Dust moisture absorption characteristic detection method based on infrared spectrum

Abstract

According to the dust moisture absorption characteristic detection method based on the infrared spectrum, a temperature control system (1) and a humidity control system (2) are installed on a constant-temperature box, and a to-be-detected dust particle inlet (3) and a dust concentration detection device (4) are located on one side of the constant-temperature box; the infrared spectrometer (6) and the optical window (7) are positioned on the other side of the constant-temperature box, and the centers of the infrared spectrometer and the optical window are positioned on the same straight line, so that the optical window is aligned with the axis of the infrared spectrometer; a stirring rod (8) and a stirring rod speed controller are arranged in the middle of the constant-temperature box, the infrared spectrometer, the dust concentration detection device, the temperature control system and the humidity control system are all connected with the data processing module through data lines, and an intelligent analysis system is arranged in the data processing module and used for analyzing moisture absorption characteristic parameters and storing data; the data processing module establishes a moisture absorption characteristic model for a test result according to the humidity of the constant-temperature box and the collected infrared spectrum, and continuously detects the moisture absorption characteristic of the dust particles to be detected through the moisture absorption characteristic model.

Description

Technical Field

[0001] The invention relates to a dust hygroscopic property detection method, in particular to a dust hygroscopic property detection method based on infrared spectroscopy, and belongs to the technical field of dust hygroscopic property detection. Background Art

[0002] In the process of global industrialization, dust management has become an important issue in environmental protection and public health. Dust not only affects air quality, but also damages industrial equipment and even causes serious safety accidents. The hygroscopic properties of dust are one of the key factors that determine its adhesion and aggregation behavior. Therefore, accurate measurement of the hygroscopic properties of dust is essential for improving the design and operation of air purification systems. At present, the detection methods of dust hygroscopic properties mainly rely on weight method and conductivity method. Although these two methods can reflect the water content of dust to a certain extent, they have problems such as long time consumption and cumbersome operation, and cannot achieve continuous and real-time monitoring. Especially when dealing with fine or highly active dust, the accuracy and reliability of these methods still have great potential for improvement. Summary of the invention

[0003] The purpose of the present invention is to provide a method for detecting the hygroscopic characteristics of dust based on infrared spectroscopy, which can continuously detect the hygroscopic characteristics of dust in a gas to be tested.

[0004] In order to achieve the above-mentioned purpose, the present invention provides a dust hygroscopic characteristic detection method based on infrared spectroscopy, and the hardware part for realizing the method includes a constant temperature box, a temperature control system and a humidity control system are installed on the constant temperature box, and the dust particle inlet to be tested and the dust concentration detection device are located on one side of the constant temperature box; the infrared spectrometer and the optical window are located on the other side of the constant temperature box, and their centers are located on the same straight line, ensuring that the optical window is aligned with the axis of the infrared spectrometer; a stirring rod and a stirring rod speed controller are provided in the middle of the constant temperature box, and the infrared spectrometer, the dust concentration detection device, the temperature control system and the humidity control system are all connected to the data processing module through a data line, and the data processing module has a built-in intelligent analysis system for analyzing hygroscopic characteristic parameters and storing data;

[0005] The detection method comprises the following steps:

[0006] ① Prepare a number of dust particles to be tested, put the prepared dust particles into a drying box for drying, and then naturally cool them to room temperature; at the same time, check the air tightness of the hardware device, turn on the temperature control system, set the temperature of the thermostat to 25°C, and preheat the hardware device for 5 minutes;

[0007] ② When there is no dust to be tested in the constant temperature box, start the infrared spectrometer, select the transmission mode for the infrared spectrometer, collect the infrared spectrum signal when the constant temperature box cavity is empty, and observe whether there is interference in the collected infrared spectrum signal. If there is no interference signal, proceed to the next step. If there is an interference signal, it is necessary to eliminate the interference signal until there is no abnormality in the infrared spectrum signal before proceeding to the next step;

[0008] ③ Blow the dust particles to be tested in step ① through the dust particle inlet to be tested, observe the dust concentration detection device during this period, and close the dust particle inlet to be tested when the target concentration is reached. When the dust is uniformly in a dynamic flow state, start the infrared spectrometer. The infrared spectrometer is in transmission mode. The infrared spectrometer is used for real-time monitoring and the infrared spectrum signal of the dust in the constant temperature box is collected. It is reflected by the characteristic peak position of the dry dust. The characteristic peak position of the dry dust includes the characteristic peak displacement v 干燥 , characteristic peak intensity A 干燥 And the characteristic peak area S 干燥 ;

