A small dust detection device and method based on combination of LIBS and TEOM

Abstract

The application discloses a small dust detection device and method based on combination of LIBS and TEOM, which comprises an airflow drying module, a LIBS spectrum analysis processing module, a TEOM oscillation frequency processing module, an airflow parameter identification module and an instrument control module; the airflow drying module comprises a sampling head, an air inlet pipeline and a drying pipeline; the LIBS spectrum analysis processing module comprises a laser, an optical lens, an optical fiber probe, a deposition groove and a spectrometer; the TEOM oscillation frequency processing module comprises a frequency oscillation measurement unit, and the dust concentration collected is measured by using the change of the microbalance oscillation frequency; the airflow parameter identification module comprises a temperature and humidity sensor, a first gas flow sensor, a second gas flow sensor and an environmental pressure sensor. The device is small in size, simple in structure and capable of meeting the dust composition and concentration detection requirements of low-cost industrial sites.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of online detection of dust components and concentration, and particularly relates to a small dust detection device and method based on combination of LIBS and TEOM. BACKGROUND

[0002] At the present stage, with the deepening of industrialization process in China, the number of workers in manufacturing industry, chemical industry and other front-line workplaces is increasing, but the occupational health protection measures corresponding to these complex work environments have not been well protected. On the one hand, the overall production process and technology of most industrial enterprises lead to high dust concentration and large number of dust in the working area, which is difficult to accurately detect. On the other hand, due to different production processes, the amount of dust produced is different, resulting in differences in dust amount and type in time and space in the same factory area, which is difficult to monitor by traditional dust detection methods. The lack of detection link brings the problem of not caring and not paying attention to protection in production, which affects the health of front-line workers. Ultimately, a portable, low-cost, high-precision and long-time continuous dust concentration detection device suitable for current industrial sites needs to be found.

[0003] Laser-induced breakdown spectroscopy (LIBS) is a substance composition detection technology based on laser emission spectrum. Its main principle is that high-energy pulsed laser irradiates the surface of the sample, so that the atoms on the surface of the sample are excited and ionized to form plasma. When these different element plasmas cool down to the ground state, they will release characteristic spectral lines of the element. By using a spectrometer to collect and measure these characteristic spectral lines and optical signals, the element composition and content in the sample can be obtained. Compared with traditional laboratory analysis techniques such as inductively coupled plasma atomic emission spectroscopy (ICP-AES), atomic absorption spectroscopy (AAS) and mass spectrometry (MS), LIBS technology has the advantages of fast measurement speed, no sample pretreatment, high precision and multi-element analysis. Due to the above advantages of this technology, it is very suitable for application in the detection of dust composition and concentration in industrial sites.

[0004] The frequency oscillation measurement unit method is a method of measuring mass based on the inertial characteristics of mass under the condition of no gravity. TEOM is based on the principle of micro-oscillation balance of conical elements. The conical elements vibrate at the natural frequency, and the oscillation frequency is determined by the following aspects: physical properties of the oscillation element, filter membrane mass participating in oscillation, and dust mass deposited on the filter membrane. When particles gradually deposit on the filter membrane, the total mass increases, which leads to a change in the oscillation frequency of the oscillation element. This change can be used to measure the dust concentration in a period of time. TEOM is a method of directly measuring the dust concentration in the air, and its sensitivity, accuracy and minimum detection limit have more outstanding advantages compared with other measurement methods.

[0005] At present, the commonly used methods for monitoring the dust concentration in the gas are manual filter membrane weighing method, light scattering method, piezoelectric crystal method, beta ray method, TEOM oscillating balance method and laser-induced breakdown spectroscopy method. Among them, the light scattering method, the piezoelectric crystal method, the beta ray method and the laser-induced breakdown spectroscopy method belong to indirect measurement method, and the manual filter membrane weighing method and the oscillating balance method belong to direct measurement method. In view of the above requirements for portable, low-cost dust detection device, the current more advanced LIBS and TEOM technologies are two kinds of dust composition and concentration detection methods which are more suitable for long-term use and have higher measurement accuracy and better adaptability to complex industrial sites. SUMMARY

[0006] The purpose of the present application is to provide a small dust detection device and method based on the combination of LIBS and TEOM, so as to solve the problems of the influence of environmental factors on the measurement results, low measurement accuracy and the inability to continuously measure the dust concentration for a long time in the prior art.

