Airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device and method

Abstract

The invention discloses an airborne particulate matter laser-induced breakdown spectroscopy (LI BS) detection and analysis device and method. The device comprises a measurement device frame; the negative pressure airborne particle flow system comprises an airborne particle flow pipe, a negative pressure airflow unit and a particulate matter supply unit, the airborne particle flow pipe is not limited by gravity and can be horizontally or vertically installed, a through hole is formed in the middle of the airborne particle flow pipe, the axis of the through hole perpendicularly intersects with the axis of the airborne particle flow pipe, and the diameter of the through hole is smaller than that of the airborne particle flow pipe. The negative pressure airflow unit is connected with the two ends of the airborne particle flow pipe, and the particle supply unit is linked with the negative pressure airflow unit and conveys particles to the airborne particle flow pipe to form stable particle flow; the particle flow LI BS detection system comprises a laser, a spectrometer and a light path, and realizes LI BS spectrum excitation and detection. The device is simple in structure, the particle flow system does not need a sealing window, and particulate matter leakage-free circulating detection analysis is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of particulate chemical composition detection and analysis, and particularly to an airborne particulate laser-induced breakdown spectroscopy (LIBS) detection and analysis device and method. Background Art

[0002] In-situ, on-line, and real-time detection and analysis of particulate matter with a particle size ranging from micrometers to millimeters is of great significance in many fields of the national economy, such fields including mineral resources, materials, manufacturing, agriculture, food industry, chemical industry, pharmaceutical industry, and environmental protection, etc. In the development and application fields of mineral resources, such particulate matter includes potassium fertilizer particles, alumina particles, pulverized coal, etc. Existing particulate matter detection and analysis mainly rely on traditional laboratory detection and analysis techniques that are applicable to solid substances. The operation process includes complex sample pretreatment steps such as sampling and sample preparation, as well as the detection and analysis of chemical components using standard instrument equipment. Such a status quo cannot meet the requirements of in-situ, on-line, and real-time detection and analysis and quickly obtaining particulate matter chemical composition information. Laser diffraction or scattering techniques, including Raman scattering, Rayleigh scattering, and Mie scattering, can perform in-situ and on-line detection and analysis of particulate matter, but they can only effectively detect and analyze tiny particulate matter with a particle size in the range of 0.1 to 10 micrometers, providing information on the concentration, particle size, refractive index, and simple chemical composition of the particulate matter. Laser-induced breakdown spectroscopy (LIBS), by virtue of its technical characteristics, shows the prospect of realizing in-situ, on-line, and real-time detection and quantitative analysis of the chemical composition of particulate matter with a particle size ranging from micrometers to millimeters. Existing research and development work have fully demonstrated the feasibility of LIBS particulate matter detection and analysis; and have clarified the typical forms of coupling between particulate matter and LIBS laser pulses, including particulate matter in a feed bin falling under the action of gravity onto a horizontal conveyor belt, stacked particulate matter entering the laser action area after being leveled by a baffle; particulate matter in a feed bin falling vertically freely or with the assistance of a diversion under the action of gravity to form a steady flow into the laser action area; particulate matter in a pneumatic powder conveying pipeline being shunted and stacked by a cyclone separator and forming a steady flow into the laser action area under the guidance of a downcomer; and a powder jet pump injecting particulate matter into a powder conveying pipe in a sample chamber and forming a steady flow into the laser action area with the assistance of a positive high pressure in the sample chamber.

[0003] Since the above-mentioned LIBS particulate matter detection and analysis technology is mainly designed and optimized for coal powder particles, there are certain deficiencies and defects not only in the technical solution, but also its scope of use and effectiveness are limited. The main manifestations are as follows:

[0004] 1) The horizontal conveyor belt mode requires a certain amount of material; at the same time, leveling the surface of stacked particulate matter places certain requirements on the traveling speed of the material and its physical properties, such as particle size, specific gravity, humidity, etc.

[0005] 2) After the particulate matter is directly diverted from the feed bin or through a cyclone separator to the downcomer and accumulates, it vertically falls under the action of gravity or with the assistance of a guide to form a steady flow, and it is impossible to perform LIBS detection and analysis on the horizontally moving particle flow. At the same time, the falling particle flow is in an environment of atmospheric pressure or slightly positive high pressure, making it necessary to install a window piece to avoid the escape of particulate matter and its splashing after interacting with the laser, thereby protecting the cleanliness of the optical system of the equipment. In addition, the accumulation of particulate matter in the feed bin or downcomer will inevitably introduce a delay between the generation of particulate matter and its detection, reducing or even destroying the real-time performance of LIBS detection and analysis.