[0009] ④ The experimental environment temperature in the constant temperature box is adjusted to 25°C through the temperature control system, and the humidity in the constant temperature box is set to 30%, 50%, 60%, 70%, 80%, and 90% through the humidity control system. At the same time, the stirring rod is started. The stirring rod speed controller adjusts the rotation speed of the stirring rod according to the experimental requirements to make the dust to be tested into a uniform and stable aerosol. During this period, the humidity control system performs real-time feedback control, starts the infrared spectrometer, and selects the transmission mode for the measurement mode of the infrared spectrometer. The infrared spectrometer is used for real-time monitoring, and the spectral signals of the aerosol in the constant temperature box at various humidities are collected, which are reflected by the characteristic peak position after the dust absorbs moisture. The characteristic peak position after the dust absorbs moisture includes the characteristic peak displacement v 吸湿 , characteristic peak intensity A 吸湿 And the characteristic peak area S 吸湿 ;

[0010] ⑤ Using the intelligent analysis system of the data processing module (11), the characteristic peak position of the dry dust collected in step ③ and the characteristic peak position of the dust after moisture absorption collected in step ④ are processed in real time and a moisture absorption characteristic model is established;

[0011] ⑥ Use the hygroscopic characteristics model determined in step ⑤ to predict the hygroscopic characteristics of the dust particles to be tested.

[0012] In step ⑤ of the present invention, the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust are processed in real time by the intelligent analysis system, including data preprocessing and feature extraction.

[0013] The data preprocessing is as follows: the moving average method is used to perform local mean processing on the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust, and then the Savitzky-Golay filter is used to suppress and eliminate high-frequency noise while maintaining the spectral peak position and shape; the next step is baseline correction, and the shape and modeling are constructed through the modeling method and the least squares smoothing method, and the background interference is modeled and eliminated; the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust are normalized, and the spectral data are normalized as peak height normalization based on the tip of the characteristic absorption peak, and the peak area in the characteristic interval is normalized as peak area normalization;

[0014] The specific feature extraction is as follows: select the key bands of the characteristic peak position after dust absorption and the characteristic peak position of dry dust, and take the peak height change, peak area change and peak intensity change of the specific group's hygroscopic degree as the key variables. According to the characteristics of infrared spectroscopy, the hygroscopic process usually stimulates the change of specific functional groups. The OH stretching vibration band is in the range of 3200-3600cm-1, and the intensity is enhanced after water absorption. The position or intensity of CH and C=O related absorption peaks may change due to interaction with water molecules. These features are screened by principal component analysis (PCA) to reduce the data dimension; for key variables, such as the change in peak position caused by the change in chemical environment caused by water adsorption, the change in peak height reflecting the hygroscopic degree of specific groups, and the overall adsorption of water molecules, the peak parameters of these variables should be extracted.

[0015] In step ⑤, the moisture absorption characteristic model is established by the intelligent analysis system as follows:

[0016] The present invention uses infrared spectroscopy to measure the hygroscopic properties of dust and characterizes the hygroscopic parameters by changes in characteristic absorption peaks of characteristic chemical bonds. These frequency changes reflect the interaction between dust and water molecules, as well as changes in dust structure and surface properties during the hygroscopic process.

[0017] Characteristic peak shift

[0018] During the water adsorption process, due to the formation of hydrogen bonds or changes in the chemical environment, the vibration frequency of the characteristic absorption peak will shift, and the hygroscopicity is characterized by the shift in frequency v:

[0019] Δv=v 吸湿 -v 干燥

[0020] Where: Δv represents the frequency offset (cm -1 );

[0021] v 吸湿 Indicates the characteristic peak position of dust after absorbing moisture;

[0022] v 干燥Indicates the characteristic peak position of dry dust;

[0023] The magnitude of the frequency offset Δv is related to the dust's ability to adsorb moisture. Generally, the larger the offset, the stronger the interaction between the dust particles and water molecules.

[0024] Changes in characteristic peak intensity

[0025] During the dust moisture absorption process, the intensity of the characteristic peaks related to water molecules will increase, and the hygroscopicity can be characterized by the change in absorbance A:

[0026] ΔA=A 吸湿 -A 干燥

[0027] Where: ΔA represents the change in the intensity of the characteristic peak;

[0028] A 吸湿 It indicates the absorbance of characteristic peak after dust absorbs moisture;

[0029] A 干燥 Indicates the characteristic peak absorbance of dry dust;

[0030] Peak area change

[0031] The characteristic peak area (related to the total absorption) is obtained by integration

[0032] ΔS=S 吸湿 -S 干燥

[0033] Where: ΔS represents the change in peak area;

[0034] S 吸湿 It indicates the characteristic peak area after dust absorbs moisture;

