Dust particle size screening system and method

Abstract

A dust particle size screening system and method, the method includes setting the initial conditions for solution, numerical model solution, establishing a particle size screening formula, dust particle size screening and determining the mass concentration of dust particles in each particle size range. The present invention can realize the large-scale collection of floating dust at any height at the work site, accurate particle size screening and analysis and determination of dust concentrations of different particle sizes. The present invention is easy to operate and has high dust particle size screening accuracy. It can be promoted in many dust-related places such as industry, mining, construction, and atmospheric monitoring for high-precision detection of dust concentration by particle size. It can also use dust by particle size for medical research such as pathology, toxicology, and animal experiments. It has a wide range of applications and high application value.

Description

Technical Field

[0001] The invention belongs to the technical field of dust particle size screening, and in particular relates to a dust particle size screening system and method. Background Art

[0002] Screening dust particle size is a frequent and important task in many fields such as industrial production and scientific research. However, a common problem encountered in the process of carrying out this work is that screening dust particles with a particle size of less than 74μm is technically complex and expensive. Screening out dust with a particle size of less than 74μm is of great significance in conducting basic occupational health research such as dust concentration and particle size distribution analysis, animal experimental toxicology research, and personal protective equipment evaluation.

[0003] In view of the above problems, the present invention proposes a dust particle size screening system and method, which can realize the large-scale collection of the particle size of floating dust at any height at the work site, the accurate particle size screening, and the analysis and determination of the concentration and particle size distribution of dust with different particle sizes. The present invention is easy to operate and has high dust particle size screening accuracy. It can be promoted in many dust-related places such as industry, mining, construction, and atmospheric monitoring for high-precision detection of dust concentration by particle size, and the floating dust by particle size obtained on site can be used for medical research such as pathology, toxicology, and animal experiments. It has a wide range of applications and high application value. Summary of the invention

[0004] In order to solve the problem that it is difficult to screen dust particles with a particle size less than 74 μm, the present invention provides a dust particle size screening system and method.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A dust particle size screening method, the particle size screening method comprising:

[0007] S1: Set the initial conditions for the solution: the dust particle size d is 2, 4, 6, 8, 10, 14, 34, 54, and 74 μm respectively, the wind speed v of the speed-adjusting fan 12 is 0.3, 0.6, 0.9, 1.2, and 1.5 m / s respectively, and the horizontal acceleration a of the dust particles in the electromagnetic field of the shunt detection device 9 is 1.5×10 3 , 1.5×10 4 , 1.5×10 5 , 1.5×10 6 , 1.5×10 7 m / s 2 ;

[0008] S2: Numerical model solution: select density ρ as 2100kg / m 3The coal dust is measured in the cylindrical coordinate system under different wind speeds v and different accelerations a. Establish a geometric model of the magnetic diversion module, add turbulent field, magnetic field and particle tracking physical field, solve the physical field, obtain the numerical model solution results, and obtain data points reflecting the relationship between the dust particle size d and the dust settling starting coordinate r1 and the settling ending coordinate r2;

[0009] S3: Establishing a particle size screening formula: According to the solution result of step S2, the functional relationship between the dust settling starting coordinate r1 and the settling ending coordinate r2 and the dust particle size d is fitted to obtain the Logistic relationship: The parameter b1 and wind speed v in the Logistic equation conform to the Lorentz equation: b2 and wind speed v conform to the linear relationship: b2 = 4.66 × 10 -4 v+3.57×10 -6 , b3 and acceleration a conform to the Allometric1 relationship: b3 = -2.8 × 10 -4 a -0.33 , b4 and acceleration a conform to the Allometric1 relationship: b4 = 15.9a -0.12 , c1 and acceleration a conform to the Allometric1 relationship: c1 = 0.2a -0.13 , c2 and acceleration a conform to the Allometric1 relationship: c2 = 0.005a -0.13 According to Newton's second law, the acceleration a, wind speed v, electromagnet current I, particle density ρ and particle size d conform to the relationship: Combining the above equations, the equations for the relationship between the dust settling starting coordinate r1 and the settling ending coordinate r2 and the dust particle size d are as follows:

[0010]

[0011] In the formula, r1 is the starting coordinate of dust settling; r2 is the ending coordinate of dust settling; d is the particle size of dust particles; v is the wind speed of the speed-adjustable fan; a is the centripetal acceleration of dust particles; I is the current of the electromagnet, and ρ is the density of dust particles;

