes of the hollow shaft 26 and the rotating shaft 32, and the pin 44 is fixed with the bolt 43.

[0095] When performing screening operation, the material is introduced into the innermost screen component 21 in the middle from the top of the screen assembly 2, the drive assembly 31 is turned on, the main control valve 55 of the flushing water inlet pipe 54 and the flushing branch pipe control valve 53 are opened, and the flushing nozzle 52 sprays water toward the screening component 21. The drive assembly 31 drives the turntable 33, and then drives the screening assembly 2 to rotate, generating centrifugal force, so that the material passes through the screening components 21 with different screening apertures from the middle in turn, and classification is achieved. The liquid is stored in the barrel and discharged through the drain port 13.

[0096] In Examples 1 to 3, the flushing assembly is configured to adopt a backwashing method, such as Fig.12 The figure shows the state of particles in the screen component. The right side shows the material flow state with backwash water, and the left side shows no backwash water. It can be seen that in the absence of backwash water, the experimental material is subjected to the centrifugal force on the screen surface and forms a dense mud cake on the side wall screen surface; under the conditions of high-speed rotation and high-pressure water backwashing, the particles per unit area will pass through the flushing water pipeline at a high frequency and be subjected to the backwashing effect. The interaction between the backwash water and the centrifugal force makes the particles dispersed on the hydraulic side to form a suspension state. Repeated high-frequency secondary suspension and re-aggregation achieve good screening experimental results.

[0097] Example 4

[0098] This embodiment provides an experimental method for quickly determining particle size distribution, using any one of the wet sieving apparatuses in Embodiments 1 to 3 for sieving. The experimental method flow chart is as follows: Fig.13 As shown, the specific steps include:

[0099] Put the material into the screen component 21 at the center, open the main control valve 55 and the flushing branch pipe control valve 53 at the same time, start the rotating mechanism 3 to drive the screen component 2 to rotate, and flush and screen the material in the screen component 2 in the rotating state. This method is mainly for materials with relatively uniform particle size.

[0100] For materials with uneven particle sizes and complex components, such as a large amount of low-viscosity coarse materials (approximately > 500 microns) and a large amount of high-viscosity fine materials (approximately < 500 microns), each layer of the screen components can be washed separately and screened step by step. The steps include:

[0101] Put the material into the screen member 21 at the center, and control the rotation speed according to the amount of material so that the surface centrifugal force F1 of the innermost screen member is 1.8-2.3 times the acceleration of gravity;

[0102] Open the main control valve 55 and the flushing branch pipe control valve 53 corresponding to the innermost screen member 21, keep the other flushing branch pipe control valves 53 closed, control the flushing water pressure P1 to 2-3 bar, flush for several minutes, and close the flushing branch pipe control valve 53 when the material in the innermost screen member 21 is no longer reduced;

[0103] Continue the secondary flushing, adjust the rotation speed of the turntable, control the centrifugal force F2 = (1-1.3) F1 on the surface of the second layer of screen components from the inside to the outside, open the flushing branch pipe control valve 53 corresponding to the second layer of screen components 21 from the inside to the outside, keep the other flushing branch pipe control valves 53 closed, and control the flushing water pressure P2 = (1-1.3) P1; flush for several minutes, and when the material in the layer of screen components is no longer reduced, close the flushing branch pipe control valve 53;

[0104] Continue to perform three-level flushing, adjust the rotation speed of the turntable, control the centrifugal force F3 = (1.3-1.5) F1 on the surface of the third layer of screen components from the inside to the outside, and open the flushing branch pipe control valve 53 corresponding to the third layer of screen components 21 from the inside to the outside, keep other flushing branch pipe control valves 53 closed, and control the flushing water pressure P3 = (1.3-1.5) P1; flush for several minutes, and when the material in the layer of screen components 21 is no longer reduced, close the flushing branch pipe control valve;

