Nanoparticle size fractionation detection apparatus and method

Abstract

The application discloses a kind of nanoparticle particle size grading detection devices, it is related to particle detection technical field, including multistage cascade impactor aerosol classifier, multiple shunt bin, one saturation section, multiple condensation sections and multiple counters, the impactor classifier entrance of lower stage is connected with the impactor classifier outlet of upper stage, the particle size of particle gradually decreases by multiple impact plates from top to bottom trapping, each side outlet is connected to the inlet of shunt bin, the first outlet of shunt bin is connected with saturation section after passing through filter device, second outlet is located at saturation section outlet, and nanoparticle can be wrapped by sheath flow in saturation section and enter condensation section after being discharged through second outlet, one counter is provided at the outlet of each condensation section.The application further discloses a kind of nanoparticle particle size grading detection method, is implemented using the nanoparticle particle size grading detection device as described above.The application makes the detection of nanoparticle more accurate, and detection rate is faster, and device volume is smaller.

Description

Technical Field

[0001] This invention relates to the field of particle detection technology, and in particular to a device and method for classifying and detecting the size of nanoparticles. Background Technology

[0002] Currently, there are various devices for detecting nanoparticles, roughly as follows: Condensation Nucleus Particle Counter (CPC): This device uses supersaturated organic working fluid to cause nanoparticles to grow to an optically measurable size (>1μm), and measures the total number concentration using the principle of light scattering. However, it can only output the total concentration and cannot distinguish particle size distribution, failing to meet the needs of particulate matter toxicity assessment (such as the proportion of ultrafine particles UFP) or pollution source apportionment. Scanning Electromigration Particle Size Spectrometer (SMPS): This is a combined system of Differential Electromigration Analyzer (DMA) and Condensation Nucleus Particle Counter (CPC). The DMA uses an electric field to screen particles of specific sizes, and the CPC is used to detect particle size distribution (3-1000nm). However, such devices are bulky (>50L), expensive (>80,000 USD), rely on precise laboratory electrical components and environment, are complex to operate, and require frequent calibration of electric field voltage and flow rate, making them unsuitable for on-site detection. Furthermore, the differential electromobility analyzer (DMA) sequentially feeds particles into a condensation nucleus particle counter (CPC) after step-by-step size screening, with each step taking approximately 10-30 seconds. Full-spectrum measurement requires 5-15 minutes, resulting in slow detection speed (5-15 minutes for a single full-spectrum scan) and an inability to monitor dynamic emission processes in real time. Therefore, there is an urgent need for a nanoparticle size classification and detection device and method to address the aforementioned technical problems. Summary of the Invention

[0003] The purpose of this invention is to provide a nanoparticle size classification detection device and method to solve the problems existing in the prior art, so as to make the nanoparticle classification detection more accurate, the detection rate faster, and the device smaller in size.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] This invention provides a nanoparticle size classification and detection device, comprising a multi-cascade impactor aerosol classifier, multiple flow dividers, a saturation section, multiple condensation sections, and multiple counters. The multi-cascade impactor aerosol classifier includes multiple impactors distributed vertically. Each impactor classifier includes an air inlet, an air outlet, an impactor plate, and a side outlet. The inlet of the next-stage impactor classifier is connected to the outlet of the previous-stage impactor classifier. The particle size captured by the multiple impactors gradually decreases from top to bottom. Each side outlet is connected to the inlet of the flow divider. Each flow divider has a first outlet and a second outlet. The first outlet is connected to the saturation section after passing through a filter. The second outlet is located at the outlet of the saturation section. After being discharged through the second outlet, the nanoparticles can be enveloped by the sheath flow in the saturation section and enter the condensation section. Each condensation section outlet is equipped with a counter.

[0006] In some embodiments, each of the condensation sections includes a condensation device capable of providing different condensation temperatures depending on the particle size of the nanoparticles.

[0007] In some embodiments, the counter is an optical particle counter.

[0008] In some embodiments, a heating device is also included, which is disposed within the saturation section for heating the air within the saturation section.

[0009] In some embodiments, the filtering device is a first filter, the first outlet is connected to the inlet of the first filter, and the outlet of the first filter is connected to the saturation section.

[0010] In some embodiments, the system further includes an injection device and a drainage device, wherein the injection port of the injection device is connected above the saturation section, and the drainage port of the drainage device is connected to the side of the saturation section.