[0012] S4: Adjust the height-adjustable support frame 10 to the required sampling height, and simultaneously start the axial flow fan 2, the timer 3, and the flow meter 4 to capture the floating dust and store it in the dust collecting bottle 11 filled with distilled water, and record the capture time and flow value through the timer 3 and the flow meter 4 respectively;

[0013] S5: Install the dust collecting bottle (11) on the magnetic stirring base, turn on the magnetic stirring base (5-3) to drive the porous magnetic net (5-1) to rotate at a high speed, so that the dust in the dust collecting bottle (11) is in a uniformly suspended suspension state; when the horizontal initial velocity v of the outflow of the multi-hole nozzle (8) is determined, the particle density ρ and the particle size d1 of the captured particles are substituted into the screening formula, and the current I of the electromagnet (9-2) is substituted to calculate the starting coordinates r1 and r2 of the dust settling as the ending coordinates of the dust settling, then the settling area of ​​the particles with a particle size of d is a circular ring with an inner diameter of r1 and an outer diameter of r2; similarly, the particle size d2 (d2> d1) is a circular ring with an inner diameter of r3 and an outer diameter of r4; the radial difference values ​​|r2-r1| and |r4-r3| of the diverter baffle (9-3) when capturing particles with a particle size range of d1 to d2 are obtained, and then the radial difference value of the diverter baffle (9-3) can be changed by changing the current of the electromagnet (9-2), so as to achieve the effect of capturing particles with different particle size ranges by changing the current of the electromagnet (9-2); similarly, when the current I of the electromagnet (9-2) is determined, the effect of capturing particles with different particle size ranges can also be achieved by changing the horizontal initial velocity v of the multi-channel nozzle (8). The corresponding parameters of the above device are adjusted to the values ​​of the calculated results, so that the dust particles of each particle size range to be analyzed and obtained are settled on the high-efficiency filter cotton (9-5) between the slits of each group of baffles in the storage chamber (9-4) until the suspension in the dust collecting bottle (11) is sprayed out;

[0014] S6: Dust particles in each particle size range settle on the high-efficiency filter cotton 9-5 between the slits of each group of partitions in the storage chamber 9-4. The change in the mass of the filter cotton causes the change in the oscillation frequency of the nested conical element 9-8. The oscillation frequencies of the two nested conical elements are driven by the amplifier circuit 9-7 and the frequency counting circuit 9-6 to obtain two mass values, one large and one small. The two values ​​are subtracted to obtain the mass gain of the particles in the target particle size range; the weight gain is divided by the product of the time and flow value in step S4 to obtain the mass concentration of the dust particles in each particle size range.

[0015] Furthermore, the dust particle size screening system includes an on-site floating dust capture device and a dust particle size screening device;

[0016] The on-site floating dust capture device comprises a height-adjustable support frame 10, a cyclone separation device 1, an axial flow fan 2, a timer 3, a flow meter 4, and a dust collecting bottle 11; the height-adjustable support frame 10 supports the axial flow fan 2, the axial flow fan 2, the flow meter 4 and the dust collecting bottle 11 are sequentially sealed and connected in series along the axial direction, the cyclone separation device 1 is fixed to the air inlet of the axial flow fan 2, and the timer 3 is fixed to the connecting pipe between the axial flow fan 2 and the flow meter 4; the cyclone separation device 1 is used to separate dust and gas, so that the dust enters the dust collecting bottle 11 along the axial flow fan 2 and the flow meter 4;

[0017] The dust particle size screening device includes a magnetic stirring device 5, an atomizer 6, a drying tube 7, a speed-regulating fan 12, a multi-hole nozzle 8 and a diversion monitoring device 9; the atomizer 6, the drying tube 7, the speed-regulating fan 12, and the multi-hole nozzle 8 are sealed and connected in series in sequence along the axial direction, and the multi-hole nozzle 8 is connected to the diversion monitoring device 9. The magnetic stirring device 5 includes a magnetic stirring base 5-2 and a porous magnetic net 5-1. The dust collecting bottle 11 is placed on the magnetic stirring base 5-2, and the porous magnetic net 5-1 is placed inside the dust collecting bottle 11. The magnetic stirring device 5 is used to make the dust in the dust collecting bottle 11 in a uniformly suspended suspension state. The speed-regulating fan 12 allows the suspension to pass through the atomizer 6 and the drying tube 7 and then enter the diversion monitoring device 9 through the multi-hole nozzle 8.