[0105] If there are four layers of screen components, four-level flushing is performed, the rotation speed of the turntable is adjusted, and the surface centrifugal force F4 of the fourth layer of screen components from the inside to the outside is controlled to be (1.5-1.8) F1, and at the same time, the flushing branch pipe control valve 53 corresponding to the fourth layer of screen components 21 from the inside to the outside is opened, and the other flushing branch pipe control valves 53 are kept closed, and the flushing water pressure P4 is controlled to be (1.5-1.8) P1; flush for several minutes, and when the material in the layer of screen components 21 is no longer reduced, the flushing branch pipe control valve is closed;

[0106] By analogy, each time a layer of screen components is added, a flushing stage is added. The rotation speed of the turntable is adjusted accordingly to control the surface centrifugal force of the corresponding screen component to increase by (0.2-0.3) F1 relative to the previous flushing stage, and the flushing branch pipe control valve corresponding to the screen component is opened. The flushing water pressure is increased by (0.2-0.3) P1 relative to the previous flushing stage, and other flushing branch pipe control valves are kept closed; flush for several minutes, and when the material in the layer of screen components is no longer reduced, the flushing branch pipe control valve is closed;

[0107] Until all screen components are screened and flushed individually; during the whole process, the surface centrifugal force of the screen components is controlled not to exceed 10 times the acceleration of gravity, and the flushing water pressure is controlled not to exceed 12 bar.

[0108] Finally, open all the flushing branch control valves and flush with the same water pressure and speed until the water discharged from the bottom is almost clear, and the screening is completed.

[0109] During the screening process, it is observed that the water from the drain pipe 61 is almost clear and no particles are further discharged, which means that the tested material has completed the particle size classification in the barrel; at this time, the flushing branch pipe control valve 53 is closed; then the rotation speed is appropriately increased, and the screen is kept rotating for a certain period of time, so that the wet-screened material can be quickly centrifugally dehydrated; when almost no water is discharged from the drain pipe 61, the dehydration is completed; the rotating mechanism 3 is closed, and the screen components 21 are taken out in turn for subsequent drying experiments;

[0110] Since the flushing pipeline is movably connected and the screen cannot be damaged, the maximum flushing water pressure shall not exceed 12 bar. The centrifugal force in the screen shall also be controlled to be 3-5 times the acceleration of gravity. Because the centrifugal force is too large, the material will be compacted and accumulated on the surface of the screen, which is difficult to fluidize and is not conducive to screening. In addition, the material on the surface of the screen component moves from the bottom to the top in a parabolic trend due to the centrifugal force. If the centrifugal force is too large, the material can rise up to several meters in the screen. It does not meet the requirements of setting up a small, compact and convenient experimental device. The flushing water pressure is adjusted according to the centrifugal force received by the outermost screen at the corresponding speed.

[0111] Furthermore, the inner diameter of the innermost screen component is 10 cm. The control of the rotation speed of the screening instrument can make the hydraulic strength of the particles on the screen component, that is, according to the centrifugal force control range of 2-10 times the gravity, the smallest screen component corresponds to the minimum centrifugal force, the largest screen component corresponds to the maximum centrifugal force, and the inner diameter of the innermost screen component is 10 cm. The rotation speed of the screen can be calculated according to the formula of centrifugal force; the flushing frequency, that is, the high-pressure water flushing frequency can reach 10-24 times / s. With this technical solution, the flushing frequency and hydraulic strength per unit area are at least 5 times that of traditional screens; lower flushing water consumption is achieved; in addition, since the screening instrument also has a centrifugal dehydration function that traditional screening instruments do not have, the subsequent drying time can be shortened to less than 2 hours (traditional vibration dehydration requires 4 hours to completely dry); the overall experimental time is shortened by at least half.