[0035] S 干燥 Indicates the characteristic peak area of ​​dry dust;

[0036] The data of infrared spectrum characteristic peak position shift, peak intensity change and peak area change under humidity of 30%, 50%, 60%, 70%, 80% and 90% were normalized and averaged respectively;

[0037] The characteristic peak position shift, peak intensity change, and the average value of the peak area are combined with the moisture absorption amount q to establish a joint model to obtain the hygroscopic characteristic model to quantify the hygroscopicity of dust:

[0038] q=κ 1 ·Δv+κ 2 ΔA+κ 3 ΔS

[0039] Where: 1 , κ 2 , κ3 The correction factor is calibrated experimentally (calibrated by an experiment on the amount of moisture adsorbed by a standard sample under known humidity conditions).

[0040] The present invention provides a detachable bottom cover at the bottom of the thermostatic box, which is convenient for removing the bottom cover after the detection is completed, so as to facilitate cleaning of the inside of the device.

[0041] Compared with the prior art, the present invention sets up a constant temperature box which can detect the temperature and humidity of dust and aerosol in real time. The constant temperature box is equipped with an infrared spectrometer and a real-time concentration monitoring module, which can perform transmission or attenuated total reflection (ATR) measurement. A stirring rod is set in the middle of the device to produce a stable and uniform flowing aerosol from the dust to be tested in the device; a detachable bottom cover is set at the bottom to remove the bottom cover after using the device, so as to facilitate cleaning the inside of the device; a data processing module establishes a hygroscopic characteristic model for the test results according to the humidity of the constant temperature box and the collected infrared spectrum, and continuously detects the hygroscopic characteristics of the dust particles to be tested through the hygroscopic characteristic model. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural schematic diagram of the present invention.

[0043] In the figure: 1. temperature control system, 2. humidity control system, 3. inlet for dust particles to be tested, 4. dust concentration detection device, 5. detachable bottom cover, 6. infrared spectrometer, 7. optical window, 8. stirring rod, 9. constant temperature box, 10. stirring rod speed controller, 11. data processing module. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings.

[0045] like Figure 1 As shown, a method for detecting the hygroscopic characteristics of dust based on infrared spectroscopy, the hardware part for realizing the method includes a thermostat 9, on which a temperature control system 1 and a humidity control system 2 are installed, which are used to detect the temperature of the aerosol in the thermostat 9 and control the humidity in real time; the dust particle inlet 3 to be tested and the dust concentration detection device 4 are located on one side of the thermostat 9; the infrared spectrometer 6 and the optical window 7 are located on the other side of the thermostat 9, and their centers are located on the same straight line, ensuring that the optical window 7 and the infrared spectrometer 6 are aligned in the axis; a stirring rod 8 and a stirring rod speed controller 10 are provided in the middle of the thermostat 9, which are used to produce a stable and uniform flowing aerosol from the dust in the device; a removable bottom cover 5 is provided at the bottom of the thermostat 9, which is used to remove the bottom cover after using the device, so as to facilitate cleaning of the inside of the device. The infrared spectrometer 6, the dust concentration detection device 4, the temperature control system 1 and the humidity control system 2 are all connected to the data processing module 11 through a data line, and the data processing module 11 has a built-in intelligent analysis system for analyzing the hygroscopic characteristic parameters and storing data;

[0046] The detection method comprises the following steps:

[0047] ① Prepare a number of dust particles to be tested, put the prepared dust particles into a drying box for drying, and then naturally cool them to room temperature; at the same time, check the air tightness of the hardware device, turn on the temperature control system 1, set the temperature of the thermostat 9 to 25°C, and preheat the hardware device for 5 minutes;

[0048] ② When there is no dust to be measured in the constant temperature box 9, start the infrared spectrometer 6. The measurement mode of the infrared spectrometer 6 is the transmission mode, and the spectral range is 600-4000cm -1 , the spectral resolution is 4cm -1 , the number of scans is 32 times, the infrared spectrum signal when the constant temperature box 9 cavity is collected, and whether there is interference in the collected infrared spectrum signal is observed, if there is no interference signal, proceed to the next step, if there is an interference signal, it is necessary to eliminate the interference signal until there is no abnormality in the infrared spectrum signal before proceeding to the next step;