[0018] Furthermore, the flow diversion monitoring device 9 includes a magnetic flow diversion module and a concentration monitoring module; the magnetic flow diversion module includes a spiral guide blade 9-1, an electromagnet 9-2, a flow diversion baffle 9-3, a storage chamber 9-4 and a high-efficiency filter cotton 9-5; the spiral guide blade 9-1 provides a radial force on the particles, and the electromagnet 9-2 provides an axial force on the particles; particles of different particle sizes are subjected to different combined forces, so that they fall into the flow diversion baffle 9-3 between the corresponding radii. 3 and then enter the storage chamber 9-4; the magnetic induction intensity of the electromagnet 9-2 can be adjusted by controlling the current; the diversion baffle 9-3 is composed of multiple groups of concentric mechanical guide baffles, which can expand / contract radially. The electromagnet 9-2 and the diversion baffle 9-3 cooperate to adjust and store particles of different particle size segments; the high-efficiency filter cotton 9-5 is placed at the outlet of the diversion baffle 9-3 at the bottom of the storage chamber 9-4; the concentration monitoring module is connected to the bottom of the storage chamber 9-4, including a frequency counting circuit 9-6, a driving amplifier circuit 9-7, and a nested conical element 9-8, a fixed base 9-9 and an exhaust pipe 9-10; the nested conical element 9-8 is formed by two nested conical elements, the upper end of which is connected to the high-efficiency filter cotton 9-5, and the lower end is installed on the top of the fixed base 9-9; when working, the driving amplifier circuit 9-7 drives the high-efficiency filter cotton 9-5 and the nested conical element 9-8 to vibrate at a natural frequency, and when particles fall on the high-efficiency filter cotton 9-5, the vibration frequency of the nested conical element 9-8 changes. The frequency counting circuit 9-6 measures the vibration frequency of the nested conical element 9-8 to calculate the mass increment of the particulate matter.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention can obtain a large number of different types of dust particles with different particle size ranges at low cost, which can be used for basic occupational health research such as animal toxicology experiments and personal protective equipment evaluation;

[0021] (2) The screening and analysis process of dust particle size of the present invention can be used to detect the concentration and particle size distribution of suspended dust at different heights in dust-related workplaces, which can effectively avoid the problems of easy dust blockage and poor accuracy of the photoelectric direct reading method in the existing high-concentration dust workplace filter weighing sampling method;

[0022] (3) The present invention has a simple structure, is easy to operate, and has high particle size screening accuracy. It can be used in both engineering practice and scientific research, has a wide range of applications, and has high application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the structure of the dust particle size screening device of the present invention.

[0025] Figure 2 It is a schematic structural diagram of the magnetic stirring device of the present invention.

[0026] Figure 3 It is a schematic diagram of the structure of the particle size screening box with adjustable width of the present invention.

[0027] Figure 4 This is a schematic diagram of the disassembled structure of the storage chamber of the present invention.

[0028] In the figure: 1. Cyclone separation device; 2. Axial flow fan; 3. Timer; 4. Flow meter; 5. Magnetic stirring device; 5-1. Porous magnetic net; 5-2. Iron frame; 5-3. Magnetic stirring base; 6. Atomizer; 7. Drying tube; 8. Multi-hole nozzle; 9. Diversion monitoring device; 9-1. Spiral guide blade; 9-2 Electromagnet; 9-3. Diversion baffle; 9-4. Storage chamber; 9-5. High-efficiency filter cotton; 9-6. Frequency counting circuit; 9-7. Drive amplifier circuit; 9-8. Nested conical element; 9-9. Fixed base; 9-10. Exhaust pipe; 10. Height-adjustable support frame; 11. Dust collection bottle; 12. Speed-regulating fan. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] In conjunction with the instruction manual Figure 1-4 A dust particle size screening system includes an on-site floating dust capture device and a dust particle size screening device.