[0112] The screening method of flushing each layer of screen components separately is slightly more complicated, but for difficult-to-handle materials or highly polluted materials, the particle size distribution can be accurately and efficiently determined by controlling the centrifugal force on different levels of screens and the high-pressure backwash water distributed on the screens; under the condition of lower specific surface area load and washing water consumption, the experimental time is effectively shortened, and better screening effect and lower washing water consumption can be achieved; the overall experimental efficiency produces less highly polluted waste liquid requiring secondary disposal and less energy consumption.

[0113] In this embodiment, the material in the screen component will diffuse and separate from the middle to the outside under the action of centrifugal force, and the heavy material of large particles will stay in the middle, and the light material of fine particles and water will be carried to the outside by centrifugal force for diffusion and separation, and the particle size classification will be gradually completed in the screen set in the barrel. In addition, while adopting graded flushing and screening, a graded centrifugal dehydration experiment can also be carried out; that is, after the centrifugal dehydration of materials in different particle size ranges, the moisture content is measured to find out the components with relatively high moisture content, that is, it is more difficult to physically dehydrate; for materials with high dehydration requirements in production, such as gasified slag recovered by wet method, activated sludge that can be incinerated and reused; according to the guidance of the above experimental data, the materials can be roughly screened and graded first, and the parts that are easy to mechanically dehydrate will be dehydrated by traditional low-cost dehydration methods, while the parts that are difficult to mechanically dehydrate will be dehydrated by high-energy consumption steam and other heat sources. This segmented reduction treatment method not only meets the production requirements, but also achieves low energy consumption, which has an important experimental guidance role in energy saving and efficiency improvement in actual production.

[0114] The sieving device of the present invention has a centrifugal dehydration function. After sieving, the sample on the sieve can be directly dehydrated to a moisture content of 30-50% in situ, and the subsequent drying time only takes 1.5-2 hours. The specific operation process is described in detail below.

[0115] 1. Select the required clean and dry test sieves and weigh the empty weight m of each sieve in turn. 1 To m n , stacked together from bottom to top;

[0116] 2. Weigh the required original sample A grams and add it to the coarsest experimental sieve (the top in the traditional method and the middle in this scheme); and rinse all the samples on the container into the sieve.

[0117] 3. At the same time, the moisture content W of the original sample is detected, and the absolute dry weight of the original sample is WxA grams;

[0118] 4. Add flushing water from the top, and shake manually or automatically while flushing;

[0119] 5. The screening is considered complete when the material on each layer of the sieve no longer decreases and the bottom drainage is clear. If a large amount of sample splashes out or overflows during this process, the experiment will be invalid and must be restarted.

[0120] 6. After the screening is completed and there is no obvious water dripping from the sample, put it into the oven together with the test sieve at 105 degrees for 4 hours until the weight stops decreasing and the sample reaches an absolutely dry state;

[0121] 7. Take out the sieves one by one and weigh them; and record M 1 To M n ; This total weight M 1 Minus the empty weight of the screen m 1 It is the absolute dry weight of the sample on the first sieve G 1 ; i.e. G 1 =M 1 -m 1 ; The quality score F of this level 1 =G 1 / AxW%; The calculation method of other levels of screens is the same as above;

[0122] 8. The mass fraction of the finest material at the bottom layer, i.e. the material under the sieve, is calculated as 100% minus the sum of the mass fractions of all other sieves;

[0123] 9. Error calibration: if the error of the whole experiment process exceeds 0.1%, the experimental data will be deemed invalid and the experiment will be invalidated and need to be re-tested. If obvious quality loss occurs during the experiment, such as overturning the container, material flowing out, etc., the experiment will be invalidated and the operation must be terminated immediately and re-tested.

[0124] From the above experimental steps, it can be seen that the conventional wet screening experiment is difficult to read, and if the material needs to be dehydrated or any other treatment, it must be done together with the test sieve; it is best to do it in situ because material loss is not allowed; the traditional method is to take out all the test sieves and cannot put them into the centrifuge for dehydration; any operation of taking the material out of the sieve for secondary dehydration does not meet the experimental standards.

