A method for detecting dust moisture absorption characteristics based on infrared spectroscopy

Abstract

A method for detecting dust hygroscopic characteristics based on infrared spectroscopy comprises the following steps: a temperature control system (1) and a humidity control system (2) are installed on a constant temperature box; a dust particle inlet (3) to be tested and a dust concentration detection device (4) are located on one side of the constant temperature box; an infrared spectrometer (6) and an optical window (7) 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 (8) and a stirring rod speed controller are provided 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 to a data processing module via a data line; the data processing module has a built-in intelligent analysis system for analyzing hygroscopic characteristic parameters and storing data; the data processing module establishes a hygroscopic characteristic model for the test results based on 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 using the hygroscopic characteristic model.

Description

Technical Field

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

[0002] In the process of global industrialization, dust management has become a major issue in environmental protection and public health. Dust not only affects air quality, but also damages industrial equipment and can even cause serious safety accidents. The hygroscopic properties of dust are one of the key factors that determine its adhesion and aggregation behavior. Therefore, accurately measuring the hygroscopic characteristics of dust is crucial for improving the design and operation of air purification systems. Currently, the detection methods for the hygroscopic properties of dust mainly rely on gravimetric and electrical conductivity methods. Although these two methods can reflect the moisture content of dust to a certain extent, they are time-consuming and cumbersome to operate, and they cannot achieve continuous, 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] To achieve the above-mentioned objectives, the present invention provides a method for detecting the hygroscopic characteristics of dust based on infrared spectroscopy. The hardware for implementing the method includes a constant temperature chamber, on which a temperature control system and a humidity control system are installed. An inlet for dust particles to be measured and a dust concentration detection device are located on one side of the constant temperature chamber; an infrared spectrometer and an optical window are located on the other side of the constant temperature chamber, and their centers are located on the same straight line to ensure 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 chamber, and the infrared spectrometer, the dust concentration detection device, the temperature control system, and the humidity control system are all connected to a data processing module via a data cable. 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, and place the prepared dust particles in a drying oven to dry, and then naturally cool 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 constant temperature box to 25℃, and preheat the hardware device for 5 minutes;

[0007] ② When there is no dust to be measured in the constant temperature chamber, start the infrared spectrometer and select the transmission mode of the infrared spectrometer to collect the infrared spectrum signal when the constant temperature chamber cavity is empty. 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 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 collects the infrared spectrum signal of the dust in the constant temperature box. The characteristic peak information of the dry dust is reflected. The characteristic peak information of the dry dust includes the characteristic peak position 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, and 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 and starts the infrared spectrometer. The measurement mode of the infrared spectrometer is selected in the transmission mode. The infrared spectrometer is used for real-time monitoring and the spectral signals of the aerosol in the constant temperature box at various humidity levels are collected. The characteristic peak information after the dust absorbs moisture is reflected. The characteristic peak information after the dust absorbs moisture includes the characteristic peak position 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 information of the dry dust collected in step ③ and the characteristic peak information 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 information of the dust after moisture absorption and the characteristic peak information 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 characteristic peak information of the dust after moisture absorption and the characteristic peak information of the dry dust are processed locally by the moving average method, and then the high-frequency noise is eliminated while maintaining the spectral peak position and shape through the Savitzky-Golay filter; the baseline correction is followed by the shape and modeling constructed by the modeling method and the least squares smoothing method, and the background interference is modeled and eliminated; the characteristic peak information of the dust after moisture absorption and the characteristic peak information of the dry dust are then normalized, and the spectral data are normalized as peak height normalization based on the tip of the characteristic absorption peak, and the peak area within the characteristic interval is normalized as peak area normalization;

[0014] The specific feature extraction is to select the key bands of the characteristic peak information of the dust after moisture absorption and the characteristic peak information of the dry dust, and take the peak position shift, peak area change and peak intensity change of the moisture absorption degree of the specific group as the key variables. According to the characteristics of infrared spectroscopy, the moisture absorption process usually stimulates the change of specific functional groups. The OH stretching vibration band is between 3200-3600cm - 1 interval, the intensity increases after water absorption, and 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 key variables, such as the peak position change caused by the change of chemical environment due to water adsorption, the peak height change reflecting the hygroscopicity of specific groups, and the overall adsorbed water molecules, the peak parameters of these variables should be extracted.

[0015] In step ⑤, the hygroscopic characteristics 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 through the changes in the characteristic absorption peaks of characteristic chemical bonds. These frequency changes reflect the interaction between dust and water molecules, as well as the changes in dust structure and surface properties during the hygroscopic process.