[0031] The on-site floating dust capture device comprises a height-adjustable support frame, a cyclone separation device 1, an axial flow fan 2, a timer 3, a flow meter 4, and a dust collecting bottle 11; the height-adjustable support frame 10 supports the axial flow fan 2, the axial flow fan 2, the flow meter 4 and the dust collecting bottle 11 are sequentially sealed and connected in series along the axial direction, the cyclone separation device 1 is fixed to the air inlet of the axial flow fan 2, and the timer 3 is fixed to the connecting pipe between the axial flow fan 2 and the flow meter 4; the cyclone separation device 1 is used to separate dust and gas, so that the dust enters the dust collecting bottle 11 along the axial flow fan 2 and the flow meter 4;

[0032] The dust particle size screening device includes a magnetic stirring device 5, an atomizer 6, a drying tube 7, a speed-regulating fan 12, a multi-hole nozzle 8 and a diversion monitoring device 9; the atomizer 6, the drying tube 7, the speed-regulating fan 12, and the multi-hole nozzle 8 are sealed and connected in series in sequence along the axial direction, and the multi-hole nozzle 8 is connected to the diversion monitoring device 9. The magnetic stirring device 5 includes a magnetic stirring base 5-2 and a porous magnetic net 5-1. The dust collecting bottle 11 is placed on the magnetic stirring base 5-2, and the porous magnetic net 5-1 is placed inside the dust collecting bottle 11. The magnetic stirring device 5 is used to make the dust in the dust collecting bottle 11 in a uniformly suspended suspension state. The speed-regulating fan 12 allows the suspension to pass through the atomizer 6 and the drying tube 7 and then enter the diversion monitoring device 9 through the multi-hole nozzle 8.

[0033] Furthermore, the flow diversion monitoring device 9 includes a magnetic flow diversion module and a concentration monitoring module; the magnetic flow diversion module includes a spiral guide blade 9-1, an electromagnet 9-2, a flow diversion baffle 9-3, a storage chamber 9-4 and a high-efficiency filter cotton 9-5; the spiral guide blade 9-1 provides a radial force on the particles, and the electromagnet 9-2 provides an axial force on the particles; particles of different particle sizes are subjected to different combined forces, so that they fall into the flow diversion baffle 9-3 between the corresponding radii. 3 and then enter the storage chamber 9-4; the magnetic induction intensity of the electromagnet 9-2 can be adjusted by controlling the current; the diversion baffle 9-3 is composed of multiple groups of concentric mechanical guide baffles, which can expand / contract radially. The electromagnet 9-2 and the diversion baffle 9-3 cooperate to adjust and store particles of different particle size segments; the high-efficiency filter cotton 9-5 is placed at the outlet of the diversion baffle 9-3 at the bottom of the storage chamber 9-4; the concentration monitoring module is connected to the bottom of the storage chamber 9-4, including a frequency counting circuit 9-6, a driving amplifier circuit 9-7, and a nested conical element 9-8, a fixed base 9-9 and an exhaust pipe 9-10; the nested conical element 9-8 is formed by two nested conical elements, the upper end of which is connected to the high-efficiency filter cotton 9-5, and the lower end is installed on the top of the fixed base 9-9; when working, the driving amplifier circuit 9-7 drives the high-efficiency filter cotton 9-5 and the nested conical element 9-8 to vibrate at a natural frequency, and when particles fall on the high-efficiency filter cotton 9-5, the vibration frequency of the nested conical element 9-8 changes. The frequency counting circuit 9-6 measures the vibration frequency of the nested conical element 9-8 to calculate the mass increment of the particulate matter.

[0034] Particle size screening methods include:

[0035] S1: Set the initial conditions for the solution: the dust particle size d is 2, 4, 6, 8, 10, 14, 34, 54, and 74 μm respectively, the wind speed v of the speed-adjusting fan 12 is 0.3, 0.6, 0.9, 1.2, and 1.5 m / s respectively, and the horizontal acceleration a of the dust particles in the electromagnetic field of the shunt detection device 9 is 1.5×10 3 , 1.5×10 4 , 1.5×10 5 , 1.5×10 6 , 1.5×10 7 m / s 2 ;

[0036] S2: Numerical model solution: select density ρ as 2100kg / m 3 The coal dust is measured in the cylindrical coordinate system under different wind speeds v and different accelerations a. Establish a geometric model of the magnetic diversion module, add turbulent field, magnetic field and particle tracking physical field, solve the physical field, obtain the numerical model solution results, and obtain data points reflecting the relationship between the dust particle size d and the dust settling starting coordinate r1 and the settling ending coordinate r2;

