Solid dust particulate matter screening device and screening method

Abstract

The invention belongs to the technical field of air solid dust particulate matter detection, and particularly relates to a solid dust particulate matter screening device and method. The device comprises a gas driving and flow stabilizing module used for providing and adjusting working gas, so that the working gas enters the device at a set flow; the resuspension module is used for accommodating solid particle samples to be screened; the particle size cutting module is used for performing inertial cutting classification on the airflow carrying the particles, separating and removing the particles with the particle size larger than the preset cutting particle size and outputting fine particles with the particle size smaller than or equal to the preset cutting particle size; the enrichment module is specifically a filter membrane fixer and is used for enriching and fixing the fine particulate matters on a filter membrane; according to the dry-method controllable and repeatable fine particle screening and enriching device, dry-method controllable and repeatable fine particle screening and enriching are achieved, and physicochemical property analysis, toxicological evaluation or component comparison research can be conveniently conducted on inhalable particles such as PM2.5.

Description

Technical Field

[0001] This invention belongs to the field of airborne solid dust particulate matter detection technology, specifically relating to a sieving device and method for solid dust particulate matter (such as dust / sand / dust). Background Technology

[0002] Solid dust samples (such as road dust, sandstorms, industrial dust, and dust collected by bag filters) have a wide particle size range and are prone to agglomeration. Different particle size ranges often show significant differences in mineral phases, trace elements, soluble salts, and organic components. PM2.5 is particularly prone to this. 2.5 Fine particles can enter the respiratory system and have higher value for health-related research.

[0003] Existing mechanical screening methods are used for micron-level screening, especially for PM2.5. 2.5 Separation by scale is difficult to achieve effectively; wet fractionation may introduce problems such as dissolution, adsorption, secondary reactions and changes in surface properties; and air particle sampling and cutting devices are mostly for direct sampling of ambient air and lack a laboratory sieving system for "solid sample → resuspension → cutting → filter membrane enrichment".

[0004] Therefore, there is a need for a fine particulate matter sieving device and method that is simple in structure, has controllable operating conditions, good repeatability, and is convenient for subsequent chemical / morphological analysis. Summary of the Invention

[0005] The purpose of this invention is to provide a solid dust particle sieving device and method capable of stably resuspending solid dust particles, classifying and cutting them according to a preset particle size, and enriching them with a filter membrane, so as to obtain a target particle size range (such as PM2.5). 2.5 The enriched sample can be used to recover coarse particles for control analysis.

[0006] The solid dust particle screening device provided by this invention includes: a gas-driven and flow-stabilizing module, a resuspension module, a particle size cutting module, and an enrichment module; wherein:

[0007] The gas drive and flow stabilization module is used to provide and regulate the working gas so that the working gas enters the device at a set flow rate; the gas drive and flow stabilization module is provided with at least one of a pressure regulating valve, a flow meter and / or a mass flow controller to achieve a constant or repeatable working flow rate.

[0008] The resuspension module is a closed resuspension cavity (e.g., a suspension bottle) used to contain solid particle samples to be screened. The resuspension module is provided with a gas inlet and a gas outlet. After the working gas enters through the gas inlet, it produces a purging / fluidizing effect on the particle sample in the cavity, causing the particles to be resuspended and output through the gas outlet with the gas flow. The bottom of the resuspension module is a conical or arc-shaped converging structure to form a particle carrying area, so as to reduce the deposition dead zone and improve the resuspension stability.

[0009] In the resuspension module, the gas inlet is located at the bottom of the cavity, so that the incoming gas forms a directional blowing or fluidizing airflow on the particle carrying area to improve the resuspension efficiency; the gas inlet is a tangential air intake structure, so that a cyclone flow field is formed in the resuspension cavity; the gas outlet is located at the top or center of the cavity, and is used to output the airflow carrying the particles.

[0010] The particle size cutting module has its inlet connected to the gas outlet of the resuspension module. It is used to perform inertial cutting and classification on the airflow carrying particulate matter, separate and remove particles with a particle size larger than the preset cutting particle size, and output fine particles with a particle size less than or equal to the preset cutting particle size.

[0011] The particle size cutting module includes a cyclone cutting head, which uses centrifugal inertia to achieve graded cutting according to a preset particle size;

[0012] The enrichment module is connected to the output end of the particle size cutting module; specifically, it is a filter membrane holder used to enrich and fix the fine particles onto the filter membrane; the filter membrane holder includes an upper cover, a lower seat and a sealing ring, the filter membrane is clamped between the upper cover and the lower seat to form an effective filtration area, and it has a quick-release structure to enable quick replacement of the filter membrane and reduce secondary pollution.