[0007] The present application adopts the following technical solutions:

[0008] A small dust detection device based on the combination of LIBS and TEOM, comprising: an airflow drying module, a TEOM oscillation frequency processing module, a LIBS spectral analysis processing module, an airflow parameter identification module and an instrument control module.

[0009] The airflow drying module comprises a sampling head, an air inlet pipeline and a drying pipeline which are sequentially connected, and is used for collecting airflow containing dust of a desired particle size and drying the airflow.

[0010] The TEOM oscillation frequency processing module comprises a frequency oscillation measurement unit and an environmental pressure sensor, and the frequency oscillation measurement unit measures the collected dust concentration by using the change of the oscillation frequency of the oscillating microbalance.

[0011] The LIBS spectral analysis processing module comprises a LIBS spectral analysis processing module cavity, a spectrometer, an optical fiber probe, and a laser, an optical lens and a deposition groove arranged in the LIBS spectral analysis processing module, and the LIBS spectral analysis processing module measures the collected dust concentration by using the laser-induced breakdown spectroscopy method, and the measured gas enters the airflow parameter identification module.

[0012] The airflow parameter identification module comprises an airflow parameter identification module cavity, and a temperature and humidity sensor, a first gas flow sensor and a second gas flow sensor arranged in the airflow parameter identification module cavity, and is used for collecting related parameters in the data processing process.

[0013] The instrument control module includes a control computer and a flow gas pump, which are used to control the overall operation of the device and process the measurement results obtained by the two measurement methods of the TEOM oscillation frequency processing and the LIBS spectrum analysis processing modules.

[0014] The tail end of the drying tube is connected to the TEOM oscillation frequency processing module and the LIBS spectrum analysis processing module through two paths, respectively. An ambient pressure sensor is arranged on the path connecting the frequency oscillation measurement unit and the gas flow parameter identification module. The cavity of the gas flow parameter identification module is provided with a first chamber and a second chamber. The upper parts of the first chamber and the second chamber are separated by a partition, and the lower parts of the two chambers are connected to the outside. A flow gas pump is arranged on the pipeline connected to the outside. The tail end of the pipeline connected to the outside is a gas flow outlet. A first gas flow sensor is arranged in the upper part of the first chamber, and a second gas flow sensor is arranged in the upper part of the second chamber. Temperature and humidity sensors are arranged in the upper parts of the first chamber and the second chamber. The frequency oscillation measurement unit is connected to the upper part of the first chamber.

[0015] Another gas path of the tail end of the drying tube is connected to the cavity of the LIBS spectrum analysis processing module. A laser is arranged in the cavity of the LIBS spectrum analysis processing module. An optical lens and a deposition groove are arranged in sequence below the laser. The deposition groove is detachably arranged on the cavity of the LIBS spectrum analysis processing module. One end of the laser is connected to a spectrometer. An optical fiber probe is arranged on the side wall of the cavity of the LIBS spectrum analysis processing module and is above the deposition groove, used to receive the light signal of the plasma of the excited substance. The optical fiber probe is connected to the spectrometer. The cavity of the LIBS spectrum analysis processing module is connected to the upper part of the second chamber.

[0016] The control computer is connected to the frequency oscillation measurement unit, the flow pump, the laser, the spectrometer, the ambient pressure sensor, the temperature and humidity sensor, the first gas flow sensor, and the second gas flow sensor.

[0017] Preferably, the drying tube is filled with a drying agent.

[0018] Preferably, the spectrometer of the LIBS spectrum analysis processing module and the control computer are connected to a battery pack.

[0019] Preferably, the material of the deposition groove is an ablation-resistant and high-temperature-resistant material.

[0020] Preferably, the deposition groove is a drawer-type bowl structure.

[0021] Preferably, the center angle of the recess is 70°.

[0022] Preferably, the ambient pressure sensor includes an external sensor and an internal sensor. The internal sensor is arranged in the pipeline, and the external sensor is exposed to the external environment, used to measure the atmospheric pressure in the external environment and the gas pressure in the internal gas pipeline.

[0023] Another technical solution adopted by the present application is as follows: a detection method of a small dust detection device based on combination of LIBS and TEOM, comprising the following steps:

[0024] Step 1: the airflow passes through the sampling head, and then the airflow passes through the air inlet pipeline into the drying pipe.