[0011] In some embodiments, a collection pipe and a flow-limiting orifice are also included. The collection pipe is connected to the outlet of each of the condensation sections and is used to collect the substances discharged from the condensation sections. The outlet of each of the condensation sections is provided with the flow-limiting orifice.

[0012] In some embodiments, a second filter and a vacuum pump are also included, the second filter being disposed on the manifold and the vacuum pump being connected to the outlet end of the second filter.

[0013] In some embodiments, the device further includes an injection solenoid valve and an outlet solenoid valve, wherein the injection solenoid valve is disposed between the injection device and the saturation section, and the outlet solenoid valve is disposed between the saturation section and the drainage device.

[0014] The present invention also provides a method for detecting nanoparticles, which is implemented using the nanoparticle size classification detection device described above, and includes the following steps:

[0015] Step 1: Inject gas containing the nanoparticles to be detected into the multi-cascade impactor aerosol classifier;

[0016] Step 2: The diversion chamber diverts the gas discharged from the side outlet of each stage of the impact classifier into a first part and a second part. The gas volume of the first part is 88%-92% and is discharged through the first outlet. The gas volume of the second part is 8%-12% and is discharged through the second outlet.

[0017] Step 3: The filtration device filters the gas in the first part and passes it into the saturation section to combine with the gas in the second part.

[0018] Step four: Read the reading of the counter.

[0019] The present invention achieves the following technical effects compared to the prior art:

[0020] The nanoparticle size classification and detection device provided by this invention employs a multi-stage impactor aerosol classifier to achieve physical particle classification. It utilizes mechanical sorting instead of electric field screening, achieving a higher particle flow velocity and avoiding the electric field dependence and speed bottleneck of DMA (Dispersive Aerosol Classifier). This results in faster detection speed and stronger environmental adaptability. Furthermore, multiple condensation sections share a single saturation section, reducing the number of saturation sections and overall size, making it easier to carry and use. Regarding the UFP (Ultra-Fine Particle Size) ratio of ultrafine particles, the design of the condensation and saturation sections allows the ultrafine particles to agglomerate and grow, making them detectable by the counter. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the principle of the nanoparticle size classification and detection device in some embodiments of the present invention;

[0023] Figure 2 This is a schematic diagram of the saturation section and condensation section of the nanoparticle size classification and detection device in some embodiments of the present invention.

[0024] In the diagram: 1-Multi-stage impact aerosol classifier; 101-Impact plate; 102-Side outlet; 2-Saturation section; 3-Condensation section; 4-Diverter chamber; 401-First outlet; 402-Second outlet; 5-Optical particle counter; 6-Collection pipe; 7-Flow limiting orifice; 8-First filter; 9-Liquid injection device; 10-Liquid injection solenoid valve; 11-Liquid outlet device; 12-Drain solenoid valve; 13-Second filter; 14-Air pump. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The purpose of this invention is to provide a nanoparticle size classification and detection device and method to solve the problems existing in the prior art, so as to make the nanoparticle size classification and detection more accurate, faster, and smaller in size.

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] like Figures 1-2As shown, the present invention provides a nanoparticle size classification and detection device, including a multi-cascade impactor aerosol classifier 1, multiple flow chambers 4, a saturation section 2, multiple condensation sections 3, and multiple counters. The multi-cascade impactor aerosol classifier 1 includes multiple impactor classifiers (preferably five) distributed vertically. Each impactor classifier includes an air inlet, an air outlet, an impact plate 101, and a side outlet 102. The inlet of the next-level impactor classifier is connected to the outlet of the previous-level impactor classifier. The particle size captured by the multiple impact plates 101 gradually decreases from top to bottom. Each side outlet 102 is connected to the inlet of the flow chamber 4. Each flow chamber 4 has a first outlet 401 and a second outlet 402. The first outlet 401 is connected to the saturation section 2 after passing through a filter device. The second outlet 402 is located at the outlet of the saturation section 2. After the nanoparticles are discharged through the second outlet 402, they can be wrapped by the sheath flow (filtered nanoparticles mixed with supersaturated n-butanol) in the saturation section 2 and enter the condensation section 3. A counter is provided at the outlet of each condensation section 3. A multi-stage impactor aerosol classifier 1 is used to achieve physical particle classification, replacing electric field screening with mechanical sorting. This allows for higher particle flow velocities, avoiding the electric field dependence and speed bottleneck of DMA (Dispersive Aerosol Classifier), resulting in faster detection speeds and stronger environmental adaptability. Furthermore, multiple condensation sections 3 share a single saturation section 2, reducing the number of saturation sections 2 and decreasing the overall volume (less than 20L, less than 10kg), making it convenient to carry and use. Regarding the UFP (Ultra-Fine Particle Size) ratio of ultrafine particles, the design of the condensation section 3 and saturation section 2 allows the ultrafine particles to agglomerate and grow, making them detectable by the counter.