[0049] ③ Blow the dust particles to be tested in step ① through the dust particle inlet 3 to be tested, observe the dust concentration detection device 4 during this period, and close the dust particle inlet 3 to be tested when the target concentration is reached. When the dust is uniformly in a dynamic flow state, start the infrared spectrometer 6. The measurement mode of the infrared spectrometer 6 is the transmission mode, and the spectral range is 600-4000cm -1 , the spectral resolution is 4cm -1 The number of scans is 32 times. The infrared spectrometer 6 is used for real-time monitoring to collect the infrared spectrum signal of the dust in the constant temperature box 9. The infrared spectrum signal of the dust is reflected by the characteristic peak position of the dry dust. The characteristic peak position of the dry dust includes the characteristic peak displacement v 干燥 , characteristic peak intensity A 干燥 And the characteristic peak area S 干燥 ;

[0050] ④ The experimental environment temperature in the constant temperature box 9 is adjusted to 25°C through the temperature control system 1, and the humidity in the constant temperature box 9 is set to 30%, 50%, 60%, 70%, 80%, and 90% through the humidity control system 2. At the same time, the stirring rod 8 is started, and the stirring rod speed controller 10 adjusts the rotation speed of the stirring rod 8 according to the experimental requirements to make the dust to be tested into a uniform and stable flowing aerosol. During this period, the humidity control system 2 performs real-time feedback control and starts the infrared spectrometer 6. The measurement mode of the infrared spectrometer 6 selects the transmission mode, and the spectral range is 600-4000cm -1 , the spectral resolution is 4cm -1The scanning number is 32 times, and the infrared spectrometer 6 is used for real-time monitoring to collect the spectral signal of the aerosol in the constant temperature box 9 at various humidity levels. The spectral signal of the aerosol is reflected by the characteristic peak position after the dust absorbs moisture. The characteristic peak position after the dust absorbs moisture includes the characteristic peak displacement v 吸湿 , characteristic peak intensity A 吸湿 And the characteristic peak area S 吸湿 ;

[0051] ⑤ Using the intelligent analysis system of the data processing module 11, the characteristic peak position of the dry dust collected in step ③ and the characteristic peak position of the dust after moisture absorption collected in step ④ are processed in real time and a moisture absorption characteristic model is established;

[0052] ⑥ Use the hygroscopic characteristics model determined in step ⑤ to predict the hygroscopic characteristics of the dust particles to be tested.

[0053] In step ⑤, the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust are processed in real time by the intelligent analysis system, including data preprocessing and feature extraction.

[0054] The data preprocessing is as follows: the moving average method is used to perform local mean processing on the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust to reduce noise, and then the Savitzky-Golay filter is used to suppress and eliminate high-frequency noise while maintaining the spectral peak position and shape; the next step is baseline correction, and the shape and modeling are constructed through the modeling method and the least squares smoothing method, and the background interference is modeled and eliminated; the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust are normalized, and the spectral data are normalized as peak height normalization based on the tip of the characteristic absorption peak, and the peak area in the characteristic interval is normalized as peak area normalization;

[0055] The smoothing curve, baseline correction and normalization techniques used in the present invention are conventional operating methods in the art and will not be described in detail here.

[0056] The specific feature extraction is as follows: select the key bands of the characteristic peak position after dust absorption and the characteristic peak position of dry dust, and take the peak height change, peak area change and peak intensity change of the specific group's hygroscopic degree as the key variables. According to the characteristics of infrared spectroscopy, the hygroscopic process usually stimulates the change of specific functional groups. The OH stretching vibration band is in the range of 3200-3600cm-1, and the intensity is enhanced after water absorption. The position or intensity of CH and C=O related absorption peaks may change due to interaction with water molecules. These features are screened by principal component analysis (PCA) to reduce the data dimension; for key variables, such as the change in peak position caused by the change in chemical environment caused by water adsorption, the change in peak height reflecting the hygroscopic degree of specific groups, and the overall adsorption of water molecules, the peak parameters of these variables should be extracted.

[0057] During the dust moisture absorption process, the changes in dust structure and surface properties are as follows:

[0058] 1. Key chemical bonds and their vibration frequencies

[0059] (1) OH bond vibration frequency

[0060] Hygroscopicity is mainly related to the OH stretching vibration frequency and HOH bending vibration frequency in water molecules;

[0061] OH stretching vibration frequency:

[0062] In free water molecules, the stretching vibration of the OH bond typically appears at ~3700 cm-1.

[0063] When water molecules are adsorbed onto the surface of dust particles, hydrogen bonding occurs, causing the frequency to shift to the range of 3000–3600 cm-1, depending on the adsorption strength.

[0064] HOH bending vibration frequency:

[0065] It usually appears at ~1600 cm-1, and slight shifts may occur during the adsorption process.

[0066] (2) Surface group vibration frequency

[0067] The interaction between active groups on the surface of dust particles (such as hydroxyl, carboxyl or siloxy) and water molecules will also affect the characteristic frequency:

[0068] Si-OH vibration: appears at 3200–3400 cm-1. The signal may be enhanced or shifted after water adsorption.