[0017] Characteristic peak position shift

[0018] During the water adsorption process, the vibration frequency of the characteristic absorption peak will shift due to the formation of hydrogen bonds or changes in the chemical environment. 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 peak 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 characteristic peak intensity;

[0028] A 吸湿 Indicates the absorbance of the 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 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 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 average value of the normalized characteristic peak position shift, peak intensity change, and peak area change is combined with the moisture absorption amount q to establish a joint model to obtain the moisture absorption characteristic model to quantify the moisture absorption of dust:

[0038] q=κ1·Δv+κ2·ΔA+κ3·ΔS

[0039] Wherein: κ1, κ2, κ3 are correction coefficients, which are calibrated by experiments (calibrated by experiments on the amount of moisture adsorbed by standard samples under known humidity conditions).

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

[0041] Compared with the existing technology, the present invention sets up a constant temperature box that 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 provided 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 provided at the bottom to be removed after using the device to facilitate cleaning the inside of the device; the data processing module establishes a hygroscopic characteristic model for the test results based on 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 measured, 4. Dust concentration detection device, 5. Removable 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 with reference to the accompanying drawings.

[0045] like Figure 1 As shown, a method for detecting the hygroscopic characteristics of dust based on infrared spectroscopy is provided. The hardware part for implementing this method includes a constant temperature box 9, on which a temperature control system 1 and a humidity control system 2 are installed, for real-time detection of the temperature and humidity of the aerosol in the constant temperature box 9; an inlet 3 for the dust particles to be tested 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 in the axis; a stirring rod 8 and a stirring rod speed controller 10 are provided in the middle of the constant temperature box 9, for generating a stable and uniform flowing aerosol from the dust in the device; a removable bottom cover 5 is provided at the bottom of the constant temperature box 9, for removing the bottom cover after using the device to facilitate cleaning 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 via a data cable. The data processing module 11 has a built-in intelligent analysis system for analyzing 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, place the prepared dust particles in a drying oven to dry, and then naturally cool 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 constant temperature box 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 selected as the transmission mode, and the spectral range is 600-4000cm -1 , spectral resolution is 4cm -1 , the number of scans is 32 times, the infrared spectrum signal of the constant temperature box 9 cavity is collected, and the collected infrared spectrum signal is observed to see if there is 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;

[0049] ③ Blow the dust particles to be tested in step ① through the dust particle inlet 3 to be tested. During this period, observe the dust concentration detection device 4. When the target concentration is reached, close the dust particle inlet 3 to be tested. When the dust is uniformly in a dynamic flow state, start the infrared spectrometer 6. The measurement mode of the infrared spectrometer 6 is selected as the transmission mode, and the spectral range is 600-4000cm -1 , 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 information of the dry dust. The characteristic peak information of the dry dust includes the characteristic peak position 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% respectively 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 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 is selected as the transmission mode, and the spectral range is 600-4000cm -1 , 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 spectral signals of the aerosol in the constant temperature box 9 at various humidity levels. The spectral signals of the aerosol are reflected by the characteristic peak information after the dust absorbs moisture. The characteristic peak information after the dust absorbs moisture includes the characteristic peak position 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 information of the dry dust collected in step ③ and the characteristic peak information 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 information of the dust after moisture absorption and the characteristic peak information 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 characteristic peak information of the dust after moisture absorption and the characteristic peak information of the dry dust are processed locally by the moving average method 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 baseline correction is followed by the modeling method and the least squares smoothing method to construct the shape and modeling and eliminate background interference; the characteristic peak information of the dust after moisture absorption and the characteristic peak information of the dry dust are then normalized, and the spectral data are normalized as peak height normalization based on the tip of the characteristic absorption peak, and the peak area within the characteristic interval is normalized as peak area normalization;

[0055] The curve smoothing, 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 to select the key bands of the characteristic peak information of the dust after moisture absorption and the characteristic peak information of the dry dust, and take the peak position shift, peak area change and peak intensity change of the moisture absorption degree of the specific group as the key variables. According to the characteristics of infrared spectroscopy, the moisture absorption process usually stimulates the change of specific functional groups. The OH stretching vibration band is between 3200-3600cm - 1 interval, the intensity increases after water absorption, and 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 key variables, such as the peak position change caused by the change of chemical environment due to water adsorption, the peak height change reflecting the hygroscopicity of specific groups, and the overall adsorbed 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 usually 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 3000–3600 cm -1 The specific position depends on the adsorption strength.

[0064] HOH bending vibration frequency:

[0065] Usually appears at ~1600cm -1 , a slight offset 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 frequency shifted after water adsorption.

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

[0070] In step ⑤, the hygroscopic characteristics 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 through the changes in the characteristic absorption peaks of characteristic chemical bonds. These frequency changes reflect the interaction between dust and water molecules, as well as the changes in dust structure and surface properties during the hygroscopic process.