[0030] The process is as follows: A multi-stage impactor aerosol classifier 1 separates nanoparticles into multiple parts based on their diameter. A flow divider 4 separates the gas discharged from the side outlet 102 of each impactor classifier into a first part and a second part. The first part, containing 88%-92% of the gas, is discharged through the first outlet 401 to a filter. The filter removes the particles from the first part of the gas and re-introduces the filtered pure sheath stream into the saturation section 2. The saturation section 2 creates a supersaturated vapor environment. The second part, containing 8%-12% of the gas, is discharged through the second outlet 402. After discharge, the particles act as condensation nuclei, their surfaces coated with supersaturated vapor. The main gas, after filtration, returns to the saturation section 2 as a pure sheath stream, ensuring a stable vapor environment within the saturation section 2 and preventing impurities from interfering with the particle coating process. Particles carrying supersaturated vapor enter the condensation section 3, forming condensation nuclei. These condensation nuclei are counted by a counter to determine the number of nanoparticles within each particle size range.

[0031] In some embodiments, each condensation section 3 includes a condensation device that can provide different condensation temperatures according to the particle size of the nanoparticles. When nanoparticles of different sizes act as condensation nuclei, their surface tension and vapor adsorption efficiency vary, and the required supersaturated vapor condensation conditions (such as temperature) also differ. The condensation device provides different condensation temperatures according to different particle sizes, generally in a gradient setting (e.g., ΔT = 10-30℃). If particles of different sizes share the same condensation temperature, the difference in condensation rate may lead to excessive growth of large particles and insufficient growth of small particles, or particles of different sizes may collide and agglomerate within the condensation section 3, affecting the accuracy of counting. Therefore, setting different temperatures can, to a certain extent, ensure that particles of different sizes can effectively grow to an optically measurable size. For extremely fine particles (e.g., <5nm), a lower condensation temperature is required to maintain a higher vapor saturation and promote condensation nucleus formation; for larger nanoparticles (e.g., close to 100nm), condensation can be completed at a relatively higher temperature. By adjusting the temperature gradient, the device can detect a full range of particles, from ultrafine particles (UFP) to larger nanoparticles, breaking through the detection limitations of traditional single-temperature condensation devices for small-diameter particles. Each condensation section 3 has its temperature independently controlled, allowing for the selective activation or deactivation of specific particle size channels based on detection needs (e.g., adjusting the temperature of the corresponding condensation section 3 and deactivating other channels when only focusing on 10-30nm particles), improving detection efficiency and reducing energy consumption. Traditional single-condensation devices may need to maintain a minimum operating temperature to cover the entire particle size range, resulting in wasted energy. The independent temperature control design ensures that each condensation section 3 operates only within the required temperature range, avoiding energy waste, and is particularly suitable for long-term field monitoring or battery life optimization of portable devices.