[0025] Step 2: the airflow dried through the step 1 enters the LIBS spectral analysis processing module and the TEOM frequency oscillation processing module through two branches respectively. When the dust-containing airflow enters the LIBS spectral analysis processing module excitation chamber from the upper passage entrance, it will be deposited into the groove of the deposition groove under the action of gravity. At this time, the control calculator controls the laser to release the laser quickly. The laser converges at the bottom of the deposition groove through the focusing effect of the optical lens, excites the deposited particulate matter, releases the light signal, and the spectral characteristic wavelength and the spectral intensity information corresponding to the wavelength are received by the optical fiber probe and transmitted to the spectrometer for signal processing. The data processed by the spectrometer are transmitted to the control calculator.

[0026] Step 3: the airflow entering the TEOM frequency oscillation processing module is deposited on the frequency oscillation measurement unit. Due to the change of mass, the oscillation frequency of the frequency oscillation measurement unit changes. The control calculator collects and analyzes the frequency change, and obtains the mass of the deposited particulate matter on the frequency oscillation measurement unit through a formula. The gas flow in the branch is obtained by the first gas flow sensor, and the particulate matter concentration in any period of time is obtained by calculation. The concentration is then transmitted to the control calculator. The airflow of the frequency oscillation measurement unit enters the environmental pressure sensor, and the gas pressure in the pipeline is obtained by measurement.

[0027] Step 4: after the control calculator obtains the total dust concentration of particulate matter detected by the LIBS spectral analysis processing module and the TEOM frequency oscillation processing module, the parameters of the temperature and humidity sensor, the environmental gas pressure sensor, the first gas flow sensor and the second gas flow sensor are combined, and the corrected particulate matter concentration is obtained after comprehensive calculation. The measured particulate matter concentration is displayed on the display screen on the shell, and the real-time data is displayed in real time.

[0028] Preferably, the control calculator controls the opening and closing of the flow air pump, the natural oscillation of the frequency oscillation measurement unit, the emission of the spectrometer trigger signal and the operation of the laser, the air flow suction of the flow air pump control device, and the setting of the air pump flow.

[0029] Preferably, the calculation formula in step 4 is as follows:

[0030] C 修正 =α L *CT

[0031] C 修正 : the total particulate matter concentration obtained after correction;

[0032] alpha L : the particulate matter percentage content measured by LIBS technology;

[0033] C T : the particulate matter concentration measured by TEOM technology.

[0034] The beneficial effects of the present application are:

[0035] 1. The indirect measurement methods such as LIBS and SIBS require good pre-experimental tests on spectral data and corresponding data, however, the spectral measurement itself has certain fluctuation, thus causing some technical deviations. The direct measurement methods such as TEOM are affected by environmental factors, physical properties of oscillation elements, filter membrane quality and other factors, thus causing measurement errors, and the errors change with the measurement (such as changes in filter membrane quality, physical properties of oscillation elements, changes in oscillation frequency, etc.), thus a small dust detection device and method combining LIBS and TEOM are considered. The present application combines indirect measurement and direct measurement, reduces the influence of environmental factors on the measurement results, and improves the measurement accuracy, thus effectively solving the problems of inconvenient carrying, low cost, low precision and inability to continuously measure dust concentration for a long time in the current industrial sites. The LIBS technology belongs to an indirect measurement method based on spectroscopy, and the frequency oscillation measurement unit technology is a direct measurement method based on mass, which are combined and applied in the same device to detect the atmospheric sample at the same place and at the same time, so as to eliminate the influence of environmental factors and improve the measurement accuracy through data comparison and processing.

[0036] 2. The double-pipeline design skillfully utilizes the distribution of the pipelines to make the atmospheric flow entering the LIBS detection system and the TEOM detection system the same and maintain the same dust composition (simultaneous detection at the same place), and maximally reduce the volume of the device.