[0069] C=O vibration (carboxyl or ester group): at ~1700cm-1, interaction with water may lead to an increase in the intensity of the absorption peak.

[0070] In step ⑤, the moisture absorption characteristic model is established by the intelligent analysis system as follows:

[0071] The present invention uses infrared spectroscopy to measure the hygroscopic properties of dust and characterizes the hygroscopic parameters by changes in characteristic absorption peaks of characteristic chemical bonds. These frequency changes reflect the interaction between dust and water molecules, as well as changes in dust structure and surface properties during the hygroscopic process.

[0072] Characteristic peak shift

[0073] During the water adsorption process, due to the formation of hydrogen bonds or changes in the chemical environment, the vibration frequency of the characteristic absorption peak will shift, and the hygroscopicity is characterized by the shift in frequency v:

[0074] Δv=v 吸湿 -v 干燥

[0075] Where: Δv represents the frequency offset (cm -1 );

[0076] v 吸湿 Indicates the characteristic peak position of dust after absorbing moisture;

[0077] v 干燥 Indicates the characteristic peak position of dry dust;

[0078] The magnitude of the frequency offset Δv is related to the dust's ability to adsorb moisture. Generally, the larger the offset, the stronger the interaction between the dust particles and water molecules.

[0079] Changes in characteristic peak intensity

[0080] During the dust moisture absorption process, the intensity of the characteristic peaks related to water molecules will increase, and the hygroscopicity can be characterized by the change in absorbance A (usually the infrared spectrometer currently used will automatically display the absorbance):

[0081] ΔA=A 吸湿 -A 干燥

[0082] Where: ΔA represents the change in the intensity of the characteristic peak;

[0083] A 吸湿 It indicates the absorbance of characteristic peak after dust absorbs moisture;

[0084] A 干燥 Indicates the characteristic peak absorbance of dry dust;

[0085] Characteristic peak area changes

[0086] The characteristic peak area (related to the total absorption) is obtained by integration. Usually, the infrared spectrometer currently used will automatically display the characteristic peak area. The peak area calculation formula is: A(x) is the absorption intensity on the x-axis corresponding to the wave number in the infrared spectrum. 1 and x 2 It is the starting and ending wave number of the peak; it can also be quantitatively analyzed by Bell-Lambert law: area A = ε·c·l, ε is the molar coefficient of dust, c is the concentration of the dust to be measured, and l is the optical path length;

[0087] ΔS=S 吸湿 -S 干燥

[0088] Where: ΔS represents the change in peak area;

[0089] S 吸湿 It indicates the characteristic peak area after dust absorbs moisture;

[0090] S 干燥 Indicates the characteristic peak area of ​​dry dust;

[0091] The data of infrared spectrum characteristic peak position shift, peak intensity change and peak area change under humidity of 30%, 50%, 60%, 70%, 80% and 90% were normalized and averaged respectively;

[0092] The characteristic peak position shift, peak intensity change, and the average value of the peak area are combined with the moisture absorption amount q to establish a joint model to obtain the hygroscopic characteristic model to quantify the hygroscopicity of dust:

[0093] q=κ 1 ·Δv+κ 2 ΔA+κ 3 ΔS

[0094] Where: 1 , κ 2 , κ 3 The correction factor is calibrated experimentally (calibrated by an experiment on the amount of moisture adsorbed by a standard sample under known humidity conditions).

[0095] The principle of measuring the hygroscopicity of dust by infrared spectroscopy is based on the interaction between the vibration of chemical bonds between molecules and infrared radiation. Infrared spectroscopy technology analyzes and quantifies the hygroscopicity of dust by detecting the vibration modes of chemical bonds within molecules, especially the OH bonds in water molecules. Infrared light is a type of electromagnetic radiation, and its energy just matches the vibration energy of molecules. When infrared light is irradiated on a molecule, if the vibration frequency of the molecule is the same as the frequency of the irradiated light, resonance will occur, resulting in the absorption of light energy, which appears as an absorption peak on the spectrum. Each molecule has its own "vibrational fingerprint", so by analyzing the absorption spectrum, we can identify the specific type of molecule. The water molecule is composed of one oxygen atom and two hydrogen atoms, forming a V-shaped structure. The OH bond is very polar because the oxygen atom has a much greater ability to attract electrons than the hydrogen atom, resulting in an asymmetric charge distribution. The dipole moment formed in this way makes the water molecule an excellent infrared spectroscopy marker, because polar molecules change their dipole moment when they vibrate, and this process can effectively absorb infrared radiation. When dust comes into contact with an environment containing water vapor in the air, water molecules will be adsorbed on the surface of the dust or in the micropores. This adsorption will cause changes in the physical and chemical properties of the dust, including its infrared spectral characteristics. In particular, the vibration mode of the OH bond will change, which is manifested in the infrared spectrum as an increase in the intensity or change in the shape of the absorption peak at a specific wavelength position. Infrared spectroscopy to measure the hygroscopicity of dust is a non-destructive, highly sensitive and repeatable method that is suitable for quickly and accurately monitoring the hygroscopic properties of materials in laboratories and industrial production. This technology can not only detect the presence of water, but also reveal the interaction between water and other molecules, which plays an important role in understanding the behavior of dust under different environmental conditions.