[0006] 3) The method of injecting particulate matter through a powder jet pump can meet the requirements of laser excitation for both vertical and horizontal particle flows. However, the required positive high pressure causes the escape of particulate matter and the dust after its interaction with the laser, which can lead to the pollution and damage of the window piece.

[0007] Based on the above technical problems, the present invention provides an airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device and method. Summary of the Invention

[0008] The object of the present invention is to provide an airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device and method to solve the problems existing in the prior art.

[0009] To achieve the above object, the present invention provides an airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device, including:

[0010] A measurement device rack;

[0011] A negative-pressure airborne particle flow system, the negative-pressure airborne particle flow system includes an airborne particle flow pipe, a negative-pressure air flow unit, and a particulate matter supply unit. The airborne particle flow pipe is not restricted by gravity and is fixed horizontally or vertically on the measurement device rack. A perforation is provided at the middle position of the airborne particle flow pipe, and the axis of the perforation is perpendicular to and intersects with the axis of the airborne particle flow pipe. The diameter of the perforation is smaller than the diameter of the airborne particle flow pipe. The negative-pressure air flow unit is connected to both ends of the airborne particle flow pipe, and the particulate matter supply unit is linked with the negative-pressure air flow unit to convey particulate matter to the airborne particle flow pipe to form a stable particle flow;

[0012] A particle flow LIBS detection system, the particle flow LIBS detection system includes a laser, a spectrometer, and an optical path. The laser, the spectrometer, and the optical path are all arranged on the measurement device rack corresponding to the negative-pressure airborne particle flow system to achieve LIBS spectral excitation and detection.

[0013] According to the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device provided by the present invention, the negative pressure air flow unit includes a first vacuum generator, an air compressor, and a second vacuum generator connected in series in sequence. The exhaust port of the first vacuum generator is connected to the input end of the airborne particle flow tube, and the vacuum port of the second vacuum generator is connected to the output end of the airborne particle flow tube. Air valves are respectively arranged between the first vacuum generator and the air compressor, and between the second vacuum generator and the air compressor.

[0014] According to the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device provided by the present invention, the particulate matter supply unit includes a particulate matter bin. The bottom of the particulate matter bin is connected to the vacuum port of the first vacuum generator through a pipeline, the top of the particulate matter bin is connected to the exhaust port of the second vacuum generator through a pipeline, an air pipe communicating with the ambient atmosphere is installed at the top of the particulate matter bin, and a particle filter is installed on the air pipe.

[0015] According to the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device provided by the present invention, the particulate matter supply unit includes a particulate matter dish. The particulate matter dish is connected to the vacuum port of the first vacuum generator, and the exhaust port of the second vacuum generator is connected to the ambient atmosphere.

[0016] According to the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device provided by the present invention, the length of the airborne particle flow tube is 0.5 m, the inner diameter is 14 mm, the outer diameter is 16 mm, and the diameter of the perforation is 3.0 mm.

[0017] According to the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device provided by the present invention, the input air pressure at the air supply port of the first vacuum generator is 0.16 Mpa, and the input air pressure at the air supply port of the second vacuum generator is 0.30 MPa.

[0018] According to the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device provided by the present invention, the output pulse parameters of the laser are 1064 nm, 20 Hz, 8 ns, and 50 mJ.

[0019] An airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis method includes the following steps:

[0020] Step 1, build a measurement device;

[0021] Step 2: Pre-run the measuring device. The particulate matter supply unit conveys particulate matter to the airborne particle flow tube through the negative pressure air flow unit, and adjusts the air pressure at the input and output ends of the airborne particle flow tube through the negative pressure air flow unit until a stable particle flow is formed. The particle flow returns to the particulate matter supply unit through the output end of the airborne particle flow tube or is discharged to the environment.

[0022] Step 3: The laser passes vertically through the stable particle flow through the perforation in the middle position of the airborne particle flow tube and focuses near the axis of the airborne particle flow tube, interacting with the particulate matter to excite the LIBS spectral signal.

[0023] Step 4: The spectrometer (3) records the LIBS spectral signal for inferring and analyzing the physical and chemical properties of the particulate matter.