[0037] S3: Establishing a particle size screening formula: According to the solution result of step S2, the functional relationship between the dust settling starting coordinate r1 and the settling ending coordinate r2 and the dust particle size d is fitted to obtain the Logistic relationship: The parameter b1 and wind speed v in the Logistic equation conform to the Lorentz equation: b2 and wind speed v conform to the linear relationship: b2 = 4.66 × 10 -4 v+3.57×10 -6 , b3 and acceleration a conform to the Allometric1 relationship: b3 = -2.8 × 10 -4 a -0.33 , b4 and acceleration a conform to the Allometric1 relationship: b4 = 15.9a -0.12 , c1 and acceleration a conform to the Allometric1 relationship: c1 = 0.2a -0.13 , c2 and acceleration a conform to the Allometric1 relationship: c2 = 0.005a -0.13 According to Newton's second law, the acceleration a, wind speed v, electromagnet current I, particle density ρ and particle size d conform to the relationship: Combining the above equations, the equations for the relationship between the dust settling starting coordinate r1 and the settling ending coordinate r2 and the dust particle size d are as follows:

[0038]

[0039] In the formula, r1 is the starting coordinate of dust settling; r2 is the ending coordinate of dust settling; d is the particle size of dust particles; v is the wind speed of the speed-adjustable fan; a is the centripetal acceleration of dust particles; I is the current of the electromagnet, and ρ is the density of dust particles;

[0040] S4: Adjust the height-adjustable support frame 10 to the required sampling height, and simultaneously start the axial flow fan 2, the timer 3, and the flow meter 4 to capture the floating dust and store it in the dust collecting bottle 11 filled with distilled water, and record the capture time and flow value through the timer 3 and the flow meter 4 respectively;

[0041] S5: Install the dust collecting bottle (11) on the magnetic stirring base, turn on the magnetic stirring base (5-3) to drive the porous magnetic net (5-1) to rotate at a high speed, so that the dust in the dust collecting bottle (11) is in a uniformly suspended suspension state; when the horizontal initial velocity v of the outflow of the multi-hole nozzle (8) is determined, the particle density ρ and the particle size d1 of the captured particles are substituted into the screening formula, and the current I of the electromagnet (9-2) is substituted to calculate the starting coordinates r1 and r2 of the dust settling as the ending coordinates of the dust settling, then the settling area of ​​the particles with a particle size of d is a circular ring with an inner diameter of r1 and an outer diameter of r2; similarly, the particle size d2 (d2> d1) is a circular ring with an inner diameter of r3 and an outer diameter of r4; the radial difference values ​​|r2-r1| and |r4-r3| of the diverter baffle (9-3) when capturing particles with a particle size range of d1 to d2 are obtained, and then the radial difference value of the diverter baffle (9-3) can be changed by changing the current of the electromagnet (9-2), so as to achieve the effect of capturing particles with different particle size ranges by changing the current of the electromagnet (9-2); similarly, when the current I of the electromagnet (9-2) is determined, the effect of capturing particles with different particle size ranges can also be achieved by changing the horizontal initial velocity v of the multi-channel nozzle (8). The corresponding parameters of the above device are adjusted to the values ​​of the calculated results, so that the dust particles of each particle size range to be analyzed and obtained are settled on the high-efficiency filter cotton (9-5) between the slits of each group of baffles in the storage chamber (9-4) until the suspension in the dust collecting bottle (11) is sprayed out;

[0042] S6: Dust particles in each particle size range settle on the high-efficiency filter cotton 9-5 between the slits of each group of partitions in the storage chamber 9-4. The change in the mass of the filter cotton causes the change in the oscillation frequency of the nested conical element 9-8. The oscillation frequencies of the two nested conical elements are driven by the amplifier circuit 9-7 and the frequency counting circuit 9-6 to obtain two mass values, one large and one small. The two values ​​are subtracted to obtain the mass gain of the particles in the target particle size range; the weight gain is divided by the product of the time and flow value in step S4 to obtain the mass concentration of the dust particles in each particle size range.

[0043] In this step, the percentage of dust particles in each particle size range in the total suspended dust particles or dust particles in a wider particle size range can also be further calculated.