[0096] An embodiment of the present invention is given

[0097] Step 1: (1) Prepare a number of dust particles to be tested; (2) Place the prepared dust particles in a drying oven and dry them for 4 hours, then cool them naturally to room temperature; (3) Check the air tightness of the device; (4) Turn on the temperature controller, set the constant temperature of the oven to 25°C, and preheat the detection device for 5 minutes; (5) Select the transmission mode of the infrared spectrometer, and the spectral range is 600–4000cm -1 , the spectral resolution is 4cm -1 , the number of scans is 32 times;

[0098] Step 2: When there is no dust to be tested in the constant temperature box, start the spectrometer. The infrared spectrometer is set to the transmission mode with a spectral range of 600–4000 cm -1 , the spectral resolution is 4cm -1The scanning times are 32 times, and the infrared spectrum signal of the constant temperature box cavity is collected. The purpose of this test is to ensure that there is no excessive interference in the test environment. After the test, observe whether there is interference in the collected spectrum signal. If not, proceed to the next step. If there is interference, it is necessary to eliminate the interference until there is no abnormality in the spectrum signal before proceeding to the next step.

[0099] Step 3: Blow dry dust particles to be tested through the dust particle inlet to be tested, and observe the dust concentration detection device during this period. When the target concentration is reached, the dust particle inlet to be tested can be closed (the target concentration recommended range of this embodiment is: 50-500mg / m 3 , 50–100 mg / m 3 :Applicable to the test of fine dust (particle size <10μm); 100–300mg / m 3 : Suitable for measurements under general environmental conditions, balancing signal intensity and particle uniformity; 300–500 mg / m 3 :Suitable for experiments with coarse dust particles (particle size>10μm) or low hygroscopic dust). Note that the dust particle concentration in the constant temperature box should not be too high to avoid excessive absorption or low absorption of particle pigments. When the dust is in a uniform dynamic flow state, start the spectrometer. The infrared spectrometer is in transmission mode with a spectral range of 600–4000cm -1 , the spectral resolution is 4cm -1 The scanning number is 32 times, real-time monitoring, and collecting infrared spectrum signals of dust in the constant temperature box.

[0100] Step 4: The experimental environment temperature in the constant temperature box is adjusted to 25°C through the temperature control system, and the humidity of the humidity control system is set to 30%, 50%, 60%, 70%, 80%, and 90% respectively. The final humidity value is the normalized average value. At the same time, the stirring rod 8 is started, and the stirring rod speed controller 10 adjusts the rotation speed of the stirring rod 8 according to the experimental requirements (the recommended range of the stirring speed of the stirring rod 8: low-speed stirring (<100rpm) is suitable for dust with lighter particles and easy suspension (such as fine particles or nanoparticles) to prevent excessive stirring speed from causing particle agglomeration or detachment from the test area; medium-speed stirring (100-300rpm) is suitable for dust with medium particle size (10-50μm), which can ensure uniform dust dispersion and promote the dynamic balance of surface adsorption; high-speed stirring (>300rpm) is suitable for larger particles (>50μm) or high-concentration dust, but it is necessary to Avoid excessive dust dispersion caused by too high speed, which will affect the optical path. Use a medium speed (150-200rpm) for preliminary tests to observe the suspension state of the dust and the changes in the water absorption peak (such as the OH vibration intensity). If the dust is unevenly distributed or the signal is unstable, gradually adjust the speed to find the optimal speed with uniform particle distribution and sufficient adsorption. Monitor the spectral signal in real time to monitor the stability of the water adsorption peak (such as 3700-3000cm-1) to ensure that the stirring speed does not introduce unnecessary fluctuations. In the experiment, it is usually adjusted from 150-300rpm. The final speed depends on the characteristics of the dust particles and the experimental objectives). The dust to be tested is made into a uniform and stably flowing aerosol. During this period, the humidity control system 2 performs real-time feedback control. Start the infrared spectrometer 6. The measurement mode of the infrared spectrometer 6 is selected in the transmission mode, and the spectral range is 600-4000cm -1 , the spectral resolution is 4cm -1 The scanning number is 32 times, real-time monitoring is performed, and the spectral signals of the aerosol in the constant temperature box 9 at various humidity levels are collected.