[0024] The present invention discloses the following technical effects:

[0025] 1) The structure of the present invention is simple, the operation is convenient, and the cyclic detection of particulate matter can be realized, which is suitable for the LIBS spectral analysis of particulate matter in the gas-solid two-phase state in the particulate matter transmission pipeline.

[0026] 2) The applicable particle size range of the present invention is expanded: particulate matter with a particle size of 1 - 1500 μm can be detected.

[0027] 3) The present invention does not require a window piece or a positive pressure environment to confine the particle flow. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 It is a schematic structural diagram of the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device of the present invention (during the cyclic detection and analysis of particulate matter);

[0030] Figure 2 It is a schematic structural diagram of the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device of the present invention (during the real-time detection and analysis of particulate matter);

[0031] Figure 3 It is the spectrogram of Embodiment 2 of the present invention.

[0032] Among them, 1. Airborne particle flow tube; 2. Laser; 3. Spectrometer; 4. First vacuum generator; 5. Air compressor; 6. Second vacuum generator; 7. Air valve; 8. Particulate matter bin; 9. Particulate matter dish. Detailed Embodiments

[0033] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0034] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Embodiment 1:

[0036] Referring to Figure 1-2 , the present invention provides an airborne particulate laser-induced breakdown spectroscopy (LIBS) detection and analysis device, including:

[0037] A measurement device frame;

[0038] A negative-pressure airborne particle flow system, which includes an airborne particle flow tube 1, a negative-pressure air flow unit, and a particulate matter supply unit. The airborne particle flow tube 1 is horizontally fixed on the measurement device frame. A perforation is provided at the middle position of the airborne particle flow tube 1. The axis of the perforation is perpendicular to and intersects the axis of the airborne particle flow tube. The diameter of the perforation is smaller than the diameter of the airborne particle flow tube 1. The negative-pressure air flow unit is connected to both ends of the airborne particle flow tube 1. The particulate matter supply unit is linked with the negative-pressure air flow unit to transport particulate matter to the airborne particle flow tube to form a stable particle flow;

[0039] A particle flow LIBS detection system, which includes a laser 2, a spectrometer 3, and an optical path. The laser 2, the spectrometer 3, and the optical path are all arranged on the measurement device frame corresponding to the negative-pressure airborne particle flow system to achieve LIBS spectral excitation and detection.

[0040] Use a three-module fiber-coupled CCD spectrometer 3 to record spectra in the near-ultraviolet, visible, and near-infrared bands respectively;

[0041] The optical path includes an expander and a quartz focusing mirror for focusing the output laser pulse. The optical path also includes a dichroic mirror and a quartz focusing mirror for reversely collecting the LIBS spectral signal; the optical path also includes a splitting optical fiber for coupling the collected plasma spectral signal into the spectrometer 3; the expander uses a combination of two optical glass lenses with negative and positive focal lengths respectively; the quartz lens for focusing the laser pulse has a focal length of 100 mm; the quartz lens for converging the plasma spectral signal has a focal length of 50 mm.

[0042] For a further optimized solution, the negative pressure air flow unit includes a first vacuum generator 4, an air compressor 5, and a second vacuum generator 6 connected in series in sequence. The exhaust port of the first vacuum generator 4 is connected to the input end of the airborne particle flow tube 1, and the vacuum port of the second vacuum generator 6 is connected to the output end of the airborne particle flow tube 1. Air valves 7 are respectively arranged between the first vacuum generator 4 and the air compressor 5, and between the second vacuum generator 6 and the air compressor 5.

[0043] The air compressor 5 provides a higher air pressure to the second vacuum generator 6 than to the first vacuum generator 4, so that the second vacuum generator 6 generates a lower vacuum air pressure than the first vacuum generator 4. With such an arrangement, the air flow entering from the input end of the airborne particle flow tube 1 converges with the air flow entering through its perforations and is discharged from its output end. By adjusting the above two air valves 7 until a stable particle flow is formed in the airborne particle flow tube 1 and there is no particle overflow.