[0125] Compared with the traditional screen structure with a large bottom surface and a small height, the screening device of the present invention has a high height and a relatively small bottom surface, which can better receive materials and avoid spilling, and the experimental success rate is high; it is also convenient for drying after dehydration.

[0126] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A wet sieving apparatus, characterized in that: It comprises a centrifugal screening barrel and a rotating mechanism. The centrifugal screening barrel comprises a barrel body, a screen assembly and a flushing assembly connected to a flushing water pipeline are arranged in the barrel body, the screen assembly comprises a plurality of nested screen members, and a plurality of screen holes are arranged on the side wall of the screen member; the screen apertures of the screen members decrease in sequence from the middle of the screen assembly to the outside; an annular channel for receiving the accumulated materials on the screen is formed between adjacent screen members; the flushing assembly is located on the outside of each screen member, and the water spray port of the flushing assembly faces the outer wall of the screen member; The rotating mechanism is connected with the screen assembly to drive the screen assembly to rotate; and a drainage port is arranged at the bottom of the barrel body.

2. The wet sieving apparatus according to claim 1, characterized in that: The rotating mechanism includes a driving assembly, a rotating shaft, and a turntable. The turntable is located in the barrel body. The driving assembly is connected to one end of the rotating shaft, and the other end of the rotating shaft is connected to the turntable. The turntable is connected to the screen assembly to drive the screen assembly to rotate.

3. The wet sieving apparatus according to claim 2, characterized in that: The turntable is fixedly connected to the outer side of the screen assembly via a fixing assembly; the fixing assembly comprises a fixing rod, the lower part of which is fixedly connected to the turntable, and the upper part of which is connected to the outer side of the screen assembly via a fixing buckle.

4. The wet sieving apparatus according to claim 3, characterized in that: The rotating disk is provided with a U-shaped groove in the radial direction, the lower part of the fixing rod extends into the U-shaped groove, and the fixing rod and the rotating disk are connected by a fixing piece at the upper side and / or the lower side of the U-shaped groove; the adjacent screen members are fixed by a screen fixing piece, and the screen fixing piece is located at the bottom of the annular channel of the adjacent screen members; The screen fixing piece is a U-shaped fixing piece or an adjustable V-shaped fixing piece; the V-shaped fixing piece includes two support rods, one end of the two support rods are connected by a rotating shaft, a fixed support piece and an elastic element are provided at the connection between the two support rods, and the other ends of the two support rods are provided with a fixed connecting piece for connecting to the corresponding screen component.

5. The wet sieving apparatus according to claim 2, characterized in that: A hollow shaft is erected in the middle of the screen component, the hollow shaft is fixedly connected to the bottom of the screen component and passes through the bottom of the screen component, the hollow shafts of several screen components are stacked in sequence, the rotating shaft extends into the stacked hollow shafts, and is fixedly connected to the hollow shafts through a fixing assembly; the fixing assembly includes a pin and a bolt, the hollow shaft and the rotating shaft are both provided with through holes in the radial direction, the pin is inserted into the through holes of the hollow shaft and the rotating shaft, and is fixed by bolts.

6. The wet sieving apparatus according to claim 2, characterized in that: A sealing ring is provided between the barrel body and the rotating shaft; the ratio of the height to the inner diameter of the screen component Hn / Dn≥1, and the ratio of the gap between adjacent screen components to the inner diameter of the screen component with the larger aperture satisfies bn / Dn=0.1-0.

5.