[0032] In some embodiments, the counter is an optical particle counter 5 (OPC). The optical particle counter 5 detects particles through light scattering or extinction principles (e.g., laser irradiation of particles generates scattered light, which is converted into an electrical signal by a photoelectric sensor), without requiring the particles to be charged. Compared to electrical counters that rely on particle charge (e.g., condensation nucleus counters require particles as condensation nuclei to be charged), the OPC can directly detect all types of nanoparticles, including neutral particles, charged particles, and organic / inorganic particles, making it particularly suitable for complex samples (e.g., aerosols containing oil mist, salt mist, or biological particles). The optical detection process is a purely physical signal conversion, with a response time down to the millisecond level, allowing for real-time tracking of particle concentration changes (e.g., peak monitoring in sudden pollution events), meeting the needs of industrial online monitoring or emergency detection. The optical particle counter 5 can directly calculate particle size through the quantitative relationship between scattered light intensity and particle size (e.g., Mie scattering theory), and combined with the pre-sorting function of a classifier, achieves accurate counting of particles in each size range (e.g., independent concentration data for channels such as 10nm, 20nm, and 50nm). Compared to traditional condensation nucleus counters (which can only count particles and cannot directly measure particle size), OPCs can simultaneously provide particle number concentration and particle size distribution data, reducing the complexity of using multiple devices together. OPC designs typically have a wide dynamic detection range (e.g., particle concentration from 1 particle / cm³ to 10). 5 (particles / cm³), by adjusting the laser power or photoelectric sensor sensitivity, signal saturation in high-concentration scenarios or noise interference in low-concentration scenarios can be avoided, adapting to diverse detection needs from cleanrooms to heavily polluted environments. Furthermore, the optical particle counter 5 has a mature internal structure (high integration of laser source, optical lens, and photoelectric detector), allowing for miniaturized design and direct embedding into the outlet of the condenser section 3. It is compactly integrated with modules such as the classifier and saturation section 2, making it easier to achieve portable device miniaturization compared to traditional electrical counters (which require complex gas paths or circuits). The optical system also has good sealing properties, is unaffected by external electric or magnetic fields (such as electromagnetic radiation from industrial equipment), and can operate stably in environments with strong interference (such as near motors or laboratory mass spectrometers). It has low sensitivity to gas flow rate fluctuations (only requiring stable flow rate when particles pass through the detection area), and with the sheath flow stabilization design of the split chamber 4, it can withstand slight airflow disturbances in actual detection (such as vibrations during mobile detection).

[0033] In some embodiments, the nanoparticle size classification detection device further includes a heating device, preferably a heating resistor, which is disposed within the saturation section 2 to heat the air within the saturation section 2. The heating device increases the evaporation rate of liquid n-butanol by raising the temperature of the saturation section 2, thereby increasing the vapor partial pressure in the gas phase. Combined with the temperature control of the condensation section 3, the supersaturation (the ratio of vapor pressure to saturated vapor pressure) can be precisely adjusted to ensure that particles of different sizes can act as condensation nuclei to fully adsorb vapor. For example, for particles with poor hygroscopicity (such as hydrophobic organic matter), the vapor concentration can be increased by raising the temperature of the saturation section 2, enhancing its encapsulation effect; for easily condensable particles (such as inorganic salts), the temperature can be appropriately lowered to avoid excessive growth leading to particle size overlap. If the temperature of the saturation section 2 is insufficient, n-butanol may not evaporate sufficiently, resulting in an unstable supersaturated environment. Especially when detecting high-concentration particles or high-flow gas paths, problems such as insufficient n-butanol vapor supply and incomplete particle encapsulation may occur. The heating device maintains a constant high temperature to ensure that the n-butanol vapor remains in a highly saturated state. Even when the gas flow rate fluctuates, it can quickly replenish the evaporation, avoiding detection errors caused by vapor lag (such as missed detection of small particles). In low-temperature environments, unheated saturation section 2 may experience premature particle agglomeration before entering condensation section 3 due to rapid vapor cooling, resulting in distorted particle size distribution (such as multi-sized particles agglomerating into large particles). By maintaining the high temperature of saturation section 2 through heating, the condensation process of particles in the gas path is slowed down, ensuring that particles only grow in a precisely temperature-controlled environment after entering the corresponding condensation section 3, avoiding the damage to classification accuracy caused by "pre-condensation". Moreover, the heating device can be equipped with a temperature control module (such as a PID controller) to activate heating only before detection begins or when the vapor concentration is insufficient, and maintain a constant temperature after reaching the set temperature, avoiding energy waste caused by continuous full-power heating, which is suitable for battery management of portable devices.