[0072] Characteristic peak position shift

[0073] During the water adsorption process, the vibration frequency of the characteristic absorption peak will shift due to the formation of hydrogen bonds or changes in the chemical environment. 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 peak related to water molecules will increase, and the hygroscopicity can be characterized by the change in absorbance A (usually the infrared spectrometer used now will automatically display the absorbance):

[0081] ΔA=A 吸湿 -A 干燥

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

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

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

[0085] Changes in characteristic peak area

[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 corresponding wavenumber x-axis in the infrared spectrum, and x1 and x2 are the starting and ending wavenumbers of the peak. Quantitative analysis can also be performed using the Bell-Lambert law: area A = ε·c·l, where ε is the molar coefficient of the 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 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 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 average value of the normalized characteristic peak position shift, peak intensity change, and peak area change is combined with the moisture absorption amount q to establish a joint model to obtain the moisture absorption characteristic model to quantify the moisture absorption of dust:

[0093] q=κ1·Δv+κ2·ΔA+κ3·ΔS

[0094] Wherein: κ1, κ2, κ3 are correction coefficients, which are calibrated by experiments (calibrated by experiments on the amount of moisture adsorbed by standard samples under known humidity conditions).

[0095] Infrared spectroscopy (IR spectroscopy) measures the hygroscopicity of dust based on the interaction between the vibrations of intermolecular chemical bonds and infrared radiation. IR spectroscopy analyzes and quantifies the hygroscopic properties of dust by detecting the vibrational modes of chemical bonds within molecules, particularly the OH bonds in water molecules. Infrared light is a type of electromagnetic radiation whose energy precisely matches the vibrational energy of molecules. When infrared light strikes a molecule, if the molecule's vibrational frequency matches the frequency of the incident light, resonance occurs, resulting in absorption of the light energy, manifesting as an absorption peak on the spectrum. Each molecule has its own unique "vibrational fingerprint," and analyzing the absorption spectrum allows identification of specific molecular types. A water molecule consists of one oxygen atom and two hydrogen atoms, forming a V-shaped structure. The OH bond is highly polar because the oxygen atom attracts electrons much more strongly than the hydrogen atom, resulting in an asymmetric charge distribution. The resulting dipole moment makes water molecules an excellent infrared spectroscopy marker, as polar molecules alter their dipole moment during vibration, effectively absorbing infrared radiation. When dust comes into contact with air containing water vapor, water molecules are adsorbed on the dust surface or in its micropores. This adsorption changes the physical and chemical properties of the dust, including its infrared spectral characteristics. In particular, the vibrational modes of the OH bonds change, which manifests itself in the infrared spectrum as an increase in the intensity or change in the shape of the absorption peak at a specific wavelength. Measuring the hygroscopicity of dust by infrared spectroscopy is a non-destructive, highly sensitive, and repeatable method suitable for quickly and accurately monitoring the hygroscopic properties of materials in laboratories and industrial production. This technology not only detects the presence of water, but also reveals 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 airtightness 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 for measurement, with a spectral range of 600–4000 cm -1 , spectral resolution is 4cm -1 , the number of scans is 32 times;

[0098] Step 2: When there is no dust to be measured in the constant temperature chamber, start the spectrometer. The infrared spectrometer is set to the transmission mode with a spectral range of 600–4000 cm -1 , spectral resolution is 4cm -1 The number of scans is 32, 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. During this period, observe the dust concentration detection device. When the target concentration is reached, close the dust particle inlet to be tested (the target concentration recommended range in this embodiment is 50–500 mg / m 3 , 50–100 mg / m 3 : Applicable to the test of fine dust particles (particle size <10μm); 100–300mg / m 3 : Suitable for measurements under general environmental conditions, able to balance 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 chamber 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 measurement mode is selected in transmission mode, and the spectral range is 600–4000cm -1 , spectral resolution is 4cm -1 , the scanning times are 32 times, real-time monitoring, and collection of infrared spectrum signals of dust in the constant temperature box.