[0037] 3、LIBS detection module sets detachable deposition groove, which can quickly deposit particles to the bottom of the groove under a certain air flow rate. After high-energy excitation by the laser, the deposited particles will be impacted into the air flow circuit and discharged from the chamber with the air flow. Considering the problem of still a certain amount of dust deposition, the deposition groove is set to be detachable for easy cleaning and replacement; the design is reasonable, small in size, and meets the requirements of portability. The filter membrane method, for example, in the case of high dust concentration, the filter membrane will quickly deposit a large amount of particles, at which time the filter membrane needs to be quickly recovered and replaced, so it cannot be measured continuously for a long time, which will waste a lot of manpower and resources, and this method cannot display real-time dust concentration data, which requires subsequent data processing. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 A structure diagram of a small dust detection device based on the combination of LIBS and TEOM according to the present application.

[0039] Figure 2 A structure diagram of a LIBS excitation chamber according to the present application.

[0040] Figure 3 A structure diagram of a device panel and display screen according to the present application.

[0041] 1. Sampling head; 2. Air inlet pipeline; 3. Drying pipe; 4. Ambient pressure sensor; 5. Frequency oscillation measurement unit; 6. Control calculator; 7. First gas flow sensor; 8. Temperature and humidity sensor; 9. Flow air pump; 10. Second gas flow sensor; 11. Battery pack; 12. Air outlet pipeline; 13. Air outlet; 14. Spectrometer; 15. Deposition groove; 16. Optical fiber probe; 17. Optical lens; 18. Laser; 19. Fastening screw; 20. Charging indicator light; 21. Running state indicator light; 22. Data display area; 23. Status display column; 24. Operation area. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0043] The present application will be described in detail below in combination with the drawings and specific embodiments in the specification.

[0044] Embodiment 1

[0045] As Figure 1As shown, a small dust detection device based on the combination of LIBS and TEOM includes: airflow drying module, TEOM oscillation frequency processing module, LIBS spectral analysis processing module, airflow parameter identification module and instrument control module.

[0046] The airflow drying module includes a sampling head 1, an air inlet pipeline 2 and a drying pipe 3 connected in sequence, the sampling head 1 is detachable and replaceable, the air inlet pipeline 2 is connected with the drying pipe 3, and the drying pipe 3 internally stores a large amount of drying agent for collecting airflow containing dust of a required particle size and drying the airflow.

[0047] The TEOM oscillation frequency processing module includes a frequency oscillation measurement unit 5 and an environmental pressure sensor 4, the frequency oscillation measurement unit 5 measures the collected dust concentration by using the change of the oscillation frequency of the oscillation microbalance.

[0048] The oscillation microbalance is a conical element, the upper part of which is a circular filter membrane tray, and the lower part is a hollow thin circular tube which can freely oscillate up and down, and a large number of electronic elements are installed on the sidewall of the hollow thin circular tube for measuring the oscillation frequency of the frequency oscillation measurement unit 5, and the electronic elements on the sidewall of the tube vibrate at the natural frequency under the action of the electronic elements, and the opening and closing of the vibration are controlled by the control calculator 6. Then the oscillation frequency of the oscillation microbalance is measured by the frequency oscillation measurement unit, and the measurement result is transmitted to the control calculator 6.

[0049] The LIBS spectral analysis processing module includes a LIBS spectral analysis processing module cavity, a spectrometer 14, an optical fiber probe 16, and a laser 18, an optical lens 17 and a deposition groove 15 arranged in the LIBS spectral analysis processing module, the LIBS spectral analysis processing module is used to measure the collected dust concentration by using the laser-induced breakdown spectroscopy method, and the measured gas enters the airflow parameter identification module.

[0050] As shown in the figure, Figure 2 The laser 18 is an Nd:YAG laser, which is fixed on the upper side of the excitation chamber by a screw, and emits laser after receiving the trigger signal of the spectrometer 14, the optical lens 17 is two adjustable convex lenses, which are installed on the sidewall of the excitation chamber and opposite to the laser 18, the laser emitted by the laser 18 is focused on the bottom of the deposition groove 15 by the focusing action of the optical lens 17, the deposition groove 15 is a drawer type bowl structure, which can be taken out from the outside of the device for cleaning or replacement, the laser 18 excites the collected particulate matter with high energy, the light signal and characteristic spectrum released by the plasma generated by the excitation are collected by the optical fiber probe 16 of the spectrometer 14, the optical fiber probe 16 is fixed on the sidewall of the excitation chamber by matching parts and opposite to the upper part of the deposition groove 15, and the spectrometer 14 processes the data and transmits the obtained result to the control calculator 6.