[0044] Among them, S1 to S3 of the particle size screening method are based on the COMSOL Multiphysics numerical model solution to establish the particle size screening formula; S4 to S6 are the implementation process of dust particle size screening.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for screening dust particles by particle size, characterized in that: The particle size screening method comprises: S1: Set the initial conditions for the solution: the dust particle size d is 2, 4, 6, 8, 10, 14, 34, 54, and 74 μm, respectively; the wind speed v of the speed-adjusting fan (12) is 0.3, 0.6, 0.9, 1.2, and 1.5 m / s, respectively; the horizontal acceleration a of the dust particles in the electromagnetic field of the diversion monitoring device (9) is 1.5×10 3 , 1.5×10 4 , 1.5×10 5 , 1.5×10 6 , 1.5×10 7 m / s 2 ; S2: Numerical model solution: select density ρ as 2100kg / m 3 The coal dust is measured in the cylindrical coordinate system (r, z) Establishing the geometric model of magnetic diversion module, adding turbulent field, magnetic field and particle tracking physical field, solving the physical field, obtaining the numerical model solution results, and obtaining the data points reflecting the relationship between the dust particle size d and the dust settling starting coordinate r1 and the settling ending coordinate r2; S3: Establishing a particle size screening formula: According to the solution result of step S2, the functional relationship between the dust settling starting coordinate r1 and the settling ending coordinate r2 and the dust particle size d is fitted to obtain the Logistic relationship: The parameter b1 and wind speed v in the Logistic equation conform to the Lorentz equation: b2 and wind speed v conform to the linear relationship: b2 = 4.66 × 10 -4 v+3.57×10 -6 , b3 and acceleration a conform to the Allometric relationship: b3 = -2.8 × 10 -4 a -0.33 , b4 and acceleration a conform to the Allometric relationship: b4 = 15.9a -0.12 , c1 and acceleration a conform to the Allometric relationship: c1 = 0.2a -0.13 , c2 and acceleration a conform to the Allometric relationship: c2 = 0.005a -0.13 According to Newton's second law, the acceleration a, wind speed v, electromagnet current I, particle density ρ and particle size d conform to the relationship: Combining the above equations, the equations for the relationship between the dust settling starting coordinate r1 and the settling ending coordinate r2 and the dust particle size d are as follows: In the formula, r1 is the starting coordinate of dust settling; r2 is the ending coordinate of dust settling; d is the particle size of dust particles; v is the wind speed of the speed-adjustable fan; a is the centripetal acceleration of dust particles; I is the current of the electromagnet, and ρ is the density of dust particles; S4: adjusting the height-adjustable support frame (10) to the desired sampling height, and simultaneously turning on the axial flow fan (2), the timer (3), and the flow meter (4), capturing the floating dust and storing it in a dust collecting bottle (11) filled with distilled water, and recording the capturing time and flow value through the timer (3) and the flow meter (4); S5: Install the dust collecting bottle (11) on the magnetic stirring base, turn on the magnetic stirring base (5-3) to drive the porous magnetic net (5-1) to rotate at a high speed, so that the dust in the dust collecting bottle (11) is in a uniformly suspended suspension state; when the horizontal initial velocity v of the outflow of the multi-hole nozzle (8) is determined, the particle density ρ and the particle size d1 of the captured particulate matter are substituted into the screening formula, and the current I of the electromagnet (9-2) is substituted to calculate the dust settling starting coordinates r1 and r2 as the dust settling ending coordinates, then the particle settling range of the particle with a particle size of d is a ring with an inner diameter of r1 and an outer diameter of r2; similarly, the particle settling range of the particle with a particle size of d2 (d2>d1) is a ring with an inner diameter of r3 and an outer diameter of r4; the captured particle size range of d1 to d2 is obtained. The radial difference values ​​of the diverter baffle (9-3) when capturing particles |r2-r1| and |r4-r3| can be changed by changing the current of the electromagnet (9-2) to change the radial difference value of the diverter baffle (9-3), so as to achieve the effect of capturing particles of different particle size ranges by changing the current of the electromagnet (9-2); similarly, when the current I of the electromagnet (9-2) is determined, the effect of capturing particles of different particle size ranges can also be achieved by changing the horizontal initial velocity v of the multi-hole nozzle (8); the corresponding parameters of the above device are adjusted to the values ​​of the calculated results, so that the dust particles of each particle size range to be analyzed and obtained are deposited on the high-efficiency filter cotton (9-5) between the slits of each group of baffles in the storage chamber (9-4) until the suspension in the dust collecting bottle (11) is sprayed out; S6: Dust particles in each particle size range are deposited on the high-efficiency filter cotton (9-5) between the slits of each group of partitions in the storage chamber (9-4). The change in the mass of the filter cotton causes the oscillation frequency of the nested conical element (9-8) to change. The oscillation frequencies of the two nested conical elements are driven by the amplifier circuit (9-7) and the frequency counting circuit (9-6) to obtain two mass values, one large and one small. The two values ​​are subtracted to obtain the mass gain of the particles in the target particle size range; the weight gain is divided by the product of the time and flow value in step S4 to obtain the mass concentration of the dust particles in each particle size range.