[0034] In some embodiments, the filtration device is a first filter 8, with a first outlet 401 connected to the inlet of the first filter 8, and the outlet of the first filter 8 connected to the saturation section 2. Although the gas discharged from the first outlet 401 of the split chamber 4 (88%-92%) has undergone preliminary separation by the classifier, it may still carry a small amount of uncaptured residual particles. The first filter 8 (such as a HEPA or ULPA high-efficiency particulate air filter) can trap residual nanoparticles, microorganisms, dust, and other impurities in the gas, ensuring that the sheath flow entering the saturation section 2 is pure, particle-free clean air. The pure sheath flow, as the background gas for the saturation section 2, prevents impurity particles from competing with target particles for condensation nuclei, preventing counter miscounting due to non-target particle encapsulation (e.g., including particles outside the classification into the target particle size channel). If unfiltered sheath flow gas carrying large-diameter particles enters the saturation section 2, they may collide and agglomerate with small-diameter target particles, forming false positive particles with mixed particle sizes (e.g., 10nm and 50nm particles agglomerating into 60nm particles), causing the counter to misjudge as larger-diameter particles, thus compromising classification accuracy. The filtration design removes large particles and cuts off potential pathways for cross-size aggregation, ensuring that each condensation section 3 receives only pure particles within a single size range, thus maintaining the particle size separation effect of the classifier.

[0035] In some embodiments, the nanoparticle size classification detection device further includes a liquid injection device 9 (liquid injection bottle) and a liquid discharge device 11 (liquid discharge pump). The liquid injection port of the liquid injection device 9 is connected above the saturation section 2 and is located between the outlet of the first filter 8 and the saturation section 2. The liquid discharge port of the liquid discharge device 11 is connected to the side of the saturation section 2 and is located between the saturation section 2 and the inlet of the first filter 8. During continuous operation, the vapor medium (such as water, glycerol, etc.) in the saturation section 2 may be consumed by evaporation or discharged with particle encapsulation, resulting in a decrease in vapor concentration and insufficient supersaturation. The liquid injection device 9 injects liquid medium into the gas path (clean sheath flow path) between the saturation section 2 and the first filter 8, and uses a heating device or the high-temperature environment of the saturation section 2 to make it evaporate rapidly, replenishing the vapor consumption in real time, ensuring the stability of the supersaturated environment, and avoiding the missed detection of small particles due to insufficient vapor. After detecting high-concentration particle samples, a large number of unencapsulated particles or agglomerates may remain in the saturation section 2, affecting the detection accuracy of subsequent low-concentration samples (e.g., residual particles act as false agglomeration nuclei, causing baseline drift). The residual liquid is drained by the draining device 11 and the cleaning medium is injected by the injection device 9, which can quickly clean the interior of the saturation section 2, realize automatic cleaning between testing batches, and improve the efficiency of multi-task testing. Incompletely evaporated liquid medium, water-soluble impurities (such as inorganic salts) carried by particles, or chemical contaminants in the saturation section 2 will form condensate and deposit at the bottom. If not drained in time, this may: clog the gas nozzle or drain port; breed microorganisms (e.g., in a long-term humid environment); corrode metal parts (e.g., with acidic condensate). The draining device 11 drains the condensate periodically or in real time, reducing the risk of impurity accumulation. This is especially suitable for industrial monitoring scenarios that operate continuously for several days or even months, reducing the frequency of manual maintenance.

[0036] In some embodiments, the nanoparticle size classification and detection device further includes a collecting pipe 6 and a flow-limiting orifice 7. The flow rate of the flow-limiting orifice 7 is limited to 0.4 L / min. Each outlet of the condensing section 3 is provided with a flow-limiting orifice 7. The collecting pipe 6 is connected to the outlet of each condensing section 3 to collect the substances discharged from the condensing section 3. When multiple condensing sections 3 operate in parallel, differences in processing precision and pipe length may lead to uneven flow rates in each channel (e.g., a certain condensing section 3 has low gas resistance and a large flow rate), causing deviations in the counter detection signal (e.g., the particle concentration in the channel with a large flow rate is diluted). The flow-limiting orifice 7 provides a constant flow resistance to the outlet of each condensing section 3 by precisely controlling the orifice size (e.g., a micron-level capillary), forcibly balancing the gas flow rate in each channel, ensuring that regardless of particle size, particles in each condensing section 3 enter the collecting pipe 6 at the same flow rate, maintaining the lateral comparability of the detection results. If the internal pressure of a certain condensing section 3 increases due to counter blockage or airflow interruption, it may cause gas backflow into the saturation section 2 or the classifier, disrupting the overall classification process. The one-way flow restriction characteristic of the flow restrictor 7 can prevent reverse airflow. At the same time, through the total flow resistance design of the manifold 6, the pressure of each condensation section 3 is maintained within a safe range, improving the system's anti-interference capability (such as in the case of sudden airflow impact).