[0100] Step 4: Adjust the experimental environment temperature in the constant temperature box to 25°C through the temperature control system, and set the humidity control system to 30%, 50%, 60%, 70%, 80%, and 90% respectively. The final humidity value is the average value after normalization. At the same time, start the stirring rod 8, 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 particles to agglomerate or detach from the test area; medium-speed stirring (100-300rpm) is suitable for medium-particle Dust with a diameter of 10-50 μm can ensure uniform dust dispersion and promote the dynamic balance of surface adsorption; high-speed stirring (>300 rpm) is suitable for larger particles (>50 μm) or high-concentration dust, but it is necessary to avoid excessive dust blowing due to excessive speed, which affects the light path. Preliminary tests use a medium speed (150-200 rpm) for preliminary experiments to observe the suspension state of the dust and the changes in the water absorption peak (such as OH vibration intensity). If the dust distribution is uneven or the signal is unstable, gradually adjust the speed to find the optimal speed with uniform particle distribution and sufficient adsorption, and monitor the spectral signal to monitor the water adsorption peak (such as 3700-3000 cm) in real time. -1 ) to ensure that the stirring speed does not introduce unnecessary fluctuations. In the experiment, the stirring speed is usually adjusted from 150-300 rpm, and 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 stable 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 is the transmission mode, and the spectral range is 600-4000 cm -1 , spectral resolution is 4cm -1 The number of scans is 32, and real-time monitoring is performed to collect the spectral signals of the aerosol in the constant temperature box 9 at various humidity levels.

[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. The tip of the characteristic absorption peak is used as the benchmark, and the spectral data is normalized as peak height normalization. The peak area within the characteristic interval is normalized as area normalization; the second step is feature extraction, and the key bands are selected. According to the characteristics of the infrared spectrum, 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. The peak position shift, 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. The characteristic peak position shift, peak intensity change and the average value of the peak area are combined with the moisture absorption amount to establish a joint model 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), an inlet for dust particles to be tested (3) 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 each other; 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, and place the prepared dust particles in a drying oven for drying, and then naturally cool to room temperature; at the same time, check the airtightness of the hardware device, turn on the temperature control system (1), set the temperature of the constant temperature box (9) to 25°C, and preheat the hardware device for 5 minutes; ② When there is no dust to be measured in the constant temperature box (9), start the infrared spectrometer (6), select the transmission mode for 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 for 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). The characteristic peak information of the dry dust is reflected. The characteristic peak information of the dry dust includes the characteristic peak position v 干燥 , characteristic peak intensity A 干燥 And the characteristic peak area S 干燥 ; ④ The experimental environment temperature in the constant temperature box (9) is adjusted to 25° C. by the temperature control system (1), and the humidity in the constant temperature box (9) is set to 30%, 50%, 60%, 70%, 80%, and 90% respectively by the humidity control system (2). At the same time, the stirring rod (8) is started, and 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 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) is selected as the transmission mode. The infrared spectrometer (6) is used for real-time monitoring and collects the spectral signals of the aerosol in the constant temperature box (9) at various humidity levels. The characteristic peak information after the dust absorbs moisture is used to reflect the characteristic peak information. The characteristic peak information after the dust absorbs moisture includes the characteristic peak position 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 information of the dry dust collected in step ③ and the characteristic peak information 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 moisture absorption characteristics based on infrared spectroscopy according to claim 1, characterized in that: In step ⑤, the characteristic peak information of the dust after moisture absorption and the characteristic peak information of the dry dust are processed in real time by the intelligent analysis system, including data preprocessing and feature extraction. Data preprocessing involves performing local mean processing on the characteristic peaks of moisture-absorbed dust and dry dust using a moving average method. High-frequency noise is then eliminated through a Savitzky-Golay filter while maintaining the spectral peak position and shape. Next, baseline correction is performed, using modeling and least-squares smoothing to construct the shape and eliminate background interference. Then, the characteristic peak information of the dust after moisture absorption and the characteristic peak information of the dry dust are normalized. The tip of the characteristic absorption peak is used as the benchmark, and the spectral data is normalized as peak height normalization. The peak area within the characteristic interval is normalized as peak area normalization. The specific feature extraction is as follows: selecting the key bands of the characteristic peak information of dust after moisture absorption and the characteristic peak information of dry dust, and taking the peak position shift, peak area change and peak intensity change of the moisture absorption degree of specific groups as key variables.

3. The method for detecting dust moisture absorption characteristics based on infrared spectroscopy according to claim 2, characterized in that: In step ⑤, the hygroscopic characteristics 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 position shift During the water adsorption process, the vibration frequency of the characteristic absorption peak will shift due to the formation of hydrogen bonds or changes in the chemical environment. 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 peak 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 characteristic peak intensity; A 吸湿 Indicates the absorbance of the characteristic peak after dust absorbs moisture; A 干燥 Indicates the characteristic peak absorbance of dry dust; Changes in characteristic peak area 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 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 shift, peak intensity change and peak area change under humidity of 30%, 50%, 60%, 70%, 80% and 90% were normalized and averaged respectively; The average value of the normalized characteristic peak position shift, peak intensity change, and peak area change is combined with the moisture absorption amount q to establish a joint model to obtain the moisture absorption characteristic model to quantify the moisture absorption 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 moisture absorption characteristics based on infrared spectroscopy according to claim 3, characterized in that: A detachable bottom cover (5) is provided at the bottom of the thermostatic box (9).

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