7. The wet sieving apparatus according to any one of claims 1 to 6, characterized in that: The flushing assembly comprises a vertically arranged flushing water branch pipe, on which a plurality of flushing nozzles are arranged, wherein the flushing nozzle at the uppermost end of the flushing water branch pipe is obliquely downwardly directed toward the outer side of the screen member, and the flushing nozzle at the lowermost end of the flushing water branch pipe is obliquely upwardly directed toward the outer side of the screen member; The angles between the flushing nozzle located at the uppermost end of the flushing water branch pipe and the flushing nozzle located at the lowermost end of the flushing water branch pipe and the flushing water branch pipe are 30°-90°; a main control valve is provided on the flushing water inlet pipe, and a flushing branch pipe control valve is provided on the flushing water branch pipe; the drain outlet is connected to a drain pipe, and the drain pipe is provided with a drain valve.

8. An experimental method for determining particle size distribution of particles, characterized in that: The wet sieving apparatus as claimed in claim 7 is used for measurement, comprising the following steps: putting the material into the screen component at the center, opening the main control valve and the flushing branch pipe control valve at the same time, starting the rotating mechanism to drive the screen component to rotate, and flushing and screening the material in the screen component in the rotating state; Alternatively, each layer of the screen component can be flushed separately. First, the material is put into the screen component at the center. According to the amount of material, the rotation speed is controlled so that the surface centrifugal force F1 of the innermost screen component is 1.8-2.3 times the gravity acceleration; open the main control valve and the flushing branch pipe control valve corresponding to the innermost screen component, and keep the other flushing branch pipe control valves closed at this time. Flush for several minutes, and close the flushing branch pipe control valve when the material in the innermost screen component is no longer reduced; Continue the secondary flushing, adjust the rotation speed of the turntable, control the centrifugal force F2 on the surface of the second layer of screen components from the inside to the outside = (1-1.3) F1, and at the same time open the flushing branch pipe control valve corresponding to the second layer of screen components from the inside to the outside, and keep the other flushing branch pipe control valves closed; flush for several minutes, and when the material in the second layer of screen components from the inside to the outside is no longer reduced, close the flushing branch pipe control valve; Continue to perform three-level flushing, adjust the rotation speed of the turntable, control the centrifugal force F3 of the surface of the third layer of screen components from the inside to the outside = (1.3-1.5) F1, and at the same time open the flushing branch pipe control valve corresponding to the third layer of screen components from the inside to the outside, and keep other flushing branch pipe control valves closed; flush for several minutes, and when the material in the third layer of screen components from the inside to the outside is no longer reduced, close the flushing branch pipe control valve; By analogy, each time a layer of screen components is added, a flushing stage is added. The rotating speed of the turntable is adjusted accordingly to control the surface centrifugal force of the corresponding screen component to increase by (0.2-0.3) F1 relative to the previous flushing stage, and the flushing branch pipe control valve corresponding to the screen component is opened, and other flushing branch pipe control valves are kept closed; flush for several minutes, and when the material in the layer of screen components is no longer reduced, the flushing branch pipe control valve is closed; Until all the screen components are screened and flushed individually; During the whole process, the surface centrifugal force of the screen component is controlled not to exceed 10 times the acceleration of gravity.

9. The experimental method for determining particle size distribution of particles according to claim 8, characterized in that: When the main control valve and the flushing branch control valve corresponding to the innermost screen component are opened, the flushing water pressure P1 is controlled to be 2-3 bar; when performing secondary flushing, the flushing water pressure P2 is controlled to be (1-1.3) P1; when performing tertiary flushing, the flushing water pressure P3 is controlled to be (1.3-1.5) P1; and so on, for each additional layer of screen component, one level of flushing is added, and the flushing water pressure is controlled to increase by (0.2-0.3) P1 relative to the previous level of flushing; until the individual flushing and screening of each layer of screen is completed, the maximum flushing water pressure during the entire process shall not exceed 12 bar.

10. The experimental method for measuring particle size distribution of particles according to claim 8, characterized in that: When each layer of screen components is flushed separately, after each layer is flushed separately, all flushing branch pipe control valves are opened and flushed with the same water pressure and speed until the water discharged from the bottom is almost clear, and the screening is completed.

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