[0044] For a further optimized solution, the particulate matter supply unit includes a particulate matter bin 8. The bottom of the particulate matter bin 8 is connected to the vacuum port of the first vacuum generator 4 through a pipeline, and the top of the particulate matter bin 8 is connected to the exhaust port of the second vacuum generator 6 through a pipeline. An air pipe is installed on the top of the particulate matter bin 8 to communicate with the ambient atmosphere, and a particle filter is installed on the air pipe. The excess gas generated during operation in the particulate matter bin 8 is directly output or output after passing through the filter to discharge the positive pressure inside it. When the device operates stably, the filling level of the particulate matter sample to be measured in the particulate matter bin 8 is higher than the connection port of the first vacuum generator 4, and at the same time, lower than the connection ports of the second vacuum generator 6 and the third interface of the particulate matter bin 8. This mode can realize the cyclic detection of particulate matter.

[0045] For a further optimized solution, the particulate matter supply unit includes a particulate matter dish 9. The particulate matter dish 9 is connected to the vacuum port of the first vacuum generator 4, and the exhaust port of the second vacuum generator 6 is connected to the ambient atmosphere. The vacuum port of the first vacuum generator 4 is connected to an open particulate matter dish 9 or any particulate matter generation source through a pipeline. When there is enough particulate matter collected in the particulate matter dish 9, the connection pipeline is completely buried in the particulate matter and starts to inhale the particulate matter. The exhaust port of the second vacuum generator 6 directly discharges the particulate matter output from the output end of the airborne particle flow tube 1 to the atmospheric environment. This mode can be used for the one-time detection of particulate matter.

[0046] For a further optimized solution, the length of the airborne particle flow tube 1 is 0.5 m, the inner diameter is 14 mm, the outer diameter is 16 mm, and the diameter of the perforation is 3.0 mm.

[0047] For a further optimized solution, the input air pressure at the air supply port of the first vacuum generator 4 is 0.16 Mpa, and the input air pressure at the air supply port of the second vacuum generator 6 is 0.30 MPa.

[0048] For a further optimized solution, the laser 2 outputs pulse parameters of 1064 nm, 20 Hz, 8 ns, and 50 mJ.

[0049] An airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis method includes the following steps:

[0050] Step 1, set up a measurement device;

[0051] Step 2, pre-run the measurement device. The particulate matter supply unit conveys particulate matter to the airborne particle flow tube 1 through the negative pressure air flow unit, and adjusts the air pressures at the input and output ends of the airborne particle flow tube 1 through the negative pressure air flow unit until a stable particle flow is formed. The particle flow returns to the particulate matter supply unit through the output end of the airborne particle flow tube 1 or is discharged to the environment.

[0052] Step 3, the laser 2 vertically passes through the stable particle flow through the perforation at the middle position of the airborne particle flow tube 1 and focuses near the axis of the airborne particle flow tube 1, interacting with the particulate matter to excite LIBS spectral signals.

[0053] Step 4, the spectrometer 3 records the LIBS spectral signals for inferring and analyzing the physical and chemical properties of the particulate matter.

[0054] Example 2:

[0055] Taking alumina particulate matters with particle sizes of 200 μm, 400 μm, and 800 μm as examples for the test experiment, the effective spectral excitation rates reach 86%, 88%, and 89% respectively. The collected LIBS spectra are as Figure 3 shown (invalid spectra are excluded, and 10 single emission spectra are averaged). The experimental results show that for alumina particles with different particle sizes, this device can detect aluminum atomic lines at 308.51 nm, 309.28 nm, 394.40 nm, and 396.15 nm, oxygen atomic lines at 777.19 nm, and emission lines of nitrogen atoms, oxygen atoms, and hydrogen atoms generated by the excitation of some background gases.

[0056] The specific experimental procedure is as follows:

[0057] 1) Taking alumina particles as an example, prepare a particulate matter sample with a stacking volume of not less than 0.2 L for the optimization and testing of the experimental device, as well as the optimization and testing of spectral data.

[0058] 2) Open the threaded screw cap below the particulate matter bin 8 and clean the original sample.

[0059] 3) Open the threaded screw cap above the particulate matter bin 8 and add an alumina particulate matter sample. The stacking volume should cover the connection pipe orifice between the particulate matter bin 8 and the first vacuum generator 4 to ensure a stable particle flow circulation.

[0060] 4) Turn on the air compressor 5, and adjust the air pressure and gas flow rate in the pipeline through the air valve 7 to ensure the stable flow of particulate matter in the airborne particle flow tube 1. For alumina particles, when the input air pressures of the two vacuum generators are 0.16 MPa (the first vacuum generator) and 0.30 MPa (the second vacuum generator) respectively, a stable particle flow can be formed.

[0061] 5) Turn on the laser 2: The laser pulse is focused on the particle flow to excite the particulate matter to generate plasma and produce LIBS spectral signals.