[0051] The recessed groove has a center angle of about 70°, and the distance from the groove to the chamber opening of the pipeline is about 7 cm. Considering that laser-induced breakdown has a high excitation energy, a large amount of deposited dust will be ejected and lifted up each time. The advantage of a large angle of the recessed groove is that small particles can be lifted and discharged along with the airflow, while large particles are difficult to be lifted and deposited in the groove. If the angle is too small, particles of different sizes will be ejected into the chamber, and long-term use will cause serious dust deposition in the chamber, increasing the cost of replacement and detection. As a portable and small instrument, the volume of the LIBS detection module is limited by the overall instrument volume, and secondly, in order to leave enough focusing distance for the focusing lens of the laser emitter, the length of 7 cm is selected for the deposition groove.

[0052] The airflow parameter identification module includes an airflow parameter identification module cavity, and a temperature and humidity sensor 8, a first gas flow sensor 7 and a second gas flow sensor 10 arranged in the airflow parameter identification module cavity, for collecting relevant parameters in the data processing process.

[0053] The instrument control module includes a control computer 6 and a flow gas pump 9, for controlling the overall operation of the device and processing the measurement results obtained by the two measurement methods; and can be used to receive the particulate matter concentration provided by the LIBS spectral analysis processing module and the TEOM frequency oscillation processing module, and give the proportion of the concentrations measured by the two technologies through a pre-designed formula combined with various parameters, and finally get the accurate particulate matter concentration after correction. The flow gas pump 9 is set with a flow rate in advance, and starts to work after being powered on to complete the collection of the ambient airflow. The battery pack 11 is installed on the lower left side of the device to supply power to each component in the entire device.

[0054] From Figure 1 As can be seen, after entering the TEOM module, the diameter of the pipeline is obviously narrowed, and due to the operating principle of the TEOM, the T-shaped oscillation tube will make the airflow collide on it, so that the particulate matter trapped on it changes the oscillation efficiency of the oscillation tube, and then the particulate matter concentration is obtained. Therefore, it is necessary to correct the internal pressure of the TEOM pipeline and chamber, because the internal pressure changes significantly compared to the external pressure, which needs to be corrected. The LIBS pipeline part has little relationship with the gas pressure in the detection principle, and mainly considers parameters such as temperature, so no corresponding gas pressure detection sensor is set.

[0055] The tail end of the drying tube 3 is communicated with the frequency oscillation measuring unit 5, and the environmental pressure sensor 4 is arranged on the path communicated with the frequency oscillation measuring unit 5 and the airflow parameter identification module; the airflow parameter identification module cavity is provided with a first chamber and a second chamber, the upper parts of the first chamber and the second chamber are separated by a partition, the lower parts of the two chambers are communicated and communicated to the outside, the flow gas pump 9 is arranged on the pipeline communicated to the outside, and the tail end of the pipeline communicated to the outside is the airflow outlet 13; the first gas flow sensor 7 is arranged in the upper part of the first chamber, the second gas flow sensor 10 is arranged in the upper part of the second chamber, the upper parts of the first chamber and the second chamber are provided with the temperature and humidity sensor 8, and the frequency oscillation measuring unit 5 is communicated with the upper part of the first chamber;

[0056] The temperature and humidity sensor 8 is arranged on the partition plate between the two chambers, and the temperature sensor and the humidity sensor are arranged on the partition plate, so as to detect the temperature and humidity of the airflow in the LIBS technology chamber and the temperature and humidity in the TEOM technology chamber. The measurement range of the temperature sensor is 0-50 DEG C, the measurement range of the humidity sensor is 10%-90%, and the sampling interval of the two is at least 100 ms.

[0057] Another gas path of the tail end of the drying tube 3 is communicated with the LIBS spectrum analysis processing module cavity, the laser 18 is arranged in the LIBS spectrum analysis processing module cavity, the optical lens 17 and the deposition groove 15 are sequentially arranged below the laser 18, the deposition groove 15 is detachably arranged on the LIBS spectrum analysis processing module cavity, one end of the laser 18 is connected with the spectrometer 14; the optical fiber probe 16 is arranged on the side wall of the LIBS spectrum analysis processing module cavity, and the optical fiber probe 16 is above the deposition groove 15, used for receiving the light signal of the plasma of the excited substance, the optical fiber probe 16 is connected with the spectrometer 14, and the LIBS spectrum analysis processing module cavity is communicated with the upper part of the second chamber.