[0013] Furthermore:

[0014] The gas-driven and flow-stabilizing module also includes a particle filter and / or a dryer to reduce the impact of background particles and humidity on the screening results.

[0015] In the resuspension module, the gas inlet supplies gas to the particle carrying area through a porous diffuser plate, nozzle array, or annular slit structure to form a uniform fluidized airflow and reduce particle agglomeration.

[0016] The resuspension module is also equipped with anti-deposition guides, baffles and / or external vibration / tapping mechanisms to reduce the impact of wall deposition and fall on the fluctuation of output concentration.

[0017] The cyclone cutting head is a detachable and replaceable structure, which can achieve different preset cutting particle sizes by replacing the cutting head body, inlet part and / or nozzle part.

[0018] The particle size cutting module is equipped with a coarse particle collection chamber or collection cup for collecting the coarse particle samples that have been cut away for weighing or comparative analysis.

[0019] The filter membrane is any one or more of the following: quartz filter membrane, polytetrafluoroethylene filter membrane, glass fiber filter membrane, nylon filter membrane, or polycarbonate filter membrane.

[0020] The device is a blowing type and / or a suction type; in the suction type, a negative pressure source is provided downstream of the enrichment module and a flow controller is used to maintain a constant flow rate.

[0021] The particle size cutting module is a single-stage cutting structure or a multi-stage tandem cutting structure to obtain graded samples of different particle size ranges.

[0022] The present invention also provides a method for screening solid dust particles using the above-mentioned device, the specific steps of which are as follows:

[0023] S1, Add the solid particle sample to the resuspension module and seal it;

[0024] S2, turn on the gas drive and flow stabilization module, so that the working gas enters the resuspension module at a set flow rate, so that the particle sample is resuspended and output through the gas outlet with the gas flow.

[0025] S3, the airflow carrying particulate matter is sent into the particle size cutting module to separate and remove particles with a particle size larger than the preset cutting particle size;

[0026] S4, fine particles with a particle size less than or equal to the preset cutting particle size enter the enrichment module and are enriched and fixed on the filter membrane;

[0027] S5, stop the gas supply or stop the suction, and remove the filter membrane for weighing or subsequent analysis.

[0028] Furthermore:

[0029] Samples are dried, lightly broken up, and / or oversized impurities are removed before sieving to improve resuspension uniformity and repeatability.

[0030] In S2, the working gas is clean air, nitrogen, or an inert gas; and humidity and background particles are reduced through drying and filtration.

[0031] In S3, the particle size cutting module is first calibrated to establish the correspondence between the working flow rate and the cutting particle size, so as to improve the cutting accuracy and batch comparability.

[0032] In S3, the preset cutting particle size is PM 2.5 PM can be achieved by replacing the cutting components and / or adjusting the working flow rate. 10 PM4, PM 2.5 Any cutting particle size in PM1.

[0033] The particulate matter screening device provided by this invention forms a stable dust-carrying airflow by driving a resuspension module with a steady-flow gas; the dust-carrying airflow enters a particle size cutting module for inertial classification; the target fine particles are enriched and fixed on the filter membrane; the resuspension module uses a lower tangential air inlet and a top center air outlet to form a cyclone flow field, and is equipped with a conical bottom, diffuser or anti-deposition / vibration structure to improve stability; the particle size cutting module is preferably a replaceable cyclone cutting head and is equipped with a coarse particle collection chamber; the enrichment module is a sealed quick-release filter membrane holder; the system can be a blowing or suction constant flow structure, and the correspondence between the cutting particle size and the flow rate can be obtained through calibration.

[0034] Beneficial effects of the invention

[0035] (1) Dry screening reduces the risk of wet screening altering surface chemistry;

[0036] (2) The cutting particle size can be switched (PM) 10 / PM 2.5 / PM1, etc.), with a wide range of applications;

[0037] (3) Fine particles are directly enriched on the filter membrane, which facilitates weighing and various analyses;

[0038] (4) Resuspension and steady-flow structures improve repeatability and batch comparability;

[0039] (5) Both coarse and fine samples can be obtained simultaneously for particle size effect control studies;

[0040] (6) It can cover both blowing and suction system forms, reducing the possibility of being bypassed. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the fine particulate matter screening device of the present invention.

[0042] The numbers in the diagram are: 1—Gas source; 2—Resuspension module; 3—Gas inlet; 4—Gas outlet; 5—Cyclone cutter head; 6—Filter membrane holder. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make equivalent substitutions in terms of structural form, parameter range, and material selection without departing from the concept of the present invention, and all such substitutions should fall within the scope of protection of the present invention.