[0062] 6) Turn on the spectrometer 3 to collect LIBS spectra.

[0063] 7) Remove the background from the original spectrum, smooth, normalize and average it to obtain average normalized spectral data, and then perform subsequent processing.

[0064] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "vertical", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0065] The embodiments described above are only for describing the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. An airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device, characterized in that, Comprising: A measuring device rack; A negative-pressure airborne particle flow system, which includes an airborne particle flow pipe (1), a negative-pressure air flow unit, and a particulate matter supply unit. The airborne particle flow pipe (1) is not restricted by gravity and is fixed horizontally or vertically on the measuring device rack. A perforation is provided at the middle position of the airborne particle flow pipe (1), and the axis of the perforation intersects perpendicularly with the axis of the airborne particle flow pipe (1). The diameter of the perforation is smaller than the diameter of the airborne particle flow pipe (1). The negative-pressure air flow unit is connected to both ends of the airborne particle flow pipe (1), and the particulate matter supply unit is linked with the negative-pressure air flow unit to convey particulate matter to the airborne particle flow pipe, forming a stable particle flow; A particle flow LIBS detection system, which includes a laser (2), a spectrometer (3), and an optical path. The laser (2), the spectrometer (3), and the optical path are all arranged on the measuring device rack corresponding to the negative-pressure airborne particle flow system to achieve LIBS spectral excitation and detection.

2. The airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device according to claim 1, wherein: The negative-pressure air flow unit includes a first vacuum generator (4), an air compressor (5), and a second vacuum generator (6) connected in series in sequence. The exhaust port of the first vacuum generator (4) is connected to the input end of the airborne particle flow pipe (1), and the vacuum port of the second vacuum generator (6) is connected to the output end of the airborne particle flow pipe (1). Air valves (7) are respectively provided between the first vacuum generator (4) and the air compressor (5), and between the second vacuum generator (6) and the air compressor (5).

3. The airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device according to claim 2, characterized in that: The particulate matter supply unit includes a particulate matter bin (8). The bottom of the particulate matter bin (8) is connected to the vacuum port of the first vacuum generator (4) through a pipeline. The top of the particulate matter bin (8) is connected to the exhaust port of the second vacuum generator (6) through a pipeline. An air pipe is installed at the top of the particulate matter bin (8) to communicate with the ambient atmosphere, and a particle filter is installed on the air pipe.

4. The airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device according to claim 2, wherein: The particulate matter supply unit includes a particulate matter dish (9). The particulate matter dish (9) is connected to the vacuum port of the first vacuum generator (4), and the exhaust port of the second vacuum generator (6) is connected to the ambient atmosphere.

5. The airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device according to claim 1, characterized in that: The length of the airborne particle flow pipe (1) is 0.5 m, the inner diameter is 14 mm, the outer diameter is 16 mm, and the diameter of the perforation is 3.0 mm.

6. The airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device according to claim 1, characterized in that: The input air pressure at the air supply port of the first vacuum generator (4) is 0.16 Mpa, and the input air pressure at the air supply port of the second vacuum generator (6) is 0.30 MPa.

7. An airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device according to claim 1, characterized in that: The laser (2) outputs pulse parameters of 1064 nm, 20 Hz, 8 ns, and 50 mJ.

8. A method for detecting and analyzing airborne particulate matter by laser-induced breakdown spectroscopy (LIBS), based on the airborne particulate matter laser-induced breakdown spectroscopy (LIBS) detection and analysis device according to any one of claims 1-7, characterized in that, Including the following steps: Step 1, set up the measuring device; Step 2, pre-run the measuring device. The particulate matter supply unit conveys particulate matter to the airborne particle flow pipe (1) through the negative-pressure air flow unit, and adjusts the air pressure at the input and output ends of the airborne particle flow pipe (1) through the negative-pressure air flow unit until a stable particle flow is formed. The particle flow returns to the particulate matter supply unit through the output end of the airborne particle flow pipe (1) or is discharged to the environment; Step 3: The laser (2) vertically passes through the stable particle flow through the perforation at the middle position of the airborne particle flow tube (1), and focuses near the axis of the airborne particle flow tube (1), interacting with the particulate matter to excite the LIBS spectral signal; Step 4: The spectrometer (3) records the LIBS spectral signal for inferring and analyzing the physical and chemical properties of the particulate matter.

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