[0058] The control calculator 6 is connected with the frequency oscillation measuring unit 5, the flow pump 9, the laser 18, the spectrometer 14, the environmental pressure sensor 4, the temperature and humidity sensor 8, the first gas flow sensor 7 and the second gas flow sensor 10; the spectrometer 14 and the control calculator 6 are connected with the battery pack 11.

[0059] As Figure 3As shown, the device housing panel is divided into a data display area 22, a status display column 23 and an operation area 24, in addition to two indicator lights, namely the charging indicator light 20 and the running status indicator light 21. The data display area 22 mainly displays the real-time dust concentration and the time-weighted average dust concentration in the measurement, and in addition, the environmental pressure, the temperature, the humidity, the gas flow and the like in the LIBS and TEOM gas circuit are displayed on the screen, so as to facilitate the safety personnel to master the real-time environmental information. The status display column 23 mainly displays the instrument lighting, the instrument running state, whether the instrument is placed horizontally and the like. The flow adjustment button in the operation area 24 is used to adjust the flow of the flow gas pump 9; the parameter display button is used to select which data to display on the screen; the TEOM data and LIBS data buttons respectively display the dust concentration information monitored by the LIBS and TEOM separate modules in the device on the screen; the data correction button is mainly used to combine the TEOM and LIBS data and correct the dust concentration data according to the environmental parameters; the data printing button is used to print the data stored in the control calculator 6; the measurement / stop button is used to start detection and stop detection; and the power on / off button is used to turn on and turn off the device.

[0060] The detection method of the above-mentioned small dust detection device based on the combination of LIBS and TEOM is as follows:

[0061] First, power is supplied to the battery pack 11 through the charging socket, and when the battery is full, the indicator light on the housing will display green; before starting the detection, the deposition groove 15 needs to be taken out for cleaning or replaced with a new deposition groove 15; the working sound of the flow gas pump is checked when starting, and if there is no abnormality, the required detection flow is set, and then the detection process can be started.

[0062] The gas flow passes through the sampling head 1 under the action of the flow gas pump, and the sampling head 1 can screen the particle size of the particulate matter in the gas flow, and then the gas flow containing particulate matter of a specific particle size passes through the inlet pipe 2 and enters the drying pipe 3.

[0063] After drying, the gas flow enters the LIBS spectral analysis processing module and the TEOM frequency oscillation processing module through the left and right two branches, respectively. The gas flow entering the LIBS spectral analysis processing module is deposited on the deposition groove 15 after entering the laser emission chamber, at which time the control calculator 6 controls the laser 18 to release the laser quickly. The laser is focused by the focusing action of the two optical lenses 17 and converges at the bottom of the deposition groove 15, exciting the deposited particulate matter. The released light signal and characteristic spectrum are received by the optical fiber probe 16 and transmitted to the spectrometer 14 for signal processing, and the data after signal processing by the spectrometer 14 is transmitted to the control calculator 6.

[0064] The air flow into the TEOM frequency oscillation processing module is deposited on the circular filter membrane at the upper end of the frequency oscillation measuring unit 5 after entering the TEOM frequency oscillation processing module. Due to the change in mass, the oscillation frequency of the oscillation microbalance changes. The control calculator collects and analyzes the frequency change data, and obtains the mass of the particles deposited on the oscillation microbalance with the change in frequency by formula. The gas flow in the branch is obtained by the first gas flow sensor 7, and the particle concentration in a period of time is obtained by calculation. The concentration is then transmitted to the control calculator 6. The air flow through the frequency oscillation measuring unit 5 enters the ambient pressure sensor 4, and the gas pressure in the pipeline is measured by the ambient pressure sensor 4 located outside the device to measure the pressure of the external environment.

[0065] After the control calculator 6 obtains the particle concentration provided by the LIBS spectrum analysis processing module and the TEOM frequency oscillation processing module respectively, the parameters of the temperature and humidity sensor 8, the ambient gas pressure sensor 4, the first gas flow sensor 7 and the second gas flow sensor 10 are combined and calculated to obtain the corrected particle concentration. The measured particle concentration is displayed on the display screen on the shell, and the real-time data is displayed generally every 2 seconds.