[0044] Example 1: PM 2.5 Screening (sand / dust particle size difference study)

[0045] Device structure:

[0046] Gas-driven and flow-stabilizing module: gas source (compressed air or gas cylinder) + pressure regulating valve + flow meter or mass flow controller (MFC) + dryer + particulate filter;

[0047] Resuspension module: a sealed resuspension chamber with tangential air intake at the bottom, a cone-shaped particle-collecting area at the bottom, and an air outlet at the top center; slight vibration / tapping can be added if necessary.

[0048] Particle size cutting module: Removable and replaceable cyclone cutting head (PM) 2.5 ), with a coarse particle collection cup;

[0049] Enrichment module: Sealed quick-release filter membrane holder, filter membrane can be selected from quartz (suitable for carbon composition / thermo-optic analysis) or PTFE (suitable for inorganic ion / metal digestion).

[0050] Operating steps:

[0051] (1) Sample pretreatment: The dust deposited on a city road was selected as the test object. After the sample was dried in an oven at 40 ℃ for 4 hours to remove moisture, it was passed through a 20-mesh (0.85 mm) standard sieve to remove obviously large impurities such as stones, and the "original fine soil sample" was obtained.

[0052] (2) Sample loading and debugging: Accurately weigh 20g of the original fine soil sample and place it in the resuspension module. Load the enrichment module with a pre-weighed 47mm quartz fiber filter membrane.

[0053] (3) Resuspension and sieving: Turn on the gas source and adjust the mass flow controller (MFC) to stabilize the system flow rate at 16.7 L / min (simulating PM2.5). 2.5 (Standard sampling flow rate). The airflow enters the cavity through the tangential inlet, forming a cyclone flow field, which drives the bottom particles to be resuspended and output with the airflow.

[0054] (4) Cutting and enrichment: The airflow carrying particulate matter enters the PM 2.5 Cyclone cutting head utilizes centrifugal inertia to remove aerodynamically oriented particles larger than 2.5 mm. Coarse particles (m) are collected, while the remaining fine particles are carried by the airflow into the enrichment module and retained on the filter membrane. The device runs continuously for 40 minutes, during which the resuspending bottle wall is gently tapped every 10 minutes to reduce powder adhesion.

[0055] (5) End and sampling: Stop the gas supply, take out the filter membrane carrying the particulate matter, put it into the constant temperature and humidity chamber for equilibration and weigh it; at the same time, recover the coarse particulate sample in the collection cup below the cyclone cutter head.

[0056] (6) Results presentation and analysis:

[0057] To verify the performance of the device, the "original sample" and the "PM" obtained by screening by this device were compared. 2.5Comparative analysis was conducted on the enriched samples. Particle size sieving effect: A laser particle size analyzer was used to detect the particles eluted from the filter membrane. The results showed that the particle size distribution curve of the enriched samples exhibited a clear cutoff characteristic, with its D... 90 (90% of particles are smaller than this particle size) The value is 2.38 m, D 50 The value is 1.12 m. This indicates that the flow field control and cyclone cutting of this device are precisely coordinated, successfully removing PM. 2.5 The dust was separated from the widely distributed dust, and the sieving accuracy met the experimental requirements.

[0058] Differences in chemical composition:

[0059] Heavy metal analysis: ICP-MS detection revealed that PM2.5... 2.5 The concentrations (mg / kg) of heavy metals such as lead (Pb) and zinc (Zn) in the enriched sample were 4.2 times and 3.6 times that of the original sample, respectively. This confirms that toxic heavy metals tend to accumulate in fine particulate matter, indicating that directly analyzing the original sample would severely underestimate the environmental toxicity risk of fine particulate matter.

[0060] Water-soluble ion analysis: Detection using ion chromatography (IC) for PM. 2.5 The sulfate and nitrate content in the sample was significantly higher than that in the coarse particle fraction. More importantly, because this device uses dry airflow sieving, it completely avoids the problems of water-soluble ion dissolution and loss or chemical reactions caused by traditional wet sieving (such as sedimentation), ensuring the authenticity of the chemical composition data.

[0061] In summary, this embodiment verifies that the device can achieve efficient, dry, and high-precision PM2.5 analysis of solid dust samples in a laboratory environment. 2.5 Component sieving and enrichment provide a reliable sample preparation method for subsequent studies on the physical and chemical properties and toxicology of particles, and solve the technical problem of non-destructive classification of micron-sized dust.