[0101] Step 5: Use the built-in intelligent analysis system of the data processing module to perform real-time processing and hygroscopic characteristics modeling analysis on the infrared spectral data collected in the first two steps. The first step is to preprocess the data. Due to equipment noise and environmental interference, the collected spectral data may fluctuate. The moving average method is used to perform local mean processing on the spectral signal to reduce noise. Then, Savitzky-Golay suppression is used to eliminate high-frequency noise while maintaining the spectral peak position and shape; then baseline correction is performed. The shape and modeling are constructed through the modeling method and the least squares smoothing method, and the background interference is modeled and eliminated; in order to compare the hygroscopic characteristics under different humidity, the spectral signal should be normalized. Taking the tip of the characteristic absorption peak as the reference, the spectral data should be normalized as the peak height normalization, and the peak area in the characteristic interval should be normalized as the area normalization; the second step is feature extraction, selecting key bands. According to the characteristics of infrared spectroscopy, the hygroscopic process usually excites changes in specific functional groups. The OH stretching vibration band is between 3200-3600cm -1 The intensity increases after water absorption. The position or intensity of the absorption peaks related to CH and C=O may change due to the interaction with water molecules. These features are screened by principal component analysis (PCA) to reduce the data dimension. For the extraction of peak parameters, the key bands of the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust are selected, and the peak height change, peak area change and peak intensity change of the moisture absorption degree of the specific group are taken as key variables to extract the peak parameters. The third step is to build a model, and a joint model is established between the characteristic peak position shift, peak intensity change and the average value of the peak area and the moisture absorption amount to obtain a hygroscopic characteristic model to quantify the hygroscopicity of the dust.

[0102] Step 6: Use the determined model to predict the hygroscopic characteristics of the dust particles to be tested.

Claims

1. A method for detecting dust hygroscopic characteristics based on infrared spectroscopy, wherein the hardware part for realizing the method comprises a constant temperature box (9), a temperature control system (1) and a humidity control system (2) are installed on the constant temperature box (9), a dust particle inlet (3) to be detected and a dust concentration detection device (4) are located on one side of the constant temperature box (9); an infrared spectrometer (6) and an optical window (7) are located on the other side of the constant temperature box (9), and their centers are located on the same straight line, ensuring that the optical window (7) and the infrared spectrometer (6) are aligned with the axis; a stirring rod (8) and a stirring rod speed controller (10) are provided in the middle of the constant temperature box (9), the infrared spectrometer (6), the dust concentration detection device (4), the temperature control system (1) and the humidity control system (2) are all connected to a data processing module (11) via a data line, and the data processing module (11) has a built-in intelligent analysis system for analyzing hygroscopic characteristic parameters and storing data; It is characterized in that The detection method comprises the following steps: ① Prepare a number of dust particles to be tested, put the prepared dust particles into a drying box for drying, and then naturally cool them to room temperature; at the same time, check the air tightness of the hardware device, turn on the temperature control system (1), set the temperature of the thermostat (9) to 25°C, and preheat the hardware device for 5 minutes; ② When there is no dust to be tested in the constant temperature box (9), start the infrared spectrometer (6), select the transmission mode as the measurement mode of the infrared spectrometer (6), collect the infrared spectrum signal when the constant temperature box (9) cavity is empty, and observe whether the collected infrared spectrum signal has interference. If there is no interference signal, proceed to the next step. If there is an interference signal, it is necessary to eliminate the interference signal until there is no abnormality in the infrared spectrum signal before proceeding to the next step; ③ Blow the dust particles to be tested in step ① through the dust particle inlet (3) to be tested, observe the dust concentration detection device (4) during this period, and close the dust particle inlet (3) to be tested when the target concentration is reached. When the dust is uniformly in a dynamic flow state, start the infrared spectrometer (6), and select the transmission mode as the measurement mode of the infrared spectrometer (6). The infrared spectrometer (6) is used for real-time monitoring and collects the infrared spectrum signal of the dust in the constant temperature box (9), which is reflected by the characteristic peak position of the dry dust. The characteristic peak position of the dry dust includes the characteristic peak displacement v 干燥 , characteristic peak intensity A 干燥 And the characteristic peak area S 干燥 ; ④ The temperature control system (1) is used to adjust the experimental environment temperature in the constant temperature box (9) to 25° C. The humidity control system (2) is used to set the humidity in the constant temperature box (9) to 30%, 50%, 60%, 70%, 80%, and 90%, respectively. At the same time, the stirring rod (8) is started. The rotation speed of the stirring rod (8) is adjusted according to the experimental requirements to make the dust to be tested into a uniform and stable flowing aerosol. During this period, the humidity control system (2) performs real-time feedback control, starts the infrared spectrometer (6), and the measurement mode of the infrared spectrometer (6) is selected as the transmission mode. The infrared spectrometer (6) is used for real-time monitoring, and the spectral signal of the aerosol in the constant temperature box (9) at each humidity is collected, which is reflected by the characteristic peak position after the dust absorbs moisture. The characteristic peak position after the dust absorbs moisture includes the characteristic peak displacement v 吸湿 , characteristic peak intensity A 吸湿 And the characteristic peak area S 吸湿 ; ⑤ Using the intelligent analysis system of the data processing module (11), the characteristic peak position of the dry dust collected in step ③ and the characteristic peak position of the dust after moisture absorption collected in step ④ are processed in real time and a moisture absorption characteristic model is established; ⑥ Use the hygroscopic characteristics model determined in step ⑤ to predict the hygroscopic characteristics of the dust particles to be tested.