[0066] After the comprehensive calculation, the corrected particle concentration is obtained,

[0067] The calculation formula in step 4 is as follows:

[0068] C 修正 = α L *C T

[0069] C 修正 : the total particle concentration obtained after correction;

[0070] α L : the percentage content of particles measured by LIBS technology;

[0071] C T : the particle concentration measured by TEOM technology.

[0072] The measurement time set by the staff changes mainly refers to the last displayed time-weighted average concentration, such as 2 hours, 4 hours, 8 hours measurement, etc., rather than real-time data display. However, these data will be recorded during actual operation.

[0073] The above measurement process is completely continuous and automatic within the required measurement time, without additional manual operation process, so as to meet the needs of real-time and on-site measurement in industrial places, and to help understand the dust distribution of different time and space in industrial places. The measured data can provide reasonable reference for occupational health management scheme after being summarized.

[0074] While the application has been described in detail by reference to preferred embodiments thereof, it is to be understood that the description is not to be construed as limiting the scope of the application. Various modifications and changes can occur to those skilled in the art, once they learn of the basic concept of the application. Therefore, the scope of the application is to be defined by the appended claims, rather than by the description of the preferred embodiments.

Claims

1. A small dust detection device based on a combination of LIBS and TEOM, characterized in that, Includes: airflow drying module, TEOM oscillation frequency processing module, LIBS spectral analysis and processing module, airflow parameter identification module, and instrument control module; The airflow drying module includes a sampling head (1), an air inlet pipe (2), and a drying pipe (3) connected in sequence, which are used to collect airflow containing dust of the required particle size and dry it. The TEOM oscillation frequency processing module includes: a frequency oscillation measurement unit (5) and an environmental pressure sensor (4). The frequency oscillation measurement unit (5) measures the collected dust concentration by the change in the oscillation frequency of the oscillation microbalance. The LIBS spectral analysis and processing module includes: a LIBS spectral analysis and processing module cavity, a spectrometer (14), an optical fiber probe (16), and a laser (18), an optical lens (17), and a deposition groove (15) disposed in the LIBS spectral analysis and processing module. The LIBS spectral analysis and processing module uses laser-induced breakdown spectroscopy to measure the collected dust concentration, and the gas after measurement enters the airflow parameter identification module. The airflow parameter identification module includes: an airflow parameter identification module cavity, and a temperature and humidity sensor (8), a first gas flow sensor (7), and a second gas flow sensor (10) disposed in the airflow parameter identification module cavity, for collecting relevant parameters during the data processing process; The instrument control module includes a control calculator (6) and a flow pump (9), which are used to control the overall operation of the equipment and process the measurement results obtained by the two measurement methods, namely the TEOM oscillation frequency processing module and the LIBS spectral analysis processing module. The drying tube (3) is connected to the TEOM oscillation frequency processing module and the LIBS spectral analysis processing module at its tail end. An environmental pressure sensor (4) is installed on the path connecting the frequency oscillation measurement unit (5) and the airflow parameter identification module. The airflow parameter identification module is provided with a first chamber and a second chamber. The upper parts of the first chamber and the second chamber are separated by a partition. The lower parts of the two chambers are connected to the outside. A flow pump (9) is installed on the pipeline connected to the outside. The tail end of the pipeline connected to the outside is the airflow outlet (13). A first gas flow sensor (7) is installed in the upper part of the first chamber. A second gas flow sensor (10) is installed in the upper part of the second chamber. Temperature and humidity sensors (8) are installed in the upper parts of both the first chamber and the second chamber. The frequency oscillation measurement unit (5) is connected to the upper part of the first chamber. The other gas path at the end of the drying tube (3) is connected to the cavity of the LIBS spectral analysis and processing module. A laser (18) is installed in the cavity of the LIBS spectral analysis and processing module. An optical lens (17) and a deposition groove (15) are arranged in sequence below the laser (18). The deposition groove (15) is detachably installed on the cavity of the LIBS spectral analysis and processing module. One end of the laser (18) is connected to the spectrometer (14). A fiber optic probe (16) is installed on the side wall of the cavity of the LIBS spectral analysis and processing module. The fiber optic probe (16) is located above the deposition groove (15) and is used to receive the optical signal of the plasma of the excited material. The fiber optic probe (16) is connected to the spectrometer (14). The cavity of the LIBS spectral analysis and processing module is connected to the upper part of the second chamber. The control calculator (6) is connected to the frequency oscillation measurement unit (5), the flow pump (9), the laser (18), the spectrometer (14), the environmental pressure sensor (4), the temperature and humidity sensor (8), the first gas flow sensor (7), and the second gas flow sensor (10).