Claims

1. A solid dust particle screening device, characterized in that, include: Gas-driven and flow-stabilizing module, resuspension module, particle size distribution module, enrichment module; among which: The gas drive and flow stabilization module is used to provide and regulate the working gas so that the working gas enters the device at a set flow rate; the gas drive and flow stabilization module is equipped with at least one of a pressure regulating valve, a flow meter and / or a mass flow controller to achieve a constant or repeatable working flow rate; The resuspension module is a closed resuspension cavity used to contain solid particle samples to be screened. The resuspension module is equipped with a gas inlet and a gas outlet. After the working gas enters through the gas inlet, it produces a purging / fluidizing effect on the particle sample in the cavity, causing the particles to be resuspended and output through the gas outlet with the gas flow. The bottom of the resuspension module is a conical or arc-shaped converging structure to form a particle carrying area, so as to reduce the deposition dead zone and improve the resuspension stability. In the resuspension module, the gas inlet is located at the bottom of the cavity, so that the incoming gas forms a directional blowing or fluidizing airflow on the particle carrying area to improve the resuspension efficiency; the gas inlet is a tangential air intake structure, so that a cyclone flow field is formed in the resuspension cavity; the gas outlet is located at the top or center of the cavity, and is used to output the airflow carrying the particles. The particle size cutting module has its inlet connected to the gas outlet of the resuspension module. It is used to perform inertial cutting and classification on the airflow carrying particulate matter, separate and remove particles with a particle size larger than the preset cutting particle size, and output fine particles with a particle size less than or equal to the preset cutting particle size. The particle size cutting module includes a cyclone cutting head, which uses centrifugal inertia to achieve graded cutting according to a preset particle size; The enrichment module is connected to the output end of the particle size cutting module; specifically, it is a filter membrane holder used to enrich and fix the fine particles onto the filter membrane; the filter membrane holder includes an upper cover, a lower seat and a sealing ring, the filter membrane is clamped between the upper cover and the lower seat to form an effective filtration area, and it has a quick-release structure to enable quick replacement of the filter membrane and reduce secondary pollution.

2. The solid dust particle screening device according to claim 1, characterized in that, The gas-driven and flow-stabilizing module also includes a particle filter and / or a dryer to reduce the impact of background particles and humidity on the screening results.

3. The solid dust particle screening device according to claim 1, characterized in that: In the resuspension module, the gas inlet supplies gas to the particle carrying area through a porous diffuser plate, nozzle array, or annular slit structure to form a uniform fluidized airflow and reduce particle agglomeration. The resuspension module is also equipped with anti-deposition guides, baffles and / or external vibration / tapping mechanisms to reduce the impact of wall deposition and fall on the fluctuation of output concentration.

4. The solid dust particle screening device according to claim 1, characterized in that, The cyclone cutting head is a detachable and replaceable structure, and different preset cutting particle sizes can be achieved by replacing the cutting head body, inlet part and / or nozzle part.

5. The solid dust particle screening device according to claim 1, characterized in that, The particle size cutting module is equipped with a coarse particle collection chamber or collection cup for collecting the coarse particle samples that have been cut away for weighing or comparative analysis.

6. The solid dust particulate matter screening device according to claim 1, characterized in that, The particle size cutting module is a single-stage cutting structure or a multi-stage tandem cutting structure to obtain graded samples of different particle size ranges.

7. The solid dust particle screening device according to claim 1, characterized in that, In the enrichment module, the filter membrane is any one or more of the following: quartz filter membrane, polytetrafluoroethylene filter membrane, glass fiber filter membrane, nylon filter membrane, or polycarbonate filter membrane.

8. The solid dust particle screening device according to any one of claims 1-7, characterized in that, The device is a blowing type and / or a suction type; in the suction type, a negative pressure source is provided downstream of the enrichment module and a flow controller is used to maintain a constant flow rate.

9. The method for screening solid dust particles using the apparatus described in any one of claims 1-8, characterized in that, The specific steps are as follows: S1, Add the solid particle sample to the resuspension module and seal it; S2, turn on the gas drive and flow stabilization module, so that the working gas enters the resuspension module at a set flow rate, so that the particle sample is resuspended and output through the gas outlet with the gas flow. S3, the airflow carrying particulate matter is sent into the particle size cutting module to separate and remove particles with a particle size larger than the preset cutting particle size; S4, fine particles with a particle size less than or equal to the preset cutting particle size enter the enrichment module and are enriched and fixed on the filter membrane; S5, stop the gas supply or stop the suction, and remove the filter membrane for weighing or subsequent analysis.

10. The method for screening solid dust particles according to claim 1, characterized in that: Drying, lightly breaking up and / or removing oversized impurities from the sample before sieving improves resuspension uniformity and repeatability. In S2, the working gas is clean air, nitrogen, or an inert gas; and humidity and background particles are reduced through drying and filtration. In S3, the particle size cutting module is first calibrated to establish the correspondence between working flow rate and cutting particle size, so as to improve cutting accuracy and batch comparability. In S3, the preset cutting particle size is PM 2.5 PM can be achieved by replacing the cutting components and / or adjusting the working flow rate. 10 PM4, PM 2.5 Any cutting particle size in PM1.

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