2. A dust particle size screening system used in the dust particle size screening method according to claim 1, characterized in that: The dust particle size screening system includes an on-site floating dust capture device and a dust particle size screening device; The on-site floating dust collection device comprises a height-adjustable support frame (10), a cyclone separation device (1), an axial flow fan (2), a timer (3), a flow meter (4), and a dust collecting bottle (11); the height-adjustable support frame (10) supports the axial flow fan (2); the axial flow fan (2), the flow meter (4), and the dust collecting bottle (11) are sequentially connected in series and sealed along the axial direction; the cyclone separation device (1) is fixed to the air inlet of the axial flow fan (2); the timer (3) is fixed to the connection pipe between the axial flow fan (2) and the flow meter (4); the cyclone separation device (1) is used to separate dust and gas, so that the dust enters the dust collecting bottle (11) along the axial flow fan (2) and the flow meter (4); The dust particle size screening device comprises a magnetic stirring device (5), an atomizer (6), a drying tube (7), a speed regulating fan (12), a multi-hole nozzle (8) and a flow diversion monitoring device (9); the atomizer (6), the drying tube (7), the speed regulating fan (12) and the multi-hole nozzle (8) are connected in series in a sealed manner in the axial direction, and the multi-hole nozzle (8) is connected to the flow diversion monitoring device (9); the magnetic stirring device (5) comprises a magnetic stirring base (5-2) and a multi-porous magnetic net (5-1); the dust collecting bottle (11) is placed on the magnetic stirring base (5-2), and the multi-porous magnetic net (5-1) is placed inside the dust collecting bottle (11); the magnetic stirring device (5) is used to make the dust in the dust collecting bottle (11) in a uniformly suspended suspension state; the speed regulating fan (12) causes the suspension to pass through the atomizer (6) and the drying tube (7) and then enter the flow diversion monitoring device (9) through the multi-hole nozzle (8).

3. A dust particle size screening system according to claim 2, characterized in that: The flow diversion monitoring device (9) comprises a magnetic flow diversion module and a concentration monitoring module; the magnetic flow diversion module comprises a spiral guide blade (9-1), an electromagnet (9-2), a flow diversion baffle (9-3), a storage chamber (9-4) and a high-efficiency filter cotton (9-5); the spiral guide blade (9-1) provides radial force on the particles, and the electromagnet (9-2) provides axial force on the particles; particles of different particle sizes are subjected to different resultant forces, so that they fall into the flow diversion baffle (9-3) between corresponding radii and then enter the storage chamber (9-4); the magnetic induction intensity of the electromagnet (9-2) can be adjusted by controlling the current; the flow diversion baffle (9-3) is composed of multiple groups of concentric mechanical flow diversion baffles, which can expand / contract radially, and the electromagnet (9-2) and the flow diversion baffle (9-3) can be adjusted to store particles of different particle size segments; the high-efficiency filter cotton (9-5) is placed in the storage chamber (9-4) at the outlet of the diversion baffle (9-3) at the bottom; the concentration monitoring module is connected to the bottom of the storage chamber (9-4), including a frequency counting circuit (9-6), a driving amplifier circuit (9-7), a nested conical element (9-8), a fixed base (9-9) and an exhaust pipe (9-10); the nested conical element (9-8) is formed by two conical elements being nested, the upper end of which is connected to the high-efficiency filter cotton (9-5), and the lower end is installed on the top of the fixed base (9-9); when working, the driving amplifier circuit (9-7) drives the high-efficiency filter cotton (9-5) and the nested conical element (9-8) to vibrate at a natural frequency, and when particles fall on the high-efficiency filter cotton (9-5), the vibration frequency of the nested conical element (9-8) changes, and the frequency counting circuit (9-6) measures the vibration frequency of the nested conical element (9-8) to calculate the mass increment of the particulate matter.

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