2. The small dust detection device based on the combination of LIBS and TEOM as described in claim 1, characterized in that, The drying tube (3) is filled with desiccant.

3. The small dust detection device based on the combination of LIBS and TEOM as described in claim 1, characterized in that, The spectrometer (14) and control calculator (6) of the LIBS spectral analysis and processing module are connected to the battery pack (11).

4. The small dust detection device based on the combination of LIBS and TEOM as described in claim 1, characterized in that, The deposition groove (15) is made of ablation-resistant and high-temperature-resistant material.

5. The small dust detection device based on the combination of LIBS and TEOM as described in claim 4, characterized in that, The deposition groove (15) has a drawer-type bowl-shaped structure.

6. The small dust detection device based on the combination of LIBS and TEOM as described in claim 5, characterized in that, The center of the groove (15) is 70°.

7. The small dust detection device based on the combination of LIBS and TEOM as described in claim 1, characterized in that, The environmental pressure sensor (4) consists of two parts: an external sensor and an internal sensor. The internal sensor is located inside the pipeline, while the external sensor is exposed to the external environment. It is used to measure the atmospheric pressure in the external environment and the gas pressure in the internal airflow pipeline.

8. A detection method for a small dust detection device based on the combination of LIBS and TEOM as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: The airflow passes through the sampling head (1), and then the airflow enters the drying tube (3) through the air inlet pipe (2); Step 2: After drying in Step 1, the airflow enters the LIBS spectral analysis and processing module and the TEOM frequency oscillation processing module through two branch pipes respectively. When the dust-laden airflow enters the excitation chamber of the LIBS spectral analysis and processing module from the upper passage inlet, it will be deposited into the groove of the deposition groove (15) under the action of gravity. At this time, the control calculator (6) controls the laser (18) to release laser rapidly. The laser is focused by the optical lens (17) and converges at the bottom of the deposition groove (15) to excite the deposited particles and the released light signal. The spectral characteristic wavelength and the spectral intensity information corresponding to the wavelength are received by the fiber optic probe (16) and transmitted to the spectrometer (14) for signal processing. The data after signal processing by the spectrometer (14) is transmitted to the control calculator (6). Step 3: The airflow entering the TEOM frequency oscillation processing module is deposited on the frequency oscillation measurement unit (5). Due to the change in mass, the oscillation frequency of the frequency oscillation measurement unit (5) changes. This frequency change is collected and analyzed by the control calculator (6), and the mass of the particles deposited on the frequency oscillation measurement unit (5) with the frequency change is obtained by formula. Then, the gas flow rate in the branch is obtained by the first gas flow sensor (7). The particle concentration in any time period is obtained by calculation. This concentration is then transmitted to the control calculator (6). The airflow through the frequency oscillation measurement unit (5) enters the environmental pressure sensor (4), and the gas pressure inside the pipeline is obtained by measurement. Step 4: After the control calculator (6) obtains the total particulate matter concentration detected by the LIBS spectral analysis processing module and the TEOM frequency oscillation processing module, it combines the parameters of the temperature and humidity sensor (8), the ambient gas pressure sensor (4), the first gas flow sensor (7), and the second gas flow sensor (10) to obtain the corrected particulate matter concentration after comprehensive calculation, and displays the measured particulate matter concentration on the display screen on the housing, displaying real-time data.

9. The detection method of the small dust detection device based on the combination of LIBS and TEOM as described in claim 8, characterized in that, The control calculator (6) controls the opening and closing of the flow pump (9), the natural oscillation of the frequency oscillation measurement unit (5), the emission of the trigger signal of the spectrometer (14), and the operation of the laser (18). The flow pump (9) controls the airflow intake of the device and sets the pump flow rate.

10. The detection method of the small dust detection device based on the combination of LIBS and TEOM as described in claim 8, characterized in that, The calculation formula in step 4 is as follows: C 修正 =α L *C T C 修正 The total particulate matter concentration obtained after correction; α L The percentage content of particulate matter measured by LIBS technology; C T : Particulate matter concentration measured by TEOM technology.

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