2. The method for detecting dust hygroscopicity based on infrared spectroscopy according to claim 1, characterized in that: In step ⑤, the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust are processed in real time by the intelligent analysis system, including data preprocessing and feature extraction. The data preprocessing is as follows: the moving average method is used to perform local mean processing on the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust, and then the Savitzky-Golay filter is used to suppress and eliminate high-frequency noise while maintaining the spectral peak position and shape; the next step is baseline correction, and the shape and modeling are constructed through the modeling method and the least squares smoothing method, and the background interference is modeled and eliminated; the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust are normalized, and the spectral data are normalized as peak height normalization based on the tip of the characteristic absorption peak, and the peak area in the characteristic interval is normalized as peak area normalization; The feature extraction is specifically as follows: selecting the key bands of the characteristic peak position of the dust after moisture absorption and the characteristic peak position of the dry dust, and taking the peak height change, peak area change and peak intensity change of the moisture absorption degree of the specific group as the key variables.

3. The method for detecting dust hygroscopicity based on infrared spectroscopy according to claim 2 is characterized in that: In step ⑤, the hygroscopic characteristic model is established by the intelligent analysis system as follows: Infrared spectroscopy is used to measure the hygroscopic properties of dust, and the hygroscopic parameters are characterized by the changes in the characteristic absorption peaks of characteristic chemical bonds. Characteristic peak shift During the water adsorption process, due to the formation of hydrogen bonds or changes in the chemical environment, the vibration frequency of the characteristic absorption peak will shift, and the hygroscopicity is characterized by the shift in frequency v: Δv=v 吸湿 -v 干燥 Where: Δv represents the frequency offset (cm -1 ); v 吸湿 Indicates the characteristic peak shift after dust absorbs moisture; v 干燥 Indicates the characteristic peak shift of dry dust; The magnitude of the frequency offset Δv is related to the dust's ability to absorb moisture; Changes in characteristic peak intensity During the dust moisture absorption process, the intensity of the characteristic peaks related to water molecules will increase, and the hygroscopicity can be characterized by the change in absorbance A: ΔA=A 吸湿 -IN 干燥 Where: ΔA represents the change in the intensity of the characteristic peak; A 吸湿 It indicates the absorbance of characteristic peak after dust absorbs moisture; A 干燥 Indicates the characteristic peak absorbance of dry dust; Characteristic peak area changes The characteristic peak area is obtained by integration ΔS=S 吸湿 -S 干燥 Where: ΔS represents the change in peak area; S 吸湿 It indicates the characteristic peak area after dust absorbs moisture; S 干燥 Indicates the characteristic peak area of ​​dry dust; The data of infrared spectrum characteristic peak position shift, peak intensity change and peak area change under humidity of 30%, 50%, 60%, 70%, 80% and 90% were normalized and averaged respectively; The characteristic peak position shift, peak intensity change, and the average value of the peak area are combined with the moisture absorption amount q to establish a joint model to obtain the hygroscopic characteristic model to quantify the hygroscopicity of dust: q=κ1·Δv+κ2·ΔA+κ3·ΔS Among them: κ1, κ2, κ3 are correction coefficients, which are calibrated through experiments.

4. The method for detecting dust hygroscopicity based on infrared spectroscopy according to claim 3 is characterized in that: A detachable bottom cover (5) is provided at the bottom of the thermostatic box (9).

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