[0037] In some embodiments, the nanoparticle size classification and detection device further includes a second filter 13 and a vacuum pump 14, wherein the vacuum pump 14 is preferably a diaphragm vacuum pump 14. The second filter 13 is disposed on the manifold 6, and the vacuum pump 14 is connected to the outlet end of the second filter 13. The particle collection efficiency of the multi-stage impact classifier is highly dependent on the gas flow rate (e.g., the inertial impact force of particles of different sizes is positively correlated with the flow rate). The vacuum pump 14 (e.g., a diaphragm pump or a peristaltic pump) provides stable negative pressure power for the entire process, including the classifier, the diversion chamber 4, and the condensation section 3, by precisely controlling the total gas flow rate (e.g., 10 L / min), thus avoiding particle size classification deviations caused by flow rate fluctuations (e.g., if the flow rate is too fast, small particles may not be captured and enter the next stage). Although the gas discharged from the manifold 6 removes most of the particles through the condensation section 3, it may still carry a small number of uncounted nanoparticles (e.g., particles at the classification boundary size, particles that are not completely condensed).

[0038] The second filter 13 (such as a high-efficiency HEPA filter or activated carbon filter) can trap residual nanoparticles, volatile organic compounds (VOCs), or biological particles in the exhaust gas, preventing the gases released during the detection process from causing harm to operators or the environment (such as when detecting hazardous industrial particles). If the suction pump 14 draws air directly from the outside (such as when portable equipment is used outdoors), dust and moisture in the environment may seep back into the gas path through the pump body, contaminating the condenser section 3 or the counter. The second filter 13 is located between the manifold 6 and the suction pump 14, which can filter external impurities drawn in by the pump, and at the same time prevent pump oil vapor (such as oil mist from a piston pump) from diffusing back into the detection gas path, avoiding false positive signals generated by the optical particle counter (OPC) due to oil mist scattering.

[0039] In some embodiments, the nanoparticle size classification and detection device further includes an injection solenoid valve 10 and an outlet solenoid valve 12. The injection solenoid valve 10 is disposed between the injection device 9 and the saturation section 2, and the outlet solenoid valve 12 is disposed between the saturation section 2 and the drainage device 11. The injection solenoid valve 10 precisely adjusts the liquid medium injection volume (e.g., 0.1 mL per injection) through pulse width modulation (PWM) or on / off control, avoiding the over- or under-injection problems of traditional manual injection or constant flow pumps. For example, when detecting highly hygroscopic particles, the solenoid valve can be triggered after classification to quickly inject high-concentration glycerol vapor, enhancing encapsulation efficiency; when detecting low-concentration particles, the injection volume is reduced to decrease vapor background interference. The outlet solenoid valve 12 can open at a preset cycle (e.g., once per hour) to discharge the condensate (containing particulate impurities and dilution medium) at the bottom of the saturation section 2, preventing inorganic salt crystallization from clogging the nozzle or microbial growth.

[0040] Example 2

[0041] This embodiment also provides a method for nanoparticle size classification and detection, implemented using the nanoparticle size classification and detection device in Embodiment 1, including the following steps:

[0042] Step 1: Inject gas containing the nanoparticles to be detected into the multi-cascade impactor aerosol classifier 1.

[0043] Step 2: The diversion chamber 4 diverts the gas discharged from the side outlet 102 of each impact classifier into a first part and a second part. The gas volume of the first part is 88%-92%, preferably 90%, and is discharged through the first outlet 401. The gas volume of the second part is 8%-12%, preferably 10%, and is discharged through the second outlet 402.

[0044] Step 3: The filtration device filters the gas in the first part and passes it into the saturation section 2 to combine with the gas in the second part.

[0045] Step 4: Read the counter reading.

[0046] More specifically, the multi-stage impactor aerosol classifier utilizes the principle of inertial impaction. Through nozzles of different orifice diameters and controlled airflow velocity, particles of different sizes impact the corresponding impact plates due to inertial differences, achieving preliminary classification of polydisperse particles. A split chamber between the saturation and condensation sections divides the sample gas after each impact into two streams. Approximately 10% of the stream, carrying particles, directly enters the condensation section via a capillary tube. The remaining 90% of the stream is filtered through a first filter to form a pure sheath stream, which then enters the saturation section. In the saturation section, the sheath stream is wetted with organic working fluid, creating a supersaturated vapor environment. Particles at the capillary outlet are enveloped by the supersaturated sheath stream and undergo heterogeneous condensation in the condensation section. The particles act as condensation nuclei, causing the working fluid to condense on their surface, increasing the particle size to the micrometer level. An optical particle counter (OPC) is used to measure the micrometer-sized particles condensed and grown from the condensation section. A data acquisition card collects the pulse signals from five optical particle counters, and the original concentration is calculated through flow calibration and a differential algorithm. After the five detections, the airflow is combined, filtered by the second filter, and then discharged by the diaphragm pump.

[0047] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A nanoparticle size classification and detection device, characterized in that: The system includes a multi-stage impactor aerosol classifier, multiple flow dividers, a saturation section, multiple condensation sections, and multiple counters. The multi-stage impactor aerosol classifier comprises multiple impactor classifiers distributed vertically. Each impactor classifier includes an air inlet, an air outlet, an impact plate, and a side outlet. The inlet of the next-stage impactor classifier is connected to the outlet of the previous-stage impactor classifier. The particle size captured by the multiple impact plates gradually decreases from top to bottom. Each side outlet is connected to the inlet of a flow divider. Each flow divider has a first outlet and a second outlet. One outlet is connected to the saturation section after passing through a filter device. The second outlet is located at the outlet of the saturation section. After the nanoparticles are discharged through the second outlet, they can be wrapped by the sheath flow in the saturation section and enter the condensation section. Each outlet of the condensation section is equipped with a counter. The diversion chamber diverts the gas discharged from the side outlet of each stage of the impact classifier into a first part and a second part. The gas volume of the first part is 88%-92% and is discharged through the first outlet. The gas volume of the second part is 8%-12% and is discharged through the second outlet.

2. The nanoparticle size classification and detection device according to claim 1, characterized in that: Each of the condensation sections includes a condensation device capable of providing different condensation temperatures depending on the particle size of the nanoparticles.

3. The nanoparticle size classification and detection device according to claim 1, characterized in that: The counter is an optical particle counter.

4. The nanoparticle size classification and detection device according to claim 1, characterized in that: It also includes a heating device, which is disposed within the saturation section for heating the air within the saturation section.

5. The nanoparticle size classification and detection device according to claim 1, characterized in that: The filtration device is a first filter, the first outlet is connected to the inlet of the first filter, and the outlet of the first filter is connected to the saturation section.

6. The nanoparticle size classification and detection device according to claim 5, characterized in that: It also includes an injection device and a drainage device, wherein the injection port of the injection device is connected above the saturation section, and the drainage port of the drainage device is connected to the side of the saturation section.

7. The nanoparticle size classification and detection device according to claim 1, characterized in that: It also includes a collection pipe and a flow-limiting orifice. The collection pipe is connected to the outlet of each of the condensation sections and is used to collect the substances discharged from the condensation sections. Each outlet of the condensation section is provided with the flow-limiting orifice.

8. The nanoparticle size classification and detection device according to claim 7, characterized in that: It also includes a second filter and an air pump, the second filter being disposed on the manifold and the air pump being connected to the outlet end of the second filter.

9. The nanoparticle size classification and detection device according to claim 6, characterized in that: It also includes an injection solenoid valve and an outlet solenoid valve, wherein the injection solenoid valve is disposed between the injection device and the saturation section, and the outlet solenoid valve is disposed between the saturation section and the drainage device.

10. A method for determining the particle size of nanoparticles, characterized in that: The nanoparticle size classification and detection device according to any one of claims 1-9 is used, and includes the following steps: Step 1: Inject gas containing the nanoparticles to be detected into the multi-cascade impactor aerosol classifier; Step 2: The diversion chamber diverts the gas discharged from the side outlet of each stage of the impact classifier into a first part and a second part. The gas volume of the first part is 88%-92% and is discharged through the first outlet. The gas volume of the second part is 8%-12% and is discharged through the second outlet. Step 3: The filtration device filters the gas in the first part and passes it into the saturation section to combine with the gas in the second part. Step four: Read the reading of the counter.

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